NEW YORK, Feb 25 (Reuters Health) -- Scientists have discovered a key
component of the sperm development process, and the finding may one day lead to
treatments that reverse some types of male infertility, according to a new study
in mice.
Normally, cells in the testicle called stem cells undergo a process known
as
spermatogenesis and mature into sperm cells. The new study suggests that this
process
is regulated by a molecule called GDNF (glial cell line-derived neurotrophic
factor), according to a report in the February 25th issue of Science. GDNF is
produced by another type of cell found in the testicle, the Sertoli cell.
"This paper shows that GDNF is the signal" that induces stem cells to
turn into sperm cells, said senior investigator Dr. Hannu Sariola, a professor
of biology at the Viikki Biocenter in Helsinki, Finland.
The study showed that when mice were genetically engineered to have low
levels of GDNF, they didn't produce any stem cells -- and thus could not produce
sperm. When the mice had high levels of GDNF, they produced stem cells, but
these only turned into the
precursors to sperm, not sperm cells themselves. In that case, the mice were
infertile.
"Many cases of male infertility are caused by lack of stem cells," said
Sariola. "It is
theoretically possible that...GDNF could be used in certain cases of male
infertility."
GDNF could be injected into infertile men, but he noted that "this is
speculation, we have only shown it in mice."
Sariola also cautioned that any such treatment could be only "very
short-term," because some of the mice developed testicular tumors after
receiving GDNF. "These tumors make any long-term treatment completely
impossible," Sariola said. However, "the tumors appear in very old mice...we
didn't see a single one in adult mice...so I don't think any short-term
treatment would have a serious risk of cancer," he said.
