Osteogenic gene markers are epigenetically reprogrammed during contractile-to-calcifying vascular smooth muscle cell phenotype transition.

The understanding of vascular calcification-based mechanism is an urgent pending task in vascular biology and this prompted us to better address this issue by investigating whether DNA methylation mechanism might drive osteogenic marker genes modulation in primary human vascular smooth muscle cells (VSMCs) responding to calcium and phosphate levels overload up to 72 h. Firstly, our data shows this calcifying process recapitulates the molecular repertory of osteogenic biomarkers and specifically requiring RUNX2, Osterix and ALP, BSP genes activations along 72 h in vitro, and this behavior was validated here using other lineages. Conversely, both BMPs 4 and 7 were significantly overexpressed, maybe already as a mechanism in response to RUNX2 and Osterix genes activities identified earlier in response to the calcifying condition, and taken into maintain the calcifying phenotype of VSMCs. Additionally, survival signaling was maintained active and accompanied by a dynamic cytoskeleton rearrangement signaling requiring MAPK and AKT phosphorylations. Moreover, during the contractile-to-calcifying transition phenotype of VSMCs, epigenetic machinery was finely modulated, requiring the translocation of DNMT3B and TET2 into nucleus and this prompted us evaluating whether the profile of osteogenic-related gene promoters' methylation might contribute with this process. By firstly estimating 5meC/5 hmeC ratio changes, we further specifically show the significance of the epigenetic modulation of Osterix and Bone sialoprotein related gene promoters, presenting a positive correlation between the epigenetic signature of their gene promoters and transcriptional patterns. Altogether, our results show for the first time the importance of epigenetic mechanism on modulating osteogenic gene markers reprogramming during calcifying VSMCs phenotype acquisition, which might drive the genesis of vascular ectopic calcification.