Adaptive autophagy reprogramming in Schwann cells during peripheral demyelination.

The myelin sheath is an essential structure for the rapid transmission of electrical impulses through axons, and peripheral myelination is a well-programmed postnatal process of Schwann cells (SCs), the myelin-forming peripheral glia. SCs transdifferentiate into demyelinating SCs (DSCs) to remove the myelin sheath during Wallerian degeneration after axonal injury and demyelinating neuropathies, and macrophages are responsible for the degradation of myelin under both conditions. In this study, the mechanism by which DSCs acquire the ability of myelin exocytosis was investigated. Using serial ultrastructural evaluation, we found that autophagy-related gene 7-dependent formation of a "secretory phagophore (SP)" and tubular phagophore was necessary for exocytosis of large myelin chambers by DSCs. DSCs seemed to utilize myelin membranes for SP formation and employed p62/sequestosome-1 (p62) as an autophagy receptor for myelin excretion. In addition, the acquisition of the myelin exocytosis ability of DSCs was associated with the decrease in canonical autolysosomal flux and was demonstrated by p62 secretion. Finally, this SC demyelination mechanism appeared to also function in inflammatory demyelinating neuropathies. Our findings show a novel autophagy-mediated myelin clearance mechanism by DSCs in response to nerve damage.

COUP-TFII plays a role in cAMP-induced Schwann cell differentiation and in vitro myelination by up-regulating Krox20.

Schwann cells (SCs) are known to produce myelin for saltatory nerve conduction in the peripheral nervous system (PNS). Schwann cell differentiation and myelination processes are controlled by several transcription factors including Sox10, Oct6/Pou3f1, and Krox20/Egr2. Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII/NR2F2) is an orphan receptor that plays a role in the development and differentiation. However, the role of COUP-TFII in the transcriptional regulatory network of SC differentiation has not been fully identified yet. Thus, the objective of this study was to investigate the role and molecular hierarchy of COUP-TFII during cAMP-induced SC differentiation. Our results showed that dibutyryl-cAMP (db-cAMP) increased expression levels of COUP-TFII along with the expressions of Oct6, Krox20, and myelin-related genes known to be related to SC differentiation. Our mechanistic studies showed that COUP-TFII acted downstream of Hsp90/ErbB2/Gab1/ERK-AKT pathway during db-cAMP-induced SC differentiation. In addition, we found that COUP-TFII induced Krox20 expression by directly binding to Krox20-MSE8 as revealed by chromatin immunoprecipitation assay and promoter activity assay. In line with this, the expression of COUP-TFII was increased before up-regulation of Oct6, Krox20, and myelin-related genes in the sciatic nerves during early postnatal myelination period. Finally, COUP-TFII knockdown by COUP-TFII siRNA or via AAV-COUP-TFII shRNA in SCs inhibited db-cAMP-induced SC differentiation and in vitro myelination of sensory axons, respectively. Taken together, these findings indicate that COUP-TFII might be involved in postnatal myelination through induction of Krox20 in SCs. Our results present a new insight into the transcriptional regulatory mechanism in SC differentiation and myelination.

Regulation of the V-ATPase subunit ATP6V0D2 and its role in demyelination after peripheral nerve injury.

After peripheral nerve injury, demyelinating Schwann cells discharge myelin debris and macrophages execute myelin degradation, leading to demyelination of degenerating axons, which is essential for efficient nerve regeneration. In this study, we show that vacuolar-type proton ATPase subunit d2 (Atp6v0d2) is among the most highly upregulated genes in degenerating mouse sciatic nerves after nerve injury using microarray analysis. ATP6V0D2 is mostly expressed in macrophages of injured nerves. Atp6v0d2 knockout mice display delayed peripheral nerve demyelination and significantly attenuated myelin lipid digestion after nerve injury. However, macrophage recruitment and Schwann cell dedifferentiation are unaffected by loss of Atp6v0d2 expression. Taken together, these data demonstrate that ATP6V0D2 in macrophages is specifically required for demyelination during Wallerian degeneration.

ßPix Guanine Nucleotide Exchange Factor Regulates Regeneration of Injured Peripheral Axons.

Axon regeneration is essential for successful recovery after peripheral nerve injury. Although growth cone reformation and axonal extension are crucial steps in axonal regeneration, the regulatory mechanisms underlying these dynamic processes are poorly understood. Here, we identify ßPix (Arhgef7), the guanine nucleotide exchange factor for Rac1 GTPase, as a regulator of axonal regeneration. After sciatic nerve injury in mice, the expression levels of ßPix increase significantly in nerve segments containing regenerating axons. In regrowing axons, ßPix is localized in the peripheral domain of the growth cone. Using ßPix neuronal isoform knockout (NIKO) mice in which the neuronal isoforms of ßPix are specifically removed, we demonstrate that ßPix promotes neurite outgrowth in cultured dorsal root ganglion neurons and in vivo axon regeneration after sciatic nerve crush injury. Activation of cJun and STAT3 in the cell bodies is not affected in ßPix NIKO mice, supporting the local action of ßPix in regenerating axons. Finally, inhibiting Src, a kinase previously identified as an activator of the ßPix neuronal isoform, causes axon outgrowth defects in vitro, like those found in the ßPix NIKO neurons. Altogether, these data indicate that ßPix plays an important role in axonal regrowth during peripheral nerve regeneration.

Potential neuron-autonomous Purkinje cell degeneration by 2',3'-cyclic nucleotide 3'-phosphodiesterase promoter/Cre-mediated autophagy impairments.

Studies of neuroglial interaction largely depend on cell-specific gene knockout (KO) experiments using Cre recombinase. However, genes known as glial-specific genes have recently been reported to be expressed in neuroglial stem cells, leading to the possibility that a glia-specific Cre driver results in unwanted gene deletion in neurons, which may affect sound interpretation. 2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is generally considered to be an oligodendrocyte (OL) marker. Accordingly, Cnp promoter-controlled Cre recombinase has been used to create OL-specific gene targeting mice. However, in this study, using Rosa26-tdTomato-reporter/Cnp-Cre mice, we found that many forebrain neurons and cerebellar Purkinje neurons belong to the lineages of Cnp-expressing neuroglial stem cells. To answer whether gene targeting by Cnp-Cre can induce neuron-autonomous defects, we conditionally deleted an essential autophagy gene, Atg7, in Cnp-Cre mice. The Cnp-Cre-mediated Atg7 KO mice showed extensive p62 inclusion in neurons, including cerebellar Purkinje neurons with extensive neurodegeneration. Furthermore, neuronal areas showing p62 inclusion in Cnp-Cre-mediated Atg7 KO mice overlapped with the neuronal lineage of Cnp-expressing neuroglial stem cells. Moreover, Cnp-Cre-mediated Atg7-KO mice did not develop critical defects in myelination. Our results demonstrate that a large population of central neurons are derived from Cnp-expressing neuroglial stem cells; thus, conditional gene targeting using the Cnp promoter, which is known to be OL-specific, can induce neuron-autonomous phenotypes.

Scaffolding protein Gab2 is involved in postnatal development and lipopolysaccharide-induced activation of microglia in the mouse brain.

Grb2-associated-binding protein-2 (Gab2) is a member of the Gab/DOS family and functions as an adapter protein downstream of several growth factor signaling pathways. Gab2 is considered an Alzheimer's disease susceptibility gene. However, the role of Gab2 in the brain is still largely unknown. Herein, we report that Gab2 is involved in the postnatal development of microglia in mice. The Gab2 expression in the brain was detected at postnatal day 1 (P1) and increased until P14 but decreased thereafter. The tyrosine phosphorylation of Gab2 (pGab2) was also detected at P1 and increased until P14. Next, we focused on microglial development in Gab2 knockout and heterozygous mice. Although differences were not detected in the cytoplasmic area of Iba1-labeled microglia between Gab2(±) and Gab2(-/-) mice, the analysis of CD68 and cathepsin D (indicators of microglial lysosomal activation) immunolabeling within Iba1+ cells revealed significant underdevelopment of microglial lysosomes in Gab2(-/-) mice at P60. In addition to the developmental abnormality of microglia in Gab2(-/-) mice, lipopolysaccharide-induced lysosomal activation was selectively suppressed in Gab2(-/-) mice compared to that in Gab2(±) mice. Our findings suggest that Gab2 is involved not only in postnatal development but also in lysosomal activation of microglia, therefore Gab2 dysfunction in microglia might potentially contribute to the development of neurodegenerative diseases.

Palmitate induces lipoapoptosis in Schwann cells through ROS generation-mediated STAMP2 downregulation.

Free fatty acids (FFAs) are considered the principal inducers of lipotoxicity, leading to cell dysfunction and/or cell death. Lipotoxicity in Schwann cells (SCs) damages neurons, which may be associated with peripheral neuropathies and axon degeneration. However, the molecular mechanism by which FFAs exert lipotoxicity in SCs remains to be established. In the present study, we demonstrate that palmitate exerts lipotoxicity in SCs through apoptosis and that palmitate-induced lipotoxicity in SCs is mediated through reactive oxygen species (ROS) generation. We observed that the six-transmembrane protein of prostate 2 (STAMP2), which plays a pivotal role in lipid homeostasis, is expressed in SCs. We further demonstrate that palmitate induces lipoapoptosis in SCs through ROS generation-mediated STAMP2 downregulation and that STAMP2 depletion accelerates the palmitate-exerted lipoapoptosis in SCs, indicating that STAMP2 confers on SCs the ability to resist palmitate-induced lipotoxicity. In conclusion, palmitate induces lipoapoptosis in SCs through ROS generation-mediated STAMP2 downregulation. Our findings indicate that ROS and STAMP2 may represent suitable targets for pharmacological interventions targeting lipotoxicity-associated peripheral neuropathies and axon degeneration.

Schwann cell dedifferentiation-associated demyelination leads to exocytotic myelin clearance in inflammatory segmental demyelination.

Schwann cells (SCs), which form the peripheral myelin sheath, have the unique ability to dedifferentiate and to destroy the myelin sheath under various demyelination conditions. During SC dedifferentiation-associated demyelination (SAD) in Wallerian degeneration (WD) after axonal injury, SCs exhibit myelin and junctional instability, down-regulation of myelin gene expression and autophagic myelin breakdown. However, in inflammatory demyelinating neuropathy (IDN), it is still unclear how SCs react and contribute to segmental demyelination before myelin scavengers, macrophages, are activated for phagocytotic myelin digestion. Here, we compared the initial SC demyelination mechanism of IDN to that of WD using microarray and histochemical analyses and found that SCs in IDN exhibited several typical characteristics of SAD, including actin-associated E-cadherin destruction, without obvious axonal degeneration. However, autophagolysosome activation in SAD did not appear to be involved in direct myelin lipid digestion by SCs but was required for the separation of SC body from destabilized myelin sheath in IDN. Thus, lysosome inhibition in SCs suppressed segmental demyelination by preventing the exocytotic myelin clearance of SCs. In addition, we found that myelin rejection, which might also require the separation of SC cytoplasm from destabilized myelin sheath, was delayed in SC-specific Atg7 knockout mice in WD, suggesting that autophagolysosome-dependent exocytotic myelin clearance by SCs in IDN and WD is a shared mechanism. Finally, autophagolysosome activation in SAD was mechanistically dissociated with the junctional destruction in both IDN and WD. Thus, our findings indicate that SAD could be a common myelin clearance mechanism of SCs in various demyelinating conditions.

Autophagic myelin destruction by Schwann cells during Wallerian degeneration and segmental demyelination.

As lysosomal hydrolysis has long been suggested to be responsible for myelin clearance after peripheral nerve injury, in this study, we investigated the possible role of autophagolysosome formation in myelin phagocytosis by Schwann cells and its final contribution to nerve regeneration. We found that the canonical formation of autophagolysosomes was induced in demyelinating Schwann cells after injury, and the inhibition of autophagy via Schwann cell-specific knockout of the atg7 gene or pharmacological intervention of lysosomal function caused a significant delay in myelin clearance. However, Schwann cell dedifferentiation, as demonstrated by extracellular signal-regulated kinase activation and c-Jun induction, and redifferentiation were not significantly affected, and thus the entire repair program progressed normally in atg7 knockout mice. Finally, autophagic Schwann cells were also found during segmental demyelination in a mouse model of inflammatory peripheral neuropathy. Together, our findings suggest that autophagy is the self-myelin destruction mechanism of Schwann cells, but mechanistically, it is a process distinct from Schwann cell plasticity for nerve repair.

Grb2-associated binder-1 is required for neuregulin-1-induced peripheral nerve myelination.

Grb2-associated binders (Gabs) are scaffolding proteins implicated in cell signaling via receptor tyrosine kinases including neuregulin-1(NRG1)-ErbB receptor signaling, which is essential for peripheral nerve myelination. Here, we show that the conditional removal of Gab1 from Schwann cells resulted in hypomyelination and abnormal development of Remak bundles. In contrast, hypomyelination was not observed in conventional Gab2 knock-out mice. Tyrosine phosphorylation of Gab1, but not Gab2, in sciatic nerves was upregulated during the myelination period and was found to be suppressed in NRG1-type III(+/-) mice, which display a hypomyelinated phenotype similar to that observed in Gab1 knock-out mice. Gab1 knock-out and NRG1-type III(+/-) mice both exhibited reduced extracellular signal-regulated kinase activity in myelinating nerves. In addition, Krox20, a transcription factor that is critical for myelination, has been identified as a target of the NRG1-Gab1 pathway during the myelination process. Our findings suggest that Gab1 is an essential component of NRG1-type III signaling during peripheral nerve development.

Prognostic impact of erythropoietin-stimulating agent use during front-line chemotherapy in patients with ovarian cancer: A Korean multicenter cohort study.

OBJECTIVE: To evaluate whether treatment with erythropoiesis-stimulating agents (ESAs) for chemotherapy-induced anemia affects progression-free survival (PFS) in patients receiving front-line chemotherapy following surgery for ovarian cancer (OC). METHODS: We retrospectively reviewed all consecutive patients who received front-line chemotherapy after surgery between 2013 and 2019 at six institutions. The patients were divided according to the use of ESAs during front-line chemotherapy. The primary endpoint was PFS. The secondary endpoint was the occurrence of thromboembolism. Propensity score matching (PSM) analysis was used to compare survival between matched cohorts. RESULTS: Overall, 2147 patients (433 receiving ESA and 1714 for no-ESA) were identified, with a median follow-up of 44.0 months. The ESA group showed a significantly higher proportion of stage III/IV disease (81.8% vs 61.1%; P < 0.001) and postoperative gross residual disease (32.3% vs 21.2%; P < 0.001) than the no-ESA group. In the multivariable Cox regression analysis, the use of ESAs did not affect PFS (adjusted hazard ratio, 1.03; 95% confidence interval [CI]: 0.89-1.20; P = 0.661). The incidence of thromboembolism was 10.2% in the ESA group and 4.6% in the no-ESA group (adjusted odds ratio, 6.58; 95% CI: 3.26-13.28; P < 0.001). When comparing the well-matched cohorts after PSM, PFS did not differ between the ESA (median PFS 23.5 months) and no-ESA groups (median PFS 22.2 months) (P = 0.540, log-rank test). CONCLUSIONS: The use of ESAs during front-line chemotherapy did not negatively affect PFS in patients with OC after surgery but increased the risk of thromboembolism.

Chemotherapy response score no longer predicts survival outcomes in high-grade serous ovarian cancer patients with BRCA mutation and/or maintenance therapy.

OBJECTIVE: We aimed to revalidate the chemotherapy response score (CRS) system as a prognostic factor for ovarian cancer patients with breast cancer gene (BRCA) mutations or those receiving frontline poly-ADP ribose polymerase (PARP) inhibitors or bevacizumab as maintenance therapy. METHODS: A retrospective analysis was performed using medical records of patients with high-grade serous carcinoma who received neoadjuvant chemotherapy followed by interval debulking surgery between January 2007 and December 2021 at 5 tertiary medical institutions in South Korea. At each hospital, pathologists independently assessed each slide of omental tissues obtained from surgery using the CRS system. Progression-free survival (PFS) and overall survival (OS) values were obtained using Kaplan-Meier analysis to evaluate the effect of BRCA mutation, maintenance therapy, and CRS on survival time. RESULTS: Of 466 patients, BRCA mutations were detected in 156 (33.5%) and 131 (28.1%) were treated with maintenance therapy; 98 (21.0%) and 42 (9.0%) were treated with PARP inhibitors or bevacizumab, respectively. Patients with CRS3 had significantly longer PFS than those with CRS1 or 2 (24.7 vs. 16.8 months, p<0.001). However, there was no significant difference in PFS improvement between CRS3 patients and those with CRS1 or 2 with BRCA mutation (22.0 vs. 19.3 months, p=0.193). Moreover, no significant PFS prolongation was observed in CRS3 patients compared to CRS1 or 2 patients treated with PARP inhibitors or bevacizumab (24.3 vs. 22.4 months, p=0.851; 27.5 vs. 15.7 months, p=0.347, respectively). CONCLUSION: CRS may not be a prognostic factor in patients with BRCA mutations and those receiving frontline maintenance therapy.

The Neuregulin-Rac-MKK7 pathway regulates antagonistic c-jun/Krox20 expression in Schwann cell dedifferentiation.

Schwann cells respond to nerve injury by dedifferentiating into immature states and producing neurotrophic factors, two actions that facilitate successful regeneration of axons. Previous reports have implicated the Raf-ERK cascade and the expression of c-jun in these Schwann cell responses. Here we used cultured primary Schwann cells to demonstrate that active Rac1 GTPase (Rac) functions as a negative regulator of Schwann cell differentiation by upregulating c-jun and downregulating Krox20 through the MKK7-JNK pathway, but not through the Raf-ERK pathway. The activation of MKK7 and induction of c-jun in sciatic nerves after axotomy was blocked by Rac inhibition. Microarray experiments revealed that the expression of regeneration-associated genes, such as glial cell line-derived neurotrophic factor and p75 neurotrophin receptor, after nerve injury was dependent on Rac but not on ERK. Finally, the inhibition of ErbB2 signaling prevented MKK7 activation, c-jun induction, and Rac-dependent gene expression in sciatic nerve explant cultures. Taken together, our results indicate that the neuregulin-Rac-MKK7-JNK/c-jun pathway regulates Schwann cell dedifferentiation following nerve injury.

Actin polymerization is essential for myelin sheath fragmentation during Wallerian degeneration.

The mechanisms that trigger Wallerian degeneration (WD) of peripheral nerves after injury are not well understood. During the early period of WD, fragmentation of myelin into ovoid structures occurs near the Schmidt-Lantermann incisures (SLI), a noncompact region of the myelin sheath containing autotypical adherens junction. In this study, we found that new filamentous actin polymerization occurs in the SLI of mouse sciatic nerves after injury and that its inhibition prevented not only the degradation of E-cadherin in the SLI but also myelin ovoid formation. However, the inhibition of actin polymerization could not block Schwann cell dedifferentiation. The activation of Rac GTPase was observed in the distal stump of the injured nerves, and a specific Rac inhibitor, a dominant-negative Rac, and Rac1-RNA interference blocked myelin ovoid formation. Together, these findings suggest that dynamic changes in actin in the SLI are essential for initiation of demyelination after peripheral nerve injury.

Local production of serum amyloid a is implicated in the induction of macrophage chemoattractants in Schwann cells during wallerian degeneration of peripheral nerves.

The elevation of serum levels of serum amyloid A (SAA) has been regarded as an acute reactive response following inflammation and various types of injuries. SAA from the liver and extrahepatic tissues plays an immunomodulatory role in a variety of pathophysiological conditions. Inflammatory cytokines in the peripheral nerves have been implicated in the Wallerian degeneration of peripheral nerves after injury and in certain types of inflammatory neuropathies. In the present study, we found that a sciatic nerve axotomy could induce an increase of SAA1 and SAA3 mRNA expression in sciatic nerves. Immunohistochemical staining showed that Schwann cells are the primary sources of SAA production after nerve injury. In addition, interleukin-6-null mice, but not tumor necrosis factor-α-null mice showed a defect in the production of SAA1 in sciatic nerve following injury. Dexamethasone treatment enhanced the expression and secretion of SAA1 and SAA3 in sciatic nerve explants cultures, suggesting that interleukin-6 and corticosteroids might be major regulators for SAA production in Schwann cells following injury. Moreover, the stimulation of Schwann cells with SAA1 elicited the production of the macrophage chemoattractants, Ccl2 and Ccl3, in part through a G-protein coupled receptor. Our findings suggest that locally produced SAA might play an important role in Wallerian degeneration after peripheral nerve injury.

Outcomes of vaginal hysterectomy combined with anterior and posterior colporrhaphy for pelvic organ prolapse: a single center retrospective study.

OBJECTIVE: To evaluate the efficacy of vaginal hysterectomy combined with anterior and posterior colporrhaphy (VH APR) for the management of pelvic organ prolapse (POP). METHODS: A total of 610 patients with POP who underwent VH APR from January 2010 to June 2019 at Asan Medical Center were included in this study. We analyzed the patient characteristics and surgical outcomes. In addition, we compared the POP quantification system (POP-Q) pre- and postoperatively at 2 weeks, 3 months, and 1 year, and analyzed the risk factors for recurrence. RESULTS: The mean age of the patients was 65.5±7.6 years. The most common preoperative POP-Q stage was stage 2 (60.8%), followed by stage 3 (35.9%). Complications were identified during surgery in 1.6% of the patients. The most common postoperative complication (6.4%) was voiding difficulty. All POP-Q scores significantly decreased at 1 year after surgery (P<0.0001). The recurrence rate was 9.6%, and most recurrences (77.5%) occurred in the anterior compartment. An advanced stage of preoperative POP was a risk factor for recurrence (stage 3 or 4 vs. stage 1 or 2; odds ratio [OR], 5.337, 95% confidence interval [CI], 2.58-11.036, P<0.0001). Only two patients underwent surgical correction for POP recurrence, and most of the remaining patients did not undergo further treatment for prolapse. CONCLUSION: VH APR is a safe and effective surgical procedure for POP, with a low recurrence rate. In addition, advanced preoperative stage was the only risk factor for recurrent POP.

Pathological adaptive responses of Schwann cells to endoplasmic reticulum stress in bortezomib-induced peripheral neuropathy.

Bortezomib, a proteasome inhibitor, has been considered as a promising anticancer drug in the treatment of recurrent multiple myeloma and some solid tumors. The bortezomib-induced peripheral neuropathy (BIPN) is a prominent cause of dose-limiting toxicities after bortezomib treatment. In this study, we found that BIPN in a mouse model is characterized by acute but transient endoplasmic reticulum (ER) damages to Schwann cells. These damaged Schwann cells exhibit abnormal outcomes from healing processes such as the myelination of Remak bundles. A morphometric analysis of polymyelinated Remak bundles revealed that the pathological myelination was not related to the axonal parameters that regulate the normal myelination process during development. In addition, demyelinating macrophages were focally infiltrated within endoneurium of the sciatic nerve. To identify the mechanism underlying these pathologies, we applied a gene microarray analysis to bortezomib-treated primary Schwann cells and verified the changes of several gene expression in bortezomib-treated sciatic nerves. The analysis showed that bortezomib-induced ER stress was accompanied by the activation of several protective molecular chaperones and the down-regulation of myelin gene expression. ER stress inducers such as thapsigargin and bredelfin A also suppressed the mRNA expression of myelin gene P0 at transcriptional levels. In addition, the expression of chemokines such as the macrophage chemoattractants Ccl3 and Cxcl2 was significantly increased in Schwann cells in response to bortezomib and ER stress inducers. Taken together, these observations suggest that the pathological adaptive responses of Schwann cells to bortezomib-induced ER stress may, in part, participate in the development of BIPN.

Prevalence, comorbidities and risk factors of restless legs syndrome in the Korean elderly population - results from the Korean Longitudinal Study on Health and Aging.

The aim of this study was to determine the prevalence, neuropsychiatric comorbidities, iron metabolism and potential risk factors of restless legs syndrome (RLS) in the elderly Korean population. As a community-based epidemiological study, a simple random sample of 1118 was drawn from a roster of 61 730 adult individuals aged 65 years and older and 714 participated. The diagnosis of RLS was established in face-to-face interviews using the four minimal diagnostic criteria for RLS recommended by National Institute of Health. Depressive symptoms, nocturnal sleep disturbances, daytime sleepiness and quality of life were evaluated. Laboratory tests of iron metabolism, markers of inflammation, renal and endocrine function, hormones and vitamins were performed. A total of 59 patients (42 women and 17 men) were diagnosed as RLS with a prevalence of 8.3% (95% confidence interval: 6.2-10.3%), with an almost twofold higher prevalence in women (10.2%) than in men (5.7%). Depression was more prevalent among the subjects with RLS than without RLS and poor nocturnal sleep and quality of life were also observed in subjects with RLS. Daytime sleepiness was observed in 32.8% of subjects with RLS. No significant differences were found in iron metabolism or other risk factors between the subjects with and without RLS. The prevalence of RLS in the Korean elderly population was comparable with that in the Caucasian population. RLS had undesirable effects on mood, sleep quality and general wellbeing of elderly individuals.

Exosomes derived from differentiated Schwann cells inhibit Schwann cell migration via microRNAs.

Exosomes derived from Schwann cells have been known to have a variety of functions in the development and repair of the peripheral nervous system, and cyclic AMP (cAMP) is a key inducer of Schwann cell differentiation. In the present study, we aimed to study the effect of exosomes derived from differentiated Schwann cells on the expression of microRNAs (miRNAs). To show that miRNAs were altered from exosomes derived from Schwann cells, we conducted next-generation sequencing (NGS) arrays with exosomes derived from cAMP-induced differentiated Schwann cells and control. NGS arrays revealed that 22 miRNAs, 33 small nucleolar RNAs, one antisense RNA, and two mRNAs were upregulated, while 37 mRNAs, one tRNA, and 35 antisense RNAs were downregulated. We also confirmed that miRNA211 and miR92a-3p were upregulated, while the expression levels of hypoxia-inducible factor, rat cyclin-dependent kinase 2, and rat platelet-derived growth factor C were reduced in exosomes derived from cAMP-induced differentiated Schwann cells. Venn diagrams were used to identify overlapping miRNA targets from highly expressed miRNAs (miR211-5p, miR211-3p, and miR92a-3p). The pathways identified via Kyoto Encyclopedia of Genes and Genomes analysis of the target genes are associated with nerve regeneration and Schwann cell proliferation such as the tumor necrosis factor signaling pathway, dopaminergic synapse, and neurotrophin signaling, and cAMP-dependent signaling pathways. Additionally, we observed that exosomes derived from differentiated Schwann cells suppressed Schwann cell migration, while control exosomes obtained from undifferentiated Schwann cells did not. Together, the results suggested that exosomes released from differentiated Schwann cells regulated Schwann cell migration through changes in miRNA expression.

Proteasome inhibition suppresses Schwann cell dedifferentiation in vitro and in vivo.

The ubiquitin-proteasome system (UPS), lysosomes, and autophagy are essential protein degradation systems for the regulation of a variety of cellular physiological events including the cellular response to injury. It has recently been reported that the UPS and autophagy mediate the axonal degeneration caused by traumatic insults and the retrieval of nerve growth factors. In the peripheral nerves, axonal degeneration after injury is accompanied by myelin degradation, which is tightly related to the reactive changes of Schwann cells called dedifferentiation. In this study, we examined the role of the UPS, lysosomal proteases, and autophagy in the early phase of Wallerian degeneration of injured peripheral nerves. We found that nerve injury induced an increase in the ubiquitin conjugation and lysosomal-associated membrane protein-1 expression within 1 day without any biochemical evidence for autophagy activation. Using an ex vivo explant culture of the sciatic nerve, we observed that inhibiting proteasomes or lysosomal serine proteases prevented myelin degradation, whereas this was not observed when inhibiting autophagy. Interestingly, proteasome inhibition, but not leupeptin, prevented Schwann cells from inducing dedifferentiation markers such as p75 nerve growth factor receptor and glial fibrillary acidic protein in vitro and in vivo. In addition, proteasome inhibitors induced cell cycle arrest and cellular process formation in cultured Schwann cells. Taken together, these findings indicate that the UPS plays a role in the phenotype changes of Schwann cells in response to nerve injury.