To investigate the expression of bax and bcl-2 in normal human articular chondrocytes and in osteoarthritic articular cartilage.
The samples of articular cartilage were obtained from 9 patients and 6 normal subjects. Bax and bcl-2 mRNA were detected by reverse transcriptase/polymerase chain reaction (RT-PCR) and their expression proteins were analyzed immunohistochemically. TUNEL technique was used to study apoptosis in situ.
Bax and bcl-2 mRNA was detectable in chondrocytes of both osteoarthritic and normal cartilage. Bax mRNA of chondrocytes from patients with osteoarthritis (OA) was overexpressed compared with the normal controls (P < 0.01), and OA cartilage chondrocyte also expressed more bcl-2 mRNA than the controls (P < 0.05). There was no statistically significant difference of bax/bcl-2 between the two groups. Immunohistochemical staining demonstrated the same level of bax and bcl-2 proteins as their mRNA. A greater proportion of apoptotic chondrocytes were found in the OA cartilage than that in normal controls (4% - 14% versus 0 - 2%).
Our results suggested that chondrocyte apoptosis was co-regulated by both bax and bcl-2. The ratio of bax to bcl-2 may contribute not only to the lower percentage of apoptotic chondrocytes, but also to the chronic pathologic process in OA.