Smads regulate collagen gel contraction by human dermal fibroblasts

Background Transforming growth factor (TGF)-beta induces fibroblast contraction that is implicated in efficient wound healing. The Smad family of proteins mediates signal transduction of the TGF-beta superfamily. However, its role in fibroblast contraction remains unclear. Objectives To determine whether Smad proteins regulate fibroblast contraction. Methods We used an in vitro type I collagen gel contraction assay with human dermal fibroblasts infected with adenoviruses carrying Smads. Results Overexpression of Smad3, a major signal transducer in the Smad family, enhanced collagen gel contraction by fibroblasts when compared with fibroblasts overexpressing a control lacZ. Addition of a very low concentration of TGF-beta1 that did not affect the collagen gel contraction by itself enhanced the contraction by fibroblasts overexpressing Smad3. In contrast, TGF-beta1-mediated collagen gel contraction was suppressed by overexpression of Smad7, a major inhibitory regulator in the Smad family, in fibroblasts. In addition, inhibitors of the Erk and p38 pathways, PD98059 and SB203580, did not affect TGF-beta1-mediated collagen gel contraction by dermal fibroblasts. Conclusions Modulation of Smad3 or Smad7 expression in dermal fibroblasts affected their contraction of collagen gels possibly by regulating TGF-beta signalling in fibroblasts.