Meiotic maturation of vitrified immature chousingha (Tetracerus quadricornis) oocytes recovered postmortem

Short- and Long-Term Storage of Non-Domesticated European Mouflon (Ovis aries musimon) Cumulus-Oocyte Complexes Recovered in Field Conditions

Reproductive biotechnologies can be used as a supporting tool, through gamete conservation and in vitro embryo production, in the preservation of invaluable and irreplaceable animal genetic resources. In the present study, immature mouflon cumulus-oocyte complexes (COCs) collected from ovariectomized female ovaries underwent short- or long-term conservation (24 h maintained in Earle's/Hank's (EH) medium or vitrification) under field conditions and afterwards transported to the laboratory where they were cultured for in vitro maturation (IVM) and assessed for oocyte meiotic competence and bioenergetic-oxidative status. Utilization of both storage techniques led to COC morphology preservation, as well as cumulus expansion and oocyte meiotic resumption after the IVM procedure. Quantitative bioenergetic-oxidative parameters were reduced in vitrified oocytes compared with EH ones. Immature COC storage needs to be optimized in both domesticated and non-domesticated sheep as a part of the strategy to avoid the loss of valuable genotypes of these animal species.

The ART of bringing extinction to a freeze - History and future of species conservation, exemplified by rhinos

The ongoing mass extinction of animal species at an unprecedented rate is largely caused by human activities. Progressive habitat destruction and fragmentation is resulting in accelerated loss of biodiversity on a global scale. Over decades, captive breeding programs of non-domestic species were characterized by efforts to optimize species-specific husbandry, to increase studbook-based animal exchange, and to improve enclosure designs. To counter the ongoing dramatic loss of biodiversity, new approaches are warranted. Recently, new ideas, particularly the application of assisted reproduction technologies (ART), have been incorporated into classical zoo breeding programs. These technologies include semen and oocyte collection, artificial insemination, and in-vitro embryo generation. More futuristic ideas of advanced ART (aART) implement recent advances in biotechnology and stem-cell related approaches such as cloning, inner cell mass transfer (ICM), and the stem-cell-associated techniques (SCAT) for the generation of gametes and ultimately embryos of highly endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni) of which only two female individuals are left. Both, ART and aART greatly depend on and benefit from the rapidly evolving cryopreservation techniques and biobanking not only of genetic, but also of viable cellular materials suitable for the generation of induced pluripotent stem cells (iPSC). The availability of cryopreserved materials bridges gaps in time and space, thereby optimizing the available genetic variability and enhancing the chance to restore viable populations.

Strong Heterogeneity in Advances in Cryopreservation Techniques in the Mammalian Orders

Between 1970 and 2012, vertebrate abundance has declined by 58% with an average annual decline of 2%, calling for serious action to prevent a mass extinction and an irreversible loss of biodiversity. Cryobanks and cryopreservation have the potential to assist and improve ex situ and in situ conservation strategies by storing valuable genetic material. A great deal of studies concerning cryopreservation have been performed within the class Mammalia, although no systematic overview has previously been presented. The objective of this study is therefore to evaluate the status, pattern and future of cryopreservation within Mammalia. A strong disproportional distribution of studies in examined orders is displayed. For the majority of examined orders less than 10% of species has been examined. However, the cryopreservation of germplasm has in several cases been successful and resulted in successful applications of assisted reproductive techniques (ARTs). Various obstacles are associated with the development of cryopreservation protocols, and among them the most prominent is interspecific differences in cryotolerance. Extrapolation of protocols in closely related species is considered the most applicable procedure, and a future supplement to overcome this problem is the examination and comparison of cryobiological traits. Successful protocols have been developed for the vast majority of domesticated mammals, which gives incentive for the further extrapolation of protocols in threatened species.

Association of heat shock protein 90 with the developmental competence of immature oocytes following Cryotop and solid surface vitrification in yaks (Bos grunniens)

The correlation between the 90 kDa heat-shock protein (HSP90) and the developmental competence of yak (Bos grunniens) oocytes following the process of vitrification has not been studied clearly. In the present study, we compare the efficacies of Cryotop (CT) and solid surface vitrification (SSV) methods for the cryopreservation of immature yak oocytes. Yak cumulus oocyte complexes were randomly allocated into three groups: (1) controls, (2) CT vitrification, and (3) SSV vitrification. Oocytes were vitrified and in vitro maturated and fertilized. The percentages of nuclear maturation and in vitro development were evaluated. The vitrified-warmed oocytes were evaluated for mRNA and protein expression levels of HSP90 using quantitative real-time PCR and western blotting at various stages: matured oocytes, 2-8 cells embryos and blastocysts. No difference was found in the percentages of nuclear maturation, cleavage or blastocyst in the two vitrified groups; however, the rates of maturation were significantly lower than those in the control group. Among the three groups, the maturation rates in CT: 51.14±0.86% and SSV: 50.82±1.34% were less than those of the controls: 69.65±1.13%; the cleavage rates in CT: 39.16±1.01% and SSV: 39.08±0.92%, were less than those of the controls: 58.14±0.76%; but the blastocysts rates and total cell number in the blastocysts were similar: CT: 32.20±0.73% and 104.6±3.72; SSV: 32.35±0.81% and 102.4±1.34; and controls: 34.38±1.32% and 103.8±4.13, respectively. The HSP90 expression level in the matured oocytes and 2-8 cell embryos of the control group was significantly higher than that in the two vitrified groups; there was not significant difference in the blastocysts in the three groups. We thus conclude that CT and SSV perform equally in the vitrification of immature yak oocytes during the process of cryopreservation, and their influence on oocytes mainly occured from the maturation to cleavage stages. The HSP90 levels in the blastocysts of the vitrified groups increased is associated with the developmental competence of the embryo.