What is an embryonic stem cell line?
A stem cell line is a population of cells derived from a single embryo that can replicate themselves for long periods of time in vitro, meaning out of the body. These cell lines are grown in incubators with specialized nutrient and growth factor-containing media, at body temperature. Embryonic stem cell lines, both human and mouse, can be grown indefinitely in vitro if the correct conditions are met. Importantly, these cells continue to retain their ability to form different, specialized cell types once they are removed from the special conditions that keep them in an undifferentiated, or unspecialized, state. A very limited number of human embryonic stem cell lines have been approved for use by scientists receiving federal funds in the United States. In August 2001, President George W. Bush mandated that if scientists were using federal funds, research could only be conducted on the cell lines that were already in existence, grown from fertilized eggs that were to be discarded at in v
