Vascular remodeling in the ovary

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PROJECT SUMMARY Corpus luteum removal during the first trimester of pregnancy leads to pregnancy termination. With rising infertility rates and ~25% of pregnancies ending in the first trimester, research in luteal physiology is increasingly relevant. Disruption of luteal function is mediated by inflammatory cytokines and lipid mediators. The key lipid mediator prostaglandin F2α (PGF2α) is produced within the gland in humans and non-human primates and by the non-pregnant endometrium in domestic farm animals. The corpus luteum is one of the most vascularized organs in the adult body. Development of the luteal vasculature following ovulation is vital for the production of progesterone. The luteal vasculature is unique because it is possibly the only case of full angiogenesis and angioregression in the adult. When the corpus luteum regresses at the end of a non-fertile reproductive cycle, microvascular endothelial cells are the first cells to die. However, these cells do not express receptors for the luteolytic signal, PGF2α. Only the steroidogenic large luteal cells (LLC), which derive from the granulosa cells of the ovulated follicle, possess this receptor in the corpus luteum. Therefore, the endothelial cell death response during the early stages of regression is likely initiated by factors released by large luteal cells in response to PGF2α. Our overarching hypothesis is that the disruption of endothelial cell networks during luteal regression are due to factors produced by large luteal cells in response to PGF2α. The goals of this study are to: (1) identify cell-specific temporal changes in gene transcription during induced luteal regression in vivo, and (2) conduct mechanistic studies to determine mediators of luteal angioregression utilizing a novel 3D organoid culture system. We will use single nuclear RNA sequencing (snRNA-seq) to determine the cell-type specific temporal patterns of gene expression during luteal regression. Hypothesis: Large steroidogenic luteal cells respond to PGF2α by rapidly increasing production of inflammatory mediators and anti-angiogenic factors, followed by induction of genes in endothelial cells that contribute to vascular disruption and cell death. We recently developed novel 3D luteal organoid model to allow us to determine which large luteal cell secretory product(s) affect the regression of luteal endothelial structures. Hypothesis: inflammatory mediators produced by LLC will disrupt endothelial networks and alter cell fate. The state-of-the-art approach using snRNA-seq profiling will provide the first unbiased transcriptomic atlas of the cell type specific gene expression in the corpus luteum. The studies will provide novel insight into the temporal changes in gene expression in specific luteal cell types during the process of luteal regression. Successful completion of the proposed research will fill a gap in knowledge about the pathways crucial for maintaining gonadal function and identify novel mechanisms by which the lipid mediator PGF2α disrupts gonadal function. Insight into luteal angioregression will provide the foundations for identifying mechanisms to maintain vasculature structures in the ovary and other reproductive tissues.