Scientists have coaxed human embryonic stem cells to become spinal motor neurons.

With healthy cells grown in the lab, scientists could, in theory, replace dying motor neurons to restore function and alleviate the symptoms of disease or injury.

The researchers deduced that there is only a thin sliver of time – roughly the third and fourth week of human development – in which stem cells could be successfully prodded to transform themselves into spinal motor neurons.

It was also critical to expose the growing stem cells to an array of complex chemical cocktails.

They found that human stem cells do not necessarily differentiate in linear fashion, as scientists always believed. Rather, a series of complex overlapping changes may well be the developmental norm in higher vertebrates such as humans.

University of Wisconsin-Madison news release