Endometrial regeneration and uterine disorders : cellular and molecular studies

The human endometrium, a unique mucosal tissue, exhibits remarkable regenerative capacity, undergoing monthly cycles of breakdown and renewal. Such a dynamic remodeling process is hypothesized to be initiated and orchestrated by putative stem/progenitor cells residing in the basalis layer. However, precise characterization of these stem cell populations and their regulatory networks remains elusive due to limited 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 therefore essential for understanding the cellular and molecular mechanisms governing endometrial regeneration, thereby enhancing our mechanistic insight into the pathogenesis of various uterine disorders and facilitating the development of more targeted therapeutics.

In Study I, we explored the therapeutic action of vaginal bromocriptine for adenomyosis. Our findings revealed that bromocriptine treatment exerted anti-proliferative effects on eutopic endometrium from adenomyosis both ex vivo and in vitro, potentially acting by regulating certain microRNAs and signaling pathways linked to cell proliferation.

In Study II, we investigated the role of microRNAs in endometriosis through small RNA sequencing. Comparative analysis between women with and without endometriosis 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 contribute to endometriosis development through modulation of cell migration and relevant pathways.

In Study III, we analyzed transcriptional profiles of placental tissues from SARS-CoV-2 - infected and non-infected women during the third trimester of pregnancy. Despite the absence of detectable viral load in placental tissue, we observed significant downregulation of nine immunoglobulin superfamily genes in the maternal compartment of actively infected cases, suggesting potential molecular mechanisms underlying the increased risks of pregnancy complications associated with COVID-19 infection.

In Study IV, utilizing high-resolution spatial transcriptomics(Visium HD), we mapped cellular heterogeneity within full-thickness endometrium across three distinct time points during the proliferative phase. Our results provide a highly resolved spatial transcriptional atlas of the proliferative endometrium that aligns well with tissue morphology, revealing pronounced spatial cellular heterogeneity and dynamic molecular change during endometrial regeneration.

In conclusion, this thesis advances our understanding of basic endometrial biology and provides mechanistic insights into several endometrial pathologies through integrated multi?scale analyses spanning histological, cellular, and molecular investigations. By applying cutting-edge next-generation sequencing technologies across four distinct studies, we have explored both physiological and pathological aspects of human endometrial tissue. The insights gained in the thesis will lead to future research in regenerative medicine and the development of targeted therapies for uterine disorders, ultimately improving women’s fertility and reproductive health.

List of scientific papers

I. Tang Y† , Ponandai-Srinivasan S† , 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 C† , Tang Y† , 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 Y† , 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/ijms25031608

IV. Tang Y† , Frisendahl C† , 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