Name: assessing functional metrics of skeletal muscle health in human skeletal muscle microtissues
Uploaded: 2021-02-18T15:00:00
Description: Watch this Scientific Journal Video about Assessing Functional Metrics of Skeletal Muscle Health in Human Skeletal Muscle Microtissues at JoVE.com

We would like to thank Mohammad Afshar, Haben Abraha, Mohsen Afshar-Bakooshli, and Sadegh Davoudi for contributing to the invention of the MyoTACTIC culture platform and establishing the fabrication and analysis methods described herein. HL received funding from a Natural Sciences and Engineering Research Council (NSERC) Training Program in Organ-on-a-Chip Engineering and Entrepreneurship Scholarship and a University of Toronto Wildcat graduate scholarships. PMG is the Canada Research Chair in Endogenous Repair and received support for this study from the Ontario Institute for Regenerative Medicine, the Stem Cell Network, and from Medicine by Design, a Canada First Research Excellence Program. Schematic diagrams were created with BioRender.com.

1. PDMS MyoTACTIC plate fabrication
NOTE: PDMS MyoTACTIC plate fabrication requires a PU&#160;negative mold, which can be manufactured as previously described30. The computer-aided design (CAD) SolidWorks file for the MyoTACTIC plate design has been made available on GitHub (https://github.com/gilbertlabcode/MyoTACTIC-SolidWork-CAD-file).
<ol>
	<li>Prepare ~ 110 g of PDMS polymer solution in a disposable plastic cup at a 1:15 ratio of monomer to curing agent using the...

<ol>
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This manuscript describes methods to fabricate and analyze a 3D hMMT culture model that can be applied to studies of basic muscle biology, disease modeling, or for candidate molecule testing. The MyoTACTIC platform is cost-friendly, easy to manufacture, and requires a relatively small number of cells to produce skeletal muscle microtissues. hMMTs formed within the MyoTACTIC culture platform are comprised of aligned, multinucleated, and striated myotubes, and respond to electrical stimuli by initiating calcium transients ...

Skeletal muscle is one of the most abundant tissues in the human body and supports key body functions such as locomotion, heat homeostasis and metabolism1. Historically, animal models and two-dimensional (2D) cell culture systems have been used to study biological processes and disease pathogenesis, as well as for testing pharmacological compounds in the treatment of skeletal muscle diseases2,3. While animal models have greatly improved our knowledge of skeletal muscle in health and in disease, their translational impact has been hampered by high costs, ethical considerations and interspecies differences2,4. In turning to human cell-based systems to study skeletal muscle, 2D cell culture systems are favorable due to their simplicity. However, there is a limitation. This format often fails to recapitulate the cell-cell and cell-extracellular matrix interactions that occur naturally within the body5,6. Over the last several years, three dimensional (3D) skeletal muscle models have emerged as a powerful alternative to whole animal models and conventional 2D culture systems by allowing the modeling of physiologically and pathologically relevant processes ex vivo7,8. Indeed, a plethora of studies have reported strategies to model human skeletal muscle in a bioartificial 3D culture format1. One limitation for many of these studies is that active force is quantified following the removal of the muscle tissues from the culture platforms and attachment to a force transducer, which is destructive and hence, limited to serving as an endpoint assay9,10,11,12,13,14,15,16,17,18,19,20,21. Others have designed culture systems that allow for non-invasive methods of measuring active force, but not all are amenable to high content molecule testing applications7,8,9,10,14,18,22,23,24,25,26,27,28,29.
This protocol describes a detailed method to fabricate human muscle microtissues (hMMTs) in the skeletal muscle (Myo) microTissue Array deviCe To Investigate forCe (MyoTACTIC) platform; a 96 well plate device that supports the bulk production of 3D skeletal muscle microtissues30. The MyoTACTIC plate fabrication method enables generation of a 96 well polydimethylsiloxane (PDMS) culture plate and all corresponding well features in a single casting step, whereby each well requires a relatively small number of cells for microtissue formation. Microtissues formed within MyoTACTIC contain aligned, striated, and multinucleated myotubes that are reproducible from well to well of the device, and upon maturation, can respond to chemical and electrical stimuli in situ30. Herein, the technique to manufacture a PDMS MyoTACTIC culture plate device from a polyurethane (PU) replica, an optimized method to implement immortalized human myogenic progenitor cells to fabricate hMMTs, and the functional assessment of engineered hMMT force generation and calcium handling properties are outlined and discussed.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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		<tr>
			<td>0.9% Saline Solution, Sterile</td>
			<td>House Brand</td>
			<td>1010</td>
			<td>10 mL aliquots of the solution are made and stored at 4&#176;C</td>
		</tr>
		<tr>
			<td>25G Needle</td>
			<td>BD, Medstore, University of Toronto</td>
			<td>2548-CABD305127</td>
			<td></td>
		</tr>
		<tr>
			<td>6-Aminocaproic Acid, &#8805;99% (titration), Powder</td>
			<td>Sigma - Aldrich</td>
			<td>A2504-100G</td>
			<td>A 50 mg / mL stock solution is generated by dissolving 5 mg of 6-aminocaproic acid powder in 100 mL of autoclaved, distilled water. The solution is vaccum filtered and 10 mL aliquots are stored at 4&#176;C</td>
		</tr>
		<tr>
			<td>6.35 mm ID Tubing</td>
			<td>VWR</td>
			<td>60985-528</td>
			<td></td>
		</tr>
		<tr>
			<td>AB1167 Myoblast Cell Line</td>
			<td>Institut de Myologie (Paris, France)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Arbitrary Waveform Generator</td>
			<td>Rigol</td>
			<td>DG1022Z</td>
			<td></td>
		</tr>
		<tr>
			<td>Basement Membrane Extract (Geltrex)</td>
			<td>Thermo Fisher Scientific</td>
			<td>A14132-02</td>
			<td>Stored as aliquots of 50 &#181;L or 100 &#181;L at -80&#176;C</td>
		</tr>
		<tr>
			<td>Benchtop Vacuum Chamber</td>
			<td>Sigma - Aldrich</td>
			<td>D2672</td>
			<td></td>
		</tr>
		<tr>
			<td>BNC to Aligator Clip Cable</td>
			<td></td>
			<td></td>
			<td>Ordered from Amazon</td>
		</tr>
		<tr>
			<td>Culture Plastics</td>
			<td>Sarstedt</td>
			<td></td>
			<td>Includes culture plates, serological pipettes, etc</td>
		</tr>
		<tr>
			<td>Dimethyl Sulfoxide</td>
			<td>Sigma - Aldrich</td>
			<td>D8418-250ML</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS, Powder, No Calcium, No Magnesium</td>
			<td>Thermo Fisher Scientific</td>
			<td>21600069</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM) (1X)</td>
			<td>Gibco</td>
			<td>11995-065</td>
			<td>This is a high glucose DMEM with L-glutamine and sodium pyruvate</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Fisher Scientific</td>
			<td>10437028</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibrinogen from Bovine Plasma</td>
			<td>Sigma - Aldrich</td>
			<td>F8630-5G</td>
			<td>Aliquots ranging from 7 - 10 mg of fibrinogen powder are made and stored at -20&#176;C</td>
		</tr>
		<tr>
			<td>Filtropur Syringe Filter, 0.22um Pore Size</td>
			<td>Sarstedt</td>
			<td>83.1826.001</td>
			<td></td>
		</tr>
		<tr>
			<td>Horse Serum</td>
			<td>Gibco</td>
			<td>16050-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Human Recombinant Insulin</td>
			<td>Sigma - Aldrich</td>
			<td>91077C</td>
			<td>Stock solution is 100X and made by dissolving 1 mg of human recombinant insulin in 1 mL of DMEM and 1 &#181;L of NaOH 10N. Solution is filtered and stored as 1 mL aliquots at 4&#176;C</td>
		</tr>
		<tr>
			<td>Image Acquisition Software</td>
			<td>Olympus</td>
			<td>cellSens Dimension</td>
			<td></td>
		</tr>
		<tr>
			<td>Image Processing Software</td>
			<td>National Institutes of Health</td>
			<td>ImageJ</td>
			<td></td>
		</tr>
		<tr>
			<td>Isotemp Oven</td>
			<td>Thermo Fisher Scientific</td>
			<td>201</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Olympus</td>
			<td>IX83</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope - Camera Mount</td>
			<td>Labcam</td>
			<td>Labcam for iPhone</td>
			<td>Ordered from Amazon</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin (10,000 U/mL)</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Disposable Syringes, 1cc</td>
			<td>BD</td>
			<td>2606-309659</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Disposable Syringes, 50cc</td>
			<td>BD</td>
			<td>2612-309653</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F-127, Powder, BioReagent</td>
			<td>Sigma - Aldrich</td>
			<td>P2443-250G</td>
			<td>A 5% stock solution of pluronic acid is made by dissolving 5 g of pluronic acid powder in 100 mL of chilled, autoclaved, distilled water. The solution is vaccum filtered and 10 mL aliquots are stored at 4&#176;C</td>
		</tr>
		<tr>
			<td>Polydimethylsiloxane (Sylgard 184 Silicone Elastomer Kit)</td>
			<td>Dow</td>
			<td>4019862</td>
			<td>Kits are also available at Thermo Fisher Scientific, Sigma - Aldrich, etc.</td>
		</tr>
		<tr>
			<td>Polyurethane Negative Mold</td>
			<td>In House</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Release Agent</td>
			<td>Mann Release Technologies</td>
			<td>200</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotary Vane Vacuum Pump</td>
			<td>Edwards</td>
			<td>A65401906</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Almedic, Medstore, University of Toronto</td>
			<td>2586-M36-0100</td>
			<td></td>
		</tr>
		<tr>
			<td>Single Edge Razor Blade</td>
			<td>VWR</td>
			<td>55411-050</td>
			<td></td>
		</tr>
		<tr>
			<td>Skeletal Muscle Cell Basal Medium</td>
			<td>Promocell</td>
			<td>C-23260</td>
			<td>30 mL aliquotes are generated and at stored at 4&#176;C.</td>
		</tr>
		<tr>
			<td>Skeletal Muscle Cell Growth Medium (Ready-to-use)</td>
			<td>Promocell</td>
			<td>C-23060</td>
			<td>42 mL aliquots are generated and stored at 4&#176;C.</td>
		</tr>
		<tr>
			<td>Smartphone (iPhone)</td>
			<td>Apple</td>
			<td>SE</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard Duty Dry Vacuum Pump</td>
			<td>Welch</td>
			<td>2546B-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilization Bag</td>
			<td>Alliance</td>
			<td>211-SCM2</td>
			<td></td>
		</tr>
		<tr>
			<td>Thimble</td>
			<td>Igege</td>
			<td></td>
			<td>Ordered from Amazon</td>
		</tr>
		<tr>
			<td>Thrombin from human plasma</td>
			<td>Sigma - Aldrich</td>
			<td>T6884-250UN</td>
			<td>100 units of thrombin is dissolved in 1 mL of a 0.1% BSA solution. 10 &#181;L aliquots are prepared and stored at - 20&#176;C.</td>
		</tr>
		<tr>
			<td>Tin coated copper wire</td>
			<td>Arco</td>
			<td>B8871K48</td>
			<td>Ordered from Amazon</td>
		</tr>
		<tr>
			<td>Trypan Blue Solution, 0.4%</td>
			<td>Thermo Scientific</td>
			<td>15250061</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA, 0.25%</td>
			<td>Thermo FIsher Scientific</td>
			<td>25200072</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum Chamber 2</td>
			<td>SP Bel-Art</td>
			<td>F42027-0000</td>
			<td></td>
		</tr>
	</tbody>
</table>

assessing functional metrics of skeletal muscle health in human skeletal muscle microtissues

Three-dimensional (3D) in vitro models of skeletal muscle are a valuable advancement in biomedical research as they afford the opportunity to study skeletal muscle reformation and function in a scalable format that is amenable to experimental manipulations. 3D muscle culture systems are desirable as they enable scientists to study skeletal muscle ex vivo in the context of human cells. 3D in vitro&#160;models closely mimic aspects of the native tissue structure of adult skeletal muscle. However, their universal application is limited by the availability of platforms that are simple to fabricate, cost and user-friendly, and yield relatively high quantities of human skeletal muscle tissues. Additionally, since skeletal muscle plays an important functional role that is impaired over time in many disease states, an experimental platform for microtissue studies is most practical when minimally invasive calcium transient and contractile force measurements can be conducted directly within the platform itself. In this protocol, the fabrication of a 96-well platform known as &#39;MyoTACTIC&#39;, and en masse production of 3D human skeletal muscle microtissues (hMMTs) is described. In addition, the methods for a minimally invasive application of electrical stimulation that enables repeated measurements of skeletal muscle force and calcium handling of each microtissue over time are reported.

Described herein are methods to cast a 96-well PDMS-based MyoTACTIC culture platform from a PU mold, to fabricate arrays of hMMT replica tissues, and to analyze two aspects of hMMT function within the culture device-force generation and calcium handling. Figure 1 offers a schematic overview of the preparation of MyoTACTIC culture wells before hMMT seeding. PDMS is a widely used silicone-based polymer, that can be easily molded to create complex devices32. A PDMS-based...

Watch this Scientific Journal Video about Assessing Functional Metrics of Skeletal Muscle Health in Human Skeletal Muscle Microtissues at JoVE.com

Assessing Functional Metrics of Skeletal Muscle Health in Human Skeletal Muscle Microtissues

This manuscript describes a detailed protocol to produce arrays of 3D human skeletal muscle microtissues and minimally invasive downstream in situ assays of function, including contractile force and calcium handling analyses.

Three-dimensional (3D) in vitro models of skeletal muscle are a valuable advancement in biomedical research as they afford the opportunity to study ...

Our protocol describes detailed methods to fabricate and analyze a 3D human skeletal muscle microtissue culture. Muscle microtissues can be applied to studies of basic muscle biology, disease modeling, or for candidate molecule testing. The main advantage of this technique is that it permits in-situ assessment of contractile force and calcium transients.Because of this, you can conduct longitudinal studies of muscle tissue function. Demonstrating the procedure will be Brennen Musgrave and Heta Lad, graduate students from my laboratory. Two to three hours before cell seeding, place a six well mild tactic plate portion into a 10 centimeter cell culture dish.Prepare each individual myotactic culture well by adding 100 microliters of a 5%pluronic F-127 solution. Use the lid to cover the wells, and apply a paraffin film to seal the dish. Centrifuge the dish at 1, 550 times G for one minute in a centrifuge outfitted with a plate spinner adapter.Store the culture dish at four degrees Celsius until the cells are ready for seeding. Then slowly thaw 150 microliter aliquot of basement membrane extract, and 110 microliter aliquot of thrombin on ice in the culture hood. Working in the cell culture hood, add 700 microliters of 0.9%saline solution to a 1.5 milliliter micro centrifuge tube containing seven milligrams of powdered fibrinogen.Place the tube in a 37 degrees Celsius cell culture incubator for three to five minutes without vortexing. Remove and flick the tube gently, then pulse spin the dissolved solution in a micro centrifuge before returning it to the culture hood. Filter the fibrinogen solution using a one milliliter syringe outfitted with a 0.22 micrometer syringe filter.Then transfer the dissolved fibrinogen solution to ice alongside the basement membrane extract and thrombin aliquots. Prepare and pre-warm the tissue growth media at 37 degrees Celsius, which will be introduced to the culture wells after seeding the tissues. Remove the cell culture plates from the incubator and aspirate the culture media.Then wash the cells once by adding five milliliters of DPBS into each culture plate. Aspirate the DPBS and detach the cells by adding one milliliter of 0.25%trypsin EDTA into each culture dish. Place the plate in the cell culture incubator for three minutes, hold the trypsin by adding three milliliters of wash medium to the culture dish, then transfer the cells to an appropriately sized conical tube.Pellet the cells by centrifuging at 400 times G for 10 minutes. Aspirate the media carefully without damaging the cell pellet, then re-suspend the cells in one milliliter of the wash medium. Count the cells using a hemocytometer and trypan blue dye under bright field microscopy.To seed six tissues, prepare enough cells and extracellular matrix for eight tissues, thus accounting for losses and bubble formation. Transfer 1.2 million cells to a new conical tube, then increase the volume to 10 millimeters with wash medium. Pellet the cells by centrifuging at 400 times G for 10 minutes.Prepare 150 microliters of ECM mixture in a 1.5 milliliter micro centrifuge tube, and store the mixture on ice until use. Aspirate the media from the conical tube containing the cells, taking care to avoid the cell pellet. Vigorously flick the end of the tube with a gloved finger until the pellet appears as a cell slurry.Transfer 120 microliters of the ECM solution to the tube containing the cell slurry, and carefully pipette up and down to completely re-suspend the cells within the ECM to generate a single cell suspension. Avoid creating bubbles, then place the cell ECM suspension on ice until use. Place the refrigerated 10 centimeter dish containing the myotactic wells on top of an ice pack inside of the cell culture hood, and aspirate the pluronic F-127 solution from each well.Allow residual pluronic F-127 solution to release from the porous PDMS, and settle to the bottom of the well by letting the wells sit for five minutes on ice, then aspirate again. Pipette the cell ECM suspension carefully to re-suspend the cells, then transfer 105 microliters of the suspension into a fresh, pre-chilled 1.5 milliliter tube by grasping it close to the top. Add 0.84 microliters of 100 units per milliliter thrombin stock solution to the 105 microliters of cell ECM suspension.Pipette rapidly and thoroughly to mix, avoiding the introduction of bubbles. Add 15 microliters of the cell ECM mixture to each well without pressing the pipette into the bottom of the well. With two light motions, spread the cell suspension behind each post in the well.Place the lid on the 10 centimeter culture plate and transfer it to a 37 degrees Celsius tissue culture incubator for approximately five minutes. Add 200 microliters of pre-warmed tissue growth media to each myotactic well after the cell ECM mixture has polymerized. Replace the lid on the 10 centimeter dish and keep it in the incubator until the differentiation.During a 14 day culture period, myoblasts displayed the aspects of native tissue by self-organizing in the mild tactic well to form a 3D microtissue with multi-nucleated striated myotubes. Myotubes have sarcomere striations, which were visualized by immunostaining for sarcomeric alpha actinin. To achieve well-aligned myotubes, technical errors such as bubble formation while pipetting, or damaging pluronic coating during aspiration, should be avoided.A representative displacement of the myotactic well plate post in response to low and high frequency electrical stimulation, is shown here, indicating that myotubes responds to varying electrical stimuli and contract accordingly. Quantification of the post displacement allows for conversion to absolute contractile force of the HMMTs. Calcium transience on HMMTs made from GCaMP6-transduced myoblasts were also analyzed in response to low and high frequency stimulation.Quantification of fluorescent intensity can be used as measurement for the calcium handling properties of HMMTs. Most people who perform this tissue seeding for the first time, struggle with adding the cell extracellular matrix to the wells, and with bubble formation. We recommend practicing the technique on some spare microtissue culture wells with a very simple viscous solution before the first attempt with cells.

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Bioengineering

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