A Macrophage-Derived Factor on Human iPSC-Derived Cardiomyocyte Function: The Role of Osteopontin

Following MI, massive cardiomyocytes are lost, and inflammatory cells such as monocytes and macrophages migrate into the damaged region to remove dead cells and tissue. While cardiac macrophages are abundant in the injured heart post-MI, the role of inflammation in cardiovascular disease has been under-appreciated in the past. Consequently, the contribution of specific macrophage subsets or macrophage-derived factors on cardiac cells is not well known. Thus, this study investigated the paracrine signaling between human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and macrophages, with the focus on the effects of macrophage-derived osteopontin (OPN) on hiPSC-CM function. HiPSC-CM were first co-cultured with unpolarized (M0), pro-inflammatory (M1), or anti-inflammatory (M2) macrophages. The co-culture of hiPSC-CM with M2 macrophages specifically led to notable changes in the electrophysiological properties of hiPSC-CM, including prolonged contraction time (RT90), action potential duration (APD90), and calcium decay time (CSD RT90). Moreover, a significant upregulation of action potential-related genes such as CACNA1C and SCN5A was demonstrated, which coincided with the elevated OPN level in the hiPSC-CM with M2 macrophages co-culture. These functional changes were not observed in the hiPSC-CM-M0 and M1 co-culture groups, likely due to the OPN level remaining below the threshold required to induce detectable changes in hiPSC-CM. Subsequent experiments involving exogenous OPN supplementation and inhibition in hiPSC-CM culture yielded concordant results, further confirming the direct role of OPN in modulating hiPSC-CM gene expression. This study highlights the differential effect of specific macrophage subtypes on hiPSC-CM, as well as the potent bioactivity of OPN and its ability to directly modulate cardiomyocyte behavior, even in the absence of direct cell-cell interactions within a co-culture system. These findings further suggest that OPN could be a novel target for therapeutic intervention in cardiac diseases.