Adipose Tissue-Derived Mesenchymal Stem Cells Attenuate Pulmonary Infection Caused by Pseudomonas aeruginosa via Inhibiting Overproduction of Prostaglandin E2

Adipose-derived stem cells ameliorate radiation-induced lung injury by activating the DDAH1/ADMA/eNOS signaling pathway

Background

Ionizing radiation-induced lung injury is caused by the initial inflammatory reaction and leads to advanced fibrosis of lung tissue. Adipose-derived stem cells (ASCs) are a type of mesenchymal stem cell that can differentiate into various functional cell types with broad application prospects in the treatment of tissue damage. The purpose of this study was to explore the protective effect of ASCs against radiation-induced lung injury and to provide a novel basis for prevention and treatment of radiation-induced lung injury.

Materials and methods

Fifty mice were randomly divided into a control group (Ctrl), radiation exposure group (IR), radiation exposure plus ASC treatment group (IR + ASC), radiation exposure plus L-257 group (IR + L-257), and radiation exposure plus ASC treatment and L-257 group (IR + ASC + L-257). Mice in IR, IR + ASC, and IR + ASC + L-257 groups were exposed to a single whole-body dose of 5 Gy X-rays (160 kV/25 mA, 1.25 Gy/min). Within 2 h after irradiation, mice in IR + ASC and IR + ASC + L-257 groups were injected with 5 × 106 ASCs via the tail vein. Mice in IR + L-257 and IR + ASC + L-257 groups were intraperitoneally injected with 30 mg/kg L-257 in 0.5 mL saline.

Results

The mice in the IR group exhibited lung hemorrhage, edema, pulmonary fibrosis, and inflammatory cell infiltration, increased release of proinflammatory cytokines, elevation of oxidative stress and apoptosis, and inhibition of the dimethylarginine dimethylamino hydratase 1 (DDAH1)/ADMA/eNOS signaling pathway. ASC treatment alleviated radiation-induced oxidative stress, apoptosis, and inflammation, and restored the DDAH1/ADMA/eNOS signaling pathway. However, L-257 pretreatment offset the protective effect of ASCs against lung inflammation, oxidative stress, and apoptosis.

Conclusions

These data suggest that ASCs ameliorate radiation-induced lung injury, and the mechanism may be mediated through the DDAH1/ADMA/eNOS signaling pathway.

Combinational therapy of mesenchymal stem cell-derived extracellular vesicles and azithromycin improves clinical and histopathological recovery in CLP sepsis model

BACKGROUND

Sepsis is a syndrome that occurs following an infection and marked by severe inflammatory responses, and if not treated in time, it can lead to multi-organ failure syndrome and death. This study examines the effects of a novel combination therapy using azithromycin and mesenchymal stem cell-derived extracellular vesicles (EVs) on a cecal ligation and puncture (CLP) model of sepsis.

METHODS

Human Wharton's jelly-mesenchymal stem cells were cultured, characterized, and used to extract EVs. The CLP sepsis model was induced in mice, followed by treatments: saline, AZM, EVs, and combination therapy (A+E). Clinical sepsis scores were recorded 24 h post-treatment. Serum, peritoneal fluid, and organ tissues (kidney, liver, lung) were collected and analyzed for biochemical parameters (AST ALT, and creatinine), inflammatory markers, bacterial load, and histopathological changes.

RESULTS

The A+E combined treatment improved the clinical scores of septic mice. The administration of A+E reduced bacterial loads in the peritoneum of septic mice, contributing to effective control of infection. Inflammatory markers of neutrophils-to-lymphocytes ratio (NLR) and TNF-α serum levels were significantly lower in the combinational therapy group, indicating significant anti-inflammatory effect of this combination. Additionally, combination of AZM and EVs alleviated organ damage mainly within liver, kidneys and lungs. Based on histopathological assessments and biochemical parameters, there was diminished tissue damage as well as reduced inflammation, which is correlated with improved functions of these vital organs.

CONCLUSION

The combined use of azithromycin and EVs offers a promising therapeutic approach for sepsis by effectively controlling infection and modulating the inflammatory response.

Molybdenum Nanodots for Acute Lung Injury Therapy

Acute respiratory disease syndrome (ARDS) is a common critical disease with high morbidity and mortality rates, yet specific and effective treatments for it are currently lacking. ARDS was especially apparent and rampant during the COVID-19 pandemic. Excess reactive oxygen species (ROS) production and an uncontrolled inflammatory response play a critical role in the disease progression of ARDS. Herein, we developed molybdenum nanodots (MNDs) as a functional nanomaterial with ultrasmall size, good biocompatibility, and excellent ROS scavenging ability for the treatment of acute lung injury (ALI). MNDs, which were administered intratracheally, significantly ameliorated lung oxidative stress, inflammatory response, protein permeability, and histological severity in ALI mice without inducing any safety issues. Importantly, transcriptomics analysis indicated that MNDs protected lung tissues by inhibiting the activation of the Nod-like receptor protein 3 (NLRP3)-dependent pyroptotic pathway. This work presents a promising therapeutic agent for patients suffering from ARDS.

Human umbilical cord mesenchymal stromal cell small extracellular vesicle transfer of microRNA-223-3p to lung epithelial cells attenuates inflammation in acute lung injury in mice

BACKGROUND

Acute lung injury (ALI), manifested as strong pulmonary inflammation and alveolar epithelial damage, is a life-threatening disease with high morbidity and mortality. Small extracellular vesicles (sEVs), secreted by multiple types of cells, are critical cellular communication mediators and can inhibit inflammation by transferring bioactive molecules, such as microRNAs (miRNAs). Thus, we hypothesized that sEVs derived from mesenchymal stromal cells (MSC sEVs) could transfer miRNAs to attenuate inflammation of lung epithelial cells during ALI.

METHODS

C57BL/6 male mice were intratracheally administered LPS (10 mg/kg). Six hours later, the mice were randomly administered with MSC sEVs (40 µg per mouse in 150 µl of saline), which were collected by ultracentrifugation. Control group received saline administration. After 48 h, the mice were sacrificed to evaluate pulmonary microvascular permeability and inflammatory responses. In vitro, A549 cells and primary human small airway epithelial cells (SAECs) were stimulated with LPS with or without MSC sEVs treatment.

RESULTS

In vitro, MSC sEVs could also inhibit the inflammation induced by LPS in A549 cells and SAECs (reducing TNF-α, IL-1β, IL-6 and MCP-1). Moreover, MSC sEV treatment improved the survival rate, alleviated pulmonary microvascular permeability, and inhibited proinflammatory responses (reducing TNF-α, IL-1β, IL-6 and JE-1) in ALI mice. Notably, miR-223-3p was found to be served as a critical mediator in MSC sEV-induced regulatory effects through inhibition of poly (adenosine diphosphate-ribose) polymerase-1 (PARP-1) in lung epithelial cells.

CONCLUSIONS

Overall, these findings suggest that MSC sEVs may offer a novel promising strategy for ALI.

Can mesenchymal stem/stromal cells and their secretomes combat bacterial persisters?

The increasing number of life-threatening infections caused by persister bacteria is associated with various issues, including antimicrobial resistance and biofilm formation. Infections due to persister cells are often difficult to suppress without the use of last-resort antibiotics. Throughout the world, bacterial persistence and resistance create an unmet clinical demand for the exploration of newly introduced therapeutic approaches. Mesenchymal stem / stromal cells (MSCs) have an antimicrobial activity to protect against bacterial infections, including those caused by bacterial persisters. MSCs have substantial potential to secrete antimicrobial peptides (AMPs), including cathelicidin, beta-defensins, lipocalin-2, hepcidin, indoleamine 2,3-dioxygenase (IDO), cysteine proteases, and inducible nitric oxide synthases (iNOS). MSCs possess the potential to contribute to innate immunity by regulating the immune response. Recently, MSCs and their secreted components have been reported to improve antimicrobial activity. Bactericidal activity by MSCs and their secretomes has been shown to be mediated in part by the secretion of AMPs. Even though they were discovered more than 80 years ago, therapeutic options for persisters are restricted, and there is an urgent need for alternative treatment regimens. Hence, this review intends to critically assess the current literature on the effects of MSCs and their secretomes on persister bacteria. MSCs and their secretome-based therapies could be preferred as an up-and-coming approach to reinforce the antimicrobial efficiency in persister infections.

Mesenchymal stem cells in lung diseases and their potential use in COVID-19 ARDS: A systematized review

COVID-19 can converge with the pro-inflammatory immunoregulatory mechanisms of chronic lung diseases. Given the disorders inherent to lung transplantation and the inexistence of other definitive therapeutic alternatives, Adipose tissue-derived Stem Cells (ASCs) presented themselves as a therapeutic hope. The purpose of this review is to assess the basis for the potential use of ASCs in lung diseases unresponsive to conventional therapy, relating to their possible use in COVID-19 ARDS. 35 studies comprised this review, 14 being narrative reviews, 19 preclinical trials and two proofs of concept. COVID-19 can converge with the pro-inflammatory immunoregulatory mechanisms of chronic lung diseases. In view of the disorders inherent to lung transplantation and the inexistence of definitive therapeutic alternatives, Adipose tissue-derived Stem Cells (ASCs) presented themselves as a therapeutic hope. Its detailed reading indicated the absence of serious adverse effects and toxicity to the administration of ASCs and suggested possible effectiveness in reducing lung damage, in addition to promoting the recovery of leukocytes and lymphocytes with its immunomodulatory and anti-apoptotic effects. The revised clinical data suggests optimism in the applicability of ASCs in other immunoinflammatory diseases and in severe COVID-19 ARDS. However, further studies are needed to develop a consensus on the methods of collection of ASCs, the ideal dosage schedule, the most effective time and route of administration, as well as on the definition of indications for the administration of ASCs in cases of COVID-19 for conducting clinical trials in near future.

Clinical progress in MSC-based therapies for the management of severe COVID-19

Considering the high impact that severe Coronavirus disease 2019 (COVID-19) cases still pose on public health and their complex pharmacological management, the search for new therapeutic alternatives is essential. Mesenchymal stromal cells (MSCs) could be promising candidates as they present important immunomodulatory and anti-inflammatory properties that can combat the acute severe respiratory distress syndrome (ARDS) and the cytokine storm occurring in COVID-19, two processes that are mainly driven by an immunological misbalance. In this review, we provide a comprehensive overview of the intricate inflammatory process derived from the immune dysregulation that occurs in COVID-19, discussing the potential that the cytokines and growth factors that constitute the MSC-derived secretome present to treat the disease. Moreover, we revise the latest clinical progress made in the field, discussing the most important findings of the clinical trials conducted to date, which follow 2 different approaches: MSC-based cell therapy or the administration of the secretome by itself, as a cell-free therapy.

Mesenchymal stem cell-based therapy as a new therapeutic approach for acute inflammation

Acute inflammatory diseases such as acute colitis, kidney injury, liver failure, lung injury, myocardial infarction, pancreatitis, septic shock, and spinal cord injury are significant causes of death worldwide. Despite advances in the understanding of its pathophysiology, there are many restrictions in the treatment of these diseases, and new therapeutic approaches are required. Mesenchymal stem cell-based therapy due to immunomodulatory and regenerative properties is a promising candidate for acute inflammatory disease management. Based on preclinical results, mesenchymal stem cells and their-derived secretome improved immunological and clinical parameters. Furthermore, many clinical trials of acute kidney, liver, lung, myocardial, and spinal cord injury have yielded promising results. In this review, we try to provide a comprehensive view of mesenchymal stem cell-based therapy in acute inflammatory diseases as a new treatment approach.

Time-resolved proteome and transcriptome of paraquat-induced pulmonary fibrosis

BACKGROUNDS

Pulmonary fibrosis (PF) is a pathological state presenting at the progressive stage of heterogeneous interstitial lung disease (ILD). The current understanding of the molecular mechanisms involved is incomplete. This clinical toxicology study focused on the pulmonary fibrosis induced by paraquat (PQ), a widely-used herbicide. Using proteo-transcriptome analysis, we identified differentially expressed proteins (DEPs) derived from the initial development of fibrosis to the dissolved stage and provided further functional analysis.

METHODS

We established a mouse model of progressive lung fibrosis via intratracheal instillation of paraquat. To acquire a comprehensive and unbiased understanding of the onset of pulmonary fibrosis, we performed time-series proteomics profiling (iTRAQ) and RNA sequencing (RNA-Seq) on lung samples from paraquat-treated mice and saline control. The biological functions and pathways involved were evaluated through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analysis. Correlation tests were conducted on comparable groups 7 days and 28 days post-exposure. Differentially expressed proteins and genes following the same trend on the protein and mRNA levels were selected for validation. The functions of the selected molecules were identified in vitro. The protein level was overexpressed by transfecting gene-containing plasmid or suppressed by transfecting specific siRNA in A549 cells. The levels of endothlial-mesenchymal transition (EMT) markers, including E-cadherin, vimentin, FN1, and α-SMA, were determined via western blot to evaluate the fibrotic process.

RESULTS

We quantified 1358 DEPs on day 7 and 426 DEPs on day 28 post exposure (Fold change >1.2; Q value < 0.05). The top 5 pathways - drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, complement and coagulation cascades, chemical carcinogenesis, protein digestion and absorption - were involved on both day 7 and day 28. Several pathways, including tight junction, focal adhesion, platelet activation, and ECM-receptor interaction, were more enriched on day 28 than on day 7. Integrative analysis of the proteome and transcriptome revealed a moderate correlation of quantitative protein abundance ratios with RNA abundance ratios (Spearman R = 0.3950 and 0.2477 on days 7 and 28, respectively), indicating that post-transcriptional regulation plays an important role in lung injury and repair. Western blot identified that the protein expressions of FN1, S100A4, and RBM3 were significantly upregulated while that of CYP1A1, FMO3, and PGDH were significantly downregulated on day 7. All proteins generally recovered to baseline on day 28. qPCR showed the mRNA levels of Fn1, S100a4, Rbm3, Cyp1a1, Fmo3, and Hpgd changed following the same trend as the levels of their respective proteins. Further, in vitro experiments showed that RBM3 was upregulated while PGDH was downregulated in an EMT model established in human lung epithelial A549 cells. RBM3 overexpression and PGDH knockout could both induce EMT in A549 cells. RBM3 knockout or PGDH overexpression had no reverse effect on EMT in A549 cells.

CONCLUSIONS

Our proteo-transcriptomic study determined the proteins responsible for fibrogenesis and uncovers their dynamic regulation from lung injury to repair, providing new insights for the development of biomarkers for diagnosis and treatment of fibrotic diseases.

15-Hydroxyprostaglandin Dehydrogenase Is a Predictor of Stroke-Associated Pneumonia

Background and Purpose

Stroke is a serious fatal and disabling disease. Stroke-associated pneumonia (SAP) is the most common complication of stroke, which may further aggravate the stroke. The prevention and early prediction of SAP is a key clinical strategy. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is involved in pneumonia, while its relationship with SAP has yet to be determined. Therefore, we investigated the predictive value of 15-PGDH for SAP and visualized their relationship.

Methods

Stroke patients were recruited and divided into SAP group and Non-SAP group. Baseline demographic and clinical data were obtained from the medical record system, blood samples were collected to detect relevant variables and 15-PGDH levels. Patient characteristics were compared with a t-test. Binary logistic regression analysis was performed to determine the predictive value of 15-PGDH for SAP. Restricted cubic splines (RCS) were performed to visualize the relationship between 15-PGDH and SAP risk. Finally, the SAP patient characteristics between the severe group and mild group were compared.

Results

50 patients were enrolled and divided into SAP group (n = 26) and Non-SAP group (n = 24). 15-PGDH in the SAP group was lower than that in the Non-SAP group (0.258 ± 0.275 vs. 0.784 ± 0.615, p = 0.025). Binary logistic regression analysis revealed that the lower 15-PGDH, the higher the risk of SAP (OR = 0.04, 95%CI, 0.010–0.157, p < 0.001). The RCS model showed the L-shaped relationship between 15-PGDH and SAP.

Conclusions

In stroke patients, serum 15-PGDH is a valuable biomarker for predicting SAP. There is an L-shaped relationship between the level of 15-PGDH and the risk of SAP.

Safety and efficacy study of allogeneic human menstrual blood stromal cells secretome to treat severe COVID-19 patients: clinical trial phase I & II

BACKGROUND

Cell-free Mesenchymal stromal cells (MSCs) have been considered due to their capacity to modulate the immune system and suppress cytokine storms caused by SARS-CoV-2. This prospective randomized double-blind placebo-controlled clinical trial aimed to assess the safety and efficacy of secretome derived from allogeneic menstrual blood stromal cells (MenSCs) as a treatment in patients with severe COVID-19.

METHODS

Patients with severe COVID-19 were randomized (1:1) to either MenSC-derived secretome treatment or the control group. Subjects received five intravenous infusions of 5 mL secretome or the same volume of placebo for five days and were monitored for safety and efficacy for 28 days after treatment. Adverse events, laboratory parameters, duration of hospitalization, clinical symptom improvement, dynamic of O₂ saturation, lymphocyte number, and serial chest imaging were analyzed.

RESULTS

All safety endpoints were observed without adverse events after 72 h of secretome injection. Within 28 days after enrollment, 7 patients (50%) were intubated in the treated group versus 12 patients (80%) in the control group. Overall, 64% of patients had improved oxygen levels within 5 days of starting treatment (P < 0.0001) and there was a survival rate of 57% in the treatment group compared to 28% in the control group was (P < 0.0001). Laboratory values revealed that significant acute phase reactants declined, with mean C-reactive protein, ferritin, and D-dimer reduction of 77% (P < 0.001), 43% (P < 0.001), and 42% (P < 0.05), respectively. Significant improvement in lymphopenia was associated with an increase in mean CD4⁺ and CD8⁺ lymphocyte counts of 20% (P = 0.06) and 15% (P < 0.05), respectively. Following treatment, percentage of pulmonary involvement showed a significant improvement in the secretome group (P < 0.0001). This improvement differed significantly between survivors and those who were dying (P < 0.005).

CONCLUSIONS

For the first time, this study demonstrated that in hospitalized patients with severe COVID-19, therapy with MenSCs-derived secretome leads to reversal of hypoxia, immune reconstitution, and downregulation of cytokine storm, with no adverse effects attributable to the treatment. Given these outcomes, it may be possible to use this type of treatment for serious inflammatory lung disease with a mechanism similar to COVID-19 in the future. However, it is necessary to evaluate the safety and efficacy of MenSCs-derived secretome therapy in clinical trials on a larger population of patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05019287. Registered 24AGUEST 2021, retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT05019287 . IRCT, IRCT20180619040147N6. Registered 04/01/2021.

Gut microbiota is involved in the antidepressant effects of adipose-derived mesenchymal stem cells in chronic social defeat stress mouse model

RATIONALE

Growing evidence supports the role of microbiota in regulating gut-brain interactions and, thus, contributing to the pathogenesis of depression and the antidepressant actions. Adipose-derived mesenchymal stem cells (ADSCs), as important members of the stem cell family, were demonstrated to alleviate depression behaviors. However, the role of gut microbiota in ADSCs alleviating depression in chronic social defeat stress (CSDS) model is unknown.

OBJECTIVES

To examine the effects of ADSCs on depression symptoms and detect the changes in the composition of gut microbiota.

RESULTS

We found that ADSCs administration significantly ameliorated CSDS-induced depression behaviors, which was accompanied by alteration in the gut microbiota. The principal co-ordinates analysis (PCoA) results showed that there was a significant difference between the gut microbiota among the groups. Remarkably, receiver operating characteristic (ROC) curves revealed that order Micrococcales, order Rhizobiales and species Bacteroides acidifaciens are potentially important biomarkers for the antidepressant effects of ADSCs in CSDS model.

CONCLUSIONS

ADSCs are effective in treating depression behaviors in CSDS model, which might be partly due to the regulation of abnormal composition of gut microbiota. Thus, ADSCs offer a promising therapeutic strategy for treating depression in patients.

The critical role of mesenchymal stromal/stem cell therapy in COVID-19 patients: An updated review

New coronavirus disease 2019 (COVID-19), as a pandemic disaster, has drawn the attention of researchers in various fields to discover suitable therapeutic approaches for the management of COVID-19 patients. Currently, there are many worries about the rapid spread of COVID-19; there is no approved treatment for this infectious disease, despite many efforts to develop therapeutic procedures for COVID-19. Emerging evidence shows that mesenchymal stromal/stem cell (MSC) therapy can be a suitable option for the management of COVID-19. These cells have many biological features (including the potential of differentiation, high safety and effectiveness, secretion of trophic factors and immunoregulatory features) that make them suitable for the treatment of various diseases. However, some studies have questioned the positive role of MSC therapy in the treatment of COVID-19. Accordingly, in this paper, we will focus on the therapeutic impacts of MSCs and their critical role in cytokine storm of COVID-19 patients.

CD69 mediates the protective role of adipose tissue-derived mesenchymal stem cells against Pseudomonas aeruginosa pulmonary infection

BACKGROUND

Our previous study shows that Adipose tissue-derived mesenchymal stem cells (ASCs) are a promising strategy for cell-based therapy against pulmonary infection with Pseudomonas aeruginosa (P. aeruginosa), but the underlying mechanisms remain unclear.

METHODS

cDNA microarray assay was performed to explore the transcriptome of ASCs primed by P. aeruginosa. Small interfering RNA (siRNA) was constructed to select the receptor candidates for P. aeruginosa recognition and granulocyte-macrophage colony-stimulating factor (GM-CSF) production in ASCs. The soluble protein chimeras containing the extracellular domain of human CD69 fused to the Fc region of human immunoglobulin IgG1 were used as a probe to validate the recognition of P. aeruginosa. The association between CD69 and extracellular regulated protein kinases 1/2 (ERK1/2) was explored via co-immunoprecipitation, siRNA, and inhibitor. The murine models of P. aeruginosa pneumonia treated with WT-ASCs, GM-CSF-/- -ASCs Cd69-/- -ASCs or Erk1-/- -ASCs were used to determine the role of GM-CSF, CD69, and ERK1 in ASCs against P. aeruginosa infection.

RESULTS

We showed that C-type lectin receptor CD69 mediated the protective effects of ASCs partly through GM-CSF. CD69 could specifically recognize P. aeruginosa and regulate GM-CSF secretion of ASCs. CD69 regulated the production of GM-CSF via ERK1 in ASCs after P. aeruginosa infection. Moreover, the Administration of ASCs with deficiency of CD69 or ERK1 completely blocked its protective effects in a murine model of P. aeruginosa pneumonia.

CONCLUSIONS

CD69 recognizes P. aeruginosa and further facilitates ERK1 activation, which plays a crucial role in ASCs-based therapy against P. aeruginosa pneumonia. CD69 may be a novel target molecule to improve ASCs-based therapy against P. aeruginosa infection.

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: an Antimicrobial and Host-Directed Therapy for Complex Infectious Diseases

There is an urgent need for new antimicrobial strategies for treating complex infections and emerging pathogens. Human mesenchymal stromal cells (MSCs) are adult multipotent cells with antimicrobial properties, mediated through direct bactericidal activity and modulation of host innate and adaptive immune cells. More than 30 in vivo studies have reported on the use of human MSCs for the treatment of infectious diseases, with many more studies of animal MSCs in same-species models of infection. MSCs demonstrate potent antimicrobial effects against the major classes of human pathogens (bacteria, viruses, fungi, and parasites) across a wide range of infection models. Mechanistic studies have yielded important insight into their immunomodulatory and bactericidal activity, which can be enhanced through various forms of preconditioning. MSCs are being investigated in over 80 clinical trials for difficult-to-treat infectious diseases, including sepsis and pulmonary, intra-abdominal, cutaneous, and viral infections. Completed trials consistently report MSCs to be safe and well tolerated, with signals of efficacy against some infectious diseases. Although significant obstacles must be overcome to produce a standardized, affordable, clinical-grade cell therapy, these studies suggest that MSCs may have particular potential as an adjunct therapy in complex or resistant infections.

Adipose-Derived Stem Cells in the Treatment of Perianal Fistulas in Crohn's Disease: Rationale, Clinical Results and Perspectives

Between 20 to 25% of Crohn’s disease (CD) patients suffer from perianal fistulas, a marker of disease severity. Seton drainage combined with anti-TNFα can result in closure of the fistula in 70 to 75% of patients. For the remaining 25% of patients there is room for in situ injection of autologous or allogenic mesenchymal stem cells such as adipose-derived stem/stromal cells (ADSCs). ADSCs exert their effects on tissues and effector cells through paracrine phenomena, including the secretome and extracellular vesicles. They display anti-inflammatory, anti-apoptotic, pro-angiogenic, proliferative, and immunomodulatory properties, and a homing within the damaged tissue. They also have immuno-evasive properties allowing a clinical allogeneic approach. Numerous clinical trials have been conducted that demonstrate a complete cure rate of anoperineal fistulas in CD ranging from 46 to 90% of cases after in situ injection of autologous or allogenic ADSCs. A pivotal phase III-controlled trial using allogenic ADSCs (Alofisel^®) demonstrated that prolonged clinical and radiological remission can be obtained in nearly 60% of cases with a good safety profile. Future studies should be conducted for a better knowledge of the local effect of ADSCs as well as for a standardization in terms of the number of injections and associated procedures.

Preclinical efficacy and clinical safety of clinical-grade nebulized allogenic adipose mesenchymal stromal cells-derived extracellular vesicles

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) turn out to be a promising source of cell-free therapy. Here, we investigated the biodistribution and effect of nebulized human adipose-derived MSC-EVs (haMSC-EVs) in the preclinical lung injury model and explored the safety of nebulized haMSC-EVs in healthy volunteers. DiR-labelled haMSC-EVs were used to explore the distribution of nebulized haMSC-EVs in the murine model. Pseudomonas aeruginosa-induced murine lung injury model was established, and survival rate, as well as WBC counts, histology, IL-6, TNF-α and IL-10 levels in bronchoalveolar lavage fluid (BALF) were measured to explore the optimal therapeutic dose of haMSC-EVs through the nebulized route. Twenty-four healthy volunteers were involved and received the haMSC-EVs once, ranging from 2 × 108 particles to 16 × 108 particles (MEXVT study, NCT04313647). Nebulizing haMSC-EVs improved survival rate to 80% at 96 h in P. aeruginosa-induced murine lung injury model by decreasing lung inflammation and histological severity. All volunteers tolerated the haMSC-EVs nebulization well, and no serious adverse events were observed from starting nebulization to the 7th day after nebulization. These findings suggest that nebulized haMSC-EVs could be a promising therapeutic strategy, offering preliminary evidence to promote the future clinical applications of nebulized haMSC-EVs in lung injury diseases.

Human mesenchymal stromal cells small extracellular vesicles attenuate sepsis-induced acute lung injury in a mouse model: the role of oxidative stress and the mitogen-activated protein kinase/nuclear factor kappa B pathway

BACKGROUND AIMS

Acute lung injury (ALI) secondary to sepsis is a complex disease associated with high morbidity and mortality. Mesenchymal stem cells (MSCs) and their conditioned medium have been demonstrated to reduce alveolar inflammation, improve lung endothelial barrier permeability and modulate oxidative stress in vivo and in vitro. Recently, MSCs have been found to release small extracellular vesicles (sEVs) that can deliver functionally active biomolecules into recipient cells. The authors' study was designed to determine whether sEVs released by MSCs would be effective in sepsis-induced ALI mice and to identify the potential mechanisms.

METHODS

A total of 6 h after cercal ligation and puncture, the mice received saline, sEV-depleted conditioned medium (sEVD-CM) or MSC sEVs via the tail vein.

RESULTS

The administration of MSC sEVs improved pulmonary microvascular permeability and inhibited both histopathological changes and the infiltration of polymorphonuclear neutrophils into lung tissues. In addition, the activities of antioxidant enzymes were significantly increased in the group treated with sEVs compared with the saline and sEVD-CM groups, whereas lipid peroxidation was significantly decreased. Furthermore, sEVs were found to possibly inhibit phosphorylation of the mitogen-activated protein kinase/nuclear factor kappa B (MAPK/NF-κB) pathway and degradation of IκB but increase the activities of nuclear factor erythroid 2-related factor 2 and heme oxygenase 1.

CONCLUSIONS

These findings suggest that one of the effective therapeutic mechanisms of sEVs against sepsis-induced ALI may be associated with upregulation of anti-oxidative enzymes and inhibition of MAPK/NF-κB activation.

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.

Adipose-Derived Mesenchymal Stem Cells Ameliorating Pseudomonas aeruginosa-induced Acute Lung Infection via Inhibition of NLRC4 Inflammasome

Background

Pseudomonas aeruginosa (PA) is one of the most common Gram-negative bacteria causing hospital-acquired pulmonary infection, with high drug resistance and mortality. Therefore, it is urgent to introduce new non-antibiotic treatment strategies. Mesenchymal stem cells (MSCs), as important members of the stem cell family, were demonstrated to alleviate pathological damage in acute lung injury. However, the potential mechanism how MSC alleviate acute lung infection caused by PA remains unclear.

Objective

The purpose of this study was to investigate the effects of Adipose-derived mesenchymal stem cells (ASCs) on acute pulmonary infections and the possible mechanisms how ASCs reduce pulmonary inflammation induced by PA.

Methods

The therapeutic and mechanistic effects of ASCs on PA pulmonary infection were evaluated respectively in a murine model as well as in an in vitro model stimulated by PA and co-cultured with ASCs.

Results

1. ASCs treatment significantly reduced the bacterial load, inflammation of lung tissue and histopathological damage by PA. 2. PA infection mainly activated Nod-like receptor containing a caspase activating and recruitment domain 4 (NLRC4) inflammasome in the lung of mice. ASCs attenuated acute lung infection in mice by inhibiting NLRC4 inflammasome activation. 3. NLRC4^-/- mice showed a significant improvement in survival rate and lung bacterial load after PA infection. 4. ASCs mainly increased expression and secretion of STC-1 in response to PA-stimulated NLRC4 inflammasome activation.

Conclusions

PA infection attenuated macrophage phagocytosis through activation of NLRC4 inflammasome in macrophages, which eventually led to pulmonary inflammatory damage in mouse; ASCs reduced the activation of NLRC4 inflammasome in macrophages induced by PA infection, thereby increasing the phagocytic ability of macrophages, and ultimately improving lung tissue damage in mouse; ASCs may inhibit NLRC4 inflammasome through the secretion of STC-1.

Role of miR-466 in mesenchymal stromal cell derived extracellular vesicles treating inoculation pneumonia caused by multidrug-resistant Pseudomonas aeruginosa

RATIONALE

The effects of mesenchymal stromal cells (MSCs) and MSC-derived extracellular vesicles (MSC EVs) on multidrug-resistant pseudomonas aeruginosa (MDR-PA)-induced pneumonia remain unclear.

MATERIALS AND METHODS

MicroRNA array and RT-PCR were used to select the major microRNA in MSC EVs. Human peripheral blood monocytes were obtained and isolated from qualified patients. The crosstalk between MSCs/MSC EVs and macrophages in vitro was studied. MDR-PA pneumonia models were further established in C57BL/6 mice and MSC EVs or miR-466 overexpressing MSC EVs were intratracheally instilled.

RESULTS

MiR-466 was highly expressed in MSC EVs. MSCs and miR-466 promoted macrophage polarization toward Type 2 phenotype through TIRAP-MyD88-NFκB axis. Moreover, cocultured macrophages with miR-466 overexpressing MSCs significantly increased the phagocytosis of macrophages. MSC EVs significantly reduced mortality and decreased influx of BALF neutrophils, proinflammatory factor levels, protein, and bacterial load in murine MDR-PA pneumonia. Administration of miR-466 overexpressing MSC EVs further alleviated the inflammatory severity.

CONCLUSIONS

MSC-derived EVs containing high levels of miR-466 may partly participate in host immune responses to MDR-PA. Both MSCs and MSC EVs have therapeutic effects in treating MDR-PA-induced pneumonia.

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.

The Immunomodulatory Effects of Mesenchymal Stem Cells on Regulatory B Cells

The therapeutic potential of mesenchymal stem cells (MSCs) has been investigated in many preclinical and clinical studies. This potential is dominantly based on the immunosuppressive properties of MSCs. Although the therapeutic profiles of MSC transplantation are still not fully characterized, accumulating evidence has revealed that B cells change after MSC infusion, in particular inducing regulatory B cells (Bregs). The immunosuppressive effects of Bregs have been demonstrated, and these cells are being evaluated as new targets for the treatment of inflammatory diseases. MSCs are capable of educating B cells and inducing regulatory B cell production via cell-to-cell contact, soluble factors, and extracellular vesicles (EVs). These cells thus have the potential to complement each other's immunomodulatory functions, and a combined approach may enable synergistic effects for the treatment of immunological diseases. However, compared with investigations regarding other immune cells, investigations into how MSCs specifically regulate Bregs have been superficial and insufficient. In this review, we discuss the current findings related to the immunomodulatory effects of MSCs on regulatory B cells and provide optimal strategies for applications in immune-related disease treatments.

The Coronavirus Pandemic (SARS-CoV-2): New Problems Demand New Solutions, the Alternative of Mesenchymal (Stem) Stromal Cells

Mesenchymal (stem) stromal cells (MSC) can be a therapeutic alternative for COVID-19 considering their anti-inflammatory, regenerative, angiogenic, and even antimicrobial capacity. Preliminary data point to therapeutic interest of MSC for patients with COVID-19, and their effect seems based on the MSC's ability to curb the cytokine storm caused by COVID-19. In fact, promising clinical studies using MSC to treat COVID-19, are currently underway. For this reason, now is the time to firmly consider new approaches to MSC research that addresses key issues, like selecting the most optimal type of MSC for each indication, assuming the heterogeneity of the donor-dependent MSC and the biological niche where MSC are located.

Induction of ASC pyroptosis requires gasdermin D or caspase-1/11-dependent mediators and IFNβ from pyroptotic macrophages

Mesenchymal stem cells (MSCs) have been used in cell-based therapies for a variety of disorders. Some factors such as inflammatory mediators in the diseased area might damage the survival of MSCs and affect their efficacy. Pyroptosis is a form of programmed necrosis as a response for immune cells to cytosolic pathogenic stimuli. Whether MSCs develop pyroptosis under pathological stimulation, its underlying mechanism and biological significance are still unclear. Here, we found that LPS, flagellin, dsDNA, nigericin (NIG), or LPS combined with nigericin (LPS/NIG) could not induce pyroptosis in adipose-tissue-derived mesenchymal stem cells (ASCs). However, when applied the culture media collected from LPS/NIG-induced pyroptotic bone marrow-derived macrophages (BMDMs) to incubate ASCs, ASCs developed pyroptosis. Inhibition of caspases or deletion of Caspase-1/11 in ASCs did not affect the pyroptotic macrophage media-triggered ASC pyroptosis while ablation of Caspase-1/11 abolished BMDM pyroptosis induced by LPS/NIG. Media collected from LPS/NIG stimulated Gsdmd^−/− or Caspase-1/11^−/− BMDMs could not induce pyroptosis of ASCs. In addition, RNA-seq analysis showed that interferon (IFN)-stimulated genes were upregulated in pyroptotic ASCs. Adding IFNβ could boost LPS/NIG stimulated BMDM media-induced ASC pyroptosis. Surprisingly, the pyroptotic ASCs had a lower bactericidal ability to P. Aeruginosa. Taken together, induction of ASC pyroptosis requires gasdermin D or caspase-1/11-dependent mediators and IFNβ from pyroptotic macrophages.

Rationale for the clinical use of adipose-derived mesenchymal stem cells for COVID-19 patients

In late 2019, a novel coronavirus (SARS-CoV-2) emerged in Wuhan, capital city of Hubei province in China. Cases of SARS-CoV-2 infection quickly grew by several thousand per day. Less than 100 days later, the World Health Organization declared that the rapidly spreading viral outbreak had become a global pandemic. Coronavirus disease 2019 (COVID-19) is typically associated with fever and respiratory symptoms. It often progresses to severe respiratory distress and multi-organ failure which carry a high mortality rate. Older patients or those with medical comorbidities are at greater risk for severe disease. Inflammation, pulmonary edema and an over-reactive immune response can lead to hypoxia, respiratory distress and lung damage. Mesenchymal stromal/stem cells (MSCs) possess potent and broad-ranging immunomodulatory activities. Multiple in vivo studies in animal models and ex vivo human lung models have demonstrated the MSC's impressive capacity to inhibit lung damage, reduce inflammation, dampen immune responses and aid with alveolar fluid clearance. Additionally, MSCs produce molecules that are antimicrobial and reduce pain. Upon administration by the intravenous route, the cells travel directly to the lungs where the majority are sequestered, a great benefit for the treatment of pulmonary disease. The in vivo safety of local and intravenous administration of MSCs has been demonstrated in multiple human clinical trials, including studies of acute respiratory distress syndrome (ARDS). Recently, the application of MSCs in the context of ongoing COVID-19 disease and other viral respiratory illnesses has demonstrated reduced patient mortality and, in some cases, improved long-term pulmonary function. Adipose-derived stem cells (ASC), an abundant type of MSC, are proposed as a therapeutic option for the treatment of COVID-19 in order to reduce morbidity and mortality. Additionally, when proven to be safe and effective, ASC treatments may reduce the demand on critical hospital resources. The ongoing COVID-19 outbreak has resulted in significant healthcare and socioeconomic burdens across the globe. There is a desperate need for safe and effective treatments. Cellular based therapies hold great promise for the treatment of COVID-19. This literature summary reviews the scientific rationale and need for clinical studies of adipose-derived stem cells and other types of mesenchymal stem cells in the treatment of patients who suffer with COVID-19.

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.

Gestational diabetes impacts fetal precursor cell responses with potential consequences for offspring

Fetal programming has been proposed as a key mechanism underlying the association between intrauterine exposure to maternal diabetes and negative health outcomes in offspring. To determine whether gestational diabetes mellitus (GDM) might leave an imprint in fetal precursors of the amniotic membrane and whether it might be related to adverse outcomes in offspring, a prospective case‐control study was conducted, in which amniotic mesenchymal stem cells (AMSCs) and resident macrophages were isolated from pregnant patients, with either GDM or normal glucose tolerance, scheduled for cesarean section. After characterization, functional characteristics of AMSCs were analyzed and correlated with anthropometrical and clinical variables from both mother and offspring. GDM‐derived AMSCs displayed an impaired proliferation and osteogenic potential when compared with control cells, accompanied by superior invasive and chemotactic capacity. The expression of genes involved in the inflammatory response (TNFα, MCP‐1, CD40, and CTSS) was upregulated in GDM‐derived AMSCs, whereas anti‐inflammatory IL‐33 was downregulated. Macrophages isolated from the amniotic membrane of GDM mothers consistently showed higher expression of MCP‐1 as well. In vitro studies in which AMSCs from healthy control women were exposed to hyperglycemia, hyperinsulinemia, and palmitic acid confirmed these results. Finally, genes involved in the inflammatory response were associated with maternal insulin sensitivity and prepregnancy body mass index, as well as with fetal metabolic parameters. These results suggest that the GDM environment could program stem cells and subsequently favor metabolic dysfunction later in life. Fetal adaptive programming in the setting of GDM might have a direct negative impact on insulin resistance of offspring.

The effect of human adipose-derived stem cells on lipopolysaccharide-induced acute respiratory distress syndrome in mice

Background

Acute respiratory distress syndrome (ARDS) is a type of acute respiratory failure in critically ill patients. Recently, several treatment modalities have been proposed for ARDS, but it still has a high mortality rate. In general, the role of mesenchymal stem cells (MSCs) in controlling inflammatory responses has been studied in various immune-associated diseases in humans and animals. However, only a few studies reported adipose-derived stem cells (ASCs), which are easier to isolate, are currently emerging as an attractive treatment option in ARDS. Therefore, in this study, we investigated the therapeutic effects of human ASCs and the regulation of inflammatory responses in an ARDS mouse model.

Methods

In the ARDS model, lipopolysaccharide (LPS) (5 mg/kg) was administered via the intra tracheal injection method. The mice were divided into the following four groups: (I) saline + medium; (II) saline + ASCs (2×10⁵); (III) LPS + medium; (IV) LPS + ASCs. The ARDS observation time was divided into short and long term. LPS administration increased the concentration of proinflammatory cytokines, which was a consistent systemic inflammatory response.

Results

LPS/ASC group showed less neutrophil infiltration and less alveolar hemorrhage or congestion than did the LPS group. The lung injury scores of the LPS/ASC group were lower than those of the LPS group (3.8±0.9 vs. 6.8±1.1; P=0.03) at day 2. Compared to the LPS group, LPS/ASC group showed reduced collagen deposition around the vessels and fibrosis accompanied by alveolar septal or interstitial thickening and lower MPO levels than did the LPS group (453.2±26.2 vs. 670.2±65.9 pg/mL; P<0.01) at day 7.

Conclusions

ASC therapy can inhibit neutrophil recruitment, which shows trend of reducing short term lung injury (day 2) and affecting fibrosis in long term (day 7). Further studies are warranted to understand the mechanism and improve the therapeutic effect of ASCs.

Inoculation Pneumonia Caused by Coagulase Negative Staphylococcus

Rationale

Although frequently retrieved in tracheal secretions of critically ill patients on mechanical ventilation, the existence of pneumonia caused by coagulase-negative staphylococci (CoNS) remains controversial.

Objective

To assess whether Staphylococcus haemolyticus (S. haemolyticus) inoculated in mice’s trachea can infect normal lung parenchyma, increasing concentrations of S. haemolyticus were intratracheally administered in 221 immunocompetent mice.

Methods

Each animal received intratracheally phosphate-buffered saline (PBS) (n = 43) or live (n = 141) or inactivated (n = 37) S. haemolyticus at increasing load: 1.0 × 10⁶, 1.0 × 10⁷, and 1.0 × 10⁸ colony forming units (CFU). Forty-three animals were sacrificed at 12 h and 178 were sacrificed at 36 h; 64 served for post-mortem lung histology, 157 served for pre-mortem bronchoalveolar lavage (BAL) analysis, and 42 served for post-mortem quantitative bacteriology of lung tissue. The distribution of biofilm-associated genes was investigated in the S. haemolyticus strain used in our in vivo experiment as well as among 19 other clinical S. haemolyticus strains collected from hospitals or nursing houses.

Measurements and Main Results

Intratracheal inoculation of 1.0 × 10⁸ CFU live S. haemolyticus caused macroscopic and histological confluent pneumonia with significant increase in BAL white cell count, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-2. At 12 h, high concentrations of S. haemolyticus were identified in BAL. At 36 h, lung injury and BAL inflammation were less severe than at 12 h and moderate concentrations of species belonging to the oropharyngeal flora were identified in lung tissue. The inoculation of 1.0 × 10⁶ and 1.0 × 10⁷ CFU live S. haemolyticus caused histologic interstitial pneumonia and moderate BAL inflammation. Similar results were observed after inoculation of inactivated S. haemolyticus. Moreover, biofilm formation was a common phenotype in S. haemolyticus isolates. The low prevalence of the ica operon in our clinical S. haemolyticus strain collection indicated icaA and icaD independent-biofilm formation.

Conclusion

In immunocompetent spontaneously breathing mice, inoculation of S. haemolyticus causes concentration-dependent lung infection that spontaneously recovers over time. icaA and icaD independent biofilm formation is a common phenotype in S. haemolyticus isolates.

Role of tissue factor in the procoagulant and antibacterial effects of human adipose-derived mesenchymal stem cells during pneumosepsis in mice

Background

Adult mesenchymal stem cells (MSCs) improve the host response during experimental sepsis in animals. MSCs from various sources express a procoagulant activity that has been linked to the expression of tissue factor. This study sought to determine the role of tissue factor associated with adipose-derived MSCs (ASCs) in their procoagulant and antibacterial effects during pneumonia-derived sepsis.

Methods

Mice were infused intravenously with ASCs or vehicle after infection with the common human pathogen Klebsiella pneumoniae via the airways.

Results

Infusion of freshly cultured or cryopreserved ASCs induced the expression of many genes associated with tissue factor signaling and coagulation activation in the lungs. Freshly cultured and cryopreserved ASCs, as well as ASC lysates, exerted procoagulant activity in vitro as determined by a fibrin generation assay, which was almost completely inhibited by an anti-tissue factor antibody. Infusion of cryopreserved ASCs was associated with a rise in plasma thrombin-antithrombin complexes (indicative of coagulation activation) and formation of multiple thrombi in the lungs 4 h post-infusion. Preincubation of ASCs with anti-tissue factor antibody prior to infusion prevented the rise in plasma thrombin-antithrombin complex concentrations but did not influence thrombus formation in the lungs. ASCs reduced bacterial loads in the lungs and liver at 48 h after infection, which was not influenced by preincubation with anti-tissue factor antibody. At this late time point, microthrombi in the lungs were not detected anymore.

Conclusion

These data indicate that ASC-associated tissue factor is responsible for systemic activation of coagulation after infusion of ASCs but not for the formation of microthrombi in the lungs or antibacterial effects.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1391-x) contains supplementary material, which is available to authorized users.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Decrease Lung Injury in Mice

Human mesenchymal stem cell (MSC) extracellular vesicles (EV) can reduce the severity of bacterial pneumonia, but little is known about the mechanisms underlying their antimicrobial activity. In the current study, we found that bacterial clearance induced by MSC EV in Escherichia coli pneumonia in C57BL/6 mice was associated with high levels of leukotriene (LT) B₄ in the injured alveolus. More importantly, the antimicrobial effect of MSC EV was abrogated by cotreatment with a LTB₄ BLT1 antagonist. To determine the role of MSC EV on LT metabolism, we measured the effect of MSC EV on a known ATP-binding cassette transporter, multidrug resistance-associated protein 1 (MRP1), and found that MSC EV suppressed MRP1 mRNA, protein, and pump function in LPS-stimulated Raw264.7 cells in vitro. The synthesis of LTB₄ and LTC₄ from LTA₄ are competitive, and MRP1 is the efflux pump for LTC₄ Inhibition of MRP1 will increase LTB₄ production. In addition, administration of a nonspecific MRP1 inhibitor (MK-571) reduced LTC₄ and subsequently increased LTB₄ levels in C57BL/6 mice with acute lung injury, increasing overall antimicrobial activity. We previously found that the biological effects of MSC EV were through the transfer of its content, such as mRNA, microRNA, and proteins, to target cells. In the current study, miR-145 knockdown abolished the effect of MSC EV on the inhibition of MRP1 in vitro and the antimicrobial effect in vivo. In summary, MSC EV suppressed MRP1 activity through transfer of miR-145, thereby resulting in enhanced LTB₄ production and antimicrobial activity through LTB₄/BLT1 signaling.

How does Pseudomonas aeruginosa affect the progression of bronchiectasis?

BACKGROUND

Pseudomonas aeruginosa is one of the most common pathogens isolated from respiratory tract specimen in patients with bronchiectasis. It is considered highly responsible for pathogenicity, progression and clinical outcomes of bronchiectasis.

AIMS

To summarize existing evidence on how different factors of Pseudomonas aeruginosa affect the pathogenicity, progression and clinical outcomes of bronchiectasis, so as to provide possible insights for clinical practice and related research in the future.

SOURCES

PubMed was searched for studies pertaining to bronchiectasis and P. aeruginosa published to date, with no specific inclusion or exclusion criteria. Reference lists of retrieved reviews were searched for additional articles.

CONTENT

This review focused on non-cystic fibrosis bronchiectasis and also provided some data on cystic fibrosis when studies in bronchiectasis were limited. We discussed various factors in relation to P. aeruginosa: virulence factors, drug resistance, regulatory systems, genomic diversity and transmission of P. aeruginosa, as well as treatment for P. aeruginosa. Their impacts on bronchiectasis and its management were discussed.

IMPLICATIONS

The impact of P. aeruginosa on bronchiectasis is definite, although conclusions in some aspects are still vague. Faced with the worrying drug-resistance status and treatment bottleneck, individualized management and novel therapies beyond the classic pathway are most likely to be a future trend. To confirm the independent or integrated impact of various factors of P. aeruginosa on bronchiectasis and to figure out all the problems mentioned, larger randomized control trials are truly needed in the future.

Mesenchymal Stem Cells From Bone Marrow, Adipose Tissue, and Lung Tissue Differentially Mitigate Lung and Distal Organ Damage in Experimental Acute Respiratory Distress Syndrome

OBJECTIVES

Mesenchymal stem cells-based therapies have shown promising effects in experimental acute respiratory distress syndrome. Different mesenchymal stem cells sources may result in diverse effects in respiratory diseases; however, there is no information regarding the best source of mesenchymal stem cells to treat pulmonary acute respiratory distress syndrome. We tested the hypothesis that mesenchymal stem cells derived from bone marrow, adipose tissue, and lung tissue would lead to different beneficial effects on lung and distal organ damage in experimental pulmonary acute respiratory distress syndrome.

DESIGN

Animal study and primary cell culture.

SETTING

Laboratory investigation.

SUBJECTS

Seventy-five Wistar rats.

INTERVENTIONS

Wistar rats received saline (control) or Escherichia coli lipopolysaccharide (acute respiratory distress syndrome) intratracheally. On day 2, acute respiratory distress syndrome animals were further randomized to receive saline or bone marrow, adipose tissue, or lung tissue mesenchymal stem cells (1 × 10 cells) IV. Lung mechanics, histology, and protein levels of inflammatory mediators and growth factors were analyzed 5 days after mesenchymal stem cells administration. RAW 264.7 cells (a macrophage cell line) were incubated with lipopolysaccharide followed by coculture or not with bone marrow, adipose tissue, and lung tissue mesenchymal stem cells (10 cells/mL medium).

MEASUREMENTS AND MAIN RESULTS

Regardless of mesenchymal stem cells source, cells administration improved lung function and reduced alveolar collapse, tissue cellularity, collagen, and elastic fiber content in lung tissue, as well as decreased apoptotic cell counts in liver. Bone marrow and adipose tissue mesenchymal stem cells administration also reduced levels of tumor necrosis factor-α, interleukin-1β, keratinocyte-derived chemokine, transforming growth factor-β, and vascular endothelial growth factor, as well as apoptotic cell counts in lung and kidney, while increasing expression of keratinocyte growth factor in lung tissue. Additionally, mesenchymal stem cells differently modulated the secretion of biomarkers by macrophages depending on their source.

CONCLUSIONS

Mesenchymal stem cells from different sources led to variable responses in lungs and distal organs. Bone marrow and adipose tissue mesenchymal stem cells yielded greater beneficial effects than lung tissue mesenchymal stem cells. These findings may be regarded as promising in clinical trials.

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.

Prostaglandin E2 secreted by mesenchymal stem cells protects against acute liver failure via enhancing hepatocyte proliferation

Bone marrow-derived mesenchymal stem cells (MSCs) have been recently used in clinical trials as treatment for liver diseases. However, the underlying mechanism of their effectiveness remains largely unexplored. In the present study, we confirmed that the protective effects of MSCs on mouse model of acute liver failure (ALF) were based on MSC-secreted prostaglandin (PG)E₂. Our data confirmed that MSC-secreted PGE₂ not only inhibited apoptosis but also enhanced hepatocyte proliferation, thus attenuating ALF. Moreover, Yes-associated protein (YAP) played a major role in PGE₂-triggered hepatocyte proliferation. In vitro studies showed that PGE₂ increased the expression of PGE₄ and enhanced the phosphorylation of cAMP response element binding protein, resulting in YAP activation and increased expression of YAP-related genes. Furthermore, the mammalian target of rapamycin, another major regulator of cell proliferation, was activated by YAP via suppressing phosphatase and tensin homolog through miR-29a-3p. These pathways coordinated to control cell proliferation. Collectively, MSCs could promote the recovery of ALF through PGE₂-induced hepatocyte proliferation.-Liu, Y., Ren, H., Wang, J., Yang, F., Li, J., Zhou, Y., Yuan, X., Zhu, W., Shi, X. Prostaglandin E₂ secreted by mesenchymal stem cells protects against acute liver failure via enhancing hepatocyte proliferation.

Cell therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is driven by a severe pro-inflammatory response resulting in lung damage, impaired gas exchange and severe respiratory failure. There is no specific treatment that effectively improves outcome in ARDS. However, in recent years, cell therapy has shown great promise in preclinical ARDS studies. A wide range of cells have been identified as potential candidates for use, among these are mesenchymal stromal cells (MSCs), which are adult multi-lineage cells that can modulate the immune response and enhance repair of damaged tissue. The therapeutic potential of MSC therapy for sepsis and ARDS has been demonstrated in multiple in vivo models. The therapeutic effect of these cells seems to be due to two different mechanisms; direct cellular interaction, and paracrine release of different soluble products such as extracellular vesicles (EVs)/exosomes. Different approaches have also been studied to enhance the therapeutic effect of these cells, such as the over-expression of anti-inflammatory or pro-reparative molecules. Several clinical trials (phase I and II) have already shown safety of MSCs in ARDS and other diseases. However, several translational issues still need to be addressed, such as the large-scale production of cells, and their potentiality and variability, before the therapeutic potential of stem cells therapies can be realized.

Mesenchymal stem cells: A double-edged sword in radiation-induced lung injury

Radiation therapy is an important treatment modality for multiple thoracic malignancies. However, radiation‐induced lung injury (RILI), which is the term generally used to describe damage to the lungs caused by exposure to ionizing radiation, remains a critical issue affecting both tumor control and patient quality of life. Despite tremendous effort, there is no current consensus regarding the optimal treatment approach for RILI. Because of a number of functional advantages, including self‐proliferation, multi‐differentiation, injury foci chemotaxis, anti‐inflammation, and immunomodulation, mesenchymal stem cells (MSCs) have been a focus of research for many years. Accumulating evidence indicates the therapeutic potential of transplantation of MSCs derived from adipose tissue, umbilical cord blood, and bone marrow for inflammatory diseases, including RILI. However, reports have also shown that MSCs, including fibrocytes, lung hematopoietic progenitor cells, and ABCG²⁺ MSCs, actually enhance the progression of lung injuries. These contradictory results suggest that MSCs may have dual effects and that caution should be taken when using MSCs to treat RILI. In this review, we present and discuss recent evidence of the double‐edged function of MSCs and provide comments on the prospects of these findings.

Stem Cell–based Therapies for Sepsis

Sepsis is a life-threatening syndrome resulting in shock and organ dysfunction stemming from a microbial infection. Sepsis has a mortality of 40% and is implicated in half of all in-hospital deaths. The host immune response to microbial infection is critical, with early-phase sepsis characterized by a hyperinflammatory immune response, whereas the later phase of sepsis is often complicated by suppression. Sepsis has no treatment, and management remains supportive.

Stem cells constitute exciting potential therapeutic agents for sepsis. In this review, we examine the rationale for stem cells in sepsis, focusing on mesenchymal stem/stromal cells, which currently demonstrate the greatest therapeutic promise. We examine the preclinical evidence base and evaluate potential mechanisms of action of these cells that are important in the setting of sepsis. We discuss early-phase clinical trials and critically appraise translational barriers to the use of mesenchymal stem/stromal cells in patients with sepsis.

Activated Mesenchymal Stem Cells Interact with Antibiotics and Host Innate Immune Responses to Control Chronic Bacterial Infections

Chronic bacterial infections associated with biofilm formation are often difficult to resolve without extended courses of antibiotic therapy. Mesenchymal stem cells (MSC) exert antibacterial activity in vitro and in acute bacterial infection models, but their activity in chronic infection with biofilm models has not been previously investigated. Therefore, we studied the effects of MSC administration in mouse and dog models of chronic infections associated with biofilms. Mice with chronic Staphylococcus aureus implant infections were treated by i.v. administration of activated or non-activated MSC, with or without antibiotic therapy. The most effective treatment protocol was identified as activated MSC co-administered with antibiotic therapy. Activated MSC were found to accumulate in the wound margins several days after i.v. administration. Macrophages in infected tissues assumed an M2 phenotype, compared to untreated infections which contained predominately M1 macrophages. Bacterial killing by MSC was found to be mediated in part by secretion of cathelicidin and was significantly increased by antibiotics. Studies in pet dogs with spontaneous chronic multi drug-resistant wound infections demonstrated clearance of bacteria and wound healing following repeated i.v. administration of activated allogeneic canine MSC. Thus, systemic therapy with activated MSC may be an effective new, non-antimicrobial approach to treatment of chronic, drug-resistant infections.

Fifty Years of Research in ARDS. Cell-based Therapy for Acute Respiratory Distress Syndrome. Biology and Potential Therapeutic Value

On the basis of several preclinical studies, cell-based therapy has emerged as a potential new therapeutic for acute respiratory distress syndrome (ARDS). Of the various cell-based therapy options, mesenchymal stem/stromal cells (MSCs) from bone marrow, adipose tissue, and umbilical cord have the most experimental data to support their potential efficacy for lung injury from both infectious and noninfectious causes. Mechanistically, MSCs exert their beneficial effects by release of paracrine factors, microvesicles, and transfer of mitochondria, all of which have antiinflammatory and pro-resolving effects on injured lung endothelium and alveolar epithelium, including enhancing the resolution of pulmonary edema by up-regulating sodium-dependent alveolar fluid clearance. MSCs also have antimicrobial effects mediated by release of antimicrobial factors and by up-regulating monocyte/macrophage phagocytosis. Phase 2a clinical trials to establish safety in ARDS are in progress, and two phase 1 trials did not report any serious adverse events. Several issues need further study, including: determining the optimal methods for large-scale production, reconstitution of cryopreserved cells for clinical use, defining cell potency assays, and determining the therapeutic potential of conditioned media derived from MSCs. Because ARDS is a heterogeneous syndrome, targeting MSCs to patients with ARDS with a more hyperinflammatory endotype may further enhance their potential for efficacy.

Mesenchymal Stem Cell Microvesicles Attenuate Acute Lung Injury in Mice Partly Mediated by Ang-1 mRNA

Microvesicles (MVs) derived from human mesenchymal stem cells (MSC MVs) were demonstrated to ameliorate inflammation in lungs. We have found their content of mRNA for keratinocyte growth factor was partly involved in their therapeutic effects. As MSC MVs also contained a substantial quantity of angiopoietin-1 (Ang-1) mRNA, which plays an essential role in vascular stabilization and resolving inflammation, we hypothesized that Ang-1 mRNA might similarly account for a part of their therapeutic effects. We downregulated Ang-1 mRNA expression in MVs, using a lentivirus vector carrying Ang-1 short hairpin RNA to transfect MSCs. A mouse model of lipopolysaccharide induced acute lung injury (ALI) was used in vivo. We also studied in vitro interactions between Ang-1 mRNA deficient MVs on macrophages and human lung microvascular endothelial cells. Compared with negative control, Ang-1 mRNA deficient MVs increased the influx of neutrophils and macrophage inflammatory protein-2 levels in bronchoalveolar lavage fluid by 136% and 105%, respectively, suggesting a deteriorative lung inflammation and a failure to restore pulmonary capillary permeability assessed by Evan's blue dye and bronchoalveolar lavage albumin level. In vitro, the addition of Ang-1 mRNA deficient MVs failed to maintain the integrity of endotoxin-stimulated microvascular endothelial cells and abrogated the decrease in tumor necrosis factor-α level and the increase in interleukin-10 level mediated by negative control in RAW 264.7 cells. In summary, the therapeutic effects of MVs in ALI, and their immunomodulatory properties on macrophages were partly mediated through their content of Ang-1 mRNA. Stem Cells 2017;35:1849-1859.

Stem cell therapy for acute respiratory distress syndrome: a promising future?

PURPOSE OF REVIEW

Acute respiratory distress syndrome (ARDS) is a devastating disease process with a 40% mortality rate, and for which there is no therapy. Stem cells are an exciting potential therapy for ARDS, and are currently the subject of intensive ongoing research efforts. We review data concerning the therapeutic promise of cell-based therapies for ARDS.

RECENT FINDINGS

Recent experimental studies suggest that cell-based therapies, particularly mesenchymal stem/stromal cells (MSCs), endothelial progenitor cells, and embryonic or induced pluripotent stem cells all offer considerable promise for ARDS. Of these cell types, mesenchymal stromal cells offer the greatest potential for allogeneic therapy, given the large body of preclinical data supporting their use, and the advanced state of our understanding of their diverse mechanisms of action. Although other stem cells such as EPCs also have therapeutic potential, greater barriers exist, particularly the requirement for autologous EPC therapy. Other stem cells, such as ESCs and iPSCs, are at an earlier stage in the translational process, but offer the hope of directly replacing injured lung tissue. Ultimately, lung-derived stem cells may offer the greatest hope for lung diseases, given their homeostatic role in replacing and repairing damaged native lung tissues.MSCs are currently in early phase clinical trials, the results of which will be of critical importance to subsequent translational efforts for MSCs in ARDS. A number of translational challenges exist, including minimizing variability in cell batches, developing standard tests for cell potency, and producing large amounts of clinical-grade cells for use in patients.

SUMMARY

Cell-based therapies, particularly MSCs, offer considerable promise for the treatment of ARDS. Overcoming translational challenges will be important to fully realizing their therapeutic potential for ARDS.

Long-term safety of umbilical cord mesenchymal stem cells transplantation for systemic lupus erythematosus: a 6-year follow-up study

The aim of this study is to assess the long-term safety of allogeneic umbilical cord mesenchymal stem cells (UC MSCs) transplantation for patients with refractory systemic lupus erythematosus (SLE). Nine SLE patients, who were refractory to steroid and immunosuppressive drugs treatment and underwent MSCs transplantation in 2009, were enrolled. One million allogeneic UC MSCs per kilogram of body weight were infused intravenously at days 0 and 7. The possible adverse events, including immediately after MSCs infusions, as well as the long-term safety profiles were observed. Blood and urine routine test, liver function, electrocardiogram, chest radiography and serum levels of tumor markers, including alpha fetal protein (AFP), cancer embryo antigen (CEA), carbohydrate antigen 155 (CA155) and CA199, were assayed before and 1, 2, 4 and 6 years after MSCs transplantation. All the patients completed two times of MSCs infusions. One patient had mild dizzy and warm sensation 5 min after MSCs infusion, and the symptoms disappeared quickly. No other adverse event, including fluster, headache, nausea or vomit, was observed. There was no change in peripheral white blood cell count, red blood cell count and platelet number in these patients after followed up for 6 years. Liver functional analysis showed that serum alanine aminotransferase, glutamic-oxalacetic transaminase, total bilirubin and direct bilirubin remained in normal range after MSCs infusions. No newly onset abnormality was detected on electrocardiogram and chest radiography. Moreover, we found no rise of serum tumor markers, including AFP, CEA, CA125 and CA199, before and 6 years after MSCs infusions. Our long-term observational study demonstrated a good safety profile of allogeneic UC MSCs in SLE patients.

NSFC spurs significant basic research progress of respiratory medicine in China

Over the years, research in respiratory medicine has progressed rapidly in China. This commentary narrates the role of the National Natural Science Foundation of China (NSFC) in supporting the basic research of respiratory medicine, summarizes the major progress of respiratory medicine in China, and addresses the main future research directions sponsored by the NSFC.