Ultrastructural changes of fat-storing cells in experimental hepatic fibrosis

Kim, Mi Jin; Choi, Won Hee; Lee, Tae Sook

Abstract

Hepatic fibrosis was induced in Sprague-Dawley rate to evaluate the ultrastructural changes of fat-storing cells (Ito cells). For experimental induction of liver fibrosis, the rats were administered intraperitoneally with 0.5 ml of 50% Ccl4 solution per Kg body weight, twice weekly for 12 weeks. The rats were sacrificed every week. The liver tissues were examined under light and electron microscopes. And the immunohistochemical study of desmin was also performed. The results were summarized as follows: Light microscopic findings: The cellular infiltrations was inflammatory cells and Kupffer cells developed from 1 week after Ccl4 injection, and were the most severe in 4 weeks. The strong immunoreactivity for desmin was also evident in 4 weeks. The centrilobular necrosis and fibrosis developed from 2 weeks after injection, and the necrosis persisted until 8 weeks. The progress of fibrosis was accompanied by decreases in cellular infiltration and reactivity for desmin, and increased gradual nodular formation was also observed. The cirrhosis was developed after 10 weeks. Electron microscopic findings: An increase in number of fat-storing cells was observed from 1 week after injection. Transitional cells characterized by a depletion of lipid droplets and a hypertrophy of the rER appeared after 2 weeks. The number of transitional cells with abundant collagen fibers in the extracellular spaces increased in 4 weeks. With progression of fibrosis the number of fat-strong cells decreased and proliferating fibroblasts with dilated rER were observed. According to these results it was revealed that there was an apparent transition from fatstrong cells to transitional cells and to fibroblasts. These cells had a few similar characteristics and may belong to the same cell population. Thus it was suggested that fatstrong cells might play an important role in hepatic fibrosis.