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Selecting sources of tissue for culture

  • Adult or embryonic tissue

Cultures can be derived from adult tissue or from embryonic tissue. Cultures derived from embryonic tissue generally survive and grow better than those taken from adult tissue. Tissues from almost all parts of the embryo are easy to culture, whereas tissues from adult are often difficult or even impossible to culture. This presumably reflects the lower level of specialization and presence of replicating precursor or stem cells in the embryo. Adult tissues will usually have a lower growth fraction and a high proportion of non-replicating specialized cells, often within a more structured, and less readily disaggregated, extracellular matrix. Initiation and propagation are more difficult, and the lifespan of the culture is often shorter.

Embryonic or fetal tissue has many practical advantages, but it must always be remembered that in some instances the cells will be different from adult cells and it cannot be assumed that they will mature into adult-type cells unless this can be confirmed by appropriate characterization.

Examples of widely used embryonic cell lines are the various 3T3 lines (mouse embryo fibroblasts) and MRC-5 and other human fetal lung fibroblasts. Mesodermally derived cells (fibroblasts, endothelium, myoblasts) are also easier to culture than epithelium, neurons or endocrine tissue but this may reflect the extensive use of fibroblast cultures during the early years of the development of culture media together with the response of mesodermally derived cells to mitogenic factors present in serum. A number of new selective media have now been designed for epithelial and other cell types and with some of these it has been shown that serum is inhibitory to growth and may promote differentiation.

  • Embryonic stem cells

A more recent development has been the removal of embryonic stem cells (ES-cells) from the embryo during the blastocyst stage of development. These cells can be grown in culture for many generations and are of particular interest because they can be mani- pulated in culture and then re-introduced into embryos.