Brain-derived neurotrophic factor promotes nerve regeneration by activating the JAK/STAT pathway in Schwann cells

Age‑related changes in endoplasmic reticulum stress response‑associated protein expression in rat tibial nerves

In age-related peripheral neurodegeneration, changes in the promotion or inhibition of endoplasmic reticulum (ER) stress response related to the ubiquitin-proteasome degradation system (UPS), autophagy and apoptosis signaling factors during aging remain unclear. In the present study, the expression of ER stress response signaling-related protein factors was examined in tibial nerves during aging in rats. Tibial nerves were extracted from continuously housed rats at 20, 50, 70, 90 and 105 weeks of age. Expression of factors associated with ER stress-related degradation, including X-box binding protein 1 (XBP1s), eukaryotic translation initiation factor 2 subunit 1 (eIF2α), Beclin-1 (Becn1), and Caspase-3 (Casp3); ER stress-related repair, including binding immunoglobulin protein [also known as 78 kDa glucose-regulated protein (BiP/GRP78)], protein disulfide isomerase (PDI), brain-derived neurotrophic factor (BDNF) and the inflammatory cytokine IL6, was assessed by western blotting of tibial nerves from rats in each age group. Expression of XBP1s and Becn1, which promote UPS and autophagy, decreased significantly after 50 weeks of age. However, expression of eIF2α and Casp3, which inhibit new protein biosynthesis and promote apoptosis, increased significantly after 50 weeks. Expression of BiP/GRP78 and PDI, which are refolding factors for denatured proteins, showed a significant decrease after 50 (or 70) weeks of age. The expression of BDNF, a ligand protein for the repair cascade, showed a significant increase after 70 weeks of age, while that of IL6 increased significantly after 50 weeks of age. These results indicate that ER stress-related degradation (UPS and autophagy) and refolding repair functions are reduced in rat tibial nerves after 50 weeks, followed by enhanced apoptosis and inflammation. These findings shed light on the progression of age-related peripheral neurodegeneration in rats.

Characterisation of the antinociceptive effect of baricitinib in the collagen antibody-induced arthritis mouse model

OBJECTIVES

Many rheumatoid arthritis (RA) patients continue to experience persistent pain even after successful management of joint inflammation. Clinical data indicate that RA patients treated with the JAK inhibitor baricitinib consistently achieve pain relief that cannot be entirely attributed to its anti-inflammatory effects. In this study, we investigated the antinociceptive properties of baricitinib using the collagen antibody-induced arthritis (CAIA) model in which mechanical hypersensitivity persists long after resolution of joint inflammation.

METHODS

The effects of baricitinib, etanercept (tumour necrosis factor inhibitor), and LP-922761 (adaptor protein-2 (AP2) associated kinase 1 (AAK1) inhibitor) on pain-like behaviour in CAIA mice were examined. Tissue samples from the late, low-grade inflammatory phase were examined for the effect of the treatments. Additionally, in vitro experiments using dorsal root ganglion (DRG) cells were conducted to assess baricitinib's influence on neuronal excitability and cell morphology.

RESULTS

Baricitinib reduced CAIA-induced joint inflammation, but its antinociceptive effects were most pronounced during the late phase when etanercept was ineffective. Administering baricitinib both early and late significantly decreased CAIA-induced bone loss, synovial innervation, and baseline STAT3 phosphorylation in ankle joints and DRGs. Unlike etanercept, baricitinib effectively reduced pain-like behaviour and synovial hyperinnervation when administered exclusively in the late phase. Additionally, baricitinib modulated glial cell morphology and neuronal excitability in vitro. Notably, it inhibited AAK1 signalling in DRGs, with AAK1 kinase activity blockade providing an antinociceptive effect in the CAIA model.

CONCLUSIONS

Our data suggests that baricitinib has antinociceptive effects by targeting not only immune cells but also neurons and glia cells via inhibition of 2 signalling pathways linked to chronic pain.

Physical modulation and peripheral nerve regeneration: a literature review

Peripheral nerve injury (PNI) usually causes severe motor, sensory and autonomic dysfunction. In addition to direct surgical repair, rehabilitation exercises, and traditional physical stimuli, for example, electrical stimulation, have been applied in promoting the clinical recovery of PNI for a long time but showed low efficiency. Recently, significant progress has been made in new physical modulation to promote peripheral nerve regeneration. We hereby review current progress on the mechanism of peripheral nerve regeneration after injury and summarize the new findings and evidence for the application of physical modulation, including electrical stimulation, light, ultrasound, magnetic stimulation, and mechanical stretching in experimental studies and the clinical treatment of patients with PNI.

Establishment of a Serum-Free Human iPSC-Derived Model of Peripheral Myelination

Myelination and the formation of nodes of Ranvier are essential for the rapid conduction of nerve impulses along axons in the peripheral nervous system (PNS). While many animal-based and serum-containing models of peripheral myelination have been developed, these have limited ability when it comes to studying genetic disorders affecting peripheral myelination. We report a fully induced pluripotent stem cell (iPSC)-derived human model of peripheral myelination using Schwann cells (SCs) and motoneurons, cultured in a serum-free medium on patterned and nonpatterned surfaces. Results demonstrated iPSC-derived SC-expressed early growth response protein 2 (Egr2), a key transcription factor for myelination, and after ∼30 days in coculture, hallmark features of myelination, including myelin segment and node of Ranvier formation, were observed. Myelin segments were stained for the myelin basic protein, which surrounded neurofilament-stained motoneuron axons. Clusters of voltage-gated sodium channels flanked by paranodal protein contactin-associated protein 1, indicating node of Ranvier formation, were also observed. High-resolution confocal microscopy allowed for 3D reconstruction and measurement of myelin g-ratios of myelin segments, with an average g-ratio of 0.67, consistent with reported values in the literature, indicating mature myelin segment formation. This iPSC-based model of peripheral myelination provides a platform to investigate numerous PNS diseases, including Charcot-Marie Tooth disorder, Guillian-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, and antimyelin-associated glycoprotein peripheral neuropathy, with the potential for greater translatability to humans for improving the applicability for drug-screening programs.

Combining external physical stimuli and nanostructured materials for upregulating pro-regenerative cellular pathways in peripheral nerve repair

Peripheral nerve repair remains a major clinical challenge, particularly in the pursuit of therapeutic approaches that ensure adequate recovery of patient's activity of daily living. Autografts are the gold standard in clinical practice for restoring lost sensorimotor functions nowadays. However, autografts have notable drawbacks, including dimensional mismatches and the need to sacrifice one function to restore another. Engineered nerve guidance conduits have therefore emerged as promising alternatives. While these conduits show surgical potential, their clinical use is currently limited to the repair of minor injuries, as their ability to reinnervate limiting gap lesions is still unsatisfactory. Therefore, improving patient functional recovery requires a deeper understanding of the cellular mechanisms involved in peripheral nerve regeneration and the development of therapeutic strategies that can precisely modulate these processes. Interest has grown in the use of external energy sources, such as light, ultrasound, electrical, and magnetic fields, to activate cellular pathways related to proliferation, differentiation, and migration. Recent research has explored combining these energy sources with tailored nanostructured materials as nanotransducers to enhance selectivity towards the target cells. This review aims to present the recent findings on this innovative strategy, discussing its potential to support nerve regeneration and its viability as an alternative to autologous transplantation.

Effect of 28 days treatment of baricitinib on mechanical allodynia, osteopenia, and loss of nerve fibers in an experimental model of type-1 diabetes mellitus

BACKGROUND

Type-1 diabetes mellitus (T1DM) is associated with numerous health problems, including peripheral neuropathy, osteoporosis, and bone denervation, all of which diminish quality of life. However, there are relatively few therapies to treat these T1DM-related complications. Recent studies have shown that Janus kinase (JAK) inhibitors reverse aging- and rheumatoid arthritis-induced bone loss and reduce pain associated with peripheral nerve injuries, and rheumatoid arthritis. Thus, we assessed whether a JAK1/JAK2 inhibitor, baricitinib, ameliorates mechanical pain sensitivity (a measure of peripheral neuropathy), osteoporosis, and bone denervation in the femur of mice with T1DM.

METHODS

Female ICR mice (13 weeks old) received five daily administrations of streptozotocin (ip, 50 mg/kg) to induce T1DM. At thirty-one weeks of age, mice were treated with baricitinib (po; 40 mg/kg/bid; for 28 days) or vehicle. Mechanical sensitivity was evaluated at 30, 33, and 35 weeks of age on the plantar surface of the right hind paw. At the end of the treatment, mice were sacrificed, and lower extremities were harvested for microcomputed tomography and immunohistochemistry analyses.

RESULTS

Mice with T1DM exhibited greater blood glucose levels, hind paw mechanical hypersensitivity, trabecular bone loss, and decreased density of calcitonin gene-related peptide-positive and tyrosine hydroxylase-positive axons within the marrow of the femoral neck compared to control mice. Baricitinib treatment significantly reduced mechanical hypersensitivity and ameliorated sensory and sympathetic denervation at the femoral neck, but it did not reverse trabecular bone loss.

CONCLUSIONS

Our findings suggest that baricitinib may represent a new therapeutic alternative to treat T1DM-induced peripheral neuropathy and bone denervation.

hESC- and hiPSC-derived Schwann cells are molecularly comparable and functionally equivalent

Establishing robust models of human myelinating Schwann cells is critical for studying peripheral nerve injury and disease. Stem cell differentiation has emerged as a key human cell model and disease motivating development of Schwann cell differentiation protocols. Human embryonic stem cells (hESCs) are considered the ideal pluripotent cell but ethical concerns regarding their use have propelled the popularity of human induced pluripotent stem cells (hiPSCs). Given that the equivalence of hESCs and hiPSCs remains controversial, we sought to compare the molecular and functional equivalence of hESC- and hiPSC-derived Schwann cells generated with our previously reported protocol. We identified only modest transcriptome differences by RNA sequencing and insignificant proteome differences by antibody array. Additionally, both cell types comparably improved nerve regeneration and function in a chronic denervation and regeneration animal model. Our findings demonstrate that Schwann cells derived from hESCs and hiPSCs with our protocol are molecularly comparable and functionally equivalent.

Lacosamide alleviates bilateral cavernous nerve injury-induced erectile dysfunction in the rat model by ameliorating pathological changes in the corpus cavernosum

Bilateral cavernous nerve injury-related erectile dysfunction (BCNI-ED) shows a limited response to type 5 phosphodiesterase inhibitors. Furthermore, lacosamide (LCM) can alleviate peripheral neuropathy. To explore whether LCM can improve the erectile response after BCNI, we randomly divided 30 young Sprague-Dawley rats into three groups (n = 10 per group), namely, the sham operation, 0.9% normal saline-treated (BCNI + 0.9% NS), and LCM-treated BCNI (BCNI + LCM) groups. LCM was injected intraperitoneally at a dose of 90 mg/kg/day for 7 consecutive days. Erectile function was assessed by measuring the ratio of peak intracavernous pressure (ICP) to mean arterial pressure (MAP), and tissues were harvested for transmission electron microscopy, immunofluorescence, Masson's trichrome staining, TUNEL staining, and Western blot analysis. The BCNI + 0.9% NS group showed reduced ICP/MAP ratio (0.93 ± 0.04 vs. 0.44 ± 0.05, P < 0.0001). An increased proportion of TUNEL-positive cells (0.04 ± 0.01 vs 0.87 ± 0.03, P < 0.0001) and a decreased smooth muscle/collagen ratio (0.44 ± 0.01 vs. 0.33 ± 0.01, P < 0.001) were observed in the BCNI + 0.9% NS compared with the sham group. Administration of LCM significantly restored the ICP/MAP ratio (0.44 ± 0.05 vs. 0.74 ± 0.05, P < 0.001) and decreased the proportion of TUNEL positive cells (0.87 ± 0.03 vs. 0.60 ± 0.04, P < 0.0001) in the corpus cavernosum following BCNI. The ratio of smooth muscle to collagen (0.43 ± 0.01vs. 0.33 ± 0.01, P < 0.01) and expression of α-SMA (P < 0.0001) in the BCNI + LCM group significantly increased compared with BCNI + 0.9% NS group, indicating alleviation of fibrosis. Apoptotic markers, including Bax/Bcl-2 (P < 0.01) and Caspase-3 (P < 0.0001) in the BCNI + LCM group was significantly lower than that in the BCNI + 0.9% NS group. LCM treatment partially upregulated the expression of vWF and eNOS in cavernous tissue in rats subjected to BCNI (P < 0.05). Increases in S100-β and nNOS expression in the major pelvic ganglion (MPG) were observed after LCM administration. In summary, LCM can recover erectile function in BCNI-ED rat model by suppressing corporal apoptosis and fibrosis, and protecting the cavernous nerve.

Stat3 Has a Different Role in Axon Growth During Development Than It Does in Axon Regeneration After Injury

Signal transducer and activator of transcription 3 (STAT3) is essential for neural development and regeneration as a key transcription factor and mitochondrial activator. However, the mechanism of Stat3 in axon development and regeneration has not been fully understood. In this study, using zebrafish posterior lateral line (PLL) axons, we demonstrate that Stat3 plays distinct roles in PLL axon embryonic growth and regeneration. Our experiments indicate that stat3 is required for PLL axon extension. In stat3 mutant zebrafish, the PLL axon ends were stalled at the level of the cloaca, and expression of stat3 rescues the PLL axon growth in a cell-autonomous manner. Jak/Stat signaling inhibition did not affect PLL axon growth indicating Jak/Stat was dispensable for PLL axon growth. In addition, we found that Stat3 was co-localized with mitochondria in PLL axons and important for the mitochondrial membrane potential and ATPase activity. The PLL axon growth defect of stat3 mutants was mimicked and rescued by rotenone and DCHC treatment, respectively, which suggests that Stat3 regulates PLL axon growth through mitochondrial Stat3. By contrast, mutation of stat3 or Jak/Stat signaling inhibition retarded PLL axon regeneration. Meanwhile, we also found Schwann cell migration was also inhibited in stat3 mutants. Taken together, Stat3 is required for embryonic PLL axon growth by regulating the ATP synthesis efficiency of mitochondria, whereas Stat3 stimulates PLL axon regeneration by regulating Schwann cell migration via Jak/Stat signaling. Our findings show a new mechanism of Stat3 in axon growth and regeneration.

Neurobiological insights into lower urinary tract dysfunction: evaluating the role of brain-derived neurotrophic factor

Lower urinary tract dysfunction (LUTD) encompasses a range of debilitating conditions that affect both sexes and different age groups. Understanding the underlying neurobiological mechanisms contributing to LUTD has emerged as a critical avenue for the development of targeted therapeutic strategies. Brain-derived neurotrophic factor (BDNF), a prominent member of the neurotrophin family, has attracted attention due to its multiple roles in neural development, plasticity, and maintenance. This review examines the intricate interplay between neurobiological factors and LUTD, focusing on the central involvement of BDNF. The review emphasizes the bidirectional relationship between LUTD and BDNF and explores how LUTD-induced neural changes may affect BDNF dynamics and vice versa. Growth factor therapy and the combined administration of controlled release growth factors and stem cells are minimally invasive treatment strategies for neuromuscular injury. Among the many growth factors and cytokines, brain-derived neurotrophic factor (BDNF) plays a prominent role in neuromuscular repair. As an essential neurotrophin, BDNF is involved in the modulation of neuromuscular regeneration through tropomyosin receptor kinase B (TrkB). Increasing BDNF levels facilitates the regeneration of the external urethral sphincter and contributes to the regulation of bladder contraction. Treatments targeting the BDNF pathway and sustained release of BDNF may become novel treatment options for urinary incontinence and other forms of lower urinary tract dysfunction. This review discusses the applications of BDNF and the theoretical basis for its use in the treatment of lower urinary tract dysfunction, including urinary incontinence (UI), overactive bladder (OAB), and benign prostatic hyperplasia (BPH), and in the clinical diagnosis of bladder dysfunction.

Review on electrically conductive smart nerve guide conduit for peripheral nerve regeneration

At present, peripheral nerve injuries (PNIs) are one of the leading causes of substantial impairment around the globe. Complete recovery of nerve function after an injury is challenging. Currently, autologous nerve grafts are being used as a treatment; however, this has several downsides, for example, donor site morbidity, shortage of donor sites, loss of sensation, inflammation, and neuroma development. The most promising alternative is the development of a nerve guide conduit (NGC) to direct the restoration and renewal of neuronal axons from the proximal to the distal end to facilitate nerve regeneration and maximize sensory and functional recovery. Alternatively, the response of nerve cells to electrical stimulation (ES) has a substantial regenerative effect. The incorporation of electrically conductive biomaterials in the fabrication of smart NGCs facilitates the function of ES throughout the active proliferation state. This article overviews the potency of the various categories of electroactive smart biomaterials, including conductive and piezoelectric nanomaterials, piezoelectric polymers, and organic conductive polymers that researchers have employed latterly to fabricate smart NGCs and their potentiality in future clinical application. It also summarizes a comprehensive analysis of the recent research and advancements in the application of ES in the field of NGC.

Role of JAK-STAT signaling pathway in pathogenesis and treatment of primary Sjögren's syndrome

ABSTRACT

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease with high prevalence and possible poor prognosis. Though the pathogenesis of pSS has not been fully elucidated, B cell hyperactivity is considered as one of the fundamental abnormalities in pSS patients. It has long been identified that Janus kinases-signal transducer and activator of transcription (JAK-STAT) signaling pathway contributes to rheumatoid arthritis and systemic lupus erythematosus. Recently, increasing numbers of studies have provided evidence that JAK-STAT pathway also has an important role in the pathogenesis of pSS via direct or indirect activation of B cells. Signal transducer and activator of transcription 1 (STAT1), STAT3, and STAT5 activated by various cytokines and ribonucleic acid contribute to pSS development, respectively or synergically. These results reveal the potential application of Janus kinase inhibitors for treatment of pSS, which may fundamentally improve the quality of life and prognosis of patients with pSS.

Causal association between JAK2 and erectile dysfunction: a Mendelian randomization study

BACKGROUND

As one of the most critical proteins in the JAK/STAT signaling pathway, Janus kinase 2 (JAK2) is involved in many biological processes and diseases. Several observational studies have reported the role of JAK2 in erectile dysfunction. However, the causal relationship between JAK2 and erectile dysfunction remains unclear. Here we investigated the causal relationship between JAK2 and erectile dysfunction.

RESULTS

Genetically predicted JAK2 was causally associated with erectile dysfunction in inverse variance weighting (OR = 1.109, 95% CI = 1.029-1.196, p = 0.007) and weighted median method (OR = 1.117, 95% CI = 1.003-1.245, p = 0.044). No heterogeneity was observed in Cochran Q-test (p = 0.855) and MR-PRESSO (p = 0.866). Pleiotropy was not observed in our study (p = 0.617).

CONCLUSIONS

These findings highlighted JAK2 as a risk factor for erectile dysfunction and proved the causal relationship between JAK2 and erectile dysfunction, suggesting that targeting JAK2 signaling might be a novel and promising therapeutic candidate in the treatment of erectile dysfunction.

The factors affecting neurogenesis after stroke and the role of acupuncture

Stroke induces a state of neuroplasticity in the central nervous system, which can lead to neurogenesis phenomena such as axonal growth and synapse formation, thus affecting stroke outcomes. The brain has a limited ability to repair ischemic damage and requires a favorable microenvironment. Acupuncture is considered a feasible and effective neural regulation strategy to improve functional recovery following stroke via the benign modulation of neuroplasticity. Therefore, we summarized the current research progress on the key factors and signaling pathways affecting neurogenesis, and we also briefly reviewed the research progress of acupuncture to improve functional recovery after stroke by promoting neurogenesis. This study aims to provide new therapeutic perspectives and strategies for the recovery of motor function after stroke based on neurogenesis.

Regulatory significance of CULLIN2 in neuronal differentiation and regeneration

BACKGROUND

Scaffold proteins coordinate multiple signalling pathways by integrating various proteins but the role of these proteins in neuronal pathways remains to be elucidated. The present study focused to evaluate the expression of the scaffold protein CULLIN2 in neuronal cells.

METHODS

The neuronal precursor cell line N2A was differentiated to neurons in-vitro with retinoic acid and biochemical assays were used to understand the gene expression profiling of CULLIN2. Moreover, neddylation inhibitor MLN4924 was used to inhibit the activity of CULLIN2 and the downstream substrates were validated. Finally, the role of CULLIN2 in nerve regeneration was evaluated in an in vivo zebrafish model.

RESULTS

Experimental data showed that the neuronal cells N2A have lower expression of CULLIN2 compared to skin cell lines (HaCaT and A431) and inactivation with the neddylation inhibitor resulted in cell death. Furthermore differentiating the neural precursor cell line into neurons with retinoic acid enhanced the expression of CULLIN2. Examining downstream signalling molecules with the neddylation inhibitor illuminates that MLN4924 treatment influences the cytokine signalling cascade (JAK-STAT) in neuronal cells. Moreover, for the first time, we show that the ubiquitin ligase protein CULLIN2 is perturbed in neural regeneration. Expression profile of CULLIN2 was significantly decreased in response to a nerve injury in Zebra fish and as the nerve regenerates there is corresponding reduction in the mRNA levels.

CONCLUSION

During differentiation CULLIN2 is upregulated whereas during regeneration there is significant downregulation. Thus, our findings reveal a crucial role of the scaffold protein CULLIN2 in nerve differentiation and regeneration which can be vital for the treatment of nerve injury.

Interactions Among Brain-Derived Neurotrophic Factor and Neuroimmune Pathways Are Key Components of the Major Psychiatric Disorders

The purpose of this review is to summarize the current knowledge regarding the reciprocal associations between brain-derived neurotrophic factor (BDNF) and immune-inflammatory pathways and how these links may explain the involvement of this neurotrophin in the immune pathophysiology of mood disorders and schizophrenia. Toward this end, we delineated the protein-protein interaction (PPI) network centered around BDNF and searched PubMed, Scopus, Google Scholar, and Science Direct for papers dealing with the involvement of BDNF in the major psychosis, neurodevelopment, neuronal functions, and immune-inflammatory and related pathways. The PPI network was built based on the significant interactions of BDNF with neurotrophic (NTRK2, NTF4, and NGFR), immune (cytokines, STAT3, TRAF6), and cell-cell junction (CTNNB, CDH1) DEPs (differentially expressed proteins). Enrichment analysis shows that the most significant terms associated with this PPI network are the tyrosine kinase receptor (TRKR) and Src homology region two domain-containing phosphatase-2 (SHP2) pathways, tyrosine kinase receptor signaling pathways, positive regulation of kinase and transferase activity, cytokine signaling, and negative regulation of the immune response. The participation of BDNF in the immune response and its interactions with neuroprotective and cell-cell adhesion DEPs is probably a conserved regulatory process which protects against the many detrimental effects of immune activation and hyperinflammation including neurotoxicity. Lowered BDNF levels in mood disorders and schizophrenia (a) are associated with disruptions in neurotrophic signaling and activated immune-inflammatory pathways leading to neurotoxicity and (b) may interact with the reduced expression of other DEPs (CTNNB1, CDH1, or DISC1) leading to multiple aberrations in synapse and axonal functions.

Radix Astragalus Polysaccharide Accelerates Angiogenesis by Activating AKT/eNOS to Promote Nerve Regeneration and Functional Recovery

Peripheral nerve injury (PNI) results in loss of neural control and severe disabilities in patients. Promoting functional nerve recovery by accelerating angiogenesis is a promising neuroprotective treatment strategy. Here, we identified a bioactive Radix Astragalus polysaccharide (RAP) extracted from traditional Chinese medicine (TCM) as a potent enhancer of axonal regeneration and remyelination. Notably, RAP promoted functional recovery and delayed gastrocnemius muscle atrophy in a rat model of sciatic nerve crush injury. Further, RAP treatment may induce angiogenesis in vivo. Moreover, our in vitro results showed that RAP promotes endothelial cell (EC) migration and tube formation. Altogether, our results show that RAP can enhance functional recovery by accelerating angiogenesis, which was probably related to the activation of AKT/eNOS signaling pathway, thereby providing a polysaccharide-based therapeutic strategy for PNI.

Application of Human Epineural Conduit Supported with Human Mesenchymal Stem Cells as a Novel Therapy for Enhancement of Nerve Gap Regeneration

Various therapeutic methods have been suggested to enhance nerve regeneration. In this study, we propose a novel approach for enhancement of nerve gap regeneration by applying human epineural conduit (hEC) supported with human mesenchymal stem cells (hMSC), as an alternative to autograft repair. Restoration of 20 mm sciatic nerve defect with hEC created from human sciatic nerve supported with hMSC was tested in 4 experimental groups (n = 6 each) in the athymic nude rat model (Crl:NIH-Foxn1^rnu): 1 - No repair control, 2 - Autograft control, 3 - Matched diameter hEC filled with 1 mL saline, 4 - Matched diameter hEC supported with 3 × 10⁶ hMSC. Assessments included: functional tests: toe-spread and pinprick, regeneration assessment by immunofluorescence staining: HLA-1, HLA-DR, NGF, GFAP, Laminin B, S-100, VEGF, vWF and PKH26 labeling; histomorphometric analysis of myelin thickness, axonal density, fiber diameter and myelinated nerve fibers percentage; Gastrocnemius Muscle Index (GMI) and muscle fiber area ratio. Best sensory and motor function recovery, as well as GMI and muscle fiber area ratio, were observed in the autograft group, and were comparable to the hEC with hMSC group (p = 0.038). Significant improvements of myelin thickness (p = 0.003), fiber diameter (p = 0.0296), and percentage of myelinated fibers (p < 0.0001) were detected in hEC group supported with hMSC compared to hEC with saline controls. At 12-weeks after nerve gap repair, hEC combined with hMSC revealed increased expression of neurotrophic and proangiogenic factors, which corresponded with improvement of function comparable with the autograft control. Application of our novel hEC supported with hMSC provides a potential alternative to the autograft nerve repair.

Gastrodin modified polyurethane conduit promotes nerve repair via optimizing Schwann cells function

Peripheral nerve regeneration and functional recovery remain a major clinical challenge. Nerve guidance conduit (NGC) that can regulate biological behavior of Schwann cells (SCs) and facilitate axonal regeneration through microenvironmental remodeling is beneficial for nerve regeneration and functional recovery. Gastrodin, a main constituent of a Chinese traditional herbal medicine, has been known to display several biological and pharmacological properties, especially antioxidative, anti‐inflammatory and nerve regeneration. Herein, polyurethane (PU) NGCs modified by different weight ratio of Gastrodin (0, 1 and 5 wt%) were designed for sequential and sustainable drug release, that created a favorable microenvironment for nerve regeneration. The scaffold showed suitable pore structure and biocompatibility in vitro, and evidently promoted morphological and functional recovery of regenerated sciatic nerves in vivo. Compared to the PU and 1%Gastrodin/PU scaffolds, the 5%Gastrodin/PU significantly enhanced the proliferation, migration and myelination of SCs and up-regulated expression of neurotrophic factors, as well as induction of the differentiation of PC12 cells. Interestingly, the obvious anti-inflammatory response was observed in 5%Gastrodin/PU by reduced expression of TNF-α and iNOS, which also evidenced by the few fibrous capsule formation in the subcutaneous implantation. Such a construct presented a similarity to autograft in vivo repairing a 10 mm sciatic nerve defects. It was able to not only boost the regenerated area of nerve and microvascular network, but also facilitate functional axons growth and remyelination, leading to highly improved functional restoration. These findings demonstrate that the 5%Gastrodin/PU NGC efficiently promotes nerve regeneration, indicating their potential for use in peripheral nerve regeneration applications.

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NGC with a sustained release of Gastrodin creates a favorable microenvironment. .

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Gastrodin/PU has superior anti-inflammatory effects.

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SCs-mediated tissue engineering strategies effectively drive myelination.

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5Gastrodin/PU boosts nerve regeneration and functional restoration in vivo.

In Vitro and In Vivo Effects of Nobiletin on DRG Neurite Elongation and Axon Growth after Sciatic Nerve Injury

Sciatic nerve injury (SNI) leads to sensory and motor dysfunctions. Nobiletin is a major component of polymethoxylated flavonoid extracted from citrus fruits. The role of nobiletin on sciatic nerve regeneration is still unclear. Thus, the purpose of this study was to investigate whether nobiletin increases DRG neurite elongation and regeneration-related protein expression after SNI. Cytotoxicity of nobiletin was measured in a concentration–dependent manner using the MTT assay. For an in vitro primary cell culture, the sciatic nerve on the middle thigh was crushed by holding twice with forceps. Dorsal root ganglion (DRG) and Schwann cells were cultured 3 days after SNI and harvested 36 h later and 3 days later, respectively. In order to evaluate specific regeneration-related markers and axon growth in the injured sciatic nerve, we applied immunofluorescence staining and Western blot techniques. Nobiletin increased cell viability in human neuroblastoma cells and inhibited cytotoxicity induced by exposure to H₂O₂. Mean neurite length of DRG neurons was significantly increased in the nobiletin group at a dose of 50 and 100 μM compared to those at other concentrations. GAP-43, a specific marker for axonal regeneration, was enhanced in injury preconditioned Schwann cells with nobiletin treatment and nobiletin significantly upregulated it in injured sciatic nerve at only 3 days post crush (dpc). In addition, nobiletin dramatically facilitated axonal regrowth via activation of the BDNF-ERK1/2 and AKT pathways. These results should provide evidence to distinguish more accurately the biochemical mechanisms regarding nobiletin-activated sciatic nerve regeneration.

Bone Marrow Mesenchymal Stem Cell Condition Medium Loaded on PCL Nanofibrous Scaffold Promoted Nerve Regeneration After Sciatic Nerve Transection in Male Rats

Nowadays, researchers pay a vast deal of attention to neural tissue regeneration due to its tremendous effect on the patient's life. There are many strategies, from using conventional autologous nerve grafts to the newly developed methods for reconstructing damaged nerves. Among the various therapeutic methods, incorporating highly potent biomolecules and growth factors, the damaged nerve site would promote nerve regeneration. The aim was to examine the efficiency of a mesenchymal stem cell condition medium (MSC-CM) loaded on a 3D-polycaprolactone (PCL) scaffold as a nerve conduit in an axotomy rat model. Twenty-four mature male rats were classified into four groups: controls (the animals of this group were intact), axotomy (10 mm piece of the nerve was removed), axotomy (10-mm piece of the nerve was removed) + scaffold, and axotomy (10-mm piece of the nerve was removed) + MSC-CM-loaded scaffold. We followed up nerve motor function using a sciatic function index and electromyography activity of the gastrocnemius muscle. At 12 weeks post axotomy, sciatic nerve and dorsal root ganglion specimens and L4 and L5 spinal cord segments were separated from the rats and were analyzed by stereological, immunohistochemistry, and RT-PCR procedures. The rats of the axotomy group presented the expected gross locomotor deficit. Stereological parameters, immunohistochemistry of GFAP, and gene expression of S100, NGF, and BDNF were significantly enhanced in the CM-loaded scaffold group compared with the axotomy group. The most observed similarity was noted between the results of the control group and the CM-loaded scaffold group. Our results support the potential applicability of MSC-CM-loaded PCL nanofibrous scaffold to treat peripheral nerve injury (PNI).

Insulin Promotes Schwann-Like Cell Differentiation of Rat Epidermal Neural Crest Stem Cells

Schwann cells (SCs) are considered potentially attractive candidates for transplantation therapies in neurodegenerative diseases. However, problems arising from the isolation and expansion of the SCs restrict their clinical applications. Establishing an alternative Schwann-like cell type is a prerequisite. Epidermal neural crest stem cells (EPI-NCSCs) are well studied for their autologous accessibility, along with the ability to produce major neural crest derivatives and neurotrophic factors. In the current study, we explored insulin influence, a well-known growth factor, on directing EPI-NCSCs into the Schwann cell (SC) lineage. EPI-NCSCs were isolated from rat hair bulge explants. The viability of cells treated with a range of insulin concentrations (0.05-100 μg/ml) was defined by MTT assay at 24, 48, and 72 h. The gene expression profiles of neurotrophic factors (BDNF, FGF-2, and IL-6), key regulators involved in the development of SC (EGR-1, SOX-10, c-JUN, GFAP, OCT-6, EGR-2, and MBP), and oligodendrocyte (PDGFR-α and NG-2) were quantified 1 and 9 days post-treatment with 0.05 and 5 μg/ml insulin. Furthermore, the protein expression of nestin (stemness marker), SOX-10, PDGFR-α, and MBP was analyzed following the long-term insulin treatment. Insulin downregulated the early-stage SC differentiation marker (EGR-1) and increased neurotrophins (BDNF and IL-6) and pro-myelinating genes, including OCT-6, SOX-10, EGR-2, and MBP, as well as oligodendrocyte differentiation markers, upon exposure for 9 days. Insulin can promote EPI-NCSC differentiation toward SC lineage and possibly oligodendrocytes. Thus, employing insulin might enhance the EPI-NCSCs efficiency in cell transplantation strategies.

Growth factors-based therapeutic strategies and their underlying signaling mechanisms for peripheral nerve regeneration

Peripheral nerve injury (PNI), one of the most common concerns following trauma, can result in a significant loss of sensory or motor function. Restoration of the injured nerves requires a complex cellular and molecular response to rebuild the functional axons so that they can accurately connect with their original targets. However, there is no optimized therapy for complete recovery after PNI. Supplementation with exogenous growth factors (GFs) is an emerging and versatile therapeutic strategy for promoting nerve regeneration and functional recovery. GFs activate the downstream targets of various signaling cascades through binding with their corresponding receptors to exert their multiple effects on neurorestoration and tissue regeneration. However, the simple administration of GFs is insufficient for reconstructing PNI due to their short half‑life and rapid deactivation in body fluids. To overcome these shortcomings, several nerve conduits derived from biological tissue or synthetic materials have been developed. Their good biocompatibility and biofunctionality made them a suitable vehicle for the delivery of multiple GFs to support peripheral nerve regeneration. After repairing nerve defects, the controlled release of GFs from the conduit structures is able to continuously improve axonal regeneration and functional outcome. Thus, therapies with growth factor (GF) delivery systems have received increasing attention in recent years. Here, we mainly review the therapeutic capacity of GFs and their incorporation into nerve guides for repairing PNI. In addition, the possible receptors and signaling mechanisms of the GF family exerting their biological effects are also emphasized.

Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse-Associated Cavernous Nerve Regeneration

BACKGROUND

Neurogenic erectile dysfunction (ED) is often refractory to treatment because of insufficient functional nerve recovery after injury or insult. Noninvasive mechano-biological intervention, such as microenergy acoustic pulse (MAP), low-intensity pulsed ultrasound, and low-intensity extracorporeal shockwave treatment, is an optimal approach to stimulate nerve regeneration.

AIM

To establish a new model in vitro to simulate nerve injury in neurogenic ED and to explore the mechanisms of MAP in vitro.

METHODS

Sprague-Dawley rats were used to isolate Schwann cells (SCs), major pelvic ganglion (MPG), and cavernous nerve with MPG (CN/MPG). SCs were then treated with MAP (0.033 mJ/mm², 1 Hz, 100 pulses), and SC exosomes were isolated. The MPG and CN/MPG were treated with MAP (0.033 mJ/mm², 1 Hz) at different dosages (25, 50, 100, 200, or 300 pulses) or exosomes derived from MAP-treated SCs in vitro.

OUTCOMES

Neurite growth from the MPG fragments and CN was photographed and measured. Expression of neurotropic factors (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) was checked.

RESULTS

Neurite outgrowth from MPG and CN/MPG was enhanced by MAP in a dosage response manner, peaking at 100 pulses. MAP promoted SC proliferation, neurotropic factor (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) expression, and exosome secretion. SC-derived exosomes significantly enhanced neurite outgrowth from MPG in vitro.

CLINICAL IMPLICATIONS

MAP may have utility in the treatment of neurogenic ED by SC-derived exosomes.

STRENGTH & LIMITATIONS

We confirmed that MAP enhances penile nerve regeneration through exsomes. Limitations of this study include that our study did not explore the exact mechanisms of how MAP increases SC exosome secretion nor whether MAP modulates the content of exosomes.

CONCLUSION

This study revealed that neurite outgrowth from MPG was enhanced by MAP and by SC-derived exosomes which were isolated after MAP treatment. Our findings indicate that one mechanism by which MAP induces nerve regeneration is by stimulation of SCs to secrete exosomes. Peng D, Reed-Maldonado AB, Zhou F, et al. Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse-Associated Cavernous Nerve Regeneration. J Sex Med 2020;17:1618-1628.

Self-assembling peptide hydrogels functionalized with LN- and BDNF- mimicking epitopes synergistically enhance peripheral nerve regeneration

The regenerative capacity of the peripheral nervous system is closely related to the role that Schwann cells (SCs) play in construction of the basement membrane containing multiple extracellular matrix proteins and secretion of neurotrophic factors, including laminin (LN) and brain-derived neurotrophic factor (BDNF). Here, we developed a self-assembling peptide (SAP) nanofiber hydrogel based on self-assembling backbone Ac-(RADA)4-NH2 (RAD) dual-functionalized with laminin-derived motif IKVAV (IKV) and a BDNF-mimetic peptide epitope RGIDKRHWNSQ (RGI) for peripheral nerve regeneration, with the hydrogel providing a three-dimensional (3D) microenvironment for SCs and neurites. Methods: Circular dichroism (CD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the secondary structures, microscopic structures, and morphologies of self-assembling nanofiber hydrogels. Then the SC adhesion, myelination and neurotrophin secretion were evaluated on the hydrogels. Finally, the SAP hydrogels were injected into hollow chitosan tubes to bridge a 10-mm-long sciatic nerve defect in rats, and in vivo gene expression at 1 week, axonal regeneration, target muscular re-innervation, and functional recovery at 12 weeks were assessed. Results: The bioactive peptide motifs were covalently linked to the C-terminal of the self-assembling peptide and the functionalized peptides could form well-defined nanofibrous hydrogels capable of providing a 3D microenvironment similar to native extracellular matrix. SCs displayed improved cell adhesion on hydrogels with both IKV and RGI, accompanied by increased cell spreading and elongation relative to other groups. RSCs cultured on hydrogels with IKV and RGI showed enhanced gene expression of NGF, BDNF, CNTF, PMP22 and NRP2, and decreased gene expression of NCAM compared with those cultured on other three groups after a 7-day incubation. Additionally, the secretion of NGF, BDNF, and CNTF of RSCs was significantly improved on dual-functionalized peptide hydrogels after 3 days. At 1 week after implantation, the expressions of neurotrophin and myelin-related genes in the nerve grafts in SAP and Autograft groups were higher than that in Hollow group, and the expression of S100 in groups containing both IKV and RGI was significantly higher than that in groups containing either IKV or RGI hydrogels, suggesting enhanced SC proliferation. The morphometric parameters of the regenerated nerves, their electrophysiological performance, the innervated muscle weight and remodeling of muscle fibers, and motor function showed that RAD/IKV/RGI and RAD/IKV-GG-RGI hydrogels could markedly improve axonal regeneration with enhanced re-myelination and motor functional recovery through the synergetic effect of IKV and RGI functional motifs. Conclusions: We found that the dual-functionalized SAP hydrogels promoted RSC adhesion, myelination, and neurotrophin secretion in vitro and successfully bridged a 10-mm gap representing a sciatic nerve defect in rats in vivo. The results demonstrated the synergistic effect of IKVAV and RGI on axonal regrowth and function recovery after peripheral nerve injury.

EEF1A1 deacetylation enables transcriptional activation of remyelination

Remyelination of the peripheral and central nervous systems (PNS and CNS, respectively) is a prerequisite for functional recovery after lesion. However, this process is not always optimal and becomes inefficient in the course of multiple sclerosis. Here we show that, when acetylated, eukaryotic elongation factor 1A1 (eEF1A1) negatively regulates PNS and CNS remyelination. Acetylated eEF1A1 (Ac-eEF1A1) translocates into the nucleus of myelinating cells where it binds to Sox10, a key transcription factor for PNS and CNS myelination and remyelination, to drag Sox10 out of the nucleus. We show that the lysine acetyltransferase Tip60 acetylates eEF1A1, whereas the histone deacetylase HDAC2 deacetylates eEF1A1. Promoting eEF1A1 deacetylation maintains the activation of Sox10 target genes and increases PNS and CNS remyelination efficiency. Taken together, these data identify a major mechanism of Sox10 regulation, which appears promising for future translational studies on PNS and CNS remyelination.

The molecular mechanisms regulating remyelination are unclear. Here, the authors show that promoting deacetylation of eEF1A1 prevents the translocation of Sox10 outside the nucleus, contributing to maintaining the expression of Sox10 target genes and increasing remyelination efficiency.

Exendin-4 Promotes Schwann Cell Proliferation and Migration via Activating the Jak-STAT Pathway after Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a common clinical disease that causes the partial loss of segmental exercise and sensory and autonomic nervous function, placing a heavy burden on patients and their families. A previous study confirmed that exendin-4 can effectively improve nerve regeneration and functional recovery after PNI. However, the specific mechanisms by which exendin-4-mediates this repair have not been clarified. To explore the mechanism of exendin-4 in the treatment of PNI, we used microarray analysis to detect gene expression in the distal segment of the sciatic nerve after sciatic injury. Bioinformatics analyses were used to predict the roles of differentially expressed genes (DEGs) in nerve damage repair. Schwann cells (SCs) were cultured, and we verified the molecular mechanism of exendin-4 in SCs and the effect of exendin-4 on peripheral nerve regeneration through in vitro molecular biology and cell biology experiments. In vivo, exendin-4 could significantly promote peripheral nerve regeneration. A total of 180 DEGs between the exendin-4 group and the control group were detected. Bioinformatics analysis indicated that these DEGs were mainly enriched in the Jak-STAT signaling pathway. In vitro, exendin-4 could significantly promote the proliferation and migration of SCs by activating the Jak-STAT pathway, which promoted peripheral nerve regeneration. Our results indicate that exendin-4 promotes SC proliferation, migration and nerve regeneration after PNI by activating the Jak-STAT pathway. Our findings provide a basis and direction for further elucidation of the mechanisms of exendin-4 in the repair of PNI and provide a new way to treat PNI.

Neuroprotective effects of leptin on cerebral ischemia through JAK2/STAT3/PGC-1-mediated mitochondrial function modulation

Neuroprotective effects of leptin have been shown in mouse model of cerebral ischemia/reperfusion injury and primary cortical neuronal culture with oxygen-glucose deprivation (OGD), while the underlying mechanisms are less understood. In the present study, we investigated whether leptin modulated mitochondrial function through JAK2/STAT3 in vivo mouse model of transient middle cerebral artery occlusion (MCAO) and in OGD-challenged primary neuronal cultures. JAK2/STAT3; mitochondrial biogenesis markers (PGC-1α); and apoptosis-associated proteins (caspase-3, BCL-2, BCL-XL, and cytochrome c) were detected by western blotting and reverse transcription-polymerase chain reaction at 1 h before and after ischemia/reperfusion. P-STAT3 and PGC-1α in neurons and astrocytes were detected. Moreover, mitochondrial morphology of the ischemic ipsilateral penumbra is examined using transmission electron microscopy. Primary cerebral cortical neurons were evaluated for viability, mitochondrial membrane potential (MMP), and apoptosis to assess whether dose-dependent neuroprotective effects of leptin during OGD were mitigated by the JAK2/STAT3 inhibitor AG490. Leptin activated JAK2/STAT3 signaling in neurons and astrocytes distributed in the ischemic ipsilateral penumbra, with peak p-STAT3 levels observed at 1 h after reperfusion. Leptin increased PGC-1α, BCL-2, and BCL-XL protein levels, cell viability, and MMP and decreased apoptosis both in vitro and in vivo; these effects were reversed by AG490 treatment. Our findings suggest that leptin-mediated neuroprotective effects in tMCAO may peak at 1 h to induce the transcription of its target gene PGC-1α, stabilization of MMP, inhibition of mitochondrial permeability transition pore opening, release of cytochrome c, and apoptosis.

Modern Trends for Peripheral Nerve Repair and Regeneration: Beyond the Hollow Nerve Guidance Conduit

Peripheral nerve repair and regeneration remains among the greatest challenges in tissue engineering and regenerative medicine. Even though peripheral nerve injuries (PNIs) are capable of some degree of regeneration, frail recovery is seen even when the best microsurgical technique is applied. PNIs are known to be very incapacitating for the patient, due to the deprivation of motor and sensory abilities. Since there is no optimal solution for tackling this problem up to this day, the evolution in the field is constant, with innovative designs of advanced nerve guidance conduits (NGCs) being reported every day. As a basic concept, a NGC should act as a physical barrier from the external environment, concomitantly acting as physical guidance for the regenerative axons across the gap lesion. NGCs should also be able to retain the naturally released nerve growth factors secreted by the damaged nerve stumps, as well as reducing the invasion of scar tissue-forming fibroblasts to the injury site. Based on the neurobiological knowledge related to the events that succeed after a nerve injury, neuronal subsistence is subjected to the existence of an ideal environment of growth factors, hormones, cytokines, and extracellular matrix (ECM) factors. Therefore, it is known that multifunctional NGCs fabricated through combinatorial approaches are needed to improve the functional and clinical outcomes after PNIs. The present work overviews the current reports dealing with the several features that can be used to improve peripheral nerve regeneration (PNR), ranging from the simple use of hollow NGCs to tissue engineered intraluminal fillers, or to even more advanced strategies, comprising the molecular and gene therapies as well as cell-based therapies.

Functional polymeric nerve guidance conduits and drug delivery strategies for peripheral nerve repair and regeneration

Peripheral nerve injuries can be extremely debilitating, resulting in sensory and motor loss-of-function. Endogenous repair is limited to non-severe injuries in which transection of nerves necessitates surgical intervention. Traditional treatment approaches include the use of biological grafts and alternative engineering approaches have made progress. The current article serves as a comprehensive, in-depth perspective on peripheral nerve regeneration, particularly nerve guidance conduits and drug delivery strategies. A detailed background of peripheral nerve injury and repair pathology, and an in-depth look into augmented nerve regeneration, nerve guidance conduits, and drug delivery strategies provide a state-of-the-art perspective on the field.

Peripheral Nerve Conduit: Materials and Structures

Peripheral nerve injuries (PNIs) are the most common injury types to affect the nervous system. Restoration of nerve function after PNI is a challenging medical issue. Extended gaps in transected peripheral nerves are only repaired using autologous nerve grafting. This technique, however, in which nerve tissue is harvested from a donor site and grafted onto a recipient site in the same body, has many limitations and disadvantages. Recent studies have revealed artificial nerve conduits as a promising alternative technique to substitute autologous nerves. This Review summarizes different types of artificial nerve grafts used to repair peripheral nerve injuries. These include synthetic and natural polymers with biological factors. Then, desirable properties of nerve guides are discussed based on their functionality and effectiveness. In the final part of this Review, fabrication methods and commercially available nerve guides are described.

The advances in nerve tissue engineering: From fabrication of nerve conduit to in vivo nerve regeneration assays

Peripheral nerve damage is a common clinical complication of traumatic injury occurring after accident, tumorous outgrowth, or surgical side effects. Although the new methods and biomaterials have been improved recently, regeneration of peripheral nerve gaps is still a challenge. These injuries affect the quality of life of the patients negatively. In the recent years, many efforts have been made to develop innovative nerve tissue engineering approaches aiming to improve peripheral nerve treatment following nerve injuries. Herein, we will not only outline what we know about the peripheral nerve regeneration but also offer our insight regarding the types of nerve conduits, their fabrication process, and factors associated with conduits as well as types of animal and nerve models for evaluating conduit function. Finally, nerve regeneration in a rat sciatic nerve injury model by nerve conduits has been considered, and the main aspects that may affect the preclinical outcome have been discussed.

Biodelivery of nerve growth factor and gold nanoparticles encapsulated in chitosan nanoparticles for schwann-like cells differentiation of human adipose-derived stem cells

The constant release of neurotrophic factors through a nanomaterial-based delivery system can be an important strategy in medical and pharmaceutical fields for nerve tissue engineering. The present study was aimed at encapsulating NGF and AuNPs in chitosan nanoparticles (NGF-CNPs and AuNPs-CSNPs) and its evaluation on the differentiation potential of human adipose-derived stem cells (h-ADSCs) to Schwann-like cells. The NGF-CNPs were prepared by ionotropic gelation method with tripolyphosphate (TPP) as a crosslinker. After synthesis and characterization of nanoparticles, NGF encapsulation efficiency and release profile were observed by Bradford assay. Next, the effects of NGF-CSNPs and AuNPs-CSNPs on h-ADSCs survival were assessed through MTT assay. Also, the efficacy of Schwann-like cells differentiation was assessed by immunocytochemistry and real-time RT-PCR for S100β and MBP markers. NGF encapsulation efficiency was found about 85% and controlled and sustained release of NGF was observed during 7 days in vitro (74.63 ± 2.07%). The findings revealed that these nanoparticles are cytocompatible. The immunocytochemical analysis indicated that NGF-CSNPs and AuNPs-CSNPs could significantly increase the differentiated rate and myelinogenic potential of Schwann-like cells (p < 0.05). Besides, the expression level of GFAP, S100β, and MBP demonstrated significant upregulation in NGF-CSNPs and AuNPs-CSNPs groups compared to the control group (p < 0.05). Hence, it can be proposed that NGF-CNPs and AuNPs-CSNPs are capable of controlled release with improving the ability of h-ADSCs differentiation to Schwann-like cells. Also, the results show the potential future application of this differentiation in nerve tissue regeneration.

Protective effects of leptin against cerebral ischemia/reperfusion injury

In recent years, the use of thrombolytic therapy for treating ischemia/reperfusion injury has resulted in damage to the self-regulatory mechanisms of the brain. This is due to the increased production of free radicals, excitatory amino acids and pro-inflammatory cytokines causing secondary damage to the brain. Simple thrombolytic therapy has not been the best approach for treating ischemia/reperfusion injury. Excessive perfusion leads to failure of the body's self-regulatory functions, which in turn increases the area of cerebral edema and aggravates cerebral ischemia. Previous studies have evaluated the satiety hormone leptin as a link between energy expenditure and obesity. Of note, leptin, which is involved in brain development, synaptic transmission and angiogenesis following ischemia/reperfusion injury, has been considered an important factor for treating ischemia/reperfusion injury. The present review outlines the discovery of leptin and discusses its association with cerebral ischemia/reperfusion.

Hierarchically aligned gradient collagen micropatterns for rapidly screening Schwann cells behavior

To penetrate the effect of protein gradient micropattern on peripheral nerve regeneration, the hierarchically aligned gradient collagen micropattern was prepared by micromoulding method and the influence on Schwann cells growth behavior was studied. The morphology, wettability, stability and component variation of the micropatterns were firstly characterized. Then, Schwann cells were cultured and the related mechanism was penetrated. The results showed that the gradient collagen micropattern could be well fabricated. The surface wettability varied with the change of collagen concentration, and the prepared gradient micropattern showed a good stability after PBS immersion for 15 days. The results of Schwann cells culture and morphological index analysis displayed that the prepared gradient collagen micropatten could well regulate the orientation growth of Schwann cells, while a much better cell alignment growth was obtained on the gradient micropattern with higher collagen concentration and wider pattern size. PCR and WB showed that the micropattern structure could effectively up-regulate the key specific genes for axon regeneration and myelination process. Overall, the study provides a systematic and facile method for understanding the effect of various sized micropatterns on cell behavior, which may have a great significance for the development of artificial implants for tissue engineering and regenerative medicine.

A potential treatment of low intensity pulsed ultrasound on cavernous nerve injury for erectile dysfunction

Erectile dysfunction after nerve injury is a common disease after radical prostatectomy. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, which plays an important role in the survival of existing neurons, the differentiation of new neurons, and synaptic plasticity. It has been demonstrated that low-intensity pulsed ultrasound (LIPUS) accelerates bone healing and axonal regeneration after injury. LIPUS may also be able to stimulate neuronal activity and enhance the levels of neurotrophic factors. Evidence suggests that elevated levels of BDNF in the brain have protective effects against neurodegenerative diseases. Previous studies have shown that the treatment on cavernous nerve injury repair, and protective effect plus neuro-regeneration effect by low-intensity pulsed ultrasound. They shared the similar mechanism including several trophic factors stimulation, Pl3K/akt pathway activation, and anti-fibrosis mechanism. We hypothesized that due to its combined neuroregenerative and protective effects, the non-invasive and easy-to-use method of LIPUS stimulation could have a therapeutic effect on erectile dysfunction stemming from cavernous nerve injury.

Stem cells purified from human induced pluripotent stem cell-derived neural crest-like cells promote peripheral nerve regeneration

Strategies for therapeutic cell transplantation have been assessed for use in the treatment of massive peripheral nerve defects. To support safe and efficient cell transplantation, we have focused on the purification of cells using cell surface markers. Our group previously reported low-affinity nerve growth factor receptor (LNGFR)- and thymocyte antigen-1 (THY-1)-positive neural crest-like cells (LT-NCLCs), generated from human induced pluripotent stem cells (hiPSCs). In the present study, we investigated the efficacy of transplantation of hiPSC-derived LT-NCLCs in a murine massive peripheral nerve defect model. Animals with a sciatic nerve defect were treated with a bridging silicone tube prefilled with LT-NCLCs or medium in the transplantation (TP) and negative control (NC) groups, respectively. The grafted LT-NCLCs survived and enhanced myelination and angiogenesis, as compared to the NC group. Behavioral analysis indicated that motor functional recovery in the TP group was superior to that in the NC group, and similar to that in the autograft (Auto) group. LT-NCLCs promoted axonal regrowth and remyelination by Schwann cells. Transplantation of LT-NCLCs is a promising approach for nerve regeneration treatment of massive peripheral nerve defects.

Impaired Angiogenic Supportive Capacity and Altered Gene Expression Profile of Resident CD146+ Mesenchymal Stromal Cells Isolated from Hyperoxia-Injured Neonatal Rat Lungs

Bronchopulmonary dysplasia (BPD), the most common complication of extreme preterm birth, can be caused by oxygen-related lung injury and is characterized by impaired alveolar and vascular development. Mesenchymal stromal cells (MSCs) have lung protective effects. Conversely, BPD is associated with increased MSCs in tracheal aspirates. We hypothesized that endogenous lung (L-)MSCs are perturbed in a well-established oxygen-induced rat model mimicking BPD features. Rat pups were exposed to 21% or 95% oxygen from birth to postnatal day 10. On day 12, CD146⁺ L-MSCs were isolated and characterized according to the International Society for Cellular Therapy criteria. Epithelial and vascular repair potential were tested by scratch assay and endothelial network formation, respectively, immune function by mixed lymphocyte reaction assay. Microarray analysis was performed using the Affymetrix GeneChip and gene set enrichment analysis software. CD146⁺ L-MSCs isolated from rat pups exposed to hyperoxia had decreased CD73 expression and inhibited lung endothelial network formation. CD146⁺ L-MSCs indiscriminately promoted epithelial wound healing and limited T cell proliferation. Expression of potent antiangiogenic genes of the axonal guidance cue and CDC42 pathways was increased after in vivo hyperoxia, whereas genes of the anti-inflammatory Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and lung/vascular growth-promoting fibroblast growth factor (FGF) pathways were decreased. In conclusion, in vivo hyperoxia exposure alters the proangiogenic effects and FGF expression of L-MSCs. In addition, decreased CD73 and JAK/STAT expression suggests decreased immune function. L-MSC function may be perturbed and contribute to BPD pathogenesis. These findings may lead to improvements in manufacturing exogenous MSCs with superior repair capabilities.

Interplay of Brain-Derived Neurotrophic Factor and Cytokines in Schizophrenia

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and plays an important role in neuroplasticity, differentiation and survival of neurons, as well as their function. Neuroinflammation has been explored in the pathophysiology of many mental disorders, such as schizophrenia. Cytokines representing different types of immune responses have an impact on neurogenesis and BDNF expression. Cross-regulation of BDNF and cytokines is accomplished through several signalling pathways. Also, typical and atypical antipsychotic drugs variously modulate the expression of BDNF and serum levels of cytokines, which can possibly be used in evaluation of therapy effectiveness. Comorbidity of metabolic syndrome and atopic diseases has been considered in the context of BDNF and cytokines interplay in schizophrenia.

Drug Targets in Neurotrophin Signaling in the Central and Peripheral Nervous System

Neurotrophins are a family of proteins that play an important role in the regulation of the growth, survival, and differentiation of neurons in the central and peripheral nervous system. Neurotrophins were earlier characterized by their role in early development, growth, maintenance, and the plasticity of the nervous system during development, but recent findings also indicate their complex role during normal physiology in both neuronal and non-neuronal tissues. Therefore, it is important to recognize a deficiency in the expression of neurotrophins, a major factor driving the debilitating features of several neurologic and psychiatric diseases/disorders. On the other hand, overexpression of neurotrophins is well known to play a critical role in pathogenesis of chronic pain and afferent sensitization, underlying conditions such as lower urinary tract symptoms (LUTS)/disorders and osteoarthritis. The existence of a redundant receptor system of high-and low-affinity receptors accounts for the diverse, often antagonistic, effects of neurotrophins in neurons and non-neuronal tissues in a spatial and temporal manner. In addition, studies looking at bladder dysfunction because of conditions such as spinal cord injury and diabetes mellitus have found alterations in the levels of these neurotrophins in the bladder, as well as in sensory afferent neurons, which further opens a new avenue for therapeutic targets. In this review, we will discuss the characteristics and roles of key neurotrophins and their involvement in the central and periphery nervous system in both normal and diseased conditions.

Neurotrophically Induced Mesenchymal Progenitor Cells Derived from Induced Pluripotent Stem Cells Enhance Neuritogenesis via Neurotrophin and Cytokine Production

Adult tissue‐derived mesenchymal stem cells (MSCs) are known to produce a number of bioactive factors, including neurotrophic growth factors, capable of supporting and improving nerve regeneration. However, with a finite culture expansion capacity, MSCs are inherently limited in their lifespan and use. We examined here the potential utility of an alternative, mesenchymal‐like cell source, derived from induced pluripotent stem cells, termed induced mesenchymal progenitor cells (MiMPCs). We found that several genes were upregulated and proteins were produced in MiMPCs that matched those previously reported for MSCs. Like MSCs, the MiMPCs secreted various neurotrophic and neuroprotective factors, including brain‐derived neurotrophic factor (BDNF), interleukin‐6 (IL‐6), leukemia inhibitory factor (LIF), osteopontin, and osteonectin, and promoted neurite outgrowth in chick embryonic dorsal root ganglia (DRG) cultures compared with control cultures. Cotreatment with a pharmacological Trk‐receptor inhibitor did not result in significant decrease in MiMPC‐induced neurite outgrowth, which was however inhibited upon Jak/STAT3 blockade. These findings suggest that the MiMPC induction of DRG neurite outgrowth is unlikely to be solely dependent on BDNF, but instead Jak/STAT3 activation by IL‐6 and/or LIF is likely to be critical neurotrophic signaling pathways of the MiMPC secretome. Taken together, these findings suggest MiMPCs as a renewable, candidate source of therapeutic cells and a potential alternative to MSCs for peripheral nerve repair, in view of their ability to promote nerve growth by producing many of the same growth factors and cytokines as Schwann cells and signaling through critical neurotrophic pathways. stemcellstranslational Medicine2018;7:45–58

Low-Intensity Extracorporeal Shock Wave Therapy Enhances Brain-Derived Neurotrophic Factor Expression through PERK/ATF4 Signaling Pathway

Low-intensity extracorporeal shock wave therapy (Li-ESWT) is used in the treatment of erectile dysfunction, but its mechanisms are not well understood. Previously, we found that Li-ESWT increased the expression of brain-derived neurotrophic factor (BDNF). Here we assessed the underlying signaling pathways in Schwann cells in vitro and in penis tissue in vivo after nerve injury. The result indicated that BDNF were significantly increased by the Li-ESWT after nerve injury, as well as the expression of BDNF in Schwann cells (SCs, RT4-D6P2T) in vitro. Li-ESWT activated the protein kinase RNA-like endoplasmic reticulum (ER) kinase (PERK) pathway by increasing the phosphorylation levels of PERK and eukaryotic initiation factor 2a (eIF2α), and enhanced activating transcription factor 4 (ATF4) in an energy-dependent manner. In addition, GSK2656157—an inhibitor of PERK—effectively inhibited the effect of Li-ESWT on the phosphorylation of PERK, eIF2α, and the expression of ATF4. Furthermore, silencing ATF4 dramatically attenuated the effect of Li-ESWT on the expression of BDNF, but had no effect on hypoxia-inducible factor (HIF)1α or glial cell-derived neurotrophic factor (GDNF) in Schwann cells. In conclusion, our findings shed new light on the underlying mechanisms by which Li-ESWT may stimulate the expression of BDNF through activation of PERK/ATF4 signaling pathway. This information may help to refine the use of Li-ESWT to further improve its clinical efficacy.

Low-Dose Pulsatile Interleukin-6 As a Treatment Option for Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) remains one of the most common and serious complications of diabetes. Currently, pharmacological agents are limited to treating the pain associated with DPN, and do not address the underlying pathological mechanisms driving nerve damage, thus leaving a significant unmet medical need. Interestingly, research conducted using exercise as a treatment for DPN has revealed interleukin-6 (IL-6) signaling to be associated with many positive benefits such as enhanced blood flow and lipid metabolism, decreased chronic inflammation, and peripheral nerve fiber regeneration. IL-6, once known solely as a pro-inflammatory cytokine, is now understood to signal as a multifunctional cytokine, capable of eliciting both pro- and anti-inflammatory responses in a context-dependent fashion. IL-6 released from muscle in response to exercise signals as a myokine and as such has a unique kinetic profile, whereby levels are transiently elevated up to 100-fold and return to baseline levels within 4 h. Importantly, this kinetic profile is in stark contrast to long-term IL-6 elevation that is associated with pro-inflammatory states. Given exercise induces IL-6 myokine signaling, and exercise has been shown to elicit numerous beneficial effects for the treatment of DPN, a causal link has been suggested. Here, we discuss both the clinical and preclinical literature related to the application of IL-6 as a treatment strategy for DPN. In addition, we discuss how IL-6 may directly modulate Schwann and nerve cells to explore a mechanistic understanding of how this treatment elicits a neuroprotective and/or regenerative response. Collectively, studies suggest that IL-6, when administered in a low-dose pulsatile strategy to mimic the body's natural response to exercise, may prove to be an effective treatment for the protection and/or restoration of peripheral nerve function in DPN. This review highlights the studies supporting this assertion and provides rationale for continued investigation of IL-6 for the treatment of DPN.