Relationship between the Expression of Connexin 43 and Chondrogenic Differentiation in a Cartilaginous Transplanted Tumor and a Chondrocytic Cell Line

Gap junctions are associated with cell growth and differentiation i tissue organization. However, the association of gap junctions with chondrogenesis or chondrogenic differentiation isstill unclear. We succeeded in establishing a cartilaginous transplanted tumor in a nude mouse from a human chondroblastic osteosarcoma, nd a cell line (USAC) expressing chondrocytic phenotypes from the transplanted tumor. Using these transplanted tumor and USAC cells, we investigated the relationship between the expression of gap junctions and chondrogenesis or chondrogenic differentiation. Gap junctions are observed by immunostaining with connexin 43 (Cx 43) protein, which is an intrinsic component of gap junctions. The results revealed that Cx 43 in the tumor tissue was found both on chondrocytic and hypertrophic ells. In cultured cells, gap junctions composed of Cx 43 appearing as USAC cells were condensed and progressed toward mature chondrocytic ells. A high density micro-mass culture of USAC cells showed that dexamethasone and 1 a, 25 (OH)21)3, which stimulated chondrogenic differentiation, enhanced the expression of Cx 43. These results indicate that expression of gap junctions is closely linked to chondrogenesis and chondrogenic differentiation.