An introduction to Tissue Culture
Tissue culture typically refers to the growth of cells derived from a living organism, kept viable outside of the organism’s body. Tissue culture could possibly be the hallmark of in vitro studies. The cells obtained from the donor are generally immersed in a suitable growth medium. This medium is generally liquid saline containing essential vitamins, hormones and growth factors that provide the cells nutrition. Tissue culture is often used interchangeably with the term “cell culture”, although tissue culture more correctly incorporates fragments of tissue excised from parts of plants or animals into an artificial medium. Modern tissue culture techniques have an important role in research- both clinical and conventional. Having a means of observing live tissue cells allows us to see the effect of various components on tissue morphology and the other reactions they elicit. Tissue cultures can also be manipulated and tinkered around with using the right fit of hormones and inducers to get a certain desirable product. Additionally, tissue cultures can be used as an alternate means to live animals, eliminating the ethical conflicts that often arise out of a medical study. Animal cell cultures also have very important application in the cultivation of viruses- so that they can be studied. Tissue culture has two obvious sub types: Animal Tissue Culture and Plant Tissue culture. These two are separate entities because not only do plant and animal cells have different morphologies and requirement, but they differ in one important aspect: plant cells are pluripotent, meaning in very basic terms that an excised tissue or a single cell from a fully developed plant can give rise to the whole plant or different types of cells. In the case of animal cells, only stem cells show this kind of regenerative and differentiative power. Stem cell isolation elicits a whole new factor- they can most readily be obtained from embryos as embryonic stem cells or as adult stem cells. So, generally speaking, Plant tissue culture is simpler in the context of acquiring pluripotent cells. Primary Cell Cultures, Secondary Cell cultures and cell lines This part acknowledges certain terms common to animal and plant tissue culture techniques. Again, the term “cell culture” is used interchangeably with “tissue culture”. This is a generalised schematic; the finer techniques may be defined by the requirements of a particular type of cell culture. Subculturing is an important step in generating a stable cell line- a culture consisting of cells with a uniform physical and genetic makeup. During subculturing, an explant, that is the excised plant or animal tissue is subjected to disaggregation. So, the individual cells of the tissue are separated; care is taken not to lyse or destroy the cells. These cells are then counted and introduced into a suitable medium, i.e. they undergo inoculation. This step is usually accompanied by trypsinization- the treatment administered to dissociate cells from the wall of the flask they’re in and from each other. Successful inoculation gives rise to a primary culture. This is generally stored in a confluent flask. Primary cell cultures are passaged to give secondary cell cultures. Subculturing ensures that we have a stock of viable cells for a longer period and also favours uniformity of the cell culture. Secondary cell cultures can further be passaged to give different divisions-called cell lines. Plant tissue cultures are very commonly used to produce clones of plants with desirable properties. This method quickly produces mature plants, eliminating the need of seeds altogether. Regeneration of whole plants from plant cells that have been genetically modified gives rise to many possibilities, like being able to reproduce particularly good flowers or fruits. Animal tissue culture has proved invaluable in cancer cell research. The study to cell to cell interactions, monoclonal antibodies, vaccines and recombinant proteins are just a few applications of animal tissue culture.