Bone Abstracts

Mineralized tissues like bone, articular calcified cartilage or mineralized turkey leg tendon (MTLT) are build by a composite of hydroxyapatite nano-particles and organic matrix. In bone and MTLT the matrix is formed by collagen type-I, but in contrast to bone in MTLT the collagen is uniaxial orientated, while in cartilage the matrix consists of collagen type-II and proteoglycans.Composition/orientation differences were investigated by a new scanning aco...

The local mechanical properties of bone are influenced not only by the material chemical composition but also by the spatial arrangement of the component’s e.g. orientation of collagen matrix. However, not much is known about local elastic modulus variations in cortical bone. Our goal was to use acoustic imaging to map elastic properties of murine bone with a several microns resolution. Rodent long bones exhibit a permanent growth with endosteal/periosteal bone formation ...

Deficiency of Cyclophilin B (CyPB) causes recessively inherited Type IX osteogenesis imperfecta, a moderately severe to lethal bone dysplasia. CyPB, encoded by PPIB, is an ER-resident peptidyl-prolyl cis-trans isomerase (PPIase) that catalyzes the rate-limiting step in collagen folding, and also functions as a component of the collagen prolyl 3-hydroxylation complex. We previously demonstrated in a Ppib−/− mouse model that CyPB PPIase activity r...

Objectives: Osteocytes play a major role in bone metabolism as mechanosensors, key regulators of osteoblast and osteoclast activity and of the mineral homeostasis. Therefore the assessment of osteocytes characteristics is important to understand bone pathology. We propose to study indirectly the osteocytes by performing quantitative backscattered electron imaging to quantify the sectioned osteocyte lacunae density and size in 2D on bone samples.Methods: ...

Objectives: Mice with a non-functioning vitamin D receptor (VDR mutants) develop severe secondary hyperparathyroidism, which can be rescued by a diet enriched with calcium, phosphate and lactose. In this work, we studied the effects of a low calcium challenge (CD), normal calcium (ND) and a calcium enriched rescue diet (RD) on the bone mineralization density distribution (BMDD) and osteocyte lacunae sections (OLS) in these mice.Methods: BMDD and OLS were...

Objectives: Osteogenesis Imperfecta (OI) is a collagen-related disorder. Type V OI, caused by a recurrent dominant mutation in the plasma membrane protein IFITM5/BRIL, and type VI OI, caused by recessive null mutations in the anti-angiogenic factor PEDF, have distinct features. IFITM5 S40L, reported in six patients, causes severe dominant OI with phenotype and bone histology similar to type VI, rather than Type V, OI. Our objective is to understand the pathway connecting IFITM...

Objectives: A common feature of nearly all forms of osteogenesis imperfecta (OI) is a hypermineralized bone matrix. Null mutations in SERPINF1, encoding the potent antiangiogenic factor PEDF, lead to type VI OI with excessive osteoid formation, abnormal osteoblast-osteocyte development and increased matrix mineralization. Recently, atypical type VI OI has been delineated, caused by a loss-of-function mutation (p.S40L) in IFITM5 the causative gene for type V OI. The 6 cases rep...

Mutations in the C-propeptide cleavage site of both COL1A1 and COL1A2 cause dominant high bone mass (HBM) osteogenesis imperfecta (OI), characterized by bone hypermineralization. To elucidate the role of C-propeptide processing in bone formation, we generated heterozygous HBM mice in which both residues of the COL1A1 cleavage site were mutated to prevent cleavage by BMP1. HBM mice are smaller than WT in both weight and length and have extremely brittle bones....

High Bone Mass (HBM) osteogenesis imperfecta (OI) is caused by dominant mutations in the C-propeptide cleavage site of COL1A1 or COL1A2, characterized by bone hypermineralization. To elucidate the role of C-propeptide processing in bone mineralization and development, we generated heterozygous HBM mice with both residues (Ala-Asp) of the COL1A1 cleavage site substituted (Thr-Asn) to prevent processing by BMP1. Two, 6- and 12-month WT and HBM bones were examin...