Testing whether the human embryonic stem cells are pluripotent by:
- Allowing the cells to differentiate spontaneously in cell culture
- Manipulating the cells so they will differentiate to form cells characteristics of the three germ layers
- Injecting the cells into a mouse with a suppressed immune system to test for the formation of benign tumour called a teratoma. Since the mouse’s immune system is suppressed, the injected human stem cells are not rejected by the mouse immune system and scientists can observe growth and differentiation of the human stem cells. Teratomas typically contain a mixture of many differentiated or partly differentiated cell types-an indication that the embryonic stem cells are capable of differentiating into multiple cell types.