The boundaries of the cloning saga have shifted yet again as new discoveries - and failures - cast doubt on whether human cloning is actually possible. Scientists seem reluctant to abandon trying to develop some way of successfully cloning humans, but have been moving away from the cell nuclear replacement (CNR) method used to create Dolly the sheep. Evidence suggests that cloning processes may damage cellular material in ways we don't yet understand, raising questions about the use of cloning technology as a therapeutic tool.
Is cloning really possible?
A study involving pigs has demonstrated that cloned litters vary in the same way as sexually produced litters, demonstrating differences in looks, behaviour and even blood chemistry.[1] It is thought that this may be due to environmental variations such as position in utero as well as genetic errors introduced during the cloning process. These findings suggest that it may be impossible to create truly identical clones, but they are not likely to impact the use of cloning and stem cells for therapeutic purposes.
Cloning for stem cells is more likely to be affected by the continuing failure to clone primates. Several research groups, including Massachusetts-based biotech company Advanced Cell Technology, have repeatedly tried to clone monkeys but cannot get the embryos to develop beyond day seven. The embryos appear normal, but on closer inspection they lack distinct nuclei.[2] The eggs lose a critical protein during the cloning process that is needed for spindle function, and without it the chromosomes are scattered throughout the cells.[3] The same is thought to be true for human cells. Gerald Schatten, leader of the research team at the University of Pittsburgh School of Medicine in Pennsylvania, said, 'It's almost as if God in her wisdom said, "go ahead and clone cows and sheep, but if you clone a human I'm going to paralyse the egg."'
Schatten is determined to find a way of overcoming this obstacle, however, and is already investigating different techniques to bypass the problem. He added, 'I hope this natural obstacle affords us time to make responsible and enforceable legislation to prevent anyone attempting human reproductive cloning.' Claims by Clonaid, the company liked to the Raelian sect, to have created a clutch of cloned human babies remain as yet unfounded,[4] despite the release of a photograph showing a Japanese 'cloned' baby boy in an incubator.[5] The difficulty in cloning primates, teamed with Clonaid's failure to produce DNA evidence for their claims, fuels the conclusion that their report was little more than a publicity stunt.
The promise of stem cells
Stem cell therapy has been a driving force behind cloning research. Scientists may be against reproductive cloning, but want to develop the technology so that they can create cloned embryos and harvest embryonic stem cells (ESCs). These cells will be compatible with the specific patient undergoing treatment. The problems with reproductive cloning however indicate that ESCs may also have genetic and chromosomal aberrations - making them inappropriate for therapeutic use.
Stem cells derived from adult tissue (ASCs) are proving increasingly promising for treatment purposes, and reports of new developments are frequent.[6] Different cell lines vary in their properties. The Multipotent Adult Progenitor Cell can apparently give rise to all tissues in the body. Mesenchymal cells are more limited in their properties but produce little or no immune response, so cells from one person could technically be used to treat others.[7]
Another option: parthenogenesis
Literally meaning 'virgin birth', parthenogenesis is a natural process that enables invertebrates and some plants to reproduce asexually. Mammals cannot naturally reproduce this way but scientists have found that a mammalian oocyte can be coaxed into re-recruiting its polar body to become diploid again and continue with cell division as if fertilised.[8] The resulting parthenote will develop far enough to act as a source of ESCs, but is unable to develop fully as the duplication of maternal chromosomes is lethal beyond the eight cell stage.[9] For this reason, parthenotes are considered by some as an ethical source of stem cells on the basis that they can be harvested without the destruction of an embryo. This remains a point of contention however.
The Roslin Institute in Edinburgh has been granted a licence by the Human Fertilisation and Embryology Authority to employ parthenogenesis as a research tool.[10] They plan to create stem cell lines and use them to test new medicines. The stem cells will not, at this stage, be transplanted into human subjects.
More alternatives: gametes from stem cells
In May researchers described creating mouse oocytes directly from ESCs.[11] The technique may be applicable in humans and could provide an unlimited source of eggs for experimentation. Oocytes were produced from both female and male ESCs. Creating sperm from ESCs is more complicated; the cells automatically develop down the egg route unless specific signals promote sperm production. A team in Tokyo found that when germ cell ESCs were implanted into testicular tissue they formed apparently normal sperm.[12] The next stage will be to test whether the 'artificial' gametes can fuse with normal gametes to create embryos - success could present new parenting options for those unable to use traditional methods.
Chasing the wind?
A Christian may wonder at the motives of a society that seems so determined to be able to clone humans, even though there is no consensus that we should. The need for cloning is questionable in the face of promising ASC results and suspected genetic aberrations in cloned cells. Yet any barrier to 'progress' is perceived as a hurdle to overcome rather than a natural limit to our capabilities. We are, it seems, unable to accept any natural boundaries to our dominion over life.
One may also question the ethics of using our finite resources for such research when there are so many greater needs in the world. Furthermore, the research displays a complete lack of respect for the processes of embryonic life and the wonder of human development. Our bodies, and our babies it seems, are little more than loot to be plundered in our continual quest to recreate ourselves.
