Low doses of uranium and osteoclastic bone resorption: key reciprocal effects evidenced using new in vitro biomimetic models of bone matrix.

Uranium is widely spread in the environment due to its natural and anthropogenic occurrences, hence the importance of understanding its impact on human health. The skeleton is the main site of long-term accumulation of this actinide. However, interactions of this metal with biological processes involving the mineralized extracellular matrix and bone cells are still poorly understood. To get a better insight into these interactions, we developed new biomimetic bone matrices containing low doses of natural uranium (up to 0.85 µg of uranium per cm2). These models were characterized by spectroscopic and microscopic approaches before being used as a support for the culture and differentiation of pre-osteoclastic cells. In doing so, we demonstrate that uranium can exert opposite effects on osteoclast resorption depending on its concentration in the bone microenvironment. Our results also provide evidence for the first time that resorption contributes to the remobilization of bone matrix-bound uranium. In agreement with this, we identified, by HRTEM, uranium phosphate internalized in vesicles of resorbing osteoclasts. Thanks to the biomimetic matrices we developed, this study highlights the complex mutual effects between osteoclasts and uranium. This demonstrates the relevance of these 3D models to further study the cellular mechanisms at play in response to uranium storage in bone tissue, and thus better understand the impact of environmental exposure to uranium on human bone health.

Tailored Microstructured Hyperpolarizing Matrices for Optimal Magnetic Resonance Imaging.

Tailoring the physical features and the porous network architecture of silica-based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (hybrid polarizing solids), enabled unprecedented performance of dissolution dynamic nuclear polarization (d-DNP). High polarization values up to P(1 H)=99 % were reached for samples impregnated with a mixture of H2 O/D2 O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices, which provide hyperpolarized solutions free of any-potentially toxic-additives (radicals and glass-forming agents). The hyperpolarized solutions can be expelled from the porous solids, filtered, and rapidly transferred either to a nuclear magnetic resonance (NMR) spectrometer or to a magnetic resonance imaging (MRI) system.

AlN hollow-nanofilaments by electrospinning.

We present for the first time an original method to elaborate AlN nanofilaments (NFs) by using a preceramic-based electrospinning process. Initially, an Al-containing precursor (poly(ethylimino)alane) is mixed with an organic spinnable polymer to be electrospun and generate polymeric filaments with a homogeneous diameter. A ceramization step at 1000 °C under ammonia and a crystallization step at 1400 °C under nitrogen are performed to get the final product made of AlN NFs with a diameter ranging from 150 to 200 nm. Studies carried out by high resolution electron microscopy and 3D tomography show their regular morphology, with high chemical purity and polycrystalline nature.

Distribution of strontium and mineralization in iliac bone biopsies from osteoporotic women treated long-term with strontium ranelate.

OBJECTIVE: To investigate interactions between strontium (Sr) and bone mineral and its effects on mineralization in osteoporotic women treated long-term with Sr ranelate (SrRan). DESIGN: In this study, 34 iliac bone biopsies were analyzed after 2, 12, 24, 36, 48, and 60 months of treatment with SrRan. METHODS: Sr global distribution was analyzed by X-ray cartography and the percentage of bone area containing Sr was calculated in the bone samples. The focal distribution of Sr in all bone samples was investigated by X-ray microanalysis. The degree of mineralization was assessed by quantitative microradiography. RESULTS: Absent from old bone formed before the beginning of treatment, Sr was exclusively present in bone formed during this treatment with a much higher focal Sr content in new bone structural units than in old ones. A progressive increase in the extent of areas containing Sr was observed during treatment. The focal bone Sr content in recently formed bone was constant over treatment. Secondary mineralization was maintained at a normal level during treatment. CONCLUSION: Thus, the quality of bone mineralization (density and heterogeneity at tissue level) was preserved after a long-term treatment with SrRan.