Earlier work has identified excessive collagenolytic activity in the hypertrophic zone of the growth plate (see Poole 1991, 1997). The content of inhibitors of collagenase (tissue inhibitors of metalloproteinases) is also reduced. Net collagen breakdown results. Collagenase has been localized in the extracellular matrix of the hypertrophic zone in the growth plates (see review Poole 1997, Blair et al 1989). Using a newly developed antibody to the collagenase-generated neoepitope in type II collagen (Billinghurst et al 1997), we have shown that collagen cleavage is present throughout the growth plate, although it is enhanced in the hypertrophic zone where net loss of type II collagen is observed (F. Mwale, I. Pidocux, E. Tchetina & A. R. Poole, unpublished results).
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