Endometrial regeneration and uterine disorders : cellular and molecular studies

The human endometrium is a unique mucosal tissue with remarkable regenerative capacity, undergoing monthly cycles of repair and regeneration. It is populated that this dynamic remodeling process is initiated and orchestrated by putative stem/progenitor cells residing in the basalis. However, lacking accurate localization and characterization of these stem cell populations and their regulatory networks hampers a deeper understanding of cellular and molecular mechanisms of endometrial regeneration, due to restricted access to full-thickness endometrial specimens and insufficient exploration of tissue heterogeneity at single-cell resolution. Many pathological factors can disrupt normal endometrial remodeling, leading to various common uterine disorders, including endometriosis, adenomyosis, intrauterine adhesions, and thin endometrium, therefore extensively affecting women's reproductive health. Elucidating the spatial and temporal dynamics of endometrial tissue heterogeneity at single- cell resolution is essential for understanding the underlying cellular and molecular mechanisms of endometrial regeneration, thereby enabling improved mechanistic insight into the pathogenesis of uterine disorders and the development of targeted therapeutic strategies in the future.In Study I, we explored the therapeutic efficacy of vaginal bromocriptine for adenomyosis. Our findings revealed that bromocriptine treatment exhibited anti-proliferative effects in adenomyosis patients' endometrium both ex vivo and in vitro, potentially acting through the regulation of specific microRNAs and proliferation-associated signaling pathways.In Study II, to understand the roles of microRNAs in the pathogenesis of endometriosis, we investigated dysregulated microRNAs in endometriosis through small RNA sequencing. By comparing women with and without endometriosis, we identified 14 differentially expressed microRNAs. Through integrated analysis combining target gene prediction, mRNA sequencing, experimental validation, and bioinformatic analysis, we characterized two key microRNAs and their potential target genes that may influence endometriosis development through the regulation of cell migration.In Study III, we analyzed the transcriptional profiles of placental tissues from SARS-CoV-2 - infected and non-infected women during the third trimester of pregnancy. While we did not detect any viral load in placental tissue, we observed significant downregulation of nine immunoglobulin superfamily genes in the maternal compartment of active infected cases, suggesting potential molecular regulation and pathways underlying increased risks of pregnancy complications associated with COVID-19.In Study IV, using high-resolution spatial transcriptomics (Visium HD), we mapped cellular heterogeneity within the full-thickness endometrium during three different time points at the proliferative phase. Our results provide a highly resolved spatial transcriptional map of the proliferative endometrium, aligning well with tissue morphology, and revealing a high level of spatial cellular heterogeneity and its dynamic molecular change during endometrial remodeling.In summary, the thesis advances our understanding of basic endometrial biology and provides mechanistic insights into several endometrial pathologies through integrated multi-scale analyses spanning from histology to cellular and molecular investigations. By applying cutting- edge next-generation sequencing technologies in four distinct studies, we explored both physiological and pathological aspects of human endometrial tissue. The insights gained in the thesis may inform future research into regenerative medicine and the development of targeted therapies for uterine disorders, ultimately improving women's fertility and reproductive health.List of scientific papersI. Tang Yt, Ponandai-Srinivasan St, Frisendahl C, Andersson JK, Pavone D, Stewart EA, Lalitkumar PGL, Korsching E, Bogavarappu NR, Gemzell- Danielsson K. Bromocriptine inhibits proliferation in the endometrium from women with adenomyosis. Front Endocrinol (Lausanne). 2023 Mar 9;14:1026168. https://doi.org/10.3389/fendo.2023.1026168 II. Frisendahl Ct, Tang Yt, Peters, M., Bogavarappu, N. R., Lalitkumar, P. G., Piltonen, T., Arffman, R.K., Salumets, A., Gotte, M., Korsching, E., Gemzell- Danielsson, K. miR-193b-5p and miR-374b-5p are aberrantly expressed in endometriosis and suppress cell migration in vitro. Biomolecules. 2024;14(11):1400. https://doi.org/10.3390/biom14111400 III. Tang Yt, Boggavarapu NR+, Aronsson A, Gemzell-Danielsson K, Lalitkumar PG. Global transcriptomic analysis of placentas from women with gestational SARS-CoV-2 infection during the third trimester of pregnancy. Int J Mol Sci. 2024; Jan 28;25(3):1608. https://doi.org/10.3390/ijms25031608IV. Tang Yt, Frisendahl Ct, Nair K, Boggavarapu NR, Flam F, Kopp Kallner H, Papaikonomou K, Lalitkumar PG, Gemzell-Danielsson K. Spatio-temporal transcriptome of the human proliferative endometrium at single-cell scale. [Manuscript]+ Shared first author