Immunolocalization of vascularization factors in normal, tibial dyschondroplasia and rachitic cartilage

Tibial dyschondroplasia is a skeletal abnormality characterized by an avascular plug of cartilage in the metaphysis of the long bones of rapidly growing birds. An avascular, thickened growth plate also occurs in vitamin D/calcium-deficient rickets. This research was conducted to evaluate tibial dyschondroplasia and rachitic tissue for factors shown to be important in normal growth plate vascularization. Immunohistochemical analysis demonstrated the presence of vascular endothelial growth factor, its receptor Flk-1, and matrix metalloproteinases MMP-9 and MMP-13 to be present in all tissues examined. In most cases, immunostaining was intracellular, except near blood vessels where the matrix was also stained. The results suggest that, for the four proteins examined, disruption of their expression is not a key factor in the development of these avascular cartilage lesions in avians. The relationship of these observations to the pathology of tibial dyschondroplasia is discussed.