bims-reprim Biomed News
on Reproductive immunology
Issue of 2021‒01‒10
eleven papers selected by
Iva Filipovic
Karolinska Institutet

  1. Cell Discov. 2021 Jan 04. 7(1): 1
      Maintaining homeostasis of the decidual immune microenvironment at the maternal-fetal interface is essential for placentation and reproductive success. Although distinct decidual immune cell subpopulations have been identified under normal conditions, systematic understanding of the spectrum and heterogeneity of leukocytes under recurrent miscarriage in human deciduas remains unclear. To address this, we profiled the respective transcriptomes of 18,646 primary human decidual immune cells isolated from patients with recurrent pregnancy loss (RPL) and healthy controls at single-cell resolution. We discovered dramatic differential distributions of immune cell subsets in RPL patients compared with the normal decidual immune microenvironment. Furthermore, we found a subset of decidual natural killer (NK) cells that support embryo growth were diminished in proportion due to abnormal NK cell development in RPL patients. We also elucidated the altered cellular interactions between the decidual immune cell subsets in the microenvironment and those of the immune cells with stromal cells and extravillous trophoblast under disease state. These results provided deeper insights into the RPL decidual immune microenvironment disorder that are potentially applicable to improve the diagnosis and therapeutics of this disease.
  2. mBio. 2021 Jan 05. pii: e03115-20. [Epub ahead of print]12(1):
      Invasive bacterial infections during pregnancy are a major risk factor for preterm birth, stillbirth, and fetal injury. Group B streptococci (GBS) are Gram-positive bacteria that asymptomatically colonize the lower genital tract but infect the amniotic fluid and induce preterm birth or stillbirth. Experimental models that closely emulate human pregnancy are pivotal for the development of successful strategies to prevent these adverse pregnancy outcomes. Using a unique nonhuman primate model that mimics human pregnancy and informs temporal events surrounding amniotic cavity invasion and preterm labor, we show that the animals inoculated with hyaluronidase (HylB)-expressing GBS consistently exhibited microbial invasion into the amniotic cavity, fetal bacteremia, and preterm labor. Although delayed cytokine responses were observed at the maternal-fetal interface, increased prostaglandin and matrix metalloproteinase levels in these animals likely mediated preterm labor. HylB-proficient GBS dampened reactive oxygen species production and exhibited increased resistance to neutrophils compared to an isogenic mutant. Together, these findings demonstrate how a bacterial enzyme promotes GBS amniotic cavity invasion and preterm labor in a model that closely resembles human pregnancy.IMPORTANCE Group B streptococci (GBS) are bacteria that commonly reside in the female lower genital tract as asymptomatic members of the microbiota. However, during pregnancy, GBS can infect tissues at the maternal-fetal interface, leading to preterm birth, stillbirth, or fetal injury. Understanding how GBS evade host defenses during pregnancy is key to developing improved preventive therapies for these adverse outcomes. In this study, we used a unique nonhuman primate model to show that an enzyme secreted by GBS, hyaluronidase (HylB) promotes bacterial invasion into the amniotic cavity and fetus. Although delayed immune responses were seen at the maternal-fetal interface, animals infected with hyaluronidase-expressing GBS exhibited premature cervical ripening and preterm labor. These observations reveal that HylB is a crucial GBS virulence factor that promotes bacterial invasion and preterm labor in a pregnancy model that closely emulates human pregnancy. Therefore, hyaluronidase inhibitors may be useful in therapeutic strategies against ascending GBS infection.
    Keywords:  group B streptococcus; hyaluronidase; immune evasion; neutrophils; pregnancy; preterm labor
  3. J Matern Fetal Neonatal Med. 2021 Jan 06. 1-6
      INTRODUCTION: Placental villitis is characterized by the presence of inflammatory infiltrate in the placental villous. The objective of this study was to characterize in villitis of unknown etiology (VUE) of the human placentas the subpopulation of M1, important effector cells, and M2 macrophages, immunoregulatory cells.METHODS: Sixteen cases of VUE and three control placentas were examined using immunohistochemistry with antibodies for CD3, CD68, CD11c, and CD163.
    RESULTS: CD11c appeared predominantly in the inflamed villi when compared to the normal areas (p<.001). These cells corresponded to 41.2% of the macrophage population in the inflamed area and were mainly present inside the villi (36%). With regards to CD163, these cells tended to be in higher amounts in the inflamed villi when compared to CD11c and normal areas.
    DISCUSSION: We conclude that the almost exclusive presence of M1 macrophages in the inflamed areas suggests the influence of these cells in the pathogenesis VUE. The greater amount of M2 in villitis and normal areas suggests a possible immunoregulatory mechanism of the inflammatory process in VUE.
    Keywords:  Placenta; chronic villitis; placental macrophages; villitis; villitis of unknown etiology
  4. Arch Pathol Lab Med. 2020 Dec 31.
      CONTEXT: Increasing numbers of neonates with systemic acute respiratory coronavirus 2 (SARS-CoV-2) infection are occurring, and in a small number there are reports of intrauterine infection.OBJECTIVE: To characterize the placental pathology findings in a preselected cohort of neonates infected by transplacental transmission arising from maternal infection with SARS-CoV-2, and to identify pathology risk factors for placental and fetal infection.
    DESIGN: Case-based retrospective analysis by a multinational group of 19 perinatal specialists of the placental pathology findings from 2 cohorts of infants delivered to mothers testing positive for SARS-CoV-2 - liveborn neonates infected via transplacental transmission who tested positive for SARS-CoV-2 after delivery and had SARS-CoV-2 identified in cells of the placental fetal compartment by molecular pathology; and stillborn infants with syncytiotrophoblast positive for SARS-CoV-2.
    RESULTS: In placentas from all 6 liveborn neonates acquiring SARS-CoV-2 via transplacental transmission the syncytiotrophoblast was positive for coronavirus using immunohistochemistry, RNA in situ hybridization, or both. All 6 placentas had chronic histiocytic intervillositis and necrosis of the syncytiotrophoblast. The 5 stillborn/terminated infants had placental pathology findings that were similar including SARS-CoV-2 infection of the syncytiotrophoblast, chronic histiocytic intervillositis and syncytiotrophoblast necrosis.
    CONCLUSIONS: Chronic histiocytic intervillositis together with syncytiotrophoblast necrosis accompany SARS-CoV-2 infection of syncytiotrophoblast in liveborn and stillborn infants. Their coexistence in all placentas from liveborn infants acquiring their infection prior to delivery indicates that that these findings constitute a pathology risk factor for transplacental fetal infection. Potential mechanisms of infection of the placenta and fetus with SARS-CoV-2, and potential future studies, are discussed.
  5. Am J Reprod Immunol. 2021 Jan 07. e13388
      PROBLEM: Unexplained recurrent miscarriage (uRM) is defined as two or more spontaneous abortions prior to 20 weeks of gestation with unknown etiology. Peripheral blood natural killer (pNK) cells contact with the villus and exert important role in normal pregnancy. However, it is still controversial about the association between pNK cytotoxicity and uRM, and the underlying mechanism remains unknown so far.METHOD OF STUDY: In this study, we aim to compare the percentage, immunophenotype and function of pNK cells between patients with uRM and fertile controls. The peripheral blood was collected from 49 patients with uRM and 11 fertile women in their middle luteal phase of the menstrual cycle. pNK cells were co-cultured with K562 cells at different cell ratios to measure the cytotoxicity. The percentage of CD3- CD56+ , CD3- CD56bright , CD3- CD56dim pNK was analyzed by flow cytometry and quantified to evaluate the expression of cytotoxic granules (granzyme B, granulysin, and perforin), and the cell surface receptors related to pNK cell cytotoxicity (NKG2D, NKp30, NKp46, CD158a, CD158b) were also detected.
    RESULTS: The general linear model analysis showed that pNK cell cytotoxicity in patients with uRM was significantly lower than that in fertile controls. In addition, the ratios of NKG2D/CD158a, NKp30/CD158a, and NKp46/CD158a in CD3- CD56bright pNK subsets were significantly lower in uRM group than that in fertile control. The logistical regression analysis showed that the reduced NKp30/CD158a, NKp46/CD158a ratios in CD3- CD56bright pNK subsets were significantly associated with uRM.
    CONCLUSION: Our results suggested that a low pNK cytotoxicity, which is mediated by inhibitory signals, might be associated with uRM.
    Keywords:  Cytotoxic activity; NK cell; Peripheral blood; Unexplained recurrent miscarriage
  6. Hum Reprod Update. 2021 Jan 04. 27(1): 1-26
      There is emerging evidence that early uterine development in humans is an important determinant of conditions such as ontogenetic progesterone resistance, menstrual preconditioning, defective deep placentation and pre-eclampsia in young adolescents. A key observation is the relative infrequency of neonatal uterine bleeding and hormone withdrawal at birth. The origin of the uterus from the fusion of the two paramesonephric, or Müllerian, ducts was described almost 200 years ago. The uterus forms around the 10th week of foetal life. The uterine corpus and the cervix react differently to the circulating steroid hormones during pregnancy. Adult uterine proportions are not attained until after puberty. It is unclear if the endometrial microbiome and immune response-which are areas of growing interest in the adult-play a role in the early stages of uterine development. The aim is to review the phases of uterine development up until the onset of puberty in order to trace the origin of abnormal development and to assess current knowledge for features that may be linked to conditions encountered later in life. The narrative review incorporates literature searches of Medline, PubMed and Scopus using the broad terms individually and then in combination: uterus, development, anatomy, microscopy, embryology, foetus, (pre)-puberty, menarche, microbiome and immune cells. Identified articles were assessed manually for relevance, any linked articles and historical textbooks. We included some animal studies of molecular mechanisms. There are competing theories about the contributions of the Müllerian and Wolffian ducts to the developing uterus. Endometrium features are suggestive of an oestrogen effect at 16-20 weeks gestation. The discrepancy in the reported expression of oestrogen receptor is likely to be related to the higher sensitivity of more recent techniques. Primitive endometrial glands appear around 20 weeks. Features of progestogen action are expressed late in the third trimester. Interestingly, progesterone receptor expression is higher at mid-gestation than at birth when features of endometrial maturation are rare. Neonatal uterine bleeding occurs in around 5% of neonates. Myometrial differentiation progresses from the mesenchyme surrounding the endometrium at the level of the cervix. During infancy, the uterus and endometrium remain inactive. The beginning of uterine growth precedes the onset of puberty and continues for several years after menarche. Uterine anomalies may result from fusion defects or atresia of one or both Müllerian ducts. Organogenetic differentiation of Müllerian epithelium to form the endometrial and endocervical epithelium may be independent of circulating steroids. A number of genes have been identified that are involved in endometrial and myometrial differentiation although gene mutations have not been demonstrated to be common in cases of uterine malformation. The role, if any, of the microbiome in relation to uterine development remains speculative. Modern molecular techniques applied to rodent models have enhanced our understanding of uterine molecular mechanisms and their interactions. However, little is known about functional correlates or features with relevance to adult onset of uterine disease in humans. Prepubertal growth and development lends itself to non-invasive diagnostics such as ultrasound and MRI. Increased awareness of the occurrence of neonatal uterine bleeding and of the potential impact on adult onset disease may stimulate renewed research in this area.
    Keywords:  cervix; embryo; embryogenesis; endometrium; menarche; mesonephric (Wolffian) duct; myometrium; paramesonephric (Müllerian) duct; uterus
  7. BMC Genomics. 2021 Jan 06. 22(1): 6
      BACKGROUND: DNA methylation (DNAm) profiling has emerged as a powerful tool for characterizing the placental methylome. However, previous studies have focused primarily on whole placental tissue, which is a mixture of epigenetically distinct cell populations. Here, we present the first methylome-wide analysis of first trimester (n = 9) and term (n = 19) human placental samples of four cell populations: trophoblasts, Hofbauer cells, endothelial cells, and stromal cells, using the Illumina EPIC methylation array, which quantifies DNAm at > 850,000 CpGs.RESULTS: The most distinct DNAm profiles were those of placental trophoblasts, which are central to many pregnancy-essential functions, and Hofbauer cells, which are a rare fetal-derived macrophage population. Cell-specific DNAm occurs at functionally-relevant genes, including genes associated with placental development and preeclampsia. Known placental-specific methylation marks, such as those associated with genomic imprinting, repetitive element hypomethylation, and placental partially methylated domains, were found to be more pronounced in trophoblasts and often absent in Hofbauer cells. Lastly, we characterize the cell composition and cell-specific DNAm dynamics across gestation.
    CONCLUSIONS: Our results provide a comprehensive analysis of DNAm in human placental cell types from first trimester and term pregnancies. This data will serve as a useful DNAm reference for future placental studies, and we provide access to this data via download from GEO (GSE159526), through interactive exploration from the web browser ( ), and through the R package planet, which allows estimation of cell composition directly from placental DNAm data.
    Keywords:  DNA methylation; EPIC array; EWAS; Epigenetics; Human; Immune cells; Microarray; Placenta; Pregnancy; Trophoblasts
  8. Am J Obstet Gynecol. 2021 Jan 04. pii: S0002-9378(20)32631-4. [Epub ahead of print]
      BACKGROUND: Intra-amniotic infection or inflammation (IAI) is common in early preterm birth and associated with significant neonatal lung morbidity due to fetal exposure to pro-inflammatory cytokines and infectious organisms. Amniotic fluid interleukin-8 (IL-8), a pro-inflammatory cytokine, was previously correlated with development of neonatal bronchopulmonary dysplasia, but whether amniotic fluid cytokines or placental pathology more accurately predicts neonatal lung pathology and morbidity is unknown. We have used a pregnant nonhuman primate (NHP) model of Group B Streptococcus (GBS) infection to study the pathogenesis of IAI, bacterial invasion of the amniotic cavity and fetus, as well as microbial-host interactions. In this NHP model, we have studied the pathogenesis of several GBS strains with differing potential for virulence, which has resulted in a spectrum of IAI and fetal lung injury that affords the opportunity to study the inflammatory predictors of fetal lung pathology and injury.OBJECTIVES: To determine whether fetal lung injury is best predicted by placental histopathology or the cytokine response in amniotic fluid or maternal plasma.
    STUDY DESIGN: Chronically catheterized pregnant monkeys (Macaca nemestrina, pigtail macaque) at 116-125 days gestation (term=172 days) received a choriodecidual inoculation of either saline (n=5), weakly hemolytic (WH) GBS strain (N=5, low virulence), or hyper-hemolytic (HH) GBS strain (N=5, high virulence). Adverse pregnancy outcomes were defined as either preterm labor, microbial invasion of the amniotic cavity or development of the fetal inflammatory response syndrome (FIRS). Amniotic fluid, maternal and fetal plasma samples were collected after inoculation and pro-inflammatory cytokines (TNF-α, IL-β, IL-6, IL-8) were measured by a multiplex assay. Cesarean section was performed at the time of preterm labor or within one week of inoculation. Fetal necropsy was performed at the time of delivery. Placental pathology was scored by a pediatric pathologist and fetal lung injury was determined by semi-quantitative score from histopathology evaluating inflammatory infiltrate, necrosis, tissue thickening or collapse scored by a veterinary pathologist.
    RESULTS: The principal findings in our study are: (1) adverse pregnancy outcomes occurred more frequently in animals receiving HH GBS (80% with preterm labor, 80% with FIRS) compared to WH GBS (40% with preterm labor, 20% with FIRS) and controls (0% preterm labor, 0% FIRS); (2) despite differences in the rate of adverse pregnancy outcomes and FIRS, fetal lung injury scores were similar between animals receiving the WH and HH GBS strains; (3) fetal lung injury score was significantly correlated with peak amniotic fluid cytokines IL-6 and IL-8, but not TNF-α or IL-1β; and (4) fetal lung scores were poorly correlated with maternal and fetal plasma cytokine levels and placental pathology.
    CONCLUSIONS: Amniotic fluid IL-6 and IL-8 levels were a superior predictor of fetal lung injury compared to placental histopathology or maternal plasma cytokines. This evidence supports a role for amniocentesis in the prediction of neonatal lung morbidity due to IAI, which cannot be provided by cytokine analysis of the maternal plasma or placental histopathology.
    Keywords:  bronchopulmonary dysplasia; chorioamnionitis; fetus; inflammation; intra-amniotic infection; lung; nonhuman primate; pigtail macaque; placenta; pregnancy; preterm birth
  9. Nat Commun. 2021 Jan 08. 12(1): 132
      The use of pesticides to reduce mosquito vector populations is a cornerstone of global malaria control efforts, but the biological impact of most pesticides on human populations, including pregnant women and infants, is not known. Some pesticides, including carbamates, have been shown to perturb the human immune system. We measure the systemic absorption and immunologic effects of bendiocarb, a commonly used carbamate pesticide, following household spraying in a cohort of pregnant Ugandan women and their infants. We find that bendiocarb is present at high levels in maternal, umbilical cord, and infant plasma of individuals exposed during pregnancy, indicating that it is systemically absorbed and trans-placentally transferred to the fetus. Moreover, bendiocarb exposure is associated with numerous changes in fetal immune cell homeostasis and function, including a dose-dependent decrease in regulatory CD4 T cells, increased cytokine production, and inhibition of antigen-driven proliferation. Additionally, prenatal bendiocarb exposure is associated with higher post-vaccination measles titers at one year of age, suggesting that its impact on functional immunity may persist for many months after birth. These data indicate that in utero bendiocarb exposure has multiple previously unrecognized biological effects on the fetal immune system.
  10. Nat Commun. 2021 01 04. 12(1): 87
      Anterior vaginal prolapse (AVP) is the most common form of pelvic organ prolapse (POP) and has deleterious effects on women's health. Despite recent advances in AVP diagnosis and treatment, a cell atlas of the vaginal wall in AVP has not been constructed. Here, we employ single-cell RNA-seq to construct a transcriptomic atlas of 81,026 individual cells in the vaginal wall from AVP and control samples and identify 11 cell types. We reveal aberrant gene expression in diverse cell types in AVP. Extracellular matrix (ECM) dysregulation and immune reactions involvement are identified in both non-immune and immune cell types. In addition, we find that several transcription factors associated with ECM and immune regulation are activated in AVP. Furthermore, we reveal dysregulated cell-cell communication patterns in AVP. Taken together, this work provides a valuable resource for deciphering the cellular heterogeneity and the molecular mechanisms underlying severe AVP.
  11. J Clin Invest. 2021 Jan 04. pii: 140715. [Epub ahead of print]131(1):
      Immunological tolerance to semiallogeneic fetuses is necessary to achieving successful first pregnancy and permitting subsequent pregnancies with the same father. Paradoxically, pregnancy is an important cause of sensitization, resulting in the accelerated rejection of offspring-matched allografts. The underlying basis for divergent outcomes following reencounter of the same alloantigens on transplanted organs versus fetuses in postpartum females is incompletely understood. Using a mouse model that allows concurrent tracking of endogenous fetus-specific T and B cell responses in a single recipient, we show that semiallogeneic pregnancies simultaneously induce fetus-specific T cell tolerance and humoral sensitization. Pregnancy-induced antibodies, but not B cells, impeded transplantation tolerance elicited by costimulation blockade to offspring-matched cardiac grafts. Remarkably, in B cell-deficient mice, allogeneic pregnancy enabled the spontaneous acceptance of fetus-matched allografts. The presence of pregnancy-sensitized B cells that cannot secrete antibodies at the time of heart transplantation was sufficient to precipitate rejection and override pregnancy-established T cell tolerance. Thus, while induction of memory B cells and alloantibodies by pregnancies establishes formidable barriers to transplant success for multigravid women, our observations raise the possibility that humoral desensitization will not only improve transplantation outcomes, but also reveal an unexpected propensity of multiparous recipients to achieve tolerance to offspring-matched allografts.
    Keywords:  Cellular immune response; Immunology; Transplantation