In ovo culturing of turkey (Meleagris gallopavo) ovarian tissue to assess graft viability and maturation of prefollicular germ cells and follicles

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.

Major Histocompatibility Complex-B haplotype and ovarian graft response

Gonadal tissue transfer is considered one of the best methods to preserve genetic variability. Poultry hosts can receive a gonad from a donor of a different genetic background, sustain the growth of this graft, and produce gametes from it. Unfortunately, the host's strong immune response may significantly reduce the gonadal graft's ability to reach maturity. Our study aimed to evaluate the influence of MHC-B alleles in rejecting a gonadal graft of similar or different genetic backgrounds. In the first experiment, ovarian tissue was transplanted to chicks of similar genetic backgrounds, either Lohmann White (LW) with variable MHC-B or Barred Rock (BR) with fixed MHC-B. The sustained growth of donor ovarian tissues occurred in (4/7 hosts) BR (MHC-B matched) hosts only-one of these graft-positive-BR hens produced eggs derived from the donor ovary. No grafts were recovered when the host and the donor had an LW background (0/9; MHC-B mismatched). In the second experiment, ovarian transplantation was done between chicks of either similar or different genetic backgrounds (Brown Leghorn [BL], BR, and BL/BR F1). The 2 pure lines contained only one MHC-B allele, whereas the F1 heterozygotes had both. All host birds were given a daily dose of an immunosuppressant (mycophenolate mofetil) until maturity. The success rate was assessed by microsatellite genotype confirmation of donor-derived ovaries plus physiological and histological analyses of ovarian grafts. In this second experiment, 11 out of 43 ovarian hosts laid eggs. However, all fertilized eggs from these hens were derived from the remnant host ovarian tissue, not from the donor ovaries. A necropsy assessment was done on all 43 host birds. Ten donor grafts were recovered from hosts having matched (6 hosts) and mismatched (4 hosts) MHC-B, and none were functional. Interestingly, 6 of them were enclosed by a serous membrane capsule filled with fluid and had various tissue growth. In addition, clusters of immune cells were observed in all recovered donor grafts. Our results demonstrated that genetic background could greatly influence the success of gonadal transfer in chickens.

Cyclosporin A Prevents Ovarian Graft Rejection, and Permits Normal Germ Cell Maturation Within the First 5 Weeks Post-transplantation, in the Domestic Turkey (Meleagris gallopavo)

Biobanked ovaries collected from recently hatched poults can only be revived through transplantation, using a recipient bird. The main hurdle in transplantation is preventing graft rejection, which appears as lymphocytic infiltration upon histologic evaluation of the graft. In this study, the condition of the transplants [immunological compatibility (auto- vs. allotransplants), donor age, time in holding media, and temperature of holding media] and treatment of recipient poults with varying immunosuppressants [mycophenolate mofetil (MFM), cyclophosphamide (CY), and cyclosporin A (CsA)] were studied to determine which factors could reduce lymphocytic infiltration, during the first 35 days post-transplantation. Lymphocytic infiltration was determined via cytoplasmic CD3 (T cell) and nuclear PAX5 (B cell) expression. There was no significant difference in the percent of cytoplasmic CD3 or nuclear PAX5 immunostained area between the unoperated group and the autotransplants, by 6 days post-transplantation. However, the allotransplants had more (P < 0.05) positive cytoplasmic and nuclear immunostained areas compared to autotransplants, irrespective of donor age, time in holding media or temperature of the media. By 14 days post-transplantation, the CsA 25 and 50 mg/kg/day treatment groups had less (P < 0.05) CD3 and PAX5 positive areas in their allotransplants, compared to the unsuppressed group. At 35 days post-transplantation, the CsA 25 mg/kg/day allotransplant group also had less (P < 0.05) CD3 and PAX5 positive areas compared to the unsuppressed group. The CsA 25 mg/kg/day transplants also had a similar ovarian follicular size compared to the unoperated group, although they contained fewer (P < 0.05) follicles based on follicular density. Donor age, duration in holding media, temperature of media, and treatment of recipients with MFM or CY had no effect on reducing lymphocytic infiltration. However, immunological compatibility was associated with decreased lymphocytic infiltration, as autotransplants had little lymphocytic infiltration. Treatment of recipients with CsA at 25 mg/kg/day was also associated with reduced lymphocytic infiltration and allowed transplants to develop normally during the first 35 days post transplantation.

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.