Use of Frozen-Thawed Oocytes for Efficient Production of Normal Offspring from Cryopreserved Mouse Spermatozoa Showing Low Fertility

摘要

Freezingofspermatozoaandunfertilizedoocytesisausefultoolfortheconservationofmousegeneticresources.However,theproportionoffrozen-thawedoocytesfertilizedwithspermatozoainvitroislowbecausespermatozoa,especiallythosefrozen-thawed,cannotpenetrateintooocytesbecauseofhardeningofthezonapellucidafollowingprematurereleaseofcorticalgranules.Toproduceoffspringefficientlyfromcryopreservedtransgenicmousegametes,wefertilizedfrozen-thawedgametesbyusingintracytoplasmicsperminjection(ICSI)andassessedpre-andpostimplantationdevelopmentofembryos.Comparedwithfreshunfertilizedoocytes,frozen-thawedunfertilizedoocyteswerehighlytoleranttodamagebyinjection,asthesurvivalratesafterinjectionoffrozenspermatozoawere51and78%,respectively.Frozen-thawedoocytesthatsurvivedaftersperminjectiondevelopednormallytotheblastocyststageandgaverisetooffspring.Moreover,offspringwithtransgenesalsowereobtainedfromfrozengametesfertilizedbyICSI.TheseresultsdemonstratethatICSIisanefficienttechniqueforproducingoffspringfromtransgenicspermatozoashowinglowfertilityandthatuseoffrozen-thawedoocytesleadstoconservationofgeneticresourcesbecausesuboptimallypreservedgametesarenotwasted.