Concise review: Mesenchymal stem cells for acute lung injury: role of paracrine soluble factors

Use of Autologous Cord Blood Mononuclear Cells Infusion for the Prevention of Bronchopulmonary Dysplasia in Extremely Preterm Neonates: A Study Protocol for a Placebo-Controlled Randomized Multicenter Trial [NCT03053076]

Background: Despite the rapid advance of neonatal care, bronchopulmonary dysplasia (BPD) remains a significant burden for the preterm population, and there is a lack of effective intervention. Stem cell depletion because of preterm birth is regarded as one of the underlying pathological mechanisms for the arrest of alveolar and vascular development. Preclinical and small-sample clinical studies have proven the efficacy and safety of stem cells in treating and preventing lung injury. However, there are currently no randomized clinical trials (RCTs) investigating the use of autologous cord blood mononuclear cells (ACBMNC) for the prevention of BPD in premature infants. The purpose of this study is to investigate the effects of infusion of ACBMNC for the prevention of BPD in preterm neonates <28 weeks. Methods: In this prospective, randomized controlled double-blind multi-center clinical trial, 200 preterm neonates <28 weeks gestation will be randomly assigned to receive intravenous ACBMNC infusion (5 × 107 cells/kg) or placebo (normal saline) within 24 h after birth in a 1:1 ratio using a central randomization system. The primary outcome will be survival without BPD at 36 weeks of postmenstrual age or at discharge, whichever comes first. The secondary outcomes will include the mortality rate, other common preterm complication rates, respiratory support duration, length, and cost of hospitalization, and long-term outcomes after a 2-year follow-up. Conclusion: This will be the first randomized, controlled, blinded trial to evaluate the efficacy of ACBMNC infusion as a prevention therapy for BPD. The results of this trial will provide valuable clinical evidence for recommendations on the management of BPD in extremely preterm infants. Clinical Trial Registration: ClinicalTrials.gov, NCT03053076, registered 02/14/2017, retrospectively registered, https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S0006WN4&selectaction=Edit&uid=U0002PLA&ts=2&cx=9y23d4 (Additional File 2).

Bone marrow stem cells accelerate lung maturation and prevent the LPS-induced delay of morphological and functional fetal lung development in the presence of ErbB4

ErbB4 is a regulator in lung development and disease. Prenatal infection is an important risk factor for the delay of morphologic lung development, while promoting the maturation of the surfactant system. Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to prevent lung injury. We hypothesized that BMSCs in comparison with hematopoietic control stem cells (HPSCs) minimize the lipopolysaccharide (LPS)-induced lung injury only when functional ErbB4 receptor is present. We injected LPS and/or murine green fluorescent protein-labeled BMSCs or HPSCs into the amniotic cavity of transgenic ErbB4^heart mothers at gestational day 17. Fetal lungs were analyzed 24 h later. BMSCs minimized significantly LPS-induced delay in morphological lung maturation consisting of a stereologically measured increase in mesenchyme and septal thickness and a decrease of future airspace and septal surface. This effect was more prominent and significant in the ErbB4^heart+/- lungs, suggesting that the presence of functioning ErbB4 signaling is required. BMSC also diminished the LPS induced increase in surfactant protein (Sftp)a mRNA and decrease in Sftpc mRNA is only seen if ErbB4 is present. The reduction of morphological delay of lung development and of levels of immune-modulating Sftp was more pronounced in the presence of the ErbB4 receptor. Thus, ErbB4 may be required for the protective signaling of BMSCs.

Comparative Analysis of Adipose-Derived Stromal Cells and Their Secretome for Auricular Cartilage Regeneration

Adipose-derived stromal cells (ADSCs) can repair auricular cartilage defects. Furthermore, stem cell secretome may also be a promising biological therapeutic option, which is equal to or even superior to the stem cell. We explored the therapeutic efficacies of ADSCs and their secretome in terms of rabbit auricular cartilage regeneration. ADSCs and their secretome were placed into surgically created auricular cartilage defects. After 4 and 8 weeks, the resected auricles were histopathologically and immunohistochemically examined. We used real-time PCR to determine the levels of genes expressing collagen type II, transforming growth factor-β1 (TGF-β1), and insulin-like growth factor-1 (IGF-1). ADSCs significantly improved auricular cartilage regeneration at 4 and 8 weeks, compared to the secretome and PBS groups, as revealed by gross examination, histopathologically and immunohistochemically. ADSCs upregulated the expression of collagen type II, TGF-β1, and IGF-1 more so than did the secretome or PBS. The expression levels of collagen type II and IGF-1 were significantly higher at 8 weeks than at 4 weeks after ADSC injection. Although ADSCs thus significantly enhanced new cartilage formation, their secretome did not. Therefore, ADSCs may be more effective than their secretome in the repair of auricular cartilage defect.

Liraglutide combined with human umbilical cord mesenchymal stem cell transplantation inhibits beta-cell apoptosis via mediating the ASK1/JNK/BAX pathway in rats with type 2 diabetes

OBJECTIVE

Accumulating evidence suggests an association between beta-cell apoptosis and the ASK1/JNK/BAX pathway. The aim of this study was to investigate the effects of a combined therapy of liraglutide and human umbilical cord mesenchymal stem cells (hUC-MSCs) on the glucose metabolism and islet beta-cell apoptosis, and further explore its relationship to the ASK1/JNK/BAX pathway.

METHOD

Type 2 diabetes mellitus (T2DM) rat model was induced by a high-sugar and high-fat diet and intraperitoneal injection of low-dose streptozotocin (STZ) (30 mg/kg). Three days after STZ injection, diabetic rats were randomly treated with subcutaneous injection of liraglutide (200 μg/kg/12 h) for 8 weeks and or hUC-MSCs (1 × 10⁶ /rat) at the first and fifth weeks. Diabetes-related physical and biochemical parameters, pancreatic histopathological changes, immunohistochemical staining, quantitative real-time polymerase chain reaction, and western blot were used to measure the expression of apoptosis signal-regulating kinase 1 (ASK1), Jun N-terminal kinase (JNK), Bcl-2 associated X protein (BAX), and B-cell lymphoma-2 (Bcl-2).

RESULTS

Eight weeks after liraglutide or human umbilical cord mesenchymal stem cell administration, FPG, HbA_1c , glucagon, body weight, and pancreatic ASK1, JNK, and BAX mRNA and proteins were significantly decreased, and the levels of serum C-p, INS and GLP-1, ratio of insulin positive area, and Bcl-2 expression were significantly increased in three treatment groups compared with T2DM group (P<.05).

CONCLUSION

Liraglutide combined with hUC-MSCs improve glucose metabolism and inhibit islet beta-cell apoptosis in a ASK1/JNK/BAX pathway-dependent manner.

Stem cell therapy for preventing neonatal diseases in the 21st century: Current understanding and challenges

Diseases of the preterm newborn such as bronchopulmonary dysplasia, necrotizing enterocolitis, cerebral palsy, and hypoxic-ischemic encephalopathy continue to be major causes of infant mortality and long-term morbidity. Effective therapies for the prevention or treatment for these conditions are still lacking as recent clinical trials have shown modest or no benefit. Stem cell therapy is rapidly emerging as a novel therapeutic tool for several neonatal diseases with encouraging pre-clinical results that hold promise for clinical translation. However, there are a number of unanswered questions and facets to the development of stem cell therapy as a clinical intervention. There is much work to be done to fully elucidate the mechanisms by which stem cell therapy is effective (e.g., anti-inflammatory versus pro-angiogenic), identifying important paracrine mediators, and determining the timing and type of therapy (e.g., cellular versus secretomes), as well as patient characteristics that are ideal. Importantly, the interaction between stem cell therapy and current, standard-of-care interventions is nearly completely unknown. In this review, we will focus predominantly on the use of mesenchymal stromal cells for neonatal diseases, highlighting the promises and challenges in clinical translation towards preventing neonatal diseases in the 21st century.

Mesenchymal stromal cells in cancer: a review of their immunomodulatory functions and dual effects on tumor progression

Mesenchymal stem or stromal cells (MSCs) are pluripotent cells implicated in a broad range of physiological events, including organogenesis and maintenance of tissue homeostasis as well as tissue regeneration and repair. Because their current definition is somewhat loose – based primarily on their ability to differentiate into a variety of mesenchymal tissues, adhere to plastic, and express, or lack, a handful of cell surface markers – MSCs likely encompass several subpopulations, which may have diverse properties. Their diversity may explain, at least in part, the pleiotropic functions that they display in different physiological and pathological settings. In the context of tissue injury, MSCs can respectively promote and attenuate inflammation during the early and late phases of tissue repair. They may thereby act as sensors of the inflammatory response and secrete mediators that boost or temper the response as required by the stage of the reparatory and regenerative process. MSCs are also implicated in regulating tumor development, in which they are increasingly recognized to play a complex role. Thus, MSCs can both promote and constrain tumor progression by directly affecting tumor cells via secreted mediators and cell–cell interactions and by modulating the innate and adaptive immune response. This review summarizes our current understanding of MSC involvement in tumor development and highlights the mechanistic underpinnings of their implication in tumor growth and progression. © 2020 Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

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.

The role of pulmonary mesenchymal cells in airway epithelium regeneration during injury repair

Background

The airways of mammalian lung are lined with highly specialized cell types that are the target of airborne toxicants and injury. Several epithelial cell types and bone marrow-derived mesenchymal stem cells have been identified to serve as stem cells during injury repair. However, the contributions of endogenous mesenchymal cells to recruitment, expansion or differentiation of stem cells, and repair and reestablishment of the normal composition of airway epithelium following injury have not been addressed.

Methods

The role of mouse pulmonary mesenchymal cells was investigated by lineage tracing using Dermo1-Cre; ROSA^mTmG mice. In experimental models of lung injury by lipopolysaccharide and naphthalene, GFP-labeled Dermo1⁺ mesenchymal cells were traced during injury repair. In vitro lung explant culture treated with or without lipopolysaccharide was also used to verify in vivo data.

Results

During injury repair, a subgroup of GFP-labeled Dermo1⁺ mesenchymal cells were found to contribute to normal repair of the airway epithelium and differentiated into Club cells, ciliated cells, and goblet cells. In Club cell-specific naphthalene injury model, the process of Dermo1⁺ stem cell regenerating epithelial cells was dissected. The Dermo1⁺ stem cells was migrated into the airway epithelium layer sooner after injury, and sequentially differentiated transitionally to epithelial stem cells, such as neuroendocrine cells, and finally to newly differentiated Club cells, ciliated cells, and goblet cells in injury repair.

Conclusion

In this study, a population of Dermo1⁺ mesenchymal stem cell was identified to serve as stem cells in airway epithelial cell regeneration during injury repair. The Dermo1⁺ mesenchymal stem cell differentiated into epithelial stem cells before reestablishing various epithelial cells. These findings have implications for understanding the regulation of lung repair and the potential for usage of mesenchymal stem cells in therapeutic strategies for lung diseases.

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.

Strategies to Enhance Mesenchymal Stem Cell-Based Therapies for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a multifaced disease characterized by the acute onset of hypoxemia, worsened pulmonary compliance, and noncardiogenic pulmonary edema. Despite over five decades of research, specific treatments for established ARDS are still lacking. MSC-based therapies have the advantage of targeting nearly all pathophysiological components of ARDS by means of a variety of secreted trophic factors, exerting anti-inflammatory, antioxidative, immunomodulatory, antiapoptotic, and proangiogenic effects, resulting in significant structural and functional recovery following ARDS in various preclinical models. However, the therapeutic efficacy of transplanted MSCs is limited by their poor engraftment and low survival rate in the injured tissues, major barriers to clinical translation. Accordingly, several strategies have been explored to improve MSC retention in the lung and enhance the innate properties of MSCs in preclinical models of ARDS. To provide a comprehensive and updated view, we summarize a large body of experimental evidence for a variety of strategies directed towards strengthening the therapeutic potential of MSCs in ARDS.

Extracellular vesicles derived from human Wharton's jelly mesenchymal stem cells protect hippocampal neurons from oxidative stress and synapse damage induced by amyloid-β oligomers

Background

Mesenchymal stem cells (MSCs) have been explored as promising tools for treatment of several neurological and neurodegenerative diseases. MSCs release abundant extracellular vesicles (EVs) containing a variety of biomolecules, including mRNAs, miRNAs, and proteins. We hypothesized that EVs derived from human Wharton’s jelly would act as mediators of the communication between hMSCs and neurons and could protect hippocampal neurons from damage induced by Alzheimer’s disease-linked amyloid beta oligomers (AβOs).

Methods

We isolated and characterized EVs released by human Wharton’s jelly mesenchymal stem cells (hMSC-EVs). The neuroprotective action of hMSC-EVs was investigated in primary hippocampal cultures exposed to AβOs.

Results

hMSC-EVs were internalized by hippocampal cells in culture, and this was enhanced in the presence of AβOs in the medium. hMSC-EVs protected hippocampal neurons from oxidative stress and synapse damage induced by AβOs. Neuroprotection by hMSC-EVs was mediated by catalase and was abolished in the presence of the catalase inhibitor, aminotriazole.

Conclusions

hMSC-EVs protected hippocampal neurons from damage induced by AβOs, and this was related to the transfer of enzymatically active catalase contained in EVs. Results suggest that hMSC-EVs should be further explored as a cell-free therapeutic approach to prevent neuronal damage in Alzheimer’s disease.

Therapeutic potential of mesenchymal stem/stromal cell-derived secretome and vesicles for lung injury and disease

Introduction: The acute respiratory distress syndrome (ARDS) is a devastating clinical condition common in patients with respiratory failure. Based largely on numerous preclinical studies and recent Phase I/II clinical trials, administration of stem cells, specifically mesenchymal stem or stromal cells (MSC), as a therapeutic for acute lung injury (ALI) holds great promise. However, concern for the use of stem cells, specifically the risk of iatrogenic tumor formation, remains unresolved. Accumulating evidence now suggest that stem cell-derived conditioned medium (CM) and/or extracellular vesicles (EV) might constitute compelling alternatives.Areas covered: The current review focuses on the preclinical studies testing MSC CM and/or EV as treatment for ALI and other inflammatory lung diseases.Expert opinion: Clinical application of MSC or their secreted CM may be limited by the cost of growing enough cells, the logistic of MSC storage, and the lack of standardization of what constitutes MSC CM. However, the clinical application of MSC EV remains promising, primarily due to the ability of EV to maintain the functional phenotype of the parent cell as a therapeutic. However, utilization of MSC EV will also require large-scale production, the cost of which may be prohibitive unless the potency of the EV can be increased.

Placenta-Derived Mesenchymal Stem Cells Reduce the Interleukin-5 Level Experimentally in Children with Asthma

Background: Mesenchymal stem cells (MSCs) have been investigated as a new treatment option for various diseases in recent years. However, the role of placenta-derived MSCs in children with asthma remains unclear. We assessed the effect of placenta-derived MSCs on T cell immune responses and cytokine IL-5 levels according to cultures in children with and without asthma. Study design: We enrolled children with and without asthma and recorded asthma symptom scores in the asthma group. Blood samples from children were collected to isolate peripheral blood mononuclear cells (PBMCs) and determine the total IgE level. The PBMCs were cultured in vitro with or without MSCs after stimulation with human anti-CD3 and anti-CD28 antibodies (0.5 μg/mL) to evaluate the effect of placenta-derived MSCs. Flow cytometry was performed to detect the activation and proliferation of CD4+ and CD8+ T cells. Pre- and post-culture IL-5 levels were measured in all samples. Results: The percentages of activation and proliferation among CD4+ and CD8+ T cells after coculture with MSCs were significantly lower in the asthma group (P < 0.05). IL-5 levels differed significantly between the PBMC culture and PBMC + MSC (P+S) coculture in the asthma group (P < 0.05). IL-5 levels differed significantly between the PBMC culture and P+S coculture in both the lower (P < 0.05) and higher (P < 0.0005) IgE asthma subgroups. IL-5 levels were also decreased in children with all severities of asthma (P < 0.05). Conclusions: Placenta-derived MSCs exerted an anti-IL-5 effect and reduced the IL-5 level in culture in different subgroups of children with asthma.

Reversal of bleomycin-induced rat pulmonary fibrosis by a xenograft of human umbilical mesenchymal stem cells from Wharton's jelly

Pulmonary fibrosis (PF) is a progressive and irreversible condition with various causes, and no effective treatment has been found to rescue fibrotic lungs. Successful recovery from PF requires inhibiting inflammation, promoting collagen degradation and stimulating alveolar regeneration. Human umbilical mesenchymal stem cells (HUMSCs) not only regulate immune responses but also synthesize and release hyaluronan to improve lung regeneration. This study investigated the feasibility of HUMSC engraftment into rats with bleomycin (BLM)-induced PF to explore HUMSC therapeutic effects/outcomes.

Methods: A unique BLM-induced left-lung-dominated PF animal model was established. Rats were transplanted with low-dose (5×10⁶) or high-dose (2.5×10⁷) HUMSCs on Day 21 after BLM injection. Combinations in co-culture of pulmonary macrophages, fibroblasts, HUMSCs treated with BLM and the same conditions on alveolar epithelia versus HUMSCs were evaluated.

Results: Rats with high-dose HUMSC engraftment displayed significant recovery, including improved blood oxygen saturation levels and respiratory rates. High-dose HUMSC transplantation reversed alveolar injury, reduced cell infiltration and ameliorated collagen deposition. One month posttransplantation, HUMSCs in the rats' lungs remained viable and secreted cytokines without differentiating into alveolar or vascular epithelial cells. Moreover, HUMSCs decreased epithelial-mesenchymal transition in pulmonary inflammation, enhanced macrophage matrix-metallopeptidase-9 (MMP-9) expression for collagen degradation, and promoted toll-like receptor-4 (TLR-4) expression in the lung for alveolar regeneration. In coculture studies, HUMSCs elevated the MMP-9 level in pulmonary macrophages, released hyaluronan into the medium and stimulated the TLR-4 quantity in the alveolar epithelium.

Principal Conclusions: Transplanted HUMSCs exhibit long-term viability in rat lungs and can effectively reverse rat PF.

Adipose-derived mesenchymal stem cells ameliorate the inflammatory reaction in CLP-induced septic acute lung injury rats via sTNFR1

We hypothesized that the adipose-derived mesenchymal stem cells (ADMSCs), which secrete high amounts of soluble molecules, such as soluble tumor necrosis factor receptor 1 (sTNFR1), may ameliorate sepsis-induced acute lung injury (ALI). A total of 120 male adult Sprague-Dawley rats were separated into four groups: the sham control (SC), sepsis induced by cecal ligation and puncture (CLP), CLP-ADMSCs, and CLP-sTNFR1 small interfering RNA (siRNA) groups; CLP groups underwent CLP and then received 1 × 106 ADMSCs with or without knockdown of sTNFR1 intravenously at 1 hr after surgery. Rats were killed at 3, 6, 24, and 48 hr after the SC or CLP procedures. 5-Ethynyl-2'-deoxyuridine-labeled ADMSCs extensively colonized the lungs at 6, 24, and 72 hr after injection. The lung wet/dry (W/D) weight ratios in the CLP group were higher than those in SC group; however, ADMSCs ameliorated the W/D weight ratios following CLP, and this effect was abolished by sTNFR1 siRNA treatment. The levels of serum sTNFR1 and interleukin-10 (IL-10) were higher in the CLP-ADMSCs group and lower in the SC group than in other groups; interestingly, these levels were higher in CLP and CLP-sTNFR1 siRNA groups than in SC group. Tumor necrosis factor-α and IL-6 levels increased significantly after CLP, and ADMSCs could alleviate these changes, but the effect was weakened by sTNFR1 siRNA treatment. The lung cell apoptosis and edema levels were consistent with IL-6 levels among all groups. Therapeutically administered ADMSCs secrete sTNFR1, which most likely protects against ALI in septic rats by ameliorating inflammation and lung edema.

Mesenchymal stem cell-derived extracellular vesicles improve the molecular phenotype of isolated rat lungs during ischemia/reperfusion injury

BACKGROUND

Lung ischemia/reperfusion (IR) injury contributes to the development of severe complications in patients undergoing transplantation. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) exert beneficial actions comparable to those of MSCs without the risks of the cell-based strategy. This research investigated EV effects during IR injury in isolated rat lungs.

METHODS

An established model of 180-minutes ex vivo lung perfusion (EVLP) was used. At 60 minutes EVs (n = 5) or saline (n = 5) were administered. Parallel experiments used labeled EVs to determine EV biodistribution (n = 4). Perfusate samples were collected to perform gas analysis and to assess the concentration of nitric oxide (NO), hyaluronan (HA), inflammatory mediators, and leukocytes. Lung biopsies were taken at 180 minutes to evaluate HA, adenosine triphosphate (ATP), gene expression, and histology.

RESULTS

Compared with untreated lungs, EV-treated organs showed decreased vascular resistance and a rise of perfusate NO metabolites. EVs prevented the reduction in pulmonary ATP caused by IR. Increased medium-high-molecular-weight HA was detected in the perfusate and in the lung tissue of the IR + EV group. Significant differences in cell count on perfusate and tissue samples, together with induction of transcription and synthesis of chemokines, suggested EV-dependent modulation of leukocyte recruitment. EVs upregulated genes involved in the resolution of inflammation and oxidative stress. Biodistribution analysis showed that EVs were retained in the lung tissue and internalized within pulmonary cells.

CONCLUSIONS

This study shows multiple novel EV influences on pulmonary energetics, tissue integrity, and gene expression during IR. The use of cell-free therapies during EVLP could constitute a valuable strategy for reconditioning and repair of injured lungs before transplantation.

Fibrosis in tissue engineering and regenerative medicine: treat or trigger?

Fibrosis is a life-threatening pathological condition resulting from a dysfunctional tissue repair process. There is no efficient treatment and organ transplantation is in many cases the only therapeutic option. Here we review tissue engineering and regenerative medicine (TERM) approaches to address fibrosis in the cardiovascular system, the kidney, the lung and the liver. These strategies have great potential to achieve repair or replacement of diseased organs by cell- and material-based therapies. However, paradoxically, they might also trigger fibrosis. Cases of TERM interventions with adverse outcome are also included in this review. Furthermore, we emphasize the fact that, although organ engineering is still in its infancy, the advances in the field are leading to biomedically relevant in vitro models with tremendous potential for disease recapitulation and development of therapies. These human tissue models might have increased predictive power for human drug responses thereby reducing the need for animal testing.

Mesenchymal Stem Cell-Conditioned Medium Induces Neutrophil Apoptosis Associated with Inhibition of the NF-κB Pathway in Endotoxin-Induced Acute Lung Injury

The immunomodulatory effects of mesenchymal stem cells (MSCs) are established. However, the effects of MSCs on neutrophil survival in acute lung injury (ALI) remain unclear. The goal of this study was to investigate the effect of an MSC-conditioned medium (MSC-CM) on neutrophil apoptosis in endotoxin-induced ALI. In this study, an MSC-CM was delivered via tail vein injection to wild-type male C57BL/6 mice 4 h after an intratracheal injection of lipopolysaccharide (LPS). Twenty-four hours later, bronchoalveolar lavage fluid (BALF) and lung tissue were collected to perform histology, immunohistochemistry, apoptosis assay of neutrophil, enzyme-linked immunosorbent assays, and an electrophoretic mobility shift assay. Human neutrophils were also collected from patients with sepsis-induced acute respiratory distress syndrome (ARDS). Human neutrophils were treated in vitro with LPS, with or without subsequent MSC-CM co-treatment, and were then analyzed. Administration of the MSC-CM resulted in a significant attenuation of histopathological changes, the levels of interleukin-6 and macrophage inflammatory protein 2, and neutrophil accumulation in mouse lung tissues of LPS-induced ALI. Additionally, MSC-CM therapy enhanced the apoptosis of BALF neutrophils and reduced the expression of the anti-apoptotic molecules, Bcl-xL and Mcl-1, both in vivo and in vitro experiments. Furthermore, phosphorylated and total levels of nuclear factor (NF)-κB p65 were reduced in lung tissues from LPS + MSC-CM mice. Human MSC-CM also reduced the activity levels of NF-κB and matrix metalloproteinase-9 in the human neutrophils from ARDS patients. Thus, the results of this study suggest that the MSC-CM attenuated LPS-induced ALI by inducing neutrophil apoptosis, associated with inhibition of the NF-κB pathway.

Mesenchymal Stem Cell-Based Therapy of Inflammatory Lung Diseases: Current Understanding and Future Perspectives

During acute or chronic lung injury, inappropriate immune response and/or aberrant repair process causes irreversible damage in lung tissue and most usually results in the development of fibrosis followed by decline in lung function. Inhaled corticosteroids and other anti-inflammatory drugs are very effective in patients with inflammatory lung disorders, but their long-term use is associated with severe side effects. Accordingly, new therapeutic agents that will attenuate ongoing inflammation and, at the same time, promote regeneration of injured alveolar epithelial cells are urgently needed. Mesenchymal stem cells (MSCs) are able to modulate proliferation, activation, and effector function of all immune cells that play an important role in the pathogenesis of acute and chronic inflammatory lung diseases. In addition to the suppression of lung-infiltrated immune cells, MSCs have potential to differentiate into alveolar epithelial cells in vitro and, accordingly, represent new players in cell-based therapy of inflammatory lung disorders. In this review article, we described molecular mechanisms involved in MSC-based therapy of acute and chronic pulmonary diseases and emphasized current knowledge and future perspectives related to the therapeutic application of MSCs in patients suffering from acute respiratory distress syndrome, pneumonia, asthma, chronic obstructive pulmonary diseases, and idiopathic pulmonary fibrosis.

Mesenchymal Stem Cells Increase Alveolar Differentiation in Lung Progenitor Organoid Cultures

Lung epithelial cell damage and dysfunctional repair play a role in the development of lung disease. Effective repair likely requires the normal functioning of alveolar stem/progenitor cells. For example, we have shown in a mouse model of bronchopulmonary dysplasia (BPD) that mesenchymal stem cells (MSC) protect against hyperoxic lung injury at least in part by increasing the number of Epcam⁺ Sca-1⁺ distal lung epithelial cells. These cells are capable of differentiating into both small airway (CCSP⁺) and alveolar (SPC⁺) epithelial cells in three-dimensional (3D) organoid cultures. To further understand the interactions between MSC and distal lung epithelial cells, we added MSC to lung progenitor 3D cultures. MSC stimulated Epcam⁺ Sca-1⁺ derived organoid formation, increased alveolar differentiation and decreased self-renewal. MSC-conditioned media was sufficient to promote alveolar organoid formation, demonstrating that soluble factors secreted by MSC are likely responsible for the response. This work provides strong evidence of a direct effect of MSC-secreted factors on lung progenitor cell differentiation.

Mesenchymal Stromal Cell Exosomes Ameliorate Experimental Bronchopulmonary Dysplasia and Restore Lung Function through Macrophage Immunomodulation

RATIONALE

Mesenchymal stem/stromal cell (MSC) therapies have shown promise in preclinical models of pathologies relevant to newborn medicine, such as bronchopulmonary dysplasia (BPD). We have reported that the therapeutic capacity of MSCs is comprised in their secretome, and demonstrated that the therapeutic vectors are exosomes produced by MSCs (MSC-exos).

OBJECTIVES

To assess efficacy of MSC-exo treatment in a preclinical model of BPD and to investigate mechanisms underlying MSC-exo therapeutic action.

METHODS

Exosomes were isolated from media conditioned by human MSC cultures. Newborn mice were exposed to hyperoxia (HYRX; 75% O₂), treated with exosomes on Postnatal Day (PN) 4 and returned to room air on PN7. Treated animals and appropriate controls were harvested on PN7, -14, or -42 for assessment of pulmonary parameters.

MEASUREMENTS AND MAIN RESULTS

HYRX-exposed mice presented with pronounced alveolar simplification, fibrosis, and pulmonary vascular remodeling, which was effectively ameliorated by MSC-exo treatment. Pulmonary function tests and assessment of pulmonary hypertension showed functional improvements after MSC-exo treatment. Lung mRNA sequencing demonstrated that MSC-exo treatment induced pleiotropic effects on gene expression associated with HYRX-induced inflammation and immune responses. MSC-exos modulate the macrophage phenotype fulcrum, suppressing the proinflammatory "M1" state and augmenting an antiinflammatory "M2-like" state, both in vitro and in vivo.

CONCLUSIONS

MSC-exo treatment blunts HYRX-associated inflammation and alters the hyperoxic lung transcriptome. This results in alleviation of HYRX-induced BPD, improvement of lung function, decrease in fibrosis and pulmonary vascular remodeling, and amelioration of pulmonary hypertension. The MSC-exo mechanism of action is associated with modulation of lung macrophage phenotype.

Upcycling umbilical cords: bridging regenerative medicine with neonatology

Preterm birth is a major health concern that affects 10% of all worldwide deliveries. Many preterm infants are discharged from the hospital with morbidities that lead to an increased risk for neurodevelopmental impairment, recurrent hospitalizations, and life-long conditions. Unfortunately, the treatment of these conditions is palliative rather than curative, which calls for novel and innovative strategies. Progress in regenerative medicine has offered therapeutic options for many of these conditions. Specifically, human umbilical cord mesenchymal stem cells (MSCs) and cord blood (UCB) cells have shown promise in treating adult-onset diseases. Unlike bone-marrow and embryonic derived stem cells, umbilical cord-derived cells are easily and humanely obtained, have low immunogenicity, and offer the potential of autologous therapy. While there are several studies to uphold the efficacy of umbilical cord MSCs in adult therapies, there remains an unmet need for the investigation of its use in treating neonates. The purpose of this review is to provide a summary of current information on the potential therapeutic benefits and clinical applicability of umbilical cord MSCs and UCB cells. Promising preclinical studies have now led to a research movement that is focusing on cell-based therapies for preterm infants.

Insights into animal models for cell-based therapies in translational studies of lung diseases: Is the horse with naturally occurring asthma the right choice?

Human asthma is a widespread disease associated with chronic inflammation of the airways, leading to loss of quality of life, disability and death. Corticosteroid administration is the mainstream treatment for asthmatic patients. Corticosteroids reduce airway obstruction and improve quality of life, although symptoms persist despite treatment in many patients. Moreover, available therapies failed to reverse the lung pathology present in asthma. Animal models, mostly rats and mice, in which the disease is experimentally induced, have been studied to identify new therapeutic targets for human asthma. Alternative animal models could include horses in which naturally occurring asthma could represent an important step to test therapies, potentially designed around mouse studies, before being translated to human testing. Horses naturally suffer from asthma, which has striking parallels with human asthma. Severe equine asthma (SEA) is characterized by reversible bronchospasms and neutrophil accumulation in the lungs immunologically mediated mainly by Th2. Moreover, the pulmonary remodelling that occurs in SEA closely resembles that of human asthma, making the equine model unique for investigation of tissue repair and new therapies. Cell therapy, consisting on mesenchymal stromal cells (MSCs) and derivatives (conditioned medium and extracellular vesicles), could represent a novel therapeutic contribution for tissue regeneration. Cell therapy may prove advantageous over conventional therapy in that it may repair or regenerate the site of injury and reduce the reaction to allergens, rather than simply modulating the inflammatory process.

The therapeutic effects of bone marrow-derived mesenchymal stromal cells in the acute lung injury induced by sulfur mustard

Background

Sulfur mustard (SM) is a notorious chemical warfare agent that can cause severe acute lung injury (ALI), in addition to other lesions. Currently, effective medical countermeasures for SM are lacking. Bone marrow-derived mesenchymal stromal cells (BMSCs) possess self-renewal and multipotent differentiation capacity. BMSCs can also migrate to inflammation and injury sites and exert anti-inflammatory and tissue repair functions. Here, we report the curative effect of BMSCs on SM-induced ALI in a mouse model.

Methods

Mice BMSCs were injected into mice via the tail vein 24 h after SM exposure. The distribution of BMSCs in mice was detected by fluorescence imaging. The therapeutic potential of BMSCs was evaluated by the calculating survival rate. The effects of BMSCs on lung tissue injury and repair assessment were examined by staining with H&E and measuring the lung wet/dry weight ratio, BALF protein level, and respiratory function. The effects of BMSCs on the infiltration and phenotypic alteration of inflammatory cells were analyzed by immunohistochemistry and flow cytometry. The levels of chemokines and inflammatory cytokines were examined using the Luminex Performance Assay and ELISA. RNA interference, western blotting, and ELISA were applied to explore the role of the TLR4 signaling pathway in the anti-inflammatory effects of BMSCs. The extent of tissue repair was analyzed by ELISA, western blotting, and immunohistochemistry.

Results

Fluorescence imaging indicated that the lung is the major target organ of BMSCs after injection. The injection of BMSCs significantly improved the survival rate (p < 0.05), respiratory function, and related lung damage indexes (wet/dry weight ratio, total proteins in BALF, etc.) in mice. BMSC administration also reduced the level of pro-inflammatory cytokines, chemokines, and inflammatory cell infiltration, as well as affected the balances of M1/M2 and Th17/Treg. Furthermore, solid evidence regarding the effects of BMSCs on the increased secretion of various growth factors, the differentiation of alveolar epithelial cells, and the enhancement of cell barrier functions was also observed.

Conclusion

BMSCs displayed protective effects against SM-induced ALI by alleviating inflammation and promoting tissue repair. The present study provides a strong experimental basis in a mouse model and suggests possible application for future cell therapy.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1189-x) contains supplementary material, which is available to authorized users.

Paving the Road for Mesenchymal Stem Cell-Derived Exosome Therapy in Bronchopulmonary Dysplasia and Pulmonary Hypertension

Bronchopulmonary dysplasia (BPD) is a chronic neonatal lung disease characterized by inflammation and arrest of alveolarization. Its common sequela, pulmonary hypertension (PH), presents with elevated pulmonary vascular resistance associated with remodeling of the pulmonary arterioles. Despite notable advancements in neonatal medicine, there is a severe lack of curative treatments to help manage the progressive nature of these diseases. Numerous studies in preclinical models of BPD and PH have demonstrated that therapies based on mesenchymal stem/stromal cells (MSCs) can resolve pulmonary inflammation and ameliorate the severity of disease. Recent evidence suggests that novel, cell-free approaches based on MSC-derived exosomes (MEx) might represent a compelling therapeutic alternative offering major advantages over treatments based on MSC transplantation. Here, we will discuss the development of MSC-based therapies, stressing the centrality of paracrine action as the actual vector of MSC therapeutic functionality, focusing on MEx. We will briefly present our current understanding of the biogenesis and secretion of MEx, and discuss potential mechanisms by which they afford such beneficial effects, including immunomodulation and restoration of homeostasis in diseased states. We will also review ongoing clinical trials using MSCs as treatment for BPD that pave the way for bringing cell-free, MEx-based therapeutics from the bench to the NICU setting.

Oxidative Stress and Bronchopulmonary Dysplasia: Evidences From Microbiomics, Metabolomics, and Proteomics

Bronchopulmonary dysplasia is a major issue affecting morbidity and mortality of surviving premature babies. Preterm newborns are particularly susceptible to oxidative stress and infants with bronchopulmonary dysplasia have a typical oxidation pattern in the early stages of this disease, suggesting the important role of oxidative stress in its pathogenesis. Bronchopulmonary dysplasia is a complex disease where knowledge advances as new investigative tools become available. The explosion of the "omics" disciplines has recently affected BPD research. This review focuses on the new evidence coming from microbiomics, metabolomics and proteomics in relation to oxidative stress and pathogenesis of bronchopulmonary dysplasia. Since the pathogenesis is not yet completely understood, information gained in this regard would be important for planning an efficacious prevention and treatment strategy for the future.

LL-37 and its analog FF/CAP18 attenuate neutrophil migration in sepsis-induced acute lung injury

INTRODUCTION

Sepsis can result in acute lung injury. LL-37 is a small cationic host defense peptide involved in anti-inflammatory. In the current study, it was hypothesized that antimicrobial peptide LL-37 could play a protective role in attenuating the progression of sepsis-induced acute lung injury.

METHODS

Forty male C57BL/6 mice were induced into sepsis using cecal ligation and puncture, and subsequently administered with recombinant mouse osteopontin. Peptides LL-37, the LL-37 analog (FF/CAP18, called sLL-37), or normal saline was intravenously administered into septic mice for 20 hours. Then, proinflammatory cytokines (IL-6 and IL-1β), acute lung injury markers (alanine aminotransferase [ALT], aspartate aminotransferase [AST], and lactate dehydrogenase [LDH]), the neutrophil infiltration marker (myeloperoxidase [MPO]), and neutrophil infiltration were detected. Furthermore, the neutrophil migration and expression of migration-related factors (focal adhesion kinase [FAK], ERK, and P38) in differentiated HL-60 cells were detected.

RESULTS

Septic mice had upregulated IL-6, IL-1β, ALT, AST, LDH, MPO, p-FAK, p-ERK, and p-P38, infiltrated neutrophils, and migrated neutrophil-like HL-60 cells. In contrast, the administration of peptide LL-37 and sLL-37 inhibited all these changes. Compared with septic mice, it was found that proinflammatory cytokines, lung injury markers, MPO, and infiltrated neutrophils decreased in mice treated with LL-37 and sLL-37. In addition, the migrated neutrophil-like HL-60 cells and activated p-FAK, p-ERK, and p-P38 proteins were suppressed by LL-37 and sLL-37 treatments.

CONCLUSIONS

Peptide LL-37 and its analog sLL-37 attenuated the progression of sepsis-induced acute lung injury by inhibiting neutrophil infiltration and migration through the FAK, ERK, and P38 pathways.

Therapeutic potential of products derived from mesenchymal stem/stromal cells in pulmonary disease

Multipotent mesenchymal stem/stromal cells (MSCs) possess robust self-renewal characteristics and the ability to differentiate into tissue-specific cells. Their therapeutic potential appears promising as evident from their efficacy in several animal models of pulmonary disorders as well as early-phase clinical trials of acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). Such therapeutic efficacy might be attributed to MSC-derived products (the "secretome"), namely conditioned media (CM) and extracellular vesicles (EVs), which have been shown to play pivotal roles in the regenerative function of MSCs. Importantly, the EVs secreted by MSCs can transfer a variety of bioactive factors to modulate the function of recipient cells via various mechanisms, including ligand-receptor interactions, direct membrane fusion, endocytosis, or phagocytosis.Herein, we review the current state-of-the-science of MSC-derived CM and EVs as potential therapeutic agents in lung diseases. We suggest that the MSC-derived secretome might be an appropriate therapeutic agent for treating aggressive pulmonary disorders because of biological and logistical advantages over live cell therapy. Nonetheless, further studies are warranted to elucidate the safety and efficacy of these components in combating pulmonary diseases.

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

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

Nanotherapies for micropreemies: Stem cells and the secretome in bronchopulmonary dysplasia

Improved survival of extreme preterm infants has made the task of protecting the ever more immature lung from injury more challenging. As a consequence, the incidence of bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, has remained unchanged. The multifactorial disease pathogenesis of BPD - including amongst others inflammation, oxidative stress and excessive lung stretch - adds further complexity to finding effective therapies that would prevent lung injury and promote lung growth. Mesenchymal stromal cells and the discovery of their pleiotropic effects represent an appealing approach for the prevention of BPD. Mesenchymal stromal cells do not engraft but exert their therapeutic benefit through paracrine effects. These paracrine effects seem to be mediated through the release of nanosized extra-cellular vesicles used for cell-cell communication. This review will summarize our current knowledge on these potential nanotherapies for micropreemies.

Therapeutic use of mesenchymal stem cell-derived extracellular vesicles in acute lung injury

Acute respiratory distress syndrome is a major cause of respiratory failure in critically ill patients. Despite extensive research into its pathophysiology, mortality remains high. No effective pharmacotherapy exists. Based largely on numerous preclinical animal studies, administration of mesenchymal stem or stromal cell (MSC) as a therapeutic for acute lung injury (ALI) holds great promise, and Phase I and II clinical trials are currently under way internationally. However, concern for the use of stem cells, specifically the risk of iatrogenic tumor formation, as well as the prohibitive cost of production, storage, and distribution of cells in bone marrow transplant facilities, may limit access to this lifesaving therapy. Accumulating evidence now suggest that novel stem cell-derived therapies, including MSC-conditioned medium and extracellular vesicles (EVs) released from MSCs, might constitute compelling alternatives. The current review summarizes the preclinical studies testing MSC EVs as treatment for ALI and other inflammatory lung diseases. While certain logistic obstacles limit the clinical applications of MSC-conditioned medium such as the volume required for treatment and lack of standardization of what constitutes the components of conditioned medium, the therapeutic application of MSC EVs remains promising, primarily due to ability of EVs to maintain the functional phenotype of the parent cell. However, utilization of MSC EVs will require large-scale production and standardization concerning identification, characterization, and quantification.

Mesenchymal stem cells overexpressing heme oxygenase-1 ameliorate lipopolysaccharide-induced acute lung injury in rats

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and potentially lethal clinical syndromes characterized by acute respiratory failure resulting from excessive pulmonary inflammation, noncardiogenic pulmonary edema, and alveolar-capillary barrier disruption. At present, there is no effective and specific therapy for ALI/ARDS. Mesenchymal stem cells (MSCs) have well-known therapeutic potential in patients with ALI/ARDS. Heme oxygenase-1 (HO-1), a cytoprotective enzyme, possesses antioxidative, anti-inflammatory, and antiapoptotic effects. Thus, a combination of MSC transplantation with HO-1 delivery may have an additional protective effect against ALI/ARDS. This study investigated the effect of HO-1-modified bone-marrow-derived MSCs (MSCs-HO-1) on lipopolysaccharide (LPS)-induced ALI and its underlying mechanisms. We established MSCs-HO-1 through lentiviral transduction. The ALI rat model was established by successive LPS inhalations following injection with MSCs-HO-1. The survival rate, histological changes in the lungs, total protein concentration and neutrophil counts in bronchoalveolar lavage fluid, lung wet/dry weight ratio, cytokine levels in serum and lungs, nuclear transcription factor-κB activity, and protein expression of Toll-like receptor 4 signaling adaptors were examined. Furthermore, the cell viability, apoptosis, and paracrine activity of MSCs-HO-1 were examined under inflammatory stimuli in vitro. MSCs-HO-1 injection improved these parameters compared with primary unmodified MSCs. Moreover, MSCs-HO-1 had superior prosurvival and antiapoptotic properties and enhanced paracrine functions in vitro. Therefore, MSCs-HO-1 exert an enhanced protective effect to alleviate LPS-induced ALI in rats, and the mechanisms may be partially associated with superior prosurvival, antiapoptosis, and enhanced paracrine functions of MSCs-HO-1. These findings provide a novel insight into MSC-based therapeutic strategies for treating ALI/ARDS.

LincRNA-p21 promotes mesenchymal stem cell migration capacity and survival through hypoxic preconditioning

Background

Mesenchymal stem cells (MSCs) derived from bone marrow have potent stabilizing effects for the treatment of acute respiratory distress syndrome (ARDS). However, low efficiency and survival in MSC homing to injured lung tissue remains to be solved. Therefore, the aim of this study was to assess whether large intergenic noncoding RNA (LincRNA)-p21 promote MSC migration and survival capacity through hypoxic preconditioning in vitro.

Methods

MSCs were cultured and divided into the normoxia culture group (20% O2) and hypoxia culture group (1% O2). To determine roles and mechanisms, lentivirus vector-mediated LincRNA-p21 knockdown of MSCs and hypoxia-inducible factor (HIF-1α) inhibitor KC7F2 were introduced. Additionally, MSC migration was analyzed by scratch test and transwell migration assays. MSC proliferation was tested by cell counting kit-8 and trypan blue dye. Apoptosis was detected by Annexin V-PE/7-AAD stained flow cytometry. Moreover, LincRNA-p21 and HIF-1α mRNA was measured by reverse transcription-polymerase chain reaction, and HIF-1α and CXCR4/7 protein were assayed by western blot (WB) or enzyme-linked immunosorbent assay (ELISA). Apoptosis protein caspase-3 and cleaved-caspase-3 were investigated by WB analysis. Considering interactions between VHL and HIF-1α under LincRNA-p21 effect, co-immunoprecipitation was detected.

Results

Hypoxic preconditioning MSC promoted migration capacity and MSC survival than normoxia culture group. MSCs induced by hypoxic preconditioning evoked an increase in expression of LincRNA-p21, HIF-1α, and CXCR4/7(both were chemokine stromal-derived factor-1(SDF-1) receptors). Contrarily, blockade of LincRNA-p21 by shRNA and HIF-1α inhibitor KC7F2 abrogated upregulation of hypoxic preconditioning induced CXCR4/7 in MSCs, cell migration, and survival. Furthermore, co-immunoprecipitation assay revealed that hypoxic preconditioning isolated VHL and HIF-1α protein by increasing HIF-1α expression.

Conclusions

Hypoxic preconditioning was identified as a promoting factor of MSC migration and survival capacity. LincRNA-p21 promotes MSC migration and survival capacity through HIF-1α/CXCR4 and CXCR7 pathway under hypoxic preconditioning in vitro.

Exosomes Secreted from Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells Accelerate Skin Cell Proliferation

Induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) serve as a unique source for cell therapy. We investigated whether exosomes from iMSCs promote the proliferation of human keratinocytes (HaCaT) and human dermal fibroblasts (HDFs). iPSCs were established from human Wharton's jelly MSCs and were allowed to differentiate into iMSCs. Exosomes were collected from the culture supernatant of MSCs (MSC-exo) and iMSCs (iMSC-exo), and their characteristics were investigated. Both exosome types possessed basic characteristics of exosomes and were taken up by skin cells in vitro and in vivo. A significant increase in HaCaT proliferation was observed with iMSC-exo, although both exosomes increased the viability and cell cycle progression in HaCaT and HDFs. No significant difference was observed in the closure of wound scratch and the expression of reparative genes between cells treated with the two exosome types. Both exosomes enhanced the secretion of collagen in HaCaT and HDFs; however, an increase in fibronectin level was observed only in HaCaT, and this effect was better with iMSC-exo treatment. Only iMSC-exo increased the phosphorylation of extracellular signal-regulated kinase (ERK)-1/2. Our results indicate that iMSC-exo promote the proliferation of skin cells by stimulating ERK1/2 and highlight the application of iMSCs for producing exosomes.

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.

Umbilical cord-derived mesenchymal stem (stromal) cells for treatment of severe sepsis: aphase 1 clinical trial

The aim of this phase 1 clinical trial was to test the safety and feasibility of a single dose of allogeneic umbilical cord-derived mesenchymal stem cells (MSCs) in patients with severe sepsis. This is a single-center, open-label, dose-escalation phase 1 clinical trial of a single dose of intravenous MSCs in patients with severe sepsis. We enrolled 15 patients who averagely divided into low (1 × 10⁶ cells/kg), intermediate (2 × 10⁶ cells/kg), and high (3 × 10⁶ cells/kg) dosing cohorts. Primary outcomes included the incidence of infusion-associated events and serious adverse events. Secondary outcomes included systemic endpoints, mortality, and inflammation biologic markers. A historical case-matched comparison group was set as the control. This study enrolled 15 patients (10 male and 5 female), with a median age of 58. Compared to those in the historical, case-matched group, neither there were infusion-associated serious events or treatment-related adverse events in any of the 15 patients in this trial, nor were there any safety or efficacy signals for serious adverse events or the measured cytokines. A single intravenous infusion of allogeneic MSCs up to a dose of 3 × 10⁶ cells/kg was safe and well tolerated in 15 patients with severe sepsis.

Macrophage Immunomodulation: The Gatekeeper for Mesenchymal Stem Cell Derived-Exosomes in Pulmonary Arterial Hypertension?

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of the pulmonary arteries, increased pulmonary infiltrates, loss of vascular cross-sectional area, and elevated pulmonary vascular resistance. Despite recent advances in the management of PAH, there is a pressing need for the development of new tools to effectively treat and reduce the risk of further complications. Dysregulated immunity underlies the development of PAH, and macrophages orchestrate both the initiation and resolution of pulmonary inflammation, thus, manipulation of lung macrophage function represents an attractive target for emerging immunomodulatory therapies, including cell-based approaches. Indeed, mesenchymal stem cell (MSC)-based therapies have shown promise, effectively modulating the macrophage fulcrum to favor an anti-inflammatory, pro-resolving phenotype, which is associated with both histological and functional benefits in preclinical models of pulmonary hypertension (PH). The complex interplay between immune system homeostasis and MSCs remains incompletely understood. Here, we highlight the importance of macrophage function in models of PH and summarize the development of MSC-based therapies, focusing on the significance of MSC exosomes (MEx) and the immunomodulatory and homeostatic mechanisms by which such therapies may afford their beneficial effects.

The Importance of Biophysical and Biochemical Stimuli in Dynamic Skeletal Muscle Models

Classical approaches to engineer skeletal muscle tissue based on current regenerative and surgical procedures still do not meet the desired outcome for patient applications. Besides the evident need to create functional skeletal muscle tissue for the repair of volumetric muscle defects, there is also growing demand for platforms to study muscle-related diseases, such as muscular dystrophies or sarcopenia. Currently, numerous studies exist that have employed a variety of biomaterials, cell types and strategies for maturation of skeletal muscle tissue in 2D and 3D environments. However, researchers are just at the beginning of understanding the impact of different culture settings and their biochemical (growth factors and chemical changes) and biophysical cues (mechanical properties) on myogenesis. With this review we intend to emphasize the need for new in vitro skeletal muscle (disease) models to better recapitulate important structural and functional aspects of muscle development. We highlight the importance of choosing appropriate system components, e.g., cell and biomaterial type, structural and mechanical matrix properties or culture format, and how understanding their interplay will enable researchers to create optimized platforms to investigate myogenesis in healthy and diseased tissue. Thus, we aim to deliver guidelines for experimental designs to allow estimation of the potential influence of the selected skeletal muscle tissue engineering setup on the myogenic outcome prior to their implementation. Moreover, we offer a workflow to facilitate identifying and selecting different analytical tools to demonstrate the successful creation of functional skeletal muscle tissue. Ultimately, a refinement of existing strategies will lead to further progression in understanding important aspects of muscle diseases, muscle aging and muscle regeneration to improve quality of life of patients and enable the establishment of new treatment options.

Extracellular Vesicles, Ageing, and Therapeutic Interventions

A more comprehensive understanding of the human ageing process is required to help mitigate the increasing burden of age-related morbidities in a rapidly growing global demographic of elderly individuals. One exciting novel strategy that has emerged to intervene involves the use of extracellular vesicles to engender tissue regeneration. Specifically, this employs their molecular payloads to confer changes in the epigenetic landscape of ageing cells and ameliorate the loss of functional capacity. Understanding the biology of extracellular vesicles and the specific roles they play during normative ageing will allow for the development of novel cell-free therapeutic interventions. Hence, the purpose of this review is to summarise the current understanding of the mechanisms that drive ageing, critically explore how extracellular vesicles affect ageing processes and discuss their therapeutic potential to mitigate the effects of age-associated morbidities and improve the human health span.

Protective Effects of Neural Crest-Derived Stem Cell-Conditioned Media against Ischemia-Reperfusion-Induced Lung Injury in Rats

Current treatments for ischemia-reperfusion (IR)-induced acute lung injury are limited. Mesenchymal stem cell-conditioned medium (CM) has been reported to attenuate lung injury. Neural crest stem cells (NCSCs), a type of multipotent stem cells, are more easily obtained than mesenchymal stem cells. We hypothesize that NCSC-CM has anti-inflammatory properties that could protect against IR-induced lung injury in rats. In this study, NCSC-CM was derived from rat NCSCs. Typical acute lung injury was induced by 30-min ischemia followed by 90-min reperfusion in adult male Sprague–Dawley rats. Bronchoalveolar lavage fluid (BALF) and lung tissues were collected to analyze the degree of lung injury after the experiment. NCSC-CM was administered before ischemia and after reperfusion. NCSC-CM treatment significantly attenuated IR-induced lung edema, as indicated by decreases in pulmonary vascular permeability, lung weight gain, wet to dry weight ratio, lung weight to body weight ratio, pulmonary arterial pressure, and protein level in BALF. The levels of tumor necrosis factor-α and interleukin-6 in the BALF were also significantly decreased. Additionally, NCSC-CM improved lung pathology and neutrophil infiltration in the lung tissue, and significantly suppressed nuclear factor (NF)-κB activity and IκB-α degradation in the lung. However, heating NCSC-CM eliminated these protective effects. Our experiment demonstrates that NCSC-CM treatment decreases IR-induced acute lung injury and that the protective mechanism may be attributable to the inhibition of NF-κB activation and the inflammatory response. Therefore, NCSC-CM may be a novel approach for treating IR-induced lung injury.

Novel mechanisms regulating endothelial barrier function in the pulmonary microcirculation

The pulmonary epithelial and vascular endothelial cell layers provide two sequential physical and immunological barriers that together form a semi-permeable interface and prevent alveolar and interstitial oedema formation. In this review, we focus specifically on the continuous endothelium of the pulmonary microvascular bed that warrants strict control of the exchange of gases, fluid, solutes and circulating cells between the plasma and the interstitial space. The present review provides an overview of emerging molecular mechanisms that permit constant transcellular exchange between the vascular and interstitial compartment, and cause, prevent or reverse lung endothelial barrier failure under experimental conditions, yet with a clinical perspective. Based on recent findings and at times seemingly conflicting results we discuss emerging paradigms of permeability regulation by altered ion transport as well as shifts in the homeostasis of sphingolipids, angiopoietins and prostaglandins.

Stem cell therapy in chronic obstructive pulmonary disease. How far is it to the clinic?

Chronic obstructive pulmonary disease (COPD) is a respiratory disease that has a major impact worldwide. The currently-available drugs mainly focus on relieving the symptoms of COPD patients. However, in the latter stages of the disease, the airways become largely obstructed and lung parenchyma becomes destructed due to underlying inflammation. The inappropriate repair of lung tissue after injury may contribute to the development of disease. Novel regenerative therapeutic approaches have been investigated with the aim of repairing or replacing the injured functional structures of the respiratory system. Endogenous and exogenous sources of stem cells are available for the treatment of many diseases. Stem cell therapy is newly introduced to the field of COPD. Currently the research is in its infancy; however, the field is profoundly growing. Previous studies suggest that cell-based therapies and novel bioengineering approaches may be potential therapeutic strategies for lung repair and remodelling. In this paper, we review the current evidence of stem cell therapy in COPD.

Early gestational mesenchymal stem cell secretome attenuates experimental bronchopulmonary dysplasia in part via exosome-associated factor TSG-6

BACKGROUND

Mesenchymal stem cells (MSCs) are promising tools for the treatment of human lung disease and other pathologies relevant to newborn medicine. Recent studies have established MSC exosomes (EXO), as one of the main therapeutic vectors of MSCs in mouse models of multifactorial chronic lung disease of preterm infants, bronchopulmonary dysplasia (BPD). However, the mechanisms underlying MSC-EXO therapeutic action are not completely understood. Using a neonatal mouse model of human BPD, we evaluated the therapeutic efficiency of early gestational age (GA) human umbilical cord (hUC)-derived MSC EXO fraction and its exosomal factor, tumor necrosis factor alpha-stimulated gene-6 (TSG-6).

METHODS

Conditioned media (CM) and EXO fractions were isolated from 25 and 30 weeks GA hUC-MSC cultures grown in serum-free media (SFM) for 24 h. Newborn mice were exposed to hyperoxia (> 95% oxygen) and were given intraperitoneal injections of MSC-CM or MSC-CM EXO fractions at postnatal (PN) day 2 and PN4. They were then returned to room air until PN14 (in a mouse model of severe BPD). The treatment regime was followed with (rh)TSG-6, TSG-6-neutralizing antibody (NAb), TSG-6 (si)RNA-transfected MSC-CM EXO and their appropriate controls. Echocardiography was done at PN14 followed by harvesting of lung, heart and brain for assessment of pathology parameters.

RESULTS

Systemic administration of CM or EXO in the neonatal BPD mouse model resulted in robust improvement in lung, cardiac and brain pathology. Hyperoxia-exposed BPD mice exhibited pulmonary inflammation accompanied by alveolar-capillary leakage, increased chord length, and alveolar simplification, which was ameliorated by MSC CM/EXO treatment. Pulmonary hypertension and right ventricular hypertrophy was also corrected. Cell death in brain was decreased and the hypomyelination reversed. Importantly, we detected TSG-6, an immunomodulatory glycoprotein, in EXO. Administration of TSG-6 attenuated BPD and its associated pathologies, in lung, heart and brain. Knockdown of TSG-6 by NAb or by siRNA in EXO abrogated the therapeutic effects of EXO, suggesting TSG-6 as an important therapeutic molecule.

CONCLUSIONS

Preterm hUC-derived MSC-CM EXO alleviates hyperoxia-induced BPD and its associated pathologies, in part, via exosomal factor TSG-6. The work indicates early systemic intervention with TSG-6 as a robust option for cell-free therapy, particularly for treating BPD.

Protective Effect of Mesenchymal Stem Cells Against the Development of Intracranial Aneurysm Rupture in Mice

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem or stromal cells found in multiple tissues. Intravenous MSC injections have been used to treat various diseases with an inflammatory component in animals and humans. Inflammation is emerging as a key component of pathophysiology of intracranial aneurysms. Modulation of inflammation by MSCs may affect sustained inflammatory processes that lead to aneurysmal rupture.

OBJECTIVE

To assess the effect of MSCs on the development of aneurysm rupture using a mouse model.

METHODS

Intracranial aneurysms were induced with a combination of a single elastase injection into the cerebrospinal fluid and deoxycorticosterone acetate salt-induced hypertension in mice. We administered allogeneic bone marrow-derived MSCs or vehicle, 6 and 9 d after aneurysm induction.

RESULTS

MSC administration significantly reduced rupture rate (vehicle control vs MSCs, 90% vs 36%; P < .05). In cell culture experiments with an MSC and mast cell coculture, MSCs stabilized mast cells through cyclooxygenase-2 (COX-2)-dependent production of prostaglandin E2, thereby reducing the release of proinflammatory cytokines from mast cells. Pretreatment of MSCs with COX-2 inhibitor, NS-398, abolished the protective effect of MSCs against the development of aneurysm rupture.

CONCLUSION

Intravenous administration of MSCs after aneurysm formation prevented aneurysmal rupture in mice. The protective effect of MSCs against the development of aneurysm rupture appears to be mediated in part by the stabilization of mast cells by MSCs.

Exosomes Derived from Human Induced Pluripotent Stem Cells Ameliorate the Aging of Skin Fibroblasts

Stem cells and their paracrine factors have emerged as a resource for regenerative medicine. Many studies have shown the beneficial effects of paracrine factors secreted from adult stem cells, such as exosomes, on skin aging. However, to date, few reports have demonstrated the use of exosomes derived from human pluripotent stem cells for the treatment of skin aging. In this study, we collected exosomes from the conditioned medium of human induced pluripotent stem cells (iPSCs) and investigated the effect on aged human dermal fibroblasts (HDFs). Cell proliferation and viability were determined by an MTT assay and cell migration capacity was shown by a scratch wound assay and a transwell migration assay. To induce photoaging and natural senescence, HDFs were irradiated by UVB (315 nm) and subcultured for over 30 passages, respectively. The expression level of certain mRNAs was evaluated by quantitative real-time PCR (qPCR). Senescence-associated-β-galactosidase (SA-β-Gal) activity was assessed as a marker of natural senescence. As a result, we found that exosomes derived from human iPSCs (iPSCs-Exo) stimulated the proliferation and migration of HDFs under normal conditions. Pretreatment with iPSCs-Exo inhibited the damages of HDFs and overexpression of matrix-degrading enzymes (MMP-1/3) caused by UVB irradiation. The iPSCs-Exo also increased the expression level of collagen type I in the photo-aged HDFs. In addition, we demonstrated that iPSCs-Exo significantly reduced the expression level of SA-β-Gal and MMP-1/3 and restored the collagen type I expression in senescent HDFs. Taken together, it is anticipated that these results suggest a therapeutic potential of iPSCs-Exo for the treatment of skin aging.

Therapeutic Applications of Extracellular Vesicles: Perspectives from Newborn Medicine

With the advancements in antenatal steroid therapies and surfactant replacement, current clinical practices in neonatal intensive care units allow the survival of infants at very low gestational age. Despite these advances, there continues to be significant morbidity associated with extreme preterm birth that includes both short-term and long-term cardiorespiratory impairment. With no effective single therapy in preventing or treating developmental lung injuries, the need for new tools to treat and reduce risk of complications associated with extreme preterm birth is urgent. Stem cell-based therapies, in particular therapies utilizing mesenchymal stem (stromal) cells (MSCs), have shown promise in a number of animal models of lung pathologies relevant to neonatology. Recent studies in this field have consolidated the concept that the therapeutic mechanism of MSC action is paracrine, and this led to wide acceptance of the concept that the delivery of the MSC secretome rather than live cells may provide an alternative therapeutic approach for many complex diseases. Here, we summarize the significance and application of cell-free based therapies in preclinical models of neonatal lung injury. We emphasize the development of extracellular vesicle (EV)-based therapeutics and focus on the challenges that remain to be addressed before their application to clinical practice.