VEGFR-1 mediates endothelial differentiation and formation of blood vessels in a murine model of infantile hemangioma

Immune-privileged cord blood-derived endothelial colony-forming cells: advancing immunomodulation and vascular regeneration

Cord blood-derived endothelial colony-forming cells (CB-ECFCs) hold significant promise for regenerative medicine due to their unique vasculogenic and immunomodulatory properties. These cells exhibit a superior proliferative capacity, robust ability to form vascular networks, and lower immunogenicity compared to adult and embryonic stem cell-derived counterparts. The immune-privileged characteristics of CB-ECFCs, including reduced expression of pro-inflammatory mediators and tolerance-inducing molecules such as HLA-G, further enhance their therapeutic potential. Their low immunogenicity minimizes the risk of immune rejection, making them suitable for allogenic cell therapies. Their application extends to complex tissue engineering and organ revascularization, where their ability to integrate into three-dimensional scaffolds and support vascular tree formation represents a significant advancement. Moreover, CB-ECFCs' capability to adapt to inflammatory stimuli and retain immunological memory highlights their functional versatility in dynamic microenvironments. This review highlights the remarkable ontogeny of ECFCs while unveiling the unparalleled potential of CB-ECFCs in revolutionizing regenerative medicine. From pre-vascularizing engineered tissues and organoids to pioneering cell-based therapies for cardiovascular, dermatological, and degenerative diseases, CB-ECFCs stand at the forefront of cutting-edge biomedical advancements, offering unprecedented opportunities for therapeutic innovation. By leveraging their vasculogenic, immune-regulatory, and regenerative capacities, CB-ECFCs offer a robust alternative for addressing the challenges of vascular repair and organ engineering. Future research should focus on unraveling their transcriptomic and functional profiles to optimize clinical applications and advance the field of regenerative medicine.

An endothelial SOX18-mevalonate pathway axis enables repurposing of statins for infantile hemangioma

Infantile hemangioma (IH) is the most common tumor in children and a paradigm for pathological vasculogenesis, angiogenesis, and regression. Propranolol, the mainstay of treatment, inhibits IH vessel formation via a β-adrenergic receptor-independent off-target effect of its R(+) enantiomer on endothelial SOX18 - a member of the SOX (SRY-related HMG-box) family of transcription factors. Transcriptomic profiling of patient-derived hemangioma stem cells uncovered the mevalonate pathway (MVP) as a target of R(+) propranolol. Loss and gain of function of SOX18 confirmed it is both necessary and sufficient for R(+) propranolol suppression of the MVP, including regulation of sterol regulatory element-binding protein 2 (SREBP2) and the rate-limiting enzyme HMG-CoA reductase (HMGCR). A biological relevance of the endothelial SOX18-MVP axis in IH patient tissue was demonstrated by nuclear colocalization of SOX18 and SREBP2. Functional validation in a preclinical IH xenograft model revealed that statins - competitive inhibitors of HMGCR - efficiently suppress IH vessel formation. We propose an endothelial SOX18-MVP axis as a central regulator of IH pathogenesis and suggest statin repurposing to treat IH. The pleiotropic effects of R(+) propranolol and statins along the SOX18-MVP axis to disable an endothelial cell-specific program may have therapeutic implications for other vascular disease entities involving pathological vasculogenesis and angiogenesis.

Cell Fate Regulation During the Development of Infantile Hemangioma

As the most common benign vascular tumor in infants, infantile hemangioma (IH) is characterized by rapid growth and vasculogenesis early in infancy, followed by spontaneous involution into fibrofatty tissues over time. Extensive evidence suggests that IH originates from hemangioma stem cells (HemSCs), a group of stem cells with clonal expansion and multi-directional differentiation capacity. However, the intricate mechanisms governing the cell fate transition of HemSCs during IH development remain elusive. Here we comprehensively examine the cellular composition of IH, emphasizing the nuanced properties of various IH cell types and their correlation with the clinical features of the tumor. We also summarize the current understanding of the regulatory pathways directing HemSC differentiation into endothelial cells (ECs), pericytes, and adipocytes throughout the stages of IH progression and involution. Furthermore, we discuss recent advances in unraveling the transcriptional and epigenetic regulation of EC and adipocyte development under physiological conditions, which offer crucial perspectives for understanding IH pathogenesis.

Endothelial Colony-Forming Cells (ECFCs) in cerebrovascular aging: Focus on the pathogenesis of Vascular Cognitive Impairment and Dementia (VCID), and treatment prospects

Endothelial colony-forming cells (ECFCs), a unique endothelial progenitor subset, are essential for vascular integrity and repair, providing significant regenerative potential. Recent studies highlight their role in cerebrovascular aging, particularly in the pathogenesis of vascular cognitive impairment and dementia (VCID). Aging disrupts ECFC functionality through mechanisms such as oxidative stress, chronic inflammation, and cellular senescence, leading to compromised vascular repair and reduced neurovascular resilience. ECFCs influence key cerebrovascular processes, including neurovascular coupling (NVC), blood-brain barrier (BBB) integrity, and vascular regeneration, which are critical for cognitive health. Age-related decline in ECFC quantity and functionality contributes to vascular rarefaction, diminished cerebral blood flow (CBF), and BBB permeability-processes that collectively exacerbate cognitive decline. This review delves into the multifaceted role of ECFCs in cerebrovascular aging and underscores their potential as therapeutic targets in addressing age-related vascular dysfunctions, presenting new directions for mitigating the effects of aging on brain health.

Once a day administration of R(+) propranolol is sufficient to block vasculogenesis in a xenograft model of infantile hemangioma

OBJECTIVES

Infantile hemangioma (IH) is a benign vascular tumor that occurs in 5% of infants, predominantly in female and preterm neonates. Propranolol is the mainstay of treatment for IH. Given the short half-life of propranolol regarding β-adrenergic receptor inhibition as well as its side effects, propranolol is administered to infants 2-3 times daily with 1 mg/kg/dose. We previously demonstrated propranolol inhibits IH vessel formation via an effect of its R(+) enantiomer on the endothelial-specific transcription factor SRY box 18 (SOX18). In light of this, we hypothesized that R(+) propranolol inhibition of SOX18 is long-lived compared to the beta-blocker effects, and therefore administration of R(+) propranolol once a day would be sufficient to block IH vessel formation.

METHODS

We tested the effect of one dose versus two doses of R(+) propranolol in a xenograft model of IH wherein patient-derived hemangioma stem cells (HemSC) were implanted subcutaneously into nude mice. Mice were treated for 7 days with 2 × 12.5 mg/kg/day (n=12) versus 1 × 25 mg/kg/day (n=14) as well as PBS (vehicle control) (n=16) via intraperitoneal injections. The doses were estimated to correlate with those given to infants with IH.

RESULTS

Treatment with R(+) propranolol significantly inhibited vasculogenesis in our IH xenograft model at both 2 × 12.5 mg/kg/day and 1 × 25 mg/kg/day, compared to vehicle controls. No significant difference was observed between the two treatment regimens.

CONCLUSIONS

Our results suggest implications for the clinical management of infants with IH: Administration of R(+) propranolol can possibly minimize or omit concerning β-adrenergic side effects while only requiring one dose per day.

Insights into the mechanisms of angiogenesis in infantile hemangioma

Infantile hemangioma (IH) is the most common benign tumor in infants and usually resolves on its own. However, a small portion of IH cases are accompanied by serious complications and other problems, impacting the physical and psychological health of the children affected. The pathogenesis of IH is highly controversial. Studies have shown that abnormal blood vessel formation is an important pathological basis for the development of IH. Compared with that in normal tissues, the equilibrium of blood vessel growth at the tumor site is disrupted, and interactions among other types of cells, such as immune cells, promote the rapid proliferation and migration of vascular tissue cells and the construction of vascular networks. Currently, propranolol is the most common systemic drug used to inhibit the growth of IHs and accelerate their regression. The purpose of this review is to provide the latest research on the mechanisms of angiogenesis in IH. We discuss the possible roles of three major factors, namely, estrogen, hypoxia, and inflammation, in the development of IH. Additionally, we summarize the key roles of tumor cell subpopulations, such as pericytes, in the proliferation and regression of IH considering evidence from the past few years, with an emphasis on the possible mechanisms of propranolol in the treatment of IH. Angiogenesis is an important event during the development of IH, and an in-depth understanding of the molecular mechanisms of angiogenesis will provide new insights into the biology and clinical treatment of IH.

KLF2 Orchestrates Pathological Progression of Infantile Hemangioma through Hemangioma Stem Cell Fate Decisions

Infantile hemangioma (IH) is the most prevalent vascular tumor during infancy, characterized by a rapid proliferation phase of disorganized blood vessels and spontaneous involution. IH possibly arises from a special type of multipotent stem cells called hemangioma stem cells (HemSCs), which could differentiate into endothelial cells, pericytes, and adipocytes. However, the underlying mechanisms that regulate the cell fate determination of HemSCs remain elusive. In this study, we unveil KLF2 as a candidate transcription factor involved in the control of HemSCs differentiation. KLF2 exhibits high expression in endothelial cells in proliferating IH but diminishes in adipocytes in involuting IH. Using a combination of in vitro culture of patient-derived HemSCs and HemSCs implantation mouse models, we show that KLF2 governs the proliferation, apoptosis, and cell cycle progression of HemSCs. Importantly, KLF2 acts as a crucial determinant of HemSC fate, directing their differentiation toward endothelial cells while inhibiting adipogenesis. Knockdown of KLF2 induces a proadipogenic transcriptome in HemSCs, leading to impaired blood vessel formation and accelerated adipocyte differentiation. Collectively, our findings highlight KLF2 as a critical regulator controlling the progression and involution of IH by modulating HemSC fate decisions.

R(+) Propranolol decreases lipid accumulation in hemangioma-derived stem cells

Background

Infantile hemangioma (IH) is a benign vascular tumor that undergoes an initial rapid growth phase followed by spontaneous involution. A fibrofatty residuum remains in many tumors and often necessitates resection. We recently discovered that R(+) propranolol, the non-β blocker enantiomer, inhibits blood vessel formation of IH patient-derived hemangioma stem cells (HemSC) xenografted in mice. HemSC are multipotent cells with the ability to differentiate into endothelial cells, pericytes, and adipocytes.

Objectives

We investigated how R(+) propranolol affects HemSC adipogenic differentiation and lipid accumulation, in vitro and in a preclinical murine model for IH.

Methods

We conducted a 10-day adipogenesis assay on 4 IH patient-derived HemSCs. Oil Red O (ORO) staining was used to identify the onset and level of lipid accumulation in HemSC while quantitative real-time polymerase chain reaction was conducted to determine the temporal expression of key factors implicated in adipogenesis. 5-20µM R(+) propranolol treatment was added to HemSC induced to undergo adiogenesis for 4 and 8 days, followed by quantification of lipid-stained areas and transcript levels of key adipogenic factors. We immunostained for lipid droplet-associated protein Perilipin 1 (PLIN1) in HemSC-xenograft sections from mice treated with R(+) propranolol and quantified the area using ImageJ.

Results

We found that different patient-derived HemSC exhibit a robust and heterogenous adipogenic capacity when induced for adipogenic differentiation in vitro. Consistently across four IH patient-derived HemSC isolates, R(+) propranolol reduced ORO-stained areas and lipoprotein lipase (LPL) transcript levels in HemSC after 4 and 8 days of adipogenic induction. In contrast, R(+) propranolol had no significant inhibitory effect on transcript levels encoding adipogenic transcription factors. In a pre-clinical HemSC xenograft model, PLIN1-positive area was significantly reduced in xenograft sections from mice treated with R(+) propranolol, signifying reduced lipid accumulation.

Conclusions

Our findings suggest a novel regulatory role for the R(+) enantiomer of propranolol in modulating lipid accumulation in HemSC. This highlights a novel role of R(+) propranolol in the involuting phase of IH and a strategy to reduce fibrofatty residua in IH.

What is already known about this topic?

Propranolol is the mainstay treatment for infantile hemangioma (IH), the most common tumor of infancy, but its use can be associated with concerning β-blocker side effects.R(+) propranolol, the enantiomer largely devoid of β-blocker activity, was recently shown to inhibit endothelial differentiation of hemangioma-derived stem cells (HemSC) in vitro and reduce blood vessel formation in a HemSC-derived xenograft murine model of IH.

What does this study add?

R(+) propranolol inhibits lipid accumulation in HemSC in vitro.R(+) propranolol does not affect mRNA transcript levels of key adipogenic transcription factors in differentiating HemSC in vitro.R(+) propranolol reduces lipid accumulation in a pre-clinical xenograft murine model of IH.

What is the translational message?

The R(+) enantiomer of propranolol could be advantageous in terms of reduction in β-adrenergic side effects and fibrofatty tissue formation in the involuting phase of IH.Less fibrofatty residua might reduce the need for surgical resection.Disfigurement and associated psychosocial impacts might be improved in this young patient cohort.

Infantile hemangioma: the common and enigmatic vascular tumor

Infantile hemangioma (IH) is a benign vascular tumor that occurs in 5% of newborns. The tumor follows a life cycle of rapid proliferation in infancy, followed by slow involution in childhood. This unique life cycle has attracted the interest of basic and clinical scientists alike as a paradigm for vasculogenesis, angiogenesis, and vascular regression. Unanswered questions persist about the genetic and molecular drivers of the proliferating and involuting phases. The beta blocker propranolol usually accelerates regression of problematic IHs, yet its mechanism of action on vascular proliferation and differentiation is unclear. Some IHs fail to respond to beta blockers and regrow after discontinuation. Side effects occur and long-term sequelae of propranolol treatment are unknown. This poses clinical challenges and raises novel questions about the mechanisms of vascular overgrowth in IH.

Global research trends of infantile hemangioma: A bibliometric and visualization analysis from 2000 to 2022

Background

Infantile hemangioma (IH) has received global attention, resulting in a significant volume of literature. However, there is a lack of bibliometric analyses specifically focusing on IH publications. This study aims to fill this gap by conducting a comprehensive analysis of IH publications, investigating their characteristics, contribution distribution, and developmental trends. By enhancing our understanding of IH and identifying potential research topics and collaborators, this study will contribute to the advancement of the field.

Methods

A total of 4333 articles and reviews on IH were collected from the Web of Science (WoS) database, spanning the years 2000-2022. The study encompassed a comprehensive analysis of IH publications, evaluating their quantity and quality. Additionally, we profiled publishing groups based on country, institution, author publication records, and collaboration networks. Lastly, we identified and summarized the prominent research topics.

Results

Annual publications on IH have increased over the past 20 years. The United States has the highest number of publications and the highest total number of citations. Pediatric Dermatology was the most influential journal in the IH field. The citation analysis indicated that the articles published by Léauté-Labrèze in 2008 had the highest number of citations. The articles published by North PE in 2000 and Boye E in 2001 laid a certain research foundation for this field. Concerning institutions, most of the cooperative relationships were established in the same country/region. The United States has the largest number of scientific research institutions and IH researchers, leading most of the cross-country collaboration. The University of California, San Francisco, Medical College of Wisconsin, Harvard University, and Shanghai Jiaotong University were the research centers that published the most IH-related research. Frieden IJ, Mulliken JB, and Drolet BA were the top three most influential authors. Frieden IJ, Garzon MC, and Mulliken JB were the top three authors with the most cited frequency. In addition, keywords and keyword co-occurrence networks prompted that the pathological mechanism of IH, clinical analysis, and other vascular anomalies are research hotspots. Analysis of trending topics suggests that research on IH has evolved from treatment-focused studies towards investigations of other vascular diseases and a series of clinical case studies. Currently, clinical case studies receive the most attention in the field.

Conclusions

This comprehensive bibliometric study provides a thorough analysis of post-2000 publications in the field of IH, offering insights into current research trends for the first time. The findings suggest that future investigations will continue to prioritize understanding IH mechanisms, treatment approaches, and treatment evaluation. Furthermore, the exploration of other vascular diseases and the inclusion of clinical case studies are expected to contribute to advancements in IH clinical practice. By identifying potential collaborators, partner institutions, and new research avenues, this study offers valuable guidance for future in-depth research on IH.

Differential pericyte marker expression in craniofacial benign and malignant vascular tumors

BACKGROUND

Vascular anomalies and tumors are common in the head, neck, and craniofacial areas and are associated with abnormalities in the angiomatous architecture. However, the etiology and molecular basis for the pathogenesis of most vascular lesions are still unknown. Pericytes are mural cells that surround endothelial cells. Besides angiogenesis and other physiological functions, pericytes play an important role in vascularized tissue repair and as resident mesenchymal stem/progenitor cells. Perivascular cells demonstrate a distinct immunohistochemical profile, including expression of alpha-smooth muscle actin (α-SMA), CD146, CD105, and PDGFRβ, without endothelial differentiation (absence of CD31 and CD34 immunoreactivity). These pericyte markers have been shown to be expressed in soft tissue hemangiomas. However, they have not been fully examined in intraosseous hemangiomas.

METHODS

In this study, we compared mesenchymal stem cell (MSC) expression of CD146 and α-SMA markers in pericytes from hemangiomas from different tissues and malignant vascular tumors.

RESULTS

The results demonstrated an increased expression of pericyte markers in perivascular cells of benign hemangiomas, especially intraosseous hemangiomas and a significantly reduced expression of pericyte markers in malignant angiosarcomas.

CONCLUSION

The evidence provides insight into the function of pericytes in vascular tumors and suggests their role in vascular tumor disease types.

A Combination of Distinct Vascular Stem/Progenitor Cells for Neovascularization and Ischemic Rescue

BACKGROUND

Peripheral vascular disease remains a leading cause of vascular morbidity and mortality worldwide despite advances in medical and surgical therapy. Besides traditional approaches, which can only restore blood flow to native arteries, an alternative approach is to enhance the growth of new vessels, thereby facilitating the physiological response to ischemia.

METHODS

The ActinCreER/R26VT2/GK3 Rainbow reporter mouse was used for unbiased in vivo survey of injury-responsive vasculogenic clonal formation. Prospective isolation and transplantation were used to determine vessel-forming capacity of different populations. Single-cell RNA-sequencing was used to characterize distinct vessel-forming populations and their interactions.

RESULTS

Two populations of distinct vascular stem/progenitor cells (VSPCs) were identified from adipose-derived mesenchymal stromal cells: VSPC1 is CD45-Ter119-Tie2+PDGFRa-CD31+CD105highSca1low, which gives rise to stunted vessels (incomplete tubular structures) in a transplant setting, and VSPC2 which is CD45-Ter119-Tie2+PDGFRa+CD31-CD105lowSca1high and forms stunted vessels and fat. Interestingly, cotransplantation of VSPC1 and VSPC2 is required to form functional vessels that improve perfusion in the mouse hindlimb ischemia model. Similarly, VSPC1 and VSPC2 populations isolated from human adipose tissue could rescue the ischemic condition in mice.

CONCLUSIONS

These findings suggest that autologous cotransplantation of synergistic VSPCs from nonessential adipose tissue can promote neovascularization and represents a promising treatment for ischemic disease.

CD146+ mural cells from infantile hemangioma display proangiogenic ability and adipogenesis potential in vitro and in xenograft models

Objective

Infantile hemangioma (IH), the most common infantile vascular neoplasm, is uniquely characterized by rapid proliferation followed by slow spontaneous involution lasting for years. In IH lesions, perivascular cells are the most dynamic cell subset during the transition from the proliferation phase to the involution phase, and we aimed to systematically study this kind of cell.

Methods and results

CD146-selective microbeads were used to isolate IH-derived mural-like cells (HemMCs). Mesenchymal markers of HemMCs were detected by flow cytometry, and the multilineage differentiation potential of HemMCs was detected by specific staining after conditioned culture. CD146-selected nonendothelial cells from IH samples showed characteristics of mesenchymal stem cells with distinct angiogenesis-promoting effects detected by transcriptome sequencing. HemMCs spontaneously differentiated into adipocytes 2 weeks after implantation into immunodeficient mice, and almost all HemMCs had differentiated into adipocytes within 4 weeks. HemMCs could not be induced to differentiate into endothelial cells in vitro. However, 2 weeks after implantation in vivo, HemMCs in combination with human umbilical vein endothelial cells (HUVECs) formed GLUT1⁺ IH-like blood vessels, which spontaneously involuted into adipose tissue 4 weeks after implantation.

Conclusions

In conclusion, we identified a specific cell subset that not only showed behavior consistent with the evolution of IH but also recapitulated the unique course of IH. Thus, we speculate that proangiogenic HemMCs may be a potential target for the construction of hemangioma animal models and the study of IH pathogenesis.

Metabolic reprogramming and membrane glycan remodeling as potential drivers of zebrafish heart regeneration

The ability of the zebrafish heart to regenerate following injury makes it a valuable model to deduce why this capability in mammals is limited to early neonatal stages. Although metabolic reprogramming and glycosylation remodeling have emerged as key aspects in many biological processes, how they may trigger a cardiac regenerative response in zebrafish is still a crucial question. Here, by using an up-to-date panel of transcriptomic, proteomic and glycomic approaches, we identify a metabolic switch from mitochondrial oxidative phosphorylation to glycolysis associated with membrane glycosylation remodeling during heart regeneration. Importantly, we establish the N- and O-linked glycan structural repertoire of the regenerating zebrafish heart, and link alterations in both sialylation and high mannose structures across the phases of regeneration. Our results show that metabolic reprogramming and glycan structural remodeling are potential drivers of tissue regeneration after cardiac injury, providing the biological rationale to develop novel therapeutics to elicit heart regeneration in mammals.

Nano‐gold micelles loaded Dox and Elacridar for reversing drug resistance of breast cancer

The aim of this study was to provide a new effective carrier for rescuing the sensitivity of drug-resistant in breast cancer cells. Nano-gold micelles loaded with Dox and Elacridar (FP-ssD@A-E) were chemically synthesised. With the increase in the amount of Dox and Elacridar, the encapsulation rate of FP-ssD@A-E gradually increased, and the drug loading rate gradually decreased. FP-ss@A-E had a sustained-release effect. Dox, Elacridar, FP-ss@AuNPs, and FP-ssD@A-E significantly improved cell apoptosis, in which, FP-ssD@A-E was the most significant. FP-ssD@A-E significantly decreased the cell viability and improved the Dox uptake. The levels of VEGFR-1, P-gp, IL-6, and i-NOS were significantly decreased after Dox, Dox + Elacridar, FP-ss@AuNPs, and FP-ssD@A-E treatment. It was worth noting that FP-ssD@A-E had the most significant effects. The prepared FP-ssD@A-E micelles, which were spherical in shape, uniform in particle size distribution, and had good drug loading performance and encapsulation efficiency.

Hemangioma Endothelial Cells and Hemangioma Stem Cells in Infantile Hemangioma

BACKGROUND

Hemangioma is one of the most common benign tumors in infants and young children. The 2 most important cells in the course of infantile hemangioma (IH) are hemangioma stem cells (HemSCs) and hemangioma endothelial cells (HemECs). Infantile hemangioma is characterized by massive proliferation of HemECs, but current studies indicate that HemSCs play an important role in pathogenesis of IH.

OBJECTIVE

This review aimed to identify molecules that influence HemSC differentiation and HemEC proliferation and apoptosis to help clarify the pathogenesis of IH and provide novel drug targets for the treatment of IH.

METHODS

Relevant basic science studies related to IH were identified by searching Google Scholar, Embase, PubMed, MEDLINE, and peer-reviewed journal articles.

RESULT

Hemangioma stem cells can differentiate into HemECs, pericytes, and adipocytes. In the proliferating phase of IH, HemSCs mainly differentiate into HemECs and pericytes to promote angiogenesis. In the regressive phase, they mainly differentiate into adipocytes. Therefore, increasing the proportion of HemSCs differentiating into adipocytes, inhibiting the proliferation of HemECs, and promoting the apoptosis of HemECs can facilitate the regression of IH.

Treatment of choroidal hemangioma with photodynamic therapy and bevacizumab

Eyes with choroidal hemangioma (CCH) treated with photodynamic therapy and intravitreal bevacizumab injection had a shorter time to best vision compared to eyes treated with PDT alone (98.3±80.8 days compared to 335.7±394.2, p = 0.031).

Endothelial GNAQ p.R183Q Increases ANGPT2 (Angiopoietin-2) and Drives Formation of Enlarged Blood Vessels

OBJECTIVE

Capillary malformation (CM) occurs sporadically and is associated with Sturge-Weber syndrome. The somatic mosaic mutation in GNAQ (c.548G>A, p.R183Q) is enriched in endothelial cells (ECs) in skin CM and Sturge-Weber syndrome brain CM. Our goal was to investigate how the mutant Gαq (G-protein αq subunit) alters EC signaling and disrupts capillary morphogenesis. Approach and Results: We used lentiviral constructs to express p.R183Q or wild-type GNAQ in normal human endothelial colony forming cells (EC-R183Q and EC-WT, respectively). EC-R183Q constitutively activated PLC (phospholipase C) β3, a downstream effector of Gαq. Activated PLCβ3 was also detected in human CM tissue sections. Bulk RNA sequencing analyses of mutant versus wild-type EC indicated constitutive activation of PKC (protein kinase C), NF-κB (nuclear factor kappa B) and calcineurin signaling in EC-R183Q. Increased expression of downstream targets in these pathways, ANGPT2 (angiopoietin-2) and DSCR (Down syndrome critical region protein) 1.4 were confirmed by quantitative PCR and immunostaining of human CM tissue sections. The Gαq inhibitor YM-254890 as well as siRNA targeted to PLCβ3 reduced mRNA expression levels of these targets in EC-R183Q while the pan-PKC inhibitor AEB071 reduced ANGPT2 but not DSCR1.4. EC-R183Q formed enlarged blood vessels in mice, reminiscent of those found in human CM. shRNA knockdown of ANGPT2 in EC-R183Q normalized the enlarged vessels to sizes comparable those formed by EC-WT.

CONCLUSIONS

Gαq-R183Q, when expressed in ECs, establishes constitutively active PLCβ3 signaling that leads to increased ANGPT2 and a proangiogenic, proinflammatory phenotype. EC-R183Q are sufficient to form enlarged CM-like vessels in mice, and suppression of ANGPT2 prevents the enlargement. Our study provides the first evidence that endothelial Gαq-R183Q is causative for CM and identifies ANGPT2 as a contributor to CM vascular phenotype.

Non-β-blocker enantiomers of propranolol and atenolol inhibit vasculogenesis in infantile hemangioma

Propranolol and atenolol, current therapies for problematic infantile hemangioma (IH), are composed of R(+) and S(–) enantiomers: the R(+) enantiomer is largely devoid of beta blocker activity. We investigated the effect of R(+) enantiomers of propranolol and atenolol on the formation of IH-like blood vessels from hemangioma stem cells (HemSCs) in a murine xenograft model. Both R(+) enantiomers inhibited HemSC vessel formation in vivo. In vitro, similar to R(+) propranolol, both atenolol and its R(+) enantiomer inhibited HemSC to endothelial cell differentiation. As our previous work implicated the transcription factor sex-determining region Y (SRY) box transcription factor 18 (SOX18) in propranolol-mediated inhibition of HemSC to endothelial differentiation, we tested in parallel a known SOX18 small-molecule inhibitor (Sm4) and show that this compound inhibited HemSC vessel formation in vivo with efficacy similar to that seen with the R(+) enantiomers. We next examined how R(+) propranolol alters SOX18 transcriptional activity. Using a suite of biochemical, biophysical, and quantitative molecular imaging assays, we show that R(+) propranolol directly interfered with SOX18 target gene trans-activation, disrupted SOX18-chromatin binding dynamics, and reduced SOX18 dimer formation. We propose that the R(+) enantiomers of widely used beta blockers could be repurposed to increase the efficiency of current IH treatment and lower adverse associated side effects.

Current concepts on endothelial stem cells definition, location, and markers

Ischemic vascular disease is a major cause of mortality and morbidity worldwide, and regeneration of blood vessels in perfusion-deficient tissues is a worthwhile therapeutic goal. The idea of delivering endothelial stem/progenitor cells to repair damaged vasculature, reperfuse hypoxic tissue, prevent cell death, and consequently diminish tissue inflammation and fibrosis has a strong scientific basis and clinical value. Various labs have proposed endothelial stem/progenitor cell candidates. This has created confusion, as there are profound differences between these cell definitions based on isolation methodology, characterization, and reparative biology. Here, a stricter definition based on stem cell biology principles is proposed. Although preclinical studies have often been promising, results from clinical trials have been highly contradictory and served to highlight multiple challenges associated with disappointing therapeutic benefit. This article reviews recent accomplishments in the field and discusses current difficulties when developing endothelial stem cell therapies. Emerging evidence that disputes the classic view of the bone marrow as the source for these cells and supports the vascular wall as the niche for these tissue-resident endothelial stem cells is considered. In addition, novel markers to identify endothelial stem cells, including CD157, EPCR, and CD31low VEGFR2low IL33+ Sox9+ , are described.

Giant Hepatic Hemangioma Regressed Significantly Without Surgical Management: A Case Report and Literature Review

Hepatic hemangioma (HH) is a congenital vascular anomaly comprising networks of abnormal blood and/or lymphatic vessels with endothelial cell proliferation. Their pathophysiology is not fully understood, and no specific drug is available to treat them. Conservative management, which limits observation, is preferred for most patients. A HH larger than 4 cm is considered a giant HH that may be treated using surgery ranging from embolization to hepatic resection or liver transplantation. Here, we describe a case with multiple and giant HHs that regressed significantly after treatment with azithromycin (AZM). A systematic literature review of HH and the effects of AZM on angiogenesis was then conducted.

The flavonoid luteolin suppresses infantile hemangioma by targeting FZD6 in the Wnt pathway

Infantile hemangioma is the most common vascular tumor of childhood. It is characterized by clinical expansion of endothelial cells and promoted by angiogenic factors. Luteolin is a flavonoid compound that carries anti-cancer and anti-angiogenesis properties. The study aimed to investigate the effect of luteolin in treating infantile hemangioma. We first tested the effect of luteolin on cell proliferative potential and VEGFA expression in hemangioma-derived stem cells (HemSCs). We then examined the efficacy of systemic application of luteolin in a murine hemangioma model. We then identified the downstream factor regulated by luteolin in HemSCs and validated its causative relationship with knock-down method in both in vitro and in vivo models. We also investigated the protein expression change of this targeting factor in proliferating hemangiomas. Luteolin inhibited HemSC growth and suppressed VEGF-A expression in a dose-dependent manner. Luteolin inhibited microvessel formation and de novo vasculogenesis in the murine model. FZD6 was induced by luteolin and exerted the anti-angiogenesis effect in our tumor models. Lastly, FZD6 level was repressed in the clinical tissues of human proliferating hemangiomas. Luteolin is a promising new agent to treat infantile hemangioma. Targeting the Wnt pathway may represent a potential therapeutic strategic to inhibit angiogenesis in proliferating hemangiomas.

Peripheral vascular disease: preclinical models and emerging therapeutic targeting of the vascular endothelial growth factor ligand-receptor system

Introduction: Vascular endothelial growth factor (VEGF)-A is a sought therapeutic target for PAD treatment because of its potent role in angiogenesis. However, no therapeutic benefit was achieved in VEGF-A clinical trials, suggesting that our understanding of VEGF-A biology and ischemic angiogenic processes needs development. Alternate splicing in VEGF-A produces pro- and anti-angiogenic VEGF-A isoforms; the only difference being a 6-amino acid switch in the C-terminus of the final 8th exon of the gene. This finding has changed our understanding of VEGF-A biology and may explain the lack of benefit in VEGF-A clinical trials. It presents new therapeutic opportunities for peripheral arterial disease (PAD) treatment.Areas covered: Literature search was conducted to include: 1) predicted mechanism by which the anti-angiogenic VEGF-A isoform would inhibit angiogenesis, 2) unexpected mechanism of action, and 3) how this mechanism revealed novel signaling pathways that may enhance future therapeutics in PAD.Expert opinion: Inhibiting a specific anti-angiogenic VEGF-A isoform in ischemic muscle promotes perfusion recovery in preclinical PAD. Additional efforts focused on the production of these isoforms, and the pathways altered by modulating different VEGF receptor-ligand interactions, and how this new data may allow bedside progress offers new approaches to PAD are discussed.I.

EGFR/VEGFR-2 dual inhibitor and apoptotic inducer: Design, synthesis, anticancer activity and docking study of new 2-thioxoimidazolidin-4one derivatives

AIMS

EGFR and VEGFR-2 have emerged as promising targets for cancer management as they play a crucial role in tumor growth, angiogenesis and metastasis. A novel series of 2-thioxoimidazolidin-4-one derivatives were synthesized and evaluated as apoptotic inducers and EGFR/VEGFR-2 dual inhibitors.

MAIN METHODS

The cytotoxic activities of all synthesized compounds were tested against MCF-7, HepG2 and A549 cell lines. The molecular mechanism of the most promising cytotoxic compounds was investigated via a series of assays including in vitro EGFR and VEGFR-2 inhibitory activity in MCF-7 cell line. Additionally, levels of p53, Bax, Bcl-2, caspase 7, 9 as well as cell cycle analysis were assessed in MCF-7 cell line to gain better understanding of their apoptotic activity. Molecular docking study was carried out to predict binding pattern of these compounds with EGFR and VEGFR-2 active sites. Finally, in silico ADME and drug-likeness profiling were calculated.

KEY FINDINGS

Compounds 6 and 8a exhibited superior cytotoxic activity compared to sorafenib and erlotinib, against the three tested cell lines. In the same context, 6 and 8a showed better EGFR and VEGFR-2 inhibitory activity compared to the reference compounds. The later effect was further supported by the docking study. Furthermore, these compounds displayed potent apoptotic activity as evident by cell accumulation at pre-G1 phase and cell cycle arrest at G2/M phase together with increased p53, caspae-7 and caspase-9 levels and Bax/Bcl-2 ratio. Finally, synthesized compounds have acceptable drug likeness.

SIGNIFICANCE

Compounds 6 and 8a act as potent dual EGFR/VEGFR-2 inhibitors with evident apoptotic activity.

A data-driven computational model enables integrative and mechanistic characterization of dynamic macrophage polarization

Macrophages are highly plastic immune cells that dynamically integrate microenvironmental signals to shape their own functional phenotypes, a process known as polarization. Here we develop a large-scale mechanistic computational model that for the first time enables a systems-level characterization, from quantitative, temporal, dose-dependent, and single-cell perspectives, of macrophage polarization driven by a complex multi-pathway signaling network. The model was extensively calibrated and validated against literature and focused on in-house experimental data. Using the model, we generated dynamic phenotype maps in response to numerous combinations of polarizing signals; we also probed into an in silico population of model-based macrophages to examine the impact of polarization continuum at the single-cell level. Additionally, we analyzed the model under an in vitro condition of peripheral arterial disease to evaluate strategies that can potentially induce therapeutic macrophage repolarization. Our model is a key step toward the future development of a network-centric, comprehensive "virtual macrophage" simulation platform.

Oral atenolol treatment for infantile hemangiomas: clinical analysis of 133 consecutive patients

Background

Infantile hemangiomas (IHs) are the most frequently occurring pediatric lesions. Oral propranolol has been shown to be safe and effective in infants with IHs. Side effects such as sleep disturbances have been associated with propranolol. Atenolol is a hydrophilic, selective β1-blocker and therefore may be not associated with side effects attributable to β2-adrenergic receptor blockade and lipophilicity. However, the efficacy of atenolol in the treatment of IHs is poorly understood. The aim of this study was to evaluate the efficacy of atenolol in the treatment of proliferating IHs in a clinical cohort including 133 consecutive patients.

Methods

In this study, we enrolled 133 patients diagnosed as proliferating IHs from the routine clinical and referral practices of the authors. The procedures followed were in accordance with the ethical standards of the Institute Review Board of Shanghai Ninth People's Hospital and Helsinki Declaration. Clinical characteristics, including demographic data and clinical morphology, were collated. Responses to oral atenolol therapy were graded as: excellent, good, fair and poor. According to the reaction to atenolol treatment, additional medications or therapy were used for IH patients to achieve satisfactory clinical results.

Results

In this study, 128 (96.2%) of 133 IH patients responded to oral atenolol, and the response rate (RR) was significantly different for different ages of patients (P<0.05), with the youngest patients having the highest RR. The mean time of treatment was 4.9 months. Forty-one patients who exhibited residual hyperpigmentation or telangiectasia were further treated with timolol maleate cream (n=32) or pulsed dye laser (n=9). All the 41 patients showed positive response. No life-threatening complications were noted during and after oral atenolol. Only 4 (3.0%) of 133 patients developed minor complications including diarrhea. No agitation and bronchospasm were noted in our study.

Conclusions

This study demonstrated that atenolol was effective in the treatment of IHs. Compared to propranolol, atenolol seems to have a similar effect on IHs. Furthermore, atenolol seems to be less frequently associated with potentially life-threatening side effects.

Human Aortic Valve Interstitial Cells Display Proangiogenic Properties During Calcific Aortic Valve Disease

OBJECTIVE

The study's aim was to analyze the capacity of human valve interstitial cells (VICs) to participate in aortic valve angiogenesis. Approach and Results: VICs were isolated from human aortic valves obtained after surgery for calcific aortic valve disease and from normal aortic valves unsuitable for grafting (control VICs). We examined VIC in vitro and in vivo potential to differentiate in endothelial and perivascular lineages. VIC paracrine effect was also examined on human endothelial colony-forming cells. A pathological VIC (VICp) mesenchymal-like phenotype was confirmed by CD90+/CD73+/CD44+ expression and multipotent-like differentiation ability. When VICp were cocultured with endothelial colony-forming cells, they formed microvessels by differentiating into perivascular cells both in vivo and in vitro. VICp and control VIC conditioned media were compared using serial ELISA regarding quantification of endothelial and angiogenic factors. Higher expression of VEGF (vascular endothelial growth factor)-A was observed at the protein level in VICp-conditioned media and confirmed at the mRNA level in VICp compared with control VIC. Conditioned media from VICp induced in vitro a significant increase in endothelial colony-forming cell proliferation, migration, and sprouting compared with conditioned media from control VIC. These effects were inhibited by blocking VEGF-A with blocking antibody or siRNA approach, confirming VICp involvement in angiogenesis by a VEGF-A dependent mechanism.

CONCLUSIONS

We provide here the first proof of an angiogenic potential of human VICs isolated from patients with calcific aortic valve disease. These results point to a novel function of VICp in valve vascularization during calcific aortic valve disease, with a perivascular differentiation ability and a VEGF-A paracrine effect. Targeting perivascular differentiation and VEGF-A to slow calcific aortic valve disease progression warrants further investigation.

NOTCH pathway activation in infantile hemangiomas

OBJECTIVE

The objective of this study was to characterize the role of NOTCH signaling cascade activation in the angiogenic drive of infantile hemangioma (IH) tissue.

METHODS

Both IH tissue and normal skin were collected from 55 surgical patients. Of these, 14 were proliferating hemangiomas, 14 were stationary, 14 were involuted, and 13 had been treated with propranolol. Protein and RNA were extracted from all tissues and subjected to Western blotting and reverse transcription-polymerase chain reaction, respectively, for components of the NOTCH signaling pathway.

RESULTS

Compared with normal skin from the same patients, proliferating IHs contained higher levels of messenger RNA and protein for the majority of NOTCH receptors and ligands as well as the downstream coactivator MAML1. Expression of NOTCH receptor ligand messenger RNA and protein was significantly lower in involuting and propranolol-treated IHs.

CONCLUSIONS

Perturbations in NOTCH signaling follow the natural course and treatment outcome of IHs, suggesting a critical role in their pathogenesis.

VEGF/Flk1 Mechanism is Involved in Roxarsone Promotion of Rat Endothelial Cell Growth and B16F10 Xenograft Tumor Angiogenesis

The potential angiogenic effect of roxarsone, a feed additive widely used to promote animal growth worldwide, was demonstrated recently. We explored the mechanism of vascular endothelial growth factor (VEGF) and its receptor (VEGFR) in roxarsone promotion of rat vascular endothelial cells (ECs) and B16F10 mouse xenografts. ECs were treated with 0.1–50 μM roxarsone or with roxarsone plus 10 ng/mL VEGF, VEGFR1 (Flt1), or VEGFR2 (Flk1) antibodies for 12–48 h to examine their role in cell growth promotion. Small interfering RNA (siRNA) targeting Vegf, Flt1, and Flk1 were transfected in the ECs, and we measured the expression level, cell proliferation, migration, and tube formation ability. The siRNA targeting Vegf or Flk1 were injected intratumorally in the B16F10 xenografts of mice that received 25 mg/kg roxarsone orally. Cell viability and VEGF expression following roxarsone treatment were significantly higher than that of the control (P < 0.05), peaking following treatment with 1.0 μM roxarsone. Compared to roxarsone alone, the VEGF antibody decreased cell promotion by roxarsone (P < 0.05), and the Flk1 antibody greatly reduced cell viability compared to the Flt1 antibody (P < 0.01). Roxarsone and Flk1 antibody co-treatment increased supernatant VEGF significantly, while cellular VEGF was obviously decreased (P < 0.01), whereas there was no significant difference following Flt1 antibody blockade. The siRNA against Vegf or Flk1 significantly attenuated the roxarsone promotion effects on EC proliferation, migration, and tube-like formation (P < 0.01), whereas the siRNA against Flt1 effected no obvious differences. Furthermore, the RNA interference significantly weakened the roxarsone-induced increase in xenograft weight and volume, and VEGF and Flk1 expression. Roxarsone promotion of rat EC growth, migration, and tube-like formation in vitro and of B16F10 mouse xenograft model tumor growth and angiogenesis involves a VEGF/Flk1 mechanism.

R-propranolol is a small molecule inhibitor of the SOX18 transcription factor in a rare vascular syndrome and hemangioma

Propranolol is an approved non-selective β-adrenergic blocker that is first line therapy for infantile hemangioma. Despite the clinical benefit of propranolol therapy in hemangioma, the mechanistic understanding of what drives this outcome is limited. Here, we report successful treatment of pericardial edema with propranolol in a patient with Hypotrichosis-Lymphedema-Telangiectasia and Renal (HLTRS) syndrome, caused by a mutation in SOX18. Using a mouse pre-clinical model of HLTRS, we show that propranolol treatment rescues its corneal neo-vascularisation phenotype. Dissection of the molecular mechanism identified the R(+)-propranolol enantiomer as a small molecule inhibitor of the SOX18 transcription factor, independent of any anti-adrenergic effect. Lastly, in a patient-derived in vitro model of infantile hemangioma and pre-clinical model of HLTRS we demonstrate the therapeutic potential of the R(+) enantiomer. Our work emphasizes the importance of SOX18 etiological role in vascular neoplasms, and suggests R(+)-propranolol repurposing to numerous indications ranging from vascular diseases to metastatic cancer.

Propranolol for the treatment of vascular sarcomas

Vascular sarcomas are abnormal proliferations of endothelial cells. They range from benign hemangioma to aggressive angiosarcoma, and are characterized by dysregulated angiogenic signaling. Propranolol is a β-adrenergic receptor inhibitor that has demonstrated clinical efficacy in benign infantile hemangioma, and is now being used experimentally for more aggressive vascular sarcomas and other cancers. In this review, we discuss the use of propranolol in targeting these receptors in vascular tumors and other cancers.

Vascular Anomalies of the Orbit--A Reappraisal

The recent International Society for the Study of Vascular Anomalies (ISSVA) classification of vascular anomalies can be applied to orbital lesions, dividing them into vascular tumors and vascular malformations. Orbital cavernous hemangiomas are probably best considered cavernous venous malformations under this classification. Management of symptomatic lesions can be with surgical excision or stereotactic fractionated radiotherapy in selected cases. Beta-blockers including propranolol and topical timolol maleate represent first-line therapy for infantile hemangiomas, although surgery has a role in selected cases. Orbital venous-lymphatic malformations are problematic but with improved imaging, neuroradiological intervention, and a multidisciplinary approach to management, outcomes are improving.

VEGF-A inhibits agonist-mediated Ca2+ responses and activation of IKCa channels in mouse resistance artery endothelial cells

KEY POINTS

Prolonged exposure to vascular endothelial growth factor A (VEGF-A) inhibits agonist-mediated endothelial cell Ca²⁺ release and subsequent activation of intermediate conductance Ca²⁺ -activated K⁺ (IK_Ca ) channels, which underpins vasodilatation as a result of endothelium-dependent hyperpolarization (EDH) in mouse resistance arteries. Signalling via mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) downstream of VEGF-A was required to attenuate endothelial cell Ca²⁺ responses and the EDH-vasodilatation mediated by IK_Ca activation. VEGF-A exposure did not modify vasodilatation as a result of the direct activation of IK_Ca channels, nor the pattern of expression of inositol 1,4,5-trisphosphate receptor 1 within endothelial cells of resistance arteries. These results indicate a novel role for VEGF-A in resistance arteries and suggest a new avenue for investigation into the role of VEGF-A in cardiovascular diseases.

ABSTRACT

Vascular endothelial growth factor A (VEGF-A) is a potent permeability and angiogenic factor that is also associated with the remodelling of the microvasculature. Elevated VEGF-A levels are linked to a significant increase in the risk of cardiovascular dysfunction, although it is unclear how VEGF-A has a detrimental, disease-related effect. Small resistance arteries are central determinants of peripheral resistance and endothelium-dependent hyperpolarization (EDH) is the predominant mechanism by which these arteries vasodilate. Using isolated, pressurized resistance arteries, we demonstrate that VEGF-A acts via VEGF receptor-2 (R2) to inhibit both endothelial cell (EC) Ca²⁺ release and the associated EDH vasodilatation mediated by intermediate conductance Ca²⁺ -activated K⁺ (IK_Ca ) channels. Importantly, VEGF-A had no direct effect against IK_Ca channels. Instead, the inhibition was crucially reliant on the downstream activation of the mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 (MEK1/2). The distribution of EC inositol 1,4,5-trisphosphate (IP₃ ) receptor-1 (R1) was not affected by exposure to VEGF-A and we propose an inhibition of IP₃ R1 through the MEK pathway, probably via ERK1/2. Inhibition of EC Ca²⁺ via VEGFR2 has profound implications for EDH-mediated dilatation of resistance arteries and could provide a mechanism by which elevated VEGF-A contributes towards cardiovascular dysfunction.

Effect of the monoclonal antibody TRC105 in combination with Sunitinib on renal tumor derived endothelial cells

Anti-angiogenic therapy is an important strategy to limit growth, development and expansion of solid tumors. However, resistance to VEGF-targeting agents may develop, due to activation of alternative pro-angiogenic pathways, indicating the need of multiple target strategy. Here we obtained tumor endothelial cells (TEC) either from total renal carcinomas or from renal cancer stem cells (CSC-TEC) and we tested the effect of a CD105 targeting monoclonal antibody, TRC105, alone or in association with anti-VEGF drugs. We demonstrated that TRC105 impaired the ability of TEC and CSC-TEC to organize in tubular structures, whereas it did not limit proliferation or survival. The combination of TRC105 with different anti-angiogenic drugs showed a synergistic effect of TRC105 only in combination with the tyrosine kinase inhibitor Sunitinib. In particular, TRC105 plus Sunitinib reduced tubulogenesis, proliferation and survival of CSC-TEC and tumor-derived TEC in a similar manner. At a molecular level, we showed that the combination of TRC105 and Sunitinib induced the phosphorylation of Smad 2/3 to promote endothelial cell death. Moreover, TRC105 enhanced the inhibitory effect of Sunitinib on VEGF signaling and reduced VEGFR2-Akt-Creb activation, suggesting a molecular cooperation between the two drugs. Our results highlight that the combined inhibition of VEGF and TGF-β pathway may have a potential use in renal cell carcinoma therapy.

Mechanisms of Action of MicroRNAs in Infantile Hemangioma Tissue and Vascular Endothelial Cells in Different Periods

Background

The aim of this study was to investigate the developmental mechanisms of infantile hemangioma (IH) from the microRNA level.

Material/Methods

A total of 63 biological specimens of IH were obtained from the First Affiliated Hospital of Jinzhou Medical University and we assessed related miRNAs. Magnetic bead sorting, endocytosis test, canalization assay, and immunofluorescence detection were performed. The IH-derived cells were transfected with related factors and then we assessed the apoptosis and invasion.

Results

The contents of MiR-455, miR-206, and miR-29a in the proliferative period group (PP) were lower than in the complete regression period group (CR) (P<0.05), and the content of miR-29a in the regression period group (RP) was lower than in the group CR (P<0.05). The post-sorting proliferation capacity was faster than in human umbilical vein endothelial cells, and IH-derived vascular endothelial cells (VECs) exhibited faster canalization ability. The cells transfected with miR-29a exhibited obvious apoptosis 48 h later, the cells transfected with miR-206 exhibited significantly reduced proliferation capacity as well as apoptosis 48 h later, and the invasion capacity was decreased 24 h after transfection.

Conclusions

miR-29a, miR-206, and miR-455 are differently expressed in different periods of IH, and may participate in regulating multiple functions during the progression of IH.

Altered ratios of pro- and anti-angiogenic VEGF-A variants and pericyte expression of DLL4 disrupt vascular maturation in infantile haemangioma

Infantile haemangioma (IH), the most common neoplasm in infants, is a slowly resolving vascular tumour. Vascular endothelial growth factor A (VEGF‐A), which consists of both the pro‐ and anti‐angiogenic variants, contributes to the pathogenesis of IH. However, the roles of different VEGF‐A variants in IH progression and its spontaneous involution is unknown. Using patient‐derived cells and surgical specimens, we showed that the relative level of VEGF‐A₁₆₅b was increased in the involuting phase of IH and the relative change in VEGF‐A isoforms may be dependent on endothelial differentiation of IH stem cells. VEGFR signalling regulated IH cell functions and VEGF‐A₁₆₅b inhibited cell proliferation and the angiogenic potential of IH endothelial cells in vitro and in vivo. The inhibition of angiogenesis by VEGF‐A₁₆₅b was associated with the extent of VEGF receptor 2 (VEGFR2) activation and degradation and Delta‐like ligand 4 (DLL4) expression. These results indicate that VEGF‐A variants can be regulated by cell differentiation and are involved in IH progression. We also demonstrated that DLL4 expression was not exclusive to the endothelium in IH but was also present in pericytes, where the expression of VEGFR2 is absent, suggesting that pericyte‐derived DLL4 may prevent sprouting during involution, independently of VEGFR2. Angiogenesis in IH therefore appears to be controlled by DLL4 within the endothelium in a VEGF‐A isoform‐dependent manner, and in perivascular cells in a VEGF‐independent manner. The contribution of VEGF‐A isoforms to disease progression also indicates that IH may be associated with altered splicing. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Vertebral hemangiomas in the thoracic spine of multiple sclerosis patients are connected with fewer demyelinating lesions at the same level. Possible impact on pathophysiology and clinical course

OBJECTIVES

Mechanisms of angiogenesis regulate multiple sclerosis (MS) lesions' evolution, displaying both neuroprotective and harmful effects. Factors traditionally considered as purely angiogenic, like vascular endothelial growth factor (VEGF), exert complex heterogenous actions on both neural and vascular malformation-derived tissues. Aim of this retrospective study was to examine, for the first time, potential associations between the presence of common vascular malformations, like vertebral hemangiomas (VHs), and several clinico-radiological MS parameters.

METHODS

236 MS patients who were followed in our Outpatient Clinic were recruited in this study. Outcome measures concerned demographics, disease-derived variables, and MS-lesions' distribution in VHs - positive and negative patients. All data were collected retrospectively. Potential correlations were assessed with univariate statistical analyses (p = 0.05), followed by multivariate regression models, for purposes of confounder-effects elimination.

RESULTS

VH presence showed significant negative correlations with presence of MS lesions in the thoracic (p = 0.005 for thoracic VHs), but not the cervical cord. Trends towards negative associations of VH presence with subtentorial MS lesions and positive family history for MS were also observed.

DISCUSSION

Our observations suggest that VH presence may reduce the risk of thoracic demyelinating lesions in MS patients. They could be explained as part of a multifaceted angiogenic process, concomitantly enhancing neural repair and abnormal hemangioma vascularization.

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.

Macrophages Contribute to the Progression of Infantile Hemangioma by Regulating the Proliferation and Differentiation of Hemangioma Stem Cells

Macrophage infiltration has been implicated in infantile hemangioma (IH), the most common tumor of infancy. However, the exact role of macrophages in IH remains unknown. This study aims to clarify the functional significance of macrophages in the progression of IH. The distribution of macrophages in human IH was analyzed, and our results revealed that polarized macrophages were more prevalent in proliferating IHs than in involuting IHs, which was consistent with the increased macrophage-related cytokines in proliferating IHs. In vitro results further demonstrated that polarized macrophages effectively promoted the proliferation of hemangioma stem cells (HemSCs) and suppressed their adipogenesis in an Akt- and extracellular signal-regulated kinase 1/2 (Erk1/2)-dependent manner. Moreover, M2- but not M1-polarized macrophages promoted the endothelial differentiation of HemSCs. Furthermore, mixing macrophages in a murine hemangioma model elevated microvessel density and postponed fat tissue formation, which was concomitant with the activation of Akt and Erk1/2 signals. Cluster analysis revealed a close correlation among the macrophage markers, Ki67, vascular endothelial growth factor (VEGF), p-Akt, and p-Erk1/2 in human IH tissues. Collectively, our results suggest that macrophages in IH contribute to tumor progression by promoting the proliferation and endothelial differentiation while suppressing the adipogenesis of HemSCs. These findings indicate that targeting the infiltrating macrophages in IH is a promising therapeutic approach to accelerate IH regression.

Infantile hemangioma-derived stem cells and endothelial cells are inhibited by class 3 semaphorins

Class 3 semaphorins were discovered as a family of axon guidance molecules, but are now known to be involved in diverse biologic processes. In this study, we investigated the anti-angiogenic potential of SEMA3E and SEMA3F (SEMA3E&F) in infantile hemangioma (IH). IH is a common vascular tumor that involves both vasculogenesis and angiogenesis. Our lab has identified and isolated hemangioma stem cells (HemSC), glucose transporter 1 positive (GLUT1(+)) endothelial cells (designated as GLUT1(sel) cells) based on anti-GLUT1 magnetic beads selection and GLUT1-negative endothelial cells (named HemEC). We have shown that these types of cells play important roles in hemangiogenesis. We report here that SEMA3E inhibited HemEC migration and proliferation while SEMA3F was able to suppress the migration and proliferation in all three types of cells. Confocal microscopy showed that stress fibers in HemEC were reduced by SEMA3E&F and that stress fibers in HemSC were decreased by SEMA3F, which led to cytoskeletal collapse and loss of cell motility in both cell types. Additionally, SEMA3E&F were able to inhibit vascular endothelial growth factor (VEGF)-induced sprouts in all three types of cells. Further, SEMA3E&F reduced the level of p-VEGFR2 and its downstream p-ERK in HemEC. These results demonstrate that SEMA3E&F inhibit IH cell proliferation and suppress the angiogenic activities of migration and sprout formation. SEMA3E&F may have therapeutic potential to treat or prevent growth of highly proliferative IH.

Actin-tethered junctional complexes in angiogenesis and lymphangiogenesis in association with vascular endothelial growth factor

Vasculature is present in all tissues and therefore is indispensable for development, biology, and pathology of multicellular organisms. Endothelial cells guarantee proper function of the vessels and are the original component in angiogenesis. Morphogenesis of the vascular system utilizes processes like cell adhesion, motility, proliferation, and survival that are closely related to the dynamics of actin filaments and actin-tethered adhesion complexes. Here we review involvement of actin cytoskeleton-associated junctional molecules of endothelial cells in angiogenesis and lymphangiogenesis. Particularly, we focus on F-actin binding protein afadin, an adaptor protein involved in broad range of signaling mechanisms. Afadin mediates the pathways of vascular endothelial growth factor- (VEGF-) and sphingosine 1-phosphate-triggered angiogenesis and is essential for embryonic development of lymph vessels in mice. We propose that targeting actin-tethered junctional molecules, including afadin, may present a new approach to angiogenic therapy that in combination with today used medications like VEGF inhibitors will benefit against development of pathological angiogenesis.

Inflammation-induced endothelial cell-derived extracellular vesicles modulate the cellular status of pericytes

Emerging lines of evidence have shown that extracellular vesicles (EVs) mediate cell-to-cell communication by exporting encapsulated materials, such as microRNAs (miRNAs), to target cells. Endothelial cell-derived EVs (E-EVs) are upregulated in circulating blood in different pathological conditions; however, the characteristics and the role of these E-EVs are not yet well understood. In vitro studies were conducted to determine the role of inflammation-induced E-EVs in the cell-to-cell communication between vascular endothelial cells and pericytes/vSMCs. Stimulation with inflammatory cytokines and endotoxin immediately induced release of shedding type E-EVs from the vascular endothelial cells, and flow cytometry showed that the induction was dose dependent. MiRNA array analyses revealed that group of miRNAs were specifically increased in the inflammation-induced E-EVs. E-EVs added to the culture media of cerebrovascular pericytes were incorporated into the cells. The E-EV-supplemented cells showed highly induced mRNA and protein expression of VEGF-B, which was assumed to be a downstream target of the miRNA that was increased within the E-EVs after inflammatory stimulation. The results suggest that E-EVs mediate inflammation-induced endothelial cell-pericyte/vSMC communication, and the miRNAs encapsulated within the E-EVs may play a role in regulating target cell function. E-EVs may be new therapeutic targets for the treatment of inflammatory diseases.

Mechanisms of propranolol action in infantile hemangioma

Infantile hemangioma is a common tumor of infancy. Although most hemangiomas spontaneously regress, treatment is indicated based on complications, risk to organ development and function, and disfigurement. The serendipitous discovery of propranolol, a non-selective β-adrenergic receptor blocker, as an effective means to regress hemangiomas has made this a first-line therapy for hemangioma patients. Propranolol has shown remarkable response rates. There are, however, some adverse effects, which include changes in sleep, acrocyanosis, hypotension, and hypoglycemia. Over the last few years, researchers have focused on understanding the mechanisms by which propranolol causes hemangioma regression. This has entailed study of cultured vascular endothelial cells including endothelial cells isolated from hemangioma patients. In this article, we review recent studies offering potential mechanisms of how various cell types found in hemangioma may respond to propranolol.

Bone-marrow-derived very small embryonic-like stem cells in patients with critical leg ischaemia: evidence of vasculogenic potential

Very small embryonic-like stem cells (VSELs) are multipotent stem cells localised in adult bone marrow (BM) that may be mobilised into peripheral blood (PB) in response to tissue injury. We aimed to quantify VSELs in BM and PB of patients with critical limb ischaemia (CLI) and to test their angiogenic potential in vitro as well as their therapeutic capacity in mouse model of CLI. We isolated BM VSELs from patients with CLI and studied their potential to differentiate into vascular lineages. Flow and imaging cytometry showed that VSEL counts were lower in BM (p< 0.001) and higher (p< 0.001) in PB from CLI patients compared to healthy controls, suggesting that ischaemia may trigger VSELs mobilisation in this patient population. Sorted BM-VSELs cultured in angiogenic media acquired a mesenchymal phenotype (CD90+, Thy-1 gene positive expression). VSEL-derived cells had a pattern of secretion similar to that of endothelial progenitor cells, as they released low levels of VEGF-A and inflammatory cytokines. Noteworthy, VSELs triggered post-ischaemic revascularisation in immunodeficient mice (p< 0.05 vs PBS treatment), and acquired an endothelial phenotype either in vitro when cultured in the presence of VEGF-B (Cdh-5 gene positive expression), or in vivo in Matrigel implants (human CD31+ staining in neo-vessels from plug sections). In conclusion, VSELs are a potential new source of therapeutic cells that may give rise to cells of the endothelial lineage in humans.

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.

PDGFR-β (+) perivascular cells from infantile hemangioma display the features of mesenchymal stem cells and show stronger adipogenic potential in vitro and in vivo

Infantile hemangioma, a common benign tumor of infancy, grows quickly in the first year of life, and then regresses slowly to fibrofatty tissue in childhood. The accumulation of fibrofatty tissue in hemangioma involution indicates adipogenesis during this period. Perivascular cells (PCs) from multiple organs display multi-lineage differentiation, including adipogenesis. So we supposed that PCs in hemangioma may contribute to the adipogenesis in the involution. In this study, PDGFR-β (+) PCs was isolated from hemangioma tissue (hemangioma-derived perivascular cells, Hem-PCs) by fluorescence-activated cell sorter. In vitro, Hem-PCs showed fibroblast-like morphology. Immunofluorescence staining and flow cytometry showed Hem-PCs expressed MSCs markers CD105, CD90, CD29 and vimentin, pericyte markers α-SMA and PDGFR-β, stem cell marker CD133, and the adipogenic transcription factor PPAR-γ, but not hematopoietic/endothelial markers CD45, CD34, CD31, and flt-1. In vitro inductions confirmed multi-lineage differentiation of Hem-PCs, especially strong adipogenic potential. Then a murine model was established to observe in vivo differentiation of Hem-PCs by subcutaneous injection of cells/Matrigel compound into nude mice. The results showed Hem-PCs differentiated into adipocytes in vivo. To the best of our knowledge, this is the first study reporting the isolation of multipotential PDGFR-β (+) PCs from hemangioma, and observing their adipogenic differentiation in vivo. PCs may be the cellular basis of adipogenesis in hemangioma involution, and may be the target cells of adipogenic induction to promote hemangioma involution.