[Immunohistochemical localization of transforming growth factor-beta 1 in growth plate freshly transplanted into a full-thickness defect in articular cartilage].

Transplants of the epiphyseal growth plate obtained from the proximal tibia of Lewis rats at 3 weeks of age were inserted into full-thickness defects in the patellofemoral articular surface of Lewis rats at 5 weeks of age. As controls, similar surface defects were induced but no transplants were inserted. Transplants were studied immunohistochemically at varying intervals up to 72 weeks in order to determine the effects of transforming growth factor-beta 1 (TGF-beta 1) on the repair of the articular cartilage by the epiphyseal growth plate. TGF-beta 1 was present in chondrocytes in the region corresponding to the hypertrophic zone of the transplanted growth plate at 1 week after transplantation. The distribution pattern of TGF-beta 1 in this hypertrophic zone was similar to that prior to transplantation. At 2 weeks after transplantation, TGF-beta 1 was detected in the matrix, but the hypertrophic chondrocyte cell membranes were not clear. TGF-beta 1 was undetectable in the transplanted growth plate at 4 weeks after transplantation, at which time a morphological examination revealed metaplastically-transformed articular cartilage but no hypertrophic cartilage cells. No immunostaining of TGF-beta 1 was present in the untreated articular defect. These findings suggested that TGF-beta 1 in the hypertrophic chondrocytes was probably transferred from the cytoplasm to the extracellular matrix and stimulated the ossification of the matrix with vessel induction and osteoid formation during the process of incorporation of the transplant into the articular cartilage defect.