Name: measuring global cellular matrix metalloproteinase and metabolic activity in 3d hydrogels
Uploaded: 2019-01-22T15:00:00
Description: Watch this Scientific Journal Video about Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels at JoVE.com

The authors would like to acknowledge Ohio Cancer Research (OCR), OH, USA for funding this work as well as King Saud University (KSU), Riyadh, KSA for sponsoring the first author.&#160;Molecular weight of the fluorescent peptide sensor was measured using matrix assisted, laser desorption-ionization, time-of-flight (MALDI-TOF) mass spectrometry with assistance from the Campus Chemical Instrument Center Mass Spectrometry and Proteomics Facility at The Ohio State University.

1. Hydrogel components preparation
<ol>
	<li>Synthesize the fluorescent protease-degradable peptides as described elsewhere8, utilizing fluorescein as the fluorescent molecule and dabcyl as the quencher. Dissolve the peptide in DMSO to a concentration of 10 mM and store in a -80 &#176;C freezer in small (~30 &#181;L) aliquots to avoid repeated freeze-thaw cycles. 
	NOTE: These peptides can also be purchased commercially. This protocol requires a C-terminal cysteine in the peptide sequence t...

<ol>
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M., Schroeder, M. E., Payne, S. Z., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Dimensional+High-Throughput+Cell+Encapsulation+Platform+to+Study+Changes+in+Cell-Matrix+Interactions.">Three-Dimensional High-Throughput Cell Encapsulation Platform to Study Changes in Cell-Matrix Interactions.</a> ACS Applied Materials &amp; Interfaces. 8 (34), 21914-21922 (2016).</li><li>Sridhar, B. V., Doyle, N. R., Randolph, M. A., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalently+tethered+TGF-&#946;1+with+encapsulated+chondrocytes+in+a+PEG+hydrogel+system+enhances+extracellular+matrix+production.">Covalently tethered TGF-&#946;1 with encapsulated chondrocytes in a PEG hydrogel system enhances extracellular matrix production.</a> Journal of Biomedical Materials Research. 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3D in vitro cell culture recapitulates many important aspects of the in vivo environment. However, 3D culture also makes assessing cell function and signaling challenging, as many biological assays require cellular retrieval and large numbers of cells. Therefore, the development of a simple 3D culture system that enables measurement of cellular function without further sample processing would greatly increase the utility of 3D culture systems. The 3D system described here can be adapted for a variety of different applica...

Three-dimensional (3D) culture systems often more closely recapitulate in vivo cellular responses than traditional two-dimensional (2D) culture systems, see several excellent publications1,2,3. However, utilizing 3D culture systems to measure cell function has been challenging due to the difficulty of cellular retrieval and further sample processing. This difficulty limits the measurement of many cellular functions in 3D culture systems. To overcome this difficulty, new techniques are needed that enable easy measurement of cell function within 3D environments. One way to address this need is the development of materials that not only support 3D cell culture but also incorporate sensors to measure cell function. For example, several hydrogel systems have incorporated fluorogenic protease cleavable moieties to enable visualization of protease activity within 3D environments4,5,6,7. While these systems were originally utilized for microscopic imaging, these systems can also be adapted for use in a global matrix metalloproteinase (MMP) activity assay using a standard plate reader, enabling facile measurement of a cell function in a 3D environment8.
MMPs, a superfamily of zinc proteases, play critical roles in normal tissue homeostasis and in many diseases. MMPs degrade and remodel extracellular matrix (ECM), cleave cell surface receptors and cytokines and activate other MMPs9,10. MMPs play critical roles in physiological processes such as wound healing and in diseases such as arthritis, atherosclerosis, Alzheimer&#39;s, and cancer (see reviews in 9,10,11). In cancer, high MMP expression levels are strongly correlated with cancer metastasis and poor prognosis12. Furthermore, MMPs contribute to tumor progression by promoting cancer cell invasion and migration, cellular processes that are inherently 3D phenomena13,14. Therefore, there is much interest in the ability to measure MMP activity in 3D culture in many contexts, including fundamental biological studies and drug screening assays.
PEG hydrogels are widely used for 3D cell culture due to their high water content, resistance to protein adsorption, and tunable nature. PEG hydrogels have been functionalized with a number of moieties to direct cell function, such as with ECM mimetic peptides like RGD, RLD, and IKVAV to facilitate cell adhesion, or direct tethering of growth factors such as transforming growth factor-&#946; (TGF-&#946;)15,16. More recently, PEG hydrogels have been functionalized with sensor peptides that enable measurement of cell function as well5,8. Specifically, the use of a PEG hydrogel system functionalized with a fluorogenic MMP-degradable peptide enabled measurement of cellular MMP activity in 3D cultures with a standard plate reader and required no further processing. These systems are also compatible with other measurements of cellular function, including metabolic activity. Here, a protocol is described for the measurement of MMP activity of cells cultured in a 3D PEG hydrogel functionalized with a fluorogenic MMP-degradable peptide, and results presented demonstrating the initial optimization experiments needed for use of this assay. Human melanoma cells (A375) were encapsulated in the fluorogenic hydrogels over a range of seeding densities to determine the appropriate seeding densities that are within the working range of the assay. After 24 h of encapsulation, MMP and metabolic activity were measured utilizing a standard microplate reader. Next, MMP activity was normalized to metabolic activity to determine the seeding densities within the linear range of the assay. Finally, intra-plate coefficient of variation percentages (% CV) were calculated between triplicates to reflect the reproducibility of the obtained results. This method enables simple and fast 3D cell culture, and easy measurement of protease activity with minimal sample processing.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1X Phosphate Buffered Saline</td>
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			<td style="width:119px;">10-010-049</td>
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			<td height="21" style="height:21px;width:272px;">Activated charcoal&#160;</td>
			<td style="width:268px;">Sigma-Aldrich</td>
			<td style="width:119px;">C3345</td>
			<td style="width:64px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Black round bottom 96-well plate</td>
			<td style="width:268px;">Brand-Tech</td>
			<td style="width:119px;">89093-600</td>
			<td style="width:64px;"></td>
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			<td height="21" style="height:21px;width:272px;">Cell adhesion peptide (CRGDS)</td>
			<td style="width:268px;">GenScript USA Inc.</td>
			<td style="width:119px;">custom made</td>
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			<td height="21" style="height:21px;width:272px;">Collagenase enzyme type I&#160;</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">17100-017</td>
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			<td height="21" style="height:21px;width:272px;">Dextran</td>
			<td style="width:268px;">Sigma-Aldrich</td>
			<td style="width:119px;">D4876</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">DMEM High Glucose Media</td>
			<td style="width:268px;">Invitrogen</td>
			<td style="width:119px;">11965118</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Fetal bovine serum (FBS)&#160;</td>
			<td style="width:268px;">Seradigm</td>
			<td style="width:119px;">1500-500</td>
			<td style="width:64px;"></td>
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			<td height="21" style="height:21px;width:272px;">Fluorescence microplate reader&#160;</td>
			<td style="width:268px;">BioTek</td>
			<td style="width:119px;">Cytation 3</td>
			<td style="width:64px;"></td>
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			<td height="21" style="height:21px;width:272px;">Hemocytometer</td>
			<td style="width:268px;">Hausser Scientific Co.</td>
			<td style="width:119px;">3200</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">L-glutamine</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">25030-081</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:272px;">MMP-degradable peptide crosslinker (KCGPQG&#8595;IWGQCK)</td>
			<td style="width:268px;">GenScript USA Inc.</td>
			<td style="width:119px;">custom made</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">NaOH</td>
			<td style="width:268px;">Fisher Scientific</td>
			<td style="width:119px;">S318500</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Penicillin /streptomycin</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">15140-122</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Resazurin (Alamar Blue)</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">DAL1100</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:272px;">UV light&#160;</td>
			<td style="width:268px;">UVP</td>
			<td style="width:119px;">95-0006-02</td>
			<td style="width:64px;"></td>
		</tr>
	</tbody>
</table>

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.

The current assay was adapted from a previously developed and characterized 3D hydrogel culture system functionalized with a fluorogenic MMP cleavable sensor8. The fluorogenic MMP sensor used here consists of a peptide sequence, GPLAC(pMeOBzl)&#8595;WARKDDK(AdOO)C (&#8595; indicates the cleavage site) that was previously optimized for cleavage by MMP-14 and MMP-1119. The peptide is labeled with a fluorescent molecule (fluorescein) and a quen...

Watch this Scientific Journal Video about Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels at JoVE.com

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

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) ...

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