Table 2.

Main differences and limitations for use of stem cells.

Limits of stem cells
Embryonic stem cells		Adult stem cells
In vitro fertilization	Nuclear transport	Production of a limited number of cell types. They are not found in all tissues. Difficulties in identification, isolation, preservation, and cultivation in the laboratory.
Limited number of cell lines for federally funded research needs. Risks for the creation of teratomas (tumors) from the transplantation of undifferentiated stem cells.	It has not yet been achieved in humans. Risks for the creation of teratomas (tumors) from the transplantation of undifferentiated stem cells.