Boyde, A

Farquharson, C

Javaheri, B

Millan, JL

Pitsillides, AA

Staines, KA

Queen Mary Research Online

Characterising the spotty osteomalacia in Phospho1 knockout mice  SEM FW 636µm Alan Boyde, Katherine A Staines, Behzad Javaheri, Jose-Luis Millan, Andrew A Pitsillides, Colin Farquharson QMUL London E1 4NS UK, Roslin Edinburgh EH25 9RG UK, RVC London NW1 0TU UK, Sanford-Burnham, La Jolla, CA 92037, USA Introduction • Recent evidence has implicated PHOSPHO1, a soluble cytosolic phosphatase, in the initiation of biomineralisation.  • Phospho1 deficient bones are less mineralised and contain smaller mineral crystals, leading to hyperosteoidosis, spontaneous fractures, and bowed long bones.  • The consequences of Phospho1 ablation on the microscale structure of mineralised bone are not yet fully elucidated: such information might help to understand the function of PHOSPHO1 in biomineralisation.  Methodology • Bones from wild-type and Phospho1-/ - mice (25-32 week-old) embedded in PMMA, cut and polished to produce near longitudinal sections.  • 20kV backscattered electron (BSE) imaging, uncoated samples, 50 Pa pressure in the Zeiss EVO MA10 SEM, revealed large patches with no mineral deposition.   • To characterise this further, block surfaces were stained with ammonium tri-iodide to reveal non-mineralised matrix and cellular components before further BSE SEM.  • For 3D characterisation, we used x-ray microtomography of whole bones before, and of trimmed PMMA blocks after SEM. We also opened bones with carbide milling tools to expose endosteal surfaces - macerated to produce 3D surfaces for study with 3D BSE SEM. Findings •Extensive regions of both compact cortical and trabecular bone matrix in Phospho1-/ - mice contained no significant mineral and/or showed arrested mineralisation fronts (failure of fusion of the separately mineralising micro-volumes) at trabecular, endosteal and periosteal surfaces. •Osteoclastic resorption of the uncalcified matrix was attenuated compared with surrounding normally-mineralised bone.  •The extent and position of this aberrant biomineralisation varied considerably between animals, contralateral limbs and anatomical sites. •The most frequent manifestation lay in the nearly complete failure of mineralisation in the bone surrounding the numerous transverse blood vessel canals in the cortices.  Conclusion • Extensive histological osteomalacia, varying widely in extent, is found in Phospho1-/- lower limb bones.  25 micron voxel resolution XMT data set, raw data and Drishti renderings, showing HDMP complexes projecting above subchondral bone plate. Human femoral head removed at arthroplasty: AKU. In glycerol. MRI DESS  shows HDMP as low signal area in bright HAC above subchondral bone plate.  6 micron XMT PMMA block non-mineralised matrix  20kV BSE SEM, tri-iodide stained, no coating, 50Pa non-mineralised matrix  periosteal patches of mineralised matrix 20kV BSE SEM, tri-iodide stained, no coating, 50Pa marrow periost patches of mineralised matrix  in non-mineralised background  20kV BSE SEM, tri-iodide stained, no coating, 50Pa marrow patches of mineralised matrix  in non-mineralised background  femur tibia 20kV BSE SEM, tri-iodide stained, no coating, 50Pa substantial area of non-mineralised matrix beneath periosteum  20kV BSE SEM, unstained, no coating, 50Pa 20kV BSE SEM, tri-iodide stained, no coating, 50Pa Periosteal muscle non-mineralised matrix  TGZ macerated endosteal surfaces Focus foreground on trabecula Focus background on endosteal surface Two images of same field focussed on a trabecula and on the endosteal surface, showing the mineralisation anomaly in both regions. TGZ macerated endosteal surfaces ko-fem-recut067/068/069 NB distrib of dark endost patches These three images montage the length of the femoral shaft endosteum in a KO femur. The dark patches all show unfused mineralising centres. TGZ macerated endosteal surfaces femoral shaft endosteum  in a KO femur. The dark patches all show unfused mineralising centres. TGZ macerated endosteal surfaces 100um 20kV BSE  tri-iodide stained, no coating 50Pa tibia tibia muscle Drishti uCT  Drishti negatives  osteocytes BV canals Tergazyme macerated femur, endosteal surface, showing abnormal mineralising front and unmineralised borders of penetrating ‘canals’  OP6 Anaglyph stereos: use colour  filter spectacles, green or cyan for right eye 

Characterising the spotty osteomalacia in Phospho1 knockout mice

https://qmro.qmul.ac.uk/xmlui/bitstream/123456789/49629/1/2015%20Bone%20Res%20Soc%20%26%20%20BSMB%20Edinburgh%202015%20OP6%20Spotty%20osteomalacia%20poster.pdf

Characterising the spotty osteomalacia in Phospho1 knockout mice

Abstract

Similar works

Full text

Available Versions

Queen Mary Research Online