Objective      To determine the effect of low-intensity pulsed ultrasound (LIPUS) on the cell apoptosis and extracellular matrix (ECM) of primarily cultured human osteoarthritis (OA) chondrocytes in vitro. Methods      Human OA chondrocytes were isolated from abandoned articular cartilage tissues and cultured. After the cells were identified by Toluidine Blue staining and immunochemical staining for type Ⅱ collagen

the cells at passage 2 were stimulated by LIPUS at different intensities (0

30

60 and 90 mW/cm ) 20 min per day for 1 week. Then the apoptotic rate was evaluated by flow cytometry. The mRNA and protein expression levels of collagen type Ⅱ α1 (COL2α1)

aggrecan and matrix metalloproteases 13 (MMP13) were detected by qPCR and Western blotting. Results     The apoptotic rates were (7.75±0.79)%

(8.52±091)% and (11.38±0.85)% respectively in the cells stimulated by 30

60 and 90 mW/cm2 LIPUS

which were significantly lower than that in the control group [(18.13±0.83)%

P0.05]. The mRNA and protein expression levels of COL2α1 and aggrecan were significantly higher (P0.05)

but those of MMP13 were obviously lower (P0.05) in the cells stimulated with different intensity LIPUS than in the control cells

but no intensitydependent manner was found in the stimulated groups. Conclusion     LIPUS can reduce the rate of apoptosis of human osteoarthritis chondrocytes primarily cultured in vitro. Further LIPUS can promote the synthesis and inhibit the decomposition of ECM. It might be an useful treatment for OA and delay the progression of OA.