Bone marrow mesenchymal stem cells upregulate PI3K/AKT pathway and down-regulate NF-κB pathway by secreting glial cell-derived neurotrophic factors to regulate microglial polarization and alleviate deafferentation pain in rats

Application of cell transplantation in the treatment of neuropathic pain

Nerve injury can not only lead to sensory and motor dysfunction, but also be complicated with neuropathic pain (NPP), which brings great psychosomatic injury to patients. At present, there is no effective treatment for NPP. Based on the functional characteristics of cell transplantation in nerve regeneration and injury repair, cell therapy has been used in the exploratory treatment of NPP and has become a promising treatment of NPP. In this article, we discuss the current mainstream cell types for the treatment of NPP, including Schwann cells, olfactory ensheathing cells, neural stem cells and mesenchymal stem cells in the treatment of NPP. These bioactive cells transplanted into the host have pharmacological properties of decreasing pain threshold and relieving NPP by exerting nutritional support, neuroprotection, immune regulation, promoting axonal regeneration, and remyelination. Cell transplantation can also change the microenvironment around the nerve injury, which is conducive to the survival of neurons. It can effectively relieve pain by repairing the injured nerve and rebuilding the nerve function. At present, some preclinical and clinical studies have shown that some encouraging results have been achieved in NPP treatment based on cell transplantation. Therefore, we discussed the feasible strategy of cell transplantation as a treatment of NPP and the problems and challenges that need to be solved in the current application of cell transplantation in NPP therapy.

Bone marrow mesenchymal stem cells in treatment of peripheral nerve injury

Peripheral nerve injury (PNI) is a common neurological disorder and complete functional recovery is difficult to achieve. In recent years, bone marrow mesenchymal stem cells (BMSCs) have emerged as ideal seed cells for PNI treatment due to their strong differentiation potential and autologous transplantation ability. This review aims to summarize the molecular mechanisms by which BMSCs mediate nerve repair in PNI. The key mechanisms discussed include the differentiation of BMSCs into multiple types of nerve cells to promote repair of nerve injury. BMSCs also create a microenvironment suitable for neuronal survival and regeneration through the secretion of neurotrophic factors, extracellular matrix molecules, and adhesion molecules. Additionally, BMSCs release pro-angiogenic factors to promote the formation of new blood vessels. They modulate cytokine expression and regulate macrophage polarization, leading to immunomodulation. Furthermore, BMSCs synthesize and release proteins related to myelin sheath formation and axonal regeneration, thereby promoting neuronal repair and regeneration. Moreover, this review explores methods of applying BMSCs in PNI treatment, including direct cell transplantation into the injured neural tissue, implantation of BMSCs into nerve conduits providing support, and the application of genetically modified BMSCs, among others. These findings confirm the potential of BMSCs in treating PNI. However, with the development of this field, it is crucial to address issues related to BMSC therapy, including establishing standards for extracting, identifying, and cultivating BMSCs, as well as selecting application methods for BMSCs in PNI such as direct transplantation, tissue engineering, and genetic engineering. Addressing these issues will help translate current preclinical research results into clinical practice, providing new and effective treatment strategies for patients with PNI.

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

FAM76B regulates PI3K/Akt/NF-κB-mediated M1 macrophage polarization by influencing the stability of PIK3CD mRNA

Macrophage polarization is closely related to inflammation development, yet how macrophages are polarized remains unclear. In our study, the number of M1 macrophages was markedly increased in Fam76b knockout U937 cells vs. wild-type U937 cells, and FAM76B expression was decreased in M1 macrophages induced from different sources of macrophages. Moreover, Fam76b knockout enhanced the mRNA and protein levels of M1 macrophage-associated marker genes. These results suggest that FAM76B inhibits M1 macrophage polarization. We then further explored the mechanism by which FAM76B regulates macrophage polarization. We found that FAM76B can regulate PI3K/Akt/NF-κB pathway-mediated M1 macrophage polarization by stabilizing PIK3CD mRNA. Finally, FAM76B was proven to protect against inflammatory bowel disease (IBD) by inhibiting M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vivo. In summary, FAM76B regulates M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vitro and in vivo, which may inform the development of future therapeutic strategies for IBD and other inflammatory diseases.

Modulating the polarization phenotype of microglia - A valuable strategy for central nervous system diseases

Central nervous system (CNS) diseases have become one of the leading causes of death in the global population. The pathogenesis of CNS diseases is complicated, so it is important to find the patterns of the disease to improve the treatment strategy. Microglia are considered to be a double-edged sword, playing both harmful and beneficial roles in CNS diseases. Therefore, it is crucial to understand the progression of the disease and the changes in the polar phenotype of microglia to provide guidance in the treatment of CNS diseases. Microglia activation may evolve into different phenotypes: M1 and M2 types. We focused on the roles that M1 and M2 microglia play in regulating intercellular dialogues, pathological reactions and specific diseases in CNS diseases. Importantly, we summarized the strategies used to modulate the polarization phenotype of microglia, including traditional pharmacological modulation, biological therapies, and physical strategies. This review will contribute to the development of potential strategies to modulate microglia polarization phenotypes and provide new alternative therapies for CNS diseases.

Advances in Stem Cell-Based Therapies in the Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic, degenerative joint disease presenting a significant global health threat. While current therapeutic approaches primarily target symptom relief, their efficacy in repairing joint damage remains limited. Recent research has highlighted mesenchymal stem cells (MSCs) as potential contributors to cartilage repair, anti-inflammatory modulation, and immune regulation in OA patients. Notably, MSCs from different sources and their derivatives exhibit variations in their effectiveness in treating OA. Moreover, pretreatment and gene editing techniques of MSCs can enhance their therapeutic outcomes in OA. Additionally, the combination of novel biomaterials with MSCs has shown promise in facilitating the repair of damaged cartilage. This review summarizes recent studies on the role of MSCs in the treatment of OA, delving into their advantages and exploring potential directions for development, with the aim of providing fresh insights for future research in this critical field.

The effect of different sources of mesenchymal stem cells on microglia states

Microglial reaction plays a key role in the prognosis of traumatic CNS injuries (TBI and SCI). A growing number of studies have shown that mesenchymal stem cells (MSCs) play an important role in regulating microglial states. This review summarizes the effects and mechanisms of different sources of MSCs on microglial states in the last 5 years. In general, bone marrow-derived mesenchymal stem cells are the most accessible and widely used, and can produce immunosuppressive effects on a variety of brain injuries including TBI through tissue engineering in situ implantation; MSCs mainly regulate inflammatory pathways and promote the states of microglia in the anti-inflammatory direction, which also secrete certain cytokines or extracellular vesicles to affect apoptotic pathways, such as the extracellular vesicles miR-21-5p, acting as a neuronal protector.

Exosomes-loaded electroconductive nerve dressing for nerve regeneration and pain relief against diabetic peripheral nerve injury

Over the years, electroconductive hydrogels (ECHs) have been extensively applied for stimulating nerve regeneration and restoring locomotor function after peripheral nerve injury (PNI) with diabetes, given their favorable mechanical and electrical properties identical to endogenous nerve tissue. Nevertheless, PNI causes the loss of locomotor function and inflammatory pain, especially in diabetic patients. It has been established that bone marrow stem cells-derived exosomes (BMSCs-Exos) have analgesic, anti-inflammatory and tissue regeneration properties. Herein, we designed an ECH loaded with BMSCs-Exos (ECH-Exos) electroconductive nerve dressing to treat diabetic PNI to achieve functional recovery and pain relief. Given its potent adhesive and self-healing properties, this laminar dressing is convenient for the treatment of damaged nerve fibers by automatically wrapping around them to form a size-matched tube-like structure, avoiding the cumbersome implantation process. Our in vitro studies showed that ECH-Exos could facilitate the attachment and migration of Schwann cells. Meanwhile, Exos in this system could modulate M2 macrophage polarization via the NF-κB pathway, thereby attenuating inflammatory pain in diabetic PNI. Additionally, ECH-Exos enhanced myelinated axonal regeneration via the MEK/ERK pathway in vitro and in vivo, consequently ameliorating muscle denervation atrophy and further promoting functional restoration. Our findings suggest that the ECH-Exos system has huge prospects for nerve regeneration, functional restoration and pain relief in patients with diabetic PNI.

Bibliometric and visual analysis of microglia-related neuropathic pain from 2000 to 2021

Background

Microglia has gradually gained researchers' attention in the past few decades and has shown its promising prospect in treating neuropathic pain. Our study was performed to comprehensively evaluate microglia-related neuropathic pain via a bibliometric approach.

Methods

We retrospectively reviewed publications focusing on microglia-related neuropathic pain from 2000 to 2021 in WoSCC. VOS viewer software and CiteSpace software were used for statistical analyses.

Results

A total of 2,609 articles were finally included. A steady increase in the number of relevant publications was observed in the past two decades. China is the most productive country, while the United States shares the most-cited and highest H-index country. The University of London, Kyushu University, and the University of California are the top 3 institutions with the highest number of publications. Molecular pain and Pain are the most productive and co-cited journals, respectively. Inoue K (Kyushu University) is the most-contributed researcher and Ji RR (Duke University) ranks 1st in both average citations per article and H-index. Keywords analyses revealed that pro-inflammatory cytokines shared the highest burst strength. Sex differences, neuroinflammation, and oxidative stress are the emerging keywords in recent years.

Conclusion

In the field of microglia-related neuropathic pain, China is the largest producer and the United States is the most influential country. The signaling communication between microglia and neurons has continued to be vital in this field. Sexual dimorphism, neuroinflammation, and stem-cell therapies might be emerging trends that should be closely monitored.

Bone marrow mesenchymal stem cells alleviate stress-induced hyperalgesia via restoring gut microbiota and inhibiting neuroinflammation in the spinal cord by targeting the AMPK/NF-κB signaling pathway

Aim Spinal neuroinflammation contributes to the mechanism of stress-induced hyperalgesia (SIH). Recent research has demonstrated that bone marrow mesenchymal stem cells (BMSCs) alleviate chronic pain. However, what remains unidentified is whether BMSCs could improve hyperalgesia induced by chronic restraint stress (CRS). In another dimension, our previous study proved that gut microbiota played an important role in CRS-induced hyperalgesia in mice. Yet, whether BMSCs treatments change gut microbiota composition in CRS mice remains unexplored.

MAIN METHODS

Mechanical allodynia and thermal hyperalgesia were used to assess pain behavior. Composition of fecal samples were verified by 16S rRNA analysis. Western blot was used to investigate the expression of adenosine monophosphate-activated protein kinase (AMPK)/ nuclear factor kappa B (NF-κB) signaling pathway, pro-inflammatory cytokines [interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), IL-6], and the markers of microglia and astrocytes. The morphology of glia cells was evaluated by immunofluorescence staining.

KEY FINDINGS

CRS down-regulated phosphorylated AMPK (p-AMPK), up-regulated phosphorylated NF-κB p65 (p-NF-κB p65), activated microglia and astrocytes and promoted the secretion of IL-1β, TNF-α and IL-6 in the spinal cord. BMSCs alleviated CRS-induced hyperalgesia by inhibiting the activation of microglia and astrocytes and by reducing neuroinflammation via improving the disrupted AMPK/NF-κB pathway. Furthermore, BMSCs also raised the relative abundance of Muribaculaceae and Lachnospiraceae in CRS mice feces, which was significantly related to its effect of relieving hyperalgesia.

SIGNIFICANCE

Our results support that BMSCs could alleviate CRS-induced hyperalgesia by reducing AMPK/NF-κB-dependent neuroinflammation in the spinal cord and restoring the homeostasis of gut microbiota.

Cell therapy for neuropathic pain

Neuropathic pain (NP) is caused by a lesion or a condition that affects the somatosensory system. Pathophysiologically, NP can be ascribed to peripheral and central sensitization, implicating a wide range of molecular pathways. Current pharmacological and non-pharmacological approaches are not very efficacious, with over half of NP patients failing to attain adequate pain relief. So far, pharmacological and surgical treatments have focused primarily on symptomatic relief by modulating pain transduction and transmission, without treating the underlying pathophysiology. Currently, researchers are trying to use cell therapy as a therapeutic alternative for the treatment of NP. In fact, mounting pre-clinical and clinical studies showed that the cell transplantation-based therapy for NP yielded some encouraging results. In this review, we summarized the use of cell grafts for the treatment of NP caused by nerve injury, synthesized the latest advances and adverse effects, discussed the possible mechanisms to inform pain physicians and neurologists who are endeavoring to develop cell transplant-based therapies for NP and put them into clinical practice.

Astrocytic SARM1 promotes neuroinflammation and axonal demyelination in experimental autoimmune encephalomyelitis through inhibiting GDNF signaling

Astrocytes are important components of the innate immune response in the central nervous system (CNS), involving in the inflammatory and neurotoxic responses that occur in CNS diseases, such as multiple sclerosis (MS). Recent studies have shown that SARM1 plays a critical role in axonal degeneration and inflammation. However, the detailed role of astrocytic SARM1 in MS remains unclear. Here, we established the MS model of mice - experimental autoimmune encephalomyelitis (EAE) and found that SARM1 was upregulated in astrocytes of the spinal cords of EAE mice. Moreover, conditional knockout of astrocytic SARM1 (SARM1GFAP-CKO mice, SARM1Aldh1L1-CKO mice) delayed EAE with later onset, alleviated the inflammatory infiltration, and inhibited the demyelination and neuronal death. Mechanically, RNA-seq revealed that the expression of glial-derived neurotrophic factor (GDNF) was upregulated in SARM1-/- astrocytes. Western blot and immunostaining further confirmed the upregulation of GDNF in spinal cord astrocytes of SARM1GFAP-CKO EAE mice. Interestingly, the downregulation of GDNF by streptozotocin (STZ, a drug used to downregulate GDNF) treatment worsened the deficits of SARM1GFAP-CKO EAE mice. These findings identify that astrocytic SARM1 promotes neuroinflammation and axonal demyelination in EAE by inhibiting the expression of GDNF, reveal the novel role of SARM1/GDNF signaling in EAE, and provide new therapeutic ideas for the treatment of MS.

Activation of GDNF-ERK-Runx1 signaling contributes to P2X3R gene transcription and bone cancer pain

Bone cancer pain is a common symptom in cancer patients with bone metastases and its underlying mechanisms remain unknown. Here, we report that Runx1 directly upregulates the transcriptional activity of P2X3 receptor (P2X3R) gene promoter in PC12 cells. Knocking down Runx1 in dorsal root ganglion (DRG) neurons suppresses the functional upregulation of P2X3R, attenuates neuronal hyperexcitability and pain hypersensitivity in tumor-bearing rats, whereas overexpressing Runx1 promotes P2X3R gene transcription in DRG neurons, induces neuronal hyperexcitability and pain hypersensitivity in naïve rats. Activation of GDNF-GFRα1-Ret-ERK signaling is required for Runx1-mediated P2X3R gene transcription in DRG neurons, and contributes to neuronal hyperexcitability and pain hypersensitivity in tumor-bearing rats. These findings indicate that the Runx1-mediated P2X3R gene transcription resulted from activation of GDNF-GFRα1-Ret-ERK signaling contributes to the sensitization of DRG neurons and pathogenesis of bone cancer pain. Our findings identify a potentially targetable mechanism that may cause bone metastasis-associated pain in cancer patients.

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Runx1 directly upregulates the transcriptional activity of P2X3R gene promoter

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Upregulation of Runx1-mediated P2X3R gene transcription underlies bone cancer pain

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Involvement of GDNF-Ret-ERK signaling in Runx1-mediated P2X3R gene transcription

Mesenchymal stromal cell secretome for traumatic brain injury: Focus on immunomodulatory action

The severity and long-term consequences of brain damage in traumatic brain injured (TBI) patients urgently calls for better neuroprotective/neuroreparative strategies for this devastating disorder. Mesenchymal stromal cells (MSCs) hold great promise and have been shown to confer neuroprotection in experimental TBI, mainly through paracrine mechanisms via secreted bioactive factors (i.e. secretome), which indicates significant potential for a cell-free neuroprotective approach. The secretome is composed of cytokines, chemokines, growth factors, proteins, lipids, nucleic acids, metabolites, and extracellular vesicles; it may offer advantages over MSCs in terms of delivery, safety, and variability of therapeutic response for brain injury. Immunomodulation by molecular factors secreted by MSCs is considered to be a key mechanism involved in their multi-potential therapeutic effects. Regulated neuroinflammation is required for healthy remodeling of central nervous system during development and adulthood. Moreover, immune cells and their secreted factors can also contribute to tissue repair and neurological recovery following acute brain injury. However, a chronic and maladaptive neuroinflammatory response can exacerbate TBI and contribute to progressive neurodegeneration and long-term neurological impairments. Here, we review the evidence for MSC-derived secretome as a therapy for TBI. Our framework incorporates a detailed analysis of in vitro and in vivo studies investigating the effects of the secretome on clinically relevant neurological and histopathological outcomes. We also describe the activation of immune cells after TBI and the immunomodulatory properties exerted by mediators released in the secretome. We then describe how ageing modifies central and systemic immune responses to TBI and discuss challenges and opportunities of developing secretome based neuroprotective therapies for elderly TBI populations. Finally, strategies aimed at modulating the secretome in order to boost its efficacy for TBI will also be discussed.

Stem cell-based therapy for human diseases

Recent advancements in stem cell technology open a new door for patients suffering from diseases and disorders that have yet to be treated. Stem cell-based therapy, including human pluripotent stem cells (hPSCs) and multipotent mesenchymal stem cells (MSCs), has recently emerged as a key player in regenerative medicine. hPSCs are defined as self-renewable cell types conferring the ability to differentiate into various cellular phenotypes of the human body, including three germ layers. MSCs are multipotent progenitor cells possessing self-renewal ability (limited in vitro) and differentiation potential into mesenchymal lineages, according to the International Society for Cell and Gene Therapy (ISCT). This review provides an update on recent clinical applications using either hPSCs or MSCs derived from bone marrow (BM), adipose tissue (AT), or the umbilical cord (UC) for the treatment of human diseases, including neurological disorders, pulmonary dysfunctions, metabolic/endocrine-related diseases, reproductive disorders, skin burns, and cardiovascular conditions. Moreover, we discuss our own clinical trial experiences on targeted therapies using MSCs in a clinical setting, and we propose and discuss the MSC tissue origin concept and how MSC origin may contribute to the role of MSCs in downstream applications, with the ultimate objective of facilitating translational research in regenerative medicine into clinical applications. The mechanisms discussed here support the proposed hypothesis that BM-MSCs are potentially good candidates for brain and spinal cord injury treatment, AT-MSCs are potentially good candidates for reproductive disorder treatment and skin regeneration, and UC-MSCs are potentially good candidates for pulmonary disease and acute respiratory distress syndrome treatment.

Protective effects of CHIP overexpression and Wharton's jelly mesenchymal-derived stem cell treatment against streptozotocin-induced neurotoxicity in rats

Diabetic neuropathy is a common complication of diabetes mellitus, posing a challenge in treatment. Previous studies have indicated the protective role of mesenchymal stem cells against several disorders. Although they can repair nerve injury, their key limitation is that they reduce viability under stress conditions. We recently observed that overactivation of the carboxyl terminus of heat shock protein 70 (Hsp70) interacting protein (CHIP) considerably rescued cell viability under hyperglycemic stress and played an essential role in promoting the beneficial effects of Wharton's jelly-derived mesenchymal stem cells (WJMSCs). Thus, the present study was designed to unveil the protective effects of CHIP-overexpressing WJMSCs against neurodegeneration using in vivo animal model based study. In this study, western blotting observed that CHIP-overexpressing WJMSCs could rescue nerve damage observed in streptozotocin-induced diabetic rats by activating the AMPKα/AKT and PGC1α/SIRT1 signaling pathway. In contrast, these signaling pathways were downregulated upon silencing CHIP. Furthermore, CHIP-overexpressing WJMSCs inhibited inflammation induced in the brains of diabetic rats by suppressing the NF-κB, its downstream iNOS and cytokines signaling nexus and enhancing the antioxidant enzyme system. Moreover, TUNEL assay demonstrated that CHIP carrying WJMSCs suppressed the apoptotic cell death induced in STZ-induced diabetic group. Collectively, our findings suggests that CHIP-overexpressing WJMSCs might exerts beneficial effects, which may be considered as a therapeutic strategy against diabetic neuropathy complications.

IMT504 blocks allodynia in rats with spared nerve injury by promoting the migration of mesenchymal stem cells and by favoring an anti-inflammatory milieu at the injured nerve

ABSTRACT

IMT504, a noncoding, non-CpG oligodeoxynucleotide, modulates pain-like behavior in rats undergoing peripheral nerve injury, through mechanisms that remain poorly characterized. Here, we chose the spared nerve injury model in rats to analyze the contribution of mesenchymal stem cells (MSCs) in the mechanisms of action of IMT504. We show that a single subcutaneous administration of IMT504 reverses mechanical and cold allodynia for at least 5 weeks posttreatment. This event correlated with long-lasting increases in the percentage of MSCs in peripheral blood and injured sciatic nerves, in a process seemingly influenced by modifications in the CXCL12-CXCR4 axis. Also, injured nerves presented with reduced tumor necrosis factor-α and interleukin-1β and increased transforming growth factor-β1 and interleukin-10 protein levels. In vitro analysis of IMT504-pretreated rat or human MSCs revealed internalized oligodeoxynucleotide and confirmed its promigratory effects. Moreover, IMT504-pretreatment induced transcript expression of Tgf-β1 and Il-10 in MSCs; the increase in Il-10 becoming more robust after exposure to injured nerves. Ex vivo exposure of injured nerves to IMT504-pretreated MSCs confirmed the proinflammatory to anti-inflammatory switch observed in vivo. Interestingly, the sole exposure of injured nerves to IMT504 also resulted in downregulated Tnf-α and Il-1β transcripts. Altogether, we reveal for the first time a direct association between the antiallodynic actions of IMT504, its promigratory and cytokine secretion modulating effects on MSCs, and further anti-inflammatory actions at injured nerves. The recapitulation of key outcomes in human MSCs supports the translational potential of IMT504 as a novel treatment for neuropathic pain with a unique mechanism of action involving the regulation of neuroimmune interactions.

Human neural stem cells secretome inhibits lipopolysaccharide-induced neuroinflammation through modulating microglia polarization by activating PPAR-γ

Neuroinflammation is one of the typical events in multiple neurodegenerative diseases, whereas microglia are the critical participants in the pathogenesis of neuroinflammation. Several studies suggest that neural stem cells (NSCs) present immunomodulatory benefits due to their paracrine products, which contain mounting trophic factors. In the current study, the anti-inflammatory effects of neural stem cells secretome (NSC-S) on lipopolysaccharide (LPS)-induced neuroinflammatory models were evaluated in vivo and the underlying mechanism was further investigated in vitro. It was revealed that NSC-S significantly attenuated the severity of LPS-induced behaviour disorders and inflammatory response in mice. In vitro studies found that NSC-S significantly promoted the polarization of microglia from proinflammatory M1 to anti-inflammatory M2 phenotype, and reduced the production of proinflammatory cytokines while elevated anti-inflammatory cytokines in BV2 cells. NSC-S promoted peroxisome proliferator-activated receptor gamma (PPAR-γ) pathway activation. However, these effects of NSC-S were abrogated by PPAR-γ inhibitor GW9662. Notably, the fatty acid binding protein 5 (FABP5) in NSC-S may mediate PPAR-γ activation and inflammation remission. In summary, NSC-S promotes the regression of LPS-induced microglia-mediated inflammation through the PPAR-γ pathway. This function might be achieved via FABP5.

A Novel Progress: Glial Cells and Inflammatory Pain

Inflammatory pain is the perception of noxious stimuli that occurs during inflammation or an immune response. Glial cells are widespread in the central and peripheral nervous systems, supporting and guiding the migration of neurons, participating in the immune response, forming the myelin sheath and blood-brain barrier, and maintaining the concentration of potassium ions outside nerve cells. Recent studies have shown that glial cells have a significant connection with the production and development of inflammatory pain. This article reviews the relationship, mechanisms, therapeutic targets between five types of glial cells and inflammatory pain, and the medicine composition that can effectively inhibit inflammatory pain. It expands the study on the mechanism of glial cells regulating pain and provides new ideas for the therapy of inflammatory pain.

Immunomodulatory effects of mesenchymal stem cells in peripheral nerve injury

Various immune cells and cytokines are present in the aftermath of peripheral nerve injuries (PNI), and coordination of the local inflammatory response is of great significance for the recovery of PNI. Mesenchymal stem cells (MSCs) exhibit immunosuppressive and anti-inflammatory abilities which can accelerate tissue regeneration and attenuate inflammation, but the role of MSCs in the regulation of the local inflammatory microenvironment after PNI has not been widely studied. Here, we summarize the known interactions between MSCs, immune cells, and inflammatory cytokines following PNI with a focus on the immunosuppressive role of MSCs. We also discuss the immunomodulatory potential of MSC-derived extracellular vesicles as a new cell-free treatment for PNI.

Shaping the Microglia in Retinal Degenerative Diseases Using Stem Cell Therapy: Practice and Prospects

Retinal degenerative disease (RDD) refers to a group of diseases with retinal degeneration that cause vision loss and affect people's daily lives. Various therapies have been proposed, among which stem cell therapy (SCT) holds great promise for the treatment of RDDs. Microglia are immune cells in the retina that have two activation phenotypes, namely, pro-inflammatory M1 and anti-inflammatory M2 phenotypes. These cells play an important role in the pathological progression of RDDs, especially in terms of retinal inflammation. Recent studies have extensively investigated the therapeutic potential of stem cell therapy in treating RDDs, including the immunomodulatory effects targeting microglia. In this review, we substantially summarized the characteristics of RDDs and microglia, discussed the microglial changes and phenotypic transformation of M1 microglia to M2 microglia after SCT, and proposed future directions for SCT in treating RDDs.

Activation of Three Major Signaling Pathways After Endurance Training and Spinal Cord Injury

We aimed to investigate the effects of endurance training on expression of growth factors (GFs) and stimulation of neurotrophin-dependent signaling pathways (PI3k/Akt, PLCγ/PKC, PLCγ/CAMKII, Ras-Erk1/2 and Rac1-Cdc42) responsible for neuroplasticity, neuroregeneration, survival and growth after spinal cord injury (SCI). Wistar rats were divided into four groups: (i) intact controls; (ii) 6 weeks of endurance training; (iii) SCI; (iv) pre-training + SCI. The animals survived for 6 weeks after SCI. Firstly, endurance training markedly upregulated mRNA expression and protein levels (up to four times) of growth factors (BDNF, GDNF) and their receptors (TrkB, Gfrα) in low thoracic segments (Th8–Th10) compared to levels in untrained animals. Secondly, we found that spontaneous neuroplasticity seen in the SCI alone group was GF-specific and was activated through both PLCγ-PKC and PLC-CAMKII signaling pathways. In addition, training prior to SCI markedly increased the activity of PLCγ-PKC signaling at both transcript and protein levels at and around the lesion site. Similar effects were seen in expression of PI3k/Akt and Ras/Erk1/2 signaling responsible for cell survival and regeneration. Thirdly, rats which underwent physical activity prior to SCI were more active and had significantly better neurological scores at the 14th and 42nd days of survival. These results suggest that regular physical activity could play an important role after SCI, as it maintains increased expression of GFs in spinal cord tissue 6 weeks post-SCI. The BDNF- and/or BDNF + GDNF-dependent signaling pathways were significantly affected in pre-trained SCI animals. In contrast, GDNF-dependent Rac1-Cdc42 signaling was not involved in training-affected SCI response.

The Role of NF-κB/NLRP3 Inflammasome Signaling Pathway in Attenuating Pyroptosis by Melatonin Upon Spinal Nerve Ligation Models

Accumulated evidence has demonstrated causative links between neuropathic pain (NP) and immune-mediated inflammatory disorders. However, the role of inflammasome-induced pyroptosis in NP remains elusive. Melatonin possesses a well-documented analgesic action in various pain models. The current study aimed to test our hypothesis that melatonin regulated pyroptosis to alleviate NP by inhibiting NF-κB/NLRP3-dependent signaling. A rat model of spinal nerve ligation (SNL) was established to explore the potential association between melatonin and pyroptosis. Behavioral experiments revealed that SNL provoked severe allodynia which was suppressed by the administration of melatonin, a caspase-1 inhibitor (VX-765), or an NF-κB inhibitor (BAY 11-7085). SNL significantly up-regulated the inflammatory cytokines associated with the excessive activation of NLRP3 components and NF-κB signaling, as well as a marked pyroptosis activation. These effects were partially inhibited by melatonin, VX-765 or BAY 11-7085, and when melatonin and inhibitors were added together, the effect was enhanced. In conclusion, melatonin has potent analgesic and anti-inflammatory effects in SNL models through preventing pyroptosis via the NF-κB/NLRP3 inflammasome signaling pathway.

Immunopolarization-regulated 3D printed-electrospun fibrous scaffolds for bone regeneration

Three-dimension (3D)-printed bioscaffolds are precise and personalized for bone regeneration. However, customized 3D scaffolds may activate the immune response in vivo and consequently impede bone formation. In this study, with layer-by-layer deposition and electrospinning technology to control the physical structure, 3D-printed PCL scaffolds with PLLA electrospun microfibrous (3D-M-EF) and nanofibrous (3D-N-EF) composites were constructed, and their immunomodulatory effect and the subsequent osteogenic effects were explored. Compared to 3D-N-EF scaffolds, 3D-M-EF scaffolds polarized more RAW264.7 cells toward alternatively activated macrophages (M2), as demonstrated by increased M2 and deceased classically activated macrophage (M1) phenotypic marker expression in the cells. In addition, the 3D-M-EF scaffolds shifted RAW264.7 cells to the M2 phenotype through PI3K/AKT signaling and enhanced VEGF and BMP-2 expression. Conditional medium from the RAW264.7 cells seeded in 3D-M-EF scaffolds promoted osteogenesis of MC3T3-E1 cells. Furthermore, in vivo study of repairing rat calvarial defects, the 3D-M-EF scaffolds increased the polarization of M2 macrophages, enhanced angiogenesis, and accelerated new bone formation. Collectively, our data suggested that well-designed 3D-M-EF scaffolds are favorable for osteogenesis through regulation of M2 polarization. Therefore, it is potential to utilize the physical structure of 3D-printed scaffolds to manipulate the osteoimmune environment to promote bone regeneration.

Silencing Proteasome 26S Subunit ATPase 2 (PSMC2) Protects the Osteogenic Differentiation In Vitro and Osteogenesis In Vivo

Osteoporosis is a commonly seen degenerative bone disorder in the elderly and postmenopausal women, with a low bone mineral density as a major risk factor. The osteogenic potential of bone marrow stromal cells (BMSCs) showed to be impaired during osteoporosis. We established a postmenopausal osteoporosis model in ovariectomized (OVX) mice and found the upregulation of proteasome 26S subunit ATPase 2 (PSMC2) in OVX mice. PSMC2 silencing improved OVX-impaired biomechanical properties of mice femur, OVX-decreased BMD, and OVX-destroyed bone structure. Histopathological analysis indicated that PSMC2 silencing improved bone trabecular structure and increased the contents of collagen fibers and newly formed bone or cartilage in OVX mice. In the meantime, PSMC2 silencing increased Runx2, PI3K, Wnt3a, and β-catenin protein contents while reduced CTSK protein. Within BMSCs isolated from OVX mice, PSMC2 silencing promoted BMSC osteogenic differentiation and elevated osteogenic markers' protein contents, including HOXA10, Runx2, OCN, OPN, and COL1A2. In conclusion, PSMC2 expression is upregulated in the postmenopausal osteoporosis model in OVX mice. PSMC2 silencing promotes the osteogenic differentiation of BMSCs in vitro, promotes bone formation, and inhibits bone resorption in vivo.

FGF21 alleviates chronic inflammatory injury in the aging process through modulating polarization of macrophages

Previous studies reported that FGF21 prolongs life span and delays the body senescence, but the mechanism is not clear. The present study was designed to investigate the effects of FGF21 on hepatic senescence in aging mice and further research the mechanism. The 14-month-old male mice were administered with PBS, FGF21 or metformin once daily for 6 months. Results showed that FGF21 alleviated liver injury and inhibited accumulation of senescence markers SASP, P53 and P16 in the livers of aging mice. Subsequently we found that the aging mice treated by FGF21 showed transition of type 1 macrophages (M1) to type 2 macrophages (M2) in the livers. Next, we used THP-1 macrophages triggered by LPS to study effects of FGF21 on macrophages. Macrophages triggered by LPS exhibited features of M1, but the addition of FGF21 decreased the expression of M1 markers, and promoted the macrophages to exhibit features of M2. Results showed that the effects of FGF21 on macrophages were associated with the AMPK pathway. After adding AMPK inhibitor, the effects of FGF21 were inhibited, which was associated with the NF-κB signaling pathway. Finally, co-culturing differentiated macrophages and hepatocytes, we found that the large amount of pro-inflammatory factors such as IL-6 promoted hepatocyte senescence, which exhibited enhanced P53, P16 and β-galactosidase. This was contrary to hepatocytes co-cultured with macrophages treated by FGF21. These results indicate that FGF21 alleviates hepatic senescence injury by modulating the polarization of macrophages through the AMPK /NF-κB signaling pathway.

Glial Cell Line-Derived Neurotrophic Factor Family Ligands, Players at the Interface of Neuroinflammation and Neuroprotection: Focus Onto the Glia

Well-known effects of neurotrophic factors are related to supporting the survival and functioning of various neuronal populations in the body. However, these proteins seem to also play less well-documented roles in glial cells, thus, influencing neuroinflammation. This article summarizes available data on the effects of glial cell line derived neurotrophic factor (GDNF) family ligands (GFLs), proteins providing trophic support to dopaminergic, sensory, motor and many other neuronal populations, in non-neuronal cells contributing to the development and maintenance of neuropathic pain. The paper also contains our own limited data describing the effects of small molecules targeting GFL receptors on the expression of the satellite glial marker IBA1 in dorsal root ganglia of rats with surgery- and diabetes-induced neuropathy. In our experiments activation of GFLs receptors with either GFLs or small molecule agonists downregulated the expression of IBA1 in this tissue of experimental animals. While it can be a secondary effect due to a supportive role of GFLs in neuronal cells, growing body of evidence indicates that GFL receptors are expressed in glial and peripheral immune system cells. Thus, targeting GFL receptors with either proteins or small molecules may directly suppress the activation of glial and immune system cells and, therefore, reduce neuroinflammation. As neuroinflammation is considered to be an important contributor to the process of neurodegeneration these data further support research efforts to modulate the activity of GFL receptors in order to develop disease-modifying treatments for neurodegenerative disorders and neuropathic pain that target both neuronal and glial cells.

Evaluation of CD49f as a novel surface marker to identify functional adipose-derived mesenchymal stem cell subset

OBJECTIVES

CD49f is expressed on a variety of stem cells and has certain effects on their cytological functions, such as proliferation and differentiation potential. However, whether CD49f is expressed on the surface of adipose tissue-derived mesenchymal stem cells (ADSCs) and its effect on ADSCs has not been clarified.

MATERIALS AND METHODS

The effects of in vitro culture passage and inflammatory factor treatment on CD49f expression and the adhesion ability of ADSCs from mice and rats were investigated. CD49f⁺ cells were selected from rat ADSCs (rADSCs) by magnetic-activated cell sorting (MACS), and the cellular functions of CD49f⁺ ADSCs and unsorted ADSCs, including their clonogenic, proliferation, adipogenic and osteogenic differentiation, migration and anti-apoptotic capacities, were compared.

RESULTS

CD49f expression and the adhesion ability of ADSCs decreased with increasing in vitro culture passage number. TNF-α and IFN-γ treatment decreased CD49f expression but increased the adhesion ability of ADSCs. After CD49f was blocked with an anti-CD49f antibody, the adhesion ability of ADSCs was decreased. No significant difference in clonogenic activity was observed between unsorted ADSCs and CD49f⁺ ADSCs. CD49f⁺ ADSCs had greater proliferation, adipogenic and osteogenic differentiation, migration and anti-apoptotic capacities than unsorted ADSCs.

CONCLUSION

In the current study, the expression of CD49f on ADSCs was identified for the first time. The expression of CD49f on ADSCs was influenced by in vitro culture passage number and inflammatory factor treatment. Compared with unsorted ADSCs, CD49f ⁺ ADSCs exhibited superior cellular functions, thus may have great application value in mesenchymal stem cell (MSC)-based therapies.

Old Friends with Unexploited Perspectives: Current Advances in Mesenchymal Stem Cell-Based Therapies in Asthma

Mesenchymal stem cells (MSCs) have a great regenerative and immunomodulatory potential that was successfully tested in numerous pre-clinical and clinical studies of various degenerative, hematological and inflammatory disorders. Over the last few decades, substantial immunoregulatory effects of MSC treatment were widely observed in different experimental models of asthma. Therefore, it is tempting to speculate that stem cell-based treatment could become an attractive means to better suppress asthmatic airway inflammation, especially in subjects resistant to currently available anti-inflammatory therapies. In this review, we discuss mechanisms accounting for potent immunosuppressive properties of MSCs and the rationale for their use in asthma. We describe in detail an intriguing interplay between MSCs and other crucial players in the immune system as well as lung microenvironment. Finally, we reveal the potential of MSCs in maintaining airway epithelial integrity and alleviating lung remodeling.

Treatment of Optic Canal Decompression Combined with Umbilical Cord Mesenchymal Stem (Stromal) Cells for Indirect Traumatic Optic Neuropathy: A Phase 1 Clinical Trial

PURPOSE

This study was aimed to investigate the safety and feasibility of umbilical cord-derived mesenchymal stem cell (MSC) transplantation in patients with traumatic optic neuropathy (TON).

METHODS

This is a single-center, prospective, open-labeled phase 1 study that enrolled 20 patients with TON. Patients consecutively underwent either optic canal decompression combined with MSC local implantation treatment (group 1) or only optic canal decompression (group 2). Patients were evaluated on the first day, seventh day, first month, third month, and sixth month postoperatively. Adverse events, such as fever, urticarial lesions, nasal infection, and death, were recorded at each visit. The primary outcome was changes in best-corrected visual acuity. The secondary outcomes were changes in color vision, relative afferent pupillary defect, and flash visual evoked potential.

RESULTS

All 20 patients completed the 6-month follow-up. None of them had any systemic or ocular complications. The change in best-corrected visual acuity at follow-up was not significantly different between group 1 and group 2 (p > 0.05); however, group 1 showed better visual outcome than group 2. Both groups showed significant improvements in vision compared with the baseline (p < 0.05); however, there were no statistically significant differences between the groups (p > 0.05). In addition, no adverse events related to local transplantation were observed in the patients.

CONCLUSIONS

A single, local MSC transplantation in the optic nerve is safe for patients with TON.

Oxidative Stress and Neuroinflammation as a Pivot in Drug Abuse. A Focus on the Therapeutic Potential of Antioxidant and Anti-Inflammatory Agents and Biomolecules

Drug abuse is a major global health and economic problem. However, there are no pharmacological treatments to effectively reduce the compulsive use of most drugs of abuse. Despite exerting different mechanisms of action, all drugs of abuse promote the activation of the brain reward system, with lasting neurobiological consequences that potentiate subsequent consumption. Recent evidence shows that the brain displays marked oxidative stress and neuroinflammation following chronic drug consumption. Brain oxidative stress and neuroinflammation disrupt glutamate homeostasis by impairing synaptic and extra-synaptic glutamate transport, reducing GLT-1, and system X_c⁻ activities respectively, which increases glutamatergic neurotransmission. This effect consolidates the relapse-promoting effect of drug-related cues, thus sustaining drug craving and subsequent drug consumption. Recently, promising results as experimental treatments to reduce drug consumption and relapse have been shown by (i) antioxidant and anti-inflammatory synthetic molecules whose effects reach the brain; (ii) natural biomolecules secreted by mesenchymal stem cells that excel in antioxidant and anti-inflammatory properties, delivered via non-invasive intranasal administration to animal models of drug abuse and (iii) potent anti-inflammatory microRNAs and anti-miRNAs which target the microglia and reduce neuroinflammation and drug craving. In this review, we address the neurobiological consequences of brain oxidative stress and neuroinflammation that follow the chronic consumption of most drugs of abuse, and the current and potential therapeutic effects of antioxidants and anti-inflammatory agents and biomolecules to reduce these drug-induced alterations and to prevent relapse.

FGF21 attenuates neurodegeneration through modulating neuroinflammation and oxidant-stress

Previous studies indicate that FGF21 has ability to repair nerve injury, but the specific mechanism is less studied. The present study was designed to investigate the effects of FGF21 on neurodegeneration changes in aging and diabetic mice and its mechanism. The diabetic and aging mice were used to study the effects of FGF21 on neurodegeneration and possible mechanisms. These mice were administrated with PBS, FGF21 or metformin once daily for 4 or 6 months, then the mechanism was studied in SH-SY5Y cells. The relevant gene expression for neurodegeneration was assessed by Quantitative Real Time-PCR, Western blot, H&E staining, immunohistochemistry and ELISA. The Western blot results of NeuN showed that FGF21 inhibited the loss of neurons in diabetic and aging mice. H&E staining results showed that the karyopyknosis and tissue edema around dentate gyrus and Cornu Amonis 3 (CA3) area of hippocampus were also inhibited by FGF21 in aging and diabetes mice. In vivo results revealed that administration of FGF21 suppressed the aggregation of tau and β-amyloid_1-42 in the brains of diabetic and aging mice. The aggregation resulted in apoptosis of neurons. Meanwhile, FGF21 significantly reduced the expression of Iba1, NF-κB, IL6 and IL8 (p < 0.05) and enhanced anti-oxidant enzymes (p < 0.05) in aging and diabetic mice. In addition, the phosphorylation of AKT and AMPKα were increased by FGF21 treatment. In vitro experiment showed that the aggregation of tau and β-amyloid_1-42 wereincreased by LPS in SH-SY5Y cells, and FGF21 inhibited the aggregation through inhibiting the expression of NF-κB and promoting the phosphorylation of AKT and AMPKα. In conclusion, FGF21 attenuates neurodegeneration by reducing neuroinflammation and oxidant stress through regulating the NF-κB pathway and AMPKα/AKT pathway, which enhances the protective effect on mitochondria in neurons.