Degenerative conditions of the brain are generally considered incurable, including Alzheimer’s and Parkinsons disease. There have been limited attempts at curing neuronal degeneration, specifically in Parkinson’s, using embryonic stem cell implantation, notably in humans by Curt Freed of the University of Colorado Health Sciences Center, and in mice by Ron McKay of the US National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. The procedure is highly controversial due to the requirement for tissues from human embryos, each treament requiring approximately two individual foetuses. Therapeutic cloning of reprogrammed cells has been proposed as a more ethical acceptable alternative, but there have been no reports of a successful demonstration of this. Additionally, allogeneic cell therapy requires immune system suppression to allow the grafts to survive.
Lorenz Studer of the Sloan-Kettering Institute in New York, however, has successfully lead an international collaboration in implanting autologous skin cells that were reprogrammed into neurons and expanded in vitro, consequently restoring normal brain function in mice that were expressing degeneration similar to Parkinson’s disease. This is the first time that brain degeneration has been cured with therapeutic cloning. It is too early to predict if the same concept can be applied in humans.
In order to perform the research Lorenz Studer had to develop a method of imitating Parkinson’s disease, as the condition doesn’t occur naturally in mice. To do this, they administered drugs which killed the dopamine-producing brain cells.
Embryonic stem cells were produced from skin cells of the mice tails in Wakayama’s labs in Kobe, Japan. This was done using the standard procedure for mammalian cloning, where the donor cell nucei are implanted in eggs fron which the chromosomes have been removed, and embryos created from whcih embryoinic cells can be extracted. These were then differentiated into dopamine-secreting neurons. The advantage, compared to previous experiments, is that no immune suppression is required as the donor and recipient cells are genetically identical.
The form of cloning described in Studer’s experiments has not been achieved in humans, but would, in any case require a supply of human eggs. However, of more scientific and technical interest would be the application of Yamanaka’s techniques of fibroblastic genetic reprogramming, where terminally differentiated cells can be reprogrammed into embryonic-like cells. Much technical work is required before this could be applied in humans, but is promising enough to have many labs abandoning research on pure embryonic stems cells, including the Roslin Institute, who were first to clone a mammal.
Nick Rhodes
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