Fast-Freeze May Help Sperm Survive Storage, Study
TUESDAY, Sept. 14 (HealthDay News) -- Researchers say they have
developed a new and better method of freezing human sperm for later
use in pregnancy attempts.
The new technique could potentially improve in vitro
fertilization treatment and perhaps make it possible for
HIV-positive men to donate sperm safely, the researchers say.
The freezing approach used in the study is already used for
embryos and eggs, "and this is the next step, so it is logical,"
said Dr. Ian Cooke, emeritus professor of obstetrics and gynecology
at the University of Sheffield in England, who is familiar with the
"Any improvements in sperm freezing would be welcome," said Mathew Tomlinson, a fertility specialist and scientist at Nottingham University Hospitals in England.
"We can store sperm for many years, but only 25 to 30 percent of sperm survive from even the best samples," said Tomlinson.
Among cancer patients who want their sperm stored before they
undergo chemotherapy, as little as 5 percent of sperm may survive,
When study lead author Raul Sanchez of La Frontera University in
Chile and colleagues tested their alternative freezing approach,
known as vitrification, they found that almost 80 percent of sperm
remained viable after thawing.
In the traditional approach, sperm is frozen slowly and stored
in liquid nitrogen. Vitrification involves removing the plasma in
sperm, suspending the sperm in a sucrose solution and fast-freezing
it in liquid nitrogen. It is then stored in liquid nitrogen or
another kind of deep freeze.
This process results in greater sperm vitality and motility, and
is less damaging to sperm, the researchers explained in a news
release from the International Federation of Fertility
Because the sperm plasma -- potentially home to the virus that
causes AIDS -- is extracted, the researchers think their approach
may also allow HIV-positive men to donate sperm without passing on
the illness to a mother or baby.
But Dr. Robert D. Oates, professor of urology at Boston
University School of Medicine, said he's skeptical of the
researchers' claims. The findings don't "translate directly into
anything related to whether this allows better pregnancy rates," he
Moreover, the research doesn't prove that the freezing approach
leaves the sperm free of disease, he added. "This is a technique
that may have an application," Oates said, "but their claims are
The findings are scheduled for presentation Tuesday at the World
Congress on Fertility and Sterility in Munich, Germany.
The U.S. National Library of Medicine has details on
semen analysis, which measures the quality of sperm.
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