Cloning of a mRNA preferentially expressed in chondrocytes by differential display- PCR: Identity with connective tissue growth factor (CTGF) mRNA

In the process of endochondral ossification, many kinds of hormones and cytokincs have been shown to regulate the proliferation and differentiation of chondrocytcs. However, many of these factors are widely distributed in many tissues and little is known about their molecular mechanism of chondrocytc-specific regulation. To isolate a chondrocytc-specific regulatory factor, chondrocyte- or chondrosarcoma cell line (HCS)-spccific sequence tags were obtained using differential display-PCR. Nuclcotide sequences of 32 species derived from HCS cells were determined. One of the sequence tags corresponded to the nuclcotidc sequence of connective tissue growth factor (CTGF). Northern blot analysis showed that CTGF was highly expressed in HCS cells and rabbit growth cartilage cells in culture but was not expressed in osteoblastic cells in culture. In situ hybridization revealed that CTGF was expressed only in the hypertrophic chondrocytcs of costal cartilage and the vertebral column in embryonic mice. The expression of CTGF in HCS cells was up-regulated by the addition of TGF-β or BMP-2. An anti-sense oligonuclcotide of CTGF strongly suppressed the proliferation but slightly enhanced the alkaline phosphatasc activity and proteoglycan synthesis of HCS cells. These results suggest that CTGF play an important role in the growth and differentiation of chondrocytes.