Long term maintenance of frozen mouse spermatozoa at -80 °C

Maintaining mouse stocks as frozen materials offers both ethical and economical advantages over live animal breeding if the lines are not actively used. The European Mouse Mutant Archive (EMMA) promotes the archiving and distribution of important mouse models for biomedical research through the cryopreservation of their embryos and gametes. Embryo freezing in liquid nitrogen (LN2) at -196 degrees C has traditionally been the method of choice for archiving mouse lines. However, sperm freezing is emerging as a more convenient alternative due to the application of innovative cryopreservation and recovery protocols. In addition, frozen spermatozoa are less sensitive to post-freezing temperature fluctuations. We have previously reported that spermatozoa frozen using standard laboratory protocols can be safely stored in a -80 degrees C freezer or in dry ice (-79 degrees C) for at least seven days.