Sphingomyelin is a major lipid of the plasma membrane and is enriched in microdomains of the plasma membrane that are critical for signal transduction. However, the function of sphingomyelin in the cell membrane of osteoblasts has not been clarified. Therefore, we examined how sphingomyelin synthase 2 (SMS2) affects osteoclast differentiation by osteoblasts. We knocked down the expression of SMS2 with siRNA targeting the Sgms2 gene in mouse primary osteoblasts. The effects of SMS2 knockdown in osteoblasts were examined using polymerase chain reaction and western blotting. The knockdown of SMS2 suppressed the formation of TRAP-positive multinucleated cells by co-culture of osteoblasts and bone marrow cells compared to the control. We found that receptor activator of nuclear factor κB ligand (RANKL) mRNA expression was significantly reduced by 1,25(OH)2D3 stimulation in SMS2 siRNA osteoblasts. The knockdown of SMS2 repressed the expression of retinoid-X-receptor-α (RXRα) regardless of 1,25(OH)2D3 stimulation. TRAP-positive multinucleated cell formation was significantly reduced by RXRα siRNA in osteoblasts in a co-culture system. These results suggest that SMS2 regulates osteoclast differentiation by inducing RANKL expression via RXRα.

中文翻译：

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降低神经鞘磷脂合成酶2可以通过降低小鼠原代成骨细胞中RANKL的表达来抑制破骨细胞生成。

鞘磷脂是质膜的主要脂质，富含质膜的微区，微区对于信号转导至关重要。但是，鞘磷脂在成骨细胞的细胞膜中的功能尚未阐明。因此，我们检查了鞘磷脂合成酶2（SMS2）如何影响成骨细胞对破骨细胞的分化。我们用靶向Sgms2基因的siRNA敲除了小鼠原代成骨细胞中SMS2的表达。使用聚合酶链反应和蛋白质印迹检测了SMS2敲低对成骨细胞的影响。与对照组相比，通过与成骨细胞和骨髓细胞共培养，SMS2的敲低抑制了TRAP阳性多核细胞的形成。我们发现核因子κB配体（RANKL）mRNA表达的受体激活剂显着降低了1，SMS2 siRNA成骨细胞中的25（OH）2D3刺激。不管1,25（OH）2D3刺激如何，SMS2的敲低均会抑制类视黄醇X受体α（RXRα）的表达。在共培养系统中，RXRαsiRNA在成骨细胞中显着减少了TRAP阳性多核细胞的形成。这些结果表明，SMS2通过经由RXRα诱导RANKL表达来调节破骨细胞分化。