Molecular changes in extracellular matrix turnover after renal ischaemia-reperfusion injury

Background: Renal ischaemia-reperfusion (IR) injury is an inevitable conseq uence of transplantation and contributes to later graft fibrosis. This stud y aimed to elucidate the possible mechanisms by studying the expression of genes associated with extracellular matrix (ECM) turnover. Methods: Male Wistar rats underwent laparotomy, clamping of the right renal pedicle for 45 min, and left nephrectomy. Control animals underwent left n ephrectomy only, or had no operation. Animals were killed at 8, 16 and 24 w eeks and messenger RNA was extracted from renal tissue. Genes of interest w ere amplified and then quantified in an enzyme-linked immunosorbent assay s ystem with levels expressed as a ratio to a known housekeeping gene (GAPDH) . Results: Experimental animals developed progressive proteinuria from 16 wee ks onwards. At 8 weeks after IR injury, gene levels of matrix metalloprotei nase (MMP) 2, an ECM-degrading enzyme, were significantly increased. Levels then fell progressively. This was associated with increasing expression of tissue inhibitor of metalloproteinases (TIMP) 1, an inhibitor of MMP-2, an d of transforming growth factor (TGF) beta, a profibrotic cytokine, by 24 w eeks following injury. Conclusion: These results suggest that, after an initial phase of increased ECM turnover following IR injury, the balance turns towards one of reduced degradation. This is likely to be an important mechanism in the subsequent development of fibrosis.