In a feat of cellular alchemy, connective tissue from a mouse鈥檚 tail has been transformed directly into working brain cells.
Ordinarily, so drastic a makeover would require the creation of so-called induced pluripotent stem (iPS) cells and then turning these into neurons, an inefficient process that can take weeks.
and colleagues at Stanford University in California discovered that inserting a cocktail of three genes into fibroblasts turns them directly into neurons in just days. 鈥淭he real surprise was that this conversion is extremely efficient,鈥� he says.
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By many indications, these neurons are the real deal. Under a microscope, they look like a kind of mouse brain cell found in the cortex and they can form synapses to send and receive signals from others. Wernig expects that the cells will integrate into a mouse鈥檚 brain 鈥� an experiment that鈥檚 in the works.
If they do, cells produced using a similar process might one day be used to treat conditions such as Parkinson鈥檚 disease in humans.
No teratoma
Because such cells are derived from adult cells, not pluripotent cells 鈥� which have the potential to form a kind of tumour called a teratoma 鈥� they might be safer than iPS cells.
But first, Wernig must work out how to produce different kinds of neurons and show that the method is safe. 鈥淭hese are very early days,鈥� he says.
In the meantime, researchers could use the cells to study neurological and psychiatric disorders in Petri dishes. The new technique also offers the hope that other kinds of cells can live a second life. 鈥淚f we just know the right factors, we can turn any cell into any other cell we want,鈥� says Wernig.
Future for iPS
However, the new approach won鈥檛 make iPS cells obsolete, says , a cell biologist at the Scripps Research Institute in La Jolla, California, who was not involved in the study.
That鈥檚 because the new technique yields cells that have a lower, but not negligible, risk of forming tumours once implanted. But as with iPS cells destined for transplant, researchers will have to work out how to create neurons without using a virus to deliver the genes that reprogram the cells, as these viruses could also cause cancer.
鈥淓ventually you have to replace those genes with small molecules, with proteins, with whatever,鈥� says Ding, who is working on cellular reprogramming methods that use small molecules, rather than viruses.
Ding also questions whether the increased efficiency of direct reprogramming offers any tangible advantage. The induced neurons cannot divide, so you get what you put in, whereas iPS cells can multiply themselves indefinitely, he points out.
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