PPARγ和α-SMA在单侧输尿管梗阻大鼠肾组织中的表达及其意义

Expression of peroxisome proliferators-activated receptor γ and α-smooth muscle actin in unilateral ureteral obstruction in rats

目的观察单侧输尿管梗阻(UUO)模型大鼠肾组织α-平滑肌肌动蛋白(α-SMA)、过氧化物酶体增殖物激活受体(PPARγ)表达变化及其与肾小管间质纤维化间的关系.方法 36只SD大鼠随机分为假手术组(n=6)和模型组(n=30).模型组行UUO术,并随机分为3、7、14、21和28 d组.相应时间点活杀动物,取肾脏,用常规苏木素-伊红(HE)、Masson、高碘酸-乌洛托品银(PASM)染色,观察肾小管病变程度;用免疫组化法测定UUO大鼠梗阻肾不同时间点α-SMA和PPARγ表达变化及与肾脏病理变化间的关系.结果病理学结果显示,UUO 3和7 d时肾小管上皮细胞肿胀,炎症细胞浸润,纤维组织增生尚不明显;14 d和21 d时肾皮质大量炎症细胞浸润及纤维组织增生;28 d时表现为肾小管严重破坏,纤维组织弥漫增生.免疫组化结果显示,PPARγ在假手术组肾组织中几乎无表达;UUO模型大鼠随着病变进展,肾组织PPARγ表达增加,主要分布在肾小管上皮细胞、浸润的单核细胞,3 d时表达量开始增加,14 d达高峰,此后表达略有减少,但仍显著高于假手术组及3 d和7 d组.假手术组α-SMA仅表达于血管平滑肌肌层,3 d时肾间质出现表达,14～21 d表达显著增加,阳性信号弥漫分布,高峰持续至28 d实验结束.结论 PPARγ在UUO大鼠显著升高, 其表达与α-SMA的表达量及肾小管间质病变程度早期一致,14 d达峰值后表达不再随病变加重而进一步升高.UUO病变早期PPARγ反应性升高可能在肾脏局部炎症和纤维化病程中发挥了重要作用.

Objective To evaluate the expression of peroxisome proliferators - activated receptor γ （PPARγ） and α - smooth muscle actin （α - SMA） in unilateral ureteral obstruction （UUO） in rats and the relationship between them and the extent of tubulointerstitial injury. Methods Male SD rats were randomly subjected to either left ureteral ligation （n= 30） or sham operation （n= 6）, and they were sacrificed on 3, 7, 14, 21 or 28 days after UUO. Sections of renal tissue were stained with hematoxylin and eosin （HE）, Masson, or periodic acid -silver methenamine （PASM）. The extent of tubulointerstitial injury was determined by Banff classification. Immunohistochemical staining was performed to investigate the expression of PPARγ and α - SMA in the renal tissue. Results Swelling of tubular epithelia cells, infiltration of inflammatory cells and proliferation of fibroblasts were not so obvious on days 3 and 7 after UUO. A diffuse inflammatory cells infiltration, and massive fibrous hyperplasia were detectable on days 14 and 21 after UUO. Most tubules showed serious damage and replaced by proliferative fibrous tissue on day 28. The expression of PPARγ was almost undectable in sham operation group. However, it was upregulated on day 3 and peaking on day 14, and then it was slightly decreased on days 21 and 28. The expression of a -SMA was only found in vascular smooth muscle cells in sham operation group. It was upregulated mainly in some interstitial cells on day 3 and increased with the progression of tubulointerstitial fibrosis. Conclusion PPARγ expression increases in rat renal tissue after UUO, but does not always correlate with the extent of the α - SMA expression and tubulointerstitial injury. These data suggest that increase in PPARγ in renal tissue may play an important role in response to inflammation and fibrosis.