Evolution of hemangioma endothelium

Beyond Traditional Medicine: EVs-Loaded Hydrogels as a Game Changer in Disease Therapeutics

Extracellular vesicles (EVs), especially exosomes, have shown great therapeutic potential in the treatment of diseases, as they can target cells or tissues. However, the therapeutic effect of EVs is limited due to the susceptibility of EVs to immune system clearance during transport in vivo. Hydrogels have become an ideal delivery platform for EVs due to their good biocompatibility and porous structure. This article reviews the preparation and application of EVs-loaded hydrogels as a cell-free therapy strategy in the treatment of diseases. The article also discusses the challenges and future outlook of EVs-loaded hydrogels.

Liposomal propranolol for treatment of infantile hemangioma at compounding pharmacies

Infantile hemangiomas (IH) are common benign soft tissue tumors, frequently affecting infants. While Propranolol Hydrochloride (Pro HCl) has emerged as a promising treatment for IH, its topical application remains challenging due to the need for stable and efficacious carriers. This study investigates the potential of preformulated liposomes as carriers for topical delivery of Pro HCl for the treatment of IH in compounding pharmacies. Liposomes loaded with Pro HCl were prepared using active pharmaceutical ingredient or commercially available propranolol tablets and various dilution media, including Water for Injection (WFI), Dextrose 5%, and NaCl 0.9%. The physicochemical properties of the liposomal formulations (Pro HCl content, encapsulation efficiency, loading capacity, and colloidal stability) were assessed over a 90-day storage at 4 °C. In vitro release kinetics and transdermal permeation of Pro HCl from liposomes were also evaluated. Liposome properties were influenced by the dilution medium. Pro HCl content remained stable in liposomes encapsulating API (Lipo-Pro), regardless of the dilution medium. Lipo-Pro showed sustained drug release over time, suggesting its potential for maintaining therapeutic levels. Pro HCl exhibited enhanced transdermal permeability from Lipo-Pro compared to aqueous solution, indicating its potential for topical IH treatment. Preformulated liposomes offer a stable and effective carrier for Pro HCl, potentially suitable for extemporaneous preparations in compounding pharmacies. Their enhanced transdermal permeability presents a promising alternative for topical IH treatment. This study provides valuable insights into the development of innovative and effective drug delivery strategies for managing IH, with future research focusing on in vivo applications and therapeutic potential.

The Mechanism of Oxymatrine Targeting miR-27a-3p/PPAR-γ Signaling Pathway through m6A Modification to Regulate the Influence on Hemangioma Stem Cells on Propranolol Resistance

OBJECTIVE

The proliferation and migration of hemangioma stem cells (HemSCs) induced apoptosis and adipose differentiation as well as increased the sensitivity of HemSCs to propranolol (PPNL). MiR-27a-3p negatively controlled the peroxisome-proliferator-activated receptor γ (PPAR-γ) level, counteracting the effect of PPAR-γ on HemSC progression and PPNL resistance. OMT accelerated HemSC progression and adipocyte differentiation via modulating the miR-27a-3p/PPAR-γ axis, inhibiting HemSC resistance to PPNL. In tumor-forming experiments, OMT exhibited a dose-dependent inhibitory effect on the volume of IH PPNL-resistant tumors, which was partially dependent on the regulation of m6A methylation transfer enzyme METTL3 and the miR-27a-3p/PPAR-γ axis, thereby inducing apoptosis.

CONCLUSIONS

We conclude that OMT regulates IH and influences PPNL resistance via targeting the miR-27a-3p/PPAR-γ signaling pathway through m6A modification.

Mechanism of the HIF-1α/VEGF/VEGFR-2 pathway in the proliferation and apoptosis of human haemangioma endothelial cells

Haemangiomas (HAs) are prevalent vascular endothelial cell tumours. With respect to the possible involvement of HIF-1α in HAs, we have explored its role in haemangioma endothelial cell (HemEC) proliferation and apoptosis. shRNA HIF-1α and pcDNA3.1 HIF-α were manipulated into HemECs. HIF-α, VEGF, and VEGFR-2 mRNA and protein levels were assessed by qRT-PCR and Western blotting. Cell proliferation and viability, cell cycle and apoptosis, migration and invasion, and ability to form tubular structures were assessed by colony formation assay, CCK-8, flow cytometry, Transwell assay, and tube formation assay. Cell cycle-related protein levels, and VEGF and VEGFR-2 protein interaction were detected by Western blot and immunoprecipitation assays. An Haemangioma nude mouse model was established by subcutaneous injection of HemECs. Ki67 expression was determined by immunohistochemical staining. HIF-1α silencing suppressed HemEC neoplastic behaviour and promoted apoptosis. HIF-1α facilitated VEGF/VEGFR-2 expression and the VEGF had interacted with VEGFR-2 at protein - protein level. HIF-1α silencing arrested HemECs at G0/G1 phase, diminished Cyclin D1 protein level, and elevated p53 protein level. VEGF overexpression partially abrogated the effects of HIF-1α knockdown on inhibiting HemEC malignant behaviours. Inhibiting HIF-1α in nude mice with HAs repressed tumour growth and Ki67-positive cells. Briefly, HIF-1α regulated HemEC cell cycle through VEGF/VEGFR-2, thus promoting cell proliferation and inhibiting apoptosis.

Can Propranolol Affect Platelet Indices in Infantile Hemangioma?

INTRODUCTION

Propranolol, a nonselective beta-blocker used in the medical treatment of infantile Hemangioma (IH), has been shown to decrease the levels of vascular endothelial growth factor and reduce angiogenesis with its antiproliferative and antiangiogenetic effects.

MATERIALS AND METHODS

It has been reported that the storage, transport, and secretion of vascular endothelial growth factor (VEGF) are associated with platelet volume indices (PVI). We aimed to investigate the effect of propranolol on PVI in IH patients. Propranolol treatment was started on 22 IH patients. Platelets, mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit values in the follow-ups at months 0, 1, and 2 were compared between 22 patients who received treatment and 25 patients who did not.

RESULTS

While a statistically significant difference between months 0, 1, and 2 in PDW and MPV values was detected in the treated group, it was not detected in the untreated group. Taking into consideration that VEGF levels were higher at the beginning of the treatment in the pathophysiology of the disease, it was thought that the decrease in VEGF levels by propranolol may have led to a decrease in MPV and PDW levels in the treatment group.

CONCLUSION

Consequently, in IH cases, propranolol response follow-up can be evaluated with PVIs, especially MPV and PDW, and it may facilitate clinicians' monitoring of the disease after propranolol administration.

Case report: Left atrial myxoma with morphology of cavernous hemangioma supplied by the right coronary artery

Here, we report an unusual case of left atrial myxoma presented with morphology of cavernous hemangioma supplied by the right coronary artery. Surgical resection of the left atrium myxoma was performed, and the patient experienced an uneventful recovery during hospitalization.

Benign and low-grade superficial endothelial cell neoplasms in the molecular era

Vascular tumors are the most common mesenchymal neoplasms of the skin and subcutis, and they encompass a heterogeneous group with diverse clinical, histological, and molecular features, as well as biological behavior. Over the past two decades, molecular studies have enabled the identification of pathogenic recurrent genetic alterations that can be used as additional data points to support the correct classification of these lesions. The purpose of this review is to summarize the available data related to superficially located benign and low-grade vascular neoplasms and to highlight recent molecular advances with the role of surrogate immunohistochemistry to target pathogenic proteins as diagnostic biomarkers.

Early redox homeostasis disruption contributes to the differential cytotoxicity of imiquimod on transformed and normal endothelial cells

The off-label use of imiquimod (IQ) for hemangioma treatment has shown clinical benefits. We have previously reported a selective direct IQ-cytotoxic effect on transformed (H5V) vs. normal (1G11) endothelial cells (EC). In the present study, we investigated the mechanism underlying this selective cytotoxicity in terms of TLR7/8 receptor expression, NF-κB signalling and time-dependent modifications of oxidative stress parameters (ROS: reactive oxygen species, catalase and superoxide dismutase activities, GSH/GSSG and lipid peroxidation). TLR7/8 level was extremely low in both cell lines, and IQ did not upregulate TLR7/8 expression or activate NF-κB signalling. IQ significantly induced ROS in H5V after 2 h and strongly affected antioxidant defenses. After 12 h, enzyme activities were restored to baseline levels but a robust drop in GSH/GSSG persisted together with increased lipid peroxidation levels and a marked mitochondrial dysfunction. Although in normal IQ-treated EC some oxidative stress parameters were affected after 4 h, mitochondrial health and GSH/GSSG ratio remained notably unaffected after 12 h. Therefore, the early alterations (0-2 h) in transformed EC breached redox homeostasis as strongly as to enhance their susceptibility to IQ. This interesting facet of IQ as redox disruptor could broaden its therapeutic potential for other skin malignancies, alone or in adjuvant schemes.

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

Background

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

Methods

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

Results

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

Conclusions

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

NOGOB receptor-mediated RAS signaling pathway is a target for suppressing proliferating hemangioma

Infantile hemangioma is a vascular tumor characterized by the rapid growth of disorganized blood vessels followed by slow spontaneous involution. The underlying molecular mechanisms that regulate hemangioma proliferation and involution still are not well elucidated. Our previous studies reported that NOGOB receptor (NGBR), a transmembrane protein, is required for the translocation of prenylated RAS from the cytosol to the plasma membrane and promotes RAS activation. Here, we show that NGBR was highly expressed in the proliferating phase of infantile hemangioma, but its expression decreased in the involuting phase, suggesting that NGBR may have been involved in regulating the growth of proliferating hemangioma. Moreover, we demonstrate that NGBR knockdown in hemangioma stem cells (HemSCs) attenuated growth factor-stimulated RAS activation and diminished the migration and proliferation of HemSCs, which is consistent with the effects of RAS knockdown in HemSCs. In vivo differentiation assay further shows that NGBR knockdown inhibited blood vessel formation and adipocyte differentiation of HemSCs in immunodeficient mice. Our data suggest that NGBR served as a RAS modulator in controlling the growth and differentiation of HemSCs.

A new clinical and dermoscopic monitoring of infantile hemangiomas treated with oral propranolol

Oral propranolol (OP) demonstrated high efficacy and safety profile for treatment of critical infantile hemangiomas (IHs). Our aim was to assess the morphologic changes of IHs with standard and high-resolution video dermoscopy (HRVD) from baseline to 18 months either in presence or absence of OP therapy; to investigate if extended anamnestic perinatal data and clinical-dermoscopic characteristics of the IHs can correlate with therapeutic outcome. We enrolled 94 patients (112 IHs): 58 were treated with OP, 35 (42 IHs) for 6 months (group 1), and 23 (25 IHs) for 12-months (group 2); 36 (45 IHs) were followed-up. Clinical-dermoscopic examinations were performed every 3 months during therapy and follow-up. Among 67 treated IHs, superficial and deep IHs with homogenous clinical-dermoscopic aspect developed after the 2 weeks of life achieved the better outcome, stable at 9-month follow-up, independently form treatment duration. Under HRVD, glomerular vessels were prevalent at baseline; corckscrew, comma, and linear-irregular vessels were the prevalent pattern at 1, 3, and 6 months of therapy, respectively. At 12-month follow-up, adequate healing was achieved by 96% of IHs in group 2 and by 78% in group 1, showing dotted vessels. Persistent IHs displayed a reticulated aspect and linear irregular vessels, while arborizing vessels characterized relapsed IHs. A 12-month OP therapy can be considered for newborns presenting with nonhomogenous mixed IHs >3 cm on the perineal area/lower extremities. In conclusion, HRVD allows a real time monitoring of vascular changes in IHs treated with OP and can support physicians in identifying relapses before they become clinically evident.

Therapeutic effect of high-frequency ultrasound-assisted dye laser on hemangioma and its influence on serum HIF-1α in patients

Background

To analyze the therapeutic effect of high‐frequency ultrasound (HFU)‐assisted dye laser on hemangioma patients and changes in serum hypoxia‐inducible factor‐1α (HIF‐1α).

Methods

A total of 20 patients diagnosed with hemangioma in our hospital from January 2013 to March 2018 were selected, including 12 males and eight females. All patients were treated with HFU‐assisted dye laser. The site and type of hemangioma and age distribution of patients were collected, and changes in data and area of hemangioma and serum HIF‐1α before and after treatment were analyzed.

Results

The vascular condition of hemangioma in all patients was significantly improved at 7, 14, and 30 days after treatment. Gray‐scale ultrasound displayed that the tumor area was reduced by more than 50%. After treatment, the serum HIF‐1α level declined obviously after treatment compared with that before treatment, showing a statistically significant difference (P < 0.05).

Conclusion

HFU‐assisted dye laser can effectively reduce the tumor area, decrease the serum HIF‐1α level, and improve the prognosis in the treatment of hemangioma.

Divergent roles of Plexin D1 in cancer

Plexin D1 belongs to a family of transmembrane proteins called plexins. It was characterized as a receptor for semaphorins and is known to be essential for axonal guidance and vascular patterning. Mutations in Plexin D1 have been implicated in pathologic conditions such as truncus arteriosus and Möbius syndrome. Emerging data show that expression of Plexin D1 is deregulated in several cancers; it can support tumor development by aiding in tumor metastasis and EMT; and conversely, it can act as a dependence receptor and stimulate cell death in the absence of its canonical ligand, semaphorin 3E. The role of Plexin D1 in tumor development and progression is thereby garnering research interest for its potential as a biomarker and as a therapeutic target. In this review, we describe its discovery, structure, mutations, role(s) in cancer, and therapeutic potential.

Insulin-like growth factor 2 promotes the adipogenesis of hemangioma-derived stem cells

Infantile hemangioma (IH), which is the most common tumor in infants, is characterized by rapid proliferation followed by spontaneous regression into fibro-fatty tissue in childhood. However, its specific mechanism has not been clarified. Our previous studies showed that insulin-like growth factor 2 (IGF-2) is increased in the proliferative phase of IH, which is deemed to form from hemangioma-derived stem cells (HemSC). However, it remains unclear whether IGF-2 can promote the adipogenic differentiation of HemSCs and the signaling mechanisms involved require further elucidation. In the present study, CCK-8 assay was used to detect the effect of different concentrations of IGF-2 on the proliferation of HemSCs. Immunohistochemistry was applied to observe the expression of IGF-2 and its receptors in cells. Oil red o-staining of adipogenesis was conducted after cells recevied no treatment or were induced with IGF-2 or IGF-2 plus OSI-906 for 10 days. Cells were cultured in EGM-2/FBS-10% alone or containing IGF-2, IGF-2 plus OSI-906 or IGF-2 plus LY294002 and the protein expression of C/EBPα, C/EBPβ, PPARγ, adiponectin, p-AKT and total AKT was determined using western blot analysis. In another experiment, cells were treated with 25, 50 or 100 μM propranolol, or vehicle. C/EBPα, C/EBPβ, PPARγ and IGF-2 were analyzed using western blot analysis or reverse transcription-quantitative polymerase chain reaction. Results indicated that IGF-2 significantly promoted the cell proliferation and lipid accumulation of HemSCs. The expression of phosphorylated AKT (p-AKT), C/EBPα, C/EBPβ, PPARγ and adiponectin was increased in IGF-2-treated HemSCs culture, whereas these changes were repressed by the inhibition of either the IGF-1 receptor (IGF-1R) or phosphoinositide 3-kinase (PI3K). Our previous research showed that propranolol accelerated adipogenesis in HemSCs and induced the upregulation of IGF-2. The results of the present study indicate that IGF-2 is able to accelerate adipogenesis, and the propranolol-induced promotion of dysregulated adipogenesis may be mediated by the IGF-2 via IGF-1R and PI3K pathways.

miR-199a-5p inhibits proliferation and induces apoptosis in hemangioma cells through targeting HIF1A

MicroRNAs (miRNAs) exhibit a crucial role in the regulation of angiogenesis and tumor progression, of which miR-199a-5p (miR-199a) has been reported to function as a tumor suppressor in multiple malignancies. However, the precise mechanisms underlying miR-199a in hemangiomas (HAs) remain elusive. In this study, we found that miR-199a had low expression level, while proliferating cell nuclear antigen (PCNA) had high expression level in proliferating-phase HAs compared with the involuting-phase HAs and normal tissues. Spearman correlation analysis revealed the negative correlation of miR-199a with PCNA expression in proliferating-phase HAs. In vitro experiments showed that restoration of miR-199a suppressed cell proliferation capability and induced cell apoptosis in HA-derived endothelial cells (HDEC) and CRL-2586 EOMA cells, followed with decreased PCNA expression and increased cleaved caspase-3 expression, but miR-199a inhibitor reversed these effects. Furthermore, HIF1A was identified as a target of miR-199a and had negative correlation with miR-199a expression in proliferating-phase HAs. Overexpression of HIF1A attenuated the anti-proliferation effect of miR-199a mimic in HAs cells. Taken together, our findings demonstrate that miR-199a may inhibit proliferation and induce apoptosis in HAs cells via targeting HIF1A and provide a potential therapeutic target for HAs.

Arrested Development: Infantile Hemangioma and the Stem Cell Teratogenic Hypothesis

BACKGROUND

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

OBJECTIVES

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

DISCUSSION

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

CONCLUSIONS

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

Infant skin maturation: Preliminary outcomes for color and biomechanical properties

BACKGROUND

Newborn infant skin changes after birth but studies have focused on the epidermal barrier. Dermal properties are relevant for care, but literature on postnatal changes is sparse. We further characterized skin maturational changes in lightness, color and response to biomechanical stress.

METHODS

Normal skin sites from subsets of participants in a trial on the progression and stage of infantile hemangiomas were retrospectively examined. Standardized photographs were analyzed as L*, a*, and b* images. Biomechanics were measured with the Cutometer^® .

RESULTS

Color changed significantly with increasing age. Skin was darker and redder at 2.0 vs. 5.4, 8.5 and 12.8 months. Yellow color increased, with higher values at 12.8 vs. 2.0, 3.5 and 5.4 months. Chest tissue was consistently more elastic than arm and face sites, with significantly higher elasticity for the youngest and oldest age groups. Biological elasticity, elastic recovery, and total recovery were significantly greater for the oldest subjects. Viscoelasticity and elastic deformation were lower at 5.5 vs. 8.8 and 17.6 months. Arm viscoelastic creep was highest at 2.8 months.

CONCLUSION

Skin maturation continues into year two. Increasing elasticity and decreasing viscoelasticity may reflect increased collagen structure/function. The findings have implications for prevention of skin injury associated with mechanical forces.

Infantile Hemangioma Originates From A Dysregulated But Not Fully Transformed Multipotent Stem Cell

Infantile hemangioma (IH) is the most common tumor of infancy. Its cellular origin and biological signals for uncontrolled growth are poorly understood, and specific pharmacological treatment is unavailable. To understand the process of hemangioma-genesis we characterized the progenitor hemangioma-derived stem cell (HemSC) and its lineage and non-lineage derivatives. For this purpose we performed a high-throughput (HT) phenotypic and gene expression analysis of HemSCs, and analyzed HemSC-derived tumorspheres. We found that IH is characterized by high expression of genes involved in vasculogenesis, angiogenesis, tumorigenesis and associated signaling pathways. These results show that IH derives from a dysregulated stem cell that remains in an immature, arrested stage of development. The potential biomarkers we identified can afford the development of diagnostic tools and precision-medicine therapies to "rewire" or redirect cellular transitions at an early stage, such as signaling pathways or immune response modifiers.

Comparative Analysis of the Extracellular Matrix Composition in Proliferating and Involuted Infantile Hemangiomas

Background

Changes in the composition of the extracellular matrix (ECM) occur between the proliferating and involuted phases of infantile hemangiomas (IH), and are associated with angiogenic growth. We examined the composition of the ECM in proliferating and involuted IHs and assessed correlations between the composition of the ECM and whether the IH was in the proliferating or the involuted phase.

Methods

We evaluated IH samples from a cohort of patients who had five proliferating IHs and five involuted IHs. The following ECM molecules were analyzed using enzyme-linked immunosorbent assays and immunohistochemistry: laminin, fibronectin, collagen type I, collagen type II, and collagen type III.

Results

The involuted IHs had higher levels of deposition of collagen type III than the proliferating IHs. The median values (interquartile ranges) were 1.135 (0.946-1.486) and 1.008 (0.780-1.166) (P=0.019), respectively. The level of laminin was higher in involuted IHs than in proliferating IHs, with median values (interquartile ranges) of 3.191 (2.945-3.191) and 2.479 (1.699-3.284) (P=0.047), respectively. Abundant collagen type III staining was found in involuted IHs. Laminin α4 chain staining was clearly present within the basement membrane adjacent to the blood vessels, and was significantly more intense in involuted IHs than in proliferative IHs.

Conclusions

Involuted hemangiomas showed extensive deposition of collagen III and laminin, suggesting that differences in the composition of the ECM reflect stages of the development of IHs. This pattern may be due to the rapid senescence of IHs.

Mechanisms of propranolol action in infantile hemangioma

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

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.

Identification of serum regression signs in infantile hemangioma

Vessel proliferation underlies a number of serious pathological conditions. Infantile Hemangioma (IH) is a low-aggressive vascular tumor, interesting as an in vivo model of spontaneous tumor regression. Identifying mechanisms underlying IH spontaneous regression may then help to elucidate vessel-growth control, strongly deregulated in other serious conditions such as sarcoma, melanoma, diabetic retinopathy. The present study was aimed at identifying early regression indicators within hematological parameters. Thirty-four blood samples were collected from IH diagnosed babies (20-months median age), spontaneously regressing with age. Nineteen serum standard blood-tests were carried out using diagnostic reagents; in addition, serum-expression of 27 cytokine/chemokines was measured. Samples were divided in three age-groups, namely ≤12, 13 to 24 and >24 months-age, respectively. Red-cells count, Hemoglobin, Hematocrit, Neutrophils, Lymphocytes, MCP-1 and MIP-1beta were significantly different in the three age-groups, according to one-way ANOVA analysis. The same parameters showed a significant Pearson-correlation with age, supporting the direct link of age with IH-regression. ROC analysis showed that red-cells count, Hemoglobin, Hematocrit, MCP-1 and MIP-1beta levels significantly discriminate IH in the proliferating-phase from IH in the regressing-phase. Such data indicate for the first time that standard hematological tests and cytokine serum-expression values may effectively discriminate proliferating- from regressing-IH, unrevealing early regression signs, and demonstrate that standard blood-tests may have novel unsuspected diagnostic/prognostic relevance in altered vessel-growth conditions.

Propranolol inhibits growth of hemangioma-initiating cells but does not induce apoptosis

BACKGROUND

Infantile hemangioma (IH) is the most common tumor of infancy. The first-line therapy for IH is propranolol, a nonselective β-adrenergic receptor antagonist. However, mechanisms for the therapeutic effect of propranolol and regrowth of IH following cessation of treatment in some cases are not clear. We have recently shown that IH arises from multipotent stem cells. Whether IH stem cells are responsive to propranolol and are selectively targeted is unknown, and this is the focus of this study.

METHODS

IH stem cells were exposed to propranolol and were assayed for cellular and molecular alterations. We used endothelial cells (ECs) as controls and bone marrow-derived mesenchymal progenitor cells (bm-MPCs) as normal stem/progenitor counterparts to determine selectivity.

RESULTS

Our results show that propranolol significantly reduced IH stem cell growth but failed to induce caspase-3 activation. Normal bm-MPCs and mature ECs showed maintained or increased caspase-3 activation and significantly reduced cyclin-D1 levels. We further show that IH stem cells may escape apoptosis by inducing antiapoptotic pathways.

CONCLUSION

This study reveals that propranolol does not induce apoptosis in IH stem cells, which is in contrast with the result for ECs. Escape from apoptosis in IH stem cells may involve induction of antiapoptotic pathways.

Elevated T-box 2 in infantile hemangioma stem cells maintains an adipogenic differentiation-competent state

Infantile hemangioma is a benign vascular tumor that affects 4 to 10% of neonates. A unique feature of hemangiomas is the natural lifecycle, whereby the tumor rapidly grows and then spontaneously regresses to a fibrofatty residuum. We have shown that hemangiomas are derived from mutlipotential stem cells (hemSCs), which differentiate into endothelial cells during the early proliferating phase and into adipocytes during the later involutive phase. T-box 2 (TBX2) is a transcription factor involved in controlling cell-fate decisions, and is highly expressed during the proliferating phase of hemangioma development. We hypothesize that TBX2 expression would be high in hemSCs derived from human hemangiomas and inhibiting TBX2 would result in changes in hemSC differentiation potential. To test our hypothesis, we analyzed hemSCs for TBX2 mRNA and protein expression. We then used RNA interference and TBX2 overexpression to determine the effect of altering TBX2 levels on hemSC growth and differentiation. Our studies show that TBX2 is highly expressed in hemSCs compared with a panel of normal stem/progenitor cells and mature vascular cells. TBX2 knockdown completely abolished adipogenic differentiation of hemSCs without significantly altering growth. Furthermore, overexpression of TBX2 led to enhanced adipogenic differentiation ability possibly through induction of C/EBPβ. From these findings, we believe that TBX2 is active in hemSCs and that TBX2 maintains adipogenic differentiation-competent state of hemSCs. These findings may be important in the development of better treatment options for hemangiomas to accelerate involution.

Gene expression analysis reveals marked differences in the transcriptome of infantile hemangioma endothelial cells compared to normal dermal microvascular endothelial cells

Background

Infantile hemangiomas are benign vascular tumors primarily found on the skin in 10% of the pediatric population. The etiology of this disease is largely unknown and while large scale genomic studies have examined the transcriptomes of infantile hemangioma tumors as a whole, no study to date has compared the global gene expression profiles of pure infantile hemangioma endothelial cells (HEMECs) to that of normal human dermal microvascular endothelial cells (HDMVECs).

Methods

To shed light on the molecular differences between these normal and aberrant dermal endothelial cell types, we performed whole genome microarray analysis on purified cultures of HEMECs and HDMVECs. We then utilized qPCR and immunohistochemistry to confirm our microarray results.

Results

Our array analysis identified 125 genes whose expression was upregulated and 104 genes whose expression was downregulated by greater than two fold in HEMECs compared to HDMVECs. Bioinformatics analysis revealed three major classifications of gene functions that were altered in HEMECs including cell adhesion, cell cycle, and arachidonic acid production. Several of these genes have been reported to be critical regulators and/or mutated in cancer, vascular tumors, and vascular malformations. We confirmed the expression of a subset of these differentially expressed genes (ANGPT2, ANTXR1, SMARCE1, RGS5, CTAG2, LTBP2, CLDN11, and KISS1) using qPCR and utilized immunohistochemistry on a panel of paraffin embedded infantile hemangioma tumor tissues to demonstrate that the cancer/testis antigen CTAG2 is highly abundant in vessel-dense proliferating infantile hemangiomas and with significantly reduced levels during tumor involution as vascular density decreases.

Conclusion

Our data reveal that the transcriptome of HEMECs is reflective of a pro-proliferative cell type with altered adhesive characteristics. Moveover, HEMECs show altered expression of many genes that are important in the progression and prognosis of metastatic cancers.

Update on infantile hemangiomas

Infantile hemangiomas are the most common tumors of infancy. The serendipitous discovery of the therapeutic efficacy of propranolol in the management of infantile hemangiomas has revolutionized the care and understanding of these lesions, and greatly improved the prognosis for a good cosmetic outcome. In addition, there has been an expansion of indications for treatment of hemangiomas, taking into account not only those hemangiomas that can cause airway compromise, amblyopia, and cardiac overload, but also those lesions that can lead to unsatisfactory cosmetic outcome or deformity after involution. Current concepts of pathogenesis of infantile hemangiomas, of segmental hemangiomas with systemic associations, of hepatic hemangiomas, and of the use of systemic and topical beta-blockers for the management of IH are all reviewed.

Elevated IGF2 prevents leptin induction and terminal adipocyte differentiation in hemangioma stem cells

Infantile hemangioma is a benign vascular tumor that exhibits a unique yet predictable lifecycle of rapid proliferation followed by spontaneous regression. Recent studies have identified that insulin-like growth factor-2 (IGF2), a fetal mitogen, is highly expressed during the proliferative phase of hemangioma growth. Since hemangiomas arise from CD133+ stem cells, high levels of IGF2 may regulate the activity of the stem cells and therefore, hemangioma growth. The aim of this study was to understand the functional significance of elevated IGF2 in hemangiomas. We show that IGF2 localizes to the CD133+ cells in hemangioma specimens. We, therefore, hypothesized that IGF2 may be regulating the plasticity of hemangioma stem cells. To test our hypothesis, we used CD133-selected cells from hemangiomas to knockdown the expression of IGF2. We found that IGF2 is a mitogen for hemangioma stem cells and prevents leptin induction and full terminal differentiation of hemangioma stem cells into adipocytes. We also show that IGF2 does not alter the initial commitment phase. These findings implicate an important role of IGF2 in expanding hemangioma stem cells and preventing terminal adipocyte differentiation.