Vitrified turkey ovarian tissue cultured and assessed through gene expression patterns: A potential screening tool

Biobanking of turkey ovarian tissue has the potential to play a crucial part in preserving female genetics. To date, ovarian tissue has only been vitrified using a standard protocol, with immediate analyses after warming, therefore, long-term cryoinjury is unknown. Long-term cryoinjury was investigated here by in-ovo culturing, fresh (non-vitrified), a purposefully suboptimal poor vitrification (PV), and the standard vitrified (StV) protocol. Assessments were performed via cellular morphological changes and mRNA gene expression differences, immediately (day 0) or after 2, 4, or 6 days of in-ovo culturing. On day 0, the mRNA levels of heat-shock protein A2 (HSPA2) were lowest in the fresh tissue, and increased 5-fold in the StV treatment, and 18-fold in the PV treatment. Whereas, by day 6, growth determining factor 9 (GDF9) mRNA levels within the fresh tissue were over 3-fold and 21-fold higher than StV and PV treatments, respectively. After 6 days of in-ovo culture the follicle density was highest in the fresh ovarian tissue (4701 ± 950 #/mm3), followed by the StV (1601 ± 300 #/mm3), with PV having the lowest density (172 ± 145 #/mm3). This shows that although the density of follicles was higher in StV versus PV, a considerable number (∼65 %) were lost compared to the fresh treatment. Additionally, the HSPA2 expression could be an early screening tool, whereas GDF9 expression could be a late screening tool, used to assess turkey ovarian tissue vitrification protocols. We conclude that the StV protocol should be further optimized to try and improve follicle numbers post-warming.

Resetting the paradigm of reproductive science and conservation

In the application of reproductive science to conservation breeding, it has long been assumed that artificial insemination using frozen thawed sperm would be the default technology. This has always been problematic considering the wide range of tolerance to freeze thawing among vertebrate sperm. Furthermore, those providing leadership for genome banking should be proactive to preserve maximum genetic diversity, however, for many species there is little or no sperm motility after thawing of cryopreserved sperm. In this review article, there is the contention that a much wider range of tissues should be banked, and the range of evolving advanced reproductive and developmental technologies should be considered for conservation breeding programs, to realize the maximum opportunities of genome banking to contribute to conservation of animal species.

Cryopreservation Competence of Chicken Oocytes as a Model of Endangered Wild Birds: Effects of Storage Time and Temperature on the Ovarian Follicle Survival

For the conservation of endangered avian species, developing gamete preservation technologies is essential. However, studies in oocytes have not been widely conducted. In this study, assuming that the ovaries are transported to a research facility after death, we investigated the effect of ovary storage on oocytes for the purpose of cryopreserving avian female gametes by using a chicken as a model of endangered avian species. After excision, the ovaries were stored at either a low temperature (4 °C) or room temperature for 1–3 days. Ovarian follicles stored under different conditions for each period were examined by neutral red staining, histology, and gene and protein expression analysis. In addition, the pH of the storage medium after preserving the ovaries was measured. Then, ovarian tissues were vitrified to determine the cryopreservation competence. Storing the ovarian tissues at 4 °C kept the follicles viable and morphologically normal for 3 days with slow decline. In contrast, although different storage temperature did not influence follicle viability and morphology after only 1 day of storage, ovarian tissues stored at room temperature rapidly declined in structurally normal follicles, and viable follicles were rarely seen after 3 days of storage. Gene and protein expression analysis showed that apoptosis had already started on the first day, as shown by the higher expression of CASP9 under room temperature conditions. Furthermore, high expression of SOD1 and a rapid decline of pH in the storage medium under room temperature storage suggested the influence of oxidative stress associated with low pH in this condition on the follicle survivability in hen ovarian tissues. Our cryopreservation study also showed that ovarian tissues stored at 4 °C could recover after cryopreservation even after 3 days of storage. The described storage conditions and cryopreservation methods, which preserve chicken follicle survival, will lay the foundation of ovarian tissue preservation to preserve the fertility of wild female birds.

Turkey ovarian tissue transplantation: effects of surgical technique on graft attachment and immunological status of the grafts, 6 days post-surgery

Biobanked poultry ovaries can be revived via transplantation into a recipient female, which upon maturity will produce donor-derived progeny. Previously, a large portion of these recipients also produced recipient-derived progeny, making them gonadal chimeras. These were potentially created when portions of the recipient's ovary were inadvertently left behind. Completely removing the recipient ovary would solve this problem; however, leaving a portion of the recipient's ovary may have inadvertently increased the transplant attachment rate by providing a damaged area for attachment. To test this hypothesis in the turkey, we removed various portions (33–100%) of recipient ovarian tissue and determined the transplant attachment rate. Furthermore, the use of the abdominal air sac membrane as an additional anchoring point was tested. The overall attachment rate of transplants was 91% (27/30), while the average size of the transplants was 4.2 ± 0.6 mm², 6 d postsurgery. There was no difference (P > 0.05) in the attachment rates, or transplant size between groups with varying amounts of recipent tissue removed, or by using the abdominal air sac membrane as an anchor. Finally, the immunological status of the grafts were evaluated by analyzing the presences of CD3 and MUM-1 (T and B cell markers). This showed that all transplants were infiltrated by large numbers of T and B cells. Shown by a high (P ≤ 0.001) percentage of CD3-positive immunostained cytoplasmic area (49.78 ± 3.90%) in transplants compared to remnant recipient tissue (0.30 ± 0.10%), as well as a high (P ≤ 0.001) percentage of MUM-1-positive immunostained nuclear area (9.85 ± 1.95%) in transplants over remnant recipient tissues (0.39 ± 0.12%). From this study we would recommend removing the entire recipient ovary, and not covering the transplants with the abdominal air sac membrane, to prevent gonadal chimeras. The high levels of lymphocytes within the grafts indicate possible tissue rejection, which could be overcome via immunosuppression with or without histocompatibility matching between donors and recipients.

Improvement of the application of gonadal tissue allotransplantation in the in vitro conservation of chicken genetic lines

In avian species, the surgical technique for ovarian allotransplantation has been developed for domestic chickens; however, not all genotypes can be effectively used as recipients. The aims of the present study were to ascertain donor/recipient combinations for production of offspring from frozen/thawed ovarian tissues. The development of the technique is important because domestic chicken offspring have only been produced from fresh (never frozen) ovarian and from frozen-thawed testicular tissues. Information obtained from evaluating genetic differences of intensively selected lines in which there was successful pairing was compared in the indigenous breeds. Results indicate donor/recipient combinations were created which could be effectively used for gonadal tissue allotransplantations. Gonadal tissues of Yellow, Speckled and Partridge-color Hungarian, Black and Speckled Transylvanian Naked Neck chicken breeds were allotransplanted into White Leghorn or Novogen White breeds for offspring production. The gonadal tissues of these indigenous breeds were cryopreserved using vitrification procedures. There was successful allografting of frozen/thawed gonadal tissues at a rate between 20 % and 100 % depending on the genotype and sex, and histological examination and microsatellite marker analysis provided evidence that the donor ovarian and testicular tissues had the capacity for producing gametes. The hens of Speckled Transylvanian Naked Neck/White Leghorn combination using frozen/thawed ovarian tissues were produced for progeny tests. Of these, 58 % produced eggs and 9.1 % produced donor-derived offspring, based on data for both feather color markers and genetic analysis.

Ethylene Glycol and Dimethyl Sulfoxide Combination Reduces Cryoinjuries and Apoptotic Gene Expression in Vitrified Laying Hen Ovary

Successful cryopreservation of avian gonads is important not only for avian breeding but is also crucial for preservation of species, especially of endangered birds. The aim of this study was to evaluate the effect of vitrification by several cryoprotectants on the ovarian tissues of laying hens. Ovarian tissues were randomly divided into six groups: control (nonvitrified: C), dehydrated using ethylene glycol (EG), dehydrated with propylene glycol (PROH), dehydrated using dimethyl sulfoxide (DMSO), and two combined groups, EG+DMSO and EG+PROH. The composition of vitrification solutions was as follows: EG group: V1 = 7.5% EG and V2 = 15% EG +0.5 M sucrose, DMSO group: V1 = 7.5% DMSO and V2 = 15% DMSO +0.5 M sucrose, PROH group: V1 = 7.5% PROH and V2 = 15% PROH +0.5 M sucrose, EG+DMSO group: V1 = 7.5% EG +7.5% DMSO and V2 = 15% EG +15% DMSO +0.5 M sucrose and EG+PROH group: V1 = 7.5% EG +7.5% PROH and V2 = 15% EG +15% PROH +0.5 M sucrose. Ovarian tissues of each group were dehydrated for 10 minutes with V1 solution and 2 minutes with V2. Among the vitrified groups, intact primordial and primary follicles showed significant increase in EG+DMSO, but follicular attrition had the highest rate in the PROH group (p < 0.05). Immunohistochemical analysis showed that the percentage of active caspase 3-positive cells was lower (p < 0.05) when using EG+DMSO versus PROH. Further gene expression of caspase 3, 8, and 9 was highest in the PROH group (p < 0.05). Vitrification of ovaries of laying hens using EG+DMSO can afford effective protection of primordial and primary follicles during preservation and may therefore be successfully used for storing avian gonadal tissues.

Microscopic Morphology and Apoptosis of Ovarian Tissue after Cryopreservation using a Vitrification Method in Post-Hatching Turkey Poults, Meleagris gallopavo

The objectives of this study were to examine morphological changes of oogonia and primordial follicles in the ovaries of turkey poults within the first week after hatching, and to evaluate the effect of cryopreservation on histology and apoptosis of these immature ovaries. Ovaries from poults at Day 1, Day 3, Day 5 and Day 7 post-hatch were cryopreserved using a modified vitrification method. The histology of oogonia and primordial follicles in fresh and cryopreserved tissue was assessed, and the apoptosis of tissue in different age groups was identified using a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The mean oogonium diameter in fresh tissue increased from 11.9±1.3 µm (Day 1) to 15.2±2.7 µm (Day 7) within the first week; however, oogonia in cryopreserved tissue from Day 3 and Day 7 ovaries were smaller than those in fresh tissue (P<0.05). Formation of primordial follicles was observed as early as Day 5. For Day 7 ovaries, follicles in cryopreserved tissue were smaller than those in fresh tissue; this was also true for oocyte diameter (P<0.05). Apoptosis was most frequent in Day 1 fresh tissue, which was reduced as the poults aged. The frequency of apoptosis in cryopreserved tissue was comparable among age groups. This study provides the first documentation of morphological changes in the turkey ovary within the first week post-hatching. Results suggest that oogonia and primordial follicles that are smaller in size could be more resistant to the damage caused by cryopreservation. Of the ages assessed in this study, it is concluded that 3 days of age appears optimal for recovery of donor ovaries for cryopreservation, taking the advance of reduced cryoinjury and ease of tissue handling at this age.

Fertility preservation through gonadal cryopreservation

Fertility preservation is an area of immense interest in today's society. The most effective and established means of fertility preservation is cryopreservation of gametes (sperm and oocytes) and embryos. Gonadal cryopreservation is yet another means for fertility preservation, especially if the gonadal function is threatened by premature menopause, gonadotoxic cancer treatment, surgical castration, or diseases. It can also aid in the preservation of germplasm of animals that die before attaining sexual maturity. This is especially of significance for valuable, rare, and endangered animals whose population is affected by high neonatal/juvenile mortality because of diseases, poor management practices, or inbreeding depression. Establishing genome resource banks to conserve the genetic status of wild animals will provide a critical interface between ex-situ and in-situ conservation strategies. Cryopreservation of gonads effectively lengthens the genetic lifespan of individuals in a breeding program even after their death and contributes towards germplasm conservation of prized animals. Although the studies on domestic animals are quite promising, there are limitations for developing cryopreservation strategies in wild animals. In this review, we discuss different options for gonadal tissue cryopreservation with respect to humans and to laboratory, domestic, and wild animals. This review also covers recent developments in gonadal tissue cryopreservation and transplantation, providing a systematic view and the advances in the field with the possibility for its application in fertility preservation and for the conservation of germplasm in domestic and wild species.

Cryopreservation and other assisted reproductive technologies for the conservation of threatened amphibians and reptiles: bringing the ARTs up to speed

Amphibians and reptiles are experiencing serious declines, with the number of threatened species and extinctions growing rapidly as the modern biodiversity crisis unfolds. For amphibians, the panzootic of chytridiomycosis is a major driver. For reptiles, habitat loss and harvesting from the wild are key threats. Cryopreservation and other assisted reproductive technologies (ARTs) could play a role in slowing the loss of amphibian and reptile biodiversity and managing threatened populations through genome storage and the production of live animals from stored material. These vertebrate classes are at different stages of development in cryopreservation and other ARTs, and each class faces different technical challenges arising from the separate evolutionary end-points of their reproductive biology. For amphibians, the generation of live offspring from cryopreserved spermatozoa has been achieved, but the cryopreservation of oocytes and embryos remains elusive. With reptiles, spermatozoa have been cryopreserved in a few species, but no offspring from cryopreserved spermatozoa have been reported, and the generation of live young from AI has only occurred in a small number of species. Cryopreservation and ARTs are more developed and advanced for amphibians than reptiles. Future work on both groups needs to concentrate on achieving proof of concept examples that demonstrate the use of genome storage and ARTs in successfully recovering threatened species to increase awareness and support for this approach to conservation.

Biobanking genetic resources: challenges and implementation at the USDA National Animal Germplasm Program

There is adequate infrastructure in the US to identify and acquire germplasm from the major beef and dairy cattle and swine breeds. However, when we venture outside these species, the same tasks become more difficult because of a lack of breed associations, databases that include genotypic and phenotypic data and low numbers of animals. Furthermore, acquisition of germplasm from non-cattle and non-swine species can be difficult because these animals are often not located near the National Animal Germplasm Program, which makes collection and preservation of the samples in a timely manner that much more complicated. This problem is compounded because not all preservation protocols are optimised for field collection conditions or for all types of germplasm. Since 1999, the USDA National Animal Germplasm Program has worked to overcome these obstacles by developing policies, procedures and techniques in order to create a germplasm repository for all agricultural species (wild and domesticated) in the US. Herein, we describe these activities and illustrate them via a case study on how our efforts collecting Navajo-Churro sheep have created a secure backup of germplasm and how we specifically overcome these issues as they relate to rare and minor breeds of agricultural species.

Recovery of fertility from adult ovarian tissue transplanted into week-old Japanese quail chicks

Fertility of cryopreserved ovarian tissue from immature chickens and Japanese quail has been recovered by transplantation. This is of special importance for non-mammalian vertebrates in which cryopreservation and in vitro maturation of oocytes are challenging because their oogenesis is characterised by vitellogenesis. This study tested whether fertility of adult quail ovarian tissue could be recovered by transplantation. Ovaries were isolated from mature Japanese quail hens, trimmed, cut into 3- to 4-mm2 pieces and transplanted into ovariectomised, week-old chicks. Recipients were administered an immunosuppressant for two weeks. Ten of 12 recipients survived until sexual maturity and seven laid eggs, but all stopped laying by 17 weeks of age. The age at first egg of recipients laying eggs (75.7 ± 4.2 days) was greater than that of untreated hens (51.8 ± 1.7 days) and egg production of recipients during the laying period (21.7 ± 5.7) was less than that of untreated hens (60.8 ± 3.5). Recipients were paired with males from the WB line for test mating. Only two hens laid eggs during the test period but both produced 100% donor-derived offspring. This research demonstrated that the reproductive potential of ovarian tissue from adult quail hens can be restored by transplantation.