Department of Fixed Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan.
Pathobiology. 2010;77(1):28-37. doi: 10.1159/000272952. Epub 2010 Feb 25.
In a human mesenchymal stem cell (hMSC) model of osteoblast differentiation, we identified expression of the retinoic acid-related orphan receptor-alpha (RORalpha) gene as a candidate osteogenesis-related gene using gene expression profiling. RORalpha is a member of the nuclear receptor family of intracellular transcription factors and plays multifunctional roles in tissue development and differentiation, inflammation metabolism and circadian rhythms. However, the important role of RORalpha in the differentiation of hMSC along the osteoblastic lineage is not yet fully understood.
To investigate the role of RORalpha during osteoblast differentiation, we eliminated RORalpha from hMSCs with a small interfering RNA molecule (siRNA), and investigated the effects of suppressing RORalpha by RT-PCR analysis.
We showed that suppressing the expression of RORalpha by the siRNA inhibited the expression of both bone sialoprotein and dentin matrix protein 1. It was discovered coincidentally that the inhibitory effect of RORalpha resulted in failure of mineralization and bone nodule formation during the course of osteogenesis.
The results of this study indicate that RORalpha must be an imperative modulator of bone sialoprotein and dentin matrix protein 1 involved in osteoblast differentiation and bone formation downstream of Wnt/beta-catenin signaling and just prior to the start of mineralization.
在成骨细胞分化的人骨髓间充质干细胞（hMSC）模型中，我们通过基因表达谱鉴定出视黄酸相关孤儿受体-α（RORα）基因的表达是候选成骨相关基因。RORα 是细胞内转录因子核受体家族的成员，在组织发育和分化、炎症代谢和昼夜节律中发挥多种功能。然而，RORα 在 hMSC 沿着成骨细胞谱系分化中的重要作用尚未完全阐明。
为了研究 RORα 在成骨细胞分化过程中的作用，我们使用小干扰 RNA 分子（siRNA）从 hMSCs 中消除 RORα，并通过 RT-PCR 分析研究抑制 RORα 的作用。
我们表明，通过 siRNA 抑制 RORα 的表达抑制了骨涎蛋白和牙本质基质蛋白 1 的表达。出人意料的是，RORα 的抑制作用导致成骨过程中矿化和骨结节形成失败。
这项研究的结果表明，RORα 必须是 Wnt/β-catenin 信号下游参与成骨细胞分化和骨形成的骨涎蛋白和牙本质基质蛋白 1 的必要调节剂，并且就在矿化开始之前。
