E-selectin mediates stem cell adhesion and formation of blood vessels in a murine model of infantile hemangioma

Apelin Receptor Can Act as a Specific Marker and Promising Therapeutic Target for Infantile Hemangioma

Infantile hemangioma (IH), the most common benign tumor in infancy, is generally sensitive to propranolol treatment. However, the challenge remains because resistance or recurrence could occur in some patients, and the mechanism or target of propranolol remains unknown. Therefore, advancement in the drug development is needed. In this study, we explored whether apelin receptor (APJ) can become a candidate target. We found that APJ is expressed only in endothelial cells of IH (HemECs) but not in other vascular anomalies, and its antagonist, ML221, can negatively regulate cellular viability and functions of HemECs. This inhibitory effect could be replicated in a murine hemangioma model. Importantly, in vitro experiments also indicated that ML221 failed to affect the proliferation or angiogenesis of normal endothelial cells or APJ-knockout HemECs. Through analysis of the phosphoantibody microarray data, ML221 was revealed to have an inhibitory effect on HemECs by suppressing the activation of mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. These results verified the distinctive expression of APJ in IH and specific inhibition of HemEC activity caused by ML221. In addition, APJ was also detected in propranolol-resistant IH. Collectively, we propose that APJ can act as a specific marker and a promising therapeutic target for IH, which will facilitate further drug development.

Critical role of Aquaporin-1 and telocytes in infantile hemangioma response to propranolol beta blockade

Propranolol, a nonselective β-adrenergic receptor (ADRB) antagonist, is the first-line therapy for severe infantile hemangiomas (IH). Since the incidental discovery of propranolol efficacy in IH, preclinical and clinical investigations have shown evidence of adjuvant propranolol response in some malignant tumors. However, the mechanism for propranolol antitumor effect is still largely unknown, owing to the absence of a tumor model responsive to propranolol at nontoxic concentrations. Immunodeficient mice engrafted with different human tumor cell lines were treated with anti-VEGF bevacizumab to create a model sensitive to propranolol. Proteomics analysis was used to reveal propranolol-mediated protein alteration correlating with tumor growth inhibition, and Aquaporin-1 (AQP1), a water channel modulated in tumor cell migration and invasion, was identified. IH tissues and cells were then functionally investigated. Our functional protein association networks analysis and knockdown of ADRB2 and AQP1 indicated that propranolol treatment and AQP1 down-regulation trigger the same pathway, suggesting that AQP1 is a major driver of beta-blocker antitumor response. Examining AQP1 in human hemangioma samples, we found it exclusively in a perivascular layer, so far unrecognized in IH, made of telocytes (TCs). Functional in vitro studies showed that AQP1-positive TCs play a critical role in IH response to propranolol and that modulation of AQP1 in IH-TC by propranolol or shAQP1 decreases capillary-like tube formation in a Matrigel-based angiogenesis assay. We conclude that IH sensitivity to propranolol may rely, at least in part, on a cross talk between lesional vascular cells and stromal TCs.

Valproic Acid Decreases Endothelial Colony Forming Cells Differentiation and Induces Endothelial-to-Mesenchymal Transition-like Process

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor is a widely used anticonvulsant drug. VPA is also under clinical evaluation to be employed in anticancer therapy, as an antithrombotic agent or a molecule to be used in the stem cells expansion protocols. Since endothelial colony forming cells (ECFC) has been identified as the human postnatal vasculogenic cells involved in thrombotic disorders and serve as a promising source of immature cell for vascular repair, objectives of the present study were to determine how VPA contributes to ECFC commitment and their angiogenic properties. We examined the effect of VPA on ECFC obtained from cord blood by evaluating colony number, proliferation, migration and their sprouting ability in vitro, as well as their in vivo vasculogenic properties. VPA inhibited endothelial differentiation potential from of cord blood derived stem cells associated with decreased proliferation and sprouting activity of cultured ECFC. VPA treatment significantly decreased the vessel-forming ability of ECFC transplanted together with mesenchymal stem cells (MSC) in Matrigel implants in nude mice model. Surprisingly, a microscopic evaluation revealed that VPA induces marked morphological changes from a cobblestone-like EC morphology to enlarged spindle shaped morphology of ECFC. RT-qPCR and a CD31/CD90 flow cytometry analysis confirmed a phenotypic switch of VPA-treated ECFC to mesenchymal-like phenotype. In conclusion, the pan-HDAC inhibitor VPA described for expansion of hematopoietic stem cells and very small embryonic like stem cells cannot be successfully employed for differentiation of endothelial lineage committed ECFC into functional endothelial cells. Our data also suggest that VPA based therapeutics may induce endothelial dysfunction associated with fibrosis that might induce thrombosis recurrence or venous insufficiency.

Exosome-derived miR-196b-5p facilitates intercellular interaction in infantile hemangioma via down-regulating CDKN1B

Background

Though infantile hemangioma (IH) is a common benign vascular tumor, its pathogenesis remains unclear. This study explored the function of hemangioma-derived stem cells (HemSCs) derived exosomes, which exerted an intercellular effect on hemangioma-derived endothelial cells (HemECs).

Methods

First, HemSCs and HemECs were extracted and cultured. HemSCs derived exosomes (HemSCs-exos) were harvested. miRNA sequencing and target prediction were used to explore differentially expressed miRNAs and potential binding targets. After HemECs were co-cultured with HemSCs-exos, a series of in vitro assays were then performed including cell counting kit-8 (CCK-8) assay, cell apoptosis assay, cell cycle assay and tube formation assay to evaluate proliferation, angiogenesis abilities, etc. qRT-PCR and Western blot were conducted to detect the expression level of target genes and proteins.

Results

After co-culturing with HemSCs-exos, proliferation, and angiogenesis abilities of HemECs were enhanced, while apoptosis and cell cycle arrest rate were decreased. MiR-196b-5p was observed to be significantly highly expressed in HemSCs-exos. CDKN1B was identified as the binding target of miR-196b-5p. HemECs' proliferation and angiogenesis abilities were elevated when co-cultured with exosomes from HemSCs transfected with miR-196b-5p mimic. In addition, apoptosis rate declined, and lower cells were arrested in G0/G1 phases. Cyclin E, bcl-2 were significantly highly expressed, whereas p27, Bax expression were significantly down-regulated. The positive effect of miR-196b-5p in HemSCs-exos was dramatically reversed when HemECs were transfected with oe-CDKN1B.

Conclusions

The current study found a novel intercellular interaction between IH cells. Briefly, exosome-derived miRNA-196b-5p in HemSCs could facilitate proliferation and angiogenesis abilities, and attenuate apoptosis and cell cycle repression rate of HemECs by directly binding with CDKN1B.

Silencing microRNA-210 in Hypoxia-Induced HUVEC-Derived Extracellular Vesicles Inhibits Hemangioma

BACKGROUND

Hemangioma (Hem) is a benign tumor commonly seen in infancy with a relative high morbidity. Human umbilical vein endothelial cell (HUVEC)-derived extracellular vesicles (EVs) are actively participated in Hem. Therefore, this study is designed to figure out the underlying mechanism of HUVEC-derived EVs in Hem.

METHODS

Initially, EVs were separated from HUVECs and identified. HUVEC-derived EVs in normoxia or hypoxia were then cultivated with Hem endothelial cells (HemECs) to test the proliferation, apoptosis, and migration of HemECs. Microarray analysis was performed to select microRNAs (miRs) with differential expression. miR-210 in hypoxia-induced HUVECs was silenced, and the relevant EVs were extracted and then co-cultured with HemECs to perform biological effect experiments. Then, the target relation between miR-210 and homeobox A9 (HOXA9) was identified by the dual luciferase reporter gene assay and RNA immunoprecipitation assay. Moreover, xenograft transplantation was also applied to confirm the in vitro experiments.

RESULTS

Hypoxia-induced HUVECs promoted release of EVs, which were absorbed by HemECs. Hypoxia-induced HUVEC-EVs promoted HemEC proliferation and migration and inhibited apoptosis. miR-210 from the hypoxia-induced HUVEC-EVs was highly expressed and promoted HemEC growth. Silencing miR-210 expression in the hypoxia-induced HUVEC-EVs suppresses Hem development in vivo. In addition, miR-210 targeted HOXA9.

CONCLUSION

Silencing miR-210 in HUVEC-derived EVs could suppress Hem by targeting HOXA9. This investigation may provide novel insights for Hem treatment.

Human Endothelial Colony Forming Cells Express Intracellular CD133 that Modulates their Vasculogenic Properties

Stem cells at the origin of endothelial progenitor cells and in particular endothelial colony forming cells (ECFCs) subtype have been largely supposed to be positive for the CD133 antigen, even though no clear correlation has been established between its expression and function in ECFCs. We postulated that CD133 in ECFCs might be expressed intracellularly, and could participate to vasculogenic properties. ECFCs extracted from cord blood were used either fresh (n = 4) or frozen (n = 4), at culture days <30, to investigate the intracellular presence of CD133 by flow cytometry and confocal analysis. Comparison with HUVEC and HAEC mature endothelial cells was carried out. Then, CD133 was silenced in ECFCs using specific siRNA (siCD133-ECFCs) or scramble siRNA (siCtrl-ECFCs). siCD133-ECFCs (n = 12), siCtrl-ECFCs (n = 12) or PBS (n = 12) were injected in a hind-limb ischemia nude mouse model and vascularization was quantified at day 14 with H&E staining and immunohistochemistry for CD31. Results of flow cytometry and confocal microscopy evidenced the positivity of CD133 in ECFCs after permeabilization compared with not permeabilized ECFCs (p < 0.001) and mature endothelial cells (p < 0.03). In the model of mouse hind-limb ischemia, silencing of CD133 in ECFCs significantly abolished post-ischemic revascularization induced by siCtrl-ECFCs; indeed, a significant reduction in cutaneous blood flows (p = 0.03), capillary density (CD31) (p = 0.01) and myofiber regeneration (p = 0.04) was observed. Also, a significant necrosis (p = 0.02) was observed in mice receiving siCD133-ECFCs compared to those treated with siCtrl-ECFCs. In conclusion, our work describes for the first time the intracellular expression of the stemness marker CD133 in ECFCs. This feature could resume the discrepancies found in the literature concerning CD133 positivity and ontogeny in endothelial progenitors.

Angiopoietin-2 as a marker of endothelial activation is a good predictor factor for intensive care unit admission of COVID-19 patients

Background

Coronavirus disease-2019 (COVID-19), a respiratory disease has been associated with ischemic complications, coagulation disorders, and an endotheliitis.

Objectives

To explore endothelial damage and activation-related biomarkers in COVID-19 patients with criteria of hospitalization for referral to intensive care unit (ICU) and/or respiratory worsening.

Methods

Analysis of endothelial and angiogenic soluble markers in plasma from patients at admission.

Results

Study enrolled 40 consecutive COVID-19 patients admitted to emergency department that fulfilled criteria for hospitalization. Half of them were admitted in conventional wards without any ICU transfer during hospitalization; whereas the 20 others were directly transferred to ICU. Patients transferred in ICU were more likely to have lymphopenia, decreased SpO2 and increased D-dimer, CRP and creatinine levels. In those patients, soluble E-selectin and angiopoietin-2 were significantly increased (p value at 0.009 and 0.003, respectively). Increase in SELE gene expression (gene coding for E-selectin protein) was confirmed in an independent cohort of 32 patients using a whole blood gene expression profile analysis. In plasma, we found a strong association between angiopoetin-2 and CRP, creatinine and D-dimers (with p value at 0.001, 0.001 and 0.003, respectively). ROC curve analysis identified an Angiopoietin-2 cut-off of 5000 pg/mL as the best predictor for ICU outcome (Se = 80.1%, Sp = 70%, PPV = 72.7%, NPV = 77%), further confirmed in multivariate analysis after adjustment for creatinine, CRP or D-dimers.

Conclusion

Angiopoietin-2 is a relevant predictive factor for ICU direct admission in COVID-19 patients. This result showing an endothelial activation reinforces the hypothesis of a COVID-19-associated microvascular dysfunction.

TSGA10 overexpression inhibits angiogenesis of HUVECs: A HIF-2α biased perspective

Testis-specific gene antigen 10 (TSGA10) is a protein overexpressed in most cancers; except for some certain types where its expression is reduced. TSGA10 overexpression in HeLa cells has been shown to disrupt hypoxia inducible factor-1α (HIF-1α) axis and exert potent inhibitory effects. Since HIF-1α is structurally and biochemically similar to HIF-2α, TSGA10 is expected to bind HIF-2α and inhibit its function as well. This study elucidated that increased expression of TSGA10 in manipulated human umbilical vein endothelial cells (HUVECs) decreased the proliferation and migration of these cells as affirmed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and wound healing tests, respectively. It also inhibited in vitro angiogenesis of these cells in 3D collagen-cytodex model. Expression levels of genes controlled by HIF-2α including autocrine vascular endothelial growth factor (VEGF) were also assessed using real-time PCR. Our bioinformatic analysis also showed that TSGA10 could bind HIF-2α. Moreover, flow cytometry results indicated a cell cycle arrest in G2/M. Therefore, this study showed that overexpression of TSGA10, as a tumor suppressor gene, in endothelial cells resulted in decreased proliferation, migration and therefore, angiogenic activity of HUVECs. Since angiogenesis is vital for tumor development and metastasis, our findings could be of clinical significance in cancer therapy.

Exercise and Cardiovascular Progenitor Cells

Autologous stem/progenitor cell-based methods to restore blood flow and function to ischemic tissues are clinically appealing for the substantial proportion of the population with cardiovascular diseases. Early preclinical and case studies established the therapeutic potential of autologous cell therapies for neovascularization in ischemic tissues. However, trials over the past ∼15 years reveal the benefits of such therapies to be much smaller than originally estimated and a definitive clinical benefit is yet to be established. Recently, there has been an emphasis on improving the number and function of cells [herein generally referred to as circulating angiogenic cells (CACs)] used for autologous cell therapies. CACs include of several subsets of circulating cells, including endothelial progenitor cells, with proangiogenic potential that is largely exerted through paracrine functions. As exercise is known to improve CV outcomes such as angiogenesis and endothelial function, much attention is being given to exercise to improve the number and function of CACs. Accordingly, there is a growing body of evidence that acute, short-term, and chronic exercise have beneficial effects on the number and function of different subsets of CACs. In particular, recent studies show that aerobic exercise training can increase the number of CACs in circulation and enhance the function of isolated CACs as assessed in ex vivo assays. This review summarizes the roles of different subsets of CACs and the effects of acute and chronic exercise on CAC number and function, with a focus on the number and paracrine function of circulating CD34+ cells, CD31+ cells, and CD62E+ cells. © 2019 American Physiological Society. Compr Physiol 9:767-797, 2019.

Vasculogenic Stem and Progenitor Cells in Human: Future Cell Therapy Product or Liquid Biopsy for Vascular Disease

New blood vessel formation in adults was considered to result exclusively from sprouting of preexisting endothelial cells, a process referred to angiogenesis. Vasculogenesis, the formation of new blood vessels from endothelial progenitor cells, was thought to occur only during embryonic life. Discovery of adult endothelial progenitor cells (EPCs) in 1997 opened the door for cell therapy in vascular disease. Endothelial progenitor cells contribute to vascular repair and are now well established as postnatal vasculogenic cells in humans. It is now admitted that endothelial colony-forming cells (ECFCs) are the vasculogenic subtype. ECFCs could be used as a cell therapy product and also as a liquid biopsy in several vascular diseases or as vector for gene therapy. However, despite a huge interest in these cells, their tissue and molecular origin is still unclear. We recently proposed that endothelial progenitor could come from very small embryonic-like stem cells (VSELs) isolated in human from CD133 positive cells. VSELs are small dormant stem cells related to migratory primordial germ cells. They have been described in bone marrow and other organs. This chapter discusses the reported findings from in vitro data and also preclinical studies that aimed to explore stem cells at the origin of vasculogenesis in human and then explore the potential use of ECFCs to promote newly formed vessels or serve as liquid biopsy to understand vascular pathophysiology and in particular pulmonary disease and haemostasis disorders.

Effects of RNA interference-mediated E-selectin gene silencing on cell adhesion molecule expression and cell-cell adhesion in vascular endothelial cells in mice with immunologic contact urticaria

Contact urticaria is recognized as the wheal and flare reaction at a site from direct contact with a chemical or protein agent. Ongoing studies have proposed that gene silencing may have a promising future in finding optimal treatment of a variety of disease; hence, the aim of the study was to investigate the effect of RNA interference-mediated E-selectin ( SELE) gene silencing on cell adhesion molecule expression and on cell-cell adhesion in vascular endothelial cells (VECs) in a mouse model of immunologic contact urticaria (ICU). Following the successful establishment of mouse models of ICU induced by antidinitrophenol immunoglobulin E (IgE) combining 2,4-dinitrofluorobenzene challenge, enzyme-linked immunosorbent assay and immunohistochemistry were used to measure the levels of IgE, interleukin 4 (IL-4), interferon-γ (IFN-γ), and histamine as well as the positive expression rate of SELE, respectively. The siRNA- SELE vector was constructed and transfection efficiency was estimated prior to performing quantitative reverse-transcription polymerase chain reaction and Western blot assay to determine the relative expression of SELE, eosinophil cationic protein (ECP), intercellular adhesion molecule 1 (ICAM-1), L-selectin (CD62L), and the alpha chain of leukocyte function-associated antigen-1 (CD11a). Adhesion assay was then performed to assess the cell adhesion ability in VECs. Elevated levels of IgE, IL-4, IFN-γ, and histamine and increased positive expression rate of SELE were indicative of successful establishment of mouse models of ICU. Furthermore, the relative expression levels of SELE, ECP, ICAM-1, CD62L, and CD11a were highest in the OE- SELE group. Besides, cell adhesion ability of VECs was notably promoted. Collectively, the current study define the potential role of SELE silencing as an inhibitor to ICU development by inhibiting cell adhesion ability of VECs.

NOTCH3 regulates stem-to-mural cell differentiation in infantile hemangioma

Infantile hemangioma (IH) is a vascular tumor that begins with rapid vascular proliferation shortly after birth, followed by vascular involution in early childhood. We have found that NOTCH3, a critical regulator of mural cell differentiation and maturation, is expressed in hemangioma stem cells (HemSCs), suggesting that NOTCH3 may function in HemSC-to-mural cell differentiation and pathological vessel stabilization. Here, we demonstrate that NOTCH3 is expressed in NG2+PDGFRβ+ perivascular HemSCs and CD31+GLUT1+ hemangioma endothelial cells (HemECs) in proliferating IHs and becomes mostly restricted to the αSMA+NG2loPDGFRβlo mural cells in involuting IHs. NOTCH3 knockdown in HemSCs inhibited in vitro mural cell differentiation and perturbed αSMA expression. In a mouse model of IH, NOTCH3 knockdown or systemic expression of the NOTCH3 inhibitor, NOTCH3 Decoy, significantly decreased IH blood flow, vessel caliber, and αSMA+ perivascular cell coverage. Thus, NOTCH3 is necessary for HemSC-to-mural cell differentiation, and adequate perivascular cell coverage of IH vessels is required for IH vessel stability.

The role of stem cells in benign tumors

As stem cells contribute to the development and homeostasis of normal adult tissues, malfunction of stem cells in self-renewal and differentiation has been associated with tumorigenesis. A growing number of evidences indicating that tumor initiating cells play a crucial role, not only in malignancies, but also in generation and development of benign tumors. Here we offer an overview of the identification and functional characterization of benign tumor initiating cells in several tissues and organs, which typically show capacities of uncontrolled self-renewal to fuel the tumor growth and abnormal differentiation to give rise to tumor heterogeneity. They may originate from alteration of normal stem cells, which confer the benign tumor initiating cells with different repertoire of "stemness". The plastic functions of benign tumor initiating cells are determined by niche regulation mediated via several signaling and epigenetic cues. Therefore, targeting stem cell function represents an important strategy for understanding the biology and management of benign tumors.

Glucose transporter 1-positive endothelial cells in infantile hemangioma exhibit features of facultative stem cells

Endothelial glucose transporter 1 (GLUT1) is a definitive and diagnostic marker for infantile hemangioma (IH), a vascular tumor of infancy. To date, GLUT1-positive endothelial cells in IH have not been quantified nor directly isolated and studied. We isolated GLUT1-positive and GLUT1-negative endothelial cells from IH specimens and characterized their proliferation, differentiation, and response to propranolol, a first-line therapy for IH, and to rapamycin, an mTOR pathway inhibitor used to treat an increasingly wide array of proliferative disorders. Although freshly isolated GLUT1-positive cells, selected using anti-GLUT1 magnetic beads, expressed endothelial markers CD31, VE-Cadherin, and vascular endothelial growth factor receptor 2, they converted to a mesenchymal phenotype after 3 weeks in culture. In contrast, GLUT1-negative endothelial cells exhibited a stable endothelial phenotype in vitro. GLUT1-selected cells were clonogenic when plated as single cells and could be induced to redifferentiate into endothelial cells, or into pericytes/smooth muscle cells or into adipocytes, indicating a stem cell-like phenotype. These data demonstrate that, although they appear and function in the tumor as bona fide endothelial cells, the GLUT1-positive endothelial cells display properties of facultative stem cells. Pretreatment with rapamycin for 4 days significantly slowed proliferation of GLUT1-selected cells, whereas propranolol pretreatment had no effect. These results reveal for the first time the facultative nature of GLUT1-positive endothelial cells in IH.

Treprostinil indirectly regulates endothelial colony forming cell angiogenic properties by increasing VEGF-A produced by mesenchymal stem cells

Pulmonary vasodilators and prostacyclin therapy in particular, have markedly improved the outcome of patients with pulmonary hypertension (PH). Endothelial dysfunction is a key feature of PH, and we previously reported that treprostinil therapy increases number and proliferative potential of endothelial colony forming cells (ECFC) isolated from PH patients' blood. In the present study, the objective was to determine how treprostinil contributes to the proangiogenic functions of ECFC. We examined the effect of treprostinil on ECFC obtained from cord blood in terms of colony numbers, proliferative and clonogenic properties in vitro, as well as in vivo vasculogenic properties. Surprisingly, treprostinil inhibited viability of cultured ECFC but did not modify their clonogenic properties or the endothelial differentiation potential from cord blood stem cells. Treprostinil treatment significantly increased the vessel-forming ability of ECFC combined with mesenchymal stem cells (MSC) in Matrigel implanted in nude mice. In vitro, ECFC proliferation was stimulated by conditioned media from treprostinil-pretreated MSC, and this effect was inhibited either by the use of VEGF-A blocking antibodies or siRNA VEGF-A in MSC. Silencing VEGF-A gene in MSC also blocked the pro-angiogenic effect of treprostinil in vivo. In conclusion, increased VEGF-A produced by MSC can account for the increased vessel formation observed during treprostinil treatment. The clinical relevance of these data was confirmed by the high level of VEGF-A detected in plasma from patients with paediatric PH who had been treated with treprostinil. Moreover, our results suggest that VEGF-A level in patients could be a surrogate biomarker of treprostinil efficacy.

Thrombin receptor PAR-1 activation on endothelial progenitor cells enhances chemotaxis-associated genes expression and leukocyte recruitment by a COX-2-dependent mechanism

BACKGROUND

Endothelial colony forming cells (ECFC) represent a subpopulation of endothelial progenitor cells involved in endothelial repair. The activation of procoagulant mechanisms associated with the vascular wall's inflammatory responses to injury plays a crucial role in the induction and progression of atherosclerosis. However, little is known about ECFC proinflammatory potential.

AIMS

To explore the role of the thrombin receptor PAR-1 proinflammatory effects on ECFC chemotaxis/recruitment capacity.

METHODS AND RESULTS

The expression of 30 genes known to be associated with inflammation and chemotaxis was quantified in ECFC by real-time qPCR. PAR-1 activation with the SFLLRN peptide (PAR-1-ap) resulted in a significant increase in nine chemotaxis-associated genes expression, including CCL2 and CCL3 whose receptors are present on ECFC. Furthermore, COX-2 expression was found to be dramatically up-regulated consequently to PAR-1 activation. COX-2 silencing with the specific COX-2-siRNA also triggered down-regulation of the nine target genes. Conditioned media (c.m.) from control-siRNA- and COX-2-siRNA-transfected ECFC, stimulated or not with PAR-1-ap, were produced and tested on ECFC capacity to recruit leukocytes in vitro as well in the muscle of ischemic hindlimb in a preclinical model. The capacity of the c.m. from ECFC stimulated with PAR-1-ap to recruit leukocytes was abrogated when COX-2 gene expression was silenced in vitro (in terms of U937 cells migration and adhesion to endothelial cells) as well as in vivo. Finally, the postnatal vasculogenic stem cell derived from infantile hemangioma tumor (HemSC) incubated with PAR-1-ap increased leukocyte recruitment in Matrigel(®) implant.

CONCLUSIONS

PAR-1 activation in ECFC increases chemotactic gene expression and leukocyte recruitment at ischemic sites through a COX-2-dependent mechanism.

Educational paper: Pathogenesis of infantile haemangioma, an update 2014 (part I)

Infantile haemangioma (IH) is the most frequent childhood tumour. Although it is benign and self-limiting, severe complications can arise due to localisation and fast tumour growth. Management and therapy of IH has changed greatly after 2008 with propranolol. However, the pathogenesis remains elusive. This update provides an overview of all possible mechanisms currently considered. We discuss the possibility that several mechanisms act together, although local hypoxia seems to be important. Clinically, in about half of the cases, an IH is preceded by an anaemic macula (local ischaemia) or a so-called precursor lesion. Laboratory findings indicate stabilisation and an increased transcription activity of hypoxia-inducible factor 1 alpha (HIF1α), leading to up-regulation of its downstream target genes (such as vascular endothelial growth factor (VEGF)), which normally occurs in cases of hypoxia.

CONCLUSION

Three main hypotheses have been proposed, namely (1) the theory of tissue hypoxia, (2) the theory of embolization of placental endothelial cells and (3) the theory of increased angiogenic and vasculogenic activity.

α6-Integrin is required for the adhesion and vasculogenic potential of hemangioma stem cells

Infantile hemangioma (IH) is the most common tumor of infancy. Hemangioma stem cells (HemSC) are a mesenchymal subpopulation isolated from IH CD133+ cells. HemSC can differentiate into endothelial and pericyte/smooth muscle cells and form vascular networks when injected in immune-deficient mice. α6-Integrin subunit has been implicated in the tumorgenicity of glioblastoma stem cells and the homing properties of hematopoietic, endothelial, and mesenchymal progenitor cells. Therefore, we investigated the possible function(s) of α6-integrin in HemSC. We documented α6-integrin expression in IH tumor specimens and HemSC by RT-qPCR and flow cytometry. We examined the effect of blocking or silencing α6-integrin on the adhesive and proliferative properties of HemSC in vitro and the vasculogenic and homing properties of HemSC in vivo. Targeting α6-integrin in cultured HemSC inhibited adhesion to laminin but had no effect on proliferation. Vessel-forming ability in Matrigel implants and hepatic homing after i.v. delivery were significantly decreased in α6-integrin siRNA-transfected HemSC. In conclusion, α6-integrin is required for HemSC adherence to laminin, vessel formation in vivo, and for homing to the liver. Thus, we uncovered an important role for α6 integrin in the vasculogenic properties of HemSC. Our results suggest that α6-integrin expression on HemSC could be a new target for antihemangioma therapy.

Propranolol targets the contractility of infantile haemangioma-derived pericytes

BACKGROUND

Propranolol, a β-adrenergic receptor (AR) antagonist, is an effective treatment for endangering infantile haemangioma (IH). Dramatic fading of cutaneous colour is often seen a short time after initiating propranolol therapy, with accelerated regression of IH blood vessels discerned after weeks to months.

OBJECTIVES

To assess a possible role for haemangioma-derived pericytes (HemPericytes) isolated from proliferating and involuting phase tumours in apparent propranolol-induced vasoconstriction.

METHODS

HemPericytes were assayed for contractility on a deformable silicone substrate: propranolol (10 μmol L(-1)) restored basal contractile levels in HemPericytes that were relaxed with the AR agonist epinephrine. Small interfering RNA knockdown of β2-AR blunted this response. HemPericytes and haemangioma-derived endothelial cells were co-implanted subcutaneously in nude mice to form blood vessels; at day 7 after injection, mice were randomized into vehicle and propranolol-treated groups.

RESULTS

HemPericytes expressed high levels of β2-AR mRNA compared with positive control bladder smooth muscle cells. In addition, β2-AR mRNA levels were relatively high in IH specimens (n = 15) compared with β1-AR, β3-AR and α1b-AR. Normal human retinal and placental pericytes were not affected by epinephrine or propranolol in this assay. Propranolol (10 μmol L(-1)) inhibited the proliferation of HemPericytes in vitro, as well as normal pericytes, indicating a nonselective effect in this assay. Contrast-enhanced microultrasonography of the implants after 7 days of treatment showed significantly decreased vascular volume in propranolol-treated animals, but no reduction in vehicle-treated animals.

CONCLUSIONS

These findings suggest that the mechanism of propranolol's effect on proliferating IH involves increased pericytic contractility.

Cooperation between human fibrocytes and endothelial colony-forming cells increases angiogenesis via the CXCR4 pathway

Fibrotic diseases of the lung are associated with a vascular remodelling process. Fibrocytes (Fy) are a distinct population of blood-borne cells that co-express haematopoietic cell antigens and fibroblast markers, and have been shown to contribute to organ fibrosis. The purpose of this study was to determine whether fibrocytes cooperate with endothelial colony-forming cells (ECFC) to induce angiogenesis. We isolated fibrocytes from blood of patient with idiopathic pulmonary fibrosis (IPF) and characterised them by flow cytometry, quantitative reverse transcriptase PCR (RTQ-PCR), and confocal microscopy. We then investigated the angiogenic interaction between fibrocytes and cord-blood-derived ECFC, both in vitro and in an in vivo Matrigel implant model. Compared to fibroblast culture medium, fibrocyte culture medium increased ECFC proliferation and differentiation via the SDF-1/CXCR4 pathway. IPF-Fy co-implanted with human ECFC in Matrigel plugs in immunodeficient mice formed functional microvascular beds, whereas fibroblasts did not. Evaluation of implants after two weeks revealed an extensive network of erythrocyte-containing blood vessels. CXCR4 blockade significantly inhibited this blood vessel formation. The clinical relevance of these data was confirmed by strong CXCR4 expression in vessels close to fibrotic areas in biopsy specimens from patients with IPF, by comparison with control lungs. In conclusion, circulating fibrocytes might contribute to the intense remodelling of the pulmonary vasculature in patients with idiopathic pulmonary fibrosis.

Pathogenesis of infantile haemangioma

Haemangioma is a vascular tumour of infancy that is well known for its rapid growth during the first weeks to months of a child's life, followed by a spontaneous but slow involution. During the proliferative phase, the vessels are disorganized and composed of immature endothelial cells. When the tumour involutes, the vessels mature and enlarge but are reduced in number. Fat, fibroblasts and connective tissue replace the vascular tissue, with few, large, feeding and draining vessels evident. Both angiogenesis and vasculogenesis have been proposed as mechanisms contributing to the neovascularization in haemangioma tumours. In recent years, several of the 'building blocks', the cells comprising the haemangioma, have been isolated. Among them are haemangioma progenitor/stem cells, endothelial cells and pericytes. This review focuses on these cell types, and the molecular pathways within these cells that have been implicated in driving the pathogenesis of infantile haemangioma.

Correlations of SELE genetic polymorphisms with risk of coronary heart disease and myocardial infarction: a meta-analysis

This meta-analysis of case-control studies was conducted to determine whether SELE genetic polymorphisms contribute to the pathogenesis of coronary heart disease (CHD) and myocardial infarction (MI). The PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library, and CBM databases were searched for relevant articles published before November 1st, 2013 without any language restrictions. Meta-analysis was conducted using the STATA 12.0 software. Twenty case-control studies met the inclusion criteria, with a total of 2,292 CHD patients, 901 MI patients and 3,233 healthy controls. Six common polymorphisms in the SELE gene were evaluated, including 554L/F, 98G/T, 128S/R, 2692G/A, 1901C/T, and 1856A/G. The results of our meta-analysis suggest that SELE genetic polymorphisms might be strongly correlated with an increased risk of CHD (allele model: OR 2.08, 95% CI 1.67-2.58, P<0.001; dominant model: OR 2.12, 95% CI 1.68-2.68, P<0.001; respectively), especially the SELE 554L/F, 98G/T and 128S/R polymorphisms. Furthermore, our findings indicated that SELE genetic polymorphisms were closely linked to the risk of CHD in Asians but not Caucasians. However, our findings reveal no positive correlations between SELE genetic polymorphisms and MI risk (allele model: OR 1.39, 95% CI 1.00-1.94, P=0.054; dominant model: OR 1.40, 95% CI 0.96-2.04, P=0.081; respectively). The current meta-analysis suggests that SELE genetic polymorphisms may contribute to an increased risk of CHD, especially the SELE 554L/F, 98G/T and 128S/R polymorphisms in Asians. However, SELE genetic polymorphisms may not be important determinants of susceptibility to MI.