Expression of cell adhesion molecule E-cadherin in human arachnoid villi

Molecular anatomy of adult mouse leptomeninges

Leptomeninges, consisting of the pia mater and arachnoid, form a connective tissue investment and barrier enclosure of the brain. The exact nature of leptomeningeal cells has long been debated. In this study, we identify five molecularly distinct fibroblast-like transcriptomes in cerebral leptomeninges; link them to anatomically distinct cell types of the pia, inner arachnoid, outer arachnoid barrier, and dural border layer; and contrast them to a sixth fibroblast-like transcriptome present in the choroid plexus and median eminence. Newly identified transcriptional markers enabled molecular characterization of cell types responsible for adherence of arachnoid layers to one another and for the arachnoid barrier. These markers also proved useful in identifying the molecular features of leptomeningeal development, injury, and repair that were preserved or changed after traumatic brain injury. Together, the findings highlight the value of identifying fibroblast transcriptional subsets and their cellular locations toward advancing the understanding of leptomeningeal physiology and pathology.

The distribution of E-cadherin expression in listeric rhombencephalitis of ruminants indicates its involvement in Listeria monocytogenes neuroinvasion

AIM

To investigate the expression of E-cadherin, a major host cell receptor for Listeria monocytogenes (LM) internalin A, in the ruminant nervous system and its putative role in brainstem invasion and intracerebral spread of LM in the natural disease.

METHODS

Immunohistochemistry and double immunofluorescence was performed on brains, cranial nerves and ganglia of ruminants with and without natural LM rhombencephalitis using antibodies against E-cadherin, protein gene product 9.5, myelin-associated glycoprotein and LM.

RESULTS

In the ruminant brain, E-cadherin is expressed in choroid plexus epithelium, meningothelium and restricted neuropil areas of the medulla, but not in the endothelium. In cranial nerves and ganglia, E-cadherin is expressed in satellite cells and myelinating Schwann cells. Expression does not differ between ruminants with or without listeriosis and does not overlap with the presence of microabscesses in the medulla. LM is observed in phagocytes, axons, Schwann cells, satellite cells and ganglionic neurones.

CONCLUSION

Our results support the view that the specific ligand-receptor interaction between LM and host E-cadherin is involved in the neuropathogenesis of ruminant listeriosis. They suggest that oral epithelium and Schwann cells expressing E-cadherin provide a port of entry for free bacteria offering a site of primary intracellular replication, from where the bacterium may invade the axonal compartment by cell-to-cell spread. As E-cadherin expression in the ruminant central nervous system is weak, only very locally restricted and not related to the presence of microabscesses, it is likely that further intracerebral spread is independent of E-cadherin and relies primarily on axonal spread.

Characterization of a novel type of adherens junction in meningiomas and the derived cell line HBL-52

Adhering junctions are generally grouped into desmosomes and adherens junctions based on their ultrastructural appearance and molecular composition. The armadillo-protein plakoglobin is common to both types of junctions, which are otherwise composed of mutually exclusive proteins. This view is based on observations in epithelial tissues but cannot easily be transferred to other cell types and tissues, as has become apparent during the last decade with the identification of new junctional proteins and the investigation of further non-epithelial junctions. Using a broad array of well-characterized specific antibodies against key junctional proteins in immunoblot reactions, high-resolution double-label laser scanning confocal microscopy, and immunoelectron microscopy, we describe a new type of adherens junction in human meningiomas and the human meningioma cell line HBL-52. This novel junction has a unique composition of proteins not found in any other tissue; it contains the desmosomal armadillo-protein plakophilin 2 together with the classic proteins of "epithelial" adherens junctions, i.e., E-cadherin (in some instances replaced by N-cadherin), alpha-catenin, beta-catenin, plakoglobin, and p120(ctn). Ultrastructurally, it is formed between two or three neighboring cells. For pragmatic reasons, we suggest the name "meningeal junction" for this new structure.

Characterization of arachnoidal cells cultured on three-dimensional nonwoven PET matrix

PURPOSE

To culture physiologically functional primary arachnoidal cells on a suitable polymer substrate for an in-vitro model of the cerebrospinal fluid outflow pathway.

METHODS

Primary cultures of arachnoidal cells were prepared within 24 hours post-mortem from brain tissue obtained from human cadavers at autopsy. Arachnoidal cells were characterized using immunocytochemistry and seeded onto needle punched non-woven poly(ethylene terephthalate)(PET) scaffolds. Metabolic rate, cell growth rate in log phase, morphologic assessment, immunocytochemistry, and protein analysis were used to characterize the cultures in both 2-D and 3-D-culture. Functional outflow assessment was performed using the Lucifer Yellow (LY) permeability assay and hydraulic conductivity (Lp) determination.

RESULTS

Cells cultured on PET scaffold grew slightly slower than cells grown in 2-D-culture as measured by metabolic rate and growth rate, however, they often formed sheets that bridged between the adjacent scaffold filaments forming many junctional protein connections. LY permeability coefficients of 2-D cells were compared with cells from scaffolds, and were not significantly different (p > 0.05) for both culture conditions. Average Lp of cells from 2-D-culture and 3-D-scaffolds were compared and shown not to be significantly different.

CONCLUSION

Based on the biochemical and functional analysis, it has been shown that cells cultured on 3D-PET scaffolds retained the same properties as cells from 2D-culture plates.

Altered expression of beta-catenin/E-cadherin in meningiomas

AIMS

Meningiomas are generally slow-growing benign tumours representing approximately 20% of all primary intracranial tumours. The hallmark of tumorigenesis of meningiomas is the loss of chromosome 22, including loss of heterozygosity of the neurofibromatosis type 2 (NF2) gene. The NF2 encoded protein merlin appears to function as a tumour suppressor gene by controlling cadherin-mediated cell-cell adhesion. The E-cadherin cell adhesion system includes beta-catenin that indirectly connects cadherin to actin filaments. The aim of this study was to analyse the expression and the subcellular location of E-cadherin and beta-catenin in human meningiomas, including meningiomas of different histomorphological subtypes and different World Health Organization (WHO) grades.

METHODS AND RESULTS

Immunohistochemical analysis revealed lack of E-cadherin expression at the cell membrane in 34% of meningiomas independent of their WHO grade. Loss of membranous beta-catenin occurred in 79% of meningiomas. An intense perinuclear granular immunoreactivity of beta-catenin without nuclear location was detected in the majority of meningiomas. Both immunofluorescence and Western blot analysis of fractionated meningioma cells located beta-catenin mostly on the Golgi apparatus and ER/Golgi intermediate compartment (ERGIC). Cytogenetic analysis of meningiomas showed no correlation between NF2 loss and the loss of the proper location of beta-catenin.

CONCLUSIONS

The lack of membranous beta-catenin and/or membranous E-cadherin in meningiomas may indicate an altered interaction between meningioma cells independent of loss of NF2 and independent of the tumour grade.

Membrane organization and tumorigenesis--the NF2 tumor suppressor, Merlin

The NF2 tumor-suppressor gene was cloned more than a decade ago, but the function of its encoded protein, Merlin, remains elusive. Merlin, like the closely related ERM proteins, appears to provide regulated linkage between membrane-associated proteins and the actin cytoskeleton and is therefore poised to function in receiving and interpreting signals from the extracellular milieu. Recent studies suggest that Merlin may coordinate the processes of growth-factor receptor signaling and cell adhesion. Varying use of this organizing activity by different types of cells could provide an explanation for the unique spectrum of tumors associated with NF2 deficiency in mammals.

Characterization of cytoskeletal and junctional proteins expressed by cells cultured from human arachnoid granulation tissue

BACKGROUND

The arachnoid granulations (AGs) are projections of the arachnoid membrane into the dural venous sinuses. They function, along with the extracranial lymphatics, to circulate the cerebrospinal fluid (CSF) to the systemic venous circulation. Disruption of normal CSF dynamics may result in increased intracranial pressures causing many problems including headaches and visual loss, as in idiopathic intracranial hypertension and hydrocephalus. To study the role of AGs in CSF egress, we have grown cells from human AG tissue in vitro and have characterized their expression of those cytoskeletal and junctional proteins that may function in the regulation of CSF outflow.

METHODS

Human AG tissue was obtained at autopsy, and explanted to cell culture dishes coated with fibronectin. Typically, cells migrated from the explanted tissue after 7-10 days in vitro. Second or third passage cells were seeded onto fibronectin-coated coverslips at confluent densities and grown to confluency for 7-10 days. Arachnoidal cells were tested using immunocytochemical methods for the expression of several common cytoskeletal and junctional proteins. Second and third passage cultures were also labeled with the common endothelial markers CD-31 or VE-cadherin (CD144) and their expression was quantified using flow cytometry analysis.

RESULTS

Confluent cultures of arachnoidal cells expressed the intermediate filament protein vimentin. Cytokeratin intermediate filaments were expressed variably in a subpopulation of cells. The cultures also expressed the junctional proteins connexin43, desmoplakin 1 and 2, E-cadherin, and zonula occludens-1. Flow cytometry analysis indicated that second and third passage cultures failed to express the endothelial cell markers CD31 or VE-cadherin in significant quantities, thereby showing that these cultures did not consist of endothelial cells from the venous sinus wall.

CONCLUSION

To our knowledge, this is the first report of the in vitro culture of arachnoidal cells grown from human AG tissue. We demonstrated that these cells in vitro continue to express some of the cytoskeletal and junctional proteins characterized previously in human AG tissue, such as proteins involved in the formation of gap junctions, desmosomes, epithelial specific adherens junctions, as well as tight junctions. These junctional proteins in particular may be important in allowing these arachnoidal cells to regulate CSF outflow.

Immunohistochemical and ultrastructural study of gap junction proteins connexin26 and 43 in human arachnoid villi and meningeal tumors

Human arachnoid villi and meningiomas are known to have gap junctions formed by connexin (Cx) proteins. We examined the expression and localization of Cxs in normal human arachnoid villi and meningeal tumors (meningiomas and hemangiopericytomas) by immunohistochemistry and Western blots. In arachnoid villi, strong immunopositivity for connexin26 (Cx26) and connexin43 (Cx43) was detected in the cap cell layer, cap cell cluster, and central core. They were weakly expressed in the fibrous capsule. In meningiomas they were strongly expressed in the meningotheliomatous area and weakly positive in the fibrous area. None of them were expressed in hemangiopericytomas. By immunoelectron microscopy, Cx26 and Cx43 were distributed on the cell membranes in arachnoid villi and meningiomas. In the Western blots in arachnoid villi and meningiomas, Cx26 and Cx43 were shown at bands with molecular weights of 26 kD and 42-47 kD, respectively. The degree of positivity for Cxs was different between subtypes of meningiomas. These findings suggest that expression of Cx26 and Cx43 might be related to the differentiation of the arachnoid villi and meningiomas, and exhibit the different origin of various subtypes of meningiomas. We proposed that Cx expression is one of the useful markers for the differentiation of meningioma and hemangiopericytoma.

On Arachnoid Villi and Meningiomas: Functional Implication of Ultrastructure, Cell Adhesion Mechanisms, and Extracellular Matrix Composition

Arachnoid villi or granulations are small projections of the arachnoid barrier layer into the venous sinus and its major tributaries. They are closely related to the absorption of cerebrospinal fluid, and are widely accepted to be the origin of human meningiomas. Arachnoid villi and meningiomas show a number of similarities in ultrastructure, cell adhesion mechanisms, and extracellular matrix composition. Ultrastructurally, both arachnoid and meningioma cells are characterized by interdigitations connected with junctional complexes, and extracellular cisterns related to the fluid transport. Extracellular cisterns and the intercellular space reveal abundant membrane-derived multilamellar phospholipids when a conventional ultrastructural fixative supplemented with tannic acid is used. Both arachnoid and meningioma cells are connected by Ca2+-dependent adhesion molecules: epithelial-cadherins which are concentrated at the adherens junctions. Membrane-cytoskeleton interactions by means of merlin and a-catenin molecules are thought to be crucial in signal transduction resulting in contact inhibition of cell growth in normal arachnoid cells. Impairment of these molecules might be related to meningioma-genesis. Glutathione-independent prostaglandin D2 synthase [EC 5.3.99.2] responsible for the biosynthesis of prostaglandin D2 in the central nervous system is also consistently expressed in human arachnoid villi and meningiomas. The multilamellar phospholipids are conceivably related to this arachidonate metabolism.

Ultrastructural localization of E-cadherin and alpha-/beta-catenin in adenoid cystic carcinoma

AIMS

To investigate the disturbance of intercellular adhesion in adenoid cystic carcinoma (ACC), we examined the ultrastructural localization of E-cadherin (E-cad), alpha-catenin (alpha-cat) and beta-catenin (beta-cat) in ACC, and compared it with that in the normal labial gland.

METHODS AND RESULTS

Using immuno-electron microscopy, in the normal labial gland, E-cad was found to be uniformly distributed along the plasmalemma, where cells were in close contact with each other, with junctional complexes, desmosomes and interdigitations; expression of alpha-cat and beta-cat was also detected. In ACC, which was classified into tubular, cribriform and trabecular types, E-cad expression seemed not to be uniform, but was observed to be along the plasmalemma where cell-to-cell contact was made. On the other hand, expression of alpha-cat or beta-cat was uneven in the trabecular-type cells which were very slender and grew in an infiltrative scattered pattern into the extracellular matrix; that was absent in the cribriform-type cells which made contact with each other mostly at the tip of the cytoplasmic processes.

CONCLUSION

These findings suggest that the neoplastic cells of ACC express E-cad for use in intercellular adhesion, but the cadherin-catenin complex might not operate properly, which is the cause of neoplastic cell dissociation, followed by invasion and metastasis.

Distribution of E-cadherin and Ep-CAM in the human lung during development and after injury

Paraffin sections were obtained of human fetal, adult, and pathological lung (pulmonary fibrosis after radiotherapy or chemotherapy). The localization of epithelial adhesion molecules E-cadherin and Ep-CAM (former epithelial surface 40 kDa glycoprotein) was investigated by immunoperoxidase and/or immunofluorescence techniques with monoclonal antibodies. During development, the epithelia of the primary pulmonary primordium, the secondary bronchi and the adult bronchial epithelium retained immunoreactivity for E-cadherin and Ep-CAM with lateral immunostaining of cell membranes. In normal adult lungs, Ep-CAM was detected in type I and II alveolar epithelial cells, whereas E-cadherin was confined to the basolateral domain of type II cells. In pulmonary fibrosis, Ep-CAM could be further detected on the cell surface of epithelial remnants. In contrast, E-cadherin expression was characterized by a change of the membrane localization to a spotty, cytoplasmic pattern in the alveolar epithelium, possibly indicating functional inactivation of the protein during fibrogenesis.