Fibronectin-mediated cell adhesion

The objective of this paper is to review our knowledge of the biochemical events which lead to cell adhesion both in vivo and to polymeric substrata in vitro. Prior to presenting studies involving cell adhesion, a brief review of our current knowledge of the molecules involved in fibronectin-mediated cell adhesion will be... 

In addition to gangliosides, heparin related molecules have also been shown to be involved in fibronectin mediated cell adhesion. Heparin binding sites have been described on many cell adhesion proteins e.g., fibronectin (25-26), laminin (27), and vitronectin... 

Cell Biology of Fibronectin-Mediated Cell Adhesion... 

As indicated above, most, if not all, the molecules required for cell adhesion have now been identified nevertheless, many important features of the echanism of cell adhesion remain at the phenomenological level. In the following section, a brief review of cell biological studies of fibronectin-mediated cell adhesion will be presented. 

Kleinman, H. K., Martin, G. R., and Fishman, P. H., 1979, Ganglioside inhibition of fibronectin-mediated cell adhesion to collagen, Proc. Natl. Acad. Sci. USA 76 3367-3371. 

If we consider that cell adhesion under biological circumstances is mainly brought about with the aid of preadsorbed protein on the material s surface, we may explain the unique behavior of amino-containing materials against the cell-adhesion process in terms of the reduced residence-time of protein molecules at the interface. Actually, a recent study [129] revealed that the surface of polyamine-gra/t-polystyrene copolymer (SA) containing 6 wt.% polyamine portion exhibited a minimal adsorptive property against bovine plasma fibronectin (FN) and vitronectin (VN), both of which are known to mediate cell-adhesion processes. 

In addition to mediating cell adhesion, it has been demonstrated that integrin expression by osteoblasts determines their phenotypic expression (see the section Osteoblasts The Bone-Forming Cells ). For example, addition of either soluble concentrations of RGD (Moursi et al, 1996) or antibodies of the integrin pair avp() (Moursi et al., 1997) to confluent osteoblast cultures, blocked initiation and formation of mineral nodules these results provided evidence that integrin-fibronectin interactions leading to extracellular matrix development play a crucial role in osteoblast function (Moursi etal., 1996,1997). 

Fibronectin mediates the adhesion of cells to collagen by first binding to the collagen substrate followed by attachment of the cells to the fibronectin-collagen complex. Bovine brain gangliosides prevented the adhesion of cells to the fibronectin-collagen complex, but had no effect on the initial formation of the fibronectin-collagen complex. The order of efficiency was and G > Gd, j Gj > was not an inhibitor. Only the carbohydrate portions of... 

Figure. 4. Principle of the cell adhesion to artificial materials. In cell culture media or body fluids, the material is spontaneously adsorbed with cell adhesion-mediating extracellular matrix proteins (e g., vitronectin, fibronectin). The cells then adhere to specific amino acid sequences of these proteins by their adhesion receptors of integrin or non-integrin type [38-41].

Whitesides and coworkers describe the use of an elastomeric membrane to pattern proteins and cells on bacteriological polystyrene (PS), glass, and poly(dimethyl-siloxane) (PDMS) substrates [92], A patterned PDMS membrane was casted from lithographically structured photoresists and brought into close contact with the substrates (Fig. 6). When incubated with a solution of fibronectin (FN), adsorption of the cell-adhesion-mediating protein to the surface was restricted to the exposed areas. The membrane was peeled off and cells were seeded from a serum-free medium. Passivation to cell attachment of the untreated portions of the surface was achieved by adding 1% bovine serum albumin (BSA) to the cell-seeding medium, which... 

Select proteins that mediate adhesion of specific anchorage-dependent cells (such as osteoblasts, fibroblasts, and endothelial cells) on substrate surfaces have been identified (Underwood and Bennett, 1989 Thomas et al., 1997 Ayad et al, 1994). For example, adsorption of fibronectin and vitronectin on tissue-culture polystryene subsequently enhanced osteoblast, fibroblast, and endothelial cell adhesion (Underwood and Bennett, 1989). More importantly, fibronectin and vitronectin adsorption on borosilicate glass, in a competitive environment, maximized fibroblast and osteoblast adhesion, respectively (Thomas et al., 1997). Ayad et al. (1994) reported that enhanced adsorption of laminin on tissue-culture polystyrene promoted subsequent endothelial cell adhesion. These studies provided evidence that adsorption of specific protein(s) can, subsequently, control select cell adhesion on material surfaces. 

Investigations of the underlying mechanism(s) revealed that the concentration, conformation, and bioactivity of vitronectin (a protein contained in serum that is known to mediate osteoblast adhesion ((Thomas et al., 1997) see the section Vitronectin ) was responsible for the select, enhanced adhesion (a crucial prerequisite for subsequent, anchorage-dependent-cell function) of osteoblasts on these novel nanoceramic formulations. Specifically, of the proteins (such as albumin, laminin, fibronectin, collagen, and vitronectin) tested, vitronectin adsorbed in the highest concentration on nanophase alumina after 4 hr moreover, competitive adsorption of vitronectin was 10% greater on nanophase compared to conventional alumina (Webster et al.,... 

Laterra, J., Silbert, J. E., and Culp, L. A., Cell surface heparan sulfate mediates some adhesive responses to glycosaminoglycan-binding matrices including fibronectin. J. Cell Biol. 96, 112-121 (1983). 

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