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PubMed2001

Matrix metalloproteinases: they're not just for matrix anymore!

The matrix metalloproteinases (MMPs) have been viewed as bulldozers, destroying the extracellular matrix to permit normal remodeling and contribute to pathological tissue destruction and tumor cell invasion. More recently, the identification of specific matrix and non-matrix substrates for MMPs and the elucidation of the biological consequence of cleavage indicates that perhaps MMPs should be viewed more as pruning shears, playing sophisticated roles in modulating normal cellular behavior, cell-cell communication and tumor progression.

Animals↗
PubMed1983

Three-dimensional reconstruction of a rat stage V Sertoli cell: III. A study of specific cellular relationships.

Specific Sertoli--Sertoli and Sertoli--germ-cell contacts and/or junctions were investigated employing micrographs used to reconstruct serially a model of a rat stage V Sertoli cell. The Sertoli--Sertoli junctional contact areas occurred in a belt-like arrangement near the base of the Sertoli cell. This configuration is consistent with their proposed function as a sealing element limiting the passage of materials toward the tubular lumen. Sertoli ectoplasmic specializations also formed a continuous belt, or band, around the reconstructed cell at the junctional contact area. Eighteen Sertoli--Sertoli tubulobulbar complexes were found; some (12 in number) invaginated the reconstructed cell, while others (6) emanated from it. Of 37 round germ cells that were sectioned in their entirety and adjoined the reconstructed cell, 23 displayed desmosome-gap junctions with either the reconstructed cell or an adjoining cell. Since there were multiple junctions connecting some germ cells to Sertoli cells, the total number of junctions was much greater (35). Desmosome-gap junctions of the Sertoli cell were numerous connecting pachytene spermatocytes, less numerous connecting type B spermatogonia, and even less numerous connecting step 5 spermatids; and none was seen joining Sertoli cells with elongate spermatids. Most desmosome-gap junctions join germ cells to the body of the Sertoli cell at its basal aspect. Their numbers and position indicate that they play a role in the maintenance of the integrity of the seminiferous epithelium and may provide a route for cell-to-cell communication. Ectoplasmic specializations of the reconstructed cell were seen facing only 3 of 37 round germ cells, and 7 ectoplasmic specializations from adjoining Sertoli cells faced these germ cells, all of which were step 5 spermatids. That there were no ectoplasmic specializations facing pachytene cells indicates that ectoplasmic specializations are not acquired as these cells pass through Sertoli--Sertoli junctions, but are acquired later in spermatogenesis.

Animals↗
PubMed2006

Molecular characterization of pannexins in the lens.

PURPOSE: Cell communication in the lens is critical for the life-long homeostasis of this tissue. Abundant gap junctions and cell-cell fusions are reported to be indispensable to the metabolic requirements and optical properties of the highly interconnected syncytial lens tissue. The expression of the recently characterized Panx1 and Panx2 gap junction proteins in the lens is, therefore, rather intriguing. Co-expression of pannexins and abundant connexins in the lens suggests that the two gap junction protein families have distinct roles in cell communication. METHODS: Panx1 and Panx2 expression was studied by in situ hybridization and quantitative RT-PCR. We examined properties and tissue distribution of Panx1 isoforms by Western blot analysis. Immunohistochemistry was used to visualize lens regions that accumulate Panx1 to study intercellular localization and spatial relationship with lens connexin gap junctions. RESULTS: Panx1 and Panx2 expression peaked in lens epithelial cells prior to differentiation. We detected one ubiquitously expressed Panx1 isoform and two additional isoforms that were only detected in the lens and the retina. Our results indicated that the ubiquitous 58 kDa and the oligomeric 120 kDa isoforms were plasma membrane-bound, resistant to Triton X-100 treatment, and was likely associated with cholesterol-enriched membrane microdomains. Immunohistochemistry revealed Panx1-specific punctuate labeling in the plasma membrane, and intensive labeling of the organelles in the epithelial and immature fiber cells. In addition, we detected Panx1 immunoreactivity in blood endothelial cells of the tunica vasculosa lentis capillaries and in blood erythrocytes. CONCLUSIONS: Despite similarity in detergent solubility of pannexins and connexins, the lack of spatial co-localization in the lens membranes suggested a distinct, non-redundant to connexin function for these proteins in the membrane.

Animals↗
PubMed1988

Patterns of junctional communication during development of the early amphibian embryo.

Cell-cell communication through gap junctions was examined in Xenopus laevis embryos between the 16-cell and early blastula stages using Lucifer Yellow, Fluorescein, lead EDTA and dicyanoargentate as probes of junctional permeability. Injections were made into cells whose position was identified with respect to the primary cleavage axis and the grey crescent. FITC dextrans revealed cytoplasmic bridges between the injected cell and its sister only. In the animal pole at the 16-cell stage at the future dorsal side of the embryo, Lucifer Yellow was frequently and extensively transferred between cells through gap junctions. At the future ventral side gap junctional transfer of Lucifer Yellow was significantly less frequent and less extensive. The asymmetry of transfer between future dorsal and ventral sides of the animal pole was more marked at the 32-cell stage. In the vegetal pole also at the 32-cell stage, a dorsoventral difference in junctional permeability to Lucifer Yellow was observed. At the 64-cell stage the transfer of Lucifer Yellow was relatively frequent between cells lying in the same radial segment in the animal pole; transfer into cells outside each segment was infrequent, except at the grey crescent. At the 128-cell stage, Lucifer transfer between future dorsal or future ventral cells in the equatorial region was infrequent. A high incidence of transfer was restored at the future dorsal side at the 256-cell stage. At the 32-cell stage, fluorescein was infrequently transferred between animal pole cells although lead EDTA moved from cell to cell with high, comparable frequency in future dorsal and ventral regions. Dicyanoargentate always transferred extensively, both at the 32- and 64-cell stages. Treatment of embryos with methylamine raised intracellular pH by 0.15 units, increased the electrical conductance of the gap junction and produced a 10-fold increase in the frequency of Lucifer Yellow transfer through gap junctions in future ventral regions of the animal pole at the 32-cell stage.

Animals↗
PubMed1994

Effect of interactions between granulosa and thecal cells on meiotic arrest in bovine oocytes.

An in vitro culture system in which two types of cell from ovarian follicular walls were attached to opposite surfaces of a collagen membrane was developed. The effect of granulosa-theca cell communication on oocyte maturation was investigated using this culture system. Bovine cumulus-oocyte complexes were incubated with granulosa cells, with or without theca cells. The time course of germinal vesicle breakdown was assessed. When cultured with granulosa cells alone, oocytes showed 100% germinal vesicle breakdown after incubation for 6 h. However, when cultured with granulosa and theca cells, germinal vesicle breakdown was significantly delayed for up to 12 h. Breakdown was further delayed by 12 h when cumulus-oocyte complexes were incubated with FSH-treated granulosa and thecal cultures. FSH did not exert this inhibitory effect when in culture with granulosa cells alone. When cumulus-oocyte complexes were incubated with thecal cells alone, all oocytes underwent germinal vesicle breakdown within 6 h; the addition of FSH to the culture medium did not affect the time course of breakdown. It is concluded that a signal(s) from thecal cells augments the meiosis-arresting activity of granulosa cells and that FSH increases the meiosis-arresting activity of granulosa cells under the influence of thecal cells.

Animals↗
PubMed2006

Heterotypic cell interactions on a dually patterned surface.

It is worth investigating heterotypic cell-cell interactions by mimicking their in vivo structures and environment. In the present study, physiological cellular response and behavior of hepatocytes and endothelial cells were investigated by controlling their contact periphery in a new co-culture system. Rat primary hepatocytes and bovine endothelial cells were co-cultured on a dually patterned surface. Hepatic physiological functions such as albumin secretion and ammonium metabolism were enhanced by increasing heterotypic cell-cell interactions in a patterned co-culture. Furthermore, enhanced hepatic functions through heterotypic interactions are effective within a limited area apart from endothelial cells as evidenced by immunofluorescence staining of hepatic intracellular albumin, indicating that heterotypic interactions act in a paracrine manner. Thus, heterotypic cell communications that play indispensable roles in increasing hepatic physiological functions should be obtained with an increasing periphery of two-cell domains. These findings are important for the reconstruction of complex tissues such as liver and pancreas.

Animals↗
PubMed1989

[A study of intercellular communication of human transitional cell carcinoma cell lines].

Intercellular communication (IC) was investigated by a dye transfer method in 5 human bladder carcinoma cell lines, JTC-29, JTC-30, JTC-32, HUB-41 and T-24 which showed various histological anaplasia when transplanted into nude mice. IC was investigated as follows; 1) IC among cells of each bladder carcinoma cell lines, 2) IC between various combination of different cell lines and 3) IC between cells of bladder carcinoma cell lines and fibroblasts prepared from the human skin or prostate. High IC was observed among JTC-30 cells which showed a differentiated pattern when transplanted into nude mice. JTC-32 and HUB-41, of which transplanted tumors showed poorly differentiated patterns, demonstrated lower IC than JTC-30. Statistical significance was present only between JTC-30 and JTC-32 cells (p less than 0.05). T-24 which formed histologically anaplastic tumor in nude mice demonstrated markedly poor IC. Second, IC between two different cell lines was demonstrated only between JTC-30 and JTC-32. Third, fibroblast from the skin and prostate had high IC but showed apparent IC with none of bladder carcinoma cell lines. These findings indicate that ICs of bladder tumor cells vary with cell lines tested and appear to decrease with progress of malignant anaplasia. Furthermore, the fact that there is sometimes high IC and sometimes lack of IC between differentiated and undifferentiated tumor cells suggests a possible role of IC in prevention of malignant progression. The present study provides no evidence of IC between bladder tumor cells and fibroblasts, which in some reports have been suggested to be an important phenomenon in evaluating the metastatic capacity of cancer cells.

Animals↗
PubMed1982

Homologies between cell interaction molecular controlled by major histocompatibility complex- and Igh-V-linked genes that T cells use for communication. Tandem "adaptive" differentiation of producer and acceptor cells.

We have asked the question: how do partner cells in immunoregulatory interactions between T cell subsets acquire the ability to recognize and react appropriately with one another? In particular, we have asked whether these communication events are completely determined by the cell's genetic constitution, or whether the recognition events can be learned during ontogeny. We have found that the T cells of parent into F1 chimeras and homozygous nude mice with F1 thymus grafts not only learn to react with genetically disparate acceptor cells, but that the receptors on the acceptor cells themselves learn to react with genetically disparate producer cells. This learning process can overcome both major histocompatibility complex- and immunoglobulin heavy chain variable region-linked restricted communication between T cell subsets. We interpret these findings to indicate that thymic elements can start a cascade of differential events. The thymic elements, whether endogenous or passively acquired, select from a pool of producer cells those that will react appropriately with the thymic selecting cells, and these cells become expanded. Then, the private markers (idiotype) on the expanded pool of producer cells act as selecting and expanding elements that choose from a pool of acceptor cells those that recognize the producer cells idiotype as self. This second differentiational event, although apparently thymus evidence that this type of acceptor cell differentiation could also take place during the course of an immune response.

Animals↗
PubMedDate not supplied

Intercellular electrical coupling in vascular cells present in rat intact cerebral arterioles.

Using arterioles dissected from rat cerebral pial membrane, we investigated cell-to-cell communication by means of the amphotericin-B-perforated whole-cell patch clamp technique. During a brief voltage step or ramp in voltage clamp mode, the leak current through the membrane of a smooth muscle cell in situ in an arteriole was attenuated by different types of gap junction inhibitors. Macroscopic current recording via two electrodes attached to adjacent smooth muscle cells or to a smooth muscle cell and a nearby endothelial cell revealed transjunctional current flow between cells of the same or different types. The pseudo-junctional conductance-voltage relationship obtained from adjacent smooth muscle cells differed from that obtained from a smooth muscle cell and an endothelial cell (symmetrical for the former and asymmetrical for the latter). Single- or multiple-channel events could be recorded from weakly coupled cells of the two types: simultaneous, equal-sized events in opposite directions were recorded via two electrodes, demonstrating electrical coupling directly between cell pairs. The single-channel conductance observed most frequently varied: 200-230 pS for pairs of two smooth muscle cells and 240-260 pS for mixed pairs. These data suggest the existence of differential patterns of electrical communication in vascular cells present in rat intact cerebral arterioles.

Amphotericin B↗
PubMed1989

Gap junctional communication and development.

Embryonic development requires extensive interaction between cells; cell-to-cell communication through gap junctions may be one mechanism involved. Much correlative evidence suggests gap junctions are involved in cellular interactions during development. Recently, the biological role of junctions has been investigated using antibodies prepared against the major rat liver gap junction protein. Disrupting normal patterns of intercellular communication with such antibodies can drastically perturb development. Recent experiments emphasize, in particular, the importance of gap junctional communication for patterning processes.

Animals↗
PubMed1999

Genes, gene knockouts, and mutations in the analysis of gap junctions.

Gop junctions are cell junctions found between most cells and tissues. They contain membrane channels that mediate the cell-to-cell diffusion of ions, metabolites, and small cell signaling molecules. Cell-cell communication mediated by gap junctions has been proposed to have a variety of functions, including roles in regulating events in development, cell differentiation, and cell growth and proliferation. The analysis of these possibilities has been confounded by the fact that there are over a dozen connexin genes encoding polypeptides that make up vertebrate gap junctions. This complexity, coupled with the fact that most cells express multiple connexin isotypes, likely explains why recent studies using reverse genetic and genetic approaches to disrupt connexin gene function have yielded only limited insights into the physiological roles of gap junctions. Nevertheless, studies in vivo and in vitro together have provided evidence for gap junctions being involved in the regulation of cell metabolism, growth, and differentiation in restricted cell and tissue types. Surprisingly, studies in invertebrates suggest that their gap junctions are encoded not by connexins, but by a family of proteins referred to as innexins. Analysis of various Drosophila and C. elegans mutants suggest that innexins may be functional homologs to the connexins. However, whether innexins are the elusive invertebrate gap junction proteins or, rather, accessory proteins that facilitate gap junction formation remains an open question. Given the rapid progress being made in the cloning and functional analysis of gap junctions in many diverse species, confusion and difficulties with nomenclature are coming to a head in this rapidly expanding field. It may be timely to form a Nomenclature Committee to establish a uniform classification scheme for naming gap junction proteins.

Animals↗
PubMed2005

Coordinated movement of bile canalicular networks reconstructed by rat small hepatocytes.

Hepatocytes in vivo have a potential for liver regeneration, but it has been very difficult to reconstruct hepatic organoids in vitro. Recent studies have shown that small hepatocytes (SHs) can reconstruct hepatic organoids including functional bile canaliculi (BC). In the present study we analyzed the movement of BC formed in the hepatic organoids, focusing on the coordination of contraction and dilation among cells and the mechanism producing the coordination. Hepatic cells, including SHs, were isolated from an adult rat liver and cultured. Time-lapse images of BC movements were taken and analyzed in cells treated with or without cytochalasin B (CB). Time-lapse images revealed that all BC, regardless of region contracted in a coordinated manner. Actin filaments were observed along the BC even after the BC networks treated with CB dilated markedly. Microinjection of dye was also carried out to investigate the flow thorough BC. Secreted fluorescein from the injected cell flowed along BC, and gap junctional protein connexin 32 was expressed along BC networks, suggesting cell-to-cell communication. Thus, groups of hepatocytes in the hepatic organoids act in a coordinated manner through intercellular communication.

Animals↗
PubMed1997

Ammonia mediates communication between yeast colonies.

Under certain growth conditions unicellular organisms behave as highly organized multicellular structures. For example, the fruiting bodies of myxobacteria and of the slime mould Dictyostelium discoideum form structures composed of non-dividing motile cells. Although non-motile, yeasts can create organized structures, colonies in which cells communicate and act in a coordinated fashion. Colony morphologies are characteristic for different species and strains. Here we describe that, in addition to short-range intracolony cell-cell communication, yeasts exhibit long-distance signals between neighbouring colonies. The volatile alkaline compound ammonia, transmitted by yeast colonies in pulses, has been identified as a substance mediating the intercolony signal. The first alkaline pulse produced by neighbouring colonies is non-directed and is followed by acidification of the medium. The second pulse seems to be enhanced and is oriented towards the neighbour colony. Ammonia signalling results in growth inhibition of the facing parts of both colonies. This phenomenon is observed in different yeast genera. The presence of amino acids in the medium is required for ammonia production. Colonies derived from the yeast Saccharomyces cerevisiae shr3 mutant, defective in localization of amino-acid permeases, do not produce detectable amounts of ammonia and do not exhibit asymmetric growth inhibition.

Amino Acids↗
PubMed2001

VEGF transiently disrupts gap junctional communication in endothelial cells.

Vascular endothelial growth factor, VEGF, stimulates angiogenesis by directly acting on endothelial cells. The effects of VEGF are mediated by two tyrosine kinase receptors, VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR) that are highly related to receptors of the platelet derived growth factor (PDGF) receptor family. We are interested in early signalling events downstream from VEGF receptors that affect blood vessel homeostasis. Endothelial cells form multiple types of cell-cell junctions that are required for cellular organization into complex networks. These junctions also regulate communication among adjacent cells. Stimulation by various growth factors such as epidermal growth factor (EGF) or PDGF has been shown to disrupt cell-cell junctions, consequently affecting cell-to-cell communication. We investigated gap junctional communication (GJC) by monitoring the transfer of a low molecular mass fluorescent tracer molecule between adjacent cells using immunofluorescence microscopy. VEGF maximally blocked GJC 15 minutes after growth factor administration. The cells resumed communication via gap junctions within 1-2 hours after treatment. This early effect of VEGF on communication correlated with changes in the phosphorylation state of one of the proteins involved in gap junction formation, connexin 43 (Cx43). The signalling mechanisms involved in this phenomenon depend on activation of VEGFR-2, impinge on a tyrosine kinase of the Src family and activate the Erk family of MAP kinases. The function of VEGF-mediated disruption of GJC might be to restrict an increase in endothelium permeability to the environment affected by local injury to blood vessels.

CSK Tyrosine-Protein Kinase↗
PubMed2006

Reversal of the TPA-induced inhibition of gap junctional intercellular communication by Chaga mushroom (Inonotus obliquus) extracts: effects on MAP kinases.

Chaga mushroom (Inonotus obliquus) has continued to receive attention as a folk medicine with indications for the treatment of cancers and digestive diseases. The anticarcinogenic effect of Chaga mushroom extract was investigated using a model system of gap junctional intercellular communication (GJIC) in WB-F344 normal rat liver epithelial cells. The cells were pre-incubated with Chaga mushroom extracts (5, 10, 20 microg/ml) for 24 h and this was followed by co-treatment with Chaga mushroom extracts and TPA (12-O-tetradecanoylphorbol-13-acetate, 10 ng/ml) for 1 h. The inhibition of GJIC by TPA (12-O-tetradecanoylphorbol-13-acetate), promoter of cancer, was prevented with treatment of Chaga mushroom extracts. Similarly, the increased phosphorylated ERK1/2 and p38 protein kinases were markedly reduced in Chaga mushroom extracts-treated cells. There was no change in the JNK kinase protein level, suggesting that Chaga mushroom extracts could only block the activation of ERK1/2 and p38 MAP kinase. The Chaga mushroom extracts further prevented the inhibition of GJIC through the blocking of Cx43 phosphorylation. Indeed cell-to-cell communication through gap junctional channels is a critical factor in the life and death balance of cells because GJIC has an important function in maintaining tissue homeostasis through the regulation of cell growth, differentiation, apoptosis and adaptive functions of differentiated cells. Thus Chaga mushroom may act as a natural anticancer product by preventing the inhibition of GJIC through the inactivation of ERK1/2 and p38 MAP kinase.

Agaricales↗
PubMed1986

Importance of critical metabolites and cellular interactions in the biology of microregions of tumors.

Heterogeneity of cellular microenvironments and associated differences in phenotypic expression of cells in solid tumors occur as a consequence of deficiencies of vascularization. Intervascular microregions of tumors and micrometastases can be modeled by multicellular spheroids in vitro. These develop concentration gradients of critical metabolites such as oxygen, glucose, and probably also other important nutrients, hormones, and growth factors. Drug penetration may also be reduced. Concentrations of these factors decrease from the periphery towards the center, but gradients develop in the opposite direction for certain metabolic and necrotic products such as lactate and pH. Such gradients significantly modify the proliferative status of the cells, viability, clonogenicity, cell cycle distribution, antigen expression, and differentiation. Stress of oxygen and glucose deprivation induces synthesis of a specific set of proteins. Cellular interactions can also modulate phenotypic expression, including oxygen and glucose consumption rates and sensitivity to radiation and drugs. The mechanisms of these are unknown, but changes in cell-cell communication and DNA damage and repair have been demonstrated in spheroids. Microenvironmental and cellular changes may be transient. Thus, the characteristics of cells in tumor microregions may be quite different from the intrinsic cellular properties observed after growth of cells in standard culture systems. These changes may have significant effects on responses to therapeutic agents.

Adenocarcinoma↗
PubMed1983

Alteration of calcium transport by tumor promoters, 12-O-tetradecanoyl phorbol-13-acetate and p,p'-dichlorodiphenyltrichloroethane, in the Chinese hamster V79 fibroblast cell line.

Effects of two tumor promoters, 12-O-tetradecanoyl phorbol-13-acetate (TPA) and p,p'-dichlorodiphenyltrichloroethane (DDT), on cellular calcium regulatory mechanisms were studied by using the Chinese hamster V79 fibroblast cell line. Both compounds at concentrations known to inhibit cell-cell communication, increased the cellular 45Ca2+ uptake and inhibited its efflux. DDT inhibited Ca,Mg-ATPase of the plasma membrane, while TPA stimulated cellular uptake of Ca2+. A working hypothesis has been proposed that the increase in intracellular concentration of Ca2+ by the action of these chemicals directly results in the closure of the central opening of the gap junction, and thereby causing a cessation of gap junction-mediated intercellular communication.

Animals↗
PubMed2000

In ovo time-lapse analysis of chick hindbrain neural crest cell migration shows cell interactions during migration to the branchial arches.

Hindbrain neural crest cells were labeled with DiI and followed in ovo using a new approach for long-term time-lapse confocal microscopy. In ovo imaging allowed us to visualize neural crest cell migration 2-3 times longer than in whole embryo explant cultures, providing a more complete picture of the dynamics of cell migration from emergence at the dorsal midline to entry into the branchial arches. There were aspects of the in ovo neural crest cell migration patterning which were new and different. Surprisingly, there was contact between neural crest cell migration streams bound for different branchial arches. This cell-cell contact occurred in the region lateral to the otic vesicle, where neural crest cells within the distinct streams diverted from their migration pathways into the branchial arches and instead migrated around the otic vesicle to establish a contact between streams. Some individual neural crest cells did appear to cross between the streams, but there was no widespread mixing. Analysis of individual cell trajectories showed that neural crest cells emerge from all rhombomeres (r) and sort into distinct exiting streams adjacent to the even-numbered rhombomeres. Neural crest cell migration behaviors resembled the wide diversity seen in whole embryo chick explants, including chain-like cell arrangements; however, average in ovo cell speeds are as much as 70% faster. To test to what extent neural crest cells from adjoining rhombomeres mix along migration routes and within the branchial arches, separate groups of premigratory neural crest cells were labeled with DiI or DiD. Results showed that r6 and r7 neural crest cells migrated to the same spatial location within the fourth branchial arch. The diversity of migration behaviors suggests that no single mechanism guides in ovo hindbrain neural crest cell migration into the branchial arches. The cell-cell contact between migration streams and the co-localization of neural crest cells from adjoining rhombomeres within a single branchial arch support the notion that the pattern of hindbrain neural crest cell migration emerges dynamically with cell-cell communication playing an important guidance role.

Animals↗