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.

Temporal expression of the matrix metalloproteinase MMP-2 correlates with fibronectin immunoreactivity during the development of the vascular system in the chick embryo chorioallantoic membrane

In this study we have examined in the chick embryo chorioallantoic membrane (ChAM) the expression of the matrix metalloproteinase 2 (MMP-2) and have correlated this parameter with the expansion of the ChAM vasculature and with the expression of 3 extracellular matrix components (fibronectin, laminin and type IV collagen), which differentially modulate angiogenesis. In the early phases of ChAM development, between d 6 and d 8 of incubation, when the increase of the ChAM vasculature is maximal, higher values of MMP-2 and, respectively, of fibronectin immunoreactive area, are detectable. These results indicate that MMP-2 activity and fibronectin expression are 2 strictly related components of angiogenesis occurring in vivo.

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.

Effects of Aroclor 1254 on intercellular communication in human keratinocytes

It has been previously described that Aroclor 1254 can inhibit GJIC in rodent liver cells where it is known to be a tumor promoter, while the possibility that Aroclor 1254 exerts its inhibitory effects on GJIC in human keratinocytes and acts as a human skin tumor promoter, deserves further attention. In the present study the effects of Aroclor 1254 were examined on gap junction channel permeability, on connexin 43 (Cx 43) expression at mRNA and protein level and on ultrastructural modification to add further experimental evidence to its inhibitory effect on GJIC. The results were compared to those induced by 12-O-tetradecanoylphorbol-13 acetate (TPA), a tumor promoter known to be a potent inhibitor of GJIC in human skin cells and to those induced by benzo[a]pyrene (B[a]P) known for its genotoxic activity. Our data show increased Cx 43 protein expression in Aroclor 1254 and TPA-treated cultures compared to controls, decreased Cx 43 protein level in those exposed to B[a]P, while Cx 43 gene expression (Cx 43 mRNA) was unaffected by the treatments. In Aroclor and TPA-treated keratinocytes, the ultrastructural examination showed residues of junctional systems expressed by specular, short tracts of the faced plasma membranes. In contrast, the contacts between plasma membranes of adjacent B[a]P treated keratinocytes were more extended. A clear inhibition of gap junction channel permeability due to Aroclor 1254 and TPA was also manifest by Lucifer yellow dye test compared to B[a]P-treated cultures where dye spreading to the neighbouring cells and to the extracellular space occurred. The present data, in addition to confirming inhibition of GJIC mediated by Aroclor 1254 in human keratinocytes, which were found to be comparable to those induced by TPA, suggest that GJIC inhibition is associated with increased Cx 43 protein expression without significant modification of its gene expression.

Human erythropoietin induces a pro-angiogenic phenotype in cultured endothelial cells and stimulates neovascularization in vivo

Hematopoietic and endothelial cell lineages share common progenitors. Accordingly, cytokines formerly thought to be specific for the hematopoietic system have been shown to affect several functions in endothelial cells, including angiogenesis. In this study, we investigated the angiogenic potential of erythropoietin (Epo), the main hormone regulating proliferation, differentiation, and survival of erythroid cells. Epo receptors (EpoRs) have been identified in the human EA.hy926 endothelial cell line by Western blot analysis. Also, recombinant human Epo (rHuEpo) stimulates Janus Kinase-2 (JAK-2) phosphorylation, cell proliferation, and matrix metalloproteinase-2 (MMP-2) production in EA.hy926 cells and significantly enhances their differentiation into vascular structures when seeded on Matrigel. In vivo, rHuEpo induces a potent angiogenic response in the chick embryo chorioallantoic membrane (CAM). Accordingly, endothelial cells of the CAM vasculature express EpoRs, as shown by immunostaining with an anti-EpoR antibody. The angiogenic response of CAM blood vessels to rHuEpo was comparable to that elicited by the prototypic angiogenic cytokine basic fibroblast growth factor (FGF2), it occurred in the absence of a significant mononuclear cell infiltrate, and it was not mimicked by endothelin-1 (ET-1) treatment. Taken together, these data demonstrate the ability of Epo to interact directly with endothelial cells and to elicit an angiogenic response in vitro and in vivo and thus act as a bona fide direct angiogenic factor.

Bone marrow angiogenesis and mast cell density increase simultaneously with progression of human multiple myeloma

Immunohistochemical, cytochemical and ultrastructural data showing vivid angiogenesis and numerous mast cells (MCs) in the bone marrow of 24 patients with active multiple myeloma (MM) compared with 34 patients with non-active MM and 22 patients with monoclonal gammopathy of undetermined significance (MGUS) led us to hypothesize that angiogenesis parallels progression of MM, and that MCs participate in its induction via angiogenic factors in their secretory granules.

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.

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.

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.

ICAM 1 expression and fluid phase endocytosis of cultured brain microvascular endothelial cells following exposure to interferon beta-1a and TNFalpha

We have studied the effect of interferon (IF) beta-1a on the basal and TNFalpha-induced intercellular adhesion molecule 1 (ICAM 1) expression and fluid phase endocytosis (FPE) of horseradish peroxidase in cultured rat brain microvascular endothelial cells. Neither basal ICAM 1 expression nor basal FPE were significantly affected by 24-72 h exposure to 1000 U/ml IFbeta-1a. ICAM 1 induction and FPE enhancement caused by 100 U/ml TNFalpha for 24 h was not influenced by simultaneous administration of 1000 U/ml IFbeta-1a. Treatment of cultures with IFbeta-1a for 48 h followed by 24-h coincubation with TNFalpha (100 U/ml) and IFbeta-1a (1000 U/ml) resulted in significant downregulation of TNFalpha-induced ICAM 1 expression and FPE. Downregulation of TNFalpha-induced ICAM 1 expression was not observed when combined treatment with TNFalpha (100 U/ml) and IFbeta-1a (1000 U/ml) for 24 h was followed by 48 h exposure to IFbeta-1a. We concluded that the blood-brain barrier endothelium may be a target of IFbeta-1a. Further, these in vitro findings may correlate with the results of recent clinical trials indicating that chronic treatment of relapsing remitting multiple sclerosis with IFbeta-1a prevents both clinical exacerbations and the appearance on Magnetic Resonance Imaging of new lesions enhanced by gadolinium which is taken up by increased transendothelial fluid phase vesicular transport.

Lipoprotein (a) induces angiogenesis on the chick embryo chorioallantoic membrane

BACKGROUND

Both lipoprotein (a) [Lp(a)] and angiogenesis have been shown to be associated with initiation and progression of atherosclerotic plaque. Lp(a) and two neutralizing anti-Lp(a) antibodies were investigated for their capacity to affect the vasoproliferative processes of the chick embryo chorioallantoic membrane (CAM), a useful model for such an investigation.

METHODS

Gelatin sponges loaded with Lp(a) alone or together with anti-Lp(a) antibodies, or with vehicle alone, phosphate-buffered saline (PBS), were implanted in vivo onto the CAM at incubation day 8. Four days later, sponges and the adjacent CAM tissues were assessed for the extent of angiogenesis in terms of microvessel counts.

RESULTS

Lp(a)-loaded sponges gave significantly higher counts than those loaded with the LP(a)-anti-Lp(a) antibodies complex, which overlapped those treated with PBS. The angiogenic response was similar to that obtained with basic fibroblast growth factor, a well known angiogenic molecule.

CONCLUSION

These data suggest that Lp(a) is capable of inducing angiogenesis in vivo, which might account for its ability to enhance and support atherosclerosis.

Free laminin in the extracellular matrix of B-cell non Hodgkin's lymphomas

The authors show that in the perivascular stroma of B-cell non-Hodgkin's lymphomas (B-NHL) is present a granular, speckled pattern of expression of laminin, similar to the 'free-laminin' firstly described by Lugassy et al. (1997) in human melanoma. The role of this form of laminin may be to promote the migration of tumor cells, which express a variety of binding-laminin surface proteins, whose expression is significantly increased in several human cancer models.

Angiogenesis in hepatocellular carcinoma: an experimental study in the chick embryo chorioallantoic membrane

Ten samples of human hepatocellular carcinoma and three of a laceration injure of the liver (controls) were grafted onto the chick embryo chorioallantoic membrane (CAM) to investigate their possible angiogenic activity. The angiogenic response in pathological and control implants was assessed on histologic sections by a morphometric method, 4 days after grafting. The vascular count in the CAMs treated with the pathological implants was significantly higher compared to control ones and the angiogenic response induced by pathological implants was comparable to that of a well known angiogenic molecule, namely basic fibroblast growth factor. The role played in vasoproliferative response by angio-genic cytokines released by tumor cells, by CAM extracellular matrix and by the perivascular mononuclear cells was supported by this study.

Systemic sclerosis stimulates angiogenesis in the chick embryo chorioallantoic membrane

Skin biopsies from patients with systemic sclerosis (SSc) were investigated for their angiogenic activity by using the chick embryo chorioallantoic membrane (CAM) assay. Ten samples of SSc and 10 of normal skin from age- and sex-matched subjects were grafted onto the CAM, and the angiogenic response in pathological and control implants was assessed on histological sections by a planimetric point-count method 4 days after grafting. The vascular counts in the area underlying the SSc were significantly higher than those of normal skin and a dense mononuclear cell infiltrate was detectable around the blood vessels in pathological specimens. These results suggest that SSc may promote angiogenesis, perhaps leading to the release of several angiogenic factors. Moreover, the role played in the angiogenic response by the inflammatory cells forming the cellular infiltrate is suggested by this study.

Do mast cells help to induce angiogenesis in B-cell non-Hodgkin's lymphomas?

Morphological and morphometric data showing a higher number of mast cells (MCs) in the stroma of B-cell non-Hodgkin's lymphomas (B-NHL) than in benign lymphadenopathies are presented in support of the suggestion that angiogenesis during the progression of B-NHL may be partly mediated by angiogenic factors in their secretory granules.

Expression of tenascin is related to angiogenesis in pre-eclampsia

METHODS

Ten samples of decidua basalis from pre-eclamptic women and 10 from healthy primigravid women subjected to caesarean section (control tissues) were investigated immunohistochemically for changes in angiogenesis and expression of tenascin, an extracellular matrix protein thought to modulate angiogenesis. In addition, pre-eclamptic and control samples were grafted onto the chick embryo chorioallantoic membrane (CAM) to study their possible angiogenic activity in vivo.

RESULTS

Although the microvessel area was low in control samples, it increased significantly in the pre-eclamptic decidua. In parallel, the area covered by tenascin staining underwent a significant expansion that was highly correlated with the microvessel area. Angiogenic activity was assessed both macroscopically and microscopically on histological sections 4 days after grafting. In contrast to control samples, pre-eclamptic decidua induced an intense capillary growth, and numerous capillaries converging towards the implant and forming a spoke-wheel pattern were evident. Histological examination using a planimetric point-count method showed that microvessel counts in the CAM area under and around the pre-eclamptic implants were significantly higher than those of control samples. Again, the extracellular matrix of nearby microvessels was strongly immunoreactive with tenascin.

CONCLUSION

It is suggested that, unlike normal decidua, pre-eclamptic decidua displays an intense, autonomous angiogenic activity, probably mediated by tenascin in addition to its own angiogenic factors.

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.

New model for the study of angiogenesis and antiangiogenesis in the chick embryo chorioallantoic membrane: the gelatin sponge/chorioallantoic membrane assay

Several methods for the in vivo study of angiogenesis are available, and each angiogenic assay presents distinct advantages and disadvantages. In this study, we present a new method for the quantitation of angiogenesis and antiangiogenesis in the chick embryo chorioallantoic membrane (CAM), based on the implantation of gelatin sponges on the top of growing CAM, on day 8 of incubation. After implantation, the sponges were treated with a stimulator (recombinant human basic fibroblast growth factor, FGF2) or an inhibitor (a rabbit polyclonal anti-FGF2 antibody) of blood vessel formation. Blood vessels growing vertically into the sponge and at the boundary between sponge and surrounding CAM mesenchyme were counted by a morphometric method on day 12. In addition, to assess whether the gelatin sponge is an appropriate vehicle to deliver cultured cells and evaluate their angiogenic potential, mouse aortic endothelial cells were cotransfected with human FGF2 and the Escherichia coli beta-galactosidase (beta-GAL) reporter gene. Stable transfectants were absorbed by the sponge, and evaluation of the angiogenic response was paralleled by beta-GAL staining to visualize implanted cells. This technique may facilitate the discovery and development of agonists or antagonists of angiogenesis.

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.

Exogenous heparin induces fibronectin overexpression parallel to angiogenesis in the extracellular matrix of the chick embryo chorioallantoic membrane

Heparin (HE) was injected into the allantoic sac of chick embryo eggs on the 5th day of incubation. After 48 h, a morphometric analysis of angiogenic response and an immunohistochemical investigation of fibronectin (FN) and type IV collagen immunoreactivity in developing vasculature were performed in order to verify whether HE-related choriollantoic membrane (CAM) angiogenic activity was associated with overexpression of FN and/or type IV collagen changes in CAM extracellular matrix. Data to be presented show a close relationship between HE treatment, angiogenic processes, and overexpression of FN, but not of type IV collagen in CAM extracellular matrix. They agree with other studies proving a facilitating role of FN in angiogenic processes.

Developmental study of ultrastructural and biochemical changes in isolated chick brain microvessels

The morphology of the endothelial junctions, the expression of the alkaline phosphatase (ALKP) and gamma-glutamyltranspeptidase (GGT) activities, and the transport systems for neutral amino acids (NAA) and for d-glucose were studied in parallel in isolated microvessels from the brains of 9-, 12-, and 21-day chick embryos and 30-day chickens using freeze-fracturing and biochemical techniques. In the 9-day embryos, the endothelium junctional plasma membranes show alignments of discrete intramembrane particles (Imps) on the replica P-faces. In the 12-day embryos, the junctional membranes show short fibrils of loosely interconnected fused Imps. In the 21-day embryos, the junction is characterized by simple networks, and in the 30-day chickens, by very dense meshworks of continuous, fibrillary strands. In early embryonic life, the ALKP activity is expressed at high levels, more markedly in the microvessels than in the whole brain. ALKP progressively declines in later embryos and even more in adulthood, when the activity is fivefold higher in the microvessels than in the whole brain. No GGT activity is expressed in either embryonic or adult microvessels. The transport systems for NAA and for d-glucose are most active in 12-day embryonic microvessels, and progressively less expressed by the 21st day and in the adult. The results taken as a whole suggest a close relationship between the morphological and the metabolic maturation of the endothelial barrier of cerebral vessels.

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.