Quantitative Investigation of Bone Microvascularization from 3D Synchrotron Micro-Computed Tomography in a Rat Model

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Simultaneous 3D Imaging of Bone and Vessel Microstructure in a Rat Model

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Simultaneous 3D Imaging of Bone and Vessel Microstructure in a Rat Model: Measurement of Vascular-Trabecular Interdistance

International audienceA method for simultaneous 3D imaging and analysis of microvascularization and bone microstructure in rat bone is presented. The method is based on the use of quantitative synchrotron micro-computed tomography (SR-¿CT) coupled to an automatic image analysis procedure. Previously, analysis of bone microvascularization has generally been performed from 2D histology. The proposed method enables for the first time to simultaneously analyze in 3D the microvascularization and bone microstructure in a rat model. We also propose a new parameter, utilizing the availablilty of both microstructures to relate the two, which we dub the vascular-trabecular interdistance (VTI). The proposed method was applied to investigate the effect of intermittent parathyroid hormone (PTH) administration on angiogenesis and osteogenesis in rats. It was possible to extract 3D quantitative parameters both on bone microstructure and micro-vascularization. Due to the short acquisition times of SR-¿CT and the efficiency of the image analysis algorithm, a large data set was analyzed, which permitted statistical analysis of the measured parameters. Statistical analysis showed that treatment with PTH significantly modulated several bone and vessel parameters, including the VTI

Bone Sialoprotein Deficiency Impairs Osteoclastogenesis and Mineral Resorption In Vitro

International audienceBone sialoprotein (BSP) and osteopontin (OPN) belong to the small integrin-binding ligand N-linked glycoprotein (SIBLING) family, whose members interact with bone cells and bone mineral Previously, we showed that BSP knockout (BSP(-/-)) mice have a higher bone mass than wild type (BSP(+/+)) littermates, with very low bone-formation activity and reduced osteoclast surfaces and numbers Here we report that approximately twofold fewer tartrate-resistant acid phosphatase (TRACP)-positive cells and approximately fourfold fewer osteoclasts form in BSP(-/-) compared with BSP(+/+) spleen cell cultures BSP(-/-) preosteoclast cultures display impaired proliferation and enhanced apoptosis Addition of RGD-containing proteins restores osteoclast number in BSP(-/-) cultures to BSP(+/+) levels The expression of osteoclast-associated genes is markedly altered in BSP(-/-) osteoclasts, with reduced expression of cell adhesion and migration genes (alpha V integrin chain and OPN) and increased expression of resorptive enzymes (TRACP and cathepsin K) The migration of preosteoclasts and mature osteoclasts is impaired in the absence of BSP, but resorption pit assays on dentine slices show no significant difference in pit numbers between BSP(+/+) and BSP(-/-) osteoclasts However, resorption of mineral-coated slides by BSP(-/-) osteoclasts is markedly impaired but is fully restored by coating the mineral substrate with hrBSP and partly restored by hrOPN coating In conclusion, lack of BSP affects both osteoclast formation and activity, which is in accordance with in vivo findings Our results also suggest at least some functional redundancy between BSP and OPN that remains to be clarified (C) 2010 American Society for Bone and Mineral Researc

Protective Effect on Bone of Nacre Supplementation in Ovariectomized Rats

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Intermittent PTH(1-84) Is Osteoanabolic but Not Osteoangiogenic and Relocates Bone Marrow Blood Vessels Closer to Bone-Forming Sites

International audienceIntermittent parathyroid hormone (PTH) is anabolic for bone. Our aims were to determine (1) whether PTH stimulates bone angiogenesis and (2) whether vascular endothelial growth factor (VEGF A) mediates PTH-induced bone accrual. Male Wistar rats were given PTH(1-84) daily, and trabecular bone mass increased 150% and 92% after 30 and 15 days, respectively. The vascular system was contrasted to image and quantify bone vessels with synchrotron radiation microtomography and histology. Surprisingly, bone vessel number was reduced by approximately 25% and approximately 40% on days 30 and 15, respectively. PTH redistributed the smaller vessels closer to bone-formation sites. VEGF A mRNA expression in bone was increased 2 and 6 hours after a single dose of PTH and returned to baseline by 24 hours. Moreover, anti-VEGF antibody administration (1) blunted the PTH-induced increase in bone mass and remodeling parameters, (2) prevented the relocation of bone vessels closer to bone-forming sites, and (3) inhibited the PTH-induced increase in mRNA of neuropilin 1 and 2, two VEGF coreceptors associated with vascular development and function. In conclusion, PTH(1-84) is osteoanabolic through VEGF-related mechanism(s). Further, PTH spatially relocates blood vessels closer to sites of new bone formation, which may provide a microenvironment favorable for growt