The Raelian Movement
for those who are not afraid of the future : http://www.rael.org
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Which Fertilized Eggs Will Become Healthy Human Fetuses? Researchers
Predict With 93% Accuracy
http://www.sciencedaily.com/releases/2010/10/101003205930.htm
ScienceDaily (Oct. 4, 2010) — Two-thirds of all human embryos fail to
develop successfully. Now, in a new study, researchers at the Stanford
University School of Medicine have shown that they can predict with 93
percent certainty which fertilized eggs will make it to a critical
developmental milestone and which will stall and die. The findings are
important to the understanding of the fundamentals of human
development at the earliest stages, which have largely remained a
mystery despite the attention given to human embryonic stem cell
research.
Because the parameters measured by the researchers in this study occur
before any embryonic genes are expressed, the results indicate that
embryos are likely predestined for survival or death before even the
first cell division. Assessing these parameters in the clinic could
make it easier for in vitro fertilization specialists to select
embryos for transfer for a successful pregnancy.
"Until recently, we've had so little knowledge about the basic science
of our development," said the study's senior author Renee Reijo Pera,
PhD. "In addition to beginning to understand more about our
development, we're hopeful that our research will help improve
pregnancy rates arising from in vitro fertilization, while also
reducing the frequency of miscarriage and the need for the selective
reduction of multiple embryos."
Reijo Pera is a professor of obstetrics and gynecology at the medical
school and the director of the Center for Human Embryonic Stem Cell
Research and Education at Stanford's Institute for Stem Cell Biology
and Regenerative Medicine. The study will be published online Oct. 3
in Nature Biotechnology. Postdoctoral scholar Connie Wong, PhD, and
former postdoctoral scholar Kevin Loewke, PhD, are the co-first
authors of the research. Loewke is currently the lead engineer at the
Menlo Park, Calif., biotechnology company Auxogyn Inc.
The researchers conducted their studies on a unique set of 242 frozen,
one-cell human embryos from the Reproductive Medicine Center at the
University of Minnesota. The embryos were created at the in vitro
fertilization program at Lutheran General Hospital in Illinois over a
period of several years prior to 2002, and when the clinic was closed,
the patients gave their consent for their embryos to be used in
research.
Nowadays it's unusual to freeze embryos so soon after fertilization
(about 12 to 18 hours). Instead, clinicians monitor embryonic
development for three to five days in an attempt to identify those
that are more likely to result in healthy pregnancies after transfer.
Despite their best efforts, though, they have only about a 35 percent
success rate. As a result, most women elect to transfer two or more
embryos to increase the chance of a live birth. However, if multiple
embryos implant and develop successfully, a woman and her physician
may choose to selectively abort one or more to better the odds for the
remaining embryos.
Reijo Pera and her colleagues received a large grant from an anonymous
donor to investigate ways to better predict embryonic developmental
success within one or two days of fertilization. Not only would such
an advance decrease the likelihood of miscarriage or the possible need
for a selective reduction, it would also reduce the amount of time the
embryo would be have to be cultured in the laboratory before transfer.
(Although it's not been conclusively shown, some researchers are
concerned that genetic changes may accumulate in a cultured embryo and
cause subtle, long-lasting effects in the fetus.)
The researchers thawed the embryos, split them into four groups and
tracked their development during the first few days using time-lapse
video microscopy and computer software specially designed by Loewke, a
former Stanford mechanical engineering graduate student, for this
study. They followed the cells through the development of a hollow
ball called a blastocyst, which typically occurs within five to six
days after fertilization. A blastocyst is usually an indication of a
healthy embryo.
They found that of the 242 embryos, 100 were able within five or six
days to form normal-looking blastocysts -- about the same proportion
that would be expected to be successful in normal pregnancies. Because
they had tracked the embryos' development so closely, they were then
able to go back and identify three specific parameters collectively
associated with successful blastocyst formation: the duration of first
cytokinesis (the last step of a period in the cell cycle called
mitosis in which the cell physically divides), the time between first
and second mitoses, and the synchronicity of the second and third
mitoses. All of these events occur as the embryo progresses from one
cell to four cells within the first two days after fertilization.
"It completely surprised me that we could predict embryonic fate so
well and so early," said Reijo Pera. If an embryo's values fell within
certain windows of time for the three predictive parameters, that
embryo was more than 90 percent likely to go on to develop
successfully into a blastocyst.
When the researchers looked at the gene expression profiles of
individual cells from the embryos, they found that, as had been
previously shown, the embryos at first express only genes from the
maternally derived egg. By roughly the third day (the eight-cell
stage) they begin to express genes specific to embryonic development,
and the relative proportion of embryonic to egg genes increases
steadily during the next few cell divisions.
Surprisingly, however, they found that not all cells in an embryo are
behaving identically: While some cells may be expressing mostly
maternal genes, others in the same embryo are churning out mostly
embryonic genes.
Similarly, not all cells in an embryo are dividing in synchrony: The
researchers found embryos in which some cells were dividing on
schedule while others were seemingly stuck, or paused.
"We've always thought of embryos as living or dying, but in reality we
find that each cell in the embryo is making decisions autonomously,"
said Reijo Pera. "No one has ever looked at this before." She and her
colleagues found that embryos in which individual cells varied
significantly in their cell-division schedules or gene-expression
profiles were less likely to become successful blastocysts.
Together the research indicates that the maternal RNA transcripts --
that is, the molecules that carry instructions from the mother's DNA
to the embryo's protein-making factories -- must be actively degraded
in each cell of the embryo, and that this degradation is necessary for
the cells to begin to express embryonic genes. Cells that fail to
execute some part of this delicate process get out of sync with their
neighbors and jeopardize the life of the embryo. The whole endeavor is
complicated, and may explain why human embryonic development is so
precarious and unique.
The research also highlights the importance of studying human embryos,
which currently cannot be supported by federal funds. (Every year
since 1996, Congress has approved a provision known as the
Dicky-Wicker amendment that prohibits the use of federal funds for
research in which a human embryo is destroyed -- even ones that would
otherwise be discarded.)
"In mice, about 80 to 90 percent of embryos develop to the blastocyst
stage. In humans, it's about 30 percent," said Reijo Pera. "In
addition, about one in 100 mouse embryos are chromosomally abnormal,
versus about seven out of 10 human embryos. That's why human studies
like these are so important. Women, their families and their
physicians want to increase the chances of having one healthy baby and
avoid high-risk pregnancies, miscarriages or other adverse maternal
and fetal outcomes. It's truly a women's health issue that affects the
broader family."
The research was funded by an anonymous donor, the March of Dimes and
the Stanford Institute for Stem Cell Biology and Regenerative
Medicine.
The researchers have developed an automated algorithm for clinical use
that could assess these time-lapse microscopy videos and determine
with high accuracy which of these very early embryos would be
successful by the four-cell stage. That technology has been licensed
exclusively to Auxogyn Inc. by Stanford. Reijo Pera and the other
coauthors of the manuscript own or have the right to purchase stock in
the company.
Story Source:
The above story is reprinted (with editorial adaptations by
ScienceDaily staff) from materials provided by Stanford University
Medical Center, via EurekAlert!, a service of AAAS.
Journal Reference:
1. Connie C Wong, Kevin E Loewke, Nancy L Bossert, Barry Behr,
Christopher J De Jonge, Thomas M Baer & Renee A Reijo Pera.
Non-invasive imaging of human embryos before embryonic genome
activation predicts development to the blastocyst stage. Nature
Biotechnology, October 3, 2010 DOI: 10.1038/nbt.1686
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"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
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