Phase I and pharmacodynamic study of high-dose NGR-hTNF in patients with refractory solid tumours.

BACKGROUND: NGR-hTNF exploits the peptide asparagine-glycine-arginine (NGR) for selectively targeting tumour necrosis factor (TNF) to CD13-overexpressing tumour vessels. Maximum-tolerated dose (MTD) of NGR-hTNF was previously established at 45 µg m(-2) as 1-h infusion, with dose-limiting toxicity being grade 3 infusion-related reactions. We explored further dose escalation by slowing infusion rate (2-h) and using premedication (paracetamol). METHODS: Four patients entered each of 12 dose levels (n=48; 60-325 µg m(-2)). Pharmacokinetics, soluble TNF receptors (sTNF-R1/sTNF-R2), and volume transfer constant (K(trans)) by dynamic imaging (dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)) were assessed pre- and post-treatment. RESULTS: Common related toxicity included grade 1/2 chills (58%). Maximum-tolerated dose was not reached. Both C(max) (P<0.0001) and area under the plasma concentration-time curve (P=0.0001) increased proportionally with dose. Post-treatment levels of sTNF-R2 peaked significantly higher than sTNF-R1 (P<0.0001). Changes in sTNF-Rs, however, did not differ across dose levels, suggesting a plateau effect in shedding kinetics. As best response, 12/41 evaluable patients (29%) had stable disease. By DCE-MRI, 28/37 assessed patients (76%) had reduced post-treatment K(trans) values (P<0.0001), which inversely correlated with NGR-hTNF C(max) (P=0.03) and baseline K(trans) values (P<0.0001). Lower sTNF-R2 levels and greater K(trans) decreases after first cycle were associated with improved survival. CONCLUSION: asparagine-glycine-arginine-hTNF can be safely escalated at doses higher than MTD and induces low receptors shedding and early antivascular effects.

Effects of methylmercury on the microvasculature of the developing brain.

The study, undertaken with the aim of further investigating the effects of methylmercury (MeHg) exposure on the developing brain, was performed in the cerebellum of chick embryos, chronically treated with a MeHgCl solution dropped onto the chorioallantoic membrane, and in control embryo cerebella. Quantitative evaluations, performed by cold vapour atomic absorption spectrophotometry, demonstrated a high mercury content in the chorioallantoic membrane, encephalon, liver and kidney of the treated embryos. The morphological observations showed severe neuronal damage consisting of degenerative changes of the granules and Purkinje neurons. The effects on astrocytes were even more severe, since they were extremely rare both in the neuropil and around the vessel wall. Compared with the controls, the cerebellar vessels of MeHg-treated embryos showed immature morphology, poor differentiation of endothelial barrier devices, and high permeability to the exogenous protein horseradish peroxidase. These findings support the hypothesis that MeHg-related neuronal sufferance may be secondary to astrocytic damage and suggest that the developmental neurotoxicity of this compound could also be related to astrocyte loss-dependent impairment of blood-brain barrier (BBB) differentiation.

Expression of caveolin-1 in human brain microvessels.

Caveolae are microinvaginations of the cell plasma membrane involved in cell transport and metabolism as well as in signal transduction; these functions depend on the presence of integral proteins named caveolins in the caveolar frame. In the brain, various caveolin subtypes have been detected in vivo by immunocytochemistry: caveolin-1 and -2 were found in rat brain microvessels, caveolin-3 was revealed in astrocytes. The aim of this study was to identify the site(s) of cellular expression of caveolin-1 in the microvessels of the human cerebral cortex by immunofluorescence confocal microscopy and immunogold electron microscopy. Since in the barrier-provided brain microvessels tight relations occur between the endothelium-pericyte layer and the surrounding vascular astrocytes, double immunostaining with caveolin-1 and the astroglia marker, glial fibrillary acidic protein, was also carried out. Immunocytochemistry by confocal microscopy revealed that caveolin-1 is expressed by endothelial cells and pericytes in all the cortex microvessels; caveolin-1 is also expressed by cells located in the neuropil around the microvessels and identified as astrocytes. Study of the cortex microvessels carried out by immunoelectron microscopy confirmed that in the vascular wall caveolin-1 is expressed by endothelial cells, pericytes, and vascular astrocytes, and revealed the association of caveolin-1 with the cell caveolar compartment. The demonstration of caveolin-1 in the cells of the brain microvessels suggests that caveolin-1 may be involved in blood-brain barrier functioning, and also supports co-ordinated activities between these cells.

Developmental effects of lead acetate on the chick embryo metanephros.

The developmental effects of lead acetate were studied in the chick embryo metanephros, the third renal rudiment that acquires morphological characteristics of functioning kidney already during the prenatal life. Lead exposure was obtained by applying a lead acetate solution on the chick embryo chorioallantoic membrane at the days 9, 10 and 11 of incubation. Quantitative evaluation of the lead concentration assessed by furnace atomic absorption spectrophotometry at the days 14 and 21 of incubation demonstrated metal presence both in the chorioallantoic membrane (CAM) and in metanephros (MN). The lead concentration was higher in CAM than in MN; the metal amount was similar in the CAM of 14 and 21 day embryos, but significantly higher in the 14day embryo MN than in the 21 day embryo MN. Morphological observations on metanephros tissue of control and lead-treated embryos were performed under light, electron transmission and electron scanning microscopes. Peculiar attention was devoted to the expression of the junctional protein connexin 43, the major component of the gap junctions in the renal cells. The results indicated that lead treatment does not intervene in the general differentiation of the metanephric nephrons. The lead is reabsorbed by the proximal tubule cells that are engulfed by endocytotic vacuoles and metal deposits and show long term degenerative changes. Expression of Cx43 protein and ultrastructure of gap junctions between proximal tubule cells appeared to be unchanged. The morphological aspects of the MN corpuscles and tubules agree with the suggestion of a lead cytotoxic effect but do not corroborate, at least in this experimental model, the view of primary damage exerted by lead on the gap junctions of the renal epithelial cells.

Immunogold cytochemistry of the blood-brain barrier glucose transporter GLUT1 and endogenous albumin in the developing human brain.

The blood-brain barrier (BBB) glucose transporter, GLUT1, was detected by immunogold electron microscopy on the microvascular compartment of the human foetus telencephalon at the 12th and 18th weeks of gestation. By computerized morphometry, the cellular and subcellular localization of the immunosignal for GLUT1 was quantitatively evaluated. The study showed that the glucose transporter is strongly expressed by endothelial cells while a very low signal is detected on vascular pericytes. The GLUT1 antigenic sites are preferentially associated to the ablumenal and junctional plasma membranes of the endothelial cells and tend to increase significantly with age. A parallel study carried out by the endogenous serum protein albumin demonstrated that already at the 12th week the endothelial routes are hindered to the protein as happens at the blood-endothelium interface of mature brain. The results demonstrate that in the human foetus the brain microvessels express BBB-specific functional activities early.

Cholinergic nerve fibres associated with the microvessels of the human cerebral cortex: a study based on monoclonal immunocytochemistry for choline acetyltrasferase.

The distribution of cholinergic nerve fibres associated with the microvasculature of the human parietal cerebral cortex was investigated by immunocytochemistry, employing monoclonal antibodies against choline acetyl-transferase, the acetylcholine-synthesizing enzyme. The results revealed strongly immunoreactive nerve fibres in the tunica adventitia of arterioles penetrating the superficial cortical layers from the pial vasculature. Networks of stained nerve fibres were seen within the tunica muscularis of the radially directed arterioles that cross the intermediate and deep cortical laminae, and of their transverse and recurrent branches. Tiny positive nerve fibres were also seen around the cortex capillaries, some reaching the endothelial cells. The morphological data support the involvement of acetylcholine in microvasculature local regulation, possibly with a differentiated role in the arterioles and capillaries.

Regional distribution and cell type-specific expression of the mouse F3 axonal glycoprotein: a developmental study.

The expression of the mouse axonal adhesive glycoprotein F3 and of its mRNA was studied on sections of mouse cerebellar cortex, cerebral cortex, hippocampus, and olfactory bulb from postnatal days 0 (P0) to 30 (P30). In cerebellar cortex, a differential expression of F3 in granule versus Purkinje neurons was observed. F3 was highly expressed during migration of and initial axonal growth from cerebellar granule cells. The molecule was then downregulated on cell bodies and remained expressed, although at low levels, on their axonal extensions. On Purkinje cells, F3 was strongly expressed on cell bodies and processes at the beginning of the second postnatal week; by P16 it was restricted to neurites of Purkinje cells subpopulations. In the cerebral cortex, the molecule was highly expressed on migrating neurons at P0; by P16, it was found essentially within the neuropil with a diffuse pattern. In the hippocampal formation, where F3 was expressed on both pyramidal and granule neurons, a clear shift from the cell bodies to neurite extensions was observed on P3. In the olfactory pathway, F3 was expressed mainly on olfactory nerve fibers, mitral cells, and the synaptic glomeruli from P0 to P3, with a sharp decline from P11 to P16. As a whole, the data show that F3 protein expression is regulated at the regional, cellular, and subcellular levels and suggest that, in different regions, it can be proposed as a reliable neuronal differentiation marker.

Immunohistochemical and ultrastructural characterization of cortical plate microvasculature in the human fetus telencephalon.

The blood-brain barrier (BBB) differentiation was investigated by immunohistochemistry and electron microscopy in the radial microvasculature of the telencephalon cortical plate (CP) of 12- and 18-week human fetuses. The BBB-specific glucose transporter isoform 1 (GLUT1) is expressed in both stages, with a main localization on the ablumenal and lateral plasma membranes of the endothelial cells. The endothelial cells are welded by short junctions with fusion points of the plasma membranes at 12 weeks and by extensive tight junctions at 18 weeks. The basal lamina is discontinuous beneath the endothelium-pericyte layer at 12 weeks and splits into two continuous layers circumscribing the pericytes in the later stage. The expression of laminin, a basal lamina glycoprotein, is continuous already at 12 weeks. The CP microvessels are tightly surrounded by processes of glial cells. Immunodetection of the cytoskeletal filament proteins, vimentin (VIM), and glial fibrillary acidic protein (GFAP), demonstrates that at 12 weeks the perivascular glial processes are mostly represented by VIM-stained fibers of the radial glia. At 18 weeks, GFAP-stained radial glia fibers, processes of VIM-stained astroblasts, and GFAP-positive astrocytes also build the perivascular envelopes. The results indicate that the vessel differentiation is already under way in the human CP at the midgestational age and entails the establishment of some barrier devices. The early relationship between perivascular glia coverage formation and endothelial barrier maturation suggests that also immature astroglial cells are involved in the setting up of the BBB.

Developmental expression of ZO-1 antigen in the mouse blood-brain barrier.

Tight junction biogenesis during blood-brain barrier development (BBB) in mesencephalon microvessels of mouse embryos of day 9, foetuses of day 15 and 19 and new-born (2-day-old) mice was examined by light and electron microscopy, using monoclonal antibodies recognizing the tight junction peripheral membrane protein ZO-1. A faint spot-like staining began to be recognizable under the light microscope in day 15 vessels in which the endothelial cells showed isolated fusion points between the external plasma membrane leaflets under the electron microscope. A stronger labelling was present in microvessels of day 19 foetuses and new-born animals when the endothelial tight junction appeared completely differentiated. In the immunogold study, gold particles were seen scattered throughout the cytoplasm of endothelial cells of day 15 foetuses. In day 19 foetuses and in the new-born mice, gold particles were located only at the cytoplasmic surfaces of the tight junctions. The results indicate that the ZO-1 protein is a specific molecular marker in the developing brain endothelial tight junctions and that its expression takes place parallel to BBB morphofunctional maturation.

Angiogenesis and endothelium phenotype expression in embryonic adrenal gland and cerebellum grafted onto chorioallantoic membrane.

Vascularization and endothelial phenotype were investigated in embryonic tissues grafted onto chorioallantoic membrane (CAM) by means of immunocytochemistry and electron microscopy. Single grafts of adrenal gland or cerebellum and double grafts of adrenal gland plus cerebellum were performed, using tissues from chick or quail embryos as donors and CAMs of chick embryos as recipients. Vessels of quail origin were discriminated from those of chick origin by the anti-MB1 monoclonal antibody, specific for antigenic determinants of the quail endothelial cells. The cerebellum endothelia were distinguished from the adrenal and CAM endothelia by a polyclonal antibody against the isoform 1 of the glucose transporter (GLUT1), which is a marker of barrier-provided brain vessels. The observations, carried out, 6 days after implantation, revealed the new-growth of microvessels from the CAM into the grafted tissues, and vice versa, in both single and double transplants. In addition, in the double grafts, adrenal-derived vessels were seen to grow into the cerebellum and cerebellum-native vessels into the adrenal tissue. The combined immunocytochemical and electronmicroscopical study demonstrated that the adrenal, fenestrated sinusoids and the cerebellar, barrier-provided capillaries maintain their original phenotype when they grow within the non-native tissues. The conventional theory on the endothelial responsiveness to environmental signals has been discussed and some concluding remarks have been made.

Glucose transporter GLUT1 localization in human foetus telencephalon.

The endothelial cells of the mature cerebral microvessels, provided with barrier devices (blood-brain barrier, BBB), selectively express the glucose transporter isoform 1 (GLUT1). Presence and localization of the GLUT1 were studied by immunogold silver staining (IGSS) labelling on ultrathin sections of foetal human telencephalon tissue embedded in Lowicryl HM20 according to the progressive lowering of temperature (PLT) method. In the microvascular endothelial cells of the human telencephalon GLUT1 molecules are detected at the 12th gestational week and their expression is increased at the 18th week. In both ages, the transporter is mainly localized on the ablumenal and lateral endothelial cell membranes, and at 18 weeks a greater number of GLUT1 antigenic sites are also seen at the lumenal membrane. Our findings demonstrate both the expression and subcellular localization of GLUT1 be developmentally regulated and suggest an early functioning of the BBB-GLUT1 transporter in the developing human brain.

Vascularization of embryonic adrenal gland grafted onto chorioallantoic membrane.

Vascularization and endothelial phenotype expression were analysed in embryonic adrenal tissue grafted onto chorioallantoic membrane (CAM), by means of routine light microscopy and immunocytochemical staining, and of electron microscopy. Adrenal gland tissue from chick or quail embryos (donors) was grafted onto CAMs of chick or quail embryos (host). Vessels of chick origin were discriminated from those of quail origin by monoclonal antibodies, anti-MB1, specific for quail endothelial and haemopoietic cells, and QCPN, which labels quail cell nuclei. Vessels of adrenal type were distinguished from those of CAM-type by their ultrastructural endothelial phenotype - porous in the former and continuous in the latter. The observations carried out 6 days after implantation indicate that the adrenal gland develops and differentiates according to a virtually normal histological pattern. As regards the adrenal and CAM vascularization, the grafting procedure elicits angiogenic events consisting in the formation of peripheral anastomoses between the graft and the CAM original microvasculature and in new-growth of vessels from the CAM into the grafted tissue and vice versa. As to the endothelial phenotype, the ultrastructural results demonstrate that besides its own native vasculature, the adrenal tissue contains vessels with continuous endothelium and the CAM mesenchyme is supplied by adrenal-type, fenestrated vessels.

Ultrastructural localization of lectin binding sites in the developing brain microvasculature.

The temporo-spatial patterning of lectin-binding sites was examined by lectin histochemistry and quantitative methods in the microvasculature of the optic tectum of 9-, 14-, 20-day-old embryos and 30-day-old chickens. Horseradish peroxidase and colloidal-gold-labelled lectins were used for detection of beta-D-galactose (RCA-I, Ricinus communis agglutinin-I) and of N-acetylglucosamine and sialic residues (WGA, Wheat germ agglutinin) at light and electron microscopical levels. At the light microscopical level, RCA-I and WGA binding sites were detectable in the early embryonic capillaries in a diffuse staining pattern; in later embryonic stages and in adult animals, RCA-I labelling became located on the abluminal surface of the vessels, while WGA staining was detected on the luminal surface. Ultrastructurally, gold labelling for RCA-I was seen intracytoplasmically in endothelial cells in 9-day-old embryos. In 14-to 20-day-old embryos and in chickens, binding sites for RCA-I were detected in endothelial tight junctions and basement membranes. In contrast, labelling of the gold-coupled WGA lectin was distributed almost exclusively on the luminal endothelial surface already in early embryos. The results indicate that the endothelial cells of the optic tectum acquire functional polarity early in their development and that glycoconjugates containing beta-D-galactose residues are involved in the biochemical composition of the tight junctions and basement membrane, which are considered to be key structures in blood-brain barrier (BBB) differentiation.

Role of basic fibroblast growth factor in the formation of the capillary plexus in the chick embryo chorioallantoic membrane. An in situ hybridization, immunohistochemical and ultrastructural study.

The chick embryo chorioallantoic membrane (CAM) is supplied by an extensive capillary network. We have previously demonstrated that a Mr 16,000 basic fibroblast growth factor (FGF2)-like molecule is present in the CAM. At present, no data are available on the cellular source(s) of FGF2 in the CAM. In this work, CAM has been investigated by in situ hybridization with the aim to identify the source(s) of endogenous FGF2 during development. The immunohistochemical expression of fibronectin, laminin and type IV collagen in the CAM extracellular matrix (ECM) and the ultrastructural relationships between chorionic epithelium and the underlying capillary plexus were also studied. Our findings strongly suggest that FGF2 regulates the development of the capillary plexus by two sequential steps. In an early paracrine phase, chorionic epithelial cells secrete FGF2, thus eliciting an angiogenic response in the undifferentiated mesodermal blood vessels. In response to this paracrine signalling, the newly formed endothelial cells move through a permissive ECM and migrate beneath the chorion. Here, they synthesize an autocrine supply of FGF2 necessary to further proliferate and differentiate, thus originating the capillary plexus.

Astroglia-microvessel relationship in the developing human telencephalon.

The telencephalon of 12 and 18 week-old human foetuses was examined for evidence of astroglia-microvessel relationship. Immature astroglia cells (radial glia and astroblasts) and astrocytes were immunostained using antibodies to the cytoskeletal proteins vimentin (VIM) and glial fibrillary acidic protein (GFAP). The microvessels were detected using an antibody to the blood-brain barrier (BBB)-specific glucose transporter GLUT1. Two extracellular matrix (ECM) glycoproteins, laminin (LM), an endothelial-derived molecule, and tenascin-C (TN-C), a glia-derived molecule, were also analyzed. In the two stages examined, VIM- and GFAP-positive fibers of the radial glia establish close relationships with the radial and periventricular microvessels, which are GLUT1-positive and lined by an LM-positive basal lamina-like matrix. At the 18th week, also radial glia transitional forms and immature astrocytes exhibit extensive contacts with the microvasculature. A TN-C-rich ECM is revealed around the vascular plexus of ventricular zones at the 12th week, and around the newly growing radial microvessels and the microvessel branching sites at the 18th week. The observations taken as a whole, suggest that during the telencephalon morphogenesis the immature astroglia cells play a role in the early establishment of the distribution pattern of the neural microvessels and in their growth and maturation.

An immunohistochemical and morphometric study on astrocytes and microvasculature in the human cerebral cortex.

In this study, astrocytes and microvessels of the human cerebral cortex were analysed morphometrically with the aim of acquiring quantitative information on the glio-vascular relationships, considered to be of great importance in the formation and functioning of the blood-brain barrier. Immunohistochemistry for the astrocytic marker, glial fibrillary acidic protein, was used with a computerized image analysis system. The brain tissue was embedded using the progressive lowering of temperature method, and the image analyser was applied to semithin sections subjected to immunogold-silver staining and viewed by epipolarization microscopy. The results show that, in the human cerebral cortex, astrocytes cover 11.4% of the cortex area and that their perivascular processes are nearly as extensive as the vascular bed (0.8% versus 1.72% of the cortex area). These processes form a virtually continuous sheath around the vascular walls, only 11% of the vessel perimeter lacking this astrocytic glia covering. The present results, compared with previous unpublished data obtained by conventional immunocytochemical procedures on wax sections, indicate that low-temperature methods combined with gold-silver immunolabelling on semithin sections significantly improve the detection of immunoreactivity and the performance of the image analyser.

Glucose transporter GLUT1 in human brain microvessels revealed by ultrastructural immunocytochemistry.

The brain glucose transporter GLUT1 is a transmembrane glycoprotein belonging to the glucose carrier family comprising five isoforms characterized by different functional properties and tissue specificity. Biochemical and immunohistochemical analyses have demonstrated that GLUT isoform 1 is localised within the brain microvascular endothelium, where it controls glucose uptake through the blood-brain barrier (BBB). In this study the expression of GLUT1 was analysed by means of light and electron immunocytochemistry in the adult human cerebellar cortex. The glucose transporter is strongly expressed in cerebellum microvessels, and is localised not only within endothelial cells but also in microvascular pericytes. Moreover, some glial expression of GLUT1 was observed in the neutrophil and in perivascular glial sheaths. The observations demonstrate that different cellular types are involved in the control of brain glucose homeostasis by GLUT1 expression at the BBB site, and support the postulated highly specialised role of brain microvascular pericytes.

Ultrastructural and morphometric investigation of human brain capillaries in normal and peritumoral tissues.

Capillaries of peritumoral and normal brain tissues were ultrastructurally and morphometrically investigated to evaluate the changes in peritumoral capillaries connected with the tumor-associated vasogenic edema. The endothelial cells of peritumoral capillaries showed varying thickness, electron-lucent cytoplasm, and structurally normal tight junctions. The basal lamina was thickened, rarefied, and vacuolated. The pericytes were provided with pinocytotic vesicles and phagocytic bodies. The astrocytic glia appeared empty or swollen, with few glycogen granules and a disarranged cytoskeleton; well-preserved glia was occasionally observed. The brain tissue was slightly edematous. No statistically significant differences were observed between normal and peritumoral capillaries as regards diameter, wall thickness, endothelial thickness, and endothelial vesicle density. Instead, the peritumoral capillaries displayed three times as many endothelial surface-connected vesicles, a markedly thicker basal lamina, and significantly reduced extension of pericytic and glial investments. The kind and severity of the vascular modifications, compared with the slight edematous appearance of the nervous tissue, strengthen the hypothesis that peritumoral capillaries could be involved in the edema resolution process.