Q. Chen et al., CHICKEN TIBIAL DYSCHONDROPLASIA - A LIMB MUTANT WITH 2 GROWTH PLATES AND POSSIBLE DEFECTS OF COLLAGEN CROSS-LINKING, Developmental dynamics, 196(1), 1993, pp. 54-61
In the cartilaginous epiphyseal growth plate, extracellular matrix mol
ecules such as collagens are believed to play important roles during b
oth normal and abnormal development. One defect of the epiphyseal plat
e occurs in chickens with a condition termed tibial dyschondroplasia (
TD). This abnormality occurs in certain strains of juvenile chickens a
nd other rapidly developing animals. It is characterized by the presen
ce of a mass of avascular, uncalcified cartilage which is retained in
the proximal metaphysis of the tibiotarsus. To elucidate the developme
ntal events which may be involved in this lesion, we have performed bo
th immunohistochemistry and in situ hybridizations for collagen types
II and X, known components of the extracellular matrix of the growth p
late. By immunohistochemical analyses, the TD lesion contains both of
these collagen types; therefore, the presence of these molecules per s
e is not sufficient for calcification of vascularization to occur. Sin
ce type X collagen is expressed exclusively in hypertrophic cartilage,
the chondrocytes in the lesion must have undergone hypertrophy before
their developmental arrest. The matrix of the lesion also reacted wit
h a monoclonal antibody which is directed against an epitope in the NH
2-terminal telopeptide of the alpha1(II) chain. Our previous data sugg
est that this epitope is rendered unavailable in type II collagen whic
h has undergone crosslink formation; its availability in the lesion su
ggests that crosslinking may be abnormal. Lastly, analyses by in situ
hybridization failed to detect mRNA for either type II or type X colla
gen within the lesion, but chondrocytes distal to the lesion do contai
n mRNAs for these collagens in a spatial pattern suggesting the presen
ce of a second growth plate.