Altered biochemical properties of mitochondria in mouse mammary epithelial cells during primary culture

Review-progress in concept and practice of growing anchorage-dependent mammalian cells in three dimension

Tissue culture has played a major role in the rapid advances made in medical science in the past 50 yr. The full potential of the technique, however, is limited by the fact that growth of cells is usually restricted to a monolayer accompanied by major decreases in many of their tissue-specific functions. This has been shown to be due, in large part, to the inadequate oxygenation of cells growing in tissue culture dishes. Studies that show that the high charge density and rigidity of the plastic and glass surfaces used for culture are also major factors limiting growth of cells to a monolayer, are reviewed. A new culture system has been developed in which cells are grown on substrata made using perfluorocarbons (PFCs) coated with collagen type 1 and other adhesive factors. Perfluorocarbons have a much higher solubility for oxygen than water and have been used as oxygen delivery systems to protect cells from hypoxia. These new PFC-based substrata can provide both the optimal level of oxygen cells need to maintain differentiated functions and the flexible and weaker type of adhesion that allows cells to round up, interact with each other, and when provided with adequate nutritional support, to grow in three dimension.

An hypothesis on the role of cellular colloid osmotic pressure in determining behavior of cells in vitro including anchorage dependency and maintenance of the differentiated state

The osmotic problems involved when cells are isolated from tissues are analyzed. Evidence is considered which indicates that in vivo the Na pump is operating at maximal or near maximal rates and that this depends on low leak rates for salts and water due to various aspects of the tissues structure. Dispersion of the tissue results in breakdown of these barriers on free diffusion and the isolated cell is subjected to an enormous increase in passive influx due to colloid osmotic pressure without being able to increase its pumping rate to the extent needed to maintain volume control. It is proposed that the primary problem the cell faces in vitro is to compensate for the effective increase in its colloid pressure, e.g. the colloid osmotic pressure excess, emerging with the breakdown of the tissue structure. The finding that most normal cells have to adhere to a surface in order to grow or "anchorage dependency" is analyzed in terms of the way adhesion and spreading result in changes in ion and water movements into cells enabling them to achieve fluid balance in the face of the colloid pressure excess. It is also proposed that the differentiated state is more dependent on colloid osmotic balance than proliferation. The failure of conditions used in tissue culture to compensate adequately for the colloid pressure excess results in limiting the amount of protein which can be synthesized, dissipation of cellular energy, and changes in orientation of cellular components which contribute directly to the loss of differentiation which occurs during growth in vitro.

Regulation of glutamine and pyruvate oxidation in cultured adrenocortical cells by cortisol, antioxidants, and oxygen: effects on cell proliferation

The regulation of CO2 production from [U-14C]glutamine and C2 of [2-14C]pyruvate was investigated in cultured bovine adrenocortical cells, and the effect of alterations in the relative rates of oxidation of these substrates on cell proliferation, particularly in the presence of an inhibitor of transamination reactions, was examined. 14CO2 production from 2 mM [U-14C]glutamine and 2 mM [2-14C]pyruvate was measured in the presence of 100 microM 2,4-dinitrophenol, an uncoupler of oxidative phosphorylation. Treatment of primary cultures of 24 h with 50 microM cortisol increased the oxidation of [14C]glutamine relative to that of [14C]pyruvate, an effect dependent on prior low cell density. Cortisol treatment also resulted in a prolonged delay in the onset of proliferation from low density, and completely inhibited growth in the presence of 2 mM aminooxyacetate, which reduces mitochondrial utilization of glutamine. The effects on glutamine and pyruvate metabolism and on cell growth, with or without aminooxyacetate, were prevented by simultaneous treatment with the antioxidants dimethyl sulfoxide (10 mM) and butylated hydroxyanisole (100 microM), suggesting the involvement of lipid peroxidation in the action of cortisol, as previously demonstrated for its action on 11 beta-hydroxylase. During continued proliferation of adrenocortical cells in the absence of cortisol there was also a slower increase in the oxidation of [14C]glutamine relative to that of [14C]pyruvate as a function of population doubling level. The rate of this increase was slowed by growth of cells in 2% O2 rather than the standard 19% O2, and accelerated by continued growth of cells in the presence of cortisol. The rate of increase in the oxidation of [14C]glutamine relative to that of [14C]pyruvate under these three conditions correlated with inhibition of cell growth by aminooxyacetate. In contrast to the complete inhibition of growth in aminooxyacetate demonstrated by cortisol-treated cells, control cells (19% O2) did proliferate, although growth was limited, whereas cells at 2% O2 proliferated to a much greater extent. In the absence of aminooxyacetate the rate of growth in primary adrenocortical cell cultures under these three conditions was similar. Lipid peroxidation appears to make cultured adrenocortical cells dependent on glutamine for mitochondrial function and proliferation by inhibiting the utilization of the normal substrate, pyruvate.