Epimorphin, a morphogenic protein, induces proteases in rodent hepatocytes through NF-κB

Abstract

Epimorphin, expressed by hepatic stellate cells in the liver, directs normal morphogenesis in various organs. The aim of this study was to clarify the mechanism by which epimorphin functions as a morphogen in vitro. Male Balb/c mice and Sprague-Dawley rats were used. First, we explored the relationship between epimorphin expression and distribution of protease-positive cells in carbon tetrachloride-induced acute liver injury. We then examined protease levels in cultured hepatocytes and signal transduction of epimorphin. Finally, we determined the requirement for proteases and NF-kappaB in spheroid formation induced by epimorphin. Epimorphin expression was enhanced in injured areas during late recovery phase, in which protease-positive hepatocytes were localized adjacent to epimorphin-expressing cells. In vitro, epimorphin induced matrix metalloproteinase (MMP) 9, MMP 3 and urokinase type plasminogen activator (uPA) in hepatocytes. NF-kappaB mediated these protease expressions in hepatocytes. These proteases were required for epimorphin-induced and Matrigel induced spheroid. An epimorphin-neutralizing antibody also blocked spheroid formation on Matrigel, which contained epimorphin. In addition, NF-kappaB activation was also required for spheroid formation. Epimorphin elicits hepatocyte spheroids by inducing proteases in rodent hepatocytes through NF-kappaB.