Geometrically controlled cardiac microtissues promote vascularization and reduce inflammation in vitro and in vivo

Cardiac tissue engineering faces challenges due to inadequate vascularization, poor engraftment, and ineffective strategies to control inflammation. This study explores the benefits of geometrically controlled cardiac microtissues over-dispersed cells. Microtissues derived from human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and affixed between two polydimethylsiloxane (PDMS) pillars exhibited cellular alignment and contractile function and were necessary to serve as suitable building blocks for assembling larger tissues. Following implantation into the omentum in nude rats, these tissues exhibited robust engraftment, contractility, and vascularization, with significantly reduced inflammation. Compared to dispersed cells, microtissues demonstrated enhanced vessel network formation, reduced cell death (lower lactate dehydrogenase [LDH]), decreased cytotoxicity (lower cell-free mitochondrial DNA [mtDNA]), and decreased Yes-associated protein (YAP) activation in cardiomyocytes and associated non-cardiomyocyte populations. Cytokine analysis revealed elevated pro-angiogenic factors (placenta growth factor [PIGF], endocan, and angiopoietin-2) and reduced inflammatory markers (interleukin-31 receptor A [IL-31 RA], interleukin [IL]-2 R beta, and OX40 ligand) in microtissues compared with dispersed cells, offering a promising approach for cardiac repair and regeneration.