Millimeter wave treatment inhibits the mitochondrion-dependent apoptosis pathway in chondrocytes

Millimeter wave (MW) is an electromagnetic wave with a wavelength between 1 and 10 mm and a frequency of 30-300 GHz that causes multiple biological effects, both locally and globally. MW has been widely used in clinical medicine. Although our previous work demonstrated that MW is capable of inhibiting sodium nitroprussiate (SNP)-induced apoptosis in chondrocytes, the precise mechanism of the anti-apoptotic activity remains to be elucidated. The purpose of this study was to investigate the effects of MW in SNP-induced apoptotic chondrocytes. Sprague Dawley rat chondrocytes were isolated and cultured, and the cells were counted. Cell viability was evaluated using MTT assay. Cells were then treated with SNP and MW, and flow cytometry was used to detect apoptosis. Our results showed that MW treatment inhibited a SNP-induced mitochondrion-dependent pathway of apoptosis. MW treatment inhibited the loss of plasma membrane asymmetry (externalization of phosphatidylserine), collapse of mitochondrial membrane potential, and activation of caspase-9 and caspase-3. Taken together, the results indicate that MW inhibits the mitochondrion-dependent pathway of apoptosis in chondrocytes and this may, in part, explain its clinical effect in the treatment of osteoarthritis.