Growth of mammalian cells on substrates coated with cellular microexudates. I. Effect on cell growth at low population densities.

Abstract

Mammalian and avian cells cultured on glass or plastic substrates produce microexudates of cellular macromolecules which remain bound to the substrate when the cells are detached. The gross macromolecular composition of microexudates from a range of diploid, heteroploid, and virus-transformed cells was determined with cells labeled with radioisotopes. Significant differences in the amounts of cellular glycoproteins, proteins, and RNA present in microexudates were found between different cell types and between cells of the same type at different stages of growth. Inoculation of cells onto substrates "coated" with microexudates altered their growth behavior. Microexudates from exponentially growing subconfluent homotypic and heterotypic cell populations enhanced the growth of mouse and chick embryo cells seeded at very low densities, but similar microexudates had no effect on the proliferation of cells seeded at higher densities. The enhanced growth of low-density cell populations seeded on microexudates was compared with the growth enhancement produced by feeder cell layers and conditioned medium.Mammalian cells cultured in vitro on solid substrates produce a thin layer of "microexudate" that remains attached to the substrate when the cells are removed. This material is not detected by light microscopy, but can be demonstrated by electron microscopy (1, 3, 5, 14, 27, 31, 37, 40, 45), ellipsometry (25, 32, 34), mixed hemadsorption (26, 42), immunofluorescence techniques (3,26,43), and the incorporation of radioisotopes (8,34,44,45). The microexudates deposited on substrates by mammalian cells are actively synthesized by the cell and do not result merely from the passive leakage of intracellular macromolecules onto the substrate (18,25). The demonstration of cellspecific antigens (3,26,42,43), virus receptors (25), and lectin-binding sites (23,25) in cellular microexudates, together with data on the synthesis (25) and chemical characterization of such materials (8), have prompted the proposal that microexudates represent cell surface macromolecules derived from the so-called "cell coat" (25).In this paper we present information on the composition of cellular microexudates deposited on glass and plastic substrates by a variety of diploid, heteroploid, and transformed cells and on alterations in the growth behavior of cells plated at

Two functionally distinct pools of glycosaminoglycan in the substrate adhesion site of murine cells.

“…KEY WORDS substrate glycosaminoglycan LETS glycoprotein microfilament adhesion When normal or SV4(P-transformed murine cells are detached from their tissue culture substrate by treatment with the Ca+*-specific chelating agent EGTA, they leave a small pool of protein and polysaccharide strongly adherent to the substrate, so-called substrate attached material (SAM) (12,36,6,10). SAM is probably similar to the "microexudates" described previously from ellipsometric (37,46,47,31) and electron microscope (34,53) investigations. SAM-coated substrates were subsequently shown to affect the reattachment kinetics (6), the morphological spread and movement (6), and the growth behavior of virustransformed cells (6,47).…”

Stimulation of clonal growth of normal fibroblasts with substrata coated with basic polymers.

“…This residual "microexudate" is rich in high molecular weight acidic proteoglycans (27). Surfaces coated with microexudate from rapidly proliferating cultures support enhanced growth of cells at low population density, although there is no effect with larger inocula (30,33). Culp (2) has proposed a model in which the negatively charged proteoglycans of the microexudate from the cells bind to the culture surface, which is normally coated with serum proteins.…”

Correlation between perchloric‐acid‐soluble serum proteins, cellular immunity and tumor‐cell burden

“…These glycoproteins are found on the surface of the culture dish on which the cells are grown (Culp and Black, 1972;Poste et al, 1973;Rosenberg, 1960;Weiss et al, 1975;Yaoi and Kanaseki, 1972).…”

“…Analysis of surface glycoproteins of various human and experimental tumor cells, by a combination of selective radiolabelling and polyacrylamide gel electrophoresis, revealed that neoplastic cells express and shed or secrete different surface glycoprotein patterns depending on cell type, stage of maturation and functional differentiation (Gahmberg et al, 1976;Anderson and Gahmberg, 1978). These glycoproteins are found on the surface of the culture dish on which the cells are grown (Culp and Black, 1972;Poste et al, 1973;Rosenberg, 1960;Weiss et al, 1975;Yaoi and Kanaseki, 1972).…”