Three-dimensional visualization of the molecular architecture of cell-cell junctions in situ by cryo-electron tomography of vitreous sections

Cryo-electron tomography of vitreous sections is currently the only method for visualizing the eukaryotic ultrastructure at close to native state with molecular resolution. Here, we describe the detailed procedure of how to prepare suitable vitreous sections from mammalian skin for cryo-electron tomography, how to align the projection images of the tilt-series, and finally how to perform sub-tomogram averaging on macromolecular complexes with periodic arrangement such as desmosomes.

Regulation of signaling at regions of cell-cell contact by endoplasmic reticulum-bound protein-tyrosine phosphatase 1B

Protein-tyrosine phosphatase 1B (PTP1B) is a ubiquitously expressed PTP that is anchored to the endoplasmic reticulum (ER). PTP1B dephosphorylates activated receptor tyrosine kinases after endocytosis, as they transit past the ER. However, PTP1B also can access some plasma membrane (PM)-bound substrates at points of cell-cell contact. To explore how PTP1B interacts with such substrates, we utilized quantitative cellular imaging approaches and mathematical modeling of protein mobility. We find that the ER network comes in close proximity to the PM at apparently specialized regions of cell-cell contact, enabling PTP1B to engage substrate(s) at these sites. Studies using PTP1B mutants show that the ER anchor plays an important role in restricting its interactions with PM substrates mainly to regions of cell-cell contact. In addition, treatment with PTP1B inhibitor leads to increased tyrosine phosphorylation of EphA2, a PTP1B substrate, specifically at regions of cell-cell contact. Collectively, our results identify PM-proximal sub-regions of the ER as important sites of cellular signaling regulation by PTP1B.

Effects of aberrant Pax6 gene dosage on mouse corneal pathophysiology and corneal epithelial homeostasis

Background

Altered dosage of the transcription factor PAX6 causes multiple human eye pathophysiologies. PAX6^+/− heterozygotes suffer from aniridia and aniridia-related keratopathy (ARK), a corneal deterioration that probably involves a limbal epithelial stem cell (LESC) deficiency. Heterozygous Pax6^+/Sey-Neu (Pax6^+/−) mice recapitulate the human disease and are a good model of ARK. Corneal pathologies also occur in other mouse Pax6 mutants and in PAX77^Tg/− transgenics, which over-express Pax6 and model human PAX6 duplication.

Methodology/Principal Findings

We used electron microscopy to investigate ocular defects in Pax6^+/− heterozygotes (low Pax6 levels) and PAX77^Tg/− transgenics (high Pax6 levels). As well as the well-documented epithelial defects, aberrant Pax6 dosage had profound effects on the corneal stroma and endothelium in both genotypes, including cellular vacuolation, similar to that reported for human macular corneal dystrophy. We used mosaic expression of an X-linked LacZ transgene in X-inactivation mosaic female (XLacZ^Tg/−) mice to investigate corneal epithelial maintenance by LESC clones in Pax6^+/− and PAX77^Tg/− mosaic mice. PAX77^Tg/− mosaics, over-expressing Pax6, produced normal corneal epithelial radial striped patterns (despite other corneal defects), suggesting that centripetal cell movement was unaffected. Moderately disrupted patterns in Pax6^+/− mosaics were corrected by introducing the PAX77 transgene (in Pax6^+/−, PAX77^Tg/− mosaics). Pax6^Leca4/+, XLacZ^Tg/− mosaic mice (heterozygous for the Pax6^Leca4 missense mutation) showed more severely disrupted mosaic patterns. Corrected corneal epithelial stripe numbers (an indirect estimate of active LESC clone numbers) declined with age (between 15 and 30 weeks) in wild-type XLacZ^Tg/− mosaics. In contrast, corrected stripe numbers were already low at 15 weeks in Pax6^+/− and PAX77^Tg/− mosaic corneas, suggesting Pax6 under- and over-expression both affect LESC clones.

Conclusions/Significance

Pax6^+/− and PAX77^Tg/− genotypes have only relatively minor effects on LESC clone numbers but cause more severe corneal endothelial and stromal defects. This should prompt further investigations of the pathophysiology underlying human aniridia and ARK.

Cardiac autoantibodies from patients affected by a new variant of endemic pemphigus foliaceus in Colombia, South America

Several patients affected by a new variant of endemic pemphigus foliaceus in El Bagre, Colombia (El Bagre-EPF) have experienced a sudden death syndrome, including persons below the age of 50. El Bagre-EPF patients share several autoantigens with paraneoplastic pemphigus patients, such as reactivity to plakins. Further, paraneoplastic pemphigus patients have autoantibodies to the heart. Therefore, we tested 15 El Bagre-EPF patients and 15 controls from the endemic area for autoreactivity to heart tissue using direct and indirect immunofluorescence, confocal microscopy, immunohistochemistry, immunoblotting, and immunoelectron microscopy utilizing heart extracts as antigens. We found that 7 of 15 El Bagre patients exhibited a polyclonal immune response to several cell junctions of the heart, often colocalizing with known markers. These colocalizing markers included those for the area composita of the heart, such as anti-desmoplakins I and II; markers for gap junctions, such as connexin 43; markers for tight junctions, such as ezrin and junctional adhesion molecule A; and adherens junctions, such pan-cadherin. We also detected colocalization of the patient antibodies within blood vessels, Purkinje fibers, and cardiac sarcomeres. We conclude that El Bagre-EPF patients display autoreactivity to multiple cardiac epitopes, that this disease may resemble what is found in patients with rheumatic carditis, and further, that the cardiac pathophysiology of this disorder warrants further evaluation.

Scanning electron microscopic study of surface epithelial cells in erosive and nonerosive oral lichen planus

AIM

Aim of the study is to study the surface epithelial cells of erosive, nonerosive lichen planus by scanning electron microscope (SEM) and to correlate it with that of normal mucosa and oral leukoplakia.

MATERIALS AND METHODS

Twenty biopsies of lichen planus and five biopsies of normal mucosa were taken. Half piece of each biopsy was processed for H&E stain and another half for SEM study.

RESULT

Surface epithelial cells were showing different features.

CONCLUSION

Definite different features were seen in lichen planus-leukoplakia group than in normal oral mucosa. These changes are due to abnormality in cell maturation and differentiation.

CLINICAL SIGNIFICANCE

SEM study is helpful in early detection of dysplasia. It can lead to early treatment of the lesion and thus prevention of squamous cell carcinoma.

Forming a tough shell via an intracellular matrix and cellular junctions in the tail epidermis of Oikopleura dioica (Chordata: Tunicata: Appendicularia)

A postanal tail is a major synapomorphy of the phylum Chordata, which is composed of three subphyla: Vertebrata, Cephalochordata, and Tunicata (Urochordata). Among tunicates, appendicularians are the only group that retains the tail in the adult, and the adult tail functions in locomotion and feeding in combination with a cellulose-based house structure. Given the phylogenetic position of tunicates, the appendicularian adult tail may possess ancestral features of the chordate tail. We assess the ultrastructural development of the tail epidermis of the appendicularian Oikopleura dioica. The epidermis of the larval tail is enclosed by the larval envelope, which is a thin sheet similar to the outer tunic layer of ascidian larvae. The epidermis of the adult tail seems to bear no tunic-like cellulosic integuments, and the tail fin is a simple folding of the epidermis. Every epidermal cell, except for the triangular cells at the edge of the tail fin, has a conspicuous matrix layer of fibrous content in the apical cytoplasm without enclosing membranes. The epidermis of the larval tail does not have a fibrous matrix layer, suggesting the production of the layer during larval development and metamorphosis. Zonulae adhaerentes firmly bind the epidermal cells of the adult tail to one another, and the dense microfilaments lining the cell borders constitute a mechanical support for the cell membranes. The intracellular matrix, cell junctions, and cytoskeletons probably make the tail epidermis a tough, flexible shell supporting the active beating of the oikopleuran adult tail.

Uncoordinated transcription and compromised muscle function in the lmna-null mouse model of Emery- Emery-Dreyfuss muscular dystrophy

LMNA encodes both lamin A and C: major components of the nuclear lamina. Mutations in LMNA underlie a range of tissue-specific degenerative diseases, including those that affect skeletal muscle, such as autosomal-Emery-Dreifuss muscular dystrophy (A-EDMD) and limb girdle muscular dystrophy 1B. Here, we examine the morphology and transcriptional activity of myonuclei, the structure of the myotendinous junction and the muscle contraction dynamics in the lmna-null mouse model of A-EDMD. We found that there were fewer myonuclei in lmna-null mice, of which ∼50% had morphological abnormalities. Assaying transcriptional activity by examining acetylated histone H3 and PABPN1 levels indicated that there was a lack of coordinated transcription between myonuclei lacking lamin A/C. Myonuclei with abnormal morphology and transcriptional activity were distributed along the length of the myofibre, but accumulated at the myotendinous junction. Indeed, in addition to the presence of abnormal myonuclei, the structure of the myotendinous junction was perturbed, with disorganised sarcomeres and reduced interdigitation with the tendon, together with lipid and collagen deposition. Functionally, muscle contraction became severely affected within weeks of birth, with specific force generation dropping as low as ∼65% and ∼27% of control values in the extensor digitorum longus and soleus muscles respectively. These observations illustrate the importance of lamin A/C for correct myonuclear function, which likely acts synergistically with myotendinous junction disorganisation in the development of A-EDMD, and the consequential reduction in force generation and muscle wasting.

[Culture of human amniotic fluid stem cells in 3D collagen matrix]

Most of the researchers attribute amniotic fluid stem cells (AF SCs) to mesenchymal stem cells (MSCs). However, AF SCs express both mesenchymal and epithelial markers, which distinguishes them from postnatal MSCs. Cultivation in the three-dimensional matrix provides a different look at the nature of these cells. We showed that, in 3D collagen gel, AF SCs form epithelial structures (tubules and cysts). Active contraction of the gel during the first days of cultivation, which is characteristic if mesenchymal cells, does not occur. Electron microscopic study showed that typical to epithelial cell adherent junctions are formed between AF SCs. On the other hand, AF SCs continue to express MSCs markers during cultivation in the gel. Thus, AF SCs may not be true mesenchymal cells because they can display properties of epithelial cells. Perhaps these cells undergo epithelial-mesenchymal transition, the process which actively takes place during embryogenesis.

[Electron microscopic study of the intestinal epithelium of Saccoglossus mereschkowskii (Enteropneusta, Hemichordata)]

Epithelium of the hepatic region of the intestine in Saccoglossus mereschkowskii, a representative of enteropneusts (Enteropneusta, Hemichordata) standing at the base of Chordata, has been investigated using electron microscope. The ultrastructure of ciliated and granular epithelial cells, elements of the intraepithelial nerve layer, and intercellular junctions have been characterized. The data concerning details of the organization of the ciliary apparatus and rootlets system are presented. It is justified the presence of complicated supporting construction of cilia which performs a mechanical stabilizing function and possibly also provide synchronization of ciliary movements. The presence of cilia with two centrioles is considered as an adaptation to high functional load on ciliary apparatus. Well developed bundles of myofilaments are found in the cytoplasm of the basal portions of ciliary cells that characterizes these cells as myoepithelial. The features indicating the role of ciliary cells in absorption are described. The capability of these cells to balloon-like secretion is considered. Data on the accumulation of food reserves in the form of lipid droplets and glycogen in the cell cytoplasm are presented. Ciliated cells are characterized by their function as ciliated secretory-absorptive myoepithelial cells. Based on the location of secretory granules both in the apical and basal portions of granular cells, an exocrine-endocrine function of these cells has been suggested. Typical endocrine cells in the intestinal epithelium of S. mereschkowskii are absent. Several types of granules in the nerve fibers cytoplasm are described. Junctions between the nerve fibers and basal portions of ciliary and granular epithelial cells are found. Nerve regulation of contractile and secretory functions of epithelial cells is supposed. The presence of the regulatory nerve-endocrine system that includes receptor cells of open type, secretory endocrine-like cells and nerve elements of nerve layer is supposed in the intestinal epithelium of enteropneusts.

[Fusion of brain neurons in rat embryos]

Syncytial interneuronal connections were studied in the sensomotor cortex and caudate nucleus of twenty 14-22 day rat embryos. It was shown that with the extremely weak development of glial processes, many neuronal bodies and their processes were in the direct contact with each other. The contacting membranes in these areas formed oblong and dot-like contacts resembling gap and tight junctions. As a result, the intercellular cleft experienced varicose-like deformations. In the area of contacts, barely visible membrane pores were formed that broadened to form large perforations. The perforation margins presented the rounded shape of fused plasma membranes of adjacent neurons. Inside the perforations, residual vesicular membranous bodies were formed. The areas of the paired membranes between perforations were fragmented, thus increasing the number of residual vesicles, until the neurons fused with each other completely by unifying the neuroplasm of contacting cells. The results of these studies suggest that that the fusion of neurons in vertebrate brain cortex and brainstem nuclei could occur not only in pathology, but also in normal animals at the stage of embryonic development.

Electron tomography of paranodal septate-like junctions and the associated axonal and glial cytoskeletons in the central nervous system

The polarized domains of myelinated axons are specifically organized to maximize the efficiency of saltatory conduction. The paranodal region is directly adjacent to the node of Ranvier and contains specialized septate-like junctions that provide adhesion between axons and glial cells and that constitute a lateral diffusion barrier for nodal components. To complement and extend earlier studies on the peripheral nervous system, electron tomography was used to image paranodal regions from the central nervous system (CNS). Our three-dimensional reconstructions revealed short filamentous linkers running directly from the septate-like junctions to neurofilaments, microfilaments, and organelles within the axon. The intercellular spacing between axons and glia was measured to be 7.4 ± 0.6 nm, over twice the value previously reported in the literature (2.5-3.0 nm). Averaging of individual junctions revealed a bifurcated structure in the intercellular space that is consistent with a dimeric complex of cell adhesion molecules composing the septate-like junction. Taken together, these findings provide new insight into the structural organization of CNS paranodes and suggest that, in addition to providing axo-glial adhesion, cytoskeletal linkage to the septate-like junctions may be required to maintain axonal domains and to regulate organelle transport in myelinated axons.

Orthodontic mechanical tension effects on the myofibroblast expression of alpha-smooth muscle actin

OBJECTIVE

To detect myofibroblast formation on the tension side during orthodontic tooth movement in vivo and myofibroblast expression of alpha-smooth muscle actin (alpha-SMA) induced by tension both in vivo and in vitro.

MATERIALS AND METHODS

Fifty 6-week male rats were used in this in vivo study, and the right maxillary first molar was moved mesially, which served as the experimental group, and the left maxillary first molar served as the control. Rats were sacrificed at days 0, 3, 5, 7, and 14 after force loading. Myofibroblasts, identified with alpha-SMA, were examined through immunohistochemistry. For the in vitro study, human periodontal ligament (PDL) fibroblasts were obtained. Cyclic mechanical tension was applied to the fibroblasts for 0, 1, 3, 6, and 12 hours. Transmission electron microscopy was used to detect the ultrastructure of myofibroblasts. alpha-SMA mRNA gene expression was quantified by real-time quantitative PCR. The expression of alpha-SMA was detected by immunofluorescence and quantified by Western blotting.

RESULTS

In vivo, the myofibroblasts expressing alpha-SMA were identified both in the experimental group and in the control group. The expressions of alpha-SMA were increased in the tension areas of the experimental group over time, and reached the maximum in day 14. In vitro, fibronexus junctions and actin microfilaments in the cells could be found with transmission electron microscopy. Cyclic mechanical tension could significantly induce alpha-SMA expression at 12 hours (P < .01) than the controls.

CONCLUSIONS

Myofibroblasts existed in the PDL. The expressions of alpha-SMA in the myofibroblasts were significantly up regulated under tension both in vivo and in vitro.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation

In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation.

Lumen formation in salivary gland development

During salivary gland morphogenesis, the developing ducts and acini must hollow out to form lumina which will eventually allow the free passage and modification of saliva on its journey from acini to oral cavity. The molecular mechanisms that participate in the creation of this tubular structure are of great research interest. Histological studies show that lumen formation begins during the mid stages of branching morphogenesis. At this stage, apoptotic cells are detectable in the developing salivary ducts at sites where lumina are forming, suggesting that programmed cell death is instrumental in clearing the luminal space. The formation of cell-cell junctions between the epithelial cells lining the space is also an integral part of lumen formation, since these junctions form a barrier around the lumen and allow the surfaces of the lumen-lining cells to become specialized. This chapter will discuss the mechanisms involved in salivary gland lumen formation during development, and draw on the most recent research in this interesting field.

The junctions that don't fit the scheme: special symmetrical cell-cell junctions of their own kind

Immunocytochemical, electron-, and immunoelectron-microscopical studies have revealed that, in addition to the four major "textbook categories" of cell-cell junctions (gap junctions, tight junctions, adherens junctions, and desmosomes), a broad range of other junctions exists, such as the tiny puncta adhaerentia minima, the taproot junctions (manubria adhaerentia), the plakophilin-2-containing adherens junctions of mesenchymal or mesenchymally derived cell types including malignantly transformed cells, the composite junctions (areae compositae) of the mature mammalian myocardium, the cortex adhaerens of the eye lens, the interdesmosomal "sandwich" or "stud" junctions in the subapical layers of stratified epithelia and the tumors derived therefrom, and the complexus adhaerentes of the endothelial and virgultar cells of the lymph node sinus. On the basis of their sizes and shapes, other morphological criteria, and their specific molecular ensembles, these junctions and the genes that encode them cannot be subsumed under one of the major categories mentioned above but represent special structures in their own right, appear to serve special functions, and can give rise to specific pathological disorders.

Changes in hepatic cell junctions structure during experimental necrotizing enterocolitis: effect of EGF treatment

Necrotizing enterocolitis (NEC) is a devastating disease of premature babies. Previously, we have shown that EGF reduces NEC and that overproduction of hepatic TNF-alpha is associated with intestinal damage. Leakage of TNF-alpha may be a consequence of epithelial hepatic cellular junction dysfunction. The aim of this study was to investigate changes in the composition of hepatic tight junctions (TJs) and adherens junctions (AJs). Using an established rat model of NEC, animals were divided into the following groups: dam fed (DF), formula fed (NEC), or fed with formula supplemented with EGF (EGF). Serum EGF and histologic localization of major TJ and AJ proteins were evaluated. Distribution patterns of hepatic TJ and AJ proteins were significantly altered in the NEC group compared with those in DF or EGF groups. Cytoplasmic accumulation of occludin, claudin-2, and ZO-1 with reduction of claudin-3 signal was detected in the liver of NEC rats. Localization of beta-catenin was associated with the hepatocyte membrane in EGF and DF groups, but diffused in the NEC group. These data show that hepatic cellular junctions are significantly altered during NEC pathogenesis. EGF-mediated reduction of experimental NEC is associated with protection of hepatic integrity and structure.

Endothelial Cell-Cell Adhesion and Mechanosignal Transduction

Recent reports indicate that in addition to proteins that form various types of intercellular junctions, a considerable number of proteins are localized to the area of endothelial cell-cell association. Many of these are signaling proteins, suggesting that this is an area of active signaling. In this article, we have attempted to compile a list of proteins that have been localized to the area of interendothelial association and to briefly discuss what is known about each. Since various investigators including ourselves have proposed that the region of interendothelial cell association is an important site for mechanosignaling, we will focus our discussion on the possible role of these proteins in mechanosignal transduction. We will also review the available evidence for PECAM-1 as a mechanotransducing molecule in endothelial cells.

[Syncytial cytoplasmic anastomoses between the neurites of caudal mesenteric ganglion cells in adult cats]

Since the majority of the published data on syncytial cytoplasmic anastomoses relate to the autonomic nervous system in the early postnatal period of development, when many nerve fibers are still poorly covered by glia or have no glial sheaths at all, it was suggested that such anastomoses were not present in adults due to the significant development of glia separating individual neurites from each other. To check this assumption, we have performed an electron microscopic study of the adult cat dorsal caudal mesenteric ganglion. The cell neurites were found to be frequently covered by glial sheaths. However, almost in every sample, the syncytial pores were detected between the contacting neurites lacking glial covering layers. Sometimes serial syncytially connected neurites were seen. Axo-dendritic synapses with presynaptic perforations outside the synaptic specializations were described in the autonomic nervous system for the first time. These observations therefore provide evidence of syncytial cytoplasm connections in normal adult animals, however this does not reject the neuronal doctrine.

The gastric epithelial progenitor cell niche and differentiation of the zymogenic (chief) cell lineage

In the mammalian gastrointestinal tract, the cell fate decisions that specify the development of multiple, diverse lineages are governed in large part by interactions of stem and early lineage progenitor cells with their microenvironment, or niche. Here, we show that the gastric parietal cell (PC) is a key cellular component of the previously undescribed niche for the gastric epithelial neck cell, the progenitor of the digestive enzyme secreting zymogenic (chief) cell (ZC). Genetic ablation of PCs led to failed patterning of the entire zymogenic lineage: progenitors showed premature expression of differentiated cell markers, and fully differentiated ZCs failed to develop. We developed a separate mouse model in which PCs localized not only to the progenitor niche, but also ectopically to the gastric unit base, which is normally occupied by terminally differentiated ZCs. Surprisingly, these mislocalized PCs did not maintain adjacent zymogenic lineage cells in the progenitor state, demonstrating that PCs, though necessary, are not sufficient to define the progenitor niche. We induced this PC mislocalization by knocking out the cytoskeleton-regulating gene Cd2ap in Mist1(-/-) mice, which led to aberrant E-cadherin localization in ZCs, irregular ZC-ZC junctions, and disruption of the ZC monolayer by PCs. Thus, the characteristic histology of the gastric unit, with PCs in the middle and ZCs in the base, may depend on establishment of an ordered adherens junction network in ZCs as they migrate into the base.

Protective action of intravesical oxybutynin on bladder ultrastructure in rabbits with detrusor overactivity

To evaluate the protective effect of intravesical oxybutynin on the ultrastructure of rabbits with detrusor overactivity (DO). Seventeen North Folk male rabbits were distributed into three groups: GI (n = 5) used as control, GII (n = 5), and GIII (n = 5) with DO. One animal from GII and one from GIII were excluded because they did not develop DO. In GIII, the animals were treated with daily intravesical application of 0.5 mg/Kg of oxybutynin for 30 days. Bladder weight was significantly higher in animals from GII and GIII as compared to GI. After 30 days, cystometric study revealed that vesical capacity was significantly decreased in GII and GIII. Detrusor pressure was significantly higher in GII. Electron microscopy showed increase of intercellular space, cell junctions and caveolae areas asymmetries, mitochondria and cellular degeneration in GII, while in GIII, these alterations have improved after a 30-day treatment. Animals treated with intravesical oxybutynin presented ultrastructural aspect similar to normal.

Cell-cell contact: cooperating clusters of actin and cadherin

Cooperation between cadherins and actin critically influences tissue organization. A new report identifies distinct pools of actin filaments that influence the spatial distribution of cadherins at cell-cell contacts.

Effect of heat stress on expression of junction-associated molecules and upstream factors androgen receptor and Wilms' tumor 1 in monkey sertoli cells

Sertoli cells are important in determining the fate of spermatogenic cells by providing nutrition and structural support via cell junctions. In this study, we sought to examine the effect of 43 C warming on cell junctions in seminiferous epithelium and the expression of junction-associated molecules in Sertoli cells. Electron microscopy showed the appearance of large vacuoles between Sertoli and germ cells and adjacent Sertoli cells, leading to disruption of corresponding cell junctions 24 h after terminating the heat treatment. Using primary Sertoli cells isolated from pubertal monkey testes, we demonstrated that expression of adherens junction-associated molecules, such as N-cadherin and beta-catenin, and tight junction-associated molecule zonula occludens protein 1 was significantly reduced in 24-48 h after heat treatment. In contrast, intermediate filament vimentin expression was up-regulated in 6-48 h. Androgen receptor (AR) and Wilms' tumor gene 1 expression dramatically decreased after heat treatment. Both proteins completely disappeared immediately after terminating heat treatment and began to recover after 6 h. Treatment of the monkey Sertoli cells with an AR antagonist, flutamide, could mimic the heat-induced changes in the expression of junction-associated molecules in Sertoli cells. Furthermore, overexpression of AR in the Sertoli cells up-regulated the expression of N-cadherin, beta-catenin, and zonula occludens protein 1 and down-regulated vimentin expression. Their expression after heat treatment could be rescued by the AR overexpression. These results indicate that the decreased AR expression after heat treatment is involved in heat-induced cell junction disruption.

Characterization and comparison of intercellular adherent junctions expressed by human corneal endothelial cells in vivo and in vitro

PURPOSE

Human corneal endothelial cell (HCEC) proliferation is controlled by HCEC junctions, but the mechanism of proliferation remains unknown. The authors sought to characterize adherent junction components of in vivo HCECs and to compare their gene expression and their proliferative potential with those of in vitro counterparts.

METHODS

Stripped human Descemet membranes were digested with collagenase A, and the resultant HCEC aggregates were cultured for 7, 14, and 21 days in supplemented hormonal epithelial medium (SHEM). The growth of HCEC monolayers was monitored by BrdU labeling performed 24 hours before termination. In vivo and in vitro HCECs were subjected to immunostaining to FITC-phalloidin and antibodies to different junction components and BrdU. Their mRNA expressions were determined by RT-PCR.

RESULTS

In vivo HCECs expressed transcripts of N-, VE-, E-, and P-cadherins, alpha-, beta-, gamma-, and p120-catenins, and p190. In vitro HCEC counterparts also expressed all these mRNAs except P-cadherin. In vivo HCECs displayed continuous circular F-actin, N-cadherin, beta- and p120-catenins, and p190, discontinuous circular VE-cadherin bands at or close to cell junctions, and E-cadherin in the cytoplasm. Such an in vivo pattern was gradually achieved by in vitro HCECs at day 21 and was correlated with a progressive decline of BrdU labeling.

CONCLUSIONS

In vivo and in vitro HCECs displayed distinct protein cytolocalization of N-, VE-, and E-cadherins, beta- and p120-catenins, and p190. Progressive maturation of adherent junctions was associated with a decline of the proliferative potential. This information allows us to devise new strategies to engineer in vitro HCECs by targeting these components.