The effects of sonication on human osteoarthritis cartilage in ex vivo tissue culture

Min, Byoung Hyun; Woo, Jeong Im; Cho, Hong Sik; Rho, Jae Young; Lee, Jeong Mo; Park, So Ra

Abstract

This study was initiated to investigate the effect of ultrasound(US) stimulation on therapeutic effects on human osteoarthritic cartilage repair. Cartilage explants from human osteoarthritic knee were sonicated for 10 minutes every day using continuous wave at frequency 1 MHz US signals with spatial and temporal average intensities of 0, 40, 200, 500 and 700mW/cm2. One group of explants was exposed to sham ultrasound as a control. After 1 week of culture, the intensity-dependent effects of US on DNA, proteoglycan (PG) and collagen synthesis were measured by 3H-thymidine, 35S-sulfate, 3H-proline incorporation, respectively. The expression of PG and type II collagen released into medium were measured by DMB (dimethylmethylene blue) method and western blot analysis. Safranin O/fast green and immunohistochemical staining with anti-collagen type II antibody were performed using the serial sections of cartilage explants. The histochemical examination showed that the expression of PG at the pericellular area in the deep layer increased continuously up to 700mW/cm2. In contrast, the depth of the superficial layer significantly decreased after treatment of sonication at 500 and 700mW/cm2. The expression of PG and type II collagen assessed by the isotope incorporation was significantly enhanced to the level up to 140%, 120% respectively, although US had no stimulatory effect on cell proliferation. These results suggest that optimum intensity of US for the effective expression of extracellular matrix in osteoarthritic cartilage may be around 200mW/cm2. In conclusion, our study suggests the possibilities that sonication may be therapeutically utilized for the repair of human osteoarthritic cartilage.