Animal cell culture has added enormous value to disciplines such as pharmacology, medicinal chemistry, and medicine.

For instance, research into cell culture paved the way for the development of the polio vaccine. It has also had innumerable other practical implications that has transformed the world of medicine.

But, what is animal cell culture and why does it continue to prove to be an invaluable means in scientific and medicinal research?

That’s the question we explore and analyze today.

What is Cell Culture?

Animal cell culture is a major tool used in clinical research in which cells are grown in vitro under specific, controlled artificial conditions. Cell culture is also commercially important particularly for the biopharmaceutical industry since cell cultures are used for the manufacture of some therapeutics. This tool helped with the progression of areas like cancer research, biochemistry, pharmacology, drug discovery and development, medicinal chemistry and immunology!

When cells are cultured directly from animal tissues and grown in an appropriate medium under specific controlled
conditions, they are referred to as primary cells. The term confluency refers to the percentage of the culture vessel surface area covered by a cell layer. At high confluency, primary cells must be subcultured (or passaged) and after the first subculture, primary cultures are then referred to as cell lines (or sub-clones).

In research, although primary cells are more representative of the tissues they originated from, established immortal cell lines are generally preferred as models over of primary cells due to advantages such as ease of handling, large availability of protocols for established cell lines, and cost-effectiveness. The HeLa cell line, originally from the cervical cancer cells of Henrietta Lacks (obtained without consent), is one of the most widely used cell lines in
scientific research. Cells grown in the cell culture laboratory can be classified into anchorage-dependent
(adherent) cells which attach to the surface of the vessel, or suspension cells which can be grown as a suspension in the medium.

Cells can also be cryopreserved (usually in the presence of a cryoprotectant like dimethyl sulfoxide [DMSO] or glycerol) and thawed for later use. It is important to mention that cell culture must be conducted under very strict aseptic conditions as microbial contamination can be frustrating and lead to a waste of time and resources. Recent examples of research involving cell cultures include:

1. Induction of Apoptosis by Pierisin-6 in HPV Positive HeLa and HepG2 Cancer Cells is Mediated by the Caspase-3 Dependent
   Mitochondrial Pathway: S. Sarathbabu, S. K. Marimuthu, S. Ghatak, S. Vidyalakshmi, G. Gurusubramanian, S. K. Ghosh, S. Subramanian, W. Zhang and N. S. Kumar, Anticancer. Agen. Medicinal Chemistry, 2019, 19, 337–346.
2. Natural β-carboline alkaloids regulate the PI3K/Akt/mTOR pathway and induce autophagy in insect Sf9 cells: G. Cui, B. Shu, S. Veeran, H. Yuan, X. Yi and G. Zhong,Pestic. Biochemistry and Physiology, 2019, 154, 67–77.

What’s in a typical Cell Culture Laboratory?

Equipment or reagents that may be found in
a typical cell laboratory include:

• Laminar flow hood
• Refrigerator
• Freezer
• Autoclave
• Oven
• Centrifuge
• Disinfectant solutions (e.g.70% isopropanol/water (v/v) solutions, hypochlorite solutions)
• Incubator
• Inverted Microscope
• Sterile vessels
• Sterile cell culture media (e.g. Eagle’s minimal essential medium (EMEM or MEM) and Roswell Park Memorial Institute (RPMI) medium 1640
• Sterile Single-Use Disposable Consumables (e.g. pipettes)

Aseptic Technique and Prevention of Contamination

Microbial contamination is one of the major issues in cell culture. Strict employment of aseptic techniques can significantly mitigate the probability of microbial contamination in the laboratory:

• Good personal hygiene
• Wash your thoroughly hands before entering the laboratory. This can remove a lot of dead skin particles which are potential sources of contamination
• Wear dedicated personal protective equipment. The wearing of disposable head caps and face masks are also recommended by some
• Regularly disinfect worn gloves
• Frequently disinfect all work surfaces
• Disinfect incubators and baths often
• Make sure that the laminar flow hood is functioning properly prior to use
• Any material that is placed in the laminar flow hood must be disinfected before being placed in the hood
• Only open media bottles and reagent bottles when in a sterile field
• Cap bottles that are not in use and avoid leaving them open for long periods of time
• Avoid clutter in the cell culture hood as this could disrupt the air flow of the laminar flow hood
• Only use sterilised or sterile tools in the laminar flow hood
• Clean up any spills immediately and disinfect the area with your disinfectant solution
• Avoid the continuous use of antibiotics as this could give rise to bacteria with antimicrobial resistance!
• Frequently screen for mycoplasma contamination

Recommendations on how to minimise the risk of contamination in the cell culture laboratory are also detailed on these following websites:

• ThermoFisher Scientific
• Sigma Aldrich

Cell Culture Assays

Several assays exist for the evaluation of cell viability, angiogenesis, cell adhesion, hypoxia and many more. Examples of cell culture assays include:

• Trypan Blue Staining Assay: An assay based on the exclusion of a cell membrane-impermeable dye (trypan blue). This dye only enters cells with compromised membranes where within the cell, the dye binds to intracellular proteins, giving the cells with compromised cells a blue colour.
• MTT Assay: A colourimetric assay for the evaluation of cell metabolic activity. This is based on the reduction of the MTT dye (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), which is yellow, to purple formazan dye molecules in metabolically active cells.