X-Message-Number: 30902
Date: Wed, 30 Jul 2008 20:25:59 -0700 (PDT)
From: 
Subject: Mouse Sperm Cryopreservation Breakthrough

[IMHO, a similar improvement in vitrification solutions could very
well make whole organ cryopreservation a reality.]

Scientists Announce Mouse Sperm Cryopreservation Breakthrough

ScienceDaily (July 30, 2008) - A team of Jackson Laboratory scientists have
figured out a simple, cost-effective process to freeze mouse sperm and get
it to achieve high fertilization rates with mouse eggs. The breakthrough
will greatly reduce the cost of developing and distributing new mouse models
of human disease.

Freezing sperm is an efficient, cost-effective way to conserve and
distribute genetics in the agricultural industry and putting male sex cells
on ice is a fundamental part of human fertility programs. But the sperm of
certain varieties of mice under-achieve woefully after being frozen and
thawed. What's worse: the thawed sperm of the most popular mouse strain in
the scientific world, the C57BL/6 or "Black 6", are known to under-perform
when it comes to fertilizing mouse eggs.
Drs. Michael Wiles and Chuck Ostermeier in Jackson's Technology Evaluation
and Development group, and Dr. Robert Taft and Ms. Jane Farley in the
Reproductive Sciences group, have published a paper on the new technique in
the open-access journal PLoS ONE, where it can be freely accessed online.
The technology has already attracted interest from international academic
and pharmaceutical laboratories.
The Jackson team reports that their technique consistently yields
fertilization rates of about 70 percent - a six-fold increase over previous
mouse sperm freezing techniques. The results were achieved by collecting the
sperm into a cocktail of raffinose (a plant-based sugar complex), skim milk
and the antioxidant monothioglycerol. The sperm suspension is loaded into
narrow plastic straws about the size of a swizzle stick, and then slowly
cooled before storage in liquid nitrogen.
When frozen sperm are needed for fertilization, they are thawed and
incubated in in vitro fertilization media for an hour before adding oocyte
cumulus masses (clusters of egg cells).
Dr. Wiles noted, "The world research community is making literally thousands
of new mouse models," using stem cells to introduce specific genetic
variations that mimic the mutations identified in human diseases. "The
problem is that it costs about $10,000 a year to maintain a particular mouse
strain, and worldwide only a few hundred strains are in actual laboratory
experiments at any given time."
Since the 1970s, the Laboratory has addressed this problem by
cryopreserving - freezing and storing - mouse embryos from little-used
strains, which allows the live mice from those strains to be safely removed
from the mouse room. However, freezing embryos is far less efficient and
cost-effective than freezing sperm. "If you freeze 250 embryos," Dr. Wiles
said, "you can only count on about 125 live pups. But a single male mouse
can produce millions of sperm, which can give rise to 100s or even 1,000s of
offspring. Thus, making sperm cryopreservation work has long been a goal of
ours."

Journal reference:
Ostermeier GC, Wiles MV, Farley JS, Taft RA. Conserving, Distributing and
Managing Genetically Modified Mouse Lines by Sperm Cryopreservation. PLoS
ONE, 2008; 3 (7): e2792 DOI: 10.1371/journal.pone.0002792


Full text>
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002792

Snip from full text>
"CryoProtective Medium [CPM - 18% w/v raffinose (Sigma Aldrich; cat #
R7630); 3% w/v skim milk (BD Diagnostics; cat # 232100);
477 mM monothioglycerol (Sigma cat # M6145); water (Invitrogen,
cat # 15230-238"

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