Fundamentals and Techniques Used in Cell Culture

Cell culture - The processes by which cells are maintained in a growth culture medium, using careful control of the media composition (essential nutrients, various growth factors, O₂ and CO₂ gas concentrations, pH and temperature). To replicate the conditions within the living organism as closely as possible. Cells may be either free in solution, such as continuous culture, or may adhere to the surface of the container typically as a cell monolayer (single layer of cells).

Cell confluence - a measure of coverage of a cell monolayer i.e. 100% would mean the full area within the culture container is covered by the cells. This affects the activity of the cells and gene expression. Immortal cells lines however are not bound by such restrictions as contact inhibition and will form multiple layers.

Passaging – This is the process, also known as sub-culturing, by which cells are introduced to a new growth container. This may need to be done, for example at defined intervals to maintain reproducibility of results, because of cell confluence.

Transfection – Transfecting cells is the process by which DNA of interest can be introduced into the cells by a variety of methods, via plasmids, chemically or via electrophoresis or other means.

Transduction - introducing DNA into a cell by use of a suitable virus as a vector to transport the desired sequence into the target cell.

Transformation- broadly speaking, transformation covers transfection and transduction, but for animal cells this term is specifically used to describe cells progressing, or transforming, into cancerous cells.

Cell morphology- cells can be classified according to their morphology: fibroblasts, epithelial, lymphoblasts and other specialised cells like neuronal cells.

Contamination- good laboratory practices and aseptic techniques are an essential part of cell culture studies. Bacteria, mycoplasma, yeasts, viruses and indeed even other cell types may readily affect cell cultures and influence their behaviour. Antibiotics (or antimycotics) should be avoided if at all possible, but may need to be added for some applications such as production of live attenuated virus vaccines.

Cell line - a population of cells that are derived from a single defined cell with the same genetic composition. Normal cell lines are cells that have been derived from an organism and will continue to divide a finite number of times before becoming senescent; this is known as Hayflick’s limit. An immortal cell line is derived from a “cancerous” cell so will continue to divide indefinitely when suitable conditions are present. Stem cells can also divide indefinitely as a normal function within complex multicellular organisms. In contrast, immortalized cell lines are cells that have gained mutations that allow them to ignore normal cellular control to continue cell division. The mutations may either be intentionally engineered or may have happened naturally by chance.

Cell strain – this is a subpopulation of a cell line that has been selected for a particular trait.

Cryopreservation – cells can be prepared in an appropriate medium for storage via freezing and thawed at a later time.

Sources of cell lines - are kept in the general collections such as the ATCC and ECACC General Cell Collections, as well as other commercial companies. Many cell lines are available on request by contacting the lab that isolated and characterised that specific cell line. When obtaining cells from other labs contamination is always a consideration to be aware of.