Regulation of Partial Endothelial-to-Mesenchymal Transition by circATXN1 in Ischemic Diseases

We conducted circRNA sequencing of endothelial cells (ECs) subjected to hypoxia and serum deprivation to ascertain molecules linked to partial or transient mesenchymal activation in endothelial cells (ECs) following tissue ischemia/hypoxia. The outcome demonstrated that the circATXN1 expression was significantly raised. Herein, we estimated the circATXN1 function in regulating mesenchymal characteristics during the partial endothelial-to-mesenchymal transition (EndMT) and its impact on angiogenesis. Over-expression of circATXN1 inhibited mesenchymal traits in endothelial cells, whereas circATXN1 knockdown promoted partial EndMT by upregulating mesenchymal markers and partially reducing endothelial markers. In vivo, circATXN1 knockdown enhanced angiogenesis and functional recovery post-ischemia, while circATXN1 overexpression impeded these processes. Mechanistically, circATXN1 specifically stabilized SLUG mRNA by interacting with ALKBH5, an mRNA demethylase, without altering its transcription. CircATXN1 regulated the subcellular localization of ALKBH5, preventing its nuclear entry and thus stabilizing SLUG mRNA via decreased m6A methylation. This interaction was confirmed through RNA pulldown, LC-MS/MS, and RIP assays. Our findings position circATXN1 as a crucial regulator in ischemic diseases, particularly in angiogenesis. CircATXN1’s downregulation enhances SLUG-mediated partial EndMT, leading to increased ECs proliferation, migration, and sprouting. Targeting circATXN1 with RNA interference (RNAi) represents a potential therapeutic strategy for ischemic disorders.