Paracrine Effects of Mesenchymal Stem Cells in Ischemic Stroke: Opportunities and Challenges

Microglial polarization pathways and therapeutic drugs targeting activated microglia in traumatic brain injury

Traumatic brain injury can be categorized into primary and secondary injuries. Secondary injuries are the main cause of disability following traumatic brain injury, which involves a complex multicellular cascade. Microglia play an important role in secondary injury and can be activated in response to traumatic brain injury. In this article, we review the origin and classification of microglia as well as the dynamic changes of microglia in traumatic brain injury. We also clarify the microglial polarization pathways and the therapeutic drugs targeting activated microglia. We found that regulating the signaling pathways involved in pro-inflammatory and anti-inflammatory microglia, such as the Toll-like receptor 4 /nuclear factor-kappa B, mitogen-activated protein kinase, Janus kinase/signal transducer and activator of transcription, phosphoinositide 3-kinase/protein kinase B, Notch, and high mobility group box 1 pathways, can alleviate the inflammatory response triggered by microglia in traumatic brain injury, thereby exerting neuroprotective effects. We also reviewed the strategies developed on the basis of these pathways, such as drug and cell replacement therapies. Drugs that modulate inflammatory factors, such as rosuvastatin, have been shown to promote the polarization of anti-inflammatory microglia and reduce the inflammatory response caused by traumatic brain injury. Mesenchymal stem cells possess anti-inflammatory properties, and clinical studies have confirmed their significant efficacy and safety in patients with traumatic brain injury. Additionally, advancements in mesenchymal stem cell-delivery methods-such as combinations of novel biomaterials, genetic engineering, and mesenchymal stem cell exosome therapy-have greatly enhanced the efficiency and therapeutic effects of mesenchymal stem cells in animal models. However, numerous challenges in the application of drug and mesenchymal stem cell treatment strategies remain to be addressed. In the future, new technologies, such as single-cell RNA sequencing and transcriptome analysis, can facilitate further experimental studies. Moreover, research involving non-human primates can help translate these treatment strategies to clinical practice.

Preserving Blood-Brain Barrier Integrity in Ischemic Stroke: a Review on MSCs-sEVs Content and Potential Molecular Targets

Ischemic stroke (IS) is a life-threatening condition that constitutes the second leading cause of death globally. Despite its high impact on public health, there is a shortage of treatments due to the complexity of the cellular and molecular mechanisms implicated. One main limiting factor for successful IS therapeutic intervention is stroke-induced blood-brain barrier (BBB) damage, particularly over tight junction proteins (TJs). BBB disruption is a well-established feature of IS, accelerating ischemic tissue damage and worsening prognosis. In recent years, mesenchymal stem cells (MSCs) and their small extracellular vesicles (MSCs-sEVs) have emerged as promising therapeutic interventions for several neurological disorders, including IS. However, its effects on BBB repair after IS are not completely understood. In this review, we will discuss novel experimental evidence of MSCs-sEVs effects in BBB protection and highlight the relevance of molecules reported in MSCs-sEVs, their potential cellular and molecular targets, and putative mechanisms implicated in BBB repair, providing a promising research avenue that may translate into effective therapeutic strategies for IS.

Research progress of quantitative electroencephalography in post-ischemic stroke mental disorders

Quantitative electroencephalography (qEEG) has significantly advanced in the field of neuroscience as a highly sensitive tool for routine monitoring following a stroke. It holds promise in diagnosing post-stroke psychiatric disorders and evaluating treatment outcomes. This review systematically examined published papers and thoroughly analyzed research findings on using qEEG indicators to monitor mental abnormalities in patients with ischemic stroke. The review covers key time periods, including the early stage (within 72 h), subacute stage (72 h to 1 month), and chronic stage (over 1 month) post-onset. The current evidence suggests that correlation indicators from electroencephalography (EEG) monitoring vary across different time periods, with Power spectrum analysis is a current research hotspot. This review summarizes and analyzes specialized studies on utilizing these qEEG indicators for monitoring and evaluating mental disorders in ischemic stroke, identifying key monitoring indicators highlighted in current research.

Esophageal Reconstruction with Myogenesis-Inducing Gene Transfected Mesenchymal Stem Cell-Seeded Film with Leaf-Stacked Structure

In the domain of tissue engineering and regenerative medicine, artificial replacements have been developed as viable options for esophageal reconstruction and serve as alternatives to traditional surgical procedures. Restoration of smooth muscle functionality is crucial in esophageal regeneration. We evaluated the efficacy of esophageal reconstructions in an animal model, using tissue-engineered films with a leaf-stacked structure (FLSS), seeded with mesenchymal stem cells (MSCs), which were genetically modified with myogenic genes. Esophageal partial defects were variously reconstructed in animals (n = 8 per group, except the no-implantation group), categorized as (1) normal rats; (2) rats implanted with naked FLSS; (3) rats implanted with FLSS with MSCs; (4) rats implanted using FLSS with myogenesis-inducing gene transfected MSCs; and (5) rats without implantation at the defect site (n = 3). The FLSS exhibited appropriate mechanical characteristics for transplantation. Successful repair of esophageal defects was observed with significantly enhanced epithelial regeneration in the MSC-seeded FLSS group compared to that in the naked FLSS group. Moreover, smooth muscle regeneration was notably higher in the FLSS with myogenesis-inducing gene transfected MSCs than in the group without myogenic gene transfection. The myogenesis-inducing gene-transfected MSC-seeded FLSS group showed a tendency toward increased smooth muscle regeneration, this indicates that FLSS with myogenesis-inducing genes transfected MSC may contribute positively to the maintenance of function in the reconstructed esophagus.

Harnessing stem cell therapeutics in LPS-induced animal models: mechanisms, efficacies, and future directions

The severity and threat posed by inflammation are well documented, and lipopolysaccharides (LPS), as important inducers of inflammatory responses, are widely recognized for studying host immunity and the resulting tissue and organ damage. The LPS-induced disease model, triggers a remarkable release of inflammatory factors, immune and coagulation dysfunction, and damage to vital organs such as the brain, lungs, heart, liver, and kidneys. Recently, the role of mesenchymal stem cells (MSCs) in various clinical diseases has garnered significant attention due to their immunomodulatory, anti-inflammatory, tissue healing, anti-apoptotic, and antibacterial properties. Despite the common use of LPS models to induce disease models and simulate acute inflammation, the integration of stem cell therapy within these models remains underexplored. This article integrates the LPS induced animal model and reviews the current evidence regarding the therapeutic mechanisms of stem cells in LPS-induced disease models across various human body systems. Furthermore, this review predicts and hypothesizes the feasibility and potential of using stem cells in disease models that have not yet been extensively studied, based on existing animal inflammation models.

Distinct roles of MIF in the pathogenesis of ischemic heart disease

The role of macrophage migration inhibitory factor (MIF) as a multifunctional cytokine in immunomodulation and inflammatory response is increasingly appreciated. Ischemic heart disease (IHD), the leading cause of global mortality, remains a focal point of research owing to its intricate pathophysiology. MIF has been identified as a critical player in IHD, where it exerts distinct roles. On one hand, MIF plays a protective role by enhancing energy metabolism through activation of AMPK, resisting oxidative stress, inhibiting activation of the JNK pathway, and maintaining intracellular calcium ion homeostasis. Additionally, MIF exerts protective effects through mesenchymal stem cells and exosomes. On the other hand, MIF can assume a pro-inflammatory role, which contributes to the exacerbation of IHD's development and progression. Furthermore, MIF levels significantly increase in IHD patients, and its genetic polymorphisms are positively correlated with prevalence and severity. These findings position MIF as a potential biomarker and therapeutic target in the management of IHD. This review summarizes the structure, source, signaling pathways and biological functions of MIF and focuses on its roles and clinical characteristics in IHD. The genetic variants of MIF associated with IHD is also discussed, providing more understandings of its complex interplay in the disease's pathology.

Stem cell-derived exosomes for ischemic stroke: a conventional and network meta-analysis based on animal models

Objective

We aimed to evaluate the efficacy of stem cell-derived exosomes for treating ischemic stroke and to screen for the optimal administration strategy.

Methods

We searched PubMed, Web of Science, Embase, Cochrane Library, and Scopus databases for relevant studies published from their inception to 31 December 2023. Conventional and network meta-analyses of the routes of administration, types, and immune compatibility of stem cell-derived exosomes were performed using the cerebral infarct volume (%) and modified neurological severity score (mNSS) as outcome indicators.

Results

A total of 38 randomized controlled animal experiments were included. Conventional meta-analysis showed that compared with the negative control group: intravenous administration significantly reduced the cerebral infarct volume (%) and mNSS; intranasal administration significantly reduced the cerebral infarct volume (%); and intracerebral administration significantly reduced the mNSS. Adipose-derived mesenchymal stem cell-derived exosomes (ADSC-Exos), bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exos), dental pulp stem cell-derived exosomes (DPSC-Exos) and neural stem cell-derived exosomes (NSC-Exos) significantly reduced the cerebral infarct volume (%) and mNSS; Endothelial progenitor cell-derived exosomes (EPC-Exos), embryonic stem cell-derived exosomes (ESC-Exos), induced pluripotent stem cell-derived exosomes (iPSC-Exos) and neural progenitor cell-derived exosomes (NPC-Exos) significantly reduced the cerebral infarct volume (%); Umbilical cord mesenchymal stem cell-derived exosomes (UCMSC-Exos) significantly reduced the mNSS; and there was no significant difference between urogenital stem cell-derived exosomes (USC-Exos) and negative controls. Engineered modified exosomes had better efficacy than unmodified exosomes. Both allogeneic and xenogeneic stem cell-derived exosomes significantly reduced the cerebral infarct volume (%) and the mNSS. The network meta-analysis showed that intravenous administration was the best route of administration for reducing the cerebral infarct volume (%) and mNSS. Among the 10 types of stem cell-derived exosomes that were administered intravenously, BMSC-Exos were the best type for reducing the cerebral infarct volume (%) and the mNSS. Allogeneic exosomes had the best efficacy in reducing the cerebral infarct volume (%), whereas xenogeneic stem cell-derived exosomes had the best efficacy in reducing the mNSS.

Conclusion

This meta-analysis, by integrating the available evidence, revealed that intravenous administration is the best route of administration, that BMSC-Exos are the best exosome type, that allogeneic exosomes have the best efficacy in reducing the cerebral infarct volume (%), and that xenogeneic exosomes have the best efficacy in reducing mNSS, which can provide options for preclinical studies. In the future, more high-quality randomized controlled animal experiments, especially direct comparative evidence, are needed to determine the optimal administration strategy for stem cell-derived exosomes for ischemic stroke.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42024497333, PROSPERO, CRD42024497333.

Priming and Combined Strategies for the Application of Mesenchymal Stem Cells in Ischemic Stroke: A Promising Approach

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Tissue plasminogen activator (tPA) administration and mechanical thrombectomy are the main treatments but have a narrow time window. Mesenchymal stem cells (MSCs), which are easily scalable in vitro and lack ethical concerns, possess the potential to differentiate into various types of cells and secrete a great number of growth factors for neuroprotection and regeneration. Moreover, MSCs have low immunogenicity and tumorigenic properties, showing safety and preliminary efficacy both in preclinical studies and clinical trials of IS. However, it is unlikely that MSC treatment alone will be sufficient to maximize recovery due to the low survival rate of transplanted cells and various mechanisms of ischemic brain damage in the different stages of IS. Preconditioning was used to facilitate the homing, survival, and secretion ability of the grafted MSCs in the ischemic region, while combination therapies are alternatives that can maximize the treatment effects, focusing on multiple therapeutic targets to promote stroke recovery. In this case, the combination therapy can yield a synergistic effect. In this review, we summarize the type of MSCs, preconditioning methods, and combined strategies as well as their therapeutic mechanism in the treatment of IS to accelerate the transformation from basic research to clinical application.

Role of intracranial bone marrow mesenchymal stem cells in stroke recovery: A focus on post-stroke inflammation and mitochondrial transfer

Stem cell therapy has become a hot research topic in the medical field in recent years, with enormous potential for treating a variety of diseases. In particular, bone marrow mesenchymal stem cells (BMSCs) have wide-ranging applications in the treatment of ischemic stroke, autoimmune diseases, tissue repair, and difficult-to-treat diseases. BMSCs can differentiate into multiple cell types and exhibit strong immunomodulatory properties. Although BMSCs can regulate the inflammatory response activated after stroke, the mechanism by which BMSCs regulate inflammation remains unclear and requires further study. Recently, stem cell therapy has emerged as a potentially effective approach for enhancing the recovery process following an ischemic stroke. For example, by regulating post-stroke inflammation and by transferring mitochondria to exert therapeutic effects. Therefore, this article reviews the therapeutic effects of intracranial BMSCs in regulating post-stroke inflammation and mitochondrial transfer in the treatment of stroke, providing a basis for further research.

Exosomal miR-486 derived from bone marrow mesenchymal stem cells promotes angiogenesis following cerebral ischemic injury by regulating the PTEN/Akt pathway

Bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exos) have been shown to promote angiogenesis after ischemic stroke, in which microRNAs (miRs) are believed to play an important role in exosome-mediated therapeutic effects, though the mechanism is still not clear. In this study, a series of molecular biological and cellular assays, both in vitro and in vivo, were performed to elucidate the role of exosomal miR-486 in angiogenesis following cerebral ischemic and its molecular mechanisms. Our results revealed that BMSC-Exos significantly improved neurological function and increased microvessel density in ischemic stroke rats. In vitro assays showed that BMSC-Exos promoted the proliferation, migration, and tube formation ability of oxygen-glucose deprivation/reoxygenation (OGD/R) injured rat brain microvascular endothelial cells (RBMECs). Importantly, BMSC-Exos increased the expression of miR-486 and phosphorylated protein kinase B (p-Akt) and down-regulated the protein level of phosphatase and tensin homolog (PTEN) in vivo and in vitro. Mechanistic studies demonstrated that transfection with miR-486 mimic enhanced RBMECs angiogenesis and increased p-Akt expression, while inhibited PTEN expression. On the other hand, the miR-486 inhibitor induced an opposite effect, which could be blocked by PTEN siRNA. It was thus concluded that exosomal miR-486 from BMSCs may enhance the functional recovery by promoting angiogenesis following cerebral ischemic injury, which might be related to its regulation of the PTEN/Akt pathway.

Mesenchymal Stromal Cell Therapy Alleviates Ovalbumin-Induced Chronic Airway Remodeling by Suppressing M2 Macrophage Polarization

Chronic asthma is characterized by airway hyperresponsiveness, inflammation, and remodeling. Previous studies have shown that mesenchymal stromal/stem cells (MSCs) exert anti-inflammatory effects on asthma via regulation of the immune cells. However, the therapeutic mechanism of MSCs, especially the mechanism of airway remodeling in chronic asthma, remains to be elucidated. Here, we aimed to investigate the therapeutic effect of MSCs on airway remodeling in chronic asthma and explored the mechanisms by analyzing the polarization phenotype of macrophages in the lungs. We established a mouse model of chronic asthma induced by ovalbumin (OVA) and evaluated the effect of MSCs on airway remodeling. The data showed that MSCs treatment before the challenge exerted protective effects on OVA-induced chronic asthma, i.e., decreased the inflammatory cell infiltration, Th2 cytokine levels, subepithelial extracellular matrix deposition, and transforming growth factor β (TGF-β)/Smad signaling. Additionally, we found that MSCs treatment markedly suppressed macrophage M2 polarization in lung tissue. At the same time, MSCs treatment inhibited NF-κB p65 nuclear translocation, ER stress, and oxidative stress in the OVA-induced chronic allergic airway remodeling mice model. In conclusion, these results demonstrated that MSCs treatment prevents OVA-induced chronic airway remodeling by suppressing macrophage M2 polarization, which may be associated with the dual inhibition of ER stress and oxidative stress. This discovery may provide a new theoretical basis for the future clinical application of MSCs.

Advancing stroke therapy: innovative approaches with stem cell-derived extracellular vesicles

Stroke is a leading cause of mortality and long-term disability globally, with acute ischemic stroke (AIS) being the most common subtype. Despite significant advances in reperfusion therapies, their limited time window and associated risks underscore the necessity for novel treatment strategies. Stem cell-derived extracellular vesicles (EVs) have emerged as a promising therapeutic approach due to their ability to modulate the post-stroke microenvironment and facilitate neuroprotection and neurorestoration. This review synthesizes current research on the therapeutic potential of stem cell-derived EVs in AIS, focusing on their origin, biogenesis, mechanisms of action, and strategies for enhancing their targeting capacity and therapeutic efficacy. Additionally, we explore innovative combination therapies and discuss both the challenges and prospects of EV-based treatments. Our findings reveal that stem cell-derived EVs exhibit diverse therapeutic effects in AIS, such as promoting neuronal survival, diminishing neuroinflammation, protecting the blood-brain barrier, and enhancing angiogenesis and neurogenesis. Various strategies, including targeting modifications and cargo modifications, have been developed to improve the efficacy of EVs. Combining EVs with other treatments, such as reperfusion therapy, stem cell transplantation, nanomedicine, and gut microbiome modulation, holds great promise for improving stroke outcomes. However, challenges such as the heterogeneity of EVs and the need for standardized protocols for EV production and quality control remain to be addressed. Stem cell-derived EVs represent a novel therapeutic avenue for AIS, offering the potential to address the limitations of current treatments. Further research is needed to optimize EV-based therapies and translate their benefits to clinical practice, with an emphasis on ensuring safety, overcoming regulatory hurdles, and enhancing the specificity and efficacy of EV delivery to target tissues.

Dental pulp mesenchymal stem cell-derived exosomes inhibit neuroinflammation and microglial pyroptosis in subarachnoid hemorrhage via the miRNA-197-3p/FOXO3 axis

BACKGROUND

Subarachnoid hemorrhage (SAH) is a severe stroke subtype that lacks effective treatment. Exosomes derived from human dental pulp stem cells (DPSCs) are a promising acellular therapeutic strategy for neurological diseases. However, the therapeutic effects of DPSC-derived exosomes (DPSC-Exos) on SAH remain unknown. In this study, we investigated the therapeutic effects and mechanisms of action of DPSC-Exos in SAH.

MATERIALS AND METHODS

SAH was established using 120 male Sprague-Dawley rats. One hour after SAH induction, DPSC-Exos were administered via tail vein injection. To investigate the effect of DPSC-Exos, SAH grading, short-term and long-term neurobehavioral assessments, brain water content, western blot (WB), immunofluorescence staining, Nissl staining, and HE staining were performed. The role of miR-197-3p/FOXO3 in regulating pyroptosis was demonstrated through miRNA sequencing, bioinformatics analysis, and rescue experiments. The SAH model in vitro was established by stimulating BV2 cells with hemoglobin (Hb) and the underlying mechanism of DPSC-Exos was investigated through WB and Hoechst/PI staining.

RESULTS

The expressions of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) were increased after SAH. DPSC-Exos alleviated brain edema and neuroinflammation by inhibiting the expression of FOXO3 and reducing NLRP3 inflammasome activation, leading to improved neurobehavioral functions at 24 h after SAH. In vitro, the expression of the NLRP3 inflammasome components (NLRP3 and caspase1-p20), GSDMD-N, and IL-18 was inhibited in BV2 cells pretreated with DPSC-Exos. Importantly, DPSC-Exos overexpressing miR-197-3p had a more obvious protective effect than those from NC-transfected DPSCs, while those from DPSCs transfected with the miR-197-3p inhibitor had a weaker protective effect. Functional studies indicated that miR-197-3p bound to the 3'-untranslated region of FOXO3, inhibiting its transcription. Furthermore, the overexpression of FOXO3 reversed the protective effects of miR-197-3p.

CONCLUSIONS

DPSC-Exos inhibited activation of the NLRP3 inflammasome and related cytokine release via the miR-197-3p/FOXO3 pathway, alleviated neuroinflammation, and inhibited microglial pyroptosis. These findings suggest that using DPSC-Exos is a promising therapeutic strategy for SAH.

Research progress and challenges of stem cell therapy for ischemic stroke

Ischemic stroke is a significant global cause of death and disability. Currently, treatment options for acute ischemic stroke are limited to intravenous thrombolysis and mechanical recanalization. Therefore, novel neuroprotective strategies are imperative. Stem cell transplantation possesses the capabilities of differentiation, proliferation, neuronal replacement, nerve pathway reconstruction, secretion of nerve growth factors, and enhancement of the microenvironment; thus, it is a potential therapeutic approach for ischemic stroke. In addition, the immunomodulatory function of stem cells and the combined treatment of stem cells and exosomes exhibit a favorable protective effect on brain injury and neurological dysfunction following stroke. Meanwhile, the theory of microbiota-gut-brain axis provides us with a novel perspective for comprehending and managing neurological diseases. Lastly, stem cell transplantation has demonstrated promising outcomes not only in treating ischemic stroke but also in dealing with other neurological disorders, such as brain tumors. Furthermore, challenges related to the tissue source, delivery method, immune response, and timing of transplantation still need to be addressed to optimize the treatment.

Comparison of morphology, protein concentration, and size distribution of bone marrow and Wharton's jelly-derived mesenchymal stem cells exosomes isolated by ultracentrifugation and polymer-based precipitation techniques

Exosomes which are tiny extracellular vesicles (30-150 nm), transport vital proteins and gene materials such as miRNA, mRNA, or DNA, whose role in cell communication and epithelia regulation is critical. Many techniques have been developed as a result of studying exosomes' biochemical and physicochemical properties, although there is still no standard method to isolate exosomes simply with high yield. Commercial kits have gained popularity for exosome extraction despite concerns about their effectiveness in scientific research. On the other hand, ultracentrifugation remains the gold standard isolation method. This study compares these two common exosome isolation methods to determine their impact on the quality and quantity of exosomes isolated from bone marrow (BM) and Wharton's jelly (WJ)-derived mesenchymal stem cells. Isolated exosomes from the two sources of the cell's conditioned medium by two methods (polymer kit and ultracentrifuge) were characterized using western blotting, scanning electron microscopy (SEM), dynamic light scattering (DLS), and the Bradford assay. Western blot analysis confirmed separation efficiency based on CD81 and CD63 markers, with the absence of calnexin serving as a negative control. The Morphology of exosomes studied by SEM image analysis revealed a similar round shape appearance and their sizes (30-150 nm) were the same in both isolation techniques. The DLS analysis of the sample results was consistent with the SEM ones, showing a similar size range and very low disparity. The exosome protein content concentration analysis revealed that exosomes isolated by the polymer-based kits contained higher protein concentration density and purity (p <0.001). In general, though the protein yield was higher when the polymer-based kits were used, there were no significant differences in morphology, or size between WJ-derived and BM-derived exosomes, regardless of the isolation method employed.

Neuroprotective effects of exosomes derived from bone marrow mesenchymal stem cells treated by Musk Ketone on ischemic stroke

OBJECTIVES

Ischemic stroke (IS) is a leading cause of morbidity and mortality globally. This study aimed to investigate the role of exosomes (Exo) derived from bone marrow mesenchymal stem cells (BMSCs) treated with Musk Ketone (Mus treated-Exo) in the development of IS injury.

METHODS

BMSCs were pretreated with 10 μM Mus for 36 h, and Exo derived from these Mus-treated BMSCs (Mus-treated Exo) were extracted. Rats with middle cerebral artery occlusion (MCAO) were administered either 2 mg/kg of control Exo (Ctrl-Exo), 2 mg/kg of Mus treated-Exo, or 10 μM Mus. Neurological deficit and cerebral infarction in the MCAO rats were assessed utilizing neurological scores and TTC staining. Neuronal apoptosis, activation of microglia/macrophages, and inflammation were evaluated through TUNEL staining, immunofluorescence staining, and western blot analysis, respectively.

RESULTS

Our findings revealed that Mus-treated Exo possessed a more pronounced neuroprotective effect on MCAO rats when compared to Ctrl-Exo and Mus treatment alone. Specifically, Mus treated-Exo effectively ameliorated neurological function, reduced the volume of cerebral infarction, and diminished hemispheric swelling in MCAO rats. Moreover, it inhibited neuronal apoptosis and activation of microglia/macrophages, promoted the expression of the anti-apoptotic protein Bcl-2 while decreasing the expression of pro-apoptotic protein Bax, Cleaved-caspase 3, and pro-inflammatory factors IL-6 and COX-2.

CONCLUSIONS

The findings imply that Mus treated-Exo could confer neuroprotection in rats affected by IS, potentially by attenuating apoptosis and neuroinflammation. The underlying mechanisms, however, warrant further investigation. Mus treated-Exo shows potential as a new therapeutic strategy for IS.

Stem cell-based ischemic stroke therapy: Novel modifications and clinical challenges

Ischemic stroke (IS) causes severe disability and high mortality worldwide. Stem cell (SC) therapy exhibits unique therapeutic potential for IS that differs from current treatments. SC's cell homing, differentiation and paracrine abilities give hope for neuroprotection. Recent studies on SC modification have enhanced therapeutic effects for IS, including gene transfection, nanoparticle modification, biomaterial modification and pretreatment. These methods improve survival rate, homing, neural differentiation, and paracrine abilities in ischemic areas. However, many problems must be resolved before SC therapy can be clinically applied. These issues include production quality and quantity, stability during transportation and storage, as well as usage regulations. Herein, we reviewed the brief pathogenesis of IS, the "multi-mechanism" advantages of SCs for treating IS, various SC modification methods, and SC therapy challenges. We aim to uncover the potential and overcome the challenges of using SCs for treating IS and convey innovative ideas for modifying SCs.

Secretome Derived from Mesenchymal Stem/Stromal Cells: A Promising Strategy for Diabetes and its Complications

Diabetes is a complex metabolic disease with a high global prevalence. The health and quality of life of patients with diabetes are threatened by many complications, including diabetic foot ulcers, diabetic kidney diseases, diabetic retinopathy, and diabetic peripheral neuropathy. The application of mesenchymal stem/stromal cells (MSCs) in cell therapies has been recognized as a potential treatment for diabetes and its complications. MSCs were originally thought to exert biological effects exclusively by differentiating and replacing specific impaired cells. However, the paracrine function of factors secreted by MSCs may exert additional protective effects. MSCs secrete multiple compounds, including proteins, such as growth factors, chemokines, and other cytokines; nucleic acids, such as miRNAs; and lipids, extracellular vesicles (EVs), and exosomes (Exos). Collectively, these secreted compounds are called the MSC secretome, and usage of these chemicals in cell-free therapies may provide stronger effects with greater safety and convenience. Recent studies have demonstrated positive effects of the MSC secretome, including improved insulin sensitivity, reduced inflammation, decreased endoplasmic reticulum stress, enhanced M2 polarization of macrophages, and increased angiogenesis and autophagy; however, the mechanisms leading to these effects are not fully understood. This review summarizes the current research regarding the secretome derived from MSCs, including efforts to quantify effectiveness and uncover potential molecular mechanisms in the treatment of diabetes and related disorders. In addition, limitations and challenges are also discussed so as to facilitate applications of the MSC secretome as a cell-free therapy for diabetes and its complications.

Effect of Metformin on Epidermal Neural Crest Stem Cells and Their Potential Application in Ameliorating Paclitaxel-induced Neurotoxicity Phenotype

AIMS

Epidermal Neural Crest Stem Cells (EPI-NCSCs) have emerged as prospective ideal candidates to meet the fundamental requirements of cell-based therapies in neurodegenerative disorders. The present study aimed to identify the potential of metformin in driving EPI-NCSCs to neuronal/glial differentiation and express neurotrophic factors as well as assess their therapeutic potential for mitigating the main behavioral manifestations of chemotherapy-induced neurotoxicity (CIN).

MAIN METHODS

EPI-NCSCs were extracted from the bulge region of hair follicle. Following expansion, transcript and protein expression profiles of key markers for stemness (Nestin, EGR-1, SOX-2 and 10), neurotrophic activity (BDNF, GDNF, NGF, FGF-2, and IL-6), and neuronal (TUB3, DCX, NRF and NeuN) and glial (PDGFRα, NG2, GFAP, and MBP) differentiation were determined on days 1 and 7 post-treatment with 10 and 100 μM metformin using real time-PCR and immunocytochemistry methods. Then, the in vivo function of metformin-treated stem cells was evaluated in the context of paclitaxel CIN. To do so, thermal hyperalgesia, mechanical allodynia, and spatial learning and memory tests were evaluated by Hotplate, Von Frey, and Morris water maze tests.

KEY FINDINGS

Our result indicated that exposure of EPI-NCSCs to metformin was associated with progressive decline in stemness markers and enhanced expression levels of several neurotrophic, neuron and oligodendrocyte-specific markers. Further, it was observed that intranasal metformin-treated EPI-NCSCs improved the cognitive impairment, and mechanical and thermal hypersensitivity induced by paclitaxel in rats.

SIGNIFICANCE

Collectively, we reasoned that metformin pretreatment of EPI-NCSCs might further enhance their therapeutic benefits against CIN.

Tumor Necrosis Factor Alpha Preconditioned Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles Enhance the Inhibition of Necroptosis of Acinar cells in Severe Acute Pancreatitis

Severe acute pancreatitis (SAP) is a common abdominal emergency with a high mortality rate and a lack of effective therapeutic options. Although mesenchymal stem cell (MSC) transplantation is a potential treatment for SAP, the mechanism remains unclear. It has been suggested that MSCs may act mainly through paracrine effects; therefore, we aimed to demonstrate the therapeutic efficacy of extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (UCMSCs) for SAP. Na-taurocholate was used to induce a rat SAP model through retrograde injection into the common biliopancreatic duct. After 72 h of EVs transplantation, pancreatic pathological damage was alleviated, along with a decrease in serum amylase activity and pro-inflammatory cytokine levels. Interestingly, when UCMSCs were preconditioned with 10 ng/mL tumor necrosis factor alpha (TNF-α) for 48 h, the obtained EVs (named TNF-α-EVs) performed an enhanced efficacy. Furthermore, both animal and cellular experiments showed that TNF-α-EVs alleviated the necroptosis of acinar cells of SAP through RIPK3/MLKL axis. In conclusion, our study demonstrated that TNF-α-EVs were able to enhance the therapeutic effect on SAP by inhibiting necroptosis compared to normal EVs. This study heralds that TNF-α-EVs may be a promising therapeutic approach for SAP in the future.

Dual impacts of mesenchymal stem cell-derived exosomes on cancer cells: unravelling complex interactions

Mesenchymal stem cells (MSCs) are multipotent, self-renewing stromal cells found in a variety of adult tissues. MSCs possess a remarkable ability to migrate towards tumor sites, known as homing. This homing process is mediated by various factors, including chemokines, growth factors, and extracellular matrix components present in the tumor microenvironment. MSCs release extracellular vesicles known as exosomes (MSC-Exos), which have been suggested to serve a key role in mediating a wide variety of MSC activities. Through cell-cell communication, MSC-Exos have been shown to alter recipient cell phenotype or function and play as a novel cell-free alternative for MSC-based cell therapy. However, MSC recruitment to tumors allows for their interaction with cancer cells and subsequent regulation of tumor behavior. MSC-Exos act as tumor niche modulators via transferring exosomal contents, such as specific proteins or genetic materials, to the nearby cancer cells, leading to either promotion or suppression of tumorigenesis, angiogenesis, and metastasis, depending on the specific microenvironmental cues and recipient cell characteristics. Consequently, there is still a debate about the precise relationship between tumor cells and MSC-Exos, and it is unclear how MSC-Exos impacts tumor cells. Although the dysregulation of miRNAs is caused by the progression of cancer, they also play a direct role in either promoting or inhibiting tumor growth as they act as either oncogenes or tumor suppressors. The utilization of MSC-Exos may prove to be an effective method for restoring miRNA as a means of treating cancer. This review aimed to present the existing understanding of the impact that MSC-Exos could have on cancer. To begin with, we presented a brief explanation of exosomes, MSCs, and MSC-Exos. Following this, we delved into the impact of MSC-Exos on cancer growth, EMT, metastasis, angiogenesis, resistance to chemotherapy and radiotherapy, and modulation of the immune system. Opposing effects of mesenchymal stem cells-derived exosomes on cancer cells.

Signaling pathways in brain ischemia: Mechanisms and therapeutic implications

Ischemic stroke occurs when the arteries supplying blood to the brain are narrowed or blocked, inducing damage to brain tissue due to a lack of blood supply. One effective way to reduce brain damage and alleviate symptoms is to reopen blocked blood vessels in a timely manner and reduce neuronal damage. To achieve this, researchers have focused on identifying key cellular signaling pathways that can be targeted with drugs. These pathways include oxidative/nitrosative stress, excitatory amino acids and their receptors, inflammatory signaling molecules, metabolic pathways, ion channels, and other molecular events involved in stroke pathology. However, evidence suggests that solely focusing on protecting neurons may not yield satisfactory clinical results. Instead, researchers should consider the multifactorial and complex mechanisms underlying stroke pathology, including the interactions between different components of the neurovascular unit. Such an approach is more representative of the actual pathological process observed in clinical settings. This review summarizes recent research on the multiple molecular mechanisms and drug targets in ischemic stroke, as well as recent advances in novel therapeutic strategies. Finally, we discuss the challenges and future prospects of new strategies based on the biological characteristics of stroke.

A Human Brain Model Mimicking Umbilical Cord Mesenchymal Stem Cells for the Treatment of Hypoxic-Ischemic Brain Injury

We used an in vitro model of the human brain immune microenvironment to simulate hypoxic-ischemic brain injury (HIBI) and treatment with human umbilical cord mesenchymal stem cells (hUMSCs) to address the transformation barriers of gene differences between animals and humans in preclinical research. A co-culture system, termed hNAME, consisted of human hippocampal neurons (N), astrocytes (A), microglia (M), and brain microvascular endothelial cells (E). Flow cytometry measured the apoptosis rates of neurons and endothelial cells. hNAME-neurons and endothelial cells experienced more severe damage than monolayer cells, particularly after 48 h and 24 h of reoxygenation (OGD48/R24). Western blotting identified neuroinflammatory response markers, including HIF-1α, C1q, C3, TNF-α, and iNOS. Inflammatory factors originated from the glial chamber rather than the neurons and vascular endothelial chambers. A gradual increase in the release of inflammatory factors was observed as the OGD and reoxygenation times increased, peaking at OGD48/R24. The hNAME value was confirmed in human umbilical cord mesenchymal stem cells (hUMSCs). Treatment with hUMSCs resulted in a notable decrease in the severity of neuronal and endothelial cell damage in hNAME. The hNAME is an ideal in vitro model for simulating the immune microenvironment of the human brain because of the interactions between neurons, vessels, astrocytes, and microglia.

Regulatory Effects of Three-Dimensional Cultured Lipopolysaccharide-Pretreated Periodontal Ligament Stem Cell-Derived Secretome on Macrophages

Phenotypic transformation of macrophages plays important immune response roles in the occurrence, development and regression of periodontitis. Under inflammation or other environmental stimulation, mesenchymal stem cells (MSCs) exert immunomodulatory effects through their secretome. It has been found that secretome derived from lipopolysaccharide (LPS)-pretreated or three-dimensional (3D)-cultured MSCs significantly reduced inflammatory responses in inflammatory diseases, including periodontitis, by inducing M2 macrophage polarization. In this study, periodontal ligament stem cells (PDLSCs) pretreated with LPS were 3D cultured in hydrogel (termed SupraGel) for a certain period of time and the secretome was collected to explore its regulatory effects on macrophages. Expression changes of immune cytokines in the secretome were also examined to speculate on the regulatory mechanisms in macrophages. The results indicated that PDLSCs showed good viability in SupraGel and could be separated from the gel by adding PBS and centrifuging. The secretome derived from LPS-pretreated and/or 3D-cultured PDLSCs all inhibited the polarization of M1 macrophages, while the secretome derived from LPS-pretreated PDLSCs (regardless of 3D culture) had the ability to promote the polarization of M1 to M2 macrophages and the migration of macrophages. Cytokines involved in the production, migration and polarization of macrophages, as well as multiple growth factors, increased in the PDLSC-derived secretome after LPS pretreatment and/or 3D culture, which suggested that the secretome had the potential to regulate macrophages and promote tissue regeneration, and that it could be used in the treatment of inflammation-related diseases such as periodontitis in the future.

Exosomes derived from hypoxia-preconditioned mesenchymal stem cells (hypoMSCs-Exo): advantages in disease treatment

Mesenchymal stem cells (MSCs)-based therapy has been reported to be a potential approach to treat various diseases and the paracrine role might be the underlying mechanism. Exosomes were considered an important part of this paracrine role. It was reported that maintenance of MSCs in hypoxia conditions for a short time has shown to be beneficial for the therapeutic effect of MSCs and MSCs-derived exosomes. In this review, we summarized the recent developments on exosomes derived from hypoxia-preconditioned mesenchymal stem cells (hypoMSCs-Exo), including the characteristics of hypoMSCs-Exo in morphology and contents, diseases in which hypoMSCs-Exo showed more effective, and the cellular and molecular mechanisms that hypoMSCs-Exo showed more effective in disease treatment. Besides, we also discussed the limitations of current studies and the issues that needed to be improved in the application of hypoMSCs-Exo. This review aimed to promote a comprehensive and systematic understanding of this type of exosome with great therapeutic potential.

Regulation of Extracellular Vesicle-Mediated Immune Responses against Antigen-Specific Presentation

Extracellular vesicles (EVs) produced by various immune cells, including B and T cells, macrophages, dendritic cells (DCs), natural killer (NK) cells, and mast cells, mediate intercellular communication and have attracted much attention owing to the novel delivery system of molecules in vivo. DCs are among the most active exosome-secreting cells of the immune system. EVs produced by cancer cells contain cancer antigens; therefore, the development of vaccine therapy that does not require the identification of cancer antigens using cancer-cell-derived EVs may have significant clinical implications. In this review, we summarise the molecular mechanisms underlying EV-based immune responses and their therapeutic effects on tumour vaccination.