Immunohistochemical analysis of Bcl-2 and Bax oncoproteins in rabbit craniomandibular joint

The purpose of this study was to elucidate the expression of proto-oncogene Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic) in fibrocartilage of the disc and hyaline cartilage of the condyle in the rabbit craniomandibular joint (CMJ). Ten New Zealand white rabbit heads were used. Sections were processed by the immunohistochemical techniques using mouse anti-Bcl-2 and anti-Bax antibodies. Intensity levels of immunostaining in condylar cartilage were quantified by a computer-image system. Immunoreactivity for Bcl-2 was mainly observed in the cytoplasm of the reserve cell and chondrocytic cell layers. A mild heterogeneous Bax expression was detected in the cytoplasm of chondrocytes of the upper hypertrophic layer and a few cells of the chondrocytic layer. The cytoplasm of chondrocytes in the disc exhibited a high intensity for Bcl-2, while Bax activity was only sporadically observed. We have shown that Bcl-2 and Bax proteins are present in CMJ cartilage and their expression patterns suggest that these oncoproteins are involved in chondrocyte survival or death via apoptotic pathways.