Different Sources of Stem Cells National Academy of Sciences Embryonic Stem Cells Embryonic Stem Cells (Therapeutic Cloning) Adult Stem Cells AttributesIn Vitro Fertilization Can produce any cell type (totipotent) Easy to identify, isolate, maintain and grow in lab Large source of Excess” blastocysts from IVF clinics Nuclear Transfer Can produce all cell types (totipotent) Relatively easy to identify, isolate, maintain and grow in lab Stem cells may be genetically matched to patient Adult Tissues Demostrated success in some treatments Stem cells may be genetically matched to patient

Different Sources of Stem Cells Embryonic Stem Cells Embryonic Stem Cells (Therapeutic Cloning) Adult Stem Cells LimitationsIn Vitro Fertilization Limited number of cell lines available for federally funded research Risk of creating tumors from implanting undifferentiated stem cells Nuclear Transfer Not yet achieved with human cells Risk of creating tumors from implanting undifferentiated stem cells Adult Tissues Produce limited number of cell types (multipotent) Not found in all tissues Difficult to identify, isolate, maintain, and grow in the lab

Different Sources of Stem Cells Embryonic Stem Cells Adult Stem Cells Ethical ConcernsIn Vitro Fertilization Destruction of human blastocysts Donation of blastocysts requires informed consent Nuclear Transfer (Therapeutic cloning) Destruction of human blastocysts Donation of eggs requires informed consent Concern about misaplication for reproductive cloning Adult Tissues No major ethical concerns have been raised