1 / 56

The Brave New World of Cloning and Stem Cells

The Brave New World of Cloning and Stem Cells. Daniel P. Sulmasy, OFM, MD, PhD Department of Medicine & Divinity School The University of Chicago. Back to High School: Developmental Biology. Zygote. Morula 3d. Blastocyst 5 d. Implantation 6-7 d. 14 d Embryo. 21 d Embryo.

Download Presentation

The Brave New World of Cloning and Stem Cells

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Brave New World of Cloning and Stem Cells Daniel P. Sulmasy, OFM, MD, PhD Department of Medicine & Divinity School The University of Chicago

  2. Back to High School:Developmental Biology Zygote Morula 3d Blastocyst 5 d Implantation 6-7 d 14 d Embryo 21 d Embryo 28 d Embryo 8 weeks -- Fetus

  3. In Vitro Fertilization • Egg retrieval • Sperm collection • Fertilization “in glass” • Maturation to embryo stage • Embryo transfer • Inefficiency • Pregnancy “reduction” • “Spare” embryos

  4. In Vitro Fertilization Zygote Morula 3d Blastocyst 5 d

  5. As cells divide and the embryo grows • Chemical changes in DNA • Genes turned on and off • “Telomeres” and aging

  6. Three basic kinds of cells (layers of the embryo) • Ectoderm: • skin, brain nerves • Endoderm: • gut, digestive organs • Mesoderm: • muscle, bone, blood

  7. Development continues in adults: cells “turn over” • Blood cells last 120 days • Skin cells • Lining of the gut

  8. Some tissues do not regenerate naturally • Brain and spinal cord • Heart muscle

  9. Stem Cells • “Rookie” cells • Good young players • Can become shortstop, third baseman, or outfielder • Not yet “committed” • Can be “trained”

  10. Development and regeneration depend on stem cells! • Embryo • Regenerating tissues • e.g. blood “juvenile” cells Red cell Red stem cell Platelet Platelet stem cell Lymphocyte Hematopoetic stem cell Monocyte White stem cell Polymorphoncuclear white cell

  11. “Plasticity” of stem cells • “Totipotent” – can develop into any kind of cell, even a new individual organism (i.e., a twin) • “Pluripotent” – can develop into a variety of tissue types • “Committed” – can develop only into one tissue type

  12. Stem Cells • Embryonic – “totipotent” • Adult – “pluripotent” • A misnomer • Umbilical cord blood • Bone marrow • Brain • Other tissues

  13. “Somatic cell nuclear transfer” Even less efficient than IVF Developmental problems Process Cloning Egg + Somatic Cell Clonal zygote

  14. “Reproductive” vs. “Non-Reproductive” • Begs the question – • Assumes that making embryos is not reproduction unless gestated • But a major point of contention is whether or not making a human embryo is reproducing a human being • So…..

  15. “Research cloning” vs. “Cloning to bring babies to birth” Awkward but Accurate

  16. Why Cloning? • To bring babies to birth • Total infertility • Gays and lesbians • “Reproductive freedom” • Research • Run out of spare embryos for stem cells • Immuno-compatible stem cells or fetal tissue • Pure basic research

  17. Scientific problems with cloning • Not yet done in human beings (?) • Hwang was a fraud • Poor success rate in other animals • 1 in 277 for Wilmut to make Dolly • Not enough animal experiments • Genetic abnormalities: “old wine in new wineskins” • Premature aging

  18. Moral problems with cloning to bring babies to birth • “Offense to Human Dignity” • Blurs the line between natural kind & artifact • Role problems: my twin or my son? • Begetting vs. manufacture • Threat to human freedom

  19. Banning only cloning to make babies won’t work: • Once research cloning is allowed, cloning to bring babies to birth will follow • All it takes is implantation, as in IVF • Once in the freezer, how tell if cloned?

  20. Why Stem Cells? • Not all body parts repair themselves • Repair of injury due to myocardial infarction and stroke • Degenerative diseases (e.g. diabetes; Parkinson’s) • Immune rejection

  21. Possible sources of stem cells • “Adult” stem cells (e.g. blood stem cells for chemotherapy) • Umbilical cord blood (e.g. Krabbe or Hinter-Hurler) • Amniotic fluid • Fetal tissue (e.g. Parkinson) • “Spare” embryos • Cloned embryos

  22. Moral issues • Stem cells per se are not problematic • Everyone wants to help treat disabling human conditions • No one is seriously opposed to all stem cell research and therapy • Moral status of the human embryo • Practically speaking, the clinical use of embryonic stem cells entails cloning

  23. Basic objection to embryonic stem cells • Develop (or create de novo) a new human being for the express purpose of killing that human being in order to extract cells • Violates the Kantian principle that every human being is an end in him/herself and ought never be treated as a means only

  24. Major counter-arguments • Before 14 days twinning can occur. Therefore there really isn’t an individual person before that time. • Embryo is so small you can’t see it without a microscope. How could that be a person? • IVF embryos will die anyway. Why not make the best of a bad job? • If we can help people, then not using stem cells will kill even more people. • What will all those people with so-called principles do once it has been proven that embryonic stem cells can cure people.

  25. Twinning • Since it can twin, isn’t an individual • Reply: • One ameba  two amebas • If a legitimate argument, then internally contradictory: • none of us would be persons, since we could also potentially be twinned through cloning

  26. Size shouldn’t matter • As cogent as teenage boys in a locker room • Societal prejudice against the small • Growth hormone • Dr. Seuss – Horton Hears a Who • “A person’s a person no matter how small”

  27. Against Orin Hatch • “Embryo wastage” – many will die anyway • Reply: • Infant mortality in developing nations • Death row • Jack Kevorkian

  28. Leftover IVF embryos • There aren’t enough! • 400,000 in U.S. • Not all are viable • Need informed consent (< 3%) • Won’t “match” recipients

  29. “If we don’t pursue stem cells we’re killing all the people who could be cured using them” • Confuses the basic distinction between killing and allowing to die • All the money we’re spending on all stem cell research could provide clean water in the developing world • Ignores the fundamental principle that the end ought not justify the means • Philippa Foot – serum for five

  30. What will become of their principles? • If the moral basis for public policy is that people will abandon their principles whenever it is in their self-interest, then there is no moral basis for public policy.

  31. Problems with embryonic stem cells • “First do no harm” • Numerous genetic abnormalities in clones • Potentially harmful to a recipient of stem cells derived from clones • Embryonic stem cells tend to form tumors -- teratomas

  32. Slippery slope: • Eugenics • Egg donors: • 17 million US diabetics (type 1 + type 2) • 250 eggs per stem cell line (if as easy as sheep) • 4.2 billion eggs for all US diabetics • Where will these eggs come from?

  33. Moral status of the embryo: what’s in the dish? • Property? • Commodification and human dignity • Just a tiny bit of “tissue,” not a person • Further than Roe v. Wade • No “privacy” argument • Individual member of the human natural kind in the initial stages of development

  34. • Only natural kinds have intrinsic value• Artifacts always have attributed value

  35. Intrinsic Human Dignity • The value we have by virtue of being the kind of thing that we are – i.e. – a human being • The foundation of all human rights • The basis for all interpersonal morality

  36. What’s at stake, then? • The fundamental basis of human morality

  37. A phase sortal is not a kind sortal… zygote  embryo  fetus  neonate  infant  toddler  child  adolescent  young adult  middle-aged  older adult  very old

  38. What’s in the dish? • An individual member of the human natural kind at the earliest stages of development

  39. The intrinsic value of the kind of thing that is in the dish: • Whatever is in the dish is the same kind of thing, whether it is to be brought to birth or disaggregated for its stem cells • Therefore it must have the same intrinsic value regardless of the purposes for which it is used

  40. Dignity and Embryonic Stem Cells • Troubling because obtaining these cells by the destruction of embryos tends to blur the distinction between an artifact and a natural kind • To the extent that human beings are created de novo, especially for the benefit of others, they tend to be considered artifacts and this explains our worries about dignity • Explains “begetting vs. manufacture”

  41. Is the disaggregation of a cloned human embryo compatible with respect? • To clone a human embryo (or create through IVF) with the premeditated plan of taking it apart, killing it, and using its parts, even for a noble cause, cannot conceivably be considered ‘respectful’

  42. Alternatives: • Hematologic stem cells  malignancy • Stem cells in brain, liver, elsewhere • Umbilical cord stem cells  sickle cell, Krabbe, Hurler’s • Bone marrow  heart cells • Amniotic fluid • Biochemically “de-differentiating” adult stem cells (iPS cells)

  43. Alternatives • Adult stem cells • Induced pluripotent stem cells (iPS cells)

  44. Adult stem cells • Proven successes • Problem of de-differentiation • Problem of immortalization

  45. iPS cells: “de-differentiating Embryonic Ectodermal Cutaneous Dermal stem cell Dermal skin cell Totipotent Pluripotent Committed

  46. iPS cells • First accomplished in humans 2 years ago • “Toggling” no more than 4 genes with transcription factors (Oct3/4; Sox2 critical) • Appear to be immortalized • Can be “re-differentiated” into retinal cells, heart muscle cells • The problem of viral vectors • Has been overcome in mice (valproic acid) • Still, all the problems of embryonic stem cells (e.g. tumors) if pushed back to the embryonic stage

More Related