Avian dyschondroplasia: Local deficiencies in growth factors are integral to the aetiopathogenesis

Abstract

Rabbit polyclonal antibodies to chicken transforming growth factor-beta 3 (TGF-/J3) and to insulin-like growth factor-I (IGF-I) were used to detect the two growth factors in normal and dyschondroplastic broiler growth plates (physes). Histo-morphometry was used to estimate the percentage of chondrocytes containing IGF-I and TGF-beta3 in the lower proliferative, transitional and hypertrophic zones of the growth plate. In the normal chick growth plates IGF-I was present in 63% of transitional chondrocytes and in 67% of hypertrophic chondrocytes and TGF-beta3 was present in 81% of transitional chondrocytes and in 93% of hypertrophic chondrocytes. Both growth factors were found to be deficient within transitional chondrocytes at sites of dyschondroplasia, a condition in which there is a local defect in chondrocyte differentiation and the subsequent replacement of the cartilage by bone. In addition, both growth factors were identified in chondrocytes within areas of repair, where chondrocyte differentiation and endochondral ossification have resumed. This supports the hypothesis that the reduction in TGF-beta3 and IGF-I in dyschondroplasia is integral to the aetiopathogenesis and indicative that both these growth factors are part of the cascade of events associated with chondrocyte differentiation during endochondral ossification.