大麻素受体2在激素性股骨头坏死骨修复中的作用及机制研究

Impaired bone repair is an important pathological feature of steroid-induced osteonecrosis of the femoral head (SIONFH), which has not been effectivly solved. The endocannabinoid system has two receptors, which are members of the superfamily of seven transmembrane G-coupled receptors, and play an important role in the regulation of cell proliferation, differentiation, function, and death. The two specific CB receptors have been identified as CB receptors-1 (CB1) and CB receptors-2 (CB2). CB1 is predominantly expressed in brain and peripheral neurons and is responsible for the psychotropic action of cannabinoids. Whereas CB2 is absent in brain but is mainly expressed in immune cells, osteoblast, osteoclast and macrophage. However, the role of CB2 play in the regulation of SIONFH is still unknown. We have demonstrated that level of CB2 is elevated in femoral head of rat SIONFH, bone marrow derived macrophages (BMMs) and bone marrow stromal cell (BMSCs) stimulation with glucocorticoid at concentration of 1μM. Meanwhile, we also demonstrated that inhibition of CB2 promotes β-catenin translocation, and inhibits steroid-induced apoptosis of osteoblast. Accordingly, we hypothesize that the bone repair in SIONFH process was promoted by down-regulation the expression of CB2. This may provide a new explanation for SIONFH disease. In the current study, we decided to investigate the important role of CB2 in bone formation of SIONFH process. First, we explore the time-dependent expression and location of CB2 in the process of SIONFH in rats. Second, we investigate the role of CB2 in BMSCs differentiation, osteoblast proliferation and apoptosis. In order to clarify the mechanism of CB2 in bone repair, we investigate the effects of CB2 in the regulation of osteoclast differentiation stimulated with RANKL and steroid. In this study, we performed a detailed analysis of how CB2 affects bone repair on SIONFH in rats. The purpose of this study was to clarify the relationship between CB2 and steroid induced impaired bone repair in SIONFH, and provided a promising therapeutic target for treating or preventing the signs of SIONFH.

骨修复不足是激素性股骨头坏死（SIONFH）的重要病理特征，至今未能有效解决。大麻素受体2（CB2）是G蛋白偶联受体，在细胞增殖、分化及凋亡等多种应激事件中起重要作用。项目组预研结果证实CB2在大鼠SIONFH模型中高表达，且CB2能调控β-catenin核转位，抑制CB2能减少激素引起的成骨细胞凋亡。据此，我们推测CB2在SIONFH疾病进展中起重要作用，阻断CB2能有效促进SIONFH后的骨修复。为验证该假说，本项目从分子、细胞、动物模型等层面研究以下内容：①明确CB2在SIONFH后不同时间点的表达、定位变化及其与骨修复不足的相关性；②探讨SIONFH条件下，CB2对骨髓基质干细胞成骨、成脂分化以及成骨细胞增殖和凋亡的影响；③明确CB2对激素活化破骨细胞的影响及作用机制；④明确干预CB2对SIONFH骨修复的影响。本项目将从新的视觉阐明SIONFH的发生机制并为其防治提供新思路。

股骨头坏死（ONFH）是一种骨科常见的关节骨病，其特征是成骨能力下调和血供受损。大麻素受体2（CB2）已被证实在骨组织中表达，并在骨组织中对多种细胞多项功能发挥重要调控作用，因此，CB2有可能在激素性ONFH的发生和防治中扮演关键角色。我们的研究结果发现：CB2激活可减轻大鼠ONFH病变严重程度和关节破坏；CB2选择性激动剂JWH-133可以改善激素性ONFH局部骨代谢，保护股骨头内的血管化和血供。JWH-133可促进成骨细胞矿化水平，内皮细胞迁移和成管能力，抑制破骨细胞功能和骨细胞凋亡；JWH-133可通过GSK-3β/ β-catenin信号通路减轻GCs诱导的成骨抑制。上述结果表明，激活CB2通过成骨、破骨、骨细胞凋亡、成血管以及血管灌注等多重方面发挥对股骨头的保护作用。CB2有望成为未来针对激素性ONFH疾病诊断、预防和治疗的新策略。

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