Endometrial Vascularization Characterized by Optical Coherence Tomography and Immunohistochemistry in Women Undergoing In Vitro Fertilization-Embryo Transfer Treatment

Background and objective: Endometrial angiogenesis is a prerequisite for successful pregnancy. Optical coherence tomography (OCT) is a non-invasive physically optical imaging technique widely used in ophthalmology and cardiology. However, there is no study using OCT to evaluate endometrium. The aim of this study was to use OCT and traditionally histological methods to investigate endometrial vascularization in women undergoing in vitro fertilization-embryo transfer (IVF-ET) treatment and to determine the association with the pregnancy outcome. Methods: A total of 47 women were included in this study. OCT was used to assess endometrial vascularization by determining the high signal areas precisely on the seventh day after luteinizing hormone surge in non-conception natural cycles. Endometrial biopsies were obtained following OCT and immunohistochemistry was used to determine micro vessel and expression of vascular endothelial growth factor-A (VEGF-A) in the luminal epithelium, glandular epithelium and stroma, separately. Micro vessel counting was performed and the result was expressed as micro vessel density (MVD). A semi-quantitative H-score was used to determine the staining intensity of VEGF-A. Results: In women who successfully conceived after embryo transfer, the proportion of extensive high signal area in the uterine body detected by OCT (80%, 8/10), MVD (median number of micro vessels/mm(2) of 10, range 4–17) and stromal expression of VEGF-A (median H-score of 189, range 72–395) were found to be significantly higher than those of women who did not conceive after embryo transfer in the subsequent IVF-ET treatment (OCT: 30%, 3/10; MVD: median number of micro vessels/mm(2) of 7, range 4–10; VEGF-A: median H-score of 125, range 86–299, respectively). In addition, a significantly higher stromal expression of VEGF-A (median H-score of 196, range 84–395) and MVD (median number of micro vessels/mm(2) of 9, range 5–16) was found in women with extensive high signal area in uterine body, compared to those with focal or no high signal area (stromal VEGF-A: median H-score of 135, range 92–302; MVD: number of micro vessels/mm(2) of 6, range 4-11). Conclusions: Both immunohistochemistry and OCT demonstrated significant difference in vascularization of the peri-implantation endometrium between subjects who did and did not conceive after IVF-ET treatment. Our findings also suggest OCT appears to be a promising non-invasive or minimally invasive alternative to study endometrial vascularity in women with reproductive failure.