This study characterized the heterogeneity of ECs and other cells in the heart tissues of MI and Sham mice through scRNA-seq, and obtained the DEGs of ECs between the MI and Sham groups. Clustering analysis was performed to identify and analyze EC sub-clusters. Then, through trajectory analysis, EC4 was revealed to have close association with MI, and cell fate-dependent genes were obtained by BEAM. At the same time, DEGs in another Micro array dataset containing both MI and Sham mice were analyzed, and interested with the above-mentioned genes. Additionally, hub genes (Timp1 and Fn1) were identified through PPI network construction. They were shown to be enriched in wound healing through enrichment analysis of the functional pathways about the above intersected genes. To study the role of Timp1 and Fn1 in ECs and MI, we treated MI in vitro by inducing hypoxia in ECs, which is the key angiogenic factor. Under hypoxia, Timp1 and Fn1 were significantly upregulated in HUVECs. Silencing of Timp1 and Fn1 increased the migration and angiogenesis of hypoxia-treated HUVECs. Taken together, deficiency of Timp1 and Fn1 may improve MI by promoting angiogenesis.
Timp1 is a member of the tissue inhibitor of matrix metalloproteinase family, and its function is to mediate the turnover of extracellular matrix [
26]. Studies have shown that Timp1 is involved in pathological processes [
27], and is a key antiangiogenic factor [
28]. In addition, recombinant Timp1 was revealed to inhibit the migration and tube formation of HUVECs [
29]. The research of Jung-Kyun Choi et al. [
30] shows that TIMP1 knockdown in FECS-Ad inhibited angiogenesis and muscle regeneration induced by FECS-Ad transplanted into ischemic mouse tissue. Consistent with the findings of previous literature, Timp1 knockdown was revealed to promote the migration and tube formation of HUVECs, but its specific mechanism is still unclear. Fibronectin 1 (Fn1), as a member of the glycoprotein family [
31], is essential for cell growth, differentiation, and plays an important part in wound healing [
32]. As reported, VEGF regulated Fn1 to affect the proliferation, migration and angiogenesis of HUVECs [
33]. For example, the elimination of Fn1 leads to inhibition of tumor angiogenesis [
34]. In addition, Tianyi Chen et al. [
35] found that Fn1 is located in human skin ECs and promotes the migration and tube formation of HUVECs. Restricted blood supply can lead to irreversible damage to myocardial cells, eventually leading to ventricular failure [
36]. Angiogenesis, the process by which new blood vessels form from the existing vasculature, is often inhibited in MI [
37]. Therefore, in recent years, scholars have conducted many studies on promoting angiogenesis to stimulate the recovery of the microvascular system. Rescue of damaged angiogenesis is a prerequisite for developing new treatments. Both Timp1 and Fn1 have demonstrated inhibitory effects on angiogenesis in multiple studies. These studies indirectly prove the important role of inhibitingTimp1 and Fn1 in improving MI.
The limitation of the current study is that only one MI and one Sham sample were analyzed by scRNA-seq. Although the reliability of scRNA-seq results was supported by the expression of hub genes in GEO datasets and HUVECs, however, due to the limitation of sample size in this study, we expect to obtain more robust results through further in vivo or in vitro experimental analyses.