Effect of post-ovulatory age and calcium in the injection medium on the male pronucleus formation and metaphase entry following injection of human spermatozoa into golden hamster oocytes

Abstract

The occurrence of parthenogenetic activation is a major hurdle in obtaining sperm chromosome metaphases after heterospecific intracytoplasmic sperm injection (ICSI) of golden hamster oocytes with human spermatozoa. We addressed two potential contributors to parthenogenetic activation namely, post-ovulatory age of the oocyte and Ca2+ content of the injection medium. In serial experiments, hamster oocytes were retrieved at 11.5, 13, 16 and 21 h after the ovulatory dose of human chorionic gonadotrophin (HCG) and microinjected with human spermatozoa suspended alternately in a regular (1.9 mM Ca2+) or a Ca2+-free medium. A progressive decrease in the rates of male pronucleus (MPN) formation and metaphase entry and increase in the rates of parthenogenetic activation without male pronucleus occurred with increasing post-ovulatory age. The favourable influence of Ca2+-free injection medium on the mean rates of MPN and metaphase entry was restricted to the relatively older oocytes (MPN 16 h: 49.5 versus 32.3%, P< 0.008; 21 h: 22.2 versus 11.1%, P< 0.001; metaphase entry 16 h: 36.8 versus 25.1%, P< 0.02; 21 h: 13.3 versus 5.2%, P< 0.01 in the Ca2+-free and regular groups respectively). Our data confirm the increased activation sensitivity with post-ovulatory ageing and its adverse influence on the MPN formation and metaphase entry after heterospecific ICSI of hamster oocytes.

Nitric oxide extends the ‘oocyte temporal window for optimal fertilization’

“…This possibility further underscores a novel and critical role played by NO improving and sustaining the oocyte quality. NO may also have prevented temporal decline in oocyte factors involved in optimal sperm chromatin decondensation [49], which is critical for gene expression during development [50][51][52][53][54][55].…”

Melatonin prevents postovulatory oocyte aging and promotes subsequent embryonic development in the pig

“…The changes include cortical granule exocytosis [1], zona pellucida (ZP) hardening [2], chromosome and spindle anomalies [3], decreased fertilization rates [4] and abnormal and/or retarded development of embryos/fetuses [5]. Therefore, it is important to determine the mechanisms that are implicated in oocyte aging, in order to develop strategies to delay oocyte aging and increase the time that may be needed to manipulate oocytes to perform assisted reproductive technologies (ARTs).…”

Postovulatory aging causes the deterioration of porcine oocytes via induction of oxidative stress

“…A handful of studies have reported that postovulatory aging is highly correlated with a variety of defects in oocytes, including precocious release of cortical granules, zona pellucida hardening, spindle/chromosome abnormalities, weakened fertilization ability, and abnormal development of embryos and fetuses (5)(6)(7)(8)(9). In addition, postovulatory aging is accompanied by diverse molecular, cellular, and biochemical changes, such as dysfunction of mitochondria, generation of reactive oxygen species (ROS), reduced maturation-promoting factor activities, decreased expression of antiapoptotic factor B-cell lymphoma 2 (BCL-2), activation of caspase-3, and changes in epigenetic modifications (4,(10)(11)(12).…”