Morphological studies of the epiphyseal growth zone in the brachymorphic (bm/bm) mouse.
Light microscopy, including immunohistochemical techniques, and electron microscopy were performed on epiphyseal growth cartilage from brachymorphic (bm/bm) mice and age-matched phenotypically normal siblings aged 5, 16 and 25 days. In the bm/bm mice light microscopy showed a disturbed columnar arrangement and numerous chondrocytes with pronounced regressive changes. The normal development of proliferative cells into hypertrophic cells was halted and thus only a rather small and ill-defined hypertrophic zone was seen. The calcifying zone was irregular and the normal lacunae were replaced by a densely staining matrix. Using immunofluorescence techniques, the presence of considerable amounts of both type II and type V collagen was demonstrated in the bm/bm mice, while the cartilage from controls contained only type II. Ultrastructurally the lacunar matrix contained bundles of fine fibrils without the typical collagen periodicity which might indicate synthesis of a defective procollagen. Our observations together with the previously demonstrated deficiency of 3'-phosphoadenosine 5'-phosphosulphate, illustrate the complexity of the growth cartilage disturbance in the bm/bm mouse. Most of our findings are at variance with those described in the literature and possible pathogenetic mechanisms for the observed alterations in the growth cartilage are discussed.
D000818:Animals; D003094:Collagen / Q000378:metabolism; D004392:Dwarfism / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006132:Growth Plate / Q000378:metabolism / Q000648:ultrastructure*; D051379:Mice; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron
D003094:Collagen