A placental chorionic villous mesenchymal core cellular origin for infantile haemangioma

Cell Fate Regulation During the Development of Infantile Hemangioma

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

Molecular Mechanisms of Carcinogenesis in Pediatric Airways Tumors

Primary tumors of the airways in the pediatric population are very rare entities. For this reason, little is known about the pathogenesis of these neoplasms. Understanding the biology has different practical implications: for example, it could help in the differential diagnosis, have a prognostic significance, or may lead to the development of a targeted therapy. The aim of this article is to present the current knowledge about pediatric airways tumors, focusing on the molecular mechanisms that cause the onset and progression of these neoplasms. After a brief introduction of epidemiology and clinical presentation, the tumorigenesis of the most frequent pediatric airways tumors will be described: Juvenile-onset recurrent respiratory papillomatosis (JORRP), Subglottic Hemangiona (SH), Rhabdomyosarcoma (RMS), and Mucoepidermoid carcinoma (MEC).

Propranolol in the Treatment of Infantile Hemangiomas

Propranolol, as the first generation of β-blocker family, was initially introduced in the clinical application for tachycardia and hypertension in the 1960s. However, the occasional discovery of propranolol in the involution of infantile hemangiomas (IHs) brought us a new perspective. IHs are the most common infantile tumor, affecting 4–10% newborns. So far, oral propranolol is the first-line medication for IHs treatment. At the same time, local injection and topical propranolol are developing. Despite the worldwide application, the precise mechanism of propranolol of IHs has not been completely studied. In this article, we reviewed and summarized the current information on pharmacology, mechanism, efficacy, and adverse effects of propranolol. Novel design of biomaterials and bioactive molecules are needed for new treatment and ideal pathway to attain the minimal effective treatment concentration and eliminate the adverse effects.

Infantile hemangioma. Part 1: Epidemiology, pathogenesis, clinical presentation and assessment

Infantile hemangioma (IH) is the most common pediatric vascular tumor. Its pathogenesis is poorly understood but thought to represent an aberrant response of pluripotent stem cells to stimuli such as hypoxia and the renin-angiotensin-system. IH usually appears during the first few weeks of life and follows a characteristic natural trajectory of proliferation and involution. Their clinical appearance depends on their depth and distribution. Classification comprises superficial, mixed and deep IH as well as IH with minimal or arrested growth. Multifocal IHs are more likely to be associated with infantile hepatic hemangioma, and although the need for screening based on a specific number of IH has been recently debated, 5 remains the most widely acceptable cut off point. Large facial or lumbar IH warrants investigation for PHACE and LUMBAR syndrome, respectively. Complications of IH include ulceration, obstruction or functional impairment, hypothyroidism, and cosmetic sequelae. Differential diagnoses mostly consist of other vascular tumors and vascular malformations, though IH may sometimes mimic non-vascular tumors or developmental anomalies. Diagnosis is usually clinical and biopsy rarely indicated. High-frequency ultrasonography may help with the differential diagnosis, particularly with subcutaneous lesions. Referral to other specialists may be required in specific cases.

Presence of estrogen and progesterone receptors in proliferating and involuting infantile hemangiomas

BACKGROUND

Studies in the literature have demonstrated the presence of sex hormone receptors in infantile hemangiomas (IHs), but further investigation is needed to determine the role of these receptors in their proliferation and involution. To date, there are no studies in the literature that aimed to quantitatively examine the expression of sex hormone receptors throughout the different phases of hemangioma development.

OBJECTIVE

The objective of our study was to quantitatively evaluate the expression of estrogen (ER) and progesterone (PR) receptors in the proliferative and involuting phases of IHs through the use of real-time polymerase chain reaction (RT-PCR).

METHODS

Twenty IHs (10 proliferating and 10 involuting) were harvested and prepared for molecular investigation. ER receptor alpha (ERα) and beta (ERβ) and the PR expression were examined by RT-PCR and western blot.

RESULTS

RT-PCR analysis demonstrated that mRNA expression of ERα, ERβ, and PR was significantly lower in proliferating versus involuting IH. Western blot analysis revealed increased protein expression of ERα in involuting hemangiomas as compared to proliferating ones.

CONCLUSIONS

Our study demonstrates the variable expression of ER and PR receptors in proliferating and involuting hemangiomas. Further studies are needed to determine the exact role of these hormone receptors in the growth and involution of IHs.

Cell Populations Expressing Stemness-Associated Markers in Vascular Anomalies

Treatment of vascular anomalies (VAs) is mostly empirical and, in many instances unsatisfactory, as the pathogeneses of these heterogeneous conditions remain largely unknown. There is emerging evidence of the presence of cell populations expressing stemness-associated markers within many types of vascular tumors and vascular malformations. The presence of these populations in VAs is supported, in part, by the observed clinical effect of the mTOR inhibitor, sirolimus, that regulates differentiation of embryonic stem cells (ESCs). The discovery of the central role of the renin-angiotensin system (RAS) in regulating stem cells in infantile hemangioma (IH) provides a plausible explanation for its spontaneous and accelerated involution induced by β-blockers and ACE inhibitors. Recent work on targeting IH stem cells by inhibiting the transcription factor SOX18 using the stereoisomer R(+) propranolol, independent of β-adrenergic blockade, opens up exciting opportunities for novel treatment of IH without the β-adrenergic blockade-related side effects. Gene mutations have been identified in several VAs, involving mainly the PI3K/AKT/mTOR and/or the Ras/RAF/MEK/ERK pathways. Existing cancer therapies that target these pathways engenders the exciting possibility of repurposing these agents for challenging VAs, with early results demonstrating clinical efficacy. However, there are several shortcomings with this approach, including the treatment cost, side effects, emergence of treatment resistance and unknown long-term effects in young patients. The presence of populations expressing stemness-associated markers, including transcription factors involved in the generation of induced pluripotent stem cells (iPSCs), in different types of VAs, suggests the possible role of stem cell pathways in their pathogenesis. Components of the RAS are expressed by cell populations expressing stemness-associated markers in different types of VAs. The gene mutations affecting the PI3K/AKT/mTOR and/or the Ras/RAF/MEK/ERK pathways interact with different components of the RAS, which may influence cell populations expressing stemness-associated markers within VAs. The potential of targeting these populations by manipulating the RAS using repurposed, low-cost and commonly available oral medications, warrants further investigation. This review presents the accumulating evidence demonstrating the presence of stemness-associated markers in VAs, their expression of the RAS, and their interaction with gene mutations affecting the PI3K/AKT/mTOR and/or the Ras/RAF/MEK/ERK pathways, in the pathogenesis of VAs.

β-blocker therapy for infantile hemangioma

INTRODUCTION

Fifteen percent of proliferating infantile hemangioma (IH) require intervention because of the threat to function or life, ulceration, or tissue distortion. Propranolol is the mainstay treatment for problematic proliferating IH. Other β-blockers and angiotensin-converting enzyme (ACE) inhibitors have been explored as alternative treatments.

AREAS COVERED

The demonstration of a hemogenic endothelium origin of IH, with a neural crest phenotype and multi-lineage differentiation capacity, regulated by the renin-angiotensin system, underscores its programmed biologic behavior and accelerated involution induced by propranolol, other β-blockers and ACE inhibitors. We review the indications, dosing regimens, duration of treatment, efficacy and adverse effects of propranolol, and therapeutic alternatives including oral atenolol, acebutolol, nadolol, intralesional propranolol injections, topical propranolol and timolol, and oral captopril.

EXPERT OPINION

Improved understanding of the biology of IH provides insights into the mechanism of action underscoring its accelerated involution induced by propranolol, other β-blockers and ACE inhibitors. More research is required to understand the optimal dosing and duration, efficacy and safety of these alternative therapies. Recent demonstration of propranolol's actions mediated by non-β-adrenergic isomer R-propranolol on stem cells, offers an immense opportunity to harness the efficacy of β-blockers to induce accelerated involution of IH, while mitigating their β-adrenergic receptor-mediated adverse effects.

Infantile hemangiomas: what have we learned from propranolol?

PURPOSE OF REVIEW

Infantile hemangiomas are the most common vascular tumor of infancy. Treatment of infantile hemangiomas was revolutionized when propranolol, a nonselective β-blocker, was reported to be effective therapy. In this review, we highlight the lessons learned using propranolol to treat infantile hemangiomas. We also describe the ongoing effort to understand the mechanism of action of propranolol.

RECENT FINDINGS

Although the pathogenesis of infantile hemangiomas is not fully understood, maternal hypoxic stress and embolization of placental tissue are suggested to be critical components in their development. The mechanism of action of propranolol remains unclear, however various molecular mechanisms are detailed in this review. Propranolol treatment remains a well tolerated therapy, with low risk of adverse events or long-term neurocognitive effects. Dosing recommendations and optimal treatment duration vary among studies, and should be altered in patients with certain medical conditions such as Posterior fossa anomalies, Hemangioma, Arterial lesions, Cardiac abnormalities/coarctation of the aorta, Eye anomalies (PHACE) syndrome.

SUMMARY

Propranolol is a well tolerated and effective treatment for infantile hemangiomas. The efficacy of propranolol for infantile hemangiomas is clear, however questions pertaining to mechanism of action, pretreatment risk stratification, and optimal dosing remain unanswered. The guidelines for managing infantile hemangiomas with propranolol will continue to adapt as research catches up to clinical experience.

Zika-virus-infected human full-term placental explants display pro-inflammatory responses and undergo apoptosis

Zika virus (ZIKV) is a flavivirus that has been highly correlated with the development of neurological disorders and other malformations in newborns and stillborn fetuses after congenital infection. This association is supported by the presence of ZIKV in the fetal brain and amniotic fluid, and findings suggest that infection of the placental barrier is a critical step for fetal ZIKV infection in utero. Therefore, relevant models to investigate the interaction between ZIKV and placental tissues are essential for understanding the pathogenesis of Zika syndrome. In this report, we demonstrate that explant tissue from full-term human placentas sustains a productive ZIKV infection, though the results depend on the strain. Viral infection was found to be associated with pro-inflammatory cytokine expression and apoptosis of the infected tissue, and these findings confirm that placental explants are targets of ZIKV replication. We propose that human placental explants are useful as a model for studying ZIKV infection ex vivo.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Infantile hemangioma: pathogenesis and mechanisms of action of propranolol

Infantile hemangioma (IH) is the most common benign tumor of childhood, with a prevalence of 4 % to 10 %. It is characterized by a proliferative rapid growth phase, which starts after a few weeks of life, followed by a slow regression phase. In IH cases that are potentially disfiguring or life-threatening (10 % to 15 % of all cases), systemic therapy should be promptly initiated. Data source The present study reviews published scientific articles available in reliable electronic databases. Selected were all studies that evaluated the pathogenesis of IH and the mechanisms of action of propranolol. Conclusions The pathogenesis of IH has not been fully elucidated. Studies show that, in the proliferative phase of IH, there is an imbalance of angiogenic factors and an increase in the levels of vascular endothelial growth factor and matrix metalloproteinases 2 and 9. In the regression phase, the levels of these factors decrease, whereas those of antiangiogenic factors, including tissue inhibitors of matrix metalloproteinases, increase. Since 2008, propranolol has become the drug of choice in the treatment of IH, targeting vascular tone, angiogenesis, and apoptosis. Current insights into the pathogenesis of IH allow for the development of new therapeutic strategies.

The expression of renin-angiotensin-aldosterone axis components in infantile hemangioma tissue and the impact of propranolol treatment

BackgroundPropranolol's mechanism of action for controlling infantile hemangioma (IH) remains unclear. We hypothesize that this nonselective beta antagonist downregulates renin-angiotensin-aldosterone (RAA) axis components, preventing angiogenic substrate induction of IH.MethodsIH tissue and serum were collected from children with propranolol-treated or -untreated IH during surgery. Normal skin and serum from demographically matched children were used as controls. Real-time PCR and western blot quantified RAA components in proliferative (n=10), involuting (n=10), propranolol-treated (n=12) IH, and normal specimens (n=11). Serum was analyzed by enzyme-linked immunosorbent assay (ELISA).ResultsThere were significantly greater messenger RNA (mRNA) levels of angiotensinogen (AGT) in proliferating IH, but not in involuting or treated IH, when compared with controls (P<0.05). Angiotensin-converting enzyme (ACE) and angiotensin II receptor 1 (AGTR1) mRNA expression was higher in all IH specimens when comparedwith controls (P<0.05). ACE and AGTR1 protein expression was greater in proliferating IH tissue compared with that in controls and in involuting and treated IH tissue (P<0.05). ELISA showed no significant difference in ACE serum levels but did show a significant reduction in renin in involuting compared with proliferating IH (P<0.05).ConclusionsThe protein and mRNA expression of several RAA pathway constituents is elevated in IH tissue when compared with that in normal tissue. The action of propranolol on IH may be the result of reductions in ACE and AGTR1.

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.

Elevated Serum Levels of Alpha-Fetoprotein in Patients with Infantile Hemangioma Are Not Derived from within the Tumor

Aims

The embryonic-like stem cell origin of infantile hemangioma (IH) and the observed elevated serum levels of alpha-fetoprotein (AFP) in patients with hepatic IH led us to investigate if this tumor was the source of AFP.

Materials and methods

We measured serial serum levels of AFP in patients with problematic proliferating IH treated with surgical excision or propranolol treatment. We also investigated the expression of AFP in extrahepatic IH samples using immunohistochemical staining, mass spectrometry, NanoString gene expression analysis, and in situ hybridization.

Results

Serum levels of AFP normalized following surgical excision or propranolol treatment. Multiple regression analysis for curve fittings revealed a different curve compared to reported normal values in the general populations. AFP was not detected in any of the IH samples examined at either the transcriptional or translational levels.

Conclusion

This study demonstrates the association of proliferating IH with elevated serum levels of AFP, which normalized following surgical excision or propranolol treatment. We have shown that IH is not the direct source of AFP. An interaction between the primitive mesoderm-derived IH and the endogenous endodermal tissues, such as the liver, via an intermediary, may explain the elevated serum levels of AFP in infants with extrahepatic IH.

PHACE syndrome--clinical features, aetiology and management

PHACE syndrome comprises a spectrum of anomalies including posterior fossa malformations, haemangioma, arterial anomalies, cardiac defects and eye anomalies. PHACE should be considered in any patient with a large facial segmental infantile haemangioma (IH), and multidisciplinary management is crucial. Low-dose propranolol is effectively for the treatment of IH associated with PHACE syndrome. Recent evidence suggests IH is comprised of mesoderm-derived haemogenic endothelium.

CONCLUSION

The embryonic developmental anomaly nature of IH provides an insight into the origin of PHACE syndrome.

Characterisation of lymphocyte subpopulations in infantile haemangioma

Aims

Interstitial CD45+ cells and T lymphocytes have previously been demonstrated within infantile haemangioma (IH). This study investigated the expression of B and T lymphocyte markers by the CD45+ population, and the expression of Thy-1, a marker of thymocyte progenitors, which have the ability to give rise to both B and T cells.

Methods

Immunohistochemical (IHC) staining was performed on proliferating and involuted IHs for the expression of CD45, CD3, CD20, CD79a, Thy-1 and CD34. The presence of mRNA corresponding to CD45, CD3G, CD20 and Thy-1 was confirmed by reverse transcriptase-polymerase chain reaction in snap-frozen IH tissues. Cell counting of 3,3-diaminobenzidine IHC-stained slides was performed on CD45+ only cells and dually stained CD45+/CD3+ cells or CD45+/CD20+ cells and analysed statistically. In situ hybridisation and mass spectrometry were also performed to confirm the presence and abundance of Thy-1, respectively.

Results

IHC staining showed a subpopulation of CD45+ interstitial cells that expressed the T lymphocyte marker, CD3, and another subpopulation that expressed the B lymphocyte marker, CD20, in proliferating and diminished in involuted IHs. The abundant expression of Thy-1 on the endothelium of proliferating, but not involuted IH, was demonstrated by IHC staining and confirmed by in situ hybridisation and mass spectrometry.

Conclusions

Both B and T lymphocytes are present within the interstitium of proliferating and involuted IH. The expression of Thy-1 by the endothelium suggests that B and T cells in IH may have originated from within the lesion, rather than migrating from the peripheral circulation.

Prospective study of infantile haemangiomas: incidence, clinical characteristics and association with placental anomalies

BACKGROUND

The aetiology and exact incidence of infantile haemangiomas (IHs) are unknown. Prior studies have noted immunohistochemical and biological characteristics shared by IHs and placental tissue.

OBJECTIVES

We investigated the possible association between placental anomalies and the development of IHs, as well as the demographic characteristics and other risk factors for IHs.

PATIENTS AND METHODS

Pregnant women (n = 578) were prospectively enrolled and their offspring followed for 9 months. Placental evaluations were performed and demographic data collected on all mother-infant pairs.

RESULTS

We evaluated 594 infants: 34 haemangiomas [either IH or congenital (CH)] were identified in 29 infants, yielding an incidence of 4·5% for IH (27 infants) and 0·3% for CH (two infants). Placental anomalies were noted in almost 35% of haemangioma-related pregnancies, approximately twice the incidence noted in pregnancies with unaffected infants (P = 0·025). Other risk factors for IH included prematurity (P = 0·016) and low birth weight (P = 0·028). All IHs were present by 3 months of age, and cessation of growth had occurred in all by 9 months of age. Most occurred on the trunk. Of note, 20% of identified IHs were abortive or telangiectatic in nature, small focal lesions that did not proliferate beyond 3 months of age. Only one IH required intervention.

CONCLUSIONS

This is the first prospective American study to document the incidence of IHs in infants followed from birth to early infancy. The association with placental anomalies was statistically significant. The overall incidence mirrors prior estimates, but the need for treatment was lower than previously reported.

Heightened potency of human pluripotent stem cell lines created by transient BMP4 exposure

Human pluripotent stem cells (PSCs) show epiblast-type pluripotency that is maintained with ACTIVIN/FGF2 signaling. Here, we report the acquisition of a unique stem cell phenotype by both human ES cells (hESCs) and induced pluripotent stem cells (iPSCs) in response to transient (24-36 h) exposure to bone morphogenetic protein 4 (BMP4) plus inhibitors of ACTIVIN signaling (A83-01) and FGF2 (PD173074), followed by trypsin dissociation and recovery of colonies capable of growing on a gelatin substratum in standard medium for human PSCs at low but not high FGF2 concentrations. The self-renewing cell lines stain weakly for CDX2 and strongly for NANOG, can be propagated clonally on either Matrigel or gelatin, and are morphologically distinct from human PSC progenitors on either substratum but still meet standard in vitro criteria for pluripotency. They form well-differentiated teratomas in immune-compromised mice that secrete human chorionic gonadotropin (hCG) into the host mouse and include small areas of trophoblast-like cells. The cells have a distinct transcriptome profile from the human PSCs from which they were derived (including higher expression of NANOG, LEFTY1, and LEFTY2). In nonconditioned medium lacking FGF2, the colonies spontaneously differentiated along multiple lineages, including trophoblast. They responded to PD173074 in the absence of both FGF2 and BMP4 by conversion to trophoblast, and especially syncytiotrophoblast, whereas an A83-01/PD173074 combination favored increased expression of HLA-G, a marker of extravillous trophoblast. Together, these data suggest that the cell lines exhibit totipotent potential and that BMP4 can prime human PSCs to a self-renewing alternative state permissive for trophoblast development. The results may have implications for regulation of lineage decisions in the early embryo.

Low-dose propranolol regimen for infantile haemangioma

AIMS

Propranolol, now the preferred treatment for problematic proliferating infantile haemangioma (IH), at an empirical cardiovascular dosage of 2-3 mg/kg/day is associated with variable complication rates. A meta-analysis shows complications in 31% of patients at a mean dosage of 2.12 mg/kg/day. This study reports on the minimal dosage and duration of treatment to achieve accelerated involution and side effects using a stepwise escalation regimen.

METHODS

Consecutive patients with problematic proliferating IH treated with propranolol were identified from our vascular anomalies database. Propranolol was commenced at 0.5 mg/kg/day in two divided doses and increased to 1 mg/kg/day after 24 h. The patients were reviewed after 1 week, and the dosage was increased to 1.5 mg/kg/day. The dosage was further increased by 0.5 mg/kg/day, if necessary, to achieve accelerated involution.

RESULTS

Forty-four patients, aged 3 weeks to 11 months (mean, 3.8 months), received propranolol therapy for problematic proliferating IH. The minimal dosage required to achieve accelerated involution was 1.5-2 mg/kg/day. Treatment was maintained for an average of 9.3 months and discontinued at an average age of 14.2 months. Rebound growth occurred in the first patient of this series when propranolol was withdrawn at 7.5 months of age, requiring reinstitution of treatment. Slight rebound growth following cessation of treatment was observed in four other patients, but reinstitution of propranolol was not required. Minor complications were observed in three (6.8%) patients.

CONCLUSIONS

Propranolol at 1.5-2 mg/kg/day, administered in divided doses with stepwise escalation, is safe and effective for treating problematic proliferating IH. Treatment is continued to an average age of 14.2 months.

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.

Effects of propranolol and isoproterenol on infantile hemangioma endothelial cells in vitro

The aim of the present study was to investigate the effects of propranolol and isoproterenol on the growth curve of infantile hemangioma endothelial cells (IHECs) in vitro and determine the functions of the β-adrenergic receptor in the pathogenesis of infantile hemangioma. IHECs were divided into three groups: The control group, the propranolol group (PG) and the isoproterenol group (IG). The PG and IG were administered with high, medium and low concentrations of the corresponding drugs. The cell growth in each group was determined using the MTT assay. A high propranolol concentration resulted in the inhibition of cell growth. By comparison, isoproterenol promoted cell growth. Within a specific time-frame (72–96 h), high drug concentrations (20 μg/ml) elicited strong effects on the cells. At certain concentrations, propranolol inhibited cell growth once the proliferation stage of IHECs had been affected for a specific length of time, whereas isoproterenol yielded opposite results. The β-adrenergic receptor elicits an important effect in the pathogenesis of infantile hemangioma.

Twenty-four-hour hospitalization for patients initiating systemic propranolol therapy for infantile hemangiomas--is it indicated?

In recent years, oral propranolol has risen from serendipitous discovery to first-line, albeit off-label, therapy for infantile hemangiomas (IHs). This retrospective study explored the utility of a 24-hour hospitalization for the initiation of propranolol therapy in children with problematic IHs by evaluating the effects of systemic propranolol on hemodynamics and blood sugar levels. Thirty-one children were admitted to the hospital to begin oral propranolol at a dose of 2 mg/kg/per day. Heart rate (HR), blood pressure (BP), and blood glucose (BG) measurements were obtained at baseline and 1 to 3 hours before and after each dose of propranolol. No caregivers reported any adverse effects during the hospitalization. On average, HR decreased by 5 beats per minute (bpm) (p < 0.01) and systolic BP decreased by 4 mmHg (p < 0.01) after propranolol administration. There was no statistically significant change in diastolic BP or BG with propranolol therapy. Over the first three doses of propranolol we saw statistically significant attenuation of the effects of propranolol on HR, with HR approaching baseline values during the hospitalization (p = 0.04). We did not see statistically significant changes in BP over the course of three doses of propranolol. This study suggests that 24-hour hospitalization with hemodynamic monitoring may not be necessary for safe initiation of propranolol therapy in otherwise healthy infants. Parental education on frequent feedings to decrease the chance of hypoglycemia may be as effective as 24-hour hospitalization.

Mast cells in infantile haemangioma possess a primitive myeloid phenotype

AIMS

Recent reports on infantile haemangioma (IH) have demonstrated a primitive population of interstitial cells expressing the embryonic transcription factor, Nanog, with decreasing abundance during involution. In this report we investigated the expression of Nanog on mast cells in all three phases of IH progression.

METHODS

Paraffin-embedded sections of six proliferating, six involuting and six involuted IH lesions were used to investigate the expression of tryptase, Nanog, CD45, CD34 and GLUT-1 by immunostaining.

RESULTS

Mast cells, identified by their expression of tryptase, were located in the interstitium of IH lesions. 93%, 42% and 0% of these tryptase(+) cells also expressed Nanog, in proliferating, involuting and involuted IH, respectively.

CONCLUSIONS

The identification of an abundant population of tryptase(+)/Nanog(+) cells in IH is novel. The relative loss of Nanog expression as IH involutes may be a result of maturation and/or proliferation of these cells. This report supports the primitive nature of IH.

Infantile hemangiomas: an update

Infantile hemangioma (IH) is a common vascular tumor of infancy. Although benign, infants with IH can experience complications including ulceration, visual and airway impairment, and residual scarring and disfigurement. It is often challenging for clinicians to predict which tumors are in need of systemic treatment. However, data from various demographic and other studies have revealed further insights into this tumor. This article reviews the identification, evaluation, and management of high-risk IHs, including the indications for treatment and the use of systemic treatments such as corticosteroids, β-blockers, and vincristine.

Verrucous hemangioma expresses primitive markers

BACKGROUND

Verrucous hemangioma (VH) presents clinically as a vascular malformation but has similar histopathologic features to infantile hemangioma. This study characterized the cell population within VH.

MATERIAL AND METHODS

Paraffin-embedded sections from two male patients with VH were processed for immunohistochemistry. The expression of SMA, CD34, glucose transporter-1 (Glut-1), D2-40, brachyury, angiotensin converting enzyme (ACE), Oct-4, hemoglobin ζ chain (HBZ), Wilms tumor protein (WT-1) and CD45 was examined.

RESULTS

The lymphatic marker, D2-40, was not expressed in VH, whereas Glut-1 was widely expressed in infantile hemangioma, it was only focally expressed by the endothelium of VH. The endothelium of VH expressed the primitive markers, Oct-4, brachyury and ACE. The primitive marker, WT-1, was expressed predominantly on the pericyte layer of both VH and infantile hemangioma. However, HBZ was only expressed in infantile hemangioma. CD45, a mature hematopoetic marker, was expressed by cells within the interstitium, away from the endothelium of VH and infantile hemangioma.

DISCUSSION

The expression of the primitive markers, Oct-4, brachyury and ACE on the endothelium, and WT-1 predominantly on the pericyte layer of VH shows a primitive microvascular phenotype similar to infantile hemangioma. However, the absence of the embryonic marker, HBZ, expressed only in first trimester placenta and in proliferating infantile hemangioma, suggests a different cellular origin. HBZ could be used to distinguish between the two conditions.

Treatment of infantile haemangioma with captopril

BACKGROUND

Infantile haemangioma (IH) has recently been reported as an aberrant proliferation and differentiation of a primitive mesoderm-derived haemogenic endothelium regulated by the renin-angiotensin system (RAS), leading us to propose angiotensin converting enzyme (ACE) as a potential therapeutic target.

OBJECTIVES

To present initial results of our open-labelled observational clinical trial using captopril, an ACE inhibitor (ACEi), in the treatment of problematic proliferating IH.

METHODS

After initial screening investigations, infants with problematic IH were admitted for initiation of captopril with a 0·1 mg kg(-1) test dose orally, followed by 0·15 8-hourly over 24 h. This was then followed by dose escalation to 0·3 mg kg(-1) 8-hourly for another 24 hours. The dosage was increased to 0·5 mg kg(-1) 8-hourly 1 week later, if a noticeable involution had not already occurred. The response of IH to captopril was documented clinically and photographically before and after treatment and any side-effect was recorded.

RESULTS

Two boys and six girls aged 5-22 weeks (mean 12·9) with problematic IH were recruited with the lesions located in nasal tip (n = 1), cervicofacial (n = 3), periorbital (n = 1) and perineal (n = 2) areas, and shoulder (n = 1). Transient mild renal impairment occurred in one subject but resolved spontaneously. No other complication was observed. The IHs in all patients responded to captopril at a dosage of 1·5 mg kg(-1) daily which led to a dramatic response in three, moderate response in two, and slow response in three patients. Continued involution of IHs was observed during the follow-up period of 8-19 months (mean 15·8) in all subjects. Treatment was ceased at 14 months of age in seven patients with no rebound growth. In the remaining patient, rapid healing occurred with ongoing gradual reduction in the size and colour of a large ulcerated retroauricular lesion following 5·5 months of treatment. The lesion was excised to address its persistent distortion of the ear.

CONCLUSIONS

The response of IH to an ACEi supports a critical role for the RAS in IH and represents a paradigm shift in the understanding and treatment of this enigmatic condition.