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

Objectives: 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.

Methods: 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.

Results: 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).

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