Fig. 1

Preosteoblasts accumulate and activate in subchondral bone of ACLT OA mice. a, -b Representative Safranin O-Fast green and H&E staining of sagittal sections of tibia articular cartilage and subchondral bone in ACLT OA mice. Scale bars, 100 μm. c OARSI scores at 2, 6, and 12 weeks post surgery compared with that of the sham control. d, e TRAP staining and quantitative analysis of osteoclasts in mouse tibial subchondral bone at 2, 6, and 12 weeks post ACLT surgery compared with that of the sham control. Scale bars, 50 μm. f, g Representative immunohistochemical images and quantitative analysis of Osterix⁺ preosteoblasts in mouse tibial subchondral bone at 2, 6, and 12 weeks post ACLT surgery compared with that of the sham control. Scale bars, 100 μm. h, i Immunostaining images and quantitative analysis of Ki-67 in Osterix⁺ preosteoblasts in mouse tibial subchondral bone at 2, 6, and 12 weeks post ACLT surgery compared with that of the sham control. Boxed area is magnified on the top left corner. Scale bars, 100 μm. AC, articular cartilage; SCB, subchondral bone; GP, growth plate. j Representative 3D reconstructed micro-CT images of sagittal sections of mouse tibia subchondral bone at 2, 6, and 12 weeks post ACLT surgery compared with that of the sham control. Scale bars, 1mm. k, l Quantitative analysis of bone mass in subchondral bone: bone volume/total volume (BV/TV) and bone mineral density (BMD). Data are shown as mean±s.d. and analyzed by one-way ANOVA with Bonferroni post hoc test. n = 8, **P < 0.01