Human mesenchymal stem cells reduce the severity of acute lung injury in a sheep model of bacterial pneumonia

Identifying Clinical Research Priorities in Adult Pulmonary and Critical Care. NHLBI Working Group Report

Preventing, treating, and promoting recovery from critical illness due to pulmonary disease are foundational goals of the critical care community and the NHLBI. Decades of clinical research in acute respiratory distress syndrome, acute respiratory failure, pneumonia, and sepsis have yielded improvements in supportive care, which have translated into improved patient outcomes. Novel therapeutics have largely failed to translate from promising preclinical findings into improved patient outcomes in late-phase clinical trials. Recent advances in personalized medicine, "big data," causal inference using observational data, novel clinical trial designs, preclinical disease modeling, and understanding of recovery from acute illness promise to transform the methods of pulmonary and critical care clinical research. To assess the current state of, research priorities for, and future directions in adult pulmonary and critical care research, the NHLBI assembled a multidisciplinary working group of investigators. This working group identified recommendations for future research, including 1) focusing on understanding the clinical, physiological, and biological underpinnings of heterogeneity in syndromes, diseases, and treatment response with the goal of developing targeted, personalized interventions; 2) optimizing preclinical models by incorporating comorbidities, cointerventions, and organ support; 3) developing and applying novel clinical trial designs; and 4) advancing mechanistic understanding of injury and recovery to develop and test interventions targeted at achieving long-term improvements in the lives of patients and families. Specific areas of research are highlighted as especially promising for making advances in pneumonia, acute hypoxemic respiratory failure, and acute respiratory distress syndrome.

Large Animal Models in Regenerative Medicine and Tissue Engineering: To Do or Not to Do

Rapid developments in Regenerative Medicine and Tissue Engineering has witnessed an increasing drive toward clinical translation of breakthrough technologies. However, the progression of promising preclinical data to achieve successful clinical market authorisation remains a bottleneck. One hurdle for progress to the clinic is the transition from small animal research to advanced preclinical studies in large animals to test safety and efficacy of products. Notwithstanding this, to draw meaningful and reliable conclusions from animal experiments it is critical that the species and disease model of choice is relevant to answer the research question as well as the clinical problem. Selecting the most appropriate animal model requires in-depth knowledge of specific species and breeds to ascertain the adequacy of the model and outcome measures that closely mirror the clinical situation. Traditional reductionist approaches in animal experiments, which often do not sufficiently reflect the studied disease, are still the norm and can result in a disconnect in outcomes observed between animal studies and clinical trials. To address these concerns a reconsideration in approach will be required. This should include a stepwise approach using in vitro and ex vivo experiments as well as in silico modeling to minimize the need for in vivo studies for screening and early development studies, followed by large animal models which more closely resemble human disease. Naturally occurring, or spontaneous diseases in large animals remain a largely untapped resource, and given the similarities in pathophysiology to humans they not only allow for studying new treatment strategies but also disease etiology and prevention. Naturally occurring disease models, particularly for longer lived large animal species, allow for studying disorders at an age when the disease is most prevalent. As these diseases are usually also a concern in the chosen veterinary species they would be beneficiaries of newly developed therapies. Improved awareness of the progress in animal models is mutually beneficial for animals, researchers, human and veterinary patients. In this overview we describe advantages and disadvantages of various animal models including domesticated and companion animals used in regenerative medicine and tissue engineering to provide an informed choice of disease-relevant animal models.

A synergistic role of convalescent plasma and mesenchymal stem cells in the treatment of severely ill COVID-19 patients: a clinical case report

Acute respiratory distress syndrome virus-2 (SARS-CoV-2) responsible for coronavirus disease 2019 (COVID-19) infection, which causes global public health emergencies, has sped widely for more than 5 months and has the risk of long-term transmission. No effective treatment has been discovered to date. In the cases we report, the patient continued to deteriorate even after administration of antiviral drugs such as lopinavir/ritonavir, interferon-α, and ribavirin, as well as intravenous injection of meropenem, methylprednisolone, and immunoglobulin. So, we infused the patient with convalescent plasma (CP), and the absolute lymphocyte count increased the next day and returned to normal on the fourth day. Followed by intravenous infusion of mesenchymal stem cells (MSCs), bilateral infiltrates were absorbed and the pulmonary function was significantly improved. We note that the intravenous infusion of CP and MSCs for the treatment of severe COVID-19 patients may have synergistic characteristics in inhibiting cytokine storm, promoting the repair of lung injury, and recovering pulmonary function. We hope to provide a reference for the research direction of COVID-19 clinical strategies.

Current status of potential therapeutic candidates for the COVID-19 crisis

As of April 15, 2020, the ongoing coronavirus disease 2019 (COVID-2019) pandemic has swept through 213 countries and infected more than 1,870,000 individuals, posing an unprecedented threat to international health and the economy. There is currently no specific treatment available for patients with COVID-19 infection. The lessons learned from past management of respiratory viral infections have provided insights into treating COVID-19. Numerous potential therapies, including supportive intervention, immunomodulatory agents, antiviral therapy, and convalescent plasma transfusion, have been tentatively applied in clinical settings. A number of these therapies have provided substantially curative benefits in treating patients with COVID-19 infection. Furthermore, intensive research and clinical trials are underway to assess the efficacy of existing drugs and identify potential therapeutic targets to develop new drugs for treating COVID-19. Herein, we summarize the current potential therapeutic approaches for diseases related to COVID-19 infection and introduce their mechanisms of action, safety, and effectiveness.

Combating COVID-19 with mesenchymal stem cell therapy

The COVID-19 disease is caused by a positive stranded RNA virus called SARS-CoV-2. The virus mainly targets the pulmonary epithelial cells as it's initial site of infection by letting its surface spike protein interact and bind to the host ACE2 receptor. The internalization and gradual replication of the virus results in an exaggerated immune response triggering release of many pro-inflammatory cytokines and chemokines. This immune storm is responsible for multiple health hazards in the host ultimately leading to multiple organ failure. Mesenchymal stem cell therapy offers a promising approach towards mitigating the delirious effects of the infection in the COVID-19 patients. This therapy has shown to reduce the expression of pro-inflammatory cytokines as well as repair of damaged tissues in COVID-19 patients. This review has been organized to put forward the positive aruments and implications in support of mesenchymal stem cell therapy as a necessary approach for treating COVID-19 patients.

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.

Mesenchymal stem cell use in acute respiratory distress syndrome: a potential therapeutic application

Acute respiratory distress syndrome (ARDS) is a condition of acute respiratory failure resulting from noncardiogenic pulmonary edema. It may occur as a consequence of lung infection, sepsis, trauma, aspiration or drug reaction. The pathogenesis of ARDS is understood to be an unregulated inflammatory cascade with both endothelial and epithelial layer damage leading to alveolar fluid collection and pulmonary edema. Despite improved understanding of the cause of ARDS, treatment remains supportive with a mortality rate ranging from 25–40%. Preclinical and early phase clinical trials have highlighted the potential role of mesenchymal stem cells in combating the inflammatory cascade through immunomodulatory mechanisms and assisting in tissue repair.

Acute respiratory distress syndrome (ARDS) is a condition of sudden respiratory failure due to fluid in the lungs as a consequence of factors such as trauma and bacterial or viral lung infections. ARDS is understood to occur as a result of uncontrolled inflammation. Conventional treatment is supportive only with ARDS having a high death rate of up to 40%. Evidence from both preclinical and clinical trials highlight the potential role of mesenchymal stem cells in combating the inflammatory reactions that cause ARDS as this therapy both modifies the immune response and provides assistance with tissue repair.

Mesenchymal stem/stromal cells: the therapeutic effects in animal models of acute pulmonary diseases

The pulmonary diseases are one of the most important causes of death in the world. The successful therapies in the field of lung diseases are very limited and the medical treatments available are ineffective in many of the lung diseases. Many studies have evaluated the new therapies in the acute pulmonary diseases, and the transplantation of mesenchymal stem/stromal cells (MSCs), which is a branch of cell therapy, has a special place among the new medical techniques. The MSCs are present throughout the body and are thought to play a role in tissue regeneration and inflammation control. In the event of injury, the local MSCs traverse the shortest possible distance from the tissue or blood vessels to reach the affected site. But, there are few undifferentiated cells in the tissues. The exogenous MSCs are used to immunity modify or regenerative treatments in preclinical models of acute pulmonary diseases. Several studies have shown the positive effects of MSCs replacement in the acute lung disorders. The effection mechanism of the MSCs include the differentiation ability and the secretion of paracrine agents such as the anti-inflammatory mediators. Many studies suggest that this treatment method is safe and is probably to be widely used in future clinical trials. This review will describe the therapeutic effects of the MSCs in the experimental models of the acute pulmonary diseases for use as a method of treatment in clinical trials in future.

Umbilical Cord-derived Mesenchymal Stem Cells for COVID-19 Patients with Acute Respiratory Distress Syndrome (ARDS)

The coronavirus SARS-CoV-2 is cause of a global pandemic of a pneumonia-like disease termed Coronavirus Disease 2019 (COVID-19). COVID-19 presents a high mortality rate, estimated at 3.4%. More than 1 out of 4 hospitalized COVID-19 patients require admission to an Intensive Care Unit (ICU) for respiratory support, and a large proportion of these ICU-COVID-19 patients, between 17% and 46%, have died. In these patients COVID-19 infection causes an inflammatory response in the lungs that can progress to inflammation with cytokine storm, Acute Lung Injury (ALI), Acute Respiratory Distress Syndrome (ARDS), thromboembolic events, disseminated intravascular coagulation, organ failure, and death. Mesenchymal Stem Cells (MSCs) are potent immunomodulatory cells that recognize sites of injury, limit effector T cell reactions, and positively modulate regulatory cell populations. MSCs also stimulate local tissue regeneration via paracrine effects inducing angiogenic, anti-fibrotic and remodeling responses. MSCs can be derived in large number from the Umbilical Cord (UC). UC-MSCs, utilized in the allogeneic setting, have demonstrated safety and efficacy in clinical trials for a number of disease conditions including inflammatory and immune-based diseases. UC-MSCs have been shown to inhibit inflammation and fibrosis in the lungs and have been utilized to treat patients with severe COVID-19 in pilot, uncontrolled clinical trials, that reported promising results. UC-MSCs processed at our facility have been authorized by the FDA for clinical trials in patients with an Alzheimer's Disease, and in patients with Type 1 Diabetes (T1D). We hypothesize that UC-MSC will also exert beneficial therapeutic effects in COVID-19 patients with cytokine storm and ARDS. We propose an early phase controlled, randomized clinical trial in COVID-19 patients with ALI/ARDS. Subjects in the treatment group will be treated with two doses of UC-MSC (l00 × 10⁶ cells). The first dose will be infused within 24 hours following study enrollment. A second dose will be administered 72 ± 6 hours after the first infusion. Subject in the control group will receive infusion of vehicle (DPBS supplemented with 1% HSA and 70 U/kg unfractionated Heparin, delivered IV) following the same timeline. Subjects will be evaluated daily during the first 6 days, then at 14, 28, 60, and 90 days following enrollment (see Schedule of Assessment for time window details). Safety will be determined by adverse events (AEs) and serious adverse events (SAEs) during the follow-up period. Efficacy will be defined by clinical outcomes, as well as a variety of pulmonary, biochemical and immunological tests. Success of the current study will provide a framework for larger controlled, randomized clinical trials and a means of accelerating a possible solution for this urgent but unmet medical need. The proposed early phase clinical trial will be performed at the University of Miami (UM), in the facilities of the Diabetes Research Institute (DRI), UHealth Intensive Care Unit (ICU) and the Clinical Translational Research Site (CTRS) at the University of Miami Miller School of Medicine and at the Jackson Memorial Hospital (JMH).

Genetically modified mesenchymal stem cell therapy for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a devastating hypoxemic respiratory failure, characterized by disruption of the alveolar-capillary membrane barrier. Current management for ARDS remains supportive, including lung-protective ventilation and a conservative fluid strategy. Mesenchymal stem cells (MSCs) have emerged as a potentially attractive candidate for the management of ARDS through facilitating lung tissue regeneration and repair by releasing paracrine soluble factors. Over the last decade, a variety of strategies have emerged to optimize MSC-based therapy. Among these, the strategy using genetically modified MSCs has received increased attention recently due to its distinct advantage, in conferring incremental migratory capacity and, enhancing the anti-inflammatory, immunomodulatory, angiogenic, and antifibrotic effects of these cells in numerous preclinical ARDS models, which may in turn provide additional benefits in the management of ARDS. Here, we provide an overview of recent studies testing the efficacy of genetically modified MSCs using preclinical models of ARDS.

Endothelial-platelet interactions in influenza-induced pneumonia: A potential therapeutic target

Every year, influenza viruses spread around the world, infecting the respiratory systems of countless humans and animals, causing illness and even death. Severe influenza infection is associated with pulmonary epithelial damage and endothelial dysfunction leading to acute lung injury (ALI). There is evidence that an aggressive cytokine storm and cell damage in lung capillaries as well as endothelial/platelet interactions contribute to vascular leakage, pro-thrombotic milieu and infiltration of immune effector cells. To date, treatments for ALI caused by influenza are limited to antiviral drugs, active ventilation or further symptomatic treatments. In this review, we summarize the mechanisms of influenza-mediated pathogenesis, permissive animal models and histopathological changes of lung tissue in both mice and men and compare it with histological and electron microscopic data from our own group. We highlight the molecular and cellular interactions between pulmonary endothelium and platelets in homeostasis and influenza-induced pathogenesis. Finally, we discuss novel therapeutic targets on platelets/endothelial interaction to reduce or resolve ALI.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

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

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

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.

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

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

Effects of adjunct treatments on end-organ damage and histological injury severity in acute respiratory distress syndrome and multiorgan failure caused by smoke inhalation injury and burns

BACKGROUND

We investigated effects of mesenchymal stem cells (MSC) or low-flow extracorporeal life support (ECLS) as adjunctive treatments for acute respiratory distress syndrome (ARDS) due to inhalation injury and burns. We hypothesized that these interventions decrease histological end-organ damage.

METHODS

Anesthetized female swine underwent smoke inhalation injury and 40% TBSA burns, then critical care for 72h. The following groups were studied: CTR (no injury, n = 4), ICTR (injured untreated, n = 10), Allo (injured treated with allogenic MSC, n = 10), Auto (injured treated with autologous MSC, n = 10), Hemo (injured and treated with the Hemolung low flow ECLS system, n = 9), and Nova (injured and treated with the NovaLung low flow ECLS system, n = 8). Histology scores from lung, kidneys, liver, and jejunum were calculated. Data are presented as means±SEM.

RESULTS

Survival at 72h was 100% in CTR; 40% in ICTR; 50% in Allo; 90% in Auto; 33% in Hemo; 63% in Nova. ARDS developed in 0/10 CTR; 10/10 ICTR; 8/9 Hemo; 5/8 Nova; 9/10 Allo; 6/10 Auto. Diffuse alveolar damage (DAD) was present in all injured groups. MSC groups had significantly lower DAD scores than ICTR animals (Allo 26.6 ± 3.4 and Auto 18.9 ± 1.5 vs. ICTR 46.8 ± 2.1, p < 0.001). MSC groups also had lower DAD scores than ECLS animals (Allo vs. Nova, p < 0.05, Allo vs. Hemo p < 0.001, Auto vs. Nova p < 0.001, Auto vs. Hemo, p < 0.001). Kidney injury ICTR (p < 0.05) and Hemo (p < 0.01) were higher than in CTR. By logistic regression, a PaO₂-to-FiO₂ ratio (PFR) < 300 was a function of the DAD score: logit (PFR < 300) = 0.84 + 0.072*DAD Score, odds ratio 1.074 (1.007, 1.147, p < 0.05) with a ROC AUC of 0.76, p < 0.001.

CONCLUSION

Treatment with Auto MSC followed by Allo and then Nova were most effective in mitigating ARDS and MOF severity in this model. Further studies will elucidate the role of combination therapies of MSC and ECLS as comprehensive treatments for ARDS and MOF.

Human Adipose Tissue-Derived Stromal Cells Attenuate the Multiple Organ Injuries Induced by Sepsis and Mechanical Ventilation in Mice

Mechanical ventilation (MV) can augment sepsis-induced organ injury. Previous studies indicate that human mesenchymal stem cells (hMSCs) have immune-modulatory effect. We hypothesize that human adipose tissue-derived stromal cells (hADSCs) could attenuate MV and sepsis-induced organ injury. Male C57BL/6 mice were randomized to five groups: Sham group; MV group; cecal ligation and puncture (CLP) group; CLP + MV group; and CLP + MV + hADSC group. Anesthetized mice were subjected to cecal ligation and puncture surgery. The mice then received mechanical ventilation (12 ml/kg), with or without the intervention of hADSCs. The survival rate, organ injury of the liver and kidney, total protein and cells in bronchoalveolar lavage fluid (BALF), and histological changes of the lung and liver were examined. The level of IL-6 in BALF was measured by ELISA. Real-time quantitative PCR was used to analyze mRNA of IL-6 and tumor necrosis factor-α (TNF-α). hADSC treatment increased survival rate of septic mice with MV. hADSCs attenuated dysfunction of the liver and kidney and decreased lung inflammation and tissue injury of the liver and lung. IL-6 level in BALF and TNF-α and IL-6 mRNA expression in the tissue of the lung, liver, and kidney were significantly reduced by hADSC treatment. MV with conventional tidal volume aggravates CLP-induced multiple organ injuries. hADSCs inhibited the compound injuries possibly through modulation of immune responses.

Surgical anatomy of the ovine sural nerve for facial nerve regeneration and reconstruction research

The lack of a clinically relevant animal models for research in facial nerve reconstruction is challenging. In this study, we investigated the surgical anatomy of the ovine sural nerve as a potential candidate for facial nerve reconstruction, and performed its histological quantitative analysis in comparison to the buccal branch (BB) of the facial nerve using cadaver and anesthetized sheep. The ovine sural nerve descended to the lower leg along the short saphenous vein. The length of the sural nerve was 14.3 ± 0.5 cm. The distance from the posterior edge of the lateral malleolus to the sural nerve was 7.8 ± 1.8 mm. The mean number of myelinated fibers in the sural nerve was significantly lower than that of the BB (2,311 ± 381vs. 5,022 ± 433, respectively. p = 0.003). The number of fascicles in the sural nerve was also significantly lower than in the BB (10.5 ± 1.7 vs. 21.3 ± 2.7, respectively. p = 0.007). The sural nerve was grafted to the BB with end-to-end neurorrhaphy under surgical microscopy in cadaver sheep. The surgical anatomy and the number of fascicles of the ovine sural nerve were similar of those reported in humans. The results suggest that the sural nerve can be successfully used for facial nerve reconstruction research in a clinically relevant ovine model.

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.

Exosomes derived from microRNA-30b-3p-overexpressing mesenchymal stem cells protect against lipopolysaccharide-induced acute lung injury by inhibiting SAA3

Mesenchymal stem cells (MSCs) have been widely documented for their potential role in the treatment of various clinical disorders, including acute lung injury (ALI). ALI represents a clinical syndrome associated with histopathological diffuse alveolar damage. Recent evidence has demonstrated that exosomes derived from MSCs may serve as a reservoir of anti-apoptotic microRNAs (miRs) conferring protection from certain diseases. Hence, the current study was performed with the aim of investigating whether MSCs-exosomal miR-30b-3p could confer protection against ALI. A bioinformatic analysis and a dual luciferase assay were initially performed to verify that SAA3 was highly-expressed in ALI which was confirmed to be a target gene of miR-30b-3p. Next, the lipopolysaccharide (LPS)-treated type II alveolar epithelial cells (AECs) (MLE-12) were transfected with mimics or inhibitors of miR-30b-3p, or sh-SAA3. It was revealed that LPS induced AEC apoptosis, which could be inhibited by overexpressing miR-30b-3p by down-regulating the expression of SAA3. After co-culture of PKH26-labeled exosomes with MLE-12 cells, we found that the number of PKH26-labeled exosomes endocytosed by MLE-12 cells gradually increased. Furthermore, the LPS-treated MLE-12 cells co-cultured with MSC-exosomes overexpressing miR-30b-3p exhibited increased miR-30b-3p, decreased SAA3 level, as well as increased cell proliferation, accompanied by diminished cell apoptosis in LPS-treated MLE-12 cells. Finally, the protective effect of MSCs-exosomal miR-30b-3p on the AECs in vivo was investigated in an ALI mouse model with tail vein injection of MSC-exosomes with elevated miR-30b-3p, showing that overexpression of miR-30b-3p in MSC-exosomes conferred protective effects against ALI. Taken together, these findings highlighted the potential of MSC-exosomes overexpressing miR-30b-3p in preventing ALI. The exosomes derived from MSCs hold potential as future therapeutic strategies in the treatment of ALI.

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.

Optimization of the adipose-derived mesenchymal stem cell delivery time for radiation-induced lung fibrosis treatment in rats

The present study attempts to identify the optimal time duration for the administration of Ad-MSCs, in order to maximize its therapeutic benefits, and compare the degree of fibrosis among three different administration time points using the RILF rat model system. Ad-MSCs were delivered to Sprague-Dawley rats through the tail vein at the following different time points after thorax irradiation: two hours, seven days, and two hours + seven days. Post Ad-MSCs transplantation and the histopathological analysis of the lungs were performed along with analysis of inflammatory cytokine levels, including interleukin (IL)-1, IL-2, IL-6, IL-10 and tumor necrosis factor-α (TNF-α). In particular, pro-fibrotic factors (TGF-β1 and α-SMA) were also evaluated in serum and lung tissues. In addition, it was also determined whether Ad-MSCs had any role in inhibiting the transition of type II alveolar epithelial cells into fibroblasts in the lungs of injured rats. The present results demonstrated that the intravenous delivery of Ad-MSCs twice at the 2-hour and 7-day (R + MSC_2h+7d group) was effective in reducing lung fibrosis for long term durations, when compared with single delivery either at the two-hour or 7-day time points. In addition, a marked anti-inflammatory effect was also observed in RILF rats in the R + MSC_2h+7d group, as indicated by the reduced serum levels of pro-inflammatory cytokines (TNF-α, IL-1 and IL-6) and increased levels of anti-inflammatory cytokines IL-10 and IL-2. Rats that were delivered twice with Ad-MSCs (R + MSC_2h+7d group) exhibited significantly reduced TGF-β1 and α-SMA levels, in contrast to rats in the R + MSC_7d or R + MSC_2h groups, after four weeks. Furthermore, it was also noted that after four weeks, Ad-MSCs increased the number of lung epithelial cells (SP-C) and inhibited the lung fibroblastic cells (α-SMA) of rats in the R + MSC_2h and R + MSC_2h+7d groups. The present study concluded that two injections of Ad-MSCs (R + MSC_2h+7d group) appear to be optimal for therapeutic efficacy and safety during RILF.

Syndecan-2-positive, Bone Marrow-derived Human Mesenchymal Stromal Cells Attenuate Bacterial-induced Acute Lung Injury and Enhance Resolution of Ventilator-induced Lung Injury in Rats

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Human mesenchymal stromal cells demonstrate promise for acute respiratory distress syndrome, but current studies use highly heterogenous cell populations. We hypothesized that a syndecan 2 (CD362)-expressing human mesenchymal stromal cell subpopulation would attenuate Escherichia coli-induced lung injury and enhance resolution after ventilator-induced lung injury.

METHODS

In vitro studies determined whether CD362 human mesenchymal stromal cells could modulate pulmonary epithelial inflammation, wound healing, and macrophage phagocytosis. Two in vivo rodent studies determined whether CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced lung injury (n = 10/group) and enhanced resolution of ventilation-induced injury (n = 10/group).

RESULTS

CD362 human mesenchymal stromal cells attenuated cytokine-induced epithelial nuclear factor kappa B activation, increased epithelial wound closure, and increased macrophage phagocytosis in vitro. CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced injury in rodents, improving arterial oxygenation (mean ± SD, 83 ± 9 vs. 60 ± 8 mmHg, P < 0.05), improving lung compliance (mean ± SD: 0.66 ± 0.08 vs. 0.53 ± 0.09 ml · cm H2O, P < 0.05), reducing bacterial load (median [interquartile range], 1,895 [100-3,300] vs. 8,195 [4,260-8,690] colony-forming units, P < 0.05), and decreasing structural injury compared with vehicle. CD362 human mesenchymal stromal cells were more effective than CD362 human mesenchymal stromal cells and comparable to heterogenous human mesenchymal stromal cells. CD362 human mesenchymal stromal cells enhanced resolution after ventilator-induced lung injury in rodents, restoring arterial oxygenation (mean ± SD: 113 ± 11 vs. 89 ± 11 mmHg, P < 0.05) and lung static compliance (mean ± SD: 0.74 ± 0.07 vs. 0.45 ± 0.07 ml · cm H2O, P < 0.05), resolving lung inflammation, and restoring histologic structure compared with vehicle. CD362 human mesenchymal stromal cells efficacy was at least comparable to heterogenous human mesenchymal stromal cells.

CONCLUSIONS

A CD362 human mesenchymal stromal cell population decreased Escherichia coli-induced pneumonia severity and enhanced recovery after ventilator-induced lung injury.

Treatment with allogeneic mesenchymal stromal cells for moderate to severe acute respiratory distress syndrome (START study): a randomised phase 2a safety trial

BACKGROUND

Treatment with bone-marrow-derived mesenchymal stromal cells (MSCs) has shown benefits in preclinical models of acute respiratory distress syndrome (ARDS). Safety has not been established for administration of MSCs in critically ill patients with ARDS. We did a phase 2a trial to assess safety after administration of MSCs to patients with moderate to severe ARDS.

METHODS

We did a prospective, double-blind, multicentre, randomised trial to assess treatment with one intravenous dose of MSCs compared with placebo. We recruited ventilated patients with moderate to severe ARDS (ratio of partial pressure of oxygen to fractional inspired oxygen <27 kPa and positive end-expiratory pressure [PEEP] ≥8 cm H₂O) in five university medical centres in the USA. Patients were randomly assigned 2:1 to receive either 10 × 10⁶/kg predicted bodyweight MSCs or placebo, according to a computer-generated schedule with a variable block design and stratified by site. We excluded patients younger than 18 years, those with trauma or moderate to severe liver disease, and those who had received cancer treatment in the previous 2 years. The primary endpoint was safety and all analyses were done by intention to treat. We also measured biomarkers in plasma. MSC viability was tested in a post-hoc analysis. This trial is registered with ClinicalTrials.gov, number NCT02097641.

FINDINGS

From March 24, 2014, to Feb 9, 2017 we screened 1038 patients, of whom 60 were eligible for and received treatment. No patient experienced any of the predefined MSC-related haemodynamic or respiratory adverse events. One patient in the MSC group died within 24 h of MSC infusion, but death was judged to be probably unrelated. 28-day mortality did not differ between the groups (30% in the MSC group vs 15% in the placebo group, odds ratio 2·4, 95% CI 0·5-15·1). At baseline, the MSC group had numerically higher mean scores than the placebo group for Acute Physiology and Chronic Health Evaluation III (APACHE III; 104 [SD 31] vs 89 [33]), minute ventilation (11·1 [3·2] vs 9·6 [2·4] L/min), and PEEP (12·4 [3·7] vs 10·8 [2·6] cm H₂O). After adjustment for APACHE III score, the hazard ratio for mortality at 28 days was 1·43 (95% CI 0·40-5·12, p=0·58). Viability of MSCs ranged from 36% to 85%.

INTERPRETATION

One dose of intravenous MSCs was safe in patients with moderate to severe ARDS. Larger trials are needed to assess efficacy, and the viability of MSCs must be improved.

FUNDING

National Heart, Lung, and Blood Institute.

Short-term physiological hypoxia potentiates the therapeutic function of mesenchymal stem cells

Background

In the bone marrow, MSCs reside in a hypoxic milieu (1–5% O₂) that is thought to preserve their multipotent state. Typically, in vitro expansion of MSCs is performed under normoxia (~ 21% O₂), a process that has been shown to impair their function. Here, we evaluated the characteristics and function of MSCs cultured under hypoxia and hypothesized that, when compared to normoxia, dedicated hypoxia will augment the functional characteristics of MSCs.

Methods

Human and porcine bone marrow MSCs were obtained from fresh mononuclear cells. The first study evaluated MSC function following both long-term (10 days) and short-term (48 h) hypoxia (1% O₂) culture. In our second study, we evaluated the functional characteristics of MSC cultured under short-term 2% and 5% hypoxia. MSCs were evaluated for their metabolic activity, proliferation, viability, clonogenicity, gene expression, and secretory capacity.

Results

In long-term culture, common MSC surface marker expression (CD44 and CD105) dropped under hypoxia. Additionally, in long-term culture, MSCs proliferated significantly slower and provided lower yields under hypoxia. Conversely, in short-term culture, MSCs proliferated significantly faster under hypoxia. In both long-term and short-term cultures, MSC metabolic activity was significantly higher under hypoxia. Furthermore, MSCs cultured under hypoxia had upregulated expression of VEGF with concomitant downregulation of HMGB1 and the apoptotic genes BCL-2 and CASP3. Finally, in both hypoxia cultures, the pro-inflammatory cytokine, IL-8, was suppressed, while levels of the anti-inflammatories, IL-1ra and GM-CSF, were elevated in short-term hypoxia only.

Conclusions

In this study, we demonstrate that hypoxia augments the therapeutic characteristics of both porcine and human MSCs. Yet, short-term 2% hypoxia offers the greatest benefit overall, exemplified by the increase in proliferation, self-renewing capacity, and modulation of key genes and the inflammatory milieu as compared to normoxia. These data are important for generating robust MSCs with augmented function for clinical applications.

Difficulties in modelling ARDS (2017 Grover Conference Series)

Fifty years after the first description of acute respiratory distress syndrome (ARDS), none of the many positive drug studies in animal models have been confirmed in clinical trials and translated into clinical practice. This bleak outcome of so many animal experiments shows how difficult it is to model ARDS. Lungs from patients are characterized by hyperinflammation, permeability edema, and hypoxemia; accordingly, this is what most models aim to reproduce. However, in animal models it is very easy to cause inflammation in the lungs, but difficult to cause hypoxemia. Often - and not unlike in patients - models with hypoxemia are accompanied by cardiovascular failure that necessitates fluid support and ventilation, raising the question as to the role of intensive care measures in models of ARDS. In our opinion, there are two major arguments in favor of modelling intensive care medicine in models of ARDS: (1) preventing death from shock; and (2) modelling ventilation and other ICU measures as a second hit. The preferable predictive endpoints in any model of ARDS remain unclear. At present, the best recommendation is to use endpoints that can be compared across studies (i.e. PaO₂/FiO₂ ratio, compliance, wet-to-dry weight ratio) rather than percentage data. Another important and often overlooked issue is the fact that the thermoneutral environmental temperatures for mice and rats are 30℃ and 28℃, respectively; thus, at room temperature (20-22℃) they suffer from cold stress with the associated significant metabolic changes. While, by definition, any model is an abstraction, we suggest that clinically relevant models of ARDS will have to closer recapitulate important properties of the disease while taking into account species-specific confounders.

Mesenchymal stem cell-derived extracellular vesicles attenuate pulmonary vascular permeability and lung injury induced by hemorrhagic shock and trauma

BACKGROUND

Mesenchymal stem cells (MSCs) have been shown to mitigate vascular permeability in hemorrhagic shock (HS) and trauma-induced brain and lung injury. Mechanistically, paracrine factors secreted from MSCs have been identified that can recapitulate many of the potent biologic effects of MSCs in animal models of disease. Interestingly, MSC-derived extracellular vesicles (EVs), contain many of these key soluble factors, and have therapeutic potential independent of the parent cells. In this study we sought to determine whether MSC-derived EVs (MSC EVs) could recapitulate the beneficial therapeutic effects of MSCs on lung vascular permeability induced by HS in mice.

METHODS

Mesenchymal stem cell EVs were isolated from human bone marrow-derived MSCs by ultracentrifugation. A mouse model of fixed pressure HS was used to study the effects of shock, shock + MSCs and shock + MSC EVs on lung vascular endothelial permeability. Mice were administered MSCs, MSC EVs, or saline IV. Lung tissue was harvested and assayed for permeability, RhoA/Rac1 activation, and for differential phosphoprotein expression. In vitro, human lung microvascular cells junctional integrity was evaluated by immunocytochemistry and endothelial cell impedance assays.

RESULTS

Hemorrhagic shock-induced lung vascular permeability was significantly decreased by both MSC and MSC EV infusion. Phosphoprotein profiling of lung tissue revealed differential activation of proteins and pathways related to cytoskeletal rearrangement and regulation of vascular permeability by MSCs and MSC EVs. Lung tissue from treatment groups demonstrated decreased activation of the cytoskeletal GTPase RhoA. In vitro, human lung microvascular cells, MSC CM but not MSC-EVs prevented thrombin-induced endothelial cell permeability as measured by electrical cell-substrate impedance sensing system and immunocytochemistry of VE-cadherin and actin.

CONCLUSION

Mesenchymal stem cells and MSC EVs modulate cytoskeletal signaling and attenuate lung vascular permeability after HS. Mesenchymal stem cell EVs may potentially be used as a novel "stem cell free" therapeutic to treat HS-induced lung injury.

An Official American Thoracic Society Workshop Report 2015. Stem Cells and Cell Therapies in Lung Biology and Diseases

The University of Vermont College of Medicine, in collaboration with the NHLBI, Alpha-1 Foundation, American Thoracic Society, Cystic Fibrosis Foundation, European Respiratory Society, International Society for Cellular Therapy, and the Pulmonary Fibrosis Foundation, convened a workshop, "Stem Cells and Cell Therapies in Lung Biology and Lung Diseases," held July 27 to 30, 2015, at the University of Vermont. The conference objectives were to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy and ex vivo bioengineering approaches for lung diseases. These are all rapidly expanding areas of study that both provide further insight into and challenge traditional views of mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, discuss and debate current controversies, and identify future research directions and opportunities for both basic and translational research in cell-based therapies for lung diseases. This 10th anniversary conference was a follow up to five previous biennial conferences held at the University of Vermont in 2005, 2007, 2009, 2011, and 2013. Each of those conferences, also sponsored by the National Institutes of Health, American Thoracic Society, and respiratory disease foundations, has been important in helping guide research and funding priorities. The major conference recommendations are summarized at the end of the report and highlight both the significant progress and major challenges in these rapidly progressing fields.

The promise of mesenchymal stem cell therapy for acute respiratory distress syndrome

This review describes the current state of the science on mesenchymal stem cell (MSC) treatment for acute lung injury (ALI). The general characteristics, regenerative potential, and mechanism of action of MSCs are first presented. Next, particular emphasis is placed on the application of MSCs for the treatment of acute respiratory distress syndrome (ARDS) in preclinical and clinical studies. Finally, we discuss current challenges and future directions in the field presented from a clinician-researcher perspective. The objective of this work is to provide the readership with a current review of the literature discussing the hurdles and overall promise of MSCs as therapeutic interventions for the treatment of ARDS.

Animal models of smoke inhalation injury and related acute and chronic lung diseases

Smoke inhalation injury leads to various acute and chronic lung diseases and thus is the dominant cause of fire-related fatalities. In a search for an effective treatment and validation of therapies different classes of animal models have been developed, which include both small and large animals. These models have advanced our understanding of the mechanism of smoke inhalation injury, enabling a better understanding of pathogenesis and pathophysiology and development of new therapies. However, none of the animal models fully mirrors human lungs and their pathologies. All animal models have their limitations in replicating complex clinical conditions associated with smoke inhalation injury in humans. Therefore, for a correct interpretation of the results and to avoid bias, a precise understanding of similarities and differences of lungs between different animal species and humans is critical. We have reviewed and presented comprehensive comparison of different animal models and their clinical relevance. We presented an overview of methods utilized to induce smoke inhalation injuries, airway micro-/macrostructure, advantages and disadvantages of the most commonly used small and large animal models.

Alpha-Klotho Enrichment in Induced Pluripotent Stem Cell Secretome Contributes to Antioxidative Protection in Acute Lung Injury

Induced pluripotent stem cells (iPSCs) have been reported to alleviate organ injury, although the mechanisms of action remain unclear and administration of intact cells faces many limitations. We hypothesized that cell-free conditioned media (CM) containing the secretome of iPSCs possess antioxidative constituents that can alleviate pulmonary oxidant stress damage. We derived iPSCs from human dermal fibroblasts and harvested the CM. Addition of iPSC CM to cultured human alveolar type-1 epithelial cells mitigated hyperoxia-induced depletion of endogenous total antioxidant capacity while tracheal instillation of iPSC CM into adult rat lungs enhanced hyperoxia-induced increase in TAC. In both the in vitro and in vivo models, iPSC CM ameliorated oxidative damage to DNA, lipid, and protein, and activated the nuclear factor (erythroid 2)-related factor 2 (Nrf2) network of endogenous antioxidant proteins. Compared with control fibroblast-conditioned or cell-free media, iPSC CM is highly enriched with αKlotho at a concentration up to more than 10-fold of that in normal serum. αKlotho is an essential antioxidative cell maintenance and protective factor and an activator of the Nrf2 network. Immunodepletion of αKlotho reduced iPSC CM-mediated cytoprotection by ∼50%. Thus, the abundant αKlotho content significantly contributes to iPSC-mediated antioxidation and cytoprotection. Results uncover a major mechanism of iPSC action, suggest a fundamental role of αKlotho in iPSC maintenance, and support the translational potential of airway delivery of cell-free iPSC secretome for protection against lung injury. The targeted cell-free secretome-based approach may also be applicable to the amelioration of injury in other organs. Stem Cells 2018;36:616-625.

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.

Adipose-derived stem cells attenuate pulmonary microvascular hyperpermeability after smoke inhalation

Background

Pulmonary edema is a hallmark of acute respiratory distress syndrome (ARDS). Smoke inhalation causes ARDS, thus significantly increasing the mortality of burn patients. Adipose-derived stem cells (ASCs) exert potent anti-inflammatory properties. The goal of the present study was to test the safety and ecfficacy of ASCs, in a well-characterized clinically relevant ovine model of ARDS.

Methods

Female sheep were surgically prepared. ARDS was induced by cooled cotton smoke inhalation. Following injury, sheep were ventilated, resuscitated with lactated Ringer’s solution, and cardiopulmonary hemodynamics were monitored for 48 hours in a conscious state. Pulmonary microvascular hyper-permeability was assessed by measuring lung lymph flow, extravascular lung water content, protein content in plasma and lung lymph fluid. Sheep were randomly allocated to two groups: 1) ASCs: infused with 200 million of ASCs in 200mL of PlasmaLyteA starting 1 hours post-injury, n = 5; 2) control, treated with 200mL of PlasmaLyteA in a similar pattern, n = 5.

Results

Lung lymph flow increased 9-fold in control sheep as compared to baseline. Protein in the plasma was significantly decreased, while it was increased in the lung lymph. The treatment with ASCs significantly attenuated these changes. Treatment with ASCs almost led to the reversal of increased pulmonary vascular permeability and lung water content. Pulmonary gas exchange was significantly improved by ASCs. Infusion of the ASCs did not negatively affect pulmonary artery pressure and other hemodynamic variables.

Conclusions

ASCs infusion was well tolerated. The results suggest that intravenous ASCs modulate pulmonary microvascular hyper-permeability and prevent the onset of ARDS in our experimental model.

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.

Advances in Stem Cell and Cell-Based Gene Therapy Approaches for Experimental Acute Lung Injury: A Review of Preclinical Studies

Given the failure of pharmacological interventions in acute respiratory distress syndrome (ARDS), researchers have been actively pursuing novel strategies to treat this devastating, life-threatening condition commonly seen in the intensive care unit. There has been considerable research on harnessing the reparative properties of stem and progenitor cells to develop more effective therapeutic approaches for respiratory diseases with limited treatment options, such as ARDS. This review discusses the preclinical literature on the use of stem and progenitor cell therapy and cell-based gene therapy for the treatment of preclinical animal models of acute lung injury (ALI). A variety of cell types that have been used in preclinical models of ALI, such as mesenchymal stem cells, endothelial progenitor cells, and induced pluripotent stem cells, were evaluated. At present, two phase I trials have been completed and one phase I/II clinical trial is well underway in order to translate the therapeutic benefit gleaned from preclinical studies in complex animal models of ALI to patients with ARDS, paving the way for what could potentially develop into transformative therapy for critically ill patients. As we await the results of these early cell therapy trials, future success of stem cell therapy for ARDS will depend on selection of the most appropriate cell type, route and timing of cell delivery, enhancing effectiveness of cells (i.e., potency), and potentially combining beneficial cells and genes (cell-based gene therapy) to maximize therapeutic efficacy. The experimental models and scientific methods exploited to date have provided researchers with invaluable knowledge that will be leveraged to engineer cells with enhanced therapeutic capabilities for use in the next generation of clinical trials.

Intraperitoneal adoptive transfer of mesenchymal stem cells enhances recovery from acid aspiration acute lung injury in mice

Background

Mesenchymal stem cells (MSCs) might act as fine-tuners of inflammation during acute lung injury. We assessed the effects of adoptive transfer of MSCs in acid aspiration acute lung injury and explored the role of long pentraxin PTX3.

Methods

We conducted a prospective experimental interventional study on wild-type (WT) and PTX3-deficient (PTX3^−/−) mice. Acute lung injury was induced in WT and PTX3^−/− mice by instillation of hydrochloric acid into the right bronchus. One hour later, animals received intraperitoneal sterile phosphate-buffered saline (PBS), WT-MSCs (1 × 10⁶) or PTX3^−/−-MSCs (1 × 10⁶). Twenty-four hours after injury, we measured the effects of treatments on arterial blood gases, wet/dry lung weight (W/D), CT scan analysis of lung collapse, neutrophils, TNFα and CXCL1 in bronchoalveolar lavage, and plasma PTX3. d-dimer was assayed in 1 week and OH-proline in 2 weeks to track the fibrotic evolution.

Results

In 24 h, in comparison to PBS, WT-MSCs improved oxygenation and reduced W/D and alveolar collapse. These effects were associated with decreased concentrations of alveolar neutrophils and cytokines. WT-MSCs increased d-dimer concentration and decreased OH-proline levels, too.

Treatment with PTX3^−/−-MSCs ameliorated oxygenation, W/D, and alveolar TNFα, though to a lesser extent than WT-MSCs. PTX3^−/−-MSCs did not improve lung collapse, neutrophil count, CXCL1, d-dimer, and OH-proline concentrations. The protective effects of WT-MSCs were dampened by lack of endogenous PTX3, too.

Conclusions

In acid aspiration acute lung injury, MSCs improve pulmonary function and limit fibrosis by fine-tuning inflammation. The role of PTX3 in determining MSCs’ effects might merit further scrutiny.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-017-0126-5) contains supplementary material, which is available to authorized users.

The influence of macrophages on mesenchymal stromal cell therapy: passive or aggressive agents?

Mesenchymal stromal cells (MSC) have emerged as promising cell therapies for multiple conditions based on demonstrations of their potent immunomodulatory and regenerative capacities in models of inflammatory disease. Understanding the effects of MSC on T cells has dominated the majority of work carried out in this field to date; recently, however, a number of studies have shown that the therapeutic effect of MSC requires the presence of macrophages. It is timely to review the mechanisms and manner by which MSC modulate macrophage populations in order to design more effective MSC therapies and clinical studies. A complex cross-talk exists through which MSC and macrophages communicate, a communication that is not controlled exclusively by MSC. Here, we examine the evidence that suggests that MSC not only respond to inflammatory macrophages and adjust their secretome accordingly, but also that macrophages respond to encounters with MSC, creating a feedback loop which contributes to the immune regulation observed following MSC therapy. Future studies examining the effects of MSC on macrophages should consider the antagonistic role that macrophages play in this exchange.

Hepatocyte growth factor secreted by bone marrow stem cell reduce ER stress and improves repair in alveolar epithelial II cells

Idiopathic Pulmonary Fibrosis (IPF) is a progressive, irreversible lung disease with complex pathophysiology. Evidence of endoplasmic reticulum (ER) stress has been reported in alveolar epithelial cells (AEC) in IPF patients. Secreted mediators from bone marrow stem cells (BMSC-cm) have regenerative properties. In this study we investigate the beneficial effects of BMSC-cm on ER stress response in primary AEC and ER stressed A549 cells. We hypothesize that BMSC-cm reduces ER stress. Primary AEC isolated from IPF patients were treated with BMSC-cm. To induce ER stress A549 cells were incubated with Tunicamycin or Thapsigargin and treated with BMSC-cm, or control media. Primary IPF-AEC had high Grp78 and CHOP gene expression, which was lowered after BMSC-cm treatment. Similar results were observed in ER stressed A549 cells. Alveolar epithelial repair increased in presence of BMSC-cm in ER stressed A549 cells. Hepatocyte growth factor (HGF) was detected in biologically relevant levels in BMSC-cm. Neutralization of HGF in BMSC-cm attenuated the beneficial effects of BMSC-cm including synthesis of surfactant protein C (SP-C) in primary AEC, indicating a crucial role of HGF in ER homeostasis and alveolar epithelial repair. Our data suggest that BMSC-cm may be a potential therapeutic option for treating pulmonary fibrosis.

Concise Review: Mesenchymal Stem (Stromal) Cells: Biology and Preclinical Evidence for Therapeutic Potential for Organ Dysfunction Following Trauma or Sepsis

Several experimental studies have provided evidence that bone-marrow derived mesenchymal stem (stromal) cells (MSC) may be effective in treating critically ill surgical patients who develop traumatic brain injury, acute renal failure, or the acute respiratory distress syndrome. There is also preclinical evidence that MSC may be effective in treating sepsis-induced organ failure, including evidence that MSC have antimicrobial properties. This review considers preclinical studies with direct relevance to organ failure following trauma, sepsis or major infections that apply to critically ill patients. Progress has been made in understanding the mechanisms of benefit, including MSC release of paracrine factors, transfer of mitochondria, and elaboration of exosomes and microvesicles. Regardless of how well they are designed, preclinical studies have limitations in modeling the complexity of clinical syndromes, especially in patients who are critically ill. In order to facilitate translation of the preclinical studies of MSC to critically ill patients, there will need to be more standardization regarding MSC production with a focus on culture methods and cell characterization. Finally, well designed clinical trials will be needed in critically ill patient to assess safety and efficacy. Stem Cells 2017;35:316-324.

Concise Review: Mesenchymal Stromal Cell-Based Approaches for the Treatment of Acute Respiratory Distress and Sepsis Syndromes

Despite extensive research on candidate pharmacological treatments and a significant and increasing prevalence, sepsis syndrome, and acute respiratory distress syndrome (ARDS) remain areas of unmet clinical need. Preclinical studies examining mesenchymal stromal cell (MSCs) based-therapies have provided compelling evidence of potential benefit; however, the precise mechanism by which MSCs exert a therapeutic influence, and whether MSC application is efficacious in humans, remains unknown. Detailed evaluation of the limited number of human trials so far completed is further hampered as a result of variations in trial design and biomarker selection. This review provides a concise summary of current preclinical and clinical knowledge of MSCs as a cell therapy for sepsis syndrome and ARDS. The challenges of modeling such heterogeneous and rapidly progressive disease states are considered and we discuss how lessons from previous studies of pharmacological treatments for sepsis syndrome and ARDS might be used to inform and refine the design of the next generation of MSC clinical trials. Stem Cells Translational Medicine 2017;6:1141-1151.

Nonantibiotic Adjunctive Therapies for Community-Acquired Pneumonia (Corticosteroids and Beyond): Where Are We with Them?

Community-acquired pneumonia (CAP) is a leading cause of hospitalization, morbidity, and mortality. Despite advances in antibiotic treatments, mortality among patients with CAP is still high. For this reason, interest has been focused on nonantibiotic therapeutic measures directed to the host response rather than the microorganism. The development of an efficacious adjunctive treatment has important implications for reducing mortality in CAP. Some clinical studies performed in the last decade have shown a clinically beneficial effect of corticosteroids, possibly by diminishing local and systemic inflammatory host response. Recent meta-analyses showed faster resolution of symptoms, shorter time to clinically stability, reduction of mechanical ventilation needed, and reduction of mortality in the most severe population, although some methodological limitations must be taken into account. In addition, some studies using statins also suggested improved outcomes due to its anti-inflammatory effect in CAP, although this requires further research. Other adjunctive therapies such as immunoglobulins and stem cells are being explored, but are not yet in the stage of clinical trials. In summary, the use of corticosteroids and other adjuvant treatments are promising in CAP, but more studies are needed to determine their impact on mortality.

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.

Dynamic Tracking Human Mesenchymal Stem Cells Tropism following Smoke Inhalation Injury in NOD/SCID Mice

Multiple preclinical evidences have supported the potential value of mesenchymal stem cells (MSCs) for treatment of acute lung injury (ALI). However, few studies focus on the dynamic tropism of MSCs in animals with acute lung injury. In this study, we track systemically transplanted human bone marrow-derived mesenchymal stem cells (hBMSCs) in NOD/SCID mice with smoke inhalation injury (SII) through bioluminescence imaging (BLI). The results showed that hBMSCs systemically delivered into healthy NOD/SCID mouse initially reside in the lungs and then partially translocate to the abdomen after 24 h. Compared with the uninjured control group treated with hBMSCs, higher numbers of hBMSCs were found in the lungs of the SII NOD/SCID mice. In both the uninjured and SII mice, the BLI signals in the lungs steadily decreased over time and disappeared by 5 days after treatment. hBMSCs significantly attenuated lung injury, elevated the levels of KGF, decreased the levels of TNF-α in BALF, and inhibited inflammatory cell infiltration in the mice with SII. In conclusion, our findings demonstrated that more systemically infused hBMSCs localized to the lungs in mice with SII. hBMSC xenografts repaired smoke inhalation-induced lung injury in mice. This repair was maybe due to the effect of anti-inflammatory and secreting KGF of hMSCs but not associated with the differentiation of the hBMSCs into alveolar epithelial cells.