Oxford University Press, The Journal of Clinical Endocrinology & Metabolism, 9(106), p. 2547-2565, 2021
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AbstractContextSuboptimal endometrial thickening is associated with lower pregnancy rates and occurs in some infertile women treated with clomiphene.ObjectiveTo examine cellular and molecular differences in the endometrium of women with suboptimal vs optimal endometrial thickening following clomiphene.MethodsTranslational prospective cohort study from 2018 to 2020 at a university-affiliated clinic. Reproductive age women with unexplained infertility treated with 100 mg of clomiphene on cycle days 3 to 7 who developed optimal (≥8mm; n = 6, controls) or suboptimal (<6mm; n = 7, subjects) endometrial thicknessunderwent preovulatory blood and endometrial sampling.The main outcome measures were endometrial tissue architecture, abundance and location of specific proteins, RNA expression, and estrogen receptor (ER) α binding.ResultsThe endometrium of suboptimal subjects compared with optimal controls was characterized by a reduced volume of glandular epithelium (16% vs 24%, P = .01), decreased immunostaining of markers of proliferation (PCNA, ki67) and angiogenesis (PECAM-1), increased immunostaining of pan-leukocyte marker CD45 and ERβ, but decreased ERα immunostaining (all P < .05). RNA-seq identified 398 differentially expressed genes between groups. Pathway analysis of differentially expressed genes indicated reduced proliferation (Z-score = –2.2, P < .01), decreased angiogenesis (Z-score = –2.87, P < .001), increased inflammation (Z-score = +2.2, P < .01), and ERβ activation (Z-score = +1.6, P < .001) in suboptimal subjects. ChIP-seq identified 6 genes bound by ERα that were differentially expressed between groups (P < .01), some of which may play a role in implantation.ConclusionWomen with suboptimal endometrial thickness after clomiphene exhibit aberrant ER expression patterns, architectural changes, and altered gene and protein expression suggesting reduced proliferation and angiogenesis in the setting of increased inflammation.