This work was supported with funding from the NIH (R21NS093199) and the UCLA ARC 3R's Award. Our sincerest thanks go to the lab of Dr. Harley Kornblum for provision of the HK301 and HK157 cell lines. We also thank UCLA Tissue Pathology Core Laboratory (TPCL) for cryosectioning, Advanced Light Microscopy/Spectroscopy core facility (ALMS) in California Nanosystems Institute (CNSI) at UCLA for use of the confocal microscope, UCLA Crump Institute for Molecular Imaging for using IVIS imaging system, UCLA Molecular Instrumentation Center (MIC) for providing magnetic resonance spectroscopy, and Flow Cytometry Core in Jonsson Comprehensive Cancer Center (JCCC) at UCLA for providing instrumentation for flow cytometry.

All human tissue collection steps were carried out under institutionally approved protocols.
1. Thiolation of Hyaluronic Acid
Note: Molar ratios are stated with respect to total number of carboxylate groups unless otherwise specified.
<ol>
	<li>Dissolve 500 mg of sodium hyaluronate (HA, 500-750 kDa) at 10 mg/mL in deionized, distilled water (DiH2O) in an autoclave sterilized, 250 mL Erlenmeyer flask. Stir the solution (~200 rpm) at room temperature for 2 hours to fully dissolve HA. Use a stir bar and magnetic stir plate to keep reaction stirring during thiolation procedure.</li>
	<li>Using 0.1 M hydrochloric acid (HCl), adjust the pH of the HA solution to 5.5. Weigh out 69.6 mg (0.25x molar ratio) of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). 
	NOTE: Although undissolved EDC can be added directly to the HA solution, it is typically easier to dissolve EDC first in 1 mL of DiH2O and then quickly add the EDC solution to the HA solution. Pre-dissolution in 1 mL of DiH2O can also be done with N-hydroxysuccinimide (NHS) and cystamine dihydrocholoride before adding to the reaction in steps 1.3 and 1.4.</li>
	<li>Add 17.9 mg (0.125x molar ratio) of NHS to the reaction. Adjust the pH of the reaction solution to 5.5 using 0.1 M HCl and incubate the reaction at room temperature for 45 minutes.</li>
	<li>Add 70.0 mg (0.25x molar ratio) of cystamine dihydrochloride into the reaction solution. Use 0.1 M sodium hydroxide (NaOH) to adjust pH to 6.25. Incubate the reaction at room temperature overnight while stirring.</li>
	<li>On the following day, use 1 M NaOH to adjust the pH of the reaction solution to around 8. Add 192 mg (4x molar ratio) of dithiothreitol (DTT) to the reaction. Adjust the pH back to 8 after addition of DTT and leave stirring for 1-2 hours at room temperature.</li>
	<li>Use 1 M HCl to adjust pH to 4. Transfer the entire reaction mixture into pre-soaked dialysis membrane (molecular weight cut-off around 13 kDa) and dialyze against DiH2O pre-adjusted to pH 4. 
	NOTE: The volume of DiH2O for dialysis should be at least 40 times the volume of the reacted HA solution (e.g., 50 mL sample in 2 L of DiH2O, pH 4).</li>
	<li>Replace the dialysis solution (DiH2O, pH 4) twice daily for 3 days at room temperature.</li>
	<li>Filter the dialyzed solution through a 0.22 &#181;m membrane, vacuum-driven filter. Flash freeze solution of thiolated HA in liquid nitrogen. Use a lyophilizer to freeze dry samples over 2 days. Thiolated HA in dry form can be stored in a vacuum-sealed desiccator at -20 &#176;C for at least 6 months.</li>
	<li>To determine the degree of thiolation, use Ellman&#39;s test and/or proton NMR spectroscopy30,31.</li>
</ol>
2. Preparation of Crosslinking Materials
<ol>
	<li>Dissolve thiolated HA at the desired concentration (in this example, 13.3 mg/mL) in HEPES-buffered saline (20 mM HEPES in Hank&#39;s balanced salt saline (HBSS) buffer, adjusted to fall within a pH of 8-9) in an amber vial to minimize exposure to ambient light. Keep the solution stirring constantly. 
	NOTE: Formation of disulfide bonds between thiols conjugated to HA may occur if the pH is above 8, solution concentration is too high, or the solution is left stirring for too long before gelation. To avoid this issue, use below 15 mg/mL of thiolated HA and dissolve thiolated HA within 2 hours of forming hydrogels.</li>
	<li>Dissolve 4-arm-PEG-maleimide (PEG-Mal, 20 kDa) and 4-arm-PEG-thiol (PEG-thiol, 20 kDa) in phosphate buffered saline (PBS), pH 7.4, to prepare 50 mg/mL PEG-Mal and PEG-thiol stock solutions. 
	NOTE: It takes at least 1 hour to fully dissolve PEG reagents.</li>
	<li>If adding ECM-derived peptides, dissolve cysteine-containing peptides in PBS to prepare a stock solution. 
	NOTE: Use a stock concentration of 2-4 mM.</li>
	<li>Soak silicone rubber molds in ethanol for at least 20 min to clean them and then autoclave them for sterilization.</li>
</ol>
3. Hydrogel Crosslinking and Cell Encapsulation
Note: As an example here, the encapsulation of four individual, 80 &#181;L hydrogels with 0.5% (w/v) HA and compressive modulus of 1 kPa is described3. Please see Table 1 for example recipes that yield hydrogels with varying properties: two hydrogels incorporating the integrin-binding peptide RGD and two hydrogels incorporating cysteine caps as a negative control for peptide activity. Seeding concentration of patient-derived GBM cells is 500,000 cells/mL.
<ol>
	<li>Dilute PEG-Mal stock solution (50 mg/mL, from step 2.2) to 12.5 mg/mL by adding 40 &#181;L of the stock solution to 120 &#181;L PBS. Split the diluted solution into two 1.5 mL microcentrifuge tubes so that each tube has 80 &#181;L.</li>
	<li>Add 16 &#181;L of stock RGD solution (2.8 mM, from step 2.3) to one tube and 16 &#181;L of stock cysteine solution (2.8 mM, from step 2.3) to the second tube. Vortex to mix. Place the PEG-Mal-RGD or PEG-Mal-CYS solutions on ice until use in step 3.9. 
	NOTE: The procedure as described here yields hydrogels with ~140 &#181;M of peptide. This is equivalent to approximately 1 out of every 8 available PEG arms being occupied with a peptide. This can be varied by altering the molar ratio of cysteine-terminated peptides to available maleimide groups. In general, a maximum concentration of 280 &#181;M of peptide can be achieved while still leaving sufficient numbers of maleimide groups available for hydrogel crosslinking.</li>
	<li>Dilute the PEG-thiol stock solution (50 mg/mL, from step 2.2) to 5 mg/mL by mixing 4 &#181;L of 50 mg/mL stock solution with 36 &#181;L of PBS. Add 120 &#181;L of dissolved, thiolated HA from step 2.1 to the mixture. 
	NOTE: Solutions of HMW HA are very viscous. Thus, we recommend using wide-orifice micropipette tip to transfer solutions. Pipette slowly to avoid solution sticking to the walls of micropipette tip and to improve measurement accuracy.</li>
	<li>Place the clean, dry molds (prepared in step 2.4) into each well of a non-tissue culture treated 12-well plate. Using the clean, blunt end of a pipette tip, press the gel mold and double check sealing between molds and bottom of well plate. 
	NOTE: Check the seal again right before encapsulation to prevent leakage.</li>
	<li>Passage cultured GBM cells, dissociate to single cells and determine cell concentration as previously described3. 
	NOTE: Some GBM lines cannot be dissociated to single cells. In this case, whole gliomaspheres can be encapsulated. However, prepare dissociated single cells after precise cell counting to improve reproducibility. The protocol for gliomasphere passaging varies among different labs and many of these are likely compatible with hydrogel encapsulation.
	<ol>
		<li>(Recommended) Centrifuge gliomaspheres at 500 x g for 5 min. Remove the supernatant and add 1 mL of cell dissociation enzyme to the cell pellet. Then, incubate for 5 min, gently tapping the tube to agitate.</li>
		<li>Add 4 mL of complete culture medium (50 ng/mL EGF, 20 ng/mL FGF-2, 25 &#181;g/mL heparin, G21 supplement and 1% penicillin/streptomycin in DMEM/F12) to the cells.</li>
		<li>Centrifuge again at 500 x g for 5 min and remove the supernatant. Finally, resuspend the cell pellet in 1 mL of the complete medium and pass suspended cells through a 70 &#181;m cell strainer. (Recommended) wash the strainer with an additional 4 mL of the complete medium to maximize the number of cells recovered.</li>
	</ol>
	</li>
	<li>Estimate the concentration of cells in the suspension using a hemocytometer. Split the cell suspension into&#160;2 centrifuge tubes, where each tube contains ~80,000 cells. Centrifuge at 500 x g for 5 min; generally, 80,000 cells will make up 2 80 &#181;L hydrogels.</li>
	<li>Remove the supernatant and resuspend one pellet in 80 &#181;L of PEG-MAL-RGD solution and a second pellet in 80 &#181;L of PEG-MAL-CYS solution (prepared in step 3.1).</li>
	<li>Using a 200 &#181;L, wide-orifice micropipette tip, dispense 40 &#181;L of HA solution (from step 3.3 above) into each rubber silicone mold (as prepared in step 3.4).</li>
	<li>Using a 200 &#181;L, wide-orifice micropipette tip, mix the 40 &#181;L of PEG-MAL-CYS or PEG-MAL-RGD cell solution with the HA solution in the mold. Pipette up and down quickly no more than 10 times. Repeat for each gel culture being prepared. 
	NOTE: This step takes practice, since initial gelation occurs quickly (within 30 s). Pipette up and down while moving the tip to different locations in molds to ensure even mixing. Always keep the tip below liquid level to avoid formation of air bubbles. Do not mix the solution too many times as gel may get formed inside the micropipette tip. PEG-MAL-CYS and PEG-MAL-RGD can be combined at varying ratios to achieve the desired RGD peptide concentration.</li>
	<li>Place the well-plate containing gel-encapsulated cells into a 37 &#176;C cell culture incubator for 5-10 minutes to ensure completion of the reaction.</li>
	<li>Add 2-2.5 mL of culture medium to each well with formed gels. Use a sterile, 2 &#181;L pipette tip or micro-spatula, to gently separate the mold and gel. Use pre-sterilized forceps to remove the mold from the well plate. Place the well plate back to cell incubator (37 &#176;C and 5%CO2) for culture and future experiments. 
	NOTE: Pull the mold vertically upward to avoid harming the gel cultures. In general, medium in gel cultures should be replaced every 3-4 days. Take care not to aspirate hydrogels when removing medium. If this is an issue, we recommend using a plastic transfer pipette. If bioluminescence imaging to track cell number is planned, GBM cells must be transduced with lentivirus encoding constitutively luciferase expression before encapsulation, as previously described3. For bioluminescence imaging, add 1 mM of D-luciferin to culture medium 1 h prior to luminescence imaging.</li>
</ol>
4. Lysate Preparation for Western Blotting
<ol>
	<li>Chill 1.5 mL microcentrifuge tubes on ice (1 per gel samples). Cool centrifuge to 4 &#176;C.</li>
	<li>Remove medium from well plates. Transfer gels into prechilled microcentrifuge tubes.</li>
	<li>Add 100 &#181;L of RIPA buffer with 1x protease/phosphatase inhibitors.</li>
	<li>Using a 1 mL syringe with a 20 G needle, break up the gel by pushing the whole mixture through needle at least 20 times.</li>
	<li>Flash spin the sample using bench top microcentrifuge and place the sample back on ice.</li>
	<li>Vortex samples briefly every 5 min for a total of 20 min.</li>
	<li>Centrifuge samples at 14000 x g for 15 min at 4 &#176;C.</li>
	<li>Transfer supernatant to new, pre-chilled microcentrifuge tubes and store at -20 &#176;C (short-term) or and -80 &#176;C (long-term). Perform gel electrophoresis using standard procedures, as previously described3.</li>
</ol>
5. Extracting Single Cells from Hydrogel Cultures for Flow Cytometry
<ol>
	<li>Remove medium and transfer gel culture (from step 3.11) into a 1.5 mL microcentrifuge tube.</li>
	<li>Incubate gel with 500 &#181;L of cell dissociation enzyme (e.g., TrypLE Express) at 37 &#176;C for 5 min, occasionally flicking the tube to agitate.</li>
	<li>Transfer the mixture into a 50 mL centrifuge tube with 5 mL of complete medium. Place the tube on ice.</li>
	<li>Attach a 20G needle onto a 10 mL syringe. Gently pull the cell suspension up and down through the needle 8 times.</li>
	<li>Flow the mixture through 70 &#181;m cell strainer into a new 50 mL centrifuge tube. Apply an additional 5 mL of complete medium through the strainer to collect any remaining cells.</li>
	<li>Centrifuge the sample at 400 x g for 5 min. Remove the supernatant and resuspend the pellet in desired buffer for flow cytometry (using standard protocols3).</li>
</ol>
6. Cryopreservation of Hydrogels for Sectioning
<ol>
	<li>Remove medium from gel cultures (from step 3.11).</li>
	<li>Incubate gel cultures with 2 mL of 4% paraformaldehyde (PFA) at 4 &#176;C overnight. 
	CAUTION: PFA is toxic and must be handled carefully.</li>
	<li>On the next day, remove PFA. Add 2 mL of 5% sucrose in PBS to gels and incubate for 1 h at room temperature.</li>
	<li>Replace 5% sucrose solution with 2 mL of 20% sucrose in PBS and incubate for 30 min.</li>
	<li>Replace sucrose solution with 2 mL of fresh 20% sucrose in PBS and incubate for an additional 30 min.</li>
	<li>For a third time, replace the sucrose solution with 2 mL of fresh 20% sucrose in PBS. Incubate at 4 &#176;C overnight.</li>
	<li>Prepare 20% sucrose in Optimal Cutting Temperature (OCT) compound. 
	NOTE: Due to the viscosity of OCT, dissolution of sucrose can take some time (up to overnight). We recommend putting the mixture onto a shaker during dissolution to maintain agitation.</li>
	<li>The next day, remove the 20% sucrose solution and gently pour the 20% sucrose in OCT solution over the gel. Make sure to cover the entire gel. Incubate at 4 &#176;C for 3 h.</li>
	<li>Transfer the gel into the center of an embedding mold using a large, flat spatula; this must be done carefully to avoid damaging the gel.</li>
	<li>Cool 2-methylbutane inside a cryochamber with an excess of dry ice.</li>
	<li>Fill the embedding mold with pure OCT (no sucrose). Fill to just below top edge of mold.</li>
	<li>Freeze the hydrogel sample by immersion in cooled 2-methylbutane and then proceed to sectioning.</li>
	<li>Section the sample using a cryostat; section thickness of 10-18 &#181;m and sectioning temperature of around -26 &#176;C are recommended.</li>
	<li>Perform standard immunostaining procedures on sectioned gel culture, as previously described3. 
	NOTE: PFA is known irritant and carcinogen. Please handle and dispose PFA according to locally applicable standards and regulations.</li>
</ol>
7. Total RNA Extraction from Samples in Hydrogel
Note: Here, we describe a protocol using a commercial kit (see the Table of Materials) to extract total RNA from hydrogel cultured cells. The buffers and all material are available within the kit used.
<ol>
	<li>Remove culture medium. Use a P1000 transfer pipette with wide-bore tip to transfer the hydrogel culture into 1.5 mL microcentrifuge tube.</li>
	<li>Add 350 &#181;L of buffer RLT to the hydrogel culture.</li>
	<li>Using a 20 G needle attached to a 1 mL syringe, shred the gel by pushing the whole mixture through needle at least 20 times.</li>
	<li>Transfer the whole mixture into a homogenizer column placed in a 2 mL collection tube. Centrifuge at 13,000 x g for 2 min.</li>
	<li>Transfer the supernatant into a clean 1.5 mL microcentrifuge tube. Be careful not to disturb the gel precipitate at the bottom.</li>
	<li>Mix the lysate sample with 350 &#181;L of 100% ethanol. Transfer all the sample to a spin column (from the kit) place in a 2 mL collection tube. Centrifuge for 1 min at 13,000 x g.</li>
	<li>For subsequent steps for RNA purification for PCR, follow the general protocol provided by the kit manufacturer. 
	NOTE: Once RNA is extracted, standard protocols for PCR can be used.</li>
</ol>

<ol>
	<li>Xiao, W., Sohrabi, A., Seidlits, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Integrating the glioblastoma microenvironment into engineered experimental models. , (2017).</li><li>Tibbitt, M. W., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogels+as+extracellular+matrix+mimics+for+3D+cell+culture.">Hydrogels as extracellular matrix mimics for 3D cell culture.</a> Biotechnology and bioengineering. 103 (4), 655-663 (2009).</li><li>Xiao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain-mimetic+3d+culture+platforms+allow+investigation+of+cooperative+effects+of+extracellular+matrix+features+on+therapeutic+resistance+in+glioblastoma.">Brain-mimetic 3d culture platforms allow investigation of cooperative effects of extracellular matrix features on therapeutic resistance in glioblastoma.</a> Cancer Research. 78 (5), 1358-1370 (2018).</li><li>Holland, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glioblastoma+multiforme:+the+terminator.">Glioblastoma multiforme: the terminator.</a> Proceedings of the National Academy of Sciences. 97 (12), 6242-6244 (2000).</li><li>Ostrom, Q. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CBTRUS+statistical+report:+primary+brain+and+central+nervous+system+tumors+diagnosed+in+the+United+States+in+2006+-+2010.">CBTRUS statistical report: primary brain and central nervous system tumors diagnosed in the United States in 2006 - 2010.</a> Journal of Neuro-Oncology. 15 (6), 788-796 (2013).</li><li>Bellail, A. C., Hunter, S. B., Brat, D. J., Tan, C., Van Meir, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microregional+extracellular+matrix+heterogeneity+in+brain+modulates+glioma+cell+invasion.">Microregional extracellular matrix heterogeneity in brain modulates glioma cell invasion.</a> International Journal of Biochemistry and Cell Biology. 36 (6), 1046-1069 (2004).</li><li>Zamecnik, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+extracellular+space+and+matrix+of+gliomas.">The extracellular space and matrix of gliomas.</a> Acta Neuropathologica. 110 (5), 435-442 (2005).</li><li>Jadin, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan+expression+in+primary+and+secondary+brain+tumors.">Hyaluronan expression in primary and secondary brain tumors.</a> Annals of translational medicine. 3 (6), (2015).</li><li>Park, J. B., Kwak, H. J., Lee, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+hyaluronan+in+glioma+invasion.">Role of hyaluronan in glioma invasion.</a> Cell adhesion &amp; migration. 2 (3), 202-207 (2008).</li><li>Pedron, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatially+graded+hydrogels+for+preclinical+testing+of+glioblastoma+anticancer+therapeutics.">Spatially graded hydrogels for preclinical testing of glioblastoma anticancer therapeutics.</a> MRS communications. 7 (3), 442-449 (2017).</li><li>Jiglaire, C. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+cultures+of+glioblastoma+in+three-dimensional+hydrogel+maintain+the+original+tumor+growth+behavior+and+are+suitable+for+preclinical+drug+and+radiation+sensitivity+screening.">Ex vivo cultures of glioblastoma in three-dimensional hydrogel maintain the original tumor growth behavior and are suitable for preclinical drug and radiation sensitivity screening.</a> Experimental cell research. 321 (2), 99-108 (2014).</li><li>Florczyk, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+chitosan-hyaluronic+acid+scaffolds+as+a+mimic+of+glioblastoma+microenvironment+ECM.">Porous chitosan-hyaluronic acid scaffolds as a mimic of glioblastoma microenvironment ECM.</a> Biomaterials. 34 (38), 10143-10150 (2013).</li><li>Day, A. J., Prestwich, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan-binding+proteins:+tying+up+the+giant.">Hyaluronan-binding proteins: tying up the giant.</a> Journal of Biological Chemistry. 277 (7), 4585-4588 (2002).</li><li>Wiranowska, M., Tresser, N., Saporta, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+interferon+and+anti-CD44+antibody+on+mouse+glioma+invasiveness+in+vitro.">The effect of interferon and anti-CD44 antibody on mouse glioma invasiveness in vitro.</a> Anticancer Research. 18 (5A), 3331-3338 (1998).</li><li>Charles, N. A., Holland, E. C., Gilbertson, R., Glass, R., Kettenmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+brain+tumor+microenvironment.">The brain tumor microenvironment.</a> GLIA. 59 (8), 1169-1180 (2011).</li><li>Gilg, A. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+hyaluronan+interactions+in+malignant+gliomas+and+their+drug-resistant+multipotent+progenitors.">Targeting hyaluronan interactions in malignant gliomas and their drug-resistant multipotent progenitors.</a> Clinical Cancer Research. 14 (6), 1804-1813 (2008).</li><li>Misra, S., Hascall, V. C., Markwald, R. R., Ghatak, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+between+hyaluronan+and+its+receptors+(CD44,+RHAMM)+regulate+the+activities+of+inflammation+and+cancer.">Interactions between hyaluronan and its receptors (CD44, RHAMM) regulate the activities of inflammation and cancer.</a> Frontiers in immunology. 6, 201 (2015).</li><li>Varga, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+invasion-related+extracellular+matrix+molecules+in+human+glioblastoma+versus+intracerebral+lung+adenocarcinoma+metastasis.">Expression of invasion-related extracellular matrix molecules in human glioblastoma versus intracerebral lung adenocarcinoma metastasis.</a> Zentralblatt fur Neurochirurgie. 71 (4), 173-180 (2010).</li><li>Guo, W., Giancotti, F. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrin+signalling+during+tumour+progression.">Integrin signalling during tumour progression.</a> Nature Reviews Molecular Cell Biology. 5 (10), 816-826 (2004).</li><li>Bello, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=&#945;v&#946;3+and+&#945;v&#946;5+integrin+expression+in+glioma+periphery.">&#945;v&#946;3 and &#945;v&#946;5 integrin expression in glioma periphery.</a> Neurosurgery. 49 (2), 380-390 (2001).</li><li>Chamberlain, M. C., Cloughsey, T., Reardon, D. A., Wen, P. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+treatment+for+glioblastoma:+integrin+inhibition.">A novel treatment for glioblastoma: integrin inhibition.</a> Expert review of neurotherapeutics. 12 (4), 421-435 (2012).</li><li>Chopra, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Augmentation+of+integrin-mediated+mechanotransduction+by+hyaluronic+acid.">Augmentation of integrin-mediated mechanotransduction by hyaluronic acid.</a> Biomaterials. 35 (1), 71-82 (2014).</li><li>Kim, Y., Kumar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD44-mediated+adhesion+to+hyaluronic+acid+contributes+to+mechanosensing+and+invasive+motility.">CD44-mediated adhesion to hyaluronic acid contributes to mechanosensing and invasive motility.</a> Molecular Cancer Research. 12 (10), 1416-1429 (2014).</li><li>Joo, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patient-specific+orthotopic+glioblastoma+xenograft+models+recapitulate+the+histopathology+and+biology+of+human+glioblastomas+in+situ.">Patient-specific orthotopic glioblastoma xenograft models recapitulate the histopathology and biology of human glioblastomas in situ.</a> Cell Reports. 3 (1), 260-273 (2013).</li><li>Oh, Y. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+validation+of+personalized+treatment+strategy+based+on+genetic+characteristics+of+glioblastoma.">Translational validation of personalized treatment strategy based on genetic characteristics of glioblastoma.</a> PloS one. 9 (8), e103327 (2014).</li><li>Pedron, S., Becka, E., Harley, B. A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+glioma+cell+phenotype+in+3D+matrices+by+hyaluronic+acid.">Regulation of glioma cell phenotype in 3D matrices by hyaluronic acid.</a> Biomaterials. 34 (30), 7408-7417 (2013).</li><li>Wang, C., Tong, X., Yang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioengineered+3D+brain+tumor+model+to+elucidate+the+effects+of+matrix+stiffness+on+glioblastoma+cell+behavior+using+PEG-based+hydrogels.">Bioengineered 3D brain tumor model to elucidate the effects of matrix stiffness on glioblastoma cell behavior using PEG-based hydrogels.</a> Molecular pharmaceutics. 11 (7), 2115-2125 (2014).</li><li>Zhu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioactive+modification+of+poly(ethylene+glycol)+hydrogels+for+tissue+engineering.">Bioactive modification of poly(ethylene glycol) hydrogels for tissue engineering.</a> Biomaterials. 31 (17), 4639-4656 (2010).</li><li>Stern, R., Asari, A. A., Sugahara, K. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan+fragments:+an+information-rich+system.">Hyaluronan fragments: an information-rich system.</a> European journal of cell biology. 85 (8), 699-715 (2006).</li><li>Riddles, P. W., Blakeley, R. L., Zerner, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ellman's+reagent:+5,+5&#8242;-dithiobis+(2-nitrobenzoic+acid)-a+reexamination.">Ellman's reagent: 5, 5&#8242;-dithiobis (2-nitrobenzoic acid)-a reexamination.</a> Analytical biochemistry. 94 (1), 75-81 (1979).</li><li>Jin, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+characterization+of+hyaluronic+acid-poly+(ethylene+glycol)+hydrogels+via+Michael+addition:+An+injectable+biomaterial+for+cartilage+repair.">Synthesis and characterization of hyaluronic acid-poly (ethylene glycol) hydrogels via Michael addition: An injectable biomaterial for cartilage repair.</a> Acta biomaterialia. 6 (6), 1968-1977 (2010).</li><li>Ozawa, T., James, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishing+intracranial+brain+tumor+xenografts+with+subsequent+analysis+of+tumor+growth+and+response+to+therapy+using+bioluminescence+imaging.">Establishing intracranial brain tumor xenografts with subsequent analysis of tumor growth and response to therapy using bioluminescence imaging.</a> Journal of visualized experiments. 41, 3-7 (2010).</li></ol>

The authors declare that they have no competing financial interests.

Generation of reproducible data using this 3D culture system requires: 1) consistent batch-to-batch thiolation of HA, 2) practice to achieve efficient mixing of hydrogel precursors and handling of hydrogel cultures to prevent damage and 3) optimized seeding density for each cell line used.
When a particular weight percentage of HA is desired in the hydrogel, the degree of thiolation of HA determines the crosslink density. We recommend using a consistent amount of HA for each thiolation reactio...

Three-dimensional (3D) culture systems recapitulate interactions between cells and their surrounding extracellular matrix (ECM) in native tissues better than their two-dimensional (2D) counterparts1,2. Advancements in tissue engineering have yielded sophisticated, 3D culture platforms that enable controlled investigations into 1) how chemical and physical components of the matrix microenvironment affect cell behaviors and 2) efficacy of new therapeutic strategies for a number of diseases, including cancers2. While in vitro models cannot account for systemic factors, such as endocrine and immune signals, and thus cannot completely replace in vivo models, they provide several advantages including reproducibility, experimental control, affordability and speed. Here, we describe the use of brain-mimetic hydrogels in which 3D cultures of patient-derived brain tumor cells capture many aspects of tumor physiology, in particular, the dynamics of acquiring treatment resistance3. Compared to other in vitro methods, these cultures better represent in vivo tumor models and clinical observations3.
Glioblastoma (GBM) is the most frequent and lethal cancer originating in the brain, with a median survival of only 1-2 years4,5. In recent years, many studies have focused on the influence of tumor matrix environment in GBM6,7,8. The unique brain ECM has been reported to affect GBM cell migration, proliferation, and therapeutic resistance6,7,8,9,10,11,12. Hyaluronic acid (HA) is an abundant glycosaminoglycan (GAG) in the brain, where it interacts with other GAGs and proteoglycans to form a hydrogel-like mesh13. Many studies have reported HA overexpression in GBM tumors and its subsequent effects on cancer progression8,9,13,14,15,16,17. Other ECM components also affect GBM tumor growth and invasion6,7,15,18. For example, fibronectin and vitronectin, which are typically overexpressed in GBM, induce heterodimerization of cell surface integrin receptors through binding to the &#34;RGD&#34; sequence and initiate complex signaling cascades that promote tumor survival19,20,21. Besides biochemical influences, physical properties of the tissue matrix also affect GBM progression22,23.
Continual acquisition of resistance to therapies is one of the main drivers of GBM lethality4. Drugs showing promising results in 2D or gliomasphere models have failed in subsequent animal studies and clinical cases3, indicating that the effects of microenvironmental factors significantly contributed to GBM tumor response1. While animal models can provide a 3D, physiologically appropriate microenvironment to xenografted patient cells and generate clinically relevant outcomes24,25, the complexity of the brain microenvironment in vivo makes it challenging to determine which features, including cell-matrix interactions, are key to specific biological outcomes. Identification of new therapeutic targets will benefit from the use of simplified culture platforms in which biochemical and biophysical properties are defined.
Unlike previously reported biomaterial models of the GBM tumor microenvironment26,27 which have not achieved true orthogonal control over individual biochemical and physical features of the ECM, the biomaterial platform reported here enables decoupling of the contributions of multiple independent features to GBM cell phenotype. Here, we present an HA-based, orthogonally tunable, hydrogel system for 3D culture of patient-derived GBM cells. Hydrogels are formed from two polymer components: 1) biologically active HA and 2) biologically inert polyethylene glycol (PEG). PEG is a widely used biocompatible and hydrophilic material with low protein adsorption and minimal immunogenicity28. Here, approximately 5% of glucuronic acid moieties on HA chains are functionalized with thiol groups to enable crosslinking to a commercially available 4-arm-PEG terminated with maleimides via Michael-type addition. In its most common form in the body, HA exists in high molecular weight (HMW) chains. Here, a low degree of modification of HMW HA (500-750 kDa) helps to preserve native interactions of HA and its cell receptors, including CD4429. By substituting PEG-thiol for HA-thiol while maintaining a constant molar ratio of total thiols to maleimides, HA concentration can be decoupled from mechanical properties of the resulting hydrogels. Furthermore, stoichiometric controls can be used to conjugate cysteine-terminated peptides to a defined average number of maleimide-terminated arms on each 4-arm-PEG. Incorporation of ECM-derived, adhesive peptides enables interactions with integrins on cultured cells, through which biochemical and chemical signals are transduced1. Maleimide-thiol addition occurs very quickly under physiological conditions, minimizing the time required for cell encapsulation and maximizing survival of patient-derived cells. Moreover, hydrogel cultures can be treated like typical tissue specimen and are compatible with standard characterization techniques including Western blotting, flow cytometry, and immunofluorescence staining. The following protocol describes the procedures for fabricating hydrogels, establishing 3D cultures of patient-derived GBM cells and techniques for biochemical analysis.

<table border="0" cellpadding="0" cellspacing="0" style="width:2204px;" width="2203">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">pH meter</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">N/A</td>
			<td style="width:1579px;">Any pH meter that has pH 2-10 sensitivity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Stir plate</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">N/A</td>
			<td>General lab equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Erlenmeyer flask (125mL)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">FB-501-125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">dialysis tubes</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">21-152-14</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">2L polypropylene beaker</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">S01916</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">sodium hyaluronan</td>
			<td style="width:136px;">Lifecore</td>
			<td style="width:121px;">HA700k-5</td>
			<td>500-750 kDa range</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">PI-22980</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">N-hydroxysuccinimide (NHS)</td>
			<td style="width:136px;">sigma aldrich</td>
			<td style="width:121px;">130672-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Hydrochloric acid (HCl)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">SA48-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Sodium hydroxide (NaOH)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">SS266-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Cystamine dihydrochloride</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">AC111770250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Dithiolthreitol (DTT)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">BP172-25</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:368px;">Ellman&#39;s test reagent (5-(3-Carboxy-4-nitrophenyl)disulfanyl-2-nitrobenzoic acid</td>
			<td style="width:136px;">Sigma Aldrich</td>
			<td style="width:121px;">D218200-1G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Deuterated water (deuterium oxide)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">AC166301000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">0.22&#181;m vacuum driven filter</td>
			<td style="width:136px;">CellTreat</td>
			<td style="width:121px;">229706</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Phosphate buffered saline (PBS)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">P32080-100T</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Hanks&#39; balanced salt saline (HBSS)</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">MT-21-022-CV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">4-arm-PEG-maleimide</td>
			<td style="width:136px;">JenKem Technology</td>
			<td style="width:121px;">A7029-1</td>
			<td>molecular weight around 20kDa</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">4-arm-PEG-thiol</td>
			<td style="width:136px;">JenKem Technology</td>
			<td style="width:121px;">A7039-1</td>
			<td>molecular weight around 20kDa</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">L-Cysteine&#160;</td>
			<td style="width:136px;">sigma aldrich</td>
			<td style="width:121px;">C7880-100G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">RGD ECM mimetic peptide</td>
			<td style="width:136px;">Genscript Biotech</td>
			<td style="width:121px;">N/A</td>
			<td>Custom peptide with sequence &#34;GCGYGRGDSPG&#34;, N-terminal should be acetylated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">silicone molds</td>
			<td style="width:136px;">Sigma Aldrich</td>
			<td style="width:121px;">GBL664201-25EA</td>
			<td>Use razor blade to cut into single pieces</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">complete culture medium</td>
			<td style="width:136px;">Various</td>
			<td style="width:121px;">Various</td>
			<td>DMEM/F12 (Thermofisher) with non-serum supplement (G21 from GeminiBio), epidermal growth factor 50ng/mL (Peprotech), fibroblast growth factor 20ng/mL (Pepro Tech) and heprain 25&#181;g/mL (Sigma Aldrich), culture medium varies in different labs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">patient derived GBM cell</td>
			<td style="width:136px;">N/A</td>
			<td style="width:121px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">20G needle</td>
			<td style="width:136px;">BD medical</td>
			<td style="width:121px;">305175</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">1mL syringe</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">14-823-434</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">10mL syringe</td>
			<td style="width:136px;">BD medical</td>
			<td style="width:121px;">302995</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">RIPA Buffer</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">PI-89901</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">protease/phosphatase inhibitor mini tablet</td>
			<td style="width:136px;">sigma aldrich</td>
			<td style="width:121px;">5892970001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">vortex shaker</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">12-814-5Q</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">TrypLE express</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">12604013</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">70&#181;m cell strainer</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">22-363-548</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Paraformaldehyde</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">AC416785000</td>
			<td>Dissolve 4% (w/v) in PBS, keep pH 7.4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">D-sucrose</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">BP220-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Optimal Cutting Temperature (O.C.T.) compound</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">NC9373881</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Cell culture incubator</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">N/A</td>
			<td>Any General One with 5% CO2 and 37C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">fridge/freezer</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">N/A</td>
			<td>Any General Lab equipment with -20C and -80C capacity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Disposable embedding molds</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">12-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Lyapholizer</td>
			<td style="width:136px;">Labconco</td>
			<td style="width:121px;">N/A</td>
			<td>Any -105C freeze dryers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">HEPES</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">BP310-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Amber vial</td>
			<td style="width:136px;">Kimble Chase</td>
			<td style="width:121px;">60912D-2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Wide orifice pipette tips</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">9405120</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">2-methylbutane</td>
			<td style="width:136px;">Thermo Fisher</td>
			<td style="width:121px;">03551-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:368px;">Dry Ice</td>
			<td style="width:136px;">N/A</td>
			<td style="width:121px;">N/A</td>
			<td></td>
		</tr>
	</tbody>
</table>

hyaluronic-acid based hydrogels for 3-dimensional culture of patient-derived glioblastoma cells

Glioblastoma (GBM) is the most common, yet most lethal, central nervous system cancer. In recent years, many studies have focused on how the extracellular matrix (ECM) of the unique brain environment, such as hyaluronic acid (HA), facilitates GBM progression and invasion. However, most in vitro culture models include GBM cells outside of the context of an ECM. Murine xenografts of GBM cells are used commonly as well. However, in vivo models make it difficult to isolate the contributions of individual features of the complex tumor microenvironment to tumor behavior. Here, we describe an HA hydrogel-based, three-dimensional (3D) culture platform that allows researchers to independently alter HA concentration and stiffness. High molecular weight HA and polyethylene glycol (PEG) comprise hydrogels, which are crosslinked via Michael-type addition in the presence of live cells. 3D hydrogel cultures of patient-derived GBM cells exhibit viability and proliferation rates as good as, or better than, when cultured as standard gliomaspheres. The hydrogel system also enables incorporation of ECM-mimetic peptides to isolate effects of specific cell-ECM interactions. Hydrogels are optically transparent so that live cells can be imaged in 3D culture. Finally, HA hydrogel cultures are compatible with standard techniques for molecular and cellular analyses, including PCR, Western blotting and cryosectioning followed by immunofluorescence staining.

For each batch of thiolated HA, the degree of thiolation should be verified using H1-NMR or an Ellman&#39;s test. HA modification using the procedure described here consistently generates ~5% thiolation (defined as the molar ratio of thiols to HA disaccharides) (Figure 1).
Setting up this new culture platform will require each laboratory to perform rigorous testing to ens...

Watch this Scientific Journal Video about Hyaluronic-Acid Based Hydrogels for 3-Dimensional Culture of Patient-Derived Glioblastoma Cells at JoVE.com

Hyaluronic-Acid Based Hydrogels for 3-Dimensional Culture of Patient-Derived Glioblastoma Cells

Here, we present a protocol for three-dimensional culture of patient-derived glioblastoma cells within orthogonally tunable biomaterials designed to mimic the brain matrix. This approach provides an in vitro, experimental platform that maintains many characteristics of in vivo glioblastoma cells typically lost in culture.

Glioblastoma (GBM) is the most common, yet most lethal, central nervous system cancer. In recent years, many studies have focused on how the extracellular ...

hyaluronic-acid-based-hydrogels-for-3-dimensional-culture-patient

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12.9K Views.  University of California, Los Angeles. Here, we present a protocol for three-dimensional culture of patient-derived glioblastoma cells within orthogonally tunable biomaterials designed to mimic the brain matrix. This approach provides an in vitro, experimental platform that maintains many characteristics of in vivo glioblastoma cells typically lost in culture.

Video: Hyaluronic-Acid Based Hydrogels for 3-Dimensional Culture of Patient-Derived Glioblastoma Cells

Micropatterned Surfaces to Study Hyaluronic Acid Interactions with Cancer Cells

Cancer invasion and progression involves a motile cell phenotype, which is under complex regulation by growth factors/cytokines and extracellular matrix (ECM) components within the tumor microenvironment. Hyaluronic acid (HA) is one stromal ECM component that is known to facilitate tumor progression by enhancing invasion, growth, and angiogenesis1. Interaction of HA with its cell surface receptor CD44 induces signaling events that promote tumor cell growth, survival, and migration, thereby increasing metastatic spread2-3. HA is an anionic, nonsulfated glycosaminoglycan composed of repeating units of D-glucuronic acid and D-N-acetylglucosamine. Due to the presence of carboxyl and hydroxyl groups on repeating disaccharide units, native HA is largely hydrophilic and amenable to chemical modifications that introduce sulfate groups for photoreative immobilization 4-5. Previous studies involving the immobilizations of HA onto surfaces utilize the bioresistant behavior of HA and its sulfated derivative to control cell adhesion onto surfaces6-7. In these studies cell adhesion preferentially occurs on non-HA patterned regions.
To analyze cellular interactions with exogenous HA, we have developed patterned functionalized surfaces that enable a controllable study and high-resolution visualization of cancer cell interactions with HA. We utilized microcontact printing (uCP) to define discrete patterned regions of HA on glass surfaces. A "tethering" approach that applies carbodiimide linking chemistry to immobilize HA was used 8. Glass surfaces were microcontact printed with an aminosilane and reacted with a HA solution of optimized ratios of EDC and NHS to enable HA immobilization in patterned arrays. Incorporating carbodiimide chemistry with mCP enabled the immobilization of HA to defined regions, creating surfaces suitable for in vitro applications. Both colon cancer cells and breast cancer cells implicitly interacted with the HA micropatterned surfaces. Cancer cell adhesion occurred within 24 hours with proliferation by 48 hours. Using HA micropatterned surfaces, we demonstrated that cancer cell adhesion occurs through the HA receptor CD44. Furthermore, HA patterned surfaces were compatible with scanning electron microscopy (SEM) and allowed high resolution imaging of cancer cell adhesive protrusions and spreading on HA patterns to analyze cancer cell motility on exogenous HA.

A novel approach that allows the high-resolution analysis of cancer cell interactions with exogenous hyaluronic acid (HA) is described. Patterned surfaces are fabricated by combining carbodiimide chemistry and microcontact printing.

Cancer invasion and progression involves a motile cell phenotype, which is under complex regulation by growth factors/cytokines and extracellular matrix ...

Fabrication of Micropatterned Hydrogels for Neural Culture Systems using Dynamic Mask Projection Photolithography

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the need for 3D environments to represent in vitro experiments which better mimic in vivo qualities 1-3. Studies in fields such as cancer research 4, neural engineering 5, cardiac physiology 6, and cell-matrix interaction7,8have shown cell behavior differs substantially between traditional monolayer cultures and 3D constructs.
Hydrogels are used as 3D environments because of their variety, versatility and ability to tailor molecular composition through functionalization 9-12. Numerous techniques exist for creation of constructs as cell-supportive matrices, including electrospinning13, elastomer stamps14, inkjet printing15, additive photopatterning16, static photomask projection-lithography17, and dynamic mask microstereolithography18. Unfortunately, these methods involve multiple production steps and/or equipment not readily adaptable to conventional cell and tissue culture methods. The technique employed in this protocol adapts the latter two methods, using a digital micromirror device (DMD) to create dynamic photomasks for crosslinking geometrically specific poly-(ethylene glycol) (PEG) hydrogels, induced through UV initiated free radical polymerization. The resulting "2.5D" structures provide a constrained 3D environment for neural growth. We employ a dual-hydrogel approach, where PEG serves as a cell-restrictive region supplying structure to an otherwise shapeless but cell-permissive self-assembling gel made from either Puramatrix or agarose. The process is a quick simple one step fabrication which is highly reproducible and easily adapted for use with conventional cell culture methods and substrates.
Whole tissue explants, such as embryonic dorsal root ganglia (DRG), can be incorporated into the dual hydrogel constructs for experimental assays such as neurite outgrowth. Additionally, dissociated cells can be encapsulated in the photocrosslinkable or self polymerizing hydrogel, or selectively adhered to the permeable support membrane using cell-restrictive photopatterning. Using the DMD, we created hydrogel constructs up to ~1mm thick, but thin film (&lt;200 &mu;m) PEG structures were limited by oxygen quenching of the free radical polymerization reaction. We subsequently developed a technique utilizing a layer of oil above the polymerization liquid which allowed thin PEG structure polymerization.
In this protocol, we describe the expeditious creation of 3D hydrogel systems for production of microfabricated neural cell and tissue cultures. The dual hydrogel constructs demonstrated herein represent versatile in vitro models that may prove useful for studies in neuroscience involving cell survival, migration, and/or neurite growth and guidance. Moreover, as the protocol can work for many types of hydrogels and cells, the potential applications are both varied and vast.

Simple techniques are described for the rapid production of microfabricated neural culture systems using a digital micromirror device for dynamic mask projection lithography on regular cell culture substrates. These culture systems may be more representative of natural biological architecture, and the techniques described could be adapted for numerous applications.

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the ...

A Method for Ovarian Follicle Encapsulation and Culture in a Proteolytically Degradable 3 Dimensional System

The ovarian follicle is the functional unit of the ovary that secretes sex hormones and supports oocyte maturation. In vitro follicle techniques provide a tool to model follicle development in order to investigate basic biology, and are further being developed as a technique to preserve fertility in the clinic1-4. Our in vitro culture system employs hydrogels in order to mimic the native ovarian environment by maintaining the 3D follicular architecture, cell-cell interactions and paracrine signaling that direct follicle development 5. Previously, follicles were successfully cultured in alginate, an inert algae-derived polysaccharide that undergoes gelation with calcium ions6-8. Alginate hydrogels formed at a concentration of 0.25% w/v were the most permissive for follicle culture, and retained the highest developmental competence 9. Alginate hydrogels are not degradable, thus an increase in the follicle diameter results in a compressive force on the follicle that can impact follicle growth10. We subsequently developed a culture system based on a fibrin-alginate interpenetrating network (FA-IPN), in which a mixture of fibrin and alginate are gelled simultaneously. This combination provides a dynamic mechanical environment because both components contribute to matrix rigidity initially; however, proteases secreted by the growing follicle degrade fibrin in the matrix leaving only alginate to provide support. With the IPN, the alginate content can be reduced below 0.25%, which is not possible with alginate alone 5. Thus, as the follicle expands, it will experience a reduced compressive force due to the reduced solids content. Herein, we describe an encapsulation method and an in vitro culture system for ovarian follicles within a FA-IPN. The dynamic mechanical environment mimics the natural ovarian environment in which small follicles reside in a rigid cortex and move to a more permissive medulla as they increase in size11. The degradable component may be particularly critical for clinical translation in order to support the greater than 106-fold increase in volume that human follicles normally undergo in vivo .

A new method for ovarian follicle encapsulation in a 3D fibrin-alginate interpenetrating network is described. This system combines structural support with proteolytic degradation to support the development of immature follicles to produce mature oocytes. This method may be applied to culture cell aggregates to maintain cell-cell contacts without limiting expansion.

The ovarian follicle is the functional unit of the ovary that secretes sex hormones and supports oocyte maturation. In vitro  follicle techniques provide ...

Alginate Hydrogels for Three-Dimensional Organ Culture of Ovaries and Oviducts

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ovarian cancers is still in question and might be either the ovarian surface epithelium (OSE) or the distal epithelium of the fallopian tube fimbriae2,3. Culturing the normal cells as a primary culture in vitro will enable scientists to model specific changes that might lead to ovarian cancer in the distinct epithelium, thereby definitively determining the cell type of origin. This will allow development of more accurate biomarkers, animal models with tissue-specific gene changes, and better prevention strategies targeted to this disease.
Maintaining normal cells in alginate hydrogels promotes short term in vitro culture of cells in their three-dimensional context and permits introduction of plasmid DNA, siRNA, and small molecules. By culturing organs in pieces that are derived from strategic cuts using a scalpel, several cultures from a single organ can be generated, increasing the number of experiments from a single animal. These cuts model aspects of ovulation leading to proliferation of the OSE, which is associated with ovarian cancer formation. Cell types such as the OSE that do not grow well on plastic surfaces can be cultured using this method and facilitate investigation into normal cellular processes or the earliest events in cancer formation4.
Alginate hydrogels can be used to support the growth of many types of tissues5. Alginate is a linear polysaccharide composed of repeating units of &beta;-D-mannuronic acid and &alpha;-L-guluronic acid that can be crosslinked with calcium ions, resulting in a gentle gelling action that does not damage tissues6,7. Like other three-dimensional cell culture matrices such as Matrigel, alginate provides mechanical support for tissues; however, proteins are not reactive with the alginate matrix, and therefore alginate functions as a synthetic extracellular matrix that does not initiate cell signaling5. The alginate hydrogel floats in standard cell culture medium and supports the architecture of the tissue growth in vitro.
A method is presented for the preparation, separation, and embedding of ovarian and oviductal organ pieces into alginate hydrogels, which can be maintained in culture for up to two weeks. The enzymatic release of cells for analysis of proteins and RNA samples from the organ culture is also described. Finally, the growth of primary cell types is possible without genetic immortalization from mice and permits investigators to use knockout and transgenic mice.

Culture of normal cells in their three-dimensional context represents an alternative method to study early events required for cellular transformation and tumorigenesis. This method is used to grow normal ovarian and oviductal cells to study early events in ovarian cancer formation.

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ...

Organotypic Collagen I Assay: A Malleable Platform to Assess Cell Behaviour in a 3-Dimensional Context

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and metastasis of tumor cells. Migration has been studied on glass coverslips in order to make cellular dynamics amenable to investigation by light microscopy. However, it has become clear that many aspects of cell migration depend on features of the local environment including its elasticity, protein composition, and pore size, which are not faithfully represented by rigid two dimensional substrates such as glass and plastic 1. Furthermore, interaction with other cell types, including stromal fibroblasts 2 and immune cells 3, has been shown to play a critical role in promoting the invasion of cancer cells. Investigation at the molecular level has increasingly shown that molecular dynamics, including response to drug treatment, of identical cells are significantly different when compared in vitro and in vivo 4. 
Ideally, it would be best to study cell migration in its naturally occurring context in living organisms, however this is not always possible. Intermediate tissue culture systems, such as cell derived matrix, matrigel, organotypic culture (described here) tissue explants, organoids, and xenografts, are therefore important experimental intermediates. These systems approximate certain aspects of an in vivo environment but are more amenable to experimental manipulation such as use of stably transfected cell lines, drug treatment regimes, long term and high-resolution imaging. Such intermediate systems are especially useful as proving grounds to validate probes and establish parameters required to image the dynamic response of cells and fluorescent reporters prior to undertaking imaging in vivo 5. As such, they can serve an important role in reducing the need for experiments on living animals.

A method is described for the preparation of a 3-dimensional matrix consisting of collagen type I and primary human fibroblasts. This organotypic gel serves as a useful substrate to assess invasive cell migration because it mimics basic features of tissue stroma and is amenable to many forms of microscopy.

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and ...

Cultivation of Human Neural Progenitor Cells in a 3-dimensional Self-assembling Peptide Hydrogel

The influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally neuronal differentiation is of great interest in order to find new methods for cell-based and standardised therapies in neurological disorders or neurodegenerative diseases. 3D structures are expected to provide an environment much closer to the in vivo situation than 2D cultures. In the context of regenerative medicine, the combination of biomaterial scaffolds with neural stem and progenitor cells holds great promise as a therapeutic tool.1-5 Culture systems emulating a three dimensional environment have been shown to influence proliferation and differentiation in different types of stem and progenitor cells. Herein, the formation and functionalisation of the 3D-microenviroment is important to determine the survival and fate of the embedded cells.6-8 Here we used PuraMatrix9,10 (RADA16, PM), a peptide based hydrogel scaffold, which is well described and used to study the influence of a 3D-environment on different cell types.7,11-14 PuraMatrix can be customised easily and the synthetic fabrication of the nano-fibers provides a 3D-culture system of high reliability, which is in addition xeno-free.
Recently we have studied the influence of the PM-concentration on the formation of the scaffold.13 In this study the used concentrations of PM had a direct impact on the formation of the 3D-structure, which was demonstrated by atomic force microscopy. A subsequent analysis of the survival and differentiation of the hNPCs revealed an influence of the used concentrations of PM on the fate of the embedded cells. However, the analysis of survival or neuronal differentiation by means of immunofluorescence techniques posses some hurdles. To gain reliable data, one has to determine the total number of cells within a matrix to obtain the relative number of e.g. neuronal cells marked by &beta;III-tubulin. This prerequisites a technique to analyse the scaffolds in all 3-dimensions by a confocal microscope or a comparable technique like fluorescence microscopes able to take z-stacks of the specimen. Furthermore this kind of analysis is extremely time consuming. 
Here we demonstrate a method to release cells from the 3D-scaffolds for the later analysis e.g. by flow cytometry. In this protocol human neural progenitor cells (hNPCs) of the ReNcell VM cell line (Millipore USA) were cultured and differentiated in 3D-scaffolds consisting of PuraMatrix (PM) or PuraMatrix supplemented with laminin (PML). In our hands a PM-concentration of 0.25% was optimal for the cultivation of the cells13, however the concentration might be adapted to other cell types.12 The released cells can be used for e.g. immunocytochemical studies and subsequently analysed by flow cytometry. This speeds up the analysis and more over, the obtained data rest upon a wider base, improving the reliability of the data.

Here we describe the use of a self-assembling 3-dimensional scaffold to culture human neural progenitor cells. We present a protocol to release the cells from the scaffolds to be analysed subsequently e.g. by flow cytometry. This protocol might be adapted to other cell types to perform detailed mechanistically studies.

The  influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally  neuronal differentiation is of great interest in order to find new ...

Self-reporting Scaffolds for 3-Dimensional Cell Culture

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting 3D cellular construct can often be more relevant to studying the molecular events and cell-cell interactions than similar experiments studied in 2D. To create effective 3D cultures with high cell viability throughout the scaffold the culture conditions such as oxygen and pH need to be carefully controlled as gradients in analyte concentration can exist throughout the 3D construct. Here we describe the methods of preparing biocompatible pH responsive sol-gel nanosensors and their incorporation into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds along with their subsequent preparation for the culture of mammalian cells. The pH responsive scaffolds can be used as tools to determine microenvironmental pH within a 3D cellular construct. Furthermore, we detail the delivery of pH responsive nanosensors to the intracellular environment of mammalian cells whose growth was supported by electrospun PLGA scaffolds. The cytoplasmic location of the pH responsive nanosensors can be utilized to monitor intracellular pH (pHi) during ongoing experimentation.

Biocompatible pH responsive sol-gel nanosensors can be incorporated into poly(lactic-co-glycolic acid) (PLGA) electrospun scaffolds. The produced self-reporting scaffolds can be used for in&#160;situ monitoring of microenvironmental conditions whilst culturing cells upon the scaffold. This is beneficial as the 3D cellular construct can be monitored in real-time without disturbing the experiment.

Culturing cells in 3D on appropriate scaffolds is thought to better mimic the in vivo microenvironment and increase cell-cell interactions. The resulting ...

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy.
The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

We present a protocol for the synthesis of RGD-functionalized hydrogels as devices for cell and drug delivery. The procedure involves copper catalyzed alkyne-azide cycloaddition (CuAAC) between alkyne-modified polyacrylic acid (PAA) and a RGD-azide derivative. The hydrogels are formed using microwave-assisted polycondensation and their physicochemical properties are investigated.

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

Tunable Hydrogels from Pulmonary Extracellular Matrix for 3D Cell Culture

Here we present a method for establishing multiple component cell culture hydrogels for in vitro lung cell culture. Beginning with healthy en bloc lung tissue from porcine, rat, or mouse, the tissue is perfused and submerged in subsequent chemical detergents to remove the cellular debris. Histological comparison of the tissue before and after processing confirms removal of over 95% of double stranded DNA and alpha galactosidase staining suggests the majority of cellular debris is removed. After decellularization, the tissue is lyophilized and then cryomilled into a powder. The matrix powder is digested for 48 hr in an acidic pepsin digestion solution and then neutralized to form the pregel solution. Gelation of the pregel solution can be induced by incubation at 37 &#176;C and can be used immediately following neutralization or stored at 4 &#176;C for up to two weeks. Coatings can be formed using the pregel solution on a non-treated plate for cell attachment. Cells can be suspended in the pregel prior to self-assembly to achieve a 3D culture, plated on the surface of a formed gel from which the cells can migrate through the scaffold, or plated on the coatings. Alterations to the strategy presented can impact gelation temperature, strength, or protein fragment sizes. Beyond hydrogel formation, the hydrogel stiffness may be increased using genipin.

This is a method to create a 3-dimensional cell culture scaffold from pulmonary extracellular matrix. Intact lung is processed into hydrogels that can support the growth of cells in three-dimensions.

Here we present a method for establishing multiple component cell culture hydrogels for in vitro lung cell culture. Beginning with healthy en bloc lung ...