Abstract

BACKGROUND
Although chronic pancreatitis gives rise to fibrosis of pancreatic exocrine tissue, and type 2 diabetes is accompanied by pancreatic fibrosis, the mechanisms of fibrogenesis in the pancreas have been insufficiently studied. The activated Pancreatic stellate cells (PSC) have recently been identified in human and experimental fibrotic areas from chronic panceatitis tissues. As PSC are similar in their morphology and biochemistry to hepatic stellate cells, they are suspected to play the same role in pancreatic fibrogenesis as the hepatic stellate cells in liver fibrosis. The PSC were isolated from the rat pancreata, and mediators stimulating the proliferation and differentiation identified. METHODS: The pancreatic stellate shaped cells were isolated by a minor modification to the method described by Apte et al (ref), using a Nycodenz gradient. The isolated PSCs were confirmed by phase-contrast and by the immunofluorescence of vimentin, desmin and smooth muscle a-actin (a-SMA). The level of alpha-SMA was quantified by Western blot in the PSCs in the culture, over time, and the cell proliferation was measured by 3[H]-Thymidine incorporation. The effect of the proliferation and differentiation of the PSC were assessed in relation to D-glucose (500 mg/dL), Insulin (10 IU/mL) and TGF-beta (10 ng/mL) treatment of the culture medium. RESULTS: The stellate shaped cells from the rat pancreata grew readily in the culture. Unactivated PSCs, cultured for 3 days, had an angular appearance, contained lipid droplets, manifesting positive vitamin A autofliuorescence, and stained positively for vimentin and desmin, but negatively for alpha-SMA. Within 4~8 days of primary culturing, the PSCs were activated, the sizes and numbers of the fat droplets decreased, the cells flattened, developed long cytoplasmic extensions and expressed alpha-SMA. After 3 passages, almost 100% of the cells were positive for alpha-SMA expression, indicating a myofibroblast type of differentiation in vitro. The addition of high-glucose concentrations and insulin to the activated PSCs significantly stimulated cell proliferation (194.4+/-8.3, 175.0+/-31.0 vs. control), and when the combination of high- glucose and insulin was applied, the cell proliferation was increased to an even greater extent (247.0+/-21.8 vs. control). CONCLUSIONS: Pancreata stellate cells can be isolated, and cultured in vitro, from normal SD rats. High concentrations of glucose and insulin in culture medium activated the PSC proliferation.

• Keywords: Pancreas;Fibrosis;Pancreatic Stellate Cell;Hyperinsulinemia;Hyperglycemia;