Osteopontin regulates α-smooth muscle actin and calponin in vascular smooth muscle cells

Hong Gao, Marlene C. Steffen, Kenneth S. Ramos

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

vSMCs (vascular smooth muscle cells) lose differentiation markers and gain uncontrolled proliferative activity during the early stages of atherosclerosis. Previous studies have shown that OPN (osteopontin) mRNA and protein levels increase significantly on induction of proliferative activity by allylamine (an atherogenic amine) and that this response can be inhibited by OPN antibodies. We have investigated the role of OPN in vSMC differentiation. Primary cultures of aortic mouse vSMCs were transfected with an OPN expression plasmid and several vSMC differentiation markers including α-SM actin (a-smooth muscle actin), SM22-α, tropomyosin and calponin were monitored in this cellular model. α-SM actin and calponin protein levels were significantly decreased by OPN overexpression. Down-regulation of α-SM actin and calponin was also observed on extracellular treatment of mouse vSMCs with recombinant OPN. In addition, calponin mRNA was significantly decreased under serum-restricted conditions when OPN mRNA was dramatically increased, while α-SM actin mRNA remained unchanged. These data indicate that OPN down-regulates a-SM actin and calponin expression through an extracellular signalling pathway. Functional connectivity between OPN and vSMC differentiation markers has been established. Since vSMCs lose differentiation features during early atherosclerosis, a mechanistic basis for OPN functions as a critical regulator of proliferative cardiovascular disease has been presented.

Original languageEnglish (US)
Pages (from-to)155-161
Number of pages7
JournalCell Biology International
Volume36
Issue number2
DOIs
StatePublished - Feb 1 2012

Keywords

  • Actin
  • Calponin
  • Osteopontin
  • Vascular smooth muscle cell

ASJC Scopus subject areas

  • Cell Biology

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