The ability to differentiate human pluripotent stem cells (hPSCs) into cardiomyocytes (CMs) makes them an attractive source for repairing injured myocardium, disease modeling, and drug testing. Although current differentiation protocols yield hPSC-CMs to >90% efficiency, hPSC-CMs exhibit immature characteristics. With the goal of overcoming this limitation, we tested the effects of varying passive stretch on engineered heart muscle (EHM) structural and functional maturation, guided by computational modeling. Human embryonic stem cells (hESCs, H7 line) or human induced pluripotent stem cells (IMR-90 line) were differentiated to hPSC-derived cardiomyocytes (hPSC-CMs) in vitro using a small molecule based protocol. hPSC-CMs were characterized by troponin+ flow cytometry as well as electrophysiological measurements. Afterwards, 1.2 × 106 hPSC-CMs were mixed with 0.4 × 106 human fibroblasts (IMR-90 line) (3:1 ratio) and type-I collagen. The blend was cast into custom-made 12-mm long polydimethylsiloxane reservoirs to vary nominal passive stretch of EHMs to 5, 7, or 9 mm. EHM characteristics were monitored for up to 50 days, with EHMs having a passive stretch of 7 mm giving the most consistent formation. Based on our initial macroscopic observations of EHM formation, we created a computational model that predicts the stress distribution throughout EHMs, which is a functionmore »
- Award ID(s):
- 1653193
- Publication Date:
- NSF-PAR ID:
- 10212395
- Journal Name:
- Biomaterials
- Volume:
- 256
- Issue:
- 120195
- ISSN:
- 0142-9612
- Sponsoring Org:
- National Science Foundation
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Cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs) show great potential for engineering myocardium to study cardiac disease and create regenerative therapies. However, iPSC-CMs typically possess a late embryonic stage phenotype, with cells failing to exhibit markers of mature adult tissue. This is due in part to insufficient knowledge and control of microenvironmental cues required to facilitate the organization and maturation of iPSC-CMs. Here, we employed a cell-adhesive, mechanically tunable synthetic fibrous extracellular matrix (ECM) consisting of electrospun dextran vinyl sulfone (DVS) fibers and examined how biochemical, architectural, and mechanical properties of the ECM impact iPSC-CM tissue assembly and subsequent function. Exploring a multidimensional parameter space spanning cell-adhesive ligand, seeding density, fiber alignment, and stiffness, we found that fibronectin-functionalized DVS matrices composed of highly aligned fibers with low stiffness optimally promoted the organization of functional iPSC-CM tissues. Tissues generated on these matrices demonstrated improved calcium handling and increased end-to-end localization of N-cadherin as compared to micropatterned fibronectin lines or fibronectin-coated glass. Furthermore, DVS matrices supported long-term culture (45 days) of iPSC-CMs; N-cadherin end-to-end localization and connexin43 expression both increased as a function of time in culture. In sum, these findings demonstrate the importance of recapitulating the fibrous myocardial ECM inmore »
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Abstract Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) allow investigations in a human cardiac model system, but disorganized mechanics and immaturity of hPSC-CMs on standard two-dimensional surfaces have been hurdles. Here, we developed a platform of micron-scale cardiac muscle bundles to control biomechanics in arrays of thousands of purified, independently contracting cardiac muscle strips on two-dimensional elastomer substrates with far greater throughput than single cell methods. By defining geometry and workload in this reductionist platform, we show that myofibrillar alignment and auxotonic contractions at physiologic workload drive maturation of contractile function, calcium handling, and electrophysiology. Using transcriptomics, reporter hPSC-CMs, and quantitative immunofluorescence, these cardiac muscle bundles can be used to parse orthogonal cues in early development, including contractile force, calcium load, and metabolic signals. Additionally, the resultant organized biomechanics facilitates automated extraction of contractile kinetics from brightfield microscopy imaging, increasing the accessibility, reproducibility, and throughput of pharmacologic testing and cardiomyopathy disease modeling.
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