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

Endothelial progenitor cells: current issues on characterization and challenging clinical applications

Since their discovery about a decade ago, endothelial precursor cells (EPC) have been subjected to intensive investigation. The vision to stimulate respectively suppress a key player of vasculogenesis opened a plethora of clinical applications. However, as research opened deeper insights into EPC biology, the enthusiasm of the pioneer era has been damped in favour of a more critical view. Recent research is focused on three major questions: The fact that the number of EPC in peripheral blood is exceedingly low has consistently raised suspicion whether these cells can plausibly have an impact on physiological or pathophysiological processes. Secondly, whereas the key role of EPC in tumourigenesis has been strongly emphasized by various groups in the past, recent publications are challenging this hypothesis. Thirdly, the lack of consensus on EPC-defining markers and standardized protocols for their detection have repeatedly led to difficulties concerning comparability between papers. In this current review, an overview on recent findings on EPC biology is given, their challenging clinical implications are discussed and the perplexity underlying the current controversial debate is illustrated.

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

Hemangioma stem cells (HemSCs) are multipotent cells isolated from infantile hemangioma (IH), which form hemangioma-like lesions when injected subcutaneously into immune-deficient mice. In this murine model, HemSCs are the primary target of corticosteroid, a mainstay therapy for problematic IH. The relationship between HemSCs and endothelial cells that reside in IH is not clearly understood. Adhesive interactions might be critical for the preferential accumulation of HemSCs and/or endothelial cells in the tumor. Therefore, we studied the interactions between HemSCs and endothelial cells (HemECs) isolated from IH surgical specimens. We found that HemECs isolated from proliferating phase IH, but not involuting phase, constitutively express E-selectin, a cell adhesion molecule not present in quiescent endothelial cells. E-selectin was further increased when HemECs were exposed to vascular endothelial growth factor-A or tumor necrosis factor-α. In vitro, HemSC migration and adhesion was enhanced by recombinant E-selectin but not P-selectin; both processes were neutralized by E-selectin-blocking antibodies. E-selectin-positive HemECs also stimulated migration and adhesion of HemSCs. In vivo, neutralizing antibodies to E-selectin strongly inhibited formation of blood vessels when HemSCs and HemECs were co-implanted in Matrigel. These data suggest that endothelial E-selectin could be a major ligand for HemSCs and thereby promote cellular interactions and vasculogenesis in IH. We propose that constitutively expressed E-selectin on endothelial cells in the proliferating phase is one mediator of the stem cell tropism in IH.

Propranolol induces regression of hemangioma cells through HIF-1α-mediated inhibition of VEGF-A

OBJECTIVE

To investigate the mechanism of propranolol on regression of infantile hemangiomas.

BACKGROUND

Propranolol has been found to be effective in treatment of severe hemangiomas of infancy. However, its mechanism of action is as yet unknown.

METHODS

Cultured proliferating and involuting hemangioma endothelial cells were treated with varying concentrations of propranolol for up to 4 days. Analysis was performed using cell viability, migration, and tubulogenesis assays, as well as quantitative RT-PCR and flow cytometry. Western blots and ELISA assays were used to assess protein expression.

RESULTS

Treatment with propranolol led to a dose dependent cytotoxic effect in hemangioma endothelial cells with decreased cell viability, migration, and tubulogenesis. This cytotoxic effect was VEGF (vascular endothelial growth factor) dependent, as demonstrated by decreased VEGF, VEGF-R1, and VEGF-R2 production. Decreased signaling through the VEGF pathway resulted in downregulation of PI3/Akt and p38/MAPK activity. Decreased VEGF activity was mediated through the hypoxia inducible factor (HIF)-1α pathway but not through NF-κβ signaling.

CONCLUSIONS

Collectively, these data suggest that propranolol exerts its suppressive effects on hemangiomas through the HIF-1α-VEGF-A angiogenesis axis, with effects mediated through the PI3/Akt and p38/MAPK pathways. These findings provide a plausible mechanism of action of propranolol on regression of infantile hemangiomas.

Rapamycin inhibits proliferation of hemangioma endothelial cells by reducing HIF-1-dependent expression of VEGF

Hemangiomas are tumors formed by hyper-proliferation of vascular endothelial cells. This is caused by elevated vascular endothelial growth factor (VEGF) signaling through VEGF receptor 2 (VEGFR2). Here we show that elevated VEGF levels produced by hemangioma endothelial cells are reduced by the mTOR inhibitor rapamycin. mTOR activates p70S6K, which controls translation of mRNA to generate proteins such as hypoxia inducible factor-1 (HIF-1). VEGF is a known HIF-1 target gene, and our data show that VEGF levels in hemangioma endothelial cells are reduced by HIF-1α siRNA. Over-expression of HIF-1α increases VEGF levels and endothelial cell proliferation. Furthermore, both rapamycin and HIF-1α siRNA reduce proliferation of hemangioma endothelial cells. These data suggest that mTOR and HIF-1 contribute to hemangioma endothelial cell proliferation by stimulating an autocrine loop of VEGF signaling. Furthermore, mTOR and HIF-1 may be therapeutic targets for the treatment of hemangiomas.

Expression of androgen, estrogen, progesterone, and growth hormone receptors in vascular malformations

BACKGROUND

Vascular malformations frequently enlarge during adolescence, suggesting that hormones may be involved. The purpose of this study was to determine whether pubertal hormone receptors are present in vascular malformations and whether they differ from normal tissue.

METHODS

Tissue specimens (arteriovenous malformation, lymphatic malformation, and venous malformation) were prospectively collected from patients undergoing resection. Immunohistochemistry was used to determine the presence of androgen, estrogen, progesterone, and growth hormone receptors. The effects of age, sex, location, and malformation type on receptor expression were analyzed. Age-, sex-, and location-matched normal tissues served as controls.

RESULTS

Forty-five vascular malformation specimens were collected: arteriovenous malformation (n = 11), lymphatic malformation (n = 20), and venous malformation (n = 14). Growth hormone receptor expression was increased in arteriovenous malformation (72.7 percent), lymphatic malformation (65.0 percent), and venous malformation (57.1 percent) tissues compared with controls (25.8 percent) (p < 0.05). Growth hormone receptor was present primarily in the endothelium/perivasculature of malformations (93.1 percent), whereas in normal tissue growth hormone receptor was located only in the stroma (p < 0.0001). Neither age, nor sex, nor location influenced receptor expression (p = 0.9). No differences in androgen receptor, estrogen receptor, and progesterone receptor staining were found between malformations and control samples (p = 0.7).

CONCLUSIONS

Growth hormone receptor is overexpressed and principally located in the vessels of vascular malformations. Growth hormone might contribute to the expansion of vascular malformations.

Pathogenesis of infantile hemangiomas

1.Review the key features of the life cycle of infantile hemangiomas.2.Highlight cellular and molecular pathways involved in hemangioma-genesis.3.Discuss theories that may account for hemangioma-genesis.In the past, it was believed that a mother's visual impressions or behavior during pregnancy caused the growth of infantile hemangioma in her unborn child. She might have had an excessive craving for strawberries, witnessed the slaughter of an animal, directly contacted human or animal blood, or mocked a child with a similar birthmark.1 This folklore began to slowly fade once hemangiomas were examined through the light microscope. In 1863, Virchow2 suggested that hemangiomas are composed of proliferating new blood vessels resulting from progressive irritation of tissue. In 1933, Laidlow and Murray3 proposed a phylogenetic origin for hemangiomas and hypothesized that hemangiomas are remnants of vascular tufts functioning as accessory lungs for primitive amphibia. Pack and Miller4 (1950) hypothesized that hemangiomas develop from embryonic islands of angioblastic cells that were isolated from the systemic vasculature during fetal development.

Antitumor activities of human placenta-derived mesenchymal stem cells expressing endostatin on ovarian cancer

Endostatin is an important endogenous inhibitor of neovascularization that has been widely used in anti-angiogenesis therapy for the treatment of cancer. However, its clinical application is largely hampered by its low efficacy. Human placenta-derived mesenchymal stem cells (hpMSCs) are particularly attractive cells for clinical use in cell-based therapies. In the present study, hpMSCs were isolated and characterized. We then evaluated the tumor targeting properties and antitumor effects of hpMSCs as gene delivery vehicles for ovarian cancer therapy. We efficiently engineered hpMSCs to deliver endostatin via adenoviral transduction mediated by Lipofectamine 2000. The tropism capacity of the engineered hpMSCs toward tumor cells was then confirmed by in vitro migration assays and in vivo by intraperitoneal injection of hpMSCs into nude mice. The hpMSCs expressing the human endostatin gene demonstrated preferential homing to the tumor site and significantly decreased the tumor volume without apparent systemic toxic effects. These observations were associated with significantly decreased blood sprouts and tumor cell proliferation as well as a dramatically increased tumor apoptosis index. These results suggested that hpMSCs are potentially an effective delivery vehicle for therapeutic genes for the treatment of ovarian cancer.

Urinary matrix metalloproteinases-2/9 in healthy infants and haemangioma patients prior to and during propranolol therapy

The mechanism of therapeutic success of propranolol for severe infantile haemangioma remains unclear. Propranolol was shown to modify matrix metalloproteinase (MMP) levels, which are associated with tumour pathogenesis. We hypothesized that urinary MMP2/9 is higher in patients with infantile haemangioma compared to healthy infants and that propranolol reduces MMP2/9 levels and thus leads to an involution of the haemangioma. In this case, MMP2/9 could be used as a marker of indicated therapy or therapeutic success. Urinary samples were taken before, 2 weeks after, and 2 months after the beginning of propranolol treatment in haemangioma patients and once in healthy controls. Activity of MMP2/9 was determined by commercially available activity kits. Urine of 22 haemangioma patients and 21 control subjects was obtained. Propranolol therapy had significant success in all patients. MMP2/9 was present in most samples, the younger the children the higher the MMP2 levels. Haemangioma patients showed lower levels of MMP2. The MMP2 levels were significantly higher after 2 weeks of propranolol than prior to therapy. There were no differences in MMP9 levels.

CONCLUSIONS

Presence of MMP2/9 in the urine of infants <1 year can be explained by high rate of physiological tissue remodelling. Unexpectedly, MMP2 was lower in the urine of haemangioma patients and higher 2 weeks after propranolol treatment. Taking this and the diverse results in literature into account, the correlation between MMPs, proliferation, and regression of haemangiomas and propranolol remains unclear.

Propranolol treatment of infantile hemangioma: clinical and radiologic evaluations

BACKGROUND

There is no way to predict the size that proliferative infantile hemangiomas (IHs) can reach and to expect the occurrence of complications. Moreover, there are no well-known characteristics that can affect the rate of involution of IHs and to predict its completion. Accordingly, intervention is frequently indicated. Different modalities have been reported for treatment of IHs. The possible mechanisms of action of propranolol on IHs are complex.

METHODS

Fifty infants presented with 80 IHs treated by oral propranolol at a dose of 2 mg/kg body weight per day. Treatment outcomes were clinically and radiologically evaluated.

RESULTS

The first noticeable effects on propranolol treatment were the changes in color and softening of IHs, followed by regression of their sizes. The clinically elicited color changes of superficial IHs and superficial components of compound IHs have been objectively proven by statistically significant color clearance (P ≤ .001) and resisting index (P ≤ .01) (∼50% increase) as a good indicator of lower vascular activity within IHs. Moreover, the softening of lesions followed by the clinically elicited regression of sizes of deep IHs and deep components of compound IHs has been objectively proven by statistically significant changes at lesions' thickness (P ≤ .01) (∼50% regression) and resisting index (P ≤ .01) (∼50% increase).

CONCLUSIONS

Collectively, high efficacy and tolerance of propranolol treatment have been elicited. However, propranolol treatment of IHs is still an issue suitable for more studies to confirm the safety and efficacy of the drug and to investigate whether there are some hemangiomas that are, perhaps, nonresponsive to propranolol treatment.

Oral haemangioma

Vascular anomalies comprise a widely heterogeneous group of tumours and malformations. Haemangioma is the most common benign tumour of vascular origin of the head and neck region. The possible sites of occurrence in oral cavity are lips, tongue, buccal mucosa, and palate. Despite its benign origin and behaviour, it is always of clinical importance to the dental profession and requires appropriate management. This case study reports a rare case of capillary haemangioma on the palatal gingiva in a 14-year-old female.

Infantile hemangioma research: looking backward and forward

This is a remarkable time to be a student of infantile hemangiomas (IHs). IH is a common tumor, estimated to occur in approximately 4% of infants. Studied for many decades, the acquisition of knowledge and pace of IH research are accelerating. The article by Greenberger et al. in this issue is a welcome addition to the literature. It examines rapamycin as a possible treatment for IH that could potentially be curative because suppression of self-renewal of stem cells might deplete hemangiomas of the stem cells from which they originate. However, before we get too enthusiastic about using rapamycin for IHs, it is important to reflect on lessons learned from previous hemangioma therapies.

Increased endothelial progenitor cells and vasculogenic factors in higher-staged arteriovenous malformations

ACKGROUND:: Arteriovenous malformations cause significant morbidity, primarily because they expand over time and recur after treatment. The authors hypothesized that neovascularization might contribute to arteriovenous malformation progression.

METHODS

Arteriovenous malformation tissue was collected prospectively from 12 patients after resection. Schobinger stage was determined by clinical history. Neovascularization in stage II lesions (n=7) was compared with stage III arteriovenous malformations (n=5) that had progressed. Specimens were analyzed using immunohistochemistry for CD31, Ki67, and CD34/CD133. Quantitative real-time reverse-transcriptase polymerase chain reaction was used to determine mRNA expression of factors that recruit endothelial progenitor cells: vascular endothelial growth factor (VEGF), stromal cell-derived factor-1α (SDF-1α), and hypoxia-inducible factor-1α (HIF-1α). VEGF receptors (VEGFR1, VEGFR2, neuropilin 1, and neuropilin 2) also were quantified using quantitative real-time reverse-transcriptase polymerase chain reaction.

RESULTS

Stage III arteriovenous malformations showed greater microvessel density (5.8 percent) than stage II lesions (1.3 percent) (p=0.004); no difference in proliferating endothelial cells was noted (p=0.67). CD133CD34 endothelial progenitor cells were elevated in stage III (0.53 percent) compared with stage II arteriovenous malformations (0.25 percent) (p=0.03). HIF-1α and SDF-1α were increased 7.6- and 7.9-fold in stage III compared with stage II lesions (1.7-fold and 3.3-fold), respectively (p=0.02). Neuropilin 1 and neuropilin 2 expression was greater in stage III (5.8-fold and 4.6-fold) than stage II arteriovenous malformations (3.0-fold and 2.4-fold) (p=0.03).

CONCLUSIONS

Higher-staged arteriovenous malformations exhibit increased expression of endothelial progenitor cells and factors that stimulate their recruitment. Neovascularization by vasculogenesis may be involved in progression of arteriovenous malformation.

JAGGED1 signaling regulates hemangioma stem cell-to-pericyte/vascular smooth muscle cell differentiation

OBJECTIVE

The aim of our study is to determine the cellular and molecular origin for the pericytes in infantile hemangioma (IH) and their functional role in the formation of pathological blood vessels.

METHODS AND RESULTS

Here we show that IH-derived stem cells (HemSCs) form pericyte-like cells. With in vitro studies, we demonstrate that HemSC-to-pericyte differentiation depends on direct contact with endothelial cells. JAGGED1 expressed ectopically in fibroblasts was sufficient to induce HemSCs to acquire a pericyte-like phenotype, indicating a critical role for JAGGED1. In vivo, we blocked pericyte differentiation with recombinant JAGGED1, and we observed reduced formation of blood vessels, with an evident lack of pericytes. Silencing JAGGED1 in the endothelial cells reduced blood vessel formation and resulted in a paucity of pericytes.

CONCLUSIONS

Our data show that endothelial JAGGED1 controls HemSC-to-pericyte differentiation in a murine model of IH and suggests that pericytes have a fundamental role in formation of blood vessels in IH.

Infantile haemangioma: part I. Pathophysiology, epidemiology, clinical features, life cycle and associated structural abnormalities

Infantile haemangioma (IH) is the most common tumour of infancy. Its typical natural history is characterized by an early rapid growth following birth and a slow spontaneous regression phase within a period of 3 to 7 years. The exact aetiopathogeny underlying IH is still to be fully understood, but the role of fetal hypoxic stress is strongly suggested as a triggering signal in epidemiological studies. IH are composed of a complex mixture of cells including multipotent stem cells, a majority of immature endothelial cells, pericytes, dendritic cells and in the late stage, adipocytes. Most of IH are nodular and are not associated with malformations. However, in some cases, IH referred to as segmental may be associated with developmental abnormalities such as PHACES and PELVIS/SACRAL syndromes.

Oral propranolol for circumscribed choroidal hemangioma

Introduction

Several therapeutic approaches have been developed to treat choroidal hemangioma. However, all these therapies are associated with a potential risk of damaging the overlying retina.

Case Report

We report a case of circumscribed choroidal hemangioma (CCH) in a 59-year-old man refractory to laser treatment. Visual acuity was 20/200 and a serous macular detachment was present. The CCH was treated with oral propanolol, whereupon visual acuity improved to 20/20 and the macular detachment resolved without systemic or local adverse effects.

Discussion

Propanolol is a β-blocker commonly used in cardiology that may induce endothelium vasoconstriction and inhibit endothelial proliferation. It has been shown to be effective in infantile facial hemangiomas, and proved safe and effective for the CCH in our patient. Further studies are needed to confirm our observation.

Evidence of endothelial progenitor cells in the human brain and spinal cord arteriovenous malformations

BACKGROUND

Brain and spinal cord arteriovenous malformations (AVMs) are characterized by aberrant angiogenesis and vascular remodeling. Endothelial progenitor cells (EPCs) can be recruited by stromal cell-derived factor-1 (SDF-1), and participate in vascular remodeling in both physiological and pathological settings.

OBJECTIVE

To investigate whether there are increased EPC levels in the brain and spinal cord AVM nidus.

METHODS

Microsurgical specimens without endovascular embolization and radiosurgery from the brain (n = 12) and spinal cord (n = 5) AVMs were examined. Hemangioblastoma, meningioma, cerebral cortex obtained from epilepsy surgery, and the basilar artery from the autopsy were chosen for control comparisons. EPCs were identified as cells that were double-positive for the stem cell marker CD133 and the endothelial cell marker VEGFR-2 (vascular endothelial growth factor receptor-2 or KDR). In addition, SDF-1 was characterized by immunohistochemistry.

RESULTS

Both brain and spinal AVM tissues displayed more CD133-, SDF-1-, and CD68-positive signals than epilepsy and basilar artery control tissues. The level of EPCs was increased in the brain and spinal cord AVM nidus, mainly at the edge of the vessel wall. The expression of SDF-1 was colocalized with CD31-positive and α-smooth muscle cells, and was predominantly found within the vessel wall.

CONCLUSION

Our data demonstrate that EPCs are present in the nidus of the brain and spinal cord AVMs, which may mediate pathological vascular remodeling and impact the clinical course of AVMs.

Down-regulation of mir-424 contributes to the abnormal angiogenesis via MEK1 and cyclin E1 in senile hemangioma: its implications to therapy

Background

Senile hemangioma, so-called cherry angioma, is known as the most common vascular anomalies specifically seen in the aged skin. The pathogenesis of its abnormal angiogenesis is still unclear.

Methodology/Principal Findings

In this study, we found that senile hemangioma consisted of clusters of proliferated small vascular channels in upper dermis, indicating that this tumor is categorized as a vascular tumor. We then investigated the mechanism of endothelial proliferation in senile hemangioma, focusing on microRNA (miRNA). miRNA PCR array analysis revealed the mir-424 level in senile hemangioma was lower than in other vascular anomalies. Protein expression of MEK1 and cyclin E1, the predicted target genes of mir-424, was increased in senile hemangioma compared to normal skin or other anomalies, but their mRNA levels were not. The inhibition of mir-424 in normal human dermal microvascular ECs (HDMECs) using specific inhibitor in vitro resulted in the increase of protein expression of MEK1 or cyclin E1, while mRNA levels were not affected by the inhibitor. Specific inhibitor of mir-424 also induced the cell proliferation of HDMECs significantly, while the cell number was decreased by the transfection of siRNA for MEK1 or cyclin E1.

Conclusions/Significance

Taken together, decreased mir-424 expression and increased levels of MEK1 or cyclin E1 in senile hemangioma may cause abnormal cell proliferation in the tumor. Senile hemangioma may be the good model for cutaneous angiogenesis. Investigation of senile hemangioma and the regulatory mechanisms of angiogenesis by miRNA in the aged skin may lead to new treatments using miRNA by the transfection into senile hemangioma.

Estrogens and development of pulmonary hypertension: interaction of estradiol metabolism and pulmonary vascular disease

Severe pulmonary arterial hypertension (PAH) is characterized by clustered proliferation of endothelial cells (ECs) in the lumina of small size pulmonary arteries resulting in concentric obliteration of the lumina and formation of complex vascular structures known as plexiform lesions. This debilitating disease occurs more frequently in women, yet both animal studies in classical models of PAH and limited clinical data suggest protective effects of estrogens: the estrogen paradox in pulmonary hypertension. Little is known about the role of estrogens in PAH, but one line of evidence strongly suggests that the vascular protective effects of 17β-estradiol (estradiol; E2) are mediated largely by its downstream metabolites. Estradiol is metabolized to 2-hydroxyestradiol (2HE) by CYP1A1/CYP1B1, and 2HE is converted to 2-methoxyestradiol (2ME) by catechol-O-methyl transferase. 2ME is extensively metabolized to 2-methoxyestrone, a metabolite that lacks biologic activity, but which may be converted back to 2ME. 2ME has no estrogenic activity, and its effects are mediated by estrogen receptors–independent mechanism(s). Notably, in systemic and pulmonary vascular ECs, smooth muscle cells, and fibroblasts, 2ME exerts stronger antimitotic effects than E2 itself. E2 and 2ME, despite having similar effects on other cardiovascular cells, have opposing effects on ECs; that is, in ECs, E2 is promitogenic, proangiogenic, and antiapoptotic, whereas 2ME is antimitogenic, antiangiogenic, and proapoptotic. This may have significant ramifications in severe PAH that involves uncontrolled proliferation of monoclonal apoptosis-resistant ECs. Based on its cellular effects, 2ME should be expected to attenuate the progression of disease and provide protection in severe PAH. In contrast, E2, due to its mitogenic, angiogenic, and antiapoptotic effects (otherwise desirable in normal quiescent ECs), may even adversely affect endothelial remodeling in PAH, and this may be even more significant if the E2's effects on injured endothelium are not opposed by 2ME (eg, in the event of reduced E2 conversion to 2ME due to hypoxia, inflammation, drugs, environmental factors, or genetic polymorphism of metabolizing enzymes). This review focuses on the effects of estrogens and their metabolites on pulmonary vascular pathobiology and the development of experimental PAH and offers potential explanation for the estrogen paradox in PAH. Furthermore, we propose that unbalanced estradiol metabolism may lead to the development of PAH. Recent animal data and studies in patients with PAH support this concept.

Pharmacological targeting of β-adrenergic receptor functions abrogates NF-κB signaling and MMP-9 secretion in medulloblastoma cells

Targeting of the vascular endothelium compartment explains, in part, the therapeutic efficacy of the nonselective β-adrenergic antagonist propranolol against common endothelial tumors such as hemangiomas. In vitro, the antiangiogenic biological activity of propranolol was shown to inhibit human brain microvascular endothelial cell tubulogenesis. However, possible interference of propranolol with cell signaling associated with the tumoral compartment remains unexplored. We therefore assessed the potency of propranolol against a pediatric brain tumor- derived DAOY medulloblastoma cell model. Gene expression of β(1)-, β(2)-, and β(3)-adrenergic receptors was confirmed in DAOY cells by semiquantitative RT-PCR. We next found that propranolol dose-dependently inhibited induction of the key extracellular matrix-degrading and blood-brain barrier disrupting enzyme matrix metalloproteinase- 9 (MMP-9) by phorbol 12-myristate 13-acetate (PMA). Propranolol not only inhibited PMA- induced phosphorylation of the extracellular signal-regulated kinase (Erk), but also that of IkappaB (IκB), preventing the IκB phosphorylation which is a prerequisite for IκB degradation. Propranolol inhibition of IκB phosphorylation was shown to occur with optimal efficacy at 30 μM. Although propranolol, at up to 100 μM, did not affect cell viability, it potentiated PMA- mediated signaling that ultimately led to diminished phosphorylation of Akt. The anti-Erk and anti-Akt phosphorylation effects are both suggestive of antiproliferative and antisurvival signaling, respectively. Our data are therefore indicative of a pharmacological role for propranolol against β-adrenergic receptor signaling functions involving the nuclear factor-kappaB-mediated regulation of MMP-9.

Cervical and intracranial arterial anomalies in 70 patients with PHACE syndrome

BACKGROUND AND PURPOSE

Cerebral and cervical arterial abnormalities are the most common non-cutaneous anomaly in PHACE syndrome, but the location and type of arterial lesions that occur have not been systematically assessed in a large cohort. Our aim was to characterize the phenotypic spectrum of arteriopathy, assess the frequency with which different arteries are involved, and evaluate spatial relationships between arteriopathy, brain structural lesions, and hemangiomas in PHACE syndrome.

MATERIALS AND METHODS

Intracranial MRA and/or CTA images from 70 children and accompanying brain MR images in 59 patients with arteriopathy and PHACE syndrome were reviewed to identify the type and location of arterial lesions and brain abnormalities. Five categories of arteriopathy were identified and used for classification: dysgenesis, narrowing, nonvisualization, primitive embryonic carotid-vertebrobasilar connections, and anomalous arterial course or origin. Univariate logistic regression analyses were performed to test for associations between arteriopathy location, hemangiomas, and brain abnormalities.

RESULTS

By study design, all patients had arterial abnormalities, and 57% had >1 form of arteriopathy. Dysgenesis was the most common abnormality (56%), followed by anomalous course and/or origin (47%), narrowing (39%), and nonvisualization (20%). Primitive embryonic carotid-vertebrobasilar connections were present in 20% of children. Hemangiomas were ipsilateral to arteriopathy in all but 1 case. The frontotemporal and/or mandibular facial segments were involved in 97% of cases, but no other specific associations between arteriopathy location and hemangioma sites were detected. All cases with posterior fossa anomalies had either ICA anomalies or persistent embryonic carotid-basilar connections.

CONCLUSIONS

The arteriopathy of PHACE syndrome commonly involves the ICA and its embryonic branches, ipsilateral to the cutaneous hemangioma, with dysgenesis and abnormal arterial course the most commonly noted abnormalities. Brain abnormalities are also typically ipsilateral.

Infantile hemangioma

Infantile hemangiomas (IHs) are the most common soft tissue tumors of childhood. The wide spectrum of disease has made it difficult to predict need for treatment and has made it challenging to establish a standardized approach to management. This article provides the reader with an up-to-date discussion of IH, identifying features of this condition which predict need for treatment as well as associated complications and reviewing management.

Propranolol for infantile haemangiomas: insights into the molecular mechanisms of action

Infantile haemangiomas (IH) are the most common benign tumours of infancy. Although most IH are innocuous and 85-90% regress spontaneously, some may become life- or function-threatening and require immediate treatment. Previous standard therapeutic options include physical measures (laser surgery, cryosurgery) and systemic corticosteroids, in severe cases also vincristine, alpha-interferon or cyclophosphamide, all bearing the risk of serious side-effects. Oral propranolol is a very recent therapeutic option for complicated IH with impressive efficacy and generally good tolerance. The effects of propranolol on IH were discovered by chance, and very little is known about its mechanisms of action in IH. Here we present a summary of current knowledge of how propranolol interferes with endothelial cells, vascular tone, angiogenesis and apoptosis. Early, intermediate and long-term effects of propranolol on IH can be attributed to three different pharmacological targets. Early effects (brightening of the haemangioma surface within 1-3 days after start of therapy) are attributable to vasoconstriction due to decreased release of nitric oxide. Intermediate effects are due to the blocking of proangiogenic signals (vascular endothelial growth factor, basic fibroblast growth factor, matrix metalloproteinase 2/9) and result in growth arrest. Long-term effects of propranolol are characterized by induction of apoptosis in proliferating endothelial cells, and result in tumour regression.

Corticosteroid suppression of VEGF-A in infantile hemangioma-derived stem cells

BACKGROUND

Corticosteroids are commonly used to treat infantile hemangioma, but the mechanism of action of this therapy is unknown. We investigated the effect of corticosteroids in a previously described in vivo model of infantile hemangioma and in cultured hemangioma-derived cells.

METHODS

We tested hemangioma-derived stem cells for vasculogenic activity in vivo after implantation into immune-deficient (nude) mice. We studied dexamethasone treatment of both the cells before implantation and the mice after implantation. We also tested hemangioma-derived stem cells for expression of vascular endothelial growth factor A (VEGF-A) in vitro and studied the inhibition of VEGF-A expression, using short hairpin RNA (shRNA) in vivo and in vitro.

RESULTS

Systemic treatment with dexamethasone led to dose-dependent inhibition of tumor vasculogenesis in the murine model. Pretreatment of hemangioma-derived stem cells in vitro before implantation also inhibited vasculogenesis. Dexamethasone suppressed VEGF-A production by hemangioma-derived stem cells in vitro but not by hemangioma-derived endothelial cells or human umbilical-vein endothelial cells. Silencing VEGF-A in hemangioma-derived stem cells reduced vasculogenesis in vivo. VEGF-A was detected in hemangioma specimens in the proliferating phase but not in the involuting phase and was shown by immunostaining to reside outside of vessels. Corticosteroid treatment suppressed other proangiogenic factors in hemangioma-derived stem cells, including urokinase plasminogen activator receptor, interleukin-6, monocyte chemoattractant protein 1, and matrix metalloproteinase 1.

CONCLUSIONS

In a murine model, dexamethasone inhibited the vasculogenic potential of stem cells derived from human infantile hemangioma. The corticosteroid also inhibited the expression of VEGF-A by hemangioma-derived stem cells, and silencing of VEGF-A expression in these cells inhibited vasculogenesis in vivo.

[Infantile hemangioma]

Infantile hemangioma is the most common tumor in children, but its pathophysiology is still not well understood. Infantile hemangioma develops during the first weeks of life, usually builds up over 3 to 6 months, and then regresses very slowly over a period of 3 to 7 years. Three quarters of these hemangiomas are lobular and are not associated with malformations. On the other hand, the hemangiomas referred to as segmental may be associated with developmental abnormalities (PHACES and PELVIS/SACRAL syndromes). Because of their spontaneous involution, most infantile hemangiomas do not require therapeutic intervention. In 10 to 15 % of cases, treatment is necessary because of complications when life or physiological functioning is threatened, or there are local complications or the long-term esthetic risk is too high. Until now, the standard first-line treatment has been general corticosteroid therapy. The usual choice for second-line treatment is interferon or vincristine. The efficacy of propranolol, a non-cardioselective beta-blocker, was recently reported.

Overexpression of allograft inflammatory factor-1 promotes the proliferation and migration of human endothelial cells (HUV-EC-C) probably by up-regulation of basic fibroblast growth factor

Our previous study demonstrated that allograft inflammatory factor-1 (AIF-1) is present in the vessels of infantile hemangiomas but neither in the vessels of vascular malformations, pyogenic granulomas, normal skin, placental tissues nor in the neovessels of squamous cell carcinomas of the tongue. The purpose of this study was to explore the impact of AIF-1 alterations on endothelial cells (EC). Stable introduction of AIF-1 to the human umbilical vein EC line (HUV-EC-C) in vitro revealed that AIF-1 enhances the proliferation and migration of the EC and promotes G0/G1-to-S-phase transition, accompanied by up-regulation of basic fibroblast growth factor (p < 0.05). In contrast, AIF-1 did not affect the expression of granulocyte colony-stimulating factor, VEGF-a, monocyte chemoattractant protein-1, or tissue inhibitor of metalloproteinase-1. AIF-1 expression was not induced by hypoxia, VEGF-a, basic fibroblast growth factor, or insulin-like growth factor-2 in EC. Taken together, these findings suggest that the impact of AIF-1 on EC would stimulate angiogenesis and consequently affect the progression of infantile hemangiomas.

Propranolol adrenergic blockade inhibits human brain endothelial cells tubulogenesis and matrix metalloproteinase-9 secretion

In recent clinical observation, the growth of endothelial tumors, such as hemangiomas of infancy, was repressed by the non-selective beta-adrenergic antagonist propranolol possibly through targeting of the vascular endothelial compartment. As human brain microvascular endothelial cells (HBMEC) play an essential role as structural and functional components in tumor angiogenesis, we assessed whether propranolol could target HBMEC's in vitro angiogenic properties. We found that biopsies from human glioblastoma as well as from experimental brain tumor-associated vasculature expressed high levels of the beta2-adrenergic receptor, suggesting adrenergic adaptative processes could take place during tumor vascularization. We observed that in vitro tubulogenesis was significantly reduced by propranolol when HBMEC were seeded on Matrigel. Propranolol, as much as 100microM, did not reduce cell viability and did not alter HBMEC migration as assessed with Boyden chambers. Secretion of the key angiogenic and extracellular matrix degrading enzymes MMP-2 and MMP-9 was assessed by zymography. Propranolol significantly reduced MMP-9 secretion upon treatment with the tumor-promoting agent phorbol 12-myristate 13-acetate, while secretion of MMP-2 remained unaffected. This was correlated with a decrease in MMP-9 gene expression which is, in part, explained by a decrease in the nucleocytoplasmic export of the mRNA stabilizing factor HuR. Our data are therefore indicative of a selective role for propranolol in inhibiting MMP-9 secretion and HBMEC tubulogenesis which could potentially add to propranolol's anti-angiogenic properties.

A potential role for notch signaling in the pathogenesis and regulation of hemangiomas

Hemangiomas are the most common benign tumor of infancy, yet its pathogenesis and the mechanisms governing proliferation and involution are not well understood. It is believed that hemangiomas arise out of clonal, abnormal hemangioma endothelial cells (HemECs). The underlying anomaly of the HemEC is not known, although studies have shown that vascular endothelial growth factor (VEGF) and VEGF signaling may influence HemECs. Moreover, there are numerous subtypes of hemangiomas, with differences in natural history, potential for morbidity, and prognosis, and little is known how this relates to HemEC. The Notch signaling pathway is a highly conserved pathway across species from worms to mammals. Notch signaling has been shown to play a role during embryogenesis in directing vascular patterning and development and arterial and venous cell fate determination. Postnatally, it has been implicated in tumor angiogenesis in multiple malignancies. Notch signaling triggers tumor angiogenesis at least in part to stimulation by VEGF, thus establishing that there is a cross talk between the VEGF and Notch pathways. Given the presence of VEGF and its receptors in hemangiomas and known VEGF-Notch cross talk in tumor angiogenesis, the authors hypothesize that Notch signaling may contribute to hemangioma proliferation and involution. Preliminary studies of resected hemangioma specimens by reverse transcription polymerase chain reaction (RT-PCR) show that all 4 Notch receptors and 2 Notch ligands, Jagged1 and Delta-like ligand 4, are expressed by hemangiomas. These findings support a role for Notch in hemangiomas, meriting further analysis of the functional relevance of Notch signaling in hemangiomas.

Propranolol for severe infantile hemangiomas: follow-up report

OBJECTIVE

Infantile hemangiomas (IHs) are the most-common soft-tissue tumors of infancy. We report the use of propranolol to control the growth phase of IHs.

METHODS

Propranolol was given to 32 children (21 girls; mean age at onset of treatment: 4.2 months) after clinical and ultrasound evaluations. After electrocardiographic and echocardiographic evaluations, propranolol was administered with a starting dose of 2 to 3 mg/kg per day, given in 2 or 3 divided doses. Blood pressure and heart rate were monitored during the first 6 hours of treatment. In the absence of side effects, treatment was continued at home and the child was reevaluated after 10 days of treatment and then every month. Ultrasound measurements were performed after 60 days of treatment.

RESULTS

Immediate effects on color and growth were noted in all cases and were especially dramatic in cases of dyspnea, hemodynamic compromise, or palpebral occlusion. In ulcerated IHs, complete healing occurred in <2 months. Objective clinical and ultrasound evidence of longer-term regression was seen in 2 months. Systemic corticosteroid treatment could be stopped within a few weeks. Treatment was administered for a mean total duration of 6.1 months. Relapses were mild and responded to retreatment. Side effects were limited and mild. One patient discontinued treatment because of wheezing.

CONCLUSION

Propranolol administered orally at 2 to 3 mg/kg per day has a consistent, rapid, therapeutic effect, leading to considerable shortening of the natural course of IHs, with good clinical tolerance.

Signaling mechanisms in infantile hemangioma

PURPOSE OF REVIEW

Infantile hemangioma is a common vascular tumor with a unique lifecycle: rapid growth in infancy, followed by a period of involution, leading to complete regression. This review summarizes recent studies of molecular mechanisms of hemangioma formation and places new findings and hypotheses in the context of past accomplishments.

RECENT FINDINGS

The new work identifies a novel signaling pathway for vascular growth factor and extracellular matrix regulation in vascular endothelial cells and provides a basis for novel therapeutic strategies. In hemangioma-derived endothelial cells, defects in a vascular endothelial growth factor receptor/integrin complex reduce the expression of a vascular endothelial growth factor decoy receptor. As a consequence, hemangioma endothelial cells exhibit constitutive vascular endothelial growth factor signaling. Germline mutations in components of the growth factor receptor/integrin complex in some hemangioma patients, and somatic mutations in a phosphatase in sporadic hemangioma specimens, raise the possibility that hemangioma formation involves a combination of germline risk factor mutations and somatic mutations, similar to what recent studies have shown is the case for venous malformations.

SUMMARY

Alterations in pathways that negatively control vascular endothelial growth factor signaling in vascular endothelial cells are responsible for the formation and rapid growth of infantile hemangiomas.

Pathogenesis and radiobiology of brain arteriovenous malformations: implications for risk stratification in natural history and posttreatment course

Brain arteriovenous malformations (BAVMs) are an important cause of intracerebral hemorrhage (ICH) in young adults. Biological predictors of future ICH risk are lacking, and controversy exists over previous studies of natural history risk among predominantly ruptured BAVM cohorts. Recent studies have suggested that the majority of BAVMs are now diagnosed as unruptured lesions, and that the risk according to natural history among these lesions may be less than previously assumed. In the first part of this review, the authors discuss available data on the natural history of BAVMs and highlight the need for future studies that aim to develop surrogate biomarkers of disease progression that accurately predict future risk of ICH in BAVMs. The etiology of BAVM remains unknown. Recent studies have suggested a role for genetic factors in the pathogenesis of sporadic BAVM, which is further supported by reports of familial occurrence of BAVM and association with known systemic genetic disorders (such as Osler-Weber-Rendu disease, Sturge-Weber disease, and Wyburn-Mason syndrome). Molecular characterization of BAVM tissue demonstrates a highly angiogenic milieu with evidence of increased endothelial cell turnover. Taken together with a number of reports of de novo BAVM formation, radiographic growth after initial BAVM diagnosis, and regrowth after successful treatment of BAVM, these findings challenge the long-held assumption that BAVMs are static lesions of congenital origin. In the second part of this review, the authors discuss available data on the origins of BAVM and offer insights into future investigations into genetics and endothelial progenitor cell involvement in the pathogenesis of BAVM. Current treatment options for BAVM focus on removal or obliteration of the lesion in an attempt to protect against future ICH risk, including microsurgical resection, endovascular embolization, and stereotactic radiosurgery (SRS). In the third part of this review, the authors discuss available data on SRS in BAVMs and highlight the need for future studies on the radiobiology of BAVMs, especially in regard to biomarker detection for tracking SRS response during the latency period. Insights from future investigations in BAVM may not only prove important for the development of novel therapies and relevant biomarkers for BAVM, but could also potentially benefit a variety of other disorders involving new vessel formation in the CNS, including stroke, tumors, moyamoya disease, and other cerebrovascular malformations.

Pathophysiology and genetic factors in moyamoya disease

Moyamoya disease is an uncommon cerebrovascular condition characterized by progressive stenosis of the bilateral internal carotid arteries with compensatory formation of an abnormal network of perforating blood vessels providing collateral circulation. The etiology and pathogenesis of moyamoya disease remain unclear. Evidence from histological studies, proteomics, and endothelial progenitor cell analyses suggests new theories underlying the cause of vascular anomalies, including moyamoya disease. Familial moyamoya disease has been noted in as many as 15% of patients, indicating an autosomal dominant inheritance pattern with incomplete penetrance. Genetic analyses in familial moyamoya disease and genome-wide association studies represent promising strategies for elucidating the pathophysiology of this condition. In this review, the authors discuss recent studies that have investigated possible mechanisms underlying the etiology of moyamoya disease, including stem cell involvement and genetic factors. They also discuss future research directions that promise not only to offer new insights into the origin of moyamoya disease but to enhance our understanding of new vessel formation in the CNS as it relates to stroke, vascular anomalies, and tumor growth.

Serum levels of vascular endothelial growth factor and basic fibroblastic growth factor in children with hemangiomas and vascular malformations--preliminary report

Impaired balance between proangiogenic and antiangiogenic factors has been implicated in the development of hemangiomas. Elevated vascular endothelial growth factor serum levels and basic fibroblastic growth factor urine levels in patients with proliferating hemangiomas were reported. However, whether these growth factors can be used for the differential diagnosis of vascular anomalies or assessment of the clinical course of hemangiomas has yet to be determined. We report here our preliminary results of serum vascular endothelial growth factor and basic fibroblastic growth factor levels as an aid in the diagnosis of hemangiomas and in the follow up of patients with this lesion. Twenty two children with infantile hemangioma (13 with proliferating hemangiomas, nine with involuting lesions), five children with vascular malformations, and 25 healthy children study group. Vascular endothelial growth factor and basic fibroblastic growth factor serum levels were analyzed by an ELISA assay. The serum vascular endothelial growth factor concentrations in children with proliferating hemangiomas were significantly higher than in patients with involuting hemangiomas, vascular malformations and healthy patients. The serum basic fibroblastic growth factor concentrations were low and similar in all patients with no statistical correlation between study groups. We concluded that (i) ELISA can easily determine vascular endothelial growth factor concentrations in different phases of hemangioma growth and help distinguishing them from vascular malformations. (ii) A potential role for vascular endothelial growth factor in the pathophysiology of hemangiomas is probable.

PHACE syndrome: current knowledge, future directions

On November 7-8, 2008, physicians gathered in Houston Texas for the first-ever workshop on PHACE syndrome, an important and recently described neurocutaneous syndrome. This article represents a summary of the discussions held at that workshop, which was attended by a broad range of medical specialists.

Vasculogenesis in infantile hemangioma

Infantile hemangioma is a vascular tumor that occurs in 5-10% of infants of European descent. A defining feature of infantile hemangioma is the dramatic growth and development into a disorganized mass of blood vessels. Subsequently, a slow spontaneous involution begins around 1 year of age and continues for 4-6 years. The growth and involution of infantile hemangioma is very different from other vascular tumors and vascular malformations, which do not regress and can occur at any time during childhood or adult life. Much has been learned from careful study of the tissue morphology and gene expression patterns during the life-cycle of hemangioma. Tissue explants and tumor-derived cell populations have provided further insight to unravel the cellular and molecular basis of infantile hemangioma. A multipotent progenitor cell capable of de novo blood vessel formation has been isolated from infantile hemangioma, which suggests that this common tumor of infancy, long considered to be a model for pathologic angiogenesis, may also represent pathologic vasculogenesis. Whether viewed as angiogenesis or vasculogenesis, infantile hemangioma represents a vascular perturbation during a critical period of post-natal growth, and as such provides a unique opportunity to decipher mechanisms of human vascular development.

Regulation of angiogenesis by oxygen and metabolism

Blood vessels form an important interface between the environment and the organism by carrying oxygen and nutrients to all cells and thus determining cellular metabolism. It is therefore not surprising that oxygen and metabolism influence the development of the vascular network. Here, we discuss recent insights regarding the emerging crosstalk between angiogenesis and metabolism. We will highlight advances in how oxygen and metabolism regulate angiogenesis as well as how angiogenic factors in turn also regulate metabolism.

Infantile hemangiomas and retinopathy of prematurity: possible association

OBJECTIVE

The goal was to study the clinical association between infantile hemangiomas and retinopathy of prematurity in preterm infants.

METHODS

A retrospective study of preterm neonates weighing </=1250 g at birth who were born during a 5-year period (November 1, 2000, to October 31, 2005) at John Dempsey Hospital was performed by using a prospectively collected, neonatal database. Data were collected on demographic features (gestational age, birth weight, and gender) and prenatal/postnatal steroid use. In the physical examination at discharge, all infants were checked for infantile hemangiomas, and the size and number of lesions were noted. The highest stage of retinopathy of prematurity diagnosed at any time before discharge also was noted. Analyses were performed to identify associated risk factors.

RESULTS

Of 406 neonates admitted with birth weights of </=1250 g, 351 (86.4%) survived. Of the survivors, 49 (13.9%) had infantile hemangiomas at discharge. Infantile hemangiomas were present for 16.8% of neonates with retinopathy of prematurity, compared with 6.7% of those without retinopathy of prematurity. Multiple infantile hemangiomas were present in 14 (28.5%) of 49 neonates, whereas 18 (42.8%) of 42 neonates had infantile hemangiomas that were >/=1 cm in size. Univariate analyses showed lower gestational age, lower birth weight, and postnatal steroid use to be predictors of retinopathy of prematurity, whereas prenatal steroid use, race, and gender were not significantly related. In multivariate logistic regression analyses controlling for gestational age and postnatal steroid use, infantile hemangiomas were found to be independently associated with any stage of retinopathy of prematurity. Neither the number nor the size of infantile hemangiomas showed any association with the severity of retinopathy of prematurity.

CONCLUSIONS

Infantile hemangiomas are associated with the development of retinopathy of prematurity in infants weighing </=1250 g. The biological significance of this association may yield clues to the management of retinopathy of prematurity.

Estrogen and hypoxia regulate estrogen receptor alpha in a synergistic manner

Hypoxia activates and degrades estrogen receptor alpha (ERalpha) in human breast cancer cells, which may play an important role in the development and progression of breast cancer. In this study, the synergistic effects of estrogen (E(2)) and hypoxia on ERalpha-mediated transactivation and ERalpha degradation were investigated. ERalpha-mediated transcriptional activity was synergistically increased by E(2) and hypoxia, as determined by the transient expression of ERalpha and ER-responsive reporter plasmids in HEK 293 cells. Twenty hours of E(2) and hypoxia treatment synergistically induced degradation of ERalpha by 95% via a proteasome-dependent pathway in MCF-7 cells. These results provide evidence that hypoxia may stimulate yet unknown factor(s), which can further stimulate ERalpha signal transduction pathways.

Hypoxia, hormones, and endothelial progenitor cells in hemangioma

Hemangiomas are the most common tumor of infancy, and although the natural history of these lesions is well described, their etiology remains unknown. One current theory attributes the development of hemangiomas to placentally-derived cells; however, conclusive evidence to support a placental origin is lacking. While placental tissue and hemangiomas do share molecular similarities, it is possible that these parallels are the result of analogous responses of endothelial cells and vascular progenitors to similar environmental cues. Specifically, both tissue types consist of actively proliferating cells that exist within a low oxygen, high estrogen environment. The hypoxic environment leads to an upregulation of hypoxia inducible factor-1alpha (HIF-1alpha) responsive chemokines such as stromal cell derived factor-1alpha (SDF-1alpha) and vascular endothelial growth factor (VEGF), both of which are known to promote the recruitment and proliferation of endothelial progenitor cells. Increased hormone levels in the postpartum period further potentiate the growth of these lesions. In this model, increased stabilization of HIF-1 in concert with increased levels of estrogen create a milieu that promotes new blood vessel development, ultimately contributing to the pathogenesis of infantile hemangiomas.