Effects of laser irradiation on arthritic histopathology and heat shock protein 70 expression in C57 black mice with osteoarthritis.

Objective: To study the effects of three different laser treatments (650 nm alone, 10.6 μm alone and combined laser of 650 nm and 10.6 μm) on experimental osteoarthritis of the knees in C57 black mice.

Methods: Sixty C57 black mice were divided randomly into 6 groups. Ten mice were assigned to a normal control group (no intervention) and the other 5 groups were subjected to a forced running regimen to induce osteoarthritis. One group was set as the model control group. The other 4 groups were given 90 s of a 650 nm laser, 90 s of a 10.6 μm laser, 90 s of a combined laser, or a sham treatment on acupoint Dubi (ST35) of the rear left leg 3 times per week for 4 weeks. The modified Mankin score was used to evaluate the degree of cartilage degradation. Immunohistochemical staining for heat shock protein (HSP) 70 was conducted.

Results: Mankin scores of the model control group and the sham control group were significantly higher than that of the normal control group (P<0.01). Mankin score of the combined laser group was significantly lower than that of the model control group (P<0.01). Compared with the normal control group, there was a significant induction of HSP70 in the arthritic chondrocytes of the combined laser group.

Conclusion: The arthritic cartilage induced in C57 black mice improved significantly after combined laser treatment of 650 nm and 10.6 μm lasers. This effect may be related to the induction of HSP70 in the arthritic chondrocytes. The two different lasers appear to have a synergistic effect.