PROJECT SUMMARY/ABSTRACT Age-related fragility fractures impose healthcare costs exceeding $25 billion annually in the United States. Risk of fragility fracture is due to both decreased bone mineral density (bone quantity) and bone tissue quality. Current therapeutics for osteoporosis are effective at increasing bone quantity but do not directly address aspects of bone tissue quality (the contents and organization of the bone matrix). Several studies have recently discovered a link between the composition of the gut microbiome and bone strength. Previous work from the sponsor’s group has demonstrated that perturbations to the constituents of the gut microbiome can impair bone tissue material properties. A more recent, unexpected, and exciting finding demonstrated that specific alterations of the composition of the gut microbiome increased the strength of the bone matrix. Prior work generated a list of microbial taxa that had an increased abundance in animals with enhanced bone tissue strength relative to unaltered controls. Nevertheless, the specific species and functional capacity of the bacteria contributing to the increased bone strength remain to be elucidated. Additionally, prior studies manipulating the components of the gut microbiota were predominantly completed in young, male mice. Since interventions to prevent fragility fractures are most likely applied to older adults, it is critical to determine if the same alterations in the gut microbiota can influence bone tissue strength in aged animals of both sexes. This proposal addresses the following questions: what are the taxonomic and functional constituents of the microbiota responsible for increasing bone tissue strength in mice; and is it possible to increase the strength of the bone matrix by altering the gut microbiota in late adulthood? The specific aims are to 1) isolate gut microbial constituents contributing to increased bone tissue strength in young mice and 2) determine the effects of modifying the gut microbiota to increase bone tissue strength in aged mice. The overarching goal of the proposal is to isolate and characterize constituents of the gut microbiota that enhance bone tissue strength and quality in growing and aged mice. Research from this proposal builds upon prior findings from the sponsor’s group while enabling the candidate to transition to an independent investigator by gaining expertise in in vivo models and microbiome metagenomic analysis. The long-term goal of the candidate is to pursue a career developing delivery systems/biomaterials that regulate the constituents of the microbiome for applications such as musculoskeletal disorders and aging. Development of biomaterials that regulate the microbiota requires knowledge of taxonomic and metagenomic analysis of microbiota in in vivo models. Therefore, this application is to fund training in in vivo experimentation and manipulation of the gut microbiome while increasing expertise orthopaedic research. Training ac...