Name: hyaluronic-acid based hydrogels for 3-dimensional culture of patient-derived glioblastoma cells
Uploaded: 2018-08-24T14:30:00
Description: Watch this Scientific Journal Video about Hyaluronic-Acid Based Hydrogels for 3-Dimensional Culture of Patient-Derived Glioblastoma Cells at JoVE.com

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 ...

<ol>
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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. 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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 ...

This method can help answer key questions about glioblastoma tumors and how the extracellular matrix can facilitate treatment resistance. This technique enables modular construction of adaptable 3D cell culture platforms which can be used to culture patient-derived glioblastoma cells in an environment that better approximates native brain. To begin, place clean dry silicone rubber molds into each well of a non-tissue culture treated 12-well plate and use the clean blunt end of a pipette tip to adhere the molds to the bottom of the plate.After checking the seal between the molds and the well bottoms, collect the dissociated gliomaspheres from a glioblastoma cell culture by centrifugation and re-suspend the pellet in one milliliter of cell dissociation enzyme. After five minutes at room temperature, agitate the tube with gentle tapping and arrest the enzymatic reaction with four milliliters of complete medium. Centrifuge the cells again and re-suspend the pellet in one milliliter of fresh complete medium before straining the cells through a 70 micrometer filter.Wash the strainer with an additional four milliliters of complete medium and split the suspension into two aliquots of eight times 10 to the fourth cells per centrifuge tube. Collect the cells by centrifugation and re-suspend one pellet in 80 microliters of freshly prepared polyethylene glycol maleimide or PEG-Mal-RGD and one pellet in 80 microliters of freshly prepared PEG-Mal-CYS solution per mold. Using a 200 microliter wide orifice micropipette tip, add 40 microliters of hyaluronic acid solution into each rubber silicone mold, followed by 40 microliters of either the PEG-Mal-CYS or PEG-Mal-RGD cell solution.Quickly pipetting up and down no more than 10 times per mold to mix. Because of the rapid gelation time, once the two hydrogel components are mixed, it is important to use a wide orifice pipette tip to mix the solutions together quickly yet thoroughly. This step requires practice.Then, place the gel encapsulated cells into a 37 degrees celsius and 5%CO2 cell culture incubator for five to 10 minutes. At the end of the incubation, add two to two and a half milliliters of culture medium to each gel and use a sterile two microliter pipette tip and forceps to gently separate the gels from the sides of the molds. Then, use sterilized forceps to remove the molds from the plate wells and return the plate to the cell incubator.For single cell extraction, at the appropriate experimental endpoint, remove the supernatant from the wells and transfer the gel culture from each well into individual 1.5 milliliter microcentrifuge tubes. Incubate the gels with 500 microliters of cell dissociation enzyme for five minutes at 37 degrees celsius with occasional flicking and transfer the mixtures into individual 50 milliliter centrifuge tubes containing five milliliters of complete medium per tube on ice. Next, use a 10 milliliter syringe equipped with a 20-gauge needle to gently aspirate each cell suspension through the needle tip eight times and filter the mixtures through a 70 micrometer cell strainer into new 50 milliliter centrifuge tubes.When dissociating cells from the hydrogel, make sure to depress the syringe plunger slowly to avoid sheering which can compromise cell membrane integrity. Wash the strainers with five milliliters of fresh medium and collect the cells by centrifugation. Then, re-suspend the pellets in the appropriate flow cytometry buffer for staining and sorting according to standard protocols.To cryopreserve the hydrogels for sectioning, remove the supernatant from the plate wells and incubate the gel cultures with two milliliters of 4%paraformaldehyde at four degrees celsius overnight. The next morning, replace the fixative with two milliliters of 5%sucrose in PBS for a one hour incubation at room temperature. At the end of the incubation, replace the 5%sucrose with two milliliters of 20%sucrose in PBS for two 30 minute incubations at room temperature.After the second 30 minute incubation, refresh the 20%sucrose one more time for a four degrees celsius incubation overnight. The next morning, gently replace the sucrose in PBS solution with 20%sucrose in optimal cutting temperature or OCT medium taking care to cover each gel entirely and place the plate at four degrees celsius for an additional three hours. At the end of the incubation, use a large flat spatula to carefully transfer each gel into the center of an embedding mold and fill the embedding molds with pure OCT to just below the top edges of the molds.Then, freeze the hydrogel samples in cooled 2-methylbutane and section the hydrogel samples on a cryostat according to standard protocols. Seating 80 microliter hydrogels to a four times 10 to the fourth cells per gel density, consistently results in proliferation rates that are comparable to, or better than, gliomasphere cultures. For example, four days after encapsulation, glioblastoma cells in RGD containing hydrogels exhibit an invasive phenotype while cells cultured in hydrogel using PEG-Mal-CYS demonstrate a spherical morphology.These robust cultures allow the evaluation of the effects of reagents like soluble cyclo RGD which competitively disrupt interactions of cells with RGD incorporated into hydrogels. Using bioluminescence imaging, relative numbers of viable cells can be observed in hydrogel cultures, for example, during the course of a 12 day erlotinib treatment. Western blot analysis of cleaved poly ADP polymerase indicates that the relative degree of apoptosis in treated CD44 knockdown cells is higher than that observed in wildtype glioblastoma cells cultured in 0.5%hyaluronic acid hydrogels.In addition, cryosections of hydrogel based 3D cultures preserve extracellular matrix deposited by the cultured cells. For example, allowing analysis of the deposition patterns of type four collagen shifts upon erlotinib treatment. When attempting this procedure, it is important to evaluate the degree of thiolation of each batch of hyaluronic acid.It is also important to make up fresh precursor solutions for each time you do a cell encapsulation experiment. Development of this technique has paved the way for cancer researchers to evaluate the efficacy of new and existing treatments and to explore the mechanisms of treatment resistance and brain cancer progression, all using an ex vivo model.

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

Research

JoVE Journal

Bioengineering

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 ...

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 ...

Ultrathin Porated Elastic Hydrogels As a Biomimetic Basement Membrane for Dual Cell Culture

The basement membrane is a critical component of cellular bilayers that can vary in stiffness, composition, architecture, and porosity. In vitro studies of endothelial-epithelial bilayers have traditionally relied on permeable support models that enable bilayer culture, but permeable supports are limited in their ability to replicate the diversity of human basement membranes. In contrast, hydrogel models that require chemical synthesis are highly tunable and allow for modifications of both the material stiffness and the biochemical composition via incorporation of biomimetic peptides or proteins. However, traditional hydrogel models are limited in functionality because they lack pores for cell-cell contacts and functional in vitro migration studies. Additionally, due to the thickness of traditional hydrogels, incorporation of pores that span the entire thickness of hydrogels has been challenging. In the present study, we use poly-(ethylene-glycol) (PEG) hydrogels and a novel zinc oxide templating method to address the previous shortcomings of biomimetic hydrogels. As a result, we present an ultrathin, basement membrane-like hydrogel that permits the culture of confluent cellular bilayers on a customizable scaffold with variable pore architectures, mechanical properties, and biochemical composition.

Current bilayer culture models do not allow for functional in vitro studies that mimic in vivo microenvironments. Using polyethylene glycol and a zinc oxide templating method, this protocol describes the development of an ultrathin biomimetic basement membrane with tunable stiffness, porosity, and biochemical composition that closely mimics in vivo extracellular matrices.

The basement membrane is a critical component of cellular bilayers that can vary in stiffness, composition, architecture, and porosity. In vitro studies ...