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.