Objective
To explore the effect of letrozole as an ovulation inducing agent on oocyte and embryo quality in mice model.
Design
Prospective study.
Setting
Institute of Reproductive Medicine, Kolkata, India.
Animal(s)
Sixty-nine sexually mature female Swiss Albino mice 6–7 weeks old.
Intervention(s)
Metaphase II (MII) oocytes from two groups of mice, one group injected with letrozole and the other with rFSH.
Main Outcome Measure(s)
Number of MII oocytes, number of oocytes with meiotic spindle (MS), different angles of MS relative to the polar body (PB), spindle characteristics, and fertilization outcome.
Result(s)
The MS was present in 84 % and 71.2 % of the oocytes in the letrozole and rFSH group, respectively. In the letrozole group, 73 % of the oocytes had a 0° spindle position compared with 35.7 % in the rFSH group. With letrozole, 19 % of the oocytes had 0° > MS < 90° and 8 % had MS >90°, compared with 46.1 % oocytes with 0° > MS < 90° and 18.2 % with MS >90° with rFSH. Mean spindle area retardance, spindle dimensions, and 4–8-cell embryo formation rate were significantly higher with letrozole compared with rFSH. Two-cell and blastocyst formation rates were similar in both groups.
Conclusion(s)
Robust birefringent spindles were obtained in mice on superovulation with letrozole. Letrozole does not appear to increase the risk of spindle assembly and preimplantation developmental arrest in mouse oocytes.
