There have so far been no studies on the apoptosis of adult articular chondrocytes after X-ray irradiation. The purpose of this study was to assess the apoptotic resistance of articular chondrocytes in X-ray radiation, in order to examine the possibility of irradiated allogenic chondrocyte implantation. Adult human chondrocytes of the non-degenerated cartilage group without X-ray irradiation did not show positive cells of Annexin V and PI staining in a 48 h culture. The Annexin V positive chondrocytes did not increase in a radiation dose dependent manner, and the PI positive cells were slightly increased at 30 Gy irradiation. In the degenerated cartilage group, the PI positive chondrocytes without irradiation were present, and both the Annexin V and PI positive chondrocytes increased in a radiation dose dependent manner. The Annexin V and PI positive staining of chondrocytes in the non-degenerated cartilage group was less than that of the degenerated cartilage group in the same dose of X-ray irradiation exposure. Loss of the mitochondrial membrane potential, revealed in an early stage of apoptosis, did not show in the irradiated chondrocytes of the non-degenerated cartilage, but were demonstrated in those of the degenerated cartilage. These results demonstrated that the non-degenerated chondrocytes of X-ray irradiation were highly resistant for apoptosis, and this knowledge could be applied to allogenic chondrocytes implantation.

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