同种异体真皮BMPR-IB+亚群细胞诱导免疫耐受研究

In our previous study, it has been demonstrated that, bone morphogenetic protein receptor IB (BMPR-IB) positive dermal fibroblasts (FBs) subpopulation had a higher osteogenic differentiation potential and could be easily obtained in a standardized operation. They maybe one of the best sources for establishing allogenic bone tissue engineering cell bank.Therefore, immune rejection has been the main obstacle for final cell bank establishment. In the study, we firstly try to observe the immune rejection phenomenon of BMPR-IB+ FBs subpopulation by virtue of mixed lymphocyte reaction assays in vitro and histological analysis in vivo,in purpose of exploring the immunogenicity of this subpopulation. Secondly, we analyse the expression of inducible nitric oxide synthase(iNOS) and indoleamine 2,3-dioxygenase(IDO) by establishing Transwell cell culture system,in order to investgate the molecular mechanism of immune rejection. Consequently, we can regulate the expression of key molecular targets which are related to immune rejection using transgenic techniques, and then induce immunologic tolerance to BMPR-IB+ FBs subpopulation in allogenic bone tissue.

我们前期研究证实，真皮骨形成蛋白IB（BMPR-IB）阳性亚群细胞来源丰富、成骨分化潜能肯定、可标准化，是建立同种异体骨组织工程种子细胞库潜在来源之一。目前，移植后是否诱发免疫反应成为制约其建库之关键。 本课题中，我们首先通过体外混合淋巴细胞反应模拟免疫微环境以及体内构建同种异体组织工程骨，来观察免疫排斥反应情况，阐明异基因真皮BMPRIB+亚群细胞的免疫原性。通过建立Transwell细胞培养模型，分析真皮BMPRIB+亚群细胞中和免疫反应相关的诱导性一氧化氮合成酶（iNOS）和吲哚胺-2,3-加双氧酶(IDO)表达，探讨异基因真皮BMPRIB+亚群细胞诱发免疫反应的分子机制。最终应用转基因技术，通过调控细胞中和免疫耐受相关的关键分子靶点表达，诱导机体对异基因真皮BMPRIB+亚群细胞构建的组织工程骨产生免疫耐受。

既往研究证实，人真皮骨形成蛋白 IB受体（ BMPR-IB）阳性亚群细胞具有较强的成骨分化潜能，是构建同种异体组织工程骨潜在细胞来源之一。异基因真皮BMPR-IB+细胞在成骨分化前后免疫原性如何，仍不清楚。本课题中，我们首先证实，和人类相似，鼠类来源真皮BMPR-IB+细胞具有和自体BMSCs类似的成骨分化能力。进一步讲，真皮BMPR-IB+细胞膜表面不表达和免疫排斥反应相关的分子，如MHC-II和共刺激分子（CD40, CD80和CD86）等。体外模拟免疫微环境条件下，真皮BMPR-IB+细胞不刺激异基因淋巴细胞增殖，同时可以抑制活化的异基因淋巴细胞增殖；真皮BMPR-IB+细胞在成骨分化后仍保持此免疫抑制特性。重要的是，我们发现未分化真皮BMPR-IB+细胞可能是通过分泌诱导性一氧化氮合成酶（iNOS）来发挥抑制免疫作用；而成骨分化后，真皮BMPR-IB+细胞可能是通过分泌吲哚胺-2,3-加双氧酶(IDO)来发挥抑制免疫作用。综上，体外条件下，真皮BMPR-IB+细胞在成骨分化前后均具有较低的免疫原性和抑制机体免疫作用，适合构建同种异体组织工程骨。但是，真皮BMPR-IB+细胞在成骨分化前后免疫调节机制可能不同，需要进一步深入研究。