Vascular Adventitial Fibroblasts-Derived FGF10 Promotes Vascular Smooth Muscle Cells Proliferation and Migration in vitro and the Neointima Formation in vivo

Background: Activation of vascular adventitial fibroblasts (VAFs) upon vascular injury contributes greatly to the medial vascular smooth muscle cells (VSMCs) proliferation, migration and the subsequent neointima formation. A number of factors including fibroblast growth factors (FGFs) have been shown to control VSMC growth, proliferation and phenotypic switching, suggesting that they may function as paracrine signals for VAFs to modulate VSMCs functions. However, little is known about the signaling molecule(s) and its mechanism of action. This study is set to identify which and how FGF family members are involved in VAFs mediated vascular remodeling. Methods: We used qPCR, Western blot and Immunohistochemistry to observe the spatio-temporal expression of FGF10 and FGFR2 in injured vascular tissue. The proliferation and migration assays of VSMCs were performed in a co-culture system. The activation of signaling pathway was detected by Western blot, immunohistochemistry and immunofluorescence. Hematoxylin-eosin and immunofluorescence were used to assess the effects of exogenous FGF10 and siFGF10 on the neointima formation. Results: The expression of FGF10 and FGFR2 were increased from day 3 through day 14 post injury. FGF10 was significantly upregulated in adventitia, and FGFR2 was detected in both media and neointima after injury. In vitro, FGF10 was most prominently expressed in VAFs and FGFR2 was significantly expressed in VSMCs. Both were regulated by PDGF. Co-culture of VAFs and VSMCs in vitro showed that VAF-derived FGF10 promoted the proliferation and migration of VSMCs. PDGF could synergistically enhance the process. VAF-derived FGF10 can significantly activate the FGFR2 in VSMCs and furthermore significantly activate the downstream MAPK/PI3K-AKT signaling pathways. Delivery of exogenous FGF10 potentiated the neointima formation, while siFGF10 attenuated the neointima formation. Conclusion: VAFs-derived FGF10 promoted the proliferation and migration of VSMCs and neointima formation, and FGF10-FGFR2 signaling triggered the activation of MAPK/PI3KAKT pathways in VSMCs and PDGF synergistically amplified FGF10 signaling.