Definition of Embryo Death Criteria may Open Doors for Stem Cell Research
News Jun 06, 2006
A research team from Columbia has identified criteria through which embryo death can be confirmed.
The implications for stem cell research are huge - by confirmation of embryo death, embryos could be harvested, just as organs are for transplantation, in order to generate stem cells for research and, ultimately, therapeutic purposes.
The team report their findings in a special report entitled Hypocellularity and absence of compaction as criteria for embryonic death published in the journal Regenerative Medicine, published by Future Medicine.
Donald Landry, Professor of Medicine at Columbia University and Director of the Division of Experimental Therapeutics, and his colleagues analyzed de-identified records of the observations of human embryos in culture retrospectively.
The embryos had been generated by in vitro fertilization for the purpose of reproduction.
Cell number and morphology were recorded on embryonic days 2, 3, 5, and 6. Viable embryos (n = 248) were compared to nonviable embryos (n = 444) and the latter were analyzed in subgroups defined by cell number and morphology.
They found that many nonviable embryos (n = 142 out of 444) were hypocellular and lacked compaction on embryonic day 5 (ED5).
All of the hypocellular embryos failed to progress to compacted morula or normal blastocyst when observed further.
The research team conclude that arrested development at the multicellular stage on ED5 indicates an irreversible loss of integrated organic function, and hence, the condition of death.
Certain groups oppose embryonic stem cell research chiefly because it requires the destruction of human embryos.
In the USA, federal funding has been limited because these ethical considerations surrounding the destruction of human embryos involved in such research.
Approximately a fifth of all embryos generated for in vitro fertilization - conventionally classified as ‘nonviable’ - are in fact dead on ED5 by Landry’s criteria.
A precise definition of death is essential for the harvesting of tissues for transplantation to proceed.
For developed humans, life is considered to end when the criteria for brain death are met, but corresponding criteria are lacking for human embryos.
The researchers propose that the ethical framework currently used for obtaining essential organs from deceased persons for transplantation could be applied to the harvesting of live cells from dead human embryos for the creation of stem cells.
Dr Landry published a seminal paper with Dr. Howard Zucker, a co-author on the Regenerative Medicine paper, entitled Embryonic Death and the Creation of Human Embryonic Stem Cells in the Journal of Clinical Investigation.
This work advanced a proposal to harvest live embryonic cells from IVF embryos that have died in spite of best efforts.
That proposal also featured in the President’s Council on Bioethics White Paper of May 2005.
Landry asserts that the new natural history study published in Regenerative Medicine provides criteria for declaring embryos dead so that live cells can be harvested from dead embryos.
Zebrafish, in contrast to humans, have outstanding regenerative capacities: and can regrow brain cells from so-called progenitor cells. Scientists have now determined that these progenitor cells consist of eight different sub-populations. In a fish model of Alzheimer’s disease, only some of these populations increased proliferation to restore lost cells.READ MORE