Fibroblast growth factor 21 attenuates calcification of vascular smooth muscle cells in vitro

Vascular calcification is a dysfunction of the vasculature. Recent findings indicate that fibroblast growth factor21 (FGF21), a protector of the cardiovascular system, is related to the mineral deposition of bone and enhances the osteogenic activity of bone morphogenic protein (BMP)-2. In this study, we explored whether FGF21 suppresses vascular calcification.

A calcifying model was established by culturing primary rat vascular aortic smooth muscle cells (VSMCs) in a beta-glycerophosphate (BGP)-containing calcifying medium for 14 days. In addition, recombinant human FGF21 was applied to protect against VSMC calcification.

In the presence of BGP, the expression levels of osteoblastic genes, including alkaline phosphatase (ALP), BMP-2 and runt-related transcription factor (RUNX)-2, were significantly upregulated on day 3, an effect that was maintained through day 14 (P < 0.001). A concomitant increase in ALP protein expression was observed through day 9 (P < 0.05). The incubation of VSMCs with calcifying medium for 14 days increased ALP activity (P < 0.05) and led to the formation of visible calcium nodules over the course of the protocol. β-klotho expression was unaltered in BGP-induced VSMCs for the 14-day culture period. The culturing of VSMCs with calcifying medium led to opposing trends in the expression of FGFRs, namely, an increase in FGFR1 and FGFR4 mRNA levels (P < 0.001) and a decrease in FGFR2 and FGFR3 mRNA levels (P < 0.01). Reduced mineral deposition, in combination with decreased ALP activity (P < 0.001) and ALP protein expression (P < 0.001), was noted in VSMCs treated with varying doses of FGF21 and BGP in a dose-dependent manner. In addition, FGF21 downregulated osteoblastic-promoting gene expression, including ALP (P < 0.001), BMP-2 (P < 0.001) and RUNX-2 (P < 0.001). Furthermore, FGF21 enhanced β-klotho expression (P < 0.05) and increased FGFR1 and FGFR3 mRNA levels (P < 0.001). FGFR-1 inhibitor SU5402 blocked partial inhibition of FGF21 on the expression of BMP-2 (P < 0.001) and RUNX-2 (P < 0.05). Furthermore, FGF21 suppressed the phosphorylation of P38, while P38 inhibitor, SB203580, attenuated the downregulation of RUNX-2 (P < 0.05).

These data demonstrate FGF21 attenuates VSMC calcification in vitro via an FGF21/FGFR1/3/β-klotho/P38MAPK/RUNX-2 signalling pathway.