The bone was clamped at a 9° angle lateral to the vertical axis of the bone as described previously [32]. Load was applied to the femoral head until fracture occurred. Stiffness was obtained from the slope

of the force-displacement curve and the ultimate load obtained was from the maximum force that the bone was able to resist. Proximal parts of the femurs were decalcified in 11% EDTA (pH 8.0, 5 N NaOH) for 14 days. Samples were embedded in paraffin wax and 5 μm longitudinal sections were cut on a microtome (Leica RM2035, Milton Keynes, BYL719 cell line UK). Alternate sections were stained with sirius red staining for collagen content and Tartrate-resistant acid phosphatase (TRAP) staining for osteoclasts. The sirius red staining was completed using the picro-sirius red method as described [33] followed by counterstaining with haematoxylin. To standardize staining, all sections were stained in a single batch. To assess the collagen content, sections from the proximal femur shaft were stained with sirius red and bright field images collected (n = 5 for each mouse) using an Axioskop50 microscope with a 40× objective

(Zeiss, Cambridge, UK) and Carl Zeiss AxioCam MRc camera (Zeiss, Cambridge, UK). Five regions of interest (approximately 219 μm × 164 μm), were selected for quantification, and averages per section were taken as the final measures for each genotype. The % area of red pixels corresponding to collagen fibres, relative to total tissue area, was estimated using a colour segmentation

plugin in ImageJ (Biomedical Imaging Buparlisib concentration Group, EPFL, Switzerland: http://bigwww.epfl.ch/sage/soft/colorsegmentation/) using independent colour channels and the K-means algorithm. Distal femurs were sectioned transversely just above the condyles and stored in 2.5% paraformaldehyde in 0.1 M sodium phosphate buffer (pH 7.4) at 4 °C for 48 h. Adherent soft tissue was removed by immersion in 3% hydrogen peroxide solution for 48 h. After rinsing with distilled water, specimens were defatted in 50:50 methanol/chloroform for 24 h at room temperature and transferred to a 5% trypsin solution (0.1 M PB, pH 7.4) at room temperature for 48 h. After cleaning with distilled water, specimens were desiccated prior to preparing on a sputter coater (Polaron E5000, East Sussex, UK). Images were obtained using a scanning electron cAMP microscope (Stereoscan 250 MK3, Cambridge, UK). Small Angle X-ray Scattering (SAXS) was used to assess the nano-scale bone mineral structure of the cortical bone in the humerus of the female mice. Five right humeri from each group of the female mice were formalin fixed, dehydrated in a series of increasing concentration alcohol solutions and embedded in methylmethacrylate resin. A transverse slice was cut from the mid shaft and polished down to 100 μm thickness. The I911-SAXS beamline of the MAX II ring (1.5 GeV) at the MAX IV Laboratory (Lund University, Lund) was used [34]. A monochromatic beam of wavelength 0.