Is Chorionic Gonadotropin Beta Subunit the Elusive Signal of Equine Maternal Recognition of Pregnancy?

This proposal aims to: 1) characterize the initial expression, peak abundance, and expression pattern of CGB/LHB peptide in equine conceptuses within 10-15 days after ovulation; 2) identify CGB/LHB peptide in the conceptus'' secretome, including the uterine environment (in vivo) and embryo-conditioned culture media (in vitro), using low-gradient chromatography (LGC) for comprehensive proteomic coverage of low abundant proteins ; and 3) investigate the impact of eCG (CGB) administration on days 9, 11, and 13 after ovulation on CL and endometrial functions in non-pregnant mares. If validated, our hypothesis will represent a significant advancement in equine MRP research and could facilitate the development of beneficial clinical tools for the equine breeding industry. Long-term Goals: Our goal is to elucidate CGB/LHB mechanisms of action during equine early pregnancy and its potential clinical applications in equine reproduction. In this perspective, the current proposed seed grant will generate novel fundamental data for submitting a standard research grants proposal to the USDA AFRI Competitive Grants Program and, tentatively the entitled – “Integrated Multi-omics Approach to Reveal the Biological Functions of Chorionic Gonadotropin Subunit β / Lutropin Subunit β during Early Equine Pregnancy”. This future standard grant will utilize an integrated multi-omics (transcriptomic, miRNomic, and methylomic) approach to elucidate in vitro effects of CGB/LHB on equine luteal and endometrial organoids or cell lines, which will improve our understanding about this signal downstream molecules and its biological effects. Moreover, the data generated from the current seed grant will enable us to submit a grant proposal to the Wild Horse and Burro Program funded by The Bureau of Land Management''s (BLM), tentatively entitled – “Impact of Active Immunization Against Chorionic Gonadotropin Subunit β / Lutropin Subunit β and its Receptors on Equine Fertility”. This future standard grant aim to develop a vaccine against CGB/LHB or its receptor (LHCGR), which might provide a novel tool for controlling the population of wild horses. In addition to the previously mentioned two future grants, we would like to investigate other potential clinical applications of CGB/LHB in equine reproduction. For instance, if we could detect CGB in the in vitro embryo culture media (as described in specific aim 2), we would like to investigate the possibility of using CGB as a non-invasive biomarker for embryo health/quality monitoring and pregnancy outcome. Also, we would like to investigate if eCG administration on day 9±1 after ovulation would improve conception/pregnancy rate.