Sphingosine 1-phosphate (S1P), an inflammatory mediator, is abundantly contained in red blood cells and platelets. We hypothesized that the S1P concentration in the peritoneal cavity would increase especially during the menstrual phase due to the reflux of menstrual blood, and investigated the S1P concentration in the human peritoneal fluid (PF) from 14 non-endometriosis and 19 endometriosis patients. Although the relatively small number of samples requires caution in interpreting the results, S1P concentration in the PF during the menstrual phase was predominantly increased compared to the non-menstrual phase, regardless of the presence or absence of endometriosis. During the non-menstrual phase, patients with endometriosis showed a significant increase in S1P concentration compared to controls. In vitro experiments using human intra-peritoneal macrophages (MΦ) showed that S1P stimulation biased them toward an M2MΦ-dominant condition and increased the expression of IL-6 and COX-2. An in vivo study showed that administration of S1P increased the size of the endometriotic-like lesion in a mouse model of endometriosis.

Background: Macrophages are essential immune cells critical to reproductive physiology. They regulate key processes such as follicular development, ovulation, and luteinization in the ovaries. Macrophages are also involved in endometrial remodeling, immune tolerance, and placentation in the uterus. Methods: This review examined the biological characteristics of macrophages and their role in ovarian, uterine, and fallopian tube physiology. It focused on findings from both animal and human studies to provide a comprehensive understanding of macrophage functions. Main Findings: In the ovaries, M1 macrophages play a role in folliculogenesis and ovulation through the inflammatory and angiogenic pathways. Macrophages also maintain the corpus luteum and vascular integrity. In the uterus, macrophages regulate tissue repair and remodeling during the menstrual cycle and play a critical role in implantation by maintaining immune tolerance and supporting decidualization. Dysregulation of the M1/M2 balance can cause implantation failure. In the fallopian tubes, macrophages mediate tissue repair and immune responses. Macrophage polarization dynamically adapts to physiological and pathological conditions in all reproductive organs highlighting the functional plasticity of these cells. Conclusion: Macrophage polarization and functions are pivotal in maintaining reproductive health. Hence, understanding the role of macrophages in various reproductive organs provides a foundation for developing new therapies.

Objectives: This prospective study evaluated whether endometriosis is associated with chronic endometritis (CE) and affects the uterine endometrium microbiome (UEM) in women with repeated implantation failure (RIF). Methods: Forty-three women with RIF were divided into 12 with endometriosis (EM) and 31 without endometriosis (non-EM). The UEM was examined by 16S ribosomal RNA (rRNA) sequencing, and CE was determined by CD 138 staining (plasma cells > 5.15/10 mm2) simultaneously. Results: The EM group had a higher bacterial number (EM vs. non-EM; median [range], 6.5 vs. 3 [3–11, 1–16], p = 0.009), while the frequency of Lactobacillus species did not change. The rates of presence of Dialister (41.7% [5/12] vs. 3.3% [1/31], p = 0.004) and Streptococcus species (58.3% [7/12] vs. 16.1% [5/31], p = 0.017) were higher in the EM group. The prevalence of CE did not differ between the two groups. Multivariable logistic regression analysis revealed that the presence of Dialister species (odds ratio, 10.97, 95% confidence interval, 1.17–249.37, p = 0.036) was associated with endometriosis. In the EM group, five women with Dialister species had a higher number of bacterial species (10 vs. 5 [6–11, 3–7], p = 0.021) and higher Shannon diversity index (0.50 vs. 0.20 [0.19–1.39, 0.03–0.46], p = 0.026) than seven without Dialister species. Conclusions: Dialister and Streptococcus species, and the increased number of bacterial species in UEM may be related to the pathogenesis of RIF complicated by endometriosis.

Anti-β2-glycoprotein I/HLA-DR (anti-β2GPI/HLA-DR) antibody has been reported to be associated with antiphospholipid syndrome and recurrent pregnancy loss (RPL). We conducted a prospective multicenter cross-sectional study aimed at evaluating whether the anti-β2GPI/HLA-DR antibody is associated with adverse obstetric outcomes and RPL. From 2019 to 2021, serum anti-β2GPI/HLA-DR antibody levels (normal, <73.3 U) were measured in 462 women with RPL, 124 with fetal growth restriction (FGR), 138 with hypertensive disorders of pregnancy (HDP), 71 with preterm delivery before 34 gestational weeks (preterm delivery (PD) ≤ 34 GWs), and 488 control women who experienced normal delivery, by flow cytometry analysis. The adjusted odds ratios (aORs) of anti-β2GPI/HLA-DR antibody positivity for adverse obstetric outcomes and RPL were evaluated on the basis of comparisons between the control and each patient group, using multivariable logistic regression analysis. The following were the positivity rates for the anti-β2GPI/HLA-DR antibody in the patient and control groups: RPL, 16.9%; FGR, 15.3%; HDP, 17.4%; PD ≤ 34 GWs, 11.3%; and the control, 5.5%. It was demonstrated that anti-β2GPI/HLA-DR antibody positivity was a significant risk factor for RPL (aOR, 3.3 [95% confidence interval {CI} 1.9–5.6], p < 0.001), FGR (2.7 [1.3–5.3], p < 0.01), and HDP (2.7 [1.4–5.3], p < 0.01) although not for PD ≤ 34 GWs. For the first time, our study demonstrated that the anti-β2GPI/HLA-DR antibody is involved in the pathophysiology underlying FGR and HDP, as well as RPL.

Background: Relaxin (RLX)-2, produced by the corpus luteum and placenta, is known to be potentially effective in fibrotic diseases of the heart, lungs, kidneys, and bladder; however, its effectiveness in endometriosis has not yet been investigated. In the present study, we conducted a comprehensive study on the effect of RLX-2 on endometriosis. We checked the expressions of LGR-7, a primary receptor of RLX-2, in endometriomas using immunohistochemistry. Endometriotic stromal cells (ESCs) purified from surgical specimens were used in in vitro experiments. The effects of RLX-2 on ESCs were evaluated by quantitative-PCR, ELISA, and Western blotting. Gel contraction assay was used to assess the contraction suppressive effect of RLX-2. The effect of RLX-2 was also examined in the endometriosis mouse model. LGR-7 was expressed in endometriotic lesions. In ESCs, RLX-2 increased the production of cAMP and suppressed the secretion of interleukin-8, an inflammatory cytokine, by 15% and mRNA expression of fibrosis-related molecules, plasminogen activator inhibitor-1 (PAI-1), and collagen-I by approximately 50% (p < 0.05). In the gel contraction assay, RLX-2 significantly suppressed the contraction of ESCs, which was cancelled by removing RLX-2 from the medium or by adding H89, a Protein Kinase A (PKA) inhibitor. In ESCs stimulated with RLX-2, p38 MAPK phosphorylation was significantly suppressed. In the endometriosis mouse model, administration of RLX-2 significantly decreased the area of the endometriotic-like lesion with decreasing fibrotic component compared to non-treated control (p = 0.01). RLX-2 may contribute to the control of endometriotic lesion by suppressing fibrosis, scar formation, and inflammation.

Although various perinatal complications have been reported to be increased in the pregnant patients with adenomyosis, it is not clear what type of patients with adenomyosis is more likely to cause obstetric complications. In this study, we focused on the positional relationship between the placenta and adenomyosis lesion in evaluating perinatal prognosis of pregnant patients with adenomyosis. This retrospective cohort study was carried out between 1 January 2005 and 31 December 2019 in a single institution. Adenomyosis was diagnosed by magnetic resonance imaging (MRI) and/or transvaginal ultrasonography (TVUS). To evaluate the influence of adenomyosis on perinatal outcomes, we classified the positional relationship between the placenta and the adenomyosis lesion into two groups and examined the perinatal prognosis of the patients with adenomyosis by analyzing their clinical records. Group I (n = 9) was defined when the placenta was not overlaid on adenomyosis lesion. Group II (n = 11) was defined when a part of the placenta was overlaid on adenomyosis lesion. Twenty pregnant patients with adenomyosis were analyzed. There were no differences in clinical backgrounds between group I and group II. There was a significant increase in the obstetric morbidity in group II than that of Group I(group I: 6.3%, 4/63 vs group II: 18.6%, 26/77; P < 0.001). In group II, fetal growth restriction (FGR) was more frequent (0%, 0/9 vs 45.5%, 5/11; P = 0.042) and the birth weight was significantly lower than that in group I (2951.1 g ± 326.5 g vs 2318.9 ± 656.1 g; P = 0.037). There was a trend of lighter weight of the placenta in group II (550.6 ± 66.5 g vs 437.5 ± 117.8 g; P = 0.063) and the volume of bleeding during delivery was a higher trend in group II than that in group I (845.1 ± 367.1 g vs 1356 ± 604.8 g; P = 0.083). Group II was furtherly subdivided into group IIa (less than half the major axis of the placenta overlaid on adenomyosis lesion) and group IIb (more than half the major axis of placenta overlaid on adenomyosis lesion). The obstetric morbidity tended to be higher in group IIb than in group IIa (group IIa: 22.9%, 8/35 vs group IIb: 42.9%, 18/42); P = 0.09). In group IIb, the frequency of FGR was significantly higher (group IIa: 0%, 0/5 vs IIb: 83.3%, 5/6; P = 0.020) and the birth weight was significantly lower than those in group IIa (2656.8 ± 231.9 g vs 2037 ± 780.1 g; P = 0.040). All cases of FGR, hypertensive disorder of pregnancy (HDP), and oligohydramnios were observed in group IIb. Placental localization near adenomyosis may increase the risk of perinatal complications.