Immunolocalization analysis of transforming growth factor-beta 1 in the growth plates of broiler chickens with high and low incidences of tibial dyschondroplasia

Immunolocalization of transforming growth factor-beta 1 (TGF-beta 1) was de termined in growth plates of two lines of broiler chickens with low and hig h incidences of tibial dyschondroplasia (TD). Ultrathin sections of growth plates from each Line were treated with a polyclonal antibody specific for TGF-beta 1, followed by colloidal gold-labeled protein A. Immunolocalizatio n for TGF-beta 1 was observed in chondrocytes of all zones of growth plates of low and high TD incidence lines. However, immunolocalization in extrace llular matrix was restricted to the hypertrophic zones of both lines. In th e hypertrophic zone of low TD incidence line, immunolocalization of TGF-bet a 1 in the extracellular matrix adjacent to collapsed cartilage canals (mat rix streaks) was significantly greater than immunolocalization between pate nt cartilage canals. A similar increase was not observed in the high TD inc idence line. Results indicate that chondrocytes of all zones of the growth prate contain TGF-beta 1 but do not release it into extracellular matrix un til hypertrophy has occurred. Greater concentrations of TGF-beta 1 adjacent to collapsed cartilage canals may Flay a role in controlling angiogenesis and directing invasion of mineralized hypertrophic cartilage by metaphyseal blood vessels. A low concentration of TGF-beta 1 in the extracellular matr ix adjacent to collapsed cartilage canals of the high TD incidence line may be a factor in limiting vascular invasion of dyschondroplastic cartilage o f TD lesions.