Effects of partial or complete laser-assisted hatching on the hatching of mouse blastocysts and their cell numbers
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RESEARCH
Open Access
Effects of partial or complete laser-assisted hatching on the hatching of mouse blastocysts and their cell numbers Chanchai Chailert, Usanee Sanmee, Waraporn Piromlertamorn, Sudarat Samchimchom and Teraporn Vutyavanich*
Abstract Background: It is still debatable whether a full-thickness assisted hatching (AH) is better than the partial zona thinning. In this research, we used a mouse model to study the effect of partial and complete laser-AH on the rate of completely hatched blastocyst and their cell numbers. Methods: In experiment 1, mouse morulae had 0, 1, 2 or 3 full-thickness openings of 10 microns created in the zona pellucida with an infrared laser beam. In the second experiment, 0, 1 and 2 openings of 20 microns were studied. In the third experiment, a full-thickness opening of 20 microns or quarter-thinning of the zonal circumference to a depth of 90% was compared with non-AH controls. Results: No difference in blastocyst formation was found in laser-treated groups and in the controls. In experiment 1, the rate of completely hatched blastocysts was significantly lower than the controls. In experiment 2 when the size of the opening was increased, blastocysts completely hatched at a significantly higher rate than that in the controls. In experiment 3, the rate of completely hatched blastocysts was the highest in the full-thickness group. Cell numbers in completely hatched blastocysts from both AH groups were significantly fewer than those in the controls. Conclusions: Full-thickness opening resulted in a higher rate of completely hatched blastocysts than quarter zonal-thinning and controls, but the cell numbers were significantly decreased. Keywords: Assisted hatching, Laser, Differential staining, Zona drilling, Zona pellucida
Background Zona pellucida (ZP) must be shed within a time period when the uterus is receptive in order for a pregnancy to occur. Assisted hatching (AH) has been proposed to increase the hatching and embryo implantation rate, probably by enhancing early communication between the embryo and endometrium [1]. An infrared laser system appears to be the most suitable method for assisted hatching, as it has good repeatability and consistency between operators and is simple to perform [1-3]. It is debatable whether a full-thickness opening is better than the partial zona thinning. There was a concern that a hole in the zona might deprive the embryo of its protective coat against infectious or immunologic insult [3]. Blastomeres could be lost through an opening in * Correspondence: [email protected] Division of Reproductive Medicine, Department of Obstetric and Gynecology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
the zona during a difficult embryo transfer or during contraction of the uterus after the transfer [3,4]. Zonal thinning was believed to be optimal in promoting complete hatching without the potential drawbacks of the full-thickness opening [5]. In the Cochrane Systematic Review [6], subgroup analysis by the extent of assiste
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