Impaired immune response against SARS-CoV-2 infection is the major factor indirectly altering reproductive function in COVID-19 patients: a narrative review.

Coronavirus disease 2019 (COVID-19) is an infectious disease affecting multiple systems and organs, including the reproductive system. SARS-CoV-2, the virus that causes COVID-19, can damage reproductive organs through direct (angiotensin converting enzyme-2, ACE-2) and indirect mechanisms. The immune system plays an essential role in the homeostasis and function of the male and female reproductive systems. Therefore, an altered immune response related to infectious and inflammatory diseases can affect reproductive function and fertility in both males and females. This narrative review discussed the dysregulation of innate and adaptive systems induced by SARS-CoV-2 infection. We reviewed the evidence showing that this altered immune response in COVID-19 patients is the major indirect mechanism leading to adverse reproduction outcomes in these patients. We summarized studies reporting the long-term effect of SARS-CoV-2 infection on women's reproductive function and proposed the chronic inflammation and chronic autoimmunity characterizing long COVID as potential underlying mechanisms. Further studies are needed to clarify the role of autoimmunity and chronic inflammation (long COVID) in altered female reproduction function in COVID-19.

Flip a coin: cell senescence at the maternal-fetal interface†.

During pregnancy, cell senescence at the maternal-fetal interface is required for maternal well-being, placental development, and fetal growth. However, recent reports have shown that aberrant cell senescence is associated with multiple pregnancy-associated abnormalities, such as preeclampsia, fetal growth restrictions, recurrent pregnancy loss, and preterm birth. Therefore, the role and impact of cell senescence during pregnancy requires further comprehension. In this review, we discuss the principal role of cell senescence at the maternal-fetal interface, emphasizing its "bright side" during decidualization, placentation, and parturition. In addition, we highlight the impact of its deregulation and how this "dark side" promotes pregnancy-associated abnormalities. Furthermore, we discuss novel and less invasive therapeutic practices associated with the modulation of cell senescence during pregnancy.

Age-related changes in CD4+ T and NK cell compartments may contribute to the occurrence of pregnancy loss in advanced maternal age.

A recent study characterized novel immune cell subsets (T, NK, and γδ T cell subsets) related to recurrent pregnancy loss (RPL). This study aims to assess whether these RPL-related immune cell subsets are affected by aging. The percentages of peripheral blood immunes cells from nulligravida women (NGW), women with a history of normal pregnancy (NP), and women with a history of pregnancy loss (PL) were detected by flow cytometry. The correlations between maternal age and cell percentages were assessed. We found a significant positive correlation between PL and maternal age. The percentages of effector memory CD4+ T (CD3+ CD4+ CD45RA¯ CCR7¯), terminally differentiated CD4+ T (CD3+ CD4+ CD45RA+ CCR7¯), and mature NK cells (CD3¯ CD56+lo) significantly increased with maternal age. A significant decrease in the percentage of Naïve CD4+ T cells (CD3+ CD4+ CD45RA+ CCR7+) with age was observed in women from the NP group. Women aged 35 or older had significantly higher percentages of effector memory CD4+ T cells, terminally differentiated CD4+ T cells, and mature NK cells than younger women. Maternal age positively correlates with terminally differentiated CD4+ T, effector memory CD4+ T, and mature NK cell percentages. In contrast, an inverse correlation was observed between Naïve CD4+ T cell and age among women from the NP group. Our findings indicate that age-related CD4+ T and NK cell dysregulation might be involved in the pathogenesis of PL in women with advanced maternal age. The underlying mechanism needs further investigation.

Altered vitamin D metabolism is involved in the dysregulation of γδT cell function and their crosstalk with trophoblasts in recurrent pregnancy loss.

BACKGROUND: Recurrent pregnancy loss (RPL) is a common disease characterized by immune dysfunction and vitamin D deficiency. This study aimed to investigate vitamin D metabolism and γδT cell phenotypes at the maternal-fetal interface in women with early normal pregnancy (NP) and RPL and to determine the effects of vitamin D on the functions of γδT cells and their crosstalk with trophoblasts. METHODS: The levels of 25-(OH)VD3 , the expression of vitamin D metabolic enzymes in the villi, and the proportion of γδT cells in the decidua were detected in women with NP and RPL. After treatment with different concentrations of vitamin D, the mRNA expression of the vitamin D receptor (VDR), cytokines, and transcription factors were detected in Vδ2+ γδT cells. In addition, the proliferation, migration, and invasion of HTR-8/SVneo trophoblasts were determined by coculturing them with vitamin D-treated Vδ2+ γδT cells and their supernatants. RESULTS: In women with RPL, the level of 25-(OH)VD3 in the villi was increased; however, that of CYP27B1 (enzyme converting 25-(OH)VD3 into 1,25-(OH)2 VD3 ) was decreased. In addition, the proportion of Vδ2+ γδT cells increased, whereas that of Foxp3+ Vδ2+ γδT cells decreased in the decidua of women with RPL. An in vitro study showed that vitamin D increased the expression of VDR mRNA and Foxp3, but decreased the expression of IFN-γ mRNA, in Vδ2+ γδT cells. Finally, vitamin D-treated Vδ2+ γδT cells promoted trophoblast migration and invasion. CONCLUSIONS: Abnormal vitamin D metabolism and γδT cell proportions were present at the maternal-fetal interface in women with RPL. Under normal pregnancy conditions, vitamin D can induce the differentiation of decidual Vδ2+ γδT cells toward an anti-inflammatory phenotype (Treg-like γδT cells) and modulate the crosstalk between Vδ2+ γδT cells and trophoblasts.

HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells: Potential immunologic biomarkers for reproductive aging.

PROBLEM: This study aimed to identify subsets of regulatory T cells (Tregs) associated with ovarian aging and determine whether they can be used as markers of reproductive aging. METHOD: This prospective cohort study was conducted among women of reproductive age. Basic physiological characteristics, reproductive hormones, Treg cell subsets, and correlations between these parameters were assessed. The POSEIDON criteria was used to identify women with low reproductive potential. RESULTS: The percentages of HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells significantly increased with age. Women between 40 and 49 years had significantly higher percentages of HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells than those at 20-29, 30-34, and 35-39 years old. Age positively correlated with FSH levels and the percentages of HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells, but inversely correlated with antral follicle count (AFC) and AMH levels. Interestingly, a positive correlation was found between the percentages of HLA-DR+ CD45RA- Tregs and FSH levels, whereas an inverse correlation was found between those of HLA-DR+ CD45RA- Tregs and AFC or AMH levels. Furthermore, a significant positive correlation was observed between the percentages of CD28- Treg-like cells and AFC. Based on POSEIDON criteria, women with the percentages of HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells above reference value ranges were assigned to the low prognosis groups. CONCLUSION: These findings suggest that HLA-DR+ CD45RA- Tregs and CD28- Treg-like cells can be used as immunologic markers of reproductive aging, which helps clinicians identify women with low reproductive potential and establish individualized therapeutic strategies.

Immunologic Memory in Pregnancy: Focusing on Memory Regulatory T Cells.

A successful pregnancy requires the maternal immune system to tolerate an allogeneic fetus. The incidence of preeclampsia and other complications related to impaired fetal tolerance is lower during the second pregnancy than during the first pregnancy. At the same time, compared with normal pregnant women in the previous pregnancy, patients with pregnancy complications in the previous pregnancy also have an increased risk of the disease when they become pregnant again. This difference may be related to the immunological memory of pregnancy. Regulatory T cells (Tregs) are immunosuppressive CD4+ T cells that play a predominant role in maintaining immune tolerance. In addition, Tregs possess immunological memory properties, including fetal or paternal-specific memory Tregs and Tregs expressing memory cell makers, forming an immunoregulatory memory against fetal antigens. In this review, we provide an overview of the characteristics of memory Tregs in pregnancy, evidence regarding the existence of memory Tregs in human pregnancy, as well as in mouse models. We also discuss the mechanism of memory Tregs induction, maintenance, and action. In addition, we described their changes during the first pregnancy, second pregnancy, postpartum, and pathological pregnancy in order to provide new targets for the diagnosis and treatment of pregnancy related diseases.

Next generation of immune checkpoint molecules in maternal-fetal immunity.

Successful pregnancy is a unique situation requires the maternal immune system to recognize and tolerate a semi-identical fetus and allow normal invasion of trophoblast cells. Although efforts have been made, the deep mechanisms of the maternal-fetal crosstalk have not yet been fully deciphered. Immune checkpoint molecules (ICMs) are a group of negative modulators of the immune response that avoid immune damage. They have been extensively studied in the fields of oncology and transplantation, while the latest evidence suggests that they are closely associated with pregnancy outcomes via multiple inhibitory mechanisms. Although studies have mostly demonstrated the regulatory role of the well-known PD-1, CTLA-4 at the maternal-fetal interface, what is unique about the newly discovered multiple ICMs remains a mystery. Here, we review the latest knowledge on ICMs, focusing on the first generation of checkpoints (PD-1, CTLA-4) and the next generation (Tim-3, Tigit, Lag-3, VISTA) highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. The content covers three aspects: the characteristics they possess, the dynamic expression profile of their expression at the maternal-fetal interface, and their involvement in pathological pregnancy. In immunotherapy strategies for pregnancy complications, upregulation of immune checkpoints may play a role. Meanwhile, the impact on pregnancy outcomes when using ICMs in clinical cancer treatment during pregnancy is a topic worth exploring. These may serve as a guide for future basic research and clinical applications of maternal-fetal immunity.

Prunella vulgaris can improve the pregnancy outcomes of experimental autoimmune thyroiditis rats by inhibiting Th1/Th17 immune responses.

Autoimmune thyroiditis (AIT), one of the most common autoimmune diseases among women of reproductive age, is closely associated with reproductive failure and other obstetric complications. However, effective clinical strategies for the management of pregnant women with AIT are limited. It has been shown that Prunella vulgaris (PV), a traditional herbal medicine, can ameliorate AIT and other common thyroid disorders. Therefore, using an experimental autoimmune thyroiditis (EAT) rat model, we investigated the potential effects of PV on AIT-related pregnancy outcomes. According to the administered dose of PV, EAT rats were randomly divided into the untreated EAT and PV-treated EAT groups. We found that thyroid peroxidase antibody and thyroglobulin antibody serum levels and the inflammatory infiltration of the thyroid were reduced in all PV-treated groups. Increased splenic Tgfb1 mRNA levels and Treg cell proportions were associated with decreased Th1/Th17 cell proportions, and Ifng mRNA levels were reduced in rats that received low and medium doses of PV. Moreover, in the low-dose PV group, fetal development retardation and placental injuries were reversed. Overall, our findings indicated that PV could alleviate AIT and improve pregnancy outcomes in EAT rats by downregulating Th1/Th17 immune responses and inducing Treg cell proliferation.

Trophoblast-derived Lactic Acid Orchestrates Decidual Macrophage Differentiation via SRC/LDHA Signaling in Early Pregnancy.

Lactic acid (LA) metabolism in the tumor microenvironment contributes to the establishment and maintenance of immune tolerance. This pathway is characterized in tumor associated macrophages. However, the role and pathway of LA metabolism at maternal-fetal interface during early pregnancy, especially in decidual macrophage differentiation, are still unclear. Herein, for the first time, we discovered that LA can trigger either M2 or M1 macrophage polarization via oxidative phosphorylation and glycolysis regulation under normoxia or hypoxia, respectively. Also, LA metabolism played a vital role in decidual macrophages-mediated recurrent pregnancy loss (RPL), through HIF-1α/SRC/LDHA pathway. Moreover, blockade of LA intake with AZD3965 (MCT-1 inhibitor) could rescue pregnancy in an abortion-prone mouse model, suggesting a potential therapeutic target in RPL. Collectively, the present study identifies the previously unknown functions of LA metabolism in the differentiation of decidual macrophages in early normal pregnancy and RPL, and provides a potential therapeutic strategy in RPL by manipulating decidual macrophages' functions through LA metabolic pathway.

A newly intervention strategy in preeclampsia: Targeting PD-1/Tim-3 signaling pathways to modulate the polarization of decidual macrophages.

Programmed cell death-1 (PD-1) and T-cell immunoglobulin mucin-3 (Tim-3) are important immune checkpoint receptors that prevent an overreacted maternal immune response to fetal antigens during pregnancy. Disruption of complex immune regulation mechanisms is associated with adverse pregnancy outcomes, including preeclampsia (PE). Our recent study showed that the Tim-3 pathway was involved in the regulation of decidual macrophage polarization. Decidual macrophages polarized to the M1 phenotype may impair uterine vessel remodeling during placentation, accounting for the occurrence of PE. Co-blockade of the PD-1/Tim-3 pathway was shown to successfully control tumor growth in preclinical cancer models. However, the effects of activating both PD-1 and Tim-3 pathways as a combined intervention strategy in PE are never reported. Herein, we observed the skew of decidual macrophage polarization toward the M1 phenotype in patients with PE and lipopolysaccharide (LPS)-induced PE-like rat model. Moreover, we found that the activation of PD-1/Tim-3 pathway by using PD-L1 and Gal-9 fusion proteins could alleviate the manifestation of the LPS-induced PE-like rats and protect their offspring. Compared with the single intervention, the combination of PD-L1and Gal-9 fusion proteins exhibited obvious advantages in the relief of PE-like symptoms, trophoblast invasion, and fetal vascular development, indicating a synergistic effect of the activated PD-1/Tim-3 pathway. The in vitro study also revealed that the combined intervention using PD-L1 and Gal-9 fusion proteins inhibited the LPS-induced M1 macrophage polarization via the synergic activation of the ERK/GSK3ß/ß-catenin signaling pathway. Together, our findings provide the first evidence that simultaneous activation of PD-1/Tim-3 signaling pathways may have an optimal protective effect and serve as a new potential target for PE intervention.

Low vitamin D levels in follicular fluid, but not in serum, are associated with adverse outcomes in assisted reproduction.

PURPOSE: To assess the relationship between serum/follicular fluid (FF) vitamin D (VD) status and assisted reproductive technology (ART) treatment outcomes among infertile patients. METHODS: A prospective cohort study, including 132 infertile patients scheduled for their first ART treatment cycle, was carried out in a Reproductive Medical Center. Serum and FF samples were collected to assess 25-hydroxy VD [25(OH)D] levels. Low VD level was defined as 25(OH)D concentration of less than 30 ng/mL. RESULTS: Most infertile patients had low VD levels in serum (88%) and FF (90%). We observed a moderately positive correlation between VD levels in serum and FF (r = 0.34, p < 0.0001). Compared to the group of patients with low VD levels in the FF, those with sufficient VD levels had a significantly higher number of retrieved oocytes (p = 0.03), normal fertilization (p = 0.01), and high-quality embryos (p = 0.001). Moreover, patients with sufficient VD levels in the FF also had significantly higher implantation rates than those with low VD levels (76.92% vs. 46.58%, respectively, p = 0.01) and clinical pregnancy rates (92.31% vs. 61.54%, respectively, p = 0.04). CONCLUSION: These data collectively revealed that low VD levels in serum and FF were common among infertile patients. VD levels in FF, but not in serum, were associated with embryo quality, normal fertilization, implantation rates, and clinical pregnancy rates. Further studies are mandatory to determine the molecular mechanism and VD's potential therapeutic benefits in infertile patients.

Roles of γδT cells in pregnancy and pregnancy-related complications.

A successful pregnancy is a complex and unique process comprised of discrete events, including embryo implantation, placentation, and parturition. To maintain the balance between maternal-fetal immune tolerance and resistance to infections, the maternal immune system must have a high degree of stage-dependent plasticity throughout the period of pregnancy. Innate immunity is the frontline force for the establishment of early anti-infection and tolerance mechanisms in mammals. Belonging to the innate immune system, a subset of T cells called γδT cells (based on γδT cell receptors) are the main participants in immune surveillance and immune defense. Unlike traditional αßT cells, γδT cells are regarded as a bridge between innate immunity and acquired immunity. In this review, we summarize current knowledge on the functional plasticity of γδT cells during pregnancy. Furthermore, we discuss the roles of γδT cells in pathological pregnancies.

Recent insights into the impact of immune dysfunction on reproduction in autoimmune thyroiditis.

Autoimmune thyroiditis (AIT) is a common organ-specific autoimmune disease with a high incidence among women of childbearing age. Recent studies have reported that women with AIT are more susceptible to infertility, miscarriage and preterm birth. It has been investigated that abnormal changes in maternal immune system and maternal-fetal interface can dampen the immune tolerance between mother and fetus, which underlie the pathogenesis of adverse pregnancy outcomes. Hence, we summarize the immunological changes related to adverse reproductive outcomes in AIT and highlight the respective contributions of both humoral and cellular immune dysfunctions to pregnancy failures. Moreover, the direct impacts of AIT on maternal-fetal immune activation and biological influences to trophoblasts are discussed as well. All these associations require confirmation in larger studies, and the pathogenic mechanisms need to be better understood, which might provide useful information for clinical diagnosis and therapy of AIT.

Lactic Acid: A Novel Signaling Molecule in Early Pregnancy?

Aerobic glycolysis is a recognized feature shared by tumors, leading to the accumulation of lactic acid in their local microenvironments. Like the tumors, the blastocysts, placenta, trophoblasts and decidual immune cells can also produce a large amount of lactic acid through aerobic glycolysis during the early pregnancy. Moreover, the placenta expresses the transporters of the lactic acid. While several studies have described the role of lactic acid in the tumor microenvironment, especially lactic acid's modulation of immune cells, the role of lactic acid produced during pregnancy is still unclear. In this paper, we reviewed the scientific evidence detailing the effects of lactic acid in the tumor microenvironment. Based on the influence of the lactic acid on immune cells and tumors, we proposed that lactic acid released in the unique uterine environment could have similar effects on the trophoblast cells and immune cells during the early pregnancy.

Domestic violence among married women of reproductive age in Zimbabwe: a cross sectional study.

BACKGROUND: Domestic violence does not only violate women's fundamental human rights but it also undermines them from achieving their fullest potential around the world. This study was conducted to assess trends and factors associated with domestic violence among married women of reproductive age in Zimbabwe. METHOD: This was a cross-sectional study which used secondary data obtained from 2005/06, 2010/11 and 2015 Zimbabwe Demographic and Health Surveys (ZDHS). Respondents ranged from married or living with a partner (15-49 years). Multiple logistic regression analysis was used to examine factors associated with domestic violence. RESULTS: Out of 4472 women who were currently married, 1907 (42.7%) had ever experienced one form of domestic violence (physical, emotional and sexual violence). Women aged 40-49 was deemed a protective factor against domestic violence. Risk of domestic violence was higher among working women than unemployed women [AOR = 1.35; p ≤ 0.047]. Women who drink alcohol significantly risk experiencing domestic violence compared to their non-drinking counterpart; also women whose husbands drink alcohol were at higher risk of experiencing domestic violence [AOR = 1.35; p ≤ 0.001]. Domestic violence was higher among women whose husbands have ever experienced their fathers beating their mothers and significant for women whose husbands have more than one wife (polygamy) [AOR = 1.35; p ≤ 0.001]. High parity (5 or more children) was also a risk factor for domestic violence among the studied population [AOR = 1.35; p ≤ 0.038]. CONCLUSION: Domestic violence was found to be strongly associated with women whose husbands drink alcohol, products of abusive parents/father beating their mother and/or polygamous marriage (had more than one wife). Domestic violence still remains a challenge and a more biting policy efforts are needed to eradicate this public health canker in Zimbabwe.

Low circulating levels of vitamin D may contribute to the occurrence of preeclampsia through deregulation of Treg /Th17 cell ratio.

PROBLEM: Studies assessing the association between vitamin D deficiency and preeclampsia (PE) have not reached a consensus. The study aimed to investigate the role of vitamin D in the occurrence of PE through its immune-modulatory effects on Treg/Th17 cell ratio. METHOD OF STUDY: This is a case-control study of third-trimester pregnant women. Peripheral blood 25(OH)D, TGF-ß1, IL-6, and Treg/Th17 cells were analyzed. RESULTS: One hundred and sixty-three pregnant women were recruited, and 100 women (59 with a normal pregnancy (NP) and 41 with PE) were included in the study. The prevalence of vitamin D deficiency was 69.3%. Vitamin D-deficient pregnant women (25(OH) D < 20 ng/mL) had fivefold higher risk to develop PE than those with 25(OH)D level ≥20 ng/mL (OR = 5.29, CI 95% = 1.81-15.41). PE patients had lower circulating levels of 25(OH)D (12.83 ± 5.37 ng/mL vs 20.76 ± 9.63 ng/mL, P < .0001) and Treg/Th17 cell ratio (1.61 ± 0.71% vs 2.94 ± 1.35%, P < .0001), compared to women with NP. In patients with PE, 25(OH)D level correlated negatively with IL-6 levels (r = -.60, P < .0001) and positively with Treg/Th17 cell ratio (r = .89, P < .0001). We also observed a negative relationship between IL-6 levels and Treg/Th17 cell ratio (r = -.54, P = .0002). CONCLUSION: Our study demonstrated the correlation between low plasma vitamin D level and altered immune parameters in PE. We propose that, through its effects on Treg/Th17 cell ratio, vitamin D might influence the occurrence of PE.