| Objective: Renal interstitial fibrosis plays a major role in thedevelopment of chronic renal failure. Perplexing cell factors and signaltransduction pathways participate in the process of renal interstitial fibrosis,and investigating the mechanism can provide theoretical basis for preventionand treatment of interstitial fibrosis. Prior studies found that hepatocytegrowth factor (HGF) is an endogenous factor which could reverse or postponethe progression of renal interstitial fibrosis. HGF may exert its biologicalactivity through a variety of ways, while the current research is mainlyfocused on its impact on the expression of transforming growth factor-beta(TGF-β)and its interference in the signal transduction. Recent studies havefound that the renal tubular epithelial-mesenchymal transition(EMT) plays acrucial role in renal interstitial fibrosis; Meanwhile, HGF could block theEMT pathway, reduce myofibroblast-the source of the mesenchymalcomponent, thus aslo attenuate or even reverse fibrosis. Neutrophilgelatinase-associated lipocalin (NGAL) was initially found to be a biomarkerof acute renal injury. Lately more and more literatures reported that NGALmight be involved in the process of renal interstitial fibrosis, and renal tubularepithelial-mesenchymal transition. In such cases, NGAL may not only act asan early predictor of renal interstitial fibrosis, but is also able to maintain thephenotype of renal tubular epithelial cells, preventing them from converting tothe mesenchymal cells."Microarray Analysis" has found that HGF couldinduce the expression of NGAL in renal medullary collecting duct cells. Inanimals, whether HGF can intervene EMT, or other avenues leading tofibrosis by inducing NGAL in renal, has not been reported. In this experiment,we will detect the early expression of NGAL in the unilateral ureteral obstruction(UUO) rat kidney, and the correlation between HGF,NGAL andE-cadherein(E-cad) under the intervention of exogenous HGF, and thenexplore the mechanism between HGF, NGAL and the process of"damage-repair-fibrosis", thus provide new ideas for the treatment of renalfibrosis.Method:72clean level healthy male SD rats, body weight200±20g,were randomly divided into three groups:⑴s ham operation group(shamgroup): only separate the left ureter, no ligated or cut, Intraperitonealinjection(IP) of saline daily;⑵unilateral ureteral obstruction—operationgroup(UUO group): the left ureter was ligated and cut, Intraperitonealinjection of saline daily;⑶hepatocyte growth promoting factor—interventiongroup (pHGF group): the left ureter was ligated and cut, pHGF0.5mg/kg/dayby I.P daily. Rats in each group received intraperitoneal injection from1daybefore the operation until the14th postoperative day, in which the volume ofsaline in Sham group and UUO group was equal to the pHGF group. Duringthe experiment rats were provided with free food and water.6rats wererandomly selected out of each group In the1st,4th,7th,14th days after theoperation. The left kidneys were harvested and made into sections.Respectively, the pathological changes of renal tissue with hematoxylin eosin(HE) and Masson staining were observed under the light microscope; NGAL,E-cad and HGF expression were examined by Immunohistochemical method.The results were analyzed using the image analysis system IPP(Image-ProPlus) for semi-quantitative analysis. All the data were expressed as mean±standard deviation, single factor analysis of variance was used among thethree groups, two independent samples t-test between two groups, andnon-parametric tests for the data which did not meet the normality andhomogeneity of variance. Statistical analysis software SPSS17.0was used fordata statistics, with P<0.05as a statistical significance.Results: The renal tissue with HE and Masson staining was observedunder the light microscope, and the results were as follows: the relativetubulointerstitial area and the content of renal interstitial collagen fiber increased gradually with ureteral obstruction prolonged, which suggested anincreasing level of renal interstitial fibrosis. Compared with UUO group, thehistopathological changes were alleviated in the corresponding pHGF group.Immunohistochemical staining results analysed with IPP image analysissystem showed that, NGAL mainly expressed in the proximal tubulecytoplasm. Expression of NGAL was little in the Sham group. NGAL hadexpressed on postoperative1st day in both UUO and pHGF groups, whosesubsequent expression in UUO group is gradually elevated on the4th,7th dayuntil the14th day. In pHGF group, NGAL expressed to the top in the4th day,and gradually down on the following7th and14th day. NGAL barely had theslight expression in UUO group and pHGF group in the14th day. On the4thand7th day, the level of NGAL was dramatically higher in pHGF group thanUUO group. E-cad mainly expressed on the epithelial cell membrane of distaltubule, and expressed significantly in sham group in each time observed.Comparing the level of E-cad in the4th,7th and14th day between the groups,we had a conclusion as: Sham> pHGF> UUO group (P<0.05). With the timeof ureteral obstruction prolonged, expression of E-cad in UUO group andpHGF group gradually decreased. HGF mainly expressed in the tubularepithelial cells, mesangial cells, weak in the Sham group. The HGF levels inthe UUO and the Sham group gradually rose with the ureteral obstructionprocess, peakd in the7th day, then decreased in the14th day. HGF levelsbetween the three groups in the same period were compared as: pHGF>UUO>Sham group (P<0.05).The IOD values of NGAL and HGF have a linearcorrelation (r=0.726,P<0.05).Conclusion: The levels of HGF and NGAL are increased in the earlystage in the kidney of UUO rats. pHGF can raise the level of HGF in thekidney, thus alleviate renal interstitial fibrosis in rats with unilateral ureterligation by means of maintaining the expression of E-cad and promoting theexpression of NGAL; The latter is actively involved in the repairing functionof HGF on renal injury. |
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