09 Feb Human cloning plans get blessing from British government
First Dolly, now human embryos.
This week’s announcement out of King’s College London that Professor Ian Wilmut, who cloned Dolly the sheep, has been granted a license by the British government to clone human embryos is sure to spark fresh hopes among disease sufferers, scientists and advocacy groups for a cure to such diseases as Parkinson’s and amyotrophic lateral sclerosis (ALS).
These diseases could be addressed through research on stem cells, which Wilmut will be extracting from the embryos and growing into motor neurons.
But the scientific community “has a long, long way to go in terms of motor neuron disease,” said Su-Chun Zhang, the UW-Madison researcher whose team recently was the first to coax embryonic stem cells to become motor neurons.
Wilmut and Paul de Sousa of Scotland’s Roslin Institute, with King’s College London researcher Christopher Shaw, have been granted a license by the Human Fertilisation and Embryology Authority to generate stem-cell lines to study motor neuron disease (MND). The team plans to clone embryos to generate stem cells that will in turn become motor neurons with MND-causing gene defects. By turning the cells into neurons, the team hopes to discover what causes the cells to degenerate.
To generate stem cells in the laboratory, Wilmut’s team will grow skin or blood cells from people who have an inherited form of MND of unknown genetic cause, a King’s College release said. They will then remove the genetic information from an unfertilized egg and replace it with the nucleus of a cell from a familial MND patient. Eggs that have successfully received the nucleus containing the MND-causing gene defect will be encouraged to grow up to the 200-cell stage. The embryonic stem cells will be removed, grown and directed to become motor neurons using a cocktail of growth factors.
One early hope for stem cell research was the potential for developing tissues for transplantation that would not be rejected by the recipient’s body, and any use of therapeutically cloned embryos for stem cells used to that end is reasonable, Zhang said.
But Zhang warned that that there are “scientific questions [as to] whether motor neuron disease is caused only by defects in motor neuron cells,” and that problems in other cells also may be responsible for degeneration.
“I’m not sure about motor neuron disease, in particular. There are a lot of questions surrounding this particular disease,” Zhang noted. “For motor neuron disease, I actually have some reservations about that.”
On the positive side, Zhang believes that using stem cells transplantation of tissue to stave off rejection by the body is a very reasonable use of therapeutic cloning.
Shaw contends that the project “is potentially a big step forward for MND research. We have spent 20 years looking for genes that cause MND, and to date we have come up with just one gene. We believe that the use of cell nuclear replacement will greatly advance our understanding of why motor neurons degenerate in this disease, without having to first hunt down he gene defect.”
Zhang noted that one difficulty in targeting motor neuron diseases is that once a patient is diagnosed, it takes “quite a bit of time” to establish a line of stem cells, differentiate them into motor neurons and then put them back into the spinal cord of a patient.
“At this point, we have not even figured out if cells put into the brain or spinal cord will survive,” let alone if they can travel to the affected muscle tissue and reattach, Zhang said.
“Motor neurons are especially tough,” he added. “This disease progresses so fast.”
To his critics, Wilmut maintains that his research in no way is intended to create fully developed human clones.
“This is not reproductive cloning in any way,” said Wilmut. “The eggs we use will not be allowed to grow beyond 14 days. Once the stem cells are removed for cell culture the remaining cells will be destroyed. The embryonic stem cells that we derive in this way will only be used for research into motor neuron disease.”
Zhang said he believes the pertinent laws in the UK are reasonable but urged caution all the same.
“I think we have to set up some very stringent guidelines on how to work on these therapeutically cloned stem cells,” Zhang said. “The cloning of human beings absolutely should be banned.”