A human chondrogenic cell line retains multi-potency that differentiates into osteoblasts and adipocytes

We investigated the differentiation potential into various mesenchymal cell lineages of the clonal cell line (USAC) that was isolated from a human chondrogenic osteosarcoma. USAC cells produced types II and X collagens and proteoglycan, indicating chondrocyte differentiation. Production of type I collagen and osteocalcin by USAC cells demonstrated osteoblastic properties. They also differentiated into adipocytes generating numerous lipid droplets in their cytoplasm. Recombinant human bone morphogenetic protein-2 (rhBMP-2) increased production of proteoglycan, types II and X collagens and osteocalcin. This indicates that rhBMP-2 promotes both chondroblastic and osteoblastic differentiation in USAC cells. rhBMP-2 inhibited adipocyte differentiation. USAC cells transplanted with rhBMP-2 into the peritoneal cavities of athymic mice using diffusion chambers generated cartilage and bone more effectively in the diffusion chambers than those produced without rhBMP-2. Although USAC cells also produced adipose tissue in the diffusion chambers following transplantation with or without rhBMP-2, rhBMP-2 treatment reduced the amounts of adipose tissue. These results demonstrate that USAC is a suitable model to explore regulatory mechanisms involved in human mesenchymal cell differentiation.