Human Fibroblast Extracellular Matrix Research Articles

Organization of Hyaluronan and Versican in the Extracellular Matrix of Human Fibroblasts Treated With the Viral Mimetic Poly I:C

We have examined structural details of hyaluronan- and versican-rich pericellular matrices in human lung fibroblasts, as well as fixation effects after treatment with the viral mimetic, poly I:C. Lateral aggregation of hyaluronan chains was promoted by acid-ethanol-formalin fixation compared with a network appearance with formalin alone. However, hyaluronidase-sensitive cable structures were seen in live cells, suggesting that they are not a fixation artifact. With all fixatives, versican and hyaluronan probes bound alternately along strands extending from the plasma membrane. However, a yellow colocalization signal required aggregation/overlap of several hyaluronan/versican strands and was more pronounced after acid-ethanol-formalin fixation. In addition to the main cell surface, hyaluronan and versican were also associated with fine actin-positive membrane protrusions, retraction fibers, and surface blebs. After wounding plus treatment with poly I:C, cells displayed larger hyaluronan coats and cable-like structures, as well as more membrane protrusions. However, treated cells did not migrate and had increased stress fibers compared with control wounded cells. Deposition of hyaluronan into cable-like structures in response to poly I:C was diminished but still apparent following actin filament disruption with cytochalasin D, suggesting that the protrusions only partially facilitate cable formation. As seen by scanning electron microscopy, the membrane protrusions may participate in poly I:C-induced binding of monocytes to hyaluronan- and versican-rich matrices. These results suggest that poly I:C-induced hyaluronan- and versican-rich cable structures are not deposited during migration, and that cellular protrusions partially contribute to hyaluronan cable formation. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Microvascular endothelial cells from human omental tissue: Modified method for long-term cultivation and new aspects of characterization

A method for long-term cultivation of large amounts of human microvascular endothelial cells from the omental tissue (human omental tissue microvascular endothelial cells, HOTMECs) was devised. The method originally described by Kern, Knedler, and Eckel was modified: HOTMECs were isolated by enzymatic dissociation with collagenase. For primary cultivation and passages, HOTMECs were plated either onto fibronectin-coated petri dishes or onto a human fibroblast extracellular matrix (HFB-ECM) prepared from the same tissue. Omental tissue (10–15 g) yielded 4–8 × 10 5 HOTMECs; more than 90% of the cells adhered to precoated dishes and grew in Waymouth's culture medium supplemented with 20% heat-inactivated fetal calf serum. Confluence was reached 3–5 days after seeding with an average of 1–2 × 10 6 cells/dish. Confluent HOTMEC layers were subcultured at a split ratio of 1:3 up to 11 passages by plating the cells onto dishes coated with HFB-ECM and maintained in long-term culture for up to 3 months. The endothelial origin of these cells was demonstrated as follows. The cells in culture showed the typical “cobblestone” growth pattern and synthesized von Willebrand factor (vWF) as determined by metabolic labeling. Using an indirect immunostaining technique, the cytoplasm of the HOTMECs stained for vWF. A monoclonal antibody specific for human endothelial cells bound exclusively to the cultured cells. The expression of thrombomodulin on the surface of the cultured cells was demonstrated by the activation of protein C by thrombin. In control experiments, these features could be detected on neither fibroblasts nor mesothelial cells.

The effect of mannose 6-phosphate on the turnover of the proteoglycans in the extracellular matrix of human fibroblasts

Human fibroblasts (SL66) were cultured in medium containing 35SO 4 2− to label the glycosaminoglycans (GAGs). The cells were then detached from the culture dish to leave radioactively-labeled components of the extracellular matrix, hereafter termed 35S-labeled substrate-attached material. When unlabeled SL66 fibroblasts were plated onto this 35S-labeled substrate-attached material, the cells mediated two distinct events: ( a) release of radioactivity from the substrate-attached material into the medium; ( b) degradation of certain glycosaminoglycans into radioactive components of very low molecular weight including free radioactive sulfate. In the presence of mannose 6-phosphate, however, the degradation of the substrate-attached material by SL66 cells was partially inhibited. Analyses of this effect in terms of the dose-response curve, saccharide specificity, ammonium chloride sensitivity, and the requirement for cells suggest that both an intracellular compartment and the mannose 6-phosphate receptor that binds lysosomal enzymes at the cell surface may play important roles in the turnover and degradation of certain proteoglycans in substrate-attached material.

Transformation-dependent alterations is glycoproteins of extracellular matrix of human fibroblasts. Characterization of GP250 and the collagen-like GP140.

The extracellular matrix, prepared by extraction of confluent cultures of human lung WI-38 fibroblasts with a dipolar tonic detergent, contains four major glycoproteins: fibronectin, GP250, GP170, and GP140. All the glycoproteins can be surface-labeled; however, only fibronectin and GP170 can be readily removed by digestion with trypsin (Carter, W. G., and Hakomori, S. (1981) J. Biol. Chem. 256, 6953-6960). Most of the noncovalently bound GP250, GP170, and GP190, an additional minor glycoprotein, can be dissociated from the matrix by extraction with 8 M urea. The remaining insoluble matrix is stabilized by extensive intermolecular disulfide bonds and contains primarily GP140 and fibronectin (Carter, W. G. (1982) J. Biol. Chem. 257, 3249-3257). Affinity-purified, monospecific antibodies were prepared against GP[140 and fibronectin and utilized for detection of GP140 and fibronectin in extracts and conditioned media of WI-38, WI-38 VA13, WI-26, WI-26 VA4, and HT-1080 cells. Additional affinity-purified, polyspecific antibodies that react with GP250, GP190 GP170, and GP140 were also utilized. Fibronectin, GP250, GP190, GP170, and GP140 were all absent from transformed cells. With the exception of GP140, the absence of these glycoproteins from the matrix of transformed cells was paralleled by their accumulation in the conditioned culture media. Incubation of conditioned culture media with collagenase indicated that GP190, GP170, and GP140, as well as other glycoproteins, were digested. Antibodies to GP140 did not react with any other cellular component indicating that it is not a processing product of other matrix glycoproteins. GP140 has characteristics unlike all reported collagen types and appears to be a new collagen-like glycoprotein. In contrast, neither Gp250 nor fibronectin were sensitive to digestion with collagenase. Antibodies that react with GP250 did not react with fibronectin and vice versa, suggesting that GP250 and fibronectin do not share antigenic determinants. The interaction of labeled fibronectin and the labeled, gelatin-binding domain of fibronectin with cells after fractionation on polyacrylamide gels indicated that GP170 is the primary procollagen receptor for fibronectin in the extracellular matrix. GP140 also bound fibronectin but to a lesser degree. Soluble GP170 and GP190 present in the conditioned medium of cultured cells also bound to insolubilized fronectin, confirming the association of GP170 and GP190 with fibronectin. The interaction of the glycoprotein components in the matrix are discussed in relation to their potential cooperative function in cell attachment and their failure to adhere to the surface of transformed cells.