Sperm cryopreservation is a fast and cost-effective procedure, and it only requires a small number of males (1 to 3) for banking a mouse line. Mouse strains can be rapidly frozen down, and sperm cryopreserved from a single male can potentially give rise to large numbers of offspring following sperm resuscitation by in vitro fertilization (IVF) and embryo transfer procedures. The disadvantage of sperm cryo is that monoploid genome is preserved, and it is inappropriate if: 1) The total genome is of scientific interest; 2) The strains carry multiple transgenes or mutations; and 3) The strains have maternally inherited alterations.
We use R18S3+MTG as cryoprotective medium for sperm cryopreservation in cryovials (Ostermeier et al. 2008; Li et al. 2013). We assess sperm quality before freezing and provide pre-freezing sperm parameters including sperm concentration, sperm motility (total, rapid and progressive) and sperm morphology (% sperm with abnormal heads and tails).
For sperm cryopreservation, we prefer to receive 2-3 males between 10-20 weeks old. Males older than 20 weeks are acceptable as long as they are fertile and healthy. The fee for sperm cryopreservation includes the cryopreservation of two males and the storage of the cryopreserved materials for one year.
Our Murine IVF, Cryopreservation and Microinjection (MICM) laboratory routinely perform cryopreservation services, and have successfully cryoarchived and recovered numerous mouse lines on various backgrounds. As you may know, some genetically modified strains may have males with poor fertility. Sperm counts, motility and morphology are analyzed prior to cryopreservation and the sperm quality assessment is provided to you upon completion. A sperm test thaw to culture or to live pups may be requested to examine the recovery potential of the cryoarchived sperm. Both test thaw services will utilize wildtype female donors of the same background as your mouse line. Test thaw of one sperm vial to culture would allow us to assess the in vitro fertilization rate and blastocyst formation rate. A test thaw to live pups would allow for the embryos produced from IVF to be transferred into a female recipient in our conventional facility for production of live pups.
Ostermeier GC, Wiles MV, Farley JS, Taft RA 2008 Conserving, distributing and managing genetically modified mouse lines by sperm cryopreservation. PLoS ONE 3 e2792.
Li MW, Vallelunga JM, Kinchen KL, Rink KL, Zarrabi J, Shamamian A, Glass OC, Lloyd KCK 2013 Reliable recovery of C57BL/6 background mouse strains by IVF using sperm cryopreserved with MTG in cryovials. CryoLetters 35:145-153.