Hypoxia-induced mediators of stem/progenitor cell trafficking are increased in children with hemangioma

Arrested Development: Infantile Hemangioma and the Stem Cell Teratogenic Hypothesis

BACKGROUND

Early-life programming is defined by the adaptive changes made by the fetus in response to an adverse in utero environment. Infantile hemangioma (IH), a vascular anomaly, is the most common tumor of infancy. Here we take IH as the tumor model to propose the stem cell teratogenic hypothesis of tumorigenesis and the potential involvement of the immune system.

OBJECTIVES

Teratogenic agents include chemicals, heavy metals, pathogens, and ionizing radiation. To investigate the etiology and pathogenesis of IH, we hypothesized that they result from a teratogenic mechanism. Immature, incompletely differentiated, dysregulated progenitor cells (multipotential stem cells) are arrested in development with vasculogenic, angiogenic, and tumorigenic potential due to exposure to teratogenic agents such as extrinsic factors that disrupt intrinsic factors via molecular mimicry. During the critical period of immunological tolerance, environmental exposure to immunotoxic agents may harness the teratogenic potential in the developing embryo or fetus and modify the early-life programming algorithm by altering normal fetal development, causing malformations, and inducing tumorigenesis. Specifically, exposure to environmental agents may interfere with physiological signaling pathways and contribute to the generation of IH, by several mechanisms.

DISCUSSION

An adverse in utero environment no longer serves as a sustainable environment for proper embryogenesis and normal development. Targeted disruption of stem cells by extrinsic factors can alter the genetic program.

CONCLUSIONS

This article offers new perspectives to stimulate discussion, explore novel experimental approaches (such as immunotoxicity/vasculotoxicity assays and novel isogenic models), and to address the questions raised to convert the hypotheses into nontoxic, noninvasive treatments.

Association of ATF4 Expression With Tissue Hypoxia and M2 Macrophage Infiltration in Infantile Hemangioma

Accumulating studies have revealed the hypoxic condition and its crucial role in the distinctive progression of infantile hemangioma (IH), the most common benign tumor in infancy. Activating transcription factor 4 (ATF4), an important gene mediating cellular adaptation to various stress signals, could confer a survival advantage for tumor cells under hypoxia and regulate tumor progression. However, the potential role of ATF4 in IH was still unknown. In this study, the expression of hypoxia inducible factor (HIF)-1α, ATF4, and macrophage colony-stimulating factor (M-CSF) in 27 specimens of IH was measured by immunochemistry and double-labeling immunofluorescence, followed by the Spearman rank correlation test. Our results showed that the expression of HIF-1α, ATF4, and M-CSF was significantly upregulated in proliferating IH compared with involuting IH. Meanwhile, HIF-1α and ATF4, in parallel with ATF4 and M-CSF, exhibited positive correlation and synchronous expression. In addition, our in vitro studies demonstrated that hypoxia obviously upregulated the expression of HIF-1α, ATF4, and M-CSF in hemangioma stem cells. Most importantly, their expression was uniformly correlated with the percentage of M2-polarized macrophages in IH. All those results and established evidence indicated that hypoxia-induced ATF4 expression may promote progression of proliferating IH through M-CSF-induced M2-polarized macrophages infiltration.

Gender, Estrogen, and Obliterative Lesions in the Lung

Gender has been shown to impact the prevalence of several lung diseases such as cancer, asthma, chronic obstructive pulmonary disease, and pulmonary arterial hypertension (PAH). Controversy over the protective effects of estrogen on the cardiopulmonary system should be of no surprise as clinical trials of hormone replacement therapy have failed to show benefits observed in experimental models. Potential confounders to explain these inconsistent estrogenic effects include the dose, cellular context, and systemic versus local tissue levels of estrogen. Idiopathic PAH is disproportionately found to be up to 4 times more common in females than in males; however, estrogen levels cannot explain why males develop PAH sooner and have poorer survival. Since the sex steroid hormone 17β-estradiol is a mitogen, obliterative processes in the lung such as cell proliferation and migration may impact the growth of pulmonary tissue or vascular cells. We have reviewed evidence for biological differences of sex-specific lung obliterative lesions and highlighted cell context-specific effects of estrogen in the formation of vessel lumen-obliterating lesions. Based on this information, we provide a biological-based mechanism to explain the sex difference in PAH severity as well as propose a mechanism for the formation of obliterative vascular lesions by estrogens.

Infantile Hemangioma with Minimal or Arrested Growth: Further Observations on Clinical and Histopathologic Findings of this Unique but Underrecognized Entity

BACKGROUND

Infantile hemangioma (IH) with minimal or arrested growth (IH-MAG) is becoming increasingly recognized in the literature. It is important to be aware of their existence, because the correct diagnosis is essential for prognostication and treatment and, in the case of facial segmental lesions, the direction of further investigations if PHACE (posterior fossa abnormalities and other structural brain abnormalities; hemangioma(s) of the cervical facial region; arterial cerebrovascular anomalies; cardiac defects, aortic coarctation, and other aortic abnormalities; eye anomalies) syndrome or Sturge-Weber syndrome is suspected. Although the clinical and histologic characteristics of IH-MAG resemble capillary malformations, positive GLUT-1 status is a delineating feature.

METHODS

We reviewed nine cases of infants who presented after 2000 with birthmarks showing unique clinical features suggestive of a special variant of IHs. All patients had serial photographs taken demonstrating resolution of the birthmark over time. Five of these cases had skin biopsy performed, all of which confirmed GLUT-1 positivity.

RESULTS

This photographic series of IH-MAG demonstrates their unique clinical, histologic, and immunochemistry features. They were nearly fully formed at birth, and their common clinical features included telangiectasia, venules, and matte erythema with light and dark areas. Spontaneous resolution over time without cosmetic disfigurement was the observed natural history in the majority of cases.

CONCLUSION

IH-MAG is a unique clinical subset of hemangioma for which close observation is the preferred treatment. When in doubt, a biopsy for histology and GLUT-1 status may be needed to confirm the diagnosis before embarking on unnecessary laser treatment or medical interventions.

Serum Basic Fibroblastic Growth Factor Levels in Children with Infantile Hemangioma

OBJECTIVES

To determine serum levels of basic fibroblastic growth factor (b-FGF) in hemangioma patients under 2 y of age.

METHODS

The study group consisted of 43 children with infantile hemangioma and b-FGF levels were analyzed using ELISA.

RESULTS

The serum b-FGF levels were higher in hemangioma patients than in healthy control individuals (p 0.01). There were no differences between the lesion size, number of lesions, patient age and serum b-FGF levels.

CONCLUSIONS

Thus, b-FGF is an important growth factor that plays a central role in hemangioma, but determining b-FGF serum levels was not helpful in distinguishing between patients who require treatment and those who do not.

Common Pediatric Skin Lesions: A Comprehensive Review of the Current Literature

The timely diagnosis and treatment of dermatologic disease in the pediatric population can be challenging. A basic, yet comprehensive knowledge of common lesions is essential for a successful practice in plastic surgery. In this article, the authors describe vascular, cystic, and pigmented cutaneous lesions that are commonly encountered in the pediatric population. Epidemiology, pathogenesis, clinical course, and management options are discussed for each.

PHACE syndrome is associated with intracranial cavernous malformations

INTRODUCTION

PHACE syndrome is a neurocutaneous disorder involving large facial hemangiomas in association with posterior fossa abnormalities, cerebral arterial anomalies, cardiac defects, and eye abnormalities. A recent consensus statement has delineated criteria necessary for the diagnosis of PHACE syndrome. Extracutaneous manifestations of PHACE syndrome predominately affect the cerebrovascular system. To date, there are no reports of cerebral cavernous malformations (CCMs) in children with PHACE syndrome.

METHODS

We reviewed the charts of children admitted to the Children''s Hospital of Pittsburgh who met criteria for PHACE syndrome, and evaluated neuroimaging for cerebrovascular abnormalities, including the finding of CCMs.

RESULTS

Six children met criteria for PHACE syndrome at our institution over a 10-year period. All children were female. All children had cerebrovascular abnormalities sufficient to meet major criteria for diagnosis. Four children (66.7 %) were found incidentally to have CCMs; all lesions measured less than 5 mm at the time of diagnosis and were asymptomatic.

CONCLUSION

At present, CCMs are not listed among the diagnostic criteria for PHACE syndrome, and they have not previously been reported in association with PHACE syndrome. Hypoxic injury in utero may be the common denominator in the pathogenesis of many of the abnormalities already accepted in the criteria for PHACE syndrome and the formation of CCMs. In the setting of PHACE syndrome, we encourage clinicians to evaluate children for CCMs, which are readily apparent on the already-recommended screening MRIs.

Does hypoxia play a role in infantile hemangioma?

Infantile hemangioma (IH), the most common tumor of infancy, is characterized by rapid growth during infancy, followed by spontaneous involution over 5-10 years. Certain clinical observations have led to the suggestion that IH is triggered and maintained by hypoxia. We review the literature on the possible role of hypoxia in the etiology of IH, in particular, (1) the role of hypoxia inducible factor-1α (HIF-1α) and its downstream targets including GLUT-1 and VEGF; (2) the pathophysiological link between IH and retinopathy of prematurity; (3) hypoxic events in the early life including placental insufficiency, pre-eclampsia and low birthweight that have the potential to promote hypoxic stress; and (4) the evidence supporting the development of IH independent of HIF-1α. We also discuss these observations in the context of recent evidence of the crucial role of stem cells and the cytokines niche that governs their proliferation and inevitable differentiation, offering novel insights into the biology of IH. We propose that various triggers may simultaneously up-regulate HIF-1α, which is downstream of the renin-angiotensin system, specifically angiotensin II, which promotes production of HIF-1α. These developments shed light to the understanding of this enigmatic condition.

Propranolol for infantile hemangioma: Current state of affairs

Infantile hemangioma (IH) is the most common benign tumor seen in infancy. This review provides up-to-date information on the pathophysiology, variations in clinical presentation, and natural history of IH, elaborating on associated anomalies, such as PHACE(S) syndrome and LUMBAR syndrome. Because of the benign and self-limiting characteristics seen in more than 90% of cases of IH, a conservative approach is usually chosen. However, some circumstances, such as ulceration, vision loss, breathing difficulties, or potential disfigurement, will require treatment during the proliferative phase. For decades, treatment of IH has primarily consisted of corticosteroids or surgery. Since 2008, propranolol has become the treatment of first choice. In this article, we bring to light the crucial changes in the treatment of IH over the past years. To date, there is still a lack of data on the possible long-term effects of propranolol treatment in young infants. A theoretical probability of the central nervous system being affected (that is, impairment of short- and long-term memory, psychomotor function, sleep quality, and mood) has recently been suggested. This review highlights research topics concerning these long-term adverse effects. Finally, information is provided on the potential instruments to measure IH severity and activity in clinical trials and/or in clinical practice and the recently developed and first-validated IH-specific quality-of-life questionnaire.

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.

Recent advances in the pathobiology and management of Kasabach-Merritt phenomenon

Kasabach-Merritt Phenomenon (KMP) refers to the clinical constellation of thrombocytopenia, consumptive coagulopathy and purpura associated with Kaposiform haemangioedothelioma or tufted angioma, but not the more common infantile haemangioma. It shows a variable and unpredictable response to traditional pharmacological agents, such as steroids, vincristine or interferon alpha 2a or 2b. More recently, the interaction between platelets and endothelial cells and the proangiogenic phenotype that results has been recognized to underly the pathogenesis of this disorder. Recent efforts have attempted to target the platelet by using antiplatelet agents and by the withholding of platelet transfusions even in those patients who have significant thrombocytopenia and laboratory evidence of coagulopathy. Excellent response rates and prompt results have been achieved by combining antiplatelet therapy with vincristine, without the need for steroid use. This synergistic approach moves away from the conventional wisdom of treating the underlying lesion to control the coagulopathy. Sirolimus, which is directed against the PI3/AKT/mTOR downstream signalling pathway involved in lymphangiogenesis, has also shown promising results, although further study is needed.

Oxymatrine suppresses proliferation and induces apoptosis of hemangioma cells through inhibition of HIF-1a signaling

Oxymatrine (OMT), a natural quinolizidine alkaloid, has been known to have anti-inflammation, anti-anaphylaxis, and chemopreventive effects on various cancer cells. To clarify the underlying role and molecular mechanisms of OMT in human hemangioma (HA), in the present study, we examined the expression of hypoxia-inducible factor-1a (HIF-1a) and vascular endothelial growth factor (VEGF) in different phases of human HA. After HA derived endothelial cells (HDEC) were pretreated with different concentrations of OMT, cell proliferation, apoptosis, and cycle distribution were evaluated by MTT assay and flow cytometry analysis, respectively. The effects of OMT on expression of HIF-1a signaling were determined by real-time PCR and western blot assays. Our results showed that, the expression of HIF-1a and VEGF was significantly increased in proliferating phase HA, but decreased in involuting phase HA. Moreover, OMT in vitro inhibited proliferative activities and induced cell apoptosis and cycle arrest in G0/G1 phase in HA cells with decreased expression of HIF-1a, VEGF, Bcl-2, and CyclinD1, and increased expression of p53. Taken together, our findings suggest that, the expression of HIF-1a and VEGF is increased in proliferating phase HA, and OMT suppresses cell proliferation and induces cell apoptosis and cycle arrest in proliferative phase HA through inhibition of the HIF-1a signaling pathway, suggesting OMT may provide a novel therapeutic strategy for the treatment of HA.

Vascular endothelial growth factor expression and pathological changes in the local tissue of facial hemangiomas following injections with pure alcohol

The aim of the present study was to investigate the association between the formation of hemangioma and the expression of vascular endothelial growth factor (VEGF) following local injections of pure alcohol in patients exhibiting hemangioma. Ten healthy subjects (control group) and 10 hemangioma patients (treatment group) were included in the study population, with the hemangioma patients receiving one injection of pure alcohol. The VEGF levels were evaluated in the treatment and control group subjects prior to and following the injection using enzyme-linked immunosorbent assay; furthermore, local tissue was excised to perform pathological analysis one week after the injections. The VEGF levels of the healthy group were identified to be significantly lower when compared with those of the treatment group prior to the injections (P<0.01) and one week after the injections (P<0.01), however, were not significantly different when compared with the treatment group one month after the injections (P>0.01). Therefore, serum VEGF concentrations in the peripheral blood may be a clinical indicator of the efficacy of clinical treatment and aid with determination of the prognosis.

Educational paper: therapy of infantile haemangioma--history and current state (part II)

Infantile haemangioma (IH) is the most frequent tumour of infancy. Although it is benign and self-limiting, severe complications can arise due to localisation and fast tumour growth. Also, IHs leave scars after regression in more than half of the cases. Management and therapy of IH have changed greatly after 2008. This update provides an overview of the older therapy options before 2008, which mainly consisted of the administration of corticosteroids, and discusses the modern management with new therapy options such as β-blockers (both systemically and topically).

CONCLUSION

β-blockers are promising and are currently preferred above corticosteroids, but β-blockers still do not give a definitive treatment.

Regulatory mechanisms of anthrax toxin receptor 1-dependent vascular and connective tissue homeostasis

It is well known that angiogenesis is linked to fibrotic processes in fibroproliferative diseases, but insights into pathophysiological processes are limited, due to lack of understanding of molecular mechanisms controlling endothelial and fibroblastic homeostasis. We demonstrate here that the matrix receptor anthrax toxin receptor 1 (ANTXR1), also known as tumor endothelial marker 8 (TEM8), is an essential component of these mechanisms. Loss of TEM8 function in mice causes reduced synthesis of endothelial basement membrane components and hyperproliferative and leaky blood vessels in skin. In addition, endothelial cell alterations in mutants are almost identical to those of endothelial cells in infantile hemangioma lesions, including activated VEGF receptor signaling in endothelial cells, increased expression of the downstream targets VEGF and CXCL12, and increased numbers of macrophages and mast cells. In contrast, loss of TEM8 in fibroblasts leads to increased rates of synthesis of fiber-forming collagens, resulting in progressive fibrosis in skin and other organs. Compromised interactions between TEM8-deficient endothelial and fibroblastic cells cause dramatic reduction in the activity of the matrix-degrading enzyme MMP2. In addition to insights into mechanisms of connective tissue homeostasis, our data provide molecular explanations for vascular and connective tissue abnormalities in GAPO syndrome, caused by loss-of-function mutations in ANTXR1. Furthermore, the loss of MMP2 activity suggests that fibrotic skin abnormalities in GAPO syndrome are, in part, the consequence of pathophysiological mechanisms underlying syndromes (NAO, Torg and Winchester) with multicentric skin nodulosis and osteolysis caused by homozygous loss-of-function mutations in MMP2.

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.

Infantile hemangiomas, retinopathy of prematurity and cancer: a common pathogenetic role of the β-adrenergic system

The serendipitous demonstration that the nonselective β-adrenergic receptor (β-AR) antagonist propranolol promotes the regression of infantile hemangiomas (IHs) aroused interest around the involvement of the β-adrenergic system in angiogenic processes. The efficacy of propranolol was related to the β2-AR blockade and the consequent inhibition of the production of vascular endothelial growth factor (VEGF), suggesting the hypothesis that propranolol could also be effective in treating retinopathy of prematurity (ROP), a retinal pathology characterized by VEGF-induced neoangiogenesis. Consequent to the encouraging animal studies, a pilot clinical trial showed that oral propranolol protects newborns from ROP progression, even though this treatment is not sufficiently safe. Further, animal studies clarified the role of β3-ARs in the development of ROP and, together with several preclinical studies demonstrating the key role of the β-adrenergic system in tumor progression, vascularization, and metastasis, prompted us to also investigate the participation of β3-ARs in tumor growth. The aim of this review is to gather the recent findings on the role of the β-adrenergic system in IHs, ROP, and cancer, highlighting the fact that these different pathologies, triggered by different pathogenic noxae, share common pathogenic mechanisms characterized by the presence of hypoxia-induced angiogenesis, which may be contrasted by targeting the β-adrenergic system. The mechanisms characterizing the pathogenesis of IHs, ROP, and cancer may also be active during the fetal-neonatal development, and a great contribution to the knowledge on the role of β-ARs in diseases characterized by chronic hypoxia may come from research focusing on the fetal and neonatal period.

Support for the hypoxia theory in the pathogenesis of infantile haemangioma

BACKGROUND

The pathogenesis of infantile haemangioma (IH) is unknown. Several mechanisms have been proposed, including hypoxia, which triggers upregulation and stabilization of hypoxia-inducible factor (HIF)1α. HIF1α stimulates downstream transcription of target genes that enhance angiogenesis.

AIM

To identify possible involvement of hypoxia in the pathogenesis of IH, as hypoxia signalling constitutes a potential therapeutic target.

METHODS

IH tissue samples collected during the period 1991-2011 (preserved in paraffin wax) were immunohistochemically analysed for HIF1α and the known HIF1α targets: BCL2/adenovirus E1B kD-interacting protein family member 3 (BNIP3), carbon anhydrase (CA)-IX, glucose transporter (GLUT)-1, phosphorylated protein kinase B (pAKT), phosphorylated S6 protein (pS6) and vascular endothelial growth factor (VEGF). Four observers independently assessed the findings.

RESULTS

Of the 10 IH samples, 2 appeared to be in the growth phase. In all samples, GLUT-1, BNIP3, pAKT and VEGF were positive, CA-IX was weakly positive, and HIF1α was negative. pS6 was positive in 9/10 cases and negative in 1/10.

CONCLUSIONS

Several factors implicated in hypoxia-induced angiogenesis may be involved in IH development. However, the small sample size and retrospective approach of the study preclude definitive conclusions. Prospective studies are needed to conclusively determine which of the factors involved in the (hypoxia) cascade are required for an IH to grow, and could thus be a possible target of drugs for IH treatment.

Biology of infantile hemangioma

Infantile hemangioma (IH), the most common tumor of infancy, is characterized by an initial proliferation during infancy followed by spontaneous involution over the next 5-10 years, often leaving a fibro-fatty residuum. IH is traditionally considered a tumor of the microvasculature. However, recent data show the critical role of stem cells in the biology of IH with emerging evidence suggesting an embryonic developmental anomaly due to aberrant proliferation and differentiation of a hemogenic endothelium with a neural crest phenotype that possesses the capacity for endothelial, hematopoietic, mesenchymal, and neuronal differentiation. Current evidence suggests a putative placental chorionic mesenchymal core cell embolic origin of IH during the first trimester. This review outlines the emerging role of stem cells and their interplay with the cytokine niche that promotes a post-natal environment conducive for vasculogenesis involving VEGFR-2 and its ligand VEGF-A and the IGF-2 ligand in promoting cellular proliferation, and the TRAIL-OPG anti-apoptotic pathway in preventing cellular apoptosis in IH. The discovery of the role of the renin-angiotensin system in the biology of IH provides a plausible explanation for the programed biologic behavior and the β-blocker-induced accelerated involution of this enigmatic condition. This crucially involves the vasoactive peptide, angiotensin II, that promotes cellular proliferation in IH predominantly via its action on the ATIIR2 isoform. The role of the RAS in the biology of IH is further supported by the effect of captopril, an ACE inhibitor, in inducing accelerated involution of IH. The discovery of the critical role of RAS in IH represents a novel and fascinating paradigm shift in the understanding of human development, IH, and other tumors in general.

Periocular hemangiomas and lymphangiomas

Infantile hemangiomas are the most common benign tumor of childhood. Lymphangiomas are benign hamartomatous vascular tumors. Both lesions can be problematic when located in the periocular region. Pediatricians must be familiar with the characteristics of each which would necessitate referral to an ophthalmologist or other subspecialist for evaluation, including obstruction of the visual axis which can lead to amblyopia of the affected eye. Additional potential complications include proptosis, ocular motility limitation, optic nerve injury, and poor eyelid closure with or without corneal surface disease. All children with periocular hemangiomas or lymphangiomas should be referred to an ophthalmologist for further evaluation.

A complication to be aware of: hyperkalaemia following propranolol therapy for an infant with intestinal haemangiomatozis

Infantile haemangiomas, benign vascular tumours seen in 4-10% of infants are characterised by their spontaneous remission following a 3-9 month period of dynamic growth. Propranolol has been reported to be used as a successful treatment of severe symptomatic infantile haemangiomas. Hyperkalaemia has not been recognised as a serious effect of propranolol since recently. Here, we would like to portray a 2-year-old male patient with intestinal haemangiomatosis who presented with severe hyperkalaemia and was successfully managed with hydration, loop diuretics, potassium binding granules, inhaler β-2 agonists and insulin. To date, this is the first case of intestinal haemangiomatosis complicated with severe hyperkalaemia. Our case suggested the idea of close monitorisation of potassium levels as well as haemodynamic status at the initialisation of the propranolol treatment.

Signaling pathways in the development of infantile hemangioma

Infantile hemangioma (IH), which is the most common tumor in infants, is a benign vascular neoplasm resulting from the abnormal proliferation of endothelial cells and pericytes. For nearly a century, researchers have noted that IH exhibits diverse and often dramatic clinical behaviors. On the one hand, most lesions pose no threat or potential for complication and resolve spontaneously without concern in most children with IH. On the other hand, approximately 10% of IHs are destructive, disfiguring and even vision- or life-threatening. Recent studies have provided some insight into the pathogenesis of these vascular tumors, leading to a better understanding of the biological features of IH and, in particular, indicating that during hemangioma neovascularization, two main pathogenic mechanisms prevail, angiogenesis and vasculogenesis. Both mechanisms have been linked to alterations in several important cellular signaling pathways. These pathways are of interest from a therapeutic perspective because targeting them may help to reverse, delay or prevent hemangioma neovascularization. In this review, we explore some of the major pathways implicated in IH, including the VEGF/VEGFR, Notch, β-adrenergic, Tie2/angiopoietins, PI3K/AKT/mTOR, HIF-α-mediated and PDGF/PDGF-R-β pathways. We focus on the role of these pathways in the pathogenesis of IH, how they are altered and the consequences of these abnormalities. In addition, we review the latest preclinical and clinical data on the rationally designed targeted agents that are now being directed against some of these pathways.

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.

Approach to the patient with an infantile hemangioma

Infantile hemangioma is the most common soft tissue tumor of childhood. Despite its frequency, it has only been in the last decade that these lesions have been better characterized and become the subject of significant clinical and translational research. Although most infantile hemangiomas are uncomplicated and do not require intervention, they can be a significant source of parental distress, cosmetic disfigurement, and morbidity. The wide spectrum of disease in the morphology of these lesions and in their behavior has made it difficult to predict the need for treatment and has made it challenging to establish a standardized approach to management.

Receptor tyrosine kinase-mediated angiogenesis

The endothelial cell is the essential cell type forming the inner layer of the vasculature. Two families of receptor tyrosine kinases (RTKs) are almost completely endothelial cell specific: the vascular endothelial growth factor (VEGF) receptors (VEGFR1-3) and the Tie receptors (Tie1 and Tie2). Both are key players governing the generation of blood and lymphatic vessels during embryonic development. Because the growth of new blood and lymphatic vessels (or the lack thereof) is a central element in many diseases, the VEGF and the Tie receptors provide attractive therapeutic targets in various diseases. Indeed, several drugs directed to these RTK signaling pathways are already on the market, whereas many are in clinical trials. Here we review the VEGFR and Tie families, their involvement in developmental and pathological angiogenesis, and the different possibilities for targeting them to either block or enhance angiogenesis and lymphangiogenesis.

Serum-level changes of vascular endothelial growth factor in children with infantile hemangioma after oral propranolol therapy

Oral propranolol is the first-line therapy for infantile hemangioma (IH), but its mechanism of action remains unclear. The aim of this study was to evaluate the change in serum vascular endothelial growth factor (VEGF) levels in patients with IH who underwent propranolol treatment. The study included 22 patients with IH receiving propranolol treatment. At three time points-before treatment and 1 and 3 months after treatment-blood samples were examined by enzyme-linked immunosorbent assay for serum VEGF expression. The mean serum VEGF concentration in children with proliferative hemangiomas was 395.0 ± 176.7 pg/mL, approximately twice as high as in patients with venous malformations (mean 170.7 pg/mL) and in healthy controls (204.8 pg/mL, p = 0.006). After 1 month of propranolol treatment, the level had fallen 21.6% (p = 0.003), although the downward trend was less obvious after 3 months of treatment (18.0%, p = 0.63). VEGF expression correlated significantly with the lesion size (correlation coefficient [R] = 0.43, p = 0.046), whereas no correlation was observed with age (R = 0.13, p = 0.56). Serum VEGF levels were higher in patients with IH and fell after 1 month of oral propranolol treatment. Similar results, although less pronounced, were found after 3 months of treatment. Lesion volume and serum level of VEGF were significantly correlated.

Infantile hemangiomas of the head and neck

Infantile hemangiomas (IHs) are benign vascular tumors. Clinical history and physical examination are the most important factors for diagnosis, with most IHs having a typical presentation. Treatment is required for some IHs that cause significant cosmetic deformity or functional compromise. Propranolol is the first-line treatment of most IHs. Ongoing research is increasing our understanding of the pathophysiology of these tumors and should help to identify future potential therapeutic targets.

The use of propranolol for complicated infantile hemangiomas

OBJECTIVE

To assess propranolol efficacy and safety in complicated infantile hemangiomas in two different age groups.

PATIENTS AND METHODS

We report on 68 infants with infantile hemangiomas treated with oral propranolol at the lowest effective dose at different ages for a period of six months. Inclusion criteria were life-threatening hemangiomas, function-threatening hemangiomas, facial hemangiomas with risk for disfigurement, and extensive and ulcerated hemangiomas. A previously designed safety protocol was applied to all patients. The evolution of all hemangiomas since baseline (pre-therapy) until the end of follow-up was assessed on the basis of clinical features (color, palpable softening, size, and volume) and taken at follow-up visits.

RESULTS

Our results showed that propranolol was effective in arresting the proliferative phase and in accelerating the involution of infantile hemangiomas in 92.6% of cases. Propranolol efficacy was clear even when it was started after 12 months of life at low dose; after discontinuation of therapy there was a moderate-to-severe regrowth in 9.3% of cases and a mild regrowth in 22.5%. No adverse events were observed.

CONCLUSIONS

Propranolol should be used as first-line medical treatment in all cases of complicated infantile hemangiomas.

Maternal and perinatal risk factors for infantile hemangioma: a case-control study

Infantile hemangioma (IH) is the most common benign tumor occurring during childhood. We hypothesized that, in addition to already known risk factors, such as female sex, prematurity, and low birthweight (LBW), antenatal vaginal bleeding and progesterone therapy would be highly associated with IH. We randomly selected 650 individuals with IH and matched them with 650 children of the same age and nationality without IH. Trained investigators used a standardized questionnaire to collect data from both groups, including demographic, prenatal, and perinatal characteristics. Prematurity (p < .001, odds ratio [OR] = 2.22, 95% confidence interval [CI] = 1.44-3.41), LBW (p < .001, OR = 3.10, 95% CI = 1.87-5.16) and female sex (p < .001, OR = 2.06, 95% CI = 1.65-2.58) were significantly associated with IH. Maternal vaginal bleeding during the first trimester was shown to be an independent risk factor according to logistic regression analyses (p < .001, OR = 1.6, 95% CI = 1.36-1.91), which was most evident in those receiving progesterone therapy to prevent miscarriage (p < .001, OR = 2.11, 95% CI = 1.77-2.51). Subgroup analyses revealed that the effect was more pronounced in female than in male infants (OR = 2.82, 95% CI = 2.39-3.34). In addition to the known relationships, the present study identified a close relationship between maternal vaginal bleeding and progesterone therapy during early pregnancy and IH. Twins appeared to have a higher incidence of IH than singletons.

Study of the etiopathogenesis and differential diagnosis of oral vascular lesions by immunoexpression of GLUT-1 and HIF-1α

BACKGROUND

To investigate whether the immunohistochemical expression of GLUT-1 and HIF-1α is related to the diagnosis and pathogenesis of oral vascular lesions.

STUDY METHODS

Thirty cases each of pyogenic granuloma (PG) and hemangioma were studied. Antibodies against GLUT-1 and HIF-1α were detected by immunoperoxidase staining in 3-μm histological sections, and the results were analyzed qualitatively and quantitatively, respectively. Positive and negative cells were counted, and the mean number of positive cells was calculated for each case.

RESULTS

The initial diagnosis of hemangioma was maintained in only 7 (23%) of the 30 cases studied, which were positive for GLUT-1. The remaining 23 cases were reclassified as vascular malformation (VM) (n = 13) and PG (n = 10) due to the absence of staining. The endothelium of blood vessels was negative for GLUT-1 in all cases initially diagnosed as PG (n = 30). The percentage of HIF-1α-positive cells was higher in cases of PG, followed by hemangiomas and VMs (P = 0.005).

CONCLUSIONS

Histological features are not sufficient to establish the correct diagnosis of oral hemangiomas, and an accurate anamnesis is essential in these cases. In addition, these findings demonstrate that vascular lesions express mediators of angiogenesis, HIF-1α, and suggest that his process may play a role in the pathogenesis of vascular.

Infantile hemangiomas and retinopathy of prematurity: clues to the regulation of vasculogenesis

Retinopathy of prematurity (ROP) and infantile hemangiomas are vascular disorders that may share common mechanisms. This study examined a potential clinical association between these disorders in populations of preterm infants at two hospitals in the USA and Hungary. Clinically collected data from infants with gestational ages less than 32 weeks born between May 1, 2007 and December 31, 2010 seen in the University of Iowa Children's Hospital or the Department of Obstetrics and Gynecology, University of Pécs, were abstracted from electronic medical records and entered into a study database. Demographic and clinical variables were examined as potential covariates to the disorders of interest. Data were initially analyzed by center and then combined through meta-analysis. Six hundred eighty-four subjects were studied: 236 from Pécs and 448 from Iowa. There were no significant demographic differences between populations. Univariate analysis on each study population yielded covariates to ROP in each population, including infantile hemangioma, which were entered into a logistic regression model. These models were combined through random-effects meta-analysis and demonstrated a significant relationship between infantile hemangioma and ROP (odds ratio = 1.84, 95 % confidence interval 1.08-3.12).

CONCLUSION

Infantile hemangioma and ROP co-occur in premature infant populations. Further studies are needed to investigate the pathogenesis of both disorders.

Role of connexins in infantile hemangiomas

The circulatory system is one of the first systems that develops during embryogenesis. Angiogenesis describes the formation of blood vessels as a part of the circulatory system and is essential for organ growth in embryogenesis as well as repair in adulthood. A dysregulation of vessel growth contributes to the pathogenesis of many disorders. Thus, an imbalance between pro- and antiangiogenic factors could be observed in infantile hemangioma (IH). IH is the most common benign tumor during infancy, which appears during the first month of life. These vascular tumors are characterized by rapid proliferation and subsequently slower involution. Most IHs regress spontaneously, but in some cases they cause disfigurement and systemic complications, which requires immediate treatment. Recently, a therapeutic effect of propranolol on IH has been demonstrated. Hence, this non-selective β-blocker became the first-line therapy for IH. Over the last years, our understanding of the underlying mechanisms of IH has been improved and possible mechanisms of action of propranolol in IH have postulated. Previous studies revealed that gap junction proteins, the connexins (Cx), might also play a role in the pathogenesis of IH. Therefore, affecting gap junctional intercellular communication is suggested as a novel therapeutic target of propranolol in IH. In this review we summarize the current knowledge of the molecular processes, leading to IH and provide new insights of how Cxs might be involved in the development of these vascular tumors.

Infantile hemangioma-mechanism(s) of drug action on a vascular tumor

Infantile hemangioma (IH), a benign vascular tumor, is the most common tumor of infancy, with an incidence of 5%-10% at the end of the first year. The tumor displays a distinctive life cycle consisting of a proliferating phase, occurring in the first months of life, followed by an involuting phase. Thus, IH represents a unique model of postnatal vasculogenesis, angiogenesis, and vessel regression. Traditionally, corticosteroids were the drug of choice when treatment of IH was indicated. In recent years, beta-blockers, most specifically propranolol, have serendipitously been shown to be an effective pharmacological treatment. This article will focus on the mechanism of action of these two drugs, the old and the new treatments, in slowing the growth and accelerating involution of IH.

Vascular anomalies - a practical approach

Vascular anomalies are common clinical problems (around 4.5% of all patients) in pediatric dermatology. A correct diagnosis is possible on clinical grounds in around 90% of cases; the remaining patients may require radiologic evaluations (duplex ultrasonography, MRI scan) and, rarely, histology. Vascular anomalies are divided into tumors and vascular malformations. This clear division reflects the different biological behaviors of these two groups. The infantile hemangioma represents by far the most common vascular tumor and is characterized by a typical growth cycle consisting of rapid proliferation, plateau phase, and finally slow regression. The discovery in 2008 of the efficacy of beta blockers in this disease is a therapeutic milestone. Vascular malformations can affect all types of vessels (capillaries, veins, arteries and lymphatic vessels). They usually manifest at birth and grow proportionally with the affected child. Some show marked progression especially during puberty. Considerable progress has been made with innovative interventional therapies in recent years, but surgery remains an important option. Basic knowledge of these diseases is important to every dermatologist in order to be able to counsel and manage affected patients correctly.

Hypoxia-induced autophagy in endothelial cells: a double-edged sword in the progression of infantile haemangioma?

AIMS

The aim of this study was to investigate the precise role of hypoxia-induced autophagy in endothelial cells, and whether it contributes to the distinctive progression of infantile haemangioma (IH).

METHODS AND RESULTS

The endothelial cells (EOMA and HUVECs) were cultured under hypoxic conditions for indicated times (0-72 h). The results showed that short exposure of the endothelial cells to hypoxia resulted in increased cell survival and proliferation, accompanied by occurrence of autophagy. Prolonged hypoxia-induced autophagy, correlating with increased cell death, was also detected afterwards. Correspondingly, autophagy inhibition prevented the enhanced cell survival and proliferation capacity, advanced the occurrence of cell-death in early hypoxic stage, and meanwhile attenuated the ability of prolonged hypoxia in cell-death induction. Moreover, our data demonstrated that the functional transformation of hypoxia-induced autophagy, pro-survival to pro-death, was rigorously regulated by the switch between hypoxia-inducible factor-1α (HIF-1α) and mammalian target of rapamycin (mTOR) pathways. Importantly, we also revealed the activation levels of HIF-1α and mTOR, as well as the autophagy status during the progression of IH.

CONCLUSION

This study unmasks the functional switch between HIF-1α and mTOR in regulating hypoxia-induced autophagy in endothelial cells and, more importantly, indicates its potential role in the progression of IH.

Infantile hemangiomas: an update on pathogenesis and therapy

Infantile hemangiomas (IHs) are the most common vascular tumors of childhood, affecting ~5% of all infants. Although most lesions proliferate and then involute with minimal consequence, a significant minority can be disfiguring, functionally significant, or, rarely, life-threatening. Recent discoveries concerning hemangioma pathogenesis provide both an improved understanding and more optimal approach to workup and management. Important detrimental associations can be seen with IH, such as significant structural anomalies associated with segmental IH. Standards of care have dramatically changed evaluation and management of hemangiomas. The goal of timely recognition and therapy is to minimize or eliminate long-term sequelae. New modalities, such as oral propranolol, provide the caregiver with better therapeutic options, which can prevent or minimize medical risk or scarring, but the side effect profile and risk-benefit ratio of such interventions must always be evaluated before instituting therapy.