Researchers reveal what keeps bones in good function

What enables bones to selfregulate and maintain health Researchers from Charite Berlin have uncovered information about the essential role of noncollagen protein molecules and how they support the response of bone cells to external loads To clarify discrepancies in microstructures and the incorporation of water the researchers employed fish models to investigate bone samples with and without bone cellsThey were able to accurately measure the water diffusion across bone material for the first time using 3D neutron tomography at the Berlin research reactor BER II with a startling outcomeAround 500 million years ago early vertebrates in the seas became fish adopting an inner skeleton and a flexible spine based on a nanocmposite of fibers and mineral known as bone material This invention of evolution was so successful that the basic structure was also adopted for later vertebrates that lived on land However while the bones of all terrestrial vertebrates are basically equipped with bone cells osteocytes certain fish species continued to evolve and finally managed to create a more energy efficient material bone lacking bone cells found today for example in fish such as salmon medaka or tilapiaSamples with and without bone cellsWe asked ourselves how bone samples with and without bone cells actually differ in their microstructures and properties saif Prof Paul Zaslansky who heads a research group at Charite Berlin and specializes in mineralized biomaterials including teeth and bones Together with PhD student Andreia Silvera and international partners they have now compared bone samples from zebrafish and medaka Both fish species are of similar size and live in similar conditions so their skeletons must withstand similar stresses However while zebrafish have bone cells the skeleton of medaka do notThe background to the question is that the function of bone cells in bone and how they change with age is of great interest to the aging population Silvera explains Bone cells can respond to physical stress by sending biochemical signals that lead to the formation or resorption of bone tissue adapting to load But with age or in diseases such as osteoporosis this mechanism no longer seems to work With our basic research we want to find out how bones with and without bone cells differ and cope with the challenges of external stress Zaslansky saidStrength and elasticityBones have a complex structure they comprise nanofibers of collagen and nanoparticles of mineral but also other minor ingredients Certain protein compounds so called Proteoglycans PGs are embedded in a tissue of collagen fibers and nanocrystals and play important roles in tissue formation and maintenance PGs may be compared to salt in the soup Too little or too much of it is not good Zaslansky says The PGs can retain water and there are plenty of PGs in healthy cartilage making it as elastic as a sponge Together these components form an extracellular matrix ECM a 3D structure that provides strength and elasticity ensuring function for many years In bones an open network Lacunar Channel Network or LCN of channels and pores with diameters ranging from a few hundred nanometers to micrometers is created in this 3D structure This LCN hosts the bone osteocytes cells that sense load and orchestrate bone remodeling In the LCN and within the nanocomposite bone contains up to 2037 of its volume in water with many functions including toughening and adaptation to mechanical stressNeutron tomography at BER IITo determine the amount of incorporated water the researchers first immersed bone samples in water and transilluminated them with neutrons provided by the Berlin experimental reactor BER II at HZB followed by saturation in deuterated heavy water D2O 3D data was collected again and the difference between the two bone states allowed the team to determine for each spine vertebrae the precise amount of water displaced by diffusion of the D2O In addition we examined sections of the bone samples analyzed them by electron microscopy and micro CT and we also determined the PG concentration with Raman spectroscopy Silvera explainsSurprising results PGs make the differenceUntil now it was assumed that both bone types contain similar amounts of water and had very similar composition and properties In fact however the neutron examination showed that the bone material of zebrafish releases half as much water as that of medaka This is all the more surprising because these bones have a very similar microstructure of mineralized collagen fibers but zebrafish also contain large cell spaces within the LCN My first reaction was This must be wrong So we checked everything thoroughly and realized its really revolutionary recalls Zaslansky The only explanation for the difference is that the bone matrices of the two species differ in a fundamental compositional component that affects water permeability And here both histological studies and Raman spectroscopy show its the small but important contribution of PGs The medaka samples contain far less PG than the zebrafish samples This is a new finding although both fish cope with similar stresses their bone materials do not have the same water permeability properties said SilveiraNew insights for medicineWe hope these results will help us better understand bone diseases as well Zaslansky says Why are some bones better at responding to stress than others What happens when bones age Could it be that they lose PGs and become less watertight Perhaps aging or pathology such as osteoporosis changes the bone that surrounds bone cells which makes it difficult to remodel and form bone tissue that works correctlyAfter 40 years of successful neutron research in BerlinWannsee the research reactor BER II was finally shut down at the end of 2019 The shutdown was decided by the HZB Supervisory Board in summer 2013After 40 years of successful neutron research in BerlinWannsee the research reactor BER II was finally shut down at the end of 2019 But until now teams are working on the experimental data to gain new insights into materials of all kindsThis story has been sourced from a third party syndicated feed agencies Midday accepts no responsibility or liability for its dependability trustworthiness reliability and data of the text Midday managementmiddaycom reserves the sole right to alter delete or remove without notice the content in its absolute discretion for any reason whatsoever