Role Of MMP-9 And TIMP-1 In Tubular Epithelial-myofibroblast Transdifferentiation

OBJECTIVE: During the development and progression of tubulointer-stitial fibrosis, the synthesis of extracellular matrix(ECM) was increased, In stroma of kidney, myofibroblast is the dominant cell in ECM synthesis. Under certain circumstances, myofibroblast can derive from transformed tubular epithelial. In recent years, the integrity of tubular basement membrane(TBM) is associated with the tubular epithelial-mesenchymal transdifferentiation(TEMT). Matrix metalloproteinase-9 (MMP-9) could degrade type Ⅳ collagen. Tissue inhibitor of metalloproteinase-1 (TIMP-1) is an endogenous inhibitor of MMP-9. In the present study, we investigated the dynamic changes of MMP-9 and TIMP-1 expression and the association of MMP-9, TIMP-1 expression with the integrity of TBM, α-SAM expression in rat unilateral ureteral obstruction (UUO) model. The aim is to explore the role of MMP-9 and TIMP-1 in tubular epithelial-myofibroblast transdifferentiation.METHODS: Male SD rats were underwent UUO or sham operation. There were 32 rats in sham operation group and UUO group, respectively. In each group, eight rats were chosen randomly to be sacrificed at the 3d, 7d,14d and 21 d after operation. Immunohistochemistry was used to evaluate the expression of MMP-9, TIMP-1, a-SAM and FN in the obstructive kidney. The infiltration of inflammatory cells, the histopathologic changes and tubulointerstitial score(TIS) were evaluated by HE, Massion and PAS staining. Body weight, proteionuria, the levels of serum creatinine and blood urea nitrogen(BUN) were measured as well. Pearson's correlation coefficient was used to identify correlations between the expression of MMP-9 and TIMP-1 in the obstructive kidney and the integrity of TBM, a-SAM expression.RESULTS: ?In UUO rats, the disruption of the TBM in PAS staining was found at day 7. At day 14, it was observed that the TBM was thickened and wrinkled wifh partial and extensive disruption. At day 21, it was observed that the TBM was extensively disrupted, thickened and shrunken.? In UUO rats, the expression of a-SMA and FN in tubulointerstitium was obviously increased at day 3 and gradually climbed with the progression of tubulointerstitial injury. (3) In UUO rats, a strong positive renal tubulointerstitial expression of MMP-9 was found at day 3 and the expression peaked at day 7, then was decreased gradually. ?In UUO rats, TIMP-1 expression in renal tubulointerstitium was significantly increased starting from day 3 to day 21. ?The positive area of a-SMA showed a positive correlation with that of FN(r=0.996, PO.01), the relative volume of interstitium( r=0.985, P<0.01) and TIS( r=0.972, PO.01). The positive area of FN also showed a positive correlation with the relative volume of interstitium(r=0.969, P<0.05) and TIS(r=0.953, P<0.05). ?The positive area of MMP-9 showed a negative correlation with that of a-SMA (r=0.798,P<0.05; r=0.894, PO.01) at day 3 and day 7 . The positive area of MMP-9 also showed a negative correlation with that of TIMP-l(r=-0.712, PO.05; r=-0.813, PO.05) at day 14 and 21. ?The positive area of MMP-9 showed a positive correlation with the disruption of TBM(r=0.831, P<0.05; r=0.802, P<0.05; r=0.843, PO.01; r=0.820,P<0.05)and with the number of disrupted tubular (r=0.737, P<0.05; r=0.821, P<0.05; r=0.815, P<0.05; r=0.804, P<0.05)at each time point.CONCLUSION: In rat UUO model, the expression of MMP-9 was increased in the early phase of fibrotic process and the level of MMP-9 expression was closely associated with a-SMA expression. TIMP-1 expression was gradually increased with the progression of tubulointerstitial injury. The expression of MMP-9 was closely associated with the breakage of TBM. MMP-9 and TIMP-1 sustain TBM cooperatively and may play an important role in TEMT.