Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA364

Poster Communications

C-reactive protein induces osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells via oxidative stress

L. Henze1, B. Boehme1, J. Masyout1, T. Luong1, F. Lang2, B. Pieske1,3,4, I. Alesutan1,3, J. Voelkl1

1. Center for Cardiovascular Research Cardiology CVK, Charité - Universitätsmedizin Berlin, Berlin, Germany. 2. Department of Physiology I, Eberhard-Karls University, Tübingen, Germany. 3. Berlin Institute of Health, Berlin, Germany. 4. Department of Internal Medicine and Cardiology, DHZB, Berlin, Germany.

Background: Medial vascular calcification is a key risk factor associated with cardiovascular events and the excessive mortality in chronic kidney disease patients. Vascular calcification is actively promoted by osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs) and involves pro-inflammatory processes. Increased C-reactive protein (CRP) levels are associated with vascular calcification in hemodialysis patients. The present study explored whether CRP directly contributes to the progression of vascular calcification and the potential mechanisms. Methods: In-vitro experiments were performed in primary human aortic smooth muscle cells (HAoSMCs) treated with recombinant human CRP protein with or without high phosphate conditions, in the presence of antioxidants TEMPOL and TIRON or following knockdown of FCGR2A by silencing. Mineralization was determined by quantification of calcium deposition, total antioxidant capacity and ALPL activity by colorimetric methods and mRNA expression by quantitative RT-PCR. Results: Treatment with calcification medium increased calcium deposition in HAoSMCs, an effect further augmented by CRP treatment. Addition of CRP alone to the cell culture medium up-regulated osteogenic markers CBFA1 and ALPL mRNA expression in HAoSMCs, suggesting that CRP is directly inducing osteo-/chondrogenic transdifferentiation. Accordingly, ALPL activity was also increased by CRP treatment. The mRNA levels of the markers of oxidative stress and critical components of the superoxide-generating NADPH oxidase system NOX4 and CYBA were up-regulated while total antioxidant capacity of HAoSMCs was decreased after CRP treatment. Treatment of HAoSMCs with antioxidants prior to CRP treatment suppressed osteogenic markers CBFA1 and ALPL mRNA expression, and thus, the CRP-induced osteo-/chondrogenic transdifferentiation of HAoSMCs. Moreover, silencing of the FCGR2A gene encoding the Fc fragment of IgG receptor IIA was able to suppress CRP-induced oxidative stress as well as osteogenic markers mRNA expression in HAoSMCs. Conclusions: CRP may directly induce osteo-/chondrogenic transdifferentiation of VSMCs by promoting FCGR2A-dependent cellular oxidative stress. Thus, CRP may actively contribute to the progression of vascular calcification in patients suffering from chronic kidney disease.

Where applicable, experiments conform with Society ethical requirements