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

Abstract

Abstract Objective To determine whether irradiation with a low-intensity diode laser, which produces radiation at a wavelength of 810 nm, will induce nonthermal enhancement of chondrocyte metabolism. Sample Population 144 grossly normal articular cartilage expiants aseptically harvested from the femoral condyles of 6 adult horses. Procedure Treated cartilage expiants were irradiated with a diode laser at 1 of 7 fluence levels that ranged from 8 to 1,600 J/cm2. Expiants were incubated for 24 or 72 hours, labeled for 24 hours with [35S]Na2SO4, and assayed for newly synthesized sulfated glycosaminoglycan (GAG; measured incorporation of 35SO4) and endogenous GAG, chondroitin 6-sulfate (CS), and keratan sulfate (KS) content, using a dimethylmethylene blue assay. Laser-induced temperature changes were measured during irradiation with a diode laser and a neodymiumyttrium aluminum garnet (Nd:YAG) laser, which produces radiation at a wavelength of 1,064 nm, using conditions that were reported in previous studies to increase explant metabolism. Results After incubation for 24 or 72 hours, rate of 35SO4 uptake or endogenous GAG, CS, or KS content in irradiated expiants was not significantly different than in nonirradiated expiants. Cartilage temperature increased < 4.75 C during diode laser application. Cartilage temperature increased 5 to 12 C during Nd:YAG laser application. Conclusions Minimal thermal increases in cartilage expiants with use of a low-intensity diode laser resulted in no change in proteoglycan metabolism of chondrocytes. An increase in tissue temperature over a narrow range with use of a Nd:YAG laser may have contributed to the metabolic alteration of chondrocytes reported in previous studies. (Am J Vet Res 1998;59:1613-1618)