Stem Cell Expansion
Human ES cells are generated by transferring cells from a pre-implantation stage embryo into culture medium in a plastic laboratory culture dish, usually coated with a feeder layer of mouse embryonic skin cells. The feeder layer provides a means of attachment for the ES cells and releases nutrients into the culture medium.
Researchers have devised ways to grow ES cells without feeder cells, reducing the risk of hazards, such as viral infection. The process of generating an ES cell line is somewhat inefficient. However, if the plated cells survive, divide, and multiply enough to cover the surface of the culture dish, they can be removed gently and expanded in several fresh culture dishes. ES cells can be regarded as a cell line when they have proliferated in cell culture for a prolonged period of time without differentiating, and have remained pluripotent.
Growth and Differentiation
As long as ES cells are grown under appropriate conditions, they can remain undifferentiated. Growing ES cells in less than optimal conditions may lead to, for example, cell clumping or the formation of embryoid bodies, and they may differentiate spontaneously. Although spontaneous differentiation is a good indication that a culture of ES cells is healthy, it is not desirable if they are to serve as a source of a specific cell type.
In order to generate specific cell types, ES cell differentiation must be controlled. This may be achieved in a number of ways, such as changing the chemical composition of the culture medium, altering the surface of the culture dish, or modifying the cells by the insertion of specific genes.
In contrast, adult stem cells have a limited capacity to divide and their low frequency in normal tissues make the generation of large quantities a challenge. GE Healthcare offers a range of cell culture products for culturing ES cells and increasing the yield of adult-derived stem cells following extraction.