5'-tiRNA-Cys-GCA regulates VSMC proliferation and phenotypic transition by targeting STAT4 in aortic dissection.

Accumulating evidence shows that tRNA-derived fragments are a novel class of functional small non-coding RNA; however, their roles in aortic dissection (AD) are still unknown. In this study, we found that 5'-tiRNA-Cys-GCA was significantly downregulated in human and mouse models of aortic dissection. The abnormal proliferation, migration, and phenotypic transition of vascular smooth muscle cells (VSMCs) played a crucial role in the initiation and progression of aortic dissection, with 5'-tiRNA-Cys-GCA as a potential phenotypic switching regulator, because its overexpression inhibited the proliferation and migration of VSMCs and increased the expression of contractile markers. In addition, we verified that signal transducer and activator of transcription 4 (STAT4) was a direct downstream target of 5'-tiRNA-Cys-GCA. We found that the STAT4 upregulation in oxidized low-density lipoprotein (ox-LDL)-treated VSMCs, which promoted cell proliferation, migration, and phenotypic transformation, was reversed by 5'-tiRNA-Cys-GCA. Furthermore, 5'-tiRNA-Cys-GCA treatment reduced the incidence and prevented the malignant process of angiotensin II- and β-aminopropionitrile-induced AD in mice. In conclusion, our findings reveal that 5'-tiRNA-Cys-GCA is a potential regulator of the AD pathological process via the STAT4 signaling pathway, providing a novel clinical target for the development of future treatment strategies for aortic dissection.