Sonia Pérez-Albalá

Cellular and Morphological Traits of Oocytes Retrieved from Aging Mice after Exogenous Ovarian Stimulation

Abstract The present study aims to shed light on the origin of abnormal oocytes ovulated by aged females. In order to reach this goal, cellular and morphological traits of ovulated oocytes from hybrid (C57Bl/6JIco female × CBA/JIco male) female mice retrieved after exogenous ovarian stimulation at the age of 12, 40–42, 50–52, or 57–62 wk were analyzed. Aging of female mice was associated with 1) decreased number of ovulated oocytes; 2) increased percentage of cumulus-free oocytes; 3) raised percentage of oocytes with intracellular mitochondrial aggregates; 4) reduced percentage of oocytes displaying a normal distribution of chromosomes in the metaphase-II plate; 5) increased percentage of normal oocytes exhibiting a DNA-containing polar body (PB); 6) higher percentage of oocytes with chromosome scattering; 7) increased percentage of chromosome-scattered oocytes without a DNA-containing PB and with intracytoplasmic mitochondrial aggregates; 8) raised percentage of oocytes exhibiting chromosome decondensation; 9) lower percentage of chromosome-decondensed oocytes lacking both a DNA-containing PB and intracytoplasmic mitochondrial aggregates; 10) increased percentage of abnormal/degenerated oocytes; 11) reduced percentage of abnormal/degenerated oocytes displaying cellular fragmentation; and 12) higher percentage of abnormal/degenerated oocytes with mitochondrial aggregates exhibiting no nuclear/chromosomal DNA fluorescence, cellular fragmentation, milky or dark cytoplasm, or cellular remains enclosed by the zona pellucida. Although several studies suggest aging females may ovulate aged or overripened oocytes, these data support the hypothesis that old females ovulate an increased percentage of atretic/apoptotic oocytes coming from rescued follicles that would have become atretic earlier in life.

Postovulatory Aging of Oocytes Decreases Reproductive Fitness and Longevity of Offspring

Abstract We analyzed the long-term effects of postovulatory aging of mouse oocytes on reproductive fitness and longevity of offspring. Hybrid (C57BL/6JIco × CBA/JIco) parental generation (F0) females were artificially inseminated at 13 h (∼1 h postovulation) or 22 h (∼10 h postovulation) after GnRH injection. Reproductive fitness of first generation (F1) females was tested from the age of 28 wk until the end of their reproductive life. In males, the testing period ranged from the age of 2 yr until their natural death. Experimental F1 females exhibited longer between-labor intervals, decreased frequency of litters, and lower total number of litters and offspring born. Experimental second generation (F2) pups displayed teratogenic defects, higher preweaning mortality, and decreased body weight at weaning. Incidence of infertility was higher in experimental F1 males, which translated into lower total number of offspring born when compared with the control group. Life expectancy of F1 offspring was decreased in the experimental group. These results clearly show that postovulatory aging of mouse oocytes decreases reproductive fitness and longevity of offspring.

Oral administration of pharmacological doses of Vitamins C and E reduces reproductive fitness and impairs the ovarian and uterine functions of female mice

This study aims to ascertain whether oral administration of pharmacological doses of Vitamins C and E has any detrimental effect on reproductive fitness of female mice. We fed hybrid female mice from the first day of weaning a standard diet supplemented or not supplemented with pharmacological doses of Vitamins C and E. At the age of 28 weeks, we individually caged females with a male for the rest of their reproductive life. We performed a series of mating experiments to ascertain the number of oocytes ovulated and the potential for embryo development in vitro to the blastocyst stage and in vivo to Day 12 of gestation. The antioxidant diet decreased the frequency of litters, litter size, total number of offspring born and survival of male pups to weaning. This effect was associated with lower number of corpora lutea in the left ovary, decreased percentage of viable fetuses, and higher number of fetal resorptions in the left uterine horn when compared to the control group. The strategy of supplementing the diet with antioxidant vitamins to prevent the age associated decrease in reproductive potential should not be implemented in human beings until a safe and efficient diet is designed.

Effect of dietary supplementation with a mixture of Vitamins C and E on fertilization of tertiary butyl hydroperoxide-treated oocytes and parthenogenetic activation in the mouse

The present study aims to analyze the effect of dietary supplementation with a mixture of Vitamins C and E on fertilization and later development of tertiary butyl hydroperoxide (tBH)-treated mouse oocytes and on parthenogenetic activation of freshly ovulated mouse oocytes. We fed hybrid mice a standard diet supplemented or not supplemented with Vitamins C and E from the first day of weaning until the age of 12 weeks. We noted no significant effect of diet on fertilization rate, percentage of total and hatching blastocysts, total number of cells, mitotic index and percentage of apoptotic nuclei at 120 h post-insemination of oocytes incubated for 15 min in the presence of 0, 1, 5 and 10 microM tBH. Furthermore, diet did not affect the percentage of activated oocytes after treatment with Ca2+ ionophore, acid Tyrodes solution or ethanol. The percentage of parthenogenetically activated oocytes that progressed to the pronuclear stage was significantly higher in the antioxidant group. Oocytes from antioxidant females exhibited a significantly lower mitogen-activated protein kinase (MAPK) activity than oocytes from control females. We detected no significant differences between groups in M-phase-promoting factor (MPF) activity. These results show that oral administration of antioxidants decreases MAPK activity and increases the probability of reaching the pronuclear stage after parthenogenetic activation.

Collapse of blastocysts is strongly related to lower implantation success: a time-lapse study

STUDY QUESTION Is there an association between blastocyst collapse patterns and implantation potential? SUMMARY ANSWER Embryos that exhibit collapse are as likely to hatch as those that do not, but are less likely to implant and should not be replaced if alternatives are available. WHAT IS KNOWN ALREADY Studies of blastocyst collapse in different species of mammals have found that most blastocysts, that experience consecutive weak contractions, hatch successfully whereas those that exhibit strong contractions or collapse, fail to hatch. STUDY DESIGN, SIZE, DURATION Retrospective cohort study. Seven hundred and fifteen transferred blastocysts were analyzed from July 2012 to May 2013. PARTICIPANTS/MATERIALS, SETTING, METHODS University-affiliated infertility center. Participant patients were recipients of oocyte donation and autologous IVF cycles (n = 460). Embryo development was analyzed with a time-lapse imaging system. Variables studied included blastocyst collapse (defined as the separation of ≥50% of the surface of the trophectoderm of the blastocyst from the zona pellucida), kinetic variables, embryo morphology, implantation and clinical pregnancy rates. MAIN RESULTS AND THE ROLE OF CHANCE A total of 139 blastocysts presented collapse (19.4%), of these 8 presented 2 collapses and 2 presented 3 collapses. The timings of embryo cleavages and the time taken to reach the morula stage and blastulation were significantly shorter in embryos with collapse than in those without. Implantation rates were compared in cycles where either all or none of the embryos replaced, implanted so that implantation data were known for every embryo. Among 408 embryos without collapse and 94 embryos with at least one collapse (94) the implantation rates were 48.5% (95% confidence intervals (CI) 46.7-53.4%) and 35% (95% CI 25.3-44.9%), respectively. The percentage of embryos that hatched was similar in both groups 28.7 and 31%, respectively. LIMITATIONS, REASONS FOR CAUTION The retrospective nature of the study limits its potential value. WIDER IMPLICATIONS OF THE FINDINGS Study the collapse pattern of the blastocyst, may assist selection of the blastocysts most likely to implant and increase IVF/ICSI success rates.