Cells are the basic structural and functional unit of life. Cells from all organisms including multicellular organisms can perform all physiological functions independently. Therefore, cells can be maintained under artificial environment if the right condition is provided.
Cell culture can be defined as a process of maintaining cells under the artificially controlled environment in a culture dish, outside their natural environment. This definition can be applied to any organism including prokaryotes, as well as unicellular and multicellular eukaryotes. However, in practice, the term cell culture is used for cells from multicellular organisms, especially multicellular animals. Specific terminology, like bacterial culture (maintaining bacteria in the controlled laboratory environment), yeast culture (maintaining yeast in the controlled laboratory environment), plant culture are used frequently to denote other types of culture.
Cells in culture behave as an independent unit like unicellular organisms and perform all necessary functions including cell division and metabolism in the culture dish.
Classically, the term ‘Tissue culture’ was used to grow plant and animal explant in a controlled artificial environment in the laboratory. The term ‘Animal tissue culture’ refers to cell culture derived from multicellular animals whereas ‘Plant tissue culture’ refers to the culture of plant cells/tissues.
Culture condition must maintain cell’s characteristics as it possesses in its natural environment. Practically, it is very difficult, in part, due to limited knowledge of physiological requirements of specific cell type. However, many different cell types have been maintained in culture and are in use in both basic and applied research. One such example is a successful maintenance of stem cells (embryonic and adult stem cells) in culture.
Cell culture can be classified on the basis of cell’s characteristics including growth mode, lifespan, morphology and cell types.
Based on growth mode of cells, culture can be broadly classified into two types – suspension culture and adherent culture. Semi-adherent culture, which contains loosely adherent cells to the dish surface, also exist.
Based on cell morphology in the culture dish, cell culture can be broadly classified into three types – Fibroblast-like, Epithelial-like, and Lymphoid-like.
Cell culture is not static. Cells in culture acquire changes which can be genetically programmed (e.g., senescence in primary culture) or due to the accumulation of genetic abnormalities (mutations, gain or loss of whole chromosomes or part of chromosomes). Furthermore, in response to fluctuations in culture condition, cells in culture can show altered behavior due to changes in gene expression pattern which sometimes lead to permanent changes in cell behavior (e.g., stem cells can differentiate).
Cell culture technology has found wide application both in basic research and applied research including industry (pharmaceuticals, medical sciences, cancer research, diagnostics, drug and product development, manufacturing of biological compounds, etc.)