Temporal and spatial distribution of type XII collagen in high cell density culture of periosteal-derived cells.

Periosteal-derived cells of young chicks have been reported to possess the potential to undergo terminal differentiation into osteogenic or chondrogenic phenotypes under high cell density culture conditions. In this culture, the temporal and spatial distribution of type XII collagen was immunocytochemically assessed using a monoclonal antibody. These high-density plated cells first formed a multilayer of fibroblast-like cells, in which type I and XII collagen were evenly distributed throughout the full thickness of the culture. With time, the top portion of the culture differentiated into bone tissue, while cells below this top layer differentiated into hypertrophic chondrocytes. In this transition, type XII collagen was temporally and spatially colocalized primarily with type I collagen: the top portion of bone layer was positive for both type I and XII collagens, whereas their staining intensity in the bottom portion decreased with time in culture. Using this antibody, type XII collagen was also found in developing embryonic chick tibiotarsus. These observations, taken together, suggest that type XII collagen production is a characteristic property of bone-forming cells.