Fig. 2

PGE2 mediates mechanical load-induced osteoblastic bone formation. a Representative images of immunostaining and quantitative analysis of the number of COX2⁺ cells (brown) in the subchondral bone marrow (N.BM/COX2⁺) of talus, calcaneus, and tibia from 12-week-old C57BL/6 mice. Scale bars, 50 μm. Representative images of immunostaining TRAP⁺ cells per bone surface (N.Oc/BS) on the trabecular bone surface b and TRAP⁺ cells in the bone marrow c and quantitative analysis of TRAP⁺ cells d in talus, calcaneus, and tibia from 12-week-old C57BL/6 mice. Scale bars, 50 μm. Representative images of immunostaining e and quantitative analysis g of CTSK expression in osteoclasts at steady state of the subchondral bone of talus, calcaneus, and tibia from 12-week-old C57BL/6 mice. Scale bars, 50 μm. Representative images of immunostaining f and quantitative analysis h of CTSK expression in osteocytes at steady state of the subchondral bone of talus, calcaneus, and tibia from 12-week-old C57BL/6 mice. Scale bars, 50 μm. i ELISA analysis of PGE2 level in tibiae bone marrow at different time points after axial compression loading on the tibiae of WT mice. j Immunohistochemical staining and quantification of COX2⁺ cells (brown) on the trabecular tibial surface in WT mice. Scale bar, 50 µm. k ELISA analysis of PGE2 level in tibiae bone marrow at different time points after axial compression loading on the tibiae 100 cycles at 2 Hz of COX2_Ocn^−/− mice. Representative µCT images l and quantitative analysis m of trabecular bone fraction (BV/TV) and trabecular number (Tb.N) of tibial bone of WT mice loaded for one month or non‐loaded tibiae. Scale bar, 500 µm. Representative µCT images n and quantitative analysis o of trabecular bone fraction (BV/TV) and trabecular number (Tb.N) of tibial bone of COX2_Ocn^−/− mice loaded for one month or non‐loaded tibiae. Scale bar, 500 µm. n ≥ 5 per group. *P < 0.05, **P < 0.01, and N.S. indicates not significant. Statistical significance was determined by Student’s t-test