Importance and uses of stearic acid in serum-free eukaryotic, including hybridoma and Chinese Hamster Ovary (CHO) cell, cultures
Fatty acids of the n-3, n-6 and n-9 families are important supplements for cell culture systems. They are important in cell culture systems used to biomanufacture heterologous proteins, such as monoclonal antibodies. Fatty acids have been shown to be important for the growth and productivity of Chinese Hamster Ovary (CHO) cells.
Oleic acid is an (n-9) unsaturated fatty acid that is synthesized by animal cells with the consumption of energy. Oleic acid is poorly soluble in aqueous media and susceptible to peroxidation. Historically, oleic acid has been provided to cells in culture as a component of serum, albumin complex or esterified to molecules such as cholesterol. While this is potentially useful when media are prepared and used fresh, it is a problem for media that are stored for use in commercial applications such as biomanufacturing and tissue engineering. Fortunately, animal cells can synthesize oleic acid and its derivatives from its saturated precursor, stearic acid (C-18). There are two major advantages to supplementing cells in culture with stearic acid. Stearic acid is not susceptible to lipid peroxidation and as a C-18 fatty acid, the cell does not need to consume much energy to covert it to oleic acid. For a more complete discussion of palmitic, stearic, oleic and other fatty acids as a cell culture additives, visit our Media Expert.
Fatty acids (FA) are long-chain carboxylic acids that are insoluble in water. These fatty acid chains can be from 4 to 30 carbons long, but physiologically the most important fatty acids are from 16 to 22 carbons long. Since fatty acids are synthesized naturally by the addition of acetyl groups, they have an even numbers of carbon atoms-C2, C4, etc. They can be saturated or unsaturated. Natural fatty acids have their double bonds in the cis-configuration and are usually esterified to glycerol backbones to form complex lipids. Fatty acids that contain more than one double bond are called polyunsaturated fatty acids (PUFAs).
Fatty Acids Families: A simple way to designate fatty acids is illustrated for oleic acid as follows: 18:1, (n-9). The first number designates that there are 18 carbon atoms in oleic acid, the second number designates that there is one double bond, and the (n-9) indicates position of the double bond carbon closest to the methyl end.
In animals, most fatty acids with 16 or more carbons belong to one of three main fatty acid families. All unsaturated members of a family are n-3, n-6, or n-9. Members of these FA families are not interconvertible.
Animal cells cannot synthesize fatty acids of the n-3 or n-6 type. They must be provided in the diet and are considered essential fatty acids (EFAs). Animal cells can de novo synthesize palmitic and stearic fatty acid and their n-9 derivatives. However, de novo synthesis requires the utilization of energy. Palmitic acid (C16) is the immediate precursor of stearic acid (C18). In animal cells, oleic acid is created by the dehydrogenation (desaturation) of stearic acid. Oleic acid is further elongated and desaturated into a family of n-9 fatty acids. The demand for energy used to synthesize n-9 fatty acids can be reduced in cell culture by providing palmitic and stearic acids. In addition, since palmitic and stearic acid are saturated, they are not peroxidized during delivery to the cells.
Our Cell Culture Media Expert provides in depth discussion of this and other serum-free and protein-free media supplements. The Media Expert contains additional sections on raw materials, component use recommendations, formulation strategies and references. Whenever you have a questions about or problems with your eukaryotic mammalian cell culturing system visit the Media Expert for helpful guidance.