Increased radioresistance, g(2)/m checkpoint inhibition, and impaired migration of bone marrow stromal cell lines derived from Smad3(-/-) mice

Radiat Res. 2006 Jun;165(6):671-7. doi: 10.1667/RR3572.1.

Abstract

Smad3 protein is a prominent member of the Tgfb receptor signaling pathway. Smad3(-/-) mice display decreased radiation-induced skin fibrosis, suggesting a defect in both Tgfb-mediated fibroblast proliferation and migration. We established bone marrow stromal cell lines from Smad3(-/-) mice and homozygous littermate(+/+) mice. Smad3(-/-) cells displayed a significant increase in radiation resistance with a D(0)=2.25+/- 0.14 Gy compared to Smad3(+/+) cells with a D(0)=1.75+/- 0.03 (P=0.023). Radioresistance was abrogated by reinsertion of the human SMAD3 transgene, resulting in a D(0)=1.49 0.10 (P=0.028) for Smad3(-/-)(3) cells. More Smad3(-/-) cells than Smad3(+/+) cells were in the G(2)/M phase; Smad3(-/-)(3) cells were similar to Smad3(+/+) cells. Smad3(+/+) cells exhibited increased apoptosis 24 h after 5 Gy (15%) or 8 Gy (43%) compared to less than 1% in Smad3(-/-) cells exposed to either dose. The movement of Smad3(-/-) cells, measured in an automated cell tracking system, was slower than that of Smad3(+/+) cells. Smad3(-/-)(3) cells resembled Smad3(+/+) cells. These studies establish concordance of a defective Tgfb signal transduction pathway, an increased proportion of G(2)/M cells, and radioresistance. The decreased migratory capacity of Smad3(-/-) cells in vitro correlates with decreased radiation fibrosis in vivo in mice deficient in Tgfb signaling.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis / radiation effects
  • Bone Marrow Cells / cytology*
  • Bone Marrow Cells / physiology*
  • Bone Marrow Cells / radiation effects
  • Cell Line
  • Cell Movement / radiation effects
  • Cell Survival / radiation effects
  • Genes, cdc / physiology
  • Genes, cdc / radiation effects
  • Mice
  • Radiation Tolerance / physiology
  • Receptors, Transforming Growth Factor beta / metabolism*
  • Smad3 Protein / metabolism*
  • Stromal Cells / cytology
  • Stromal Cells / physiology
  • Stromal Cells / radiation effects

Substances

  • Receptors, Transforming Growth Factor beta
  • Smad3 Protein
  • Smad3 protein, mouse