L59 LAP-DPs could be detected in their media, and after treatment of TWNT-4 cells with a TGF-β receptor kinase inhibitor, SB431542, a simultaneous reduction was observed in both L59 LAP-DP levels in the culture media and the mRNA expression levels of collagen type (I) α1. In carbon tetrachloride- and bile duct ligation-induced liver fibrosis models in mice, plasma L59 LAP-DP levels increased prior to increase of hepatic hydroxyproline (HDP) contents and well correlated with α-smooth muscle actin (αSMA) expression in liver tissues. This evidence concerns the gene TGFB1 and Hepatic fibrosis.