Human Cloning - More Than a Few Grand Challenges

Human cloning remains confined to the realm of science fiction. The science that needs to be done to make reproductive cloning a reality hasn't progressed much further than the starting gate. Sheep, African wildcats, mice, and frogs have all been cloned successfully. Many of these cloned animals have given birth to live and healthy progeny. So far, cloning works for many species. But work on primate cloning has barely begun, and primate cloning needs to be achievable and reproducible before human cloning is attempted.

Many concerns exist relating to the health of the gestating mother-to-be. The human uterus is designed to gestate an embryo that was created by the process of sexual reproduction. Yet the uterus has substantial adaptability, as demonstrated by the ability of many women to successfully gestate an embryo to which they have no genetic link. But surrogate mothers gestate embryos that were created by fertilizing an egg with sperm, an artificial process which simulates sexual reproduction. Cloning is asexual and cloned embryos differ from standard embryos in numerous critical respects.

Several animal species have demonstrated successful uterine adaptability to cloned embryos. Interspecies gestation has been successful, too - domestic cats have given birth to healthy African wildcats with no apparent harm to the mother. Also, interspecies embryos have been created and successfully implanted in uteruses of a third species. For example, in 2002 researchers in China reported that nuclei from adult cells of the giant panda could be joined with enuculeated rabbit eggs, and the resulting interspecies construct could be successfully implanted into the uterus of the domestic cat.

The human uterus might be sufficiently adaptable to accept a human cloned embryo. But this hypothesis can only be tested by using human volunteers. One potential threat derives from the fact that the cloned embryo's DNA has been reprogrammed by a process drastically different from that used in sexual reproduction. The number of chromosomes to be reprogrammed (46 versus 23) is different, the amount of time for reprogramming is substantially shortened, and the egg cytoplasm has been manipulated in various ways to enable the process of development to begin. The implications for the interactions between the host uterus and the implanted cloned embryo are completely unknown. Therefore the first set of volunteers would be putting their lives at risk.

At present there exists a ban on U.S. federal funding for research on human cloning. Thus, it's not possible to learn how to successfully create human cloned embryos (HCE). Embryological development of HCE cannot be studied. Potential abnormalities in development cannot be evaluated, analyzed, and possibly avoided. The way forward to human cloning is blocked at present. If private industry undertakes this research, the health of female volunteers will be put in grave jeopardy.

David Lemberg, M.S. in Bioethics, Albany Medical College, May 2010
Consultant, Author, Speaker. Research interests - health care and health care policy, reproductive technologies, genetics and genomics, K-12 science education
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