Transplantation of Endothelial Progenitor Cells Improves Pulmonary Endothelial Function and Gas Exchange in Rabbits with Endotoxin-Induced Acute Lung Injury

Novel approaches for long-term lung transplant survival

Allograft failure remains a major barrier in the field of lung transplantation and results primarily from acute and chronic rejection. To date, standard-of-care immunosuppressive regimens have proven unsuccessful in achieving acceptable long-term graft and patient survival. Recent insights into the unique immunologic properties of lung allografts provide an opportunity to develop more effective immunosuppressive strategies. Here we describe advances in our understanding of the mechanisms driving lung allograft rejection and highlight recent progress in the development of novel, lung-specific strategies aimed at promoting long-term allograft survival, including tolerance.

ProT-α gene transfer attenuates cardiopulmonary remedying and mortality in a flow-induced pulmonary hypertension rat model

BACKGROUND

ProT is a cell survival gene, which modulates oxidative stress and transforming growth factor (TGF)-β signaling. We hypothesized that the delivery of the ProT cDNA gene in rats could protect against right heart dysfunction secondary to pulmonary hypertension (PH) induced by left-to-right shunt.

METHODS

A 2-hit rat model of flow-induced PH was used, and a single intravenous injection of adenoviral vectors (2 billion plaque-forming unit) carrying ProT or Luc gene was administered. The animals were euthanized 21 days after gene delivery to assess cardiopulmonary function, serum biochemistry, pulmonary artery (PA), and vasomotor reactivity. Immunohistology and immunoblotting of PA tissues were also performed.

RESULTS

ProT transduction significantly reduced PA pressure, right ventricle muscle mass, and wall stress, thereby improving the overall survival of the treated rat. Increased production of ProT through gene therapy preserved both the smooth muscle myosin heavy chain-II and α-smooth muscle actin while counteracting the abundance of TGF-β in PA. Protein abundances of phosphorylated p47-phox, heme oxygenase-1, caspase-3, inducible nitric oxide synthase, cyclo-oxygenase 2, and monocyte chemoattractant protein-1 in PA tissues were reduced. ProT also preserved microRNA-223, thereby suppressing the abundance of PARP-1, which is independent of hypoxia-inducible factor-1α signaling.

CONCLUSIONS

ProT gene transduction improved PA function by reducing oxidative stress, attenuating inflammation, and preserving the contractile phenotype of vascular smooth muscle cells. The modification of microRNA-223-associated downstream signaling through ProT transduction may play an important role in mitigating cardiopulmonary remodeling in flow-induced PH.

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.

Continuous Passive Motion Promotes and Maintains Chondrogenesis in Autologous Endothelial Progenitor Cell-Loaded Porous PLGA Scaffolds during Osteochondral Defect Repair in a Rabbit Model

Continuous passive motion (CPM) is widely used after total knee replacement. In this study, we investigated the effect of CPM combined with cell-based construct-transplantation in osteochondral tissue engineering. We created osteochondral defects (3 mm in diameter and 3 mm in depth) in the medial femoral condyle of 36 knees and randomized them into three groups: ED (empty defect), EPC/PLGA (endothelial progenitor cells (EPCs) seeded in the poly lactic-co-glycolic acid (PLGA) scaffold), or EPC/PLGA/CPM (EPC/PLGA scaffold complemented with CPM starting one day after transplantation). We investigated the effects of CPM and the EPC/PLGA constructs on tissue restoration in weight-bearing sites by histological observation and micro-computed tomography (micro-CT) evaluation 4 and 12 weeks after implantation. After CPM, the EPC/PLGA construct exhibited early osteochondral regeneration and prevention of subchondral bone overgrowth and cartilage degeneration. CPM did not alter the microenvironment created by the construct; it up-regulated the expression of the extracellular matrix components (glycosaminoglycan and collagen), down-regulated bone formation, and induced the biosynthesis of lubricin, which appeared in the EPC/PLGA/CPM group after 12 weeks. CPM can provide promoting signals during osteochondral tissue engineering and achieve a synergistic effect when combined with EPC/PLGA transplantation, so it should be considered a non-invasive treatment to be adopted in clinical practices.

Transplantation of Endothelial Progenitor Cells Attenuates Lipopolysaccharide-Induced Lung Injury via Inhibiting the Inflammatory Secretion of Neutrophils in Rats

BACKGROUND

Endothelial progenitor cells (EPCs) are special types of stem cells and are a potential novel therapeutic approach in acute lung injury (ALI). Transplantation of EPCs can ameliorate the inflammatory state by reducing adhesion and exudation of inflammatory cells. However, the mechanism underlying the effect of EPCs on inflammatory response modulation remains unclear. The aim of the present study was to investigate the effect of EPCs on the modulation of neutrophils in vitro and in vivo.

MATERIALS AND METHODS

EPCs were cocultured with neutrophils after lipopolysaccharide stimulation in vitro or transplanted into ALI rats, and neutrophil inflammatory mediators including tumor necrosis factor-α, interleukin-1β, neutrophil elastase, myeloperoxidase and matrix metalloproteinases-9 were detected by enzyme-linked immunosorbent assay, an myeloperoxidase detection kits, reverse transcription-polymerase chain reaction and western blotting.

RESULTS

The results showed that EPCs significantly downregulated the expression of inflammatory mediators when cocultured with neutrophils in vitro or in vivo.

CONCLUSIONS

These findings demonstrated that EPCs contributed to lung injury in ALI rats by downregulating neutrophil inflammatory mediators.

Transplantation of endothelial progenitor cells attenuated paraquat-induced acute lung injury via miR-141-3p-Notch-Nrf2 axis

Background

Paraquat (PQ) presents with high toxicity for humans and animals, and the lungs become the main target organ by the poisoning of PQ leading to acute lung injury. Endothelial progenitor cells (EPCs) were proved to have the repair function on acute lung injury (ALI). We aimed to invatigate the underlying mechanism of EPCs in PQ-induced ALI involving miR-141-3p.

Methods

Endothelial progenitor cells were isolated from peripheral blood of C57BL/6J mice and identified by flow cytometry. Lung wet-to-dry (W/D) weight ratios, lung injury score and the number of total leukocyte and the number of neutrophils in BALF were used to analyze the degree of lung injury. The transfection was performed with Lipofectamine 2000. The levels of miRNA and mRNA were determined by qRT-PCR, and the protein levels were detected by Western blot assay.

Results

Endothelial progenitor cells alleviated lung wet-to-dry (W/D) weight ratios, lung injury score and the number of total leukocyte and the number of neutrophils in BALF in PQ-induced ALI mice. EPCs inhibited miR-141-3p expression, and enhanced the levels of Notch-Nrf2 axis in PQ-induced ALI mice. MiR-141-3p knockdown reversed the PQ induced-inhibition on Notch-1 and Hesr1 expression. MiR-141-3p over-expression could inhibit the expression of Notch-1 pathway significantly in the pulmonary epithelial cell line MLE-12. Both miR-141-3p over-expression and si-Notch-1 abolished the protection effect of EPCs on lung injury induced by PQ in vivo.

Conclusions

Endothelial progenitor cells could provide therapeutic effect on PQ-induced ALI via miR-141-3p-Notch-Nrf2 Axis.

Importance and regulation of adult stem cell migration

Cell migration is an essential process throughout the life of vertebrates, beginning during embryonic development and continuing throughout adulthood. Stem cells have an inherent ability to migrate, that is as important as their capacity for self‐renewal and differentiation, enabling them to maintain tissue homoeostasis and mediate repair and regeneration. Adult stem cells reside in specific tissue niches, where they remain in a quiescent state until called upon and activated by tissue environmental signals. Cell migration is a highly regulated process that involves the integration of intrinsic signals from the niche and extrinsic factors. Studies using three‐dimensional in vitro models have revealed the astonishing plasticity of cells in terms of the migration modes employed in response to changes in the microenvironment. These same properties can, however, be subverted during the development of some pathologies such as cancer. In this review, we describe the response of adult stem cells to migratory stimuli and the mechanisms by which they sense and transduce intracellular signals involved in migratory processes. Understanding the molecular events underlying migration may help develop therapeutic strategies for regenerative medicine and to treat diseases with a cell migration component.

Exendin-4 improves cardiovascular function and survival in flow-induced pulmonary hypertension

OBJECTIVES

Systemic left-to-right shunting causes pulmonary arteriopathy, leading to progressive cardiopulmonary failure and a poor prognosis. In this study, we examined the extraglycemic effect of a synthetic glucagon-like peptide, exendin-4, on pulmonary arteriopathy regression and cardiopulmonary function in nondiabetic rats.

METHODS

Pulmonary hypertension (PH) was induced by monocrotaline (60 mg/kg, subcutaneous) injection followed by the creation of an aortocaval fistula. After 4 weeks, exendin-4 (1 μg/kg/day) was administered intraperitoneally for 3 consecutive weeks, followed by an assessment of cardiopulmonary function, pulmonary artery vasoreactivity, tissue and blood biochemistry, and lung histology.

RESULTS

Exendin-4 significantly reduced right ventricle mass and pulmonary artery pressure, which improved right ventricle function and the survival rate in rats with PH. Tissue and blood interleukin-1β levels decreased, whereas pulmonary artery cyclic adenosine monophosphate levels were restored by exendin-4. Smooth muscle-myosin heavy chain-II and α-smooth muscle actin protein levels increased in the pulmonary arteries of exendin-4-treated rats. Histology showed that exendin-4 decreased the main and intra-acinar pulmonary artery medial thickness.

CONCLUSIONS

Exendin-4 treatment improved pulmonary artery function in flow-induced PH via its direct vasoactive properties, anti-inflammatory effects, and vascular smooth muscle cell phenotypic modulation. Mitigation of pulmonary arteriopathy further potentiated right ventricle performance and reduced overall mortality. These responses were associated with suppressed expression and activity of interleukin-1β and its downstream signaling molecules. Glucagon-like peptide analogs may possess pleiotropic therapeutic potential in flow-induced PH.

Detection of intrathrombotic endothelial progenitor cells and its application to thrombus age estimation in a murine deep vein thrombosis model

Endothelial progenitor cells (EPCs), a newly identified cell type, are bone marrow-derived progenitor cells that co-express stem cell markers and Flk-1 (one of the receptors for vascular endothelial growth factor). In this study, double-color immunofluorescence analysis was performed using anti-CD34 and anti-Flk-1 antibodies in order to examine the time-dependent intrathrombotic appearance of EPCs, using the thrombi of DVT model mice with different thrombus ages (1-21 days). In thrombus cross-section specimens with an age of less than 3 days, CD34+/Flk-1+ EPCs were not detected. EPCs were initially observed in wounds aged 5 days, and their number was increased in thrombi with the advance of thrombus ages. The number of EPCs was the largest in the 10-day thrombus. Moreover, all 15 samples aged 7-14 days had an EPC number of more than 10, and, in 9 of them, the number of intrathrombotic EPCs was over 20. In contrast, in all thrombus samples aged 21 days, the number of intrathrombotic EPCs was less than 20. However, in three of them, the intrathrombotic EPC number was ≥ 10. These observations suggested that an intrathrombotic EPC number exceeding 20 would indicate a thrombus age of approximately 7-14 days.

Autologous endothelial progenitor cells improve allograft survival in porcine lung transplantation with prolonged ischemia

BACKGROUND

As endothelial progenitor cells (EPCs) attenuated acute lung injury (ALI) in rabbit model, we hypothesized that autologous EPCs preserved lung graft function during the acute reperfusion period of lung transplantation and tested the therapeutic potential of EPCs in a porcine model of lung transplantation with prolonged graft ischemia.

METHODS

Day-7 EPCs isolated from the recipient subjects or plain culture media were administered into the left pulmonary artery immediately before restoration of pulmonary blood flow in a porcine lung allotransplantation model, with the transplantation surgeons blinded to the content of injection. Hemodynamics and arterial blood gas were recorded, and the right pulmonary artery was occluded 30 min after reperfusion to evaluate the lung graft function. The lung grafts were sectioned for histological examination at the end of experiments. The total ischemic time for lung graft was approximately 14 h.

RESULTS

All animals receiving plain medium died within 40 min after reperfusion, but 3 out of 5 (60%) piglets receiving EPCs survived up to 4 h after diversion of the entire cardiac output into the lung graft (P<0.01). The donor body weight, recipient body weight, cold ischemic time, and time for anastomosis were comparable between the EPC and control group (P=0.989, 0.822, 0.843, and 0.452, respectively). The mean aortic pressure decreased, and the cardiac output and mean pulmonary artery pressure elevated after right pulmonary artery occlusion. All these parameters were gradually compensated in the EPC group but decompensated in the control group. Better preservation of gas exchange function, reduced thrombi formation in the terminal pulmonary arterioles, and attenuated interstitial hemorrhage of the lung graft were observed in the EPC group.

CONCLUSIONS

We concluded autologous EPCs significantly enhanced the function of lung allograft and improved survival in a porcine model of lung transplantation with prolonged ischemia.

Mobilization of Endothelial Progenitor Cells Following Creation of Arteriovenous Access in Patients with End-Stage Renal Disease

BACKGROUND

A patent arteriovenous (AV) fistula induces activation of regional vascular endothelium and vascular shear force. Shear stress is an important physiological force in mobilizing endothelial progenitor cells (EPCs). This study aimed to explore the perioperative changes of circulating EPC levels for patients who require hemodialysis and underwent radiocephalic fistula operation.

METHODS

This prospective cohort study included patients who received a radiocephalic fistula surgery when they were between 25 and 65 years of age. The subjects were followed for 90 days postoperatively for any stenotic events or immaturity of the fistula. Blood samples were obtained on the day before surgery and at postoperation day (POD) 3 and 30. CD133+/KDR+ cells, defined as EPCs, were analyzed using flow cytometry. Blood flow of the fistula was followed on POD 3 and 30.

RESULTS

A total of 30 patients were enrolled in the study from July 2009 to December 2011. One patient dropped out of the study and seven patients developed a stenotic (or immature) AV fistula (7/29, 24.1%). There were positive linear relationships between EPC numbers and shear rate postoperatively, which were more significant on POD 30. In addition, postoperative mobilization of EPCs was significantly higher in patients who developed a stenotic fistula than those without.

CONCLUSIONS

The mobilization of circulating EPCs correlated with a compromised arteriovenous fistula. The biological significance of increased EPC numbers need to be determined in future studies.

KEY WORDS

Arteriovenous fistula; Endothelial progenitor cells.

Regeneration of the lung: Lung stem cells and the development of lung mimicking devices

Inspired by the increasing burden of lung associated diseases in society and an growing demand to accommodate patients, great efforts by the scientific community produce an increasing stream of data that are focused on delineating the basic principles of lung development and growth, as well as understanding the biomechanical properties to build artificial lung devices. In addition, the continuing efforts to better define the disease origin, progression and pathology by basic scientists and clinicians contributes to insights in the basic principles of lung biology. However, the use of different model systems, experimental approaches and readout systems may generate somewhat conflicting or contradictory results. In an effort to summarize the latest developments in the lung epithelial stem cell biology, we provide an overview of the current status of the field. We first describe the different stem cells, or progenitor cells, residing in the homeostatic lung. Next, we focus on the plasticity of the different cell types upon several injury-induced activation or repair models, and highlight the regenerative capacity of lung cells. Lastly, we summarize the generation of lung mimics, such as air-liquid interface cultures, organoids and lung on a chip, that are required to test emerging hypotheses. Moreover, the increasing collaboration between distinct specializations will contribute to the eventual development of an artificial lung device capable of assisting reduced lung function and capacity in human patients.

Induction of Endothelial Phenotype from Wharton's Jelly-Derived MSCs and Comparison of Their Vasoprotective and Neuroprotective Potential with Primary WJ-MSCs in CA1 Hippocampal Region Ex Vivo

Ischemic stroke results in violent impairment of tissue homeostasis leading to severe perturbation within the neurovascular unit (NVU) during the recovery period. The aim of this study was to assess the potential of mesenchymal stem cells (MSCs) originating from Wharton's jelly (WJ) to differentiate into functionally competent cells of endothelial lineage (WJ-EPCs). The protective effect(s) of either primary WJ-MSCs or induced WJ-EPCs was investigated and compared after oxygen–glucose deprivation (OGD) of hippocampal organotypic slices (OHC) in the indirect coculture model. WJ-MSCs, primed in EGM-2 (Lonza commercial medium) under 5% O2, acquired cobblestone endothelial-like morphology, formed capillary-like structures and actively took up DiI-Ac-LDL. Both cell types (WJ-MSCs and WJ-EPCs) were positive for CD73, CD90, CD105, VEGFR-2, and VEGF, but only endothelial-like culture expressed vWF and PECAM-1 markers at significant levels. In the presence of either WJ-MSCs or WJ-EPCs in the compartment below OGD-injured slices, cell death and vascular atrophy in the hypoxia-sensitive CA1 region were substantially decreased. This suggests that a paracrine mechanism may mediate WJ-MSC- and WJ-EPC-dependent protection. Thus, finally, we estimated secretion of the neuro/angio/immunomodulatory molecules IL-6, TGF-β1, and VEGF by these cell cultures. We have found that release of TGF-β1 and IL-6 was TLR ligand [LPS and Poly(I:C)] concentration dependent and stronger in WJ-EPC than WJ-MSC cultures. Simultaneously, the uneven pattern of TLR receptors and modulatory cytokine gene expression was confirmed also on qRT-PCR level, but no significant differences were noticed between WJ-EPC and primary WJ-MSC cultures.

Neonatal Type II Alveolar Epithelial Cell Transplant Facilitates Lung Reparation in Piglets With Acute Lung Injury and Extracorporeal Life Support

OBJECTIVES

Type II alveolar epithelial cells have potential for lung growth and reparation. Extracorporeal membrane oxygenation is used as life support for lung impairment resulting from acute respiratory distress syndrome. We hypothesized that intratracheal transplantation of isogeneic primary type II alveolar epithelial cells in combination with extracorporeal membrane oxygenation may facilitate lung reparation for acute lung injury (ALI).

DESIGN

A randomized, controlled experiment.

SETTING

An animal laboratory in a university pediatric center.

SUBJECTS

Twenty-eight 4- to 6-week young piglets, weighing 7-8 kg.

INTERVENTIONS

Type II alveolar epithelial cells from neonatal male piglet lungs were isolated, purified, cultured, and labeled with chemical stain PKH26. After 3-6 hours of induction of ALI by IV endotoxin and mechanical ventilation (MV), young female piglets were allocated to five groups (n = 5): ALI-MV, ALI treated with MV; ALI-EC, ALI treated with both MV and venovenous extracorporeal membrane oxygenation; ALI-EC-T, ALI-EC protocol plus intratracheal type II alveolar epithelial cell transplant; CON-MV, healthy animals treated with MV; and CON-EC-T, healthy animals treated with venovenous extracorporeal membrane oxygenation. After 24 hours, animals were weaned from treatment for recovery in the ensuing 14 days, with their lungs assessed for injury and reparation.

MEASUREMENTS AND MAIN RESULTS

Lung injury for animals in ALI-MV was moderate to severe, whereas much milder injuries in ALI-EC-T and ALI-EC were found. More PKH26-labeled type II alveolar epithelial cells were detected by fluorescence in the lungs of ALI-EC-T than in CON-EC-T as further verified by the expression of messenger RNA of sex-determining region of Y chromosome. Electromicroscopically intact type II alveolar epithelial cells and prominent lattice-like tubular myelin were also found in ALI-EC-T and CON-MV but not in ALI-EC. The hydroxyproline level in lung tissue was significantly lower in ALI-EC-T than in ALI-EC and ALI-MV, with most of the lung histopathologic and pathobiologic manifestations in favor of ALI-EC-T.

CONCLUSIONS

The preliminary data suggested that type II alveolar epithelial cell transplant facilitated lung reparation for ALI in this model.

Stem cells for respiratory failure

PURPOSE OF REVIEW

The prognosis of patients with respiratory failure in the ICU remains poor, while current therapeutic approaches are aimed at minimizing ventilator-induced lung injury. Stem cell-based therapies have the potential to transform respiratory failure treatment by achieving lung repair. The purpose of this article is to critically review the large body of clinical and experimental work performed with respect to the use of stem/progenitor cells in respiratory failure, and to discuss current challenges and future directions.

RECENT FINDINGS

Since the initial report of cell therapy for lung injury in 2005, numerous preclinical and clinical studies have been performed that support the ability of various stem cell populations to improve physiologic lung function and reduce inflammation in both infective and sterile acute respiratory distress syndrome. Nevertheless, many important issues (e.g., mechanism of action, long-term engraftment, optimal cell type, dose, route of administration) remain to be resolved.

SUMMARY

Cell-based therapeutics hold promise, particularly for acute respiratory distress syndrome, and early preclinical testing has been encouraging. To advance clinical testing of cell therapies in respiratory failure, and to help ensure that this approach will facilitate bench-to-bedside and bedside-to-bench discoveries, parallel paths of basic and clinical research are needed, including measures of cell therapy effectiveness in vivo and in vitro.

Resident Endothelial Cells and Endothelial Progenitor Cells Restore Endothelial Barrier Function After Inflammatory Lung Injury

OBJECTIVE

Disruption of endothelial barrier integrity is a characteristic of many inflammatory conditions. However, the origin and function of endothelial cells (ECs) restoring endothelial barrier function remain unknown. This study defined the roles of resident ECs (RECs) and bone marrow-derived endothelial progenitor cells (BMDEPCs) in endothelial barrier restoration after endotoxemic lung injury.

APPROACH AND RESULTS

We generated mice that enable to quantify proliferating RECs or BMDEPCs and also to study the causal link between REC or BMDEPC proliferation and endothelial barrier restoration. Using these mouse models, we showed that endothelial barrier restoration was associated with increased REC and BMDEPC proliferation. RECs and BMDEPCs participate in barrier repair. Immunofluorescence staining demonstrated that RECs proliferate in situ on endothelial layer and that BMDEPCs are engrafted into endothelial layer of lung microvessels at the active barrier repair phase. In lungs, 8 weeks after lipopolysaccharide-induced injury, the number of REC-derived ECs (CD45(-)/CD31(+)/BrdU(+)/rtTA(+)) or BMDEPC-derived ECs (CD45(-)/CD31(+)/eNOS(+)/GFP(+)) increased by 22- or 121-fold, respectively. The suppression of REC or BMDEPC proliferation by blocking REC or BMDEPC intrinsic nuclear factor-κB at the barrier repair phase was associated with an augmented endothelial permeability and impeded endothelial barrier recovery. RECs and BMDEPCs contributed differently to endothelial barrier repair. In lungs, 8 weeks after lipopolysaccharide-induced injury, REC-derived ECs constituted 22%, but BMDEPC-derived ECs constituted only 3.7% of the total new ECs.

CONCLUSIONS

REC is a major and BMDEPC is a complementary source of new ECs in endothelial barrier restoration. RECs and BMDEPCs play important roles in endothelial barrier restoration after inflammatory lung injury.

Concise review: current status of stem cells and regenerative medicine in lung biology and diseases

Lung diseases remain a significant and devastating cause of morbidity and mortality worldwide. In contrast to many other major diseases, lung diseases notably chronic obstructive pulmonary diseases (COPDs), including both asthma and emphysema, are increasing in prevalence and COPD is expected to become the third leading cause of disease mortality worldwide by 2020. New therapeutic options are desperately needed. A rapidly growing number of investigations of stem cells and cell therapies in lung biology and diseases as well as in ex vivo lung bioengineering have offered exciting new avenues for advancing knowledge of lung biology as well as providing novel potential therapeutic approaches for lung diseases. These initial observations have led to a growing exploration of endothelial progenitor cells and mesenchymal stem (stromal) cells in clinical trials of pulmonary hypertension and COPD with other clinical investigations planned. Ex vivo bioengineering of the trachea, larynx, diaphragm, and the lung itself with both biosynthetic constructs as well as decellularized tissues have been used to explore engineering both airway and vascular systems of the lung. Lung is thus a ripe organ for a variety of cell therapy and regenerative medicine approaches. Current state-of-the-art progress for each of the above areas will be presented as will discussion of current considerations for cell therapy-based clinical trials in lung diseases.

Bone marrow-derived progenitor cells attenuate inflammation in lipopolysaccharide-induced acute respiratory distress syndrome

Background

Acute respiratory distress syndrome (ARDS) is the most common cause of respiratory failure among critically ill patients. Novel treatment strategies are required to address this common clinical problem. The application of exogenous adult stem cells was associated with a beneficial outcome in various pre-clinical models of ARDS. In the present study we evaluated the functional capacity and homing ability of bone marrow-derived progenitor cells (BMDPC) in vitro and investigated their potential as a treatment strategy in lipopolysaccharide (LPS)-induced ARDS.

Results

Evaluation of the BMDPC showed functional capacity to form endothelial outgrowth cell colonies, which stained positive for CD133 and CD31. Furthermore, DiI-stained BMDPC were demonstrated to home to injured lung tissue. Rats treated with BMDPC showed significantly reduced histopathological changes, a reduced expression of ICAM-1 and VCAM-1 by the lung tissue, an inhibition of proinflammatory cytokine synthesis, a reduced weight loss and a reduced mortality (p < 0.03) compared to rats treated with LPS alone.

Conclusions

These findings suggest that the application of exogenous BMDPC can attenuate inflammation in LPS-induced ARDS and thereby reduce the severity of septic organ damage. Cell therapy strategies using adult stem cells might therefore become a novel and alternative option in ARDS therapy.

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.

Adult stem cells for acute lung injury: remaining questions and concerns

Acute lung injury (ALI) or acute respiratory distress syndrome remains a major cause of morbidity and mortality in hospitalized patients. The pathophysiology of ALI involves complex interactions between the inciting event, such as pneumonia, sepsis or aspiration, and the host immune response resulting in lung protein permeability, impaired resolution of pulmonary oedema, an intense inflammatory response in the injured alveolus and hypoxemia. In multiple preclinical studies, adult stem cells have been shown to be therapeutic due to both the ability to mitigate injury and inflammation through paracrine mechanisms and perhaps to regenerate tissue by virtue of their multi-potency. These characteristics have stimulated intensive research efforts to explore the possibility of using stem or progenitor cells for the treatment of lung injury. A variety of stem or progenitor cells have been isolated, characterized and tested experimentally in preclinical animal models of ALI. However, questions remain concerning the optimal dose, route and the adult stem or progenitor cell to use. Here, the current mechanisms underlying the therapeutic effect of stem cells in ALI as well as the questions that will arise as clinical trials for ALI are planned are reviewed.

Preconditioning renoprotective effect of isoflurane in a rat model of virtual renal transplant

BACKGROUND

The development of warm-cold ischemia-reperfusion (IR) injury of the kidney grafts is inevitable during renal transplantation. However, there is currently no definite renoprotective strategy available in the protection of the graft tissue. In the present study, we compared the renal protection of preconditioning isoflurane with N-acetylcysteine (NAC) in a novel rat model of warm-cold renal IR injury.

MATERIALS AND METHODS

Adult Sprague-Dawley rats were randomly assigned to receive inhaled isoflurane (1.5% for 2 h), NAC (1 g/kg, intra-arterial injection) or placebo before the induction of brief warm ischemia (10 min) followed by cold ischemia (45 min) periods. Plasma levels of creatinine and tissue inflammatory reaction in the kidney were analyzed 72 h after reperfusion.

RESULTS

Elevated plasma level of creatinine and urea indicated the development of acute renal injury secondary to IR injury. The creatinine levels were reduced in animals pretreated with inhaled isoflurane and NAC, and the level was more significantly decreased in the isoflurane-treated group. Preconditioning with volatile isoflurane also significantly suppressed the tissue myeloperoxidase activity and expression of the inducible nitric oxide synthase. Immunostaining confirmed that myeloperoxidase expression was most significantly attenuated in the glomerulus and peritubular capillaries of rats pre-exposed to isoflurane.

CONCLUSIONS

We present the first study demonstrating that the administration of volatile isoflurane before induction of experimental warm-cold renal IR injury provides preconditioning renoprotective effect, which is superior to the treatment with NAC. The beneficial renoprotective effect of isoflurane is most likely mediated by attenuation of proinflammatory reaction in the injured kidney.

Repair of lipopolysaccharide-induced acute lung injury in mice by endothelial progenitor cells, alone and in combination with simvastatin

BACKGROUND

Endothelial progenitor cells (EPCs) are involved in endothelium repair of acute lung injury (ALI). Numerous studies have demonstrated that statins can promote EPC function in vitro and in vivo; therefore, the purpose of this study was to determine whether simvastatin enhances the function of EPCs participating in the repair of ALI.

METHODS

BALB/C mice were initially pretreated with simvastatin by intraperitoneal administration 24 h before, and again at the time of, intratracheal instillation of lipopolysaccharide (LPS) and subsequently treated with EPCs by i.v. transplantation 2 h later. The effects of capillary permeability, endothelium repair, and inflammatory cytokines were measured.

RESULTS

This study revealed that both simvastatin administration and EPC transplantation can reduce the severity of LPS-induced ALI in mice, and the effect can be further improved by combining the two therapies.

CONCLUSIONS

The administration of simvastatin and EPC transplantation can reduce the severity of LPS-induced ALI in mice, and improvement is moderately enhanced in some respects when EPC transplantation is combined with simvastatin administration. The beneficial role of simvastatin on EPCs may be a component of its pleiotropic effects. Although the exact mechanism remains unknown, the combined administration of simvastatin and EPC transplantation may be a potentially important, cell-based, inflammation-mediated therapy for patients with ALI/ARDS.

Transplantation of autologous endothelial progenitor cells in porous PLGA scaffolds create a microenvironment for the regeneration of hyaline cartilage in rabbits

OBJECTIVE

Repairing articular cartilage is clinically challenging. We investigated a simple, effective and clinically feasible cell-based therapeutic approach using a poly(lactide-co-glycolide) (PLGA) scaffold seeded with autologous endothelial progenitor cells (EPC) to repair a full-thickness osteochondral defect in rabbits using a one-step surgery.

METHODS

EPC obtained by purifying a small amount of peripheral blood from rabbits were seeded into a highly porous, biocompatible PLGA scaffold, namely, EPC-PLGA, and implanted into the osteochondral defect in the medial femoral condyle. Twenty two rabbits were randomized into one of three groups: the empty defect group (ED), the PLGA-only group or the EPC-PLGA group. The defect sites were evaluated 4 and 12 weeks after implantation.

RESULTS

At the end of testing, only the EPC-PLGA group showed the development of new cartilage tissue with a smooth, transparent and integrated articular surface. Moreover, histological analysis showed obvious differences in cartilage regeneration. At week 4, the EPC-PLGA group showed considerably higher TGF-β2 and TGF-β3 expression, a greater amount of synthesized glycosaminoglycan (GAG) content, and a higher degree of osteochondral angiogenesis in repaired tissues. At week 12, the EPC-PLGA group showed enhanced hyaline cartilage regeneration with a normal columnar chondrocyte arrangement, higher SOX9 expression, and greater GAG and collagen type II (COLII) content. Moreover, the EPC-PLGA group showed organized osteochondral integration, the formation of vessel-rich tubercular bone and significantly higher bone volume per tissue volume and trabecular thickness (Tb.Th).

CONCLUSION

The present EPC-PLGA cell delivery system generates a suitable in situ microenvironment for osteochondral regeneration without the supplement of exogenous growth factors.

Intracavernous administration of bone marrow mononuclear cells: a new method of treating erectile dysfunction?

While PDE5 inhibitors have revolutionized treatment of ED, approximately 30% of patients are non-responsive. A significant cause of this is vascular and smooth muscle dysfunction, as well as nerve atrophy. Autologous administration of bone marrow mononuclear cells (BMMC) has been performed in over 2000 cardiac patients without adverse effects, for stimulation of angiogenesis/regeneration. Despite its ease of access, and dependence on effective vasculature for function, comparatively little has been perform in terms of BMMC therapy for ED. Here we outline the rationale for use of autologous BMMC in patients with ED, as well as provide early safety data on the first use of this procedure clinically.

Endothelial progenitor cells in regeneration after acute lung injury: do they play a role?

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common disorders in patients requiring critical care. The clinical management of these disorders is difficult and unrewarding, and thus they are among the most common causes of death in intensive care units. The activation and damage of pulmonary endothelium comprise the hallmark of ALI/ARDS. Therefore, the recruitment of circulating endothelial progenitor cells (EPCs) to these lesions may exert a beneficial effect on the clinical course of ALI/ARDS. Consequently, cell-based therapies using stem cells to regenerate lung tissue have emerged as potential novel treatment strategies. Although initial studies suggested implantations of exogenously administered bone marrow-derived progenitor cells into damaged vessel walls, recent evidence indicates that this is rather a rare occurrence with uncertain physiologic significance. In the past few years, different populations of progenitor cells were identified, with different functional capacities. This review (1) highlights the different populations of EPCs identified or administered in different models of ALI/ARDS, (2) reports on whether beneficial effects of EPCs could be demonstrated, and (3) puts the conflicting results of different studies into perspective.

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.

Autologous transplantation of endothelial progenitor cells to prevent multiple organ dysfunction syndromes in pig

BACKGROUND

It was observed that the number and function of endothelial progenitor cells (EPCs) decreased sharply in the progression of multiple organ dysfunction syndrome (MODS), and it may be the main pathogenesis for MODS. We aim to perform autologous transplantation of EPCs on animal models of MODS to investigate whether EPCs might be used to prevent MODS caused by severe sepsis.

METHODS

A total of 60 pigs were randomly divided into three groups: subjected to hemorrhagic shock + resuscitation + endotoxemia only (MODS group); performed autologous transplantation of EPCs after hemorrhagic shock + resuscitation + endotoxemia (transplantation group); and control group. Mononuclear cells of animals of the transplantation group were isolated by density-gradient centrifugation for ex vivo expansion, and the six-passage EPCs labeled with 5-carboxyfluorescein diacetate succinimidyl ester were autologously transplanted at a density of 1 × 10(7) cells/kg body weight at the 24th hour after endotoxemia. The function of important organs was monitored continuously to assess the effects of autologous transplantation of EPCs on MODS.

RESULTS

All animals of the MODS group developed MODS (100%), and 17 (85%) of 20 animals died because of MODS; the incidence of MODS and mortality rate in the transplantation group were 45% (9 of 20 pigs; p < 0.01) and 35% (7 of 20 pigs; p < 0.01). In transplantation group, the incidence of pulmonary dysfunction, cardiac dysfunction, hepatosis, and renal dysfunction were 40%, 10%, 5%, and 15%, respectively. The capillary densities of important organs, including the heart, liver, kidney, intestine, and lung, after autologous transplantation of EPCs were significantly higher than those in the MODS group (p < 0.01).

CONCLUSION

Autologous transplantation of EPCs could migrate to injured organs and induce angiogenesis to restore blood flow that could improve the function of important organs. It could prevent the incidence of MODS and reduce mortality rate caused by trauma and severe sepsis. Autologous transplantation of EPCs would be a novel, cell-based, vascular endothelium-targeted therapeutic strategy for MODS.

Endothelial progenitor cells: the promise of cell-based therapies for acute lung injury

BACKGROUND

Endothelial progenitor cells (EPCs) are defined as a special type of stem cell that have been found to directly incorporate into injured vessels and that participate in angiogenesis and reconstruction by differentiation into endothelial cells. EPCs are widely used to therapeutically treat cardiovascular disease, limb ischemia and vascular repair. However, the role of EPCs in inflammatory diseases, especially in lung injury, is less studied.

OBJECTIVE

To investigate the application of EPCs to vascular repair, and the role of EPCs in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

METHODS

A computer-based online search was performed in the PubMed database and Web of Science database for articles published, concerning EPCs, angiogenesis, ALI/ARDS and stem cell transplantation

CONCLUSION

EPCs have a therapeutic potential for vascular regeneration and may emerge as novel strategy for the diseases that are associated with ALI/ARDS.

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.

The preconditioning pulmonary protective effect of volatile isoflurane in acute lung injury is mediated by activation of endogenous iNOS

PURPOSE

There is still a lack of evidence to support the use of specific anesthetic agents during major operations that could affect the development of postoperative acute lung injury (ALI). This study determined the protective effect of inhaled isoflurane in a rat model of endotoxin-induced ALI.

METHODS

Rats were exposed to volatile isoflurane (1.5 % in oxygen) or pure oxygen via a facemask for 2 h. After a 3-h recovery period, rats were reanesthetized and ALI was induced by intratracheal instillation of lipopolysaccharide (LPS, 1 mg/kg in 0.5 ml saline). In some animals, a specific inducible nitric oxide synthase (iNOS) inhibitor, 1400W, (10 mg/kg, i.p.) was administered before exposure to isoflurane. Animals were sacrificed 12 h later for analysis. Pulmonary artery vasomotor function and alveolocapillary permeability were assessed. Expression of iNOS and CD11b, and activity of myeloperoxidase in the lung were analyzed.

RESULTS

The maximal relaxation response to acetylcholine was significantly potentiated in rats pretreated with isoflurane. Lung wet-to-dry ratio was reduced in the lung of isoflurane-treated animals. Expression of iNOS and CD11b were attenuated in the lung tissue obtained from rats receiving isoflurane. Furthermore, enzymatic activity of myeloperoxidase was also reduced in the lung preexposed to isoflurane. However, these pulmonary protective effects of isoflurane were significantly abolished by pretreatment with 1400W.

CONCLUSION

Pretreatment with volatile isoflurane attenuated inflammatory process in the lung tissue of rats with LPS-induced ALI, and this preconditioning pulmonary protective effect was mainly mediated by activation of endogenous iNOS in the lung.

Autologous stromal vascular fraction therapy for rheumatoid arthritis: rationale and clinical safety

Advancements in rheumatoid arthritis (RA) treatment protocols and introduction of targeted biological therapies have markedly improved patient outcomes, despite this, up to 50% of patients still fail to achieve a significant clinical response. In veterinary medicine, stem cell therapy in the form of autologous stromal vascular fraction (SVF) is an accepted therapeutic modality for degenerative conditions with 80% improvement and no serious treatment associated adverse events reported. Clinical translation of SVF therapy relies on confirmation of veterinary findings in targeted patient populations. Here we describe the rationale and preclinical data supporting the use of autologous SVF in treatment of RA, as well as provide 1, 3, 6, and 13 month safety outcomes in 13 RA patients treated with this approach.