mTOR regulates vascular smooth muscle cell differentiation from human bone marrow-derived mesenchymal progenitors

Arterioscler Thromb Vasc Biol. 2009 Feb;29(2):232-8. doi: 10.1161/ATVBAHA.108.179457. Epub 2008 Dec 12.

Abstract

Objective: Vascular smooth muscle cells (VSMCs) and circulating mesenchymal progenitor cells (MSCs) with a VSMC phenotype contribute to neointima formation and lumen loss after angioplasty and during allograft arteriosclerosis. We hypothesized that phosphoinositol-Akt-mammalian target of rapamycin-p70S6 kinase (PI3K/Akt/mTOR/p70S6K) pathway activation regulates VSMC differentiation from MSCs.

Methods and results: We studied effects of PI3K/Akt/mTOR signaling on phenotypic modulation of MSC and VSMC marker expression, including L-type Ca(2+) channels. Phosphorylation of Akt and p70S6K featured downregulation of VSMC markers in dedifferentiated MSCs. mTOR inhibition with rapamycin at below pharmacological concentrations blocked p70S6K phosphorylation and induced a differentiated contractile phenotype with smooth muscle (sm)-calponin, sm-alpha-actin, and SM protein 22-alpha (SM22alpha) expression. The PI3K inhibitor Ly294002 abolished Akt and p70S6K phosphorylation and reversed the dedifferentiated phenotype via induction of sm-calponin, sm-alpha-actin, SM22alpha, and myosin light chain kinase. Rapamycin acted antiproliferative without impairing MSC viability. In VSMCs, rapamycin increased a homing chemokine for MSCs, stromal cell-derived factor-1-alpha, at mRNA and protein levels. The CXCR4-mediated MSC migration toward conditioned medium of rapamycin-treated VSMCs was enhanced.

Conclusions: We describe novel pleiotropic effects of rapamycin at very low concentrations that stabilized differentiated contractile VSMCs from MSCs in addition to exerting antiproliferative and enhanced homing effects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bone Marrow Cells / drug effects
  • Bone Marrow Cells / enzymology
  • Bone Marrow Cells / metabolism*
  • Calcium Channels, L-Type / metabolism
  • Cell Differentiation* / drug effects
  • Cell Survival
  • Cells, Cultured
  • Chemokine CXCL12 / metabolism
  • Chemotaxis
  • Chromones / pharmacology
  • Dose-Response Relationship, Drug
  • Humans
  • Mesenchymal Stem Cells / drug effects
  • Mesenchymal Stem Cells / enzymology
  • Mesenchymal Stem Cells / metabolism*
  • Morpholines / pharmacology
  • Muscle Proteins / metabolism
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / enzymology
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / enzymology
  • Myocytes, Smooth Muscle / metabolism*
  • Phenotype
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Signal Transduction* / drug effects
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases
  • Time Factors

Substances

  • CXCL12 protein, human
  • Calcium Channels, L-Type
  • Chemokine CXCL12
  • Chromones
  • Morpholines
  • Muscle Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Protein Kinases
  • MTOR protein, human
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • TOR Serine-Threonine Kinases
  • Sirolimus