Tissue Culture

TISSUE CULTURE IS a general term referring to the growth of cells, organs, tissue, or protoplast, either plant or animal, outside the original organism, giving rise to clones having the same genotype. The term tissue culture is usually used in context with animal tissue, whereas plant culture concerns botanical tissue. It also refers to the growth of tissue pieces (i.e., expiant culture or whole organs—thus organ culture).

The technique has found its application in both commercial and basic research areas and is looked on as an excellent alternative for the production of commercially important plants such as banana, sugarcane, teak, and rosewood to meet the requirements of the world's continuously growing population. In the direction of health and medicine, tis—sue-culturing techniques are contributing not only to the development of replacement therapies but also tissue cultures are being used to study various disorders related to sensitive tissues such as those of the brain, liver, and kidney; for example, in traumatic brain injury and renal cell cancer.

Alexis Carrel contributed the most to modern—day plant and animal culturing techniques. The technique follows the simple principle that stem cells will successfully proliferate outside the original organism if provided with optimum growth conditions and appropriate nutrition. Technological development has allowed the enhancement of the efficiency and feasibility of the practice by allowing gene modification using bacterial plas—mids or vectors and viral gene guns.

Animal and plant tissue culture techniques vary in several ways pertaining to the differences in the origins of the cell lines; the underlying principle, however, is the same. There are two types of cultures: primary cultures, which are derived from normal tissue, as expiants or monocell suspensions achieved using enzyme digestion, and can be maintained for only a limited period of time in vitro, and continuous cultures, which comprise a single cell type, which is successively replicated either indefinitely or for a limited time. The latter type of tissue culture is usually used to study cancerous tissue cells.

Morphologically, some cell cultures grow as single cells or clumps, and others grow as single adherent layers. Morphologically mixed populations containing both suspension and attached [Page 554]cultures are also observed. Normally, cell lines derived from fluids such as blood grow as single cells, and cells belonging to solid tissue grow as a monolayer. Isoenzyme analysis and DNA profiling are the two most reliable methods for cell identification and isolation.

Cell fractionation can be either highly specific or nonspecific and is carried out with nonspecific technique, based on the density and cell size, using Elutriator and effectively separating required cells. The highly specific technique is based on the propensity of specific cell surface markers or antigens to bind to specific antibody—coated magnetic beads, which are then separated by affinity column chromatography. The isolated cells are then stored or cryopreserved.