Effect of irradiation with a low-intensity diode laser on the metabolism of equine articular cartilage in vitro.

The research investigated the impact of low-intensity diode laser irradiation on the metabolism of horse articular cartilage in a lab setting. The result indicated that there were no significant changes in cartilage metabolism, even though minor thermal increases were observed.

Methods and Materials

• The study used 144 normal articular cartilage explants. These were aseptically harvested from the femoral condyles of 6 adult horses.
• The treated cartilage explants were irradiated with a diode laser at different levels that ranged from 8 to 1,600 J/cm2.
• Explants were incubated for 24, or 72 hours, and labeled for 24 hours with [35S]Na2SO4.
• The explants were assayed for newly synthesized sulfated glycosaminoglycan (GAG) and endogenous GAG, chondroitin 6-sulfate (CS), and keratan sulfate (KS) content, using a dimethylmethylene blue assay.
• The temperature changes due to the laser irradiation were measured during the procedure. A neodymium:yttrium aluminum garnet (Nd:YAG) laser was also used for comparison as it was previously reported to increase explant metabolism.

Results

• After incubation for 24 or 72 hours, there were no significant differences in the rate of 33SO4 uptake or endogenous GAG, CS, or KS content in the irradiated explants compared to non-irradiated ones.
• During the application of the diode laser, cartilage temperature increased by less than 4.75°C.
• Conversely, cartilage temperature increased 5 to 12°C during Nd:YAG laser application.

Conclusions

• The experiment concluded that minimal thermal increases in cartilage explants due to the use of a low-intensity diode laser led to no change in proteoglycan metabolism of chondrocytes (cells found in cartilage).
• Alternatively, the increase in tissue temperature made by the Nd:YAG laser possibly contributed to the metabolic changes in chondrocytes observed in prior studies.