Follicle-oocyte atresia and temporal taphonomy in cold-stored domestic cat ovaries

Abstract

In vitro oocyte maturation followed by in vitro fertilization (IVM/IVF) success in the domestic cat remains inferior to commonly studied livestock or laboratory species. The objectives here were (1) to histologically assess atresia status of freshly excised follicle/oocyte complexes, and (2) to evaluate taphonomic change (deterioration after excision) of these complexes after ovarian cold storage for up to 48 h. After excision of 50 ovarian pairs, one ovary was preserved immediately and the other stored in phosphate buffered saline (4°C) for 4, 8, 12, 24, or 48 h before fixation and examination. Ovaries were classified as luteal if prominent corpora lutea (CL) were present or as follicular if antral follicles and no CL were present. Two classes of follicle‐oocyte complexes (preantral and antral) were microscopically evaluated. Of the 2,280 complexes examined, 64.3% demonstrated clear evidence of slight to severe degeneration, with various stages being described and photographed for the first time. There was no histological evidence indicating distinctive morphological differences between oocytes recovered from follicular versus luteal donors. Storage of whole ovaries in cold saline inhibited taphonomic changes for 48 h after excision. In summary, there is marked variability in the number and quality of follicle populations in cat ovaries. A high percentage of full‐sized follicular oocytes are undergoing atresia at any given time. However, additional gross degeneration as a result of cold‐storage appears modest for up to 48 h. Nonetheless, this high level of natural atresia in the cat likely contributes to comparatively lower IVM/IVF success than in other species. Mol Reprod Dev 46:190–200, 1997. © 1997 Wiley‐Liss, Inc.

DNA degradation in mural granulosa cells of non- and slightly atretic follicles of fresh and cold-stored domestic cat ovaries

“…This is followed by nuclear pyknosis (apoptotic condensation), breakdown of the basement membrane, shrinkage and fragmentation of granulosa cells, and shedding of atretic (apoptotic) bodies into the antral cavity. The present study affirmed our recent observations (Wood et al, 1997) that the freshly excised cat follicle-oocyte complex is undergoing an extraordinary high incidence of follicular atresia (circa, 64%), which is independent of the follicular or luteal phase status of the donor. Here, we focused on the mural granulosa cell layers of antral follicles and found that half of all freshly collected antral follicles showed distinctive evidence of atresia.…”

“…These observations of granulosa cell ''chromatolysis'' made more than a century ago closely match all morphological criteria now known to be hallmarks of apoptosis (Kerr et al, 1987). Follicle atresia in the cat (Wood et al, 1997) appears similar to what occurs in other species. The first recognizable evidence is that granulosa cells lining the antral boundary change in organizational structure.…”

Morphological and ultrastructural changes occurring during degeneration of goat preantral follicles preserved in vitro

“…The greater rates of reduction of cellular metabolism may explain why there was not induction of other types of degeneration after preservation at 4°C. Similar results were also observed after analysis of fresh (caprine: Bezerra et al, 1998;Lucci et al, 1999;and ovine: Jorio et al, 1991) or cold-stored preantral follicles at 4°C (feline: Wood et al, 1997). Jorio et al (1991) showed that degeneration of the oocyte is the mode of atresia most frequently observed in preantral follicles.…”

Effect of Braun-Collins and Saline solutions at different temperatures and incubation times on the quality of goat preantral follicles preserved in situ

“…The histological analysis of preantral follicles present in the controls as well as in fragments stored at 4 or 20°C showed that changes at the oocyte level constitute the first observed degenerative sign. Similar results were also observed with fresh ovine (Jorio et al, 1991) and caprine (Lucci et al, 1999b) preantral follicles, cold stored at 4°C feline preantral follicles (Wood et al, 1997) and cultured bovine preantral follicles in vitro Braw-Tal andYossefi, 1997). These results show that the oocyte is much more sensitive to degeneration than granulosa cells.…”