Rev-erbα inhibits vascular calcification by repressing osteogenic reprogramming in atherosclerosis
Background: Atherosclerotic plaque rupture is the most deleterious atherogenic event, responsible for the majority of fatal acute atherothrombotic and myocardial infarctions. Intimal microcalcification is a major cause of atherosclerotic plaque instability. Yet, a thorough characterization of the mechanisms controlling intimal calcification is needed to develop innovative therapeutic strategies to treat high risk patients. The nuclear receptor Rev-erb regulates lipoprotein metabolism and exerts anti-inflammatory activities. Here, we hypothesized that Rev-erb modulates atherogenesis by regulating arterial calcification processes. Methods: We used a multi-omics approach in the ANGIOSAFE and the ATHEROPORTAL human cohort to identify pathways and factors associated with vascular calcification in diabetic patients. We then compared REV-ERB expression between calcified and non-calcified areas of human endarterectomies using laser capture microdissection assays (n=11-22/group). We assessed the role of Rev-erb on calcium deposition and expression of osteoblast markers in aortic roots of 18-month-old Ldlr-/-Rev-erb-/- and Ldlr-/-Rev-erb+/+ mice (n=10/group). Rev-erb-dependent molecular pathways that drive calcification were identified using gene expression profiling in aortic plaques from Ldlr-/-Rev-erb-/- and Ldlr-/-Rev-erb+/+ mice (n=8-10/group). We then confirmed omics data using primary aortic smooth muscle cells (SMCs) (n=3-6) in vitro assessing inflammation-driven calcification process as well as Rev-erb-dependent transcriptional mechanisms. Results: REV-ERB expression is significantly lower in circulating anti-inflammatory classical CD14+CD16- monocytes from diabetic patients with low coronary artery calcium (CAC) compared to those exhibiting high CAC scores while its expression is lower in highly calcified plaques from patients with diabetes mellitus compared to those with no diabetes or no calcification. Consistently, REV-ERB is markedly downregulated in calcified areas of human endarterectomy samples, while remaining higher in non-calcified regions. Rev-erb deficient Ldlr-/- mice exhibit accelerated atherogenesis and vascular calcification, and aortic smooth muscle cells (SMCs) exhibit a reprogramming toward an osteochondroblastic phenotype. Functional in vitro studies show that Rev-erb maintains SMC identity by preventing their IL-1{beta}-driven transdifferentiation into osteochondroblast-like cells, notably through the repression of key osteogenic regulators. Finally, while hyaluronic acid degradation is known to promote intimal calcification, we demonstrate that Rev-erb represses the hyaluronidase Cemip expression during SMC transdifferentiation. Conclusions: Rev-erb is identified as an important brake on SMC-driven vascular calcification, suppressing both osteogenic reprogramming and matrix-remodeling pathways. Thus, this study opens new avenues for developing novel therapeutic tools targeting Rev-erb to reduce vascular calcification and associated cardiovascular risk in high-risk patients.