Abstract
Investigations in the past decades have shown that oocytes developmental competence following in vitro fertilization is greatly influenced by an interval between isolation of the ovaries immediately after death/slaughter and oocytes recovery from the visible follicles. In order to determine the optimal conditions for long-term preservation of ovaries, an experiment was conducted with adding different doses of melatonin (0 (C), 500 (M1), 600 (M2), 700 (M3) and 800 (M4) μM) as an antioxidant to sheep ovaries preservation medium (PBS) maintained at 4 and 20 °C for 24 h. The effects on in vitro embryo production (IVEP) parameters including maturation, fertilization, cleavage, and blastocyst rates and the total number of blastomere were evaluated after the ovaries preservation. Melatonin reduced the decline in fertilization rate as an indicator of success in vitro maturation (P ≤ 0.05). Furthermore, ovarian storage time had significant negative effect (P ≤ 0.05) on IVEP parameters. Supplementation with melatonin increased the total cell number of blastocysts as an indicator of embryo quality (i.e. mean blastomeric cells in 4°C groups: 86.00 ± 3.00, 98.50 ± 3.5, 111.5 ± 1.5, 125.5 ± 2.00 and 126.50 ± 5.5 for C, M1, M2, M3 and M4. respectively). Overall, the results showed that the use of melatonin antioxidant in the ovaries storage medium had beneficial effects on sheep oocytes development and embryos quality.
Highlights
Sheep is an important species in animal husbandry industry, and a critical research model to development of assisted reproductive technologies (ARTs) in human and endangered species[1, 2].Cumulus-oocytecomplexes (COCs) from both small and large antral follicles can be isolated directly from ovarian tissue and matured in vitro to obtain mature gametes
The oocytes in this group were retrieved from ovaries which were transported to the laboratory in less than three hours in PBS at 37.5°C, 3.1 Effects of storage condition at 4°C
Preservation of ovarian tissue is challenging because there are several cell types within the tissue that need to be maintained in a normal state
Summary
Sheep is an important species in animal husbandry industry, and a critical research model to development of assisted reproductive technologies (ARTs) in human and endangered species[1, 2].Cumulus-oocytecomplexes (COCs) from both small and large antral follicles can be isolated directly from ovarian tissue and matured in vitro to obtain mature gametes. The use of ovaries from slaughtered animals has provided an affordable source of oocytes for researchers and laboratories involved in animal ART [2, 3]. Integrating ovarian transport into in vitro embryo production (IVEP) protocols has been an important challenge in large countries and/or in low resource settings where the slaughterhouse is located far from the laboratory [4]. Ovaries need to be collected and returned to the laboratory instantly after the slaughter in order to make The long distance transportation of ovaries to the laboratory has adverse effects on oocyte quality in terms of nuclear maturation and developmental competence after the in vitro maturation (IVM) and fertilization (IVF) [5].
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