Fig. 4: Early-onset osteoarthritis in Bhlhe40^−/− and Sh3pb4^−/− mice.

a Iodine contrast-enhanced μCT images of lateral tibial plateau articular cartilage (red) and subchondral bone (blue) from 16-week-old wild-type (WT) and homozygous Bhlhe40^−/− and Sh3bp4^−/− mice. Graphs show articular cartilage volume (Cg.V) and median articular cartilage thickness (Median Cg.Th) in Bhlhe40^−/− (n = 3) and Sh3bp4^−/− (n = 5) mice. b Back-scattered electron-scanning electron microscopy images of lateral tibial plateau joint surface replicas from WT, Bhlhe40^−/− and Sh3bp4^−/− mice. Graph shows articular cartilage (Cg) damage. c X-ray microradiography images of proximal tibia and the lateral tibial plateau subchondral bone region of interest (dashed box) from WT, Bhlhe40^−/− and Sh3bp4^−/− mice in which greyscale images are pseudocoloured according to a 16 color look-up table in which low bone mineral content (BMC) is yellow and high BMC is pink. Graph shows no change in subchondral BMC (SC BMC). d Coronal sections of lateral knee joint compartment stained with Safranin-O/Fast green from WT, Bhlhe40^−/− and Sh3bp4^−/− mice (n = 3 sections from one mouse each). Arrows indicate areas of cartilage damage. Orange circles: individual mutant samples, black horizontal lines: sample mean. Gray boxes: reference ranges derived from 100 wild-type samples. For normally distributed parameters (Cg.V, SC BMC), reference range is two standard deviations above and below the mean (dashed line). For non-normally distributed parameters (median Cg.Th, Cg. Damage Area), reference range is the 2.5–97.5th percentile, and dashed line is the median. Scale bars = 100 μm (a, b, d) and 1 mm (c). *P < 0.00568, **P < 0.001, Bonferroni-corrected two-tailed Wilcoxon rank sum test. Cg.V: P = 0.00311 (Sh3bp4^−/−), Median Cg.Th: P = 0.00469 (Bhlhe40^−/−), P = 0.00081 (Sh3bp4^−/−), Cg. Damage Area: P = 0.00282 (Sh3bp4^−/−). mm millimeter. Source data are provided as a Source Data file.