investigating the effect of laser assisted hatching on the development and quality of vitrified-warmed 4-cell stage mouse embryos

objective: the aim of this study was to investigate the effect of laser assisted hatching on the development and quality of vitrified-warmed 4-cell stage mouse embryos. materials and methods: the vitrified-warmed 4-cell mouse embryos were divided into two groups: control group (without laser assisted hatching) and experiment group (with laser assisted hatching). all embryos in both groups were cultured in sequential media containing g1tmver3 and g2tmver3. afterward, all expanded blastocysts were randomly selected and stained with differential (for cellularity) and tunel (for cell death) methods. results: on day 1(24hrs) of culture, the difference between the control and the experimental groups was insignificant in the rate of blastocyst formation. but on day 2(48hrs) of culture, 87.61% of embryos in the experimental group reached the blastocyst stage. this rate did not increase significantly as compared to the control group (78.14%). finally on day 3 (72 hrs), the rate of blastocyst formation reached 94.40% and 81.75%, respectively, in both the experimental and control groups. the difference between these two groups were significant (p<0.05). the number of blastomeres and apoptotic cells were similar in the experimental and control groups. conclusion: the laser assisted hatching has no decreasing effect on cellularity, but it has increasing effect on incidence of cell death. in addition, the assisted hatching significantly increases the blastocyst formation rate of intact vitrified-warmed 4-cell stage mouse embryos.