Anti-inflammatory roles of mesenchymal stromal cells during acute Streptococcus pneumoniae pulmonary infection in mice

Antimicrobial Properties of Equine Stromal Cells and Platelets and Future Directions

Increasing antimicrobial resistance in veterinary practice has driven the investigation of novel therapeutic strategies including regenerative and biologic therapies to treat bacterial infection. Integration of biological approaches such as platelet lysate and mesenchymal stromal cell (MSC) therapy may represent adjunctive treatment strategies for bacterial infections that minimize systemic side effects and local tissue toxicity associated with traditional antibiotics and that are not subject to antibiotic resistance. In this review, we will discuss mechanisms by which biological therapies exert antimicrobial effects, as well as potential applications and challenges in clinical implementation in equine practice.

Revisiting the role of mesenchymal stem cells in tuberculosis and other infectious diseases

Mesenchymal stem cells (MSCs) play diverse roles ranging from regeneration and wound healing to immune signaling. Recent investigations have indicated the crucial role of these multipotent stem cells in regulating various aspects of the immune system. MSCs express unique signaling molecules and secrete various soluble factors that play critical roles in modulating and shaping immune responses, and in some other cases, MSCs can also exert direct antimicrobial effects, thereby helping with the eradication of invading organisms. Recently, it has been demonstrated that MSCs are recruited at the periphery of the granuloma containing Mycobacterium tuberculosis and exert "Janus"-like functions by harboring pathogens and mediating host protective immune responses. This leads to the establishment of a dynamic balance between the host and the pathogen. MSCs function through various immunomodulatory factors such as nitric oxide (NO), IDO, and immunosuppressive cytokines. Recently, our group has shown that M.tb uses MSCs as a niche to evade host protective immune surveillance mechanisms and establish dormancy. MSCs also express a large number of ABC efflux pumps; therefore, dormant M.tb residing in MSCs are exposed to a suboptimal dose of drugs. Therefore, it is highly likely that drug resistance is coupled with dormancy and originates within MSCs. In this review, we discussed various immunomodulatory properties of MSCs, their interactions with important immune cells, and soluble factors. We also discussed the possible roles of MSCs in the outcome of multiple infections and in shaping the immune system, which may provide insight into therapeutic approaches using these cells in different infection models.

TLRs Gene Polymorphisms Associated with Pneumonia before and during COVID-19 Pandemic

BACKGROUND

The progression of infectious diseases depends on the characteristics of a patient's innate immunity, and the efficiency of an immune system depends on the patient's genetic factors, including SNPs in the TLR genes. In this pilot study, we determined the frequency of alleles in these SNPs in a subset of patients with pneumonia.

METHODS

This study assessed six SNPs from TLR genes: rs5743551 (TLR1), rs5743708, rs3804100 (TLR2), rs4986790 (TLR4), rs5743810 (TLR6), and rs3764880 (TLR8). Three groups of patients participated in this study: patients with pneumonia in 2019 (76 samples), patients with pneumonia caused by SARS-CoV-2 in 2021 (85 samples), and the control group (99 samples).

RESULTS

The allele and genotype frequencies obtained for each group were examined using four genetic models. Significant results were obtained when comparing the samples obtained from individuals with pneumonia before the spread of SARS-CoV-2 and from the controls for rs5743551 (TLR1) and rs3764880 (TLR8). Additionally, the comparison of COVID-19-related pneumonia cases and the control group revealed a significant result for rs3804100-G (TLR2).

CONCLUSIONS

Determining SNP allele frequencies and searching for their associations with the course of pneumonia are important for personalized patient management. However, our results need to be comprehensively assessed in consideration of other clinical parameters.

Immune Activated Cellular Therapy for Drug Resistant Infections: Rationale, Mechanisms, and Implications for Veterinary Medicine

Simple Summary

Mesenchymal stromal/stem cells have intrinsic antimicrobial properties, thus making them attractive as an alternative treatment strategy in chronic, drug-resistant bacterial infections. Recent evidence has suggested that these antimicrobial effects can be significantly enhanced by immune activation just prior to injection. This review examines the potential role for cellular therapies in treatment of drug resistant infections in veterinary medicine, drawing on insights across species and discussing the therapeutic potential of this approach overall in today’s veterinary patients.

Abstract

Antimicrobial resistance and biofilm formation both present challenges to treatment of bacterial infections with conventional antibiotic therapy and serve as the impetus for development of improved therapeutic approaches. Mesenchymal stromal cell (MSC) therapy exerts an antimicrobial effect as demonstrated in multiple acute bacterial infection models. This effect can be enhanced by pre-conditioning the MSC with Toll or Nod-like receptor stimulation, termed activated cellular therapy (ACT). The purpose of this review is to summarize the current literature on mechanisms of antimicrobial activity of MSC with emphasis on enhanced effects through receptor agonism, and data supporting use of ACT in treatment of bacterial infections in veterinary species including dogs, cats, and horses with implications for further treatment applications. This review will advance the field’s understanding of the use of activated antimicrobial cellular therapy to treat infection, including mechanisms of action and potential therapeutic applications.

Placental mesenchymal stem cells boost M2 alveolar over M1 bone marrow macrophages via IL-1β in Klebsiella-mediated acute respiratory distress syndrome

RATIONALE

Acute respiratory distress syndrome (ARDS) is a lethal complication of severe bacterial pneumonia due to the inability to dampen overexuberant immune responses without compromising pathogen clearance. Both of these processes involve tissue-resident and bone marrow (BM)-recruited macrophage (MΦ) populations which can be polarised to have divergent functions. Surprisingly, despite the known immunomodulatory properties of mesenchymal stem cells (MSCs), simultaneous interactions with tissue-resident and recruited BMMΦ populations are largely unexplored.

OBJECTIVES

We assessed the therapeutic use of human placental MSCs (PMSCs) in severe bacterial pneumonia with elucidation of the roles of resident alveolar MΦs (AMΦs) and BMMΦs.

METHODS

We developed a lethal, murine pneumonia model using intratracheal infection of a clinically relevant Klebsiella pneumoniae (KP) strain with subsequent intravenous human PMSC treatment. Pulmonary AMΦ and recruited BMMΦ analyses, histological evaluation, bacterial clearance and mice survival were assessed. To elucidate the role of resident AMΦs in improving outcome, we performed AMΦ depletion in the KP-pneumonia model with intratracheal clodronate pretreatment.

MEASUREMENTS AND MAIN RESULTS

Human PMSC treatment decreased tissue injury and improved survival of severe KP-pneumonia mice by decreasing the presence and function of recruited M1 BMMΦ while preserving M2 AMΦs and enhancing their antibacterial functions. Interestingly, PMSC therapy failed to rescue AMΦ-depleted mice with KP pneumonia, and PMSC-secreted IL-1β was identified as critical in increasing AMΦ antibacterial activities to significantly improve pathogen clearance-especially bacteraemia-and survival.

CONCLUSIONS

Human PMSC treatment preferentially rescued resident M2 AMΦs over recruited M1 BMMΦs with overall M2 polarisation to improve KP-related ARDS survival.

Enhancement strategies for mesenchymal stem cells and related therapies

Cell therapy, particularly mesenchymal stem/stromal (MSC) therapy, has been investigated for a wide variety of disease indications, particularly those with inflammatory pathologies. However, recently it has become evident that the MSC is far from a panacea. In this review we will look at current and future strategies that might overcome limitations in efficacy. Many of these take their inspiration from stem cell niche and the mechanism of MSC action in response to the injury microenvironment, or from previous gene therapy work which can now benefit from the added longevity and targeting ability of a live cell vector. We will also explore the nascent field of extracellular vesicle therapy and how we are already seeing enhancement protocols for this exciting new drug. These enhanced MSCs will lead the way in more difficult to treat diseases and restore potency where donors or manufacturing practicalities lead to diminished MSC effect.

Application of Wharton jelly-derived mesenchymal stem cells in patients with pulmonary fibrosis

Pulmonary fibrosis is a devastating disease that eventually leads to death and respiratory failure. Despite the wide range of drugs, including corticosteroids, endothelin antagonist, and pirfenidone, there is no effective treatment, and the only main goal of treatment is to alleviate the symptoms as much as possible to slow down the progression of the disease and improve the quality of life. Lung transplantation may be a treatment option for a few people if pulmonary fibrosis develops and there is no established treatment. Pulmonary fibrosis caused by the COVID19 virus is another problem that we face in most patients despite the efforts of the international medical communities. Therefore, achieving alternative treatment for patients is a great success. Today, basic research using stem cells on pulmonary fibrosis has published promising results. New stem cell-based therapies can be helpful in patients with pulmonary fibrosis. Wharton jelly-derived mesenchymal stem cells are easily isolated in large quantities and made available for clinical trials without causing ethical problems. These cells have higher flexibility and proliferation potential than other cells isolated from different sources and differentiated into various cells in laboratory environments. More clinical trials are needed to determine the safety and efficacy of these cells. This study will investigate the cellular and molecular mechanisms and possible effects of Wharton jelly-derived mesenchymal stem cells in pulmonary fibrosis.

Adverse Mechanical Ventilation and Pneumococcal Pneumonia Induce Immune and Mitochondrial Dysfunctions Mitigated by Mesenchymal Stem Cells in Rabbits

BACKGROUND

Mechanical ventilation for pneumonia may contribute to lung injury due to factors that include mitochondrial dysfunction, and mesenchymal stem cells may attenuate injury. This study hypothesized that mechanical ventilation induces immune and mitochondrial dysfunction, with or without pneumococcal pneumonia, that could be mitigated by mesenchymal stem cells alone or combined with antibiotics.

METHODS

Male rabbits underwent protective mechanical ventilation (8 ml/kg tidal volume, 5 cm H2O end-expiratory pressure) or adverse mechanical ventilation (20 ml/kg tidal-volume, zero end-expiratory pressure) or were allowed to breathe spontaneously. The same settings were then repeated during pneumococcal pneumonia. Finally, infected animals during adverse mechanical ventilation received human umbilical cord-derived mesenchymal stem cells (3 × 106/kg, intravenous) and/or ceftaroline (20 mg/kg, intramuscular) or sodium chloride, 4 h after pneumococcal challenge. Twenty-four-hour survival (primary outcome), lung injury, bacterial burden, immune and mitochondrial dysfunction, and lung transcriptomes (secondary outcomes) were assessed.

RESULTS

High-pressure adverse mechanical ventilation reduced the survival of infected animals (0%; 0 of 7) compared with spontaneous breathing (100%; 7 of 7) and protective mechanical ventilation (86%; 6 of 7; both P < 0.001), with higher lung pathology scores (median [interquartile ranges], 5.5 [4.5 to 7.0] vs. 12.6 [12.0 to 14.0]; P = 0.046), interleukin-8 lung concentrations (106 [54 to 316] vs. 804 [753 to 868] pg/g of lung; P = 0.012), and alveolar mitochondrial DNA release (0.33 [0.28 to 0.36] vs. 0.98 [0.76 to 1.21] ng/μl; P < 0.001) compared with infected spontaneously breathing animals. Survival (0%; 0 of 7; control group) was improved by mesenchymal stem cells (57%; 4 of 7; P = 0.001) or ceftaroline alone (57%; 4 of 7; P < 0.001) and improved even more with a combination treatment (86%; 6 of 7; P < 0.001). Mesenchymal stem cells reduced lung pathology score (8.5 [7.0 to 10.5] vs. 12.6 [12.0 to 14.0]; P = 0.043) and alveolar mitochondrial DNA release (0.39 (0.34 to 0.65) vs. 0.98 (0.76 to 1.21) ng/μl; P = 0.025). Mesenchymal stem cells combined with ceftaroline reduced interleukin-8 lung concentrations (665 [595 to 795] vs. 804 [753 to 868] pg/g of lung; P = 0.007) compared to ceftaroline alone.

CONCLUSIONS

In this preclinical study, mesenchymal stem cells improved the outcome of rabbits with pneumonia and high-pressure mechanical ventilation by correcting immune and mitochondrial dysfunction and when combined with the antibiotic ceftaroline was synergistic in mitigating lung inflammation.

EDITOR’S PERSPECTIVE

ADAM10 partially protects mice against influenza pneumonia by suppressing specific myeloid cell population

The influenza virus infection poses a serious health threat worldwide. Myeloid cells play pivotal roles in regulating innate and adaptive immune defense. A disintegrin and metalloproteinase (ADAM) family of proteins contributes to various immune responses; however, the role of a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) in influenza virus infection remains largely unknown. Herein, we investigated its role, focusing on myeloid cells, during influenza virus infection in mice. ADAM10 gene (Adam10)^flox/flox/Lyz2-Cre (Adam10^ΔLyz2) and control Adam10^flox/flox mice were intranasally infected with 200 plaque-forming units of influenza virus A/H1N1/PR8/34. Adam10^ΔLyz2 mice exhibited a significantly higher mortality rate, stronger lung inflammation, and a higher virus titer in the lungs than control mice. Macrophages and inflammatory cytokines, such as TNF-α, IL-1β, and CCL2, were increased in bronchoalveolar lavage fluid from Adam10^ΔLyz2 mice following infection. CD11b⁺Ly6G^-F4/80⁺ myeloid cells, which had an inflammatory monocyte/macrophage-like phenotype, were significantly increased in the lungs of Adam10^ΔLyz2 mice. Adoptive transfer experiments suggested that these cells likely contributed to the poorer prognosis in Adam10^ΔLyz2 mice. Seven days after infection, CD11b⁺Ly6G^-F4/80⁺ lung cells exhibited significantly higher arginase-1 expression levels in Adam10^ΔLyz2 mice than in control mice, whereas an arginase-1 inhibitor improved the prognosis of Adam10^ΔLyz2 mice. Enhanced granulocyte-macrophage colony-stimulating factor (GM-CSF)/GM-CSF receptor signaling likely contributed to this process. Collectively, these results indicate that myeloid ADAM10 protects against influenza virus pneumonia and may be a promising therapeutic target.

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.

Mesenchymal stromal cells as a therapeutic intervention for COVID-19: a living systematic review and meta-analysis protocol

BACKGROUND

Mesenchymal stromal cells (MSCs) have significant immunomodulatory and tissue repair capabilities, mediated partly by conditioned media or through secreted extracellular vesicles (MSC-EVs). Infection with SARS-CoV-2 can cause mild to life-threatening illness due to activated immune responses that may be dampened by MSCs or their secretome. Many clinical studies of MSCs have been launched since the beginning of the global pandemic, however, few have been completed and most lack power to assess efficacy. Repeated systematic searches and meta-analyses are needed to understand, in real time, the extent of potential benefit in different patient populations as the evidence emerges.

METHODS

This living systematic review will be maintained to provide up-to-date information as the pandemic evolves. A systematic literature search of Embase, MEDLINE, and Cochrane Central Register of Controlled Trials databases will be performed. All clinical studies (e.g., randomized, pseudorandomized and non-randomized controlled trials, uncontrolled trials, and case series) employing MSCs or their secretome as a therapeutic intervention for COVID-19 will be included. Patients must have confirmed SARS-CoV-2 infection. Study screening and data extraction will be performed in duplicate. Information concerning interventions, patient populations, methods of MSC isolation and characterization, primary and secondary clinical and/or laboratory outcomes, and adverse events will be extracted. Key clinical outcomes will be pooled through random-effects meta-analysis to determine the efficacy of MSCs and their secreted products for COVID-19.

DISCUSSION

Our systematic review and subsequent updates will inform the scientific, medical, and health policy communities as the pandemic evolves to guide decisions on the appropriate use of MSC-related products to treat COVID-19.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD 42021225431.

Host Defense against Klebsiella pneumoniae Pneumonia Is Augmented by Lung-Derived Mesenchymal Stem Cells

Klebsiella pneumoniae is a common cause of Gram-negative pneumonia. The spread of antibiotic-resistant and hypervirulent strains has made treatment more challenging. This study sought to determine the immunomodulatory, antibacterial, and therapeutic potential of purified murine stem cell Ag-1⁺ (Sca-1⁺) lung mesenchymal stem cells (LMSCs) using in vitro cell culture and an in vivo mouse model of pneumonia caused by K pneumoniae. Sca-1⁺ LMSCs are plastic adherent, possess colony-forming capacity, express mesenchymal stem cell markers, differentiate into osteogenic and adipogenic lineages in vitro, and exhibit a high proliferative capacity. Further, these Sca-1⁺ LMSCs are morphologically similar to fibroblasts but differ ultrastructurally. Moreover, Sca-1⁺ LMSCs have the capacity to inhibit LPS-induced secretion of inflammatory cytokines by bone marrow-derived macrophages and neutrophils in vitro. Sca-1⁺ LMSCs inhibit the growth of K pneumoniae more potently than do neutrophils. Sca-1⁺ LMSCs also possess the intrinsic ability to phagocytize and kill K. pneumoniae intracellularly. Whereas the induction of autophagy promotes bacterial replication, inhibition of autophagy enhances the intracellular clearance of K. pneumoniae in Sca-1⁺ LMSCs during the early time of infection. Adoptive transfer of Sca-1⁺ LMSCs in K. pneumoniae-infected mice improved survival, reduced inflammatory cells in bronchoalveolar lavage fluid, reduced inflammatory cytokine levels and pathological lesions in the lung, and enhanced bacterial clearance in the lung and in extrapulmonary organs. To our knowledge, these results together illustrate for the first time the protective role of LMSCs in bacterial pneumonia.

Function of Dental Follicle Progenitor/Stem Cells and Their Potential in Regenerative Medicine: From Mechanisms to Applications

Dental follicle progenitor/stem cells (DFPCs) are a group of dental mesenchyme stem cells that lie in the dental follicle and play a critical role in tooth development and maintaining function. Originating from neural crest, DFPCs harbor a multipotential differentiation capacity. More importantly, they have superiorities, including the easy accessibility and abundant sources, active self-renewal ability and noncontroversial sources compared with other stem cells, making them an attractive candidate in the field of tissue engineering. Recent advances highlight the excellent properties of DFPCs in regeneration of orofacial tissues, including alveolar bone repair, periodontium regeneration and bio-root complex formation. Furthermore, they play a unique role in maintaining a favorable microenvironment for stem cells, immunomodulation and nervous related tissue regeneration. This review is intended to summarize the current knowledge of DFPCs, including their stem cell properties, physiological functions and clinical application potential. A deep understanding of DFPCs can thus inspire novel perspectives in regenerative medicine in the future.

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.

Stem cells and COVID-19: are the human amniotic cells a new hope for therapies against the SARS-CoV-2 virus?

A new coronavirus respiratory disease (COVID-19) caused by the SARS-CoV-2 virus, surprised the entire world, producing social, economic, and health problems. The COVID-19 triggers a lung infection with a multiple proinflammatory cytokine storm in severe patients. Without effective and safe treatments, COVID-19 has killed thousands of people, becoming a pandemic. Stem cells have been suggested as a therapy for lung-related diseases. In particular, mesenchymal stem cells (MSCs) have been successfully tested in some clinical trials in patients with COVID-19. The encouraging results positioned MSCs as a possible cell therapy for COVID-19. The amniotic membrane from the human placenta at term is a valuable stem cell source, including human amniotic epithelial cells (hAECs) and human mesenchymal stromal cells (hAMSCs). Interestingly, amnion cells have immunoregulatory, regenerative, and anti-inflammatory properties. Moreover, hAECs and hAMSCs have been used both in preclinical studies and in clinical trials against respiratory diseases. They have reduced the inflammatory response and restored the pulmonary tissue architecture in lung injury in vivo models. Here, we review the existing data about the stem cells use for COVID-19 treatment, including the ongoing clinical trials. We also consider the non-cellular therapies that are being applied. Finally, we discuss the human amniotic membrane cells use in patients who suffer from immune/inflammatory lung diseases and hypothesize their possible use as a successful treatment against COVID-19.

The Role of MSC Therapy in Attenuating the Damaging Effects of the Cytokine Storm Induced by COVID-19 on the Heart and Cardiovascular System

The global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) has led to 47 m infected cases and 1. 2 m (2.6%) deaths. A hallmark of more severe cases of SARS-CoV-2 in patients with acute respiratory distress syndrome (ARDS) appears to be a virally-induced over-activation or unregulated response of the immune system, termed a "cytokine storm," featuring elevated levels of pro-inflammatory cytokines such as IL-2, IL-6, IL-7, IL-22, CXCL10, and TNFα. Whilst the lungs are the primary site of infection for SARS-CoV-2, in more severe cases its effects can be detected in multiple organ systems. Indeed, many COVID-19 positive patients develop cardiovascular complications, such as myocardial injury, myocarditis, cardiac arrhythmia, and thromboembolism, which are associated with higher mortality. Drug and cell therapies targeting immunosuppression have been suggested to help combat the cytokine storm. In particular, mesenchymal stromal cells (MSCs), owing to their powerful immunomodulatory ability, have shown promise in early clinical studies to avoid, prevent or attenuate the cytokine storm. In this review, we will discuss the mechanistic underpinnings of the cytokine storm on the cardiovascular system, and how MSCs potentially attenuate the damage caused by the cytokine storm induced by COVID-19. We will also address how MSC transplantation could alleviate the long-term complications seen in some COVID-19 patients, such as improving tissue repair and regeneration.

Immunomodulatory and Therapeutic Effects of Mesenchymal Stem Cells on Organ Dysfunction in Sepsis

ABSTRACT

Sepsis is a life-threatening disorder that is caused by a dysregulated inflammatory response during an infection. The disease mostly affects pregnant women, newborns, and patients in intensive care units. Sepsis treatment is a significant part of a country's health budgets. Delay in the therapy causes irreversible failure of various organs due to the lack of blood supply and reduction of oxygen in the tissues and eventually increased mortality. The involvement of four or five organs by sepsis has been attributed to an increased risk of death to over 90%. Although antibiotics are at the first line of sepsis treatment, they do not possess enough potency to control the disease and prevent subsequent organ failure. The immunomodulatory, anti-inflammatory, anti-apoptotic, and anti-microbial properties of mesenchymal stem cells (MSCs) have been reported in various studies. Therefore, the application of MSCs has been considered a potentially promising therapeutic strategy. In preclinical studies, the administration of MSCs has been associated with reduced bacterial load and decreased levels of pro-inflammatory factors as well as the improved function of the different vital organs, including heart, kidney, liver, and lungs. The current study provides a brief review of sepsis and its pathophysiology, and then highlights recent findings in the therapeutic effects of MSCs and MSC-derived secretome in improving sepsis-induced organ dysfunction. Besides, eligible sepsis candidates for MSC-therapy and the latest clinical findings in these areas have been reviewed.

Dental follicle stem cells rescue the regenerative capacity of inflamed rat dental pulp through a paracrine pathway

Background

Pulpitis is a common dental disease characterized by sustained inflammation and impaired pulp self-repair. Mesenchymal stem cell-based minimally invasive vital pulp therapy (MSC-miVPT) is a potential treatment method, but its application is limited by the difficulty in acquiring MSCs. We recently revealed the immunomodulatory effects of rat dental follicle stem cells (rDFSCs) on acute lung injury. The present study focused on the paracrine effects of rDFSCs on the inflammation and regeneration of rat injured dental pulp to detect whether DFSCs are a potential candidate for MSC-miVPT.

Methods

Conditioned medium from rDFSCs (rDFSC-CM) was applied to lipopolysaccharide (LPS)-induced inflammatory rat dental pulp cells (rDPCs). The inflammation and regeneration of rDPCs were detected by RT-qPCR, Western blotting, immunofluorescence staining, Cell Counting Kit-8 (CCK-8) assay, flow cytometry, wound-healing assay, and Masson’s staining. The effects of rDFSC-CM on inflamed rat dental pulp were further evaluated by hematoxylin-eosin and immunohistochemical staining.

Results

rDFSC-CM downregulated the ERK1/2 and NF-κB signaling pathways, which resulted in suppression of the expression of IL-1β, IL-6, and TNF-α and promotion of the expression of IL-4 and TGF-β, and these findings lead to the attenuation of rDPC inflammation. rDFSC-CM enhanced the in vitro proliferation, migration, and odontogenic differentiation of inflammatory rDPCs and their in vivo ectopic dentinogenesis. Furthermore, rDFSC-CM inhibited inflammatory cell infiltration in rat pulpitis and triggered Runx2 expression in some of the odontoblast-like cells surrounding the injured site, and these effects were conducive to the repair of inflamed dental pulp.

Conclusions

rDFSC-CM exhibits therapeutic potential by rescuing the regeneration of the inflamed rat dental pulp through an immunomodulatory mechanism, indicating the application prospects of DFSCs in biological regenerative endodontics.

Upregulated-gene expression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) via TLRs following NF-κB and MAPKs in bovine mastitis

Mastitis is the inflammation of mammary glands which causes huge economic loss in dairy cows. Inflammation, any tissue injury and pathogens in cow udder activate Toll-like Receptors (TLRs). Staphylococcus aureus (S. aureus) is the major cause of mastitis. In mastitis, activated TLRs initiate the NF-κB/MAPKs pathways which further trigger the gene expression associated with mastitis followed by innate immune response. In this study, pathogenic-induced gene expression profile of pro-inflammatory cytokines in mammary gland tissues, was investigated in mastitis. The Hematoxylin and Eosin (H & E) results indicated severe histopathological changes in infected tissues. Western blot results suggested the over expressions of TLR2/TLR4 with NF-κB/MAPKs pathways activation in infected tissues. qRT-PCR results revealed the gene expression associated with TLR2/TLR4-mediated NF-κB/MAPKs pathways in infected tissues in comparison with non-infected. Statistical analysis of mRNA and relative protein expression levels indicated the up-regulation of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in infected tissues rather than non-infected tissues. These results suggested that the up-regulation of gene expression levels implicated the underlying regulatory pathways for proper immune function in mammary glands. In conclusion, our study might give new insights for investigation and better understanding of mammary gland pathophysiology and TLRs and NF-κB/MAPKs-mediated gene expression of pro-inflammatory cytokines.

Current status of mesenchymal stem cell therapy for immune/inflammatory lung disorders: Gleaning insights for possible use in COVID-19

The broad immunomodulatory properties of human mesenchymal stem cells (MSCs) have allowed for wide application in regenerative medicine as well as immune/inflammatory diseases, including unmatched allogeneic use. The novel coronavirus disease COVID‐19 has unleashed a pandemic in record time accompanied by an alarming mortality rate mainly due to pulmonary injury and acute respiratory distress syndrome. Because there are no effective preventive or curative therapies currently, MSC therapy (MSCT) has emerged as a possible candidate despite the lack of preclinical data of MSCs for COVID‐19. Interestingly, MSCT preclinical data specifically on immune/inflammatory disorders of the lungs were among the earliest to be reported in 2003, with the first clinical use of MSCT for graft‐vs‐host disease reported in 2004. Since these first reports, preclinical data showing beneficial effects of MSC immunomodulation have accumulated substantially, and as a consequence, over a third of MSCT clinical trials now target immune/inflammatory diseases. There is much preclinical evidence for MSCT in noninfectious—including chronic obstructive pulmonary disease, asthma, and idiopathic pulmonary fibrosis—as well as infectious bacterial immune/inflammatory lung disorders, with data generally demonstrating therapeutic effects; however, for infectious viral pulmonary conditions, the preclinical evidence is more scarce with some inconsistent outcomes. In this article, we review the mechanistic evidence for clinical use of MSCs in pulmonary immune/inflammatory disorders, and survey the ongoing clinical trials—including for COVID‐19—of MSCT for these diseases, with some perspectives and comment on MSCT for COVID‐19.

ADAM17 protects against elastase-induced emphysema by suppressing CD62L+ leukocyte infiltration in mice

Pulmonary emphysema is a major manifestation of chronic obstructive pulmonary disease and is associated with chronic pulmonary inflammation caused by cigarette smoking, with contributions from immune cells such as neutrophils, macrophages, and lymphocytes. Although matrix metalloproteinases are well known to contribute to emphysema progression, the role of a disintegrin and metalloproteinase (ADAM) family proteins, other major metalloproteinases, in disease pathogenesis is largely unknown. ADAM17 is a major sheddase that cleaves various cell surface proteins, including CD62L, an adhesion molecule that plays a critical role in promoting the migration of immune cells to the site of inflammation. In the present study, we aimed to investigate the potential role of ADAM17 and CD62L in the development of elastase-induced emphysema. Control and Adam17^flox/flox/Mx1-Cre (Adam17^ΔMx1) mice (8-10 wk old) were intratracheally injected with 5 units of porcine pancreas elastase and monitored for 35 days after injection. Lung alveolar destruction was evaluated by analyzing the mean linear intercepts of lung tissue specimens and by histopathological examination. Mean linear intercepts data indicated that the degree of elastase-induced emphysema was significantly more severe in Adam17^ΔMx1 mice. Furthermore, flow cytometry showed that CD62L⁺ neutrophil, CD62L⁺ macrophage, and CD62L⁺ B lymphocyte numbers were significantly increased in Adam17^ΔMx1 mice. Moreover, the pharmacological depletion of CD62L⁺ cells with a CD62L-neutralizing antibody ameliorated the extent of emphysema in Adam17^ΔMx1 mice. Collectively, these results suggest that ADAM17 possibly suppresses the progression of emphysema by proteolytically processing CD62L in immune cells and that ADAM17 and CD62L could be novel therapeutic targets for treating pulmonary emphysema.

Mesenchymal Stromal Cells Anno 2019: Dawn of the Therapeutic Era? Concise Review

2018 was the year of the first marketing authorization of an allogeneic stem cell therapy by the European Medicines Agency. The authorization concerns the use of allogeneic adipose tissue-derived mesenchymal stromal cells (MSCs) for treatment of complex perianal fistulas in Crohn's disease. This is a breakthrough in the field of MSC therapy. The last few years have, furthermore, seen some breakthroughs in the investigations into the mechanisms of action of MSC therapy. Although the therapeutic effects of MSCs have largely been attributed to their secretion of immunomodulatory and regenerative factors, it has now become clear that some of the effects are mediated through host phagocytic cells that clear administered MSCs and in the process adapt an immunoregulatory and regeneration supporting function. The increased interest in therapeutic use of MSCs and the ongoing elucidation of the mechanisms of action of MSCs are promising indicators that 2019 may be the dawn of the therapeutic era of MSCs and that there will be revived interest in research to more efficient, practical, and sustainable MSC-based therapies. Stem Cells Translational Medicine 2019;8:1126-1134.

Human Adipose-Derived Mesenchymal Stem Cells Modify Lung Immunity and Improve Antibacterial Defense in Pneumosepsis Caused by Klebsiella pneumoniae

Adult mesenchymal stem cells exert immunomodulatory effects that might improve the host response during sepsis. Knowledge on the effect of adipose-derived mesenchymal stem cells (ASCs) in sepsis is limited. Klebsiella (K.) pneumoniae is a common cause of gram-negative pneumonia and sepsis. This study sought to determine the effect of human ASCs on the host response during pneumosepsis in mice. Mice were infected with K. pneumoniae via the airways to induce a gradually evolving infection in the lung culminating pneumosepsis. One or 6 hours after infection, mice were infused intravenously with ASCs or vehicle, and euthanized after 16 hours or 48 hours, respectively. The effects of freshly cultured and cryopreserved ASCs were compared, the latter formulation being more clinically relevant. Intravenously administered ASCs were visualized in lung tissue by immunostaining at 1 and 3 hours, but not at 15 hours after infusion. Although early after infection, ASCs did not or only modestly influence bacterial loads, they reduced bacterial burdens in lungs and distant organs at 48 hours. ASCs reduced the lung levels of pro-inflammatory cytokines and attenuated lung pathology, but did not influence distant organ injury. ASCs strongly modified the lung transcriptome in uninfected mice and especially mice with pneumosepsis. Cryopreserved and cultured ASCs induced largely similar effects on the lung transcriptome. These data indicate that human ASCs induce profound immune modulatory effects in the lungs, resulting in reduced bacterial burdens and lung inflammation during pneumosepsis caused by a common human pathogen, suggesting that ASCs may be an adjunctive therapeutic in this condition. Stem Cells Translational Medicine 2019;8:785&796.

Obesity worsens the outcome of influenza virus infection associated with impaired type I interferon induction in mice

Increasing evidence indicates that obesity is a risk factor for increased severity of influenza virus infection. However, its precise immunological mechanism is not fully understood. To investigate this, diet-induced obese (DIO) mice were established by feeding C57BL/6 male mice a high-fat diet for 16 weeks. DIO and lean control mice were infected intranasally with 3000 pfu of influenza A virus (IAV) (PR8/H1N1). Interestingly, we found adipose tissue located along the bronchus in naïve DIO mice. In addition, the Nos2 level was significantly higher and Arg1 level was significantly lower in lung macrophages of naïve DIO mice, consistent with an M1-skewed phenotype. The survival rate and body weight of DIO mice infected with IAV were significantly lower than those of lean control mice and associated with higher viral load in the lungs of DIO mice. Histopathological analysis demonstrated higher numbers of inflammatory cells in the lungs of DIO mice after IAV infection. Levels of cytokines, including TNF-α, IL-6, IL-10, and type I IFN (IFN-α and IFN-β), in bronchoalveolar lavage fluid (BALF) were altered after IAV infection; in particular, IFN-α and IFN-β levels were significantly suppressed in the BALF of DIO mice. In vitro, bone marrow-derived macrophages were stimulated with ligands of toll-like receptor (TLR) 7/8, a pattern recognition receptor for single-stranded RNA, and levels of TNF-α, IL-6, and IL-10 were similarly altered. In addition, levels of IFN-α and IFN-β were significantly lower in culture supernatants of alveolar macrophages sorted from naïve DIO mice and infected with IAV, compared to those in macrophages sorted from lean control mice. Collectively, these results suggest that macrophages may be the main contributors to poor outcomes of influenza virus infection in obesity.

Sphingosine 1-phosphate receptor modulator ONO-4641 stimulates CD11b+Gr-1+ cell expansion and inhibits lymphocyte infiltration in the lungs to ameliorate murine pulmonary emphysema

Sphingolipids play a pivotal role in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, little is known about the precise roles of sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite, and its receptor modulation in COPD. In this study, we demonstrated that the S1P receptor modulator ONO-4641 induced the expansion of lung CD11b⁺Gr-1⁺ cells and lymphocytopenia in naive mice. ONO-4641-expanded CD11b⁺Gr-1⁺ cells showed higher arginase-1 activity, decreased T cell proliferation, and lower IFN-γ production in CD3⁺ T cells, similar to the features of myeloid-derived suppressor cells. ONO-4641 treatment decreased airspace enlargement in elastase-induced and cigarette smoke-induced emphysema models and attenuated emphysema exacerbation induced by post-elastase pneumococcal infection, which was also associated with an increased number of lung CD11b⁺Gr-1⁺ cells. Adoptive transfer of ONO-4641-expanded CD11b⁺Gr-1⁺ cells protected against elastase-induced emphysema. Lymphocytopenia observed in these models likely contributed to beneficial ONO-4641 effects. Thus, ONO-4641 attenuated murine pulmonary emphysema by expanding lung CD11b⁺Gr-1⁺ cell populations and inducing lymphocytopenia. The S1P receptor might be a promising target for strategies aimed at ameliorating pulmonary emphysema progression.