[Effects of bone morphogenetic protein-2 on cartilage oligomeric matrix protein expression in chondrocytes]

To quantitatively evaluate the effects of BMP-2 on the COMP gene expression in both primary human chondrocytes and chondrogenic cell line ATDC55.

Human adult and fetal chondrocytes were stimulated by BMP-2. The COMP gene expression level was analyzed by real time reverse transcription-PCR assay and normalized to a reference mRNA (GAPDH). Next, a full-length mCOMP promoter cloned upstream of luciferase reporter gene was transfected into ATDC55 cells and stimulated by 500 micrograms.L-1 BMP-2 in the presence or absence of 10 micrograms.L-1 of Noggin.

We found that BMP-2 up-regulated COMP gene expression by approximate 3 folds in human adult chondrocytes, and 1.5 folds in human fetal chondrocytes. The difference in magnitude of COMP gene stimulation by BMP-2 might attribute to the difference of COMP gene basal expression level in chondrocytes from different sources because it was found that the COMP gene expression was 2 folds higher in quiescent fetal chondrocytes than in adult chondrocytes. For further analysis of the effect of BMP-2 on COMP gene expression by RT-PCR, a rat chondrogenic cell line of ATDC55 cells was used. While no COMP gene expression was detected in unstimulated cells, COMP expression was significantly induced after treatment with BMP-2. This induction could be specifically blocked by 10 micrograms.L-1 of Noggin. It was found that BMP-2 markedly increased the luciferase reporter activity by about 5 folds and again, Noggin specifically blocked the BMP-2 activity.

BMP-2 up-regulates the COMP gene expression in both primary human chondrocytes and chondrogenic cell line ATDC55.