Fig. 2
Trabecular bone loss and decreases of bone formation in YapOcn-Cre mice. a–k µCT analysis of femurs from 3-month-old YapOcn-Cre and control (ctrl) (Yapf/f) littermates. Five different male mice of each genotype were examined blindly. Representative images are shown in a. The 3D images shown on the right (a1, a1′, a2, and a2′) were derived from the marked corresponding regions of the femurs in the left images. Quantification analyses are presented in b–k. Note that the trabecular bone (Tb) volumes over total volumes (BV/TV), trabecular separation (Tb.Sp), and trabecular thickness (Tb.Th) but not trabecular numbers (Tb.N) by direct model of µCT analysis were all deficient in YapOcn-Cre as compared with the ctrls. The cortical BVs over TVs (BV/TV), cortical thickness (Cb.Th), and cortical cross-section area and polar mean moment of inertia (MMI, Polar) were unchanged in YapOcn-Cre mice (f, g, j, k). Note that endocortical perimeter (Ec.Perimeter) and periosteal perimeter (Ps.Perimeter) were increased (h, i). The data shown in b–k are: Means ± SD, 5 bone samples/each genotype, *P < 0.05. l Bar graph showing the number of OBs/unit bone surface (1 mm) in 3-month-old YapOcn-Cre and ctrl (Yapf/f) femur sections, representative images of H&E staining analyses of OBs in femurs from 3-month-old YapOcn-Cre and ctrl (Yapf/f) littermates in (n), Scale bars, 20 µm, arrows indicate OBs. m Reduced serum levels of osteocalcin, measured by ELISA assays, in 3-month-old YapOcn-Cre mice (mean ± SD, n = 5, male mice). o–u Attenuated bone formation, detected by dynamic histomorphometric measurements of double fluorescent-labeled femurs, in 3-month-old YapOcn-Cre mice. Ctrl and YapOcn-Cre mice (male) at the age of P76 were injected (intraperitoneal) with fluorochrome-labeled calcein green (10 mg·kg-1, Sigma–Aldrich), and 12 days after, they were re-injected to label active bone-forming surfaces. Two days after the second injection, mice were sacrificed and their femurs were fixed, sectioned, and viewed by fluorescence microscope (o). Scale bar, 10 µm. The trabecular (Tb), endocortical (Ec), and periosteum (Ps) mineral apposition rate (MAR) (calculated in µm·day-1) (p, r, t), and their bone-formation rate (BFR = MAR×minerization surface/bone surface) (q, s, u) are illustrated. In o–u, the values of mean ± SD from 5 different male mice per genotype are shown. *P < 0.05.
