Timing of oocyte activation, pronucleus formation and cleavage in humans after intracytoplasmic sperm injection (ICSI) with testicular spermatozoa and after ICSI or in-vitro fertilization on sibling oocytes with ejaculated spermatozoa

Abstract

In the first study, we evaluated 101 oocytes [2, 4, 6, 8, 16, 18 and 20 h after intracytoplasmic sperm injection (ICSI)] that had been microinjected with testicular spermatozoa. Of the 70 normally fertilized oocytes (69%) 30 (43%) had two pronuclei by 6 h after ICSI. Fifty-one (73%) by 8 h, 69 (99%) by 16 h and four of them by 20 h cleaved to the 2-cell stage. In the second study, 95 cumulus-corona-oocyte complexes (CCOC) were divided into two groups. Forty-seven CCOC were inseminated by conventional in-vitro fertilization (IVF) and 40 metaphase-II oocytes by ICSI. Oocytes were evaluated at 2, 4, 6 (only after ICSI), 8, 10, 12, 18, 20, 22, 24, 26, 28 and 30 h after both ICSI and IVF. After IVF, 35 oocytes were fertilized normally (75%), four of which (11%) had two pronuclei by 8 h, 11 (31%) by 10 h, 27 (77%) by 12 h and 35 (100%) by 14 h. The first cleavages had occurred by 24 h after insemination (four oocytes, 11%). After ICSI, 34 oocytes were fertilized normally (79%), 13 of which (38%) had two pronuclei by 6 h, 27 (79%) by 8 h and 32 (94%) by 10 h. Three oocytes cleaved by 20 h after microinjection (9%) and 19 by 24 h (56%). Pronuclei developed asynchronously in six oocytes after ICSI (18%) as opposed to 16 oocytes after IVF (46%). The results of this study suggest that the timing of pronuclear formation is no different when a testicular spermatozoon is microinjected into the oocytes from when an ejaculated spermatozoon is injected. Secondly, pronuclear development and first cleavage generally take place 4 h sooner after ICSI than after IVF. On the other hand, a higher proportion of oocytes develop two pronuclei asynchronously after IVF than after ICSI.

Nuclear Dynamics of Parthenogenesis of Human Oocytes: Effect of Oocyte Aging in vitro

“…It appears that the kinetics of pronuclear formation and polar body extrusion of parthenogenetically activated 2-day-old oocytes but not 1-day-old oocytes described herein were consistent with those of fresh oocytes after ICSI fertilization [14,15]. They reported that 68% of oocytes fertilized by ICSI had two clearly distinguishable polar bodies by 4 h. The first pronucleus appeared 6 h after ICSI and 80% of the normally fertilized oocytes revealed two pronuclei at 8 h, although time-lapse video-recording demonstrated a somewhat earlier start of pronucleus formation [16].…”

Good quality blastocyst from non-/mono-pronuclear zygote may be used for transfer during IVF

“…We found that the incidence of D5 blastocysts with normal chromosomal constitution was higher than D6 blastocysts for bi-pronuclear zygotes. Previous studies indicated that the majority of normally fertilized zygotes were bi-pronuclear at 16-18 h post-insemination [Nagy et al 1998;Rienzi et al 2005], and embryos developed to the hatching blastocysts stage on D5 [Kirkegaard et al 2013]. When the pronuclear zygotes were reanalyzed 4-6 h later, however, 25% of the mono-pronuclear zygotes at 16-18 h post-insemination were found to have developed a second pronucleus [Staessen and Van Steirteghem 1997].…”

Early cleavage is a valuable addition to existing embryo selection parameters: a study using single embryo transfers

“…They also found that embryos derived after ICSI cleaved earlier compared to those after IVF (Lundin et al, 2001). This has been explained by Nagy et al (1998). By injecting the spermatozoon into the oocyte, the zona pellucida and cumulus and corona cell barrier is overcome.…”

“…First, early cleavage of embryos had to be determined between 23 and 26 h post-injection or 25 and 28 h post-insemination, the time difference being necessary to compensate for the time difference in early development between IVF-and ICSI-derived embryos (Nagy et al, 1994(Nagy et al, , 1998. Second, there had to be at least one normally fertilized (two-pronuclear, 2PN) zygote present.…”