Abstract 4364567: Enhancing Heart Regeneration and Repair after Myocardial Infarction through Inhibition of MicroRNA-762 by Targeting XAF1 and CMPK2.

Aim: Following myocardial infarction (MI), endothelial cells (ECs) and fibroblasts are key to tissue repair. Modulating their function could improve healing and cardiac recovery. Given limited effective therapies, microRNAs (miRNAs) are promising targets. This project investigates the effects of miR-762 on endothelial and fibroblast function to explore its therapeutic potential in post-MI repair. Methods: Expression of miR-762 was analyzed in vivo after ultrasound-guided MI in C57BL/6J mice by qRT-PCR. Further, miR-762 expression was assessed in human ECs and Aortic Fibroblasts (AoF). The impact of anti-miR-762 transfection on migration, proliferation, angiogenesis, and cell death was evaluated. Potential miR-762 downstream targets were identified by RNA sequencing and validated by qRT-PCR and western blot analysis. Results: MiR-762 is significantly upregulated in vivo 24h after MI ( p <0.05), with no regulation at 72h. Similarly, in vitro, hypoxia led to increased miR-762 levels in ECs at 24h (p<0.05), but not at 72h. Functional analyses indicate that miR-762 does not affect EC proliferation. However, its downregulation significantly enhances EC migration after 6h ( p <0.0001), reduces apoptosis ( p <0.05), and improves the angiogenic capacity ( p <0.05). RNA sequencing revealed that anti-miR transfection significantly downregulates CMPK2 ( p <0.0001) and XAF1 ( p <0.05) in ECs, these findings were confirmed by qRT-PCR. Western blot analyses showed a significant reduction of CMPK2 and XAF1 protein levels ( p <0.05). Upstream pathway analysis revealed a significant downregulation of IFNGR1 and STAT1 proteins ( p <0.05), although no changes were observed at the RNA level. Novel expression analyses revealed significantly higher miR-762 levels in AoF compared to ECs ( p <0.05). Preliminary data suggest that miR-762 downregulation in AoF does not affect proliferation but appears to reduce migration capacity and increase cell death. Conclusion: In summary, our findings identify miR-762 as a promising therapeutic target for enhancing recovery after MI. Inhibition of miR-762 improves EC function and promotes angiogenesis by inhibiting XAF1 and CMPK2, acting through the IFNγ-JAK-STAT signaling pathway. Additionally, miR-762 may modulate AoF activity, potentially leading to decreased scar formation. To further investigate this aspect, additional experiments focusing on AoF are needed. The next phase of our research will explore these mechanisms and include the first in vivo therapeutic studies.