激活素A在糖尿病大鼠肾小管间质纤维化中作用的实验研究

摘要

Objective To explore the effects of activin A on tubulointerstitial fibrosis in rats with diabetic nephropathy (DN). Methods Male Wistar rats were randomized into normal control group (NC) and diabetes mellitus group (DM). Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). Six rats were sacrificed at 4, 8, 12 and 16 weeks, respectively, after establishment of the DN model. The changes of blood glucose (BS), kidney weight/body weight (KW/BW), urine albumin excretion rate (AER) and creatinine clearance rate (Ccr) were deter-mined. The morphology of tubulointerstitium was observed under light microscopy. Immunohistochemistry assay was applied to analyze the protein expression of activin A, follistatin, P-Smad2/3 and fibronectin in tubulointerstitium. Results Compared with NC group, KW/BW, AER, Ccr and interstitial fibrosis index in DM group were increased sig-nificantly (all P<0.01) from week 8 and culminated at week 16. The immunohistochemistry assay demonstrated that activin A staining was prominent in tubular epithelial cells in the DM group. Significantly higher level of activin A was observed in the DM group at week 4 and culminated at week 12. By contrast, follistatin staining was abundant in tubular epithelial cells in the NC group. However, in the DM group, the level of follistatin began to decrease gradually from week 4 to week 16, in which only traces of follistatin could be detected. P-Smad2/3 and fibronectin showed slight staining in tubulointerstitium in the NC group, but in the DM group, there was a gradual increase in the expression of P-Smad2/3 and fibronectin at week 8, which persisted to week 16. Conclusion Activin A may facilitate tubulointer-stitial fibrosis in DN by inducing the production of fibronectin via Smad signaling pathway.%目的：探讨激活素A（ACT A）在糖尿病肾病（DN）肾小管间质纤维化中的作用。方法采用随机数字表法将雄性Wistar大鼠分成对照组（NC）和糖尿病组（DM），腹腔注射链脲佐菌素（STZ）诱导糖尿病模型。各组分别在术后4、8、12和16周处死大鼠6只。观察各组血糖（BS）、肾质量/体质量（KW/BW）、24 h尿白蛋白排泄率（AER）及肌酐清除率（Ccr）的变化。过碘酸雪夫（PAS）染色观察肾小管间质形态学改变，免疫组织化学检测肾小管间质ACT A及卵泡抑素（FS）、P-Smad2/3、纤维连接蛋白（FN）的表达。结果与NC组相比，DM组大鼠从第8周末开始KW/BW、AER、Ccr及间质纤维化指数均显著上升（P＜0．01），第16周时达峰值。免疫组织化学结果显示，ACT A主要定位于DM组大鼠肾小管上皮细胞。DM组大鼠从第4周末开始ACT A蛋白表达逐渐增加，第12周末时达峰值。与ACT A相反，FS在NC组各时间点大鼠肾小管上皮细胞大量表达，在DM组其表达量从第4周开始逐渐下降，16周时只能检测到少量FS表达。P-Smad2/3和FN在NC组肾小管和间质有轻度表达，而在DM组大鼠从第8周起表达量逐渐增加，并一直延续到第16周。结论 ACT A可能通过Smad通路诱导FN的产生，促进糖尿病大鼠肾小管间质纤维化的发生。