Versican modulates gap junction intercellular communication

The Role of Connexin Hemichannels in Inflammatory Diseases

The connexin protein family consists of approximately 20 members, and is well recognized as the structural unit of the gap junction channels that perforate the plasma membranes of coupled cells and, thereby, mediate intercellular communication. Gap junctions are assembled by two preexisting hemichannels on the membranes of apposing cells. Non-junctional connexin hemichannels (CxHC) provide a conduit between the cell interior and the extracellular milieu, and are believed to be in a protectively closed state under physiological conditions. The development and characterization of the peptide mimetics of the amino acid sequences of connexins have resulted in the development of a panel of blockers with a higher selectivity for CxHC, which have become important tools for defining the role of CxHC in various biological processes. It is increasingly clear that CxHC can be induced to open by pathogen-associated molecular patterns. The opening of CxHC facilitates the release of damage-associated molecular patterns, a class of endogenous molecules that are critical for the pathogenesis of inflammatory diseases. The blockade of CxHC leads to attenuated inflammation, reduced tissue injury and improved organ function in human and animal models of about thirty inflammatory diseases and disorders. These findings demonstrate that CxHC may contribute to the intensification of inflammation, and serve as a common target in the treatments of various inflammatory diseases. In this review, we provide an update on the progress in the understanding of CxHC, with a focus on the role of these channels in inflammatory diseases.

Stress-deprivation induces an up-regulation of versican and connexin-43 mRNA and protein synthesis and increased ADAMTS-1 production in tendon cells in situ

Purpose: The proper function of the tenocyte network depends on cell-matrix as well as intercellular communication that is mechanosensitive. Building on the concept that the etiopathogenic stimulus for tendon degeneration is the catabolic response of tendon cells to mechanobiologic under-stimulation, we studied the pericellular matrix rich in versican and its predominant proteolytic enzyme ADAMTS-1, as well as Connexin-43 (Cx43), a major gap junction forming protein in tendons, in stress-deprived rat tail tendon fascicles (RTTfs).Materials and Methods: RTTfs were stress-deprived for up to 7 days under tissue culture conditions. RT-qPCR was used to measure mRNA expression of versican, ADAMTS-1, and Cx43. Protein synthesis was determined using Western blotting and immunohistochemistry.Results: Stress-deprivation (SD) caused a statistically significant up-regulation of versican, ADAMTS-1, and Cx43 mRNA expression that was persistent over the 7-day test period. Western blot analysis and immunohistochemical assessment of protein synthesis revealed a marked increase of the respective proteins with SD. Inhibition of proteolytic enzyme activity with ilomastat prevented the increased versican degradation and Cx43 synthesis in 3 days stress-deprived tendons when compared with non-treated, stress-deprived tendons.Conclusion: In the absence of mechanobiological signaling the immediate pericellular matrix is modulated as tendon cells up-regulate their production of ADAMTS-1, and versican with subsequent proteoglycan degradation potentially leading to cell signaling cues increasing Cx43 gap junctional protein. The results also provide further support for the hypothesis that the cellular changes associated with tendinopathy are a result of decreased mechanobiological signaling and a loss of homeostatic cytoskeletal tension.

Collective invasion induced by an autocrine purinergic loop through connexin-43 hemichannels

Progression of epithelial cancers predominantly proceeds by collective invasion of cell groups with coordinated cell-cell junctions and multicellular cytoskeletal activity. Collectively invading breast cancer cells express the gap junction protein connexin-43 (Cx43), yet whether Cx43 regulates collective invasion remains unclear. We here show that Cx43 mediates gap-junctional coupling between collectively invading breast cancer cells and, via hemichannels, adenosine nucleotide/nucleoside release into the extracellular space. Using molecular interference and rescue strategies, we identify that Cx43 hemichannel function, but not intercellular communication, induces leader cell activity and collective migration through the engagement of the adenosine receptor 1 (ADORA1) and AKT signaling. Accordingly, pharmacological inhibition of ADORA1 or AKT signaling caused leader cell collapse and halted collective invasion. ADORA1 inhibition further reduced local invasion of orthotopic mammary tumors in vivo, and joint up-regulation of Cx43 and ADORA1 in breast cancer patients correlated with decreased relapse-free survival. This identifies autocrine purinergic signaling, through Cx43 hemichannels, as a critical pathway in leader cell function and collective invasion.

Versican and vascular endothelial growth factor expression levels in peritoneal metastases from colorectal cancer are associated with survival after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) can increase survival of colorectal cancer (CRC) patients with peritoneal metastases (PM). This treatment is associated with high morbidity and mortality rates. Therefore, improvement of patient selection is necessary. Assuming that the clinical phenotype is dictated by biological mechanisms, biomarkers could play a crucial role in this process. Since it is unknown whether and to what extent angiogenesis influences the course of disease in patients with PM, we investigated the expression of two angiogenesis-related markers and their relation to overall survival (OS) in CRC patients after CRS and HIPEC. Clinicopathological data and tissue samples were collected from 65 CRC patients with isolated metastases to the peritoneum that underwent CRS and HIPEC. Whole tissue specimens from PM were evaluated for versican (VCAN) expression, VEGF expression and microvessel density (MVD) by immunohistochemistry. The relation between these markers and OS was assessed using univariate and multivariate analysis. Associations between VEGF expression, VCAN expression, MVD and clinicopathological data were tested. High stromal VCAN expression was associated with high MVD (p = 0.001), better resection outcome (p = 0.003) and high T-stage (p = 0.027). High epithelial VCAN expression was associated with MVD (p = 0.007) and a more complete resection (p < 0.001). In multivariate analysis, simplified peritoneal cancer index (p = 0.001), VEGF expression levels (p = 0.012), age (p = 0.030), epithelial VCAN expression levels (p = 0.042) and lymph node status (p = 0.053) were associated with OS. Concluding, VCAN and VEGF were associated with survival in CRC patients with PM after CRS and HIPEC. Independent validation in a well-defined patient cohort is required to confirm the putative prognostic role of these candidate biomarkers.

Proteoglycans in liver cancer

Proteoglycans are a group of molecules that contain at least one glycosaminoglycan chain, such as a heparan, dermatan, chondroitin, or keratan sulfate, covalently attached to the protein core. These molecules are categorized based on their structure, localization, and function, and can be found in the extracellular matrix, on the cell surface, and in the cytoplasm. Cell-surface heparan sulfate proteoglycans, such as syndecans, are the primary type present in healthy liver tissue. However, deterioration of the liver results in overproduction of other proteoglycan types. The purpose of this article is to provide a current summary of the most relevant data implicating proteoglycans in the development and progression of human and experimental liver cancer. A review of our work and other studies in the literature indicate that deterioration of liver function is accompanied by an increase in the amount of chondroitin sulfate proteoglycans. The alteration of proteoglycan composition interferes with the physiologic function of the liver on several levels. This article details and discusses the roles of syndecan-1, glypicans, agrin, perlecan, collagen XVIII/endostatin, endocan, serglycin, decorin, biglycan, asporin, fibromodulin, lumican, and versican in liver function. Specifically, glypicans, agrin, and versican play significant roles in the development of liver cancer. Conversely, the presence of decorin could potentially provide protective effects.

Impact of laminitis on the canonical Wnt signaling pathway in basal epithelial cells of the equine digital laminae

The digital laminae is a two layer tissue that attaches the distal phalanx to the inner hoof wall, thus suspending the horse's axial skeleton in the hoof capsule. This tissue fails at the epidermal:dermal junction in laminitic horses, causing crippling disease. Basal epithelial cells line the laminar epidermal:dermal junction, undergo physiological change in laminitic horses, and lose versican gene expression. Versican gene expression is purportedly under control of the canonical Wnt signaling pathway and is a trigger for mesenchymal-to-epithelial transition; thus, its repression in laminar epithelial cells of laminitic horses may be associated with suppression of the canonical Wnt signaling pathway and loss of the epithelial cell phenotype. In support of the former contention, we show, using laminae from healthy horses and horses with carbohydrate overload-induced laminitis, quantitative real-time polymerase chain reaction, Western blotting after sodium dodecylsulfate polyacrylamide gel electrophoresis, and immunofluorescent tissue staining, that positive and negative regulatory components of the canonical Wnt signaling pathway are expressed in laminar basal epithelial cells of healthy horses. Furthermore, expression of positive regulators is suppressed and negative regulators elevated in laminae of laminitic compared to healthy horses. We also show that versican gene expression in the epithelial cells correlates positively with that of β-catenin and T-cell Factor 4, consistent with regulation by the canonical Wnt signaling pathway. In addition, gene and protein expression of β-catenin correlates positively with that of integrin β4 and both are strongly suppressed in laminar basal epithelial cells of laminitic horses, which remain E-cadherin⁺/vimentin⁻, excluding mesenchymal transition as contributing to loss of the adherens junction and hemidesmosome components. We propose that suppression of the canonical Wnt signaling pathway, and accompanying reduced expression of β catenin and integrin β4 in laminar basal epithelial cells reduces cell:cell and cell:basement membrane attachment, thus, destabilizing the laminar epidermal:dermal junction.

Effects of cleavage by a disintegrin and metalloproteinase with thrombospondin motifs-4 on gene expression and protein content of versican and aggrecan in the digital laminae of horses with starch gruel-induced laminitis

OBJECTIVE

To determine whether increased gene expression of a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4) in laminae of horses with starch gruel-induced laminitis was accompanied by increased enzyme activity and substrate degradation.

SAMPLE

Laminae from the forelimb hooves of 8 healthy horses and 17 horses with starch gruel-induced laminitis (6 at onset of fever, 6 at onset of Obel grade 1 lameness, and 5 at onset of Obel grade 3 lameness).

PROCEDURES

Gene expression was determined by use of cDNA and real-time quantitative PCR assay. Protein expression and processing were determined via SDS-PAGE and quantitative western blotting. Protein distribution and abundance were determined via quantitative immunofluorescent staining.

RESULTS

ADAMTS-4 gene expression was increased and that of versican decreased in laminitic laminae, compared with expression in healthy laminae. Catalytically active ADAMTS-4 also was increased in the tissue, as were ADAMTS-4-cleavage fragments of versican. Immunofluorescent analyses indicated that versican was depleted from the basal epithelia of laminae of horses at onset of Obel grade 3 lameness, compared with results for healthy laminae, and this was accompanied by regional separation of basal epithelial cells from the basement membrane. Aggrecan gene and protein expression were not significantly affected.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in gene and protein expression of ADAMTS-4 and versican in the basal epithelium of laminitic laminae indicated a fundamental change in the physiology of basal epithelial cells. This was accompanied by and may have caused detachment of these cells from the basement membrane.

RhoGDI2 suppresses lung metastasis in mice by reducing tumor versican expression and macrophage infiltration

Half of patients with muscle-invasive bladder cancer develop metastatic disease, and this is responsible for most of the deaths from this cancer. Low expression of RhoGTP dissociation inhibitor 2 (RhoGDI2; also known as ARHGDIB and Ly-GDI) is associated with metastatic disease in patients with muscle-invasive bladder cancer. Moreover, a reduction in metastasis is observed upon reexpression of RhoGDI2 in xenograft models of metastatic cancer. Here, we show that RhoGDI2 suppresses lung metastasis in mouse models by reducing the expression of isoforms V1 and V3 of the proteoglycan versican (VCAN; also known as chondroitin sulfate proteoglycan 2 [CSPG2]). In addition, we found that high versican levels portended poor prognosis in patients with bladder cancer. The functional importance of tumor expression of versican in promoting metastasis was established in in vitro and in vivo studies in mice that implicated a role for the chemokine CCL2 (also known as MCP1) and macrophages. Further analysis indicated that RhoGDI2 suppressed metastasis by altering inflammation in the tumor microenvironment. In summary, we demonstrate what we believe to be a new mechanism of metastasis suppression that works by reducing host responses that promote metastatic colonization of the lung. Therapeutic targeting of these interactions may provide a novel adjuvant strategy for delaying the appearance of clinical metastasis in patients.

Analysis of intercellular calcium signaling using microfluidic adjustable laminar flow for localized chemical stimulation

The propagation of intercellular calcium signals provides a mechanism to coordinate cell population activity, which is essential for regulating cell behavior and organ development. However, existing analytical methods are difficult to realize localized chemical stimulation of a single cell among a population of cells that are in close contact with one another for studying the propagation of calcium wave. In this work, a microfluidic method is presented for the analysis of contact-dependent propagation of intercellular calcium wave induced by extracellular ATP using multiple laminar flows. Adjacent cells were seeded ∼300 μm downstream the intersection of a Y-shaped microchannel with negative pressure pulses. Consequently, the lateral diffusion distance of the chemical at cell locations was limited to ∼26 μm with a total flow rate of 20 μL min(-1), which prevented the interference of diffusion-induced cellular responses. Localized stimulation of the target cell with ATP induced the propagation of intercellular calcium wave among the cell population. In addition, studies on the spread of intercellular calcium wave under octanol inhibition allowed us to characterize the gap junction mediated cell-cell communication. Thus, this novel device will provide a versatile platform for intercellular signal transduction studies and high throughput drug screening.

Extracellular matrix-glial abnormalities in the amygdala and entorhinal cortex of subjects diagnosed with schizophrenia

CONTEXT

Chondroitin sulfate proteoglycans (CSPGs), a main component of the brain extracellular matrix, regulate developmental and adult neural functions that are highly relevant to the pathogenesis of schizophrenia. Such functions, together with marked expression of CSPGs in astrocytes within the normal human amygdala and evidence of a disruption of astrocytic functions in this disease, point to involvement of CSPG-glial interactions in schizophrenia.

HYPOTHESIS

Chondroitin sulfate proteoglycan-related abnormalities involve glial cells and extracellular matrix pericellular aggregates (perineuronal nets) in the amygdala and entorhinal cortex of subjects with schizophrenia.

DESIGN

Postmortem case-control study.

SETTING

The Translational Neuroscience Laboratory at McLean Hospital, Harvard Medical School. Specimens were obtained from the Harvard Brain Tissue Resource Center at McLean Hospital.

PARTICIPANTS

Two separate cohorts of healthy control (n = 15; n = 10) and schizophrenic (n = 11; n = 10) subjects and a cohort of subjects with bipolar disorder (n = 11).

INTERVENTIONS

Quantitative, immunocytological, and histological postmortem investigations.

MAIN OUTCOME MEASURES

Numerical densities of CSPG-positive glial cells and perineuronal nets, glial fibrillary acidic protein-positive astrocytes, and total numbers of parvalbumin-positive neurons in the deep amygdala nuclei and entorhinal cortex.

RESULTS

In schizophrenia, massive increases in CSPG-positive glial cells were detected in the deep amygdala nuclei (419%-1162%) and entorhinal cortex (layer II; 480%-1560%). Perineuronal nets were reduced in the lateral nucleus of the amygdala and lateral entorhinal cortex (layer II). Numerical densities of glial fibrillary acidic protein-positive glial cells and total numbers of parvalbumin-positive neurons were unaltered. Changes in CSPG-positive elements were negligible in subjects with bipolar disorder.

CONCLUSIONS

Marked changes in functionally relevant molecules in schizophrenia point to a pivotal role for extracellular matrix-glial interactions in the pathogenesis of this disease. Disruption of these interactions, unsuspected thus far, may represent a unifying factor contributing to disturbances of neuronal migration, synaptic connectivity, and GABAergic, glutamatergic, and dopaminergic neurotransmission in schizophrenia. The lack of CSPG abnormalities in bipolar disorder points to a distinctive aspect of the pathophysiology of schizophrenia in key medial temporal lobe regions.

Hormone-regulated expression and distribution of versican in mouse uterine tissues

BACKGROUND

Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination.

METHODS

Uteri from mice in all phases of the estrous cycle, and animals subjected to ovariectomy and hormone replacement were collected for immunoperoxidase staining for versican, as well as PCR and quantitative Real Time PCR.

RESULTS

In diestrus and proestrus, VER was exclusively expressed in the endometrial stroma. In estrus and metaestrus, VER was present in both endometrial stroma and myometrium. In OVX mice, VER immunoreaction was abolished in all uterine tissues. VER expression was restored by E2, MPA and E2+MPA treatments. Real Time PCR analysis showed that VER expression increases considerably in the MPA-treated group. Analysis of mRNA identified isoforms V0, V1 and V3 in the mouse uterus.

CONCLUSION

These results show that the expression of versican in uterine tissues is modulated by ovarian steroid hormones, in a tissue-specific manner. VER is induced in the myometrium exclusively by E2, whereas MPA induces VER deposition only in the endometrial stroma.

A 3'-untranslated region (3'UTR) induces organ adhesion by regulating miR-199a* functions

Mature microRNAs (miRNAs) are single-stranded RNAs of 18–24 nucleotides that repress post-transcriptional gene expression. However, it is unknown whether the functions of mature miRNAs can be regulated. Here we report that expression of versican 3′UTR induces organ adhesion in transgenic mice by modulating miR-199a* activities. The study was initiated by the hypothesis that the non-coding 3′UTR plays a role in the regulation of miRNA function. Transgenic mice expressing a construct harboring the 3′UTR of versican exhibits the adhesion of organs. Computational analysis indicated that a large number of microRNAs could bind to this fragment potentially including miR-199a*. Expression of versican and fibronectin, two targets of miR-199a*, are up-regulated in transgenic mice, suggesting that the 3′UTR binds and modulates miR-199a* activities, freeing mRNAs of versican and fibronectin from being repressed by miR-199a*. Confirmation of the binding was performed by PCR using mature miR-199a* as a primer and the targeting was performed by luciferase assays. Enhanced adhesion by expression of the 3′UTR was confirmed by in vitro assays. Our results demonstrated that upon arrival in cytoplasm, miRNA activities can be modulated locally by the 3′UTR. Our assay may be developed as sophisticated approaches for studying the mutual regulation of miRNAs and mRNAs in vitro and in vivo. We anticipate that expression of the 3′UTR may be an approach in the development of gene therapy.

Versican in health and disease

Versican is a component of the extracellular matrix, which interacts with several matrix and cell surface molecules. Versican plays central roles in tissue morphogenesis and homeostasis and is implicated in the development of numerous diseases. The expression of versican by multiple cell types is differentially regulated in a temporal and spatial manner in physiological and pathological processes. It participates in various biological events such as tissue organization, cell proliferation, adhesion, migration, and angiogenesis. The physiology of versican and its role in the progression of diseases such as atherosclerosis, cancer, and central nervous system injury are discussed.

Hyaluronan-dependent pericellular matrix

Hyaluronan is a multifunctional glycosaminoglycan that forms the structural basis of the pericellular matrix. Hyaluronan is extruded directly through the plasma membrane by one of three hyaluronan synthases and anchored to the cell surface by the synthase or cell surface receptors such as CD44 or RHAMM. Aggregating proteoglycans and other hyaluronan-binding proteins, contribute to the material and biological properties of the matrix and regulate cell and tissue function. The pericellular matrix plays multiple complex roles in cell adhesion/de-adhesion, and cell shape changes associated with proliferation and locomotion. Time-lapse studies show that pericellular matrix formation facilitates cell detachment and mitotic cell rounding. Hyaluronan crosslinking occurs through various proteins, such as tenascin, TSG-6, inter-alpha-trypsin inhibitor, pentraxin and TSP-1. This creates higher order levels of structured hyaluronan that may regulate inflammation and other biological processes. Microvillous or filopodial membrane protrusions are created by active hyaluronan synthesis, and form the scaffold of hyaluronan coats in certain cells. The importance of the pericellular matrix in cellular mechanotransduction and the response to mechanical strain are also discussed.