Compartment-Specific Endometrial Gene Analysis in Infertile Women with Thin Versus Normal Endometrium on Oocyte Retrieval Day: Insights from a Cross-Sectional Study.

Thin endometrium is an increasingly recognized challenge in infertility treatment. This study aimed to compare endometrial gene expression between women with thin and normal endometrial thickness, and also to identify ovarian stimulation-related factors associated with thin endometrium. Endometrial tissue samples were collected from infertile women undergoing controlled ovarian stimulation, including 10 samples with thin endometrium (less than 7 millimeters) and 10 with normal thickness (7 millimeters or more) on the day of egg retrieval. Gene expression was analyzed using quantitative real-time polymerase chain reaction. The relative expression of LGR5 in the luminal epithelium was slightly higher in the thin group, while POU5F1 expression in the stromal area was higher in the normal group. In the perivascular region, PDGFRB and SUSD2 were more highly expressed in the normal group, with SUSD2 showing a statistically significant difference (p=0.034). In addition, under higher serum estradiol levels, both POU5F1 and LGR5 showed greater expression in the normal group compared to the thin group with lower estradiol levels. Reduced SUSD2 expression in the perivascular region, a marker of endometrial stem and progenitor cells, may contribute to impaired endometrial growth. Serum estradiol levels also appear to influence gene expression within different endometrial compartments. These findings may offer insights into new therapeutic strategies for managing thin endometrium.