US researchers said on Saturday they had transformed immature cells
from men’s testicles into powerful stem cells, which they then coaxed
into becoming nerve, heart and bone cells.

Their work has not
been assessed by standard peer-review processes, but was presented at a
meeting of stem cell researchers in Valencia, Spain. If other
researchers can duplicate their efforts, the study offers a possible
new source of valuable stem cells.

The researchers, at Irvine,
California-based PrimeGen Biotech LLC, worked with immature cells found
in testes and ovaries known as germ cells. Scientists have hoped to use
germ cells as a source of tissues for transplant and other medical uses.

The
findings are certain to be scrutinized before they are accepted.
Earlier this year, South Korean researcher Hwang Woo-Suk was disgraced
for having faked two studies in which he claimed to have cloned human
volunteers and used the resulting embryos as a source of embryonic stem
cells.

Last week, Gerd Hasenfuss of Georg-August-University in
Goettingen, Germany and colleagues reported in the journal Nature that
they had transformed mouse germ cells into stem cells.

Francisco
Silva and colleagues said they had accomplished the same thing, and
taken it several steps further by doing the same thing with human germ
cells.

"Germ cells isolated from adult human testis can be
therapeutically reprogrammed to have the ability to differentiate into
cells that can be used therapeutically for cell-based regenerative
medicine," they wrote for a presentation at the meeting in Spain.

"We’ve
already been able to reproducibly differentiate heart, brain, bone and
cartilage cells, and we are excited to begin testing how these cells
incorporate into tissues," Silva said in a statement.

By Maggie Fox
Reuters.com