Stem Cells in the Public Eye

After several days, colonies of tightly packed, undifferentiated cells arise. Scale bar = 100 microns

If cultures become dense, differentiated cells appear after several weeks, including neurons. Scale bar = 200 microns

The use of human pluripotential stem cell lines is controversial because they are derived from fertilized human eggs, and for some people human life begins at fertilization. Theoretically, then, the use of somatic cell nuclear transfer to generate autologous pluripotential stem cells should be less controversial. This technique would involve injecting the nucleus from a patient's adult cell into an unfertilized egg from which the nucleus has been removed. In the laboratory, this egg would then grow into a blastocyst from which researchers could derive pluripotential stem cell lines. Apparently, the researchers from Monash University have recently achieved this technical tour de force with mouse cells. The scientists created one embryonic stem cell line after injecting almost a thousand eggs with nuclei from genetically marked cells. There seems to be no reason why this "therapeutic cloning" would not work with humans if it could be made more efficient.

This method for making stem cells might be ethically more acceptable to some people since the recipient eggs lack nuclei and are unfertilized. Thus the creation of a unique combination of genetic material from two people never occurs. Moreover, embryonic stem cells are not embryos, since by themselves they are unable to give rise to a complete fetus. Nevertheless, it is still theoretically possible to clone a human by implanting the blastocysts derived by somatic nuclear transfer into a woman's uterus, rather than using them to make stem cells. Any attempt to do this is contrary to all existing guidelines and violates some state laws. Moreover, such an action would require extensive collusion among many irresponsible people and would be ethically indefensible, given the likelihood that if a baby were to develop it would be malformed.

Nevertheless, these arguments are irrelevant to some detractors, who believe that nuclear transfer into an enucleated egg still brings into existence for research purposes only a human being who is subsequently killed. A great deal more public debate, based on mutual respect for strongly held beliefs, probably lies ahead before federal funds can be used to explore the potential of human pluripotential stem cells, both for therapeutic purposes and for basic knowledge.

It can be argued that this dialogue is, in itself, a good thing, since it stimulates public interest in biology and reproduction, subjects not always effectively taught in schools. (Cloning frogs does not capture the attention of high school students as vividly as does the possibility of cloning themselves, and the still farfetched idea of regenerating human limbs can lead to discussions about how embryonic limbs are patterned and which genes make arms different from legs.)

No matter what, the underlying assumption is that research on stem cells will indeed lead to substantial new therapies. Therefore scientists must be very careful not to overstate the case, and to avoid at all costs the kind of hype that surrounded gene therapy and led to a loss of public confidence. This mindfulness is of particular importance in relation to the use of human pluripotential stem cells. As we have seen, for some members of the public deriving these cells equates with destroying human life. The truth is that there are many hurdles to overcome before we know how useful stem cell therapies will be. We must be honest as we move forward to assess their potential.

1 • 2 • 3 • 4