Mailing viable mouse freeze-dried spermatozoa on postcards

Abstract

Summary Freeze-drying techniques allow the preservation of mammalian spermatozoa without using liquid nitrogen. However, the current method requires the use of glass ampoules, which are breakable, expensive, and bulky to store or transport. In this study, we evaluated whether mouse freeze-dried (FD) spermatozoa can be preserved and transported on thin materials. In this study, we demonstrated that FD sperm can be preserved in thin plastic sheets. Its DNA integrity was comparable to that of glass ampoule spermatozoa, and healthy offspring were obtained after preservation at −30°C for more than 3 months. We attached preserved FD sperm to postcards, and transported these to other laboratory inexpensively at room temperatures without any protection. This method will facilitate the preservation of thousands of mouse strains in a single card holder, promote collaboration between laboratories, conservation of genetic resources, and assisted reproductive technology.

Protocol to preserve mouse freeze-dried spermatozoa in the thin plastic sheets

“…The offspring rate was not compromised after mailing, and healthy pups were obtained after performing ET at 2-cell stage. These results have been published in iScience ( Ito et al., 2021 ).…”

“…We can also send the FD sperm domestically using a postcard without any extra equipment. For complete details on the use and execution of this protocol, please refer to Ito et al. (2021) .…”

Long-term preservation of germ cells and gonadal tissues at ambient temperatures

“…1). Recently, it has been demonstrated in mouse that freeze-drying on weighing paper and then storing in between plastic sheet had comparable outcomes, which further simplifies storage (Ito et al 2021). Freeze-drying of sperm cells in trehalose has also been successful in humans (Gianaroli et al 2012, Keskintepe & Eroglu 2021.…”

Production of mouse offspring from zygotes fertilized with freeze-dried spermatids

“…Although all spermatozoa died after the FD treatment, their DNA remained intact, and those sperm acquire strong tolerance against temperature or radiation after FD treatment 5 . Healthy offspring were obtained from FD sperm stored in a desk drawer of laboratory 6 or even on the International Space Station 7,8 , as well as from transported FD sperm on the postcard 9 . Thus, freeze drying could be the best way to preserve genetic resources for a long period in a safe, low-cost, and location-independent manner 10,11 .…”