Regulation of vascular smooth muscle cell calcification by syndecan-4/FGF-2/PKCα signalling and cross-talk with TGFβ

Borland, Samantha J.; Morris, Thomas G.; Borland, Shona C.; Morgan, Mark R.; Francis, Sheila E.; Merry, Catherine L.R.; Canfield, Ann E.

Abstract

Aims
Vascular calcification is a major cause of morbidity and mortality. Fibroblast growth factor-2 (FGF-2) plays an instructive role in osteogenesis and bone development, but its role in vascular calcification was unknown. Therefore, we investigated the involvement of FGF-2 in vascular calcification and determined the mechanism by which it regulates this process.

Methods and results
We demonstrate that FGF-2 expression is increased in vascular smooth muscle cells (VSMCs) induced to deposit a mineralized matrix by incubation with β-glycerophosphate. FGF-2 is also localized to sites of calcification within human atherosclerotic plaques. The expression of syndecan-4, a heparan sulfate proteoglycan which regulates FGF-2 signalling, is also increased in mineralizing VSMCs and co-localizes with FGF-2 in human calcified atherosclerotic plaques. Exogenous FGF-2 inhibits VSMC mineralization, and this inhibition is reduced when syndecan-4 expression is knocked-down using siRNA. Biochemical inhibition of FGFR signalling using a pan FGFR inhibitor (BGJ398) or knocking-down syndecan-4 expression in VSMCs using siRNA increases VSMC mineralization. These increases are prevented by inhibiting transforming growth factor-β (TGFβ) signalling with SB431542, suggesting cross-talk between FGF-2 and TGFβ signalling is crucial for the regulation of VSMC mineralization. Syndecan-4 can also regulate FGF-2 signalling directly via protein kinase Cα (PKCα) activation. Biochemical inhibition of PKCα activity using Gö6976, or siRNA-mediated suppression of PKCα expression increases VSMC mineralization; this increase is also prevented with SB431542. Finally, the ability of FGF-2 to inhibit VSMC mineralization is reduced when PKCα expression is knocked-down.

Conclusion
This is the first demonstration that syndecan-4 promotes FGF-2 signalling, and in turn, suppresses VSMC mineralization by down-regulating TGFβ signalling. Our discoveries that FGF-2 and syndecan-4 expression is increased in mineralizing VSMCs and that PKCα regulates FGF-2 and TGFβ signalling in VSMCs suggests that the syndecan-4/FGF-2/TGFβ signalling axis could represent a new therapeutic target for vascular calcification.

Citation

Borland, S. J., Morris, T. G., Borland, S. C., Morgan, M. R., Francis, S. E., Merry, C. L., & Canfield, A. E. (2017). Regulation of vascular smooth muscle cell calcification by syndecan-4/FGF-2/PKCα signalling and cross-talk with TGFβ. Cardiovascular Research, 113(13), 1639-1652. https://doi.org/10.1093/cvr/cvx178

• Journal Article Type: Article
• Acceptance Date: Sep 4, 2017
• Online Publication Date: Sep 6, 2017
• Publication Date: Nov 1, 2017
• Deposit Date: Aug 20, 2024
• Publicly Available Date: Sep 19, 2024
• Journal: Cardiovascular Research
• Print ISSN: 0008-6363
• Electronic ISSN: 1755-3245
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 113
• Issue: 13
• Pages: 1639-1652
• DOI: https://doi.org/10.1093/cvr/cvx178