Paracrine factors of multipotent stromal cells ameliorate lung injury in an elastase-induced emphysema model

TNF-α and IL-1β-activated human mesenchymal stromal cells increase airway epithelial wound healing in vitro via activation of the epidermal growth factor receptor

Background

Mesenchymal stromal cells (MSCs) are investigated for their potential to reduce inflammation and to repair damaged tissue. Inflammation and tissue damage are hallmarks of chronic obstructive pulmonary disease (COPD) and MSC infusion is a promising new treatment for COPD. Inflammatory mediators attract MSCs to sites of inflammation and affect their immune-modulatory properties, but little is known about their effect on regenerative properties of MSCs. This study investigates the effect of the pro-inflammatory cytokines TNF-α and IL-1β on the regenerative potential of MSCs, using an in vitro wound healing model of airway epithelial cells.

Methods

Standardized circular wounds were created by scraping cultures of the airway epithelial cell line NCI-H292 and primary bronchial epithelial cells cultured at the air-liquid interface (ALI-PBEC), and subsequently incubated with MSC conditioned medium (MSC-CM) that was generated in presence or absence of TNF-α/IL-1β. Remaining wound size was measured up to 72 h. Phosphorylation of ERK1/2 by MSC-CM was assessed using Western blot. Inhibitors for EGFR and c-Met signaling were used to investigate the contribution of these receptors to wound closure and to ERK1/2 phosphorylation. Transactivation of EGFR by MSC-CM was investigated using a TACE inhibitor, and RT-PCR was used to quantify mRNA expression of several growth factors in MSCs and NCI-H292.

Results

Stimulation of MSCs with the pro-inflammatory cytokines TNF-α and IL-1β increased the mRNA expression of various growth factors by MCSs and enhanced the regenerative potential of MSCs in an in vitro model of airway epithelial injury using NCI-H292 airway epithelial cells. Conditioned medium from cytokine stimulated MSCs induced ERK1/2 phosphorylation in NCI-H292, predominantly via EGFR; it induced ADAM-mediated transactivation of EGFR, and it induced airway epithelial expression of several EGFR ligands. The contribution of activation of c-Met via HGF to increased repair could not be confirmed by inhibitor experiments.

Conclusion

Our data imply that at sites of tissue damage, when inflammatory mediators are present, for example in lungs of COPD patients, MSCs become more potent inducers of repair, in addition to their well-known immune-modulatory properties.

Mesenchymal stem cell-based HSP70 promoter-driven VEGFA induction by resveratrol alleviates elastase-induced emphysema in a mouse model

Chronic obstructive pulmonary disease (COPD) is a sustained blockage of the airways due to lung inflammation occurring with chronic bronchitis and/or emphysema. Progression of emphysema may be slowed by vascular endothelial growth factor A (VEGFA), which reduces apoptotic tissue depletion. Previously, authors of the present report demonstrated that cis-resveratrol (c-RSV)-induced heat-shock protein 70 (HSP70) promoter-regulated VEGFA expression promoted neovascularization of genetically modified mesenchymal stem cells (HSP-VEGFA-MSC) in a mouse model of ischemic disease. Here, this same stem cell line was evaluated for its protective capacity to alleviate elastase-induced pulmonary emphysema in mice. Results of this study showed that c-RSV-treatment of HSP-VEGFA-MSC exhibited synergy between HSP70 transcription activity and induced expression of anti-oxidant-related genes when challenged by cigarette smoke extracts. Eight weeks after jugular vein injection of HSP-VEGFA-MSC into mice with elastase-induced pulmonary emphysema followed by c-RSV treatment to induce transgene expression, significant improvement was observed in respiratory functions. Expression of VEGFA, endogenous nuclear factor erythroid 2-related factor (Nrf 2), and manganese superoxide dismutase (MnSOD) was significantly increased in the lung tissues of the c-RSV-treated mice. Histopathologic examination of treated mice revealed gradual but significant abatement of emphysema and restoration of airspace volume. In conclusion, the present investigation demonstrates that c-RSV-regulated VEGFA expression in HSP-VEGFA-MSC significantly improved the therapeutic effects on the treatment of COPD in the mouse, possibly avoiding side effects associated with constitutive VEGFA expression.

Mesenchymal stem cells for therapeutic applications in pulmonary medicine

INTRODUCTION

Mesenchymal stem cells (MSCs) of different biological sources are in Phase 1 clinical trials and are being considered for Phase 2 therapy of lung disorders, and lung (progenitor) cells derived from pluripotent stem cells (SCs) are under development in preclinical animal models.

SOURCES OF DATA

PubMed.gov and ClinicalTrials.gov.

AREAS OF AGREEMENT

There is consensus about the therapeutic potential of transplanted SCs, mainly MSCs, primarily involves paracrine 'bystander' effects that confer protection of the epithelial and endothelial linings of the lung caused by inflammation and/or fibrosis and lead to increased survival in animal models. Clinical trials of Phase 1 indicate safety and suggest that the efficacy of SC therapy in patients with various lung diseases will require a higher dosage than previously evaluated.

AREAS OF CONTROVERSY

A growing interest in the re-epithelialization and re-endothelialization of damaged lung tissue involves the putative pulmonary differentiation of exogenous MSCs. Currently, it is not clear whether or not the observed regeneration of distal airways/vasculature is derived from lung-resident and/or transplanted SCs.

GROWING POINTS

Important topics under investigation include optimization of the cell source with a decrease in cell population heterogeneity characterized by defined markers, route of delivery for effective treatment, potential dose and therapeutic protocol of SC application, development of quantitative assays and biomarkers of lung disease and repair, and the potential use of tissue engineered lung.

AREAS TIMELY FOR DEVELOPING RESEARCH

Ability of MSCs to differentiate into epithelial cells of the lung, use of autologous induced pluripotent SCs (iPSCs) derived from the patients, complete biochemical characterization of the secretome of SCs used for therapy, and the incorporation of simultaneous and/or subsequent treatment with drugs which also aid in lung repair and regeneration.

CAUTIONARY NOTE

Although safety of MSC-based cell therapy was proved in Phase 1, efficacy, long-term survival and preservation of lung respiratory function need to be further evaluated, cautioning against hastily translating SCs therapy from animal models of lung injury to clinical trials of patients with lung disorders.

Reactive Oxygen Species in Mesenchymal Stem Cell Aging: Implication to Lung Diseases

MSCs have become an emerging cell source with their immune modulation, high proliferation rate, and differentiation potential; indeed, they have been challenged in clinical trials. Recently, it has shown that ROS play a dual role as both deleterious and beneficial species depending on their concentration in MSCs. Various environmental stresses-induced excessive production of ROS triggers cellular senescence and abnormal differentiation on MSCs. Moreover, MSCs have been suggested to participate in the treatment of ALI/ARDS and COPD as a major cause of high morbidity and mortality. Therapeutic mechanisms of MSCs in the treatment of ARDS/COPD were focused on cell engraftment and paracrine action. However, ROS-mediated therapeutic mechanisms of MSCs still remain largely unknown. Here, we review the key factors associated with cell cycle and chromatin remodeling to accelerate or delay the MSC aging process. In addition, the enhanced ROS production and its associated pathophysiological pathways will be discussed along with the MSC senescence process. Furthermore, the present review highlights how the excessive amount of ROS-mediated oxidative stress might interfere with homeostasis of lungs and residual lung cells in the pathogenesis of ALI/ARDS and COPD.

The Therapeutic Effects of Optimal Dose of Mesenchymal Stem Cells in a Murine Model of an Elastase Induced-Emphysema

Background

Chronic obstructive pulmonary disease is characterized by emphysema, chronic bronchitis, and small airway remodeling. The alveolar destruction associated with emphysema cannot be repaired by current clinical practices. Stem cell therapy has been successfully used in animal models of cigarette smoke- and elastase-induced emphysema. However, the optimal dose of mesenchymal stem cells (MSCs) for the most effective therapy has not yet been determined. It is vital to determine the optimal dose of MSCs for clinical application in emphysema cases.

Methods

In the present study, we evaluated the therapeutic effects of various doses of MSCs on elastase-induced emphysema in mice. When 3 different doses of MSCs were intravenously injected into mice treated with elastase, only 5×10⁴ MSCs showed a significant effect on the emphysematous mouse lung. We also identified action mechanisms of MSCs based on apoptosis, lung regeneration, and protease/antiprotease imbalance.

Results

The MSCs were not related with caspase-3/7 dependent apoptosis. But activity of matrix metalloproteinase 9 increased by emphysematous lung was decreased by intravenously injected MSCs. Vascular endothelial growth factor were also increased in lung from MSC injected mice, as compared to un-injected mice.

Conclusion

This is the first study on the optimal dose of MSCs as a therapeutic candidate. This data may provide important basic data for determining dosage in clinical application of MSCs in emphysema patients.

Hypoxia-preconditioned mesenchymal stem cells attenuate bleomycin-induced pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis is a progressive diffuse parenchymal lung disorder of unknown etiology. Mesenchymal stem cell (MSC)-based therapy is a novel approach with great therapeutic potential for the treatment of lung diseases. Despite demonstration of MSC grafting, the populations of engrafted MSCs have been shown to decrease dramatically 24 hours post-transplantation due to exposure to harsh microenvironments. Hypoxia is known to induce expression of cytoprotective genes and also secretion of anti-inflammatory, anti-apoptotic and anti-fibrotic factors. Hypoxic preconditioning is thought to enhance the therapeutic potency and duration of survival of engrafted MSCs. In this work, we aimed to prolong the duration of survival of engrafted MSCs and to enhance the effectiveness of idiopathic pulmonary fibrosis transplantation therapy by the use of hypoxia-preconditioned MSCs.

METHODS

Hypoxic preconditioning was achieved in MSCs under an optimal hypoxic environment. The expression levels of cytoprotective factors and their biological effects on damaged alveolar epithelial cells or transforming growth factor-beta 1-treated fibroblast cells were studied in co-culture experiments in vitro. Furthermore, hypoxia-preconditioned MSCs (HP-MSCs) were intratracheally instilled into bleomycin-induced pulmonary fibrosis mice at day 3, and lung functions, cellular, molecular and pathological changes were assessed at 7 and 21 days after bleomycin administration.

RESULTS

The expression of genes for pro-survival, anti-apoptotic, anti-oxidant and growth factors was upregulated in MSCs under hypoxic conditions. In transforming growth factor-beta 1-treated MRC-5 fibroblast cells, hypoxia-preconditioned MSCs attenuated extracellular matrix production through paracrine effects. The pulmonary respiratory functions significantly improved for up to 18 days of hypoxia-preconditioned MSC treatment. Expression of inflammatory factors and fibrotic factor were all downregulated in the lung tissues of the hypoxia-preconditioned MSC-treated mice. Histopathologic examination observed a significant amelioration of the lung fibrosis. Several LacZ-labeled MSCs were observed within the lungs in the hypoxia-preconditioned MSC treatment groups at day 21, but no signals were detected in the normoxic MSC group. Our data further demonstrated that upregulation of hepatocyte growth factor possibly played an important role in mediating the therapeutic effects of transplanted hypoxia-preconditioned MSCs.

CONCLUSION

Transplantation of hypoxia-preconditioned MSCs exerted better therapeutic effects in bleomycin-induced pulmonary fibrotic mice and enhanced the survival rate of engrafted MSCs, partially due to the upregulation of hepatocyte growth factor.

Smoke inhalation injury repaired by a bone marrow-derived mesenchymal stem cell paracrine mechanism: Angiogenesis involving the Notch signaling pathway

BACKGROUND

Smoke inhalation injury is an acute lung injury induced by smoke exposure characterized by vascular endothelial injury and increased permeability. Cell therapy is an attractive new therapeutic approach, although its underlying mechanism and signaling pathway remain poorly understood. We investigated the effect of systemic transplantation of preconditioned bone marrow-derived mesenchymal stem cells (BMSCs) on angiogenesis in rat model of smoke inhalation injury and explored the underlying mechanism and possible signaling pathway.

METHODS

After the establishment of a smoke inhalation injury rat model, the animals were further randomized into subgroups that received either a tail vein injection of 2 × 10(6) preconditioned or nonpreconditioned BMSCs in 5-mL phosphate-buffered saline to explore the characteristics of preconditioned BMSCs, pulmonary microvessel quantities in smoke inhalation injury, and its Notch1 expression.

RESULTS

BMSCs preconditioned by 60Co γ-ray radiation at an appropriate dose were inhibited differentiation potential in vitro without significantly affecting the paracrine activity, the ability of cell proliferation, viability, and homing. Systemic preconditioned BMSC transplantation significantly increased the quantities of microvessels in rat with smoke inhalation injury, improved the lung wet-dry weight ratio, and alleviated lung injury simply through paracrine activity. Immunofluorescence staining and Western blot analysis confirmed that the expression level of Notch microvessel and Notch1 protein increased significantly after systemic transplantation.

CONCLUSION

Our findings indicate that systemic transplantation of preconditioned BMSCs promotes angiogenesis through paracrine activity after smoke inhalation injury and that the Notch signaling pathway is involved in the angiogenesis process.

Interaction between mesenchymal stem cells and endothelial cells restores endothelial permeability via paracrine hepatocyte growth factor in vitro

Introduction

Mesenchymal stem cells (MSCs) have potent stabilising effects on vascular endothelium injury, inhibiting endothelial permeability in lung injury via paracrine hepatocyte growth factor (HGF). Recently, it has been indicated that MSCs secrete more factors by MSC-endothelial cell (MSC-EC) interactions. We hypothesised that MSC-EC interactions restore endothelial permeability induced by lipopolysaccharide (LPS) via paracrine HGF.

Methods

We investigated the endothelial permeability induced by LPS under two co-culture conditions. Human pulmonary microvascular endothelial cells (HPMECs) were added into the upper chambers of cell-culture inserts, while two different co-culture conditions were used in the lower side of the transwells, as follows: (1) MSC-EC interaction group: MSCs and HPMECs contact co-culture; (2) MSC group: MSCs only. The endothelial paracellular and transcellular permeabilities in the upper side of transwells were detected. Then the concentration of HGF was measured in the culture medium by using an enzyme-linked immunosorbent assay kit, followed by neutralisation of HGF with anti-HGF antibody in the co-culture medium. In addition, adherens junction and cytoskeleton protein expressions were measured by Western blot and immunofluorescence. HPMEC proliferation was analysed by bromodeoxyuridine incorporation assay.

Results

The paracellular permeability significantly increased after LPS stimulation in a dose-dependent and time-dependent manner. Meanwhile, MSC-EC interaction more significantly decreased endothelial paracellular and transcellular permeability induced by LPS. Moreover, HGF levels in the MSC-EC interaction group were much higher than those of the MSC group. However, neutralising HGF with anti-HGF antibody inhibited the role of MSC-EC interaction in improving endothelial permeability. Compared with the MSC group, MSC-EC interaction increased vascular endothelial (VE)-cadherin and occludin protein expression, reduced caveolin-1 protein expression in HPMECs, and restored remodelling of F-actin and junctional localisation of VE-cadherin. Furthermore, the proliferation ratio in the MSC-EC interaction group was higher than that of the MSC group. However, the effects of MSCs were significantly blocked by anti-HGF antibody.

Conclusions

These data suggested that MSC-EC interaction decreased endothelial permeability induced by LPS, which was attributed mainly to HGF secreted by MSCs. The main mechanisms by which HGF restored the integrity of endothelial monolayers were remodelling of endothelial intercellular junctions, decreasing caveolin-1 protein expression, and inducing proliferation in HPMECs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0025-1) contains supplementary material, which is available to authorized users.

In vitro augmentation of mesenchymal stem cells viability in stressful microenvironments : In vitro augmentation of mesenchymal stem cells viability

Mesenchymal stem cells (MSCs) are under intensive investigation for use in cell-based therapies because their differentiation abilities, immunomodulatory effects, and homing properties offer potential for significantly augmenting regenerative capacity of many tissues. Nevertheless, major impediments to their therapeutic application, such as low proliferation and survival rates remain as obstacles to broad clinical use of MSCs. Another major challenge to evolution of MSC-based therapies is functional degradation of these cells as a result of their exposure to oxidative stressors during isolation. Indeed, oxidative stress-mediated MSC depletion occurs due to inflammatory processes associated with chemotherapy, radiotherapy, and expression of pro-apoptotic factors, and the microenvironment of damaged tissue in patients receiving MSC therapy is typically therapeutic not favorable to their survival. For this reason, any strategies that enhance the viability and proliferative capacity of MSCs associated with their therapeutic use are of great value. Here, recent strategies used by various researchers to improve MSC allograft function are reviewed, with particular focus on in vitro conditioning of MSCs in preparation for clinical application. Preconditioning, genetic manipulation, and optimization of MSC culture conditions are some examples of the methodologies described in the present article, along with novel strategies such as treatment of MSCs with secretome and MSC-derived microvesicles. This topic material is likely to find value as a guide for both research and clinical use of MSC allografts and for improvement of the value that use of these cells brings to health care.

The clinical use of regenerative therapy in COPD

Regenerative or stem cell therapy is an emerging field of treatment based on stimulation of endogenous resident stem cells or administration of exogenous stem cells to treat diseases or injury and to replace malfunctioning or damaged tissues. Current evidence suggests that in the lung, these cells may participate in tissue homeostasis and regeneration after injury. Animal and human studies have demonstrated that tissue-specific stem cells and bone marrow-derived cells contribute to lung tissue regeneration and protection, and thus administration of exogenous stem/progenitor cells or humoral factors responsible for the activation of endogenous stem/progenitor cells may be a potent next-generation therapy for chronic obstructive pulmonary disease. The use of bone marrow-derived stem cells could allow repairing and regenerate the damaged tissue present in chronic obstructive pulmonary disease by means of their engraftment into the lung. Another approach could be the stimulation of resident stem cells by means of humoral factors or photobiostimulation.

Mesenchymal stem cells correct inappropriate epithelial-mesenchyme relation in pulmonary fibrosis using stanniocalcin-1

Current hypotheses suggest that aberrant wound healing has a critical role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). In these hypotheses, continuous TGF-β1 secretion by alveolar epithelial cells (AECs) in abnormal wound healing has a critical role in promoting fibroblast differentiation into myofibroblasts. Mesenchymal stem cells (MSCs) home to the injury site and reduce fibrosis by secreting multifunctional antifibrotic humoral factors in IPF. In this study, we show that MSCs can correct the inadequate-communication between epithelial and mesenchymal cells through STC1 (Stanniocalcin-1) secretion in a bleomycin-induced IPF model. Inhalation of recombinant STC1 shows the same effects as the injection of MSCs. Using STC1 plasmid, it was possible to enhance the ability of MSCs to ameliorate the fibrosis. MSCs secrete large amounts of STC1 in response to TGF-β1 in comparison to AECs and fibroblasts. The antifibrotic effects of STC1 include reducing oxidative stress, endoplasmic reticulum (ER) stress, and TGF-β1 production in AECs. The STC1 effects can be controlled by blocking uncoupling protein 2 (UCP2) and the secretion is affected by the PI3/AKT/mTORC1 inhibitors. Our findings suggest that STC1 tends to correct the inappropriate epithelial-mesenchymal relationships and that STC1 plasmid transfected to MSCs or STC1 inhalation could become promising treatments for IPF.

Adipose-derived stromal cell therapy affects lung inflammation and tracheal responsiveness in guinea pig model of COPD

The effects of adipose derived stromal cells (ASCs) were evaluated on tracheal responsiveness and biochemical parameters in guinea pigs model of chronic obstructive pulmonary disease (COPD). Thirty six guinea pigs were divided into 6 groups including: Control, COPD, COPD+intratracheal delivery of PBS (COPD+ITPBS), COPD+intravenous delivery of PBS (COPD+IVPBS), COPD+intratracheal delivery of ASCs (COPD+ITASC) and COPD+intravenous injection of ASCs (COPD+IVASC). COPD was induced by exposing animals to cigarette smoke for 3 months. Cell therapy was then performed and after 14 days, tracheal responsiveness, concentration of interleukin-8 (IL-8) in serum and broncho-alveolar lavage fluid (BALF), as well as total and differential white blood cells (WBC) counts were evaluated. Tracheal responsiveness, total WBC counts, neutrophil and eosinophil percentage in BALF as well as concentration of IL-8 in serum and BALF significantly increased but lymphocyte percentage decreased in COPD compared to the control group (P<0.05 to p<0.001). Cell therapy was able to restore the tracheal hyper-responsiveness and the increased IL-8 concentration in serum and BALF of COPD-ITASC but not COPD-IVASC animals (P<0.05 for all cases). Total WBC in BALF also showed a significant decrease in both treated groups and the percentages of eosinophils, neutrophils and lymphocytes in BALF were reversed in COPD-ITASC compared to COPD-ITPBS animals (P<0.05 to P<0.001). Therefore, intratracheal cell therapy with ASC can decrease tracheal hyperresponsiveness and lung inflammation in cigarette smoke induced-COPD which may be helpful in attenuation of the severity of disease in patients suffering from COPD.

Tracking intravenous adipose-derived mesenchymal stem cells in a model of elastase-induced emphysema

Background

Mesenchymal stem cells (MSCs) obtained from bone marrow or adipose tissue can successfully repair emphysematous animal lungs, which is a characteristic of chronic obstructive pulmonary disease. Here, we describe the cellular distribution of MSCs that were intravenously injected into mice with elastase-induced emphysema. The distributions were also compared to the distributions in control mice without emphysema.

Methods

We used fluorescence optical imaging with quantum dots (QDs) to track intravenously injected MSCs. In addition, we used a human Alu sequence-based real-time polymerase chain reaction method to assess the lungs, liver, kidney, and spleen in mice with elastase-induced emphysema and control mice at 1, 4, 24, 72, and 168 hours after MSCs injection.

Results

The injected MSCs were detected with QD fluorescence at 1- and 4-hour postinjection, and the human Alu sequence was detected at 1-, 4- and 24-hour postinjection in control mice (lungs only). Injected MSCs remained more in mice with elastase-induced emphysema at 1, 4, and 24 hours after MSCs injection than the control lungs without emphysema.

Conclusion

In conclusion, our results show that injected MSCs were observed at 1 and 4 hours post injection and more MSCs remain in lungs with emphysema.

Mesenchymal stem cells reduce cigarette smoke-induced inflammation and airflow obstruction in rats via TGF-β1 signaling

Cigarette smoke has been shown to cause chronic inflammation of the lungs, eventually leading to chronic obstructive pulmonary disease (COPD). Additionally, recent studies have suggested that mesenchymal stem cells (MSCs) can mediate local inflammatory responses in the lungs. Thus, the aim of the present study was to test the effects of rat MSCs (rMSCs) on inflammation of the lungs and destructive pulmonary function induced by cigarette smoke in rats. Rats were exposed to cigarette smoke for 7 weeks. rMSCs were cultured in vitro and infused intratracheally into cigarette smoke-exposed rats. The total and differential cell counts in the bronchoalveolar lavage fluid (BALF), histological changes, pro-inflammatory cytokines, transforming growth factor-β1 (TGF-β1) expression, and pulmonary function were evaluated. Additionally, human peripheral blood mononuclear cells and human MSCs were cocultured in vitro to detect cytokines and TGF-β1 levels. We found that rMSC administration resulted in downregulation of pro-inflammatory cytokines in the lungs while increasing TGF-β1 expression, reducing total inflammatory cell numbers in the BALF, and improving pulmonary histopathology and airflow obstruction. Coculture revealed that human MSCs mediated an anti-inflammatory effect partly via upregulation of TGF-β1. These findings suggested that MSCs may have therapeutic potential in cigarette smoke-induced inflammation and airflow obstruction, partly via upregulation of TGF-β1.

STAT3 signaling in pulmonary arterial hypertension

Pulmonary artery hypertension (PAH) is a proliferative disorder associated with enhanced pulmonary artery smooth muscle cell proliferation and suppressed apoptosis. The sustainability of this phenotype requires the activation of pro-survival transcription factor like the signal transducers and activators of transcription-3 (STAT3). Using multidisciplinary and translational approaches, we and others have demonstrated that STAT3 activation in both human and experimental models of PAH accounts for the modulation of the expression of several proteins already known as implicated in PAH pathogenesis, as well as for signal transduction to other transcription factors. Furthermore, recent data demonstrated that STAT3 could be therapeutically targeted in different animal models and some molecules are actually in clinical trials for cancer or PAH treatment.

Stem cells, cell therapies, and bioengineering in lung biology and diseases. Comprehensive review of the recent literature 2010-2012

A conference, "Stem Cells and Cell Therapies in Lung Biology and Lung Diseases," was held July 25 to 28, 2011 at the University of Vermont to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy and ex vivo bioengineering approaches for lung diseases. These are rapidly expanding areas of study that provide further insight into and challenge traditional views of mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, to discuss and debate current controversies, and to identify future research directions and opportunities for basic and translational research in cell-based therapies for lung diseases. The goal of this article, which accompanies the formal conference report, is to provide a comprehensive review of the published literature in lung regenerative medicine from the last conference report through December 2012.

Intravenous and intratracheal mesenchymal stromal cell injection in a mouse model of pulmonary emphysema

The aim of this study was to characterize the evolution of lung function and -structure in elastase-induced emphysema in adult mice and the effect of mesenchymal stromal cell (MSC) administration on these parameters. Adult mice were treated with intratracheal (4.8 units/100 g bodyweight) elastase to induce emphysema. MSCs were administered intratracheally or intravenously, before or after elastase injection. Lung function measurements, histological and morphometric analysis of lung tissue were performed at 3 weeks, 5 and 10 months after elastase and at 19, 20 and 21 days following MSC administration. Elastase-treated mice showed increased dynamic compliance and total lung capacity, and reduced tissue-specific elastance and forced expiratory flows at 3 weeks after elastase, which persisted during 10 months follow-up. Histology showed heterogeneous alveolar destruction which also persisted during long-term follow-up. Jugular vein injection of MSCs before elastase inhibited deterioration of lung function but had no effects on histology. Intratracheal MSC treatment did not modify lung function or histology. In conclusion, elastase-treated mice displayed persistent characteristics of pulmonary emphysema. Jugular vein injection of MSCs prior to elastase reduced deterioration of lung function. Intratracheal MSC treatment had no effect on lung function or histology.

Growth factors enhance liver regeneration in acute-on-chronic liver failure

Acute-on-chronic liver failure is a distinct syndrome characterized by a rapid progression of liver disease culminating in organ failure and death. The only definitive treatment is liver transplantation. However, there is a possible element of reversibility and hepatic regeneration if the acute insult can be tided over. Exogenously administered growth factors may stimulate hepatocytes, hepatic progenitor cells and bone marrow-derived cells to supplement hepatic regeneration. The proposed review is intended to provide an in-depth analysis of the individual components of hepatic and bone marrow niches and highlight the growing role of various growth factors in liver regeneration in health and in liver failure.

Lung regeneration and translational implications of the postpneumonectomy model

Lung regeneration research is yielding data with increasing translational value. The classical models of lung development, postnatal alveolarization, and postpneumonectomy alveolarization have contributed to a broader understanding of the cellular participants including stem-progenitor cells, cell-cell signaling pathways, and the roles of mechanical deformation and other physiologic factors that have the potential to be modulated in human and animal patients. Although recent information is available describing the lineage fate of lung fibroblasts, genetic fate mapping, and clonal studies are lacking in the study of lung regeneration and deserve further examination. In addition to increasing knowledge concerning classical alveolarization (postnatal, postpneumonectomy), there is increasing evidence for remodeling of the adult lung after partial pneumonectomy. Though limited in scope, compelling data have emerged describing restoration of lung tissue mass in the adult human and in large animal models. The basis for this long-term adaptation to pneumonectomy is poorly understood, but investigations into mechanisms of lung regeneration in older animals that have lost their capacity for rapid re-alveolarization are warranted, as there would be great translational value in modulating these mechanisms. In addition, quantitative morphometric analysis has progressed in conjunction with developments in advanced imaging, which allow for longitudinal and nonterminal evaluation of pulmonary regenerative responses in animals and humans. This review focuses on the cellular and molecular events that have been observed in animals and humans after pneumonectomy because this model is closest to classical regeneration in other mammalian systems and has revealed several new fronts of translational research that deserve consideration.

Exosomes derived from mesenchymal stem cells

The functional mechanisms of mesenchymal stem cells (MSCs) have become a research focus in recent years. Accumulating evidence supports the notion that MSCs act in a paracrine manner. Therefore, the biological factors in conditioned medium, including exosomes and soluble factors, derived from MSC cultures are being explored extensively. The results from most investigations show that MSC-conditioned medium or its components mediate some biological functions of MSCs. Several studies have reported that MSC-derived exosomes have functions similar to those of MSCs, such as repairing tissue damage, suppressing inflammatory responses, and modulating the immune system. However, the mechanisms are still not fully understood and the results remain controversial. Compared with cells, exosomes are more stable and reservable, have no risk of aneuploidy, a lower possibility of immune rejection following in vivo allogeneic administration, and may provide an alternative therapy for various diseases. In this review, we summarize the properties and biological functions of MSC-derived exosomes and discuss the related mechanisms.

The effect of adipose derived stromal cells on oxidative stress level, lung emphysema and white blood cells of guinea pigs model of chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a worldwide epidemic disease and a major cause of death and disability. The present study aimed to elucidate pharmacological effects of adipose derived stromal cells (ASCs) on pathological and biochemical factors in a guinea pig model of COPD. Guinea pigs were randomized into 5 groups including: Control, COPD, COPD + intratracheal delivery of PBS as a vehicle (COPD-PBS), COPD + intratracheal delivery of ASCs (COPD-ITASC) and COPD + intravenous injection of ASCs (COPD-IVASC). COPD was induced by exposing animals to cigarette smoke for 3 months. Cell therapy was performed immediately after the end of animal exposure to cigarette smoke and 14 days after that, white blood cells, oxidative stress indices and pathological changes of the lung were measured.

Results

Compared with control group, emphysema was clearly observed in the COPD and COPD-PBS groups (p < 0.001). Lung histopathologic changes of COPD-ITASC and COPD-IVASC groups showed non-significant improvement compared to COPD-PBS group. The COPD-ITASC group showed a significant increase in total WBC compared to COPD-PBS group but there was not a significant increase in this regard in COPD-IVASC group. The differential WBC showed no significant change in number of different types of leukocytes. The serum level of malondialdehyde (MDA) significantly decreased but thiol groups of broncho-alveolar lavage fluid (BALF) increased in both cell treated groups (p < 0.05 for all cases). Weight of animals decreased during smoke exposure and improved after PBS or cell therapy. However, no significant change was observed between the groups receiving PBS and the ones receiving ASCs.

Conclusion

Cell therapy with ASCs can help in reducing oxidative damage during smoking which may collectively hold promise in attenuation of the severity of COPD although the lung structural changes couldn’t be ameliorated with these pharmacological therapeutic methods.

Phase I clinical trial of cell therapy in patients with advanced chronic obstructive pulmonary disease: follow-up of up to 3 years

Background

Chronic obstructive pulmonary disease is a major inflammatory disease of the airways and an enormous therapeutic challenge. Within the spectrum of chronic obstructive pulmonary disease, pulmonary emphysema is characterized by the destruction of the alveolar walls with an increase in the air spaces distal to the terminal bronchioles but without significant pulmonary fibrosis. Therapeutic options are limited and palliative since they are unable to promote morphological and functional regeneration of the alveolar tissue. In this context, new therapeutic approaches, such as cell therapy with adult stem cells, are being evaluated.

Objective

This article aims to describe the follow-up of up to 3 years after the beginning of a phase I clinical trial and discuss the spirometry parameters achieved by patients with advanced pulmonary emphysema treated with bone marrow mononuclear cells.

Methods

Four patients with advanced pulmonary emphysema were submitted to autologous infusion of bone marrow mononuclear cells. Follow-ups were performed by spirometry up to 3 years after the procedure.

Results

The results showed that autologous cell therapy in patients having chronic obstructive pulmonary disease is a safe procedure and free of adverse effects. There was an improvement in laboratory parameters (spirometry) and a slowing down in the process of pathological degeneration. Also, patients reported improvements in the clinical condition and quality of life.

Conclusions

Despite being in the initial stage and in spite of the small sample, the results of the clinical protocol of cell therapy in advanced pulmonary emphysema as proposed in this study, open new therapeutic perspectives in chronic obstructive pulmonary disease. It is worth emphasizing that this study corresponds to the first study in the literature that reports a change in the natural history of pulmonary emphysema after the use of cell therapy with a pool of bone marrow mononuclear cells.

Cell therapy with bone marrow mononuclear cells in elastase-induced pulmonary emphysema

Emphysema is characterized by destruction of alveolar walls with loss of gas exchange surface and consequent progressive dyspnea. This study aimed to evaluate the efficiency of cell therapy with bone marrow mononuclear cells (BMMC) in an animal model of elastase-induced pulmonary emphysema. Emphysema was induced in C57Bl/J6 female mice by intranasal instillation of elastase. After 21 days, the mice received bone marrow mononuclear cells from EGFP male mice with C57Bl/J6 background. The groups were assessed by comparison and statistically significant differences (p < 0.05) were observed among the groups treated with BMMC and evaluated after 7, 14 and 21 days. Analysis of the mean linear intercept (Lm) values for the different groups allowed to observe that the group treated with BMMC and evaluated after 21 days showed the most significant result. The group that received no treatment showed a statistically significant difference when compared to other groups, except the group treated and evaluated after 21 days, evidencing the efficacy of cell therapy with BMMC in pulmonary emphysema.

Mesenchymal stem cell therapy in lung disorders: pathogenesis of lung diseases and mechanism of action of mesenchymal stem cell

Lung disorders such as asthma, acute respiratory distress syndrome (ARDS), chronic obstructive lung disease (COPD), and interstitial lung disease (ILD) show a few common threads of pathogenic mechanisms: inflammation, aberrant immune activity, infection, and fibrosis. Currently no modes of effective treatment are available for ILD or emphysema. Being anti-inflammatory, immunomodulatory, and regenerative in nature, the administration of mesenchymal stem cells (MSCs) has shown the capacity to control immune dysfunction and inflammation in the lung. The intravenous infusion of MSCs, the common mode of delivery, is followed by their entrapment in lung vasculature before MSCs reach to other organ systems thus indicating the feasible and promising approach of MSCs therapy for lung diseases. In this review, we discuss the mechanistic basis for MSCs therapy for asthma, ARDS, COPD, and ILD.

The potential of cell-based therapy in lung diseases

INTRODUCTION

Many lung diseases have high morbidity and mortality rates and there are no cures or treatments apart from mechanical ventilation or transplantation. Cell-based therapies are currently an area of intense research, and many groups are working to translate successful in vitro results into treatments that are safe for patients.

AREAS COVERED

This review discusses several types of stem and progenitor cells that have been proven likely candidates for cell therapies, as well as their applications so far in specific acute and chronic lung diseases, focusing on their mechanisms of action and how best they can be directed toward clinical aims.

EXPERT OPINION

The research on cell therapies for the lung, particularly regarding mesenchymal stem cells (MSCs), is promising, but there is still much uncertainty surrounding the mechanisms of MSC action and the factors relevant to clinical applications such as the optimal timing of dosage. Future studies will focus on the microenvironment of the stem cells, including the role of microRNAs and extracellular vesicles.

A placebo-controlled, randomized trial of mesenchymal stem cells in COPD

BACKGROUND

COPD is a devastating disease affecting millions worldwide. As disease pathogenesis includes both chronic pulmonary and systemic inflammation, antiinflammatory effects of systemically administered mesenchymal stem cells (MSCs) may decrease inflammation, resulting in improved lung function and quality of life. The goal of this study was to assess safety and to perform an initial evaluation of the potential efficacy of systemic MSC administration to patients with moderate to severe COPD.

METHODS

Sixty-two patients at six sites were randomized to double-blinded IV infusions of either allogeneic MSCs (Prochymal; Osiris Therapeutics Inc) or vehicle control. Patients received four monthly infusions (100 × 10⁶ cells/infusion) and were subsequently followed for 2 years after the first infusion. End points included comprehensive safety evaluation, pulmonary function testing (PFT), and quality-of-life indicators including questionnaires, 6MWT, and assessments of systemic inflammation.

RESULTS

All study patients completed the full infusion protocol, and 74% completed the 2-year follow-up. There were no infusional toxicities and no deaths or serious adverse events deemed related to MSC administration. There were no significant differences in the overall number of adverse events, frequency of COPD exacerbations, or worsening of disease in patients treated with MSCs. There were no significant differences in PFTs or quality-of-life indicators; however, an early, significant decrease in levels of circulating C-reactive protein (CRP) was observed in patients treated with MSCs who had elevated CRP levels at study entry.

CONCLUSIONS

Systemic MSC administration appears to be safe in patients with moderate to severe COPD and provides a basis for subsequent cell therapy investigations.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00683722; URL: www.clinicaltrials.gov.

A prospective, non-randomized, no placebo-controlled, phase Ib clinical trial to study the safety of the adipose derived stromal cells-stromal vascular fraction in idiopathic pulmonary fibrosis

INTRODUCTION

Regenerative medicine and particular adult stem cells represent an alternative option with several fruitful therapeutic applications in patients suffering from chronic lung diseases including idiopathic pulmonary fibrosis (IPF). Nevertheless, lack of knowledge regarding the origin and the potential of mesenchymal stem cells (MSCs) to differentiate into fibroblasts has limited their use for the treatment of this dismal disease.

PATIENTS AND METHODS

To this end, we conducted a phase Ib, non-randomized, clinical trial to study the safety of three endobronchial infusions of autologous adipose derived stromal cells (ADSCs)-stromal vascular fraction (SVF) (0.5 million cells per kgr of body weight per infusion) in patients with IPF (n=14) of mild to moderate disease severity (forced vital capacity -FVC>50% predicted value and diffusion lung capacity for carbon monoxide-DLCO>35% of predicted value). Our primary end-point was incidence of treatment emergent adverse events within 12 months. Alterations of functional, exercise capacity and quality of life parameters at serial time points (baseline, 6 and 12 months after first infusion) were exploratory secondary end-points.

RESULTS

No cases of serious or clinically meaningful adverse events including short-term infusional toxicities as well as long-term ectopic tissue formation were recorded in all patients. Detailed safety monitoring through several time-points indicated that cell-treated patients did not deteriorate in both functional parameters and indicators of quality of life.

CONCLUSIONS

The clinical trial met its primary objective demonstrating an acceptable safety profile of endobronchially administered autologous ADSCs-SVF. Our findings accelerate the rapidly expanded scientific knowledge and indicate a way towards future efficacy trials.

Mesenchymal stem cells protect cigarette smoke-damaged lung and pulmonary function partly via VEGF-VEGF receptors

Progressive pulmonary inflammation and emphysema have been implicated in the progression of chronic obstructive pulmonary disease (COPD), while current pharmacological treatments are not effective. Transplantation of bone marrow mesenchymal stem cells (MSCs) has been identified as one such possible strategy for treatment of lung diseases including acute lung injury (ALI) and pulmonary fibrosis. However, their role in COPD still requires further investigation. The aim of this study is to test the effect of administration of rat MSCs (rMSCs) on emphysema and pulmonary function. To accomplish this study, the rats were exposed to cigarette smoke (CS) for 11 weeks, followed by administration of rMSCs into the lungs. Here we show that rMSCs infusion mediates a down-regulation of pro-inflammatory mediators (TNF-α, IL-1β, MCP-1, and IL-6) and proteases (MMP9 and MMP12) in lung, an up-regulation of vascular endothelial growth factor (VEGF), VEGF receptor 2, and transforming growth factor (TGFβ-1), while reducing pulmonary cell apoptosis. More importantly, rMSCs administration improves emphysema and destructive pulmonary function induced by CS exposure. In vitro co-culture system study of human umbilical endothelial vein cells (EA.hy926) and human MSCs (hMSCs) provides the evidence that hMSCs mediates an anti-apoptosis effect, which partly depends on an up-regulation of VEGF. These findings suggest that MSCs have a therapeutic potential in emphysematous rats by suppressing the inflammatory response, excessive protease expression, and cell apoptosis, as well as up-regulating VEGF, VEGF receptor 2, and TGFβ-1.

Paracrine effects and heterogeneity of marrow-derived stem/progenitor cells: relevance for the treatment of respiratory diseases

Stem cell-based treatment may represent a hope for the treatment of acute lung injury and pulmonary fibrosis, and other chronic lung diseases, such as cystic fibrosis, asthma and chronic obstructive pulmonary disease (COPD). It is well established in preclinical models that bone marrow-derived stem and progenitor cells exert beneficial effects on inflammation, immune responses and repairing of damage in virtually all lung-borne diseases. While it was initially thought that the positive outcome was due to a direct engraftment of these cells into the lung as endothelial and epithelial cells, paracrine factors are now considered the main mechanism through which stem and progenitor cells exert their therapeutic effect. This knowledge has led to the clinical use of marrow cells in pulmonary hypertension with endothelial progenitor cells (EPCs) and in COPD with mesenchymal stromal (stem) cells (MSCs). Bone marrow-derived stem cells, including hematopoietic stem/progenitor cells, MSCs, EPCs and fibrocytes, encompass a wide array of cell subsets with different capacities of engraftment and injured tissue-regenerating potential. The characterization/isolation of the stem cell subpopulations represents a major challenge to improve the efficacy of transplantation protocols used in regenerative medicine and applied to lung disorders.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Mesenchymal stem cell: an efficient mass producer of exosomes for drug delivery

Advances in biomedical research have generated an unprecedented number of potential targets for therapeutic intervention to treat disease or delay disease progression. Unfortunately, many of these targets are not druggable as they are intracellular, present in many cell types, poorly soluble or rapidly inactivated. Although synthetic drug vehicles have successfully circumvented many of these problems, natural particulates such as exosomes that intrinsically possess many attributes of a drug delivery vehicle are highly attractive as potentially better alternatives. Of the cell types known to produce exosomes, the readily available proliferative, immunosuppressive and clinically tested human mesenchymal stem cell (MSC) is the most prolific producer. Its exosomes are therapeutic in animal model of disease and exhibit immunosuppressive activity. The quality and quantity of exosome production is not compromised by immortalization to create a permanent MSC cell line. Therefore, MSC is well suited for mass production of exosomes that are ideal for drug delivery.

Stem cell treatment for chronic lung diseases

Chronic lung diseases such as idiopathic pulmonary fibrosis and cystic fibrosis or chronic obstructive pulmonary disease and asthma are leading causes of morbidity and mortality worldwide with a considerable human, societal and financial burden. In view of the current disappointing status of available pharmaceutical agents, there is an urgent need for alternative more effective therapeutic approaches that will not only help to relieve patient symptoms but will also affect the natural course of the respective disease. Regenerative medicine represents a promising option with several fruitful therapeutic applications in patients suffering from chronic lung diseases. Nevertheless, despite relative enthusiasm arising from experimental data, application of stem cell therapy in the clinical setting has been severely hampered by several safety concerns arising from the major lack of knowledge on the fate of exogenously administered stem cells within chronically injured lung as well as the mechanisms regulating the activation of resident progenitor cells. On the other hand, salient data arising from few 'brave' pilot investigations of the safety of stem cell treatment in chronic lung diseases seem promising. The main scope of this review article is to summarize the current state of knowledge regarding the application status of stem cell treatment in chronic lung diseases, address important safety and efficacy issues and present future challenges and perspectives. In this review, we argue in favor of large multicenter clinical trials setting realistic goals to assess treatment efficacy. We propose the use of biomarkers that reflect clinically inconspicuous alterations of the disease molecular phenotype before rigid conclusions can be safely drawn.

Using Cell-Based Strategies to Break the Link between Bronchopulmonary Dysplasia and the Development of Chronic Lung Disease in Later Life

Bronchopulmonary dysplasia (BPD) is the chronic lung disease of prematurity that affects very preterm infants. Although advances in perinatal care have changed the course of lung injury and enabled the survival of infants born as early as 23-24 weeks of gestation, BPD still remains a common complication of extreme prematurity, and there is no specific treatment for it. Furthermore, children, adolescents, and adults who were born very preterm and developed BPD have an increased risk of persistent lung dysfunction, including early-onset emphysema. Therefore, it is possible that early-life pulmonary insults, such as extreme prematurity and BPD, may increase the risk of COPD later in life, especially if exposed to secondary challenges such as respiratory infections and/or smoking. Recent advances in our understanding of stem/progenitor cells and their potential to repair damaged organs offer the possibility of cell-based treatments for neonatal and adult lung injuries. This paper summarizes the long-term pulmonary outcomes of preterm birth and BPD and discusses the recent advances of cell-based therapies for lung diseases, with a particular focus on BPD and COPD.

Human mesenchymal stem cells isolated from olfactory biopsies but not bone enhance CNS myelination in vitro

Spinal cord injury (SCI) is a devastating condition with limited capacity for repair. Cell transplantation is a potential strategy to promote SCI repair with cells from the olfactory system being promising candidates. Although transplants of human olfactory mucosa (OM) are already ongoing in clinical trials, the repair potential of this tissue remains unclear. Previously, we identified mesenchymal-like stem cells that reside in the lamina propria (LP-MSCs) of rat and human OM. Little is known about these cells or their interactions with glia such as olfactory ensheathing cells (OECs), which would be co-transplanted with MSCs from the OM, or endogenous CNS glia such as oligodendrocytes. We have characterized, purified, and assessed the repair potential of human LP-MSCs by investigating their effect on glial cell biology with specific emphasis on CNS myelination in vitro. Purified LP-MSCs expressed typical bone marrow MSC (BM-MSC) markers, formed spheres, were clonogenic and differentiated into bone and fat. LP-MSC conditioned medium (CM) promoted oligodendrocyte precursor cell (OPC) and OEC proliferation and induced a highly branched morphology. LP-MSC-CM treatment caused OEC process extension. Both LP and BM-MSCs promoted OPC proliferation and differentiation, but only myelinating cultures treated with CM from LP and not BM-MSCs had a significant increase in myelination. Comparison with fibroblasts and contaminating OM fibroblast like-cells showed the promyelination effect was LP-MSC specific. Thus LP-MSCs harvested from human OM biopsies may be an important candidate for cell transplantation by contributing to the repair of SCI.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

Stem cells and pulmonary fibrosis: cause or cure?

Pulmonary fibrosis is a feature of a number of important lung diseases, and alveolar epithelial injury plays a key role in their pathogenesis. Traditionally, type II alveolar epithelial cells have been viewed as the progenitor cells of the alveolar epithelium; however, recent studies have identified a number of other progenitor and stem cell populations that may participate in alveolar epithelial repair. These studies suggest that the injury microenvironment plays a role in regulation of progenitor cell populations. In human idiopathic pulmonary fibrosis, epithelial abnormalities including altered cell cycling characteristics, hyperplasia, and metaplasia are observed, suggesting that dysregulation of epithelial progenitor cells contributes to the characteristic aberrant repair process. Reactivation of developmental signaling pathways such as the Wnt-β-catenin pathway is implicated in the dysregulation of these cells, and targeting these pathways may provide opportunities for therapeutic intervention. There has been a great deal of interest in the delivery of exogenous stem cells as a therapeutic strategy, and various stem and progenitor cell populations have improved outcomes in animal lung fibrosis models. The contributions of these cells to alveolar epithelial regeneration have been variable, and secretion of soluble mediators has been implicated in the beneficial effects. It remains to be seen whether the promising results seen in the preclinical studies will translate to human disease, and the first studies using mesenchymal stem cells in clinical trials for fibrotic lung disease are underway. Strategies using other stem cell populations hold promise, but currently these are a lot further from the bedside.

Lung injury in preterm neonates: the role and therapeutic potential of stem cells

Continuous improvements in perinatal care have allowed the survival of ever more premature infants, making the task of protecting the extremely immature lung from injury increasingly challenging. Premature infants at risk of developing chronic lung disease or bronchopulmonary dysplasia (BPD) are now born at the late canalicular stage of lung development, just when the airways become juxtaposed to the lung vasculature and when gas-exchange becomes possible. Readily available strategies, including improved antenatal management (education, regionalization, steroids, and antibiotics), together with exogenous surfactant and exclusive/early noninvasive ventilatory support, will likely decrease the incidence/severity of BPD over the next few years. Nonetheless, because of the extreme immaturity of the developing lung, the extent to which disruption of lung growth after prematurity and neonatal management lead to an earlier or more aggravated decline in respiratory function in later life is a matter of concern. Consequently, much more needs to be learned about the mechanisms of lung development, injury, and repair. Recent insight into stem cell biology has sparked interest for stem cells to repair damaged organs. This review summarizes the exciting potential of stem cell-based therapies for lung diseases in general and BPD in particular.

Cell-based strategies to reconstitute lung function in infants with severe bronchopulmonary dysplasia

Recent advances in our understanding of stem/progenitor cells and their potential to repair damaged organs offer the possibility of cell-based treatments for neonatal lung injury. This review summarizes basic concepts of stem/progenitor cell biology and discusses the recent advances and challenges of cell-based therapies for lung diseases, with a particular focus on bronchopulmonary dysplasia (BPD), a form of chronic lung disease that primarily affects very preterm infants. Despite advances in perinatal care, BPD still remains the most common complication of extreme prematurity, and there is no specific treatment.

Regenerative pulmonary medicine: potential and promise, pitfalls and challenges

BACKGROUND

Chronic lung diseases contribute significantly to the morbidity and mortality of the population. There are few effective treatments for many chronic lung diseases, and even fewer therapies that can arrest or reverse the progress of the disease.

DESIGN

In this review, we present the current state of regenerative therapies for the treatment of chronic lung diseases. We focus on endothelial progenitor cells, mesenchymal stem cells, and endogenous lung stem/progenitor cells; summarize the work to date in models of lung diseases for each of these therapies; and consider their potential benefits and risks as viable therapies for patients with lung diseases.

CONCLUSIONS

Cell-based regenerative therapies for lung diseases offer great promise, with preclinical studies suggesting that the next decade should provide the evidence necessary for their ultimate application to our therapeutic armamentarium.

Human embryonic mesenchymal stem cell-derived conditioned medium rescues kidney function in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem, affecting more than 35% of the elderly population worldwide. New interventions to slow or prevent disease progression are urgently needed. Beneficial effects of mesenchymal stem cells (MSC) have been described, however it is unclear whether the MSCs themselves or their secretome is required. We hypothesized that MSC-derived conditioned medium (CM) reduces progression of CKD and studied functional and structural effects in a rat model of established CKD.

CKD was induced by 5/6 nephrectomy (SNX) combined with L-NNA and 6% NaCl diet in Lewis rats. Six weeks after SNX, CKD rats received either 50 µg CM or 50 µg non-CM (NCM) twice daily intravenously for four consecutive days. Six weeks after treatment CM administration was functionally effective: glomerular filtration rate (inulin clearance) and effective renal plasma flow (PAH clearance) were significantly higher in CM vs. NCM-treatment. Systolic blood pressure was lower in CM compared to NCM. Proteinuria tended to be lower after CM. Tubular and glomerular damage were reduced and more glomerular endothelial cells were found after CM. DNA damage repair was increased after CM. MSC-CM derived exosomes, tested in the same experimental setting, showed no protective effect on the kidney. In a rat model of established CKD, we demonstrated that administration of MSC-CM has a long-lasting therapeutic rescue function shown by decreased progression of CKD and reduced hypertension and glomerular injury.

Stem cells and regenerative medicine in lung biology and diseases

A number of novel approaches for repair and regeneration of injured lung have developed over the past several years. These include a better understanding of endogenous stem and progenitor cells in the lung that can function in reparative capacity as well as extensive exploration of the potential efficacy of administering exogenous stem or progenitor cells to function in lung repair. Recent advances in ex vivo lung engineering have also been increasingly applied to the lung. The current status of these approaches as well as initial clinical trials of cell therapies for lung diseases are reviewed below.

Protective effects of bone marrow mononuclear cell therapy on lung and heart in an elastase-induced emphysema model

We hypothesized that bone marrow-derived mononuclear cell (BMDMC) therapy protects the lung and consequently the heart in experimental elastase-induced emphysema. Twenty-four female C57BL/6 mice were intratracheally instilled with saline (C group) or porcine pancreatic elastase (E group) once a week during 4 weeks. C and E groups were randomized into subgroups receiving saline (SAL) or male BMDMCs (2 × 10(6), CELL) intravenously 3h after the first saline or elastase instillation. Compared to E-SAL group, E-CELL mice showed, at 5 weeks: lower mean linear intercept, neutrophil infiltration, elastolysis, collagen fiber deposition in alveolar septa and pulmonary vessel wall, lung cell apoptosis, right ventricle wall thickness and area, higher endothelial growth factor and insulin-like growth factor mRNA expressions in lung tissue, and reduced platelet-derived growth factor, transforming growth factor-β, and caspase-3 expressions. In conclusion, BMDMC therapy was effective at modulating the inflammatory and remodeling processes in the present model of elastase-induced emphysema.

Multipotent stromal cell therapy for cavernous nerve injury-induced erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) following radical prostatectomy (RP) is a result of inadvertent damage to the cavernous nerves that run close to the prostate capsula. The mechanisms behind the development of post-RP ED are increasingly recognized and include cavernosal fibrosis and cavernosal smooth muscle apoptosis, resulting from cavernous nerve degeneration due to neuropraxia. In recent years, cell-based therapies have received increasing attention regarding their potential for recovery of erectile function following cavernous nerve injury (CNI). Multipotent stromal cells (MSCs) are an attractive cell source for this application based on their regenerative potential and their clinical applicability.

AIM

To review available evidence on the efficacy and mechanisms of action of MSC application for the treatment of ED, with an emphasis on ED following CNI.

METHODS

A nonsystematic review was conducted on the available English literature between 1966 and 2011 on the search engines SciVerse-sciencedirect, SciVerse-scopus, Google Scholar, and PubMed.

RESULTS

MSCs from both bone marrow and adipose tissue have shown beneficial effects in a variety of animal models for ED. While MSC application in chronic disease models such as diabetes, aging, and hyperlipidemia may result in cell engraftment and possibly MSC differentiation, this observation has not been made in the acute CNI rat model. In the latter setting, MSC effects seem to be established by cell recruitment toward the major pelvic ganglion and local paracrine interaction with the host neural tissue.

CONCLUSIONS

While the type of model may influence the mechanisms of action of this MSC-based therapy, MSCs generally display efficacy in various animal models for ED. Before translation to the clinic is established, various hurdles need to be overcome.