ChiCTR-IOC-16007882.

Embryo establishes contact with the endometrium during implantation. Proper endometrial vascular development and maintenance at the time of embryo implantation is crucial for successful pregnancy. Vascular development at the maternal-embryo interface can be regulated by various cell types, of which uterine natural killer (uNK) cells play an important role. Abnormal angiogenesis and uNK cell number/function may lead to reproductive failure, particularly in women with recurrent miscarriage (RM) and women with recurrent implantation failure (RIF) after IVF-ET treatment, which are the important clinical hurdles in reproductive medicine to overcome. In this review, we aim to discuss the current knowledge of physiological angiogenic processes and the pathological angiogenesis at the time of implantation, as well as the possible mechanism and potential treatment.

A reference range for uterine natural killer cell percentage in fertile women was established. Women with recurrent reproductive failure had uterine natural killer cell percentages both above and below the reference range.

Objective: To systematically compare the endometrial microbiota in infertile women with and without chronic endometritis (CE), as diagnosed by a quantitative and reference range-based method. Design: Case-control observational study. Setting: University-affiliated hospital. Patient(s): One hundred and thirty infertile women. Intervention(s): Endometrial biopsy and fluid (uterine lavage, UL) collected precisely 7 days after LH surge, with plasma cell density (PCD) determined based on Syndecan-1 (CD138)-positive cells in the entire biopsy section and culture-independent massively parallel sequencing of the 16S ribosomal RNA gene performed on both the CE and non-CE endometrial fluid samples. Main Outcome Measure(s): Relative abundance of bacterial taxa. Result(s): Chronic endometritis was diagnosed if the PCD was above the 95th percentile (>5.15 cells per 10 mm 2 ) of the reference range in fertile control subjects. With this stringent diagnostic criterion, 12 women (9%) were diagnosed with CE. Sequencing was successfully performed on all endometrial samples obtained by UL) (CE, n ¼ 12; non-CE, n ¼ 118). The median relative abundance of Lactobacillus was 1.89% and 80.7% in the CE and non-CE microbiotas, respectively. Lactobacillus crispatus was less abundant in the CE microbiota (fold-change, range: 2.10-2.30). Eighteen non-Lactobacillus taxa including Dialister, Bifidobacterium, Prevotella, Gardnerella, and Anaerococcus were more abundant in the CE microbiota (fold-change, 2.10-18.9). Of these, Anaerococcus and Gardnerella were negatively correlated in relative abundance with Lactobacillus (SparCC correlation magnitude, range: 0.142-0.177). Conclusion(s): Chronic endometritis was associated with a statistically significantly higher abundance of 18 bacterial taxa in the endometrial cavity.