上调CXCR4促进外源性骨髓MSCs向炎症肠道归巢对小鼠IBD治疗作用的增强及机制研究

The current therapeutic strategies against inflammatory bowel disease (IBD) are still not satisfactory. Thus looking for novel treatment options for IBD is of great importance. Previous experiments of our group have demonstrated that intravenous injection of exogenous mesenchymal stem cells (MSCs) can down-modulate bowel inflammation of IBD. It is general accepted that homing of MSCs into inflamed tissue is crucial to its therapeutic effect. However, MSCs having been amplified in vitro showed limited homing ability within intestine in our experiment. Previous studies suggest that the SDF-1/CXCR4 axis plays an important role in the regulation of homing of MSCs. And the expression of CXCR4 on the surface of MSCs can reduce significantly after in vitro amplification, which may affect its homing ability. Thus we suppose that up-regulation of CXCR4 on the surface of MSCs might facilitate the homing of MSCs into inflamed intestine, thereby enhancing its therapeutic effect against IBD. Based on the achievement of previous research, we will up-regulate the cell surface CXCR4 of MSCs via lentivirus vector in this project, then compare the difference between the CXCR4 over-expressed group and the control groups in the homing procedure in vivo and in vitro. We will also investigate the anti-inflammatory process, immunological regulation as well as the healing process of mucosa of different experimental groups in a murine model of IBD, in order to identify the promoting effect of up-regulation of CXCR4 on the homing of MSCs, its enhanced therapy for IBD, and the mechanisms of these effects. This study would provide theoretical basis which can guide the clinical application of exogenous MSCs effectively against IBD.

炎症性肠病(IBD)的疗效迄今仍不理想,迫切需要探寻新的有效治疗手段。我们前期实验显示输注外源性骨髓间充质干细胞(MSCs)可下调IBD肠道的炎症。研究表明MSCs向炎症灶的归巢是决定MSCs疗效的关键,但我们发现体外扩增的MSCs输入体内后向炎症肠道的归巢能力有限。现已知SDF-1/CXCR4信号轴调控MSCs的归巢,而MSCs体外扩增后其表面的CXCR4表达明显下降,导致归巢能力降低。那么,上调MSCs表面CXCR4的表达,能否促进MSCs向炎症肠道归巢而增强对IBD的疗效？本项目拟在前期研究基础上,利用慢病毒载体上调 MSCs表面CXCR4的表达,比较CXCR4过表达MSCs与对照组MSCs在体内/外归巢的差异,并检测各组MSCs对IBD小鼠模型的抗炎、免疫调节及黏膜修复情况,探讨上调MSCs表面CXCR4对IBD治疗的增强效应及机制,为有效应用外源性MSCs治疗IBD提供理论参考。

炎症性肠病(IBD)是一组多因素导致的肠道慢性非可控性炎症，近年来在国人中发病率日益攀升。多数患者病情呈长期反复发作，严重影响个人生活质量甚至危及患者生命，并且随着病程的迁延，发生癌变的风险逐年增加，大大增加了IBD患者的恐惧感和心理负担。已有研究表明，间充质干细胞（MSC）具有低免疫原性、免疫调节/抗炎、修复受损组织等多种特性，在IBD的治疗方面显示出诱人的临床应用前景。本研究成功分离及培养不同组织来源的MSC、构建小鼠炎症性肠病模型及炎症性肠病癌变模型。首先，我们通过对比脂肪来源MSC和骨髓来源MSC对小鼠炎症性肠病模型的治疗效果，发现脂肪来源MSC具有与骨髓来源MSC类似的治疗效果，主要表现为两种来源MSC治疗小鼠IBD模型后，肠道炎症评分、病理组织评分均有明显改善且效果相当；初步机制研究考虑MSC下调了肠道炎症介质的表达；提示可以使用较易获取的脂肪来源MSC替代较难获取的骨髓来源MSC，为今后可能的临床应用提供细胞来源方案。其次，我们研究了骨髓MSC对小鼠炎症性肠病癌变模型的影响作用，发现骨髓MSC可明显减少模型小鼠的癌变，主要表现为小鼠肠道炎症水平明显缓解，小鼠肠道肿瘤形成数量及肿瘤负荷明显减少，初步机制研究显示骨髓MSC下调了炎症介质的表达，且下调STAT3相关通路的激活；研究提示MSC不仅可以治疗IBD，且可减少其癌变可能，验证了MSC治疗IBD的肿瘤学安全性。最后，我们通过上调MSC表达CXCR4，发现上调表达CXCR4后MSC增殖水平不受影响，且体外实验显示上调CXCR4能增强MSC向SDF-1的趋化迁移能力，初步提示上调CXCR4表达可以增强MSC的归巢能力进而提高治疗效果。