BLRD Research Career Scientist Award Application

Veterans Health Administration, Decatur PA

Investigators

Abstract

The two primary goals of the principal investigator (PI)’s research are to lower the number of bone fractures associated with diabetes, aging, osteoporosis, hypertension, cancer, and genetic diseases and to facilitate timely healing when fractures do occur in patients with these co-morbidities. With respect to the first goal, the PI’s FRACTURE CURB project endeavors to identify mechanisms by which hypertension favors poor fracture resistance of bone. In doing so, aims of the project are (i) to determine whether sex steroids modulate the decline in bone mass and quality associated with hypertension using gonadectomy models, (ii) to ascertain the cellular source of colony stimulating factor (CSF) 1 in hypertension-induced bone loss using transgenic mouse models, and (iii) to test whether inhibiting CSF1 slows hypertension-related bone loss in aged mice and improves bone strength with respect to a standard osteoporosis treatment known as intermittent recombinant parathyroid hormone 1-34 (PTH1-34). One preclinical model of hypertension involves continuously delivering vehicle or angiotensin II for 6 weeks, to wild-type, adult mice or adult mice that lose Csf1 in cells of the osteoblast lineage or endothelial cells upon the administration of tamoxifen. The other model of hypertension involves removing one kidney and subcutaneously implanting a control pellet or deoxycorticosterone acetate (DOCA) salt pellet in adult mice to stimulate aldosterone and then giving the mice 1% salt water to drink for 3 weeks. The analysis techniques in all aims include: micro-computed tomography (μCT) evaluations to assess cortical structure, trabecular architecture, and volumetric bone mineral density; mechanical testing of bones (femur and lumbar vertebra) to assess fracture resistance of cortical and trabecular bone; serum markers of metabolism to understand changes in bone remodeling; gene profiling (transcriptomics) using nanoString technology to identify signaling pathways; histology of bone to further assess effects on bone resorption and formation; and flow cytometry of immune cells from the bone marrow to identify mediators. From the application of these techniques to mouse experiments, the PI will possibly identify a key driver of the hypertension-related decline in bone strength. Inhibiting CSF1 along with enhancing bone anabolism with an anabolic therapy (intermittent PTH1-34) could be identified as a potential treatment strategy in protecting bone health in hypertension. With respect to the second goal, the Validation project endeavors to validate a preclinical model of polytrauma that causes prolonged hyper-inflammation, impairments in musculoskeletal (MSK) tissue repair, and a decline in overall wellness (e.g., osteoporosis, cognition, pain perception, and mobility). In doing so, aims of the project are to determine whether (i) combining muscle injury and femur fracture with transdermal burn causes musculoskeletal complications of repair, (ii) this polytraumatic injury model also causes a decline in the fracture resistance of bone and in cognitive function, and (iii) the combined injuries cause prolonged hyper-inflammation. The validation goal of the first aim is to determine if there is a delay in fracture healing (e.g., incomplete union at 21-days post- injury) and impaired muscle regeneration (e.g., fibrosis and soft tissue mineralization at 42-days post-injury) as the injuries become more severe. The validation goal of the second aim is to determine if the combined polytrauma model causes deleterious changes in wellness, including bone fragility, impairment in memory, hypersensitivity to pain, and reduced mobility compared to non-injury sham. The validation goal of the third aim is to determine if the addition of burn to muscle injury and femur fracture prolongs the hyper-inflammatory response and prolongs tissue inflammation compared to the lesser injured or uninjured mice. If successful, this project will support the combination of skin burn, femur fracture, and muscle injury to assess prognostic indicators and pharmacologic interventions aimed at improving the ability of Veterans to recover from polytraumatic injuries.