Activin A: a possible marker for liver transplant outcome

Activin A, a homodimeric protein consisting of two ßA subunit, is a member of the transforming growth factor-beta (TGF-ß) superfamily. This protein is involved in different physiological process: regulation of pituitary gonadotrophin secretion, stimulation, of spermatogonial proliferation and induction of erythroid and mesoderm differentiation (De Bleser et al., 1997). Activin A is produced by different cell types, including hepatocytes; these cells also express specific membrane receptors (Xu et al., 1995). The binding between activin A and its receptors activate a “cascade” of events such as apoptosis in the centrolobular region, inhibition of DNA (Schwall et al., 1193) and increase of collagen I synthesis (Sugiyama et al., 1998). Activin A inhibits hepatocytes proliferation induced by hepatocyte growth factor (HGF) or epidermal growth factor (EGF) in a dose-dependent manner. Furthermore, HGF or EGF stimulate the hepatocyte synthesis of activin A (Yasuda et al., 1993). Partial hepatectomy in rats is followed by a maximal expression of activin A after 24 h (Kogure et al., 1995). Several studies suggest that activin A may be involved in regulation of hepatocytes proliferation and represents a potential inhibitor of hepatic regeneration (Fausto et al., 1995). We designed the present study in order to analyze the serum activin A levels in patients receiving a liver transplant (n=6)