Researchers are banking on the fact that people looking for cures will be hunky-dory with treatments that are part human, part animal. They're called chimeras, and things get pretty messy.
Let's start with the easy one, and then move on to the messy one.
At least three British teams are hoping to begin work on cloning later this year using animal eggs. The need of human donor eggs for cloning, given their scarcity, would make personalized stem-cell therapies prohibitively expensive.
All three U.K. teams aim to get around that bottleneck by taking DNA from patients sick with a disease like Alzheimer's and fuse it with cow eggs that have had all their genetic material removed.
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After about five days of growth, the cloned embryos would be destroyed and the stem cells extracted. The stem cells would be grown in their labs and the researchers could look for the onset of diseases, study their development and test experimental drugs on the cells.
"You can model Alzheimer's disease or Parkinson's disease in a dish," said Stephen Minger, director of the Stem Cell Laboratory at King's College in London.
Modeling diseases would be useful, but getting the cloning to actually work may prove troublesome. Joseph Cibelli, former VP of Advanced Cell Therapeutics, failed in an attempt to create a cow-human chimera using his DNA and a cow egg during the Clinton administration. Based on his experience, he doubts the cow-human cloning attempts will succeed.
Moving on, Esmail Zanjani, a University of Nevada researcher, has created chimeras by injecting human bone marrow stem cells into a developing sheep fetus. Approximatel/y 15% of the fully grown sheep's body was made of human cells.
While this option is interesting, it seems to share one major hurdle with cloning: it will be cost prohibitive.
Fear will probably be another, perhaps bigger, stumbling block.
Diacrin, the first and only company to attempt a clinical trial to treat chronic spinal cord injury thus far, transplanted fetal stem cells from pigs into six patients' spinal cords. The FDA worried that such inter-species transplants may bring with it certain risks – primarily the transfer of a virus that's harmless to pigs, but is either deadly to us or modifies the human germline – and required each trial participant to promise they would never have kids.
If this fear seems unwarranted, it would be helpful to look at simian immunodeficiency virus (SIV). SIV strains are usually safe for their natural hosts, but often deadly when introduced to another species. SIV is believed to have crossed over into humans, bringing us HIV.
The FDA may require patients getting the sheep-human chimera-based treatments to sign similar "I will not reproduce" agreements. The choice would then be between a potential cure and having kids.
The no-kids requirement would likely remain in place until the FDA has adequate data to believe that such transplants were free of risk. To ensure no changes in the germline occurred, the FDA may be able to study the sperm and eggs of transplant recipients to determine germline changes. If not, the no-kids requirement (which could only be realistically enforced by sterilization) would present a nasty Catch-22: without the ability to look for changes in the offspring of transplant recipients, the FDA would never be able to collect the data necessary to determine the transplant's safety.
For me, that would be a tough call. I want a cure, but I also want to have kids when I find someone crazy enough to marry me.
Thinking Outside the Egg, Scientists Propose Inner-species Cloning [The Age]
Now Scientists Create a Sheep That's 15% Human [Evening Standard]
