In Vivo Mouse Embryo Growth with Exposure to E‐Cig Vapor

Objective To determine the consequence of vaping during pregnancy on total embryo number, implantation, size, development and teratogenesis using a murine bioassay. Methods In order to achieve the optimal treatment dose (OTD), various exposure times, doses, and wattage were considered and tested. The OTD is based off the fact that a traditional tobacco cigarette produces cotinine levels (metabolite of nicotine) up to 35ng/mL in humans [Fu, Marcela et al., 2009]. E‐cigarettes (e‐cigs) are known to be able to produce similar cotinine values usually observed in cigarette smokers [Etter, 2016] thus, the e‐cig wattage was set to produce cotinine values from 25 – 100ng/mL. After exposing separate groups of mice to various treatments, blood was collected from a tail clip, and the serum was analyzed via ELISA for cotinine concentrations. The results demonstrated that the OTD occurred in a group that was exposed for 10 minutes of breathing after 10 seconds of 1.2% nicotine (high dose) vapor introduction into the chamber at 40 watts. This treatment bout yielded a serum cotinine value of 68.5ng/mL, which equates to roughly two cigarettes per exposure. Female mice were assigned to four groups containing a negative control, carrier fluid control (0% nicotine), medium (0.6% nicotine) and high (1.2% nicotine) doses. Female mice were vaped with the OTD prior to a hormonally induced superovulation/mating protocol. Each group was vaped three times for 10 minutes each bout, per day, in the mass dosing chamber connected to an air flow modulator set to a 5L/min draw; a total of 30 minutes of exposure per day. Negative control mice were also removed from the vivarium three times per day during each experimental treatment. On day 17 of pregnancy, all plug‐positive mice from each group was sacrificed using cervical dislocation immediately prior to fetal collection. Bilateral celiotomy was performed and uterine contents were recorded. Results Each animal was expected to produce, based on our data collected since 1979, in over 10,000 mice, an average of 15 embryos per successful mating (successful mating is approximately 1 per 2 stimulated females = (½)). Our results however, did not match this projection. No group was able to achieve a successful pregnancy of greater than 29%. The pregnancy rates for the mice were 29%, 13%, 25%, and 25% for the negative control, 0%, 0.6% and 1.2% groups, respectively. Furthermore, only one litter produced more than 10 pups. After performing a oneway Anova analysis of the weight of the mice, a P value of < 0.7 was generated. We were able to rule out the low pregnancy rate/litter size due to our treatment. Conclusions The significantly low number of viable pups per group and in total, indicates that a better model of evaluating the effects of vaping on fetal development needs to be employed. While many factors could have caused the low results such as stress, we suspect that it may have been due to the superovulatory technique used. Superovulation can produce litters larger than a natural ovulation and this might have been what resulted in so many resorption sites that were observed within the uterine horns. Support or Funding Information LUCOM Center for Research This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .