ROLE OF TYPE-X COLLAGEN ON EXPERIMENTAL MINERALIZATION OF EGGSHELL MEMBRANES

Type X collagen is a transient and developmentally regulated collagen that has been postulated to be involved in controlling the later stage s of endochondral bone formation, However, the role of this collagen i n these events is not yet known, In order to understand the function o f type X collagen, if any, in the process of biomineralization, the pr operties of type X collagen in eggshell membranes were further investi gated, Specifically, calvaria-derived osteogenic cells were tested for their ability to mineralize eggshell membranes in vitro. Immunohistoc hemistry with specific monoclonal antibodies was used to correlate the presence or absence of type X collagen or its propeptide domains with the ability of shell membranes to be mineralized, The extent of miner alization was assessed by Von Kossa staining, scanning electron micros copy and energy-dispersive spectroscopy, The results indicate that the non-helical domains of type X collagen must be removed to facilitate the cell-mediated mineralization of eggshell membranes, In this tissue , intact type X collagen does not appear to stimulate or support cell- mediated mineralization, We postulate that the non-helical domains of type X collagen function in vivo to inhibit mineralization and thereby establish boundaries which are protected from mineral deposition.