The proliferation and migration of vascular smooth muscle cells (VSMCs) after
vascular injury lead to neointimal
hyperplasia, thus aggravating
vascular diseases. However, the molecular mechanisms underlying
neointima formation are not fully elucidated. Extracellular vesicles (EVs) are mediators of various intercellular communications. The potential of EVs as regulators in
cardiovascular diseases has raised significant interest. In the current study we investigated the role of circulating small extracellular vesicles (csEVs), the most abundant EVs (1010 EVs/mL serum) in VSMC functions. csEVs were prepared from bovine, porcine or rat serum. We showed that incubation with csEVs (0.5 × 1010-2 × 1010) dose-dependently enhanced the proliferation and migration of VSMCs via the membrane
phosphatidylserine (PS). In rats with
ligation of right carotid artery, we demonstrated that application of csEVs in the ligated vessels aggravated
neointima formation via interaction of membrane PS with injury. Furthermore, incubation with csEVs markedly enhanced the phosphorylation of AXL and
MerTK in VSMCs. Pretreatment with BSM777607 (pan-TAM inhibitor),
bemcentinib (AXL inhibitor) or
UNC2250 (
MerTK inhibitor) blocked csEV-induced proliferation and migration of VSMCs. We revealed that csEV-activated AXL and
MerTK shared the downstream signaling pathways of Akt,
extracellular signal-regulated kinase (ERK) and
focal adhesion kinase (FAK) that mediated the effects of csEVs. We also found that csEVs increased the expression of AXL through activation of
transcription factor YAP, which might constitute an AXL-positive feedback loop to amplify the signals. Finally, we demonstrated that dual inhibition of AXL/
MerTK by ONO-7475 (0.1 µM) effectively hindered csEV-mediated proliferation and migration of VSMCs in ex vivo mouse aorta injury model. Based on these results, we propose an essential role for csEVs in proliferation and migration of VSMCs and highlight the feasibility of dual AXL/
MerTK inhibitors in the treatment of
vascular diseases.