[Expression of peroxisome proliferators-activated receptor gamma and alpha-smooth muscle actin in unilateral ureteral obstruction in rats].

OBJECTIVE

To evaluate the expression of peroxisome proliferators-activated receptor gamma (PPAR gamma) and alpha-smooth muscle actin (alpha-SMA) in unilateral ureteral obstruction (UUO) in rats and the relationship between them and the extent of tubulointerstitial injury.

METHODS

Male SD rats were randomly subjected to either left ureteral ligation (n=30) or sham operation (n=6), and they were sacrificed on 3, 7, 14, 21 or 28 days after UUO. Sections of renal tissue were stained with hematoxylin and eosin (HE), Masson, or periodic acid-silver methenamine (PASM). The extent of tubulointerstitial injury was determined by Banff classification. Immunohistochemical staining was performed to investigate the expression of PPAR gamma and alpha-SMA in the renal tissue.

RESULTS

Swelling of tubular epithelia cells, infiltration of inflammatory cells and proliferation of fibroblasts were not so obvious on days 3 and 7 after UUO. A diffuse inflammatory cells infiltration, and massive fibrous hyperplasia were detectable on days 14 and 21 after UUO. Most tubules showed serious damage and replaced by proliferative fibrous tissue on day 28. The expression of PPAR gamma was almost undetectable in sham operation group. However, it was upregulated on day 3 and peaking on day 14, and then it was slightly decreased on days 21 and 28. The expression of alpha-SMA was only found in vascular smooth muscle cells in sham operation group. It was upregulated mainly in some interstitial cells on day 3 and increased with the progression of tubulointerstitial fibrosis.

CONCLUSION

PPAR gamma expression increases in rat renal tissue after UUO, but does not always correlate with the extent of the alpha-SMA expression and tubulointerstitial injury. These data suggest that increase in PPAR gamma in renal tissue may play an important role in response to inflammation and fibrosis.