Endothelial progenitor cells from infantile hemangioma and umbilical cord blood display unique cellular responses to endostatin

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.

Infantile hemangioma: the common and enigmatic vascular tumor

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

Apelin Receptor Can Act as a Specific Marker and Promising Therapeutic Target for Infantile Hemangioma

Infantile hemangioma (IH), the most common benign tumor in infancy, is generally sensitive to propranolol treatment. However, the challenge remains because resistance or recurrence could occur in some patients, and the mechanism or target of propranolol remains unknown. Therefore, advancement in the drug development is needed. In this study, we explored whether apelin receptor (APJ) can become a candidate target. We found that APJ is expressed only in endothelial cells of IH (HemECs) but not in other vascular anomalies, and its antagonist, ML221, can negatively regulate cellular viability and functions of HemECs. This inhibitory effect could be replicated in a murine hemangioma model. Importantly, in vitro experiments also indicated that ML221 failed to affect the proliferation or angiogenesis of normal endothelial cells or APJ-knockout HemECs. Through analysis of the phosphoantibody microarray data, ML221 was revealed to have an inhibitory effect on HemECs by suppressing the activation of mitogen-activated protein kinase/extracellular signal-regulated kinase pathway. These results verified the distinctive expression of APJ in IH and specific inhibition of HemEC activity caused by ML221. In addition, APJ was also detected in propranolol-resistant IH. Collectively, we propose that APJ can act as a specific marker and a promising therapeutic target for IH, which will facilitate further drug development.

Three-Dimensional Microtumor Formation of Infantile Hemangioma-Derived Endothelial Cells for Mechanistic Exploration and Drug Screening

Infantile hemangioma (IH) is the most prevalent type of vascular tumor in infants. The pathophysiology of IH is unknown. The tissue structure and physiology of two-dimensional cell cultures differ greatly from those in vivo, and spontaneous regression often occurs during tumor formation in nude mice and has severely limited research into the pathogenesis and development of IH. By decellularizing porcine aorta, we attempted to obtain vascular-specific extracellular matrix as the bioink for fabricating micropattern arrays of varying diameters via microcontact printing. We then constructed IH-derived CD31+ hemangioma endothelial cell three-dimensional microtumor models. The vascular-specific and decellularized extracellular matrix was suitable for the growth of infantile hemangioma-derived endothelial cells. The KEGG signaling pathway analysis revealed enrichment primarily in stem cell pluripotency, RAS, and PI3KAkt compared to the two-dimensional cell model according to RNA sequencing. Propranolol, the first-line medication for IH, was also used to test the model's applicability. We also found that metformin had some impact on the condition. The three-dimensional microtumor models of CD31+ hemangioma endothelial cells were more robust and efficient experimental models for IH mechanistic exploration and drug screening.

ISSVA Classification of Vascular Anomalies and Molecular Biology

Vascular anomalies include various diseases, which are classified into two types according to the International Society for the Study of Vascular Anomalies (ISSVA) classification: vascular tumors with proliferative changes of endothelial cells, and vascular malformations primarily consisting of structural vascular abnormalities. The most recent ISSVA classifications, published in 2018, detail the causative genes involved in many lesions. Here, we summarize the latest findings on genetic abnormalities, with the presentation of the molecular pathology of vascular anomalies.

Infantile hepatic hemangiomas: looking backwards and forwards

Infantile hepatic hemangiomas (IHHs) are common benign tumors seen in the liver of infants. IHHs are true infantile hemangiomas (IHs) and have phases of proliferation and involution parallel to those of cutaneous IHs. The definition and classification of IHH are still confusing in the literature. The mechanisms during the pathogenesis of IHH have yet to be discovered. The clinical manifestations of IHH are heterogeneous. Although most IHH lesions are asymptomatic, some lesions can lead to severe complications, such as hypothyroidism, consumptive coagulopathy, and high-output congestive cardiac failure. Consequently, some patients can possibly encounter a fatal clinical condition. The heterogeneity of the lesions and the occurrence of disease-related comorbidities can make the treatment of IHH challenging. Oral propranolol is emerging as an effective systemic approach to IHH with obvious responses in tumor remission and symptom regression. However, the precise clinical characteristics and treatment strategies for patients with severe IHH have not yet been well established. Here, we summarize the epidemiology, pathogenic mechanism, clinical manifestations, diagnosis, and treatment of IHH. Recent updates and future perspectives for IHH will also be elaborated.

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

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

Knockdown of lncRNA MEG8 inhibits cell proliferation and invasion, but promotes cell apoptosis in hemangioma, via miR‑203‑induced mediation of the Notch signaling pathway

As a member of the long non‑coding (lnc)RNA family, lncRNA maternally expressed 8, small nucleolar RNA host gene (MEG8), has been reported to serve an oncogenic role in several types of malignancies, including hepatocellular carcinoma, non‑small cell lung cancer and pancreatic cancer. The current study aimed to investigate the effect of the knockdown of MEG8 on human hemangioma endothelial cell (HemEC) proliferation, apoptosis and invasion, in addition to determining the underlying molecular mechanism. The knockdown of lncRNA MEG8 was achieved by transfecting lncRNA MEG8 small interfering (si)RNA into HemECs, while the combined knockdown of lncRNA MEG8 knockdown and microRNA (miR)‑203 was established by co‑transfecting lncRNA MEG8 siRNA and a miR‑203 inhibitor into HemECs. The cell proliferation, apoptosis and invasion and the expression levels of miR‑34a, miR‑200b, miR‑200b and Notch signaling pathway‑related factors were detected via CCK‑8 Kit, flow cytometry, Transwell, reverse transcription‑quantitative PCR and western blot assay, respectively. The knockdown of lncRNA MEG8 significantly inhibited proliferation (P<0.05) and invasion (P<0.05), but promoted apoptosis (P<0.01) in HemECs. Furthermore, lncRNA MEG8 knockdown upregulated miR‑203 (P<0.01) expression, but did not alter miR‑34a or miR‑200b expression (both P>0.05). Subsequent experiments revealed that miR‑203 silencing exerted no significant effect on the expression levels of lncRNA MEG8 (P>0.05) in HemECs. In addition, miR‑203 silencing increased cell proliferation (P<0.05) and invasion (P<0.01), but suppressed apoptosis (P<0.05). miR‑203 silencing also reversed the effect of lncRNA MEG8 knockdown on the proliferation (P<0.05), apoptosis (P<0.001) and invasion (P<0.01) of HemECs. Moreover, lncRNA MEG8 knockdown downregulated jagged canonical notch ligand 1 (JAG1; P<0.05) and Notch1 (P<0.05) expression levels, while miR‑203 silencing upregulated JAG1 (P<0.01) and Notch1 (P<0.01) expression levels and reversed the effects of lncRNA MEG8 knockdown on JAG1 (P<0.01) and Notch1 (P<0.01) expression in HemECs. In conclusion, the findings of the present study suggested that lncRNA MEG8 knockdown may inhibit cell proliferation and invasion, but promote cell apoptosis in hemangioma via miR‑203‑induced mediation of the Notch signaling pathway.

LncRNA-MCM3AP-AS1 Promotes the Progression of Infantile Hemangiomas by Increasing miR-138-5p/HIF-1α Axis-Regulated Glycolysis

Infantile hemangioma (IH) is a common benign tumor of endothelial cells in infants. Most hemangiomas are self-limited, but a few may develop and lead to serious complications that affect the normal life of children. Therefore, finding an effective treatment strategy for IH is a pressing need. Recent studies have demonstrated that non-coding RNAs affect the progression of multiple tumors. This study aims to investigate the mechanism by which LncRNA-MCM3AP-AS1 promotes glycolysis in the pathogenesis of IH. We first documented that the expression of LncRNA MCM3AP-AS1 was significantly upregulated in IH. Furthermore, we demonstrated that MCM3AP-AS1 bound to miR-106b-3p which promotes glycolysis in IH. In addition, we found that inhibition of HIF-1α contributed to the transformation of glycolysis to normal aerobic oxidation, partially reversed the promoting effect on glycolysis by the up-regulation of LncRNA MCM3AP-AS1 in IH disease. More importantly, we demonstrated this phenomenon existed in IH patients. Taken together, we demonstrate that LncRNA-MCM3AP-AS1 promotes the progression of infantile hemangiomas by increasing the glycolysis via regulating miR-138-5p/HIF-1α axis.

LncRNA-TUG1 promotes the progression of infantile hemangioma by regulating miR-137/IGFBP5 axis

Background

Previous studies indicated that lncRNA taurine upregulated gene 1 (TUG1) played essential roles in human cancers. This study aimed to investigate its function in infantile hemangioma (IH).

Methods

A total of 30 pairs of clinical infantile specimens were used in this study. The expression of TUG1 in IH tissues was assessed by quantitative reverse transcriptase PCR (qRT-PCR). Two short hairpin RNA targeting TUG1 (sh-TUG1-1 and sh-TUG1-2) were transfected into hemangioma-derived endothelial cells, HemECs, to block its expression. The effects of TUG1 on HemECs were evaluated by Cell Counting Kit-8 (CCK-8), colony formation assay, wound healing assay, and Transwell assay. The underlying molecular mechanism of TUG1 was investigated by Starbase prediction and luciferase reporter assay and further determined by loss- and gain-of-function approaches. In addition, the role of TUG1 on tumorigenesis of HemECs was confirmed in an in vivo mouse model.

Results

TUG1 was significantly upregulated in infant hemangioma tissues compared with normal adjacent subcutaneous tissues. The loss- and gain-of-function approaches indicated that TUG1 overexpression promoted proliferation, migration, and invasion of HemECs in vitro, and TUG1 knockdown inhibited the tumorigenesis of HemECs in vivo. Specifically, TUG1 could compete with IGFBP5 for miR137 binding. Rescue experiments further confirmed the role of the TUG1/miR137/IGFBP5 axis in HemECs.

Conclusion

TUG1 was closely associated with the progression of IH by regulating the miR-137/IGFBP5 axis, which might be a potential target for IH treatment.

Silencing long non-coding RNA MEG8 inhibits the proliferation and induces the ferroptosis of hemangioma endothelial cells by regulating miR-497-5p/NOTCH2 axis

Even though long non-coding RNA (lncRNA) MEG8 plays vital roles in carcinogenesis of malignances, its roles and mechanisms in hemangioma remain unknown. Therefore, we evaluate the oncogenic roles of MEG8 in hemangioma. Small interfering RNA (siRNA)-mediated depletion of MEG8 inhibited the proliferation and increased MDA level in human hemangioma endothelial cells (HemECs). The inhibitors of ferroptosis (ferrostatin-1 and liproxstatin-1) abolished the MEG8 silence induced cell viability loss. Knockdown of MEG8 increased the miR-497-5p expression and reduced the mRNA and protein levels of NOTCH2. Using a dual-luciferase assay, we confirmed the binding between MEG8 and miR-497-5p, and between the miR-497-5p and 3'UTR of NOTCH2. We further found that silencing MEG8 significantly decreased the expressions of SLC7A11 and GPX4 both in mRNA and protein level and had no effect on the level of AIFM2. Importantly, blocking miR-497-5p abrogated the effects of MEG8 loss on cell viability, MDA level and expression levels of NOTCH2, SLC7A11 and GPX4 in HemECs. Taken together, our results suggested that knockdown of long non-coding RNA MEG8 inhibited the proliferation and induced the ferroptosis of hemangioma endothelial cells by regulating miR-497-5p/NOTCH2 axis.

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.

The expression and role of glycolysis-associated molecules in infantile hemangioma

AIMS

Infantile hemangioma (IH) is one of the most common tumors in infancy, which etiology and pathogenesis has not been fully elucidated, hypoxia and abnormal glucose metabolism is regarded as critical pathogenic factors. This study investigated the expression and function of glycolysis-associated molecules (GLUT1, HK2, PFKFB3, PKM2, and LDHA) under normoxic and hypoxic conditions to further understand the pathogenesis of IH.

MAIN METHODS

Hemangioma-derived endothelial cells (HemECs) were isolated from proliferating phase infantile hemangiomas and identified by immunofluorescence. HemECs and human umbilical vein endothelial cells (HUVECs) were cultured under normoxic and hypoxic conditions. RNA and protein expression of glycolysis-associated molecules were analyzed by quantitative real-time RT-PCR, western blotting, and immunohistochemistry. Glucose consumption, ATP production and lactate production were measured. Glycolysis-associated molecules were inhibited by WZB117, 3BP, 3PO, SKN, and GSK 2837808A and the resulting effects on HemECs proliferation, migration, and tube formation were quantified.

KEY FINDINGS

Glycolysis-associated molecules were highly expressed at both mRNA and protein levels in HemECs compared with HUVECs (P < 0.05). Glucose consumption and ATP production were higher in HemECs than in HUVECs, while lactate production in HemECs was lower than in HUVECs (P < 0.05). Inhibition of some glycolysis-associated molecules reduced the proliferation, migration, and tube formation capacity of HemECs (P < 0.05).

SIGNIFICANCE

Our study revealed that glycolysis-associated molecules were highly expressed in IH. Glucose metabolismin HemECs differed from normal endothelial cells. Altering the expression of glycolysis-associated molecules may influence the phenotype of HemECs and provide new therapeutic approaches to the successful treatment of IH.

Silencing long non‑coding RNA NEAT1 suppresses the tumorigenesis of infantile hemangioma by competitively binding miR‑33a‑5p to stimulate HIF1α/NF‑κB pathway

Infantile hemangioma (IH) is one of the most common vascular tumors that occurs during childhood, but its pathogenesis is currently not completely understood. Even though lncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) plays vital roles in tumorigenesis of malignant tumors, its roles in IH remain unclear. Therefore, we evaluate the function of lncRNA NEAT1 in IH. Reverse transcription-quantitative PCR indicated that IH tissues exhibited high expression levels of NEAT1 and hypoxia-inducible factor 1α (HIF1α), and low expression levels of the microRNA (miR)-33a-5p. Small interfering RNA-mediated depletion of NEAT1 suppressed hemangioma endothelial cell (HemEC) proliferation, migration and invasion. The data suggested that NEAT1 positively regulated HIF1α expression by sponging miR-33a-5p in HemECs. miR-33a-5p overexpression or HIF1α silencing also acted to suppress HemEC proliferation, migration and invasion. Furthermore, the results indicated that the NEAT1/miR-33a-5p/HIF1α axis regulated the NF-κB signaling pathway. Collectively, the results revealed that depletion of lncRNA NEAT1 suppressed the tumorigenesis of IH by competitively binding miR-33a-5p and thereby stimulating the HIF1α/NF-κB signaling pathway.

Long noncoding RNA LINC00342 promotes growth of infantile hemangioma by sponging miR-3619-5p from HDGF

Infantile hemangiomas (IH) are a type of benign vascular neoplasm that may cause permanent scarring. Hemangioma-derived endothelial cells (HemECs) are commonly used as an in vitro model to study IH. Long noncoding RNA is a type of RNA transcript longer than 200 nucleotides that does not encode any protein. LINC00342 was discovered to regulate proliferation and apoptosis in nonsmall cell lung cancer. However, the role of LINC00342 in IH has never been reported before. Expressions of LINC00342 and miR-3619-5p were detected in proliferating versus normal skin tissues. Colony formation and Cell-Couting Kit 8 assays were carried out to study the effects on cell proliferation after knockdown and overexpression of LINC00342, respectively. Meanwhile caspase-3 activity and nucleosomal fragmentation assay were applied to detect cell apoptosis. Micro-RNA binding sites on LINC00342 and hepatoma-derived growth factor (HDGF) were predicted and confirmed via dual-luciferase reporter assay. Biotin RNA pulldown assay was used to verify the direct binding between RNA molecules. LINC00342 enhanced proliferation and inhibited apoptosis in HemECs. MiR-3619-5p targeted both LINC00342 and HDGF, where LINC00342 sponged miR-3619-5p and positively regulated HDGF. HDGF knockdown rescued the effects of LINC00342 on HemECs. The LINC00342-miR-3619-5p-HDGF signaling pathway could regulate cell proliferation and apoptosis in HemECs.NEW & NOTEWORTHY The role of LINC00342 in infantile hemangiomas has not yet been elucidated. This paper highlights the regulatory role of LINC00342 in cell proliferation and apoptosis in hemangioma-derived endothelial cells and the underlying molecular mechanisms. The findings would provide potential target for treatment of infantile hemangiomas.

Mono (2-ethylhexyl) phthalate (MEHP) triggers the proliferation of hemangioma-derived endothelial cells via YAP signals

Hemangioma (HA) is tumor formed by hyper-proliferation of vascular endothelial cells. However, the potential effects of mono-(2-ethylhexyl) phthalate (MEHP) on the progression of HA are not well illustrated. Our present study revealed that MEHP exposure can significantly increase the in vitro proliferation of hemangioma-derived endothelial cells (HemECs). MEHP treatment can activate yes-associated protein (YAP), a key effector of Hippo pathway, by inhibiting its phosphorylation. The dephosphorylation of YAP induced by MEHP can promote the nuclear accumulation of YAP. Knockdown of YAP or its inhibitor can block MEHP triggered cell proliferation. MEHP can increase the levels of precursor and mature mRNA of YAP in HemECs. As well, MEHP extended the half-life of YAP protein. Mechanistically, MEHP can decrease the phosphorylation of YAP via suppressing the activity of large tumor suppressor kinase 1/2 (LATS1/2) to inhibit it induced degradation of YAP. Further, MEHP increased the expression of interferon regulatory factor 1 (IRF1), which can bind to the promoter of YAP to initiate its transcription. Collectively, we revealed that Hippo-YAP signal is involved in MEHP-induced proliferation of HA cells.

Silence of long non-coding RNA UCA1 inhibits hemangioma cells growth, migration and invasion by up-regulation of miR-200c

BACKGROUND

Human urothelial carcinoma associated 1 (UCA1) has been recognized as an oncogenic lncRNA in various cancers, except infantile hemangioma (IH). This study attempts to explore the functional role of lncRNA UCA1 in IH.

METHODS

qRT-PCR was carried out to detect the expression of lncRNA UCA1 in human IH tissues. Two hemangioma cell lines (EOMA and HemECs) were transfected with shRNAs specific for lncRNA UCA1, or a plasmid for expression lncRNA UCA1. The expression of miR-200c in cell was suppressed or overexpressed by miRNA-mediated transfection. CCK-8 assay, flow cytometry, Transwell assay, and Western blot were performed to detect cell survival, migration and invasion.

RESULTS

LncRNA UCA1 was up-regulated in proliferating-phase hemangioma samples, as compared to involuting-phase. Silence of lncRNA UCA1 significantly reduced EOMA cells viability, migration and invasion, and induced apoptosis. These observations were coupled with the down-regulations of CyclinD1, CDK6 and CDK4, the cleavage of caspase-3 and caspase-9, as well as the decreased expression levels of MMP-9 and Vimentin. miR-200c was highly expressed in lncRNA UCA1 silenced-cells. Besides, the anti-tumor effects of lncRNA UCA1 silence towards EOMA cells were reversed by miR-200c suppression. Same effects of lncRNA UCA1 and miR-200c on HemECs cells were observed. Furthermore, silence of lncRNA UCA1 repressed mTOR, AMPK and Wnt/β-catenin signaling via a miR-200c-dependent fashion.

CONCLUSION

This study evidences that silence of lncRNA UCA1 inhibits hemangioma cells growth, migration and invasion possibly via its regulation on miR-200c expression and the activation of mTOR, AMPK and Wnt/β-catenin signaling pathways.

The role of the vasculature niche on insulin-producing cells generated by transdifferentiation of adult human liver cells

Background

Insulin-dependent diabetes is a multifactorial disorder that could be theoretically cured by functional pancreatic islets and insulin-producing cell (IPC) implantation. Regenerative medicine approaches include the potential for growing tissues and organs in the laboratory and transplanting them when the body cannot heal itself. However, several obstacles remain to be overcome in order to bring regenerative medicine approach for diabetes closer to its clinical implementation; the cells generated in vitro are typically of heterogenic and immature nature and the site of implantation should be readily vascularized for the implanted cells to survive in vivo. The present study addresses these two limitations by analyzing the effect of co-implanting IPCs with vasculature promoting cells in an accessible site such as subcutaneous. Secondly, it analyzes the effects of reconstituting the in vivo environment in vitro on the maturation and function of insulin-producing cells.

Methods

IPCs that are generated by the transdifferentiation of human liver cells are exposed to the paracrine effects of endothelial colony-forming cells (ECFCs) and human bone marrow mesenchymal stem cells (MSCs), which are the “building blocks” of the blood vessels. The role of the vasculature on IPC function is analyzed upon subcutaneous implantation in vivo in immune-deficient rodents. The paracrine effects of vasculature on IPC maturation are analyzed in culture.

Results

Co-implantation of MSCs and ECFCs with IPCs led to doubling the survival rates and a threefold increase in insulin production, in vivo. ECFC and MSC co-culture as well as conditioned media of co-cultures resulted in a significant increased expression of pancreatic-specific genes and an increase in glucose-regulated insulin secretion, compared with IPCs alone. Mechanistically, we demonstrate that ECFC and MSC co-culture increases the expression of CTGF and ACTIVINβα, which play a key role in pancreatic differentiation.

Conclusions

Vasculature is an important player in generating regenerative medicine approaches for diabetes. Vasculature displays a paracrine effect on the maturation of insulin-producing cells and their survival upon implantation. The reconstitution of the in vivo niche is expected to promote the liver-to-pancreas transdifferentiation and bringing this cell therapy approach closer to its clinical implementation.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1157-5) contains supplementary material, which is available to authorized users.

Quality, bioactivity study, and preclinical acute toxicity, safety pharmacology evaluation of PEGylated recombinant human endostatin (M2 ES)

Endostar, a potent endogenous antiangiogenic factor, is wildly used in clinics. However, it was easily degraded by enzymes and rapidly cleared by the kidneys. To overcome these shortcomings, PEGylated recombinant human endostatin was developed. In this study, the purity of M₂ ES was evaluated by silver stain and reversed-phase high-performance liquid chromatography. Ultraviolet spectrum was used to examine the structural of M₂ ES and endostar. The bioactivity and antitumor efficacy of M₂ ES were evaluated using an in vitro endothelial cell migration model and athymic nude mouse xenograft model of a heterogeneous lung adenocarcinoma, respectively. A preclinical study was performed to evaluate the acute toxicity and safety pharmacology in rhesus monkeys. The purity of M₂ ES was more than 98%; PEG modification has no effect on endostatin structure. Compared with the control group, M₂ ES dramatically retards endothelial cell migration and tumor growth. After intravenous (IV) infusions of M₂ ES at a dose level of three and 75 mg/kg in rhesus monkeys, there was no observable serious adverse event in both acute toxicity and safety pharmacology study. On the basis of the quality and bioactivity study data of M₂ ES and the absence of serious side effect in rhesus monkeys, M₂ ES was authorized to initiate a phase I clinical trial.

Propranolol suppresses HUVEC viability, migration, VEGF expression, and promotes apoptosis by downregulation of miR-4295

Infantile hemangioma (IH) is a common benign tumor. Human umbilical vein endothelial cells (HUVECs) have the potential of stem cells, which has been widely used in vascular endothelial cell experiments. Oral propranolol was first reported to treat hemangioma in 2008. However, the role of propranolol in IH remains unclear. Therefore, in this study, we investigated the effects of propranolol on HUVECs in vitro, to explore the underlying mechanism of propranolol in IH. HUVECs were treated with 0.15, 1.5, and 15 μM of propranolol, and transfected with microRNA-4295 (miR-4295) mimic. Cell viability, migration, and apoptosis were examined using Cell Counting Kit-8, transwell assay, and flow cytometry analysis, respectively. In addition, the expressions and concentrations of miR-4295, vascular endothelial growth factor (VEGF), VEGF-A, FLT1, FLT2, and FOXF1 were assessed using real-time polymerase chain reaction, Western blot assay, and enzyme-linked immunosorbent assay. We found that 15 μM of propranolol decreased HUVEC viability the most. Then, cell migration and the concentrations of VEGF and VEGF-A were reduced, and apoptosis was increased when treated with propranolol. Meanwhile, the expressions of VEGF, VEGF-A, FLT1, FLT2, and FOXF1 were downregulated by propranolol exposure. Further study showed that miR-4295 expression was upregulated in IH tissues, and propranolol treatment downregulated miR-4295 expression in HUVECs. MiR-4295 overexpression alleviated the reductions of viability, migration, and factors expression, as well as the increase of apoptosis. Propranolol suppressed HUVEC viability, migration, the expression of VEGF, VEGF-A, FLT1/2, FOXF1, and promoted apoptosis via downregulation of miR-4295. This study lays a foundation for further study of the effect of propranolol on IH.

Pigment epithelium-derived factor/vascular endothelial growth factor ratio plays a crucial role in the spontaneous regression of infant hemangioma and in the therapeutic effect of propranolol

Infantile hemangioma (IH) is a benign tumor that is formed by aberrant angiogenesis and that undergoes spontaneous regression over time. Propranolol, the first-line therapy for IH, inhibits angiogenesis by downregulating activation of the vascular endothelial growth factor (VEGF) pathway, which is hyperactivated in IH. However, this treatment is reportedly ineffective for 10% of tumors, and 19% of patients relapse after propranolol treatment. Both pro-angiogenic and anti-angiogenic factors regulate angiogenesis, and pigment epithelium-derived factor (PEDF) is the most effective endogenous anti-angiogenic factor. PEDF/VEGF ratio controls many angiogenic processes, but its role in IH and the relationship between this ratio and propranolol remain unknown. Results of the present study showed that the PEDF/VEGF ratio increased during the involuting phase of IH compared with the proliferating phase. Similarly, in hemangioma-derived endothelial cells (HemEC), which were isolated with magnetic beads, increasing the PEDF/VEGF ratio inhibited proliferation, migration, and tube formation and promoted apoptosis. Mechanistically, the VEGF receptors (VEGFR1 and VEGFR2) and PEDF receptor (laminin receptor, LR) were highly expressed in both IH tissues and HemEC, and PEDF inhibited HemEC function by binding to LR. Interestingly, we found that propranolol increased the PEDF/VEGF ratio but did so by lowering VEGF expression rather than by upregulating PEDF as expected. Furthermore, the combination of PEDF and propranolol had a more suppressive effect on HemEC. Consequently, our results suggested that the PEDF/VEGF ratio played a pivotal role in the spontaneous regression of IH and that the combination of PEDF and propranolol might be a promising treatment strategy for propranolol-resistant IH.

Modulation of LIN28B/Let-7 Signaling by Propranolol Contributes to Infantile Hemangioma Involution

OBJECTIVE

Infantile hemangiomas (IHs) are the most common benign vascular neoplasms of infancy, characterized by a rapid growth phase followed by a spontaneous involution, or triggered by propranolol treatment by poorly understood mechanisms. LIN28/let-7 axis plays a central role in the regulation of stem cell self-renewal and tumorigenesis. However, the role of LIN28B/let-7 signaling in IH pathogenesis has not yet been elucidated.

APPROACH AND RESULTS

LIN28B is highly expressed in proliferative IH and is less expressed in involuted and in propranolol-treated IH samples as measured by immunofluorescence staining and quantitative RT-PCR. Small RNA sequencing analysis of IH samples revealed a decrease in microRNAs that target LIN28B, including let-7, and an increase in microRNAs in the mir-498(46) cistron. Overexpression of LIN28B in HEK293 cells induced the expression of miR-516b in the mir-498(46) cistron. Propranolol treatment of induced pluripotent stem cells, which express mir-498(46) endogenously, reduced the expression of both LIN28B and mir-498(46) and increased the expression of let-7. Furthermore, propranolol treatment reduced the proliferation of induced pluripotent stem cells and induced epithelial-mesenchymal transition.

CONCLUSIONS

This work uncovers the role of the LIN28B/let-7 switch in IH pathogenesis and provides a novel mechanism by which propranolol induces IH involution. Furthermore, it provides therapeutic implications for cancers in which the LIN28/let-7 pathway is imbalanced.

Endothelial Ca2+ Signaling and the Resistance to Anticancer Treatments: Partners in Crime

Intracellular Ca²⁺ signaling drives angiogenesis and vasculogenesis by stimulating proliferation, migration, and tube formation in both vascular endothelial cells and endothelial colony forming cells (ECFCs), which represent the only endothelial precursor truly belonging to the endothelial phenotype. In addition, local Ca²⁺ signals at the endoplasmic reticulum (ER)-mitochondria interface regulate endothelial cell fate by stimulating survival or apoptosis depending on the extent of the mitochondrial Ca²⁺ increase. The present article aims at describing how remodeling of the endothelial Ca²⁺ toolkit contributes to establish intrinsic or acquired resistance to standard anti-cancer therapies. The endothelial Ca²⁺ toolkit undergoes a major alteration in tumor endothelial cells and tumor-associated ECFCs. These include changes in TRPV4 expression and increase in the expression of P2X7 receptors, Piezo2, Stim1, Orai1, TRPC1, TRPC5, Connexin 40 and dysregulation of the ER Ca²⁺ handling machinery. Additionally, remodeling of the endothelial Ca²⁺ toolkit could involve nicotinic acetylcholine receptors, gasotransmitters-gated channels, two-pore channels and Na⁺/H⁺ exchanger. Targeting the endothelial Ca²⁺ toolkit could represent an alternative adjuvant therapy to circumvent patients' resistance to current anti-cancer treatments.

NOTCH3 regulates stem-to-mural cell differentiation in infantile hemangioma

Infantile hemangioma (IH) is a vascular tumor that begins with rapid vascular proliferation shortly after birth, followed by vascular involution in early childhood. We have found that NOTCH3, a critical regulator of mural cell differentiation and maturation, is expressed in hemangioma stem cells (HemSCs), suggesting that NOTCH3 may function in HemSC-to-mural cell differentiation and pathological vessel stabilization. Here, we demonstrate that NOTCH3 is expressed in NG2+PDGFRβ+ perivascular HemSCs and CD31+GLUT1+ hemangioma endothelial cells (HemECs) in proliferating IHs and becomes mostly restricted to the αSMA+NG2loPDGFRβlo mural cells in involuting IHs. NOTCH3 knockdown in HemSCs inhibited in vitro mural cell differentiation and perturbed αSMA expression. In a mouse model of IH, NOTCH3 knockdown or systemic expression of the NOTCH3 inhibitor, NOTCH3 Decoy, significantly decreased IH blood flow, vessel caliber, and αSMA+ perivascular cell coverage. Thus, NOTCH3 is necessary for HemSC-to-mural cell differentiation, and adequate perivascular cell coverage of IH vessels is required for IH vessel stability.

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

Background

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

Material/Methods

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

Results

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

Conclusions

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

EGFL6 Regulates the Asymmetric Division, Maintenance, and Metastasis of ALDH+ Ovarian Cancer Cells

Little is known about the factors that regulate the asymmetric division of cancer stem-like cells (CSC). Here, we demonstrate that EGFL6, a stem cell regulatory factor expressed in ovarian tumor cells and vasculature, regulates ALDH⁺ ovarian CSC. EGFL6 signaled at least in part via the oncoprotein SHP2 with concomitant activation of ERK. EGFL6 signaling promoted the migration and asymmetric division of ALDH⁺ ovarian CSC. As such, EGFL6 increased not only tumor growth but also metastasis. Silencing of EGFL6 or SHP2 limited numbers of ALDH⁺ cells and reduced tumor growth, supporting a critical role for EGFL6/SHP2 in ALDH⁺ cell maintenance. Notably, systemic administration of an EGFL6-neutralizing antibody we generated restricted tumor growth and metastasis, specifically blocking ovarian cancer cell recruitment to the ovary. Together, our results offer a preclinical proof of concept for EGFL6 as a novel therapeutic target for the treatment of ovarian cancer. Cancer Res; 76(21); 6396-409. ©2016 AACR.

microRNA-143 acts as a suppressor of hemangioma growth by targeting Bcl-2

Infantile hemangioma is the most common vascular tumor affecting infants, which is associated with clonal expansion of endothelial cells. The aim of this study is to determine the role of microRNA (miR)-143 in the growth and survival of hemangioma-derived endothelial cells (HemECs). We examined the expression of miR-143 in patients with proliferating-phase (n=10) and involuting-phase (n=8) hemangiomas. The effects of ectopic expression of miR-143 on the viability, proliferation, cell cycle distribution, and apoptosis of HemECs were explored. We also identified the target gene(s) that was involved in the activity of miR-143. It was found that proliferating hemangiomas had significantly (P<0.05) lower levels of miR-143 than involuting counterparts. Reexpression of miR-143 significantly reduced the viability and proliferation of HemECs, while knockdown of miR-143 led to an increase in the proliferation of HemECs. Moreover, overexpression of miR-143 arrested HemECs at the G0/G1 phase and promoted caspase-3-dependent apoptosis. At the molecular level, miR-143 overexpression significantly promoted the expression of p21 and p53 and reduced the expression of cyclin D1, CDK2, CDK4, and Bcl-2. Silencing of Bcl-2 phenocopied the effect of miR-143 overexpression on the proliferation and apoptosis of HemECs. Furthermore, co-expression of Bcl-2 reversed the growth-suppressive effect of miR-143 on HemECs. Taken together, miR-143 acts as a suppressor in the growth of HemECs, at least partially, through downregulation of Bcl-2. Reexpression of miR-143 may represent a potential therapeutic strategy for the treatment of proliferating hemangiomas.

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

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

Endothelial cell malignancies: new insights from the laboratory and clinic

Endothelial cell malignancies are rare in the Western world and range from intermediate grade hemangioendothelioma to Kaposi sarcoma to aggressive high-grade angiosarcoma that metastasize early and have a high rate of mortality. These malignancies are associated with dysregulation of normal endothelial cell signaling pathways, including the vascular endothelial growth factor, angiopoietin, and Notch pathways. Discoveries over the past two decades related to mechanisms of angiogenesis have led to the development of many drugs that intuitively would be promising therapeutic candidates for these endothelial-derived tumors. However, clinical efficacy of such drugs has been limited. New insights into the mechanisms that lead to dysregulated angiogenesis such as mutation or amplification in known angiogenesis related genes, viral infection, and chromosomal translocations have improved our understanding of the pathogenesis of endothelial malignancies and how they evade anti-angiogenesis drugs. In this review, we describe the major molecular alterations in endothelial cell malignancies and consider emerging opportunities for improving therapeutic efficacy against these rare but deadly tumors.

In-vivo quantification of the revascularization of a human acellular dermis seeded with EPCs and MSCs in co-culture with fibroblasts and pericytes in the dorsal chamber model in pre-irradiated tissue

INTRODUCTION

Transplantation of a cell-seeded graft may improve wound healing after radiotherapy. However, the survival of the seeded cells depends on a rapid vascularization of the graft. Co-culturing of adult stem cells may be a promising strategy to accelerate the vessel formation inside the graft. Thus, we compared the in vivo angiogenic potency of mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) using dorsal skinfold chambers and intravital microscopy.

MATERIALS AND METHODS

Cells were isolated from rat bone marrow and adipose tissue and characterized by immunostaining and flow cytometry. Forty-eight rats received a dorsal skinfold chamber and were divided into 2 main groups, irradiated and non-irradiated. Each of these 2 groups were further subdivided into 4 groups: unseeded matrices, matrices + fibroblasts + pericytes, matrices + fibroblasts + pericytes + MSCs and matrices + fibroblasts + pericytes + EPCs. Vessel densities were quantified semi-automatically using FIJI.

RESULTS

Fibroblasts + pericytes - seeded matrices showed a significantly higher vascular density in all groups with an exception of non-irradiated rats at day 12 compared to unseeded matrices. Co-seeding of MSCs increased vessel densities in both, irradiated and non-irradiated groups. Co-seeding with EPCs did not result in an increase of vascularization in none of the groups.

DISCUSSION

We demonstrated that the pre-radiation treatment led to a significant decreased vascularization of the implanted grafts. The augmentation of the matrices with fibroblasts and pericytes in co-culture increased the vascularization compared to the non-seeded matrices. A further significant enhancement of vessel ingrowth into the matrices could be achieved by the co-seeding with MSCs in both, irradiated and non-irradiated groups.

Endoglin regulates mural cell adhesion in the circulatory system

The circulatory system is walled off by different cell types, including vascular mural cells and podocytes. The interaction and interplay between endothelial cells (ECs) and mural cells, such as vascular smooth muscle cells or pericytes, play a pivotal role in vascular biology. Endoglin is an RGD-containing counter-receptor for β1 integrins and is highly expressed by ECs during angiogenesis. We find that the adhesion between vascular ECs and mural cells is enhanced by integrin activators and inhibited upon suppression of membrane endoglin or β1-integrin, as well as by addition of soluble endoglin (SolEng), anti-integrin α5β1 antibody or an RGD peptide. Analysis of different endoglin mutants, allowed the mapping of the endoglin RGD motif as involved in the adhesion process. In Eng (+/-) mice, a model for hereditary hemorrhagic telangectasia type 1, endoglin haploinsufficiency induces a pericyte-dependent increase in vascular permeability. Also, transgenic mice overexpressing SolEng, an animal model for preeclampsia, show podocyturia, suggesting that SolEng is responsible for podocytes detachment from glomerular capillaries. These results suggest a critical role for endoglin in integrin-mediated adhesion of mural cells and provide a better understanding on the mechanisms of vessel maturation in normal physiology as well as in pathologies such as preeclampsia or hereditary hemorrhagic telangiectasia.

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.

Expression of cancer stem cell markers and their correlation with pathogenesis in vascular tumors

Vascular tumor, which belongs to a kind of complicated lesion in soft tissue tumor, is derived from mesenchymal tissue. Although many studies have been focused on the pathogenesis of vascular tumors in human, the specific mechanism of the vascular tumors was currently unclear. Previous studies have reported an association of cancer stem cells with the development of tumor in many solid tumors. Thus the purpose of this study was to explore whether different expression level of cancer stem cell markers including CD29, CD44, CD133, nestin and ALDH1 in vascular tumor may help to elucidate the possible pathogenesis of vascular tumor. In present study, tissues of 9 cases of hemangioma, 22 cases of hemangiosarcoma, 3 cases of Kaposi's sarcoma, and 5 cases of hemangioendothelioma were immunostained for CD29, CD44, CD133, nestin and ALDH1. Of the 39 vascular tumor cases included in the current study, CD29, CD133 and nestin were positive in most vascular tumor cases. Although CD44 and ALDH1 were observed in vascular tumor cases, the percentage of cells staining for the two markers was less than 2% in all cases of vascular tumor. Capillary hemangiomas exhibited significantly higher expression rate of CD29 and nestin compared with malignant vascular tumors and hemangioendotheliomas (P<0.05, Fisher's exact test), while CD44, CD133 and ALDH1 exhibited no statistically significant difference between these two groups. Pearson correlation analysis exhibited that CD29 expression and nestin expression in vascular tumor were no statistically significant relationship (C=0.288, P=0.063>0.05). Our findings confirmed that the five cancer stem cells markers, including CD29, CD44, CD133, nestin and ALDH1, exhibited different expression levels in vascular tumors and demonstrated that immunohistochemical analysis for cancer stem cells markers may provide useful information for studying the pathogenesis of vascular tumors.

Glucose transporter 1-positive endothelial cells in infantile hemangioma exhibit features of facultative stem cells

Endothelial glucose transporter 1 (GLUT1) is a definitive and diagnostic marker for infantile hemangioma (IH), a vascular tumor of infancy. To date, GLUT1-positive endothelial cells in IH have not been quantified nor directly isolated and studied. We isolated GLUT1-positive and GLUT1-negative endothelial cells from IH specimens and characterized their proliferation, differentiation, and response to propranolol, a first-line therapy for IH, and to rapamycin, an mTOR pathway inhibitor used to treat an increasingly wide array of proliferative disorders. Although freshly isolated GLUT1-positive cells, selected using anti-GLUT1 magnetic beads, expressed endothelial markers CD31, VE-Cadherin, and vascular endothelial growth factor receptor 2, they converted to a mesenchymal phenotype after 3 weeks in culture. In contrast, GLUT1-negative endothelial cells exhibited a stable endothelial phenotype in vitro. GLUT1-selected cells were clonogenic when plated as single cells and could be induced to redifferentiate into endothelial cells, or into pericytes/smooth muscle cells or into adipocytes, indicating a stem cell-like phenotype. These data demonstrate that, although they appear and function in the tumor as bona fide endothelial cells, the GLUT1-positive endothelial cells display properties of facultative stem cells. Pretreatment with rapamycin for 4 days significantly slowed proliferation of GLUT1-selected cells, whereas propranolol pretreatment had no effect. These results reveal for the first time the facultative nature of GLUT1-positive endothelial cells in IH.

Switch from canonical to noncanonical Wnt signaling mediates high glucose-induced adipogenesis

Human bone marrow mesenchymal progenitor cells (MPCs) are multipotent cells that play an essential role in endogenous repair and the maintenance of the stem cell niche. We have recently shown that high levels of glucose, conditions mimicking diabetes, cause impairment of MPCs, resulting in enhanced adipogenesis and suppression of osteogenesis. This implies that diabetes may lead to reduced endogenous repair mechanisms through altering the differentiation potential of MPCs and, consequently, disrupting the stem cell niche. Phenotypic alterations in the bone marrow of long-term diabetic patients closely resemble this observation. Here, we show that high levels of glucose selectively enhance autogenous Wnt11 expression in MPCs to stimulate adipogenesis through the Wnt/protein kinase C noncanonical pathway. This novel mechanism may account for increased bone marrow adipogenesis, severe bone loss, and reduced vascular stem cells leading to chronic secondary complications of diabetes.

Pre-clinical toxicokinetics and safety study of M2ES, a PEGylated recombinant human endostatin, in rhesus monkeys

PEGylated recombinant human endostatin (M2ES) exhibited prolonged serum half-life and enhanced antitumor activity when compared with endostatin. A non-clinical study was performed to evaluate the toxicokinetics and safety of M2ES in rhesus monkeys. After intravenous (IV) infusions of M2ES at a dose level of 3, 10, and 30mg/kg in rhesus monkeys, the concentration-time curves of M2ES were best fitted to a non-compartment model, and area under the curve (AUC) was positively correlated with the dosage. M2ES had a tendency to accumulate in vivo following successive IV infusions. Serum anti-M2ES IgG antibodies were generated quickly during IV administration, and the antibody level in serum did not significantly decrease after four-week recovery period. Animals administered IV infusions twice weekly (M2ES at 10 or 30mg/kg body weight per day) for 3months developed mild or moderate vacuolation of proximal tubule epithelial cell in proximal convoluted tubule of kidney, but this adverse-effect was reversible. In summary, M2ES was well tolerated and did not cause any serious toxicity. These pre-clinical safety data contribute to the initiation of the ongoing clinical study.

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.

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.

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.

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.

Thrombopoietin improved ventricular function and regulated remodeling genes in a rat model of myocardial infarction

BACKGROUND

Thrombopoietin (TPO) protects against heart damages by doxorubicin-induced cardiomyopathy in animal models. We aimed to investigate the therapeutic efficacy of TPO for treatment of myocardial infarction (MI) in a rat model and explored the mechanisms in terms of the genome-wide transcriptional profile, TPO downstream protein signals, and bone marrow endothelial progenitor cells (EPCs).

METHODS

Sprague-Dawley rats were divided into 3 groups: Sham-operated, MI (permanent ligation of the left coronary artery) and MI+TPO. Three doses of TPO were administered weekly for 2 weeks, and outcomes were assessed at 4 or 8 weeks post-injury.

RESULTS AND CONCLUSIONS

TPO treatment significantly improved left ventricular function, hemodynamic parameters, myocardium morphology, neovascularization and infarct size. MI damage upregulated a large cohort of gene expressions in the infarct border zone, including those functioned in cytoskeleton organization, vascular and matrix remodeling, muscle development, cell cycling and ion transport. TPO treatment significantly reversed these modulations. While phosphorylation of janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3) and protein kinase B (AKT) was modified in MI animals, TPO treatment regulated phosphorylation of STAT3 and extracellular signal-regulated kinases (ERK), and bone morphogenetic protein 1 (BMP1) protein level. TPO also increased EPC colonies in the bone marrow of MI animals. Our data showed that TPO alleviated damages of heart tissues from MI insults, possibly mediated by multi-factorial mechanisms including suppression of over-reacted ventricular remodeling, regulation of TPO downstream signals and mobilization of endothelial progenitor cells. TPO could be developed for treatment of cardiac damages.

Unique responses of stem cell-derived vascular endothelial and mesenchymal cells to high levels of glucose

Diabetes leads to complications in selected organ systems, and vascular endothelial cell (EC) dysfunction and loss is the key initiating and perpetuating step in the development of these complications. Experimental and clinical studies have shown that hyperglycemia leads to EC dysfunction in diabetes. Vascular stem cells that give rise to endothelial progenitor cells (EPCs) and mesenchymal progenitor cells (MPCs) represent an attractive target for cell therapy for diabetic patients. Whether these vascular stem/progenitor cells succumb to the adverse effects of high glucose remains unknown. We sought to determine whether adult vascular stem/progenitor cells display cellular activation and dysfunction upon exposure to high levels of glucose as seen in diabetic complications. Mononuclear cell fraction was prepared from adult blood and bone marrow. EPCs and MPCs were derived, characterized, and exposed to either normal glucose (5 mmol/L) or high glucose levels (25 mmol/L). We then assayed for cell activity and molecular changes following both acute and chronic exposure to high glucose. Our results show that high levels of glucose do not alter the derivation of either EPCs or MPCs. The adult blood-derived EPCs were also resistant to the effects of glucose in terms of growth. Acute exposure to high glucose levels increased caspase-3 activity in EPCs (1.4x increase) and mature ECs (2.3x increase). Interestingly, MPCs showed a transient reduction in growth upon glucose challenge. Our results also show that glucose skews the differentiation of MPCs towards the adipocyte lineage while suppressing other mesenchymal lineages. In summary, our studies show that EPCs are resistant to the effects of high levels of glucose, even following chronic exposure. The findings further show that hyperglycemia may have detrimental effects on the MPCs, causing reduced growth and altering the differentiation potential.

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.

Evolution of hemangioma endothelium

Infantile hemangioma is a benign vascular tumor, characterized by a unique life cycle consisting of rapid growth and spontaneous regression. Three distinct phases (proliferating, involuting, and involuted) take place over the course of approximately 5-8 years, with specific cell types defining each separate phase. The origin of the cells comprising hemangiomas has been deliberated over since the late 1800s. We have recently provided experimental evidence that hemangiomas arise from multipotent stem cells. These hemangioma stem cells that give rise to the endothelial cells are also the essential source of adipocytes during hemangioma involution. The molecular mechanisms that regulate the differentiation of the hemangioma stem cells remain unclear. Although recent studies have elucidated a number of signaling pathways underlying hemangioma pathogenesis, many unanswered questions remain. Herein, we review the unique cellular composition of infantile hemangioma, as well as some of the signaling pathways active within hemangioma-genesis. Understanding the mechanisms behind changes in cellular fate throughout the hemangioma growth pattern will not only provide insight into the stem cell population that resides within the tumor, but will help to establish more effective eradicating therapies.

Vascular stem cells in diabetic complications: evidence for a role in the pathogenesis and the therapeutic promise

Long standing diabetes leads to structural and functional alterations in both the micro- and the macro-vasculature. Vascular endothelial cells (ECs) are the primary target of the hyperglycemia-induced adverse effects. Vascular stem cells that give rise to endothelial progenitor cells (EPCs) and mesenchymal progenitor cells (MPCs) represent an attractive target for cell therapy for diabetic patients. A number of studies have reported EPC dysfunction as a novel participant in the culmination of the diabetic complications. The controversy behind the identity of EPCs and the similarity between these progenitor cells to hematopoietic cells has led to conflicting results. MPCs, on the other hand, have not been examined for a potential role in the pathogenesis of the complications. These multipotent cells, however, do show a therapeutic role. In this article, we summarize the vascular changes that occur in diabetic complications highlighting some of the common features, the key findings that illustrate an important role of vascular stem cells (VSCs) in the pathogenesis of chronic diabetic complications, and provide mechanisms by which these cells can be used for therapy.

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.