Cryopreservation and orthotopic transplantation of rat ovaries as a means of gamete banking

Besides the exponentially increasing number of mouse strains, the rising number of rat strains, due to the establishment of transgenic and coisogenic strains in this species, surpasses the capacity of most animal houses. Cryopreservation of gametes may be a means of solving these problems. Here we describe an easy and fast method for the cryopreservation and transplantation of frozen-thawed ovaries of the rat. Ovaries of the rat inbred strain WKY/Ztm were frozen with dimethylsulphoxide as cryoprotectant and stored at -196 degrees C. Orthotopical transplantation was performed into ovariectomized syngenic recipients. Re-establishment of the reproductive cycle in the recipients was confirmed by vaginal cytology. The morphological integrity of frozen and unfrozen ovaries was compared by histological means after staining with haematoxylin and eosin. The number of litters and offspring was recorded. Reproductive cycle was re-established in all recipients of unfrozen ovaries and in more than 50% of recipients that received frozen-thawed ovaries. One-third of the former and more than 25% of the latter became pregnant and delivered at least one litter. Cyropreservation of ovaries can thus be considered as a reliable method of preserving scientifically and economically important mutant stock, as well as congenic rat strains that are currently not required.