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Stem Cells: Myths, Facts, and Ethics
Xinyu Zhao PhD
Assistant Professor
UNM School of MedicineDepartment of Neuroscience
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The ethical hot spots of stem cell research
Human embryonic stem cells isolated from
blastocyst stage human embryos
Cloning by somatic nuclear transfer
Induced pluripotent stem cells derived fromhuman skin cells.
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Part I: The myths and facts of stem cell research
Part II: The ethics of stem cell research
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Definition of stem cells:
Self-renewal
Multi-potency
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Lineage restricted
Limited self-renewal
Totipotent
Totipotent
Totipotent
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Differences betweenembryonic stem cells and adult stem cells
They have different self-renewal capabilities Embryonic stem cells: near indefinite self-renewal
Adult stem cells: limited self-renewal
They have different differentiation potentials .Embryonic stem cells: differentiate into all cell types in an
organism
Adult stem cells: differentiate into restricted cells types.
They differ in how they respond to external stimuli Embryonic stem cells are readily to change upon stimulation
Adult cells emphasize on stability and need to be activated by
cues, e.g. injuries.
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PluripotentES cells
Source of ES cells
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Human ES cellsHuman blastocyst
Inner cell mass
Mouse fibroblasts feeder layer
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DifferentiationES cells
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Applications of Human pluripotent stem Cells
Basic Knowledge of Human Development
Models of Human Disease
Transplantation-Cell Replacement
Drug Development
Organogenesis
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Scientific Challenges of Using Human ES Cells:
Challenges to cell-replacement and organtransplantation therapies:
Lack of cell type specific differentiation
Possible tumor formation
Immune rejection by recipients
Challenges to ES cells as models for studying
human diseasesDo not know the genes responsible for the diseases
Can not create the mutations corresponding to human
diseases
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The ethical hot spots of stem cell research
Human embryonic stem cells isolated from
blastocyst stage human embryos
Cloning by somatic nuclear transfer
Induced pluripotent stem cells derived fromhuman skin cells.
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Somatic cell nuclear transfer (SCNT)
For establishing and studying models of
human diseases
For generating patient-specificcells/organs for transplantation and repair
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Therapeutic Cloning: Organogenesis
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Human ES Cells: Studying the Cellular and Molecular Mechanisms of DiseaseTherapeutic cloning: Studying Mechanisms of Diseases
Example: ALS
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D
B E
C F
A
Mark Denham & Richard Mollard
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Not This
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The ethical hot spots of stem cell research
Human embryonic stem cells isolated from
blastocyst stage human embryos
Cloning by somatic nuclear transfer
Induced pluripotent stem cells derived fromhuman skin cells.
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induced pluripotent cells (iPSC)A combination of several genes can re-program
skin fibroblasts into pluripotent cells
(Takahashi and Yamanaka Cell 2007, Yu Science 07, Cowan Science 07, Wernig Nature 07, Okita Nature 07)
Why iPSC can not replace ESC research:1) Studying ESCs is critical for understanding iPSCs
2) iPSCs are induced by cancer genes therefore hinder their
use for therapies
Reprogramming
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The ethical hot spots of stem cell research
Human embryonic stem cells isolated from
blastocyst stage human embryos
Cloning by somatic nuclear transfer
Induced pluripotent stem cells derived fromhuman skin cells.
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People in the US affected by diseases that may behelped by stem cell research
Condition Number of Persons AffectedCardiovascular diseases 58 MillionAutoimmune diseases 30 MillionDiabetes 16 Million
Osteoporosis 10 MillionCancer 8.2 MillionAlzheimer's disease 4 MillionParkinson's disease 1.5 MillionBurns (severe) 0.3 Million
Spinal cord injuries 0.25 MillionBirth defects 150,000 (per year)Total 128.4 Million--------------------------------------------------------------------------------------Data from the Patients' Coalition for Urgent Research, Washington,
DC (according to Perry, Ref. 267).
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The 1st ethical hot spot of stem cell research
Human embryonic stem cells isolated fromblastocyst stage human embryos
In the case of embryonic stem cellresearch, the end that scientists hope to
achieve is the relief of human suffering.
That this is a humanitarian and worthy end
is not in dispute. The controversy is aboutthe means, namely, the consumption of
donated embryos. -- ISSCR website on stem cell ethics
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Cloning by somatic nuclear transfer
International Guideline for Stem Cell Research (by
ISSCR Stem Cell Ethics Committee):
Reproductive cloning is prohibited!!!
The 2nd ethical hot spot of stem cell research
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The 3rd ethical hot spot of stem cell research
Induced pluripotent stem cells derived from
human skin cells.
Protection of human subjects
Informed consent
Protection of genetic identity.
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Other Related Ethical Issues
Ethical issues in human clinical trialsInformed consent of patients
Protection of human subjects.
Protection of human genetic and cellular materials
Creating human/animal hybrid stem cells
Ethical issues in animal research.
Honest and integrity in biomedical research
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How can scientists ensure ethical conductin stem cell research
Education for researchers Routine emphasis by principle investigators
Emphasis by funding agencies
Classes and seminars
Education for the public Understand the importance of research
Understand that scientists are under ethical guidance
Communication and open dialogue Understand each others opinion
Reach a rationale common ground.
Last step: Legal reinforcement
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Useful Resources
National Institute of Health resource for stemcells (http://stemcells.nih.gov)
International Society for Stem Cell Research:Guidelines for the Conduct of Human Embryonic Stem CellResearch (www.isscr.org)
National Academy of Science: Guidelines forhuman embryonic stem cell research(http://www.nap.edu/openbook.php?isbn=0309096537)
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On March 9, 2009, President Obama issued
Executive Order 13505, entitled
"Removing Barriers to Responsible
Research Involving Human Stem Cells."
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Thank you !