Fig. 2

Bone stromal cells, particularly SSCs, are significant markers of senescence in osteoarthritis. A, C, E Representative images of P21 (A), IL-1β (C), and IL-6 (E) IHC in articular cartilage and subchondral bone at different points in the progression of OA. Scale bar, 100 μm. B, D, F Quantitative analysis of the P21 (B), IL-1β (D), and IL-6 (F) areas in articular cartilage and subchondral bone (n = 3). G IF staining of Lepr and P21 in mouse subchondral bones in various treatment groups. The white arrows indicate P21-positive cells. Scale bar, 100 μm. H Proportion of Lepr⁺P21⁺ cells among Lepr⁺ cells (n = 3). I IF staining of Grem1 and P21 in the subchondral bones of mice in various treatment groups. The white arrows indicate the double-positive cells. Scale bar, 100 μm. J Proportion of Grem1⁺P21⁺ cells among Grem1⁺ cells (n = 3). K, L Representative images of P21 (K) and IL-6 (L) IHC in the articular cartilage and subchondral bone of OA human samples. The N side represents the less severely diseased side of the source joint, whereas the O side represented the more severely diseased side of the joint. Scale bar, 100 μm. M, N Quantitative analysis of P21 (M) and IL-6 (N) levels in articular cartilage and subchondral bone (n = 3). Quantitative analyses were conducted using the IHC Profiler plug-in for Image J. All data are presented as the mean ± S.D. *P < 0.05; **P < 0.01; ***P < 0.001; ns, not significant