Two distinct epithelial responses may compensate for the ureteral obstruction in early and late phase of unilateral ureteral obstruction-treated rat: Cellular proliferation in acute phase and osteopontin expression in chronic phase

In order to clarify cellular responses in dilated renal tubules in the acute and chronic phase of ureteral obstruction, we investigated the expression of proliferating cell nuclear antigen and osteopontin (OPN) in unilateral ureteral obstruction (UUO)-treated rat kidneys. The results showed that renal epithelial cells proliferate in association with tubular dilatation to compensate for the ureteral obstruction in the acute phase of UUO while the proliferative activity decreases in the chronic phase. In the chronic phase, however, the expression of OPN was up-regulated in various tubules but not associated with the tubular dilatation. Taken together with its chemoattractant activity for macrophage, OPN may be involved in the interstitial fibrosis as another compensatory mechanism in the chronic phase of ureteral obstruction. Therefore, these results suggest that two distinct epithelial responses may compensate for the ureteral obstruction in the acute and chronic phase of UUO-treated rat, respectively.