Mineral Coated Microparticles for Stabilization and Delivery of Complexed mRNA for Healing of Long Bone Defects

PROJECT SUMMARY / ABSTRACT Age related traumatic and pathologic fractures are expected to increase greatly in incidence in the coming decades with aging populations. Older patients are at higher risk for non-healing, ‘critical-size’, bone defects following fracture. This is exacerbated in composite injuries with concomitant soft tissue defects. These require

multiple surgical interventions and still a majority of patients remain significantly disabled. Therapies, like bone marrow aspirate concentrate (BMAC), or recombinant bone morphogenetic protein-2 are inconsistent and ineffective or limited by dose related side effects, such as inflammation, respectively. These drawbacks

may be overcome by osteogenic stimulation with biomaterial platforms for non-viral gene delivery. The Murphy laboratory has developed nanostructured mineral coated microparticles (MCM) that improve and sustain delivery of therapeutic nucleic acid complexes. These biomimetic mineral coatings were inspired

by the structure and characteristics of fossils. Ancient DNA has been recovered from fossils which implicates a role in mineralized surfaces preserving nucleic acids. New stabilization strategies are essential as current mRNA products, like COVID-19 vaccines, require extensive cold-chain infrastructure limiting their

application. Biomimetic mineralized materials may provide a platform for the binding, long term stabilization, and delivery of mRNA therapeutics. This fellowship proposal will develop a biomaterials-based method for storage and delivery of mRNA encoding for osteogenic growth factors and train the applicant for a career as a physician scientist. We

hypothesize that MCM delivery of mRNA can 1) improve mRNA transfection after lyophilization, 2) promote an osteogenic phenotype in BMAC and 3) mRNA for osteogenic growth factors will reduce inflammation and improve bone defect healing. Aim 1 will optimize and characterize how MCMs stabilize mRNA complexes

after lyophilization. Aim 2 will assess the impact of MCM delivery of mRNA for bone morphogenetic protein -2/-7 heterodimers in a rat model of a critical size bone defect. Aim 3 will investigate the efficacy of R- Spondin-2 mRNA on a rat model of composite muscle and bone injury. Outcomes will focus on 1) transfection

after simulated accelerated degradation studies, 2/3) gene expression as well as radiographic, biomechanical and histologic bone healing. The goal of this work is to improve storage and application of materials guided mRNA therapeutics for bone regeneration. The proposal will combine the biomaterials and

orthopedic expertise of the proposal sponsor, with the vast medical, scientific, graduate training and translational resources available at the University of Wisconsin – Madison. This pre-doctoral fellowship will provide for the development of research, clinical, mentorship, innovation, and communication skills

necessary for a career as an independent physician scientist.