Targeting Schwann cell exosomes for treating neuropathic pain

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It is increasingly evident that Schwann cells (SCs) in the peripheral nervous system (PNS) function as a unit with neurons to regulate sensory function. When the PNS is injured in trauma, SCs become activated for repair. This involves dramatic phenotypic transformation. If this process is abnormal or inhibited, peripheral nerve injury can result in chronic debilitating pain, a problem observed in the general population, including numerous Veterans. Currently available treatment options for chronic neuropathic pain are very limited and fraught with dependency concerns. To address this unmet clinical need, we have developed a novel method for capturing plasma-derived SC exosomes (SCDEs) from rodents that regulate key cellular mechanisms in pain processing. These SCDEs recapitulate some of the bioactivity observed in exosomes collected in medium from cultured primary SCs. The major goal of this research project is to determine whether we can exploit the activity of SCDEs to improve pain outcomes following peripheral nerve injury. To accomplish our goals, three Specific Aims are proposed. In Specific Aim 1, we will determine whether a continuum of neuropathic SCDEs or naïve SCDEs regulate neuronal sprouting and calcium signaling in DRG neurons. We will apply advance technologies including single cell RNA transcriptome profiling so that we can define the response of specific neuronal subpopulations in the DRG to SCDEs. Central to this Aim is our discovery that neuropathic, but not naïve, SCDEs are capable of inducing robust neurite outgrowth that may contribute to maintenance of chronic pain states. We hypothesize that by targeting these SCDEs we will identify key mechanisms for improving pain outcomes following peripheral nerve injury therapeutically. In Specific Aim 2, our goal is to discover novel SCDE cargo, and specifically noncoding microRNAs, that are expressed in neuropathic paradigms. This discovery-based Aim establishes a microRNA (miR) signature in SCDEs that may be associated with pain producing and pain alleviating properties. Using NanoString™ technology to measure miRs in SCDEs, we identified a pain alleviating miR-142-3p in naïve SCDEs. The proposed work should identify the SC source (unmyelinated, myelinated, activated or repair phenotype) in nerves that contributes to SCDEs. In Specific Aim 3, we will assess whether SCDE phenotypes regulate neuropathic pain in vivo. This Aim is based on our exciting preliminary data demonstrating that naïve SCDEs delivered systemically inhibit thermal hyperalgesia after partial nerve ligation. SCDEs have intrinsic features, such as the stability, biocompatibility and stealth capacity when circulating in the blood stream. Studies using miR mimics and inhibitors are planned to discover mechanisms conferred by SCDEs to DRG neurons. We consider this project highly innovative because we target SCs and sensory neurons for treating chronic pain.