Functional assessment of extracellular vesicles from the female reproductive tract during early pregnancy

/ABSTRACT Assisted reproductive technologies (ART) have revolutionized fertility treatments, yet implantation success rates remain suboptimal. Emerging evidence reveals that maternal tubal fluid, specifically extracellular vesicles (EVs), nanoscale membrane-bound carriers rich in bioactive molecules that play a pivotal role in embryo-maternal communication essential for early embryo development and implantation. EVs transport lipids, proteins, and regulatory RNAs, including miRNAs, which influence embryo physiology and developmental competence. Although in vitro studies demonstrate embryo uptake of EVs from reproductive tract cells across species, the physiological relevance of maternal EVs during natural embryo development in vivo remains largely unexplored. Critically, EV populations and cargo profiles differ markedly between in vivo and in vitro conditions, underscoring a pressing need to investigate EVs in their native environment. Our innovative study leverages oviductal epithelial cell-specific CD9-green fluorescent protein (GFP) reporter mice to directly visualize and track maternal EVs within preimplantation embryos in vivo. We have discovered CD9-GFP+ EVs localized in the perivitelline space of 4- to 8-cell stage embryos, providing the first direct in vivo evidence of maternal EV-embryo communication during early development. Building on this, our research pursues two complementary aims: (1) to comprehensively map EV distribution and profile miRNA cargo in oviductal and uterine luminal fluid throughout early pregnancy stages, illuminating dynamic changes in EV-mediated signaling; and (2) to elucidate the functional significance of epithelial cell- derived EVs by employing pharmacological inhibitors to disrupt EV biogenesis and release in vivo, assessing consequent effects on embryo development, implantation, and pregnancy outcomes. This study offers a significant advance in reproductive biology by uncovering the in vivo role of maternal EVs in supporting embryo development and implantation. Our innovative use of epithelial-specific CD9-GFP reporter mice to directly visualize EV transfer to embryos provides valuable new insight into natural embryo-maternal communication. By combining cutting-edge molecular profiling with functional inhibition of EV biogenesis in vivo, this research is uniquely positioned to identify key EV cargos that influence embryo viability and pregnancy outcomes. The results will deepen our fundamental understanding of early developmental processes and enable the development of novel, clinically relevant strategies to improve assisted reproductive technologies. Leveraging maternal EVs as biomarkers or therapeutic agents holds strong potential to enhance ART success rates and promote healthy pregnancies, addressing critical challenges in fertility treatment. Project Number: 1R21HD119276-01A1 | Fiscal Year: 2026 | NIH Institute/Center: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) | Principal Investigator: Wipawee Winuthayanon | Institution: UNIVERSITY OF MISSOURI-COLUMBIA, COLUMBIA, MO | Award Amount: $411,539 | Activity Code: R21 | Study Section: Cellular, Molecular and Integrative Reproduction Study Section[CMIR] View on NIH RePORTER: https://reporter.nih.gov/project-details/11377190