通过对卵巢切除（OVX）大鼠中褪黑激素（MT）对骨量和血清炎症因子的影响进行研究，以及对脂多糖刺激下骨髓间充质干细胞（BMSCs）培养基中炎症因子水平和骨发生能力的影响。将15只12周大的SD大鼠随机分为3组。Sham组大鼠仅进行双侧腹侧切口和缝合，OVX组大鼠进行了双侧卵巢切除，OVX+MT组大鼠在双侧卵巢切除后接受了100 mg/（kg·d）MT口服干预。8周后，使用ELISA测定了血清炎症因子[白细胞介素-1β（IL-1β），IL-6和肿瘤坏死因子α（TNF-α）]的水平。此外，使用微CT检测远节股骨的变化以观察骨质量和微结构的变化，并定量测得骨膜体积分数、骨小梁厚度和骨小梁数量。使用全骨髓培养法从三只3周大的SD大鼠股骨中提取BMSCs并传代。将第3-5代的BMSCs用不同浓度的MT（0、1、10、100、1000 µmol/L）培养，然后使用细胞计数试剂盒8（CCK-8）检测细胞活力，以选择最佳的MT浓度进行后续实验。将细胞分为骨纤维诱导组（A组）和骨纤维诱导+1/5/10 μg/mL脂多糖组（B-D组）。在相应的干预后，使用ELISA测定细胞培养基中的炎症因子（IL-1β，IL-6和TNF-α）的水平。根据CCK-8的结果和ELISA检测，用含有最显著的脂多糖浓度的MT干预细胞以刺激炎症，以及携带最佳浓度的MT进行骨纤维诱导的E组，使用ELISA检测细胞培养基中的炎症因子水平。之后，分别在A、D和E组进行碱性磷酸酶（ALP）染色和茜素红染色，实时荧光定量PCR检测骨纤维相关基因[胶原Ⅰα1链（Col1a1）和RUNX家族转录因子2（Runx2）]的表达水平。ELISA和微CT检测结果显示，与Sham组相比，OVX组大鼠的骨量显著减少，OVX组大鼠的血清炎症因子（IL-1β，IL-6和TNF-α）的表达水平显著增加（P<0.05）。显然，OVX+MT组的上述指标均得到改善（P<0.05）。成功提取了大鼠BMSCs，并使用CCK-8试验显示100 µmol/L是不会导致细胞存活率下降的最大MT浓度，并用于后续实验。ELISA试验显示，与A组相比，在B-D组的细胞培养基中的炎症因子（IL-1β，IL-6和TNF-α）的表达水平在脂多糖刺激后显著增加（P<0.05），并呈浓度依赖性。此外，D组中炎症因子的表达水平显著高于B组和C组（P<0.05）。MT干预后，E组中炎症因子的表达水平明显低于D组（P<0.05）。ALP染色、茜素红染色和RT-qPCR试验显示，与A组相比，D组的ALP和茜素红阳性面积百分比以及Col1a1和Runx2的相对mRNA表达在D组显著降低，而E组的上述指标在MT干预后显著改善（P<0.05）。MT可能通过减少炎症来影响绝经后骨质量；MT可以减少脂多糖刺激下的BMSCs炎症，并减弱其对BMSCs骨纤维分化的抑制作用。

To investigate the effects of melatonin (MT) on bone mass and serum inflammatory factors in rats received ovariectomy (OVX) and to investigate the effects of MT on the levels of inflammatory factors in culture medium and osteogenic ability of bone marrow mesenchymal stem cells (BMSCs) stimulated by lipopolysaccharide.Fifteen 12-week-old Sprague Dawley (SD) rats were randomly divided into 3 groups. The rats in Sham group only received bilateral lateral abdominal incision and suture, the rats in OVX group received bilateral OVX, and the rats in OVX+MT group received 100 mg/(kg·d) MT oral intervention after bilateral OVX. After 8 weeks, the levels of serum inflammatory factors [interleukin-1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α)] were detected using ELISA assay. Besides, the distal femurs were detected by Micro-CT to observe changes in bone mass and microstructure, and quantitatively measured bone volume fraction, trabecular thickness, and trabecular number. The BMSCs were extracted from the femurs of three 3-week-old SD rats using whole bone marrow culture method and passaged. The 3rd-5th passage BMSCs were cultured with different concentrations of MT (0, 1, 10, 100, 1 000 µmol/L), and the cell viability was then detected using cell counting kit 8 (CCK-8) to select the optimal concentration of MT for subsequent experiments. Cells were devided into osteogenic induction group (group A) and osteogenic induction+1/5/10 μg/mL lipopolysaccharide group (group B-D). The levels of inflammatory factors (IL-1β, IL-6 and TNF-α) in cell culture medium were detected using ELISA assay after corresponding intervention. According to the results of CCK-8 method and ELISA detection, the cells were intervened with the most significant concentration of lipopolysaccharide for stimulating inflammation and the optimal concentration of MT with osteogenic induction, defining as group E, and the cell culture medium was collected to detect the levels of inflammatory factors by ELISA assay. After that, alkaline phosphatase (ALP) staining and alizarin red staining were performed respectively in groups A, D, and E, and the expression levels of osteogenic related genes [collagen type Ⅰ alpha 1 chain (Col1a1) and RUNX family transcription factor 2 (Runx2)] were also detected by real time fluorescence quantitative PCR (RT-qPCR).ELISA and Micro-CT assays showed that compared with Sham group, the bone mass of the rats in the OVX group significantly decreased, and the expression levels of serum inflammatory factors (IL-1β, IL-6, and TNF-α) in OVX group significantly increased (P<0.05). Significantly, the above indicators in OVX+MT group were all improved (P<0.05). Rat BMSCs were successfully extracted, and CCK-8 assay showed that 100 µmol/L was the maximum concentration of MT that did not cause a decrease in cell viability, and it was used in subsequent experiments. ELISA assays showed that compared with group A, the expression levels of inflammatory factors (IL-1β, IL-6, and TNF-α) in the cell culture medium of groups B-D were significantly increased after lipopolysaccharide stimulation (P<0.05), and in a concentration-dependent manner. Moreover, the expression levels of inflammatory factors in group D were significantly higher than those in groups B and C (P<0.05). After MT intervention, the expression levels of inflammatory factors in group E were significantly lower than those in group D (P<0.05). ALP staining, alizarin red staining, and RT-qPCR assays showed that compared with group A, the percentage of positive area of ALP and alizarin red and the relative mRNA expressions of Col1a1 and Runx2 in group D significantly decreased, while the above indicators in group E significantly improved after MT intervention (P<0.05).MT may affect the bone mass of postmenopausal osteoporosis by reducing inflammation in rats; MT can reduce the inflammation of BMSCs stimulated by lipopolysaccharide and weaken its inhibition of osteogenic differentiation of BMSCs.