Mesenchymal stem cells regulate airway contractile tissue remodeling in murine experimental asthma

Human macrophage migration inhibitory factor potentiates mesenchymal stromal cell efficacy in a clinically relevant model of allergic asthma

Current asthma therapies focus on reducing symptoms but fail to restore existing structural damage. Mesenchymal stromal cell (MSC) administration can ameliorate airway inflammation and reverse airway remodeling. However, differences in patient disease microenvironments seem to influence MSC therapeutic effects. A polymorphic CATT tetranucleotide repeat at position 794 of the human macrophage migration inhibitory factor (hMIF) gene has been associated with increased susceptibility to and severity of asthma. We investigated the efficacy of human MSCs in high- vs. low-hMIF environments and the impact of MIF pre-licensing of MSCs using humanized MIF mice in a clinically relevant house dust mite (HDM) model of allergic asthma. MSCs significantly attenuated airway inflammation and airway remodeling in high-MIF-expressing CATT7 mice but not in CATT5 or wild-type littermates. Differences in efficacy were correlated with increased MSC retention in the lungs of CATT7 mice. MIF licensing potentiated MSC anti-inflammatory effects at a previously ineffective dose. Mechanistically, MIF binding to CD74 expressed on MSCs leads to upregulation of cyclooxygenase 2 (COX-2) expression. Blockade of CD74 or COX-2 function in MSCs prior to administration attenuated the efficacy of MIF-licensed MSCs in vivo. These findings suggest that MSC administration may be more efficacious in severe asthma patients with high MIF genotypes (CATT6/7/8).

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.

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.

Functional enhancement strategies to potentiate the therapeutic properties of mesenchymal stromal cells for respiratory diseases

Respiratory diseases remain a major health concern worldwide because they subject patients to considerable financial and psychosocial burdens and result in a high rate of morbidity and mortality. Although significant progress has been made in understanding the underlying pathologic mechanisms of severe respiratory diseases, most therapies are supportive, aiming to mitigate symptoms and slow down their progressive course but cannot improve lung function or reverse tissue remodeling. Mesenchymal stromal cells (MSCs) are at the forefront of the regenerative medicine field due to their unique biomedical potential in promoting immunomodulation, anti-inflammatory, anti-apoptotic and antimicrobial activities, and tissue repair in various experimental models. However, despite several years of preclinical research on MSCs, therapeutic outcomes have fallen far short in early-stage clinical trials for respiratory diseases. This limited efficacy has been associated with several factors, such as reduced MSC homing, survival, and infusion in the late course of lung disease. Accordingly, genetic engineering and preconditioning methods have emerged as functional enhancement strategies to potentiate the therapeutic actions of MSCs and thus achieve better clinical outcomes. This narrative review describes various strategies that have been investigated in the experimental setting to functionally potentiate the therapeutic properties of MSCs for respiratory diseases. These include changes in culture conditions, exposure of MSCs to inflammatory environments, pharmacological agents or other substances, and genetic manipulation for enhanced and sustained expression of genes of interest. Future directions and challenges in efficiently translating MSC research into clinical practice are discussed.

Regenerative medicine in lung diseases: A systematic review

Regenerative medicine has opened the door to the exploration of new therapeutic methods for the treatment of various diseases, especially those associated with local or general disregulation of the immune system. In pulmonary diseases, new therapeutic strategies have emerged that are aimed at restoring functional lung tissue rather than alleviating symptoms. These strategies focus on tissue regeneration using stem cells and/or their derivatives or replacement of dysfunctional tissue using biomedical engineering. Animal health can directly benefit from regenerative therapy strategies and also serve as a translational experimental model for human disease. Several clinical trials have been conducted to evaluate the effects of cellular treatment on inflammatory lung disease in animals. Data reported to date show several beneficial effects in ex vivo and in vivo models; however, our understanding of the mechanisms that regenerative therapies exert on diseased tissues remains incomplete.

Mesenchymal Stem/Stromal Cells in Asthma Therapy: Mechanisms and Strategies for Enhancement

Asthma is a complex and heterogeneous disease characterized by chronic airway inflammation, airway hyperresponsiveness, and airway remodeling. Most asthmatic patients are well-established using standard treatment strategies and advanced biologicals. However, a small group of patients who do not respond to biological treatments or are not effectively controlled by available treatment strategies remain a clinical challenge. Therefore, new therapies are urgently needed for poorly controlled asthma. Mesenchymal stem/stromal cells (MSCs) have shown therapeutic potential in relieving airway inflammation and repairing impaired immune balance in preclinical trials owing to their immunomodulatory abilities. Noteworthy, MSCs exerted a therapeutic effect on steroid-resistant asthma with rare side effects in asthmatic models. Nevertheless, adverse factors such as limited obtained number, nutrient and oxygen deprivation in vitro, and cell senescence or apoptosis affected the survival rate and homing efficiency of MSCs, thus limiting the efficacy of MSCs in asthma. In this review, we elaborate on the roles and underlying mechanisms of MSCs in the treatment of asthma from the perspective of their source, immunogenicity, homing, differentiation, and immunomodulatory capacity and summarize strategies to improve their therapeutic effect.

Mesenchymal stem cell-based treatments for COVID-19: status and future perspectives for clinical applications

As a result of cross-species transmission in December 2019, the coronavirus disease 2019 (COVID-19) became a serious endangerment to human health and the causal agent of a global pandemic. Although the number of infected people has decreased due to effective management, novel methods to treat critical COVID-19 patients are still urgently required. This review describes the origins, pathogenesis, and clinical features of COVID-19 and the potential uses of mesenchymal stem cells (MSCs) in therapeutic treatments for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients. MSCs have previously been shown to have positive effects in the treatment of lung diseases, such as acute lung injury, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, lung cancer, asthma, and chronic obstructive pulmonary disease. MSC mechanisms of action involve differentiation potentials, immune regulation, secretion of anti-inflammatory factors, migration and homing, anti-apoptotic properties, antiviral effects, and extracellular vesicles. Currently, 74 clinical trials are investigating the use of MSCs (predominately from the umbilical cord, bone marrow, and adipose tissue) to treat COVID-19. Although most of these trials are still in their early stages, the preliminary data are promising. However, long-term safety evaluations are still lacking, and large-scale and controlled trials are required for more conclusive judgments regarding MSC-based therapies. The main challenges and prospective directions for the use of MSCs in clinical applications are discussed herein. In summary, while the clinical use of MSCs to treat COVID-19 is still in the preliminary stages of investigation, promising results indicate that they could potentially be utilized in future treatments.

Paeoniflorin ameliorates airway inflammation and immune response in ovalbumin induced asthmatic mice: From oxidative stress to autophagy

BACKGROUND

Asthma characterized by airway remodeling is a multiple pulmonary disease, which is associated with various physiological processes including inflammation reaction, immune response, oxidative stress and autophagy.

PURPOSE

This study aimed to investigate whether these processes are modulated by the total glucosides of Paeonia lactiflora Pall (TGP), and its active compound paeoniflorin (PF) with anti-inflammatory and immune-regulatory effects could alleviate ovalbumin (OVA)-induced mouse asthma.

METHODS

In vivo, models of mouse asthma were established by intraperitoneally with a mixture of OVA and aluminum hydroxide, plus a single nasal injected with OVA to female C57BL/6 mice. The results were observed with PET imaging, TEM, RT-PCR, western blotting. In vitro, CD4⁺ T cells were isolated and detected with flow cytometry.

RESULTS

TGP, either in its crude or processed form, and PF effectively ameliorated lung injury in mice induced by OVA, regulated immune/inflammatory response by inhibiting the release of pro-inflammatory cytokines, thereby decreasing Th2 cell proportion, inhibited oxidative stress by recovering mitochondrial membrane potential and regulating metabolic activity in dose-dependent manner. Moreover, PF could inhibit autophagy by regulating mitochondrial function. In addition, the therapeutic effects of TGP and PF on pulmonary injury in asthmatic mice were not affected by processing.

CONCLUSION

PF may be a valuable agent in ameliorating inflammation and immune response in asthmatic mice, and the possible mechanism involved in this response rang may from oxidative stress to autophagy.

Effect of intrabronchial administration of autologous adipose-derived mesenchymal stem cells on severe equine asthma

BACKGROUND

Severe equine asthma (SEA) is a common chronic respiratory disease and a significant health and well-being problem in horses. Current therapeutic strategies improve pulmonary function and clinical signs in some horses, but in the long-term, return to full athletic function appears to be rare. The aim of this study was to assess the safety and the effect of intrabronchial administration of adipose-derived mesenchymal stem cells (AD-MSC) on pulmonary inflammatory and clinical parameters in horses with SEA.

METHODS

This was a randomized controlled trial. Twenty adult horses diagnosed with SEA were randomly divided into two groups (n = 10), and treated either with a single intrabronchial application of autologous AD-MSC or oral dexamethasone for three weeks. A targeted clinical examination with determination of clinical score, maximal change in pleural pressure during the breathing cycle, and an endoscopic examination of the airways were performed at baseline and three weeks after treatment. Bronchoalveolar lavage fluid was analyzed cytologically, and IL-1β, IL-4, IL-8, IL-17, TNFα and IFNγ mRNA and protein concentrations were measured at baseline and three weeks. The horses were then monitored over one year for recurrence of SEA. A non-inferiority analysis and a linear mixed-effects model were performed to assess differences between treatments.

RESULTS

The non-inferiority of AD-MSC treatment was not established. However, AD-MSC administration significantly ameliorated the clinical score (P = 0.01), decreased the expression of IL-17 mRNA (P = 0.05) and IL-1β (P ≤ 0.001), IL-4 (P ≤ 0.001), TNFα (P = 0.02) protein levels, and had a positive long-term effect on SEA-associated clinical signs (P = 0.02).

CONCLUSIONS

Intrabronchial administration of AD-MSC had limited short-term anti-inflammatory effects but improved the clinical signs of SEA at one year.

Chronic asthmatic condition modulated the onset of aging in bone marrow mesenchymal stem cells

The emergence of an inflammatory condition such as asthma could affect the therapeutic potential of stem cells. Synopsis of previous documents yielded controversial outcomes, leading to a limitation of stem cell-based therapy in the clinical setting. This study aimed to assess the impact of asthmatic serum on the MSCs aging and dynamic growth in vitro. Rats were divided into control and asthmatic groups randomly. The asthmatic change was induced using OVA sensitization. The asthmatic structural changes are monitored by conventional Haematoxylin-Eosin staining. Thereafter, blood samples were taken and sera provided from each group. In this study, primary bone marrow mesenchymal stem cells were cultured in culture medium supplemented with normal and asthmatic serum for 7 days. The MSCs viability was examined using the MTT assay. The expression of the aging-related gene (β-galactosidase), and stemness-related markers such as Sox2, Kfl-4 and p16^INK4a were analysed by real-time PCR assay. Histological examination revealed chronic inflammatory remodelling which is identical to asthmatic changes. MTT assay showed a reduction of mesenchymal stem cell viability compared to the control group (P < .05). Real-time PCR analysis revealed a down-regulation of stemness-related markers Sox2, Kfl-4 and p16^INK4a coincided with aging changes (β-galactosidase) compared to the control group (P < .05). These data show the detrimental effect of asthmatic condition on bone marrow regenerative potential by accelerating early-stage aging in different stem cells and further progenitor cell depletion. SIGNIFICANCE OF THE STUDY: In such inflammatory conditions as asthma, the therapeutic potential of stem cells may be altered. We demonstrate that serum from asthmatic rats had the potential to reduce the viability of mesenchymal stem cells in vitro. Furthermore, we observed that the expression of the aging-related gene known β-galactosidase was statistically increased in cells co-cultured with asthmatic serum. At the same time, expression of stemness-related markers Sox2, Kfl-4 and p16^INK4a down-regulated. These results support the damaging effect of asthmatic condition on bone marrow regenerative ability by inducing early-stage aging in stem cells and additional progenitor cell reduction.

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.

A narrative review of research advances in mesenchymal stem cell therapy for asthma

Asthma is a chronic inflammatory disease of the airways that involves multiple cells, including inflammatory cells, structural cells, and cellular components. Glucocorticoids and beta-receptor agonists are still the first choices for asthma treatment. However, the asthma symptoms may still be poorly controlled in some patients after an optimal treatment. Mesenchymal stem cells (MSCs) are characterized by the potential for multi-directional differentiation and can exert immunomodulatory and anti-inflammatory effects. Its role in treating asthma has increasingly been recognized in recent years. In this review article, we sought to summarize the recent advances in the therapeutic effects of MSCs on several types of asthma and explain the relevant mechanisms. Articles on asthma treatment with MSCs as of January 2020 were searched in PubMed, Google Scholar, and Web of Science databases. It was found that MSCs have therapeutic effects on allergic asthma, non-allergic asthma and occupational asthma; gene-modified or pretreated MSCs improves the therapeutic effects of MSCs in asthma; MSC-derived conditioned medium or extracellular vesicles possess the considerable curative effect as MSC on asthma; and MSCs exert their therapeutic effects on asthma by restoring Th1/Th2 balance, reversing Th17/Tregs imbalance, inhibiting DC maturation, and promoting the switch of M1 to M2 and repairing epithelial injury. Thus, MSCs may be a promising treatment for asthma.

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.

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.

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.

Insights into animal models for cell-based therapies in translational studies of lung diseases: Is the horse with naturally occurring asthma the right choice?

Human asthma is a widespread disease associated with chronic inflammation of the airways, leading to loss of quality of life, disability and death. Corticosteroid administration is the mainstream treatment for asthmatic patients. Corticosteroids reduce airway obstruction and improve quality of life, although symptoms persist despite treatment in many patients. Moreover, available therapies failed to reverse the lung pathology present in asthma. Animal models, mostly rats and mice, in which the disease is experimentally induced, have been studied to identify new therapeutic targets for human asthma. Alternative animal models could include horses in which naturally occurring asthma could represent an important step to test therapies, potentially designed around mouse studies, before being translated to human testing. Horses naturally suffer from asthma, which has striking parallels with human asthma. Severe equine asthma (SEA) is characterized by reversible bronchospasms and neutrophil accumulation in the lungs immunologically mediated mainly by Th2. Moreover, the pulmonary remodelling that occurs in SEA closely resembles that of human asthma, making the equine model unique for investigation of tissue repair and new therapies. Cell therapy, consisting on mesenchymal stromal cells (MSCs) and derivatives (conditioned medium and extracellular vesicles), could represent a novel therapeutic contribution for tissue regeneration. Cell therapy may prove advantageous over conventional therapy in that it may repair or regenerate the site of injury and reduce the reaction to allergens, rather than simply modulating the inflammatory process.

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

Ras homolog family member A/Rho-associated protein kinase 1 signaling modulates lineage commitment of mesenchymal stem cells in asthmatic patients through lymphoid enhancer-binding factor 1

BACKGROUND

Numbers of mesenchymal stem cells (MSCs) are increased in the airways after allergen challenge. Ras homolog family member A (RhoA)/Rho-associated protein kinase 1 (ROCK) signaling is critical in determining the lineage fate of MSCs in tissue repair/remodeling.

OBJECTIVES

We sought to investigate the role of RhoA/ROCK signaling in lineage commitment of MSCs during allergen-induced airway remodeling and delineate the underlying mechanisms.

METHODS

Active RhoA expression in lung tissues of asthmatic patients and its role in cockroach allergen-induced airway inflammation and remodeling were investigated. RhoA/ROCK signaling-mediated MSC lineage commitment was assessed in an asthma mouse model by using MSC lineage tracing mice (nestin-Cre; ROSA26-EYFP). The role of RhoA/ROCK in MSC lineage commitment was also examined by using MSCs expressing constitutively active RhoA (RhoA-L63) or dominant negative RhoA (RhoA-N19). Downstream RhoA-regulated genes were identified by using the Stem Cell Signaling Array.

RESULTS

Lung tissues from asthmatic mice showed increased expression of active RhoA when compared with those from control mice. Inhibition of RhoA/ROCK signaling with fasudil, a RhoA/ROCK inhibitor, reversed established cockroach allergen-induced airway inflammation and remodeling, as assessed based on greater collagen deposition/fibrosis. Furthermore, fasudil inhibited MSC differentiation into fibroblasts/myofibroblasts but promoted MSC differentiation into epithelial cells in asthmatic nestin-Cre; ROSA26-EYFP mice. Consistently, expression of RhoA-L63 facilitated differentiation of MSCs into fibroblasts/myofibroblasts, whereas expression of RhoA-19 switched the differentiation toward epithelial cells. The gene array identified the Wnt signaling effector lymphoid enhancer-binding factor 1 (Lef1) as the most upregulated gene in RhoA-L63-transfected MSCs. Knockdown of Lef1 induced MSC differentiation away from fibroblasts/myofibroblasts but toward epithelial cells.

CONCLUSIONS

These findings uncover a previously unrecognized role of RhoA/ROCK signaling in MSC-involved airway repair/remodeling in the setting of asthma.

Simvastatin and bone marrow-derived mesenchymal stem cells (BMSCs) affects serum IgE and lung cytokines levels in sensitized mice

INTRODUCTION

The effects of bone marrow-derived mesenchymal stem cells (BMSCs) and simvastatin combination therapy on serum total and specific IgE levels and lung IL-13 and TGF-β levels in sensitized mouse were examined.

MATERIAL AND METHODS

Control (n = 5), Sensitized (S), (n = 5), S + BMSC (n = 6), S + simvastatin (n = 6) and S + BMSC + simvastatin (n = 4) groups of BALB/c mice were studied. Mice were sensitized by ovalbumin. Sensitized mice were treated with a single intravenous injection of BMSCs (1 × 10⁶) or daily intraperitoneal injection of simvastatin (40 mg/kg) or both BMSCs and simvastatin on the last week of challenge. Serum total and ovalbumin specific IgE levels as well as IL-13 and TGF-β levels in broncho-alveolar lavage (BAL) fluid were evaluated.

RESULTS

Serum total and specific IgE levels as well as lung IL-13 and TGF-β levels were significantly increased in S group compared to control group (P < 0.001 for all cases). Treatment with BMSCs, simvastatin and their combination significantly decreased serum total and specific IgE levels (P < 0.05 to P < 0.01). However, IL-13 and TGF-β levels were significantly decreased by BMSCs and BMSC + simvastatin combination therapy (P < 0.05 for all cases). The effect of simvastatin and BMSCs combination therapy on serum specific IgE levels as well as lung IL-13 and TGF-β levels were significantly higher than the effect of BMSCs and simvastatin alone (P < 0.001 for IL-13 and P < 0.01 for other cases).

CONCLUSIONS

Simvastatin and BMSCs combination therapy affects serum IgE as well as lung IL-13 and TGFβ levels more than BMSC therapy and simvastatin therapy alone which may be due to increased BMSCs migration into the lung tissue.

Therapeutic effects of adipose-tissue-derived mesenchymal stromal cells and their extracellular vesicles in experimental silicosis

BACKGROUND

Silicosis is an occupational disease that affects workers who inhale silica particles, leading to extensive lung fibrosis and ultimately causing respiratory failure. Mesenchymal stromal cells (MSCs) have been shown to exert therapeutic effects in lung diseases and represent an alternative treatment for silicosis. Recently, it has been suggested that similar effects can be achieved by the therapeutic use of extracellular vesicles (EVs) obtained from MSCs. The aim of this study was to investigate the effects of adipose-tissue-derived MSCs (AD-MSCs) or their EVs in a model of silicosis.

METHODS

Silicosis was induced by intratracheal instillation of silica in C57BL/6 mice. After the onset of disease, animals received saline, AD-MSCs, or EVs, intratracheally.

RESULTS

At day 30, AD-MSCs and EVs led to a reduction in collagen fiber content, size of granuloma, and in the number of macrophages inside granuloma and in the alveolar septa. In addition, the expression levels of interleukin 1β and transforming growth factor beta in the lungs were decreased. Higher dose of EVs also reduced lung static elastance when compared with the untreated silicosis group.

CONCLUSIONS

Both AD-MSCs and EVs, locally delivered, ameliorated fibrosis and inflammation, but dose-enhanced EVs yielded better therapeutic outcomes in this model of silicosis.

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.

Human placenta mesenchymal stem cells suppress airway inflammation in asthmatic rats by modulating Notch signaling

Neurogenic locus notch homolog protein (Notch) signaling mediates intracellular communication and may regulate cell fate decisions, including cell proliferation, differentiation, and apoptosis. Mesenchymal stem cells (MSCs) possess immunomodulatory properties and the potential for use in stem cell replacement treatments. The aim of the present study was to evaluate the therapeutic effects of human placenta‑deviated MSCs (hPMSCs) in asthma and to investigate the mechanisms of Notch signaling mediated by transplanted MSCs. A Sprague‑Dawley rat ovalbumin (OVA)‑sensitized acute asthma model was established and challenged. MSCs derived from human placenta (hPMSCs) were transplanted into the asthmatic rats. Transplantation resulted in reduced Notch‑1, Notch‑2 and jagged‑1, and increased Notch‑3, Notch‑4 and delta‑like ligand (delta)‑4 expression in lung, blood, and lymph samples. Notch‑1, Notch‑2, and jagged‑1 expression in OVA‑treated rats was significantly decreased compared with controls and hPMSC‑treated rats; however, Notch‑3, Notch‑4 and delta‑4 expression was significantly increased. Serum interferon‑γ significantly increased after hPMSCs transplantation, whereas interleukin‑4 and immunoglobulin E decreased. In OVA‑treated rats, Notch‑1, Notch‑2 and jagged‑1 levels were increased in the lymph compared with the blood, although Notch‑4 and delta‑4 levels were decreased. Peribronchial infiltration of cells and goblet cell hyperplasia were markedly decreased in the OVA + hPMSCs group compared with those in the OVA‑treated and control groups. Alterations in Notch signaling pathway expression were accompanied by decreased inflammatory cell infiltration, goblet cell hyperplasia and mucus production in lung tissues. The results of the present study are consistent with hPMSC suppression of asthma symptoms and inflammation by regulating the Notch signaling pathway in the rat asthma model.

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.

Placenta‑derived mesenchymal stem cells improve airway hyperresponsiveness and inflammation in asthmatic rats by modulating the Th17/Treg balance

Mesenchymal stem cells (MSCs) possess reparative and immunoregulatory properties, representing a hope for stem cell-based treatments. However, the mechanisms by which transplanted MSCs affect T helper (Th)17/regulatory T cell (Treg) balance in asthma patients remain unclear. The aim of the present study was to assess the therapeutic effects of human placenta MSCs (hPMSCs) in asthma, and explore the underlying mechanisms; in addition, the impact of hPMSCs transplantation on Th17/Treg balance in lymph and serum samples from asthmatic animals was evaluated. Sprague-Dawley rats were sensitized and challenged with ovalbumin (OVA). Administration of hPMSCs from human placenta resulted in increased Th17 and Treg in lymph samples compared with peripheral blood specimens. Enhanced pause values in OVA-treated animals were significantly higher than those in the control and hPMSCs treatment groups. The numbers of total cells, macrophages, neutrophils, and eosinophils were markedly increased in the OVA group compared with those of control + hPMSCs and control groups. In addition, interleukin 10, forkhead box P3 (Foxp3) and Treg levels in lymph, peripheral blood and lung tissue samples from asthma rats were increased significantly following hPMSC transplantation. Furthermore, Foxp3 protein levels increased, while those of RAR-related orphan receptor γ (RORγt) decreased after hPMSCs transplantation compared with the asthma group. Reduced IL-17, RORγt and Th17 levels were accompanied by reduced inflammatory cell infiltration, sub-epithelial smooth layer attenuation and mucus production in lung tissues. These results suggest that hPMSCs may improve airway hyperresponsiveness and inflammation by regulating the Th17/Treg balance in rats with asthma.

Human adipose tissue mesenchymal stromal cells and their extracellular vesicles act differentially on lung mechanics and inflammation in experimental allergic asthma

Background

Asthma is a chronic inflammatory disease that can be difficult to treat due to its complex pathophysiology. Most current drugs focus on controlling the inflammatory process, but are unable to revert the changes of tissue remodeling. Human mesenchymal stromal cells (MSCs) are effective at reducing inflammation and tissue remodeling; nevertheless, no study has evaluated the therapeutic effects of extracellular vesicles (EVs) obtained from human adipose tissue-derived MSCs (AD-MSC) on established airway remodeling in experimental allergic asthma.

Methods

C57BL/6 female mice were sensitized and challenged with ovalbumin (OVA). Control (CTRL) animals received saline solution using the same protocol. One day after the last challenge, each group received saline, 10⁵ human AD-MSCs, or EVs (released by 10⁵ AD-MSCs). Seven days after treatment, animals were anesthetized for lung function assessment and subsequently euthanized. Bronchoalveolar lavage fluid (BALF), lungs, thymus, and mediastinal lymph nodes were harvested for analysis of inflammation. Collagen fiber content of airways and lung parenchyma were also evaluated.

Results

In OVA animals, AD-MSCs and EVs acted differently on static lung elastance and on BALF regulatory T cells, CD3⁺CD4⁺ T cells, and pro-inflammatory mediators (interleukin [IL]-4, IL-5, IL-13, and eotaxin), but similarly reduced eosinophils in lung tissue, collagen fiber content in airways and lung parenchyma, levels of transforming growth factor-β in lung tissue, and CD3⁺CD4⁺ T cell counts in the thymus. No significant changes were observed in total cell count or percentage of CD3⁺CD4⁺ T cells in the mediastinal lymph nodes.

Conclusions

In this immunocompetent mouse model of allergic asthma, human AD-MSCs and EVs effectively reduced eosinophil counts in lung tissue and BALF and modulated airway remodeling, but their effects on T cells differed in lung and thymus. EVs may hold promise for asthma; however, further studies are required to elucidate the different mechanisms of action of AD-MSCs versus their EVs.

Bone Marrow, Adipose, and Lung Tissue-Derived Murine Mesenchymal Stromal Cells Release Different Mediators and Differentially Affect Airway and Lung Parenchyma in Experimental Asthma

Mesenchymal stromal cells (MSCs) from different sources have differential effects on lung injury. To compare the effects of murine MSCs from bone marrow (BM), adipose tissue (AD), and lung tissue (LUNG) on inflammatory and remodeling processes in experimental allergic asthma, female C57BL/6 mice were sensitized and challenged with ovalbumin (OVA) or saline (C). Twenty‐four hours after the last challenge, mice received either saline (50 µl, SAL), BM‐MSCs, AD‐MSCs, or LUNG‐MSCs (10⁵ cells per mouse in 50 µl total volume) intratracheally. At 1 week, BM‐MSCs produced significantly greater reductions in resistive and viscoelastic pressures, bronchoconstriction index, collagen fiber content in lung parenchyma (but not airways), eosinophil infiltration, and levels of interleukin (IL)‐4, IL‐13, transforming growth factor (TGF)‐β, and vascular endothelial growth factor (VEGF) in lung homogenates compared to AD‐MSCs and LUNG‐MSCs. Only BM‐MSCs increased IL‐10 and interferon (IFN)‐γ in lung tissue. In parallel in vitro experiments, BM‐MSCs increased M2 macrophage polarization, whereas AD‐MSCs and LUNG‐MSCs had higher baseline levels of IL‐4, insulin‐like growth factor (IGF), and VEGF secretion. Exposure of MSCs to serum specimens obtained from asthmatic mice promoted reductions in secretion of these mediators, particularly in BM‐MSCs. Intratracheally administered BM‐MSCs, AD‐MSCs, and LUNG‐MSCs were differentially effective at reducing airway inflammation and remodeling and improving lung function in the current model of allergic asthma. In conclusion, intratracheal administration of MSCs from BM, AD, and LUNG were differentially effective at reducing airway inflammation and remodeling and improving lung function comparably reduced inflammation and fibrogenesis in this asthma model. However, altered lung mechanics and lung remodeling responded better to BM‐MSCs than to AD‐MSCs or LUNG‐MSCs. Moreover, each type of MSC was differentially affected in a surrogate in vitro model of the in vivo lung environment. Stem Cells Translational Medicine2017;6:1557–1567

Immunomodulatory oligonucleotide IMT504: Effects on mesenchymal stem cells as a first-in-class immunoprotective/immunoregenerative therapy

The immune responses of humans and animals to insults (i.e., infections, traumas, tumoral transformation and radiation) are based on an intricate network of cells and chemical messengers. Abnormally high inflammation immediately after insult or abnormally prolonged pro-inflammatory stimuli bringing about chronic inflammation can lead to life-threatening or severely debilitating diseases. Mesenchymal stem cell (MSC) transplant has proved to be an effective therapy in preclinical studies which evaluated a vast diversity of inflammatory conditions. MSCs lead to resolution of inflammation, preparation for regeneration and actual regeneration, and then ultimate return to normal baseline or homeostasis. However, in clinical trials of transplanted MSCs, the expectations of great medical benefit have not yet been fulfilled. As a practical alternative to MSC transplant, a synthetic drug with the capacity to boost endogenous MSC expansion and/or activation may also be effective. Regarding this, IMT504, the prototype of a major class of immunomodulatory oligonucleotides, induces in vivo expansion of MSCs, resulting in a marked improvement in preclinical models of neuropathic pain, osteoporosis, diabetes and sepsis. IMT504 is easily manufactured and has an excellent preclinical safety record. In the small number of patients studied thus far, IMT504 has been well-tolerated, even at very high dosage. Further clinical investigation is necessary to demonstrate the utility of IMT504 for resolution of inflammation and regeneration in a broad array of human diseases that would likely benefit from an immunoprotective/immunoregenerative therapy.

Involvement of fibrocytes in asthma and clinical implications

Bloodborne fibrocytes are bone marrow-derived cells that participate in immune responses and exhibit pro-inflammatory and matrix remodelling properties. In patients with asthma receiving an adequate treatment, the blood fibrocyte count is very low and comparable to that obtained in healthy individuals. In these patients, a transient increase in fibrocyte numbers in the peripheral blood and in the airways occurs in concomitance with increased bronchial inflammation and reflects disease worsening and the need for more intensive treatment. Persistently elevated numbers of fibrocytes in the peripheral blood and in the bronchial mucosa are observed in chronically undertreated or corticosteroid-resistant asthma and are associated with persistent airway inflammation and ongoing remodelling of the bronchial wall. The asthmatic bronchial epithelium is the main source of fibrocyte chemoattractants in asthma and contributes with T helper type 2 lymphocytes and eosinophils to promote the proliferation and pro-remodelling function of recruited fibrocytes. The presence of elevated numbers of fibrocytes in the bronchial mucosa of allergic patients with undertreated or treatment-resistant asthma may also increase the risk of acute exacerbations because these cells can amplify T helper type 2 lymphocyte-driven inflammation on every exposure to the clinically relevant allergen and can promote further inflammation on rhinovirus infections by allowing viral replication and releasing additional pro-inflammatory factors. Improved methods for the isolation and functional analysis of pure populations of viable circulating fibrocytes have allowed a better understanding of the effector role of these cells. A reliable and clinically applicable assay has been developed to measure blood fibrocyte counts as outcome measure in future clinical trials. New therapeutic agents are needed to block both persistent inflammation and fibrocytosis in corticosteroid-resistant asthma.

Immunomodulation of airway epithelium cell activation by mesenchymal stromal cells ameliorates house dust mite-induced airway inflammation in mice

Allergic asthma is underpinned by T helper 2 (Th2) inflammation. Redundancy in Th2 cytokine function and production by innate and adaptive immune cells suggests that strategies aimed at immunomodulation may prove more beneficial. Hence, we sought to determine whether administration of mesenchymal stromal cells (MSCs) to house dust mite (HDM) (Dermatophagoides pteronyssinus)-sensitized mice would suppress the development of Th2 inflammation and airway hyperresponsiveness (AHR) after HDM challenge. We report that the intravenous administration of allogeneic donor MSCs 1 hour before allergen challenge significantly attenuated the features of allergic asthma, including tissue eosinophilia, Th2 cytokine (IL-5 and IL-13) levels in bronchoalveolar lavage fluid, and AHR. The number of infiltrating type 2 innate lymphoid cells was not affected by MSC transfer, suggesting that MSCs may modulate the adaptive arm of Th2 immunity. The effect of MSC administration was long lasting; all features of allergic airway disease were significantly suppressed in response to a second round of HDM challenge 4 weeks after MSC administration. Further, we observed that MSCs decreased the release of epithelial cell-derived alarmins IL-1α and high mobility group box-1 in an IL-1 receptor antagonist-dependent manner. This significantly decreased the expression of the pro-Th2 cytokine IL-25 and reduced the number of activated and antigen-acquiring CD11c(+)CD11b(+) dendritic cells in the lung and mediastinal lymph nodes. Our findings suggest that MSC administration can ameliorate allergic airway inflammation by blunting the amplification of epithelial-derived inflammatory cytokines induced by HDM exposure and may offer long-term protection against Th2-mediated allergic airway inflammation and AHR.

Mesenchymal stem cells and serelaxin synergistically abrogate established airway fibrosis in an experimental model of chronic allergic airways disease

This study determined if the anti-fibrotic drug, serelaxin (RLN), could augment human bone marrow-derived mesenchymal stem cell (MSC)-mediated reversal of airway remodeling and airway hyperresponsiveness (AHR) associated with chronic allergic airways disease (AAD/asthma). Female Balb/c mice subjected to the 9-week model of ovalbumin (OVA)-induced chronic AAD were either untreated or treated with MSCs alone, RLN alone or both combined from weeks 9-11. Changes in airway inflammation (AI), epithelial thickness, goblet cell metaplasia, transforming growth factor (TGF)-β1 expression, myofibroblast differentiation, subepithelial and total lung collagen deposition, matrix metalloproteinase (MMP) expression, and AHR were then assessed. MSCs alone modestly reversed OVA-induced subepithelial and total collagen deposition, and increased MMP-9 levels above that induced by OVA alone (all p<0.05 vs OVA group). RLN alone more broadly reversed OVA-induced epithelial thickening, TGF-β1 expression, myofibroblast differentiation, airway fibrosis and AHR (all p<0.05 vs OVA group). Combination treatment further reversed OVA-induced AI and airway/lung fibrosis compared to either treatment alone (all p<0.05 vs either treatment alone), and further increased MMP-9 levels. RLN appeared to enhance the therapeutic effects of MSCs in a chronic disease setting; most likely a consequence of the ability of RLN to limit TGF-β1-induced matrix synthesis complemented by the MMP-promoting effects of MSCs.

Long-term evaluation of mesenchymal stem cell therapy in a feline model of chronic allergic asthma

BACKGROUND

Mesenchymal stem cells (MSCs) decrease airway eosinophilia, airway hyperresponsiveness (AHR), and remodelling in murine models of acutely induced asthma. We hypothesized that MSCs would diminish these hallmark features in a chronic feline asthma model.

OBJECTIVE

To document effects of allogeneic, adipose-derived MSCs on airway inflammation, AHR, and remodelling over time and investigate mechanisms by which MSCs alter local and systemic immunologic responses in chronic experimental feline allergic asthma.

METHODS

Cats with chronic, experimentally induced asthma received six intravenous infusions of MSCs (0.36-2.5 × 10E7 MSCs/infusion) or placebo bimonthly at the time of study enrollment. Cats were evaluated at baseline and longitudinally for 1 year. Outcome measures included: bronchoalveolar lavage fluid cytology to assess airway eosinophilia, pulmonary mechanics and clinical scoring to assess AHR, and thoracic computed tomographic (CT) scans to assess structural changes (airway remodelling). CT scans were evaluated using a scoring system for lung attenuation (LA) and bronchial wall thickening (BWT). To assess mechanisms of MSC action, immunologic assays including allergen-specific IgE, cellular IL-10 production, and allergen-specific lymphocyte proliferation were performed.

RESULTS

There were no differences between treatment groups or over time with respect to airway eosinophilia or AHR. However, significantly lower LA and BWT scores were noted in CT images of MSC-treated animals compared to placebo-treated cats at month 8 of the study (LA P = 0.0311; BWT P = 0.0489). No differences were noted between groups in the immunologic assays.

CONCLUSIONS AND CLINICAL RELEVANCE

When administered after development of chronic allergic feline asthma, MSCs failed to reduce airway inflammation and AHR. However, repeated administration of MSCs at the start of study did reduce computed tomographic measures of airway remodelling by month 8, although the effect was not sustained at month 12. Further study of MSC therapy including repeated MSC administration is warranted to assess impact on remodelling in chronic asthma.

Bronchoconstriction and airway biology: potential impact and therapeutic opportunities

Recent work has demonstrated that mechanical forces occurring in the airway as a consequence of bronchoconstriction are sufficient to not only induce symptoms but also influence airway biology. Animal and human in vitro and in vivo work demonstrates that the airways are structurally and functionally altered by mechanical stress induced by bronchoconstriction. Compression of the airway epithelium and mechanosensing by the airway smooth muscle trigger the activation and release of growth factors, causing cell proliferation, extracellular matrix protein accumulation, and goblet cell differentiation. These effects of bronchoconstriction are of major importance to asthma pathophysiology and appear sufficient to induce remodeling independent of the inflammatory response. We review these findings in detail and discuss previous studies in light of this new evidence regarding the influence of mechanical forces in the airways. Furthermore, we highlight potential impacts of therapies influencing mechanical forces on airway structure and function in asthma.

Stem cells in animal asthma models: a systematic review

BACKGROUND AIMS

Asthma control frequently falls short of the goals set in international guidelines. Treatment options for patients with poorly controlled asthma despite inhaled corticosteroids and long-acting β-agonists are limited, and new therapeutic options are needed. Stem cell therapy is promising for a variety of disorders but there has been no human clinical trial of stem cell therapy for asthma. We aimed to systematically review the literature regarding the potential benefits of stem cell therapy in animal models of asthma to determine whether a human trial is warranted.

METHODS

The MEDLINE and Embase databases were searched for original studies of stem cell therapy in animal asthma models.

RESULTS

Nineteen studies were selected. They were found to be heterogeneous in their design. Mesenchymal stromal cells were used before sensitization with an allergen, before challenge with the allergen and after challenge, most frequently with ovalbumin, and mainly in BALB/c mice. Stem cell therapy resulted in a reduction of bronchoalveolar lavage fluid inflammation and eosinophilia as well as Th2 cytokines such as interleukin-4 and interleukin-5. Improvement in histopathology such as peribronchial and perivascular inflammation, epithelial thickness, goblet cell hyperplasia and smooth muscle layer thickening was universal. Several studies showed a reduction in airway hyper-responsiveness.

CONCLUSIONS

Stem cell therapy decreases eosinophilic and Th2 inflammation and is effective in several phases of the allergic response in animal asthma models. Further study is warranted, up to human clinical trials.

Mesenchymal stem cells regulate airway contractile tissue remodeling in murine experimental asthma

Background

Mesenchymal stem cells may offer therapeutic potential for asthma due to their immunomodulatory properties and host tolerability, yet prior evidence suggests that bloodborne progenitor cells may participate in airway remodeling. Here, we tested whether mesenchymal stem cells administered as anti‐inflammatory therapy may favor airway remodeling and therefore be detrimental.

Methods

Adipose tissue‐derived mesenchymal stem cells were retrovirally transduced to express green fluorescent protein and intravenously injected into mice with established experimental asthma induced by repeat intranasal house dust mite extract. Controls were house dust mite‐instilled animals receiving intravenous vehicle or phosphate‐buffered saline‐instilled animals receiving mesenchymal stem cells. Data on lung function, airway inflammation, and remodeling were collected at 72 h after injection or after 2 weeks of additional intranasal challenge.

Results

The mesenchymal stem cells homed to the lungs and rapidly downregulated airway inflammation in association with raised T‐helper‐1 lung cytokines, but such effect declined under sustained allergen challenge despite a persistent presence of mesenchymal stem cells. Conversely, airway hyperresponsiveness and contractile tissue underwent a late reduction regardless of continuous pathogenic stimuli and inflammatory rebound. Tracking of green fluorescent protein did not show mesenchymal stem cell integration or differentiation in airway wall tissues.

Conclusions

Therapeutic mesenchymal stem cell infusion in murine experimental asthma is free of unwanted pro‐remodeling effects and ameliorates airway hyper‐responsiveness and contractile tissue remodeling. These outcomes support furthering the development of mesenchymal stem cell‐based asthma therapies, although caution and solid preclinical data building are warranted.