Project Summary/Abstract Mitochondrial dysfunction is pivotal to the neuropathological sequelae following traumatic spinal cord injury (SCI). During this initial time window, there is a significant loss of mitochondria with an inflammatory/oxidative environment that perpetuates the pathophysiology. It is hypothesized that to rescue the cellular damage occurring following SCI, one must replace damaged mitochondria, while also changing the damaging microenvironment. We have documented that maintaining endogenous mitochondrial bioenergetics with acetyl-l-carnitine (ALC), an alternative mitochondrial biofuel, or reducing oxidative stress by replenishing endogenous antioxidant, glutathione (GSH) with N-acetylcysteine amide (NACA) after SCI results in increased, but limited long-term functional neuroprotection. We have also reported that acute mitochondrial transplantation (MitoTxp) using intraspinal injections of mitochondria isolated from rat soleus muscle significantly preserved bioenergetic function 48hr post-SCI. However, this was sporadically successful due to the challenges of both accumulating mitochondria at the site of injury and maintaining their viability prior to cellular uptake. In the current proposal, we will develop a thermo-gelling, erodible hydrogel system for the localized delivery of viable mitochondria to test the neuroprotective efficacy of combined MitoTxp and pharmaceutical interventions (ALC and/or NACA) after contusion SCI. The use of an injectable hydrogel will permit the development of a local environment which can aide in maintaining mitochondrial health through optimization of the hydrogel niche. We will determine 1) optimum constituents for isolated mitochondria to remain viable for extended periods in polymeric hydrogels, 2) whether exogenous mitochondria transplanted via less invasive intrathecal route equally preserve integrity of bioenergetics compared to intraspinal route and 3) consequences of acute or delayed MitoTxp in combination with ALC and/or NACA on bioenergetics, oxidative stress, and functional neuroprotection after SCI.