(A) Real-time PCR was carried out to analyze the mRNA levels for aggrecan (a), collagen II (b), LK1 (c), SOX9 (d), Runx2 (e), Ihh (f), collagen X (g) and MMP-13 (h) in non-stretched without OA control group, CTS group and CTS with OA group. Values were presented as mean±SD (n = 3). *P<0.05. (B) OA did not induce cell death. The viability of cells subjected to CTS with OA was assessed by using Hoechst 33342/PI double staining at 48 h post-CTS. The cells frozen at -20°C served as positive controls (B-a to c). No dead cells were detected in CTS with OA groups (B-d to f). Blue indicated cell nucleus stained by Hoechst 33342, while red indicated PI stain in dead cells.