Effects of Postmortem Interval on Mouse Ovary Oocyte Survival and Maturation

Abstract

To study the time- and temperature-dependent survival of ovarian oocytes collected from postmortem carcass, ICR mice were killed and placed for different periods (0, 1, 2, 4, 6, 8 and 10 h) at different temperatures (25°C, 4°C and 37°C). After preservation, oocyte morphology, germinal vesicle (GV) oocyte number, oocyte meiotic maturation percentage, mitochondrial distribution and intracellular glutathione (GSH) level were evaluated. The results showed no surviving oocytes could be collected by 2h, 6h, and 12 h after carcass preservation at 37°C, 25°C and 4°C, respectively. The number of collected GV oocytes in the ovary deceased as the preservation time lasted at the same temperature. Meanwhile at the same point in time, the ratio of germinal vesicle breakdown (GVBD) and the first polar body emission (PBE) gradually reduced as preservation temperature increased. In addition, the percentage of abnormal mitochondrial distribution in the preserved oocytes was obviously higher than that in the control oocytes, while GSH level was not altered in collected oocytes. Unexpectedly, neither chromosome arrangement nor spindle organization was affected as long as the oocytes from preserved carcasses could complete maturation. These data are helpful for proper use of ovary oocytes from postmortem carcass of valuable individuals.

Rescue of oocytes recovered from postmortem mouse ovaries

“…This is because ice crystals are likely to form in all cells when stored in temperatures below freezing, and it is unlikely that the viability of GV oocytes will be maintained. Moreover, in order to maintain the viability of the eggs of dead animals, it is necessary to store the carcasses at 4°C [ 3 ]. Therefore, in this study, carcasses were stored at 4°C.…”

“…Zhang et al. [ 3 ] showed that delayed excision of ovary not only decreases the number of surviving germinal vesicle (GV) oocytes but also reduces the germinal vesicle break down (GVBD) and maturation percentages after culture in vitro . They also suggested that the mouse carcass can be preserved at 4°C for 10 h without oocyte evident cytoplasmic damage, but as the preservation time longer, the quantity and quality of oocytes at the GV stage are all reduced.…”

Research progress in the estimation of the postmortem interval by Chinese forensic scholars

“…Zhang et al studied the time- and temperature-dependent survival of ovarian oocytes collected from a mouse carcass [ 101 ]. Results showed that at a constant temperature, the number of collected germinal vesicle oocytes in the ovary decreased with increasing PMI.…”