GDF9-β promotes folliculogenesis in sheep ovarian transplantation onto the chick embryo chorioallantoic membrane (CAM) in cryopreservation programs

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.

Ultrastructure of human ovarian tissues and risk of cancer cells re-implantation after transplantation to chick embryo chorioallantois membrane (CAM) following vitrification or slow freezing

Ovarian follicle depletion and premature ovarian failure are significant challenges in cancer patients subjected to radio- or chemotherapy. Ovarian tissue (OT) cryopreservation would be an option when other fertility preservation methods are not accessible. This study aimed to analyze the structure and ultrastructure of human OTs transplanted onto chick embryo chorioallantois membrane (CAM) after cryopreservation by vitrification or slow freezing. OTs from 10 cancer patients underwent cryopreservation. CAM transplantation was done on fresh and cryopreserved OTs, to assign samples to nine study groups as follows: 1) FI-FIII = fresh, 5- and 10-days post-CAM transplantation groups; 2) VI-VIII = vitrified, 5- and 10-days post-transplantation vitrified groups; 3) SFI-SFIII: slow frozen, 5- and 10-days post-transplantation slow freezing groups. Proliferation ability, folliculogenesis, and structural and ultrastructure were analyzed. The density of primordial follicles did not change after both freezing methods, but reduced after 5 (P ≥ 0.05) and 10 days (P ≤ 0.05) post-CAM transplantation. The follicular grade significantly decreased in all transplanted tissues (P ≤ 0.0). The proliferation marker increased after cryopreservation, but reduced after transplantation (P ≤ 0.05). TEM evaluation showed better follicular ultrastructure in the fresh group, after transplantation. Stromal ultrastructure appeared more preserved after vitrification compared with slow freezing. There was no sign of malignant cell contamination after transplantation. Some follicular TEM abnormalities were found in both methods of freezing, with a better transplantation rate after vitrification. Also, enhanced follicular activation resulted in faster follicular depletion in this method. The information regarding post grafting events would improve our knowledge for longer OTs' lifespans.

Proliferating cell nuclear antigen presentation, as a marker of folliculogenesis, in the transplanted ovarian tissue

AIM

One of the most important ways to understand the ovarian biology is studding the initiation of primordial follicle development and subsequent folliculogenesis control. In this study, proliferating cell nuclear antigen (PCNA) presentation was used as a marker of follicular development in the thawed ovarian tissue (OT) following transplantation onto chick embryo chorioallantoic membrane (CAM) using two methods of freezing of slow freezing and vitrification.

METHODS

Samples of OT from 10 patients were subjected to slow freezing and vitrification. After warming, CAM transplantation was done and PCNA proliferation index (PI; percent of PCNA-positive granulosa cells) was calculated for each follicle stage. Image J software was used to determine the mean staining intensity.

RESULTS

PCNA was positive for granulosa cells and oocytes nuclei, but negative for ooplasm. There were no remarkable PCNA staining in the granulosa cells of primordial follicles, but increased significantly as follicle progression (p < 0.05). Proliferation rate was also insignificantly higher in the vitrified than slow freezing group, before and after transplantation (p < 0.05). Lower PCNA presentation index was observed after CAM transplantation (p < 0.05). The earliest stage of follicular recruitment took place in the transitional follicles, before squamous cells transform to cuboidal cells.

CONCLUSION

PCNA showed that follicles had proliferation power after cryopreservation. Higher presentation after vitrification may indicate accelerated folliculogenesis in the thawed OT.

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

Biobanking of turkey ovarian tissue appears to be the most cost-effective method for the long-term preservation of female genetics. However, to ensure the successful transplantation of biobanked ovarian tissue for breed or line revival, the transplantation and development of fresh ovarian tissue must be evaluated. To assess transplantability, ovaries from poults 1 to 15 days posthatch (dph) were cultured in ovo in chicken eggs for 6 d and compared with the equivalent fresh tissue. The viability of cultured ovarian tissue was evaluated visually, whereas the level of late-stage apoptosis was measured via the TUNEL assay. In addition, the diameter and density of prefollicular germ cells and follicles (primordial and primary) were measured to assess maturation. Results showed that all cultured grafts (74/74), on surviving chicken chorioallantoic membrane, were viable with low levels (0.8 ± 0.1%) of late-stage apoptosis. The diameter of prefollicular germ cells in cultured ovaries from poults at 5 and 7 dph were larger (P < 0.002) than that of their preculture counterparts but were not able to reach their in vivo size. No significant follicular growth was observed in ovaries cultured in ovo; however, prefollicular germ cell density was over 4-fold greater in ovaries cultured from 7 dph poults (81,030 ± 17,611/mm³) than in their in vivo counterpart (16,463 ± 6,805/mm³). Interestingly, cultured ovaries from all other ages displayed equal or lower (P ≤ 0.05) prefollicular germ cell densities than their in vivo counterparts. Cultured ovaries from poults at 5 and 7 dph also exhibited an increase (P ≤ 0.05) in follicle density compared with their preculture counterparts; whereas, cultured ovaries from 15 dph poults had decreased densities (P < 0.001) compared with their preculture counterparts. This study demonstrated that, although age of ovarian tissue cultured in ovo did not affect the overall viability, 7 dph ovaries appeared to have a better cellular morphology after culturing in ovo than other ages. In addition, we also demonstrated for the first time that avian follicles can form during tissue culturing in ovo.