Immunohistochemical localization of type X collagen in the proximal tibiotarsi of broiler chickens and turkeys.

Type X collagen is a prominent component of the extracellular matrix in cartilage destined to mineralize during endochondral ossification, yet its role is only now being determined. As a prelude to determining what, if any, alterations occur in the distribution of type X collagen in growth plates of poultry with rickets or tibial dyschondroplasia, our objective in the current study was to determine the distribution of type X collagen in the proximal tibiotarsi of broiler chickens and turkeys from 1 day of age through physeal closure. Proximal tibiotarsi from five male broiler chickens, five female broiler chickens and five male turkeys were collected at 1, 7, 14, 28, 56, and 98 days of age and processed for immunohistochemistry; a monoclonal antibody for type X collagen was used to demonstrate type X collagen distribution. Our findings indicate that type X collagen is produced in the prehypertrophic and early hypertrophic zones of the avian growth plate and is incorporated into the extracellular matrix in these zones. Furthermore, intracellular type X collagen is markedly decreased in more mature areas of the growth plate, although type X collagen remains a prominent component of the extracellular matrix until the matrix is completely resorbed. In addition, the distribution of type X collagen is similar in the proximal tibiotarsi of broiler chickens and turkeys at comparable stages of endochondral ossification and distribution of type X collagen in the secondary center of ossification parallels that in the physis.