双重修饰人脐血内皮祖细胞来源外泌体靶向治疗激素性股骨头坏死的机制研究

激素性股骨头坏死（ONFH）病程难以逆转且致残率高，早期防治尤为重要。血管损伤引起组织缺血缺氧是该疾病早期的主要病理特征，明确乏氧环境下组织的代偿保护机制，并以此为靶点逆转病程是解决问题的关键。申请人前期发现疾病早期低氧诱导因子（HIF）-1α和其下游内皮型一氧化氮合成酶（eNOS）表达均上调，后者有利于内皮细胞产生NO，进一步提升HIF-1α表达量；同时证实受损血管释放的基质细胞衍生因子-1α可募集携带CXCR4的内皮祖细胞（EPCs）进行自我修复。因此，本项目提出激素性ONFH早期存在HIF-1α/eNOS/NO/HIF-1α正反馈调控机制的假说，拟利用人脐血EPCs，通过转染CXCR4提升其靶向趋化能力，经低氧培养增加其HIF-1α含量。为避免细胞移植风险，再提取其外泌体开展体内外实验，探讨双重修饰人脐血EPCs外泌体促进股骨头血管修复的作用及机制，为激素性ONFH早期防治提供依据。

With high disability rate, steroid-induced osteonecrosis of the femoral head (ONFH) is irreversible and requires timely treatment. Ischemic hypoxia caused by vascular injury is the main pathogenesis of early steroid-induced ONFH. Therefore, the compensatory mechanisms under hypoxic conditions in this stage should be deeply explored and taken seriously for targeted therapy. In our previous studies, it appears that both of hypoxia-inducible factor (HIF)-1α and endothelial nitric oxide synthase (eNOS) are upregulated in early stage of steroid-induced ONFH, which promotes NO production of endothelial cells. Moreover, increased NO volume could further enhance HIF-1α expression. Besides, it has been demonstrated that stromal-derived factor (SDF)-1α released from injured vessels specifically recruits endothelial progenitor cells (EPCs) expressing CXCR4 for vascular repair. Based on these considerations, we hypothesis that the HIF-1α/eNOS/NO/HIF-1α positive feedback regulatory mechanism may exist in endothelial cells in early steroid-induced ONFH. This project aims to improve target-specific accumulation of human umbilical cord blood EPCs (huEPCs) through CXCR4 plasmid transfection and upregulate the HIF-1α expression via hypoxic culture. In order to avoid risks related with cell transplantation, the exosomes derived from huEPCs (huEPCs-Exos) will be extracted for subsequent in vitro and in vivo experiments. The effects and mechanisms of the dual-modified huEPCs-Exos on promoting vascular repair of femoral head in early stage will be investigated. All of these findings will provide evidence for prevention or early treatment of steroid-induced ONFH.