ABSTRACT
BACKGROUND:The main component of cartilage, type Ⅱ col agen gene expression in chondrocyte is positively correlated with SOX9 concentration in a dose-dependent manner. OBJECTIVE:To observe the variation of SOX9 and type Ⅱ col agen mRNA content at different periods in the differentiation process (osteogenic, chondrogenic, adipogenic induction) of mesenchymal stem cel s, and to explore the correlation of SOX9 expression and type Ⅱ col agen. METHODS:Bone marrow mesenchymal stem cel s were isolated from 4-week-old Kunming mice, and cultured in vitro to passage 3. The cel phenotype was identified with flow cytometry. Cel s were divided into three groups and subjected to three kinds of induction conditions favorable for adipogenic, chondrogenic and osteogenic differentiation, and each group was observed at three time points. In addition, the non-induced cel s were used as a control group. The total RNA of cel s was extracted at 3, 7, 14 days after induction, and SOX9 and type Ⅱ col agen mRNA was quantified with reverse transcription-polymerase chain reaction. The induced cel s were stained by immunofluorescence to observe the differentiation and perform statistical analysis. RESULTS AND CONCLUSION:Passage 3 bone marrow mesenchymal stem cel s grew wel , and cel phenotype was confirmed as stem cel s by flow cytometry. The staining results showed that, the cel s differentiated into chondrocytes, adipocytes and osteoblasts. The SOX9 mRNA levels in the induced cel s were the highest in chondrogenic differentiation group, then in osteogenic differentiation group, and the lowest in adipogenic differentiation group. Type Ⅱ col agen mRNA levels in the induced cel s were the highest in chondrogenic differentiation group, then in adipogenic differentiation group, and the lowest in osteogenic differentiation group. SOX9 expression in chondrogenic differentiation group increased at 3 and 7 days, and then decreased at 14 days. While type Ⅱ col agen expression increased at 3, 7, 14 days. SOX9 mRNA levels increased as the osteogenic differentiation, while type Ⅱ col agen expression gradual y decreased. There was no significant difference in the SOX9 mRNA expression between adipogenic differentiation group and control group (P>0.05), while type Ⅱ col agen expression was not regularly changed. Experimental findings suggest that, critical effect of SOX9 in chondrogenic differentiation is better than that in osteogenic and adipogenic differentiation. SOX9 is associated with type Ⅱcol agen, which may alter along with the SOX9 in the early chondrogenic differentiation;SOX9 may play a fine-tuning role in the process of chondrogenic and osteogenic differentiation.