The effects of pulsed low-intensity ultrasound on chondrocyte viability, proliferation, gene expression and matrix production

This study was designed to examine the effects of pulsed low-intensity ultrasound (PLIUS) on chondrocyte viability, proliferation, matrix production and gene expression. Chondrocytes were isolated from the distal part of the sternum of 16-day-old chick embryos and cultured in alginate beads. PLIUS at 2 mW/cm² (group PLIUS₂) and 30 mW/cm² (group PLIUS₃₀) was applied to chondrocytes for a single 20-min treatment. A control group was treated without PLIUS. The viability of chondrocytes was not affected by exposure to PLIUS. PLIUS influenced chondrocyte proliferation in an intensity-dependent manner. By day 7 after application of PLIUS, the gene expression and synthesis of aggrecan was the same as in the controls. At this same time point, the expression and synthesis of type II collagen was not different between the controls and PLIUS₃₀, but was increased in PLIUS₂. PLIUS was shown to inhibit the expression of type X collagen. This inhibition of chondrocyte hypertrophy may prove to be significant in the management of cartilage degeneration.