How does the extracellular matrix direct gene expression

Identification of a fibroblast-derived epithelial morphogen as hepatocyte growth factor

Adult rat hepatocytes cultured in a collagen sandwich system maintained normal morphology and a physiological rate of albumin secretion for at least 42 days. Hepatocytes cultured on a single layer of collagen gel essentially ceased albumin secretion within 1 wk but could recover function with the overlay of a second layer of collagen gel. This culture configuration more closely mimics the hepatocytes' in vivo environment and provides a simple method for their long-term maintenance.

Hepatocyte function and extracellular matrix geometry: long-term culture in a sandwich configuration.

We have studied the behavior of cloned capillary endothelial cells grown inside a three dimensional collagen matrix. Cell monolayers established on the surface of collagen gels were covered with a second layer of collagen. This induced the monolayers of endothelial cells to reorganize into a network of branching and anastomosing capillary-like tubes. As seen by electron microscopy, the tubes were formed by at least two cells (in transverse sections) delimiting a narrow lumen. In addition, distinct basal lamina material was present between the abluminal face of the endothelial cells and the collagen matrix. These results showed that capillary endothelial cells have the capacity to form vessel-like structures with well-oriented cell polarity in vitro. They also suggest that an appropriate topological relationship of endothelial cells with collagen matrices, similar to that occurring in vivo, has an inducive role on the expression of this potential. This culture system provides a simple in vitro model for studying the factors involved in the formation of new blood vessels (angiogenesis).

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In vitro rapid organization of endothelial cells into capillary-like networks is promoted by collagen matrices.

Engineering biocompatible implant surfaces

The influence of collagen gels on the orientation of the polarity of epithelial thyroid cells in culture was studied under four different conditions. (a) Isolated cells cultured on the surface of a collagen gel formed a monolayer. The apical pole was in contact with the culture medium and the basal membrane was attached to the substratum. (b) Isolated cells embedded inside the gel organized within 8 into follicles. The basal pole was in contact with collagen and the apical pole was oriented towards the interior of the follicular lumen. (c) Cells were first organized into floating vesicles, structures in which the apical surface is in contact with the culture medium, and the vesicles were embedded inside the collagen gel. After 3 d, cell polarity was inverted, the apical pole being oriented towards the cavity encompassed by cells. Vesicles had been transformed into follicles. (d) Monolayers formed on collagen gels as in a were overlaid with a second layer of collagen, which was polymerized in contact with the apical cell surface. A disorganization of the continuous pavement occurred within 24 h; cells attached to the upper layer of collagen and reorganized into follicles in the collagen sandwich within 4-8 d. A similar process occurred when the monolayer was grown on plastic and overlaid with collagen, or grown on collagen and covered with small pieces of glass cover slips. No reorganization was observed between two glass surfaces. In conclusion, first, a basal pole was always formed in the area of contact between the cell membrane and an adhesive surface and, second, the interaction of a preformed apical pole with an adhesive surface was not compatible with the stability of this domain of the plasma membrane. The interaction of the cell membrane with extracellular components having adhesive properties appears to be a determinant factor in the orientation and stabilization of epithelial cell polarity.

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Influence of collagen gel on the orientation of epithelial cell polarity: follicle formation from isolated thyroid cells and from preformed monolayers.

When cultured in collagen gel-coated dishes, thyroid cells organized into polarized monolayers. The basal poles of the cells were in contact with the collagen gel, whereas the apical surfaces were facing the culture medium. Under these culture conditions, thyroid cells do not concentrate iodide nor respond to acute stimulation by thyroid-stimulating hormone (TSH). To allow the free access of medium components to the basal poles, the gel was detached from the plastic dish and allowed to float in the culture medium. After release of the gel, the iodide concentration and acute response to TSH stimulation were restored. Increased cAMP levels, iodide efflux, and formation of apical pseudopods were observed. When the thyroid cells are cultured on collagen-coated Millipore filters glued to glass rings, the cell layer separates the medium in contact with the apical domain of the plasma membrane (inside the ring) from that bathing the basolateral domain (outside the ring). Iodide present in the basal medium was concentrated in the cells, whereas no transport was observed when iodide was added to the luminal side. Similarly, an acute effect of TSH was observed only when the hormone was added to the basal medium. These results show that the iodide concentration mechanism and the TSH receptor-adenylate cyclase complex are present only on the basolateral domain of thyroid cell plasma membranes.

https://rupress.org/jcb/article-pdf/96/4/1172/1076633/1172.pdf

Polarization of thyroid cells in culture: evidence for the basolateral localization of the iodide "pump" and of the thyroid-stimulating hormone receptor-adenyl cyclase complex.

Filipin, a polyene antibiotic, was used to detect cholesterol in thyroid membranes in vivo and in culture during TSH stimulation. We found that apical and basolateral plasma membranes were heterogeneously modified by filipin which induced abundant lesions in apical membranes, whereas Golgi apparatus, endoplasmic reticulum, nuclear membranes were unmodified. Small apical vesicles and colloid droplets were generally highly enriched in these complexes, suggesting a high cholesterol concentration in their membranes. Pseudopod membranes, known to be highly specialized domains in the apical plasma membrane, appeared enriched in cholesterol. Consequently, we suggest that an increased cholesterol content may be involved in the stabilization of thyroid membranes during endocytotic processes.

Cholesterol-rich microdomains in rat and porcine thyroid membranes involved in TSH-induced endocytotic processes.

In contact with a collagen gel, thyroid follicular cells form a basal pole. A monolayer, with the apical side facing the culture medium is formed when cells are seeded on a collagen layer. In contrast cells reorganize into follicle-like structures when they are embedded in the collagen gel. If vesicles which have their apical pole in contact with the culture medium are embedded in the gel, collagen-cell interaction induced the inversion of cell polarity giving follicular structures. In addition after being overlaid with a collagen layer, cells forming a monolayer reorgnaize into follicles. The apical pole is formed on the free surface of the monolayer or on the internal side of structures embedded in collagen which differentiate into follicles.

Mauchamp J

Papers

Influence of collagen gel on the orientation of epithelial cell polarity: follicle formation from isolated thyroid cells and from preformed monolayers.

Polarization of thyroid cells in culture: evidence for the basolateral localization of the iodide "pump" and of the thyroid-stimulating hormone receptor-adenyl cyclase complex.

Cholesterol-rich microdomains in rat and porcine thyroid membranes involved in TSH-induced endocytotic processes.

Reorganisation of thyroid follicular cells in culture. Effect of collagen on the orientation of cell polarity

Thyroid cell polarization in culture and the expression of specialized functions.