Replicating Stem Cells in a Lab
An embryo that has developed for three to five days is called a blastocyst. A blastocyst is a mass of about 100 or so cells.
 Photo courtesy Michael Vernon, West Virginia University Blastocyst |
The stem cells are the inner cells of the blastocyst. They will ultimately develop into every cell, tissue and organ in the body.
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Scientists remove stem cells from the blastocyst and culture them (grow them in a nutrient-rich solution) in a Petri dish in the laboratory. After the cells have replicated several times and are becoming too numerous for the culture dish, they are removed and placed into several other dishes. In just a few months, several stem cells can become millions of stem cells. Embryonic stem cells that have been cultured for several months without differentiating are referred to as a stem cell line. Cell lines can be frozen and shared between laboratories.
 Photo courtesy University of Wisconsin Board of Regents Microscopic 5x view of a colony of undifferentiated human embryonic stem cells: The embryonic stem cell colonies are the rounded, dense masses of cells. The flat, elongated cells are fibroblasts used as "feeder cells." |
Adult stem cells are much harder for scientists to work with because they are more difficult to extract and culture than their embryonic counterparts. Stem cells not only are hard to find in adult tissue, but scientists also have difficulty getting them to replicate in the laboratory.
But even embryonic stem cells, which can be grown effectively in the lab, are not easy to control. Scientists are still struggling to get them to grow into specific tissue types.
