Immunohistochemical Detection of Neural Stem Cells and Glioblastoma Stem Cells in the Subventricular Zone of Glioblastoma Patients

Glioblastoma usually recurs after therapy consisting of surgery, radiotherapy, and chemotherapy. Recurrence is at least partly caused by glioblastoma stem cells (GSCs) that are maintained in intratumoral hypoxic peri-arteriolar microenvironments, or niches, in a slowly dividing state that renders GSCs resistant to radiotherapy and chemotherapy. Because the subventricular zone (SVZ) is a major niche for neural stem cells (NSCs) in the brain, we investigated whether GSCs are present in the SVZ at distance from the glioblastoma tumor. We characterized the SVZ of brains of seven glioblastoma patients using fluorescence immunohistochemistry and image analysis. NSCs were identified by CD133 and SOX2 but not CD9 expression, whereas GSCs were positive for all three biomarkers. NSCs were present in all seven samples and GSCs in six out of seven samples. The SVZ in all samples were hypoxic and expressed the same relevant chemokines and their receptors as GSC niches in glioblastoma tumors: stromal-derived factor-1α (SDF-1α), C-X-C receptor type 4 (CXCR4), osteopontin, and CD44. In conclusion, in glioblastoma patients, GSCs are present at distance from the glioblastoma tumor in the SVZ. These findings suggest that GSCs in the SVZ niche are protected against radiotherapy and chemotherapy and protected against surgical resection due to their distant localization and thus may contribute to tumor recurrence after therapy.

Development of placental abnormalities in location and anatomy

Low‐lying placentas, placenta previa and abnormally invasive placentas are the most frequently occurring placental abnormalities in location and anatomy. These conditions can have serious consequences for mother and fetus mainly due to excessive blood loss before, during or after delivery. The incidence of such abnormalities is increasing, but treatment options and preventive strategies are limited. Therefore, it is crucial to understand the etiology of placental abnormalities in location and anatomy. Placental formation already starts at implantation and therefore disorders during implantation may cause these abnormalities. Understanding of the normal placental structure and development is essential to comprehend the etiology of placental abnormalities in location and anatomy, to diagnose the affected women and to guide future research for treatment and preventive strategies. We reviewed the literature on the structure and development of the normal placenta and the placental development resulting in low‐lying placentas, placenta previa and abnormally invasive placentas.

Similarities Between Stem Cell Niches in Glioblastoma and Bone Marrow: Rays of Hope for Novel Treatment Strategies

Glioblastoma is the most aggressive primary brain tumor. Slowly dividing and therapy-resistant glioblastoma stem cells (GSCs) reside in protective peri-arteriolar niches and are held responsible for glioblastoma recurrence. Recently, we showed similarities between GSC niches and hematopoietic stem cell (HSC) niches in bone marrow. Acute myeloid leukemia (AML) cells hijack HSC niches and are transformed into therapy-resistant leukemic stem cells (LSCs). Current clinical trials are focussed on removal of LSCs out of HSC niches to differentiate and to become sensitized to chemotherapy. In the present study, we elaborated further on these similarities by immunohistochemical analyses of 17 biomarkers in paraffin sections of human glioblastoma and human bone marrow. We found all 17 biomarkers to be expressed both in hypoxic peri-arteriolar HSC niches in bone marrow and hypoxic peri-arteriolar GSC niches in glioblastoma. Our findings implicate that GSC niches are being formed in glioblastoma as a copy of HSC niches in bone marrow. These similarities between HSC niches and GSC niches provide a theoretic basis for the development of novel strategies to force GSCs out of their niches, in a similar manner as in AML, to induce GSC differentiation and proliferation to render them more sensitive to anti-glioblastoma therapies.

Cysteine cathepsins B, X and K expression in peri-arteriolar glioblastoma stem cell niches

Glioblastoma (GBM) is the most lethal brain tumor also due to malignant and therapy-resistant GBM stem cells (GSCs) that are localized in protecting hypoxic GSC niches. Some members of the cysteine cathepsin family of proteases have been found to be upregulated in GBM. Cathepsin K gene expression is highly elevated in GBM tissue versus normal brain and it has been suggested to regulate GSC migration out of the niches. Here, we investigated the cellular distribution of cathepsins B, X and K in GBM tissue and whether these cathepsins are co-localized in GSC niches. Therefore, we determined expression of these cathepsins in serial paraffin sections of 14 human GBM samples and serial cryostat sections of two samples using immunohistochemistry and metabolic mapping of cathepsin activity using selective fluorogenic substrates. We detected cathepsins B, X and K in peri-arteriolar GSC niches in 9 out of 16 GBM samples, which were defined by co-expression of the GSC marker CD133, the niche marker stromal-derived factor-1α (SDF-1α) and smooth muscle actin as a marker for arterioles. The expression of cathepsin B and X was detected in stromal cells and cancer cells throughout the GBM sections, whereas cathepsin K expression was more restricted to arteriole-rich regions in the GBM sections. Metabolic mapping showed that cathepsin B, but not cathepsin K is active in GSC niches. On the basis of these findings, it is concluded that cathepsins B, X and K have distinct functions in GBM and that cathepsin K is the most likely GSC niche-related cathepsin of the three cathepsins investigated.

Metabolic Mapping: Quantitative Enzyme Cytochemistry and Histochemistry to Determine the Activity of Dehydrogenases in Cells and Tissues

Altered cellular metabolism is a hallmark of many diseases, including cancer, cardiovascular diseases and infection. The metabolic motor units of cells are enzymes and their activity is heavily regulated at many levels, including the transcriptional, mRNA stability, translational, post-translational and functional level. This complex regulation means that conventional quantitative or imaging assays, such as quantitative mRNA experiments, Western Blots and immunohistochemistry, yield incomplete information regarding the ultimate activity of enzymes, their function and/or their subcellular localization. Quantitative enzyme cytochemistry and histochemistry (i.e., metabolic mapping) show in-depth information on in situ enzymatic activity and its kinetics, function and subcellular localization in an almost true-to-nature situation.

We describe a protocol to detect the activity of dehydrogenases, which are enzymes that perform redox reactions to reduce cofactors such as NAD(P)⁺ and FAD. Cells and tissue sections are incubated in a medium that is specific for the enzymatic activity of one dehydrogenase. Subsequently, the dehydrogenase that is the subject of investigation performs its enzymatic activity in its subcellular site. In a chemical reaction with the reaction medium, this ultimately generates blue-colored formazan at the site of the dehydrogenase's activity. The formazan's absorbance is therefore a direct measure of the dehydrogenase's activity and can be quantified using monochromatic light microscopy and image analysis. The quantitative aspect of this protocol enables researchers to draw statistical conclusions from these assays.

Besides observational studies, this technique can be used for inhibition studies of specific enzymes. In this context, studies benefit from the true-to-nature advantages of metabolic mapping, giving in situ results that may be physiologically more relevant than in vitro enzyme inhibition studies. In all, metabolic mapping is an indispensable technique to study metabolism at the cellular or tissue level. The technique is easy to adopt, provides in-depth, comprehensive and integrated metabolic information and enables rapid quantitative analysis.

Three-dimensional histochemistry and imaging of human gingiva

In the present study, 3D histochemistry and imaging methodology is described for human gingiva to analyze its vascular network. Fifteen human gingiva samples without signs of inflammation were cleared using a mixture of 2-parts benzyl benzoate and 1-part benzyl alcohol (BABB), after being immunofluorescently stained for CD31, marker of endothelial cells to visualize blood vessels in combination with fluorescent DNA dyes. Samples were imaged in 3D with the use of confocal microscopy and light-sheet microscopy and image processing. BABB clearing caused limited tissue shrinkage 13 ± 7% as surface area and 24 ± 1% as volume. Fluorescence remained intact in BABB-cleared gingiva samples and light-sheet microscopy was an excellent tool to image gingivae whereas confocal microscopy was not. Histochemistry on cryostat sections of gingiva samples after 3D imaging validated structures visualized in 3D. Three-dimensional images showed the vascular network in the stroma of gingiva with one capillary loop in each stromal papilla invading into the epithelium. The capillary loops were tortuous with structural irregularities that were not apparent in 2D images. It is concluded that 3D histochemistry and imaging methodology described here is a promising novel approach to study structural aspects of human gingiva in health and disease.

Periarteriolar Glioblastoma Stem Cell Niches Express Bone Marrow Hematopoietic Stem Cell Niche Proteins

In glioblastoma, a fraction of malignant cells consists of therapy-resistant glioblastoma stem cells (GSCs) residing in protective niches that recapitulate hematopoietic stem cell (HSC) niches in bone marrow. We have previously shown that HSC niche proteins stromal cell-derived factor-1α (SDF-1α), C-X-C chemokine receptor type 4 (CXCR4), osteopontin (OPN), and cathepsin K (CatK) are expressed in hypoxic GSC niches around arterioles in five human glioblastoma samples. In HSC niches, HSCs are retained by binding of SDF-1α and OPN to their receptors CXCR4 and CD44, respectively. Protease CatK cleaves SDF-1α to release HSCs out of niches. The aim of the present study was to reproduce the immunohistochemical localization of these GSC markers in 16 human glioblastoma samples with the addition of three novel markers. Furthermore, we assessed the type of blood vessels associated with GSC niches. In total, we found seven GSC niches containing CD133-positive and nestin-positive GSCs as a single-cell layer exclusively around the tunica adventitia of 2% of the CD31-positive and SMA-positive arterioles and not around capillaries and venules. Niches expressed SDF-1α, CXCR4, CatK, OPN, CD44, hypoxia-inducible factor-1α, and vascular endothelial growth factor. In conclusion, we show that GSC niches are present around arterioles and express bone marrow HSC niche proteins.

Is leukostasis a crucial step or epiphenomenon in the pathogenesis of diabetic retinopathy?

Leukostasis in the retinal microvasculature in animal model studies of diabetes is associated with the development of diabetes-like retinopathy. Therefore, it is generally assumed that adhesion of leukocytes is a central event inciting a chronic, low-grade form of inflammation that causes the vascular abnormalities that are specific for the early stages of diabetic retinopathy (DR), which culminate in diabetic macular edema, proliferative DR, and vision loss in humans. Here, we review the literature critically with respect to leukostasis and assess its pathologic consequences in the human diabetic retina. First, we review the pathologic processes that are known to be involved in the development of human DR. Then, we summarize experimental evidence for the role of leukostasis in the development of DR and the mechanisms involved in leukostasis in the retina. Based on our critical review, we conclude that leukostasis may be an epiphenomenon of the diabetic retinal milieu, rather than a crucial, specific step in the development of human DR.

Novel therapeutic strategies to target leukemic cells that hijack compartmentalized continuous hematopoietic stem cell niches

Acute myeloid leukemia and acute lymphoblastic leukemia cells hijack hematopoietic stem cell (HSC) niches in the bone marrow and become leukemic stem cells (LSCs) at the expense of normal HSCs. LSCs are quiescent and resistant to chemotherapy and can cause relapse of the disease. HSCs in niches are needed to generate blood cell precursors that are committed to unilineage differentiation and eventually production of mature blood cells, including red blood cells, megakaryocytes, myeloid cells and lymphocytes. Thus far, three types of HSC niches are recognized: endosteal, reticular and perivascular niches. However, we argue here that there is only one type of HSC niche, which consists of a periarteriolar compartment and a perisinusoidal compartment. In the periarteriolar compartment, hypoxia and low levels of reactive oxygen species preserve the HSC pool. In the perisinusoidal compartment, hypoxia in combination with higher levels of reactive oxygen species enables proliferation of progenitor cells and their mobilization into the circulation. Because HSC niches offer protection to LSCs against chemotherapy, we review novel therapeutic strategies to inhibit homing of LSCs in niches for the prevention of dedifferentiation of leukemic cells into LSCs and to stimulate migration of leukemic cells out of niches. These strategies enhance differentiation and proliferation and thus sensitize leukemic cells to chemotherapy. Finally, we list clinical trials of therapies that tackle LSCs in HSC niches to circumvent their protection against chemotherapy.

CD34 Promotes Pathological Epi-Retinal Neovascularization in a Mouse Model of Oxygen-Induced Retinopathy

The sialomucins CD34 and podocalyxin (PODXL) are anti-adhesive molecules expressed at the luminal membrane of endothelial cells of small blood vessels and facilitate vascular lumen formation in the developing mouse aorta. CD34 transcript and protein levels are increased during human angiogenesis, its expression is particularly enriched on endothelial tip cell filopodia and CD34 is a marker for tip cells in vitro. Here, we investigated whether CD34 merely marks endothelial tip cells or has a functional role in tip cells and angiogenesis. We assessed that silencing CD34 in human microvascular endothelial cells has little effect on endothelial cell migration or invasion, but has a significant effect on vascular-endothelial growth factor-induced angiogenic sprouting activity in vitro. In vivo, the absence of CD34 reduced the density of filopodia on retinal endothelial tip cells in neonatal mice, but did not influence the overall architecture of the retinal vascular network. In oxygen-induced retinopathy, Cd34^-/- mice showed normal intra-retinal regenerative angiogenesis but the number of pathological epi-retinal neovascular tufts were reduced. We conclude that CD34 is not essential for developmental vascularization in the retina, but its expression promotes the formation of pathological, invasive vessels during neovascularization.

Efficacy of an aluminium triformate mouthrinse during the maintenance phase in periodontal patients: a pilot double blind randomized placebo-controlled clinical trial

BACKGROUND

The aim of this prospective placebo-controlled pilot study was to evaluate short-term effects of a mouthrinse containing aluminium triformate (ATF) on gingival inflammation and plaque formation in periodontal patients who are in the maintenance phase. ATF has styptic (astringent) and anti-inflammatory effects.

METHODS

Forty non-smoking periodontal patients with modified sulcus bleeding index (MSBI) ≥40 % were randomly divided into two groups. The participants received a masked mouthrinse (ATF or placebo) and were instructed with the rinsing protocol of 3 daily rinses during 30 s for 7 days. One blinded investigator (CE) performed all clinical examinations. The primary outcome was reduction in gingival inflammation as measured by MSBI. The secondary outcomes were reduction of the amount of plaque as measured by plaque index (PI) and approximal plaque index (API) and the occurrence of side effects. The patients were evaluated at the start and the end of the rinsing period, including the compliance of the patients.

RESULTS

MSBI was reduced in both groups compared to baseline, but the ATF group showed significantly more reduction in MSBI compared to the placebo group (ATF: 17.6 %, placebo: 7.6 %, p = 0.035). ATF and placebo had no effects on dental plaque. Patients reported ATF mouthrinse not to have side effects other than oral sensation, whereas compliance of the patients was good. Almost all patients in the ATF group reported reduction of gum bleeding after 1 week of rinsing with ATF.

CONCLUSIONS

This short-term pilot clinical trial is a firm basis to design a long-term controlled clinical trial to show whether ATF helps to inhibit further periodontal breakdown in maintenance patients with high MSBI.

TRIAL REGISTRATION

This trial was registered in the WHO International Clinical Trials Registry Platform as DRKS00007672 , date of registration: 21/01/2015.

A survey of clearing techniques for 3D imaging of tissues with special reference to connective tissue

For 3-dimensional (3D) imaging of a tissue, 3 methodological steps are essential and their successful application depends on specific characteristics of the type of tissue. The steps are 1° clearing of the opaque tissue to render it transparent for microscopy, 2° fluorescence labeling of the tissues and 3° 3D imaging. In the past decades, new methodologies were introduced for the clearing steps with their specific advantages and disadvantages. Most clearing techniques have been applied to the central nervous system and other organs that contain relatively low amounts of connective tissue including extracellular matrix. However, tissues that contain large amounts of extracellular matrix such as dermis in skin or gingiva are difficult to clear. The present survey lists methodologies that are available for clearing of tissues for 3D imaging. We report here that the BABB method using a mixture of benzyl alcohol and benzyl benzoate and iDISCO using dibenzylether (DBE) are the most successful methods for clearing connective tissue-rich gingiva and dermis of skin for 3D histochemistry and imaging of fluorescence using light-sheet microscopy.

CD133+ and Nestin+ Glioma Stem-Like Cells Reside Around CD31+ Arterioles in Niches that Express SDF-1α, CXCR4, Osteopontin and Cathepsin K

Poor survival of high-grade glioma is at least partly caused by glioma stem-like cells (GSLCs) that are resistant to therapy. GSLCs reside in niches in close vicinity of endothelium. The aim of the present study was to characterize proteins that may be functional in the GSLC niche by performing immunohistochemistry on serial cryostat sections of human high-grade glioma samples. We have found nine niches in five out of five high-grade glioma samples that were all surrounding arterioles with CD31+ endothelial cells and containing cellular structures that were CD133+ and nestin+. All nine niches expressed stromal-derived factor-1α (SDF-1α), its receptor C-X-C chemokine receptor type 4 (CXCR4), osteopontin and cathepsin K. SDF-1α plays a role in homing of CXCR4+ stem cells and leukocytes, whereas osteopontin and cathepsin K promote migration of cancer cells and leukocytes. Leukocyte-related markers, such as CD68, macrophage matrix metalloprotease-9, CD177 and neutrophil elastase were often but not always detected in the niches. We suggest that SDF-1α is involved in homing of CXCR4+ GSLCs and leukocytes and that cathepsin K and osteopontin are involved in the migration of GSLCs out of the niches.

Determination of phosphate-activated glutaminase activity and its kinetics in mouse tissues using metabolic mapping (quantitative enzyme histochemistry)

Phosphate-activated glutaminase (PAG) converts glutamine to glutamate as part of the glutaminolysis pathway in mitochondria. Two genes, GLS1 and GLS2, which encode for kidney-type PAG and liver-type PAG, respectively, differ in their tissue-specific activities and kinetics. Tissue-specific PAG activity and its kinetics were determined by metabolic mapping using a tetrazolium salt and glutamate dehydrogenase as an auxiliary enzyme in the presence of various glutamine concentrations. In kidney and brain, PAG showed Michaelis-Menten kinetics with a K_m of 0.6 mM glutamine and a V_max of 1.1 µmol/mL/min when using 5 mM glutamine. PAG activity was high in the kidney cortex and inner medulla but low in the outer medulla, papillary tip, glomeruli and the lis of Henle. In brain tissue sections, PAG was active in the grey matter and inactive in myelin-rich regions. Liver PAG showed allosteric regulation with a K_m of 11.6 mM glutamine and a V_max of 0.5 µmol/mL/min when using 20 mM glutamine. The specificity of the method was shown after incubation of brain tissue sections with the PAG inhibitor 6-diazo-5-oxo-L-norleucine. PAG activity was decreased to 22% in the presence of 2 mM 6-diazo-5-oxo-L-norleucine. At low glutamine concentrations, PAG activity was higher in periportal regions, indicating a lower K_m for periportal PAG. When compared with liver, kidney and brain, other tissues showed 3-fold to 6-fold less PAG activity. In conclusion, PAG is mainly active in mouse kidney, brain and liver, and shows different kinetics depending on which type of PAG is expressed.

Determination of glutamate dehydrogenase activity and its kinetics in mouse tissues using metabolic mapping (quantitative enzyme histochemistry)

Glutamate dehydrogenase (GDH) catalyses the reversible conversion of glutamate into α-ketoglutarate with the concomitant reduction of NAD(P)(+) to NAD(P)H or vice versa. GDH activity is subject to complex allosteric regulation including substrate inhibition. To determine GDH kinetics in situ, we assessed the effects of various glutamate concentrations in combination with either the coenzyme NAD(+) or NADP(+) on GDH activity in mouse liver cryostat sections using metabolic mapping. NAD(+)-dependent GDH V(max) was 2.5-fold higher than NADP(+)-dependent V(max), whereas the K(m) was similar, 1.92 mM versus 1.66 mM, when NAD(+) or NADP(+) was used, respectively. With either coenzyme, V(max) was determined at 10 mM glutamate and substrate inhibition was observed at higher glutamate concentrations with a K(i) of 12.2 and 3.95 for NAD(+) and NADP(+) used as coenzyme, respectively. NAD(+)- and NADP(+)-dependent GDH activities were examined in various mouse tissues. GDH activity was highest in liver and much lower in other tissues. In all tissues, the highest activity was found when NAD(+) was used as a coenzyme. In conclusion, GDH activity in mice is highest in the liver with NAD(+) as a coenzyme and highest GDH activity was determined at a glutamate concentration of 10 mM.

Nanoparticles for hyperthermic therapy: synthesis strategies and applications in glioblastoma

Glioblastoma multiforme (GBM) is the most common and most aggressive malignant primary brain tumor in humans. Current GBM treatment includes surgery, radiation therapy, and chemotherapy, sometimes supplemented with novel therapies. Despite recent advances, survival of GBM patients remains poor. Major challenges in GBM treatment are drug delivery across the blood–brain barrier, restriction of damage to healthy brain tissues, and limitation of resistance to therapies. This article reviews recent advances in the application of magnetic nanoparticles (MNPs), gold nanorods (GNRs), and carbon nanotubes (CNTs) for hyperthermia ablation of GBM. First, the article introduces GBM, its current treatment, and hyperthermia as a potential modality for the management of GBM. Second, it introduces MNPs, GNRs, and CNTs as inorganic agents to induce hyperthermia in GBM. Third, it discusses different methodologies for synthesis of each inorganic agent. Finally, it reviews in vitro and in vivo studies in which MNPs, GNRs, and CNTs have been applied for hyperthermia ablation and drug delivery in GBM.

Molecular analysis of blood-retinal barrier loss in the Akimba mouse, a model of advanced diabetic retinopathy

The molecular mechanisms of vascular leakage in diabetic macular edema and proliferative retinopathy are poorly understood, mainly due to the lack of reliable in vivo models. The Akimba (Ins2(Akita)VEGF(+/-)) mouse model combines retinal neovascularization with hyperglycemia, and in contrast to other models, displays the majority of signs of advanced clinical diabetic retinopathy (DR). To study the molecular mechanism that underlies the breakdown of the blood-retinal barrier (BRB) in diabetic macular edema and proliferative diabetic retinopathy, we investigated the retinal vasculature of Akimba and its parental mice Kimba (trVEGF029) and Akita (Ins2(Akita)). Quantitative PCR, immunohistochemistry and fluorescein angiography were used to characterize the retinal vasculature with special reference to the inner BRB. Correlations between the degree of fluorescein leakage and retinal gene expression were tested by calculating the Spearman's correlation coefficient. Fluorescein leakage demonstrating BRB loss was observed in Kimba and Akimba, but not in Akita or wild type mice. In Kimba and Akimba mice fluorescein leakage was associated with focal angiogenesis and correlated significantly with Plvap gene expression. PLVAP is an endothelial cell-specific protein that is absent in intact blood-retinal barrier, but its expression significantly increases in pathological conditions such as DR. Furthermore, in Akimba mice BRB disruption was linked to decreased expression of endothelial junction proteins, pericyte dropout and vessel loss. Despite fluorescein leakage, no alteration in BRB protein levels or pericyte coverage was detected in retinas of Kimba mice. In summary, our data not only demonstrate that hyperglycemia sensitizes retinal vasculature to the effects of VEGF, leading to more severe microvascular changes, but also confirm an important role of PLVAP in the regulation of BRB permeability.

Towards digital photon counting cameras for single-molecule optical nanoscopy

Background

Optical nanoscopy based on separation of single molecules by stochastic switching and subsequent localization allows surpassing the diffraction limit of light. The growing pursuit towards live-cell imaging using nanoscopy demands advancements in both science and technology.

Results

In this article, we provide an overview of the technological advancements in the development of scientific cameras used for nanoscopy. We discuss the prospects of novel digital photon counting cameras based on a single-photon avalanche diode (SPAD) array camera for optical nanoscopy. Numerical simulations are used to evaluate and compare different scientific cameras for their performance towards single-molecule identification and localization.

Conclusion

A SPAD array camera with single-photon sensitivity and zero read-out noise allows for the detection of extremely weak signals at ultra-fast imaging speeds. With temporal resolution in the order of micro-seconds, a SPAD array camera offers great potential for live-cell imaging with super-resolution.

Connective tissue growth factor is involved in structural retinal vascular changes in long-term experimental diabetes

Early retinal vascular changes in the development of diabetic retinopathy (DR) include capillary basal lamina (BL) thickening, pericyte loss and the development of acellular capillaries. Expression of the CCN (connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed) family member CCN2 or connective tissue growth factor (CTGF), a potent inducer of the expression of BL components, is upregulated early in diabetes. Diabetic mice lacking one functional CTGF allele (CTGF⁺/⁻) do not show this BL thickening. As early events in DR may be interrelated, we hypothesized that CTGF plays a role in the pathological changes of retinal capillaries other than BL thickening. We studied the effects of long-term (6-8 months) streptozotocin-induced diabetes on retinal capillary BL thickness, numbers of pericytes and the development of acellular capillaries in wild type and CTGF⁺/⁻ mice. Our results show that an absence of BL thickening of retinal capillaries in long-term diabetic CTGF⁺/⁻ mice is associated with reduced pericyte dropout and reduced formation of acellular capillaries. We conclude that CTGF is involved in structural retinal vascular changes in diabetic rodents. Inhibition of CTGF in the eye may therefore be protective against the development of DR.

VEGF levels in plasma in relation to platelet activation, glycemic control, and microvascular complications in type 1 diabetes

OBJECTIVE

Increased levels of vascular endothelial growth factor (VEGF) in human plasma samples have suggested that circulating VEGF is a cause of endothelial dysfunction in diabetes mellitus. However, artificial release of VEGF from platelets as a source of VEGF in plasma samples, as also occurs in serum samples, has not been ruled out in these studies.

RESEARCH DESIGN AND METHODS

We determined VEGF levels in plasma collected in both citrate and PECT, a medium that inactivates platelets, in a cross-sectional cohort of 21 healthy subjects and 64 patients with type 1 diabetes. In addition, we evaluated whether VEGF levels in both types of plasma correlated with the presence of diabetes, glycemic control, markers of in vivo or ex vivo platelet activation, and degree of diabetic retinopathy and nephropathy.

RESULTS

VEGF levels were invariably low in PECT plasma of both nondiabetic and diabetic subjects and were unrelated to any other diabetes-related variable studied. In contrast, VEGF levels in citrate plasma were 150% higher in diabetic patients than in control subjects and correlated with diabetes-related variables. Multiple linear regression analysis showed that levels of platelet factor 4, a marker for ex vivo platelet activation, and HbA1c were the independent predictors of VEGF levels in citrate plasma. Platelet activation, in vivo and ex vivo, was similar in diabetic persons and control subjects.

CONCLUSIONS

Like serum, citrate plasma is not suitable for reliable measurements of circulating VEGF. The low levels of VEGF in vivo, as represented by measurements in PECT plasma in our study, do not support a role of circulating VEGF in endothelial dysfunction in type 1 diabetes. Higher levels of VEGF in citrate plasma samples of diabetic persons do not represent the in vivo situation, but mainly originate from higher artificial ex vivo release from platelets correlating with the degree of glycemic control.

NADP+ -dependent IDH1 R132 mutation and its relevance for glioma patient survival

The isocitrate dehydrogenase 1 (IDH1) mutation occurs in high frequency in glioma and secondary glioblastoma (GBM). Mutated IDH1 produces the oncometabolite 2-hydroxyglutarate rather than α-ketoglutarate or isocitrate. The oncometabolite is considered to be the major cause of the association between the IDH1 mutation and gliomagenesis. On the other hand, the IDH1 mutation in GBM is associated with prolonged patient survival. This association is not well understood yet but IDH1 involvement in epigenetic silencing of O-6-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme is considered to be an important mechanism. However, it was shown recently that the IDH1 mutation and MGMT silencing are independent prognostic factors. Here, we hypothesize that the IDH1 mutation reduces the capacity to produce NADPH and thus reduces the capacity to scavenge reactive oxygen species that are generated during irradiation and chemotherapy. IDH1 activity is responsible for two-thirds of the NADPH production capacity in normal brain, whereas the IDH1 mutation reduces this capacity by almost 40%. Therefore, we hypothesize that the reduced NADPH production capacity due to the IDH1 mutation renders GBM cells more vulnerable to irradiation and chemotherapy thus prolonging survival of the patients.

Molecular basis of the inner blood-retinal barrier and its breakdown in diabetic macular edema and other pathological conditions

Breakdown of the inner endothelial blood-retinal barrier (BRB), as occurs in diabetic retinopathy, age-related macular degeneration, retinal vein occlusions, uveitis and other chronic retinal diseases, results in vasogenic edema and neural tissue damage, causing loss of vision. The central mechanism of altered BRB function is a change in the permeability characteristics of retinal endothelial cells caused by elevated levels of growth factors, cytokines, advanced glycation end products, inflammation, hyperglycemia and loss of pericytes. Subsequently, paracellular but also transcellular transport across the retinal vascular wall increases via opening of endothelial intercellular junctions and qualitative and quantitative changes in endothelial caveolar transcellular transport, respectively. Functional changes in pericytes and astrocytes, as well as structural changes in the composition of the endothelial glycocalyx and the basal lamina around BRB endothelium further facilitate BRB leakage. As Starling's rules apply, active transcellular transport of plasma proteins by the BRB endothelial cells causing increased interstitial osmotic pressure is probably the main factor in the formation of macular edema. The understanding of the complex cellular and molecular processes involved in BRB leakage has grown rapidly in recent years. Although appropriate animal models for human conditions like diabetic macular edema are lacking, these insights have provided tools for rational design of drugs aimed at restoring the BRB as well as for design of effective transport of drugs across the BRB, to treat the chronic retinal diseases such as diabetic macular edema that affect the quality-of-life of millions of patients.

Endothelial tip cells in ocular angiogenesis: potential target for anti-angiogenesis therapy

Endothelial tip cells are leading cells at the tips of vascular sprouts coordinating multiple processes during angiogenesis. In the developing retina, tip cells play a tightly controlled, timely role in angiogenesis. In contrast, excessive numbers of tip cells are a characteristic of the chaotic pathological blood vessels in proliferative retinopathies. Tip cells control adjacent endothelial cells in a hierarchical manner to form the stalk of the sprouting vessel, using, among others, the VEGF-DLL-Notch signaling pathway, and recruit pericytes. Tip cells are guided toward avascular areas by signals from the local extracellular matrix that are released by cells from the neuroretina such as astrocytes. Recently, tip cells were identified in endothelial cell cultures, enabling identification of novel molecular markers and mechanisms involved in tip cell biology. These mechanisms are relevant for understanding proliferative retinopathies. Agents that primarily target tip cells can block pathological angiogenesis in the retina efficiently and safely without adverse effects. A striking example is platelet-derived growth factor, which was recently shown to be an efficacious additional target in the treatment of retinal neovascularization. Here we discuss these and other tip cell-based strategies with respect to their potential to treat patients with ocular diseases dominated by neovascularization.

Vitreous TIMP-1 levels associate with neovascularization and TGF-β2 levels but not with fibrosis in the clinical course of proliferative diabetic retinopathy

In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and CCN2 (connective tissue growth factor; CTGF) cause blindness by neovascularization and subsequent fibrosis. This angio-fibrotic switch is associated with a shift in the balance between vitreous levels of CCN2 and VEGF in the eye. Here, we investigated the possible involvement of other important mediators of fibrosis, tissue inhibitor of metalloproteinases (TIMP)-1 and transforming growth factor (TGF)-β2, and of the matrix metalloproteinases (MMP)-2 and MMP-9, in the natural course of PDR. TIMP-1, activated TGF-β2, CCN2 and VEGF levels were measured by ELISA in 78 vitreous samples of patients with PDR (n = 28), diabetic patients without PDR (n = 24), and patients with the diabetes-unrelated retinal conditions macular hole (n = 10) or macular pucker (n = 16), and were related to MMP-2 and MMP-9 activity on zymograms and to clinical data, including degree of intra-ocular neovascularization and fibrosis. TIMP-1, CCN2 and VEGF levels, but not activated TGF-β2 levels, were significantly increased in the vitreous of diabetic patients, with the highest levels in PDR patients. CCN2 and the CCN2/VEGF ratio were the strongest predictors of degree of fibrosis. In diabetic patients with or without PDR, activated TGF-β2 levels correlated with TIMP-1 levels, whereas in PDR patients, TIMP-1 levels, MMP-2 and proMMP-9 were associated with degree of neovascularization, like VEGF levels, but not with fibrosis. We confirm here our previous findings that retinal fibrosis in PDR patients is significantly correlated with vitreous CCN2 levels and the CCN2/VEGF ratio. In contrast, TIMP-1, MMP-2 and MMP-9 appear to have a role in the angiogenic phase rather than in the fibrotic phase of PDR.

A shift in the balance of vascular endothelial growth factor and connective tissue growth factor by bevacizumab causes the angiofibrotic switch in proliferative diabetic retinopathy

Introduction

In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) may cause blindness by neovascularisation followed by fibrosis of the retina. It has previously been shown that a shift in the balance between levels of CTGF and VEGF in the eye is associated with this angiofibrotic switch. This study investigated whether anti-VEGF agents induce accelerated fibrosis in patients with PDR, as predicted by this model.

Methods

CTGF and VEGF levels were measured by ELISA in 52 vitreous samples of PDR patients, of which 24 patients had received intravitreal bevacizumab 1 week to 3 months before vitrectomy, and were correlated with the degree of vitreoretinal fibrosis as determined clinically and intra-operatively.

Results

CTGF correlated positively, and VEGF correlated negatively with the degree of fibrosis. The CTGF/VEGF ratio was the strongest predictor of fibrosis. Clinically, increased fibrosis was observed after intravitreal bevacizumab.

Conclusions

These results confirm that the CTGF/VEGF ratio is a strong predictor of vitreoretinal fibrosis in PDR, and show that intravitreal anti-VEGF treatment causes increased fibrosis in PDR patients. These findings provide strong support for the model that the balance of CTGF and VEGF determines the angiofibrotic switch, and identify CTGF as a possible therapeutic target in the clinical management of PDR.

A novel co-culture model of the blood-retinal barrier based on primary retinal endothelial cells, pericytes and astrocytes

Loss of blood-retinal barrier (BRB) properties is an important feature in the pathology of diabetic macular edema (DME), but cellular mechanisms underlying BRB dysfunction are poorly understood. Therefore, we developed and characterized a novel in vitro BRB model, based on primary bovine retinal endothelial cells (BRECs). These cells were shown to maintain specific in vivo BRB properties by expressing high levels of the endothelial junction proteins occludin, claudin-5, VE-cadherin and ZO-1 at cell borders, and the specific pumps glucose transporter-1 (GLUT1) and efflux transporter P-glycoprotein (MDR1). To investigate the influence of pericytes and astrocytes on BRB maintenance in vitro, we compared five different co-culture BRB models, based on BRECs, bovine retinal pericytes (BRPCs) and rat glial cells. Co-cultures of BRECs with BRPCs and glial cells showed the highest trans-endothelial resistance (TEER) as well as decreased permeability of tracers after vascular endothelial growth factor (VEGF) stimulation, suggesting a major role for these cell types in maintaining barrier properties. To mimic the in vivo situation of DME, we stimulated BRECs with VEGF, which downregulated MDR1 and GLUT1 mRNA levels, transiently reduced expression levels of endothelial junctional proteins and altered their organization, increased the number of intercellular gaps in BRECs monolayers and influence the permeability of the model to differently-sized molecular tracers. Moreover, as has been shown in vivo, expression of plasmalemma vesicle-associated protein (PLVAP) was increased in endothelial cells in the presence of VEGF. This in vitro model is the first co-culture model of the BRB that mimicks in vivo VEGF-dependent changes occurring in DME.

Polyethylene wear particles do not induce inflammation or gelatinase (MMP-2 and MMP-9) activity in fibrous tissue interfaces of loosening total hip arthroplasties

In vitro and in vivo studies have suggested that polyethylene wear particles are the main cause for osteolysis in prosthetic loosening. Elevated amounts of proteases including gelatinases (or matrix metalloproteinases MMP-2 and MMP-9) have been found in fibrous tissue interfaces of loosened total hip arthroplasties suggesting that proteolysis plays a role in osteolysis. The presence of proteases does not mean that they are active, because activity of proteases is highly regulated at the post-translational level. We investigated whether the activity of two major proteases that are active extracellularly and have been associated with loosening, MMP-2 and MMP-9, is involved in loosening of non-cemented hip implants with polyethylene acetabular components. Eight interface tissues retrieved during revision were studied with light and electron microscopy and by in situ zymography to localize MMP-2 and MMP-9 activity in combination with immunohistochemistry to localize MMP-2 and MMP-9 proteins. All interface tissues contained large amounts of polyethylene wear particles, either in large accumulations or dispersed in the extracellular matrix or intracellularly in fibroblasts. Particles were not encountered in association with MMP-2 or MMP-9 activity or leukocytes. Inflammation was never found. MMP-9 activity was restricted to macrophages and MMP-2 activity was restricted to microvascular endothelial cells mainly outside areas where particles were present. Our data indicate that wear particles do not induce activation of leukocytes or MMP-2 or MMP-9 activity. Therefore, aseptic loosening may not be particle induced but initiated by other mechanisms such as mechanical stress.

WEE1 kinase targeting combined with DNA-damaging cancer therapy catalyzes mitotic catastrophe

WEE1 kinase is a key molecule in maintaining G₂-cell-cycle checkpoint arrest for premitotic DNA repair. Whereas normal cells repair damaged DNA during G₁-arrest, cancer cells often have a deficient G₁-arrest and largely depend on G₂-arrest. The molecular switch for the G₂-M transition is held by WEE1 and is pushed forward by CDC25. WEE1 is overexpressed in various cancer types, including glioblastoma and breast cancer. Preclinical studies with cancer cell lines and animal models showed decreased cancer cell viability, reduced tumor burden, and improved survival after WEE1 inhibition by siRNA or small molecule inhibitors, which is enhanced by combination with conventional DNA-damaging therapy, such as radiotherapy and/or cytostatics. Mitotic catastrophe results from premature entry into mitosis with unrepaired lethal DNA damage. As such, cancer cells become sensitized to conventional therapy by WEE1 inhibition, in particular those with insufficient G₁-arrest due to deficient p53 signaling, like glioblastoma cells. One WEE1 inhibitor has now reached clinical phase I studies. Dose-limiting toxicity consisted of hematologic events, nausea and/or vomiting, and fatigue. The combination of DNA-damaging cancer therapy with WEE1 inhibition seems to be a rational approach to push cancer cells in mitotic catastrophe. Its safety and efficacy are being evaluated in clinical studies.

Differential activity of NADPH-producing dehydrogenases renders rodents unsuitable models to study IDH1R132 mutation effects in human glioblastoma

The somatic IDH1(R132) mutation in the isocitrate dehydrogenase 1 gene occurs in high frequency in glioma and in lower frequency in acute myeloid leukemia and thyroid cancer but not in other types of cancer. The mutation causes reduced NADPH production capacity in glioblastoma by 40% and is associated with prolonged patient survival. NADPH is a major reducing compound in cells that is essential for detoxification and may be involved in resistance of glioblastoma to treatment. IDH has never been considered important in NADPH production. Therefore, the authors investigated NADPH-producing dehydrogenases using in silico analysis of human cancer gene expression microarray data sets and metabolic mapping of human and rodent tissues to determine the role of IDH in total NADPH production. Expression of most NADPH-producing dehydrogenase genes was not elevated in 34 cancer data sets except for IDH1 in glioma and thyroid cancer, indicating an association with the IDH1 mutation. IDH activity was the main provider of NADPH in human normal brain and glioblastoma, but its role was modest in NADPH production in rodent brain and other tissues. It is concluded that rodents are a poor model to study consequences of the IDH1(R132) mutation in glioblastoma.

Scientific imperatives, clinical implications, and theoretical underpinnings for the investigation of the relationship between genetic variables and patient-reported quality-of-life outcomes

Objectives

There is emerging evidence for a genetic basis of patient-reported quality-of-life (QOL) outcomes that can ultimately be incorporated into clinical research and practice. Objectives are (1) to provide arguments for the timeliness of investigating the genetic basis of QOL given the scientific advances in genetics and patient-reported QOL research; (2) to describe the clinical implications of such investigations; (3) to present a theoretical foundation for investigating the genetic underpinnings of QOL; and (4) to describe a series of papers resulting from the GENEQOL Consortium that was established to move this work forward.

Methods

Discussion of scientific advances based on relevant literature.

Results

In genetics, technological advances allow for increases in speed and efficiency and decreases in costs in exploring the genetic underpinnings of disease processes, drug metabolism, treatment response, and survival. In patient-based research, advances yield empirically based and stringent approaches to measurement that are scientifically robust. Insights into the genetic basis of QOL will ultimately allow early identification of patients susceptible to QOL deficits and to target care. The Wilson and Cleary model for patient-reported outcomes was refined by incorporating the genetic underpinnings of QOL.

Conclusions

This series of papers provides a path for QOL and genetics researchers to work together to move this field forward and to unravel the intricate interplay of the genetic underpinnings of patient-reported QOL outcomes. The ultimate result will be a greater understanding of the process relating disease, patient, and doctor that will have the potential to lead to improved survival, QOL, and health services delivery.

Osteopontin is up-regulated and associated with neutrophil and macrophage infiltration in glioblastoma

Osteopontin (OPN) is a glycophosphoprotein with multiple intracellular and extracellular functions. In vitro, OPN enhances migration of mouse neutrophils and macrophages. In cancer, extracellular OPN facilitates migration of cancer cells via its RGD sequence. The present study was designed to investigate whether osteopontin is responsible for neutrophil and macrophage infiltration in human cancer and in particular in glioblastoma. We found that in vitro mouse neutrophil migration was RGD-dependent. In silico, we found that the OPN gene was one of the 5% most highly expressed genes in 20 out of 35 cancer microarray data sets in comparison with normal tissue in at least 30% of cancer patients. In some types of cancer, such as ovarian cancer, lung cancer and melanoma, the OPN gene was one of those with the highest expression levels in at least 90% of cancer patients. In glioblastoma, the most invasive type of brain tumours/glioma, but not in lower grades of glioma it was one of the 5% highest expressed genes in 90% of patients. In situ, we found increased protein levels of OPN in human glioblastoma versus normal human brain confirming in silico results. OPN protein expression was co-localized with neutrophils and macrophages. In conclusion, OPN in tumours not only induces migration of cancer cells but also of leucocytes.

A low molecular weight heparin inhibits experimental metastasis in mice independently of the endothelial glycocalyx

Background

Some low molecular weight heparins (LMWHs) prolong survival of cancer patients and inhibit experimental metastasis. The underlying mechanisms are still not clear but it has been suggested that LMWHs (at least in part) limit metastasis by preventing cancer cell-induced destruction of the endothelial glycocalyx.

Methodology/Principal Findings

To prove or refute this hypothesis, we determined the net effects of the endothelial glycocalyx in cancer cell extravasation and we assessed the anti-metastatic effect of a clinically used LMWH in the presence and absence of an intact endothelial glycocalyx. We show that both exogenous enzymatic degradation as well as endogenous genetic modification of the endothelial glycocalyx decreased pulmonary tumor formation in a murine experimental metastasis model. Moreover, LMWH administration significantly reduced the number of pulmonary tumor foci and thus experimental metastasis both in the presence or absence of an intact endothelial glycocalyx.

Conclusions

In summary, this paper shows that the net effect of the endothelial glycocalyx enhances experimental metastasis and that a LMWH does not limit experimental metastasis by a process involving the endothelial glycocalyx.

The prognostic IDH1( R132 ) mutation is associated with reduced NADP+-dependent IDH activity in glioblastoma

Somatic mutations in the isocitrate dehydrogenase 1 gene (IDH1) occur at high frequency in gliomas and seem to be a prognostic factor for survival in glioblastoma patients. In our set of 98 glioblastoma patients, IDH1 ( R132 ) mutations were associated with improved survival of 1 year on average, after correcting for age and other variables with Cox proportional hazards models. Patients with IDH1 mutations were on average 17 years younger than patients without mutation. Mutated IDH1 has a gain of function to produce 2-hydroxyglutarate by NADPH-dependent reduction of alpha-ketoglutarate, but it is unknown whether NADPH production in gliomas is affected by IDH1 mutations. We assessed the effect of IDH1 (R132 ) mutations on IDH-mediated NADPH production in glioblastomas in situ. Metabolic mapping and image analysis was applied to 51 glioblastoma samples of which 16 carried an IDH1 (R132 ) mutation. NADP+-dependent IDH activity was determined in comparison with activity of NAD+-dependent IDH and all other NADPH-producing dehydrogenases, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malate dehydrogenase, and hexose-6-phosphate dehydrogenase. The occurrence of IDH1 mutations correlated with approx. twofold diminished NADP+-dependent IDH activity, whereas activity of NAD+-dependent IDH and the other NADP+-dependent dehydrogenases was not affected in situ in glioblastoma. The total NADPH production capacity in glioblastoma was provided for 65% by IDH activity and the occurrence of IDH1 (R132 ) mutation reduced this capacity by 38%. It is concluded that NADPH production is hampered in glioblastoma with IDH1 (R132 ) mutation. Moreover, mutated IDH1 consumes rather than produces NADPH, thus likely lowering NADPH levels even further. The low NADPH levels may sensitize glioblastoma to irradiation and chemotherapy, thus explaining the prolonged survival of patients with mutated glioblastoma.

Differential TGF-{beta} signaling in retinal vascular cells: a role in diabetic retinopathy?

Purpose. An early hallmark of preclinical diabetic retinopathy is thickening of the capillary basal lamina (BL). TGF-beta, a multipotent cytokine acting through its receptors ALK5 and -1, has been postulated to be involved in this phenomenon. In light of this possible role, TGF-beta signaling and its downstream molecular effects were characterized in cultured vascular endothelial cells and pericytes of the retina. Methods. Bovine retinal endothelial cells and pericytes were stimulated with TGF-beta1 in the presence or absence of SD-208, a specific inhibitor of the TGF-beta type I receptor ALK5, or ALK5 small interfering (si)RNA. TGF-beta-signaling pathways were characterized by analysis of phosphorylated Smad2 or -1/5/8 proteins and TGF-beta target genes (PAI-1, fibronectin, CTGF, Smad7, and Id1) and protein (fibronectin). Results. ALK5 was expressed in both cell types, whereas ALK1 was exclusively expressed in endothelial cells. In endothelial cells, TGF-beta induced Smad2 phosphorylation at high concentrations, which was efficiently blocked by ALK5 inhibition. In contrast, in pericytes, Smad2 phosphorylation was rapidly induced at low concentrations of TGF-beta. The ALK1-Smad1/5/8 pathway was activated by TGF-beta in endothelial cells only. TGF-beta caused ALK5-mediated upregulation of PAI-1, Smad7, and fibronectin and in pericytes at lower TGF-beta concentrations than in endothelial cells. CTGF mRNA expression was induced only in pericytes. Fibronectin protein was confirmed to be regulated by TGF-beta in both cell types. Conclusions. TGF-beta signaling in retinal endothelial cells and pericytes show that these cells, and in particular the pericytes, have the essential characteristics to allow for a role of TGF-beta in BL thickening in preclinical diabetic retinopathy.

Imaging enzymes at work: metabolic mapping by enzyme histochemistry

For the understanding of functions of proteins in biological and pathological processes, reporter molecules such as fluorescent proteins have become indispensable tools for visualizing the location of these proteins in intact animals, tissues, and cells. For enzymes, imaging their activity also provides information on their function or functions, which does not necessarily correlate with their location. Metabolic mapping enables imaging of activity of enzymes. The enzyme under study forms a reaction product that is fluorescent or colored by conversion of either a fluorogenic or chromogenic substrate or a fluorescent substrate with different spectral characteristics. Most chromogenic staining methods were developed in the latter half of the twentieth century but still find new applications in modern cell biology and pathology. Fluorescence methods have rapidly evolved during the last decade. This review critically evaluates the methods that are available at present for metabolic mapping in living animals, unfixed cryostat sections of tissues, and living cells, and refers to protocols of the methods of choice.

Cathepsin L, target in cancer treatment?

Cathepsin L, a cysteine protease, is considered to be a potential therapeutic target in cancer treatment. Proteases are involved in the development and progression of cancer. Inhibition of activity of specific proteases may slow down cancer progression. In this review, we evaluate recent studies on the inhibition of cathepsin L in cancer. The effects of cathepsin L inhibition as a monotherapy on apoptosis and angiogenesis in cancer are ambiguous. Cathepsin L inhibition seems to reduce invasion and metastasis, but there is concern that selective cathepsin L inhibition induces compensatory activity by other cathepsins. The combination of cathepsin L inhibition with conventional chemotherapy seems to be more promising and has yielded more consistent results. Future research should be focused on the mechanisms and effects of this combination therapy.

Active HIF-1 in the normal human retina

A unique feature of the retina is the presence of photoreceptors, which require an enormous amount of oxygen for the conversion of light to an electrical signal. Hypoxia-inducible factor-1 alpha (HIF-1alpha) is a transcription factor that is the master regulator of cellular adaptation to low oxygen tension. Only in hypoxic conditions is HIF-1alpha protein stabilized and translocated to the nucleus, where it induces transcription of target genes involved in oxygen delivery and energy metabolism. We hypothesized that HIF-1alpha is constitutively stabilized and active in the normal human retina. We investigated the cellular distribution of HIF-1alpha and the expression of its downstream targets, vascular endothelial growth factor (VEGF), glucose transporter 1 (GLUT-1), and carbonic anhydrase IX (CAIX), by immunohistochemistry and immunoblotting in the retina of normal rats and human donor eyes. Both human and rat retinas displayed prominent staining of HIF-1alpha in nuclei of most cell types in inner and outer nuclear layers and the ganglion cell layer, a cellular distribution pattern which was confirmed in human retina by immunoblotting of nuclear extracts. A negative correlation was found between HIF-1alpha protein levels and postmortem times. In human retina, staining of VEGF, GLUT-1, and CAIX was found. Our observations indicate that active HIF-1 signaling occurs constitutively in the normal human and rat retina, suggesting that HIF-1 has a physiological role in the retina.

The establishment of the GENEQOL consortium to investigate the genetic disposition of patient-reported quality-of-life outcomes

To our knowledge, no comprehensive, interdisciplinary initiatives have been taken to examine the role of genetic variants on patient-reported quality-of-life outcomes. The overall objective of this paper is to describe the establishment of an international and interdisciplinary consortium, the GENEQOL Consortium, which intends to investigate the genetic disposition of patient-reported quality-of-life outcomes. We have identified five primary patient-reported quality-of-life outcomes as initial targets: negative psychological affect, positive psychological affect, self-rated physical health, pain, and fatigue. The first tangible objective of the GENEQOL Consortium is to develop a list of potential biological pathways, genes and genetic variants involved in these quality-of-life outcomes, by reviewing current genetic knowledge. The second objective is to design a research agenda to investigate and validate those genes and genetic variants of patient-reported quality-of-life outcomes, by creating large datasets. During its first meeting, the Consortium has discussed draft summary documents addressing these questions for each patient-reported quality-of-life outcome. A summary of the primary pathways and robust findings of the genetic variants involved is presented here. The research agenda outlines possible research objectives and approaches to examine these and new quality-of-life domains. Intriguing questions arising from this endeavor are discussed. Insight into the genetic versus environmental components of patient-reported quality-of-life outcomes will ultimately allow us to explore new pathways for improving patient care. If we can identify patients who are susceptible to poor quality of life, we will be able to better target specific clinical interventions to enhance their quality of life and treatment outcomes.

Organotypic glioma spheroids for screening of experimental therapies: how many spheroids and sections are required?

Cancer spheroids are a valuable model for screening anticancer strategies. However, studies are published using various numbers of spheroids and sections per spheroid. Here, we establish the sample size requirements for valid screening strategies to treat glioma: how many spheroids per experimental group and how many sections per spheroid are required to detect one-third reduction in an endpoint measurement after treatment? From two glioblastoma patients, 32 untreated organotypic spheroids were cultured and sectioned entirely (14-100 sections per spheroid). The viable fraction was determined as endpoint by automated image analysis in sections and used to establish the minimally-detectable difference between a treatment and reference group. Variance was considerable with a coefficient of variance of 21%. The biological variation in viability in sections of spheroids produced 97% of variance when sample size was large. Variance increased when numbers of spheroids but not numbers of sections per spheroid were reduced. A minimum of 12 spheroids per group and one section per spheroid was required for a valid comparison of a treatment group and a control group. When 10 treatment groups and one control group were compared, 16 spheroids per group were required. Thus, the statistical power depended almost entirely on the number of organotypic glioma spheroids and hardly on the number of sections per spheroid. The organotypic glioma spheroid model does not appear to be suitable for high-throughput screening of anticancer strategies, because of the relatively large number of spheroids required. It is the model of choice for low-throughput screening, because this model is far more representative for the parental tumor than any other more efficient glioma model.

Glucose-6-phosphate dehydrogenase deficiency and malaria: cytochemical detection of heterozygous G6PD deficiency in women

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a X-chromosomally transmitted disorder of the erythrocyte that affects 400 million people worldwide. Diagnosis of heterozygously-deficient women is complicated: as a result of lyonization, these women have a normal and a G6PD-deficient population of erythrocytes. The cytochemical assay is the only reliable assay to discriminate between heterozygously-deficient women and non-deficient women or homozygously-deficient women. G6PD deficiency is mainly found in areas where malaria is or has been endemic. In these areas, malaria is treated with drugs that can cause (severe) hemolysis in G6PD-deficient individuals. A cheap and reliable test is necessary for diagnosing the deficiency to prevent hemolytic disorders when treating malaria. In this review, it is concluded that the use of two different tests for diagnosing men and women is the ideal approach to detect G6PD deficiency. The fluorescent spot test is inexpensive and easy to perform but only reliable for discriminating hemizygous G6PD-deficient men from non-deficient men. For women, the cytochemical assay is recommended. However, this assay is more expensive and difficult to perform and should be simplified into a kit for use in developing countries.

Differential effects of anticoagulants on tumor development of mouse cancer cell lines B16, K1735 and CT26 in lung

Cancer progression is facilitated by blood coagulation. Anticoagulants, such as Hirudin and low molecular weight heparins (LMWHs), reduce metastasis mainly by inhibition of thrombin formation and L- and P-selectin-mediated cell-cell adhesion. It is unknown whether the effects are dependent on cancer cell type. The effects of anticoagulants on tumor development of K1735 and B16 melanoma cells and CT26 colon cancer cells were investigated in mouse lung. Tumor load was determined noninvasively each week up to day 21 in all experiments using bioluminescence imaging. Effects of anticoagulants on tumor development of the three cell lines were correlated with the fibrin/fibrinogen content in the tumors, expression of tissue factor (TF), protease activated receptor (PAR)-1 and -4 and CD24, a ligand of L- and P-selectins. Hirudin inhibited tumor development of B16 cells in lungs completely but did not affect tumor growth of K1735 and CT26 cells. Low molecular weight heparin did not have an effect on K1735 melanoma tumor growth either. TF and PAR-4 expression was similar in the three cell lines. PAR-1 and CD24 were hardly expressed by K1735, whereas CT26 cells expressed low levels and B16 high levels of PAR-1 and CD24. Fibrin content of the tumors was not affected by LMWH. It is concluded that effects of anticoagulants are dependent on cancer cell type and are correlated with their CD24 and PAR-1 expression.

Dipeptidyl peptidase IV inhibitors in diabetes: more than inhibition of glucagon-like peptide-1 metabolism?

Inhibitors of the protease dipeptidyl peptidase IV (DPP-IV) are promising new drugs for the treatment of type 2 diabetes. They are thought to act by inhibiting the breakdown of glucagon-like peptide-1 and, thereby, selectively enhancing insulin release under conditions when it is physiologically required. These drugs are selective for DPP-IV, but the enzyme itself has a broad range of substrates other than glucagon-like peptide-1. Other high affinity substrates of DPP-IV including peptide YY may also play a role in the regulation of energy homeostasis. Moreover, DPP-IV is also known as CD26 and considered to be a moonlighting protein because it has a wide range of other functions unrelated to energy homeostasis, e.g. in immunity. The potential role of DPP-IV inhibition on substrates other than glucagon-like peptide-1 in diabetes patients remains to be elucidated.

Connective tissue growth factor is necessary for retinal capillary basal lamina thickening in diabetic mice

Experimental prevention of basal lamina (BL) thickening of retinal capillaries ameliorates early vascular changes caused by diabetes. Connective tissue growth factor (CTGF) is upregulated early in diabetes in the human retina and is a potent inducer of expression of BL components. We hypothesize that CTGF is causally involved in diabetes-induced BL thickening of retinal capillaries. To test this hypothesis, we compared the effects of streptozotocin (STZ)-induced diabetes on retinal capillary BL thickness between wild-type mice (CTGF+/+) and mice lacking one functional CTGF allele (CTGF+/-). Differences in BL thickness were calculated by quantitative analysis of electron microscopic images of transversally sectioned capillaries in and around the inner nuclear layer of the retina. We show that BL thickening was significant in diabetic CTGF+/+ mice compared with control CTGF+/+ mice, whereas diabetes did not significantly induce BL thickening in CTGF+/- mice. We conclude that CTGF expression is necessary for diabetes-induced BL thickening and suggest that reduction of CTGF levels may be protective against the development of diabetic retinopathy.

The angio-fibrotic switch of VEGF and CTGF in proliferative diabetic retinopathy

BACKGROUND

In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) cause blindness by neovascularization and subsequent fibrosis, but their relative contribution to both processes is unknown. We hypothesize that the balance between levels of pro-angiogenic VEGF and pro-fibrotic CTGF regulates angiogenesis, the angio-fibrotic switch, and the resulting fibrosis and scarring.

METHODS/PRINCIPAL FINDINGS

VEGF and CTGF were measured by ELISA in 68 vitreous samples of patients with proliferative DR (PDR, N = 32), macular hole (N = 13) or macular pucker (N = 23) and were related to clinical data, including degree of intra-ocular neovascularization and fibrosis. In addition, clinical cases of PDR (n = 4) were studied before and after pan-retinal photocoagulation and intra-vitreal injections with bevacizumab, an antibody against VEGF. Neovascularization and fibrosis in various degrees occurred almost exclusively in PDR patients. In PDR patients, vitreous CTGF levels were significantly associated with degree of fibrosis and with VEGF levels, but not with neovascularization, whereas VEGF levels were associated only with neovascularization. The ratio of CTGF and VEGF was the strongest predictor of degree of fibrosis. As predicted by these findings, patients with PDR demonstrated a temporary increase in intra-ocular fibrosis after anti-VEGF treatment or laser treatment.

CONCLUSIONS/SIGNIFICANCE

CTGF is primarily a pro-fibrotic factor in the eye, and a shift in the balance between CTGF and VEGF is associated with the switch from angiogenesis to fibrosis in proliferative retinopathy.

Validity of bioluminescence measurements for noninvasive in vivo imaging of tumor load in small animals

A relatively new strategy to longitudinally monitor tumor load in intact animals and the effects of therapy is noninvasive bioluminescence imaging (BLI). The validity of BLIf or quantitative assessment of tumor load in small animals is critically evaluated in the present review. Cancer cells are grafted in mice or rats after transfection with a luciferase gene--usually that of a firefly. To determine tumor load, animals receive the substrate agent luciferin intraperitoneally, which luciferase converts into oxyluciferin in an ATP-dependent manner Light emitted by oxyluciferin in viable cancer cells is captured noninvasively with a highly sensitive charge-coupled device (CCD) camera. Validation studies indicate that BLI is useful to determine tumor load in the course of time, with each animal serving as its own reference. BLI is rapid, easy to perform, and sensitive. It can detect tumor load shortly after inoculation, even when relatively few cancer cells (2500-10,000) are used. BLI is less suited for the determination of absolute tumor mass in an animal because of quenching of bioluminescence by tissue components and the exact location of tumors because its spatial resolution is limited. Nevertheless, BLI is a powerful tool for high-throughput longitudinal monitoring of tumor load in small animals and allows the implementation of more advanced orthotopic tumor models in therapy intervention studies with almost the same simplicity as when measuring traditional ectopic subcutaneous models in combination with calipers.