PROJECT SUMMARY The severity of traumatic injuries has increased in recent years, resulting in further complications that can impair patient recovery or even result in death. The rate of injuries that become chronic wounds has also increased in recent years. In both the acute and chronic injury site, there are key regulators of inflammation needed to protect the body from pathogens, remove damaged tissue, and recruit new vessels to supply nutrients to tissues undergoing repair. Failure to balance these beneficial hallmarks of inflammation with a transition to tissue regeneration has resulted in secondary tissue damage and chronic injury progression. Immune cells, such as macrophages, remodel the extracellular matrix and release cytokines to govern the injury microenvironment, but dysregulation of these processes can result in chronic inflammation and non-healing wound formation. Locally occurring or exogenously delivered chondroitin sulfate (CS) is a potent regulator of inflammatory cytokine signaling and can help restore balance in dysregulated inflammatory conditions. Moreover, CS can directly modulate immune cells towards anti-inflammatory phenotypes. However, uncontrolled CS delivery can impede tissue repair by creating a physical barrier to local cells. Establishing a balance between modulating inflammation and promoting repair with CS will require investigation of the specific role of CS-presentation on the local immune response. To that end, the goal of this project is to engineer CS biomaterials that control CS presentation in the injured tissue and reprogram inflammatory immune states to support resolution of chronic inflammation and promotion of tissue repair. Over the next 5 years, we will investigate the use of nanoscale and microscale CS biomaterials to resolve excess inflammatory cytokine activity and reprogram immune phenotypes towards an anti-inflammatory, pro-regenerative state. These materials will be evaluated through in vitro studies to identify intrinsic and extrinsic molecular mechanisms by which CS-presentation reprograms immune cells. Translational mouse mouses will be used to investigate CS-presentation in tissue localized inflammation as an acute strategy to modulate chronic disease progression as a prophylactic strategy, and as a chronic strategy to treat chronic inflammation. Two distinct injury models that experience chronic inflammation through immune dysregulation will be utilized. The first model that will be employed is a rodent model of spinal cord injury, as there is no cure for paralysis associated with the injury, in part due to the robust inflammation that results in secondary injury and progresses into a chronic diseased state. The second model used will be a rodent skin injury model, as the acute injury can be used to test therapeutic outcomes that can subsequently be evaluated in chronic, non-healing skin wounds. Development of strategies for chronic, non-healing wounds is essential as there is no unifying...