Domestic cats are invaluable research models for the study of hereditary diseases that affect both cats and humans. By necessity, most cat models are maintained as living populations; however, semen and embryo cryopreservation could provide a cost-effective alternative for model conservation if viable offspring can be readily produced with assisted reproductive techniques such as IVF, embryo transfer (ET) and AI. In our earlier research, semen and IVF-derived embryos representing 24 cat models at 7 veterinary/medical schools were frozen for liquid nitrogen storage. Our objectives in this study were to (1) assess the application of assisted reproduction using frozen semen or embryos for producing pregnancies and viable kittens in several cat models and (2) provide our university collaborators with rederived model offspring. Five cat models (i.e. spinal muscular atrophy, SMA; porphyria, POR; Chediak-Higashi syndrome, CHS; progressive retinal atrophy, PRA; and hypertrophic cardiomyopathy, HCM) were selected for propagation based on investigator research needs. For 3 models (SMA, POR and CHS), semen from affected males, frozen as pellets in Test Egg Yolk medium (with 4% glycerol), was thawed and used to inseminate (5 × 105 motile sperm mL–1) oocytes from eCG/hCG-treated queens. Resulting embryos (2- to 8-cell stage) were transferred laparoscopically (3–5 embryos/recipient) into the oviducts of anestrual queens synchronized with eCG/pLH. For PRA, IVF embryos from affected cats were frozen in 1.5 M ethylene glycol and later thawed for transfer into eCG/pLH-synchronized queens and for HCM, frozen semen from a carrier male was used for laparoscopic oviducal insemination (1 × 106 to 4 × 106 motile sperm/AI) of eCG/pLH-treated females. Ultrasonography was conducted approximately 21 days post-ET or -AI for pregnancy diagnosis. Following IVF with frozen-thawed semen, embryos were produced in all 3 models but overall fertilization success was low (21%, 34/164). All (5/5) recipients became pregnant after ET, giving birth to a total of 11 offspring (6 viable, 5 stillborn). Following frozen ET (PRA), most (3/5) recipients became pregnant with 6 kittens carried to term (3 viable, 3 stillborn), whereas with frozen semen AI (HCM), most (4/7) females conceived with the subsequent birth of 22 kittens (all viable). All surviving offspring (n = 25) for the 5 disease models were distributed to collaborating veterinary schools to reestablish breeding colonies or for ongoing studies. These results indicate that assisted reproduction using frozen semen or embryos may be applied effectively with specific cat models to propagate desired lineages or reestablish research colonies, although some other models have proven more difficult to reproduce. These findings validate our contention that cryopreservation and assisted reproduction may be used to manage and conserve these irreplaceable cat disease models.
Funded by NIH grants RR015338, RR02512, HL093603 and HD39888.
Fertility Preservation Programme in a Tertiary-Assisted Reproduction Unit in Hong Kong
