Cleavage characteristics of mouse embryos inseminated and cultured after zona pellucida drilling

Abstract

The effects of zona drilling on mouse embryo development in vitro were evaluated. Following insemination, sperm were immediately concentrated at the area of drilling, and in zona-drilled eggs, pronuclei appeared 30-50 min earlier than in zona-intact controls. Zona-drilled oocytes fertilized at significantly higher rates than undrilled controls and, consequently, a greater percentage of eggs inseminated after zona drilling reached the blastocyst stage. The attrition rates of zona-drilled embryos at each cleavage stage did not differ significantly from controls. Manipulated embryos exhibited unique cleavage patterns. Some embryos lost their zonae entirely, whereas others became partially extruded at early cleavage stages. These anomalies led to separation of blastomeres from the zygote proper, aggregation of embryos to form giant composite morulae and blastocysts, and occasionally to formation of miniature twin blastocysts. These characteristics of cleavage indicate that although zona drilling of a cohort of oocytes is likely to lead to an increased number of live births relative to controls, some developmental abnormalities can be encountered, and these may be associated with embryo loss, spontaneous chimerism, or possibly with conception of monozygotic twins.

Monozygotic twinning associated with assisted reproductive technologies: a review

“…It has been proposed that an artificial breach in the zona by ICSI or AH and subsequent herniation of blastomeres through the hole in the zona during blastocyst expansion might result in mechanical splitting of the blastocyst and formation of MZ twins (Talansky & Gordon 1988). This phenomenon has been recorded by time-lapse photography in bovine embryos (Van Langendonckt et al 2000).…”

Monozygotic Twin Pregnancy Associated with In Vitro Fertilization: Report and Revision of Three Cases Presented in a Clinic at 10,925 Feet Above Sea Level

“…It is done in ICSI, assisted hatching (AH) and blastomere biopsy for preimplantation genetic diagnosis (PGD). It is argued that artificial rupture of the zona pellucida in these procedures results in the presence of an orifice with subsequent herniation of the blastomeres, and blastocyst expansion may result in a mechanical unfolding of the embryo, resulting in MZT (Talansky & Gordon, 1988;Van Langendonckt et al, 2000). Saito et al (2000) reported 9 MZT from a total of 279 pregnancies (3.2%), with an increased risk in cases where manipulation originated wider rupture of the zona pellucida.…”

Off to a good start: the influence of pre- and periconceptional exposures, parental fertility, and nutrition on children's health.

“…Comparative studies have documented an increased risk for MZ twinning in ART pregnancies that included assisted hatching (Hershlag et al 1999;Schieve et al 2000), and animal studies have shown that MZ twinning can be induced through mechanical or chemical manipulation of the zona pellucida (Allen and Pashen 1984;Picard et al 1985;Sotomaru et al 1998;Talansky and Gordon 1988).…”