[Pathogenesis of Interstitial Kidney Fibrosis. Studies in the Rat Model of Unilateral Ureteral Obstruction]

Background: The animal model of unilateral ureteral obstruction (UUO) of the rat is suitable to cause a renal interstitial fibrosis within a few weeks. Prior to the 10th day after UUO, no fibrotic changes were detectable in ureter-ligated kidneys, whereas after day 20 fibrosis was developing strongly.

Method: Using cell cultures it was examined whether any in vivo changes in proliferation and function of fibroblasts are also detectable in cell cultures and whether, due to their persistency, they are of fundamental importance for the development of renal interstitial fibrosis.

Results: The comparison of the proliferation in cell cultures established 5 and 21 days after UUO showed that the cultures of the two experimental groups behave similarly. Consequently, the action of acute inflammatory processes on fibroblast proliferation without any existing fibrosis is comparable with that of pronounced fibrosis in the animal model. High concentrations of fetal calf serum in the culture medium cause a stimulation of the cell proliferation as well as a selection of mitotically active differentiation stages of fibroblasts.

Conclusion: Obviously, the loss of inhibition of the fibroblast proliferation under the conditions of cell culture causes similar changes to those effected by pathogenic mechanisms in the kidneys of rats with UUO. If the behaviour of fibroblasts in organs is to be assessed using results of cell culture experiments, the stimulating action of the culture conditions and the missing influence of other cells present in the tissue should be considered. These factors make the recognition of remaining differences between cells from normal and damaged kidneys more difficult under the conditions of primary cell cultures.