Changes in the components of extracellular matrix and in growth properties of cultured aortic smooth muscle cells upon ascorbate feeding.

Abstract

Culture conditions can modify the composition of the extracellular matrix of cultured calf aorta smooth muscle cells. In the absence of ascorbate the major components of the matrix are microfibrillar proteins ; deposition of collagen occurs upon ascorbate supplementation and, with increased time of exposure of cells to ascorbate, collagen becomes the dominant protein of the extracellular matrix (>80%) . Collagen accumulation follows a sigmoidal time-course, suggesting that it is a cooperative phenomenon . Covalent crosslinks are not required for collagen accumulation in the matrix . Microfibrillar proteins and increased amounts of proteoglycans and fibronectin accumulate concurrently with collagen but elastin deposition was not observed either with or without ascorbate feeding. Addition of ascorbate leads to a general stimulation of incorporation of [' 4C]proline into cellular protein and to changes in cell growth parameters and morphology: cell-doubling time decreases from 62 to 47 h and plating efficiency increases approximately fourfold . We conclude that the composition of the extracellular matrix assembled by cultured cells is subject to experimental manipulation and that changes in endogenously deposited matrix may have significant effects on cellular functions.The role of the substrata in cell attachment, proliferation, and differentiation has recently received much attention (14, 18) . Artificial collagen substrates and those of more complex composition approximating the extracellular matrix of the cell in vivo are being widely used in studies of growth and differentiation of a number of diploid cell types . For example, improved survival and maintenance of differentiated function were observed when rat hepatocytes were cultured on "biomatrix" or collagen gels than when cultured on plastic (26), and growth factors were not required when bovine vascular smooth muscle cells were maintained on the extracefular matrix assembled by corneal endothelial cells (13). Liotta et al. reported that collagen was required for cell attachment, spreading, and proliferation, and that artificial collagen substrates could substitute for the endogenously deposited collagen (22). These observations support the idea that the substrate, either provided to the cell and/or the extracellular matrix that the cell elaborates, is crucially important in determining cell behavior and diferentiatioe fate. The role of the endogenously produced extracellular matrix of cultured cells in regulating cellular properties such as growth and metabolism has received little attention . Recent studies on rat heart smooth muscle cells showed that the matrix composition can be altered by ascorbic acid; in the absence of ascorbate, elastin was the major component whereas in its presence glycoprotein and collagen were deposited (9, 30) . However, in this system, ascorbate had a variable effect on cell growth.In a previous study, we presented evidence that the major components of the extracellular matrix of the calfaorta smooth muscle cells cul...

Administration of Ascorbic Acid and an Aldose Reductase Inhibitor (Tolrestat) in Diabetes: Effect on Urinary Albumin Excretion

“…AA plays a major role in the deposition of matrix collagen through its function as a co-factor for proline hydroxylase [8]. Similarly, synthesis of matrix PG and matrix glycoproteins, such as fibronectin and laminin, is enhanced when the medium is supplemented with AA [10, 11, 12, 24].…”

“…AA is an important anti-oxidant, and this is particularly relevant in this context, as diabetes has been shown to be a state of increased oxidative stress which can affect endothelial cell function [6, 7]. Tissue culture experiments, involving a number of human and animal cell types, have also shown that deposition of matrix collagen, glycoproteins, and proteoglycans (PG) is enhanced by AA [8, 9, 10, 11, 12]. In addition, we have previously shown that AA affects PG of rat mesangial matrix qualitatively, by increasing its degree of sulphation [13].…”

Platelet adhesion to vascular cells. The role of exogenous von Willebrand factor in platelet adhesion.

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Inflammation in the vascular bed: Importance of vitamin C

“…It is necessary for VSMC collagen synthesis, since without it (Schwartz et al, 1982), or in the presence of the non-functional ascorbate analog ethyl-3,4-dihydroxybenzoate (Sasaki et al, 1987), VSMCs form little collagen. In addition to enhancing post-translational collagen modification in VSMCs, ascorbate also increases procollagen synthesis by a pre-translational mechanism (Barone et al, 1985;Davidson et al, 1997).…”

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