Title: Clinical and ethical issues in reproductive technology - Viewpoint from embryologist
1Clinical and ethical issues in reproductive
technology -Viewpoint from embryologist
scientist
- W.S.B. Yeung
- Department of Obstetrics and Gynaecology,
- University of Hong Kong
2First test tube baby
18 July 1978
3Ethical issues from IVF
- IVF
- Family structure, surrogacy
- Cryopreservation
- Posthumous baby
- Preimplantation genetic diagnosis
- Desinger baby
- Selection of embryos for HLA
4New reproductive technologies
- Human embryonic stem cells
- Somatic nuclear transfer
- patient-specific embryonic stem cells
- human-animals hybrid embryos
5Human embryonic stem cells
Cell replacement therapy
ES cells
Thomson et al., 1998 Science. 2821145-7
6Human embryonic stem cells
- Ethical issues
- Killing of embryos
- Creation of embryos
- Potential in regenerative medicine
- Source of embryos
- Supernumerary embryos (Hong Kong)
- Creation of embryos (Mainland China, United
Kingdom)
7Creation of embryos NOT for infertility treatment
- FIGO Committee for the Study of Ethical Aspects
of Human Reproduction and Womens Health - Allowed if data cannot be obtained using
supernumerary embryos - Nuclear reprogramming by oocytes
- Patient specific stem cells
- Women should not be unduly induced for donating
oocytes
8Embryonic stem cells without immunorejection is
required
- Embryonic stem cell lines with different HLA ?
immunorejection - Embryonic stem cells for cell therapy
- Production of stem cells with different HLA
- Somatic nuclear transfer
- Induced pluripotent stem cells
9Somatic nuclear transfer
Normal oocyte
277 nuclear transferred 29
implanted 1 live birth
Somatic cell
Enucleated oocyte
Cloning
10Cloning in reproductive medicine
- Natural cloning more often after assisted
reproduction (monozygotic twins) - Reproductive cloning is not allowed in most
countries - Therapeutic cloning
11Therapeutic cloning
No rejection
12Patient-specific embryonic stem cells
- Evidence of a Pluripotent Human Embryonic Stem
Cell Line Derived from a Cloned Blastocyst - Science (2004), 303 1669
Fabricated data Both papers were retracted
Patient-Specific Embryonic Stem Cells Derived
from Human SCNT Blastocysts Science. (2005)
3081777-83
13Therapeutic cloning
- Prohibitions in Hong Kong
- to bring about the creation of a human embryo
for the purpose of embryo research - to replace the nucleus of a cell of an embryo
with a nucleus taken from any other cell - to clone any embryo
14Treatment of cytoplasmic defectby somatic
nuclear transfer
Defective embryo
Nucleus
Normal oocyte
Enucleated oocyte
15Somatic nuclear transfer
- Low success rate, a high miscarriage rate, and
complications. - Research should continue as a tool for studying
- Nuclear-cytoplasmic interaction
- Nuclear reprogramming
- Genetic disorder
16Human-animal hybrid embryos
- Human oocytes are limited
- Animal oocytes readily available
- Interspecies embryos possible
- Cloning endangered gray wolves (Canis lupus)
from somatic cells collected postmortem. - Oh HJ et al. Theriogenology. 2008 Jun 3. Epub
ahead of print
17Embryonic stem cells generated by nuclear
transfer of human somatic nuclei into rabbit
oocytes
- Chen Y, He ZX, Liu A, et al
- Cell Research (2003) 13, 251263.
-
- The derived ntES cells are human based on
karyotype, . The ntES cells maintain the
capability of sustained growth in an
undifferentiated state, and form embryoid bodies,
which, on further induction, give rise to cell
types that express markers representative of
all three germ layers.
18Human-animal hybrid embryos
- No shortage of animal oocytes
- Provide experimental model on studying nuclear
reprogramming - Alternative source of patient-specific stem cells
- Hong Kong combine human and non-human gametes
or embryos or any part thereof such as to give
rise to a two-cell zygote for research is
prohibited
19Induced pluripotent stem cells
- Induction of pluripotent stem cells from mouse
embryonic and adult fibroblast cultures by
defined factors. - Takahashi K, Yamanaka S. (2006) Cell 126663-76.
- Repeated in human fibroblasts
- Takahashi et al. (2007) Cell 131861-72.
- Yu et al. (2007) Science 3181917-20.
Sciences Breakthrough of 2007
20Induced pluripotent stem cells
- Transfection of 4 transcriptional factors
- ? stem cell-like
- Treatment of Sickle Cell Anemia Mouse Model with
iPS Cells Generated from Autologous Skin - Hanna J, Wernig M, Markoulaki S, Sun CW,
Meissner A, Cassady JP, Beard C, Brambrink T, Wu
LC, Townes TM, Jaenisch R (2007) Science 318
1920-1923
21Induced pluripotent stem cells ? embryonic stem
cells
- global gene-expression patterns
- DNA methylation (Oct3/4 and Nanog, H19 and Igf2r)
- Tumor formation rate
Researches on embryonic stem cells need to be
continued
22Summary
- New reproductive techniques give rise to ethical
issues. - Ethics vs Benefit
- Prohibition vs Regulation
23Thank you