Circulating fibrocytes in ischemia-reperfusion injury and chronic renal allograft fibrosis.

Background: Interstitial fibrosis in chronic allograft injury has been suggested as a major cause of the loss of allograft. Methods: To clarify the involvement of circulating fibrocytes (CF) and α-smooth muscle actin (SMA)-positive cells in renal allograft injury, we investigated 36 renal transplanted cases at 0 h, 1 h, 2–4 weeks, 4–8 weeks, and 1 year, and 5 normal controls. Double immunofluorescence analysis for both COL1 and CD45 indicating CF (/mm2), and the positive area (%) of α-SMA and Masson trichrome (MT) stain were detected by an image analyzing system. Results: The mean number of CF was 0 in controls and 4.0 in total transplanted specimens (p 2 = 0.39, p capillaries was correlated positively with COL1-positive area (R2 = 0.72, p 2 = 0.25, p Conclusion: CF were transiently induced, probably due to ischemia-reperfusion injury, but fibrosis only slightly progressed in this process. The α-SMA-positive myofibroblasts may accelerate the expansion of fibrosis around peritubular capillaries in chronic allograft injury.