Project description:The goal of the experiment was to determine the role of the polycomb repressive complex 2 in the nerve injury response in peripheral nerve. A Schwann cell specific knockout of the Eed subunit of PRC2 was generated to compare with wild type mice in sham and injured mice at 1d and 14d timepoints after nerve injury.
Project description:Sciatic nerve crush (SNC) triggers sterile inflammation within the distal nerve and de-afferented dorsal root ganglia (DRGs). In the nerve, neutrophils and pro-inflammatory Ly6Chigh monocytes appear first and rapidly give way to Ly6Clow resolving macrophages. Transcriptional profiling of injured nerve tissue identifies six macrophage subpopulations, repair Schwann cells and mesenchymal cells as the main cell types. Macrophages at the nerve crush site are distinct from macrophages associated with degenerating nerve fibers. Monocytes and macrophages in the injured nerve “eat” apoptotic cell corpses of leukocytes and thereby contribute to an anti-inflammatory milieu. Studies with chimeric mice show that following SNC few blood-derived immune cells enter DRGs. Myeloid cells in the injured nerve, but not DRGs, express the receptor for the chemokine GM-CSF. In the absence of GM-CSF, conditioning-lesion induced regeneration of DRG neuron central projections is abrogated. Thus, a carefully orchestrated immune response in the nerve is required for conditioning-lesion induced neurorepair.
Project description:ChIP-seq of H3K4me3 in rat peripheral nerve was used to identify transcription start sites associated with Schwann cell-expressed genes. The analysis was performed in injured and control nerve to identify injury-responsive changes in Schwann cells. H3K4me3 ChIP samples were prepared from rat sciatic nerve at 1 day post-transection using both the distal stump of the injured nerve and the contralateral (sham) nerve.
Project description:Peripheral glial Schwann cells switch to a repair state after nerve injury, proliferate to supply lost cell population, migrate to form regeneration tracks, and generates a permissive microenvironment for nerve regeneration. Exploring essential regulators of the repair responses of Schwann cells may benefit the clinical treatment for peripheral nerve injury. In the present study, FOSL1 regulates Schwann cell phenotype modulation and provided a novel therapeutic approach to orchestrate the regeneration and functional recovery of injured peripheral nerves.
Project description:The goal of the experiment was to determine the role of H3 emethylases in the nerve injury response in peripheral nerve. A Schwann cell specific knockout of the H3K27 demethylases (Jmjd3 and Utx) was generated to compare with wild type mice in sham and injured mice at 1d and 7d timepoints after nerve injury.
Project description:To shed light on the early processes of immune response to peripheral nerve injury, we first used genome-wide transcriptional profiling and bioinformatics (Ingenuity, NextBio) pathway analyses of the proximal (P; regenerating) and distal (D; degenerating) nerve stumps at day 1 in the sciatic nerve axotomy model in rats. We identified a number of specific immunomodulatory genes and pathways that were regulated shortly post-injury in both the P and D segments, including all members of the interleukin (IL), chemokine, tumor necrosis factor (TNF), matrix metalloproteinase (MMP), toll-like receptor (TLR), tissue inhibitor of metalloproteinase (TIMP), ion channel and myosin families. Immunomodulatory calcium-binding S100A8 and S100A9 were the top up-regulated genes in both the D and P segments. In cultured Schwann cells stimulated with the purified S100A8/A9 heterodimer we recorded a high level of similarity of the activated genes and pathways with that of the injured nerve, especially in the activation of the chemokine and cytokine gene networks that support agranulocyte and granulocyte chemotaxis, adhesion, transmigration and rolling signaling pathways. We also confirmed activation of multiple cell death related gene networks supporting TNFR1, natural killer cell receptor and death receptor apoptosis signaling in the D stump, and the gluconeogenesis/glycolysis and cytoskeletal motility signaling in the P stump, corroborated by activation of ERK, PI3K and JNK kinase pathways. As compared to the D segment, multiple additional pathways were more efficiently upregulated in the P stump, including the IL-6 and -17, MMP-9, calcium, activated agranulocyte, leukocyte rolling and glutathione-mediated detoxification signaling pathways. These data suggest that shortly after nerve injury, upregulation of S100A8/A9 is responsible for the expression and release of chemokines and cytokines by Schwann cells, necessary to generate the initial chemotactic gradient and guide the hematogenous immune cells into the injury site. Gene expression profiling of total RNAs extracted from injured and non-injured rat sciatic nerves, and primary rat Schwann cells stimulated with S100A8/A9 proteins
Project description:The striking PNS regenerative response to injury rests on the plasticity of adult Schwann cells and their ability to transit between differentiation states, a highly unusual feature in mammals. Using mice with inactivation of Schwann cell c-Jun, we show that the injury response involves c-Jun dependent natural reprograming of differentiated cells to generate a distinct Schwann cell state specialized to promote regeneration. Transected distal stumps of c-Jun mutants show 172 disregulated genes, resulting in abnormal expression of growth factors, adhesion molecules and cytoskeletal changes that lead to neuronal death, inhibition of axon growth and striking failures of functional repair after injury. These observations provide a molecular basis for understanding Schwann cell plasticity and nerve regeneration. They offer conclusive support for the notion that Schwann cells control repair in the PNS, using dedicated transcriptional controls to generate a distinct repair cell, a transition that shows similarities to transdifferentiation seen in other systems. Total RNA was purified from a 10mm segment of the distal stump and uninjured contralateral nerve from c-Jun mutants and control mice 7 days after nerve cut. For each condition (injured/uninjured) and genotype (control/ knock-out) 2 independent samples (replicates) were generated from pooled nerves of 4/6 mice resulting in a total of 8 samples: CTRL.cut.R1, CTRL.cut.R2, CTRL.uncut.R1, CTRL.uncut.R2, KO.cut.R1, KO.cut.R2, KO.uncut.R1,KO.uncut.R2.
Project description:Peripheral nerves provide a supportive growth environment for developing and regenerating axons and are essential for maintenance and repair of many non-neural tissues. This capacity has largely been ascribed to paracrine factors secreted by nerve-resident Schwann cells. Here, we used single-cell transcriptional profiling to identify ligands made by different injured rodent nerve cell types and have combined this with cell-surface mass spectrometry to computationally model potential paracrine interactions with peripheral neurons. These analyses show that peripheral nerves make many ligands predicted to act on peripheral and CNS neurons, including known and previously uncharacterized ligands. While Schwann cells are an important ligand source within injured nerves, more than half of the predicted ligands are made by nerve-resident mesenchymal cells, including the endoneurial cells most closely associated with peripheral axons. At least three of these mesenchymal ligands, ANGPT1, CCL11, and VEGFC, promote growth when locally applied on sympathetic axons. These data therefore identify an unexpected paracrine role for nerve mesenchymal cells and suggest that multiple cell types contribute to creating a highly pro-growth environment for peripheral axons.
Project description:Primary rib chondrocyte were isoloated from P0.5-day old wildtype and Col2-Cre:floxed EED conditional knockout mouse pups,and cultured overnight in 10%FCS containing DMEM. RNA was isolated and subjected to Affymetrix Mouse Gene ST 1.0 array. Primary rib chondrocyte were isoloated from P0.5-day old wildtype and Col2-Cre:floxed EED conditional knockout mouse pups,and cultured overnight in 10%FCS containing DMEM. RNA was isolated and subjected to Affymetrix Mouse Gene ST 1.0 array. Biological duplicate. Mice were in a mixed genetic background of C57/B6 and 129sv.