Highly efficient generation of human hepatocyte-like cells from induced pluripotent stem cells

There exists a worldwide shortage of donor livers available for orthotropic liver transplantation and hepatocyte transplantation therapies. In addition to their therapeutic potential, primary human hepatocytes facilitate the study of molecular and genetic aspects of human hepatic disease and development and provide a platform for drug toxicity screens and identification of novel pharmaceuticals with potential to treat a wide array of metabolic diseases. The demand for human hepatocytes, therefore, heavily outweighs their availability. As an alternative to using donor livers as a source of primary hepatocytes, we explored the possibility of generating patient-specific human hepatocytes from induced pluripotent stem (iPS) cells.

CONCLUSION

We demonstrate that mouse iPS cells retain full potential for fetal liver development and describe a procedure that facilitates the efficient generation of highly differentiated human hepatocyte-like cells from iPS cells that display key liver functions and can integrate into the hepatic parenchyma in vivo.

Sturge-Weber syndrome and port-wine stains caused by somatic mutation in GNAQ

BACKGROUND

The Sturge-Weber syndrome is a sporadic congenital neurocutaneous disorder characterized by a port-wine stain affecting the skin in the distribution of the ophthalmic branch of the trigeminal nerve, abnormal capillary venous vessels in the leptomeninges of the brain and choroid, glaucoma, seizures, stroke, and intellectual disability. It has been hypothesized that somatic mosaic mutations disrupting vascular development cause both the Sturge-Weber syndrome and port-wine stains, and the severity and extent of presentation are determined by the developmental time point at which the mutations occurred. To date, no such mutation has been identified.

METHODS

We performed whole-genome sequencing of DNA from paired samples of visibly affected and normal tissue from 3 persons with the Sturge-Weber syndrome. We tested for the presence of a somatic mosaic mutation in 97 samples from 50 persons with the Sturge-Weber syndrome, a port-wine stain, or neither (controls), using amplicon sequencing and SNaPshot assays, and investigated the effects of the mutation on downstream signaling, using phosphorylation-specific antibodies for relevant effectors and a luciferase reporter assay.

RESULTS

We identified a nonsynonymous single-nucleotide variant (c.548G→A, p.Arg183Gln) in GNAQ in samples of affected tissue from 88% of the participants (23 of 26) with the Sturge-Weber syndrome and from 92% of the participants (12 of 13) with apparently nonsyndromic port-wine stains, but not in any of the samples of affected tissue from 4 participants with an unrelated cerebrovascular malformation or in any of the samples from the 6 controls. The prevalence of the mutant allele in affected tissues ranged from 1.0 to 18.1%. Extracellular signal-regulated kinase activity was modestly increased during transgenic expression of mutant Gαq.

CONCLUSIONS

The Sturge-Weber syndrome and port-wine stains are caused by a somatic activating mutation in GNAQ. This finding confirms a long-standing hypothesis. (Funded by the National Institutes of Health and Hunter's Dream for a Cure Foundation.).

GLUT1: a newly discovered immunohistochemical marker for juvenile hemangiomas

Juvenile hemangiomas are common, benign vascular tumors of infancy. These lesions enlarge rapidly through cellular hyperplasia during the first year of life and then involute over several years. Distinctive histopathologic features of hemangiomas diminish during this evolution, and differentiation from vascular malformations becomes increasingly difficult. This distinction has important therapeutic implications, as juvenile hemangiomas differ from malformations in natural history and in potential for recurrence. We report here that high endothelial immunoreactivity for the erythrocyte-type glucose transporter protein GLUT1 is a specific feature of juvenile hemangiomas during all phases of these lesions. In a retrospective study, we found intense endothelial GLUT1 immunoreactivity, involving more than 50% of lesional microvessels, in 97% (139 of 143) of juvenile hemangiomas from patients aged 1 month to 11 years. No endothelial GLUT1 immunoreactivity was found in any of 66 vascular malformations (17 arteriovenous, 33 venous, 11 lymphatic, and 5 port-wine) from patients aged 5 days to 75 years, or in any of 20 pyogenic granulomas or 7 granulation tissue specimens. Abundant Ki-67 positivity in these latter lesions established that GLUT1 expression does not simply reflect mitotically active endothelium. Focal GLUT1 immunoreactivity was found in 3 of 12 angiosarcomas, but not in any of 5 hemangioendotheliomas (epithelioid or infantile kaposiform). These findings establish GLUT1 immunoreactivity as a highly selective and diagnostically useful marker for juvenile hemangiomas. Because high levels of endothelial GLUT1 expression in normal tissue are restricted to microvessels with blood-tissue barrier function, these findings also have implications for the molecular and developmental pathogenic mechanisms of juvenile hemangiomas.

Kaposiform Hemangioendothelioma

Kaposiform hemangioendothelioma (KH) is a rare tumor of childhood often associated with Kasabach-Merritt phenomenon (KMP) and occasionally lymphangiomatosis. Although generally considered distinct from other vascular neoplasms, its rarity has precluded a thorough study of its immunophenotypic profile and long-term behavior. Thirty-three cases of KH were reviewed and immunostained for alpha-smooth muscle actin, various endothelial markers (CD31, CD34, vWf, FLI1), a platelet marker (CD61), and the juvenile hemangioma-associated markers GLUT-1 and Lewis Y antigen (LeY). In addition, the presence of HHV-8 was evaluated by RT-PCR. The patients (20 males and 13 females) ranged in age from 2 weeks to 20 years (mean 3 years 9 months). Tumors developed on the extremities (17 cases), head/neck (8 cases), and other sites (8 cases) and affected both superficial and deep soft tissue. Those in the skin presented as slightly raised blue-red lesions. More than half of the patients presented with KMP (14 of 25). Tumors consisted of irregular, infiltrating nodules of compressed vessels, which modulated between areas resembling a capillary hemangioma and Kaposi sarcoma (KS). Endothelial cells in nodules were CD31, CD34, and FLI1 positive but negative for GLUT1 and LeY. Scattered "epithelioid" or glomeruloid islands featuring endothelium associated with clusters of plump alpha-smooth muscle actin-positive pericytes, stippled hemosiderin, and CD61-positive fibrin thrombi likely represent the morphologic sites of platelet consumption. Small and large lymphatic channels occurred in 22 of 33 cases and were typically seen peripheral or deep to the main tumor mass. HHV-8 transcripts were not identified (0 of 3 cases). Follow-up information was available in 22 patients (range 8 months to 15 years; mean 2 years) and indicated that 3 died of disease, 8 were alive with disease, and 10 were alive without residual disease. Two patients developed regional perinodal soft tissue involvement, but none developed distant metastases. KH is a lesion having both a vascular and lymphatic component. Its common association with KMP probably relates in part to unique architectural features that favor turbulent blood flow and platelet activation. KH can also be reliably separated from JH by GLUT-1 and LeY immunostaining, indicating differences in the morphologic and functional attributes of the endothelium between the two lesions. The absence of HHV-8 in KH underscores a different pathogenesis from Kaposi sarcoma. Our study, the largest to date, emphasizes that mortality is due to KMP and not metastatic disease, which appears limited to regional perinodal soft tissue. Given this behavior, its continued classification as a vascular tumor of intermediate malignancy is warranted.

Congenital nonprogressive hemangioma: a distinct clinicopathologic entity unlike infantile hemangioma

BACKGROUND

Infantile hemangiomas are common tumors, distinctive for their perinatal presentation, rapid growth during the first year of life, and subsequent involution-and for their expression of a unique immunophenotype shared by placental microvessels. Occasional "hemangiomas" differ from the classic form in presenting fully formed at birth, then following a static or rapidly involuting course. These congenitally fully developed lesions have generally been assumed to be clinical variants of more typical, postnatally developing hemangiomas. This assumption has not been tested by rigorous histologic and immunophenotypic comparisons.

OBJECTIVE

To compare the histologic and immunohistochemical features of congenital nonprogressive hemangiomas with those of typical, postnatally proliferating, hemangiomas.

DESIGN

All cellular vascular tumors resected from infants younger than 4 months at Arkansas Children's Hospital, Little Rock, over the past 20 years (43 lesions from 36 patients) were first characterized histologically and immunohistochemically, then clinically by chart review.

SETTING

A university-affiliated pediatric hospital.

MAIN OUTCOME MEASURES

Histologic appearance, immunoreactivity for the infantile hemangioma-associated antigens GLUT1 and LeY, and clinical behavior.

RESULTS

Congenital nonprogressive hemangiomas differed from postnatally proliferating infantile hemangiomas in histologic appearance and immunohistochemical profile. Distinguishing pathologic features of these tumors were lobules of capillaries set within densely fibrotic stroma containing hemosiderin deposits; focal lobular thrombosis and sclerosis; frequent association with multiple thin-walled vessels; absence of "intermingling" of the neovasculature with normal tissue elements; and lack of immunoreactivity for GLUT1 and LeY.

CONCLUSION

Congenital nonprogressive hemangiomas are histologically and immunophenotypically distinct from classically presenting hemangiomas of infancy, unlikely to be related to the latter in pathogenesis.

Somatic mutation of vascular endothelial growth factor receptors in juvenile hemangioma

Juvenile hemangiomas are the most common tumors of infancy, occurring in as many as 10% of all births. These benign vascular lesions enlarge rapidly during the first year of life by hyperplasia of endothelial cells and attendant pericytes and then spontaneously involute over a period of years, leaving loose fibrofatty tissue. Several hypotheses have been put forth concerning hemangiogenesis, including the possibility that the tumor is the result of somatic mutation in one or more components of critical vascular growth-regulatory pathways. To test this hypothesis, we obtained 15 proliferative-phase hemangiomas after surgical resection and dissected them to enrich for the lesional (endothelial and pericytic) components of each specimen. To determine whether hemangiomas represent a clonal expansion from a single progenitor cell, we assayed X-inactivation patterns for each lesion by using the polymorphic X-linked human androgen receptor gene. Twelve of 14 informative hemangiomas showed a significant degree of allelic loss after methylation-based and transcription-based polymerase chain reaction clonality assays, suggesting a nonrandom X-inactivation pattern and, thus, a monoclonal origin. We then sequenced genes encoding the receptors of the vascular endothelial growth factors (VEGFs) as candidates for potential somatic mutation. Mutations were found in two of the 15 hemangioma specimens: a missense mutation (P1147S) in the kinase domain of the VEGFR2 (FLK1/KDR) gene in one specimen and a missense mutation (P954S) in the kinase insert of the VEGFR3 (FLT4) gene in another specimen. In each case, the mutation was detected in tumor tissue but not in adjacent normal tissue. These results suggest that one potential mechanism involved in hemangioma formation is the alteration of the VEGF signaling pathway in endothelial and/or pericytic cells.

The nonrandom distribution of facial hemangiomas

OBJECTIVE

To map sites of occurrence of facial infantile hemangiomas and correlate these with pattern of tumor growth, clinical complications, and proximity to structural and developmental landmarks.

DESIGN

A retrospective medical record review of 205 patients diagnosed with facial infantile hemangioma.

SETTING

Arkansas Children's Hospital, Little Rock, a 250-bed teaching hospital affiliated with the University of Arkansas for Medical Sciences.

PATIENTS

Based on their clinical photographs, 232 of the hemangiomas were mapped on a facial schematic. Each lesion was encoded with a number reflective of its location, and this number was shared by other lesions occurring at the same site. Frequencies of complicating ulceration and airway obstruction were determined by medical record review.

RESULTS

Two patterns of tumor growth were evident among the hemangiomas analyzed: focal (177 lesions [76.3%]) and diffuse (55 lesions [23.7%]). The focal hemangiomas mapped to 22 sites of occurrence, all near lines of mesenchymal or mesenchymal-ectodermal embryonic fusion. The 55 diffuse hemangiomas showed a segmental tissue distribution and thus were designated as frontonasal (15 lesions [27%]), maxillary (19 lesions [35%]), or mandibular (21 lesions [38%]). Ulceration was 3 times more common in patients with diffuse hemangiomas (21 [51%] of 41) than in patients with focal hemangiomas (28 [17%] of 164). Airway obstruction was characteristic of diffuse mandibular hemangiomas.

CONCLUSIONS

Facial infantile hemangiomas occurred in 2 distinct patterns of tissue involvement: a focal type with a tumorlike appearance and a less common diffuse type with a plaquelike appearance. The diffuse lesions were more likely to be complicated by ulceration or airway obstruction and showed a strikingly segmental distribution pattern. Focal hemangiomas, in contrast, showed a predilection for regions of embryological fusion.

A Protein Kinase C Phosphorylation Motif in GLUT1 Affects Glucose Transport and is Mutated in GLUT1 Deficiency Syndrome

Protein kinase C has been implicated in the phosphorylation of the erythrocyte/brain glucose transporter, GLUT1, without a clear understanding of the site(s) of phosphorylation and the possible effects on glucose transport. Through in vitro kinase assays, mass spectrometry, and phosphospecific antibodies, we identify serine 226 in GLUT1 as a PKC phosphorylation site. Phosphorylation of S226 is required for the rapid increase in glucose uptake and enhanced cell surface localization of GLUT1 induced by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Endogenous GLUT1 is phosphorylated on S226 in primary endothelial cells in response to TPA or VEGF. Several naturally occurring, pathogenic mutations that cause GLUT1 deficiency syndrome disrupt this PKC phosphomotif, impair the phosphorylation of S226 in vitro, and block TPA-mediated increases in glucose uptake. We demonstrate that the phosphorylation of GLUT1 on S226 regulates glucose transport and propose that this modification is important in the physiological regulation of glucose transport.

Phospholipase C{gamma}1 is essential for T cell development, activation, and tolerance

Phospholipase Cgamma1 (PLCgamma1) is an important signaling effector of T cell receptor (TCR). To investigate the role of PLCgamma1 in T cell biology, we generated and examined mice with T cell-specific deletion of PLCgamma1. We demonstrate that PLCgamma1 deficiency affects positive and negative selection, significantly reduces single-positive thymocytes and peripheral T cells, and impairs TCR-induced proliferation and cytokine production, and the activation of ERK, JNK, AP-1, NFAT, and NF-kappaB. Importantly, PLCgamma1 deficiency impairs the development and function of FoxP3(+) regulatory T cells, causing inflammatory/autoimmune symptoms. Therefore, PLCgamma1 is essential for T cell development, activation, and tolerance.

Infantile hemangiomas are arrested in an early developmental vascular differentiation state

Infantile hemangiomas, the most common tumors of infancy, are vascular tumors characterized by rapid proliferation of endothelial cells during the first few months of postnatal life followed by slow spontaneous involution, whose molecular pathogenesis remains unclear. The recent identification of developmental expression of vascular lineage-specific markers prompted us to characterize infantile hemangiomas for the expression of lymphatic endothelial hyaluronan receptor-1 (LYVE-1), Prox-1, CD31 and CD34. We found that LYVE-1, a specific marker for normal and tumor-associated lymphatic vessels, was strongly expressed in tumor cells of infantile hemangiomas (n=28), but not in other vascular tumors including pyogenic granulomas (n=19, P<0.0001) or intramuscular hemangiomas (n=9), using LYVE-1/CD31 double immunostains. Whereas LYVE-1 expression was detected on the endothelial cells of all proliferating infantile hemangiomas, this lymphatic marker was absent from the lesional capillaries during involution in the majority of cases (P=0.0009). The majority of LYVE-1(+) endothelial cells also expressed CD34, but were negative for the lymphatic-specific homeobox protein Prox-1. Based on coexpression of both LYVE-1 and the blood vascular marker CD34, we propose that the endothelial cells in proliferating infantile hemangioma are arrested in an early developmental stage of vascular differentiation. The immature, incompletely differentiated immunophenotype of proliferating infantile hemangiomas may contribute to their rapid growth during the first few months of life.

Multifocal Lymphangioendotheliomatosis With Thrombocytopenia

BACKGROUND

Severe thrombocytopenic coagulopathy may complicate platelet-trapping vascular tumors such as kaposiform hemangioendothelioma and tufted angioma. Low-grade, chronic consumptive coagulopathy may occur with extensive venous and lymphatic malformations. We have also observed patients with rare multifocal, congenital skin and gastrointestinal (GI) tract vascular anomalies of distinctive and remarkably similar appearance, all associated with coagulopathy. We studied the clinical and histopathologic features of 3 patients demonstrating this previously uninvestigated phenomenon.

OBSERVATIONS

All 3 patients presented with hundreds of congenital red-brown skin plaques as large as a few centimeters, with similar lesions throughout the GI tract and severe GI tract bleeding. One patient had synovial involvement. All had significant thrombocytopenia, with prothrombin and partial thromboplastin times and fibrinogen levels near the reference range. Corticosteroids and/or interferon alfa treatment resulted in equivocal or no improvement. Skin lesions from all 3 patients were histologically distinctive and similar, including dilated, thin-walled vessels in the dermis and subcutis lined by hobnailed, proliferative endothelial cells (10%-15% immunoreactive for Ki-67), most displaying intraluminal papillary projections. Immunoreaction for the lymphatic marker LYVE-1 was uniformly present.

CONCLUSIONS

We propose the term multifocal lymphangioendotheliomatosis with thrombocytopenia to distinguish this newly recognized clinicopathological entity. These congenital lesions, like tufted angioma and kaposiform hemangioendothelioma, show lymphatic differentiation, strengthening the association between abnormal lymphatic endothelium and coagulopathy.

A new mathematical approach to the diffusion approximation theory for selective photothermolysis modeling and its implication in laser treatment of port-wine stains

BACKGROUND AND OBJECTIVES

Monte Carlo (MC) simulations of light-tissue interactions and analytical solutions for the diffusion approximation theory have been used to determine the optimal laser wavelength and radiant exposure to treat port-wine stains (PWS). Both approaches suggest that optimal parameters are a wavelength of 585 or 595-nm with pulse times of 0.45-20 milliseconds. However, which parameters are optimal is still unclear. As differences in vessel size and in temperature distribution within vessels appeared to be the main reasons for the varied responses to the same laser treatments, we sought to develop a solution to the diffusion approximation in order to calculate temperature distribution and the resulting coagulation pattern within specific blood vessels.

STUDY DESIGN/MATERIALS AND METHODS

The light and heat diffusion equations were simultaneously solved with the finite element method (FEM). The latent heat of evaporation was included in the thermal analysis. The temperature and coagulation patterns across specific blood vessels, within a heterogeneous medium, were calculated for laser wavelengths of 585 and 595-nm with clinical parameters.

RESULTS

At 1.2 mm deep, the calculations predicted that vessels ranging from 50 to 100 microm in diameter would be coagulated from top to bottom, small vessels (10 microm) would be spared, and vessels larger than 150 microm would be partially coagulated. Coagulation across vessels was more uniform for the 595-nm than for the 585-nm wavelength. Maximal temperatures did not exceed 100 degrees C because of the inclusion of latent heat in the thermal calculations.

CONCLUSIONS

To study laser treatments of PWS with the diffusion approximation, FEM is an effective method to calculate the coagulation patterns within specific blood vessels. To improve coagulation efficacy at 585 and 595-nm wavelengths, the radiant exposure should be increased without increasing the irradiance.

Creation and characterization of a renin knockout rat

The renin-angiotensin system plays an important role in the control of blood pressure (BP) and renal function. To illuminate the importance of renin in the context of a disease background in vivo, we used zinc-finger nucleases (ZFNs) designed to target the renin gene and create a renin knockout in the SS/JrHsdMcwi (SS) rat. ZFN against renin caused a 10-bp deletion in exon 5, resulting in a frameshift mutation. Plasma renin activity was undetectable in the Ren-/- rat, and renin protein was absent from the juxtaglomerular cells in the kidney. Body weight was lower in the Ren-/- rats (than in the Ren+/- or wild-type littermates), and conscious BP on low-salt diet (0.4% NaCl) was 58 ± 2 mm Hg in the Ren-/- male rats versus 117 mm Hg in the Ren+/- littermates, a reduction of almost 50 mm Hg. Blood urea nitrogen (BUN) and plasma creatinine levels were elevated in the Ren-/- strain (BUN 112 ± 7 versus 23 ± 2 mg/dL and creatinine 0.53 ± 0.02 versus 0.26 ± 0.02 mg/dL), and kidney morphology was abnormal with a rudimentary inner renal medulla, cortical interstitial fibrosis, thickening of arterial walls, and abnormally shaped glomeruli. The development of the first rat knockout in the renin-angiotensin system demonstrates the efficacy of the ZFN technology for creating knockout rats for cardiovascular disease on any genetic background and emphasizes the role of renin in BP regulation and kidney function even in the low-renin SS rat.

Multi-class chemical exposure in rural Peru using silicone wristbands

Exposure monitoring with personal silicone wristband samplers was demonstrated in Peru in four agriculture and urban communities where logistic and practical constraints hinder use of more traditional approaches. Wristbands and associated methods enabled quantitation of 63 pesticides and screening for 1397 chemicals including environmental contaminants and personal care products. Sixty-eight wristbands were worn for approximately one month by volunteers from four communities of Alto Mayo, Peru. We identified 106 chemicals from eight chemical classes among all wristbands. Agricultural communities were characterized by pesticides and PAHs, while the urban communities had more personal care products present. Multiple linear regressions explained up to 40% of variance in wristbands from chlorpyrifos, cypermethrin, and DDT and its metabolites (DDx) (r²=0.39, 0.30, 0.40, respectively). All three pesticides were significantly different between communities, and cypermethrin and DDx were associated with participant age. The calculated relative age of DDT suggested some communities had more recent exposure than others. This work aids health research in the Alto Mayo and beyond by identifying typical mixtures and potential sources of exposure to organic chemicals in the personal environment. Silicone wristband sampling with chemical screening is a candidate for widespread use in exposure monitoring in remote areas.

Donor fraction cell-free DNA and rejection in adult and pediatric heart transplantation

BACKGROUND

Endomyocardial biopsy (EMB) is the current standard for rejection surveillance in heart transplant recipients. The quantification of donor-specific cell-free DNA (cfDNA) may be an appropriate biomarker for non-invasive rejection surveillance. A multicenter prospective blinded study (DNA-Based Transplant Rejection Test, DTRT) investigated the value of donor fraction (DF), defined as the ratio of cfDNA specific to the transplanted organ to the total amount of cfDNA present in a blood sample.

METHODS

A total of 241 heart transplant patients were recruited from 7 centers. Age at transplant ranged from 8 days to 73 years, with 146 subjects <18 years and 95 ≥18 years. All the patients were followed for at least 1 year, with blood samples drawn at routine and for-cause biopsies. A total of 624 biopsy-paired samples were included for analysis through a commercially available cfDNA assay (myTAI_HEART, TAI Diagnostics Inc.). A blinded analysis of repeated measures compared the outcomes using receiver operating characteristic (ROC) curves. All primary clinical end-points were monitored at 100%. All analysis and conclusions were reviewed by both an independent external oversight committee and the National Institutes of Health-mandated DTRT steering committee.

RESULTS

DF in acute cellular rejection (ACR) 1R/2R (n = 15) was higher than ACR 0R (n = 42) (p = 0.02); DF in antibody-mediated rejection pAMR1 (n = 8) and pAMR2 (n = 12) (p = 0.05) were higher than pAMR0 (n = 466) (p = 0.04 and p = 0.05 respectively). An optimal DF threshold was determined by the use of an ROC analysis, which ruled out the presence of either ACR or antibody-mediated rejection.

CONCLUSIONS

The cell-free DNA DF holds promise as a non-invasive diagnostic test to rule out acute rejection in both adult and pediatric heart transplant populations.

Vascular Actions of Angiotensin 1-7 in the Human Microcirculation: Novel Role for Telomerase

OBJECTIVE

This study examined vascular actions of angiotensin 1-7 (ANG 1-7) in human atrial and adipose arterioles.

APPROACH AND RESULTS

The endothelium-derived hyperpolarizing factor of flow-mediated dilation (FMD) switches from antiproliferative nitric oxide (NO) to proatherosclerotic hydrogen peroxide in arterioles from humans with coronary artery disease (CAD). Given the known vasoprotective properties of ANG 1-7, we tested the hypothesis that overnight ANG 1-7 treatment restores the NO component of FMD in arterioles from patients with CAD. Endothelial telomerase activity is essential for preserving the NO component of vasodilation in the human microcirculation; thus, we also tested whether telomerase activity was necessary for ANG 1-7-mediated vasoprotection by treating separate arterioles with ANG 1-7±the telomerase inhibitor 2-[[(2E)-3-(2-naphthalenyl)-1-oxo-2-butenyl1-yl]amino]benzoic acid. ANG 1-7 dilated arterioles from patients without CAD, whereas dilation was significantly reduced in arterioles from patients with CAD. In atrial arterioles from patients with CAD incubated with ANG 1-7 overnight, the NO synthase inhibitor NG-nitro-l-arginine methyl ester abolished FMD, whereas the hydrogen peroxide scavenger polyethylene glycol catalase had no effect. Conversely, in vessels incubated with ANG 1-7+2-[[(2E)-3-(2-naphthalenyl)-1-oxo-2-butenyl1-yl]amino]benzoic acid, NG-nitro-l-arginine methyl ester had no effect on FMD, but polyethylene glycol catalase abolished dilation. In cultured human coronary artery endothelial cells, ANG 1-7 significantly increased telomerase activity. These results indicate that ANG 1-7 dilates human microvessels, and dilation is abrogated in the presence of CAD. Furthermore, ANG 1-7 treatment is sufficient to restore the NO component of FMD in arterioles from patients with CAD in a telomerase-dependent manner.

CONCLUSIONS

ANG 1-7 exerts vasoprotection in the human microvasculature via modulation of telomerase activity.

Arteriovenous Malformations of the Tongue: A Spectrum of Disease

OBJECTIVES

To examine our vascular anomalies team's experience with tongue arteriovenous malformations (AVM) with specific emphasis on the spectrum on disease and surgical management.

METHODS

Retrospective chart review of 11 patients (10 female, 1 male), discovered from 1997 to 2005 with histological, radiographic, and clinical characteristics consistent with tongue AVM.

RESULTS

Four patients displayed advanced disease with malformations involving the tongue, floor of mouth, and neck. Contributions from multiple feeding arteries were identified by angiography as each patient reported a prior history of surgical or embolic procedures. These lesions required preoperative embolization and extensive resection with complex reconstruction (mean operating time, 10.9 hr). One patient had evidence of recurrent disease (mean follow-up, 24.6 mo). In contrast, seven patients presented with discreet tongue malformations with a single feeding lingual artery. These patients reported no prior intervention, required only one resection (mean operating time, 2.8 hr), and have shown no evidence of recurrence (mean follow-up, 11 mo). Slight histologic differences between advanced versus focal tongue AVM were identified.

CONCLUSIONS

This study suggests that tongue AVM can occur within a spectrum of disease with different clinical presentations, radiographic findings, and histology among patients with focal versus advanced lesions. Inadequate treatment is thought to contribute to collateral flow and disease progression in advanced AVM, making further management difficult. However, focal tongue AVM may represent early lesions that are more amenable to surgical management.

Protective role of Trpc6 knockout in the progression of diabetic kidney disease

Diabetic kidney disease (DKD) is a chronic kidney pathology that leads to end-stage renal disease. Previous studies from our laboratory indicate that there is an association between the development of DKD and the transient receptor potential canonical 6 (TRPC6) channel. Trpc6 expression and activity were increased in the streptozotocin (STZ)-treated Dahl Salt-sensitive (Dahl SS) rat, an established model of type 1 diabetes. Here, using a Trpc6 knockout created on the Dahl SS rat background (SS^Trpc6-/-), we test the hypothesis that the absence of Trpc6 will protect podocytes and kidney function during the development of DKD. Four groups of animals (control SS^WT, SS^Trpc6-/-, STZ-treated SS^WT, and STZ-SS^Trpc6-/-) were utilized in this study. Diabetes development was monitored for 11 wk after STZ injection with periodic weight, glucose, and urinary output measurements. There was an increase in albuminuria and glomerular injury following STZ treatment, which was not different between Dahl SS and SS^Trpc6-/- groups. Western blot analysis revealed elevated levels of nephrin in urine samples of STZ-SS^WT rats, which was higher compared with STZ-SS^Trpc6-/- rats. Furthermore, pathological increases in basal [Ca²⁺]_i levels and foot process damage of podocytes during the development of DKD was attenuated in the STZ-SS^Trpc6-/- compared with STZ-SS^WT rats. Overall, our data indicate that TRPC6 channel inhibition may have at least partial renoprotective effects, which could lead to the development of new pharmacological tools to treat or prevent the progression of DKD.

Congenital cardiac, aortic arch, and vascular bed anomalies in PHACE syndrome (from the International PHACE Syndrome Registry)

PHACE syndrome represents the association of large infantile hemangiomas of the head and neck with brain, cerebrovascular, cardiac, ocular, and ventral or midline defects. Cardiac and cerebrovascular anomalies are the most common extracutaneous features of PHACE, and they also constitute the greatest source of potential morbidity. Congenital heart disease in PHACE is incompletely described, and this study was conducted to better characterize its features. This study of the International PHACE Syndrome Registry represents the largest central review of clinical, radiologic, and histopathologic data for cardiovascular anomalies in patients with PHACE to date. Sixty-two (41%) of 150 subjects had intracardiac, aortic arch, or brachiocephalic vessel anomalies. Aberrant origin of a subclavian artery was the most common cardiovascular anomaly (present in 31 (21%) of 150 subjects). Coarctation was the second most common anomaly, identified in 28 (19%) of 150 subjects, and can be missed clinically in patients with PHACE because of the frequent association of arch obstruction with aberrant subclavian origin. Twenty-three (37%) of 62 subjects with cardiovascular anomalies required procedural intervention. A greater percentage of hemangiomas were located on the left side of the head and neck in patients with coarctation (46% vs 39%); however, hemangioma distribution did not predict the presence of cardiovascular anomalies overall. In conclusion, PHACE is associated with a high risk of congenital heart disease. Cardiac and aortic arch imaging with detailed assessment of arch patency and brachiocephalic origins is essential for any patient suspected of having PHACE. Longitudinal investigation is needed to determine the long-term outcomes of cardiovascular anomalies in PHACE.

RASA1-dependent cellular export of collagen IV controls blood and lymphatic vascular development

Combined germline and somatic second hit inactivating mutations of the RASA1 gene, which encodes a negative regulator of the Ras signaling pathway, cause blood and lymphatic vascular lesions in the human autosomal dominant vascular disorder capillary malformation-arteriovenous malformation (CM-AVM). How RASA1 mutations in endothelial cells (EC) result in vascular lesions in CM-AVM is unknown. Here, using different murine models of RASA1-deficiency, we found that RASA1 was essential for the survival of EC during developmental angiogenesis in which primitive vascular plexuses are remodeled into hierarchical vascular networks. RASA1 was required for EC survival during developmental angiogenesis because it was necessary for export of collagen IV from EC and deposition in vascular basement membranes. In the absence of RASA1, dysregulated Ras mitogen-activated protein kinase (MAPK) signal transduction in EC resulted in impaired folding of collagen IV and its retention in the endoplasmic reticulum (ER) leading to EC death. Remarkably, the chemical chaperone, 4-phenylbutyric acid, and small molecule inhibitors of MAPK and 2-oxoglutarate dependent collagen IV modifying enzymes rescued ER retention of collagen IV and EC apoptosis and resulted in normal developmental angiogenesis. These findings have important implications with regards an understanding of the molecular pathogenesis of CM-AVM and possible means of treatment.

Pediatric Vascular Tumors and Malformations

Pediatric vascular tumors and malformations, comprising a broad category of lesions often referred to as vascular anomalies, are a heterogenous group of clinicopathologically distinct entities. Pathologists, clinicians, and radiologists have traditionally lumped these lesions under the generic term, hemangioma, sometimes qualified by modifiers, such as capillary or cavernous. Advances in understanding underlying pathogenetic mechanisms support more specific classification and more specifically targeted therapies. Multidisciplinary consensus has moved toward a biologically based classification system and therapeutic approach for dealing with these lesions. This content focuses on the histologic, immunophenotypical, and clinical features that distinguish the major types of vascular tumors and malformations presenting in infancy and childhood. Pathogenic mechanisms are also briefly reviewed.