Japanese scientists have succeeded in creating peripheral nerve cells from the embryonic stem cells of a mouse and a monkey, an achievement that could open the way to treatments for certain difficult neural diseases.

The scientists, led by Prof. Yoshiki Sasai of Kyoto University, also succeeded in cultivating motor neurons from the ES cells of a monkey.

The report was published Tuesday in the electronic edition of the Proceedings of the National Academy of Sciences of the United States.

It was previously known that early exposure of ES cells to BMP4, a protein found in an embryo that later develops into a brain and a spinal cord, promotes change in skin cells.

The scientists at Kyoto University, Osaka University and the Institute of Physical and Chemical Research, known as Riken, discovered that late BMP4 exposure, conducted after a fourth day of coculture, caused change in peripheral neural cells.

High concentrations of BMP4 transformed the ES cells into an autonomic system, and low concentrations changed the cells into sensory tissues.

The scientists also reported that upon ES cells' exposure to another type of protein called Sonic hedgehog (Shh), ES cells were transformed into motor neurons.

The findings could "serve as a system to bridge a gap between knowledge of neural development and application in regenerative medicine of the nervous system," the scientists said in their report. Eventually, it is hoped, the findings could lead to treatments for such diseases as congenital megacolon and amyotrophic lateral sclerosis.