低强度力学刺激调控骨髓间充质干细胞定向分化和破骨细胞分化促进骨质疏松大鼠骨形成机理研究

Osteoporosis, a disease characterized by diminished bone density, is one of the most prevalent and serious age-related disorders， with atraumatic fractures severely compromising an individual's quality of life. Osteoporosis constitutes a major public health problem and the treatment and prevention of osteoporosis involve great challenges. One proposed alternative is low-magnitude whole-body vibration therapy, which may be safer than drugs and may increase bone mineral density (BMD). But it is unknown how the mechanism of the mechanical stimulation by the therapy improve BMD. We hypothesis that the ability of self-renew and differentiation in bone marrow mesenchymal stem cells (BMSCs) were decreased with aging and the bias of BMSCs lineage selection shift adipocyte formation. Number of osteoblast and pre-osteoblast were decrease because bone marrow osteoprogenitors are inversely proportional to adipocyte precursors. However, OPG/RANKL secreted by Osteoblast and pre-osteoblast were closely related to regulation of osteoclast differentiation. So, the aim of the project to investigate whether the low -magnitude mechanical stimulation increase bone formation in rat osteoprotic model by regulating the biasing of BMSCs differentiation and osteoclast differentiation.

骨质疏松症（osteoporosis）是一种最常见与年龄相关的全身性骨骼系统疾病，其所导致的骨折已成为世界公共卫生难题。控制这种疾病仍然非常困难。低强度全身振动已成为骨质疏松治疗的备选方案之一。但力学刺激如何促进骨形成的机理仍不清楚。因此，本研究假设骨质疏松症是由于成骨细胞的起源，及骨髓间充质干细胞出现增龄性退化，导致成骨细胞形成不足，进而导致破骨细胞分化异常，致使骨丢失。从动物模型到细胞分子水平，系统地研究低强度全身振动所产生的力学刺激促进绝经后骨质疏松和老年骨质疏松大鼠模型骨形成机制，以及这两种骨质疏松模型骨形成机理的异同；探讨力学刺激调控骨质疏松大鼠MSCs定向分化能力、以及破骨细胞分化能力的可能的信号途径，期望为骨质疏松症的预防和治疗提供一个非药理学的、有效的、无创性的、易于接受且可以长期坚持的治疗选项。

摘要：骨质疏松症（osteoporosis）是一种最常见与年龄相关的全身性骨骼系统疾病，其所导致的骨折已成为世界公共卫生难题。控制这种疾病仍然非常困难。低强度全身振动已成为骨质疏松治疗的备选方案之一。但力学刺激如何促进骨形成的机理仍不清楚。因此，本研究假设骨质疏松症是由于成骨细胞的起源，及骨髓间充质干细胞出现增龄性退化，导致成骨细胞形成不足，进而导致破骨细胞分化异常，致使骨丢失。选用3月龄雌性SD大鼠，采用双侧卵巢切除术，术后3月成功建立绝经后骨质疏松模型。选用18月龄雌性或雄性SD大鼠，可模拟老年女性或男性骨质疏松。绝经后骨质疏松大鼠、老年雌性或雄性骨质疏松大鼠其骨密度、骨力学强度、骨小梁数量和厚度、骨形成能力均明显低于Sham组。同时，骨质疏松各组大鼠骨髓间充质干细胞(bone marrow mesenchymal stem cells, BMSCs)的成骨分化能力明显降低，而成脂分化能力明显增强。低强度全身振动可增加正常大鼠和骨质疏松大鼠的骨密度、骨力学强度、骨小梁数量和厚度。但促进骨质疏松大鼠骨形成能力的效应明显低于正常大鼠。体外双轴拉伸应变可上调大鼠BMSCs中ERα、Wnt3a和β-catenin蛋白表达，其效应远远高于E2的作用。阻断ERα可抑制大鼠BMSCs中Wnt3a和β-catenin蛋白表达。阻断ERα可抑制拉伸应变促大鼠BMSCs向成骨细胞分化的能力。体外双轴拉伸应变可能经ERα介导，通过改变Wnt3a/β-catenin信号通路活性，调控rBMSCs的成骨分化能力。上述结果提示，低强度全身振动可以改善骨质疏松的骨形成能力，阻止骨丢失。为临床预防和治疗骨质疏松提供了参考数据。