To investigate whether ischemic postconditioning effects on the development of tubulointerstitial fibrosis follow acute renal ischemia-reperfusion.

Rat models of warm renal I/R were established by clamping left pedicles for 45 minutes after right nephrectomy, both with and without treatment with ischemic postconditioning, and then reperfused for up to 12 weeks. Hematoxylin–eosin (H&E) and Masson's trichrome staining were used to assess renal fibrosis. The expression spot and protein levels of ⍺-smooth muscle actin (⍺-SMA), transforming growth factor–β1 (TGF-β1), and phospho-Smad2 were also analyzed.

Our data showed that patchy inflammation and tubulointerstitial fibrosis were found 12 weeks later in rats subjected to I/R alone or with postconditioning. Tubulointerstitial fibrosis worsened further in rats subjected to 45-minute ischemia-reperfusion, accompanied by the increased expressions of ⍺-SMA, TGF-β1, and phospho-Smad2 at the end of 12 weeks. In contrast, the above histologic changes and molecular expressions were significantly attenuated in rats of ischemic postconditioning group.

The results indicated that 45-minute I/R injury may cause tubulointerstitial fibrosis in the long term, and ischemic postconditioning has beneficial effects on renal fibrosis. Its mechanisms may involve inhibition of the TGF-β1/phospho-Smad2 pathway to exert protective effects.