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). Epididymal sperm of each male are collected in 0.5 ml freezing medium and loaded into 8 cryovials (50 µL each vial) for cryopreservation in liquid nitrogen. 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 and Cryopreservation Laboratory (MICL) routinely perform cryopreservation services, and have successfully cryoarchived and recovered thousands of mouse lines on various backgrounds. Some genetically modified strains may have males with poor fertility, so prior to cryopreservation, we conduct a sperm quality assessment to analyze sperm counts, motility and morphology prior to cryopreservation. Results of the assessment are provided 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 embryo culture allow us to assess the in vitro fertilization rate and blastocyst formation rate, two good markers of sperm quality. A test thaw to live pups allows for the embryos produced from IVF to be transferred into oviducts of pseudo-pregnant recipients in our conventional facility for production of live pups to determine the full developmental potential of the cryopreserved sperm.
Please contact our project management team at mbp@ucdavis.edu to schedule your cryopreservation project today!
References:
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, Lloyd KCK. DNA fragmentation index (DFI) as a measure of sperm quality and fertility in mice. Sci Rep. 2020; 10(1):3833. doi: 10.1038/s41598-020-60876-9.
Li MW, Glass OC, Zarrabi J, Baker LN, Lloyd KCK. Cryorecovery of mouse sperm by different IVF methods using MBCD and GSH. JFIV Reprod Med Genet 2016; 4, 175; doi: 10.4172/2375-4508.1000175
Li MW, Vallelunga JM, Kinchen KL, Rink KL, Zarrabi J, Lloyd KC. 2014. IVF recovery of mutant mouse strains using sperm cryopreserved with MTG in cryovials. Cryo Letters. 35:145-153.
