Replicative senescence of vascular smooth muscle cells enhances the calcification through initiating the osteoblastic transition

Am J Physiol Heart Circ Physiol. 2009 Nov;297(5):H1673-84. doi: 10.1152/ajpheart.00455.2009. Epub 2009 Sep 11.

Abstract

Medial artery calcification, which does not accompany lipid or cholesterol deposit, preferentially occurs in elderly population, but its underlying mechanisms remain unclear. In the present study, we investigated the potential role of senescent vascular smooth muscle cells (VSMCs) in the formation of senescence-associated medial calcification. Replicative senescence was induced by the extended passages (until passages 11-13) in human primary VSMCs, and cells in early passage (passage 6) were used as control young cells. VSMC calcification was markedly enhanced in the senescent cells compared with that in the control young cells. We identified that genes highly expressed in osteoblasts, such as alkaline phosphatase (ALP) and type I collagen, were significantly upregulated in the senescent VSMCs, suggesting their osteoblastic transition during the senescence. Knockdown of either ALP or type I collagen significantly reduced the calcification in the senescent VSMCs. Of note, runt-related transcription factor-2 (RUNX-2), a core transcriptional factor that initiates the osteoblastic differentiation, was also upregulated in the senescent VSMCs. Knockdown of RUNX-2 significantly reduced the ALP expression and calcification in the senescent VSMCs, suggesting that RUNX-2 is involved in the senescence-mediated osteoblastic transition. Furthermore, immunohistochemistry of aorta from the klotho(-/-) aging mouse model demonstrated in vivo emergence of osteoblast-like cells expressing RUNX-2 exclusively in the calcified media. We also found that statin and Rho-kinase inhibitor effectively reduced the VSMC calcification by inhibiting P(i)-induced apoptosis and potentially enhancing matrix Gla protein expression in the senescent VSMCs. These findings strongly suggest an important role of senescent VSMCs in the pathophysiology of senescence-associated medial calcification, and the inhibition of osteoblastic transition could be a new therapeutic approach for the prevention of senescence-associated medial calcification.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aging / metabolism
  • Aging / pathology
  • Alkaline Phosphatase / metabolism
  • Animals
  • Aorta / metabolism
  • Aorta / pathology
  • Apoptosis
  • Calcinosis / genetics
  • Calcinosis / metabolism
  • Calcinosis / pathology*
  • Calcinosis / prevention & control
  • Calcium-Binding Proteins / metabolism
  • Cell Proliferation* / drug effects
  • Cell Transdifferentiation* / drug effects
  • Cell Transdifferentiation* / genetics
  • Cells, Cultured
  • Cellular Senescence* / drug effects
  • Cellular Senescence* / genetics
  • Collagen Type I / metabolism
  • Core Binding Factor Alpha 1 Subunit / metabolism
  • Extracellular Matrix Proteins / metabolism
  • Gene Expression Regulation
  • Glucuronidase / deficiency
  • Glucuronidase / genetics
  • Humans
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / pharmacology
  • Mice
  • Mice, Knockout
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism
  • Muscle, Smooth, Vascular / pathology*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism
  • Myocytes, Smooth Muscle / pathology*
  • Osteoblasts / drug effects
  • Osteoblasts / metabolism
  • Osteoblasts / pathology*
  • Protein Kinase Inhibitors / pharmacology
  • RNA Interference
  • Tunica Media / metabolism
  • Tunica Media / pathology
  • rho-Associated Kinases / antagonists & inhibitors
  • rho-Associated Kinases / metabolism

Substances

  • Calcium-Binding Proteins
  • Collagen Type I
  • Core Binding Factor Alpha 1 Subunit
  • Extracellular Matrix Proteins
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors
  • Protein Kinase Inhibitors
  • RUNX2 protein, human
  • matrix Gla protein
  • rho-Associated Kinases
  • Alkaline Phosphatase
  • Glucuronidase
  • klotho protein