Agne Velthut-Meikas

Reproduction is regulated by the endocrine system and its disturbances by endocrine disruptive chemicals (EDCs) may lead to infertility. As humans are constantly exposed to EDCs through the use of common household items and personal care products, it is important to test chemicals for their potential activity as endocrine disruptors affecting reproductive function. Project MERLON aims to study the effects of EDCs on sexual development and function in order to deliver new approach methodologies (NAMs) for EDC identification. While MERLON targets the vulnerable stages of development from fetal to puberty, MERLON2, with additional partner TalTech, will add one more sensitive window of susceptibility in female reproduction to the project: the adult preovulatory ovarian follicle, where the oocyte maturation takes place. In collaboration with TalTech, it was recently demonstrated that follicular somatic cells (FSCs) lose sensitivity to follicle stimulating hormone (FSH) in the presence of a mixture of 13 EDCs. FSH is crucial for both, the oocyte maturation and for the synthesis of steroid hormones by the FSCs. We have also demonstrated the intricate heterogeneity of somatic cells in the ovarian follicle. The roles that FSC subpopulations play in the adverse effects of EDCs is unknown and unaddressed by the initial MERLON project. MERLON2 will complement the aims of the consortium by developing NAMs based on single cell transcriptomics, automated image analysis and machine learning to understand the effect of EDCs on FSC subpopulations and their sensitivity to FSH. This will increase the research output for MERLON in the number of proposed NAMs and quantitative adverse outcome pathways. As a result of MERLON2 the range of stakeholders will enlarge, increasing the public awareness related to the harmful health effects of EDCs, and proposing new approaches to resolve the complicates issue of testing substances in everyday products for their adverse effects on human fertility.

Communication between cells in ovarian follicle is a prerequisite for oocyte maturation and ovarian functions, disturbances of which lead to infertility. Polycystic ovarian syndrome (PCOS) and poor response to hormonal stimulation in infertility treatment are types of subfertility of ovarian aetiology. The current project addresses the importance of intercellular communication in human ovarian follicle by combining various RNA sequencing methods (RNA-seq) with systems biology analysis. The full-length single molecule RNA-seq will be exploited to characterize the mRNA isoform map of ovarian granulosa cell populations. MicroRNA profile of cells and follicular fluids will also be analysed. Single-cell RNA-seq will describe immune cell populations in the ovarian pre-ovulatory follicle. The datasets will be integrated to model communication between follicular cells to reveal signalling pathways disturbed by (post-)transcriptional events in PCOS and poorly responding IVF patients.