鼠胚研究顯示, 打薄中空透明帶ZP並無法有效提高胚胎孵化率(39%)，
更可能會阻礙胚胎完全孵化過程

打穿中空透明帶ZP可有效提高胚胎孵化率(94%)，提早孵化時間14h

Hum Reprod. 2014 Dec;29(12):2670-9. doi: 10.1093/humrep/deu245. Epub 2014 Sep 29.

Laser-assisted zona pellucida thinning does not facilitate hatching and may disrupt the in vitro hatching process: a morphokinetic study in the mouse.

Schimmel T1, Cohen J2, Saunders H3, Alikani M4.

Author information

Abstract

STUDY QUESTION:

Does laser-assisted zona thinning of cleavage stage mouse embryos facilitate hatching in vitro?

SUMMARY ANSWER:

No, unlike laser zona opening, zona thinning does not facilitate embryo hatching.

WHAT IS KNOWN ALREADY:

Artificial opening of the zona pellucida facilitates hatching of mouse and human embryos. Laser-assisted zona thinning has also been used for the purpose of assisted hatching of human embryos but it has not been properly investigated in an animal model; thinning methods have produced inconsistent clinical results.

STUDY DESIGN, SIZE, DURATION:

Time-lapse microscopy was used to study the hatching process in the mouse after zona opening and zona thinning; a control group of embryos was not zona-manipulated but exposed to the same laser energy.

PARTICIPANTS/MATERIALS, SETTING, METHODS:

Eight-cell CB6F1/J mouse embryos were pooled and allocated to three groups (n = 56 per group): A control group of embryos that were exposed to a dose of laser energy focused outside the zona pellucida (zona intact); one experimental group of embryos in which the zona pellucida was opened by complete ablation using the same total number of pulses as the control group; a second experimental group of embryos in which the zona pellucida was thinned to establish a smooth lased area using the same number of pulses as used in the other two groups. The width of the zona opening was 25 μm and width of the thinned area was 35 μm. Development was monitored by time-lapse microscopy. Overall treatment differences for continuous variables were analyzed by analysis of variance and pairwise comparisons using the Student t-test allowing for unequal variances, while for categorical data, a standard chi-squared test was utilized for all pairwise comparisons.

MAIN RESULTS AND THE ROLE OF CHANCE:

The frequency of complete hatching was 33.9% in the control group, 94.4% after zona opening, and 39.3% after zona thinning (overall group comparison, P < 0.0001). Overall, 60.7% of the zona-thinned embryos did not complete the hatching process and remained trapped within the zona; when they did hatch, they did not necessarily hatch from the zona-thinned area. Hatching in about one-third of the zona-intact embryos began with breaches at multiple sites by small groups of cells. Likewise, 53.6% of zona-thinned embryos had multiple breaches, always involving an area outside the thinned zone. Zona opening decreased multiple breaching and led to blastocyst escape an average of 14 h earlier than zona-thinned embryos and 5.5 h before control embryos (P = 0.0003).