Calcification of Aortic Smooth Muscle Cells Isolated From Spontaneously Hypertensive Rats

Although hypertension and vascular calcification are well established as important risk factors for several cardiovascular diseases, the relationship between them is unknown. Here, we investigated whether hypertension is relevant to vascular calcification by examining aortic smooth muscle cells (SMCs) isolated from the descending thoracic aortas of Wistar Kyoto rats (WKY) as normotensive rats and spontaneously hypertensive rats (SHR), a typical rat model of hypertension. Cells were cultured in DMEM containing 10% FBS for 6 days after reaching confluence. Von Kossa staining revealed that the positively stained calcified area of aortic SMCs from SHR increased rapidly compared to that from WKY. The gene expressions of calcification-regulating proteins including msh homeobox homolog 2, Osterix (a master transcription factor for osteogenesis), and alkaline phosphatase (ALP) (a marker of vascular calcification) were significantly increased in aortic SMCs from SHR compared to SMCs from WKY. On the other hand, Runx2, another osteogenic transcription factor, did not upregulate. Furthermore, we confirmed that ALP activity was strongly increased in aortic SMCs from SHR compared to SMCs from WKY. These results suggest that aortic SMCs from SHR tend to become easily calcified via an Msx2-Osterix signaling pathway.