Building better vasculature

The expanding role of BAP1 in clear cell renal cell carcinoma

Mutations drive renal cell carcinoma biology and tumor growth. The BRCA1-associated protein-1 (BAP1) gene is frequently mutated in clear cell renal cell carcinoma (ccRCC) and has emerged as a prognostic and putative predictive biomarker. In this review, we discuss the role of BAP1 as a signature event of a subtype of ccRCC marked by aggressiveness, inflammation, and possibly a heightened response to immunotherapy.

Cotransplant With Pancreatic Islet Homogenate Improved Survival and Long-Term Efficacy of Islet Transplant in Streptozotocin-Diabetic Rats

OBJECTIVES

Pancreatic islet transplant is suggested as a promising treatment option in diabetes, but the number of viable and functional islets and the long-term efficacy of transplanted islets have not been satisfactory. Islet isolation leads to destruction of the extracellular matrix and loss of trophic support of islets, which reduces their survival and function. Reconstruction of islet microenvironment with biomaterials may preserve islet survival and graft efficacy. Accordingly, we investigated the effects of pancreatic islet homogenate on islet quality and graft outcomes in diabetic rats.

MATERIALS AND METHODS

Islets were isolated from the pancreas of Sprague Dawley rats and were cultured with or without pancreatic islet homogenate. Before transplant, viability, insulin content, and insulin released from cultured islets were assessed. Islets were then transplanted into subcapsular space of diabetic rat kidney. Transplant outcomes were evaluated by plasma glucose and insulin levels, glucose tolerance tests, and stress oxidative markers.

RESULTS

Viability and insulin release in the pancreatic islet homogenate-treated islets were significantly higher than that in the control islets. After transplant of islets, recipient rats with pancreatic islet homogenate showed significant decreases in blood glucose and malondialdehyde levels and increases in superoxide dismutase activity and plasma insulin levels.

CONCLUSIONS

Islet treatment with pancreatic islet homogenate could improve islet survival and transplant function and outcomes. Oxidative stress reduction might be a secondary beneficial effect of improved quality of treated islets.

Deciphering Intratumoral Molecular Heterogeneity in Clear Cell Renal Cell Carcinoma with a Radiogenomics Platform

PURPOSE

Intratumoral heterogeneity (ITH) challenges the molecular characterization of clear cell renal cell carcinoma (ccRCC) and is a confounding factor for therapy selection. Most approaches to evaluate ITH are limited by two-dimensional ex vivo tissue analyses. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can noninvasively assess the spatial landscape of entire tumors in their natural milieu. To assess the potential of DCE-MRI, we developed a vertically integrated radiogenomics colocalization approach for multi-region tissue acquisition and analyses. We investigated the potential of spatial imaging features to predict molecular subtypes using histopathologic and transcriptome correlatives.

EXPERIMENTAL DESIGN

We report the results of a prospective study of 49 patients with ccRCC who underwent DCE-MRI prior to nephrectomy. Surgical specimens were sectioned to match the MRI acquisition plane. RNA sequencing data from multi-region tumor sampling (80 samples) were correlated with percent enhancement on DCE-MRI in spatially colocalized regions of the tumor. Independently, we evaluated clinical applicability of our findings in 19 patients with metastatic RCC (39 metastases) treated with first-line antiangiogenic drugs or checkpoint inhibitors.

RESULTS

DCE-MRI identified tumor features associated with angiogenesis and inflammation, which differed within and across tumors, and likely contribute to the efficacy of antiangiogenic drugs and immunotherapies. Our vertically integrated analyses show that angiogenesis and inflammation frequently coexist and spatially anti-correlate in the same tumor. Furthermore, MRI contrast enhancement identifies phenotypes with better response to antiangiogenic therapy among patients with metastatic RCC.

CONCLUSIONS

These findings have important implications for decision models based on biopsy samples and highlight the potential of more comprehensive imaging-based approaches.

Effects of platelet-rich plasma on the pancreatic islet survival and function, islet transplantation outcome and pancreatic pdx1 and insulin gene expression in streptozotocin-induced diabetic rats

Platelet-rich plasma (PRP) is a therapeutic option in different fields based on its growth factors. We investigated influence of PRP on islet survival, function, transplantation outcomes, and pancreatic genes expression in diabetic rats. In vitro: pancreatic isolated islets were incubated with/without PRP then viability, insulin secretion, and content were assessed. In vivo: Series 1 were designed to determine whether islet treatment with PRP improves transplantation outcome in diabetic rats by evaluating plasma glucose and insulin concentrations and oxidative parameters. Series 2, effects of PRP subcutaneous injection were evaluated on pancreatic genes expression and glucose tolerance test in diabetic rats. PRP enhanced viability and secretary function of islet. Reduced glucose and malondialdehyde levels as well as increased insulin levels, superoxide dismutase activity, and expressions of pdx1 and insulin were observed in diabetic rats. PRP treatment has positive effects on islet viability, function, transplantation outcome, and pancreatic genes expression in diabetic rats.

HIF-2 Complex Dissociation, Target Inhibition, and Acquired Resistance with PT2385, a First-in-Class HIF-2 Inhibitor, in Patients with Clear Cell Renal Cell Carcinoma

PURPOSE

The heterodimeric transcription factor HIF-2 is arguably the most important driver of clear cell renal cell carcinoma (ccRCC). Although considered undruggable, structural analyses at the University of Texas Southwestern Medical Center (UTSW, Dallas, TX) identified a vulnerability in the α subunit, which heterodimerizes with HIF1β, ultimately leading to the development of PT2385, a first-in-class inhibitor. PT2385 was safe and active in a first-in-human phase I clinical trial of patients with extensively pretreated ccRCC at UTSW and elsewhere. There were no dose-limiting toxicities, and disease control ≥4 months was achieved in 42% of patients.

PATIENTS AND METHODS

We conducted a prospective companion substudy involving a subset of patients enrolled in the phase I clinical trial at UTSW (n = 10), who were treated at the phase II dose or above, involving multiparametric MRI, blood draws, and serial biopsies for biochemical, whole exome, and RNA-sequencing studies.

RESULTS

PT2385 inhibited HIF-2 in nontumor tissues, as determined by a reduction in erythropoietin levels (a pharmacodynamic marker), in all but one patient, who had the lowest drug concentrations. PT2385 dissociated HIF-2 complexes in ccRCC metastases, and inhibited HIF-2 target gene expression. In contrast, HIF-1 complexes were unaffected. Prolonged PT2385 treatment resulted in the acquisition of resistance, and we identified a gatekeeper mutation (G323E) in HIF2α, which interferes with drug binding and precluded HIF-2 complex dissociation. In addition, we identified an acquired TP53 mutation elsewhere, suggesting a possible alternate mechanism of resistance.

CONCLUSIONS

These findings demonstrate a core dependency on HIF-2 in metastatic ccRCC and establish PT2385 as a highly specific HIF-2 inhibitor in humans. New approaches will be required to target mutant HIF-2 beyond PT2385 or the closely related PT2977 (MK-6482).

Targeted protein degradation: elements of PROTAC design

Targeted protein degradation using Proteolysis Targeting Chimeras (PROTACs) has emerged as a novel therapeutic modality in drug discovery. PROTACs mediate the degradation of select proteins of interest (POIs) by hijacking the activity of E3 ubiquitin ligases for POI ubiquitination and subsequent degradation by the 26S proteasome. This hijacking mechanism has been used to degrade various types of disease-relevant POIs. In this review, we aim to highlight the recent advances in targeted protein degradation and describe the challenges that need to be addressed in order to efficiently develop potent PROTACs.

Design, synthesis of a novel 4-O-methylsaucerneol analogue LXY7824 as potent HIF-1 inhibitor and anti-cancer agent

Hypoxia-inducible factor-1 (HIF-1), an important transcription factor for tumor survival, is an attractive target for anti-cancer treatment. Herein, we present the design and synthesis of LXY7824, a simplified analogue of 4-O-methylsaucerneol. In addition, its significant HIF-1 inhibitory activity and potent anti-cancer activity in vivo and in vitro were also reported.

A stimuli responsive liposome loaded hydrogel provides flexible on-demand release of therapeutic agents

Lysolipid-based thermosensitive liposomes (LTSL) embedded in a chitosan-based thermoresponsive hydrogel matrix (denoted Lipogel) represents a novel approach for the spatiotemporal release of therapeutic agents. The entrapment of drug-loaded liposomes in an injectable hydrogel permits local liposome retention, thus providing a prolonged release in target tissues. Moreover, release can be controlled through the use of a minimally invasive external hyperthermic stimulus. Temporal control of release is particularly important for complex multi-step physiological processes, such as angiogenesis, in which different signals are required at different times in order to produce a robust vasculature. In the present work, we demonstrate the ability of Lipogel to provide a flexible, easily modifiable release platform. It is possible to tune the release kinetics of different drugs providing a passive release of one therapeutic agent loaded within the gel and activating the release of a second LTSL encapsulated agent via a hyperthermic stimulus. In addition, it was possible to modify the drug dosage within Lipogel by varying the duration of hyperthermia. This can allow for adaption of drug dosing in real time. As an in vitro proof of concept with this system, we investigated Lipogels ability to recruit stem cells and then elevate their production of vascular endothelial growth factor (VEGF) by controlling the release of a pro-angiogenic drug, desferroxamine (DFO) with an external hyperthermic stimulus. Initial cell recruitment was accomplished by the passive release of hepatocyte growth factor (HGF) from the hydrogel, inducing a migratory response in cells, followed by the delayed release of DFO from thermosensitive liposomes, resulting in a significant increase in VEGF expression. This delayed release could be controlled up to 14days. Moreover, by changing the duration of the hyperthermic pulse, a fine control over the amount of DFO released was achieved. The ability to trigger the release of therapeutic agents at a specific timepoint and control dosing level through changes in duration of hyperthermia enables sequential multi-dose profiles.

STATEMENT OF SIGNIFICANCE

This paper details the development of a heat responsive liposome loaded hydrogel for the controlled release of pro-angiogenic therapeutics. Lysolipid-based thermosensitive liposomes (LTSLs) embedded in a chitosan-based thermoresponsive hydrogel matrix represents a novel approach for the spatiotemporal release of therapeutic agents. This hydrogel platform demonstrates remarkable flexibility in terms of drug scheduling and sequencing, enabling the release of multiple agents and the ability to control drug dosing in a minimally invasive fashion. The possibility to tune the release kinetics of different drugs independently represents an innovative platform to utilise for a variety of treatments. This approach allows a significant degree of flexibility in achieving a desired release profile via a minimally invasive stimulus, enabling treatments to be tuned in response to changing symptoms and complications.

Biomaterial-Enhanced Cell and Drug Delivery: Lessons Learned in the Cardiac Field and Future Perspectives

Heart failure is a significant clinical issue. It is the cause of enormous healthcare costs worldwide and results in significant morbidity and mortality. Cardiac regenerative therapy has progressed considerably from clinical and preclinical studies delivering simple suspensions of cells, macromolecule, and small molecules to more advanced delivery methods utilizing biomaterial scaffolds as depots for localized targeted delivery to the damaged and ischemic myocardium. Here, regenerative strategies for cardiac tissue engineering with a focus on advanced delivery strategies and the use of multimodal therapeutic strategies are reviewed.

MiR675-5p Acts on HIF-1α to Sustain Hypoxic Responses: A New Therapeutic Strategy for Glioma

Hypoxia is a common feature in solid tumours. In glioma, it is considered the major driving force for tumour angiogenesis and correlates with enhanced resistance to conventional therapies, increased invasiveness and a poor prognosis for patients. Here we describe, for the first time, that miR675-5p, embedded in hypoxia-induced long non-coding RNA H19, plays a mandatory role in establishing a hypoxic response and in promoting hypoxia-mediated angiogenesis. We demonstrated, in vitro and in vivo, that miR675-5p over expression in normoxia is sufficient to induce a hypoxic moreover, miR675-5p depletion in low oxygen conditions, drastically abolishes hypoxic responses including angiogenesis. In addition, our data indicate an interaction of miR675-5p, HIF-1α mRNA and the RNA Binding Protein HuR in hypoxia-induced responses. We suggest the modulation of miR675-5p as a new therapeutic option to promote or abolish hypoxia induced angiogenesis.

ZEB1 Upregulates VEGF Expression and Stimulates Angiogenesis in Breast Cancer

Although zinc finger E-box binding homeobox 1 (ZEB1) has been identified as a key factor in the regulation of breast cancer differentiation and metastasis, its potential role in modulating tumor angiogenesis has not been fully examined. Here, we present the novel finding that conditioned medium derived from ZEB1-expressing MDA-MB-231 cells significantly increased the capillary tube formation of human umbilical vein endothelial cells (HUVECs), whereas ZEB1 knockdown by RNA interference had the opposite effect. ZEB1 caused marked upregulation of the expression of vascular endothelial growth factor A (VEGFA) at both mRNA and protein levels. Pre-incubation of HUVECs with anti-VEGFA neutralized antibody attenuated ZEB1-mediated tube formation of HUVECs. In breast cancer tissues, expression of ZEB1 was positively correlated with those of VEGFA and CD31. At the molecular level, ZEB1 activated VEGFA transcription by increasing SP1 recruitment to its promoter, which was mediated via the activation of PI3K and p38 pathways. Using a nude mouse xenograft model, we demonstrated that elevated expression of ZEB1 promotes in vivo tumorigenesis and angiogenesis in breast cancer. Collectively, we found that ZEB1-expressing breast cancer cells increase VEGFA production and thus stimulate tumor growth and angiogenesis via a paracrine mechanism.

Screening of antiangiogenic potential of twenty two marine invertebrate extracts of phylum Mollusca from South East Coast of India

OBJECTIVE

To evaluate the antiangiogenic potential of twenty two marine invertebrate species of Phylum Mollusca from south east coast of India.

METHODS

Live specimens of molluscan species were collected and their methanolic extracts were evaluated for preliminary antiangiogenic activity using the in ovo chick chorio-allantoic membrane assay. The extracts were further evaluated for in vivo antiangiogenic activity using chemical cautery induced corneal neovascularization assay in rats and oxygen induced retinopathy assay in rat pups.

RESULTS

In the chick chorio-allantoic membrane assay, four methanolic extracts of marine molluscan species viz. Meretrix meretrix, Meretrix casta, Telescopium telescopium and Bursa crumena methanolic extracts exhibited noticeable antiangiogenic activity at the tested concentration of 200 µg whereby they significantly inhibited the VEGF induced proliferation of new blood vessels. Among these four extracts, the methanolic extract of Meretrix casta exhibited relatively higher degree of antiangiogenic activity with an inhibitiory percentage (64.63%) of the VEGF induced neovascularization followed by the methanolic extracts of Telescopium telescopium (62.02%), Bursa crumena (60.48%) and Meretrix meretrix (47.01%). These four methanolic extracts were further evaluated for in vivo antiangiogenic activity whereby the methanolic extract of Telescopium telescopium exhibited most noticeable inhibition (42.58%) of the corneal neovascularization in rats in comparison to the sham treated group, and also exhibited most noticeable inhibition (31.31%) of the oxygen induced retinal neovascularization in rat pups in comparison to the hyperoxia group that was observed for considerable retinal neovascularization.

CONCLUSIONS

The significant antiangiogenic activity evinced by the extract of Telescopium telescopium merits further investigation for ocular neovascular diseases.

A nanomedicine approach to effectively inhibit contracture during bladder acellular matrix allograft-induced bladder regeneration by sustained delivery of vascular endothelial growth factor

Macroscopic evidence of contracture has been identified as a major issue during the regeneration process. We hypothesize that lack of angiogenesis is the primary cause of contracture and explore a nanomedicine approach to achieve sustained release of vascular endothelial growth factor (VEGF) to stimulate angiogenesis. We evaluate the efficacy of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) for long-term (3 months) sustained release of VEGF in bladder acellular matrix allografts (BAMA) in a swine model. We anticipate that the sustained release of VEGF could stimulate angiogenesis along the regeneration process and thereby inhibit contracture. Bladder was replaced with BAMA (5×5 cm), modified with PLGA NPs encapsulated with VEGF in a pig model. The time points chosen for sampling were 1, 2, 4, and 12 weeks. The regenerated areas were then measured to obtain the contracture rate, and the extent of revascularization was calculated using histological and morphological features. In the control group of animals, the bladder was replaced with only BAMA. The in vivo release of VEGF was evident for ∼3 months, achieving the goal of long-acting sustained release, and successfully promoted the regeneration of blood vessels and smooth muscle fibers. In addition, less collagen deposition was observed in the experimental group compared with control. Most importantly, the inhibition of contracture was highly significant, and the ultimate contracture rate decreased by ∼57% in the experimental group compared with control. In isolated strips analysis, there were no significant differences between BAMA-regenerated (either VEGF added or not) and autogenous bladder. BAMA modified with VEGF-loaded PLGA-NPs can sustainably release VEGF in vivo (>3 months) to stimulate angiogenesis leading to the inhibition of contracture. This is the first study to report a viable nanomedicine-based strategy to overcome contracture during bladder regeneration induced by BAMA. Furthermore, this study also confirms that insufficient angiogenesis plays a crucial role in the onset of contracture.

Inhibition of VEGF: a novel mechanism to control angiogenesis by Withania somnifera's key metabolite Withaferin A

Purpose

Angiogenesis, or new blood vessel formation from existing one, plays both beneficial and detrimental roles in living organisms in different aspects. Vascular endothelial growth factor (VEGF), a signal protein, well established as key regulator of vasculogenesis and angiogenesis. VEGF ensures oxygen supply to the tissues when blood supply is not adequate, or tissue environment is in hypoxic condition. Limited expression of VEGF is necessary, but if it is over expressed, then it can lead to serious disease like cancer. Cancers that have ability to express VEGF are more efficient to grow and metastasize because solid cancers cannot grow larger than a limited size without adequate blood and oxygen supply. Anti-VEGF drugs are already available in the market to control angiogenesis, but they are often associated with severe side-effects like fetal bleeding and proteinuria in the large number of patients. To avoid such side-effects, new insight is required to find potential compounds as anti-VEGF from natural sources. In the present investigation, molecular docking studies were carried out to find the potentiality of Withaferin A, a key metabolite of Withania somnifera, as an inhibitor of VEGF.

Methods

Molecular Docking studies were performed in DockingServer and SwissDock. Bevacizumab, a commercial anti-VEGF drug, was used as reference to compare the activity of Withaferin A. X-ray crystallographic structure of VEGF, was retrieved from Protein Data Bank (PDB), and used as drug target protein. Structure of Withaferin A and Bevacizumab was obtained from PubChem and ZINC databases. Molecular visualization was performed using UCSF Chimera.

Results

Withaferin A showed favorable binding with VEGF with low binding energy in comparison to Bevacizumab. Molecular Docking studies also revealed potential protein-ligand interactions for both Withaferin A and Bevacizumab.

Conclusions

Conclusively our results strongly suggest that Withaferin A is a potent anti-VEGF agent as ascertained by its potential interaction with VEGF. This scientific hypothesis might provide a better insight to control angiogenesis as well as to control solid cancer growth and metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/2193-9616-1-11) contains supplementary material, which is available to authorized users.

Illicit organogenesis: Methods and substances of doping and manipulation

Doping and manipulation are undesirable companions of professional and amateur sport. Numerous adverse analytical findings as well as confessions of athletes have demonstrated the variety of doping agents and methods as well as the inventiveness of cheating sportsmen. Besides 'conventional' misuse of drugs such as erythropoietin and insulins, experts fear that therapeutics that are currently undergoing clinical trials might be part of current or future doping regimens, which aim for an increased functionality and performance or organs and tissues. Emerging drugs such as selective androgen receptor modulators (SARMs), hypoxia-inducible factor (HIF) complex stabilizers or modulators of muscle fiber calcium channels are considered relevant for current and future doping controls due to their high potential for misuse in sports.

Serum vascular endothelial growth factor and angiopoietin-2 are associated with the severity of systemic inflammation rather than the presence of hemoptysis in patients with inflammatory lung disease

PURPOSE

Vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) are major mediators of angiogenesis and are induced by tissue inflammation and hypoxia. The purpose of this study was to investigate whether serum VEGF and Ang-2 are associated with the presence of hemoptysis and the extent of systemic inflammation in patients with inflammatory lung diseases.

MATERIALS AND METHODS

We prospectively enrolled 52 patients with inflammatory lung disease between June 2008 and October 2009.

RESULTS

The median values of VEGF and Ang-2 were 436 pg/mL and 2383 pg/mL, respectively. There was a significant positive correlation between serum Ang-2 and VEGF levels. VEGF levels were not significantly different according to the presence of hemoptysis. C-reactive protein (CRP) and Ang-2 level were significantly higher in patients without hemoptysis (n=26) than in those with hemoptysis (n=26; p<0.001 and p<0.001, respectively). CRP and arterial oxygen tension (PaO₂) were significantly correlated with both serum VEGF (p=0.032 and p=0.016, respectively) and Ang-2 levels (p<0.001 and p=0.041, respectively), after adjusting for other factors. Age and the absence of hemoptysis were factors correlated with serum Ang-2 levels.

CONCLUSION

Our study suggests that serum VEGF and Ang-2 levels are associated with PaO₂ and the severity of inflammation rather than the presence of hemoptysis in patients with inflammatory lung diseases. Thus, hemoptysis may not be mediated by increased serum levels of VEGF and Ang-2 in patients with inflammatory lung diseases, and further studies are required to determine the mechanisms of hemoptysis.

Ginsenoside-Rg1 mediates a hypoxia-independent upregulation of hypoxia-inducible factor-1α to promote angiogenesis

Hypoxia-inducible factor (HIF-1) is the key transcription regulator for multiple angiogenic factors and is an appealing target. Ginsenoside-Rg1, a nontoxic saponin isolated from the rhizome of Panax ginseng, exhibits potent proangiogenic activity and has the potential to be developed as a new angiotherapeutic agent. However, the mechanisms by which Rg1 promotes angiogenesis are not fully understood. Here, we show that Rg1 is an effective stimulator of HIF-1α under normal cellular oxygen conditions in human umbilical vein endothelial cells. HIF-1α steady-state mRNA was not affected by Rg1. Rather, HIF-1α protein synthesis was stimulated by Rg1. This effect was associated with constitutive activation of phosphatidylinositol 3-kinase (PI3K)/Akt and its effector p70 S6 kinase (p70(S6K)), but not extracellular-signal regulated kinase 1/2. We further revealed that HIF-1α induction triggered the expression of target genes, including vascular endothelial growth factor (VEGF). The use of small molecule inhibitors LY294002 or rapamycin to inhibit PI3K/Akt and p70(S6K) activities, respectively, resulted in diminished HIF-1α activation and subsequent VEGF expression. RNA interference-mediated knockdown of HIF-1α suppressed Rg1-induced VEGF synthesis and angiogenic tube formation, confirming that the effect was HIF-1α specific. Similarly, the angiogenic phenotype could be reversed by inhibition of PI3K/Akt and p70(S6K). These results define a hypoxia-independent activation of HIF-1α, uncovering a novel mechanism for Rg1 that could play a major role in angiogenesis and vascular remodeling.

Functional importance of blood flow dynamics and partial oxygen pressure in the anterior pituitary

The pulsatile release of hormone is obligatory for the control of a range of important body homeostatic functions. To generate these pulses, endocrine organs have developed finely regulated mechanisms to modulate blood flow both to meet the metabolic demand associated with intense endocrine cell activity and to ensure the temporally precise uptake of secreted hormone into the bloodstream. With a particular focus on the pituitary gland as a model system, we review here the importance of the interplay between blood flow regulation and oxygen tensions in the functioning of endocrine systems, and the known regulatory signals involved in the modification of flow patterns under both normal physiological and pathological conditions.

Cooperative signaling for angiogenesis and neovascularization by VEGF and HGF following islet transplantation

BACKGROUND

Delayed angiogenesis remains a significant challenge to the survival of transplanted islets. In this study, using a murine model of subcutaneous islet transplantation with matrigel basement membrane matrix, we determined the role of the proangiogenic growth factors in enhancing the islet engraftment.

METHODS

BALB/c islets were transplanted subcutaneously in growth factor reduced (GFR) or growth factor supplemented (GFS) matrigel into diabetic severe combined immunodeficient mice. GFS matrigel was prepared by supplementing GFR with proangiogenic factors, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The functioning grafts were harvested at 15 days and vessel formation was analyzed histopathologically.

RESULTS

Our results demonstrate that suboptimal (250) islet equivalents in GFS-VEGF+HGF were able to restore normoglycemia, whereas those transplanted in GFR failed to reverse diabetes. Histopathology of the GFS-VEGF+HGF graft revealed 12±3 blood vessels per field, whereas GFR, GFS-VEGF, and GFS-HGF grafts had only 3±1, 6±2, and 4±1 blood vessels, respectively. Insulin staining demonstrated increased number of islets in matrigel supplemented with VEGF and HGF. Protein and mRNA analysis demonstrated enhanced intercellular adhesion molecule and vascular cell adhesion molecule within the islets when supplemented with both VEGF+HGF suggesting stable blood vessel formation. Transcription factors focal adhesion kinase phosphorylation and extracellular signal-regulated kinase1/2 phosphorylation were also increased (8-fold and 4.6-fold, respectively) when both the growth factors were present. There was weak expression of transcription factors when VEGF or HGF were supplemented alone.

CONCLUSION

We conclude that proangiogenic growth factors, VEGF and HGF, synergistically enhance angiogenesis after islet transplantation leading to stable engraftment.

Loading of VEGF to the heparin cross-linked demineralized bone matrix improves vascularization of the scaffold

Deficient vascularization is one of the prominent shortcomings of porous tissue-engineering scaffolds, which results in insufficient oxygen and nutrients transportation. Here, heparin cross-linked demineralized bone matrices (HC-DBM) pre-loaded with vascular endothelial growth factor (VEGF) were designed to promote cells and new microvessels invasion into the matrices. After being chemical crosslinked with heparin by N-hydroxysuccinimide and N-(3-di-methylaminopropyl)-N'-ethylcarbodiimide, the scaffold could bind more VEGF than the non-crosslinked one and achieve localized and sustained delivery. The biological activity of VEGF binding on heparinized collagen was demonstrated by promoting endothelial cells proliferation. Evaluation of the angiogenic potential of heparinized DBM loaded with VEGF was further investigated by subcutaneous implantation. Improved angiogenesis of heparinized DBM loaded with VEGF was observed from haematoxylin-eosin staining and immunohistochemistry examination. The results demonstrated that heparin cross-linked DBM binding VEGF could be a useful strategy to stimulate cells and blood vessels invasion into the scaffolds.

Investigating expression profiles of VEGF-Flk, and Angpt1 during development of gas glands in Japanese eel (Anguilla japonica)

Angiogenesis is a highly regulated physiological process in animals. Angiopoietin-1 (Angpt1) induces the signaling pathways related to vessel maturation in late phase of angiogenesis, which recruits pericyte supplements to make compact interaction with vessel tubes. There are only few data showing Angpt1 functions in fish. By using degenerate primers, partial sequence (812 bp) of Angpt1 was cloned from Anguilla japonica, and deduced amino acids showed 80% similarity to those of zebrafish. Physiological functions of cloned eel Angpt1 were studied by in vitro and in vivo manipulations with gas glands (rete mirabile) taken as the tested target tissues. RT-PCR and immunofluorescent staining techniques were performed to examine the expression patterns of Angpt1 as well as VEGF-Flk. Experimental data showed that, in vitro, bFGF, PPAR beta agonist, and estradiol affected Angpt1 expression; while cobalt ions, a VEGF expression-inducer, did not affect Angpt1 expression. In vivo, expression levels of Angpt1 increased with body growth. Furthermore, Angpt1 expressions increased significantly in the late stage of gas glands in the stimulated eel. Successive expression patterns on VEGF-Flk, and Angpt1 on different development stages of gas glands were observed. Our results suggest that the original function of angiopoietin-1 on angiogenesis is conserved during evolution.

Cerebral arteriovenous malformations. Part 1: cellular and molecular biology

Object

The scientific understanding of the nature of arteriovenous malformations (AVMs) in the brain is evolving. It is clear from current work that AVMs can undergo a variety of phenomena, including growth, remodeling, and/or regression—and the responsible processes are both molecular and physiological. A review of these complex processes is critical to directing future therapeutic approaches. The authors performed a comprehensive review of the literature to evaluate current information regarding the genetics, pathophysiology, and behavior of AVMs.

Methods

A comprehensive literature review was conducted using PubMed to reveal the molecular biology of AVMs as it relates to their complex growth and behavior patterns.

Results

Growth factors involved in AVMs include vascular endothelial growth factor, fibroblast growth factor, transforming growth factor β, angiopoietins, fibronectin, laminin, integrin, and matrix metalloproteinases.

Conclusions

Understanding the complicated molecular milieu of developing AVMs is essential for defining their natural history. Growth factors, extracellular matrix proteins, and other molecular markers will be the key to unlocking novel targeted drug treatments for these brain malformations.

n-Propyl gallate activates hypoxia-inducible factor 1 by modulating intracellular oxygen-sensing systems

HIF-1 (hypoxia-inducible factor 1) is a master regulator of cellular adaptive responses to hypoxia. The expression and transcriptional activity of the HIF-1alpha subunit is stringently controlled by intracellular oxygen tension through the action of prolyl and asparaginyl hydroxylases. In the present study we demonstrate that PG (n-propyl gallate) activates HIF-1 and expression of its downstream target genes under normoxic conditions in cultured cells and in mice. The stability and transcriptional activity of HIF-1alpha are increased by PG. PG treatment inhibits the interaction between HIF-1alpha and VHL (von Hippel-Lindau protein) and promotes the interaction between HIF-1alpha and p300, indicating that PG inhibits the activity of both prolyl and asparaginyl HIF-1alpha hydroxylases. We conclude that PG activates HIF-1 and enhances the resultant gene expression by directly affecting the intracellular oxygen sensing system in vitro and in vivo and that PG represents a lead compound for the development of a non-toxic activator of HIF-1.

Vasculogenesis, angiogenesis, and arteriogenesis: mechanisms of blood vessel formation and remodeling

In this review, the concept of oxygen homeostasis will be presented as an organizing principle for discussion of the phylogeny, ontogeny, physiology, and pathology of blood vessel formation and remodeling, with a focus on molecular mechanisms and potential therapeutic applications.

Gas phase reaction of substituted isoquinolines to carboxylic acids in ion trap and triple quadrupole mass spectrometers after electrospray ionization and collision-induced dissociation

Within the mass spectrometric study of bisubstituted isoquinolines that possess great potential as prolylhydroxylase inhibitor drug candidates (e.g., FG-2216), unusually favored gas-phase formations of carboxylic acids after collisional activation were observed. The protonated molecule of [(1-chloro-4-hydroxy-isoquinoline-3-carbonyl)-amino]-acetic acid was dissociated, yielding the 1-chloro-4-hydroxy-isoquinoline-3-carboxylic acid methyleneamide cation. Subsequent dissociation caused the nominal elimination of 11 u that resulted from the loss of HCN and concomitant addition of oxygen to the product ion, which formed the protonated 1-chloro-4-hydroxy-isoquinoline-3-carboxylic acid. The preference of this structure under mass spectrometric conditions was substantiated by tandem mass spectrometry analyses using the corresponding methyl ester (1-chloro-4-hydroxy-isoquinoline-3-carboxylic acid methyl ester) that eliminated methylene (-14 u) upon collisional activation. Moreover, the major product ion of 1-chloro-4-hydroxy-isoquinoline-3-carboxylic acid, which resulted from the loss of water in MS3 experiments, restored the precursor ion structure by re-addition of H2O. Evidences for these phenomena were obtained by chemical synthesis of proposed gas-phase intermediates, H/D exchange experiments, high-resolution/high accuracy mass spectrometry at MSn level, and "ping-pong" analyses (MS7, in which the precursor ion was dissociated and the respective product ion isolated to regenerate the precursor ion for repeated dissociation. Based on these results, dissociation pathways for [(1-chloro-4-hydroxy-isoquinoline-3-carbonyl)-amino]-acetic acid were suggested that can be further utilized for the characterization of structurally related compounds or metabolic products in clinical, forensic, or doping control analysis.

Novel three-dimensional analysis tool for vascular trees indicates complete micro-networks, not single capillaries, as the angiogenic endpoint in mice overexpressing human VEGF(165) in the brain

To adequately supply tissues with oxygen and nutrients, the formation of functional vascular networks requires generation of normal, healthy vessels and their arrangement into an effective network architecture. While our knowledge about the development of single vessels significantly increased during the last years, mechanisms responsible for network formation are still poorly understood. This is probably due to the lack of suitable methods for quantification of structural properties of microvascular networks. Previously we showed that cerebral blood flow is not increased in mice exhibiting a 2- to 3-fold higher density of normal and perfused capillaries as a result of transgenic overexpression of the human vascular endothelial growth factor (VEGF(165)). Here we used vascular corrosion casting and hierarchical micro-computed tomography combined with a new network analysis tool to characterize the vascular architecture in gray and white matter of these mice. Our results indicate that VEGF overexpression leads to formation of additional micro-networks connected to higher order vessels rather than insertion of individual capillaries into the existing vessel structure. This implies that the smallest "angiogenic quantum", i.e. the final, stable result of angiogenesis and subsequent remodeling, is not a single microvessel, but a complete micro-network. In conclusion, high-resolution 3D imaging combined with network analysis can substantially improve our understanding of vascular architecture, beneficial for the development of therapeutic angiogenesis as a clinical tool for applications such as wound healing or treatment of ischemic diseases.

Role of renal cortical neovascularization in experimental hypercholesterolemia

Hypercholesterolemia induces renal inflammation and neovascularization, associated with renal endothelial dysfunction and injury. Neovascularization might conceivably represent a defense mechanism to sustain renal perfusion. Therefore, the present study was designed to test the hypothesis that preventing neovascularization using thalidomide, a potent anti-inflammatory and antiangiogenic agent, would impair basal renal hemodynamics in experimental hypercholesterolemia. Single-kidney function and hemodynamic responses to endothelium-dependent challenge were assessed in pigs after 12 weeks of hypercholesterolemia, hypercholesterolemia chronically supplemented with thalidomide (4 mg/kg per day), and normal controls. Renal microvascular architecture was then studied ex vivo using 3D microcomputed tomography imaging and inflammation, angiogenesis, and oxidative stress explored in renal tissue. The density of larger microvessels (200 to 500 microm) was selectively decreased in hypercholesterolemia plus thalidomide and accompanied by a decreased fraction of angiogenic, integrin beta(3)-positive microvessels (9.9%+/-0.9% versus 25.5%+/-1.7%; P<0.05 versus hypercholesterolemia), implying decreased angiogenic activity. Furthermore, thalidomide increased renal expression of endothelial NO synthase and decreased tumor necrosis factor-alpha and renal inflammation but did not decrease oxidative stress. Thalidomide also decreased basal renal blood flow and glomerular filtration rate but normalized the blunted renal hemodynamic responses in hypercholesterolemia. Attenuated inflammation and pathological angiogenesis achieved in hypercholesterolemia by thalidomide are accompanied by restoration of renovascular endothelial function but decreased basal renal hemodynamics. This study, therefore, suggests that neovascularization in the hypercholesterolemic kidney is a compensatory mechanism that sustains basal renal vascular function.

CXCR4/CXCL12 axis promotes VEGF-mediated tumor angiogenesis through Akt signaling pathway

CXC chemokine receptor 4 (CXCR4) has been shown to play a critical role in chemotaxis and homing, which are key steps in cancer metastasis. There is also increasing evidence that links this receptor to angiogenesis; however, its molecular basis remains elusive. Vascular endothelial growth factor (VEGF), one of the major angiogenic factors, promotes the formation of leaky tumor vasculatures that are the hallmarks of tumor progression. Here, we investigated whether CXCR4 induces the expression of VEGF through the PI3K/Akt pathway. Our results showed that CXCR4/CXCL12 induced Akt phosphorylation, which resulted in upregulation of VEGF at both the mRNA and protein levels. Conversely, blocking the activation of Akt signaling led to a decrease in VEGF protein levels; blocking CXCR4/CXCL12 interaction with a CXCR4 antagonist suppressed tumor angiogenesis and growth in vivo. Furthermore, VEGF mRNA levels correlated well with CXCR4 mRNA levels in patient tumor samples. In summary, our study demonstrates that the CXCR4/CXCL12 signaling axis can induce angiogenesis and progression of tumors by increasing expression of VEGF through the activation of PI3K/Akt pathway. Our findings suggest that targeting CXCR4 could provide a potential new anti-angiogenic therapy to suppress the formation of both primary and metastatic tumors.

Increased angiogenesis and blood vessel maturation in acellular collagen–heparin scaffolds containing both FGF2 and VEGF

An important issue in tissue engineering is the vascularisation of the implanted construct, which often takes several weeks. In vivo, the growth factors VEGF and FGF2 show a combined effect on both angiogenesis and maturation of blood vessels. Therefore, we hypothesise that the addition of these growth factors to an acellular construct increases blood vessel formation and maturation. To systematically evaluate the contribution of each scaffold component with respect to tissue response and in particular to blood vessel formation, five porous scaffolds were prepared and characterised, viz.: collagen, collagen with heparin, and collagen with heparin plus one or two growth factors (rrFGF2 and rrVEGF). Scaffolds were subcutaneously implanted in 3 months old Wistar rats. Of all scaffolds tested, the one with a combination of growth factors displayed the highest density of blood vessels (type IV collagen) and most mature blood vessels (smooth muscle actin). In addition, no hypoxic cells were found in this scaffold at day 7 and 21 (hypoxia inducible factor 1-alpha). These results indicate that the addition of both FGF2 and VEGF to an acellular construct enhances an early mature vasculature. This opens prospects for (acellular) tissue-engineered constructs in conditions as ischaemic heart disease or diabetic ulcers.

Transcription Factor EPAS1 Regulates Insulin Signaling Pathway

Obesity, which results from adipose differentiation and adipocyte hypertrophy, is a primary risk factor of these life-style-diseases. Obesity, is primary risk factor of these life-style-diseases, results from adipose differentiation and adipocyte hypertrophy. Adipose differentiation is regulated by several transcriptional factors, and we have focused here on the roles played by endothelial PAS domain protein1 (EPAS1) in adipogenesis. EPAS1 was identified as a factor responsible for hypoxia responses, such as angiogenesis, here we demonstrated that EPAS1 is highly induced during adipose differentiation in vivo and in vitro. We then analyzed EPAS1 promoter activity during adipose differentiation in 3T3-L1 cells. We showed that the sequence -478/-445 is responsible for the up-regulation of EPAS1 expression during adipose differentiation and that the activity of this region is controlled by Sp1 and Sp3. To examine whether EPAS1 exerts an influence on adipogenesis, we overexpressed dominant negative form of EPAS1 in 3T3-L1 cells. The expression of EPAS1 (1-485) allowed cells to accumulate only a minimum amount of lipid droplets. Therefore, induction of EPAS1 expression is necessary for execution of adipose differentiation program. The mechanism involves the direct transcriptional regulation of Glut1, Glut4 and IRS3 genes by EPAS1. These results also confirmed that the protein level of EPAS1 was increased by insulin stimulation in adipocytes. Taken together, this result also indicated that EPAS1 plays a role in the part of insulin action. Therefore, these results suggest that the quantitative and functional alteration of EPAS1 are involved in metabolic syndrome occurrence.

Gallate, the component of HIF-inducing catechins, inhibits HIF prolyl hydroxylase

Catechins have recently been reported to increase the cellular content of the hypoxia-inducible factor (HIF)-1alpha within mammalian cells. These catechins have a gallate moiety as a common structure. We now report that n-propyl gallate (nPG) also increases the HIF-1alpha protein in the rat heart-derived H9c2 cells. The increase was dose-dependent and reached a maximum at 2-4h after the addition of nPG to the cells. nPG did not change the HIF-1alpha mRNA level, showing that the increase is a posttranscriptional event. Although nPG did not inhibit the HIF prolyl hydroxylase, gallate, the hydrolysis product of nPG, inhibited the enzyme completely at submillimolar concentrations. Model building studies on the human HIF prolyl hydroxylase 2 showed that the two phenolate oxygen atoms of gallate form a chelate with the active site Fe(2+), while the carboxyl group of gallate forms a strong ionic/hydrogen bonding interaction with Arg383, explaining why nPG, which has an esterified carboxyl group, is unable to inhibit the hydroxylase. Together with the observation that gallate was detected in the H9c2 cells treated with nPG, these results suggest that nPG incorporated into the cells is hydrolyzed and the released gallate inhibits the HIF prolyl hydroxylase, thereby reducing the HIF degradation rate and increasing the HIF-1alpha content.

Hypoxia-inducible transcription factor–1 alpha determines sensitivity of endothelial cells to the proteosome inhibitor bortezomib

Angiogenesis is a complex, orchestrated process that plays a critical role in several conditions and has special relevance in the progression of cancer. Hypoxia is the major stimulus for angiogenesis, and hypoxia-inducible transcription factor–1 alpha (HIF-1α) is its key mediator. We set up a novel in vitro model of HIF-1α up-regulation by treating human umbilical vein endothelial cells (HUVECs) with the hypoxia-mimicking deferoxamine (DFO) and found that this condition was sufficient to promote angiogenesis, like the well-known HUVEC model cultured under low pO2. The proteasome inhibitor bortezomib, which induces strong apoptosis in cancer cells, abrogated proliferation and angiogenesis of HUVECs when used at a high concentration (100 nM), yet promoted both functions at a low dosage (10 nM). This double-edged effect appeared to be mediated by differential effects exerted by the different concentrations of bortezomib on 2 master regulators of tumor-associated angiogenesis, HIF-1α and nuclear factor kappa B (NF-kB). Significantly, when HUVECs were induced to express HIF-1α prior to bortezomib treatment, proliferative and angiogenic responses were abolished, and a greatly enhanced proapoptotic effect was promoted with both concentrations of the drug. These findings indicate that HIF-1α up-regulation may sensitize endothelial cells to the antiangiogenic and proapoptotic effects of bortezomib and might be exploited to target tumor-associated vessels in the course of antiangiogenic therapies.

Design and synthesis of a series of novel pyrazolopyridines as HIF 1-α prolyl hydroxylase inhibitors

Recently resolved X-ray crystal structure of HIF-1alpha prolyl hydroxylase was used to design and develop a novel series of pyrazolopyridines as potent HIF-1alpha prolyl hydroxylase inhibitors. The activity of these compounds was determined in a human EGLN-1 assay. Structure-based design aided in optimizing the potency of the initial lead (2, IC(50) of 11 microM) to a potent (11l, 190 nM) EGLN-1 inhibitor. Several of these analogs were potent VEGF inducers in a cell-based assay. These pyrazolopyridines were also effective in stabilizing HIF-1alpha.

Structure-based design, synthesis, and SAR evaluation of a new series of 8-hydroxyquinolines as HIF-1α prolyl hydroxylase inhibitors

A new series of potent 8-hydroxyquinolines was designed based on the newly resolved X-ray crystal structure of EGLN-1. Both alkyl and aryl 8-hydroxyquinoline-7-carboxyamides were good HIF-1alpha prolyl hydroxylase (EGLN) inhibitors. In subsequent VEGF induction assays, these exhibited potent VEGF activity. In addition, this class of compounds did show the ability to stabilize HIF-1alpha.

A novel series of imidazo[1,2-a]pyridine derivatives as HIF-1α prolyl hydroxylase inhibitors

Utilizing modeling information from a recently resolved structure of human HIF-1alpha prolyl hydroxylase (EGLN1) and structure-based design, a novel series of imidazo[1,2-a]pyridine derivatives was prepared. The activity of these compounds was determined in a human EGLN1 assay and a limited SAR was developed.

An endothelial-cell-enriched primary culture system to study vascular endothelial growth factor (VEGF A) expression in a teleost, the Japanese eel (Anguilla japonica)

A partial gene for eel (Anguilla japonica) vascular endothelial growth factor (VEGF) has been cloned and an endothelial-cell-enriched primary culture derived from rete mirabile established to study regulation of the expression of the eel VEGF gene. Cells were cultured in M199 medium containing 0.1% fetal calf serum (FCS) and serum-free M199 medium for long-and short-term experiments, respectively. Cells were separately treated with cobalt ions (Co2+), basic fibroblast growth factor (bFGF), and estradiol (E2), which have been demonstrated to stimulate mammalian VEGF A expression, followed by quantification of the VEGF mRNA levels by real-time reverse transcription polymerase chain reaction. Our results show that: (1) the deduced eel VEGF protein encoded by the cloned gene is about 130 amino acids in length, and is closely related to a zebrafish (Danio rerio) VEGF A; (2) the endothelial-cell-enriched rete mirabile primary culture containing mainly (over 70%) the capillary endothelial cells; (3) the expression levels of the eel VEGF transcript were increased by Co2+, bFGF, and E2 treatments in a dose-and time-dependent manner. Our data demonstrate that an eel partial VEGF gene has been cloned and its regulation of expression in endothelial-cell-enriched rete mirabile cell culture is similar to that in higher vertebrates.

Expression of integrins in cerebral arteriovenous and cavernous malformations

OBJECTIVE

To assess and compare levels and patterns of expression for integrins alphavbeta1, alphavbeta3, and alphavbeta5 in arteriovenous malformations (AVMs) and cavernous malformations (CCMs) of the brain.

MATERIALS AND METHODS

Specimens from 10 AVM and 10 CCM lesions were selected from 112 patients with AVMs and 97 patients with CCMs who were treated microsurgically in the Department of Neurosurgery, Marmara University, Istanbul, Turkey. Sections were immunohistochemically stained with antibodies for integrins alphavbeta1, alphavbeta3, and alphavbeta5. Separate histological layers of the vascular wall were evaluated, and levels of expression were graded using a four-tier system.

RESULTS

Integrin alphavbeta1 was more strongly expressed in AVMs than in CCMs. This difference was most pronounced in the endothelium and subendothelium/media. Integrin alphavbeta3 was more strongly expressed in CCM endothelium than in AVM endothelium (average grades, 0.9 and 0.4, respectively). All 10 of the CCM lesions expressed integrin alphavbeta5 in the endothelium, whereas only five of the AVMs showed minimal expression of this molecule in the endothelium.

CONCLUSION

Current scientific understanding of the roles integrins play in angiogenesis is far from complete. The levels and patterns of expression for these molecules in the histological layers of the vascular walls of AVMs and CCMs provide some clues about the complex biological activities of integrins in these lesions. If one accepts the premise that immunohistochemistry has its inherent methodological problems, integrins alphavbeta1, alphavbeta3, and alphavbeta5 are expressed in AVMs and CCMs in different ways that may be linked to stages of angiogenic maturation. Integrin alphavbeta1 is expressed more strongly in endothelium and subendothelium/media of AVMs than in the corresponding layers of CCMs. Integrins alphavbeta3 and alphavbeta5 are expressed more strongly in CCM endothelium than in AVM endothelium. In addition, integrin alphavbeta5 staining was stronger in CCM subendothelium than AVM subendothelium/media.

Sex-related dimorphic response of HIF-1 alpha expression in myocardial ischemia

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) plays a role in a number of cell-protective pathways after ischemia. There are clear sex-related differences in the remodeling process, and hearts from males tend to dilate in response to pathological loads and ischemia to a greater degree than do hearts from females. Thus we hypothesized that there would be a sex-related dimorphic response of HIF-1 alpha to an ischemic event. Male and female rats were euthanized 5 and 24 h after coronary ligation (M-MI and F-MI; MI, myocardial ischemia), and HIF-1 alpha expression was determined by immunohistochemistry, Western blot, and quantitative RT-PCR. Sham-operated male and female animals served as controls (M-SH and F-SH). In the ischemic area, histochemical analysis at 5 h showed that HIF was expressed in 33% of cell nuclei in M-MI and in 55% in F-MI. At 24 h, HIF expression increased to 49% in M-MI and to 82% in F-MI (P < 0.05 vs. SH and also M-MI vs. F-MI). This difference was not only statistically significant between the two sexes at 24 h but also within each sex at 5 and 24 h after ligation. Western blots confirmed that, at 24 h after ischemia, HIF protein increased significantly in both male and female hearts relative to sham-operated animals but that the increase in females was 60% greater than that seen in males. mRNA expression of HIF was significantly increased at 24 h in F-MI versus M-MI and sham-operated animals. Expression of downstream HIF target genes (heme oxygenase and brain natriuretic peptide) was increased in proportion to the levels of HIF expression. These data suggest a novel cellular mechanism to explain the sex-related dimorphic response to ischemia and also the possibility that exogenous modulation of HIF might represent a new therapeutic approach to preventing left ventricular remodeling.

Transcriptional regulation of the hypoxia inducible factor-2alpha (HIF-2alpha) gene during adipose differentiation in 3T3-L1 cells

Adipose differentiation is regulated by coordination of several signaling pathways and transcription factors. We recently showed that Hypoxia inducible factor-2alpha (HIF-2alpha) plays several supporting roles in adipose differentiation and adipocytes functions including regulation of glucose uptake followed by lipid synthesis. HIF-2alpha expression is increased during adipogenesis, indicating that its up-regulation is necessary for execution of adipogenesis and maintenance of mature adipocytes functions. Therefore, in this study, to understand the mechanism by which HIF-2alpha expression is induced during adipogenesis, we investigated the promoter activity of HIF-2alpha gene during adipogenesis in 3T3-L1 cells. A comparison of HIF-2alpha promoter activity between preadipocytes and adipocytes revealed that the sequence -478/-445 is the putative core element that contributes to differentiation-dependent up-regulation of HIF-2alpha promoter activity. Electrophoretic mobility shift assays showed the presence of the specific nuclear factor bound to the sequence -478/-445 in both preadipocytes and adipocytes. Computer analysis revealed that this element contains several Sp1/Sp3 binding sites. Indeed, the presence of Sp1/Sp3 consensus oligonucleotides diminished the formation of the complexes composed of the sequence -478/-445 and the nuclear factor. Furthermore, specific retarded bands were supershifted with anti-Sp1 or -Sp3 antibodies. Binding of Sp1 and Sp3 to this element was also confirmed by chromatin immunoprecipitation analysis. The element encompassing -478/-445 favors Sp3 in preadipocytes and Sp1 in adipocytes. Finally, the activity of -478/-445 was increased by Sp1 but decreased by Sp3. Consequently, these results suggest that Sp1 and Sp3 are involved in transcriptional regulation of HIF-2alpha expression during adipogenesis in 3T3-L1 cells.

Engineering of a vascularized scaffold for artificial tissue and organ generation

Tissue engineering is an emerging field in regenerative medicine to overcome the problem of end-stage organ failure. However, complex tissues and organs need a vascular supply to guaranty graft survival and render bioartificial organ function. Here we developed methods to decellularize porcine small bowl segments and repopulate the remaining venous and arterial tubular structures within these matrices with allogeneic porcine endothelial progenitor cells. Cellular adherence and vitality was characterized by quantitative 2-[18F]-fluoro-2'-desoxy-glucose (FDG) positron emission tomography (PET) and subsequent immunohistological work up. The generated matrices showed insulin-dependent FDG uptake predominantly in the region of the former vascular structures. Stain for vitality and the specific endothelial markers CD31, VE-Cadherin and Flk-1 matched this functional finding. Providing evidence for vitality up to 3 weeks post reconstitution and typical endothelial differentiation, these results indicate that our generated matrix allows the generation of complex bioartificial tissues and organs for experimental and future clinical application.

Better vascular engraftment and function in pancreatic islets transplanted without prior culture

AIMS/HYPOTHESIS

Recent studies suggest that donor endothelial cells may contribute to islet graft revascularisation. Since islet endothelial cells disappear during culture, we hypothesised that transplantation of islets without prior culture is beneficial for their engraftment.

METHODS

Cultured (4-7 days) or freshly isolated islets (<4 h after donor pancreas extirpation) were syngeneically transplanted into Wistar-Furth rats and C57Bl/6 mice beneath the renal capsule. Islet graft revascularisation was evaluated by measuring vascular density, blood flow and tissue oxygen tension. Islet graft function was investigated by a minimal islet mass model in inbred mice (C57Bl/6).

RESULTS

Four days after implantation, the partial pressure of oxygen (pO2) in the transplanted cultured islets was less than 10 mmHg (1.33 kPa), but tended to be higher in grafts composed of freshly isolated islets. The pO2 in the grafts of freshly isolated islets had more than doubled 4 weeks later, whereas the pO2 in the grafts of cultured islets remained at values similar to those recorded 4 days after transplantation. Transplanted freshly isolated islets also had a higher vascular density than transplanted cultured islets (approximately 40 vs approximately 25% of that in endogenous islets) when investigated 1 month post-implantation. When applying a minimal islet mass model in inbred mice, 200 freshly isolated islets cured alloxan-diabetic mice in all cases, whereas only 33% of the group receiving similar numbers of cultured islets were cured.

CONCLUSIONS/INTERPRETATION

Transplantation of pancreatic islets without prior culture is beneficial for their vascular engraftment and function.

A prolactin family paralog regulates reproductive adaptations to a physiological stressor

Successful species develop strategies to optimize their reproductive performance. This optimization likely includes the evolution of genes that specifically permit reproduction in physiologically challenging conditions. The prolactin (PRL) family gene cluster is one of 25 mouse-specific gene clusters, the majority of which are associated with reproduction. A prevailing theme characterizing the PRL family is its connection with pregnancy and mechanisms controlling viviparity. PRL-like protein A (PLP-A) is one of 26 genes located within the PRL family locus. It is a nonclassical member of the PRL family (e.g., PLP-A does not use the PRL receptor) produced by trophoblast cells of the chorioallantoic placenta and acts on uterine natural killer cells. In this report, the biology of PLP-A has been investigated by generating mice with a PLP-A null mutation. Under standardized animal husbandry conditions, PLP-A possesses modest effects on reproductive performance. However, this same gene is critical for reproduction when mice are exposed to a physiological stressor. Wild-type mice exposed to hypobaric hypoxia during gestation readily adapt and maintain their pregnancies, whereas PLP-A null mutant mice fail to adapt, resulting in pregnancy failure. PLP-A contributes to hypoxia-induced adaptations critical to hemochorial placentation and thus nutrient flow to extraembryonic and embryonic tissues. The findings provide insights into species-specific reproductive adaptations.

Hydroxylation of HIF-1: oxygen sensing at the molecular level

The ability to sense and respond to changes in oxygenation represents a fundamental property of all metazoan cells. The discovery of the transcription factor HIF-1 has led to the identification of protein hydroxylation as a mechanism by which changes in PO2 are transduced to effect changes in gene expression.

Massive inborn angiogenesis in the brain scarcely raises cerebral blood flow

The functional consequences of increased capillary densities in the brain resulting from vascular endothelial growth factor (VEGF165) overexpression are unknown. Therefore, the authors measured local CBF using the iodo-[14C]antipyrine technique in transgenic mice expressing brain-specifically sixfold higher VEGF165 levels and in nontransgenic littermates. To reveal possible compensatory vasoconstriction, CBF was also measured during severe hypercapnia (Paco2 > 130 mm Hg). Simultaneously, local capillary density, perfusion state, and blood-brain-barrier permeability were assessed. Using the 2-[14C]deoxyglucose method, metabolic effects of VEGF over-expression could be excluded. In transgenic mice all capillaries showed normal morphology and a tight blood-brain barrier. However, 3% nonperfused capillaries in some brain structures indicate ongoing angiogenesis. Capillary density was drastically increased in transgenic mice in white matter structures (70% to 185%), the dentate gyrus (143%), and caudate nucleus (86%). In all other brain structures investigated, capillary densities were moderately increased by approximately 20%. Normocapnic CBF did not differ between transgenic and nontransgenic mice. During maximal hypercapnic vasodilation, CBF was 20% to 30% higher in transgenic mice, although only in brain structures where capillary density was increased more than twofold. These findings suggest that attenuated CBF in transgenic mice during normocapnia is only partly due to a compensatory vasoconstriction, and that microvascular networks in transgenic brains might be ineffectively constructed.

Hypoxic Regulation of Angiopoietin-2 Expression in Endothelial Cells

Exposure of endothelial cells to hypoxia-induced angiopoietin-2 (Ang2) expression. The increase in Ang2 mRNA levels occurred by transcriptional regulation and by post-transcriptional increase in mRNA stability. Induction of Ang2 mRNA resulted in an increase of intracellular and secreted Ang2 protein levels. Since the transcriptional regulation of several genes involved in angiogenesis during hypoxia is mediated by hypoxia-inducible factor-1 (HIF-1), it was conceivable that Ang2 expression might be regulated by the same oxygen-dependent mechanism. However, our data showed that pharmacological HIF inducers, CoCl(2) and DFO, did not affect Ang2 expression. Moreover, HIF-1-deficient hepatoma cell (Hepa1 c4) and its wild-type counterpart (Hepa1 c1c4) up-regulates Ang2 during hypoxia. These results indicated that hypoxia-driven Ang2 expression may be independent of the HIF pathway. Using neutralizing VEGF antibody or pharmacological inhibitors of VEGF receptors, we showed that hypoxia-induced VEGF participates but could not account completely for Ang2 expression during hypoxia. In addition, hypoxia elicited an increase of cyclooxygenase-2 (COX-2) expression and a parallel increase in prostanglandin E(2) (PGE(2)) and prostacyclin (PGI(2)) production. COX-2 inhibitors decreased the hypoxic induction of Ang2 and the hypoxic induction of PGE(2) and PGI(2) in a dose-dependent manner. Similarly, COX-2 but not COX-1 antisense treatment decreased hypoxic induction of Ang2 expression, and this effect was reversed by exogenous PGE(2). Finally, exogenous PGE(2) and PGI(2) were able to stimulate Ang2 under normoxic conditions. These findings suggest that COX-2-dependent prostanoids may play an important role in the regulation of hypoxia-induced Ang2 expression.