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Journal of Sichuan University (Medical Sciences) logoLink to Journal of Sichuan University (Medical Sciences)
. 2021 Sep 20;52(5):825–831. [Article in Chinese] doi: 10.12182/20210960502

经膀胱颈部分结扎建立膀胱输尿管返流性肾损害动物模型

Establishment of an Animal Model of Vesicoureteral Reflux Renal Injury through Partial Bladder Outlet Obstruction

Zhao-ying WANG 1, Zhao-xia ZHANG 1, Li-ming JIN 1, Bo LIU 1, Lian-ju SHEN 1, Da-wei HE 1,2, Guang-hui WEI 1,2,*
PMCID: PMC10408891  PMID: 34622600

Abstract

Objective

To establish an animal model of reflux renal damage through bladder outlet obstruction.

Methods

Sixty male C57BL/6 mice aged 6-8 weeks were randomly assigned to a control group, a sham operation group, and a partial bladder outlet obstruction (PBOO) group, with 20 mice in each group. Laparotomy were performed on the PBOO mice under anesthesia in order to separate the bladder necks and to perform guided partial ligation of the bladder neck with a metal rod of 0.3 mm diameter. Mice in the sham operation group had laparotomy and had their bladder necks separated without ligation. The control group did not receive any treatment. 7 days after the surgery, 12 surviving mice were randomly selected from each group to observe the general changes of the bladder, ureter, renal pelvis and kidney. Retrograde urography was performed through the bladder. Kidney tissues were extracted for histopathological analysis. The expression levels of Vimentin, proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) were examined with Western blot, immunohistochemistry and immunofluorescence staining tests, respectively.

Results

Compared with the control and sham operation group, the bladder, ureter, and renal pelvis of the mice in the PBOO group were significantly enlarged, vesicoureteral reflux was more obvious, the kidney volume and mass increased (P<0.001), and renal parenchyma became thinner (P<0.000 1). Histopathological staining showed glomerular atrophy, renal tubule expansion, tubulointerstitial inflammatory cell infiltration, glomerular basement membrane hyperplasia and obvious interstitial fibrosis. Western blot, immunofluorescence and immunohistochemistry staining showed that the expression levels of Vimentin, PCNA and α-SMA in kidney tissue were elevated (P<0.000 1).

Conclusion

After PBOO, the bladder, ureter, and kidney of the mice showed obvious morphological alteration and presented reflux renal fibrosis-like damage. This can be used as an animal model to study the pathological alteration mechanism and therapeutic measures of renal fibrosis caused by bladder outlet obstruction.

Keywords: Partial bladder outlet obstruction (PBOO), Bladder outlet obstruction, Kidney fibrosis


膀胱出口梗阻(BOO)是指膀胱颈或尿道由于各种病因造成的尿液流出道阻力升高引起的尿液排出困难,可导致膀胱功能障碍、膀胱输尿管返流、双侧肾脏损害、肾衰竭。因临床观察及病理生理研究相对容易,目前针对膀胱出口梗阻的临床研究主要集中于膀胱的形态和功能改变,对膀胱出口梗阻所致返流性肾脏损害的组织病理学研究很少。因此,建立动物模型对于返流性肾脏组织病理学及治疗措施的研究具有重要价值。

目前的梗阻性肾损伤动物模型主要为上尿路单侧肾脏的梗阻,如单侧输尿管结扎术和单侧输尿管部分结扎术,针对下尿路梗阻的累及双侧肾脏的动物模型尚不完善,本实验基于原有的膀胱颈部分结扎致膀胱纤维化小鼠模型[1],改良了膀胱颈部分结扎的操作方法,避免了尿道置管这一困难操作,进一步降低了操作难度、减少手术时间、缩小切口长度,实现了膀胱输尿管返流性肾损伤小鼠模型的构建。

本实验应用膀胱颈部分结扎术(PBOO)建立膀胱出口梗阻致膀胱输尿管返流性小鼠模型,从大体形态、影像学、组织病理学、肾纤维化蛋白标志物表达水平等方面,观察该动物模型是否具有研究返流性肾损害的价值。

1. 材料和方法

1.1. 主要试剂与器材

PAS染色试剂盒,Masson染色试剂盒(北京Leagene公司);兔抗Vimentin多抗,兔抗增殖细胞核抗原( PCNA)多抗,兔抗α平滑肌肌动蛋白(α-SMA )多抗,小鼠抗甘油醛-3-磷酸脱氢酶(GAPDH)多抗,山羊抗兔IgG,山羊抗小鼠IgG(成都ZEN-BIOSCIENCE公司);FITC荧光二抗(上海 Beyotime 公司);显微外科器械(上海金钟公司)。

1.2. 实验动物

动物实验按照我国《实验动物福利伦理审查指南(GB/T 35892-2018)》要求,规范落实实验动物福利伦理。60只C57BL/6小鼠,6~8周龄,雄性,体质量20~25 g,均购自重庆医科大学实验动物中心,随机分为对照组(20只)、假手术组(20只)和PBOO组(20只),术后7 d在各组仍存活的小鼠中每组随机挑选出12只处死进行后续研究。

1.3. 小鼠膀胱颈部分结扎(PBOO)模型的构建

本实验在现有的膀胱颈部分结扎术致膀胱纤维化动物模型的基础上进行改良,将尿道内置管后结扎的步骤改为在膀胱颈外侧结扎,降低了建立小鼠模型的难度,同时也将原方法中手术切口由1.5 cm左右缩小到了0.7 cm左右。异氟烷麻醉后备皮,消毒、铺单,在小鼠下腹部正中行一长度约为0.7 cm切口,逐层开腹,分离、暴露膀胱颈,以直径为0.3 mm的金属棒为基准使用4-0缝线结扎膀胱颈(图1)。结扎完成后立即抽出金属棒,回纳膀胱,关腹,观察至小鼠可自由活动后再送回饲养间。假手术组行相同手术操作,但不结扎膀胱颈,对照组不做任何处理。术后7 d处死小鼠并取出肾脏。

图 1.

图 1

Ligature method in surgical progress of PBOO

PBOO术结扎方法

Left: Separation of bladder neck; Right: The bladder neck is ligated by a metal rod as a guide.

1.4. 小鼠经膀胱逆行性尿路造影

PBOO术后7 d,断颈处死小鼠后开腹移除双侧睾丸、胃肠道、肝脏和胆囊,充分暴露肾脏、输尿管及膀胱。使用胰岛素针经膀胱注入碘海醇,直至膀胱体积不再增大,行DR摄影。

1.5. 小鼠肾脏的HE染色、PAS染色和Masson染色

PBOO术后7 d,小鼠处死后迅速取出肾脏,固定、脱水、包埋、切片。按说明书行HE、PAS和Masson染色后观察并拍照。

1.6. 小鼠肾脏实质厚度的测量

扫描HE染色后的切片,排除肾乳头部后,用Image J测量多个径向,得出肾实质厚度平均值,根据公式:肾实质压缩率=(对照组肾实质平均厚度−实验组肾实质平均厚度)/对照组肾实质平均厚度×100%,计算出PBOO组小鼠肾实质压缩率。

1.7. Western blot检测Vimentin、PCNA、α-SMA蛋白表达

PBOO术后7 d取出肾脏,提取蛋白,定量后变性。取30 μg进行SDS-PAGE凝胶电泳,转膜,封闭,将条带置于1∶1 000稀释的相应一抗(Vimentin、PCNA、α-SMA)中4 ℃敷育过夜,洗膜,二抗孵育,洗膜,显影,以各目的蛋白条带与GAPDH条带的相对灰度值为蛋白表达量。

1.8. 免疫组化染色检测PCNA蛋白表达水平

切片脱蜡至水,浸于0.01 mmol/L枸橼酸盐缓冲液中煮至沸腾,3%过氧化氢孵育10 min,室温下封闭1 h,4 ℃下孵育抗PCNA抗体(1∶200)过夜,DAB显色、染核后脱水封片,镜下观察并拍照。

1.9. 免疫荧光染色检测α-SMA蛋白表达水平

石蜡切片脱蜡,抗原修复后3%过氧化氢孵育10 min,0.5% BSA室温封闭1 h,滴加抗α-SMA抗体(1∶200)于4 ℃过夜,加入FITC二抗于室温孵育1 h,DAPI染核,封片,荧光显微镜观察并拍照。

1.10. 统计学方法

数据以 Inline graphic 表示。组间比较采用t检验,α=0.05。

2. 结果

2.1. 造模成功率与造模后小鼠排尿状况

对照组小鼠成活率100%,假手术组小鼠成活率95%,PBOO组小鼠成活率70%。在后续多批次重复实验中,PBOO组小鼠成活率约为60%~70%。造模后对照组及假手术组小鼠排尿顺畅未见尿潴留,PBOO组存活小鼠均可见尿液成滴排出,建模成功率约为100%。

2.2. 造模后小鼠泌尿系统的大体病理学变化

图2可见,对比对照组和假手术组,PBOO组小鼠膀胱充盈,输尿管明显扩张,肾盂膨出,肾脏体积增大。经膀胱逆行性尿路造影后可见PBOO组膀胱、输尿管及肾盂影像,对照组和假手术组仅见膀胱,PBOO术后膀胱输尿管返流明显。分析天平称量肾脏,PBOO组小鼠肾脏质量较对照组增加(P<0.001)(表1)。分别测量各组肾实质厚度,PBOO组肾实质明显变薄(P<0.000 1),肾实质压缩率为20%左右。

图 2.

图 2

Pathological changes of the gross morphology of the urinary system

泌尿系统的大体形态病理学变化

A: Gross morphology of bladder, ureter, pelvis and kidney; single-headed arrow indicates ureter, double-headed arrow indicates bladder; B: Retrograde urography; C: Gross morphology of kidney; D: Renal parenchymal thickness (n=12), ****P<0.000 1.

表 1. Kidney mass of the control, sham operation and PBOO groups.

对照组、假手术组与PBOO组的肾脏质量

Group n mleft kidney/mg mright kidney/mg
 * P<0.001, vs. control group; #P<0.000 1, vs. sham operation group.
Control 12 92.06±5.06 89.83±4.45
Sham operation 12 85.78±2.91 85.93±3.94
PBOO 12 131.10±6.92*, # 137.40±9.81*, #

2.3. 肾脏的组织学改变

图3图4。PBOO组小鼠肾脏HE染色后可见肾小球明显萎缩,肾小管扩张,小管间质炎细胞浸润;PAS染色可见明显基底膜增生;Masson染色可见小管间质区域染成蓝色的胶原纤维显著增多。对照组和假手术组肾脏组织未见明显病理改变。

图 3.

图 3

Histopathological changes of kidney cortex

肾皮质的组织学改变

图 4.

图 4

Histopathological changes of kidney medulla

肾髓质的组织学改变

2.4. 肾脏纤维化相关蛋白表达情况

图5~图7。Western blot法检测发现,PBOO组相比对照组和假手术组小鼠肾组织Vimentin、PCNA、α-SMA蛋白的表达水平均升高,差异有统计学意义(P<0.000 1)。免疫组化、免疫荧光检测分别发现,相比对照组和假手术组,PBOO组小鼠PCNA、α-SMA蛋白在肾脏组织中的表达明显升高。

图 5.

图 5

Protein expression levels of Vimentin, PCNA and α-SMA in the kidney tissue of the control group, the sham operation group and the PBOO group

肾脏组织中Vimentin、PCNA和α-SMA的蛋白表达水平变化

n=12. ****P<0.000 1.

图 7.

图 7

Immunohistochemistry staining results of α-SMA. ×200

免疫荧光染色检测α-SMA表达水平。×200

图 6.

图 6

Immunohistochemistry staining results of PCNA

免疫组化染色检测PCNA表达水平

3. 讨论

膀胱出口梗阻是指膀胱颈或尿道由于各种病因引起的尿液流出道阻力升高引起的尿液排出困难,是后尿道瓣膜、尿道狭窄、膀胱颈挛缩、膀胱颈部肿瘤等疾病共同的病理生理改变。膀胱出口梗阻最终可导致一系列严重的并发症,如膀胱输尿管返流,膀胱功能障碍,双侧肾脏损害,肾功能衰竭甚至死亡[2-4]。梗阻性尿毒症是导致16岁以下的终末期肾衰竭第二常见的潜在病因(19%)[5]。对于未经治疗的病例,先天性膀胱颈梗阻的患儿围产期死亡率高达45%[6],其中约30%的进行性终末期肾衰竭需要在5岁之前进行透析和肾移植[7]。因后尿道瓣膜症引起的终末期肾衰竭发生率在6%至29%之间[8]

膀胱出口梗阻的模型动物和方法较多,最常见的是膀胱颈[9-10]、会阴部尿道[11-12]和尿道外口[13-15]梗阻,经典的结扎方法为经尿道置入留置针或探针结扎后抽出[9-10,15-17]。然而在实际操作中经尿道操作难度很大,且置管过程中极易损伤尿道。另外因小鼠尿道较薄,经尿道置管后膀胱颈无法轻易移动,因此其分离难度更高,手术时间更长,所需要的手术操作空间更大,腹部切口也相应更大。本实验游离膀胱颈后将0.3 mm直径的金属棒作为基准置于膀胱颈外部,将金属棒与膀胱颈一起结扎之后再抽出,避免了传统结扎方法中置管操作带来的尿道损伤,将金属棒作为基准解决了诸如尿道外口缝扎存在的梗阻程度不一的问题,确保一致的结扎直径,保证模型的稳定性。

本实验应术前2 h禁水,防止膀胱过度充盈。避免过度牵拉膀胱,否则易造成膀胱出血甚至破裂。本实验虽避免了尿道置管操作,减轻了部分手术难度,但是膀胱颈的分离与结扎仍是精细操作,需要由熟练的外科医生手术。

目前常见的梗阻性肾纤维化动物模型为单侧输尿管结扎术(unilateral ureter obstruction, UUO),其方法为分离并结扎输尿管两端后彻底离断[18]。UUO术操作繁琐,手术范围大时间长,术后易出现各种并发症甚至死亡[19]。临床上大多数下尿路阻塞性肾损伤并非完全阻塞,且具有一定的发生发展时间[20-21],而UUO建模的完全梗阻性肾积水发展快、程度重,UUO术后7 d,阻塞侧肾脏的质量减少26%,肾实质厚度减少33%[22],所以UUO与临床中下尿路梗阻致肾积水的病理生理发展过程存在差异。本方法术后7 d肾实质厚度减少20%左右,肾湿重增加约60%,与文献报道的因炎症水肿在短期内肾质量增加的现象符合[23]。本方法在大体病理学、组织病理学、蛋白表达水平层面都呈现明显的返流性肾纤维化特征,较UUO等建模方式拥有双侧非急性肾损伤、部分梗阻、肾实质丢失较少、肾脏损伤较轻等优点,与临床中下尿路梗阻致双侧肾损伤的病理生理变化更贴近[24-25]

国内外关于膀胱出口梗阻引起的肾脏损伤的基础性研究均缺少。目前针对膀胱出口梗阻的基础研究都集中于膀胱的形态和功能改变,而忽略了这一过程中肾脏的病理变化[26-28]。然而,临床上不同的膀胱出口梗阻患者出现肾积水等病变的时间及程度均不相同,其在手术后膀胱功能的改善情况也并不一致,许多患者甚至术后仍出现进行性的膀胱功能减退和肾脏功能损伤,成为治疗难点[29-31]。本实验通过一种更优的膀胱部分梗阻模型构建法探讨了梗阻造成的肾损害,为下一步针对膀胱出口梗阻所造成不同程度肾损伤的机制及疗法的研究奠定了理论基础。

*    *    *

利益冲突  所有作者均声明不存在利益冲突

Funding Statement

国家自然科学基金(No. 81771566)和重庆市科技局技术创新与应用发展(重点项目)(No. cstc2019jscx-tjsbX0003)资助

Contributor Information

钊颖 王 (Zhao-ying WANG), Email: 1311793853@qq.com.

光辉 魏 (Guang-hui WEI), Email: u806806@cqmu.edu.cn.

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