Study on the mechanism of bipotential cell differentiation

从温度敏感型T抗原基因转基因小鼠的骨髓中建立的TBR 31-2细胞在加入分化诱导剂后显示出向脂肪细胞和成骨细胞的双向分化。比较成骨细胞分化标志物碱性磷酸酶诱导期和钙化诱导期，发现9代细胞比15代细胞需要更长的诱导期。为了研究分化诱导剂对TBR 31-2细胞分化能力的影响，采用逆转录-聚合酶链式反应检测分化因子m-RNA的表达和分化表型。在BMP-2存在的情况下，分化因子成骨核心结合因子1的表达和分化表型碱性磷酸酶、I型胶原、骨桥蛋白、甲状旁腺素受体和维生素D受体在细胞分化期增加。此外，脂肪细胞分化因子过氧化体增殖物激活受体γ和脂酶等m-RNA的表达水平没有改变，但脂肪细胞分化标志物脂蛋白脂酶和脂酶的m-RNA表达水平也下降。典型的脂肪细胞分化诱导剂曲格列酮引起了相反的现象。通过组织化学研究进行细胞表型特异性分析，以检测分化的双潜能细胞。在BMP-2存在下，观察到一些结晶凝聚，显示出钙矿物沉积。另一方面，加入曲格列酮后，脂肪细胞出现油红O染色的胞浆脂滴，提示TBR 31-2细胞具有双向分化的特性，分化为脂肪细胞和成骨细胞。

TBR 31-2 cells, established from the bone marrow of temperature-sensitive T-antigen gene transgenic mice, showed bipotential differentiation into adipocytes and osteoblasts on addition of a differentiation inducer. Comparison of the period of induction in alkaline phosphatase and calcification, as differentiation markers of osteoblasts showed that 9-passage cells needed longer periods than 15-passage cells.To study the differentiation capacity of TBR 31-2 cells in the presence of differentiation inducer, the m-RNA expression of the differentiation factor and differentiation phenotypes were examined by reverse transcription-polymerase chain reaction. In the presence of BMP-2, expression of the differentiation factor osteoblast core binding factor 1 and differentiation phenotypes such as alkaline phosphatase, type I collagen, osteopontin, PTH receptor and vitamin D receptor were increased in the stage of cell differentiation. In addition, a decrease of the m-RNA expression level of adipocyte differentiation markers, such as lipoprotein lipase and adipsin, was also observed, although the expression level of the adipocyte differentiation factor, peroxisome proliferator-activated receptor y> was not changed. Troglitazone, a typical differentiation inducer of adipocytes, caused the opposite phenomenon.Cell phenotype-specific analysis was performed by histochemical study to detect differentiated bipotential cells. In the presence of BMP-2, some crystallized condensations were observed showing calcium mineral deposits. On the other hand, adipocytes with cytoplasmic lipid droplets with oil red O staining appeared on addition of troglitazone.These observations suggest that TBR 31-2 cells show bipotential characteristics, differentiating into adipocytes and osteoblasts.