EXPRESSION OF GROWTH-FACTORS IN CHICKEN GROWTH-PLATE WITH SPECIAL REFERENCE TO TIBIAL DYSCHONDROPLASIA

Immunoreactive growth factors were identified in chick embryonic carti lage and bone, and in the growth plate of normal tibiotarsi and tibiot arsi affected with tibial dyschondroplasia (TD). A specific pattern of temporal and spatial expression was observed for each growth factor. Transforming growth factor beta and alpha (TGF beta and TGF alpha) and epidermal growth factor (EGF) were briefly expressed in chondrocytes of early chick embryos. Immunolabelling for TGF beta then gradually sh ifted into cartilaginous matrix and was not observed in cytoplasm of h ypertrophic chondrocytes until the late embryonic and posthatch stages . The distribution and intensity of TGF beta labelling was the same in chondrocytes of the TD and normal growth plate. Insulin-like growth f actor I (IGF-I) labelling persisted from the early embryonic stage to the end of the mid-stage and then disappeared from chondrocytes. IGF-I appeared again in chondrocytes 1-2 days before hatching. After hatchi ng, the labelling intensified in prehypertrophic and hypertrophic chon drocytes. TD lesions displayed IGF-I in the distal region, mainly in c hondrocytes around small blood vessels. EGF reappeared in proliferativ e and hypertrophic chondrocytes of the mid-embryonic stage. By day 18 after hatching, EGF was present mainly in prehypertrophic and hypertro phic chondrocytes. EGF was demonstrated only in distal proliferative a nd early prehypertrophic chondrocytes of the dyschondroplastic growth plate. TGF alpha was identified in hypertrophic chondrocytes adjacent to the periosteum and in the distal tip of the mid-embryonic growth pl ate. With progressing ossification, TGF alpha labelling intensified in the embryonic hypertrophic chondrocytes. In the TD growth plate at da y 18 after hatching, TGF alpha expression was limited to 1-3 concentri c layers of chondrocytes surrounding blood vessels. (C) 1997 W.B. Saun ders Company Limited.