Adult Bovine Serum: A Valuable Resource for Cell Culture Media

 

Adult bovine serum

History and Origin of Adult Bovine Serum

Adult bovine serum (ABS) has been used widely in cell culture since the late 1940s and early 1950s. ABS refers to blood serum extracted from adult cattle (Bos taurus) which is commonly used as a supplement in cell culture media. Bovine serum is a byproduct of the slaughterhouse or meat packing industry as it is extracted from cattle during meat processing. When blood is collected from cattle during slaughter, it is allowed to clot and the resulting liquid serum is harvested. This serum contains growth factors, proteins, vitamins and minerals needed by cells grown outside their normal physiological environment in cell culture labs.

Composition and Properties of ABS

ABS is a complex mixture of over a thousand different proteins, as well as growth factors, cytokines, amino acids, lipids, vitamins, and minerals that are essential for most mammalian cell growth. Some of the key components of ABS that support cell culture include:

- Albumin: The most abundant protein in serum, albumin aids in buffering cell culture media and transporting nutrients.

- Growth factors: Adult bovine serum contains epidermal growth factor (EGF), fibroblast growth factors (FGF), insulin-like growth factors (IGF), transforming growth factors (TGF), and platelet-derived growth factors (PDGF) which stimulate cell proliferation.

- Attachment factors: Fibronectin and vitronectin found in ABS promote cell attachment to substrates like tissue culture polystyrene surfaces.

- Carrier proteins: Albumin and other proteins bind and solubilize nutrients like fatty acids, vitamins, hormones and minerals, making them bioavailable to cultured cells.

- Protease inhibitors: ABS contains protease inhibitors like alpha-2-macroglobulin that protect proteins in the media from degradation by cellular proteases secreted by cultured cells.

- pH buffering: Bicarbonate and phosphate ions in ABS help maintain physiological pH conditions ideal for most mammalian cell growth.

Due to its complex composition mimicking body fluids, ABS allows propagation of a wide variety of mammalian cell types outside their natural environment in cell culture labs across the world. However, ABS also poses some disadvantages due to its animal/xenobiotic origin.

Disadvantages and Alternatives to Adult Bovine Serum

While ABS is beneficial for routine cell culture, it also has some limitations such as:

- Variability: ABS from different bovine sources can exhibit batch-to-batch variation in protein concentration and composition impacting reproducibility.

- Contamination risk: ABS carries the potential risk of contamination with bovine viruses, prions or other pathogens that could infect cultured cells.

- Ethical concerns: Use ofABS derived from slaughterhouse byproducts raises some ethical issues related to animal welfare.

To overcome these disadvantages, researchers began development of serum-free and chemically defined media in the 1980s using recombinant growth factors, monoclonal antibodies, lipids, Transferrin, Insulin and more purified components. While initially more expensive, these xeno-free media allow reproducible, scalable cell culture without risks of bovine contamination. Some synthetic serum replacements like KnockOut Serum Replacement from ThermoFisher even support growth of specialized cell types like human embryonic stem cells.

However, even today ABS supplemented media remains invaluable as the "gold standard" for routine culture of the vast majority of adherent mammalian cell types. ABS availability is high while costs are relatively low due to the large-scale sourcing from the meat industry. With careful vendor selection and testing, ABS permits robust and consistent proliferation of most cell lines worldwide at research and clinical manufacturing scales.

Adult Bovine Serum Applications in Biomedical Research and Industry

Given its extensive history and widespread use, ABS has myriad applications across biomedical research and commercial industries:

- Cell line development and maintenance: Researchers have used ABS to establish thousands of stable mammalian cell lines which form the backbone of biological research. It supports ongoing subculture of these invaluable resources.

- Assay development: ABS allows development and optimization of cell-based assays for toxicity screening, drug discovery, immuno-oncology and more which drive therapeutic advancements.

- Bioprocessing: The biopharmaceutical industry relies on ABS to culture CHO, HEK293 and other anchorage-dependent and suspension-adapted mammalian cell lines for large scale production of recombinant therapeutics including antibodies, vaccines and more.

- Regenerative medicine: ABS facilitates expansion of stem cells, organoids and other cultures for applications like tissue engineering, regenerative therapies and disease modeling.

- Research models: ABS is integral for in vitro studies of cell signaling, differentiation, metabolic pathways, infection and more furthering our understanding of human health and disease.

- Diagnostics: ABS supports culture of clinical samples, explants and biopsies to aid disease investigation and advance personalized medicine approaches.

Adult bovine serum plays an irreplaceable role as a highly productive, economical and reliable facilitator of mammalian cell culture that has accelerated innovation across diverse biomedical domains for over 70 years. While more defined media exist, ABS remains the workhorse that fuels modern biotechnology.

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