Epimorphin expression and stellate cell status in mouse liver injury

Epimorphin, a mesenchymal morphogenic protein expressed by hepatic stellate cells, is considered important to liver morphogenesis in both healthy and pathologic conditions. However, the stellate cell phenotype, quiescent versus activated, that expresses epimorphin is unknown. We studied the relationship between epimorphin expression and stellate cell status in carbon tetrachloride-induced acute and chronic injury to mouse liver and in mouse liver regeneration following 70% partial hepatectomy. Epimorphin-positive cells in sinusoids expressed desmin, indicating that they are stellate cells. Epimorphin-positive cells were more numerous and larger in pericentral than periportal sinusoids in normal liver. In early-phase acute liver injury and liver regeneration, epimorphin expression transiently decreased while alphaSMA-positive stellate cells increased. In the recovery phase of acute and chronic injury as well as the late phase of liver regeneration, epimorphin expression was strikingly enhanced while alphaSMA-positive stellate cells decreased. This expression pattern was seen in both Balb/c and C57BL6 mouse strains irrespective of their differences in response to the hepatotoxin. In conclusion, stellate cells express epimorphin in their quiescent state and in the recovery phase, respectively associated with maintenance and reconstruction of microscopic liver structure.