Cholesterol requirement of primary diploid human fibroblasts

Decreasing variability in your cell culture

Culturing mammalian cells has not significantly changed in almost 50 years. Typically, a synthetic basal medium is chosen to meet the environmental and nutritional requirements of a given cell line. Components, such as amino acids, vitamins, inorganic salts, and a carbon source such as glucose are commonly found in the classical basal media formulation. These basal formulations normally will not support cell growth alone, but must be further supplemented with animal serum, usually fetal bovine serum (FBS) at a concentration of 5-20%. Recent advances in serum-free and chemically defined media formulations have provided cell culturists with options. When considering FDA regulations and potential risks to human health when manufacturing biologics or considering cell therapies, eliminating serum is of paramount concern. For a large majority of researchers however, using classical media with serum builds on previous generations of research and makes cell culture easier to perform.

Decreasing variability in your cell culture

Culturing mammalian cells has not significantly changed in almost 50 years. Typically, a synthetic basal medium is chosen to meet the environmental and nutritional requirements of a given cell line. Components, such as amino acids, vitamins, inorganic salts, and a carbon source such as glucose are commonly found in the classical basal media formulation. These basal formulations normally will not support cell growth alone, but must be further supplemented with animal serum, usually fetal bovine serum (FBS) at a concentration of 5–20%. Recent advances in serum-free and chemically defined media formulations have provided cell culturists with options. When considering FDA regulations and potential risks to human health when manufacturing biologics or considering cell therapies, eliminating serum is of paramount concern. For a large majority of researchers however, using classical media with serum builds on previous generations of research and makes cell culture easier to perform.

Biochemical characterization of the cholesterol-dependent growth of the NS-1 mouse myeloma cell line

The biochemical basis for the cholesterol-dependent growth phenotype of the NS-1 myeloma cell line has been investigated. In one series of experiments, the growth response of NS-1 cells to several of the intermediates of cholesterol biosynthesis was studied in serum-free medium. The cholesterol precursors, squalene and lanosterol, were totally ineffective in promoting NS-1 cell growth. In contrast, cholesterol precursors downstream from lanosterol, i.e., desmosterol and 7-dehydrocholesterol, completely replaced cholesterol in supporting NS-1 cell growth. In a second series of experiments, NS-1 cells and NS-1-503 cells (a cholesterol growth-independent variant of NS-1 cells) were labelled with [2-14C]acetate and the distributions of radioactivity between cholesterol and its precursors were determined by thin-layer chromatography using two different solvent systems. The major labelled sterol product (greater than 80%) in NS-1 cells after a 24-h exposure to [2-14C]acetate was lanosterol. In contrast, the major labelled sterol product (greater than 95%) in NS-1-503 cells after a 24-h exposure to [2-14C]acetate was cholesterol. Taken together, these results indicate that NS-1 cells are defective in cholesterol biosynthesis and identify the site of lesion as the demethylation of lanosterol to C-29 sterol intermediates.

Effect of cholesterol and growth factors on the proliferation of cultured human skin fibroblasts

A cholesterol-deficient growth medium for human skin fibroblasts was prepared by adding to Eagle's Minimum Essential Medium a bovine serum treated with ultracentrifugation to remove bulk lipoproteins followed by silicic acid adsorption to remove residual lipoproteins and cholesterol. Cell growth was slow, but the daily cell doublings could be increased by 76% by including 7.5 micrograms purified cholesterol/ml in the medium. Cell growth in cholesterol-deficient culture medium could be increased to that seen with medium containing 15% untreated fetal bovine serum by the inclusion of the following growth factors: epidermal growth factor (EGF), cortisol, non-essential amino acids, insulin, transferrin and selenium. Cholesterol increased the proliferation of these rapidly-growing cultures by 19%. No effect of cholesterol was observed in transformed L-cell mouse fibroblasts.

Fibroblasts from patients with myotonic muscular dystrophy: cholesterol requirement for proliferation and sensitivity to polyene antibiotics

The genetic defect in myotonic muscular dystrophy (MMD) remains obscure. From the evidence that drugs blocking cholesterol biosynthesis induce myotonia and increased serum concentrations of deoxycholic acids are common among patients with MMD, evidence of the abnormal sterol metabolism in MMD fibroblasts was sought by comparing them with fibroblasts from control individuals and patients with Duchenne muscular dystrophy (DMD). Although early-onset type MMD and DMD fibroblasts have lower maximal cell densities than fibroblasts from age-matched control individuals do in medium containing 10% fetal bovine serum, we could not reveal any abnormalities in exogeneous cholesterol requirements for proliferation of MMD fibroblasts. This suggests that the sterol biosynthetic pathway in MMD fibroblasts is grossly intact. Furthermore, no difference were observed in sensitivities to polyene antibiotics, which bind to membrane sterols and presumably damage the cell membrane.

Rapid clonal growth and serial passage of human diploid fibroblasts in a lipid-enriched synthetic medium supplemented with epidermal growth factor, insulin, and dexamethasone

A serum-free, hormone-supplemented medium, enriched with a mixture of lipids, has been developed that supports rapid clonal growth of human diploid fetal lung fibroblasts (Flow 2000, WI-38, MRC-5, and IMR-90) and of low-passage human foreskin fibroblasts. The medium, which contains less than 1 microgram of total protein per ml, also supports serial passage of Flow 2000 cells under totally serum-free conditions. It provides lipid at a total of 10 micrograms/ml as a liposome prepared from a mixture of soybean lecithin, cholesterol, sphingomyelin, vitamin E, and vitamin E acetate. The soybean lecithin, which contains a variety of naturally occurring phospholipids, can be replaced with a mixture of highly purified phospholipids. Except for possible contaminants in the substances used in its preparation, the serum-free medium is fully defined chemically. It consists of an optimized basal nutrient medium, MCDB 110, supplemented with insulin, epidermal growth factor, dexamethasone, prostaglandins E1 and F2 alpha, phosphoenolpyruvate, dithiothreitol, glutathione, and the lipids listed above.

Studies of alpha-protein in human cell cultures

alpha-Protein growth fraction (AGF) eliminates the 60- to 90-day adaptive phase required to establish actively growing cultures of HeLa (Gey), human heart (Girardi), KB (Eagle) and other established cell lines in serum-free chemically defined medium A3. AGF is effective at less than 0.4 microgram per ml. By using the procedures described in the text, it is possible to culture HeLa cells in very simple media such as Eagle's basal medium. The properties of AGF are such that it may be adsorbed on glass or plastic flasks. Glass flasks treated with AGF retain full activity after washing with acetone, and treatment with ethyl ether and chemically defined medium. Adsorbed AGF is destroyed by trypsin. AGF can detoxify protamines, polylysines or histones. It will reverse the aggregation response induced by adding complexes composed of carboxymethylcellulose (CMC) and basic proteins. The results support the contention that highly adsorptive AGF functions at the cell surface and is capable of modifying the response of the cell to its environment.

Defective regulation of cholesterol biosynthesis and plasma membrane fluidity in a Chinese hamster ovary cell mutant

A Chinese hamster ovary cell mutant resistant to killing by 25-hydroxycholesterol is shown to be defective in the regulation of cholesterol synthesis by exogenous cholesterol. When grown with various cholesterol supplements in delipidized serum, the mutant cell exhibits a variation in cholesterol content and plasma membrane fluidity that is not observed in the parental cell type.

Influence of incorporated cerebrosides on the interaction of liposomes with HeLa cells

The presence of synthetic N-palmitoyl dihydrolactocerebroside in preparations of neutral multilamellar liposomes enhances their fusion interaction with cultured HeLa cells some 5-7 fold. The effect appears to be carbohydrate-specific, and is probably not attributable to a change in the physical characteristics of the liposome bilayer due to the presence of the cerebroside.

Stimulation of proliferation in stationary primary cultures of monkey aortic smooth muscle cells. Part 2. Effect of varying concentrations of hyperlipemic serum and low density lipoproteins of varying dietary fat origins

The outgrowth of medial explants of thoracic aorta from Rhesus monkeys has used to study the influence of hyperlipemic serum on cell proliferation. After 5-6 weeks of rapid growth in BME plus 10% normal serum, the cultures reach a stationary phase during which they show little mitotic activity. When it replaces 5% of the normal serum in the media, hyperlipemic serum induces another proliferative phase in the cultures, as measured by [3H1thymidine incorporation and increase in culture area. Low density lipoprotein (LDL) has the greatest stimulatory effect, while high density lipoprotein (HDL) has no effect. Hyperlipemic serum or its LDL still stimulates the cells even when diluted to achieve cholesterol levels comparable to the values with normal serum or LDL. Normal LDL has no effect, even when concentrated to increase its cholesterol level in the media. Thus it appears that hyperlipemic LDL has a stimulatory effect on arterial smooth muscle cells which does not depend on its higher lipid or cholesterol level.

Preparation of delipidized serum protein for use in cell culture systems

A rapid procedure for the preparation of delipidized serum protein is described. The delipidized protein can be used for the maintenance and growth of tissue culture cells in a lipid-free environment. The extraction procedure greatly reduces all serum lipid classes and the delipidized protein supports the growth of a variety of cells in culture.

Cholesterol metabolism in the macrophage. I. The regulation of cholesterol exchange

The cholesterol metabolism of homogeneous populations of mouse peritoneal macrophages was evaluated under in vitro conditions. Macrophages are rich in free cholesterol and maintain a constant cholesterol to protein ratio (12 microg cholesterol/mg protein). No detectable cholesterol ester was present within the cell. More than 95% of total cholesterol was membrane associated and the majority was present in subcellular fractions containing lysosomes and plasma membrane. Less than 0.1% of cell cholesterol was synthesized from acetate-1-(14)C. During in vitro cultivation, macrophages rapidly exchanged their membrane cholesterol with that of lipoproteins of calf serum. About 30% of the cell cholesterol was exchanged per hour in 20% serum medium, and exchange was nearly complete by 5 hr. Exchange proceeded in a rapid exponential phase followed by a slower phase. Calculations based on a two compartment model indicated that the rapidly exchanging cholesterol compartment represented 60-70% of the total cell cholesterol, and the slowly exchanging compartment accounted for 30-40%. The relationship between serum lipoprotein concentration and exchange rate exhibited first-order kinetics. The rate was determined by thermal energy, in keeping with a Q(10) of 2, and an activation energy of 12 kcal/mole. Exchange was independent of bulk transport of lipoproteins by pinocytosis and phagocytosis, and was not linked to energy metabolism. The alpha-lipoproteins were the major class of proteins of calf serum participating in exchange.

Desmosterol as the major sterol in L-cell mouse fibroblasts grown in sterol-free culture medium

The principal sterol synthesized by L-cell mouse fibroblasts is desmosterol. Cholesterol was not detected in these cells when they were grown in a sterol-free culture medium. These findings indicate that, in cells, cholesterol can be replaced by desmosterol. Sterol analyses of six other tissue culture cell lines revealed cholesterol synthesis.