EXTENSION OF LONG CELLULAR PROCESSES OF HEPATIC STELLATE CELLS CULTURED ON EXTRACELLULAR TYPE-I COLLAGEN GEL BY MICROTUBULE ASSEMBLY - OBSERVATION UTILIZING TIME-LAPSE VIDEO-MICROSCOPY

Hepatic stellate cells cultured on or in freshly prepared type I colla gen gel as a substratum were induced to elongate long cellular process es. The extension of the cellular processes was monitored by using vid eo-enhanced optical microscopy. The cellular processes seemed to exten d along the extracellular type I collagen fibers. Once extended cellul ar processes after overnight culture on type I collagen gel were retra cted by cytoskeleton degradation with colchicine or cytochalasin B. Th e cellular processes were also retracted by treatment with protein kin ase inhibitor, herbimycin A or staurosporin, or with phosphatidylinosi tol 3-kinase inhibitor, wortmannin. The effects of colchicine, herbimy cin A, staurosporin, or wortmannin were drastic, and the cells were fi nally changed to a round shape within a few hours, as seen also after cold-treatment at 4 degrees C. Cytochalasin B also time-dependently re tracted the extended cellular processes. These results indicated that the cultured stellate cells were induced to elongate cellular processe s by cell surface binding to type I collagen fibrils, followed by prot ein or phosphatidylinositol phosphorylation and finally F-actin and mi crotubule assembly. Extended long cellular processes seem to reflect t he in vivo structure of hepatic stellate cells, and molecular mechanis m for the extension and maintenance of cellular processes was proposed .