Characterization of desmin-positive rat liver sinusoidal cells

Hepatic sinusoidal lining cells were isolated from mature male rats (12 months old) and cultured in order to clarify the characteristics of the Ito cells (fat-storing cells). Desmin staining was used as a marker in the isolation of the Ito cells, and a highly purified desmin-positive cell fraction was obtained. Less than 10% of the desmin-positive cells were positive for vitamin A auto-fluorescence. However, the number of vitamin A-positive cells increased with vitamin A treatment, and they extended to over half of the desmin-positive cells by the first week of vitamin A treatment. The cultured Ito cells were positive for both desmin and vimentin stainings. On the other hand, Kupffer and endothelial cells were positive only with vimentin staining. Ito cells lost their fat droplets after repeated subculturing. The electron microscopic features of the Ito cells became similar to those of myofibroblasts, except for the absence of dense bodies, indicating that the Ito cells may have possibly transformed into myofibroblasts. Collagen fibers were occasionally found in the extracellular space. These results indicate that Ito cells retain both their myogenic and fibrogenic properties, and that lipocytes or myofibroblasts may be desmin-positive cells which maintain specific functions. Furthermore, staining of the intermediate filaments is useful in the identification of Ito cells, and a highly purified Ito cell fraction can be easily obtained using desmin staining as a marker.