Scientists who study human embryonic stem cells have not yet agreed on a standard battery of tests that measure the cells’ fundamental properties. However, laboratories that grow human embryonic stem cell lines use several kinds of tests, including:
- Growing and subculturing stem cells for many months. This ensures that the cells are capable of long-term growth and self-renewal. Scientists inspect the cultures through a microscope to see that the cells look healthy and remain undifferentiated,
- Using specific techniques to determine the presence of transcription factors that are typically produced by undifferentiated cells. Two of the most important transcription factors are Nanog and Oct4. Transcription factors helps turn genes on and off at the right time, which is an important of cell differentiation and embryonic development. In this case, both Oct4 and Nanog are associated with maintaining the stem cells in an undifferentiated state, capable of self-renewal.
- Using specific techniques to determine the presence of particular cell surface markers that are typically produced by undifferentiated cells.
- Examining the chromosomes under a microscope. This is a method to assess whether the chromosomes are damaged or if the number of chromosomes has changed. It does not detect genetic mutations in the cells.
- Determining whether the cells can be re-grown, or subcultured, after freezing, thawing and re-plating