The growth of cell populations and the properties in tissue culture of regenerating liver of the rat

Abstract

Hitherto, quantitative investigation of the histology of regenerating liver after partial hepatectomy has been concerned almost entirely with changes in the parenchymal cells. It has long been known, however, that other kinds of cell within the liver take part, and that as a consequence the restored liver is nearly normally organized. A quantitative investigation has therefore been made into the behaviour of different types of cell in regenerating liver. The material consisted of histological sections and tissue cultures of livers of normal adult rats and of adult rats from which two-thirds of the liver had been removed 1, 2, 7 or 21 days previously. Mitosis was found at some stage of the regenerative process in parenchymal cells, bile-duct cells, lining cells of the sinusoids (including v. Kupffer cells), and peritoneal mesothelial cells. While the parenchymal cells showed maximum mitotic rate in the rats killed 1 day after operation, the other types of cel! showed negligible mitosis at this time and maximum mitotic rate at 2 days after operation. At 21 days after operation, the total liver populations of parenchymal cells, sinusoid lining cells and bile-duct cells had all returned to a normal level. In tissue cultures the number of cells appearing outside each explant after 3 days of cultivation was counted. The most important finding was that the explants from the animals killed 2 days after operation produced many more macrophages, fibroblasts and bile-duct cells than the explants from the other animals. Parenchymal cells were not successfully cultured. It is suggested that the results of the tissue cultures indicate changes in the mobility of the cells during regeneration, and that increased mobility may be important in the regenerative process.