骨髓间充质干细胞干预对缺血再灌注致小鼠肾小管上皮细胞损伤的保护作用

Protective effect of mesenchymal stem cells on renal tubular epithelial cells in mice under ischemia/ reperfusion

目的观察骨髓间充质干细胞（MSCs）干预对缺血再灌注（I／R）诱导的急性肾损伤小鼠肾小管上皮细胞（RTECs）自身修复的影响。方法Percoll密度梯度离心结合贴壁培养法分离纯化出C57BL／6小鼠的骨髓间充质干细胞（mMSCs），5-溴脱氧尿嘧啶核苷（BrdU）标记。雄性C57BIM6小鼠45只，分为正常对照组（15只）、I／R组（15只、夹闭双侧肾蒂30min开放）、I／R＋BrdU—mMSCs组（15只、夹闭双侧肾蒂30min开放的同时尾静脉注射BrdU标记的mMSCs）。留取动脉血及肾组织，检测血尿素氮（BUN）及肌酐（Scr）水平，制作肾组织切片行苏木素-伊红（HE）染色，荧光组织化学观察mMSCs在受体小鼠肾组织的分布，免疫组织化学观察RTECs增强细胞核抗原（PCNA）的表达，TUNEL法检测RTECs凋亡，Westernblot检测建模后第2天肾小管组织中Caspase-3、bcl-2蛋白的表达。结果BrdU标记mMSCs的阳性率可达（98．71±0．32）％。I／R＋BrdU—mMSCs组小鼠的BUN及Scr水平较I／R组为低，肾小管损伤病理明显减轻，且小鼠的肾脏中可检测到BrdU’细胞的分布。mMSCs干预后，RTECs细胞核PCNA阳性表达明显增多（P〈0．05或P〈0．01），而细胞凋亡的水平却较I／R组明显减少（P〈0．05或P〈0．01）。Westernblot进一步显示：I／R＋BrdU—mMSCs组小鼠的肾组织中Caspase-3蛋白水平明显下降[（1．16±0．33）比（1．64±0．27），P〈0．01]，而bcl-2水平却明显增高[（O．944-0．27）比（O．684-0．15），P〈0．01]。结论小鼠发生I／R诱导的急性肾损伤后可诱导移植的MSCs向损伤肾组织归巢，锚定在肾脏的MSCs可促进损伤RTECs的再生，抑制其凋亡，从而有助于RTECs的自身修复，延缓肾损害进展。

Objective To observe the effects of mesenchymal stem cells （MSCs） on self-repair of renal tubular epithelial cells （RTECs） in mice under ischemia/reperfusion （IR）. Methods MSCs in C57BL/6 mice were successfully isolated by Pereoll density gradient centrifugation and adherence cultivation, then marked with BrdU. Forty-five healthy male C57BL/6 mice were assigned to control group （n = 15 ）, I/R group （n = 15, clamping bilateral renal pedicles and then reopening after 30 min） , I/R ± BrdU- MSCs group （ n = 15, clamping bilateral renal pedicles and then reopening after 30 min, meanwhile, BrdU- marked MSCs were injected through caudal vein into the body of model mice）. One, 2, 3, 7 and 14 days later, the mice were killed （ n =3/each group） , and blood and kidneys were obtained. Serum creatinine （Scr） and urea nitrogen （BUN） were determined, and mice kidneys were stained with Hematoxylin and Eosin （HE） to observe their pathological changes. The distribution of MSCs in mice was observed by using fluorescence histochemistry. The expression of proliferating cell nuclear antigen （PCNA） in RTECs was assessed by using immunohistologieal staining. The apoptosis of RTECs was detected by using TUNEL. The protein levels of Caspase-3 and bcl-2 in renal tubules on the day 2 after establishing the model were detected by using Western blotting. Results The positive BrdU marking ratio was （98.71 ± 0. 32） % in MSCs. As compared with I/R group, the levels of BUN and Scr in I/R ± BrdU-MSCs group were significantly reduced, and pathological changes in renal tubules were alleviated significantly. BrdU-marked MSCs desposited in the kidneys of I/R ± BrdU-MSCs group. The positive PCNA expression of RTECs was increased significantly after intervention of BrdU-MSCs （P 〈 0.05 or P 〈 0. 01 ）, while the apoptosis relieved significantiy. Western blotting analysis revealed： as compared with I/R group, the level of Caspase-3 in L/R ± BrdU-MSCs group was decreased notably [ （ 1.16 ±0. 33） vs （ 1.64 ±0. 27）, P 〈0. 01 ], while the level of bcl-2 increased significantly [ （0. 94 ± 0. 27） vs （0. 68 ± 0. 15 ）, P 〈 0. 01 ）. Conclusion Acute renal injury by I/R can induce MSCs homing to injured kidney and anchoring here. The anchored MSCs can contribute to RTECs＇ self-repair of mice under ischemia/reperfusion, inhibit their apoptosis, which is helpful to the RTECs＇ self-repair and can delay the progression of renal injury.