bioreactor matures iPSC-CMs for MLP disease modeling.

Muscle LIM protein (MLP) is a critical regulator of cardiomyocytes (CMs) cytoarchitecture, and its deficiency results in late-onset dilated cardiomyopathy (DCM) in both mice and human. However, recapitulating this phenotype using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) has been challenging largely due to their immature state. Here, we generated MLP knockout (MLP-KO) mouse iPSCs and differentiated them into CMs. We then employed both conventional and transplantation approach using immunocompromised rat hearts to promote cardiomyocytes maturation. Our results showed that while -matured MLP-KO iPSC-CMs failed to exhibit disease phenotypes, -matured MLP-KO iPSC-CMs successfully recapitulated the hallmarks of DCM, including disrupted sarcomeric architecture and upregulation of atrial natriuretic peptide (ANP), closely mirroring disease progression observed in MLP-deficient mice. These findings demonstrate that the maturation environment is essential for the maturation of iPSC-derived cardiomyocytes to better model genetic cardiac diseases like DCM and provide valuable insights for future therapeutic strategies.