Cell culture is a technique to isolate and culture cells of interest in laboratories. The term cell generally refers to mammalian cells, although the principles apply to prokaryotes and other eukaryotic cells.
In cell cultures, animal cells are isolated from tissue sections and cultured in optimal conditions, including temperature, pH, and carbon dioxide to oxygen ratio. They feed on nutrients and growth factors in the culture medium.
To learn more about the medium components and their roles, visit our article on culture media preparation!
Primary cells are individualized cells from tissue sections that have been dissociated or digested by enzymes.[2-4]
Non-cancerous primary cells are typically slow-growing. When they proliferate to 80% confluency, primary cells are subcultured or passaged so they can continue to divide. Most primary cells are finite – they can divide after being subcultured to a certain generation before senescence. In contrast, cancerous primary cells can be indefinitely subcultured.[1-3]
Primary cells are regarded as the closest representation of the originating tissue. Initially, their genetic and phenotypic identities are heterogeneous because the cell composition in tissue sections is mixed. Hence, primary cells’ identities can change after every passage. However, primary cell identities can become more homozygous if one cell type dominates the other in its growth and proliferation rates.[1-2]
Secondary cells are primary cells that have been passaged and cultured in a fresh medium several times.
Oftentimes, secondary cells are immortal. They can be cultured indefinitely when nutrients and fresh medium are regularly provided. Compared to primary cells, they are fast-growing and have more homogeneous genotypic identities that are consistent over generations. However, secondary cells tend to differentiate into aberrant cells when grown for a prolonged period.
Secondary cells are easier to handle than primary cells. They are typically cultured to produce a population of cells with similar identities for viral, immunology, and toxicology tests.[2]
Cell lines are cells from an aggregated or monolayer of primary cells that have been passaged at least once.
The cell lines’ genotypic and phenotypic identities are derived from their sourced primary cells. Their identities are more homogeneous because cell aggregate and monolayer typically represent a group of cells with similar identities.[1-2]
Cell lines are the go-to cells in research and development, while primary cells are for confirmation studies. Examples of commercially available cell lines are human epithelial cell lines from cervical cancer cells (HeLa) and hamster ovary cell lines (CHO).[3]
Cell culture enables users to multiply specific cells for tissue regeneration or to obtain cellular products such as genetically engineered proteins and attenuated vaccines.
In addition, cell culture can be adapted into a testing or investigative platform. For example, the in vitro evaluation of candidate compounds is performed in the relevant cell culture before animal studies and clinical trials.
It screens for the compound toxicity and the target cells’ response to the candidate compounds, allowing researchers to select only promising ones for further testing. Similarly, cell culture can be used to model and demonstrate the hypothesized gene function, cancer, hereditary or viral disease pathology, and pathogenesis.[1]
Aseptic and biosafety practices are keys to running a safe and efficient cell culture laboratory. Aseptic practices keep the cell culture sterile and prevent contaminations from workers and the working areas. Biosafety practices create a safe environment by reducing threats during exposure to cell cultures, which can be infectious.[1-2]
Most cell culture works are performed in laboratories with at least biosafety level-2 (BSL-2), where access to the working area is restricted to trained personnel. It is sufficient for non-contagious cell lines but not for works involving primary cells. Most lab works involving primary cells are handled in a BSL-3 or BSL-4 laboratories, depending on the potential risks, availability of relevant therapies, and vaccines.[1]
To learn more about biosafety principles and the meaning of each biosafety level, read our article on biosafety in microbiology laboratories.
Aside from equipment for biosafety and aseptic practices, cell culture laboratories also require the following equipment:
In addition, cell culture laboratories also need general equipment for life science laboratories such as microcentrifuges, laboratory refrigerators, freezers, etc.
Most consumables in cell culture laboratories are generic, except for some that come in contact with the cell culture. The plastic consumables and glassware are used and handled like those found in most life science laboratories.[1]
For instance:[1]
Cell culture is a technique that isolates and cultivates animal cells in laboratories. It requires specialized equipment such as class II cabinets, CO2 incubators, and inverted microscopes. The crucial part of running and maintaining cell culture laboratories are aseptic and biosafety practices, which prevent contamination and create a safe working environment for workers.
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