Activin receptors are expressed on human lung fibroblast and activin A facilitates fibroblast-mediated collagen gel contraction.

Activin A is a member of the transforming growth factor-beta superfamily that exerts its diverse biological effects through bindings to activin specific transmembrane serine/threonine kinase receptors. The fibroblast-mediated contraction of a collagen gel is thought to be a model of part of the wound-repair response and tissue contraction. In this study, we found the expression of activin type I receptors (ActR-I and ActR-IB) and type II receptor (ActR-II) on human fetal lung fibroblasts (HFL-1) by RT-PCR and immunocytochemistry. We also examined the effects of activin A on the HFL-1-mediated collagen gel contraction. Activin A stimulated collagen gel contraction in a dose dependent manner and its effect was abolished by an activin-binding protein, follistatin, that specifically suppresses activin A activities. This study demonstrated that ActR-I, ActR-1B and ActR-II are expressed on human fetal lung fibroblast and that activin A regulates fibroblast-mediated collagen gel contraction, suggesting that activin A might contribute to human lung fibroblast activities and structural remodeling observed in pulmonary fibrosis.