Pro-angiogenic hematopoietic progenitor cells and endothelial colony-forming cells in pathological angiogenesis of bronchial and pulmonary circulation

Aberration in myeloid-derived pro-angiogenic cells in type-2 diabetes mellitus; implication for diabetic retinopathy?

Purpose

Diabetic retinopathy (DR) is a major microvascular complication of type 2 diabetes mellitus (T2DM). Myelomonocytic proangiogenic cells (PAC) have been implicated in DR pathogenesis, but their functional and developmental abnormalities are unclear. In this study we assessed PAC characteristics from healthy controls, T2DM patients with DR (DR) and without (NoDR) in order to determine the consequence of the diabetic condition on PAC phenotype and function, and whether these differ between DR and NoDR patients.

Methods

PAC were generated by culturing PBMC on fibronectin coating and then immunophenotyped using flow cytometry. Furthermore, cells were sorted based on CD14, CD105, and CD133 expression and added to an in vitro 3-D endothelial tubule formation assay, containing GFP-expressing human retinal endothelial cells (REC), pericytes, and pro-angiogenic growth factors. Tubule formation was quantified by fluorescence microscopy and image analysis. Moreover, sorted populations were analyzed for angiogenic mediator production using a multiplex assay.

Results

The expression of CD16, CD105 and CD31, but not CD133, was lower in PAC from T2DM patients with or without DR. Myeloid and non-myeloid T2DM-derived sorted populations increased REC angiogenesis in vitro as compared to control cultures. They also showed increased S100A8 secretion, decreased VEGF-A secretion, and similar levels of IL-8, HGF, and IL-3 as compared to healthy control (HC)-derived cell populations.

Conclusion

T2DM PAC are phenotypically and functionally altered compared to PAC from HC. Differences between DR and NoDR PAC are limited. We propose that impaired T2DM PAC provide inadequate vascular support and promote compensatory, albeit pathological, retinal neovascularization.

Liquid biopsy at the frontier of detection, prognosis and progression monitoring in colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide and a leading cause of carcinogenic death. To date, surgical resection is regarded as the gold standard by the operator for clinical decisions. Because conventional tissue biopsy is invasive and only a small sample can sometimes be obtained, it is unable to represent the heterogeneity of tumor or dynamically monitor tumor progression. Therefore, there is an urgent need to find a new minimally invasive or noninvasive diagnostic strategy to detect CRC at an early stage and monitor CRC recurrence. Over the past years, a new diagnostic concept called “liquid biopsy” has gained much attention. Liquid biopsy is noninvasive, allowing repeated analysis and real-time monitoring of tumor recurrence, metastasis or therapeutic responses. With the advanced development of new molecular techniques in CRC, circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), exosomes, and tumor-educated platelet (TEP) detection have achieved interesting and inspiring results as the most prominent liquid biopsy markers. In this review, we focused on some clinical applications of CTCs, ctDNA, exosomes and TEPs and discuss promising future applications to solve unmet clinical needs in CRC patients.

Angiogenesis: A Cellular Response to Traumatic Injury

ABSTRACT

The development of new vasculature plays a significant role in a number of chronic disease states, including neoplasm growth, peripheral arterial disease, and coronary artery disease, among many others. Traumatic injury and hemorrhage, however, is an immediate, often dramatic pathophysiologic insult that can also necessitate neovascularization to promote healing. Traditional understanding of angiogenesis involved resident endothelial cells branching outward from localized niches in the periphery. Additionally, there are a small number of circulating endothelial progenitor cells that participate directly in the process of neovessel formation. The bone marrow stores a relatively small number of so-called pro-angiogenic hematopoietic progenitor cells-that is, progenitor cells of a hematopoietic potential that differentiate into key structural cells and stimulate or otherwise support local cell growth/differentiation at the site of angiogenesis. Following injury, a number of cytokines and intercellular processes are activated or modulated to promote development of new vasculature. These processes initiate and maintain a robust response to vascular insult, allowing new vessels to canalize and anastomose and provide timely oxygen delivering to healing tissue. Ultimately as we better understand the key players in the process of angiogenesis we can look to develop novel techniques to promote healing following injury.

Human CD133-positive hematopoietic progenitor cells enhance the malignancy of breast cancer cells

BACKGROUND

Human CD133+ hematopoietic progenitor cells (HPCs) are a specific subset of cells that can regulate tumor malignancy. However, the mechanism by which CD133+ HPCs affect the malignancy of human breast cancer has not been reported.

METHODS

CD133+ HPCs were isolated and purified from human umbilical cord blood (UCB). We used in vitro culture of MCF-7 and MDA-MB-231 cell lines, and MCF-7 and MDA-MB-231 cells in nude mice to evaluate whether CD133+ HPCs affected the apoptosis, proliferation, invasion and epithelial mesenchymal transition EMT of breast cancer cells.

RESULTS

Co-culture with CD133+ HPCs, but not UCB CD133- cells, promoted the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells, accompanied by reducing in vitro spontaneous apoptosis. Co-administration of these two lines with CD133+ HPCs significantly enhanced the growth of implanted breast cancer in vivo. Furthermore, co-culture with CD133+ HPCs, enhanced the invasion of breast cancer cells, N-cadherin and Vimentin expression, but reduced E-cadherin expression in breast cancer cells.

CONCLUSIONS

Our study demonstrated that CD133+ HPCs enhance the malignancy of breast cancer cells by attenuating spontaneous apoptosis and promoting the process of epithelial mesenchymal transition. These findings may provide new insights into the role of human CD133+ HPCs in breast cancer pathogenesis. Therefore, CD133+ HPCs may be a new therapeutic target for inhibiting the progression of breast cancer.

Role of fibrocytes and endothelial progenitor cells among low-differentiated CD34+ cells in the progression of lung sarcoidosis

Background

Sarcoidosis is a multisystemic granulomatous disease with still unknown etiology. Our previous studies showed a significantly higher percentage of CD34 + cells in the peripheral blood in patients with sarcoidosis (SA) compared to the control group. The objective of the present study was to characterized of the CD34 + cell population in peripheral blood in patients with SA with reference to the control group. Moreover in patients with SA, fibrocytes and endothelial cells were analysed and their relationship to the fibrosis process based on assessment of diffusing capacity for carbon monoxide (DLCO).

Methods

Data from patients diagnosed with SA at Military Institute of Medicine (Warsaw, Poland) between January 2018 and December 2019 were collected and analysed ongoing basis. Peripheral blood was collected from 26 patients with newly diagnosed pulmonary SA and 16 healthy subjects. The immunomagnetic method and flow cytometry were used. Among the CD34+ progenitor cells were assessed: low-differentiated cells, hematopoietic progenitor cells and endothelial progenitor cells. The Statistica 12.0 software was used for a statistical analysis.

Results

We observed a significantly higher percentage of low-differentiated cells (13.8 vs. 2.3, P = 0.001) and endothelial cells (0.3 vs. 0.0, P = 0.001) in patients with SA compared to the control group. In the study group the median proportion of fibrocytes was 1.877% (0.983–2.340) in patients with DLCO< 80%, while in patients with DLCO> 80% was 0.795% (0.139–1.951) (P = 0.72). The median proportion of endothelial progenitor cells was higher in patients with DLCO< 80%: 0.889% (0.391–1.741), than in patients with DLCO> 80%: 0.451% (0.177–0.857) (P = 0.44).

Conclusions

In conclusion we demonstrated for the first time the immunophenotype of peripheral CD34 + cells with the degree of their differentiation. The study confirmed the involvement of low differentiated cells and endothelial cells in patients with SA.

Bone Marrow-Derived Cells Restore Functional Integrity of the Gut Epithelial and Vascular Barriers in a Model of Diabetes and ACE2 Deficiency

RATIONALE

There is incomplete knowledge of the impact of bone marrow cells on the gut microbiome and gut barrier function.

OBJECTIVE

We postulated that diabetes mellitus and systemic ACE2 (angiotensin-converting enzyme 2) deficiency would synergize to adversely impact both the microbiome and gut barrier function.

METHODS AND RESULTS

Bacterial 16S rRNA sequencing and metatranscriptomic analysis were performed on fecal samples from wild-type, ACE2^-/y, Akita (type 1 diabetes mellitus), and ACE2^-/y-Akita mice. Gut barrier integrity was assessed by immunofluorescence, and bone marrow cell extravasation into the small intestine was evaluated by flow cytometry. In the ACE2^-/y-Akita or Akita mice, the disrupted barrier was associated with reduced levels of myeloid angiogenic cells, but no increase in inflammatory monocytes was observed within the gut parenchyma. Genomic and metatranscriptomic analysis of the microbiome of ACE2^-/y-Akita mice demonstrated a marked increase in peptidoglycan-producing bacteria. When compared with control cohorts treated with saline, intraperitoneal administration of myeloid angiogenic cells significantly decreased the microbiome gene expression associated with peptidoglycan biosynthesis and restored epithelial and endothelial gut barrier integrity. Also indicative of diabetic gut barrier dysfunction, increased levels of peptidoglycan and FABP-2 (intestinal fatty acid-binding protein 2) were observed in plasma of human subjects with type 1 diabetes mellitus (n=21) and type 2 diabetes mellitus (n=23) compared with nondiabetic controls (n=23). Using human retinal endothelial cells, we determined that peptidoglycan activates a noncanonical TLR-2 (Toll-like receptor 2) associated MyD88 (myeloid differentiation primary response protein 88)-ARNO (ADP-ribosylation factor nucleotide-binding site opener)-ARF6 (ADP-ribosylation factor 6) signaling cascade, resulting in destabilization of p120-catenin and internalization of VE-cadherin as a mechanism of deleterious impact of peptidoglycan on the endothelium.

CONCLUSIONS

We demonstrate for the first time that the defect in gut barrier function and dysbiosis in ACE2^-/y-Akita mice can be favorably impacted by exogenous administration of myeloid angiogenic cells.

Angiogenesis in the lung

Both systemic (tracheal and bronchial) and pulmonary circulations perfuse the lung. However, documentation of angiogenesis of either is complicated by the presence of the other. Well-documented angiogenesis of the systemic circulations have been identified in asthma, cystic fibrosis, chronic thromboembolism and primary carcinomas. Angiogenesis of the vasa vasorum, which are branches of bronchial arteries, is seen in the walls of large pulmonary vessels after a period of chronic hypoxia. Documentation of increased pulmonary capillaries has been shown in models of chronic hypoxia, after pneumonectomy and in some carcinomas. Although endothelial cell proliferation may occur as part of the repair process in several pulmonary diseases, it is separate from the unique establishment of new functional perfusing networks defined as angiogenesis. Identification of the mechanisms driving the expansion of new vascular beds in the adult needs further investigation. Yet the growth factors and molecular mechanisms of lung angiogenesis remain difficult to separate from underlying disease sequelae.

Endothelial to haematopoietic transition contributes to pulmonary arterial hypertension

Aims

The pathogenic mechanisms of pulmonary arterial hypertension (PAH) remain unclear, but involve dysfunctional endothelial cells (ECs), dysregulated immunity and inflammation in the lung. We hypothesize that a developmental process called endothelial to haematopoietic transition (EHT) contributes to the pathogenesis of pulmonary hypertension (PH). We sought to determine the role of EHT in mouse models of PH, to characterize specific cell types involved in this process, and to identify potential therapeutic targets to prevent disease progression.

Methods and results

When transgenic mice with fluorescence protein ZsGreen-labelled ECs were treated with Sugen/hypoxia (Su/Hx) combination to induce PH, the percentage of ZsGreen+ haematopoietic cells in the peripheral blood, primarily of myeloid lineage, significantly increased. This occurrence coincided with the depletion of bone marrow (BM) ZsGreen+ c-kit+ CD45- endothelial progenitor cells (EPCs), which could be detected accumulating in the lung upon PH-induction. Quantitative RT-PCR based gene array analysis showed that key transcription factors driving haematopoiesis were expressed in these EPCs. When transplanted into lethally irradiated recipient mice, the BM-derived EPCs exhibited long-term engraftment and haematopoietic differentiation capability, indicating these EPCs are haemogenic in nature. Specific inhibition of the critical haematopoietic transcription factor Runx1 blocked the EHT process in vivo, prevented egress of the BM EPCs and ultimately attenuated PH progression in Su/Hx- as well as in monocrotaline-induced PH in mice. Thus, myeloid-skewed EHT promotes the development of PH and inhibition of this process prevents disease progression in mouse models of PH. Furthermore, high levels of Runx1 expression were found in circulating CD34+ CD133+ EPCs isolated from peripheral blood of patients with PH, supporting the clinical relevance of our proposed mechanism of EHT.

Conclusion

EHT contributes to the pathogenesis of PAH. The transcription factor Runx1 may be a novel therapeutic target for the treatment of PAH.

Endothelial cells in the innate response to allergens and initiation of atopic asthma

Protease-activated receptor 2 (PAR-2), an airway epithelial pattern recognition receptor (PRR), participates in the genesis of house dust mite-induced (HDM-induced) asthma. Here, we hypothesized that lung endothelial cells and proangiogenic hematopoietic progenitor cells (PACs) that express high levels of PAR-2 contribute to the initiation of atopic asthma. HDM extract (HDME) protease allergens were found deep in the airway mucosa and breaching the endothelial barrier. Lung endothelial cells and PACs released the Th2-promoting cytokines IL-1α and GM-CSF in response to HDME, and the endothelium had PAC-derived VEGF-C-dependent blood vessel sprouting. Blockade of the angiogenic response by inhibition of VEGF-C signaling lessened the development of inflammation and airway remodeling in the HDM model. Reconstitution of the bone marrow in WT mice with PAR-2-deficient bone marrow also reduced airway inflammation and remodeling. Adoptive transfer of PACs that had been exposed to HDME induced angiogenesis and Th2 inflammation with remodeling similar to that induced by allergen challenge. Our findings identify that lung endothelium and PACs in the airway sense allergen and elicit an angiogenic response that is central to the innate nonimmune origins of Th2 inflammation.

Hypoxia induces the dysfunction of human endothelial colony-forming cells via HIF-1α signaling

Endothelial injury is considered as a trigger of pulmonary vascular lesions in the pathogenesis of hypoxic pulmonary hypertension (HPH). Although endothelial colony-forming cells (ECFCs) have vascular regeneration potential to maintain endothelial integrity, hypoxia-induced precise alteration in ECFCs function remains controversial. This study investigated the impact of hypoxia on human ECFCs function in vitro and the underlying mechanism. We found that hypoxia inhibited ECFCs proliferation, migration and angiogenesis. Compared with no treatment, the expression of hypoxia inducible factor-1α (HIF-1α) in hypoxia-treated ECFCs was increased, with an up-regulation of p27 and a down-regulation of cyclin D1. The over-secreted vascular endothelial growth factor (VEGF) was detected, with the imbalanced expression of fetal liver kinase 1 (flk-1) and fms related tyrosine kinase 1 (flt-1). Hypoxia-induced changes in ECFCs could be reversed by HIF-1α inhibitor KC7F2. These data suggest that HIF-1α holds the key in regulating ECFCs function which may open a new perspective of ECFCs in HPH management.

Surgical and immune reconstitution murine models in bone marrow research: Potential for exploring mechanisms in sepsis, trauma and allergy

Bone marrow, the vital organ which maintains lifelong hemopoiesis, currently receives considerable attention, as a source of multiple cell types which may play important roles in repair at distant sites. This emerging function, distinct from, but closely related to, bone marrow roles in innate immunity and inflammation, has been characterized through a number of strategies. However, the use of surgical models in this endeavour has hitherto been limited. Surgical strategies allow the experimenter to predetermine the site, timing, severity and invasiveness of injury; to add or remove aggravating factors (such as infection and defects in immunity) in controlled ways; and to manipulate the context of repair, including reconstitution with selected immune cell subpopulations. This endows surgical models overall with great potential for exploring bone marrow responses to injury, inflammation and infection, and its roles in repair and regeneration. We review three different murine surgical models, which variously combine trauma with infection, antigenic stimulation, or immune reconstitution, thereby illuminating different aspects of the bone marrow response to systemic injury in sepsis, trauma and allergy. They are: (1) cecal ligation and puncture, a versatile model of polymicrobial sepsis; (2) egg white implant, an intriguing model of eosinophilia induced by a combination of trauma and sensitization to insoluble allergen; and (3) ectopic lung tissue transplantation, which allows us to dissect afferent and efferent mechanisms leading to accumulation of hemopoietic cells in the lungs. These models highlight the gain in analytical power provided by the association of surgical and immunological strategies.

Intravenous Arginine Administration Promotes Proangiogenic Cells Mobilization and Attenuates Lung Injury in Mice with Polymicrobial Sepsis

This study investigated the influence of intravenous arginine (Arg) administration on alteration of circulating proangiogenic cells and remote lung injury in a model of polymicrobial sepsis. Mice were assigned to one normal control group (NC) and two sepsis groups that were induced by cecal ligation and puncture (CLP). One of the sepsis groups was injected with saline (SS), whereas the other (SA) was administered with a single bolus of 300 mg Arg/kg body weight via the tail vein 1 h after CLP. Septic mice were sacrificed at either 24 or 48 h after CLP, with their blood and lung tissues collected for analysis. Results showed that septic groups had higher proangiogenic cells releasing factors and proangiogenic cells percentage in blood. Also, concentration of inflammatory cytokines and expression of angiopoietin (Angpt)/Tie-2 genes in lung tissues were upregulated. Arg administration promoted mobilization of circulating proangiogenic cells while it downregulated the production of inflammatory cytokines and expression of Angpt/Tie-2 genes in the lung. The results of this investigation suggested that intravenous administration of Arg shortly after the onset of sepsis enhanced the mobilization of circulating proangiogenic cells, maintained the homeostasis of the Angpt/Tie-2 axis, and attenuated remote organ injury in polymicrobial sepsis.

Umbilical Cord Blood Circulating Progenitor Cells and Endothelial Colony-Forming Cells Are Decreased in Preeclampsia

Preeclampsia (PE) is a pregnancy-specific disease characterized by the new onset of hypertension and proteinuria. Mothers with PE are known to develop endothelial dysfunction, but its effect on infants has been understudied, as newborns are often asymptomatic. Recent studies indicate that infants born from preeclamptic pregnancies develop endothelial dysfunction including higher blood pressure during childhood and an increased risk of stroke later in life. We hypothesize that PE reduces the number and function of fetal angiogenic progenitor cells and may contribute to this increased risk. We quantified 2 distinct types of angiogenic progenitors, pro-angiogenic circulating progenitor cells (CPCs) and endothelial colony-forming cells (ECFCs), from the umbilical cord blood of preeclamptic pregnancies and normotensive controls. Pro-angiogenic and nonangiogenic CPCs were enumerated via flow cytometry and ECFCs by cell culture. Additionally, we studied the growth, migration, and tube formation of ECFCs from PE and gestational age-matched normotensive control pregnancies. We found that PE resulted in decreased cord blood pro-angiogenic CPCs and ECFCs. Nonangiogenic CPCs were also decreased. Preeclamptic ECFCs demonstrated decreased growth and migration but formed tube-like structures in vitro similar to controls. Our results suggest that the preeclamptic environment alters the number and function of angiogenic progenitor cells and may increase the risk of later vascular disease.

Eotaxin-Rich Proangiogenic Hematopoietic Progenitor Cells and CCR3+ Endothelium in the Atopic Asthmatic Response

Angiogenesis is closely linked to and precedes eosinophilic infiltration in asthma. Eosinophils are recruited into the airway by chemoattractant eotaxins, which are expressed by endothelial cells, smooth muscles cells, epithelial cells, and hematopoietic cells. We hypothesized that bone marrow-derived proangiogenic progenitor cells that contain eotaxins contribute to the initiation of angiogenesis and inflammation in asthma. Whole-lung allergen challenge of atopic asthma patients revealed vascular activation occurs within hours of challenge and before airway inflammation. The eotaxin receptor CCR3 was expressed at high levels on submucosal endothelial cells in patients and a murine model of asthma. Ex vivo exposure of murine endothelial cells to eotaxins induced migration and angiogenesis. In mechanistic studies, wild-type mice transplanted with eotaxin-1/2-deficient bone marrow had markedly less angiogenesis and inflammation in an atopic asthma model, whereas adoptive transfer of proangiogenic progenitor cells from wild-type mice in an atopic asthma model into the eotaxin-1/2-deficient mice led to angiogenesis and airway inflammation. The findings indicate that Th2-promoting hematopoietic progenitor cells are rapidly recruited to the lung upon allergen exposure and release eotaxins that coordinately activate endothelial cells, angiogenesis, and airway inflammation.

Determining the necessity for right heart catheterization in pulmonary hypertension associated with connective tissue diseases assessed by echocardiography

AIM

The prognosis of pulmonary hypertension (PH) in systemic sclerosis (SSC) and in systemic lupus erythematosus (SLE) is different. According to the guidelines, right heart catheterization (RHC) is necessary in pulmonary arterial hypertension (PAH) associated with connective tissue diseases (CTD). However, there is little supporting evidence. Therefore, we attempted to determine the necessity for RHC and the causes of differences in prognosis of PH by comparing SSC to SLE.

METHODS

The inclusion criteria were all patients with SSC or SLE with exertional dyspnea. Echocardiography and carotid Doppler ultrasound were performed.

RESULTS

Twenty-three patients with SSC and 23 with SLE participated in this study. There was no difference in the right ventricular systolic pressure (RVSP) between SSC and SLE (33.0 mmHg, range 25.3-41.7 mmHg vs. 32.4 mmHg, range 27.0-37.7 mmHg; P = 0.835). In multiple linear regression analysis, the ratio of peak tricuspid regurgitant velocity to right ventricular outflow tract time-velocity integral, which represents pulmonary vascular resistance (PVR), was correlated with RVSP in SSC (r(2) = 0.928, β = 0.362, P = 0.003), and the independent predictor of increased RVSP was the ratio of early diastolic transmitral filling velocity to early diastolic septal mitral annular velocity, which represents diastolic dysfunction in SLE (R(2) = 0.806, β = 0.803, P = 0.023).

CONCLUSIONS

PVR was an important cause of PH in SSC. Left ventricular dysfunction was an important cause of PH in SLE. Thus, these findings demonstrate the necessity for RHC and differences in prognosis of PH in CTD.

Biology and flow cytometry of proangiogenic hematopoietic progenitors cells

During development, hematopoiesis and neovascularization are closely linked to each other via a common bipotent stem cell called the hemangioblast that gives rise to both hematopoietic cells and endothelial cells. In postnatal life, this functional connection between the vasculature and hematopoiesis is maintained by a subset of hematopoietic progenitor cells endowed with the capacity to differentiate into potent proangiogenic cells. These proangiogenic hematopoietic progenitors comprise a specific subset of bone marrow (BM)-derived cells that homes to sites of neovascularization and possess potent paracrine angiogenic activity. There is emerging evidence that this subpopulation of hematopoietic progenitors plays a critical role in vascular health and disease. Their angiogenic activity is distinct from putative "endothelial progenitor cells" that become structural cells of the endothelium by differentiation into endothelial cells. Proangiogenic hematopoietic progenitor cell research requires multidisciplinary expertise in flow cytometry, hematology, and vascular biology. This review provides a comprehensive overview of proangiogenic hematopoietic progenitor cell biology and flow cytometric methods to detect these cells in the peripheral blood circulation and BM.

The role of inflammation in hypoxic pulmonary hypertension: from cellular mechanisms to clinical phenotypes

Hypoxic pulmonary hypertension (PH) comprises a heterogeneous group of diseases sharing the common feature of chronic hypoxia-induced pulmonary vascular remodeling. The disease is usually characterized by mild to moderate pulmonary vascular remodeling that is largely thought to be reversible compared with the progressive irreversible disease seen in World Health Organization (WHO) group I disease. However, in these patients, the presence of PH significantly worsens morbidity and mortality. In addition, a small subset of patients with hypoxic PH develop "out-of-proportion" severe pulmonary hypertension characterized by pulmonary vascular remodeling that is irreversible and similar to that in WHO group I disease. In all cases of hypoxia-related vascular remodeling and PH, inflammation, particularly persistent inflammation, is thought to play a role. This review focuses on the effects of hypoxia on pulmonary vascular cells and the signaling pathways involved in the initiation and perpetuation of vascular inflammation, especially as they relate to vascular remodeling and transition to chronic irreversible PH. We hypothesize that the combination of hypoxia and local tissue factors/cytokines ("second hit") antagonizes tissue homeostatic cellular interactions between mesenchymal cells (fibroblasts and/or smooth muscle cells) and macrophages and arrests these cells in an epigenetically locked and permanently activated proremodeling and proinflammatory phenotype. This aberrant cellular cross-talk between mesenchymal cells and macrophages promotes transition to chronic nonresolving inflammation and vascular remodeling, perpetuating PH. A better understanding of these signaling pathways may lead to the development of specific therapeutic targets, as none are currently available for WHO group III disease.

Identification of a common Wnt-associated genetic signature across multiple cell types in pulmonary arterial hypertension

Understanding differences in gene expression that increase risk for pulmonary arterial hypertension (PAH) is essential to understanding the molecular basis for disease. Previous studies on patient samples were limited by end-stage disease effects or by use of nonadherent cells, which are not ideal to model vascular cells in vivo. These studies addressed the hypothesis that pathological processes associated with PAH may be identified via a genetic signature common across multiple cell types. Expression array experiments were initially conducted to analyze cell types at different stages of vascular differentiation (mesenchymal stromal and endothelial) derived from PAH patient-specific induced pluripotent stem (iPS) cells. Molecular pathways that were altered in the PAH cell lines were then compared with those in fibroblasts from 21 patients, including those with idiopathic and heritable PAH. Wnt was identified as a target pathway and was validated in vitro using primary patient mesenchymal and endothelial cells. Taken together, our data suggest that the molecular lesions that cause PAH are present in all cell types evaluated, regardless of origin, and that stimulation of the Wnt signaling pathway was a common molecular defect in both heritable and idiopathic PAH.

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.

Endothelial progenitor cells and pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterised by lung endothelial cell dysfunction and vascular remodelling. A number of studies now suggest that endothelial progenitor cells (EPCs) may induce neovascularisation and could be a promising approach for cell based therapy for PAH. On the contrary EPCs may contribute to pulmonary vascular remodelling, particularly in end-stage pulmonary disease. This review article will provide a brief summary of the relationship between PAH and EPCs, the application of the EPCs to PAH and highlight the potential clinical application of the EPCs cell therapy to PAH.

Lungs, bone marrow, and adipose tissue. A network approach to the pathobiology of chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) often suffer other concomitant disorders, such as cardiovascular diseases and metabolic disorders, that influence significantly (and independently of lung function) their health status and prognosis. Thus, COPD is not a single organ condition, and disturbances of a complex network of interorgan connected responses occur and modulate the natural history of the disease. Here, we propose a novel hypothesis that considers a vascularly connected network with (1) the lungs as the main external sensor of the system and a major source of "danger signals"; (2) the endothelium as an internal sensor of the system (also a potential target tissue); and (3) two key responding elements, bone marrow and adipose tissue, which produce both inflammatory and repair signals. According to the model, the development of COPD, and associated multimorbidities (here we focus on cardiovascular disease as an important example), depend on the manner in which the vascular connected network responds, adapts, or fails to adapt (dictated by the genetic and epigenetic background of the individual) to the inhalation of particles and gases, mainly in cigarette smoke. The caveats and limitations of the hypothesis, as well as the experimental and clinical research needed to test and explore the proposed model, are also briefly discussed.

High proliferative potential endothelial colony-forming cells contribute to hypoxia-induced pulmonary artery vasa vasorum neovascularization

Angiogenic expansion of the vasa vasorum (VV) is an important contributor to pulmonary vascular remodeling in the pathogenesis of pulmonary hypertension (PH). High proliferative potential endothelial progenitor-like cells have been described in vascular remodeling and angiogenesis in both systemic and pulmonary circulations. However, their role in hypoxia-induced pulmonary artery (PA) VV expansion in PH is not known. We hypothesized that profound PA VV neovascularization observed in a neonatal calf model of hypoxia-induced PH is due to increased numbers of subsets of high proliferative cells within the PA adventitial VV endothelial cells (VVEC). Using a single cell clonogenic assay, we found that high proliferative potential colony-forming cells (HPP-CFC) comprise a markedly higher percentage in VVEC populations isolated from the PA of hypoxic (VVEC-Hx) compared with control (VVEC-Co) calves. VVEC-Hx populations that comprised higher numbers of HPP-CFC also demonstrated markedly higher expression levels of CD31, CD105, and c-kit than VVEC-Co. In addition, significantly higher expression of CD31, CD105, and c-kit was observed in HPP-CFC vs. the VVEC of the control but not of hypoxic animals. HPP-CFC exhibited migratory and tube formation capabilities, two important attributes of angiogenic phenotype. Furthermore, HPP-CFC-Co and some HPP-CFC-Hx exhibited elevated telomerase activity, consistent with their high replicative potential, whereas a number of HPP-CFC-Hx exhibited impaired telomerase activity, suggestive of their senescence state. In conclusion, our data suggest that hypoxia-induced VV expansion involves an emergence of HPP-CFC populations of a distinct phenotype with increased angiogenic capabilities. These cells may serve as a potential target for regulating VVEC neovascularization.

Biomarkers for pediatric pulmonary arterial hypertension - a call to collaborate

Therapeutic approaches in pediatric pulmonary arterial hypertension (PAH) are based primarily on clinician experience, in contrast to the evidence-based approach in adults with pulmonary hypertension. There is a clear and present need for non-invasive and objective biomarkers to guide the accurate diagnosis, treatment, and prognosis of this disease in children. The multifaceted spectrum of disease, clinical presentation, and association with other diseases makes this a formidable challenge. However, as more progress is being made in the understanding and management of adult PAH, the potential to apply this knowledge to children has never been greater. This review explores the state of the art with regard to non-invasive biomarkers in PAH, with an eye toward those adult PAH biomarkers potentially suitable for application in pediatric PAH.

Lung stem and progenitor cells in tissue homeostasis and disease

The mammalian lung is a complex organ containing numerous putative stem/progenitor cell populations that contribute to region-specific tissue homeostasis and repair. In this review, we discuss recent advances in identifying and studying these cell populations in the context of lung homeostasis and disease. Genetically engineered mice now allow for lineage tracing of several lung stem and progenitor cell populations in vivo during different types of lung injury repair. Using specific sets of cell surface markers, these cells can also be isolated from murine and human lung and tested in 3D culture systems and in vivo transplant assays. The pathology of devastating lung diseases, including lung cancers, is likely in part due to dysregulation and dysfunction of lung stem cells. More precise characterization of stem cells with identification of new, unique markers; improvement in isolation and transplant techniques; and further development of functional assays will ultimately lead to new therapies for a host of human lung diseases. In particular, lung cancer biology may be greatly informed by findings in normal lung stem cell biology as evidence suggests that lung cancer is a disease that begins in, and may be driven by, neoplastic lung stem cells.

Circulating endothelial cells and tumor blood volume as predictors in lung cancer

The current criteria for evaluating antiangiogenic efficacy is insufficient as tumor shrinkage occurs after blood perfusion decreases. Tumor blood volume (BV) in computed tomography perfusion imaging and circulating endothelial cells (CEC) might predict the status of angiogenesis. The present study aimed to validate their representation as feasible predictors in non-small-cell lung carcinoma (NSCLC). A total of 74 patients was categorized randomly into two arms undergoing regimens of vinorelbine and cisplatin (Navelbine and platinum [NP]) with rh-endostatin or single NP. The response rate, perfusion imaging indexes and activated CEC (aCEC) during treatment were recorded. Progression-free survival (PFS) was determined through follow up. Correlations among the above indicators, response and PFS were analyzed: aCEC increased significantly in cases of progressive disease after single NP chemotherapy (P = 0.024). Tumor BV decreased significantly in cases with a clinical benefit in the combined arm (P = 0.026), whereas inverse correlations existed between ∆aCEC (post-therapeutic value minus the pre-therapeutic value) and PFS (P = 0.005) and between ∆BV and PFS (P = 0.044); a positive correlation existed between ∆aCEC and ∆BV. Therefore, both aCEC and tumor BV can serve as predictors, and detection of both indicators can help evaluate the chemo-antiangiogenic efficacy in NSCLC more accurately.

Imbalance of circulating endothelial cells and progenitors in idiopathic pulmonary fibrosis

BACKGROUND

Fibrogenesis during idiopathic pulmonary fibrosis (IPF) is strongly associated with abnormal vascular remodeling. Respective abundance of circulating endothelial cells (CEC) and endothelial progenitor cells (EPC) might reflect the balance between vascular injury and repair and potentially serve as biomarkers of the disease.

OBJECTIVES AND METHODS

We postulated that CEC and EPC subtypes might be differently modulated in IPF. Sixty-four consecutive patients with newly diagnosed IPF were prospectively enrolled and compared to thirteen healthy volunteers. CEC were counted with immunomagnetic CD146-coated beads; progenitors CD34+45(dim)/CD34+133+/CD34+KDR+were assessed through flow cytometry and EPC (colony-forming-units-Endothelial Cells, CFU-EC, and endothelial colonies forming cells, ECFC) were quantified by cell culture assays.

RESULTS

IPF patients were characterized by a marked increase in CEC associated to an EPC defect: both CD34(+)KDR(+) cells and CFU-EC were decreased versus controls. Moreover, in IPF subjects with a low diffusing capacity of the lung for carbon monoxide (DL(CO)) < 40 %, CFU-EC and ECFC were higher compared to those with DL(CO) > 40 %. Finally, ECFC were negatively correlated with DL(CO). During an 18 month follow up, CEC levels increased in patients with exacerbation, including those who died during follow up. Finally, ECFC from patients with exacerbation proliferative potential was strongly increased.

CONCLUSION

IPF is basically associated with both a vascular injury and a repair defect. This study highlights an adaptative process of EPC mobilization in the most severe forms of IPF, that could reflect enhanced homing to the pulmonary vasculature, which clinical consequences remain to be determined.

Pulmonary artery endothelium resident endothelial colony-forming cells in pulmonary arterial hypertension

Proliferative pulmonary vascular remodeling is the pathologic hallmark of pulmonary arterial hypertension (PAH) that ultimately leads to right heart failure and death. Highly proliferative endothelial cells known as endothelial colony-forming cells (ECFC) participate in vascular homeostasis in health as well as in pathological angiogenic remodeling in disease. ECFC are distinguished by the capacity to clonally proliferate from a single cell. The presence of ECFC in the human pulmonary arteries and their role in PAH pathogenesis is largely unknown. In this study, we established a simple technique for isolating and growing ECFC from cultured pulmonary artery endothelial cells (PAEC) to test the hypothesis that ECFC reside in human pulmonary arteries and that the proliferative vasculopathy of PAH is related to greater numbers and/or more proliferative ECFC in the pulmonary vascular wall. Flow cytometric forward and side scatter properties and aggregate correction were utilized to sort unmanipulated, single PAEC to enumerate ECFC in primary PAEC cultures derived from PAH and healthy lungs. After 2 weeks, wells were assessed for ECFC formation. ECFC derived from PAH PAEC were more proliferative than control. A greater proportion of PAH ECFC formed colonies following subculturing, demonstrating the presence of more ECFC with high proliferative potential among PAH PAEC. Human androgen receptor assay showed clonality of progeny, confirming that proliferative colonies were single cell-derived. ECFC expressed CD31, von Willebrand factor, endothelial nitric oxide synthase, caveolin-1 and CD34, consistent with an endothelial cell phenotype. We established a simple flow cytometry method that allows ECFC quantification using unmanipulated cells. We conclude that ECFC reside among PAEC and that PAH PAEC contain ECFC that are more proliferative than ECFC in control cultures, which likely contributes to the proliferative angiopathic process in PAH.

Transfection of VEGF(165) genes into endothelial progenitor cells and in vivo imaging using quantum dots in an ischemia hind limb model

Endothelial progenitor cells (EPCs) were transfected with fluorescently labeled quantum dot nanoparticles (QD NPs) with or without VEGF(165) plasmid DNA (pDNA) to probe the EPCs after in vivo transplantation and to test whether they presented as differentiated endothelial cells (ECs). Bare QD NPs and QD NPs coated with PEI or PEI + VEGF(165) genes were characterized by dynamic light scattering, scanning electron microscopy, and atomic force microscopy. Transfection of EPCs with VEGF(165) led to the expression of specific genes and proteins for mature ECs. A hind limb ischemia model was generated in nude mice, and VEGF(165) gene-transfected EPCs were transplanted intramuscularly into the ischemic limbs. At 28 days after transplantation, the VEGF(165) gene-transfected EPCs significantly increased the number of differentiated ECs compared with the injection of medium or bare EPCs without VEGF(165) genes. Laser Doppler imaging revealed that blood perfusion levels were increased significantly by VEGF(165) gene-transfected EPCs compared to EPCs without VEGF(165). Moreover, the transplantation of VEGF(165) gene-transfected EPCs increased the specific gene and protein expression levels of mature EC markers and angiogenic factors in the animal model.

Endothelium-selective activation of AMP-activated protein kinase prevents diabetes mellitus-induced impairment in vascular function and reendothelialization via induction of heme oxygenase-1 in mice

BACKGROUND

Endothelial damage and dysfunction are crucial mediators that link diabetes mellitus with atherosclerotic cardiovascular disease. AMP-activated kinase (AMPK) has been implicated in regulation of both energy metabolism and vascular homeostasis. The present study investigated whether endothelium-selective activation of AMPK prevents diabetes mellitus-induced endothelial damage and vascular dysfunction by improving reendothelialization in mice.

METHODS AND RESULTS

Transgenic mice with endothelium-selective expression of a constitutively active (CA) AMPK were generated and rendered diabetic by the injection of streptozotocin. Relaxation and reendothelialization of carotid arteries and circulating numbers of endothelial progenitor cells (EPCs) were examined after wire-induced denudation. Bone marrow-derived EPCs were isolated to monitor their in vivo and in vitro function. Compared with wild-type littermates, the CA-AMPK transgenic mice were resistant to diabetes mellitus-induced impairment in endothelium-dependent relaxation and reendothelialization of their injured carotid arteries. These changes in the transgenic mice were accompanied by increased mobilization of EPCs and enhanced incorporation of EPCs into injured blood vessels. Furthermore, EPCs from the transgenic mice exhibited augmented adhesion, migration, and tube formation capacities. At the molecular level, the expression of heme oxygenase (HO)-1 and the secretion of stromal cell-derived factor (SDF)-1α were upregulated in EPCs derived from the transgenic mice, whereas AMPK-mediated elevation of serum SDF-1α levels and improvements of EPC function and reendothelialization were all abrogated by pharmacological inhibition of heme oxygenase-1.

CONCLUSIONS

Endothelium-specific AMPK activation is sufficient to protect against diabetes mellitus-induced aggravation of vascular injury by promoting EPC function and reendothelialization via upregulation of heme oxygenase-1 and SDF-1α.

Untangling asthma phenotypes and endotypes

Asthma phenotypes have been developed to address the complexities of the disease. However, owing to a lack of longitudinal studies, little is known about the onset as well as the stability of phenotypes. Distinguishing phenotypes with regard to the severity or duration of the disease is essential. A phenotype covers the clinically relevant properties of the disease, but does not show the direct relationship to disease etiology and pathophysiology. Different pathogenetic mechanisms might cause similar asthma symptoms and might be operant in a certain phenotype. These putative mechanisms are addressed by the term 'endotype'. Classification of asthma based on endotypes provides advantages for epidemiological, genetic, and drug-related studies. A successful definition of endotypes should link key pathogenic mechanisms with the asthma phenotype. Thus, the identification of corresponding molecular biomarkers for individual pathogenic mechanism underlying phenotypes or subgroups within a phenotype is important. Whether newly defined asthma endotypes predict the individual course of asthma has to be validated in longitudinal studies. The accurate endotyping reflects natural history of asthma and should help to predict treatment response. Thus, understanding asthma endotypes might be useful in clinical practice.

Reversal of endothelial progenitor cell dysfunction in patients with type 2 diabetes using a conditioned medium of human embryonic stem cell-derived endothelial cells

BACKGROUND

The potential clinical application of bone marrow or peripheral blood-derived progenitor cells for cardiovascular regeneration in patients with diabetes mellitus (DM) is limited by their functional impairment. We sought to determine the mechanisms of impaired therapeutic efficacy of peripheral blood-derived progenitor cells in type 2 DM patients and evaluated the use of cell-free conditioned medium obtained from human embryonic stem cell-derived endothelial-like cells (ESC-ECs) to reverse their functional impairment.

METHODS

The angiogenic potential of late outgrowth endothelial cells (OECs) and cytokine profile of the conditional medium of proangiogenic cells (PACs) derived from peripheral blood-mononuclear cells of healthy control and DM patients and ESC-ECs was compared by in vitro tube formation assay and a multiplex bead-based immunoassay kit, respectively. The in vivo angiogenic potential of ESC-ECs derived conditioned medium in rescuing the functional impairment of PB-PACs in DM patients was investigated using a hindlimb ischemia model.

RESULTS

Human ESC-ECs had similar functional and phenotypic characteristics as OECs in healthy controls. Cytokine profiling showed that vascular endothelial growth factor, stromal cell-derived factor 1 and placental growth factor were down-regulated in PACs from DM patients. Tube formation assay that revealed functional impairment of OECs from DM patients could be rescued by ESC-ECs conditioned medium. Administration of ESC-ECs conditioned medium restored the therapeutic efficacy of PB-PACs from DM patients in a mouse model of hindlimb ischemia.

CONCLUSIONS

Our results showed that peripheral blood-derived progenitor cells from DM patients have impaired function because of defective secretion of angiogenic cytokines, which could be restored by supplementation of ESC-ECs conditioned medium.

Pulmonary arterial hypertension in systemic lupus erythematosus: current status and future direction

Pulmonary arterial hypertension (PAH) is commonly associated with connective tissue diseases (CTDs) including systemic sclerosis and systemic lupus erythematosus (SLE). The prevalence of PAH in SLE is estimated to be 0.5% to 17.5%. The pathophysiology of PAH involves multiple mechanisms from vasculitis and in-situ thrombosis to interstitial pulmonary fibrosis which increases pulmonary vascular resistance, potentially leading to right heart failure. Immune and inflammatory mechanisms may play a significant role in the pathogenesis or progression of PAH in patients with CTDs, establishing a role for anti-inflammatory and immunosuppressive therapies. The leading predictors of PAH in SLE are Raynaud phenomenon, anti-U1RNP antibody, and anticardiolipin antibody positivity. The first-line of diagnostic testing for patients with suspected SLE-associated PAH (SLE-aPAH) involves obtaining a Doppler echocardiogram. Once the diagnosis is confirmed by right heart catheterization, SLE-aPAH patients are generally treated with oxygen, anticoagulants, and vasodilators. Although the prognosis and therapeutic responsiveness of these patients have improved with the addition of intensive immunosuppressive therapies, these treatments are still largely unproven. Recent data put the one-year survival rate for SLE-aPAH patients at 94%. Pregnant women are most at risk of dying due to undiagnosed SLE-aPAH, and screening should be considered essential in this population.