The role of bone marrow-derived endothelial progenitor cells and angiogenic responses in chronic obstructive pulmonary disease

PU.1 alleviates the inhibitory effects of cigarette smoke on endothelial progenitor cell function and lung-homing through Wnt/β-catenin and CXCL12/CXCR4 pathways

INTRODUCTION

Endothelial progenitor cells (EPCs) dysfunction is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). The transcription factor PU.1 is essential for the maintenance of stem/progenitor cell homeostasis. However, the role of PU.1 in COPD and its effects on EPC function and lung-homing, remain unclear. This study aimed to explore the protective activity of PU.1 and the underlying mechanisms in a cigarette smoke extract (CSE)-induced emphysema mouse model.

METHODS

C57BL/6 mice were treated with CSE to establish a murine emphysema model and injected with overexpressed PU.1 or negative control adeno-associated virus. Morphometry of lung slides, lung function, and apoptosis of lung tissues were evaluated. Immunofluorescence co-localization was used to analyze EPCs homing into the lung. Flow cytometry was performed to detect EPC count in lung tissues and bone marrow (BM). The angiogenic ability of BM-derived EPCs cultured in vitro was examined by tube formation assay. We determined the expression levels of PU.1, β-catenin, C-X-C motif ligand 12 (CXCL12), C-X-C motif receptor 4 (CXCR4), stem cell antigen-1 (Sca-1), and stemness genes.

RESULTS

CSE exposure significantly reduced the expression of PU.1 in mouse lung tissues, BM, and BM-derived EPCs. PU.1 overexpression attenuated CSE-induced emphysematous changes, lung function decline, and apoptosis. In emphysematous mice, PU.1 overexpression markedly reversed the decreased proportion of EPCs in BM and promoted the lung-homing of EPCs. The impaired angiogenic ability of BM-derived EPCs induced by CSE could be restored by the overexpression of PU.1. In addition, PU.1 upregulation evidently reversed the decreased expression of β-catenin, CXCL12, CXCR4, Scal-1, and stemness genes in mouse lung tissues, BM, and BM-derived EPCs after CSE exposure.

CONCLUSIONS

PU.1 alleviates the inhibitory effects of CSE on EPC function and lung-homing via activating the canonical Wnt/β-catenin pathway and CXCL12/CXCR4 axis. While further research is needed, our research may indicate a potential therapeutic target for COPD patients.

Advances of Endothelial Progenitor Cells in the Development of Depression

Depression is a major psychological disease of human beings. With the severity of depression, it elevates the risk of cardiovascular disease (CVD), especially acute coronary syndrome (ACS), resulting in serious harm to human health. The number of endothelial progenitor cells (EPCs) is closely related to the development of depression. It has been reported that the number of peripheral blood EPCs in patients with depression was reduced. However, effects on the function of EPCs in depression are still unclear. This paper aims to analyze and summarize the research of EPCs in depression, and we envision that EPCs might act as a new target for evaluating the severity of depression and its complications.

Mesenchymal Stem Cell Transplantation for Ischemic Diseases: Mechanisms and Challenges

Ischemic diseases are conditions associated with the restriction or blockage of blood supply to specific tissues. These conditions can cause moderate to severe complications in patients, and can lead to permanent disabilities. Since they are blood vessel-related diseases, ischemic diseases are usually treated with endothelial cells or endothelial progenitor cells that can regenerate new blood vessels. However, in recent years, mesenchymal stem cells (MSCs) have shown potent bioeffects on angiogenesis, thus playing a role in blood regeneration. Indeed, MSCs can trigger angiogenesis at ischemic sites by several mechanisms related to their trans-differentiation potential. These mechanisms include inhibition of apoptosis, stimulation of angiogenesis via angiogenic growth factors, and regulation of immune responses, as well as regulation of scarring to suppress blood vessel regeneration when needed. However, preclinical and clinical trials of MSC transplantation in ischemic diseases have shown some limitations in terms of treatment efficacy. Such studies have emphasized the current challenges of MSC-based therapies. Treatment efficacy could be enhanced if the limitations were better understood and potentially resolved. This review will summarize some of the strategies by which MSCs have been utilized for ischemic disease treatment, and will highlight some challenges of those applications as well as suggesting some strategies to improve treatment efficacy.

Epimedin C Protects H2O2-Induced Peroxidation Injury by Enhancing the Function of Endothelial Progenitor HUVEC Populations

Endothelial cell injury and apoptosis induced by oxidative stress serve important roles in many vascular diseases. The repair of endothelial cell vascular injury relies on the function of local endothelial progenitor cells (EPCs). Our previous study indicated that epimedin C, a major flavonoid derived from Herba epimedii (yin yang huo), could promote vascularization by inducing endothelial-like differentiation of mesenchymal stem cells C3H/10T1/2 both in vivo and in vitro. In view of the significant cardiovascular protective effects of Herba epimedii, we detected a protective effect of epimedin C on hydrogen peroxide (H₂O₂)-induced peroxidation injury in human umbilical vein endothelial cells (HUVECs) and the role of EPC in this process. The results show that epimedin C increased the expression of the stem cell marker, CD34 and PROM1, and subsequently enhanced the expression and function of vascular endothelial growth factor and matrix metalloproteinase (MMP)-2 in local vascular endothelial cells. In conclusion, epimedin C protects H₂O₂-induced peroxidation injury by enhancing the function of endothelial progenitor HUVEC populations.

Progenitor cell mobilisation and recruitment in pulmonary arteries in chronic obstructive pulmonary disease

Background

Pulmonary vascular abnormalities are a characteristic feature of chronic obstructive pulmonary disease (COPD). Cigarette smoking is the most important risk factor for COPD. It is believed that its constant exposure triggers endothelial cell damage and vascular remodelling. Under pathological conditions, progenitor cells (PCs) are mobilized from the bone marrow and recruited to sites of vascular injury. The aim of the study was to investigate whether in COPD the number of circulating PCs is related to the presence of bone marrow-derived cells in pulmonary arteries and the association of these phenomena to both systemic and pulmonary endothelial dysfunction.

Methods

Thirty-nine subjects, 25 with COPD, undergoing pulmonary resection because of a localized carcinoma, were included. The number of circulating PCs was assessed by flow cytometry using a triple combination of antibodies against CD45, CD133 and CD34. Infiltrating CD45⁺ cells were identified by immunohistochemistry in pulmonary arteries. Endothelial function in systemic and pulmonary arteries was measured by flow-mediated dilation and adenosine diphosphate-induced vasodilation, respectively.

Results

COPD patients had reduced numbers of circulating PCs (p < 0.05) and increased numbers of CD45⁺ cells (< 0.05) in the pulmonary arterial wall than non-COPD subjects, being both findings inversely correlated (r = − 0.35, p < 0.05). In pulmonary arteries, the number of CD45⁺ cells correlated with the severity of vascular remodelling (r = 0.4, p = 0.01) and the endothelium-dependent vasodilation (r = − 0.3, p = 0.05). Systemic endothelial function was unrelated to the number of circulating PCs and changes in pulmonary vessels.

Conclusion

In COPD, the decrease of circulating PCs is associated with their recruitment in pulmonary arteries, which in turn is associated with endothelial dysfunction and vessel remodelling, suggesting a mechanistic link between these phenomena. Our findings are consistent with the notion of an imbalance between endothelial damage and repair capacity in the pathogenesis of pulmonary vascular abnormalities in COPD.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1024-z) contains supplementary material, which is available to authorized users.

Endothelial Progenitor Cells as Pathogenetic and Diagnostic Factors, and Potential Targets for GLP-1 in Combination with Metabolic Syndrome and Chronic Obstructive Pulmonary Disease

In clinical practice, there are patients with a combination of metabolic syndrome (MS) and chronic obstructive pulmonary disease (COPD). The pathological mechanisms linking MS and COPD are largely unknown. It remains unclear whether the effect of MS (possible obesity) has a major impact on the progression of COPD. This complicates the development of effective approaches for the treatment of patients with a diagnosis of MS and COPD. Experiments were performed on female C57BL/6 mice. Introduction of monosodium glutamate and extract of cigarette smoke was modeled to simulate the combined pathology of lipid disorders and emphysema. Biological effects of glucagon-like peptide 1 (GLP-1) and GLP-1 on endothelial progenitor cells (EPC) in vitro and in vivo were evaluated. Histological, immunohistochemical methods, biochemical methods, cytometric analysis of markers identifying EPC were used in the study. The CD31⁺ endothelial cells in vitro evaluation was produced by Flow Cytometry and Image Processing of each well with a Cytation™ 3. GLP-1 reduces the area of emphysema and increases the number of CD31⁺ endothelial cells in the lungs of mice in conditions of dyslipidemia and damage to alveolar tissue of cigarette smoke extract. The regenerative effects of GLP-1 are caused by a decrease in inflammation, a positive effect on lipid metabolism and glucose metabolism. EPC are proposed as pathogenetic and diagnostic markers of endothelial disorders in combination of MS with COPD. Based on GLP-1, it is proposed to create a drug to stimulate the regeneration of endothelium damaged in MS and COPD.

Hyperhomocysteinemia induced endothelial progenitor cells dysfunction through hyper-methylation of CBS promoter

Bone marrow (BM)-derived endothelial progenitor cells (EPCs) are the key players in angiogenesis and vascular function. Cystathionine-β-synthase (CBS), an H₂S-generating enzyme in methionine metabolism, regulates the function of these EPCs. This study aims to examine whether CBS hyper-methylation contributes to the bone marrow endothelial progenitor cell (BM-EPCs) function and subsequent bone blood flow in mice fed with a high methionine diet (HMD). Bone marrow (BM) cells were collected from HMD and control mice, differentiated into BM-EPCs, and were characterized by acLDL-DiI labeling. CBS mRNA expression was analyzed by real-time PCR, and the global methylation status and methylation of the CBS promoter were detected by nuclear 5-mC assay and methylation-specific PCR (qMSP) respectively. The result reveals that CBS promoter in BM-EPCs from HMD mice was hyper-methylated and the methylation level was, indeed, negatively correlated with CBS mRNA and angiogenic function of BM-EPCs. In addition, global methylation (5-mC) and DNA methyltransferase-1 (DNMT1) expression were increased in HMD condition. In vitro study also shows that HMD induced hyperhomocysteinemia (HHcy) impaired both adhesion and angiogenesis properties of BM-EPCs, accompanied by higher methylation level of CBS promoter that compared to control. Furthermore, bone blood flow was found to be decreased in HMD mice as compared to wild-type mice. To dissect the epigenetic mechanism, we also administrated DNMT inhibitor, 5-azacytidine (5-Aza) to HMD mice. The administration of 5-Aza in HMD mice restored the CBS expression, EPC mediated angiogenesis and blood flow by reducing abnormal DNA hyper-methylation. In conclusion, HHcy dismantles BM-EPCs function and bone blood flow through the hyper-methylation of the CBS promoter in HMD fed mice.

Endothelial Progenitor Cells and Notch-1 Signaling as Markers of Alveolar Endothelium Regeneration in Pulmonary Emphysema

We studied the effects of elastase, cigarette smoke extract, D-galactosamine hydrochloride, and tyrosine kinase inhibitor SU5416 on endothelial progenitor cells and angiogenesis precursors, as well as on Notch-1 expression by immature endothelial cells. Simultaneously with pulmonary emphysema, different damaging factors with diverse mechanisms of action caused pathological changes in the microvascular network of the lungs and destroyed the alveolar endothelium in female C57Bl/6 mice. D-galactosamine hydrochloride disturbed mobilization of endothelial progenitor cells expressing VEGFR (CD45-CD309+) and angiogenesis progenitors (CD45-CD309+CD117+) and their migration into emphysema expanded lungs. Elastase inhibited VEGFR-expressing endothelial progenitor cells, while cigarette smoke extract inhibited cells with CD45-CD31+CD34+ phenotype. In pulmonary emphysema provoked by elastase or D-galactosamine hydrochloride, angiogenesis was provided by endothelial cells with CD45-CD31+CD34+ phenotype, whereas in emphysema modeled with SU5416 or cigarette smoke extract, it was provided by the endothelial VEGFR-expressing cells and mature CD31+ endothelial cells, respectively. Replenishment of immature endothelial cells damaged by elastase and SU5416 involved Notch-1+ angiogenesis precursors and Notch-1+ endothelial progenitor cells with VEGFR.