Name: tunable hydrogels from pulmonary extracellular matrix for 3d cell culture
Uploaded: 2017-01-17T13:00:00
Description: Watch this Scientific Journal Video about Tunable Hydrogels from Pulmonary Extracellular Matrix for 3D Cell Culture at JoVE.com

We would like to thank Smithfield farms for donating the intact porcine lung tissue. We would also like to thank Dr. Hu Yang, Dr. Christina Tang and the VCU Plastic Surgery Department for allowing us to use their equipment. Hydrogel and tissue samples were prepared for SEM at the VCU Department of Anatomy and Neurobiology Microscopy Facility supported, in part, by funding from NIH-NINDS Center Core Grant 5 P30 NS047463 and, in part, by funding form NIH-NCI Cancer Center Support Grant P30 CA016059. SEM imaging of samples at the VCU Nanotechnology Core Characterization Facility (NCC). This work was funded by the National Science Foundation, CMMI 1351162.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Solution</td>
			<td>Sterile Filter</td>
			<td>Directions</td>
		</tr>
		<tr>
			<td>DiH2O</td>
			<td>Yes</td>
			<td>DiH2O; Sterile filtered</td>
		</tr>
		<tr>
			<td>0.1% Triton X-100 Solution</td>
			<td>Yes</td>
			<td>Under fume hood add 100 &#181;l Triton-X 100 Solution to 100 ml DiH2O and agitate until dissolved; 
			sterile filter.</t...

<ol>
	<li>Lee, J., Cuddihy, M., Kotov, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Three-Dimensional Cell Culture Matrices: State of the Art. 14, (2008).</li><li>Haycock, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> 3D Cell Culture. , (2011).</li><li>Walker, J. M., Ed, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Epithelial cell culture protocols. , (2012).</li><li>Badylak, S. F., Freytes, D. O., Gilbert, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+as+a+biological+scaffold+material:+Structure+and+function.">Extracellular matrix as a biological scaffold material: Structure and function.</a> Acta Biomater. 5 (1), 1-13 (2009).</li><li>Koo, H. -. J., Lim, K. -. H., Jung, H. -. J., Park, E. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-inflammatory+evaluation+of+gardenia+extract,+geniposide+and+genipin.">Anti-inflammatory evaluation of gardenia extract, geniposide and genipin.</a> J. Ethnopharmacol. 103 (3), 496-500 (2006).</li><li>Jeffords, M. E., Wu, J., Shah, M., Hong, Y., Zhang, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tailoring+Material+Properties+of+Cardiac+Matrix+Hydrogels+to+Induce+Endothelial+Differentiation+of+Human+Mesenchymal+Stem+Cells.">Tailoring Material Properties of Cardiac Matrix Hydrogels to Induce Endothelial Differentiation of Human Mesenchymal Stem Cells.</a> ACS Appl. Mater. Interfaces. 7 (20), 11053-11061 (2015).</li><li>Suckow, M. A., Voytik-Harbin, S. L., Terril, L. A., Badylak, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+bone+regeneration+using+porcine+small+intestinal+submucosa.">Enhanced bone regeneration using porcine small intestinal submucosa.</a> J. Invest. Surg. 12 (5), 277-287 (1998).</li><li>Brown, B. N., Badylak, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+matrix+as+an+inductive+scaffold+for+functional+tissue+reconstruction.">Extracellular matrix as an inductive scaffold for functional tissue reconstruction.</a> Transl. Res. J. Lab. Clin. Med. 163 (4), 268-285 (2014).</li><li>Pouliot, R. 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=Development+and+characterization+of+a+naturally+derived+lung+extracellular+matrix+hydrogel.">Development and characterization of a naturally derived lung extracellular matrix hydrogel.</a> J.Biomed.Mater.Res.A. , (2016).</li><li>Price, A. P., England, K. A., Matson, A. M., Blazar, B. R., Panoskaltsis-Mortari, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+decellularized+lung+bioreactor+system+for+bioengineering+the+lung:+the+matrix+reloaded.">Development of a decellularized lung bioreactor system for bioengineering the lung: the matrix reloaded.</a> Tissue Eng. Part A. 16 (8), 2581-2591 (2010).</li><li>Freytes, D. O., Martin, J., Velankar, S. S., Lee, A. S., Badylak, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+rheological+characterization+of+a+gel+form+of+the+porcine+urinary+bladder+matrix.">Preparation and rheological characterization of a gel form of the porcine urinary bladder matrix.</a> Biomaterials. 29 (11), 1630-1637 (2008).</li><li>Tilghman, R. 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=Matrix+rigidity+regulates+cancer+cell+growth+and+cellular+phenotype.">Matrix rigidity regulates cancer cell growth and cellular phenotype.</a> PloS One. 5 (9), e12905 (2010).</li><li>Ratner, B. D., Bryant, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomaterials:+where+we+have+been+and+where+we+are+going.">Biomaterials: where we have been and where we are going.</a> Annu. Rev. Biomed. Eng. 6, 41-75 (2004).</li><li>Fridman, R., Benton, G., Aranoutova, I., Kleinman, H. K., Bonfil, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+initiation+and+growth+of+tumor+cell+lines,+cancer+stem+cells+and+biopsy+material+in+mice+using+basement+membrane+matrix+protein+(Cultrex+or+Matrigel)+co-injection.">Increased initiation and growth of tumor cell lines, cancer stem cells and biopsy material in mice using basement membrane matrix protein (Cultrex or Matrigel) co-injection.</a> Nat Protoc. 7 (6), 1138-1144 (2012).</li><li>Zhang, W. -. 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=The+reconstruction+of+lung+alveolus-like+structure+in+collagen-matrigel/microcapsules+scaffolds+in+vitro.">The reconstruction of lung alveolus-like structure in collagen-matrigel/microcapsules scaffolds in vitro.</a> J. Cell. Mol. Med. 15 (9), 1878-1886 (2011).</li><li>Booth, A. 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=Acellular+Normal+and+Fibrotic+Human+Lung+Matrices+as+a+Culture+System+for+In+Vitro+Investigation.">Acellular Normal and Fibrotic Human Lung Matrices as a Culture System for In Vitro Investigation.</a> Am. J. Respir. Crit. Care Med. 186 (9), 866-876 (2016).</li><li>Matsuda, 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=Evidence+for+human+lung+stem+cells.">Evidence for human lung stem cells.</a> N. Engl. J. Med. 364 (19), 1795-1806 (2011).</li><li>Zuo, 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=p63+Krt5++distal+airway+stem+cells+are+essential+for+lung+regeneration.">p63+Krt5+ distal airway stem cells are essential for lung regeneration.</a> Nature. 517 (7536), 616-620 (2015).</li><li>Keane, T. J., Londono, R., Turner, N. J., Badylak, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consequences+of+ineffective+decellularization+of+biologic+scaffolds+on+the+host+response.">Consequences of ineffective decellularization of biologic scaffolds on the host response.</a> Biomaterials. 33 (6), 1771-1781 (2012).</li><li>Neill, J. D., 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=Decellularization+of+human+and+porcine+lung+tissues+for+pulmonary+tissue+engineering.">Decellularization of human and porcine lung tissues for pulmonary tissue engineering.</a> Ann Thorac Surg. 96 (3), 1046-1055 (2013).</li></ol>

One of the integral aspects of biology is the self-organization of molecules into hierarchal structures that perform a specific task.13 In the lab, self-assembly depends on numerous factors such as salt concentration, pH, and digestion duration. As shown, a self-organizing hydrogel forms when solubilized proteins return to a physiological temperature. The hydrogel formed is capable of promoting cellular attachment and proliferation in vitro.
Cellular response to biophysical...

Translating in vitro results to the clinic is one of the most challenging issues facing biomedical researchers. In vitro research on tissue culture plastic is easier, more convenient, and maintains high cell viability.1 This approach is a reasonable starting point, but the results have limited clinical translation. Increasingly, laboratories are incorporating three-dimensional constructs to replace the traditional two-dimensional methods. Reviews are available for many three-dimensional environments, from biological scaffolds to polymeric scaffolds.2,3
Biological frameworks can mimic characteristics of in vivo environments as they contain many of the protein and glycosaminoglycan components of the native matrix and provide familiar binding sites for cells to attach to and recognize. Extracellular matrix (ECM) derived materials have been shown to be capable scaffolds for cell attachment and proliferation.4 One challenge that limits the application of ECM hydrogel platforms stems from their inherently weak mechanical properties following gelation. Native tissue often has mechanical properties that are magnitudes higher than hydrogels. Non-toxic crosslinking agents can increase the mechanical properties of hydrogels to better mimic the native tissue environment. Genipin is a non-toxic, natural crosslinker derived from Gardenia plants with the ability to closely tailor mechanical properties of ECM with changes in genipin concentration5,6. 
Nearly all cells in the body exist in, and organize on, ECM that they either produce or maintain. New focus on the universal importance of ECM in the organization, condition, and function in every organ or system has sparked the production of matrix based platforms for in vitro investigation. Porcine small intestine submucosa is the most extensively studied naturally-derived scaffold, and it has been used to regenerate tendons, ligaments, skeletal muscle4, and even bone7. Matrices from other organs and donor species have also demonstrated good tissue regeneration potential. The use of foreign ECM components causes minimal issues with immunomodulation. After elimination of host cellular matter, the remaining ECM will be similar in amino acid content and organization to all other mammalian species8. There is a growing line of thinking that the best way to examine cell-ECM interactions in vitro is to utilize organ-specific ECM scaffolds. Each organ provides a unique composition of proteins and proteoglycans to create cellular niches. Niches provide structural, functional and even the enzymatic breakdown of the extracellular matrix contributing to biophysical signaling. To attain an in vitro microenvironment most similar to the in vivo microenvironment, use of tissue specific ECM would optimize the cellular niches for research. 
The goal of this protocol is to provide a method for establishing a hydrogel scaffold unique to the lung ECM. This method provides a platform for in vitro research on lung cell-ECM interactions.

<table border="0" cellpadding="0" cellspacing="0" width="841">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Triton X-100&#160;</td>
			<td style="width:135px;">Fisher Scientific</td>
			<td style="width:119px;">BP151-100</td>
			<td style="width:371px;">Use in fume hood with eye protection and gloves.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Deoxycholate</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">D6750-100g</td>
			<td>Use with eye protection and gloves.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium Sulfate</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">M7506-500g</td>
			<td>None</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Calcium Chloride</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td style="width:119px;">C1016-500g</td>
			<td>None</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td>D5025-150KU</td>
			<td>None</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HCl</td>
			<td>Sigma-Aldrich</td>
			<td>258148-500ML</td>
			<td>Use with eye protection and gloves.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pepsin</td>
			<td style="width:135px;">Sigma-Aldrich</td>
			<td>P6887-5G</td>
			<td>Use in fume hood with eye protection and gloves.</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Sodium Hydroxide</td>
			<td style="width:135px;">Fisher Scientific</td>
			<td style="width:119px;">BP359-500</td>
			<td>Use with eye protection and gloves.</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Genipin</td>
			<td style="width:135px;">Wako Chemicals</td>
			<td style="width:119px;">078-03021</td>
			<td>Use in fume hood with eye protection and gloves.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PBS 10x</td>
			<td style="width:135px;">Quality Biological</td>
			<td>119-069-151</td>
			<td>None</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS</td>
			<td style="width:135px;">VWR</td>
			<td>45000-448</td>
			<td>None</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filter Paper</td>
			<td>Whatman</td>
			<td align="right">8519</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hand pump</td>
			<td style="width:135px;">Fisher Scientific</td>
			<td>10-239-1</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Graduate Beaker</td>
			<td style="width:135px;">VitLab</td>
			<td align="right" style="width:119px;">445941</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cryomill</td>
			<td>SPEX</td>
			<td>6700</td>
			<td>Use cryogloves and eye protection.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lyophilizer</td>
			<td>FTS FlexiDry</td>
			<td></td>
			<td>Use gloves.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rheometer</td>
			<td>Discovery</td>
			<td>HR-2</td>
			<td>Use gloves and eye protection.</td>
		</tr>
	</tbody>
</table>

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.

Using this method, we have produced hydrogels from normal pig, rat, and mouse lungs (Figure 1). Processed lungs provide an estimated 5 mg, 40 mg, and 10 g of ECM powder respectively. An overview of the process is shown in Figure 2. Key visualizations during the process include: white appearance of the lungs after rinsing deoxycholate; after the pregel formation, the solution should be opaque and the solution should appear homogenous for months if stored a...

Watch this Scientific Journal Video about Tunable Hydrogels from Pulmonary Extracellular Matrix for 3D Cell Culture at JoVE.com

Tunable Hydrogels from Pulmonary Extracellular Matrix for 3D Cell Culture

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 ...

The overall goal of this method to make customized hydrogels is to study cells and culture conditions that replicate the complexity of the lung extracellular matrix. This method can help answer key questions in the pulmenary field such as how do lung cells interact with ECM under healthy and pathalogical conditions. The main advantage of this technique is that the lung ECM hydrogels are tailorable to your application in 2D or 3D culture.Generally, individuals new to this method will struggle because of the complexity of the decellularization techniques, sometimes requiring multiple people and attention to detail to optimize the amount of viable tissue. For this protocol, have a porcine lung ready for decellularization. Details on its preparation can be found in the text protocol.Once the lung is prepared, use a hand pump that is cannulated to fit the pulmonary artery. First, perfuse around one liter of water into the vasculature, and then 1.5 liters into the trachea. Do this three times, increasing the volume of water perfused as cellular debris is removed.Next, perfuse the tissue with Triton X-100, also using the hand pump. Then, submerge the tissue in a bath of Triton X-100 solution at four degrees Celsius for 24 hours. After 24 hours, rinse the vasculature and trachea three times with distilled water.After the rinses, use the hand pump to perfuse the tissue with deoxycholate. And then submerge tissue into deoxycholate for 24 hours at four degrees Celsius. The next day, rinse the tissue three times with distilled water, as before.After the rinses, use the hand pump to perfuse the tissue with filtered sodium chloride. Then submerge the tissue in filtered sodium chloride for an hour at four degrees Celsius. After the bath, perfuse the vasculature and trachea three times with distilled water to rinse.After the rinses, perfuse the tissue with DNase solution, and then submerge it in DNase solution for one hour at four degrees Celsius. After an hour, perfuse the vasculature and trachea five times using PBS, not water. Now, only using opaque white tissue, dissect away all the tubules that are two millimeters in diameter or larger.They are primarily found around the hilum and medial portions of the lungs. Leave the respiratory zones intact, which are mostly in the periphery. After removing the tubules, dissect the tissue into one inch sections or smaller.The orientation of these blocks is not important. After draining the tissue blocks, transfer them to a 50 milliliter conical tube and freeze them at 80 degrees Celsius. A few blocks can be set aside for histology to confirm the removal of the cells and debris.To process the lung tissue into decellularized powder, replace the cover on the frozen tissue tube with a filter paper, and secure this with an elastic band. Then, lyophilize the tissue until all the excess liquid is gone using a freeze dryer according to manufacture's directions. Then, store the tissue at 80 degrees Celsius until it can be milled.To ready the mill, first load it with liquid nitrogen, leaving room for the mill tube. Next, from the mill tube, remove the magnetic mill bar and cover the bottom of the tube with tissue. Then, replace the mill bar and loosely pack in more tissue to fill the tube.Then, close the mill tube, place it in the freezer/mill, and fill the mill with liquid nitrogen up to its maximum capacity. Now, run the mill for approximately five minutes with an impaction rate of about 600 per minute. Then, store the decellularized powder at 80 degrees Celsius, until needed.To make the pre-gel material, add decellularized tissue powder and pepsin to a conical tube. Then add 0.01 molar hydrochloric acid to the tube, for a final concentration of 1%decellularized tissue powder, and 0.01%pepsin. Keep this solution under constant agitation at room temperature for 48 hours to digest the tissues.After 48 hours, put the solution on ice for five minutes. Now adjust the solution's pH to 7.4 using cold 0.1 molar sodium hydroxide, and then bring the solution's PBS concentration to 1X by adding 10X PBS. We have some experience with altering times and the pH of the pre-gel.There is some flexibility in the range that can be used, but the properties can change dramatically if the procedure is altered in minor ways. The solution is not considered pre-gel and it can be used to coat non-treated plates to form hydrogels to form cells on, to form hydrogels to form cells in, or it can be further modified before forming hydrogels to increase the hydrogels'rigidity. To culture cells on two-dimensional micro-porous gel coating, add 20 microliters of pre-gel solution to wells of a 96-well non-treated tissue culture plate.Then, refrigerate the plate overnight at four degrees Celsius so proteins are absorbed onto the plate. The next day, aspirate the pre-gel solution and rinse the wells with PBS. Then, add 3, 200 cells to each well and top up the media volume in each well to 100 microliters.The plates can then be incubated. For a three-dimensional cell culture with cells inside the micro-porous gel, resuspend the cells of interest at one million per milliliter in pre-gel solution. Then, quickly dispense 16 microliters of the cell suspension into each well of a 96-well plate to form a 3D cell culture that is about 500 microns thick.The gel will form in 30 minutes once incubated at 37 degrees Celsius. After the gels form, add media to the wells up to the 100 microliter marks. For a three-dimensional cell culture with cells on top of the micro-porous gel, add the 100 microliters of the pre-gel solution to the wells of an untreated 96-well plate.Then, incubate the plate at 37 degrees Celsius for 30 minutes for gelation. Once the gels form, add 3, 200 cells in 100 microliter media on top of the hydrogels and proceed to incubate the plate. Hydrogels were produced from normal pig, rat, and mouse lungs using the described method.Rheological testing confirmed that over 90%of the gelling occurs in the first minutes after reaching 37 degrees Celsius. The formed hydrogels were stable for long periods in PBS, but cell attachment and proliferation may change with time. The pre-gel solution was tested as a coding to improve cell attachment.Human umbilical vein endothelial cell attachment and proliferation was measured using an MTTSA. Improvements were observed by coating the wells with ECM. In making 3D gels, adding Genipin increased the hydrogel crosslinking.Using frequency sweeps on a rheometer, hydrogel stiffness was directly correlated to the Genipin concentration, with the median and most relevant concentration being 0.01%Testing the more rigid gels, cell proliferation was measured to be higher by an MTTSA on the gels with increased crosslinking. Once mastered, decellularization can be performed in eight hours over four days. The pre-gel solution can be made in one hour over two days, and the gel formation can be accomplished in two hours over two days.Following this procedure, other methods like AFM, western blots, staining, and immunohistochemistry can be performed in order to answer additional questions, like elastic modulus, protein composition, and cellular response to the material.

tunable-hydrogels-from-pulmonary-extracellular-matrix-for-3d-cell

Research

JoVE Journal

Bioengineering

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 ...

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

The tissue-specific extracellular matrix (ECM) is a key mediator of cell function. This article describes methods for synthesizing pure ECM-derived foams and microcarriers that are stable in culture without the need for chemical crosslinking for applications in advanced 3D in vitro cell culture models or as pro-regenerative bioscaffolds.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus ...

Fabricating a Kidney Cortex Extracellular Matrix-Derived Hydrogel

Extracellular matrix (ECM) provides important biophysical and biochemical cues to maintain tissue homeostasis. Current synthetic hydrogels offer robust mechanical support for in vitro cell culture but lack the necessary protein and ligand composition to elicit physiological behavior from cells. This manuscript describes a fabrication method for a kidney cortex ECM-derived hydrogel with proper mechanical robustness and supportive biochemical composition. The hydrogel is fabricated by mechanically homogenizing and solubilizing decellularized human kidney cortex ECM. The matrix preserves native kidney cortex ECM protein ratios while also enabling gelation to physiological mechanical stiffnesses. The hydrogel serves as a substrate upon which kidney cortex-derived cells can be maintained under physiological conditions. Furthermore, the hydrogel composition can be manipulated to model a diseased environment which enables the future study of kidney diseases.

Here we present a protocol to fabricate a kidney cortex extracellular matrix-derived hydrogel to retain the native kidney extracellular matrix (ECM) structural and biochemical composition. The fabrication process and its applications are described. Finally, a perspective on using this hydrogel to support kidney-specific cellular and tissue regeneration and bioengineering is discussed.

Extracellular matrix (ECM) provides important biophysical and biochemical cues to maintain tissue homeostasis. Current synthetic hydrogels offer robust ...

Production of Extracellular Matrix Fibers via Sacrificial Hollow Fiber Membrane Cell Culture

Engineered scaffolds derived from extracellular matrix (ECM) have driven significant interest in medicine for their potential in expediting wound closure and healing. Extraction of extracellular matrix from fibrogenic cell cultures in vitro has potential for generation of ECM from human- and potentially patient-specific cell lines, minimizing the presence of xenogeneic epitopes which has hindered the clinical success of some existing ECM products. A significant challenge in in vitro production of ECM suitable for implantation is that ECM production by cell culture is typically of relatively low yield. In this work, protocols are described for the production of ECM by cells cultured within sacrificial hollow fiber membrane scaffolds. Hollow fiber membranes are cultured with fibroblast cell lines in a conventional cell medium and dissolved after cell culture to yield continuous threads of ECM. The resulting ECM fibers produced by this method can be decellularized and lyophilized, rendering it suitable for storage and implantation.

The goal of this protocol is production of whole extracellular matrix fibers targeted for wound repair which are suitable for preclinical evaluation as part of a regenerative scaffold implant. These fibers are produced by the culture of fibroblasts on hollow fiber membranes and extracted by dissolution of the membranes.

Engineered scaffolds derived from extracellular matrix (ECM) have driven significant interest in medicine for their potential in expediting wound closure ...

Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) culture systems. However, measurement of cell function in 3D culture is often more challenging. Many biological assays require retrieval of cellular material which can be difficult in 3D cultures. One way to address this challenge is to develop new materials that enable measurement of cell function within the material. Here, a method is presented for measurement of cellular matrix metalloproteinase (MMP) activity in 3D hydrogels in a 96-well format. In this system, a poly(ethylene glycol) (PEG) hydrogel is functionalized with a fluorogenic MMP cleavable sensor. Cellular MMP activity is proportional to fluorescence intensity and can be measured with a standard microplate reader. Miniaturization of this assay to a 96-well format reduced the time required for experimental set up by 50% and reagent usage by 80% per condition as compared to the previous 24-well version of the assay. This assay is also compatible with other measurements of cellular function. For example, a metabolic activity assay is demonstrated here, which can be conducted simultaneously with MMP activity measurements within the same hydrogel. The assay is demonstrated with human melanoma cells encapsulated across a range of cell seeding densities to determine the appropriate encapsulation density for the working range of the assay. After 24 h of cell encapsulation, MMP and metabolic activity readouts were proportional to cell seeding density. While the assay is demonstrated here with one fluorogenic degradable substrate, the assay and methodology could be adapted for a wide variety of hydrogel systems and other fluorescent sensors. Such an assay provides a practical, efficient and easily accessible 3D culturing platform for a wide variety of applications.

Here, a protocol is presented for encapsulating and culturing cells in poly(ethylene glycol) (PEG) hydrogels functionalized with a fluorogenic matrix metalloproteinase (MMP)-degradable peptide. Cellular MMP and metabolic activity are measured directly from the hydrogel cultures using a standard microplate reader.

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) ...

Pancreatic Tissue-Derived Extracellular Matrix Bioink for Printing 3D Cell-Laden Pancreatic Tissue Constructs

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary complications. However, islet transplantation still has several limitations such as the low viability of transplanted islets due to poor islet engraftment and hostile environments. In addition, the insulin-producing cells differentiated from human pluripotent stem cells have limited ability to secrete sufficient hormones that can regulate the blood glucose level; therefore, improving the maturation by culturing cells with proper microenvironmental cues is strongly required. In this article, we elucidate protocols for preparing a pancreatic tissue-derived decellularized extracellular matrix (pdECM) bioink to provide a beneficial microenvironment that can increase glucose sensitivity of pancreatic islets, followed by describing the processes for generating 3D pancreatic tissue constructs using a microextrusion-based bioprinting technique.

Decellularized extracellular matrix (dECM) can provide suitable microenvironmental cues to recapitulate the inherent functions of target tissues in an engineered construct. This article elucidates the protocols for the decellularization of pancreatic tissue, evaluation of pancreatic tissue-derived dECM bioink, and generation of 3D pancreatic tissue constructs using a bioprinting technique.

The transplantation of pancreatic islets is a promising treatment for patients who suffer from type 1 diabetes accompanied by hypoglycemia and secondary ...

A Human 3D Extracellular Matrix-Adipocyte Culture Model for Studying Matrix-Cell Metabolic Crosstalk

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of cellular function. The ECM plays a particularly important role in adipose tissue function in obesity, and alterations in adipose tissue ECM deposition and composition are associated with metabolic disease in mice and humans. Tractable in vitro models that permit dissection of the roles of the ECM and cells in contributing to global tissue phenotype are sparse. We describe a novel 3D in vitro model of human ECM-adipocyte culture that permits study of the specific roles of the ECM and adipocytes in regulating adipose tissue metabolic phenotype. Human adipose tissue is decellularized to isolate ECM, which is subsequently repopulated with preadipocytes that are then differentiated within the ECM into mature adipocytes. This method creates ECM-adipocyte constructs that are metabolically active and retain characteristics of the tissues and patients from which they are derived. We have used this system to demonstrate disease-specific ECM-adipocyte crosstalk in human adipose tissue. This culture model provides a tool for dissecting the roles of the ECM and adipocytes in contributing to global adipose tissue metabolic phenotype and permits study of the role of the ECM in regulating adipose tissue homeostasis.

We describe a 3D human extracellular matrix-adipocyte in vitro culture system that permits dissection of the roles of the matrix and adipocytes in contributing to adipose tissue metabolic phenotype.

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of ...

Preparation of Tunable Extracellular Matrix Microenvironments to Evaluate Schwann Cell Phenotype Specification

Traumatic peripheral nervous system (PNS) injuries currently lack suitable treatments to regain full functional recovery. Schwann cells (SCs), as the major glial cells of the PNS, play a vital role in promoting PNS regeneration by dedifferentiating into a regenerative cell phenotype following injury. However, the dedifferentiated state of SCs is challenging to maintain through the time-period needed for regeneration and is impacted by changes in the surrounding extracellular matrix (ECM). Therefore, determining the complex interplay between SCs and differing ECM to provide cues of regenerative potential of SCs is essential. To address this, a strategy was created where different ECM proteins were adsorbed onto a tunable polydimethylsiloxane (PDMS) substrate which provided a platform where stiffness and protein composition can be modulated. SCs were seeded onto the tunable substrates and critical cellular functions representing the dynamics of SC phenotype were measured. To illustrate the interplay between SC protein expression and cellular morphology, differing seeding densities of SCs in addition to individual microcontact printed cellular patterns were utilized and characterized by immunofluorescence staining and western blot. Results showed that cells with a smaller spreading area and higher extent of cellular elongation promoted higher levels of SC regenerative phenotypic markers. This methodology not only begins to unravel the significant relationship between the ECM and cellular function of SCs, but also provides guidelines for the future optimization of biomaterials in peripheral nerve repair.

This methodology aims to illustrate the mechanisms by which extracellular matrix cues such as substrate stiffness, protein composition and cell morphology regulate Schwann cell (SC) phenotype.

Traumatic peripheral nervous system (PNS) injuries currently lack suitable treatments to regain full functional recovery. Schwann cells (SCs), as the ...

Microgel-Extracellular Matrix Composite Support for the Embedded 3D Printing of Human Neural Constructs

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication of soft tissue constructs. However, granular gel formulations have been restricted to a limited number of biomaterials that allow for the cost-effective generation of large amounts of hydrogel microparticles. Therefore, granular gel support media have generally lacked the cell-adhesive and cell-instructive functions found in the native extracellular matrix (ECM).
To address this, a methodology has been developed for the generation of self-healing annealable particle-extracellular matrix (SHAPE) composites. SHAPE composites consist of a granular phase (microgels) and a continuous phase (viscous ECM solution) that, together, allow for both programmable high-fidelity printing and an adjustable biofunctional extracellular environment. This work describes how the developed methodology can be utilized for the precise biofabrication of human neural constructs.
First, alginate microparticles, which serve as the granular component in the SHAPE composites, are fabricated and combined with a collagen-based continuous component. Then, human neural stem cells are printed inside the support material, followed by the annealing of the support. The printed constructs can be maintained for weeks to allow the differentiation of the printed cells into neurons. Simultaneously, the collagen continuous phase allows for axonal outgrowth and the interconnection of regions. Finally, this works provides information on how to perform live-cell fluorescence imaging and immunocytochemistry to characterize the 3D-printed human neural constructs.

This work describes a protocol for the freeform embedded 3D printing of neural stem cells inside self-healing annealable particle-extracellular matrix composites. The protocol enables the programmable patterning of interconnected human neural tissue constructs with high fidelity.

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication ...

Phototunable Bioprinted Hydrogels to Probe Cellular Responses to ECM Stiffening

3D Bioprinting Phototunable Hydrogels to Study Fibroblast Activation

Phototunable hydrogels can transform spatially and temporally in response to light exposure. Incorporating these types of biomaterials in cell-culture platforms and dynamically triggering changes, such as increasing microenvironmental stiffness, enables researchers to model changes in the extracellular matrix (ECM) that occur during fibrotic disease progression. Herein, a method is presented for 3D bioprinting a phototunable hydrogel biomaterial capable of two sequential polymerization reactions within a gelatin support bath. The technique of Freeform Reversible Embedding of Suspended Hydrogels (FRESH) bioprinting was adapted by adjusting the pH of the support bath to facilitate a Michael addition reaction. First, the bioink containing poly(ethylene glycol)-alpha methacrylate (PEG&#945;MA) was reacted off-stoichiometry with a cell-degradable crosslinker to form soft hydrogels. These soft hydrogels were later exposed to photoinitator and light to induce the homopolymerization of unreacted groups and stiffen the hydrogel. This protocol covers hydrogel synthesis, 3D bioprinting, photostiffening, and endpoint characterizations to assess fibroblast activation within 3D structures. The method presented here enables researchers to 3D bioprint a variety of materials that undergo pH-catalyzed polymerization reactions and could be implemented to engineer various models of tissue homeostasis, disease, and repair.

Author Spotlight: Understanding Chronic Lung Diseases Using 3D Printed Phototunable Hydrogels 

This article describes how to 3D bioprint phototunable hydrogels to study extracellular matrix stiffening and fibroblast activation.

Phototunable hydrogels can transform spatially and temporally in response to light exposure. Incorporating these types of biomaterials in cell-culture ...