Name: developing 3d organized human cardiac tissue within a microfluidic platform
Uploaded: 2021-06-15T15:00:00
Description: Watch this Scientific Journal Video about Developing 3D Organized Human Cardiac Tissue within a Microfluidic Platform at JoVE.com

We would like to thank NSF CAREER Award #1653193, Arizona Biomedical Research Commission (ABRC) New Investigator Award (ADHS18-198872), and the Flinn Foundation Award for providing funding sources for this project. The hiPSC line, SCVI20, was obtained from Joseph C. Wu, MD, PhD at the Stanford Cardiovascular Institute funded by NIH R24 HL117756. The hiPSC line, IMR90-4, was obtained from WiCell Research Institute55,56.

Perform all cell handling and reagent preparation within a Biosafety Cabinet. Ensure all surfaces, materials, and equipment that come into contact with cells are sterile (i.e., spray down with 70% ethanol). Cells should be cultured in a humidified 37 &#176;C, 5% CO2 incubator. All hiPSC culture and differentiation is performed in 6-well plates.
1. Microfluidic device creation (approximate duration: 1 week)
<ol>
	<li>Photolithography 
	NOTE: The mask, designed...

The formation of an in vitro human cardiac tissue model with enhanced cell-cell interactions and biomimetic 3D structure is imperative for basic cardiovascular research and corresponding clinical applications1. This outlined protocol explains the development of 3D human anisotropic cardiac tissue within a microfluidic device, using co-culture of stem cell-derived CMs with connective CFs encapsulated within a collagen hydrogel, serving to model the complex cell composition and structure of...

Tissue engineering approaches have been widely explored, in recent years, to accompany in vivo clinical findings in regenerative medicine and disease modeling1,2. Significant emphasis has been particularly placed on in vitro cardiac tissue modeling due to the inherent difficulties in sourcing human primary cardiac tissue and producing physiologically relevant in vitro surrogates, limiting the fundamental understanding of the complex mechanisms of cardiovascular diseases (CVDs)1,3. Traditional models have often involved 2D monolayer culture assays. However, the importance of culturing cardiac cells within a 3D environment to mimic both the native landscape of the myocardium and complex cellular interactions has been extensively characterized4,5. Additionally, most models produced thus far have included a mono-culture of CMs differentiated from stem cells. However, the heart is comprised of multiple cell types6 within a complex 3D architecture7, warranting the critical need to improve the complexity of the tissue composition within 3D in vitro models to better mimic cellular constituents of the native myocardium.
To date, many different approaches have been explored to produce biomimetic 3D models of the myocardium8. These approaches range from experimental setups&#160;that allow for the real-time calculation of generated force, from mono-culture CMs seeded on thin films (deemed muscular thin films (MTFs))9, to co-culture cardiac cells in 3D hydrogel matrices suspended among free-standing cantilevers (deemed engineered heart tissues (EHTs))10. Other approaches have focused on implementing micromolding techniques to mimic myocardial anisotropy, from mono-culture CMs in a 3D hydrogel suspended among protruding microposts in a tissue patch11, to mono-culture CMs seeded among indented microgrooves12,13. There are inherent advantages and disadvantages to each of these methods, therefore, it is pertinent to utilize the technique that aligns with the intended application and the corresponding biological question.
The ability to enhance the maturation of stem cell-derived CMs is essential for the successful in vitro engineering of adult-like myocardial tissue and translation of subsequent findings to clinical interpretations. To this end, methods to mature CMs have been widely explored, both in 2D and 3D14,15,16. For example, electrical stimulation incorporated in EHTs, forced alignment of CMs with surface topography, signaling cues, growth factors from co-culture, and/or 3D hydrogel conditions, etc., all lead to a change in favor of CM maturation in at least one of the following: cell morphology, calcium handling, sarcomeric structure, gene expression, or contractile force.
Of these models, the approaches that utilize microfluidic platforms retain certain advantages in nature, such as control of gradients, limited cell input, and minimal necessary reagents. Furthermore, many biological replicates can be generated at once using microfluidic platforms, serving to better dissect the biological mechanism of interest and increase the experimental sample size in favor of statistical power17,18,19. Additionally, using photolithography in the microfluidic device fabrication process enables the creation of precise features (e.g., topographies) at the micro- and nano-level, which serve as mesoscopic cues to enhance the surrounding cellular structure and macro-level tissue architecture18,20,21,22 for different applications in tissue regeneration and disease modeling.
We previously demonstrated the development of a novel 3D cardiac tissue on-chip model that incorporates surface topography, in the form of innate elliptical microposts, to align hydrogel-encapsulated co-cultured cardiac cells into an interconnected, anisotropic tissue20. After 14 days of culture, the tissues formed within the microfluidic device are more mature in their phenotype, gene expression profile, calcium handling characteristics, and pharmaceutical response when compared to monolayer and 3D isotropic controls23. The protocol described herein outlines the method for creating this 3D co-cultured, aligned (i.e., anisotropic) human cardiac tissue within the microfluidic device using hiPSC-derived CMs. Specifically, we explain the methods to differentiate and purify hiPSCs towards CMs, supplementation of hCFs with CMs to produce an established co-culture population, insertion of the cell population encapsulated within the collagen hydrogel into the microfluidic devices, and subsequent analysis of the 3D constructed tissues through contractile and immunofluorescent assays. The resultant 3D engineered micro-tissues are suitable for various applications, including fundamental biology studies, CVD modeling, and pharmaceutical testing.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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			<td>0.65 mL centrifuge tubes</td>
			<td>VWR</td>
			<td>87003-290</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mm Biopsy punch</td>
			<td>VWR</td>
			<td>95039-090</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mm Biopsy punch</td>
			<td>VWR</td>
			<td>95039-088</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL Falcon tubes</td>
			<td>VWR</td>
			<td>89039-670</td>
			<td></td>
		</tr>
		<tr>
			<td>18x18mm coverslips</td>
			<td>VWR</td>
			<td>16004-308</td>
			<td>The coverslips should be No.1, to allow for high magnification imaging</td>
		</tr>
		<tr>
			<td>4% paraformaldehyde</td>
			<td>ThermoFisher</td>
			<td>101176-014</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well flat botttom tissue-culture plates</td>
			<td>VWR</td>
			<td>82050-844</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 minus insulin</td>
			<td>LifeTech</td>
			<td>A1895602</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 plus insulin</td>
			<td>LifeTech</td>
			<td>17504001</td>
			<td></td>
		</tr>
		<tr>
			<td>CHIR99021</td>
			<td>VWR</td>
			<td>10188-030</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen I, rat tail</td>
			<td>Corning</td>
			<td>47747-218</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM F12</td>
			<td>ThermoFisher</td>
			<td>11330057</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>ThermoFisher</td>
			<td>21600069</td>
			<td></td>
		</tr>
		<tr>
			<td>E8</td>
			<td>ThermoFisher</td>
			<td>A1517001</td>
			<td>can also be made in house</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>VWR</td>
			<td>45001-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
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			<td>FGM3</td>
			<td>VWR</td>
			<td>10172-048</td>
			<td></td>
		</tr>
		<tr>
			<td>GFR-Matrigel</td>
			<td>VWR</td>
			<td>47743-718</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Sigma</td>
			<td>G8898-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat serum</td>
			<td>VWR</td>
			<td>10152-212</td>
			<td></td>
		</tr>
		<tr>
			<td>hESC-Matrigel</td>
			<td>Corning</td>
			<td>BD354277</td>
			<td></td>
		</tr>
		<tr>
			<td>IPA</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
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			<td>IWP2</td>
			<td>Sigma</td>
			<td>I0536-5MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>VWR</td>
			<td>82003-820</td>
			<td></td>
		</tr>
		<tr>
			<td>MTCS</td>
			<td>Sigma</td>
			<td>440299-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>NaN3</td>
			<td>Sigma</td>
			<td>S2002-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Sigma</td>
			<td>S5881-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>VWR</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish (150x15mm)</td>
			<td>VWR</td>
			<td>25384-326</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish (60x15mm)</td>
			<td>VWR</td>
			<td>25384-092</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol Red</td>
			<td>Sigma</td>
			<td>P3532-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>ThermoFisher</td>
			<td>MT10040CM</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640 minus glucose</td>
			<td>VWR</td>
			<td>45001-110</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon Wafers (100mm)</td>
			<td>University Wafer</td>
			<td>1196</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium lactate</td>
			<td>Sigma</td>
			<td>L4263-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>SU8 2075</td>
			<td>Microchem</td>
			<td>Y111074 0500L1GL</td>
			<td></td>
		</tr>
		<tr>
			<td>SU8 Developer</td>
			<td>ThermoFisher</td>
			<td>NC9901158</td>
			<td></td>
		</tr>
		<tr>
			<td>Sylgard Elastomer</td>
			<td>Essex Brownell</td>
			<td>DC-184-1.1</td>
			<td></td>
		</tr>
		<tr>
			<td>T75 flasks</td>
			<td>VWR</td>
			<td>82050-856</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>T8787-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>TrypLE</td>
			<td>ThermoFisher</td>
			<td>12604021</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA (0.5%)</td>
			<td>ThermoFisher</td>
			<td>15400054</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween20</td>
			<td>Sigma</td>
			<td>P9416-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Y-27632</td>
			<td>Stem Cell Technologies</td>
			<td>72304</td>
			<td></td>
		</tr>
		<tr>
			<td>EVG620 Aligner</td>
			<td>EVG</td>
		</tr>
		<tr>
			<td>Plasma cleaner PDC-32G</td>
			<td>Harrick Plasma</td>
		</tr>
		<tr>
			<td>Zeiss AxioObserver Z1 microscope</td>
			<td>Nikon</td>
		</tr>
		<tr>
			<td>Leica SP8 Confocal microscope</td>
			<td>Leica</td>
		</tr>
	</tbody>
</table>

developing 3d organized human cardiac tissue within a microfluidic platform

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart muscle, the myocardium, is notoriously difficult to accomplish in vitro. Mainly, obstacles lie in the need for human cardiomyocytes (CMs) that are either adult or exhibit adult-like phenotypes and can successfully replicate the myocardium&#39;s cellular complexity and intricate 3D architecture. Unfortunately, due to ethical concerns and lack of available primary patient-derived human cardiac tissue, combined with the minimal proliferation of CMs, the sourcing of viable human CMs has been a limiting step for cardiac tissue engineering. To this end, most research has transitioned toward cardiac differentiation of human induced pluripotent stem cells (hiPSCs) as the primary source of human CMs, resulting in the wide incorporation of hiPSC-CMs within in vitro assays for cardiac tissue modeling.
Here in this work, we demonstrate a protocol for developing a 3D mature stem cell-derived human cardiac tissue within a microfluidic device. We specifically explain and visually demonstrate the production of a 3D in vitro anisotropic cardiac tissue-on-a-chip model from hiPSC-derived CMs. We primarily describe a purification protocol to select for CMs, the co-culture of cells with a defined ratio via mixing CMs with human CFs (hCFs), and suspension of this co-culture within the collagen-based hydrogel. We further demonstrate the injection of the cell-laden hydrogel within our well-defined microfluidic device, embedded with staggered elliptical microposts that serve as surface topography to induce a high degree of alignment of the surrounding cells and the hydrogel matrix, mimicking the architecture of the native myocardium. We envision that the proposed 3D anisotropic cardiac tissue-on-chip model is suitable for fundamental biology studies, disease modeling, and, through its use as a screening tool, pharmaceutical testing.

To obtain a highly purified population of CMs from hiPSCs, a modified version involving a combination of the Lian differentiation protocol33 and Tohyama purification steps34 is used (refer to Figure 1A for experimental timeline). The hiPSCs need to be colony-like, ~85% confluent, and evenly spread throughout the culture well 3-4 days after passage, at the onset of CM differentiation (Figure 1B). Specifically, on Da...

Watch this Scientific Journal Video about Developing 3D Organized Human Cardiac Tissue within a Microfluidic Platform at JoVE.com

Developing 3D Organized Human Cardiac Tissue within a Microfluidic Platform

The goal of this protocol is to explain and demonstrate the development of a three-dimensional (3D) microfluidic model of highly aligned human cardiac tissue, composed of stem cell-derived cardiomyocytes co-cultured with cardiac fibroblasts (CFs) within a biomimetic, collagen-based hydrogel, for applications in cardiac tissue engineering, drug screening, and disease modeling.

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart ...

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