Project Grant F31AG102016

DESIGN OF POLYPHENOLIC NANOPARTICLES TO PROMOTE AGE-RELATED FRACTURE HEALING - PROJECT SUMMARY: AGE-RELATED FRAGILITY FRACTURES AFFECT OVER 37 MILLION PEOPLE ANNUALLY, PUTTING A COMPROMISED POPULATION AT RISK OF DECREASED MOBILITY, INCREASED FRAILTY, AND MORTALITY DUE TO IMPAIRED REGENERATIVE POTENTIAL. IRON ACCUMULATION UNDERPINS AGE-RELATED IMPAIRED FRACTURE HEALING THROUGH THE SUSTAINED PRO-INFLAMMATORY POLARIZATION OF MACROPHAGES, INHIBITION OF OSTEOGENESIS, AND OSTEOBLAST FERROPTOSIS. DESPITE EMERGING EVIDENCE HIGHLIGHTING THE ROLE OF IRON OVERLOAD IN IMPAIRED FRACTURE HEALING ASSOCIATED WITH AGING, THERE ARE CURRENTLY NO CLINICAL INTERVENTIONS FOR TREATING FERROPTOSIS IN AGE-RELATED FRACTURES. WHILE COMBINED ANTIOXIDANT AND IRON CHELATION STRATEGIES HAVE SHOWN PROMISE AS ANTI-FERROPTOTIC TREATMENTS THAT PROMOTE FRACTURE REGENERATION IN IRON OVERLOAD MODELS, SMALL-MOLECULE THERAPIES SUFFER FROM SHORT HALF-LIVES, POOR BIOAVAILABILITY, AND SYSTEMIC SIDE EFFECTS. ANTIOXIDANT AND IRON CHELATING NANOPARTICLES (NPS) OFFER A POTENTIAL SOLUTION DUE TO THEIR ABILITY TO ACCUMULATE AT FRACTURE SITES THROUGH LEAKY VASCULATURE AND INFLAMMATORY CELL-MEDIATED SEQUESTRATION (ELVIS EFFECT). MY CENTRAL HYPOTHESIS IS THAT IRON CHELATING AND ANTIOXIDANT POLYCATECHOLIC (PCAT) NPS WILL PROMOTE AGE-RELATED FRACTURE HEALING THROUGH PRO-REGENERATIVE MACROPHAGE POLARIZATION AND MITIGATION OF OSTEOBLAST FERROPTOSIS. IN AIM 1, I WILL BUILD AND TEST A LIBRARY OF PCAT NPS USING A CENTRAL COMPOSITE DESIGN MODEL TO IDENTIFY HOW POLYMERIC INPUT PARAMETERS AFFECT CRITICAL NP OUTCOMES SUCH AS IRON CHELATION, ANTIOXIDANT CAPACITY, AND CYTOCOMPATIBILITY. IN AIM 2, THE MECHANISTIC EFFECTS OF PCAT NP TREATMENT ON PRO-REGENERATIVE MACROPHAGE POLARIZATION AND MITIGATION OF PARACRINE-MEDIATED OSTEOBLAST FERROPTOSIS WILL BE INVESTIGATED IN VITRO. FIRST, IRON- INDUCED MACROPHAGES WILL BE TREATED WITH PCAT NPS, AND PRO-REGENERATIVE POTENTIAL WILL BE MEASURED VIA GENE, PROTEIN, AND CELL SURFACE MARKER EXPRESSION. NEXT, OSTEOBLAST PROGENITORS WILL BE TREATED WITH CONDITIONED MEDIA FROM PCAT NP-TREATED MACROPHAGES TO ELUCIDATE ANTI-FERROPTOTIC AND PRO-OSTEOGENIC EFFICACY MEASURED BY GENE AND PROTEIN EXPRESSION, AND THE DECREASE IN INTRACELLULAR FERROPTOSIS MARKERS. IN AIM 3, PCAT NPS WILL BE TESTED IN AN ESTABLISHED AGE-RELATED FRACTURE MURINE MODEL FOR THEIR ABILITY TO PROMOTE FRACTURE HEALING IN VIVO VERSUS PLACEBO CONTROLS. SUCCESSFUL FRACTURE HEALING WILL BE ASSESSED THROUGH ENHANCED CALLUS FORMATION, INCREASED TORSIONAL STRENGTH, AND INCREASED PRO-REGENERATIVE MACROPHAGE POLARIZATION. EXPECTED OUTCOMES OF THIS PROJECT INCLUDE THE DEVELOPMENT OF A NOVEL PCAT NP THERAPEUTIC PLATFORM, ADVANCING THE UNDERSTANDING OF FERROPTOSIS IN AGE-RELATED IRON OVERLOAD CONDITIONS, AND ELUCIDATING THE EFFICACY OF ANTI-FERROPTOTIC TREATMENTS IN PROMOTING AGE- RELATED FRACTURE HEALING. SUCCESSFUL COMPLETION OF THIS STUDY WILL ADVANCE THE BROADER FIELD OF THERAPEUTICS FOR CHRONIC INFLAMMATORY DISEASE, AS FERROPTOSIS HAS BEEN IMPLICATED IN A MULTITUDE OF AGE-ASSOCIATED DISEASES, FROM ALZHEIMER'S TO OSTEOPOROSIS.