ARTIFICIAL INSEMINATION IN FARM ANIMALS - Phenix-Vet

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284Artificial Insemination in Farm Animalsin the initial temperature of the cryoprotectant, and-seeding temperature (Trad FS, et al.,1999). Survival rates have been further improved with vitrification, a technique that useshigh concentrations of cryoprotectant and rapid freezing by immersion in liquid nitrogen,preserving oocytes in a solid glass-like state without ice formation (Loutradi KE, et al., 2008;Oktay K, et al., 1997). With the use of intra-cytoplasmic sperm injection (ICSI), the hardenedzona is not a barrier to fertilization (Polak de Fried E, et al., 1998). Survival, fertilization, andpregnancy rates achieved with cryopreserved oocytes are rap-idly improving andapproaching those achieved with fresh oocytes (Grifo JA, & Noyes N, 2010; Nagy ZP, et al.,2009). A randomized comparison of results achieved with slow-freeze and vitrificationobserved that vitrification resulted in better oocyte survival (81% vs. 67%), fertilization (77%vs. 67%), and clinical pregnancy rates per thawed oocyte (5.2% vs. 1.7%).A study examining outcomes achieved with vitrified donor oocytes observed 87% thawsurvival, 87% fertilization, and 68% blastocyst formation, with 15/20 recipients (75%)achieving pregnancy after embryo transfer (Cobo A, Kuwayama M, Perez S, et al). Anotherusing both slow-frozen and vitrified oocytes observed 92% survival, 79% fertilization, 42%implantation, and a 57% on going pregnancy rate (Grifo JA & Noyes N, 2010). Although thenumber of pregnancies and deliveries resulting from oocyte cryopreservation is stillsomewhat small, the number is rapidly increasing, and early perinatal outcomes data arereassuring. The incidence of chromosomal abnormalities in human embryos derived fromcryopreserved oocytes is no different from that observed in control embryos derived fromfresh oocytes (Gook DA, et al., 1994; Cobo A, et al., 2001). A study comparing outcomes in200 infants derived from vitrified oocytes and in infants resulting from conventional freshIVF found no differences in birth weight or in the incidence of birth defects (Chian RC, et al.,2008). A review of over 900 live births resulting from IVF of cryopreserved oocytes alsoobserved no increase in the prevalence of congenital anomalies compared to that in thegeneral population (Noyes N, et al., 2009). Oocyte cryopreservation is a viable fertilitypreservation strategy for women without partners seeking to preserve their fertility.Unfortunately few cancer patients have sufficient time to undergo ovarian stimulationbefore their treatment begins. The technology also holds enormous promise as a means tosimplify oocyte donation, via egg banking, and is rapidly emerging as an elective fertilitypreservation strategy for women anticipating delayed childbearing and concerned abouttheir future fertility. Currently, elective oocyte cryopreservation to defer reproductive agingis controversial, primarily because the great majority of outcomes data have come fromexperience with cryopreserved oocytes obtained from healthy young oocyte donors andcannot be extrapolated to older women who represent the majority of those expressinginterest in elective oocyte cryopreservation (Rybak EA & Lieman HJ 2009; ASRM PracticeCommittee). However, when age-stratified outcomes data become available, allowingwomen to be accurately informed about their prognosis for success, elective oocytecryopreservation may realistically offer women the means to set their “biological clock.”10.2.1 Ovarian tissue cryopreservationAt least in theory, ovarian tissue cryopreservation offers the means to freeze thousands ofprimordial follicles for later in vitro maturation or to store tissue for xenografting into ananimal host or later auto transplantation (Jeruss JS, Woodruff TK., 2009). Currently,autologous transplantation of ovarian tissue seems the most practical and effective approach
Reproductive Endocrinology Diseases: Hormone Replacement and Therapy for Peri/Menopause 285because the technique has successfully restored fertility to women with ovarian failureresulting from cancer chemotherapy (Andersen CY,, et al., 2008; Demeestere I, 2006,2010; etal; Silber SJ 2009). Ovarian tissue is removed surgically via laparoscopy or laparotomy andfrozen using either a slow-cool or vitrification technique, before the insult expected to resultin ovarian failure. Later, it can be thawed and transplanted back into the patient in or nearits original location (orthotopic transplantation) or to another site, such as the forearm orabdominal wall (heterotopic transplantation). The advantage of orthotopic transplantation isthat pregnancy might be achieved without assistance, whereas heterotopic transplantationrequires IVF (Jeruss JS & Woodruff TK. 2009). Live births have been achieved aftertransplantation of frozen-thawed ovarian tissue in sheep, (Candy CJ et al., 2000) and the firstlive birth in a primate after a fresh heterotopic ovarian transplantation has been reported(Lee DM, et al). Human oocytes have been obtained from heterotopic transplants andfertilized in vitro to yield embryos for transfer, resulting in a biochemical pregnancy(Rosendahl M, et al., 2006). The only human pregnancy achieved after heterotopictransplantation was achieved without assistance, indicating that the oocyte from which itarose came from the patient’s existing ovary rather than from the transplant. Orthotopictransplantation has been successfully achieved in humans.A number of live births have been reported after autologous orthotopic transplantation ofcryopreserved ovarian tissue. Frozen ovarian tissue also has been transplanted successfullybetween monozygotic twin sisters after the receiving twin developed premature ovarianfailure (Silber SJ, & Gosden RG, 2007). A 2008 systematic review identified 25 reportsdescribing a total of 46 cases of ovarian tissue transplantation for treatment of prematureovarian failure or infertility, although most involved transplantation of fresh rather thanfrozen ovarian tissue (Bedaiwy MA, et al., 2008). The mean time to return of ovarianfunction was 120 days (range 60–244 days) and data were insufficient to evaluate functionbeyond 1 year. Fresh grafts were more likely to succeed, and in 25 women who soughtpregnancy, eight conceived nine pregnancies. At least one potential risk of ovarian tissuecryopreservation and auto-transplantation is reseeding of tumor cells in women withmalignancies. Future research focusing on defining patient suitability, tissue collectionmethods, and cryopreservation protocols is certainly warranted, but until effectivetechniques and the possibility for success can be defined, ovarian tissue cryopreservationwill remain investigational and cannot be justified solely for the purpose of future use inhealthy women.11. ReferencesAboulghar MA, Mansour RT, Serour GA, Amin YM, Sattar MA, Ramzy AM, In vitrofertilization in a spontaneous cycle: a successful simple protocol, J Obstet Gynaecol(Tokyo 1995) 21:337, 1995.Adhikari D, Liu K, Molecular mechanisms underlying the activation of mammalianprimordial follicles, Endocr Rev; 30:438, 2009.Ahmed-Ebbiary NA, Lenton EA, Cooke ID: Hypothalamic-pituitary ageing: progressiveincreases in FSH and LH concentrations throughout the reproductive life inregularly menstruating women. Clin Endocrinol; 41:199-206. 1994.Akman MA, Erden HF, Tosun SB, Bayazit N, Aksoy E, Bahceci M, Comparison of agonisticfl are-up-protocol and antagonistic multiple dose protocol in ovarian stimulation of
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ARTIFICIAL INSEMINATION IN FARM ANIMALS - Phenix-Vet

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