Activins are members of the
transforming growth factor beta (
TGF beta) superfamily, which comprises a growing group of dimeric
proteins.
TGF beta and several other members of this superfamily are known to play an important role in wound healing. However, expression of
activin during wound healing has not been demonstrated so far. In this study we have analyzed the expression pattern of
activin and
activin receptors in normal and wounded skin. We found a large induction of
activin A and a minor induction of
activin B mRNA expression 1 day after skin injury and high expression levels of
activin A and B were found within the first 7 days after wounding. At 13 days after injury, expression of
activin A mRNA had returned to the basal level, whereas high levels of
activin B persisted. In situ hybridization studies revealed expression of
activin A in the granulation tissue below the
wound and
activin B in the hyperproliferative epithelium at the
wound edge and in the migrating epithelial tongue. All known types of
activin receptors as well as the
activin binding protein follistatin were expressed in normal and wounded skin. However, no significant induction of receptor gene expression was seen during the repair process. The distribution of
activins and
activin receptors in the
wound suggests multiple autocrine and paracrine activities of the
ligands during wound healing. Our data provide evidence for a novel function of
activin and indicate that--besides
TGF beta s themselves--other members of this superfamily might also play an important role in tissue repair.