Chromosomal status of uni-pronuclear human zygotes following in-vitro fertilization and intracytoplasmic sperm injection

Abstract

Uni-pronuclear embryos (n = 42) were analysed by fluorescence in-situ hybridization (FISH) with two to four chromosome pair-specific probes. Half of these embryos resulted from conventional insemination and half from intracytoplasmic sperm injection (ICSI). The majority of uni-pronuclear embryos from conventional insemination were normally diploid (61.9%) whereas only 9.5% of uni-pronuclear ICSI embryos (P < 0.001) were diploid. In addition, a significantly higher number of uni-pronuclear embryos from conventional insemination had a Y chromosome (10/21, 47.6%) when compared with ICSI embryos (2/21, 9.5%) (P = 0.015). It is concluded that the majority of uni-pronuclear embryos following regular in-vitro fertilization are fertilized, whereas those from ICSI are parthenogenetically activated. The latter embryos should not be considered for embryo replacement.

A highly homozygous and parthenogenetic human embryonic stem cell line derived from a one-pronuclear oocyte following in vitro fertilization procedure

“…Resultant diploid embryos were previously confirmed to undergo predominantly normal fertilization owing to the asynchronous formation of two pronuclei [19,21], and a normal diploid hESC line has been derived from these oocytes [28]. These results coincide with our unpublished data, which show that, out of 16 hESC lines that are derived from one-pronuclear oocytes, the majority were of biparental origin.…”

“…With the widespread introduction of assisted reproductive technology (ART), human oocytes can be manipulated and fertilized in vitro. It is suggested that suboptimal conditions [18], intracytoplasmic sperm injections [19] and cryopreservation [20] might parthenoactivate human oocytes. In most cases, spontaneous parthenogenesis is designated by onepronucleus formation, and the resulting embryos should never be transferred back into the patients.…”

“…In most cases, spontaneous parthenogenesis is designated by onepronucleus formation, and the resulting embryos should never be transferred back into the patients. One-pronuclear oocytes are commonly seen following ART treatment and previous studies have suggested that a small part of these oocytes are of uniparental origin [19,[21][22][23]; therefore, these 'unwanted' oocytes could be used for the isolation of homozygous human pESCs rather than wasting fresh human oocytes for deliberate parthenogenetic activation.…”

The impact of pronuclear orientation to select chromosomally normal embryos

“…Scientific literature has shown that 16% of morphologically normal embryos on day transfer has exhibited chromosomal abnormalities in patients who are 20-34 years old, 37% in patients who are 35-39 years old, and over 50% when the maternal age is 40-45 years (18,37,38). Special situations required other methods of embryos assessment, such as PGD.…”

Observation of human embryonic behavior in vitro by high‐resolution time‐lapse cinematography

“…Nevertheless, because of the uncertainty of their genetic normality, transferring such embryos is controversial among ART laboratories. The etiology of zygotes forming with 1PN remains unknown; however, several plausible mechanisms have been proposed after IVF or ICSI as follows- (1) parthenogenetic activation [24,26,33,34], (2) asynchronous formation of male PN (mPN) and fPN [24,34,35], and (3) early fusion of both PN prior to syngamy [36]. In addition, we observed additional PB-like substance extruded into the perivitelline space after the 2nd PB extrusion, forming zygotes carrying a single PN (manuscript in preparation).…”