Project description:<p>This is a longitudinal prospective cohort study in patients with carpal tunnel syndrome undergoing decompression surgery. Phenotypic data and skin biopsies were collected before and 6 months after surgery to determine molecular and cellular correlates associated with neural regeneration and neuropathic pain. RNA sequencing was performed in the skin samples and differential gene expression was determined post compared to pre surgery. The molecular changes identified in skin were correlated with the clinical phenotype representing neural regeneration.</p>
Project description:Schwann cell (Büngner) repair cells play a critical role in orchestrating nerve repair after injury, but the reprogramming process that generates them is poorly understood. We present the first combined whole genome coding and non-coding RNA and CpG methylation study after nerve injury. We show that genes involved in epithelial to mesenchymal transition are enriched in repair cells and we identify long non-coding RNAs in Schwann cells. We demonstrate that the AP-1 transcription factor c-Jun regulates the expression of certain micro RNAs in repair cells, in particular miR-21 and miR-34. Surprisingly, changes in CpG methylation are limited in injury, unlike development, and restricted to specific locations, such as enhancer regions of novel Schwann cell specific genes, such as Nedd4l, and near to local enrichment of AP-1 motifs. These epigenetic changes significantly broaden our understanding of Schwann cell reprogramming in peripheral nervous system tissue repair. To identify epigenetic regulators underlying successful nerve regeneration we generated RNA-Seq, small-RNA-Seq and whole genome bisulfite sequencing libraries for uninjured nerve versus three and/or seven day post nerve transection sciatic nerves of adult C57BL/6J mice crush.
Project description:Effective regeneration after peripheral nerve injury requires macrophage recruitment. We investigated activation of remodeling pathways within the macrophage population when repair is delayed and identified alteration of key upstream regulators of the inflammatory response. We then targeted one of these regulators, using exogenous IL10 to manipulate the response to injury at the repair site. We demonstrate that this approach alters macrophage polarization, promotes macrophage recruitment, axon extension, neuromuscular junction formation and increases the number of regenerating motor units reaching their target. We also demonstrate that this approach can rescue the effects of delayed nerve graft.
Project description:After peripheral nerve injury, adult Schwann cells convert to progenitor cell-like repair Schwann cells, which are pivotal for nerve regeneration. We show that Schwann cell-specific deletion of TFEB/3 disrupts the transcriptomic reprogramming necessary for injury-induced repair Schwann cell generation in mice. The mutant mice fail to generate proliferating repair Schwann cells to populate the injured nerves. Distal Schwann cells fail to express injury-responsive genes and continue to maintain the expression of myelin-associated genes. TFEB/3 binding motifs are enriched in injury-induced enhancers, suggesting their role in repair gene activation. Autophagy-dependent myelin breakdown is not impaired in the mutant mice despite the known function of TFEB/3 as autophagy activators. However, the mutant mice exhibit defects in axon regeneration, target reinnervation, and functional recovery. Therefore, TFEB/3 play a critical role in orchestrating transcriptional changes essential for repair Schwann cell generation and function necessary for peripheral nerve regeneration.
Project description:The remarkable feature of Schwann cells (SCs) to transform into a repair phenotype turned the spotlight on this powerful cell type. SCs provide the regenerative environment for axonal re-growth after peripheral nerve injury (PNI) and play a vital role in differentiation of neuroblastic tumors into a benign subtype of neuroblastoma, a tumor originating from neural crest-derived neuroblasts. Hence, understanding their mode-of-action is of utmost interest for new approaches in regenerative medicine, but also for neuroblastoma therapy. However, literature on human SCs is scarce and it is unknown to which extent human SC cultures reflect the SC repair phenotype developing after PNI in patients. We performed high-resolution proteome profiling and RNA-sequencing on highly enriched human SC and fibroblast cultures, control and ex vivo degenerated nerve explants to identify novel molecules and functional processes active in repair SCs. In fact, we found cultured SCs and degenerated nerves to share a similar repair SC-associated expression signature, including the upregulation of JUN, as well as two prominent functions, i.e., myelin debris clearance and antigen presentation via MHCII. In addition to myelin degradation, cultured SCs were capable of actively taking up cell-extrinsic components in functional phagocytosis and co-cultivation assays. Moreover, in cultured SCs and degenerated nerve tissue MHCII was upregulated at the cellular level along with high expression of chemoattractants and co-inhibitory rather than -stimulatory molecules. These results demonstrate human SC cultures to execute an inherent program of nerve repair and support two novel repair SC functions, debris clearance via phagocytosis-related mechanisms and type II immune-regulation.
Project description:The formation of vascular niche is pivotal during the early stage of peripheral nerve regeneration. This antecedent angiogenesis meets the nutrient requirements for subsequent rapid axon regeneration and remyelination. Nevertheless, the mechanisms of vascular niche in the regulation of peripheral nerve remain unclear. The axon guidance molecule Netrin-1 (NTN1) is widely expressed in peripheral nerves and particularly was found up-regulated in sciatic nerve stump after peripheral nerve injury (PNI). Herein, we demonstrated that NTN1-high endothelial cells (NTN1+ECs) were the critical component of vascular niche, fostering angiogenesis, axon regeneration and repair-related phenotypes. And we also found that NTN1+ECs derived exosomes (NTN1 EC-EXO) were involved in the formation of vascular niche as a critical role. Multi-omics analysis further verified that NTN1 EC-EXO carried a low-level expression of let7a-5p and activated key pathways associated with niche formation including focal adhesion, axon guidance, PI3K-AKT signaling pathway and mTOR signaling pathway. Taken together, our findings suggested the potential construction of a pre-regenerative niche induced by NTN1 EC-EXO, thereby establishing a conductive microenvironment for nerve repair and facilitating the functional recovery after PNI in the early injury phase.