Targeting Neutrophil Extracellular Traps to Mitigate Post-Traumatic Lower-Extremity Soft Tissue Injury

Patients this proposal will help: This proposal will develop translatable solutions for early management of combat-related and trauma-induced extremity injury and for extremity surgery patients requiring a tourniquet to minimize morbidity and improve recovery from musculoskeletal soft tissue injury. Specifically, we will validate Food and Drug Administration (FDA)-approved, easily deployed therapeutics to prevent ischemia reperfusion injury and soft tissue injury: two of the major complications of combat injury, civilian trauma, and orthopaedic surgery. Blast-related injuries delivered by improvised explosive devices (IEDs) and explosively formed projectiles have become the principal mode of injury on the modern battlefield. Of the 14,788 battle injuries suffered in Operations Iraqi Freedom/New Dawn and Enduring Freedom, over 50% of those injuries were extremity injuries. Of these wounded Soldiers with extremity injuries, over 60% of them will develop secondary complications. Ischemia reperfusion injury (IR) after extremity trauma is characterized by destructive inflammation, endothelial cell dysfunction, and muscle and soft tissue fibrosis; this process leaves patients with decreased muscle function and debilitation delaying return to duty and reintegration. Additionally, tourniquet usage in the field or in the operating theater causes significant IR injury burden. There are currently no effective preventive strategies for ischemia reperfusion and musculoskeletal extremity trauma-induced soft tissue injury and debilitation. Current treatment strategies, once IR-induced fibrosis develops, involve surgical procedures, which fail to restore normal form or function. Though medications have been previously tested, all have substantial adverse effects and all fail to target the early changes that precede extremity trauma-induced musculoskeletal soft tissue injury. In addition to wounded Soldiers, IR injury causes significant disability in hundreds of thousands of civilian and military Veteran patients with orthopaedic injuries and surgeries and those undergoing transplantation operations. Over 20,000 tourniquets are also used daily worldwide. Thus, preventing the sequelae of extremity trauma and IR injury-induced soft tissue damage would benefit a large number of both civilian and military personnel. We offer a scientific revolution for extremity soft tissue injury from one of delayed, suboptimal treatment to that of early targeting and prevention of fibrosis. Though targeted at extremity musculoskeletal soft tissue injury, findings from this proposal can be translated to other cases of ischemia reperfusion injury such as cardiovascular disease/myocardial infarctions, and extremity transplantation. Potential clinical applications, benefits, and risks: Clinically we plan to address the two key barriers to improved treatment: (1) early targeting of the first cells that cause damage in extremity trauma and IR injury (neutrophils) and (2) drug therapies that prevent vessel damage and muscle injury from forming before it causes functional deficits. Whereas current non-selective treatments such as nonsteroidal anti-inflammatories target global inflammation, our treatment strategy targets the early signals and responsive cells (neutrophils) that support and lead to the development of pathologic healing. We present an innovative approach to target IR injury in those high-risk patients and demonstrate a link between neutrophil extracellular traps and extremity soft tissue damage. Projected timeline expected for patient-related outcomes: We plan to rapidly deploy our optimized treatment interventions. In the first 12 months, we will demonstrate the ability of FDA-approved PAD4 inhibitors to mitigate IR-induced soft tissue injury. In the last 12 months, we will validate inhibition of secondary destructive inflammation through FDA-approved TLR9 inhibitors in our extremity trauma mouse model. At the end of this pro