Alveolar macrophages are critical for the inhibition of allergic asthma by mesenchymal stromal cells

Mesenchymal stem cell-loaded hydrogel to inhibit inflammatory reaction in surgical brain injury via mitochondria transfer

Neurosurgical procedures are the key therapeutic interventions for the cerebral hemorrhage and brain tumors. However, neurosurgical procedures inevitably cause surgical brain injury (SBI), which will induce hemorrhage and inflammation. Gelatin Sponges are still the primary hemostatic materials used in clinical, but their anti-inflammatory efficacy is poor. Herein, we developed a cross-linked gelatin hydrogel (GelMA) to load mesenchymal stem cells (MSC) and directly implant them to the SBI site. Upon contacting the SBI site, the GelMA showed better clotting performance than Gelatin Sponges. Moreover, the MSC can reduce oxidative stress and enhance mitochondrial fusion via mitochondria transfer, resulting in ameliorating mitochondrial damage and reducing inflammation. Thus, the GelMA containing MSC can effectively reduce brain edema and inflammation and improve neurological function in SBI mouse models. In addition, GelMA exhibits excellent hemocompatibility and low cytotoxicity. It also enhances the proliferation of MSCs and decelerates the rapid depletion of MSCs. Therefore, MSC-loaded GelMA exhibits excellent hemostatic and anti-inflammatory effects, making it a potential new-generation biomaterial for SBI.

Mesenchymal stromal cells dampen trained immunity in house dust mite-primed macrophages expressing human macrophage migration inhibitory factor polymorphism

BACKGROUND

Trained immunity results in long-term immunological memory, provoking a faster and greater immune response when innate immune cells encounter a secondary, often heterologous, stimulus. We have previously shown that house dust mite (HDM)-induced innate training is amplified in mice expressing the human macrophage migration inhibitory factor (MIF) CATT7 functional polymorphism.

AIM

This study investigated the ability of mesenchymal stromal cells (MSCs) to modulate MIF-driven trained immunity both in vitro and in vivo.

METHODS

Compared with wild-type mice, in vivo HDM-primed bone marrow-derived macrophages (BMDMs) from CATT7 mice expressed significantly higher levels of M1-associated genes following lipopolysaccharide stimulation ex vivo. Co-cultures of CATT7 BMDMs with MSCs suppressed this HDM-primed effect, with tumor necrosis factor alpha (TNF-α) being significantly decreased in a cyclooxygenase 2 (COX-2)-dependent manner. Interestingly, interleukin 6 (IL-6) was suppressed by MSCs independently of COX-2. In an in vitro training assay, MSCs significantly abrogated the enhanced production of pro-inflammatory cytokines by HDM-trained CATT7 BMDMs when co-cultured at the time of HDM stimulus on day 0, displaying their therapeutic efficacy in modulating an overzealous human MIF-dependent immune response. Utilizing an in vivo model of HDM-induced trained immunity, MSCs administered systemically on day 10 and day 11 suppressed this trained phenomenon by significantly reducing TNF-α and reducing IL-6 and C-C motif chemokine ligand 17 (CCL17) production.

CONCLUSIONS

This novel study elucidates how MSCs can attenuate an MIF-driven, HDM-trained response in CATT7 mice in a model of allergic airway inflammation.

Mesenchymal stem cell therapy in eosinophilic granulomatosis with polyangiitis-related lower limb gangrene: a case report

BACKGROUND

Eosinophilic granulomatosis with polyangiitis (EGPA), a rare but life-threatening systemic vasculitis, is distinguished by marked eosinophilia and presents with diverse symptoms, including asthma, cutaneous purpura, ecchymosis, skin necrosis, cardiac lesions, peripheral neuropathy, and necrotizing vasculitis. The etiology of EGPA involves a complex interaction among humoral, adaptive, innate, and allergic immune responses. Standard treatment employs prolonged high-dose glucocorticoid therapy, which is critical for survival; however, some patients' symptoms cannot be relieved.

CASE REPORT

This case report details the medical management of an 11-year-old patient with EGPA, who was at risk of bilateral lower limb amputation due to differential arterial occlusion and severe, necrotizing vasculitis-induced gangrene in both feet. Treatment modalities administered included systemic infusion of Umbilical Cord Mesenchymal Stem Cells (UC-MSCs), targeted gastrocnemius muscle injections, and application of a Placenta-Derived Mesenchymal Stem Cells (PD-MSCs) hydrogel.

RESULTS

After receiving a four-month regimen of allogeneic mesenchymal stem cell therapy via intravenous and local administration, the patient showed normalized eosinophil counts, reestablished blood flow in the dorsal arteries, and marked improvement in foot ulcerations.

CONCLUSION

Mesenchymal stem cell therapy is a promising option for severe EGPA cases refractory to glucocorticoids.

Human umbilical cord mesenchymal stem cells promoted tumor cell growth associated with increased interleukin-18 in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is experiencing a concerning rise in both incidence and mortality rates. Current therapeutic strategies are limited in their effectiveness, largely due to the complex causes of the disease and significant levels of drug resistance. Given the latest developments in human umbilical cord mesenchymal stem cells (hUC-MSCs) research, there is a debate over the continued use of stem cell transplantation for treating tumors. Consequently, this study seeks to explore the role of hUC-MSCs in the management of HCC.

METHODS AND RESULTS

HUC-MSCs increased the number (10.75 ± 1.50) in the DEN/TCPOBOP-induced mice hepatoma model, compared with DMSO group (7.25 ± 1.71). Moreover, the liver index in hUC-MSCs group (0.21 ± 0.06) was greater than that in DMSO group (0.09 ± 0.01). Immunohistochemical (IHC) analysis revealed that while hUC-MSCs did not alter Foxp3 expression, they significantly stimulated Ki67 expression, indicative of increased tumor cellular proliferation. Additionally, immunofluorescence (IF) studies showed that hUC-MSCs increased CD8+ T cell counts without affecting macrophage numbers. Notably, granzyme B expression remained nearly undetectable. We observed that serum IL-18 levels were higher in the hUC-MSCs group (109.66 ± 0.38 pg/ml) compared to the DMSO group (91.14 ± 4.37 pg/ml). Conversely, IL-1β levels decreased in the hUC-MSCs group (63.00 ± 0.53 pg/ml) relative to the DMSO group (97.38 ± 9.08 pg/ml).

CONCLUSIONS

According to this study, hUC-MSCs promoted the growth of liver tumors. Therefore, we proposed that hUC-MSCs are not suitable for treating HCC, as they exhibit clinically prohibited abnormalities.

Balancing macrophage polarization via stem cell-derived apoptotic bodies for diabetic wound healing

BACKGROUND

Adipose tissue-derived stem cell-derived apoptotic bodies (ADSC-ABs) have shown great potential for immunomodulation and regeneration, particularly in diabetic wound therapy. However, their local application has been limited by unclear regulatory mechanisms, rapid clearance, and short tissue retention times.

METHODS

We analyzed the key role molecules and regulatory pathways of ADSC-ABs in regulating inflammatory macrophages by mRNA sequencing and microRNA (miRNA) sequencing and then verified them by gene knockdown. To prevent rapid clearance, we employed microfluidics technology to prepare methacrylate-anhydride gelatin (GelMA) microspheres (GMS) for controlled release of ABs. Finally, we evaluated the effectiveness of ADSC-AB-laden GMSs (ABs@GMSs) in a diabetic rat wound model.

FINDINGS

Our results demonstrated that ADSC-ABs effectively balanced macrophage inflammatory polarization through the janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, mediated by miR-20a-5p. Furthermore, we showed that AB@GMSs had good biocompatibility, significantly delayed local clearance of ABs, and ameliorated diabetic wound inflammation and promoted vascularization, thus facilitating its healing.

CONCLUSIONS

Our study reveals the regulatory mechanism of ADSC-ABs in balancing macrophage inflammatory polarization and highlightsthe importance of delaying their local clearance by GMSs. These findings have important implications for the development of novel therapies for diabetic wound healing.

FUNDING

This research was supported by the National Key Research and Development Program of China (2020YFA0908200), National Natural Science Foundation of China (82272263, 82002053, 32000937, and 82202467), Shanghai "Rising Stars of Medical Talents" Youth Development Program (22MC1940300), Shanghai Municipal Health Commission (20204Y0354), and Shanghai Science and Technology Development Funds (22YF1421400).

Mesenchymal stromal cells and their small extracellular vesicles in allergic diseases: From immunomodulation to therapy

Mesenchymal stromal cells (MSCs) have long been considered a potential tool for treatment of allergic inflammatory diseases, owing to their immunomodulatory characteristics. In recent decades, the medical utility of MSCs has been evaluated both in vitro and in vivo, providing a foundation for therapeutic applications. However, the existing limitations of MSC therapy indicate the necessity for novel therapies. Notably, small extracellular vesicles (sEV) derived from MSCs have emerged rapidly as candidates instead of their parental cells. The acquisition of abundant and scalable MSC-sEV is an obstacle for clinical applications. The potential application of MSC-sEV in allergic diseases has attracted increasing attention from researchers. By carrying biological microRNAs or active proteins, MSC-sEV can modulate the function of various innate and adaptive immune cells. In this review, we summarise the recent advances in the immunomodulatory properties of MSCs in allergic diseases, the cellular sources of MSC-sEV, and the methods for obtaining high-quality human MSC-sEV. In addition, we discuss the immunoregulatory capacity of MSCs and MSC-sEV for the treatment of asthma, atopic dermatitis, and allergic rhinitis, with a special emphasis on their immunoregulatory effects and the underlying mechanisms of immune cell modulation.

Intravenous Administration of Human Umbilical Cord Mesenchymal Stromal Cells Leads to an Inflammatory Response in the Lung

Mesenchymal stromal cells (MSCs) administered intravenously (IV) have shown efficacy in preclinical models of various diseases. This is despite the cells not reaching the site of injury due to entrapment in the lungs. The immunomodulatory properties of MSCs are thought to underlie their therapeutic effects, irrespective of whether they are sourced from bone marrow, adipose tissue, or umbilical cord. To better understand how MSCs affect innate immune cell populations in the lung, we evaluated the distribution and phenotype of neutrophils, monocytes, and macrophages by flow cytometry and histological analyses after delivering human umbilical cord-derived MSCs (hUC-MSCs) IV into immunocompetent mice. After 2 hr, we observed a significant increase in neutrophils, and proinflammatory monocytes and macrophages. Moreover, these immune cells localized in close proximity to the MSCs, suggesting an active role in their clearance. By 24 hr, we detected an increase in anti-inflammatory monocytes and macrophages. These results suggest that the IV injection of hUC-MSCs leads to an initial inflammatory phase in the lung shortly after injection, followed by a resolution phase 24 hr later.

Serum from patients with asthma potentiates macrophage phagocytosis and human mesenchymal stromal cell therapy in experimental allergic asthma

BACKGROUND/AIMS

Although several studies have demonstrated that mesenchymal stromal cells (MSCs) exhibit beneficial immunomodulatory properties in preclinical models of allergic asthma, effects on airway remodeling have been controversial. Recent evidence has shown that MSCs modify their in vivo immunomodulatory actions depending on the specific inflammatory environment encountered. Accordingly, we assessed whether the therapeutic properties of human mesenchymal stromal cells (hMSCs) could be potentiated by conditioning these cells with serum (hMSC-serum) obtained from patients with asthma and then transplanted in an experimental model of house dust mite (HDM)-induced allergic asthma.

METHODS

hMSC and hMSC-serum were administered intratracheally 24 h after the final HDM challenge. hMSC viability and inflammatory mediator production, lung mechanics and histology, bronchoalveolar lavage fluid (BALF) cellularity and biomarker levels, mitochondrial structure and function as well as macrophage polarization and phagocytic capacity were assessed.

RESULTS

Serum preconditioning led to: (i) increased hMSC apoptosis and expression of transforming growth factor-β, interleukin (IL)-10, tumor necrosis factor-α-stimulated gene 6 protein and indoleamine 2,3-dioxygenase-1; (ii) fission and reduction of the intrinsic respiratory capacity of mitochondria; and (iii) polarization of macrophages to M2 phenotype, which may be associated with a greater percentage of hMSCs phagocytosed by macrophages. Compared with mice receiving hMSCs, administration of hMSC-serum led to further reduction of collagen fiber content, eotaxin levels, total and differential cellularity and increased IL-10 levels in BALF, improving lung mechanics. hMSC-serum promoted greater M2 macrophage polarization as well as macrophage phagocytosis, mainly of apoptotic hMSCs.

CONCLUSIONS

Serum from patients with asthma led to a greater percentage of hMSCs phagocytosed by macrophages and triggered immunomodulatory responses, resulting in further reductions in both inflammation and remodeling compared with non-preconditioned hMSCs.

Programmed Cell Death in Asthma: Apoptosis, Autophagy, Pyroptosis, Ferroptosis, and Necroptosis

Bronchial asthma is a complex heterogeneous airway disease, which has emerged as a global health issue. A comprehensive understanding of the different molecular mechanisms of bronchial asthma may be an efficient means to improve its clinical efficacy in the future. Increasing research evidence indicates that some types of programmed cell death (PCD), including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis, contributed to asthma pathogenesis, and may become new targets for future asthma treatment. This review briefly discusses the molecular mechanism and signaling pathway of these forms of PCD focuses on summarizing their roles in the pathogenesis and treatment strategies of asthma and offers some efficient means to improve clinical efficacy of therapeutics for asthma in the near future.

Mesenchymal stem cells and allergic airway inflammation; a therapeutic approach to induce immunoregulatory responses

Allergic airway inflammations are among the essential disorders worldwide that are already considered a significant concern. Mesenchymal stem cells (MSCs) are stromal cells with regenerative potential and immunomodulatory characteristics and are widely administered for tissue repair as an immunoregulatory agent in different inflammatory diseases. The current review summarized primary studies conducted to evaluate the therapeutic potential of MSCs for allergic airway disorders. In this case, modulation of airway pathologic inflammation and infiltration of inflammatory cells were examined, and modulation of the Th1/Th2 cellular balance and humoral responses. Also, the effects of MSCs on the Th17/Treg ratio and inducing Treg immunoregulatory responses along with macrophage and dendritic cell function were evaluated.

Key Role of Mesenchymal Stromal Cell Interaction with Macrophages in Promoting Repair of Lung Injury

Lung macrophages (Mφs) are essential for pulmonary innate immunity and host defense due to their dynamic polarization and phenotype shifts. Mesenchymal stromal cells (MSCs) have secretory, immunomodulatory, and tissue-reparative properties and have shown promise in acute and chronic inflammatory lung diseases and in COVID-19. Many beneficial effects of MSCs are mediated through their interaction with resident alveolar and pulmonary interstitial Mφs. Bidirectional MSC-Mφ communication is achieved through direct contact, soluble factor secretion/activation, and organelle transfer. The lung microenvironment facilitates MSC secretion of factors that result in Mφ polarization towards an immunosuppressive M2-like phenotype for the restoration of tissue homeostasis. M2-like Mφ in turn can affect the MSC immune regulatory function in MSC engraftment and tissue reparatory effects. This review article highlights the mechanisms of crosstalk between MSCs and Mφs and the potential role of their interaction in lung repair in inflammatory lung diseases.

Intravenous Mesenchymal Stem Cell Administration Modulates Monocytes/Macrophages and Ameliorates Asthmatic Airway Inflammation in a Murine Asthma Model

Although asthma is a common chronic airway disease that responds well to anti-inflammatory agents, some patients with asthma are unresponsive to conventional treatment. Mesenchymal stem cells (MSCs) have therapeutic potential for the treatment of inflammatory diseases owing to their immunomodulatory properties. However, the target cells of MSCs are not yet clearly known. This study aimed to determine the effect of human umbilical cord-derived MSCs (hUC-MSCs) on asthmatic lungs by modulating innate immune cells and effector T cells using a murine asthmatic model. Intravenously administered hUC-MSCs reduced airway resistance, mucus production, and inflammation in the murine asthma model. hUC-MSCs attenuated not only T helper (Th) 2 cells and Th17 cells but also augmented regulatory T cells (Tregs). As for innate lymphoid cells (ILC), hUC-MSCs effectively suppressed ILC2s by downregulating master regulators of ILC2s, such as Gata3 and Tcf7. Finally, regarding lung macrophages, hUC-MSCs reduced the total number of macrophages, particularly the proportion of the enhanced monocyte-derived macrophage population. In a closer examination of monocyte-derived macrophages, hUC-MSCs reduced the M2a and M2c populations. In conclusion, hUC-MSCs can be considered as a potential anti- asthmatic treatment given their therapeutic effect on the asthmatic airway inflammation in a murine asthma model by modulating innate immune cells, such as ILC2s, M2a, and M2c macrophages, as well as affecting Tregs and effector T cells.

Intratracheal administration of mesenchymal stem cells modulates lung macrophage polarization and exerts anti-asthmatic effects

Mesenchymal stem cells (MSCs) possess immunomodulatory properties that have therapeutic potential for the treatment of inflammatory diseases. This study investigates the effects of direct MSC administration on asthmatic airways. Umbilical cord MSCs (ucMSCs) were intratracheally administered to six-week-old female BALB/c mice sensitized and challenged with ovalbumin; airway hyperresponsiveness (AHR), analyses of airway inflammatory cells, lung histology, flow cytometry, and quantitative real-time PCR were performed. Furthermore, ex vivo and in vitro experiments were performed to assess the effects of ucMSC on M2 activation. Intratracheally administered ucMSCs decreased degree of airway resistance and the number of inflammatory cells such as T helper 2 (Th2) cells, type 2 innate lymphoid cells (ILC2), and macrophages in the murine asthma model. Particularly, MHCII and CD86 expression diminished in dendritic cells and alveolar macrophages (AMs) following ucMSC treatment. SiglecF⁺CD11c⁺CD11b^- AMs show a negative correlation with type II inflammatory cells including Th2 cells, ILC2, and eosinophils in asthmatic mice and were restored following intratracheal ucMSCs treatment. In addition, ucMSCs decreased the macrophage polarization to M2, particularly M2a. The expression levels of markers associated with M2 polarization and Th2 inflammation were also decreased. ucMSC reduced Il-12 and Tnfa expression as well as that of M2 markers such as Cd206 and Retnla ex vivo. Furthermore, the in vitro study using IL-4 treated macrophages confirmed that both direct and indirect MSC treatment significantly reduced the expression of Il-5 and Il-13. In conclusion, ucMSCs appear to suppress type II inflammation by regulating lung macrophages via soluble mediators.

Translating MSC Therapy in the Age of Obesity

Mesenchymal stromal cell (MSC) therapy has seen increased attention as a possible option to treat a number of inflammatory conditions including COVID-19 acute respiratory distress syndrome (ARDS). As rates of obesity and metabolic disease continue to rise worldwide, increasing proportions of patients treated with MSC therapy will be living with obesity. The obese environment poses critical challenges for immunomodulatory therapies that should be accounted for during development and testing of MSCs. In this review, we look to cancer immunotherapy as a model for the challenges MSCs may face in obese environments. We then outline current evidence that obesity alters MSC immunomodulatory function, drastically modifies the host immune system, and therefore reshapes interactions between MSCs and immune cells. Finally, we argue that obese environments may alter essential features of allogeneic MSCs and offer potential strategies for licensing of MSCs to enhance their efficacy in the obese microenvironment. Our aim is to combine insights from basic research in MSC biology and clinical trials to inform new strategies to ensure MSC therapy is effective for a broad range of patients.

Secondary Lymphoid Organs in Mesenchymal Stromal Cell Therapy: More Than Just a Filter

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in inflammatory models of human disease. However, clinical translation has fallen short of expectations, with many trials failing to meet primary endpoints. Failure to fully understand their mechanisms of action is a key factor contributing to the lack of successful commercialisation. Indeed, it remains unclear how the long-ranging immunomodulatory effects of MSCs can be attributed to their secretome, when MSCs undergo apoptosis in the lung shortly after intravenous infusion. Their apoptotic fate suggests that efficacy is not based solely on their viable properties, but also on the immune response to dying MSCs. The secondary lymphoid organs (SLOs) orchestrate immune responses and play a key role in immune regulation. In this review, we will discuss how apoptotic cells can modify immune responses and highlight the importance of MSC-immune cell interactions in SLOs for therapeutic outcomes.

Mesenchymal stem cells exert their anti-asthmatic effects through macrophage modulation in a murine chronic asthma model

Despite numerous previous studies, the full action mechanism of the pathogenesis of asthma remains undiscovered, and the need for further investigation is increasing in order to identify more effective target molecules. Recent attempts to develop more efficacious treatments for asthma have incorporated mesenchymal stem cell (MSC)-based cell therapies. This study aimed to evaluate the anti-asthmatic effects of MSCs primed with Liproxstatin-1, a potent ferroptosis inhibitor. In addition, we sought to examine the changes within macrophage populations and their characteristics in asthmatic conditions. Seven-week-old transgenic mice, constitutively overexpressing lung-specific interleukin (IL)-13, were used to simulate chronic asthma. Human umbilical cord-derived MSCs (hUC-MSCs) primed with Liproxstatin-1 were intratracheally administered four days prior to sampling. IL-13 transgenic mice demonstrated phenotypes of chronic asthma, including severe inflammation, goblet cell hyperplasia, and subepithelial fibrosis. Ly6C⁺M2 macrophages, found within the pro-inflammatory CD11c⁺CD11b⁺ macrophages, were upregulated and showed a strong correlation with lung eosinophil counts. Liproxstatin-1-primed hUC-MSCs showed enhanced ability to downregulate the activation of T helper type 2 cells compared to naïve MSCs in vitro and reduced airway inflammation, particularly Ly6C⁺M2 macrophages population, and fibrosis in vivo. In conclusion, intratracheal administration is an effective method of MSC delivery, and macrophages hold great potential as an additional therapeutic target for asthma.

The influence of association between aging and reduced protein intake on some immunomodulatory aspects of bone marrow mesenchymal stem cells: an experimental study

PURPOSE

Dietary protein deficiency is common in the elderly, compromising hematopoiesis and the immune response, and may cause a greater susceptibility to infections. Mesenchymal stem cells (MSCs) have immunomodulatory properties and are essential to hematopoiesis. Therefore, this study aimed to investigate, in an aging model subjected to malnutrition due a reduced protein intake, aspects related to the immunomodulatory capacity of MSCs.

METHODS

Male C57BL/6 mice from young and elderly groups were fed with normoproteic or hypoproteic diets (12% and 2% of protein, respectively) and nutritional, biochemical and hematological parameters were evaluated. MSCs from bone marrow were isolated, characterized and their secretory parameters evaluated, along with gene expression. Additionally, the effects of aging and protein malnutrition on MSC immunomodulatory properties were assessed.

RESULTS

Malnourished mice lost weight and demonstrated anemia, leukopenia, and bone marrow hypoplasia. MSCs from elderly animals from both groups showed reduced CD73 expression and higher senescence rate; also, the malnourished state affected CD73 expression in young animals. The production of IL-1β and IL-6 by MSCs was affected by aging and malnutrition, but the IL-10 production not. Aging also increased the expression of NFκB, reducing the expression of STAT-3. However, MSCs from malnourished groups, regardless of age, showed decreased TGF-β and PGE₂ production. Evaluation of the immunomodulatory capacity of MSCs revealed that aging and malnutrition affected, mainly in lymphocytes, the production of IFN-γ and IL-10.

CONCLUSION

Aging and reduced protein intake are factors that, alone or together, influence the immunomodulatory properties of MSCs and provide basic knowledge that can be further investigated to explore whether MSCs' therapeutic potential may be affected.

Tissue-Resident Immune Cells in Humans

Tissue-resident immune cells span both myeloid and lymphoid cell lineages, have been found in multiple human tissues, and play integral roles at all stages of the immune response, from maintaining homeostasis to responding to infectious challenges to resolution of inflammation to tissue repair. In humans, studying immune cells and responses in tissues is challenging, although recent advances in sampling and high-dimensional profiling have provided new insights into the ontogeny, maintenance, and functional role of tissue-resident immune cells. Each tissue contains a specific complement of resident immune cells. Moreover, resident immune cells for each lineage share core properties, along with tissue-specific adaptations. Here we propose a five-point checklist for defining resident immune cell types in humans and describe the currently known features of resident immune cells, their mechanisms of development, and their putative functional roles within various human organs. We also consider these aspects of resident immune cells in the context of future studies and therapeutics.

A Brief Overview of Global Trends in MSC-Based Cell Therapy

Human mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells or medicinal signaling cells, are important adult stem cells for regenerative medicine, largely due to their regenerative characteristics such as self-renewal, secretion of trophic factors, and the capability of inducing mesenchymal cell lineages. MSCs also possess homing and trophic properties modulating immune system, influencing microenvironment around damaged tissues and enhancing tissue repair, thus offering a broad perspective in cell-based therapies. Therefore, it is not surprising that MSCs have been the broadly used adult stem cells in clinical trials. To gain better insights into the current applications of MSCs in clinical applications, we perform a comprehensive review of reported data of MSCs clinical trials conducted globally. We summarize the biological effects and mechanisms of action of MSCs, elucidating recent clinical trials phases and findings, highlighting therapeutic effects of MSCs in several representative diseases, including neurological, musculoskeletal diseases and most recent Coronavirus infectious disease. Finally, we also highlight the challenges faced by many clinical trials and propose potential solutions to streamline the use of MSCs in routine clinical applications and regenerative medicine.

Bronchus-associated macrophages efficiently capture and present soluble inhaled antigens and are capable of local Th2 cell activation

In allergic asthma, allergen inhalation leads to local Th2 cell activation and peribronchial inflammation. However, the mechanisms for local antigen capture and presentation remain unclear. By two-photon microscopy of the mouse lung, we established that soluble antigens in the bronchial airway lumen were efficiently captured and presented by a population of CD11c⁺ interstitial macrophages with high CX3CR1-GFP and MHC class II expression. We refer to these cells as Bronchus-Associated Macrophages (BAMs) based on their localization underneath the bronchial epithelium. BAMs were enriched in collagen-rich regions near some airway branchpoints, where inhaled antigens are likely to deposit. BAMs engaged in extended interactions with effector Th2 cells and promoted Th2 cytokine production. BAMs were also often in contact with dendritic cells (DCs). After exposure to inflammatory stimuli, DCs migrated to draining lymph nodes, whereas BAMs remained lung resident. We propose that BAMs act as local antigen presenting cells in the lung and also transfer antigen to DCs.

Mesenchymal stromal cell apoptosis is required for their therapeutic function

Multipotent mesenchymal stromal cells (MSCs) ameliorate a wide range of diseases in preclinical models, but the lack of clarity around their mechanisms of action has impeded their clinical utility. The therapeutic effects of MSCs are often attributed to bioactive molecules secreted by viable MSCs. However, we found that MSCs underwent apoptosis in the lung after intravenous administration, even in the absence of host cytotoxic or alloreactive cells. Deletion of the apoptotic effectors BAK and BAX prevented MSC death and attenuated their immunosuppressive effects in disease models used to define MSC potency. Mechanistically, apoptosis of MSCs and their efferocytosis induced changes in metabolic and inflammatory pathways in alveolar macrophages to effect immunosuppression and reduce disease severity. Our data reveal a mode of action whereby the host response to dying MSCs is key to their therapeutic effects; findings that have broad implications for the effective translation of cell-based therapies.

Mesenchymal stromal cells (MSCs) demonstrate therapeutic benefits in multiple diseases, but the mechanisms remain unclear as infused MSCs do not persist in the body. Here, the authors show that MSC apoptosis is an important mechanistic element, as MSCs rendered genetically incapable of apoptosis lose their ability to ameliorate disease.

Mesenchymal stem/stromal cell therapy in atopic dermatitis and chronic urticaria: immunological and clinical viewpoints

Allergic diseases are immune-mediated diseases. Allergies share a common immunopathogenesis, with specific differences according to the specific disease. Mesenchymal stem/stromal cells (MSCs) have been applied to people suffering from allergic and many other diseases. In this review, the immunologic roles of MSCs are systemically reviewed according to disease immunopathogenesis from a clinical viewpoint. MSCs seem to be a promising therapeutic modality not only as symptomatic treatments but also as causative and even preventive treatments for allergic diseases, including atopic dermatitis and chronic urticaria.

Macrophages: The Good, the Bad, and the Gluttony

Macrophages are dynamic cells that play critical roles in the induction and resolution of sterile inflammation. In this review, we will compile and interpret recent findings on the plasticity of macrophages and how these cells contribute to the development of non-infectious inflammatory diseases, with a particular focus on allergic and autoimmune disorders. The critical roles of macrophages in the resolution of inflammation will then be examined, emphasizing the ability of macrophages to clear apoptotic immune cells. Rheumatoid arthritis (RA) is a chronic autoimmune-driven spectrum of diseases where persistent inflammation results in synovial hyperplasia and excessive immune cell accumulation, leading to remodeling and reduced function in affected joints. Macrophages are central to the pathophysiology of RA, driving episodic cycles of chronic inflammation and tissue destruction. RA patients have increased numbers of active M1 polarized pro-inflammatory macrophages and few or inactive M2 type cells. This imbalance in macrophage homeostasis is a main contributor to pro-inflammatory mediators in RA, resulting in continual activation of immune and stromal populations and accelerated tissue remodeling. Modulation of macrophage phenotype and function remains a key therapeutic goal for the treatment of this disease. Intriguingly, therapeutic intervention with glucocorticoids or other DMARDs promotes the re-polarization of M1 macrophages to an anti-inflammatory M2 phenotype; this reprogramming is dependent on metabolic changes to promote phenotypic switching. Allergic asthma is associated with Th2-polarised airway inflammation, structural remodeling of the large airways, and airway hyperresponsiveness. Macrophage polarization has a profound impact on asthma pathogenesis, as the response to allergen exposure is regulated by an intricate interplay between local immune factors including cytokines, chemokines and danger signals from neighboring cells. In the Th2-polarized environment characteristic of allergic asthma, high levels of IL-4 produced by locally infiltrating innate lymphoid cells and helper T cells promote the acquisition of an alternatively activated M2a phenotype in macrophages, with myriad effects on the local immune response and airway structure. Targeting regulators of macrophage plasticity is currently being pursued in the treatment of allergic asthma and other allergic diseases. Macrophages promote the re-balancing of pro-inflammatory responses towards pro-resolution responses and are thus central to the success of an inflammatory response. It has long been established that apoptosis supports monocyte and macrophage recruitment to sites of inflammation, facilitating subsequent corpse clearance. This drives resolution responses and mediates a phenotypic switch in the polarity of macrophages. However, the role of apoptotic cell-derived extracellular vesicles (ACdEV) in the recruitment and control of macrophage phenotype has received remarkably little attention. ACdEV are powerful mediators of intercellular communication, carrying a wealth of lipid and protein mediators that may modulate macrophage phenotype, including a cargo of active immune-modulating enzymes. The impact of such interactions may result in repair or disease in different contexts. In this review, we will discuss the origin, characterization, and activity of macrophages in sterile inflammatory diseases and the underlying mechanisms of macrophage polarization via ACdEV and apoptotic cell clearance, in order to provide new insights into therapeutic strategies that could exploit the capabilities of these agile and responsive cells.

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.

Human umbilical cord mesenchymal stem cell-derived extracellular vesicles ameliorate airway inflammation in a rat model of chronic obstructive pulmonary disease (COPD)

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is an incurable and debilitating chronic disease characterized by progressive airflow limitation associated with abnormal levels of tissue inflammation. Therefore, stem cell-based approaches to tackle the condition are currently a focus of regenerative therapies for COPD. Extracellular vesicles (EVs) released by all cell types are crucially involved in paracrine, extracellular communication. Recent advances in the field suggest that stem cell-derived EVs possess a therapeutic potential which is comparable to the cells of their origin.

METHODS

In this study, we assessed the potential anti-inflammatory effects of human umbilical cord mesenchymal stem cell (hUC-MSC)-derived EVs in a rat model of COPD. EVs were isolated from hUC-MSCs and characterized by the transmission electron microscope, western blotting, and nanoparticle tracking analysis. As a model of COPD, male Sprague-Dawley rats were exposed to cigarette smoke for up to 12 weeks, followed by transplantation of hUC-MSCs or application of hUC-MSC-derived EVs. Lung tissue was subjected to histological analysis using haematoxylin and eosin staining, Alcian blue-periodic acid-Schiff (AB-PAS) staining, and immunofluorescence staining. Gene expression in the lung tissue was assessed using microarray analysis. Statistical analyses were performed using GraphPad Prism 7 version 7.0 (GraphPad Software, USA). Student's t test was used to compare between 2 groups. Comparison among more than 2 groups was done using one-way analysis of variance (ANOVA). Data presented as median ± standard deviation (SD).

RESULTS

Both transplantation of hUC-MSCs and application of EVs resulted in a reduction of peribronchial and perivascular inflammation, alveolar septal thickening associated with mononuclear inflammation, and a decreased number of goblet cells. Moreover, hUC-MSCs and EVs ameliorated the loss of alveolar septa in the emphysematous lung of COPD rats and reduced the levels of NF-κB subunit p65 in the tissue. Subsequent microarray analysis revealed that both hUC-MSCs and EVs significantly regulate multiple pathways known to be associated with COPD.

CONCLUSIONS

In conclusion, we show that hUC-MSC-derived EVs effectively ameliorate by COPD-induced inflammation. Thus, EVs could serve as a new cell-free-based therapy for the treatment of COPD.

What is the impact of human umbilical cord mesenchymal stem cell transplantation on clinical treatment?

Background

Human umbilical cord mesenchymal stem cells (HUC-MSCs) present in the umbilical cord tissue are self-renewing and multipotent. They can renew themselves continuously and, under certain conditions, differentiate into one or more cell types constituting human tissues and organs. HUC-MSCs differentiate, among others, into osteoblasts, chondrocytes, and adipocytes and have the ability to secrete cytokines. The possibility of noninvasive harvesting and low immunogenicity of HUC-MSCs give them a unique advantage in clinical applications. In recent years, HUC-MSCs have been widely used in clinical practice, and some progress has been made in their use for therapeutic purposes.

Main body

This article describes two aspects of the clinical therapeutic effects of HUC-MSCs. On the one hand, it explains the benefits and mechanisms of HUC-MSC treatment in various diseases. On the other hand, it summarizes the results of basic research on HUC-MSCs related to clinical applications. The first part of this review highlights several functions of HUC-MSCs that are critical for their therapeutic properties: differentiation into terminal cells, immune regulation, paracrine effects, anti-inflammatory effects, anti-fibrotic effects, and regulating non-coding RNA. These characteristics of HUC-MSCs are discussed in the context of diabetes and its complications, liver disease, systemic lupus erythematosus, arthritis, brain injury and cerebrovascular diseases, heart diseases, spinal cord injury, respiratory diseases, viral infections, and other diseases. The second part emphasizes the need to establish an HUC-MSC cell bank, discusses tumorigenicity of HUC-MSCs and the characteristics of different in vitro generations of these cells in the treatment of diseases, and provides technical and theoretical support for the clinical applications of HUC-MSCs.

Conclusion

HUC-MSCs can treat a variety of diseases clinically and have achieved good therapeutic effects, and the development of HUC-MSC assistive technology has laid the foundation for its clinical application.

Unraveling the therapeutic effects of mesenchymal stem cells in asthma

Asthma is a chronic inflammatory disease associated with airway hyper-responsiveness, chronic inflammatory response, and excessive structural remodeling. The current therapeutic strategies in asthmatic patients are based on controlling the activity of type 2 T helper lymphocytes in the pulmonary tissue. However, most of the available therapies are symptomatic and expensive and with diverse side outcomes in which the interruption of these modalities contributes to the relapse of asthmatic symptoms. Up to date, different reports highlighted the advantages and beneficial outcomes regarding the transplantation of different stem cell sources, and relevant products from for the diseases' alleviation and restoration of injured sites. However, efforts to better understand by which these cells elicit therapeutic effects are already underway. The precise understanding of these mechanisms will help us to translate stem cells into the clinical setting. In this review article, we described current knowledge and future perspectives related to the therapeutic application of stem cell-based therapy in animal models of asthma, with emphasis on the underlying therapeutic mechanisms.

In utero exposure to genistein decreased intranasal house dust mite-induced respiratory allergy in middle-aged male B6C3F1 offspring

Despite many hypothesized benefits of dietary isoflavone genistein (GEN) deriving from soy-based products, questions surrounding GEN's developmental effects are increasing. To understand if in utero GEN exposure modulated postnatal respiratory allergies in the middle age, we conducted a time course study in the B6C3F1 offspring (PND 240-330) using a common household allergen (house dust mites: HDM; 10 μg/mouse for PND 240 and 290, and 50 μg/mouse for PND 330, a middle age in mice) following intranasal instillation, a physiological route of allergen exposure. GEN was administered to dams by gavage from gestational day 14 to parturition at a physiologically relevant dose (20 mg/kg body weight). Female and male offspring were sensitized with HDM allergens beginning about one month prior to sacrifice followed by challenges with three weekly dosings of HDM extracts, and they were euthanized at day 3 following the final HDM exposure. In utero exposure to GEN decreased HDM allergen-induced respiratory allergy in male B6C3F1 offspring at PND 330 as reflected by decreases in airway hyperresponsiveness (e.g., Penh value), HDM-specific IgG₁ (a Th2 type Ab) and the activity of eosinophil peroxidase in the lung (an indication of eosinophil recruitment to the lungs). However, in utero exposure to GEN had minimal effects on HDM allergen-induced respiratory allergy in the middle-aged female offspring. Changes in serum total IgE, HDM-specific IgE, and lung histopathology scores in both male and female offspring were not biologically significant. Overall, in utero GEN exposure exerted a protective effect on respiratory allergy in the middle-aged male, but not female, B6C3F1 offspring following later-life HDM exposures.

Serum-Free Medium Enhances the Therapeutic Effects of Umbilical Cord Mesenchymal Stromal Cells on a Murine Model for Acute Colitis

The usage of animal serum may ultimately prevent the application of ex vivo cultured mesenchymal stromal cells (MSCs) in a clinical setting due to safety concerns and batch-to-batch variability. Increasing regulatory pressure to limit use of animal serum has been issued and serum-free, xeno-free, and chemically defined media (S&XFM-CD) is encouraged to replace serum-containing media (SCM) in the stem cell preparation process. We previously developed a S&XFM-CD for the expansion of umbilical cord-derived MSCs (UCMSCs). Different culture conditions affect the function of MSCs, which may further affect the therapeutic efficiency and mechanisms of action. In this study, we compared the therapeutic effect and mechanism of UCMSCs in S&XFM-CD (UCMSC^S&XFM−CD) in experimental colitis with those in SCM (UCMSC^SCM). UCMSC^S&XFM−CD exhibited better therapeutic effects than UCMSC^SCM by body weight, disease activity index, and histological colitis score. UCMSC^S&XFM−CD or UCMSC^SCM migrated to the inflammation site of injured colon, but exhibited low levels of recruitment and persistence. Systemic depletion of endogenous macrophages impaired the therapeutic effects of UCMSC^SCM and UCMSC^S&XFM−CD. Furthermore, UCMSC^S&XFM−CD more markedly promoted intestinal macrophage polarisation from M1 to M2 phenotype to produce higher levels of IL-10 and lower levels of TNF-α in colon tissue than UCMSC^SCM, while a higher level of IL-4 was produced in UCMSC^SCM-treated group. UCMSC^S&XFM−CD cocultured with RAW264.7 cells in a transwell system promoted the release of TSG-6 and IL-6, whereas UCMSC^SCM increased PGE₂ levels. Taken together, we demonstrated that UCMSCs in S&XFM-CD exhibited improved therapeutic effects with altered cytokine secretion in an experimental acute colitis model.

Evaluation of Human MSCs Treatment Frequency on Airway Inflammation in a Mouse Model of Acute Asthma

BACKGROUND

Studies in experimental models of allergic asthma have shown that mesenchymal stem cells (MSCs) have therapeutic potential for T-helper 2 (T_H2) cell-mediated inflammation. However, the mechanisms underlying these therapeutic effects are not fully understood and their safety has not been confirmed.

METHODS

Using a mouse model of experimental allergic asthma, we investigated the efficacy of human adipose-derived mesenchymal stem cells (hADSCs) or human bone marrow-derived mesenchymal stem cells (hBMSCs) according to treatment frequency and timing.

RESULTS

Ovalbumin (OVA)-sensitized and -challenged mice exhibited airway hyperresponsiveness (AHR), airway inflammation, and significant increases in T_H2 cytokine levels. Both double and single human mesenchymal stem cell (hMSC) treatments significantly decreased AHR and bronchoalveolar lavage fluid counts. In addition, single treatment with hMSCs showed significant attenuation of allergic airway inflammation. However, double treatment with hMSCs during OVA -sensitization and -challenge further increased inflammatory cell infiltration, and T_H2 cytokine levels.

CONCLUSION

The results of treatment with hADSCs or hBMSCs suppresses AHR and airway inflammation. However, double hMSC treatment significantly induces eosinophilic airway inflammation and lung histological changes. Therefore, double hMSC treatment is ineffective against asthma and single injection frequency appears to be more important for the treatment of asthma. These results suggest that hMSC therapy can be used for treatment of asthma patients but that it should be used carefully.

Small extracellular vesicles derived from human MSCs prevent allergic airway inflammation via immunomodulation on pulmonary macrophages

Allergic airway inflammation is a major public health disease that affects up to 300 million people in the world. However, its management remains largely unsatisfactory. The dysfunction of pulmonary macrophages contributes greatly to the development of allergic airway inflammation. It has been reported that small extracellular vesicles derived from mesenchymal stromal cells (MSC-sEV) were able to display extensive therapeutic effects in some immune diseases. This study aimed to investigate the effects of MSC-sEV on allergic airway inflammation, and the role of macrophages involved in it. We successfully isolated MSC-sEV by using anion exchange chromatography, which were morphologically intact and positive for the specific EV markers. MSC-sEV significantly reduced infiltration of inflammatory cells and number of epithelial goblet cells in lung tissues of mice with allergic airway inflammation. Levels of inflammatory cells and cytokines in bronchoalveolar lavage fluid were also significantly decreased. Importantly, levels of monocytes-derived alveolar macrophages and M2 macrophages were significantly reduced by MSC-sEV. MSC-sEV were excreted through spleen and liver at 24 h post-administration in mice, and were able to be taken in by macrophages both in vivo and in vitro. In addition, proteomics analysis of MSC-sEV revealed that the indicated three types of MSC-sEV contained different quantities of proteins and shared 312 common proteins, which may be involved in the therapeutic effects of MSC-sEV. In total, our study demonstrated that MSC-sEV isolated by anion exchange chromatography were able to ameliorate Th2-dominant allergic airway inflammation through immunoregulation on pulmonary macrophages, suggesting that MSC-sEV were promising alternative therapy for allergic airway inflammation in the future.

Biological Considerations in Scaling Up Therapeutic Cell Manufacturing

Cell therapeutics - using cells as living drugs - have made advances in many areas of medicine. One of the most clinically studied cell-based therapy products is mesenchymal stromal cells (MSCs), which have shown promising results in promoting tissue regeneration and modulating inflammation. However, MSC therapy requires large numbers of cells, the generation of which is not feasible via conventional planar tissue culture methods. Scale-up manufacturing methods (e.g., propagation on microcarriers in stirred-tank bioreactors), however, are not specifically tailored for MSC expansion. These processes may, in principle, alter the cell secretome, a vital component underlying the immunosuppressive properties and clinical effectiveness of MSCs. This review outlines our current understanding of MSC properties and immunomodulatory function, expansion in commercial manufacturing systems, and gaps in our knowledge that need to be addressed for effective up-scaling commercialization of MSC therapy.

Mesenchymal stem cells elicit macrophages into M2 phenotype via improving transcription factor EB-mediated autophagy to alleviate diabetic nephropathy

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. Chronic inflammation is recognized as a key causal factor in the development and progression of DN, and the imbalance of M1/M2 macrophages (Mφ) contributes to this process. Mesenchymal stem cells (MSCs) have been reported to prevent renal injuries via immune regulation in diabetic models, but whether these benefits are owing to the regulation of Mφ, and the underlying signaling pathways are unknown. Here, we showed that MSCs elicited Mφ into M2 phenotype and prevented renal injuries in DN mice, but these effects were abolished when the Mφ were depleted by clodronate liposomes (Lipo-Clod), suggesting that Mφ were necessary for renal protection of MSCs in DN mice. Moreover, the MSCs promoted M2 polarization was attributable to the activation of transcription factor EB (TFEB) and subsequent restore of lysosomal function and autophagy activity in Mφ. Furthermore, in vivo adoptive transfer of Mφ^{in vivo} (Mφ from DN + MSCs mice) or Mφ^MSCs (Mφ cocultured with MSCs in vitro) to DN mice improved renal function. While, TFEB knockdown in Mφ significantly abolished the protective role of Mφ^MSCs . Altogether, these findings revealed that MSCs suppress inflammatory response and alleviate renal injuries in DN mice via TFEB-dependent Mφ switch.

Mesenchymal stem cells in allergic diseases: Current status

Allergic diseases, which include asthma, allergic skin diseases, allergic rhinitis and allergic conjunctivitis, have already garnered worldwide public health attention over recent decades. Mesenchymal stem cells (MSCs) have gradually emerged as a potential method for treating allergic diseases due to their immunosuppressive characteristics, tissue repair ability and secretion of various biological factors. This potential of MSC-based therapy has been confirmed in clinical and preclinical studies, which report the therapeutic benefits of MSCs for various allergic diseases and explore the antiallergic mechanisms. In this review, we focus on the discoveries and biological mechanisms of MSCs as a therapeutic tool in allergic diseases. We discuss the challenges of conducting MSC studies as well as future directions.

The immunomodulatory effects of mesenchymal stem cells on long term pulmonary complications in an animal model exposed to a sulfur mustard analog

INTRODUCTION

Sulfur Mustard (SM) is one of the most lethal chemicals with major complications manifested in the lungs. Although the pathogenesis behind SM-induced lung injury still remains poorly understood, prolonged activation and the imbalance of two major macrophage populations (M1 and M2) have been suggested to be involved. Here, we tried to investigate the effectiveness of adipose-derived mesenchymal stem cells (AD-MSC) on long-term lesions induced by CEES, an SM analog. The modulation of pulmonary immune cells and alveolar macrophage phenotype alteration was studied in the animal model used.

METHODS

Histopathological changes were investigated in the lungs and analysis of surface markers of alveolar macrophages as well as their cytokine expression in the BAL fluid was carried out by flow cytometry and ELISA, respectively.

RESULTS

Treatment of mice with AD-MSC after intraperitoneal administration of CEES (10 mg/kg) reduces progressive histopathologic changes in the lung. Flow cytometric analysis of isolated alveolar macrophages in the bronchoalveolar lavage showed that the accumulation of both M1 and M2 macrophages in response to CEES was reduced by MSC administration. AD-MSCs caused a marked reduction in the CD86- and CD206-expressing macrophages compared to the untreated groups. The modulating effect of AD-MSCs in the M1-subset was much more significant compared to M2. These findings suggest that AD-MSCs understand their environment and restore the balance in disorders associated with Th1 or Th2 imbalance. Our results indicate that MSCs may represent an effective approach to repair lung injury induced by mustards.

Multiple doses of adipose tissue-derived mesenchymal stromal cells induce immunosuppression in experimental asthma

In experimental house dust mite (HDM)‐induced allergic asthma, therapeutic administration of a single dose of adipose tissue‐derived mesenchymal stromal cells (MSCs) ameliorates lung inflammation but is unable to reverse remodeling. We hypothesized that multiple doses of MSCs might exert better therapeutic effects by reducing lung inflammation and remodeling but might also result in immunosuppressive effects in experimental asthma. HDM was administered intranasally in C57BL/6 mice. After the last HDM challenge, mice received two or three doses of MSCs (10⁵ cells per day) or saline intravenously. An additional cohort of mice received dexamethasone as a positive control for immunosuppression. Two and three doses of MSCs reduced lung inflammation, levels of interleukin (IL)‐4, IL‐13, and eotaxin; total leukocyte, CD4⁺ T‐cell, and eosinophil counts in bronchoalveolar lavage fluid; and total leukocyte counts in bone marrow, spleen, and mediastinal lymph nodes. Two and three doses of MSCs also reduced collagen fiber content and transforming growth factor‐β levels in lung tissue; however, the three‐dose regimen was more effective, and reduced these parameters to control levels, while also decreasing α‐actin content in lung tissue. Two and three doses of MSCs improved lung mechanics. Dexamethasone, two and three doses of MSCs similarly increased galectin levels, but only the three‐dose regimen increased CD39 levels in the thymus. Dexamethasone and the three‐dose, but not the two‐dose regimen, also increased levels of programmed death receptor‐1 and IL‐10, while reducing CD4⁺CD8^low cell percentage in the thymus. In conclusion, multiple doses of MSCs reduced lung inflammation and remodeling while causing immunosuppression in HDM‐induced allergic asthma.

Mesenchymal stem cell treatment attenuates liver and lung inflammation after ethanol intoxication and burn injury

Cutaneous burn injury is one of the most devastating injuries one can obtain, with tissue damage extending beyond the skin wound to distal organs, including the gastrointestinal tract, liver, and lungs. Multiple organ failure is a leading cause of death after burn injury, resulting in excessive systemic and localized inflammation directly contributing to end organ damage. We postulated that the gut-liver-lung inflammatory axis underscores multiple organ failure in the context of burn injury and is hyper-activated when ethanol intoxication precedes burn. Mesenchymal stem cells (MSCs) are regenerative and anti-inflammatory, and MSC treatment has been shown to be beneficial in several immune disorders and injury models. Our objective was to determine whether intravenous infusion of exogenous bone marrow-derived MSCs could reduce post-burn and intoxication pulmonary, hepatic, and systemic inflammation. Vehicle- or ethanol- (1.6 g/kg) treated mice were subjected to sham or 15% total body surface area scald burn. One hour post-injury, mice were given 5 × 10⁵ CFSE-labeled MSCs or phosphate-buffered saline intravenously (i.v.) and were euthanized 24 h later. We assessed circulating biomarkers of inflammation and liver damage, measured cytokine and chemokine production, and quantified apoptosis in lung and liver tissue. Compared to intoxicated and burned mice, those treated with MSCs had less cellularity, limited apoptosis, and a slight reduction in the pro-inflammatory cytokine interleukin-6 (IL-6) and the neutrophil chemokine, KC (CXCL1) in lung tissue. Mice with MSCs treatment had more dramatic anti-inflammatory effects on systemic and hepatic inflammation, as serum IL-6 levels were diminished by 43%, and il6 and kc expression in liver tissue were markedly reduced, as were biomarkers of liver damage, aspartate transaminase (AST) and alanine transaminase (AST), compared with intoxicated and burned mice. Taken together, our results suggest intravenous MSCs treatment can diminish systemic inflammation, lessen hepatic damage, and decrease liver and lung apoptosis and inflammation, indicating MSCs as a novel therapy for restoring homeostasis of multiple organ systems in intoxicated burn patients.

ATP/P2X7r axis mediates the pathological process of allergic asthma by inducing M2 polarization of alveolar macrophages

Recent studies revealed that macrophages are polarized towards the M2 phenotype in an ovalbumin (OVA)-induced asthmatic model. Alveolar macrophages (AMs) are immune barriers in alveoli to various pathogens in the respiratory tract; AMs suppress Th2 cell proliferation, inhibit interleukin (IL)-4, IL-5, and IL-13 secretion, and protect against airway hyperresponsiveness in allergic asthma. However, the polarization status and effects of different types of AMs in the pathogenesis of asthma are not known. ATP/P2X7r, expressed mainly on macrophages and dendritic cells, is associated with acute and chronic asthmatic airway inflammation and Th2 immune responses in mice and humans and functions by activating the NLRP3 inflammasome complex and inducing proinflammatory cytokine release (IL-1β and IL-18). Therefore, we evaluated the association between the ATP/P2X7r axis and different types of AMs in the pathology of allergic asthma. A murine AM-depleted asthma model was established by administration of clodronate-encapsulated liposomes, and M1-or M2-AMs were adoptively transferred to confirm the effects of different AMs in allergic asthma. Brilliant Blue G and BzATP were administered to OVA/HDM-induced mice in vivo. Lipopolysaccharide + OVA, ATP, Brilliant Blue G, and BzATP were used to stimulate AMs isolated from control and asthmatic mice. We found that selective depletion of AMs aggravated lung inflammation in asthmatic mice. Further, M2-type AMs may play a key role in mediating asthmatic inflammatory responses via the adoptive transfer of M2-type AMs to AM-depleted asthmatic mice, and the phenotype of AMs differentiated to M2 type in asthma. P2X7r expression in M2-type AMs was higher than that in M1-type AMs. Activating P2X7r induced polarization of M2-type AMs and inhibited polarization of M1-type AMs, while blockage of P2X7r had the opposite effect. The ATP/P2X7r axis may participate in the pathogenesis of asthma by mediating the M2-type AM polarization.

Effect of mesenchymal stromal (stem) cell (MSC) transplantation in asthmatic animal models: A systematic review and meta-analysis

BACKGROUND

Over the years, mesenchymal stromal (stem) cells (MSCs) have been pre-clinically applied in the treatment of variety kinds of diseases including asthma and chronic lung diseases. Aim of the current study was to systematically review and to conduct meta-analysis on the published studies of MSC treatment in asthma animal models.

METHODS

Publications on the MSC and asthma treatment was thoroughly searched in the electronic databases. Statistical analysis was then performed using the Comprehensive Meta-Analysis software (Version 3). Effect of MSC therapy on asthma model was assessed by Hedges's g with 95% confidence intervals (95% CIs). Random effect model was used due to the heterogeneity between the studies.

RESULTS

Meta-analysis of the 32 included studies showed that MSC transplantation was significantly in favor of attenuating lung injury and remodeling (Hedges's g = -9.104 ± 0.951 with 95% CI: -10.969 ∼ -7.240, P < 0.001) and airway inflammation (Hedges's g = -4.146 ± 0.688 with 95% CI: -5.495 ∼ -2.797, P < 0.001). The mechanism of MSC therapy in asthma seems to be regulating the balance of Th1 cytokine and Th2 cytokines (IFN-γ: Hedges's g = 4.779 ± 1.408 with 95% CI: 1.099-2.725, P < 0.001; IL-4: Hedges's g = -10.781 ± 1.062 with 95% CI: -12.863 ∼ -8.699, P < 0.001; IL-5: Hedges's g = -10.537 ± 1.269 with 95% CI: -13.025 ∼ -8.050, P < 0.001; IL-13: Hedges's g = -6.773 ± 0.788 with 95% CI: -8.318 ∼ -5.229, P < 0.001).

CONCLUSION

Findings of the current systemic review suggested a potential role for MSCs in asthma treatment although it is still challenging in clinical practice. The mechanisms of MSCs in pre-clinical asthma treatment may be associated with attenuating airway inflammation through regulating Th1 and Th2 cytokines.

Serum from Asthmatic Mice Potentiates the Therapeutic Effects of Mesenchymal Stromal Cells in Experimental Allergic Asthma

Asthma is a chronic inflammatory disease characterized by airway inflammation and remodeling, which can lead to progressive decline of lung function. Although mesenchymal stromal cells (MSCs) have shown beneficial immunomodulatory properties in preclinical models of allergic asthma, effects on airway remodeling have been limited. Mounting evidence suggests that prior exposure of MSCs to specific inflammatory stimuli or environments can enhance their immunomodulatory properties. Therefore, we investigated whether stimulating MSCs with bronchoalveolar lavage fluid (BALF) or serum from asthmatic mice could potentiate their therapeutic properties in experimental asthma. In a house dust mite (HDM) extract asthma model in mice, unstimulated, asthmatic BALF‐stimulated, or asthmatic serum‐stimulated MSCs were administered intratracheally 24 hours after the final HDM challenge. Lung mechanics and histology; BALF protein, cellularity, and biomarker levels; and lymph‐node and bone marrow cellularity were assessed. Compared with unstimulated or BALF‐stimulated MSCs, serum‐stimulated MSCs further reduced BALF levels of interleukin (IL)‐4, IL‐13, and eotaxin, total and differential cellularity in BALF, bone marrow and lymph nodes, and collagen fiber content, while increasing BALF IL‐10 levels and improving lung function. Serum stimulation led to higher MSC apoptosis, expression of various mediators (transforming growth factor‐β, interferon‐γ, IL‐10, tumor necrosis factor‐α‐stimulated gene 6 protein, indoleamine 2,3‐dioxygenase‐1, and IL‐1 receptor antagonist), and polarization of macrophages to M2 phenotype. In conclusion, asthmatic serum may be a novel strategy to potentiate therapeutic effects of MSCs in experimental asthma, leading to further reductions in both inflammation and remodeling than can be achieved with unstimulated MSCs. stem cells translational medicine2019;8:301&312

Intratracheal administration of adipose derived mesenchymal stem cells alleviates chronic asthma in a mouse model

BACKGROUND

Adipose-derived mesenchymal stem cell (ASCs) exerts immunomodulatory roles in asthma. However, the underlying mechanism remains unclear. The present study aimed to explore the effects and mechanisms of ASCs on chronic asthma using an ovalbumin (OVA)-sensitized asthmatic mouse model.

METHODS

Murine ASCs (mASCs) were isolated from male Balb/c mice and identified by the expression of surface markers using flow cytometry. The OVA-sensitized asthmatic mouse model was established and then animals were treated with the mASCs through intratracheal delivery. The therapy effects were assessed by measuring airway responsiveness, performing immuohistochemical analysis, and examining bronchoalveolar lavage fluid (BALF). Additionally, the expression of inflammatory cytokines and lgE was detected by CHIP and ELISA, respectively. The mRNA levels of serum indices were detected using qRT-PCR.

RESULTS

The mASCs grew by adherence with fibroblast-like morphology, and showed the positive expression of CD90, CD44, and CD29 as well as the negative expression of CD45 and CD34, indicating that the mASCs were successfully isolated. Administering mASCs to asthmatic model animals through intratracheal delivery reduced airway responsiveness, the number of lymphocytes (P < 0.01) and the expression of lgE (P < 0.01), IL-1β (P < 0.05), IL-4 (P < 0.001), and IL-17F (P < 0.001), as well as increased the serum levels of IL-10 and Foxp3, and the percentage of CD4 + CD25 + Foxp3+ Tregs in the spleen, and reduced the expression of IL-17 (P < 0.05) and RORγ.

CONCLUSIONS

Intratracheal administration of mASCs alleviated airway inflammation, improved airway remodeling, and relieved airway hyperresponsiveness in an OVA-sensitized asthma model, which might be associated with the restoration of Th1/Th2 cell balance by mASCs.

The therapeutic effect of mesenchymal stem cells on pulmonary myeloid cells following neonatal hyperoxic lung injury in mice

Background

Exposure to high levels of oxygen (hyperoxia) after birth leads to lung injury. Our aims were to investigate the modulation of myeloid cell sub-populations and the reduction of fibrosis in the lungs following administration of human mesenchymal stem cells (hMSC) to neonatal mice exposed to hyperoxia.

Method

Newborn mice were exposed to 90% O₂ (hyperoxia) or 21% O₂ (normoxia) from postnatal days 0–4. A sub-group of hyperoxia mice were injected intratracheally with 2.5X10⁵ hMSCs. Using flow cytometry we assessed pulmonary immune cells at postnatal days 0, 4, 7 and 14. The following markers were chosen to identify these cells: CD45⁺ (leukocytes), Ly6C⁺Ly6G⁺ (granulocytes), CD11b⁺CD11c⁺ (macrophages); macrophage polarisation was assessed by F4/80 and CD206 expression. hMSCs expressing enhanced green fluorescent protein (eGFP) and firefly luciferase (fluc) were administered via the trachea at day 4. Lung macrophages in all groups were profiled using next generation sequencing (NGS) to assess alterations in macrophage phenotype. Pulmonary collagen deposition and morphometry were assessed at days 14 and 56 respectively.

Results

At day 4, hyperoxia increased the number of pulmonary Ly6C⁺Ly6G⁺ granulocytes and F4/80^lowCD206^low macrophages but decreased F4/80^highCD206^high macrophages. At days 7 and 14, hyperoxia increased numbers of CD45⁺ leukocytes, CD11b⁺CD11c⁺ alveolar macrophages and F4/80^lowCD206^low macrophages but decreased F4/80^highCD206^high macrophages. hMSCs administration ameliorated these effects of hyperoxia, notably reducing numbers of CD11b⁺CD11c⁺ and F4/80^lowCD206^low macrophages; in contrast, F4/80^highCD206^high macrophages were increased. Genes characteristic of anti-inflammatory ‘M2’ macrophages (Arg1, Stat6, Retnla, Mrc1, Il27ra, Chil3, and Il12b) were up-regulated, and pro-inflammatory ‘M1’ macrophages (Cd86, Stat1, Socs3, Slamf1, Tnf, Fcgr1, Il12b, Il6, Il1b, and Il27ra) were downregulated in isolated lung macrophages from hyperoxia-exposed mice administered hMSCs, compared to mice without hMSCs. Hydroxyproline assay at day 14 showed that the 2-fold increase in lung collagen following hyperoxia was reduced to control levels in mice administered hMSCs. By day 56 (early adulthood), hMSC administration had attenuated structural changes in hyperoxia-exposed lungs.

Conclusions

Our findings suggest that hMSCs reduce neonatal lung injury caused by hyperoxia by modulation of macrophage phenotype. Not only did our cell-based therapy using hMSC induce structural repair, it limited the progression of pulmonary fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0816-x) contains supplementary material, which is available to authorized users.

Eicosapentaenoic Acid Enhances the Effects of Mesenchymal Stromal Cell Therapy in Experimental Allergic Asthma

Asthma is characterized by chronic lung inflammation and airway hyperresponsiveness. Despite recent advances in the understanding of its pathophysiology, asthma remains a major public health problem and, at present, there are no effective interventions capable of reversing airway remodeling. Mesenchymal stromal cell (MSC)-based therapy mitigates lung inflammation in experimental allergic asthma; however, its ability to reduce airway remodeling is limited. We aimed to investigate whether pre-treatment with eicosapentaenoic acid (EPA) potentiates the therapeutic properties of MSCs in experimental allergic asthma. Seventy-two C57BL/6 mice were used. House dust mite (HDM) extract was intranasally administered to induce severe allergic asthma in mice. Unstimulated or EPA-stimulated MSCs were administered intratracheally 24 h after final HDM challenge. Lung mechanics, histology, protein levels of biomarkers, and cellularity in bronchoalveolar lavage fluid (BALF), thymus, lymph nodes, and bone marrow were analyzed. Furthermore, the effects of EPA on lipid body formation and secretion of resolvin-D₁ (RvD₁), prostaglandin E₂ (PGE₂), interleukin (IL)-10, and transforming growth factor (TGF)-β1 by MSCs were evaluated in vitro. EPA-stimulated MSCs, compared to unstimulated MSCs, yielded greater therapeutic effects by further reducing bronchoconstriction, alveolar collapse, total cell counts (in BALF, bone marrow, and lymph nodes), and collagen fiber content in airways, while increasing IL-10 levels in BALF and M2 macrophage counts in lungs. In conclusion, EPA potentiated MSC-based therapy in experimental allergic asthma, leading to increased secretion of pro-resolution and anti-inflammatory mediators (RvD₁, PGE₂, IL-10, and TGF-β), modulation of macrophages toward an anti-inflammatory phenotype, and reduction in the remodeling process. Taken together, these modifications may explain the greater improvement in lung mechanics obtained. This may be a promising novel strategy to potentiate MSCs effects.

Mesenchymal Stem Cells Recruit CCR2+ Monocytes To Suppress Allergic Airway Inflammation

Mesenchymal stem cells (MSC) exert immune modulatory properties and previous studies demonstrated suppressive effects of MSC treatment in animal models of allergic airway inflammation. However, the underlying mechanisms have not been fully elucidated. We studied the role of MSC in immune activation and subsequent recruitment of monocytes in suppressing airway hyperresponsiveness and airway inflammation using a mouse model of allergic airway inflammation. MSC administration prior to or after allergen challenge inhibited the development of airway inflammation in allergen-sensitized mice. This was accompanied by an influx of CCR2-positive monocytes, which were localized around injected MSC in the lungs. Notably, IL-10-producing monocytes and/or macrophages were also increased in the lungs. Systemic administration of liposomal clodronate or a CCR2 antagonist significantly prevented the suppressive effects of MSC. Activation of MSC by IFN-γ leading to the upregulation of CCL2 expression was essential for the suppressive effects, as administration of wild-type MSC into IFN-γ-deficient recipients, or IFN-γ receptor-deficient or CCL2-deficient MSC into wild-type mice failed to suppress airway inflammation. These results suggest that MSC activation by IFN-γ, followed by increased expression of CCL2 and recruitment of monocytes to the lungs, is essential for suppression by MSC in allergen-induced airway hyperresponsiveness and airway inflammation.

Role of Stem Cells in Pathophysiology and Therapy of Spondyloarthropathies-New Therapeutic Possibilities?

Considerable progress has been made recently in understanding the complex pathogenesis and treatment of spondyloarthropathies (SpA). Currently, along with traditional disease modifying anti-rheumatic drugs (DMARDs), TNF-α, IL-12/23 and IL-17 are available for treatment of such diseases as ankylosing spondylitis (AS) and psoriatic arthritis (PsA). Although they adequately control inflammatory symptoms, they do not affect the abnormal bone formation processes associated with SpA. However, the traditional therapeutic approach does not cover the regenerative treatment of damaged tissues. In this regards, stem cells may offer a promising, safe and effective therapeutic option. The aim of this paper is to present the role of mesenchymal stromal cells (MSC) in pathogenesis of SpA and to highlight the opportunities for using stem cells in regenerative processes and in the treatment of inflammatory changes in articular structures.

Therapeutic administration of bone marrow-derived mesenchymal stromal cells reduces airway inflammation without up-regulating Tregs in experimental asthma

BACKGROUND

Prophylactic administration of mesenchymal stromal cells (MSCs) derived from adipose (AD-MSC) and bone marrow tissue (BM-MSC) in ovalbumin-induced asthma hinders inflammation in a Treg-dependent manner. It is uncertain whether MSCs act through Tregs when inflammation is already established in asthma induced by a clinically relevant allergen.

OBJECTIVE

Evaluate the effect of therapeutic administration of MSCs on inflammation and Treg cells in house dust mite (HDM)-induced asthma.

METHODS

BM-MSCs and AD-MSCs were administered intratracheally to C57BL/6 mice 1 day after the last HDM challenge. Lung function, remodelling and parenchymal inflammation were assayed 3 or 7 days after MSCs treatment, through invasive plethysmography and histology, respectively. Bronchoalveolar lavage fluid (BALF) and mediastinal lymph nodes (mLNs) were assessed regarding the inflammatory profile by flow cytometry, ELISA and qRT-PCR. MSCs were studied regarding their potential to induce Treg cells from primed and unprimed lymphocytes in vitro.

RESULTS

BM-MSCs, but not AD-MSCs, reduced lung influx of eosinophils and B cells and increased IL-10 levels in HDM-challenged mice. Neither BM-MSCs nor AD-MSCs reduced lung parenchymal inflammation, airway hyperresponsiveness or mucus hypersecretion. BM-MSCs and AD-MSCs did not up-regulate Treg cell counts within the airways and mLNs, but BM-MSCs decreased the pro-inflammatory profile of alveolar macrophages. Co-culture of BM-MSCs and AD-MSCs with allergen-stimulated lymphocytes reduced Treg cell counts in a cell-to-cell contact-independent manner, although co-culture of both MSCs with unprimed lymphocytes up-regulated Treg cell counts.

CONCLUSIONS

MSCs therapeutically administered exert anti-inflammatory effects in the airway of HDM-challenged mice, but do not ameliorate lung function or remodelling. Although MSC pre-treatment can increase Treg cell numbers, it is highly unlikely that the MSCs will induce Treg cell expansion when lymphocytes are allergenically primed in an established lung inflammation.

Ly6Chi monocytes are required for mesenchymal stem/stromal cell-induced immune tolerance in mice with experimental autoimmune uveitis

The cells of the innate immune system, in addition to their capacity to elicit immunity, play a substantial role in immune tolerance induction. Our group has recently shown that a distinct subset of MHC II^hiB220^hiCD11b^mid suppressive macrophages is increased in the lung by intravenous (IV) administration of mesenchymal stem/stromal cells (MSC) and induces immune tolerance. Herein, we demonstrate that circulating CD11b^hiLy6C^hi monocytes are precursors to MHC II^hiB220^hiCD11b^mid macrophages in the lung and required for MSC-induced tolerance in a mouse model of experimental autoimmune uveitis (EAU). Analysis revealed that IV MSC induced an increase in IL-10-expressing MHC II^hiB220^hiCD11b^mid macrophages in the lung with a concomitant decrease in CD11b^hiLy6C^hi monocytes. Selective depletion of circulating CD11b^hiLy6C^hi cells abrogated the effects of MSC in the induction of IL-10^hiMHC II^hiB220^hiCD11b^mid macrophages and immune tolerance in EAU mice. Similarly, an increase in CD4⁺CD25⁺Foxp3⁺ Tregs by MSCs was also reversed by CD11b^hiLy6C^hi cell depletion. These results suggest that CD11b^hiLy6C^hi monocytes are critical for MSC-induced immune tolerance.