Accelerated maturation of hESC-CM within collagen-based 3D matrix upon niche cell supplementation and mechanical stretch

Abstract

Regenerate injured myocardium with cardiomyocytes derived from stem cells is a promising strategy formyocardial infarction patients, yet maturation of those stem cell derived cardiomyocytes is still one of the main obstacles for clinical application. Facilitated maturation in vitro could be achieved by tissue engineering technology, where stem cells further functionalize under physiological-mimicking stimuli within 3D matrix. Here we investigated the parameters with the potential to promote maturation of human embryonic stem cell derived cardiomyocytes (hESC-CM) within 3D collagen matrix. After harvest cardiospheres differentiated from hESCs between D20 and D30, engineered cardiac tissue (ECT) was fabricated by coencapsulating digested hESC-CMs with 5% hMSC/hFB in collagen gel and cast into customized PDMS mold, it was allowed to selfassemble into a solid tissue strip with fixed length for 7 days, static or cyclic stretch was applied afterwards. Maturation status of those ECTs was evaluated by qPCR, immunostaining and mechanical properties. Niche cell supplementation was found to augment expression of contractile proteins, hypertrophic genes as well as those in change with calcium handling. Moreover, spreading, modulus and beating metrics were boosted with auxiliary cells as well. Although to a less extent, stretching also significantly impact the maturation with upregulated expression of Cx45, BNP&SERCA2, better alignment and greater twitch force of ECTs. The current study demonstrated that maturation of hESC-CMECT could be accelerated by the addition of niche cells as low as 5%, while tensional loading could further strengthen the artificial tissue strip into better functional cardiac muscle for regenerative medicine.