Expression of transforming growth factor-beta 1 in normal and dyschondroplastic articular growth cartilage of the young horse.

Abstract

This study describes the distribution pattern of transforming growth factor-beta 1 (TGF-beta 1) mRNA and protein in normal pre- and post natal growth cartilage and alterations present in lesions of dyschondroplasia (osteochondrosis). TGF-beta 1 expression and immunoreactivity have been investigated by in situ hybridisation and immunolocalisation in the articular/epiphyseal growth cartilage of the lateral trochlear ridge of the distal femur. Cartilage was obtained from 19 normal Thoroughbred horses (5 prenatal and 14 post natal horses) and 15 post natal horses with dyschondroplasia (DCP). TGF-beta 1 mRNA expression and immunoreactivity were detected in the proliferative and upper hypertrophic zones in both pre- and post natal normal articular/epiphyseal cartilage. However, mRNA itself was only detected in the mid- and lower hypertrophic zones. Immunoreactivity was identified intracellularly with some nuclear staining observed. In focal lesions of DCP mRNA expression and immunoreactivity were reduced compared to normal cartilage, but strong mRNA expression was observed in the chondrocyte clusters immediately surrounding a lesion of DCP. The results described in this study demonstrate alterations in TGF-beta 1 dyschondroplastic lesions and indicate that it could be involved in the pathogenesis of this condition in the horse.