Cryopreservation of mouse ovarian tissue following prolonged exposure to an ischemic environment

In cases in which ovarian tissue is to be cryopreserved for tissue or gene banking it is important to maintain its integrity and viability. This study examined how delays between the death of an animal and the collection/cryo preservation of its ovarian tissue influenced follicle viability, Mouse ova ries were placed in PBS+antibiotic (in vitro) or left within the body (in s itu) at room temperature for 0, 3, 6, 12, or 24 h following tile death of t he donor These ovaries were cryopreserved at 1 degreesC/min on dry ice or i n a -84 degreesC freezer using a passive cooling device or by conventional slow cooling (0.3 degreesC/min). The ovaries were grafted under the kidney capsule of ovariectomized recipient mice and collected 2 weeks later, and t he size and number of follicles were determined. Cryopreserved ovarian tiss ue grafted immediately after the death uf the donor contained numerous viab le and healthy follicles independent of the cooling procedure (dry ice, 134 +/- 32; -84 degreesC, 165 +/- 54; slow, 214 +/- 55 follicles per half ovar y). Tissues stored in vitro before cryopreservation retained viable follicl es up to 12 h after death (dry ice, 30 +/- 15; -84 degreesC, 86 +/- 45; slo w, 93 +/- 33), whereas tissue left in situ had significantly reduced follic le numbers within 3 h of death (dry ice, 36 +/- 17; -84 degreesC, 19 +/- 6; slow, 28 +/- 7). No significant difference was found between the cooling r ates tested, indicating that a passive cooling container which cools at 1 d egreesC/min is a suitable alternative to conventional slow cooling. We conc lude that ovarian tissues for cryobanking should be cryopreserved as soon a s possible after collection or death of the animal to ensure maximal follic ular survival. (C) 2001 Academic Press.