Effects of low-intensity pulsed ultrasound on proliferation and chondroitin sulfate synthesis of cultured chondrocytes embedded in Atelocollagen~R gel

摘要

The effects of low-intensity pulsed ultrasound (US) on the proliferation and chondroitin sulfate synthesis of cultured chondrocytes embedded in Atelocollagen~R gel in vitro were examined. Articular cartilage was harvested from the hip, knee, and shoulder joints of 10-week-old Japanese white rabbits. Chondrocytes isolated by collagenase digestion were embedded in type I collagen gel, Atelocollagen gel, and were cultured in Dulbecco's modified eagle's medium for 3 weeks. The US apparatus, SAFHS~R , was used to deliver an ultrasound signal with spatial and temporal average intensities of 30 m/cm~2 (US group). The frequency was 1.5 MHz with a 200-microsecond tone burst repeated at 1.0 kHz. US treatments were administered for 20 min per day under culture dishes, with the medium replaced twice a week. Another group of cells was exposed to sham ultrasound as a control. Cell number, histological findings, synthesis of isomers of chondroitin sulfate, and stiffness of the chondrocyte-collagen gel composites were analyzed. US exposure promoted synthesis of chondroitin sulfate, especially chondroitin 6-sulfate, although it did not significantly enhance cell number and stiffness. In this three-dimensional culture model, these results suggest that US exposure may be clinically useful in improving the quality of chondrocyte-Atelocollagen implants for transplantation into articular cartilage defects.