Objective:To investigate the expression level of plasma miR-320c in patients with osteoarthritis(OA), and explore the clinical significance and the role in pathogenesis of OA.Methods:The clinical data and peripheral blood of 30 patients with OA, 30 patients with connective tissue diseases and 30 healthy control individuals were collected.The levels of plasma miR-320c were detected byfluorescentquantitative reverse transcription PCR(qRT-PCR). Correlation analysis was used to explore the correlation of plasma miR-320c level with knee X-ray data and VAS pain score in OA patients.Finally the miR-320c mimic, the miR-320c inhibitor, and the control material were transfected to the chondrocyte HC-a.The proliferative capacity of HC-a chondrocytes was examined at different time points as determined by the CCK-8 assay.Results:The expression level of plasma miR-320c was significantly higher in OA group(3.26±0.55)than that in the connective tissue diseases group(1.62±0.50)and in healthy control group(1.21±0.66)( F=107.66, P<0.001). Plasma miR-320c expression was positively correlated with radiographic grade( r=0.830, P<0.001), and had no correlation with VAS pain score in OA group( P>0.05). Through repeated measurement variance analysis, the time effect, the group effect and the interaction effect between group and time showed statistically significant differences in chondrocyte proliferation between NC mimic group and miR-320c mimic group( Ftime=5256.767, Fgroup=1947.436, Ftime×group=114.314, all P<0.001). The level of proliferation was significantly reduced.Apoptosis rate of chondrocytes was significantly increased in the group transfected with miR-320c( t=7.85, P<0.01). Conclusions:The expression level of plasma miR-320c is significantly higher in osteoarthritis patients and associated with knee radiographic severity grade.Furthermore, over-expression of miR-320c could suppress the proliferation of chondrocytes.Plasma miR-320c might be potential bio-marker for osteoarthritis knee severity assessment, and involves in regulating chondrocyte growth in the pathogenesis of osteoarthritis.