摘要
目的:基于CRISPR/Cas9技术构建Retnlb基因的floxp敲入小鼠Retnlbflox/+,进一步根据Cre-LoxP重组酶系统,构建肠道上皮Retnlb基因敲除小鼠(Retnlb-CKO),为后续探究Retnlb基因在炎性肠病中的发病机制提供动物模型.方法:选取8周龄基因型均为Retnlbflox/+的雌、雄C57BL/6N小鼠合笼杂交,筛选出基因型为Retnlbflox/flox的小鼠,将该基因型的小鼠与肠道上皮细胞特异性表达Cre重组酶(Vil1-Cre)工具鼠进行杂交繁育,筛选获得基因型为Retnlbflox/+,Cre+小鼠;再将Retnlbflox/+,Cre+小鼠与Retnlbflox/flox小鼠杂交获得Retnlbflox/flox,Cre+目的小鼠(Retnlb-CKO).选取8周龄Retnlbflox/flox,Cre+小鼠与同窝Retnlbflox/flox小鼠各6只进行后续实验.采用RT-qPCR和免疫组化分别检测结肠上皮Retnlb mRNA和蛋白水平.观察每组小鼠的身长、体重、饮食和生殖能力等表型,计算其各组织重量与体重的比值以分析小鼠的生长发育情况.检测小鼠的肠道屏障完整性和结肠免疫炎症因子的表达情况.结果:通过基因鉴定、mRNA及蛋白水平证实肠道上皮细胞特异性条件敲除小鼠构建成功.与对照组小鼠相比,Retnlb-CKO小鼠的身长、体重、饮食和生殖能力均未发生明显的变化,心、肝、脾、肺、肾和结肠的重量与体重之比无差异,各组织无形态学差异.检测Retnlb-CKO小鼠结肠组织的紧密连接蛋白ZO-1、Occludin和Claudin3的mRNA表达显著降低(P<0.01),PAS染色和免疫组化结果分别显示Retnlb-CKO小鼠结肠组织的杯状细胞数量和溶菌酶阳性细胞数量均显著减少(P<0.01).HE染色观察Retnlb-CKO小鼠的结肠组织显示没有明显的炎症细胞浸润,RT-qPCR进一步显示结肠组织的促炎因子NLRP3、白细胞介素6(IL-6)、IL-1β和肿瘤坏死因子α(TNF-α)表达显著下调(P<0.01),同时,炎症信号通路蛋白TLR4、MyD88和NF-κB表达也显著下调(P<0.01).结论:成功构建并验证了条件性结肠细胞Retnlb基因敲除小鼠模型.结肠细胞缺失Retnlb会导致肠道屏障受损,结肠组织促炎因子mRNA表达显著降低,炎症通路蛋白TLR4、MyD88和NF-κB的mRNA表达显著下调.
Abstract
AIM:This study utilized CRISPR/Cas9 technology to create Retnlb floxp knock-in mice,followed by the application of the Cre-LoxP recombination system to generate intestinal epithelial-specific Retnlb gene knockout mice(Retnlb-CKO).This model was developed to investigate the pathogenic mechanisms of Retnlb in inflammatory bowel disease.METHODS:Female and male C57BL/6N mice,aged 8 weeks with the Retnlbflox/+genotype,were housed togeth-er for breeding.Offsprings were screened to identify those with the Retnlbflox/flox genotype.These mice were then crossed with Vil1-Cre transgenic mice,which express Cre recombinase specifically in intestinal epithelial cells,resulting in Retnlb-flox/+,Cre+mice.Subsequent crosses between Retnlbflox/+,Cre+mice and Retnlbflox/flox mice produced Retnlbflox/flox,Cre+mice(Retnlb-CKO).Six 8-week-old Retnlbflox/flox,Cre+mice and their littermate Retnlbflox/flox mice were selected for experiments.RT-qPCR and immunohistochemistry were used to assess Retnlb mRNA and protein levels in colonic epithelium.Phenotypic observa-tions included body length,weight,diet,and reproductive capability.Tissue-to-body weight ratios were calculated to ana-lyze growth and development.Intestinal barrier integrity and colonic expression of inflammatory factors were evaluated.RESULTS:The conditional gene knockout mouse model with specific deletion of Retnlb in intestinal epithelial cells was successfully established and validated through genetic identification,mRNA and protein analysis.Compared to Retnlbflox/flox mice,Retnlb-CKO mice exhibited no significant differences in body length,weight,diet,or reproductive capability.There were no differences in the ratios of heart,liver,spleen,lung,kidney,and colon weight to body weight,nor were there morphological differences in various tissues.However,the mRNA expression of tight junction proteins ZO-1,Occlu-din,and Claudin3 in colon tissues of Retnlb-CKO mice was significantly reduced(P<0.01).PAS staining and immunohis-tochemistry revealed a significant decrease in the number of goblet cells and lysozyme-positive cells in the colon tissues of Retnlb-CKO mice(P<0.01).HE staining showed no obvious pathological change in colon tissues of Retnlb-CKO mice.RT-qPCR further demonstrated a significant downregulation of pro-inflammatory factors NLRP3,interleukin-6(IL-6),IL-1β,and tumor necrosis factor-α(TNF-α)in colon tissues(P<0.01),along with significant downregulation of inflamma-tion signaling pathway proteins TLR4,MyD88,and NF-κB(P<0.01).CONCLUSION:A conditional colon epithelial cell Retnlb gene knockout mouse model was successfully constructed and validated.The absence of Retnlb in colon cells led to impaired intestinal barrier function,decreased mRNA expression of pro-inflammatory factors in colon tissue,and downregulation of mRNA expression of inflammatory pathway proteins TLR4,MyD88,and NF-κB.
基金项目
国家自然科学基金资助项目(82200066)
湖南省自然科学基金资助项目(2022JJ40308)
长沙市自然科学基金项目(kq2202272)
湖南中医药大学院士工作站指导项目(22YS005)
中药粉体与创新药物省部共建实验室培育基地开放基金资助项目(21PTKF1001)
维普
万方数据