Activation of Wnt/β-catenin signalling promotes mesenchymal stem cells to repair injured alveolar epithelium induced by lipopolysaccharide in mice

Mesenchymal Stem Cells Suppress Inflammatory Cytokines in Lipopolysaccharide Exposed Preterm and Term Human Pregnant Myometrial Cells

Objective  The objective of this study was to determine the cytokine response in human pregnant preterm and term myometrial cells exposed to lipopolysaccharide (LPS) and cocultured with mesenchymal stem cells (MSCs). Study Design  Myometrium was obtained at cesarean delivery in term and preterm patients. Human myometrial cells were exposed to 5 μg/mL LPS for 4 hours followed by 1 μg/mL LPS for 24 hours and were cocultured with MSCs for 24 hours. Culture supernatants were collected at 24 hours and expression of cytokines, including interleukin-1β (IL-1β), IL-6, IL-8, tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), and IL-10, was quantified by enzyme-linked immunosorbent assay. Results  There was significantly increased expression of the proinflammatory cytokines IL-1β, IL-6, IL-8, and TNF-α in preterm myometrial cells treated with LPS compared with untreated preterm myometrial cells. Coculture with MSCs significantly suppressed the proinflammatory cytokine levels in LPS-treated preterm versus treated term myometrial cells. Moreover, MSC cocultured preterm myometrial cells expressed increased levels of the anti-inflammatory cytokines TGF-β and IL-10 compared with treated term myometrial cells. Conclusion  MSCs ameliorate LPS-mediated inflammation in preterm human myometrial cells compared with term myometrial cells. Immunomodulatory effects of MSCs mediated through anti-inflammatory cytokine regulation suggest a potential cell-based therapy for preterm birth.

Role of Hedgehog Signaling Pathways in Multipotent Mesenchymal Stem Cells Differentiation

Multipotent mesenchymal stem cells (MSCs) have high self-renewal and multi-lineage differentiation potentials and low immunogenicity, so they have attracted much attention in the field of regenerative medicine and have a promising clinical application. MSCs originate from the mesoderm and can differentiate not only into osteoblasts, cartilage, adipocytes, and muscle cells but also into ectodermal and endodermal cell lineages across embryonic layers. To design cell therapy for replacement of damaged tissues, it is essential to understand the signaling pathways, which have a major impact on MSC differentiation, as this will help to integrate the signaling inputs to initiate a specific lineage. Hedgehog (Hh) signaling plays a vital role in the development of various tissues and organs in the embryo. As a morphogen, Hh not only regulates the survival and proliferation of tissue progenitor and stem populations but also is a critical moderator of MSC differentiation, involving tri-lineage and across embryonic layer differentiation of MSCs. This review summarizes the role of Hh signaling pathway in the differentiation of MSCs to mesodermal, endodermal, and ectodermal cells.

Definitive Endodermal Cells Supply an in vitro Source of Mesenchymal Stem/Stromal Cells

Mesenchymal stem/Stromal cells (MSCs) have great therapeutic potentials, and they have been isolated from various tissues and organs including definitive endoderm (DE) organs, such as the lung, liver and intestine. MSCs have been induced from human pluripotent stem cells (hPSCs) through multiple embryonic lineages, including the mesoderm, neural crest, and extraembryonic cells. However, it remains unclear whether hPSCs could give rise to MSCs in vitro through the endodermal lineage. Here, we report that hPSC-derived, SOX17⁺ definitive endoderm progenitors can further differentiate to cells expressing classic MSC markers, which we name definitive endoderm-derived MSCs (DE-MSCs). Single cell RNA sequencing demonstrates the stepwise emergence of DE-MSCs, while endoderm-specific gene expression can be elevated by signaling modulation. DE-MSCs display multipotency and immunomodulatory activity in vitro and possess therapeutic effects in a mouse ulcerative colitis model. This study reveals that, in addition to the other germ layers, the definitive endoderm can also contribute to MSCs and DE-MSCs could be a cell source for regenerative medicine.

Advances in cellular senescence in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and fatal interstitial lung disease of unknown cause, with a median survival of 2-3 years. Its pathogenesis is unclear and there is currently no effective treatment for IPF. Approximately two-thirds of patients with IPF are >60 years old, with a mean age of 66 years, suggesting a link between aging and IPF. However, the mechanism by which aging promotes development of PF remains unclear. Senescence of alveolar epithelial cells and lung fibroblasts (LFs) and their senescence-associated secretion phenotype (SASP) may be involved in the occurrence and development of IPF. The present review focus on senescence of LFs and epithelial and stem cells, as well as SASP, the activation of profibrotic signaling pathways and potential treatments for pathogenesis of IPF.

Mesenchymal Stem Cell Sheet Centrifuge-Assisted Layering Augments Pro-Regenerative Cytokine Production

A focal advantage of cell sheet technology has been as a scaffold-free three-dimensional (3D) cell delivery platform capable of sustained cell engraftment, survival, and reparative function. Recent evidence demonstrates that the intrinsic cell sheet 3D tissue-like microenvironment stimulates mesenchymal stem cell (MSC) paracrine factor production. In this capacity, cell sheets not only function as 3D cell delivery platforms, but also prime MSC therapeutic paracrine capacity. This study introduces a “cell sheet multilayering by centrifugation” strategy to non-invasively augment MSC paracrine factor production. Cell sheets fabricated by temperature-mediated harvest were first centrifuged as single layers using optimized conditions of rotational speed and time. Centrifugation enhanced cell physical and biochemical interactions related to intercellular communication and matrix interactions within the single cell sheet, upregulating MSC gene expression of connexin 43, integrin β1, and laminin α5. Single cell sheet centrifugation triggered MSC functional enhancement, secreting higher concentrations of pro-regenerative cytokines vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and interleukin-10 (IL-10). Subsequent cell sheet stacking, and centrifugation generated cohesive, bilayer MSC sheets within 2 h, which could not be accomplished within 24 h by conventional layering methods. Conventional layering led to H1F-1α upregulation and increased cell death, indicating a hypoxic thickness limitation to this approach. Comparing centrifuged single and bilayer cell sheets revealed that layering increased VEGF production 10-fold, attributed to intercellular interactions at the layered sheet interface. The “MSC sheet multilayering by centrifugation” strategy described herein generates a 3D MSC-delivery platform with boosted therapeutic factor production capacity.

Advances in mesenchymal stromal cell therapy for acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) develops rapidly and has high mortality. ALI/ARDS is mainly manifested as acute or progressive hypoxic respiratory failure. At present, there is no effective clinical intervention for the treatment of ALI/ARDS. Mesenchymal stromal cells (MSCs) show promise for ALI/ARDS treatment due to their biological characteristics, easy cultivation, low immunogenicity, and abundant sources. The therapeutic mechanisms of MSCs in diseases are related to their homing capability, multidirectional differentiation, anti-inflammatory effect, paracrine signaling, macrophage polarization, the polarization of the MSCs themselves, and MSCs-derived exosomes. In this review, we discuss the pathogenesis of ALI/ARDS along with the biological characteristics and mechanisms of MSCs in the treatment of ALI/ARDS.

Mesenchymal Stem Cell Therapy for ALI/ARDS: Therapeutic Potential and Challenges

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a serious clinical common disease, which may be caused by a variety of pathological factors and can induce a series of serious complications. There is still no specific and effective method for the treatment of ALI/ARDS. Mesenchymal stem cells (MSCs) have been one of the treatment methods for ALI, which can regulate related signal pathways such as PI3K/AKT, Wnt, and NF-κB to reduce inflammation. MSCs exist in a variety of tissues and have the ability of self-renewal and differentiation, which can be activated by specific substances or environments and home to the site of tissue damage, where they differentiate into new tissue cells and repair the damage. Both exosomes and cytokines involving the paracrine mechanism of MSCs have benefits on the treatment of ALI. Lung organoids produced by 3D culture technology can simulate the characteristics of the lung and help to research the pathophysiological process of ALI. This review summarizes the mechanisms by which MSCs treat ALI/ARDS and expects to use 3D models for future challenges in this field.

Ischemic Brain Stroke and Mesenchymal Stem Cells: An Overview of Molecular Mechanisms and Therapeutic Potential

Ischemic brain injury is associated with a high rate of mortality and disability with no effective therapeutic strategy. Recently, a growing number of studies are focusing on mesenchymal stem cell-based therapies for neurodegenerative disorders. However, despite having the promising outcome of preclinical studies, the clinical application of stem cell therapy remained elusive due to little or no progress in clinical trials. The objective of this study was to provide a generalized critique for the role of mesenchymal stem cell therapy in ischemic stroke injury, its underlying mechanisms, and constraints on its preclinical and clinical applications. Thus, we attempted to present an overview of previously published reports to evaluate the progress and provide molecular basis of mesenchymal stem cells (MSCs) therapy and its application in preclinical and clinical settings, which could aid in designing an effective regenerative therapeutic strategy in the future.

SARS-CoV-2 Infection and Lung Regeneration

The lung is the primary site of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced immunopathology whereby the virus enters the host cells by binding to angiotensin-converting enzyme 2 (ACE2). Sophisticated regeneration and repair programs exist in the lungs to replenish injured cell populations. However, known resident stem/progenitor cells have been demonstrated to express ACE2, raising a substantial concern regarding the long-term consequences of impaired lung regeneration after SARS-CoV-2 infection. Moreover, clinical treatments may also affect lung repair from antiviral drug candidates to mechanical ventilation. In this review, we highlight how SARS-CoV-2 disrupts a program that governs lung homeostasis. We also summarize the current efforts of targeted therapy and supportive treatments for COVID-19 patients. In addition, we discuss the pros and cons of cell therapy with mesenchymal stem cells or resident lung epithelial stem/progenitor cells in preventing post-acute sequelae of COVID-19. We propose that, in addition to symptomatic treatments being developed and applied in the clinic, targeting lung regeneration is also essential to restore lung homeostasis in COVID-19 patients.

Drug Repurposing for Tooth Regeneration: The Promising Premises

Drug repurposing which identifies new therapeutic use(s) for drugs currently in use is a brand-new avenue of research interest worldwide. It circumvents the high-end monetary and time investment usually associated with contemporary drug discoveries. In the field of dentistry, recent studies in drug repurposing focuses in attaining dentin repair or reduction of bone resorption associated with apical periodontitis. Metformin, an anti-diabetic drug has shown pro-osteogenic properties. Aspirin a known anti-inflammatory agent with anticoagulant action is found to modulate the differentiation of dental pulp cells. The significant role of glycogen synthase kinase-3 inhibitors in activating the Wnt/-beta cat signaling pathway of mesenchymal pulp stem cells may pave the way to the pharmacological treatment of dental caries in near future. It is to be noted here that further preclinical and clinical studies are warranted for the regular therapeutic use of these potential drugs in clinical dentistry.

Cytosolic β-catenin is involved in macrophage M2 activation and antiviral defense in teleosts: Delineation through molecular characterization of β-catenin homolog from redlip mullet (Planiliza haematocheila)

β-catenin is a structural protein that makes the cell-cell connection in adherence junctions. Besides the structural functions, it also plays a role as a central transducer of the canonical Wnt signaling cascade, regulating nearly four hundred genes related to various cellular processes. Recently the immune functions of β-catenin during pathogenic invasion have gained more attention. In the present study, we elucidated the immune function of fish β-catenin by identifying and characterizing the β-catenin homolog (PhCatβ) from redlip mullet, Planiliza haematocheila. The complete open reading frame of PhCatβ consists of 2352 bp, which encodes a putative β-catenin homolog (molecular weight: 85.7 kDa). Multiple sequence alignment analysis revealed that β-catenin is highly conserved in vertebrates. Phylogenetic reconstruction demonstrated the close evolutionary relationship between PhCatβ and other fish β-catenin counterparts. The tissue distribution analysis showed the highest mRNA expression of PhCatβ in heart tissues of the redlip mullet under normal physiological conditions. While in response to pathogenic stress, the PhCatβ transcription level was dramatically increased in the spleen and gill tissues. The overexpression of PhCatβ stimulated M2 polarization and cell proliferation of murine RAW 264.7 macrophage. In fish cells, the overexpression of PhCatβ resulted in a significant upregulation of antiviral gene transcription and vice versa. Moreover, the overexpression of PhCatβ could inhibit the replication of VHSV in FHM cells. Our results strongly suggest that PhCatβ plays a role in macrophage activation and antiviral immune response in redlip mullet.

Current Status of Cell-Based Therapies for COVID-19: Evidence From Mesenchymal Stromal Cells in Sepsis and ARDS

The severe respiratory consequences of the coronavirus disease 2019 (COVID-19) pandemic have prompted the urgent need for novel therapies. Cell-based therapies, primarily using mesenchymal stromal cells (MSCs), have demonstrated safety and potential efficacy in the treatment of critical illness, particularly sepsis and acute respiratory distress syndrome (ARDS). However, there are limited preclinical data for MSCs in COVID-19. Recent studies have shown that MSCs could decrease inflammation, improve lung permeability, enhance microbe and alveolar fluid clearance, and promote lung epithelial and endothelial repair. In addition, MSC-based therapy has shown promising effects in preclinical studies and phase 1 clinical trials in sepsis and ARDS. Here, we review recent advances related to MSC-based therapy in the context of sepsis and ARDS and evaluate the potential value of MSCs as a therapeutic strategy for COVID-19.

Stem Cell Therapy for Burns: Story so Far

Burn injuries affect approximately 11 million people annually, with fatalities amounting up to 180,000. Burn injuries constitute a global health issue associated with high morbidity and mortality. Recent years have seen advancements in regenerative medicine for burn wound healing encompassing stem cells and stem cell-derived products such as exosomes and conditioned media with promising results compared to current treatment approaches. Sources of stem cells used for treatment vary ranging from hair follicle stem cells, embryonic stem cells, umbilical cord stem cells, to mesenchymal stem cells, such as adipose-derived mesenchymal stem cells, bone marrow-derived mesenchymal stem cells, and even stem cells harvested from discarded burn tissue. Stem cells utilize various pathways for wound healing, such as PI3/AKT pathway, WNT-β catenin pathway, TGF-β pathway, Notch and Hedgehog signaling pathway. Due to the paracrine signaling mechanism of stem cells, exosomes and conditioned media derived from stem cells have also been utilized in burn wound therapy. As exosomes and conditioned media are cell-free therapy and contain various biomolecules that facilitate wound healing, they are gaining popularity as an alternative treatment strategy with significant improvement in outcomes. The treatment is provided either as direct injections or embedded in a natural/artificial scaffold. This paper reviews in detail the different sources of stem cells, stem cell-derived products, their efficacy in burn wound repair, associated signaling pathways and modes of delivery for wound healing.

Overexpression of HOXB4 Promotes Protection of Bone Marrow Mesenchymal Stem Cells Against Lipopolysaccharide-Induced Acute Lung Injury Partially Through the Activation of Wnt/β-Catenin Signaling

PURPOSE

Pulmonary vascular endothelial cell (EC) injury is recognized as one of the pathological factors of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Bone marrow mesenchymal stem cell (BMSC)-based cytotherapy has attracted substantial attention over recent years as a promising therapeutic approach for ALI/ARDS; however, its use remains limited due to inconsistent efficacy. Currently, gene modification techniques are widely applied to MSCs. In the present study, we aimed to investigate the effect of BMSCs overexpressing Homeobox B4 (HOXB4) on lipopolysaccharide (LPS)-induced EC injury.

METHODS

We used LPS to induce EC injury and established EC-BMSC coculture system using transwell chambers. The effect of BMSCs on ECs was explored by detecting EC proliferation, apoptosis, migration, tube formation, and permeability, and determining whether the Wnt/β-catenin pathway is involved in the regulatory mechanism using XAV-939, inhibitor of Wnt/ β-catenin.

RESULTS

As compared to BMSCWT, BMSCHOXB4 coculture promoted EC proliferation, migration, and tube formation after LPS stimulation and attenuated LPS-induced EC apoptosis and vascular permeability. Mechanistically, BMSCHOXB4 coculture prevented LPS-induced EC injury by activating the Wnt/β-catenin pathway, which is partially reversible by XAV-939. When cocultured with BMSCHOXB4, pro-inflammatory factors were dramatically decreased and anti-inflammatory factors were greatly increased in the EC medium compared to those in the LPS group (P<0.05). Additionally, when compared to BMSCWT coculture, the BMSCHOXB4 coculture showed an enhanced modulation of IL-6, TNF-α, and IL-10, but there was no statistically significant effect on IL-1β and IL-4.

CONCLUSION

Coculturing of BMSCHOXB4 prevented LPS-induced EC injury by reversing the inactivation of the Wnt/β-catenin signaling pathway. An in vivo study remains warranted to ascertain whether engraftment of BMSCHOXB4 can be an attractive strategy for the treatment of ALI/ARDS.

The Role of MSC in Wound Healing, Scarring and Regeneration

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.

Review of the potential of mesenchymal stem cells for the treatment of infectious diseases

The therapeutic value of mesenchymal stem cells (MSCs) for the treatment of infectious diseases and the repair of disease-induced tissue damage has been explored extensively. MSCs inhibit inflammation, reduce pathogen load and tissue damage encountered during infectious diseases through the secretion of antimicrobial factors for pathogen clearance and they phagocytose certain bacteria themselves. MSCs dampen tissue damage during infection by downregulating the levels of pro-inflammatory cytokines, and inhibiting the excessive recruitment of neutrophils and proliferation of T cells at the site of injury. MSCs aid in the regeneration of damaged tissue by differentiating into the damaged cell types or by releasing paracrine factors that direct tissue regeneration, differentiation, and wound healing. In this review, we discuss in detail the various mechanisms by which MSCs help combat pathogens, tissue damage associated with infectious diseases, and challenges in utilizing MSCs for therapy.

Characteristics and Developments in Mesenchymal Stem Cell Therapy for COVID-19: An Update

The outbreak of coronavirus disease 2019 (COVID-19) has so far resulted in over a hundred million people being infected. COVID-19 poses a threat to human health around the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been confirmed as the pathogenic virus of COVID-19. SARS-CoV-2 belongs to the β-coronavirus family of viruses and is mainly transmitted through the respiratory tract. It has been proven that SARS-CoV-2 mainly targets angiotensin-converting enzyme II (ACE2) receptors on the surface of various cells in humans. The main clinical symptoms of COVID-19 include fever, cough, and severe acute respiratory distress syndrome (ARDS). Current evidence suggests that the damage caused by the virus may be closely related to the induction of cytokine storms in COVID-19. No specific drugs or measures have yet to be shown to cure COVID-19 completely. Cell-based approaches, primarily mesenchymal stem cells (MSCs), have been identified to have anti-inflammatory and immune functions in COVID-19. Clinical studies about using MSCs and its derivatives-exosomes for COVID-19 treatment-are under investigation. Here, we review the current progress of the biological characteristics, clinical manifestations, and cell-based treatment development for COVID-19. Providing up-to-date information on COVID-19 and potential MSC therapies will help highlight routes to prevent and treat the disease.

Role of iron and iron-related proteins in mesenchymal stem cells: Cellular and clinical aspects

Mesenchymal stem cells (MSCs) are located in various tissues where these cells show niche-dependent multilineage differentiation and secrete immunomodulatory molecules to support numerous physiological processes. Due to their regenerative and reparative properties, MSCs are extremely valuable for cell-based therapy in tackling several pathological conditions including COVID-19. Iron is essential for MSC processes but iron-loading, which is common in several chronic conditions, hinders normal MSC functionality. This not only aggravates disease pathology but can also affect allogeneic and autologous MSC therapy. Thus, understanding MSCs from an iron perspective is of clinical significance. Accordingly, this review highlights the roles of iron and iron-related proteins in MSC physiology. It describes the contribution of iron and endogenous iron-related effectors like hepcidin, ferroportin, transferrin receptor, lactoferrin, lipocalin-2, bone morphogenetic proteins and hypoxia inducible factors in MSC biology. It summarises the excess-iron-induced alterations in MSC components, processes and discusses signalling pathways involving ROS, PI3K/AKT, MAPK, p53, AMPK/MFF/DRP1 and Wnt. Additionally, it evaluates the endogenous and exogenous saviours of MSCs against iron-toxicity. Lastly, it elaborates on the involvement of MSCs in the pathology of clinical conditions of iron-excess, namely, hereditary hemochromatosis, diabetes, β-thalassaemia and myelodysplastic syndromes. This unique review integrates the distinct fields of iron regulation and MSC physiology. Through an iron-perspective, it describes both mechanistic and clinical aspects of MSCs and proposes an iron-linked MSC-contribution to physiology, pathology and therapeutics. It advances the understanding of MSC biology and may aid in identifying signalling pathways, molecular targets and compounds for formulating adjunctive iron-based therapies for excess-iron conditions, and thereby inform regenerative medicine.

Mesenchymal stromal cells for acute respiratory distress syndrome (ARDS), sepsis, and COVID-19 infection: optimizing the therapeutic potential

Introduction: Mesenchymal stromal (stem) cell (MSC) therapies are emerging as a promising therapeutic intervention in patients with Acute Respiratory Distress Syndrome (ARDS) and sepsis due to their reparative, immunomodulatory, and antimicrobial properties.Areas covered: This review provides an overview of Mesenchymal stromal cells (MSCs) and their mechanisms of effect in ARDS and sepsis. The preclinical and clinical evidence to support MSC therapy in ARDS and sepsis is discussed. The potential for MSC therapy in COVID-19 ARDS is discussed with insights from respiratory viral models and early clinical reports of MSC therapy in COVID-19. Strategies to optimize the therapeutic potential of MSCs in ARDS and sepsis are considered including preconditioning, altered gene expression, and alternative cell-free MSC-derived products, such as extracellular vesicles and conditioned medium.Expert opinion: MSC products present considerable therapeutic promise for ARDS and sepsis. Preclinical investigations report significant benefits and early phase clinical studies have not highlighted safety concerns. Optimization of MSC function in preclinical models of ARDS and sepsis has enhanced their beneficial effects. MSC-derived products, as cell-free alternatives, may provide further advantages in this field. These strategies present opportunity for the clinical development of MSCs and MSC-derived products with enhanced therapeutic efficacy.

Mesenchymal stem cell therapy for acute respiratory distress syndrome: from basic to clinics

The 2019 novel coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has occurred in China and around the world. SARS-CoV-2-infected patients with severe pneumonia rapidly develop acute respiratory distress syndrome (ARDS) and die of multiple organ failure. Despite advances in supportive care approaches, ARDS is still associated with high mortality and morbidity. Mesenchymal stem cell (MSC)-based therapy may be an potential alternative strategy for treating ARDS by targeting the various pathophysiological events of ARDS. By releasing a variety of paracrine factors and extracellular vesicles, MSC can exert anti-inflammatory, anti-apoptotic, anti-microbial, and pro-angiogenic effects, promote bacterial and alveolar fluid clearance, disrupt the pulmonary endothelial and epithelial cell damage, eventually avoiding the lung and distal organ injuries to rescue patients with ARDS. An increasing number of experimental animal studies and early clinical studies verify the safety and efficacy of MSC therapy in ARDS. Since low cell engraftment and survival in lung limit MSC therapeutic potentials, several strategies have been developed to enhance their engraftment in the lung and their intrinsic, therapeutic properties. Here, we provide a comprehensive review of the mechanisms and optimization of MSC therapy in ARDS and highlighted the potentials and possible barriers of MSC therapy for COVID-19 patients with ARDS.

Transcription factor-mediated signaling pathways' contribution to the pathology of acute lung injury and acute respiratory distress syndrome

The 2019 novel coronavirus (2019-nCoV) is still spreading rapidly around the world, and one cause of lethality for patients infected with 2019-nCoV is acute respiratory distress syndrome (ARDS). ARDS is a severe syndrome of acute lung injury (ALI) that is predominantly triggered by inflammation and results in a sudden loss of, or damage to, kidney function. Emerging studies reveal that multiple transcription factor-associated signaling pathways are activated in the pathology of ALI/ARDS. Of these pathways, the activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), AP-1 (activator protein 1), IRFs (interferon regulatory factors), STATs (signal transducer and activator of transcription), Wnt/β-catenin-TCF/LEF (T-cell factor/lymphoid enhancer-binding factor), and CtBP2 (C-Terminal binding protein 2)-associated transcriptional complex contributes to ALI/ARDS pathology through diverse mechanisms, such as inducing proinflammatory cytokine levels and mediating macrophage polarization. In this review, we present an updated summary of the mechanisms underlying these signaling activations and regulations, as well as their contribution to the pathogenesis of ALI/ARDS. We aim to develop a better understanding of how ALI/ARDS occurs and improve ALI/ARDS therapy.

Genetic Engineering as a Strategy to Improve the Therapeutic Efficacy of Mesenchymal Stem/Stromal Cells in Regenerative Medicine

Mesenchymal stem/stromal cells (MSCs) have been widely studied in the field of regenerative medicine for applications in the treatment of several disease settings. The therapeutic potential of MSCs has been evaluated in studies in vitro and in vivo, especially based on their anti-inflammatory and pro-regenerative action, through the secretion of soluble mediators. In many cases, however, insufficient engraftment and limited beneficial effects of MSCs indicate the need of approaches to enhance their survival, migration and therapeutic potential. Genetic engineering emerges as a means to induce the expression of different proteins and soluble factors with a wide range of applications, such as growth factors, cytokines, chemokines, transcription factors, enzymes and microRNAs. Distinct strategies have been applied to induce genetic modifications with the goal to enhance the potential of MCSs. This review aims to contribute to the update of the different genetically engineered tools employed for MSCs modification, as well as the factors investigated in different fields in which genetically engineered MSCs have been tested.

Overexpression of FoxM1 promotes differentiation of bone marrow mesenchymal stem cells into alveolar type II cells through activating Wnt/β-catenin signalling

BACKGROUND

Acute respiratory distress syndrome (ARDS) becomes a serious challenge in critical care medicine due to the lack of effective therapy. As the damage of alveolar epithelium is a characteristic feature of ARDS, inducing mesenchymal stem cells (MSCs) to differentiate into alveolar epithelial cells turns out to be a promising therapy for ARDS, but the differentiation efficiency is yet to be improved. The study aimed to investigate the effect of overexpressing FoxM1 on MSCs' differentiation into alveolar epithelial cells.

METHODS

MSCs were isolated from mouse bone marrow, followed by transfected with lentivirus carrying the FoxM1 plasmid. Small airway epithelial cell growth medium was used as a culture system for inducing MSCs' differentiation into alveolar epithelial cells. Differentiation efficiency was assessed by detecting the expression levels of specific markers of alveolar epithelial cells mainly using quantitative reverse-transcription polymerase chain reaction and Western blot. To examine whether Wnt/β-catenin signalling was involved in the regulation mechanism, a specific inhibitor of the pathway XAV-939 was used and nuclear and cytoplasmic proteins were also analysed respectively. Co-immunoprecipitation was performed to examine the potential interaction between FoxM1 and β-catenin.

RESULTS

Overexpressing FoxM1 statistically significantly increased the expression levels of specific markers of type II alveolar epithelial cells prosurfactant protein C and surfactant protein B, which was partially reversed by XAV-939 treatment, while the expression levels of specific marker of type I alveolar epithelial cells aquaporin 5 did not change significantly. Overexpressing FoxM1 also increased the nuclear translocation of β-catenin and its transcriptional activity. A direct interaction between FoxM1 and β-catenin was found in co-immunoprecipitation assay.

CONCLUSION

Overexpression of FoxM1 could improve the efficiency of MSCs' differentiation into type II alveolar epithelial cells partly by activating Wnt/β-catenin signalling.

Overexpression of TGFβ1 in murine mesenchymal stem cells improves lung inflammation by impacting the Th17/Treg balance in LPS-induced ARDS mice

Background

T helper 17 cells (Th17)/regulatory T cells (Treg), as subtypes of CD4⁺ T cells, play an important role in the inflammatory response of acute respiratory distress syndrome (ARDS). However, there is still a lack of effective methods to regulate the differentiation balance of Th17/Treg. It was proven that mesenchymal stem cells (MSCs) could regulate the differentiation of CD4⁺ T cells, but the mechanism is still unclear. TGFβ1, a paracrine cytokine of MSCs, could also regulate the differentiation of Th17/Treg but is lowly expressed in MSCs. Therefore, mouse MSCs (mMSCs) overexpressing TGFβ1 were constructed by lentivirus transduction and intratracheally transplanted into LPS-induced ARDS mice in our study. The aim of this study was to evaluate the therapeutic effects of mMSCs overexpressing TGFβ1 on inflammation and immunoregulation by impacting the Th17/Treg balance in LPS-induced ARDS mice.

Methods

mMSCs overexpressing TGFβ1 were constructed using lentiviral vectors. Then, mouse bone-marrow-derived MSCs (mBM-MSC) and mBM-MSC-TGFβ1 (mBM-MSC overexpressing TGFβ1) were transplanted intratracheally into ARDS mice induced by lipopolysaccharide. At 3 and 7 days after transplantation, the mice were sacrificed, and the homing of the mMSCs was assayed by ex vivo optical imaging. The relative numbers of Th17 and Treg in the lungs and spleens of mice were detected by FCM. IL-17A and IL-10 levels in the lungs of mice were analysed by western blot. Permeability and inflammatory cytokines were evaluated by analysing the protein concentration of BALF using ELISA. Histopathology of the lungs was assessed by haematoxylin and eosin staining and lung injury scoring. Alveolar lung fibrosis was assessed by Masson’s trichrome staining and Ashcroft scoring. The mortality of ARDS mice was followed until 7 days after transplantation.

Results

The transduction efficiencies mediated by the lentiviral vectors ranged from 82.3 to 88.6%. Overexpressing TGFβ1 inhibited the proliferation of mMSCs during days 5–7 (p < 0.05) but had no effect on mMSC differentiation or migration (p > 0.05). Compared to that in the LPS + mBM-MSC-NC group mice, engraftment of mMSCs overexpressing TGFβ1 led to much more differentiation of T cells into Th17 or Treg (p < 0.05), improved permeability of injured lungs (p < 0.05) and ameliorative histopathology of lung tissue in ARDS mice (p < 0.05). Moreover, IL-17A content was also decreased while IL-10 content was increased in the LPS + mBM-MSC-TGFβ1 group compared with those in the LPS + mBM-MSC-NC group (p < 0.05). Finally, mMSCs overexpressing TGFβ1 did not aggravate lung fibrosis in ARDS mice (p > 0.05).

Conclusion

MSCs overexpressing TGFβ1 could regulate lung inflammation and attenuate lung injuries by modulating the imbalance of Th17/Treg in the lungs of ARDS mice.

Mesenchymal Stem Cells Attenuate Lipopolysaccharide-Induced Inflammatory Response in Human Uterine Smooth Muscle Cells

Objective  The aim of this study was to determine if mesenchymal stem cells (MSCs) would suppress the inflammatory response in human uterine cells in an in vitro lipopolysaccharide (LPS)-based preterm birth (PTB) model. Study Design  Cocultures of human uterine smooth muscle cells (HUtSMCs) and MSCs were exposed to 5 μg/mL LPS for 4 hours and further challenged with 1 μg/mL LPS for a subsequent 24 hours. Key elements of the parturition cascade regulated by toll-like receptors (TLRs) through activation of mitogen-activated protein kinases (MAPKs) were quantified in culture supernatant as biomarkers of MSC modulation. Results  Coculture with MSCs significantly attenuated TLR-4, p-JNK, and p- extracellular signal-regulated kinase 1/2 (ERK1/2) protein levels compared with HUtSMCs monoculture ( p  = 0.05). In addition, coculture was associated with significant inhibition of proinflammatory cytokines interleukin (IL)-6 and IL-8 ( p  = 0.0001) and increased production of anti-inflammatory cytokines IL-10 and transforming growth factor (TGF)-β1 ( p  = 0.0001). Conclusion  MSCs appear to play a role in significantly attenuating LPS-mediated inflammation via alteration of down-stream MAPKs. MSCs may represent a novel, cell-based therapy in women with increased risk of inflammatory-mediated preterm birth.

Mesenchymal stem cells activate Notch signaling to induce regulatory dendritic cells in LPS-induced acute lung injury

Background

Mesenchymal stem cells (MSCs) have been shown to alleviate acute lung injury (ALI) and induce the production of regulatory dendritic cells (DCregs), but the potential link between these two cell types remains unclear. The goal of this study was to investigate the effect and mechanism of MSC-induced regulatory dendritic cells in ALI mice.

Material/methods

In vivo experiments, C57BL/6 wild-type male mice were sacrificed at different times after intratracheal injection of LPS to observe changes in lung DC maturation and pathological damage. MSCs, DCregs or/and carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled DCs were administered to the mice by tail vein, and flow cytometry was performed to measure the phenotype of lung DCs and T cells. Lung injury was estimated by the lung wet weight/body weight ratio and histopathological analysis. In vitro, Western blotting or flow cytometry was used to detect the expression of Notch ligand or receptor in MSCs or DCs after coculture or LPS stimulation. Finally, in vivo and in vitro, we used the Notch signaling inhibitor DAPT to verify the effect of the Notch pathway on MSC-induced DCregs and their pulmonary protection.

Results

We showed significant accumulation and maturation of lung DCs 2 h after intratracheal injection of LPS, which were positively correlated with the lung pathological injury score. MSC treatment alleviated ALI lung injury, accompanied by a decrease in the number and maturity of classical DCs in the lungs. CFSE-labeled DCs migrated to the lungs of ALI mice more than those of the normal group, and the elimination of CFSE-labeled DCs in the blood was slower. MSCs inhibited the migration of CFSE-labeled DCs to the lung and promoted their elimination in the blood. DCregs, which are obtained by contact coculture of mDCs with MSCs, expressed reduced levels of MHCII, CD86, CD40 and increased levels of PD-L1, and had a reduced ability to stimulate lymphocyte proliferation and activation (expression of CD44 and CD69). mDCs expressing Notch2 significantly increased after coculture with MSCs or rhJagged1, and MSCs expressed more Jagged1 after LPS stimulation. After stimulation of mDCs with recombinant Jagged1, DCs with low expression of MHCII, CD86 and CD40 were also induced, and the effects of both rhJagged1 and MSCs on DCs were blocked by the Notch inhibitor DAPT. Intra-airway DAPT reversed the inhibitory effect of mesenchymal stem cells on DC recruitment to the lungs and its maturation.

Conclusions

Our results suggested that the recruitment and maturation of lung DCs is an important process in early ALI, MSCs attenuate LPS-induced ALI by inducing the production of DCregs by activating Notch signaling.

In vitro potential of human mesenchymal stem cells for corneal epithelial regeneration

Aim: To determine the potential of mesenchymal stem cells (MSC) for corneal epithelial regeneration in vitro. Materials & methods: Bone marrow MSC (BM-MSC) and adipose tissue MSC were analyzed for corneal epithelial and mesenchymal markers, using limbal stem cells and corneal cells as controls. MSC with better potential were cultured with specific mediums for epithelial induction. Transepithelial electric resistance and wound healing assay with human corneal epithelial cells were performed. Results: BM-MSC showed better potential, increased corneal markers, and higher transepithelial electric resistance values when induced with limbal epithelial culture medium. Induced BM-MSC promoted better wound healing of human corneal epithelial cells by paracrine secretion. Conclusion: BM-MSC has potential for corneal epithelial induction in a protocol compatible with human application.

MSC Based Therapies-New Perspectives for the Injured Lung

Chronic lung diseases pose a tremendous global burden. At least one in four people suffer from severe pulmonary sequelae over the course of a lifetime. Despite substantial improvements in therapeutic interventions, persistent alleviation of clinical symptoms cannot be offered to most patients affected to date. Despite broad discrepancies in origins and pathomechanisms, the important disease entities all have in common the pulmonary inflammatory response which is central to lung injury and structural abnormalities. Mesenchymal stem cells (MSC) attract particular attention due to their broadly acting anti-inflammatory and regenerative properties. Plenty of preclinical studies provided congruent and convincing evidence that MSC have the therapeutic potential to alleviate lung injuries across ages. These include the disease entities bronchopulmonary dysplasia, asthma and the different forms of acute lung injury and chronic pulmonary diseases in adulthood. While clinical trials are so far restricted to pioneering trials on safety and feasibility, preclinical results point out possibilities to boost the therapeutic efficacy of MSC application and to take advantage of the MSC secretome. The presented review summarizes the most recent advances and highlights joint mechanisms of MSC action across disease entities which provide the basis to timely tackle this global disease burden.

Mesenchymal stem cells induce dendritic cell immune tolerance via paracrine hepatocyte growth factor to alleviate acute lung injury

BACKGROUND

Mesenchymal stem cells (MSCs) have been shown to alleviate acute lung injury (ALI) via paracrine hepatocyte growth factor (HGF) and to induce the differentiation of dendritic cells (DCs) into tolerogenic dendritic cells (DCregs) and participate in the immune response. However, whether MSCs induce the production of DCregs by secreting HGF to alleviate early ALI remains unclear. We observed that the protective effect of mouse bone marrow-derived MSCs against lipopolysaccharide (LPS)-induced ALI was achieved by inducing mature DCs (mDCs) to differentiate into DCregs, and its mechanism is related to the activation of the HGF/Akt pathway.

METHODS

MSCs or MSCs with overexpression or knockdown of HGF were cocultured with DCs derived from mouse bone marrow using a Transwell system for 3 days. Moreover, we used MSCs or MSCs with overexpression or knockdown of HGF to treat LPS-induced ALI mice for 24 h. Flow cytometry was performed to measure the phagocytosis, accumulation, and maturation of DCs, as well as proliferation of T cells. Lung injury was estimated by lung wet weight to body weight ratio (LWW/BW) and histopathological analysis. Furthermore, we used the Akt inhibitor MK-2206 in a coculture system to elucidate the role of the HGF/Akt pathway in regulating the differentiation of DCs into regulatory DCs and relieving lung injury in early ALI mice.

RESULTS

Immature DCs (imDCs) were induced to mature after 24 h of LPS (50 ng/ml) stimulation. MSCs or HGF induced the differentiation of mDCs into regulatory DCs characterized by low expression of MHCII, CD86, and CD40 molecules, strong phagocytic function, and the ability to inhibit T cell proliferation. The effect of MSCs on DCregs was enhanced with the increase in HGF secretion and was weakened with the decrease in HGF secretion. DCregs induced by recombinant HGF were attenuated by the Akt inhibitor MK-2206. Lung DC aggregation and mDC ratio increased in LPS-induced ALI mice, while treatment with MSCs decreased lung DC aggregation and maturation and alleviated lung pathological injury. High expression of the HGF gene enhanced the above effect of MSCs, while decreased expression of HGF weakened the above effect of MSCs.

CONCLUSIONS

MSCs alleviate early ALI via paracrine HGF by inducing mDCs to differentiate into regulatory DCs. Furthermore, the mechanism of HGF-induced differentiation of mDCs into DCregs is related to the activation of the Akt pathway.

Anti-fibrotic mechanisms of exogenously-expanded mesenchymal stromal cells for fibrotic diseases

Most chronic diseases involving inflammation have a fibrotic component that involves remodeling and excess accumulation of extracellular matrix components. Left unchecked, fibrosis leads to organ failure and death. Mesenchymal stromal cells (MSCs) are emerging as a potent cell-based therapy for a wide spectrum of fibrotic conditions due to their immunomodulatory, anti-inflammatory and anti-fibrotic properties. This review provides an overview of known mechanisms by which MSCs mediate their anti-fibrotic actions and in relation to animal models of pulmonary, liver, renal and cardiac fibrosis. Recent MSC clinical trials results in liver, lung, skin, kidney and hearts are discussed and next steps for future MSC-based therapies including pre-activated or genetically-modified cells, or extracellular vesicles are also considered.

Hippo Signaling Controls NLR Family Pyrin Domain Containing 3 Activation and Governs Immunoregulation of Mesenchymal Stem Cells in Mouse Liver Injury

The Hippo pathway, an evolutionarily conserved protein kinase cascade, tightly regulates cell growth and survival. Activation of yes-associated protein (YAP), a downstream effector of the Hippo pathway, has been shown to modulate tissue inflammation. However, it remains unknown as to whether and how the Hippo-YAP signaling may control NLR family pyrin domain containing 3 (NLRP3) activation in mesenchymal stem cell (MSC)-mediated immune regulation during liver inflammation. In a mouse model of ischemia/reperfusion (IR)-induced liver sterile inflammatory injury, we found that adoptive transfer of MSCs reduced hepatocellular damage, shifted macrophage polarization from M1 to M2 phenotype, and diminished inflammatory mediators. MSC treatment reduced mammalian Ste20-like kinase 1/2 and large tumor suppressor 1 phosphorylation but augmented YAP and β-catenin expression with increased prostaglandin E2 production in ischemic livers. However, disruption of myeloid YAP or β-catenin in MSC-transferred mice exacerbated IR-triggered liver inflammation, enhanced NLRP3/caspase-1 activity, and reduced M2 macrophage phenotype. Using MSC/macrophage coculture system, we found that MSCs increased macrophage YAP and β-catenin nuclear translocation. Importantly, YAP and β-catenin colocalize in the nucleus while YAP interacts with β-catenin and regulates its target gene X-box binding protein 1 (XBP1), leading to reduced NLRP3/caspase-1 activity after coculture. Moreover, macrophage YAP or β-catenin deficiency augmented XBP1/NLRP3 while XBP1 deletion diminished NLRP3/caspase-1 activity. Increasing NLRP3 expression reduced M2 macrophage arginase1 but augmented M1 macrophage inducible nitric oxide synthase expression accompanied by increased interleukin-1β release. Conclusion: MSCs promote macrophage Hippo pathway, which in turn controls NLRP3 activation through a direct interaction between YAP and β-catenin and regulates XBP1-mediated NLRP3 activation, leading to reprograming macrophage polarization toward an anti-inflammatory M2 phenotype. Moreover, YAP functions as a transcriptional coactivator of β-catenin in MSC-mediated immune regulation. Our findings suggest a therapeutic target in MSC-mediated immunotherapy of liver sterile inflammatory injury.

The potential of mesenchymal stem cell therapy for chronic lung disease

Introduction: Mesenchymal stem/stromal cells (MSCs) have been shown to improve lung function and survival in chronic inflammatory lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH), and silicosis.Areas covered: This review covers rationale for the use of MSC therapy, along with preclinical studies and clinical trials with MSC therapy in chronic lung diseases.Expert opinion: MSC therapy holds promise for the treatment of chronic lung diseases, mainly when administered at early stages. In clinical trials, MSC administration was safe, but associated with limited effects on clinical outcomes. Further studies are required to elucidate unresolved issues, including optimal MSC source and dose, route of administration, and frequency (single vs. multiple-dose regimens). A better understanding of the mechanisms of MSC action, local microenvironment of each disease, and development of strategies to potentiate the beneficial effects of MSCs may improve outcomes.

Aberrant activation of Wnt signaling pathway altered osteocyte mineralization

Mineralization of bone is a dynamic process, involving a complex interplay between cells, secreted macromolecules, signaling pathways, and enzymatic reactions; the dysregulation of bone mineralization may lead to serious skeletal disorders, including hypophosphatemic rickets, osteoporosis, and rheumatoid arthritis. Very few studies have reported the role of osteocytes - the most abundant bone cells in the skeletal system and the major orchestrators of bone remodeling in bone mineralization, which is owed to their nature of being deeply embedded in the mineralized bone matrix. The Wnt/β-catenin signaling pathway is actively involved in various life processes including osteogenesis; however, the role of Wnt/β-catenin signaling in the terminal mineralization of bone, especially in the regulation of osteocytes, is largely unknown. This research demonstrates that during the terminal mineralization process, the Wnt/β-catenin pathway is downregulated, and when Wnt/β-catenin signaling is activated in osteocytes, dendrite development is suppressed and the expression of dentin matrix protein 1 (DMP1) is inhibited. Aberrant activation of Wnt/β-catenin signaling in osteocytes leads to the spontaneous deposition of extra-large mineralized nodules on the surface of collagen fibrils. The altered mineral crystal structure and decreased bonding force between minerals and the organic matrix indicate the inferior integration of minerals and collagen. In conclusion, Wnt/β-catenin signaling plays a critical role in the terminal differentiation of osteocytes and as such, targeting Wnt/β-catenin signaling in osteocytes may serve as a potential therapeutic approach for the management of bone-related diseases.

Macrophages as an Emerging Source of Wnt Ligands: Relevance in Mucosal Integrity

The Wnt signaling pathway is a conserved pathway involved in important cellular processes such as the control of embryonic development, cellular polarity, cellular migration, and cell proliferation. In addition to playing a central role during embryogenesis, this pathway is also an essential part of adult homeostasis. Indeed, it controls the proliferation of epithelial cells in different organs such as intestine, lung, and kidney, and guarantees the maintenance of the mucosa in physiological conditions. The origin of this molecular pathway is the binding between Wnt ligands (belonging to a family of 19 different homologous secreted glycoproteins) and their specific membrane receptors, from the Frizzled receptor family. This specific interaction triggers the activation of the signaling cascade, which in turn activates or suppresses the expression of different genes in order to change the behavior of the cell. On the other hand, alterations of this pathway have been described in pathological conditions such as inflammation, fibrosis, and cancer. In recent years, macrophages-among other cell types-have emerged as a potential source of Wnt ligands. Due to their high plasticity, macrophages, which are central to the innate immune response, are capable of adopting different phenotypes depending on their microenvironment. In the past, two different phenotypes were described: a proinflammatory phenotype-M1 macrophages-and an anti-inflammatory phenotype-M2 macrophages-and a selective expression of Wnt ligands has been associated with said phenotypes. However, nowadays it is assumed that macrophages in vivo move through a continual spectrum of functional phenotypes. In both physiological and pathological (inflammation, fibrosis and cancer) conditions, the accumulation and polarization of macrophages conditions the future of the tissue, facilitating various scenarios, such as resolution of inflammation, activation of fibrosis, and cancer development due to the modulation of the Wnt signaling pathway, in autocrine and paracrine manner. In this work, we provide an overview of studies that have explored the role of macrophages and how they act as a source of Wnt ligands and as mediators of mucosal integrity.

Current understanding of the therapeutic benefits of mesenchymal stem cells in acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a multifaceted lung disorder in which no specific therapeutic intervention is able to effectively improve clinical outcomes. Despite an improved understanding of molecular mechanisms and advances in supportive care strategies, ARDS remains associated with high mortality, and survivors usually face long-term morbidity. In recent years, preclinical studies have provided mounting evidence of the potential of mesenchymal stem cell (MSC)-based therapies in lung diseases and critical illnesses. In several models of ARDS, MSCs have been demonstrated to induce anti-inflammatory and anti-apoptotic effects, improve epithelial and endothelial cell recovery, and enhance microbial and alveolar fluid clearance, thus resulting in improved lung and distal organ function and survival. Early-stage clinical trials have also demonstrated the safety of MSC administration in patients with ARDS, but further, large-scale investigations are required to assess the safety and efficacy profile of these therapies. In this review, we summarize the main mechanisms whereby MSCs have been shown to exert therapeutic effects in experimental ARDS. We also highlight questions that need to be further elucidated and barriers that must be overcome in order to efficiently translate MSC research into clinical practice.

Overexpressing p130/E2F4 in mesenchymal stem cells facilitates the repair of injured alveolar epithelial cells in LPS-induced ARDS mice

Background

Low differentiation rates of mesenchymal stem cells (MSCs) limit their therapeutic effects on patients in clinical studies. Our previous study demonstrated that overexpressing p130 or E2F4 affected the multipotential differentiation of MSCs, and the underlying mechanism was attributed to the regulation of the G1 phase. Improving the efficiency of MSC differentiation into epithelial cells is considered to be a new method. Therefore, this study was conducted to evaluate the effects of overexpressing p130 or E2F4 in MSCs on improving re-epithelization in lipopolysaccharide (LPS)-induced ARDS animals.

Methods

Mouse MSCs (mMSCs) stably transfected with p130 and E2F4 were transplanted intratracheally into LPS-induced ARDS mice. After 7 and 14 days, the mice were sacrificed, and the histopathology of the lungs was assessed by haematoxylin-eosin staining and lung injury scoring. Homing and differentiation of mMSCs were analysed by labelling and tracking mMSCs with NIR815 dye and immunofluorescent staining. Surfactant proteins A and C and occludin in the lungs were assessed by western blot. Permeability was evaluated by analysing the protein concentration of BALF using ELISA. Alveolar fluid clearance was assessed by absorbance measurements of BALF. Lung fibrosis was assessed by Masson’s trichrome staining and Ashcroft scoring.

Results

The engraftment of mMSCs overexpressing p130 or E2F4 led to attenuated histopathological impairment of the lung tissue, and the lung injury scores of the LPS+mBM-MSC-p130 and LPS+mBM-MSC-E2F4 groups were also decreased (p < 0.05). Overexpression of p130 or E2F4 also increased the retention of mMSCs in the lung (p < 0.05), increased differentiation into type II alveolar epithelial cells (p < 0.05), and improved alveolar epithelial permeability (p < 0.05). Additionally, mMSCs overexpressing p130 or E2F4 inhibited lung fibrosis according to the deposition of collagen and the fibrosis score in the lungs (p < 0.05).

Conclusion

Overexpressing p130 or E2F4 in mMSCs could further improve the injured structure and function of epithelial cells in the lungs of ARDS mice as a result of improved differentiation of mMSCs into epithelial cells.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1169-1) contains supplementary material, which is available to authorized users.

Mesenchymal stem cells for inflammatory airway disorders: promises and challenges

The regenerative and immunomodulatory characteristics of mesenchymal stem cells (MSCs) make them attractive in the treatment of many diseases. Although they have shown promising preclinical studies of immunomodulation and paracrine effects in inflammatory airway disorders and other lung diseases, there are still challenges that have to be overcome before MSCs can be safely, effectively, and routinely applied in the clinical setting. A good understanding of the roles and mechanisms of the MSC immunomodulatory effects will benefit the application of MSC-based clinical therapy. In this review, we summarize the promises and challenges of the preclinical and clinical trials of MSC therapies, aiming to better understand the role that MSCs play in attempt to treat inflammatory airway disorders.

Overexpression of CXCR7 promotes mesenchymal stem cells to repair phosgene-induced acute lung injury in rats

Phosgene exposure may result in acute lung injury (ALI) with high mortality. Emerging evidence suggests that mesenchymal stem cells (MSCs) have a therapeutic potential against ALI. CXC chemokine receptor 7 (CXCR7) has been identified as a receptor of stromal-cell-derived factor 1 (SDF1) involved in MSC migration and may be an important mediator of the therapeutic effects of MSCs on ALI. In our study, we initially constructed a lentiviral vector overexpressing CXCR7 and then successfully transduced it into rat bone marrow-derived MSCs (resulting in MSCs-CXCR7). We found that ALI and the wet-to-dry ratio significantly decreased in the phosgene-exposed rats after administration of MSCs-CXCR7 or MSCs-GFP. Indeed, treatment with MSCs-CXCR7 caused further improvement. Moreover, injection of MSCs-CXCR7 significantly facilitated MSC homing to injured lung tissue. Meanwhile, overexpression of CXCR7 promoted differentiation of MSCs into type II alveolar epithelial (AT II) cells and enhanced the ability of MSCs to modulate the inflammatory response in phosgene-induced ALI. Taken together, our findings suggest that CXCR7-overexpressing MSCs may markedly facilitate treatment of phosgene-induced ALI (P-ALI) in rats.

Mesenchymal stem cells overexpressing Ang1 attenuates phosgene-induced acute lung injury in rats

Phosgene-induced acute lung injury (P-ALI) is characterized by inflammation and effective treatments are lacking. Angiopoietin-1 (Ang1) has the beneficial effects on P-ALI. Mesenchymal stem cells (MSCs) have the potential for re-epithelization and recovery in lung injury. Thus, we hypothesized that Ang1 expressing MSCs would have beneficial effects on P-ALI. Here, an Ang1 expressing lentiviral vector was constructed and infected into rat bone marrow MSCs. Histological analyses revealed significant pathological improvements especially after treatment with MSCs in the rats exposed to phosgene. Ang1 facilitated the homing of MSCs to injured lung tissue and significantly increased expression of both epithelial cell marker Aquaporin-5 (AQP5) and surfactant protein-C (SPC) in the lung tissues. Moreover, MSCs-Ang1 reduced level of pro-inflammatory cytokines TGF-β1 and IL-1β and increased the expression of the anti-inflammatory cytokine IL-10 in the serum and bronchoalveolar lavage fluid (BALF) of P-ALI rats. In conclusion, our results suggest that Ang1 may improve the therapeutic potential of MSCs for P-ALI treatment.

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.

Genetic Modification of Mesenchymal Stem Cells Overexpressing Angiotensin II Type 2 Receptor Increases Cell Migration to Injured Lung in LPS-Induced Acute Lung Injury Mice

Although mesenchymal stem cells (MSCs) transplantation has been shown to promote the lung respiration in acute lung injury (ALI) in vivo, its overall restorative capacity appears to be restricted mainly because of low retention in the injured lung. Angiotensin II (Ang II) are upregulated in the injured lung. Our previous study showed that Ang II increased MSCs migration via Ang II type 2 receptor (AT2R). To determine the effect of AT2R in MSCs on their cell migration after systemic injection in ALI mice, a human AT2R expressing lentiviral vector and a lentivirus vector carrying AT2R shRNA were constructed and introduced into human bone marrow MSCs. A mouse model of lipopolysaccharide‐induced ALI was used to investigate the migration of AT2R‐regulated MSCs and the therapeutic potential in vivo. Overexpression of AT2R dramatically increased Ang II‐enhanced human bone marrow MSC migration in vitro. Moreover, MSC‐AT2R accumulated in the damaged lung tissue at significantly higher levels than control MSCs 24 and 72 hours after systematic MSC transplantation in ALI mice. Furthermore, MSC‐AT2R‐injected ALI mice exhibited a significant reduction of pulmonary vascular permeability and improved the lung histopathology and had additional anti‐inflammatory effects. In contrast, there were less lung retention in MSC‐ShAT2R‐injected ALI mice compared with MSC‐Shcontrol after transplantation. Thus, MSC‐ShAT2R‐injected group exhibited a significant increase of pulmonary vascular permeability and resulted in a deteriorative lung inflammation. Our results demonstrate that overexpression of AT2R enhance the migration of MSCs in ALI mice and may provide a new therapeutic strategy for ALI. Stem Cells Translational Medicine2018;7:721–730

Transcriptomic analysis of lung tissues after hUC-MSCs and FTY720 treatment of lipopolysaccharide-induced acute lung injury in mouse models

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) refer to acute and progressive hypoxic respiratory failure caused by non-cardiogenic factors, which is a common condition occurring in critically ill patients with widespread pulmonary inflammation. Use of a single medication or target cannot treat ALI/ARDS. Mesenchymal stem cells (MSCs) and FTY720, as an analogue of sphingosine-1-phosphate (S1P), can mitigate lipopolysaccharide (LPS)-induced inflammatory lung injury. In this investigation, the clinical efficacy of MSCs alone, FTY720 alone, and a MSC and FTY720 combination in the treatment of LPS-induced lung injury was evaluated in mouse models. The experimental results demonstrated that both MSCs and FTY720 alleviate lung injuries in mice. The combined application of MSCs and FTY720 yielded higher clinical efficacy in mitigating lung injuries compared with use of MSCs or FTY720 alone. Transcriptomic analysis was performed using an Agilent gene expression chip. By analyzing the differences in gene expression of lung tissues between treated and non-treated ALI/ARDS mice, Gene Ontology and Pathway terms related to ALI/ARDS treatment were identified. Moreover, the target genes which might play a pivotal role in the treatment of ALI/ARDS were also detected, thus providing a theoretical basis for multi-target or multi-drug combined treatment of ALI/ARDS and lay a solid foundation for clinical treatment of ALI/ARDS.

miR-155-5p Promotes Progression of Acute Respiratory Distress Syndrome by Inhibiting Differentiation of Bone Marrow Mesenchymal Stem Cells to Alveolar Type II Epithelial Cells

Background

We investigated whether microRNA-155-5p is involved in the differentiation of bone marrow mesenchymal stem cells (BMSCs) into alveolar type II epithelial (AT II) cells by regulating the Wnt signaling pathway, thus participating in the development of acute respiratory distress syndrome (ARDS).

Material/Methods

Serum levels of microRNA-155-5p in 50 ARDS patients and 50 normal controls were detected by quantitative real-time PCR (qRT-PCR). Marrow mesenchymal stem cells (MCSs) were isolated from mouse bone marrow and identified by flow cytometry. Subsequently, the effect of microRNA-155-5p on differentiation of BMSCs into AT II cells was evaluated by detecting the expression levels of AT II-specific genes. The expression levels of proteins in the Wnt signaling pathway after overexpression or knockdown of microRNA-155-5p were detected by Western blot.

Results

Serum levels of microRNA-155-5p in ARDS patients were significantly higher than that in normal controls. Expression levels of AT II-specific genes were enhanced after downregulating microRNA-155-5p in BMSCs. MicroRNA-155-5p overexpression showed the opposite result. Furthermore, microRNA-155-5p inhibited the expression levels of proteins in the Wnt signaling pathway.

Conclusions

MicroRNA-155-5p can attenuate the differentiation of BMSCs into AT II cells by inhibiting the Wnt signaling pathway, thus promoting the progression of ARDS.

Nrf2 attenuates inflammatory response in COPD/emphysema: Crosstalk with Wnt3a/β-catenin and AMPK pathways

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and abnormal inflammatory response. Wnt/β-catenin and AMP-activated protein kinase (AMPK) have been shown to modulate lung inflammatory responses and injury. However, it remains elusive whether Wnt/β-catenin and AMPK modulate nuclear factor erythroid-2 related factor-2 (Nrf2)-mediated protective responses during the development of emphysema. Here we showed that treatment with a Wnt pathway activator (LiCl) reduced elastase-induced airspace enlargement and cigarette smoke extract (CSE)-induced lung inflammatory responses in WT mice, which was associated with increased activation of Nrf2 pathway. Interestingly, these effects of LiCl were not observed in Nrf2^-/- mice exposed to elastase. In normal human bronchial epithelial (NHBE) cells, Wnt3a overexpression up-regulated, whereas Wnt3a knockdown further down-regulated the levels of Nrf2 and its target proteins heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) by CSE treatment. In contrast, Nrf2 deficiency did not have any effects on Wnt/β-catenin pathway in mouse lungs and NHBE cells. Both elastase and CSE exposures reduced AMPK phosphorylation. A specific AMPK activator metformin increased Wnt3a, β-catenin, Nrf2 phosphorylation and activation but reduced the levels of IL-6 and IL-8 in NHBE cells and mouse lungs exposed to CSE. Furthermore, Nrf2 deficiency abolished the protection of metformin against CSE-induced increase in IL-6 and IL-8 in NHBE cells. In conclusion, Nrf2 mediates the protective effects of both Wnt3a/β-catenin and AMPK on lung inflammatory responses during the development of COPD/emphysema. These findings provide potential therapeutic targets for the intervention of COPD/emphysema.

Hypoxia stimulates microenvironment in human embryonic stem cell through inflammatory signalling: An integrative analysis

Despite, several lines of evidence suggesting the possible role of hypoxia in stem cell development and differentiation its significance in conferring the stemness and pluripotency remains elusive. In the present study we sought to delineate the candidate genes and molecular pathways imposed during hypoxic microenvironment and its physiological relevance in tipping the balance between the niche and cellular differentiation. Integrated meta-analysis was performed between the hypoxia exposed and normal human embryonic stem cells, employing three transcriptomic cohorts (GSE35819, GSE9510 and GSE37761) retrieved from Gene expression omnibus (GEO) database. Results reveal that a total number of 12 genes were consistently differentially expressed (6up regulated and 6 down regulated) with FDR <0.05 and fold change >1.5. The Gene Ontology (GO) functions and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis was performed using DAVID. The GO analysis showed DEG significantly enriched in terms of Cellular process (GO:0009987), protein binding (GO:0005515) and cell part (GO:0044464). KEGG analysis indicated participation of genes associated with circadian rthyum regulation and PPAR signalling pathway. Further, gene-set signature (MsigDB) enrichment analysis showed positive regulation with inflammatory signals and negative association with PPAR and p53 pathway. Protein-protein network of gene modules suggests significant hub proteins viz. CTTNB1 (Degree = 18), IL8 (Degree = 15), NFKB1 (Degree = 15) and RELA (Degree = 15) in the PPI network. MCODE algorithm was used for subnetworks of the PPI network. Our integrative analysis documents the potential candidate genes which serves distinct roles influencing metabolic shift and induce inflammatory effectors contributing to hypoxic mediated stem cell niche.

Stem cell therapies for chronic obstructive pulmonary disease: current status of pre-clinical studies and clinical trials

Chronic obstructive pulmonary disease (COPD) is a respiratory disease that has a major impact worldwide. The currently-available drugs mainly focus on relieving the symptoms of COPD patients. Novel regenerative therapeutic approaches have been investigated with the aim of repairing or replacing the injured functional structures of the respiratory system. We summarized the progress made by regenerative therapies for COPD by analyzing results from both pre-clinical studies and completed clinical trials. These approaches include the application of exogenous stem cells or small molecules to stimulate the regeneration by endogenous lung stem/progenitor cells. Exogenous mesenchymal stem cells (MSCs) have been reported to repair the structure and improve the function of the injured respiratory system in COPD models. However, the studies that used MSCs in patients with moderate-to-severe COPD patients did not lead to clear respiratory functional improvements. Exogenous human lung stem cells applied to cryo-injured (CI) lungs of mice have been shown to organize into human-like pulmonary structures, indicating a new property of stem cells that is potentially capable of curing COPD patients. Small molecules like retinoic acid has been shown to lead to regeneration and repair of the damaged lung structures in COPD mouse models probably by activation of endogenous lung stem/progenitor cells. However, retinoic acid or agonists of retinoic acid receptor administered to moderate or severe COPD patients did not improve the density and function of the damaged lung. These novel regenerative approaches have failed in preliminary clinical trials, possibly due to the advanced severity of the disease. Further work should be done to develop the current regenerative approaches for curing patients at different stages of COPD. We suggest that some modifications of the approach in the clinical studies may lead to more successful outcomes of regenerative therapy for COPD.

IL-1β-stimulated β-catenin up-regulation promotes angiogenesis in human lung-derived mesenchymal stromal cells through a NF-κB-dependent microRNA-433 induction

Considerable attentions have been focused on the treatment of lung injury using mesenchymal stem cells that can replenish damaged tissues including the blood vessels. In human lung-derived mesenchymal stem cells (hL-MSC), we investigated the potential role of an IL-1β-stimulated miR-433 pathway in angiogenesis in vitro. The expressions of miR-433 and its target genes were examined in cells treated with IL-1β. The angiogenic activity of hL-MSC was studied by cell migration and tube formation assays in which miR-433 levels were manipulated. The reporter assay and chromatin immunoprecipitation (ChIP) were also performed to analyze the underlying regulations. We found that the expression of miR-433 was enhanced in hL-MSC by IL-1β in a NF-κB dependent manner via a NF-κB binding site at its promoter region. The effects of IL-1β on promoting angiogenic activities in hL-MSC can be mimicked by the overexpression of miR-433 and were blocked by anti-miR-433. Mechanistically, our data suggested that miR-433 directly targets the 3'-UTR of Dickkopf Wnt signaling pathway inhibitor 1 (DKK1) mRNA and decreases its expression. Consistently, the expression of β-catenin, the major mediator of canonical Wnt pathway that is capable of inducing endothelial differentiation and angiogenesis, was upregulated by IL-1β through miR-433. Thus, increasing miR-433 expression by IL-1β in mesenchymal stem cells could stimulate their capacity of vascular remodeling for efficient repair processes, which may be utilized as a therapeutic target in patients suffering from severe lung injury.

Nrf2 transfection enhances the efficacy of human amniotic mesenchymal stem cells to repair lung injury induced by lipopolysaccharide

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are clinical emergencies with no effective pharmaceutical treatment. This study aims to determine the protective effects of Nrf2-transfected human amniotic mesenchymal stem cells (hAMSCs) against lipopolysaccharide (LPS)-induced lung injury in mice. hAMSCs stably transfected with Nrf2 or green fluorescent protein control were transplanted into male C57BL/6 mice via the tail vein 4 h after intratracheal instillation of LPS. At 3, 7, and 14 days after cell transplantation, total lung injury score (the Smith score) was determined by hematoxylin and eosin staining. Lung fibrosis was assessed by Masson's trichrome staining. Alveolar epithelial apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The plasma levels of interleukin (IL)-1β, IL-6, and IL-10 were determined by enzyme-linked immunosorbent assays (ELISA). The homing and differentiation of hAMSCs into type II alveolar epithelial (AT II) cells were examined by immunofluorescent staining and/or western blot analysis. Nrf2, mRNA, and protein expression in lungs were examined by qRT-PCR and western blot analysis, and DNA-binding activity of Nrf2 was detected by ELISA. We found that, compared with control hAMSCs, treatment with Nrf2-overexpressing hAMSCs led to further reduced lung injury, lung fibrosis, and inflammation in LPS-challenged mice. Nrf2-overexpressing hAMSCs also exhibited increased cell retention in the lung, more efficient differentiation into AT II cells, and more prominent effects on the increased mRNA and protein expression as well as DNA-binding activity of Nrf2 than control. These results support Nrf2-overexpressing hAMSCs as a potential cell-based therapy for clinical ALI/ARDS.