Winter 2004

Altered Nuclear Transfer as an Alternative Way to Human Embryonic Stem Cells: Biological and Moral Notes

Roberto Colombo

“The product of ANT is not a biological entity devoid of a complete human genome, but a developing organism with its full human genome, i.e., a human organism, a human being."

1. So-called “Altered Nuclear Transfer” (ANT) is a cytologicalembryological procedure aimed at producing human embryonic stem cells by transfer into an enucleated oocyte (ooplast) of a somatic cell nucleus (caryoplast) that has been genetically silenced for one or more genes that are essential for normal early embryonic development. In one version of the proposal currently on the table—a version that typifies the conceptual approach underlying the proposal as such—after nuclear transfer (NT), activation of the recipient oocyte would start cell division (segmentation) as in conventional NT cloning. However, segregation of the trophectoderm cell line from the inner cell mass at the beginning of blastocyst formation (three to four days) would be prevented by the lack of expression of the silenced genes. Therefore, a “true human blastocyst” would not be observed under the microscope. Instead, only a cell mass—resembling teratomas or the so-called “embryoid bodies”—is expected to develop from the cell division process. From these pluripotent cells endowed with the nuclear genome of the nucleus donor, human embryonic stem cell lines could be obtained and cultured as from blastocysts.

2. According to the proponents of ANT, this laboratory procedure does not intentionally produce a human embryo for the sole purpose of destroying it at the blastocyst stage of development to obtain human embryonic stem cells. The argument for this statement is as follows. As with any human being at any stage of development, the presence of a human embryo requires the presence of a human organism. A human organism is a biological entity that is either a developed human being or is capable of developing into a mature human being. The very early stages of human development (following fertilization or NT) are considered to be those of a human organism, i.e., a human being, only if they will develop into a blastocyst, an implanted embryo, a fetus, and a newborn baby. ANT is devised to intentionally prevent an ooplast from becoming a blastocyst even after NT and activation, but not from the cell division and compaction processes that are the normal prelude to blastocyst formation. Following this meta-biological premise, the proponents of ANT declare that this procedure should be morally admissible since it neither intentionally produces a human embryo by NT nor destroys it at the blastocyst stage to harvest human embryonic stem cells.


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