title: Osteoprotegerin inhibits calcification of vascular smooth muscle cell via down regulation of the Notch1-RBP-Jκ/Msx2 signaling pathway.
abstract: OBJECTIVE
  Vascular calcification is a common pathobiological process which occurs among the elder population and in patients with diabetes and chronic kidney disease. Osteoprotegerin, a secreted glycoprotein that regulates bone mass, has recently emerged as an important regulator of the development of vascular calcification. However, the mechanism is not fully understood. The purpose of this study is to explore novel signaling mechanisms of osteoprotegerin in the osteoblastic differentiation in rat aortic vascular smooth muscle cells (VSMCs).
  
  
  RESULTS
  VSMCs were isolated from thoracic aorta of Sprague Dawley rats. Osteoblastic differentiation of VSMCs was induced by an osteogenic medium. We confirmed by Von Kossa staining and direct cellular calcium measurement that mineralization was significantly increased in VSMCs cultured in osteogenic medium; consistent with an enhanced alkaline phosphatase activity. This osteoblastic differentiation in VSMCs was significantly reduced by the addition of osteoprotegerin in a dose responsive manner. Moreover, we identified, by real-time qPCR and western blotting, that expression of Notch1 and RBP-Jκ were significantly up-regulated in VSMCs cultured in osteogenic medium at both the mRNA and protein levels, these effects were dose-dependently abolished by the treatment of osteoprotegerin. Furthermore, we identified that Msx2, a downstream target of the Notch1/RBP-Jκ signaling, was markedly down-regulated by the treatment of osteoprotegerin.
  
  
  CONCLUSIONS
  Osteoprotegerin inhibits vascular calcification through the down regulation of the Notch1-RBP-Jκ signaling pathway.
authors.affiliation: Department of Gerontology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Shaoqiong
authors.initials: S
authors.lastname: Zhou
authors.forename: Xin
authors.initials: X
authors.lastname: Fang
authors.forename: Xing
authors.initials: X
authors.lastname: Fang
authors.forename: Huaping
authors.initials: H
authors.lastname: Xin
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Hongyu
authors.initials: H
authors.lastname: Qiu
authors.forename: Siming
authors.initials: S
authors.lastname: Guan
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D018398:Homeodomain Proteins / Q000378:metabolism*; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein / Q000378:metabolism*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D053244:Osteoprotegerin / Q000494:pharmacology*; D051381:Rats; D051881:Receptor, Notch1 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D061205:Vascular Calcification / Q000188:drug therapy*
chemical_list: D018398:Homeodomain Proteins; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; C084119:MSX2 protein; D053244:Osteoprotegerin; D051881:Receptor, Notch1; D000469:Alkaline Phosphatase