MicroRNA as a Marker of Placental Health in the Mare

Placentitis is a common cause of abortion in late pregnant mares and poses a significant threat to fetal and neonatal viability. Early detection and accurate diagnosis of placentitis are essential for treatment to be effective; however, current diagnostic techniques aren't always effective at detecting placentitis at an early, manageable stage. Therefore, there is a significant unmet need for a simple, non-invasive diagnostic technique which can reliably diagnose placentitis, even at the early stages. MicroRNAs have the potential to meet that need. MicroRNAs are newly discovered, non-coding RNAs which play an important role in regulating gene expression. As more research is conducted, it is becoming increasingly apparent that these small molecules have implications in the future of both diagnostics and therapeutics. Beyond the role they play in cancer, microRNAs also play a crucial role in pregnancy regulation and maintenance. Unfortunately, the equine community has been slow to initiate research; only 13 articles on miRNAs have been published specifically in horses. This study will track miRNAs in both chorion and serum in mares throughout gestation, as well as before and after the experimental induction of placentitis. Twenty-six pony mares have been bred for the purpose of this study, and will be euthanized at various gestational time points, including four months (n = 4); six months (n = 4); nine months (n = 14) and diestrus (11 days; n = 4). A subset of pony mares will be inoculated with Streptococcus zooepidemicus equi at 9 months gestation, prior to euthanasia (n = 7). Following euthanasia, various tissues will be collected for further analysis including endometrium, chorion, as well as other maternal and fetal tissues. Chorion from three mares in each category will be submitted for next generation sequencing. These results should highlight specific miRNAs which change significantly throughout gestation, and can be used as markers of placental health. These miRNAs will be further evaluated across a larger sample subset using qPCR, including serum samples from mares with clinically diagnosed placentitis. This research has the potential to make a tremendous impact on the future knowledge of microRNAs, not only in horses, but in other species as well. Research performed to date has demonstrated the potential application of these very important molecules; however, a great deal of research remains to realize their potential application. MicroRNAs are important to cell function and essential for life, and are differentially regulated in most, if not all, diseases. The diagnostic and therapeutic potential of microRNAs is phenomenal; circulating levels typically mimic local levels, there is some degree of tissue specificity, and most microRNAs regulate a number of different, but related, messenger RNAs. Due to the minimal knowledge of microRNAs in the horse combined with their tremendous potential as biomarkers, the data generated from this project should not only be highly publishable, but should also make a remarkable impact on the future of the horse industry.