Paired box 9 regulates VSMC phenotypic transformation, proliferation, and migration via sonic hedgehog

Vascular smooth muscle cells (VSMCs) play a crucial role in the progression of atherosclerosis. Paired box 9 (Pax9) is a member of the Pax gene family which participates in the development of various tissues and organs. However, the effect of Pax9 on atherosclerosis and VSMCs and the underlying mechanisms remain unclear.

Western blotting was performed to assess Pax9 expression in atherosclerosis and VSMCs. Pax9 siRNA and overexpression plasmid were constructed to explore the biological function. Cell proliferation assay, phalloidin staining, and Transwell assay, accompanied by the sonic hedgehog (Shh) signaling pathway antagonist, cyclopamine (5 μM) and agonist, SAG (100 nM), were used to evaluate the VSMC phenotype, proliferation, and migration, as well as explore the associated mechanisms.

We first discovered Pax9 to be significantly increased in atherosclerotic mice and platelet-derived growth factor-BB (PDGF-BB)-induced VSMCs. Pax9 knockdown inhibited the phenotypic transformation, proliferation, and migration of VSMCs, whereas the opposite effect was observed when Pax9 was overexpressed. Next, we established that Shh was activated in PDGF-BB-induced VSMCs. Moreover, Pax9 overexpression further activated Shh and exacerbated the phenotypic transformation, proliferation, and migration of PDGF-BB-induced VSMCs. These changes were effectively inhibited by treatment with the Shh signaling pathway antagonist. Consistently, Pax9 knockdown down-regulated Shh expression and inhibited the phenotypic transformation, proliferation, and migration of PDGF-BB-induced VSMCs. Treatment with the Shh signaling pathway agonist prevented these changes.

Pax9 regulated VSMC phenotypic transformation, proliferation, and migration via Shh, which may represent a novel target for the treatment of atherosclerosis.