Shirley H. J. Mei

Prevention of LPS-Induced Acute Lung Injury in Mice by Mesenchymal Stem Cells Overexpressing Angiopoietin 1

Background The acute respiratory distress syndrome (ARDS), a clinical complication of severe acute lung injury (ALI) in humans, is a leading cause of morbidity and mortality in critically ill patients. ALI is characterized by disruption of the lung alveolar–capillary membrane barrier and resultant pulmonary edema associated with a proteinaceous alveolar exudate. Current specific treatment strategies for ALI/ARDS are lacking. We hypothesized that mesenchymal stem cells (MSCs), with or without transfection with the vasculoprotective gene angiopoietin 1 (ANGPT1) would have beneficial effects in experimental ALI in mice. Methods and Findings Syngeneic MSCs with or without transfection with plasmid containing the human ANGPT1 gene (pANGPT1) were delivered through the right jugular vein of mice 30 min after intratracheal instillation of lipopolysaccharide (LPS) to induce lung injury. Administration of MSCs significantly reduced LPS-induced pulmonary inflammation, as reflected by reductions in total cell and neutrophil counts in bronchoalveolar lavage (BAL) fluid (53%, 95% confidence interval [CI] 7%–101%; and 60%, CI 4%–116%, respectively) as well as reducing levels of proinflammatory cytokines in both BAL fluid and lung parenchymal homogenates. Furthermore, administration of MSCs transfected with pANGPT1 resulted in nearly complete reversal of LPS-induced increases in lung permeability as assessed by reductions in IgM and albumin levels in BAL (96%, CI 6%–185%; and 74%, CI 23%–126%, respectively). Fluorescently tagged MSCs were detected in the lung tissues by confocal microscopy and flow cytometry in both naïve and LPS-injured animals up to 3 d. Conclusions Treatment with MSCs alone significantly reduced LPS-induced acute pulmonary inflammation in mice, while administration of pANGPT1-transfected MSCs resulted in a further improvement in both alveolar inflammation and permeability. These results suggest a potential role for cell-based ANGPT1 gene therapy to treat clinical ALI/ARDS.

Mesenchymal stem cells reduce inflammation while enhancing bacterial clearance and improving survival in sepsis.

RATIONALE Sepsis refers to the clinical syndrome of severe systemic inflammation precipitated by infection. Despite appropriate antimicrobial therapy, sepsis-related morbidity and mortality remain intractable problems in critically ill patients. Moreover, there is no specific treatment strategy for the syndrome of sepsis-induced multiple organ dysfunction. OBJECTIVES We hypothesized that mesenchymal stem cells (MSCs), which have been shown to have immunomodulatory properties, would reduce sepsis-induced inflammation and improve survival in a polymicrobial model of sepsis. METHODS Sepsis was induced in C57Bl/6J mice by cecal ligation and puncture (CLP), followed 6 hours later by an intravenous injection of MSCs or saline. Twenty-eight hours after CLP, plasma, bronchoalveolar lavage fluid and tissues were collected for analyses. Longer-term studies were performed with antibiotic coadministration to assess the effect of MSCs on survival. MEASUREMENTS AND MAIN RESULTS MSC treatment significantly reduced mortality in septic mice receiving appropriate antimicrobial therapy. MSCs alone reduced systemic and pulmonary cytokine levels in mice with CLP-induced sepsis, preventing acute lung injury and organ dysfunction, despite the low levels of cell persistence. Microarray data highlighted an overall down-regulation of inflammation and inflammation-related genes (such as IL-10, IL-6) and a shift toward up-regulation of genes involved in promoting phagocytosis and bacterial killing. Finally, bacterial clearance was significantly greater in MSC-treated mice, in part due to enhanced phagocytotic activity of the host immune cells. CONCLUSIONS These data demonstrate that MSCs have beneficial effects on experimental sepsis, possibly by paracrine mechanisms, and suggest that immunomodulatory cell therapy may be an effective adjunctive treatment to reduce sepsis-related morbidity and mortality.

Network Analysis of Transcriptional Responses Induced by Mesenchymal Stem Cell Treatment of Experimental Sepsis

Although bone marrow-derived mesenchymal stem cell (MSC) systemic administration reduces sepsis-associated inflammation, organ injury, and mortality in clinically relevant models of polymicrobial sepsis, the cellular and molecular mechanisms mediating beneficial effects are controversial. This study identifies the molecular mechanisms of MSC-conferred protection in sepsis by interrogating transcriptional responses of target organs to MSC therapy. Sepsis was induced in C57Bl/6J mice by cecal ligation and puncture, followed 6 hours later by an i.v. injection of either MSCs or saline. Total RNA from lungs, hearts, kidneys, livers, and spleens harvested 28 hours after cecal ligation and puncture was hybridized to mouse expression bead arrays. Common transcriptional responses were analyzed using a network knowledge-based approach. A total of 4751 genes were significantly changed between placebo- and MSC-treated mice (adjusted P ≤ 0.05). Transcriptional responses identified three common effects of MSC administration in all five organs examined: i) attenuation of sepsis-induced mitochondrial-related functional derangement, ii down-regulation of endotoxin/Toll-like receptor innate immune proinflammatory transcriptional responses, and iii) coordinated expression of transcriptional programs implicated in the preservation of endothelial/vascular integrity. Transcriptomic analysis indicates that the protective effect of MSC therapy in sepsis is not limited to a single mediator or pathway but involves a range of complementary activities affecting biological networks playing critical roles in the control of host cell metabolism and inflammatory response.

Effects of mesenchymal stem cell therapy on the time course of pulmonary remodeling depend on the etiology of lung injury in mice.

Objective:Recent evidence suggests that mesenchymal stem cells may attenuate lung inflammation and fibrosis in acute lung injury. However, so far, no study has investigated the effects of mesenchymal stem cell therapy on the time course of the structural, mechanical, and remodeling properties in pulmonary or extrapulmonary acute lung injury. Design:Prospective randomized controlled experimental study. Setting:University research laboratory. Subjects:One hundred forty-three females and 24 male C57BL/6 mice. Interventions:Control mice received saline solution intratracheally (0.05 mL, pulmonary control) or intraperitoneally (0.5 mL, extrapulmonary control). Acute lung injury mice received Escherichia coli lipopolysaccharide intratracheally (2 mg/kg in 0.05 mL of saline/mouse, pulmonary acute lung injury) or intraperitoneally (20 mg/kg in 0.5 mL of saline/mouse, extrapulmonary acute lung injury). Mesenchymal stem cells were intravenously injected (IV, 1 × 105 cells in 0.05 mL of saline/mouse) 1 day after lipopolysaccharide administration. Measurements and Main Results:At days 1, 2, and 7, static lung elastance and the amount of alveolar collapse were similar in pulmonary and extrapulmonary acute lung injury groups. Inflammation was markedly increased at day 2 in both acute lung injury groups as evidenced by neutrophil infiltration and levels of cytokines in bronchoalveolar lavage fluid and lung tissue. Conversely, collagen deposition was only documented in pulmonary acute lung injury. Mesenchymal stem cell mitigated changes in elastance, alveolar collapse, and inflammation at days 2 and 7. Compared with extrapulmonary acute lung injury, mesenchymal stem cell decreased collagen deposition only in pulmonary acute lung injury. Furthermore, mesenchymal stem cell increased metalloproteinase-8 expression and decreased expression of tissue inhibitor of metalloproteinase-1 in pulmonary acute lung injury, suggesting that mesenchymal stem cells may have an effect on the remodeling process. This change may be related to a shift in macrophage phenotype from M1 (inflammatory and antimicrobial) to M2 (wound repair and inflammation resolution) phenotype. Conclusions:Mesenchymal stem cell therapy improves lung function through modulation of the inflammatory and remodeling processes. In pulmonary acute lung injury, a reduction in collagen fiber content was observed associated with a balance between metalloproteinase-8 and tissue inhibitor of metalloproteinase-1 expressions.

The Immunomodulatory and Therapeutic Effects of Mesenchymal Stromal Cells for Acute Lung Injury and Sepsis

It is increasingly recognized that immunomodulation represents an important mechanism underlying the benefits of many stem cell therapies, rather than the classical paradigm of transdifferentiation and cell replacement. In the former paradigm, the beneficial effects of cell therapy result from paracrine mechanism(s) and/or cell–cell interaction as opposed to direct engraftment and repair of diseased tissue and/or dysfunctional organs. Depending on the cell type used, components of the secretome, including microRNA (miRNA) and extracellular vesicles, may be able to either activate or suppress the immune system even without direct immune cell contact. Mesenchymal stromal cells (MSCs), also referred to as mesenchymal stem cells, are found not only in the bone marrow, but also in a wide variety of organs and tissues. In addition to any direct stem cell activities, MSCs were the first stem cells recognized to modulate immune response, and therefore they will be the focus of this review. Specifically, MSCs appear to be able to effectively attenuate acute and protracted inflammation via interactions with components of both innate and adaptive immune systems. To date, this capacity has been exploited in a large number of preclinical studies and MSC immunomodulatory therapy has been attempted with various degrees of success in a relatively large number of clinical trials. Here, we will explore the various mechanism employed by MSCs to effect immunosuppression as well as review the current status of its use to treat excessive inflammation in the context of acute lung injury (ALI) and sepsis in both preclinical and clinical settings. J. Cell. Physiol. 9999: 2606–2617, 2015.

Efficacy of Mesenchymal Stromal Cell Therapy for Acute Lung Injury in Preclinical Animal Models: A Systematic Review

The Acute Respiratory Distress Syndrome (ARDS) is a devastating clinical condition that is associated with a 30–40% risk of death, and significant long term morbidity for those who survive. Mesenchymal stromal cells (MSC) have emerged as a potential novel treatment as in pre-clinical models they have been shown to modulate inflammation (a major pathophysiological hallmark of ARDS) while enhancing bacterial clearance and reducing organ injury and death. A systematic search of MEDLINE, EMBASE, BIOSIS and Web of Science was performed to identify pre-clinical studies that examined the efficacy MSCs as compared to diseased controls for the treatment of Acute Lung Injury (ALI) (the pre-clinical correlate of human ARDS) on mortality, a clinically relevant outcome. We assessed study quality and pooled results using random effect meta-analysis. A total of 54 publications met our inclusion criteria of which 17 (21 experiments) reported mortality and were included in the meta-analysis. Treatment with MSCs, as compared to controls, significantly decreased the overall odds of death in animals with ALI (Odds Ratio 0.24, 95% Confidence Interval 0.18–0.34, I2 8%). Efficacy was maintained across different types of animal models and means of ALI induction; MSC origin, source, route of administration and preparation; and the clinical relevance of the model (timing of MSC administration, administration of fluids and or antibiotics). Reporting of standard MSC characterization for experiments that used human MSCs and risks of bias was generally poor, and although not statistically significant, a funnel plot analysis for overall mortality suggested the presence of publication bias. The results from our meta-analysis support that MSCs substantially reduce the odds of death in animal models of ALI but important reporting elements were sub optimal and limit the strength of our conclusions.

The Devil Is in the Details: Incomplete Reporting in Preclinical Animal Research

Incomplete reporting of study methods and results has become a focal point for failures in the reproducibility and translation of findings from preclinical research. Here we demonstrate that incomplete reporting of preclinical research is not limited to a few elements of research design, but rather is a broader problem that extends to the reporting of the methods and results. We evaluated 47 preclinical research studies from a systematic review of acute lung injury that use mesenchymal stem cells (MSCs) as a treatment. We operationalized the ARRIVE (Animal Research: Reporting of In Vivo Experiments) reporting guidelines for pre-clinical studies into 109 discrete reporting sub-items and extracted 5,123 data elements. Overall, studies reported less than half (47%) of all sub-items (median 51 items; range 37–64). Across all studies, the Methods Section reported less than half (45%) and the Results Section reported less than a third (29%). There was no association between journal impact factor and completeness of reporting, which suggests that incomplete reporting of preclinical research occurs across all journals regardless of their perceived prestige. Incomplete reporting of methods and results will impede attempts to replicate research findings and maximize the value of preclinical studies.

Efficacy and safety of mesenchymal stromal cells in preclinical models of acute lung injury: a systematic review protocol.

BackgroundAcute respiratory distress syndrome (ARDS) in humans is caused by an unchecked proinflammatory response that results in diffuse and severe lung injury, and it is associated with a mortality rate of 35 to 45%. Mesenchymal stromal cells (MSCs; ‘adult stem cells’) could represent a promising new therapy for this syndrome, since preclinical evidence suggests that MSCs may ameliorate lung injury. Prior to a human clinical trial, our aim is to conduct a systematic review to compare the efficacy and safety of MSC therapy versus controls in preclinical models of acute lung injury that mimic some aspects of the human ARDS.Methods/DesignWe will include comparative preclinical studies (randomized and non-randomized) of acute lung injury in which MSCs were administered and outcomes compared to animals given a vehicle control. The primary outcome will be death. Secondary outcomes will include the four key features of preclinical acute lung injury as defined by the American Thoracic Society consensus conference (histologic evidence of lung injury, altered alveolar capillary barrier, lung inflammatory response, and physiological dysfunction) and pathogen clearance for acute lung injury models that are caused by infection. Electronic searches of MEDLINE, Embase, BIOSIS Previews, and Web of Science will be constructed and reviewed by the Peer Review of Electronic Search Strategies (PRESS) process. Search results will be screened independently and in duplicate. Data from eligible studies will be extracted, pooled, and analyzed using random effects models. Risk of bias will be assessed using the Cochrane risk of bias tool, and individual study reporting will be assessed according to the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines.DiscussionThe results of this systematic review will comprehensively summarize the safety and efficacy of MSC therapy in preclinical models of acute lung injury. Our results will help translational scientists and clinical trialists to determine whether sufficient evidence exists to perform a human clinical trial. These results may also guide future acute lung injury preclinical and clinical research.

DJ-1/PARK7 Impairs Bacterial Clearance in Sepsis

Rationale: Effective and rapid bacterial clearance is a fundamental determinant of outcomes in sepsis. DJ‐1 is a well‐established reactive oxygen species (ROS) scavenger. Objectives: Because cellular ROS status is pivotal to inflammation and bacterial killing, we determined the role of DJ‐1 in bacterial sepsis. Methods: We used cell and murine models with gain‐ and loss‐of‐function experiments, plasma, and cells from patients with sepsis. Measurements and Main Results: Stimulation of bone marrow‐derived macrophages (BMMs) with endotoxin resulted in increased DJ‐1 mRNA and protein expression. Cellular and mitochondrial ROS was increased in DJ‐1‐deficient (−/−) BMMs compared with wild‐type. In a clinically relevant model of polymicrobial sepsis (cecal ligation and puncture), DJ‐1−/− mice had improved survival and bacterial clearance. DJ‐1−/− macrophages exhibited enhanced phagocytosis and bactericidal activity in vitro, and adoptive transfer of DJ‐1−/− bone marrow‐derived mononuclear cells rescued wild‐type mice from cecal ligation and puncture‐induced mortality. In stimulated BMMs, DJ‐1 inhibited ROS production by binding to p47phox, a critical component of the NADPH oxidase complex, disrupting the complex and facilitating Nox2 (gp91phox) ubiquitination and degradation. Knocking down DJ‐1 (siRNA) in THP‐1 (human monocytic cell line) and polymorphonuclear cells from patients with sepsis enhanced bacterial killing and respiratory burst. DJ‐1 protein levels were elevated in plasma from patients with sepsis. Higher levels of circulating DJ‐1 were associated with increased organ failure and death. Conclusions: These novel findings reveal DJ‐1 impairs optimal ROS production for bacterial killing with important implications for host survival in sepsis.

Occlusive Lung Arterial Lesions in Endothelial-Targeted, Fas-Induced Apoptosis Transgenic Mice

Pulmonary arterial hypertension (PAH) is a lethal disease that is characterized by functional and structural abnormalities involving distal pulmonary arterioles that result in increased pulmonary vascular resistance and ultimately right heart failure. In experimental models of pulmonary hypertension, endothelial cell (EC) apoptosis is a necessary trigger for the development of obliterative lung arteriopathy, inducing the emergence of hyperproliferative and apoptosis-resistant vascular cells. However, it has not been established whether EC apoptosis is sufficient for the induction of complex lung arteriolar lesions. We generated a conditional transgenic system in mice to test the hypothesis that lung endothelial cell apoptosis is sufficient to induce a PAH phenotype. The Fas-induced apoptosis (FIA) construct was expressed under the control of endothelial-specific Tie2 promoter (i.e., EFIA mice), and administration of a small molecule dimerizing agent, AP20187, resulted in modest pulmonary hypertension, which was associated with obliterative vascular lesions localized to distal lung arterioles in a proportion of transgenic mice. These lesions were characterized by proliferating cells, predominantly CD68 macrophages. Although endothelial cell apoptosis was also seen in the kidney, evidence of subsequent arteriopathy was seen only in the lung. This model provides direct evidence that lung endothelial cell apoptosis acts as a trigger to initiate a PAH phenotype and provides initial insight into the potential mechanisms that underlie a lung-specific arterial response to endothelial injury.