Where do they get stem cells?

Problem of the immune system Immune system recognizes/destroys “non-self” Organ transplants: human tissue, but still non- self –Rejection Stem cell implants –Same problem (magnified?)

Problem of the immune system A couple possible solutions: –Immune-suppressing drugs (lifetime) Increase risk of infection –Genetic compatibility: Immune system sees “self” Relative or matched stranger Your own cells

Sources of stem cells Embryonic: IVF Adult Embryonic: SCNT –Somatic cell nuclear transfer Umbilical cord blood Embryonic germ cells Parthenogenesis (virgin birth) Baby teeth

In vitro fertilization Egg is fertilized by sperm outside of the woman

Retrieval of eggs Stimulate release of plenty of eggs from the ovaries –“The Pill” for a couple months, then hormones to induce release Extract ova through a long needle –Guided by ultrasound Need sedation/anaesthesia

Fertilization Mix sperm/ovum: let them do their thing Intracytoplasmic sperm injection (ICSI)

Transfer the blastocyst Reproductive IVF Transfer 1-5 embryos –Fertilize ~10-20 eggs? Remainder are frozen –Initial tries unsuccessful –Want another baby/babies later

Most ES cells from reproductive IVF…left- over embryos What about production solely for research purposes?

Development of an ES cell line Dissociate the inner cell mass Transfer to a plastic dish Medium: liquid containing nutrients, vitamins, etc. –“Feeder” cells Subculture as needed

Blastocyst Day 5 Prof. Nakatsuji Institute for Frontier Medical Sciences Kyoto, Japan Colonies of hES cells On mouse cell feeder layer ES cells

Multiple cell lines Behave differently in research –Potency –Response to factors –Overall health Will behave differently in application –Recipient’s immune system More cell lines essential for versatility Very little support for Bush’s funding policy

Adult stem cells Isolate naturally-occurring stem cells –Usually multipotent –Maybe some pluripotent?

Drawbacks –Not as plentiful, difficult to find –Not as versatile…partially differentiated –Don’t last as long in culture –Patient’s own cells: genetic defect?

Adult stem cells Benefits: –Easier to work with –Longer time under study –Partially differentiated…on their way? –Patient’s own cells: no immune system rejection Main (?) advantage –“Nobody” argues ethics

Somatic cell nuclear transfer Creation of ‘embryonic’ stem cells from adult genetic material –Cloning: embryo is genetically identical to adult Why? –Agriculture –Custom ES cells: no chance of rejection THERAPEUTIC CLONING –Custom humans? REPRODUCTIVE CLONING

Somatic cell nuclear transfer Somatic cells: just about any cell you choose Nucleus: contains genetic material… source of identity Transfer: Nucleus from a somatic cell inserted into an ‘empty’ egg

Egg: remove its genetic material Add nucleus from a somatic cell Just like a fertilized egg! Blastocyst Harvest ES cells OR Implant

Has it been done? Animals: yes (Dolly (sheep), mice, pigs, etc.) –Source of nucleus for Dolly: mammary cell Humans: once claimed –Hwang Woo-Suk (South Korea) Turned out he basically made the whole thing up Legal in US (according to Federal law) –Several companies are working on it

Technical problems Animals: –Common problems in utero and as adults Higher loss of embryo/fetus Placental abnormalities Fetus tends to be larger Heart/Lung difficulties Altered development following birth

Technical problems Humans: –Just hasn’t happened (not for lack of trying) –Genetic/developmental complexity? –Extrapolate from animal studies: Major problems with whole organisms? Major problems with cells? Major problems with repaired tissues?

Questions Is cloning OK ethically? –Reproductive –Therapeutic/Research “Playing God?” Other issues –Human/animal hybrids Human nucleus/animal (sheep/primate) egg –Is it (will it ever be) worth it? Dolly: 277 tries, three embryos, one live birth