Hepatic organoid formation in collagen sponge of cells isolated from human liver tissues.

We examined whether small hepatocytes (SHs), which are hepatic progenitor cells, could be isolated from a normal human liver and whether human hepatic cells could form hepatic organoids in a collagen sponge. Normal liver tissues were obtained from resected specimens from nine patients who underwent hepatic resection. Isolated hepatic cells were plated on dishes and a collagen sponge. More than 1 month later, SH-like cells appeared and proliferated on the dishes, whereas cell aggregates were formed in the sponge and showed characteristic tissue architecture: columnar and/or cuboidal epithelial cells lined the surface of the sponge. Clusters of epithelial cells with a large cytoplasm and ductular structures were observed under the lining cells. The lining and ductular cells were positive for cytokeratins 7 and 19, which indicated they were biliary epithelial cells (BECs), and the epithelial cells forming clusters were positive for the anti-human hepatocyte antibody, identifying them as hepatocytes. Some lining cells were positive for both the hepatic marker and the BEC markers. The cells in the collagen sponge actively proliferated and the hepatocytes excreted albumin into the medium. Thus, hepatic organoids could be reconstructed in a collagen sponge by normal human liver cells.