缺血再灌注损伤后肾小管上皮细胞的衰老演变及其意义

目的观察肾脏缺血再灌注损伤（IRI）后正常和衰老肾小管上皮细胞的演变，探讨细胞衰老在衰老相关性肾脏病理变化中的作用。方法以低龄（2月龄）和高龄（12月龄）野生鼠为研究对象。建立左肾IRI模型。于IRI后0d、1d、3d、7d、1月、3月、6月取肾组织，用HE染色观察肾小管组织学变化；免疫组织化学检测肾小管上皮细胞增殖细胞核抗原（PCNA）的表达；组织化学染色观察肾小管上皮细胞衰老相关β-半乳糖苷酶（SA-β-gal）的活性；TUNEL法检测凋亡肾小管上皮细胞。结果肾脏IRI后0d，肾小管以坏死为主，高龄鼠比低龄鼠更为明显（P〈0．05）。IRI1d后出现肾小管上皮细胞凋亡，7d凋亡达到高峰（P〈0．05），且在同一时间点，高龄鼠比低龄鼠严重（P〈0．05）。低龄鼠IRI肾1月时出现肾小管上皮细胞衰老，而对侧肾没有出现，3月、6月点衰老细胞显著增多（P〈0．05）；高龄鼠IRI后0d双肾均可见大量衰老的肾小管上皮细胞，但IRI肾的衰老细胞在IRIld后明显减少（P〈0．05），1月后又逐渐增多。6月后高龄鼠双肾衰老的肾小管上皮细胞几乎又达到同一水平。PCNA阳性染色细胞出现的几率两组相比差异无统计学意义（P〉0．05），但低龄组细胞增殖能力要强于高龄组。对高龄鼠IRI后1d点肾小管上皮细胞凋亡与衰老之间的相关分析显示，二者存在显著负相关（r=-0．82,P〈0．001）。结论IRI可促进正常肾小管上皮细胞衰老的进程。已经进入衰老状态的肾小管上皮细胞在遭受IRI刺激后，更易走向死亡[坏死和（或）凋亡]。肾小管上皮细胞的这种演变，在老化相关性肾脏病理变化发生和进展中可能发挥着重要作用。

Senescence variation and its significance of renal tubular epithelial cells after kidney ischemia/reperfusion injury

Objective To observe the outcome of normal and senescent renal tubular epithelial cells after kidney ischemia/reperfusion injury (IRI), and investigate the role of cell senescence in the aging-related pathological changes in kidney. Methods Wild-type male mice at age of 2 (young group) and 12 months (aged group) were used to make ischemic models by clamping left renal hila for 45 minutes. At 0 d, 1 d, 3 d, 7 d, 1 month, 3 months and 6 month after reflow, renal tissues were examined for histomorphology, cell proliferation(PCNA), apoptosis and senescence (SA-β-gal). Results In both young and aged mice, renal tubule necrosis was the primary changes at day 0 after kidney IRI, but in aged mice, that was much more severe. Apoptotic tubular cells were detected at day 1 after IRI in young and aged mice, and they were much more widely distributed in aged mice. The most severe apoptosis occurred in tubular epithelial cells of both young and aged mice at day 7 after reflow (P < 0.05). In young mice, faint staining for SA-β-gal activity occasionally appeared in IRI kidney at month 1, and increased at month 3 and 6 after IRI(P < 0.05). No positive staining for SA-β-gal was noticed in contra-lateral kidney at any time mentioned above. Another pattern of SA-β-gal expression was detected in aged mice, both kidneys had widely positive staining for SA-β-gal at day 0 after IRI, but decreased notably at day 1 in the IRI kidney(P < 0.05), then increased again at month 3, but still less than that in the contra-lateral kidney, and more than that in the young mice at the same time point(P < 0.05). Six months after IRI, in both IRI kidney and contra-lateral kidney, positive staining for SA-β-gal almost reached the same level. Positive staining for nuclear PCNA in young and aged mice had no statistical significance (P > 0.05), although the number of positively stained nuclear PCNA were larger in young mice than that in aged mice. Correlation analysis between senescent and apoptotic cells in aged mice was made at day 1 after IRI, strikingly negative correlation was found between them (r=-0.82, P < 0.01). Conclusions IRI can promote the senescence process of normal tubular cells, and can accelerate the death(necrosis and/or apoptosis)process of senescent tubular cells. These variations may play an important role in the development and progression of aging-related pathological changes in kidney.