Regulation of fibronectin alternative splicing by a basement membrane-like extracellular matrix (original) (raw)
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Novel insights into the function and dynamics of extracellular matrix in liver fibrosis
American Journal of Physiology - Gastrointestinal and Liver Physiology, 2015
Key Points Box 31 32 1. The ECM is key in controlling cell fate and function. 33 2. The ECM composition and turnover in diseased tissues is different from that of 34 healthy tissue. 35 3. The ECM proteins may be modified enzymatically to gain signalling functions not 36 present in the intact native proteins, profoundly affecting cell fate and function. 37 4. There are highly specific interactions between cells and the ECM through e.g. 38 integrins that result in specific ECM-cell signalling, controlling cell fate and 39 functions. 40 41 3 3 5. ABSTRACT 42 Emerging evidence suggests that altered components and post-translational 43 modifications of proteins in the extracellular matrix (ECM) may both initiate and drive 44 disease progression. The ECM is a complex grid consisting of multiple proteins most of which 45 plays a vital role in containing the essential information needed for maintenance of a 46 sophisticated structure anchoring the cells and sustaining normal function of tissues. 47 upon treatment of the major underlying cause. Examples are effective anti-viral therapy for 87 chronic hepatitis B (22, 208) or the eradication of chronic hepatitis C with interferon alpha 88 based and interferon free regimens (94, 263, 264). The major future challenge in hepatology 89
Virchows Archiv. B, Cell pathology including molecular pathology, 1985
The behaviour of extracellular matrix glycoproteins (fibronectin, laminin, basement membrane heparan-sulphate proteoglycan, type III, IV and V collagens) has been investigated in a sequential model of experimental hepatic fibrosis, using an immunofluorescence technique. The presence of some basement membrane macromolecules (such as type IV and V collagens, laminin and basement membrane heparan-sulphate proteoglycan) is detectable only in the early stages of septa formation, while type III collagen and fibronectin persist in late septa. These data suggest that hepatic fibroplasia proceeds through different steps in which stromal glycoproteins are preferentially engaged, as happens during organogenesis.
A Major Fraction of Fibronectin Present in the Extracellular Matrix of Tissues Is Plasma-derived
Journal of Biological Chemistry, 2007
The origin of the fibronectin (FN) found in the extracellular matrix of tissues has not been defined experimentally. Previous studies suggest that there is contribution from both local tissue production and transfer from plasma, but the extent of this phenomenon has not been addressed. We have shown before that engineered mice constitutively expressing extra domain A-containing FN (EDA ؉ FN) have a significant decrease of FN levels in plasma and most tissues. We showed that hepatocytes modified to produce EDA ؉ FN have normal extracellular matrix-FN levels but secrete less soluble FN. When we performed a liver-specific EDA-exon deletion in these animals, FN levels were restored both in plasma and tissues. Therefore, an important fraction of tissue FN, approximately an equal amount of that produced by the tissue itself, is actually plasma-derived, suggesting that plasma is an important source of tissue FN. The present results have potential significance for understanding the contributions of plasma FN, and perhaps other plasma proteins, in the modulation of cellular activities and in the formation of the extracellular matrix of tissues.
Journal of Hepatology, 2000
Background/Aims: The extracellular matrix regulates hepatic development and regeneration, modulating the maintenance of liver architecture in the differentiated state. The aim of this work was to analyze how different extracellular matrix molecules modulate fetal hepatocyte morphology, growth and differentiation. Met/'&s: We cultured fetal hepatocytes either on plastic or on different extracellular matrix proteins, i.e., collagen I, fibronectin or E-C-L (entactin-collagen IV-laminin) and we analyzed cell attachment, morphological organization, proliferative response and gene expression. Results: Cell attachment was increased by all the extracellular matrix proteins to a similar extent. However, only fibronectin facilitated the formation of elongated cord-like structures, reminiscent of liver plate organization. Immnnocytochemical analysis of the cells in these structures revealed high levels of albumin and cytokeratin 18, phenotypical markers of parenchymal hepatocytes. Fibronectin did not block the mitogenic stimuli induced by epidermal growth factor in these cells and the elongated structures ap peared either in the absence or in the presence of the mitogen. Cells cultured on fibronectin, regardless of whether epidermal growth factor was present or not, also presented the maximal levels of expression for liver specific genes, such as albumin or alpha-fetoprotein. This expression was coincident with an increased expression of hepatocyte nuclear factor (HNF)-4 and a higher HNF-MHNF-l/3 ratio, when compared with those cells that were cultured on collagen or E-C-L extracellular matrix. Conclusions: These results suggest that fibronectin might play a differential role, as compared to other extracellular matrix proteins, in fetal hepatocyte organization and gene expression.
Activation of Proα2(I) Collagen Promoter during Hepatic Fibrogenesis in Transgenic Mice
Biochemical and Biophysical Research Communications, 1998
We previously identified the promoter sequence that is essential for basal and TGF--stimulated transcription of ␣2(I) collagen gene (COL1A2). In the present study, we examined whether the promoter is activated during hepatic fibrogenesis by utilizing transgenic mice harboring the COL1A2 upstream sequence. Intraperitoneal CCl4 administration activated the ؊17 kb COL1A2 promoter more than 10-fold, whereas partial hepatectomy resulted in no significant change in the promoter activity. The non-parenchymal cell fraction, but not parenchymal hepatocytes, isolated from mice harboring the ؊313 COL1A2 promoter linked to a -galactosidase reporter gene contained large amounts of -galactosidase and endogenous COL1A2 mRNAs. -galactosidase activity in the cells from CCl4-treated mice was significantly higher than in those from untreated animals. These results indicated that different molecular mechanisms control COL1A2 transcription in CCl4-induced liver injury/fibrosis and physiological regeneration after partial hepatectomy, and that the ؊313 COL1A2 promoter is activated in a cell type-specific manner during hepatic fibrogenesis.
Collagen VI is a basement membrane component that regulates epithelial cell–fibronectin interactions
Matrix Biology, 2011
Collagen VI is a heterotrimer composed of three α chains (α1, α2, α3) widely expressed throughout various interstitial matrices. Collagen VI is also found near the basement membranes of many tissues where it serves as an anchoring meshwork. The aim of this study was to investigate the distribution and role of collagen VI at the epithelial-stromal interface in the intestine. Results showed that collagen VI is a bona fide epithelial basal lamina component and constitutes the major collagen type of epithelial origin in this organ. In vitro, collagen VI co-distributes with fibronectin. Targeted knockdown of collagen VI expression in intestinal epithelial cells was used to investigate its function. Depletion of collagen VI from the matrix led to a significant increase in cell spreading and fibrillar adhesion formation coinciding with an upregulation of fibronectin expression, deposition and organization as well as activation of myosin light chain phosphorylation by the myosin light chain kinase and Rho kinase dependent mechanisms. Plating cells deficient for collagen VI on collagen VI rescued the phenotype. Taken together, these data demonstrate that collagen VI is an important basal lamina component involved in the regulation of epithelial cell behavior most notably as a regulator of epithelial cellfibronectin interactions.
Scientific reports, 2017
Liver fibrosis is characterized by the progressive accumulation of extracellular matrix (ECM) and is a strong predictor of hepatocellular carcinoma (HCC) development and progression. However, the effect of ECM in fibrotic livers on HCC cells is poorly understood. The aims of this study were to create a new culture system that retained the natural ECM of fibrotic model livers and to establish whether natural ECM regulated the characteristics of HCC cells. Using an organ decellularization technique, we created a new culture system that preserved the tissue-specific ECM of fibrotic model livers from CCl-treated rats. The content of ECM in fibrotic model liver scaffolds was increased and the ECM microstructure was distorted. Quantitative polymerase chain reaction and immunofluorescence assays of HCC cells cultured in fibrotic model liver scaffolds for 7 days showed an epithelial-mesenchymal transition phenotype. Moreover, the ECM of fibrotic model livers promoted proliferation and chemo...
Previously, we demonstrated that primary cultures of rat hepatocytes evidence higher levels of differentiated function when cultured in the presence of a dilute overlay of extracellular matrix (Matrigel). In this investigation, we used DNA microarrays, quantitative RT-PCR, immunoblotting, and cell morphology analyses to evaluate the biological responses imparted by Matrigel overlays on primary cultures of human hepatocytes from five independent donors. Although interindividual variability in responses was evident, our results demonstrated that Matrigel additions typically improved hepatocyte morphology and differentiation character. Results from RNA-profiling experiments indicated that Matrigel additions enhanced hepatocyte RNA expression levels associated with a battery of differentiated features, to levels comparable to those seen in vivo, for genes such as the cytochrome P450s, solute carrier family members, sulfotransferases, certain nuclear transcription factors, and other liver-specific markers, such as albumin, transferrin, and response to the inducer, phenobarbital. In contrast, Matrigel additions were generally associated with reduced RNA expression levels for several cytokeratins, integrins, and a number of stress-related pathways. Decreases in integrin protein expression were similarly detected, although enhanced levels of the gap junction-associated protein, connexin 32, were detected in Matrigel-treated cultures. These data support the concept that ECM functions mechanistically to augment the differentiation character of primary human hepatocytes in culture by mediating a reduction in cellular stress response signaling and by enhancing gap junctional cell-cell communication.
Changes in cell surface expression of fibronectin and fibronectin receptor during liver regeneration
Journal of cell science, 1992
The surface expression of fibronectin and its major integrin receptor in liver, integrin alpha 5 beta 1, was studied during liver regeneration after partial hepatectomy. Using immunoblotting, plasma membranes isolated from livers at different regeneration stages were found to contain 6- to 8-fold elevated levels of fibronectin, alpha 5 and beta 1 at 12-24 h after the operation. Normal levels were gradually restored during the following 8-9 days. The membrane-associated fibronectin lacked the ED-A domain, suggesting that it consisted of plasma fibronectin. A prominent fibronectin fragment (180 kDa) was present at 12-24 h after surgery, possibly reflecting turnover of the pericellular matrix during cell division. Indirect immunohistochemical staining of liver sections revealed beta 1 and fibronectin mainly in the sinusoidal region of the hepatocyte plasma membrane. The distribution was not markedly altered during liver regeneration. The results suggest that the fibronectin-mediated co...