利塞膦酸钠抑制大鼠骨髓内脂肪细胞分化及脂肪细胞核因子κB受体活化因子配体蛋白的表达

目的研究利塞膦酸钠（RIS）对大鼠骨髓间充质干细胞成脂分化的影响及对骨髓内脂肪细胞来源的核因子κB受体活化因子配体（RANKL）的调节作用，为阐明RIS抗骨质疏松的机制提供新的理论依据。方法大鼠骨髓间充质干细胞成脂诱导及非成脂诱导14 d，期间以浓度梯度0、1、5、10、25 μmol/L的RIS进行药物干预，观察并计算成脂率，提取蛋白通过Western blot实验检测RANKL蛋白表达。将24周的SD大鼠随机分成假手术组及OVX组，12周后OVX大鼠再次随机分为RIS干预组（2.4 μg/kg，皮下注射，3次/周）及对照组。8周后行骨密度检查，并取大鼠左股骨远端骨骼标本行病理检查，观察RIS对大鼠骨髓内脂肪含量的影响。结果体外实验发现RIS呈浓度依赖性抑制大鼠骨髓间充质干细胞向脂肪细胞分化，并且，随着RIS浓度的升高，骨髓内脂肪细胞RANKL蛋白的表达逐渐降低（P<0.05）。体内实验发现RIS药物干预后，OVX大鼠骨密度显著提升的同时，骨髓内脂肪的含量明显降低（P<0.05）。结论RIS可有效抑制大鼠骨髓间充质干细胞的成脂分化，降低骨髓内的脂肪含量，并通过下调脂肪细胞RANKL的表达，抑制破骨细胞的生成和功能，这可能是RIS发挥抗骨质疏松作用的机制。

Risedronate inhibits rat bone marrow adipogenesis and reduces RANKL expression inadipocytes

Objective To investigate the effects of risedronate on bone marrow adipogenesis and the expression of the receptoractivator of nuclear factor κB ligand (RANKL) in adipocytes in the bone marrow micro-environment. Methods Primarycultured rat mesenchymal stem cells (BMSCs) with or without adipogenic induction for 14 days were treated with 1, 5, 10, and25 μmol/L risedronate. The droplets of the differentiated adipocytes were analyzed, and Western blotting was performed todetect the expression level of RANKL. Female SD rats (24-week-old) were randomly divided into sham-operated group andovariectomy (OVX) group, and 12 weeks after the operation, the OVX rats were further divided into control group andrisedronate group (2.4 μg/kg, injected subcutaneously for 3 times a week). Eight weeks later, the bone mineral density (BMD)of the rats and bone marrow histopathology of the femurs was examined to evaluate the effect of risedronate on the fat fractionin the bone marrow. Results Risdronate significantly inhibited adipogenic differentiation of rat BMSCs and suppressedRANKL expression in the adipocytes derived from the BMSCs in a concentration-dependent manner. In OVX rats, risdronatetreatment significantly increased the BMD and decreased the fat content in the bone marrow. Conclusion Risdronate caneffectively inhibit the adipogenic differentiation of rat BMSCs, decrease fat content in the bone marrow, and suppress thegeneration and function of osteoclasts by down-regulating the expression of RANKL, which can be an important mechanismunderlying the therapeutic effect of risedronate against osteoporosis.