Functionally antagonistic groups of macrophages can be incorporated with human pluripotent stem-cell derived cardiomyocytes to engineer a novel human myocardial infarction model in vitro.

The innate immune response upon myocardial infarction (MI), a leading cause of congestive heart failure, results in fibrosis and cardiac remodeling. Two functionally antagonistic groups of macrophages are involved in MI: CD80+CD86+ pro-inflammatory macrophages (M1) in the initial response and CD163+CD206+ anti-inflammatory macrophages (M2) in the late response. However, their precise interactions with cardiomyocytes (CMs) during MI remain elusive. To address this, we can generate M1 and M2 from human blood CMs and CMs from human pluripotent stem cells (hPSCs), and modulate their interactions, creating a novel high-throughput human MI model in vitro. Method: We derived hPSC-CMs from NKX2.5-GFP- PSCs. Macrophages differentiated from human CD14+ monocytes were polarized towards M1 by LPS and IFNγ, and M2 by IL-4. The apoptotic response of hPSC-CMs was quantified by measuring NKX2.5+ethidium homodimer-1 (EthD-1)+ populations with M1 or M2 cytokines. Results: We differentiated OCT4+NKX2.5- PSCs into OCT4-NKX2.5+CMs. qRT-PCR confirmed high expressions of IL-6 and TNFα in M1, and MSR-1 and MRC-1 in M2 (p<0.05). Luminex analysis showed distinct cytokine secretion levels: higher levels of MIP-1β and TNFα in M1, and IL-4 in M2, and VEGF from both, cognate receptors were expressed on the human CMs. Both M1 and M2 cytokine activities increased NKX2.5+ EthD-1+ populations over time than controls, and M2 higher than M1 (4h, 8h, 12h, 18h, p<0.05). In our study, M1 and M2 activities induced CM injury, mimicking MI via cytokine-receptor interactions. Our novel model will further elucidate macrophage-mediated mechanisms in MI.