Reproductive performance of mouse oocyte after in vivo exposure of the ovary to continuous wave ultrasound

Abstract

Background: There is a lack of studies regarding the effects of ultrasound (US) and replication of its exposure on pre-implantation events in mammals. Thus, this study assesses the reproductive performance of mouse oocytes that have been obtained from ovaries irradiated with US waves versus non-irradiated ovaries. Also comparision of their parthenogenesis, ovulation, fertilization, and pre-implantation development rates.

Materials and methods: In this experimental study, we divided extracted ovaries into three experimental groups that received the same dosage, but different replicates of radiation for each group. Results were compared with the control and sham groups. Continuous wave (CW) US, at a spatial average intensity of 355 mW/cm(2) and a frequency of 3.28 MHz, was administered for 5 minutes to the ovaries at an interval between pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) injections. Statistical analysis was performed using the ANOVA test and the level of significance was determined to be 0.05.

Results: Data collection was based on microscopic visualization. According to the obtained results, metaphase II (MII) oocyte numbers and the percentage of blastocysts significantly reduced in the USexposed groups versus the unexposed groups. Fertilization rate was comparable between groups while parthenogenesis was significantly higher in the US-exposed groups compared to the unexposed groups.

Conclusion: Structural damage to cells, intracellular organelles and proteins, as well as changes in signaling pathways induced by US may be reasons for some of the observed adverse effects in groups that have received more US exposure.

Keywords: Blastocyst; Fertilization Rate; Mouse Oocyte; Parthenogenesis; Ultrasound.

Fig 1

The exposure system and mouse fulcrum. The chamber of system was filled with degassed water. The cyclic section from the center of the left lid was removed, and the US probe was positioned centrally and perpendicular to the chamber. The anesthetized mouse was placed on the cubic piece of yonolit at the opposite end of the chamber. The mouse’s paws were placed on top of the fulcrum. The ventral face of the fulcrum was concave and the mouse’s abdomen was placed inside it. A sliding metaliferous rail was positioned under the mouse fulcrum. The axial distance between the mouse ovary and probe was 25.5 cm. At the right end of the chamber there was a cylindrical plastic prominence with a 1 cm diameter to ensure accurate targeting of the mouse ovary.