Mary Zelinski, PhD finishes her reports from the annual meeting of the Society for Cryobiology held from Corvallis, Oregon with a final blog about the keynote talk from Alison Ting, PhD. In this post, she relay's Dr. Ting's findings about advancing ovarian tissue cryopreservation techniques in one species of monkey.
By Mary Zelinski, PhD-Dr. Alison Ting, Post-doctoral Fellow, Division of Reproductive Science and Development, Oregon National Primate Research Center, wound up this interesting session with an update on “Optimization of Rhesus Macaque Ovarian Tissue Cryopreservation.” She outlined the importance of ovarian tissue cryopreservation as an important option for fertility preservation in prepubertal cancer survivors or those without partners. She also pointed out that in vitro development of follicles from cryopreserved ovarian tissue was an important method of fertility preservation that would not transmit cancerous cells back to the patient, a current risk of tissue transplantation in patients with blood-born cancers.
Dr. Ting summarized various conditions that she and her colleagues examined to develop cryopreservation of the ovarian cortex in a closed system using high security tissue straws to circumvent the clinical issue of cross-contamination between samples in open systems during liquid nitrogen storage. She determined the threshold cryoprotectant concentration for vitrifying solutions in straws, compared vitrification solutions containing various concentrations of permeating cryprotectants, such as glycerol and ethylene glycol, in the presence or absence of nonpermeating cryoprotectants (with awesome names like super-cool X-1000, polyvinylpyrrolidone K12 and supercool Z-1000, PXZ) and determined the time needed for vitrification of samples at various temperatures (4 degrees Celsius, room temperature, and 37 degrees Celsius). She reported preservation of both follicular and stromal morphology (based on histology), and noted that the addition of the non-permeating PXZ cyroprotectants preserved not only primordial and primary follicles, but also secondary and multilayered follicles. In addition, growth, survival and antrum formation of secondary follicles derived from thawed tissue cryopreseved with PXZ polymers was achieved using an encapsulated, 3-dimensional culture system.
Through careful and systematic experimentation,Dr. Ting identified a vitrification protocol for macaque ovarian tissue in a closed system using 54% cryoprotectant in the presence of PXZ polymers with gentle cooling and warming. Vitrification of ovarian tissue in a closed system with minimal tissue toxicity can be achieved with effective dehydration and cryoprotectant penetration, which are tissue- and cryoprotectant-specific and also dependent on cryoprotectant exposure time and temperature.
Efforts continue to optimize the 3D encapsulated follicle culture system to yield mature oocytes derived from cryopreseved follicles, develop methods for vitrification of individual secondary follicles in closed systems, and examine follicular function in vivo following heterotopic transplantation of ovarian cortex in macaques. This is the first demonstration of vitrification of primate ovarian tissue in a closed system and offers a significant technical advancement as a method for fertility preservation in cancer survivors.
Read the earlier posts on Cryo2011 here:
- Reports from the 2011 Society for Cryobiology Conference
- Steven Mullen Discusses History of Oocyte Cryopreservation
- Fertility Preservation for Endangered Species
Thanks for the reports Dr. Zelinski! We look forward to hearing more from the Society for Cryobiology.