Case Report: Presence of volatile organic compounds (VOCs) in the OPU-oocyte searching room and its effect on equine in vitro embryo production

Abstract

Volatile organic compounds (VOCs) are hydrocarbon-based organic compounds with known detrimental effects on mammalian in vitro embryo development. Only strict air quality monitoring guarantees optimal culture conditions. Our VOC-free laboratory receives bovine and equine oocytes collected by OPU from nine different stations, to produce bovine and equine embryos in vitro by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) respectively. During fourteen consecutive equine OPU sessions, the mean blastocyst rate obtained from the oocytes collected at one of the stations were the lowest (10.4 %), when compared to the others (31.8 %). The quality of the air was suspected and passive absorption badges were placed for 5 days near where oocytes were searched for and further processed before transport (Old Room). The badges were returned for chromatographic analysis and the results indicated a poor air quality. Alcohol compounds exceeded by two-fold the recommended threshold for offices and living rooms (Ethanol: 335 ppb and Isopropanol: 129 ppb). The oocyte searching room was then moved to a different location within the station (New Room), to allow restricted access and improved air quality conditions. In vitro embryo production rates were monitored for anothereleven OPU sessions after moving the oocyte searching room to the new location. The OPU, ICSI and in vitro culture (IVC) conditions remained the same throughout the experiment. Briefly, oocytes were collected by ovum pick up (OPU) and transported to the laboratory overnight in 5 ml tubes, containing in vitro maturation (IVM) medium (IVF-Bioscience, UK) in a portable incubator at 38.2 ˚C and 5 % CO2. After 32 h of IVM, ICSI was performed on all MII oocytes and injected oocytes were cultured for nine days in Global medium (Cooper Surgical, Denmark), at 38˚C, 5 % CO2 and 5 % O2. The oocyte maturation, cleavage and blastocyst rates obtained from oocytes selected and packed in the Old vs. New Room were analyzed by ANOVA and compared by Fisher's exact test. There was no significant difference between the maturation (51.06 % vs. 48.94 %) and cleavage rates (68.75 % vs. 82.61 %) using oocytes selected and packed in the Old vs. New Room respectively. Blastocyst rates significantly improved after moving the oocyte search room to the new location: 10.42 % (5/48) for Old Room vs. 39.13 % (9/23) for New Room (P<0.01). The present work demonstrates the importance of controlling the conditions in the OPU oocyte collection room, with evidence suggesting an effect of VOCs on in vitro embryo development.