Involvement of T lymphocytes in the placentae with villitis of unknown etiology from pregnancies complicated with preeclampsia

Inflammatory placental lesions are specifically observed in healthy oocyte donation pregnancies with extreme fetal-maternal incompatibility

INTRODUCTION

Oocyte donation (OD) pregnancy is a risk factor for pre-eclampsia (PE). Due to a higher extent of fetal-maternal human leukocyte antigens (HLA) mismatching in OD pregnancies compared to naturally conceived (NC) and in vitro fertilization (IVF) pregnancies, the immune response in OD placentas is probably divergent and affects clinical outcomes. We hypothesized that placental pathology varies among diverse pregnancy conditions and is related to fetal-maternal HLA incompatibility.

METHODS

Placental lesions were scored in four patient groups: OD-PE (n = 16), OD-healthy (n = 37), NC-PE (n = 45), and IVF-healthy (n = 17). All combinations were genotyped for HLA-A, -B, -C, -DR, and -DQ to calculate fetal-maternal HLA mismatches. Placentas showing chronic deciduitis with plasma cells were immunofluorescently stained with CD138 and the anti-inflammatory cytokine interleukin-10 (IL-10).

RESULTS

The distribution and severity of placental lesions varied among groups. The OD-healthy group had the highest inflammation score and greatest extent of chronic deciduitis with plasma cells (p < 0.05). However, the majority of CD138+ plasma cells (90%) in OD-healthy group expressed IL-10, in contrast to the OD-PE group (58%). The OD-healthy group was separated into semi-allogeneic (≤5 HLA mismatches) and fully allogeneic (>5 mismatches) subgroups. The elevated inflammatory pathology score and chronic deciduitis with plasma cells were found more often in the HLA-class-I fully allogeneic OD-healthy group than the IVF-healthy group (p < 0.05).

DISCUSSION

Placental inflammatory lesions are most often present in uncomplicated OD pregnancies. Immune cells that infiltrate these lesions might play an immunosuppressive role to protect OD pregnancies from complications when facing a higher extent of fetal-maternal HLA mismatching.

Low first-trimester fetal fraction is associated with chronic inflammation in the placenta

BACKGROUND

Some data suggest an association between abnormal fetal fraction on noninvasive prenatal screening and adverse pregnancy outcomes, including low birthweight, preeclampsia, and preterm birth in the absence of aneuploidy. These findings suggest that abnormal fetal fraction may be associated with placental pathologic processes in early gestation.

OBJECTIVE

This study aimed to determine the independent association of fetal fraction on genetic noninvasive prenatal screening with histologic placental types.

STUDY DESIGN

This was a retrospective cohort study at a single institution in the period between January 2017 and March 2021, including live births at ≥24 weeks for which noninvasive prenatal screening was performed and placental pathology results were available. Results were stratified by trimester of noninvasive prenatal screening. Clinical characteristics were compared by quartile of fetal fraction using chi-square tests. Linear regression was used to model continuous fetal fraction as a function of 3 histologic types representing chronic placental injury-chronic inflammation, maternal vascular malperfusion, and fetal vascular malperfusion. Inverse probability weighting was used to account for selection bias in characteristics of patients with placental pathology examination.

RESULTS

A total of 1374 patients had noninvasive prenatal screening in the first trimester and 262 in the second trimester. Preterm birth and hypertensive disorders of pregnancy were most common in the lowest quartile of fetal fraction. Chronic inflammation was associated with a 0.56 percentage point reduction in fetal fraction (95% confidence interval, -0.95 to -0.16), and maternal vascular malperfusion was associated with a 0.48 percentage point reduction in fetal fraction (95% confidence interval, -0.91 to -0.04) in adjusted models. The association with maternal vascular malperfusion was no longer statistically significant after accounting for selection bias in placentas sent for pathologic examination. Second-trimester fetal fraction was not associated with placental pathology.

CONCLUSION

Chronic inflammation is associated with lower first-trimester fetal fraction even after accounting for selection bias. Higher fetal fraction in the second trimester was associated with fetal vascular pathology, although this association was no longer statistically significant after inverse probability weighting to account for selection bias. First-trimester fetal fraction may be a biomarker of adverse outcomes associated with chronic inflammation.

Histopathologic and Transcriptomic Profiling Identifies Novel Trophoblast Defects in Patients With Preeclampsia and Maternal Vascular Malperfusion

Preeclampsia (PE) is a heterogeneous disease for which the current clinical classification system is based on the presence or absence of specific clinical features. PE-associated placentas also show heterogeneous findings on pathologic examination, suggesting that further subclassification is possible. We combined clinical, pathologic, immunohistochemical, and transcriptomic profiling of placentas to develop integrated signatures for multiple subclasses of PE. In total, 303 PE and 1388 nonhypertensive control placentas were included. We found that maternal vascular malperfusion (MVM) in the placenta was associated with preterm PE with severe features and with small-for-gestational-age neonates. Interestingly, PE placentas with either MVM or no histologic pattern of injury showed a linear decrease in proliferative (p63+) cytotrophoblast per villous area with increasing gestational age, similar to placentas obtained from the nonhypertensive patient cohort; however, PE placentas with fetal vascular malperfusion or villitis of unknown etiology lost this phenotype. This is mainly because of cases of fetal vascular malperfusion in placentas of patients with preterm PE and villitis of unknown etiology in placentas of patients with term PE, which are associated with a decrease or increase, respectively, in the cytotrophoblast per villous area. Finally, a transcriptomic analysis identified pathways associated with hypoxia, inflammation, and reduced cell proliferation in PE-MVM placentas and further subclassified this group into extravillous trophoblast-high and extravillous trophoblast-low PE, confirmed using an immunohistochemical analysis of trophoblast lineage-specific markers. Our findings suggest that within specific histopathologic patterns of placental injury, PE can be subclassified based on specific cellular and molecular defects, allowing the identification of pathways that may be targeted for diagnostic and therapeutic purposes.

The etiology of preeclampsia

Preeclampsia is one of the "great obstetrical syndromes" in which multiple and sometimes overlapping pathologic processes activate a common pathway consisting of endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress. This article reviews the potential etiologies of preeclampsia. The role of uteroplacental ischemia is well-established on the basis of a solid body of clinical and experimental evidence. A causal role for microorganisms has gained recognition through the realization that periodontal disease and maternal gut dysbiosis are linked to atherosclerosis, thus possibly to a subset of patients with preeclampsia. The recent reports indicating that SARS-CoV-2 infection might be causally linked to preeclampsia are reviewed along with the potential mechanisms involved. Particular etiologic factors, such as the breakdown of maternal-fetal immune tolerance (thought to account for the excess of preeclampsia in primipaternity and egg donation), may operate, in part, through uteroplacental ischemia, whereas other factors such as placental aging may operate largely through syncytiotrophoblast stress. This article also examines the association between gestational diabetes mellitus and maternal obesity with preeclampsia. The role of autoimmunity, fetal diseases, and endocrine disorders is discussed. A greater understanding of the etiologic factors of preeclampsia is essential to improve treatment and prevention.

Placenta pathology in recipient versus donor oocyte derivation for in vitro fertilization in a setting of hypertensive disorders of pregnancy and IUGR

INTRODUCTION

Assisted reproductive technology including in vitro fertilization (IVF) and oocyte donation (OD) may increase risk for placenta-mediated diseases. Comprehensive analysis of histopathological placental lesions according to source of oocytes used in the IVF procedure - recipient derived (RD-IVF) vs oocyte donation (OD-IVF), has not been conducted in a population with a hypertensive disorder of pregnancy (HDP) and/or intrauterine growth restriction (IUGR).

METHODS

A retrospective cohort study of archived placenta specimens from RD-IVF and OD-IVF pregnancies affected by HDP and/or IUGR was conducted with blinded histopathological placental examination. Three categories of lesions were differentiated and defined as main outcomes: maternal vascular malperfusion (MVM), chronic inflammation, and fetal vascular malperfusion (FVM). To determine the relationship between conception method and placental lesions, multivariable regressions were performed with maternal age, gestational age, HDP, birth and placental weight percentiles as model covariates.

RESULTS

115 placentas were included 83 (72.2%) RD-IVF, 32 (27.8%) OD-IVF. Adjusted OR (aOR) for conception method was 5.05 (95%CI 0.58-43.90, p=0.142) for MVM, 1.87 (95%CI 0.68-5.15, p=0.228) for chronic inflammatory and 0.61 (95%CI 0.15-2.37, p=0.471) for FVM lesions. Multiple gestation demonstrated borderline association with MVM (aOR=0.24, 95%CI 0.04-1.51, p=0.129) and total pathology score (aRR=0.79, 95%CI 0.62-1.01, p=0.058). Subgroup analysis suggested greater odds of villitis of unknown etiology (VUE) for OD-IVF (aOR=2.98, 95%CI 1.12-7.93, p=0.029).

DISCUSSION

Source of oocyte derivation demonstrated no evidence of association with main outcomes in cases of HDP and/or IUGR. Subgroup analysis demonstrated increased rates of inflammatory lesions for OD-IVF. Multiple gestation may be associated with decreased MVM and total lesions.

Low-dose low-molecular-weight heparin prophylaxis against obstetrical complications in pregnancies with metabolic and immunological disorder-associated placental inflammation

Objective: We investigated the importance of prophylactic administration of low-dose low-molecular-weight heparin (LMWH) in women with risk factors associated with placental inflammation.Materials and methods: This retrospective cohort study included 300 pregnant women with a singleton pregnancy (30 primigravidas and 270 multigravidas) who received prophylactic low-dose LMWH to prevent placental inflammation. Based on maternal risk factors, patients were categorized into 3 groups as follows: Group 1: Patients with metabolic risk factors for placental inflammation (n = 205), Group 2: Patients with immunological risk factors for placental inflammation (n = 42), Group 3: Patients with metabolic and immunological risk factors for placental inflammation (n = 53). Obstetric histories, demographic features, clinical characteristics, and present pregnancy outcomes were compared between groups. Live birth rates, composite adverse obstetric outcomes, and the Beksac obstetric index were compared between present and previous pregnancies in multigravidas.Results: Pregnancy outcomes were significantly better in the present pregnancy than in previous pregnancies. A significant increase was observed in live birth rates (33.4% vs. 69.9%, 27.5% vs. 60.5%, and 30.1% vs. 69.4% in groups 1, 2, and 3, respectively) and in the Beksac obstetric index (0.32 vs. 0.43, 0.33 vs. 0.47, and 0.38 vs. 0.57 in groups 1, 2, and 3 respectively) (p < .001 for all). A significant decrease in composite adverse pregnancy outcome rates was observed during the present pregnancy (23.5% vs. 100%, 28.9% vs. 100%, and 24.5% vs. 100% in groups 1, 2, and 3, respectively) (p < .001 for all). Live birth and composite adverse obstetric outcome rates were 70% and 33.3%, respectively in primigravidas.Conclusion: Low-dose low-molecular-weight heparin prophylaxis is useful to prevent metabolic and immunological disorders causing placental inflammation, which is the most likely pathophysiological mechanism contributing to various obstetrical complications.

Proteasome Levels and Activity in Pregnancies Complicated by Severe Preeclampsia and Hemolysis, Elevated Liver Enzymes, and Thrombocytopenia (HELLP) Syndrome

Excessive accumulation of misfolded proteins was recently demonstrated in preeclampsia. We examined levels and activity of circulatory proteasome and immunoproteasome (inflammatory subtype) in preeclampsia and hemolysis, elevated liver enzymes, and thrombocytopenia (HELLP) syndrome. We analyzed samples from women with hypertensive pregnancy disorders (n=115), including preeclampsia with severe features (sPE) and HELLP syndrome, and normotensive controls (n=45). Plasma proteasome and immunoproteasome immunoreactivity were determined by quantifying the α-subunit of the 20S core and β5i (proteasome subunit beta 8 [PSMB8]), respectively. Plasma proteasome activity was analyzed with fluorogenic substrates. MG132, lactacystin, and ONX0914 were used to inhibit the circulating proteasome and immunoproteasome, respectively. Plasma cytokine profiles were evaluated by multiplex immunoassay. Placental expression of β5 (constitutive proteasome) and β5i (immunoproteasome) was interrogated by immunohistochemistry. Women with sPE had increased plasma 20S levels ( P<0.001) and elevated lytic activities (chymotrypsin-like 7-fold, caspase-like 4.2-fold, trypsin-like 2.2-fold; P <0.001 for all) compared with pregnant controls. Women with features of HELLP displayed the highest plasma proteasome levels and activity, which correlated with decreased IFN-γ (interferon-γ), and increased IL (interleukin)-8 and IL-10. In sPE and HELLP, chymotrypsin-like activity was suppressed by proteasome inhibitors including ONX0914. Compared with gestational age-matched controls, sPE placentas harbored increased β5 and β5i immunostaining in trophoblasts. β5i signal was elevated in HELLP with predominant staining in villous core, extravillous trophoblasts in placental islands, and extracellular vesicles in intervillous spaces. Pregnancy represents a state of increased proteostatic stress. sPE and HELLP were characterized by significant upregulation in circulating levels and lytic activity of the proteasome that was partially explained by placental immunoproteasome upregulation.

Basal Chronic Villitis and Disorders of the Placental Basal Plate: A Possible Immunological Link Between Hypertensive Disorders of Pregnancy and Morbidly Adherent Placenta

BACKGROUND

Hypertensive disorders of pregnancy (HDP) are a common cause for preterm delivery. Prior studies showed that chronic villitis (CV) is associated with intrauterine growth restriction, preeclampsia, intrauterine fetal death, and morbidly adherent placenta (MAP). The authors hypothesize that disorders of the placental basal plate, especially basal chronic villitis (BCV), are associated with HDP.

METHODS

The laboratory information system was queried over 12 years to identify placentas with or without the clinical history of HDP and with or without multifocal/focal CV or BCV. As a control for tissue sampling, a similar search was performed over 5 years for placentas evaluated for MAP.

RESULTS

Of 19,683 placentas identified, 14.8% had CV which was in 18.5% and 14.2% of placentas associated with or without HDP, respectively, a significant difference (P < .0001). BCV was present in 6.0% and 3.9% of placentas with or without HDP, respectively, also a significant difference (P < .0001). BCV was more likely than multifocal/focal CV to occur in HDP (32.4% vs 27.4%) when all cases of CV were analyzed (P = .025). Of 221 placentas with MAP, 64% had multifocal/focal CV and 36% had BCV.

CONCLUSIONS

BCV and CV are more common in placentas with HDP than in normotensive pregnancies. They are also seen in MAP, as supported by another recent study.

Placental immune state shifts with gestational age

PROBLEM

Placental immunologic functions are implicated in both the maintenance of a healthy pregnancy and the pathogenesis of obstetric complications. Immune populations at the maternal-fetal interface are hypothesized to support fetomaternal tolerance, defend the fetus from infection, and contribute to labor initiation. Despite the many potential roles of placental immune cells in normal and abnormal pregnancy, little is known about placental immune population dynamics over gestation, particularly near parturition.

METHOD OF STUDY

A daily placental immune cell census was established in a murine model by flow cytometry from mid to late gestation and compared to the maternal systemic immune census. Shifts in the placental immune state were further characterized through cytokine ELISAs.

RESULTS

The placental immune census is distinct from the maternal systemic immune census, although the cells are primarily maternal in origin. Near term parturition, the placenta contains fewer CD11c-positive myeloid cells and regulatory T cells, and there is a concurrent decrease in placental IL-9 and IL-35.

CONCLUSION

The immune profile of the placenta demonstrates a decrease in both regulatory immune cell types and cytokines late in gestation. Establishing the placental immune population dynamics over a healthy pregnancy will allow future investigation of placental immune cells during abnormal pregnancy.

Chronic inflammation of the placenta: definition, classification, pathogenesis, and clinical significance

Chronic inflammatory lesions of the placenta are characterized by the infiltration of the organ by lymphocytes, plasma cells, and/or macrophages and may result from infections (viral, bacterial, parasitic) or be of immune origin (maternal anti-fetal rejection). The 3 major lesions are villitis (when the inflammatory process affects the villous tree), chronic chorioamnionitis (which affects the chorioamniotic membranes), and chronic deciduitis (which involves the decidua basalis). Maternal cellular infiltration is a common feature of the lesions. Villitis of unknown etiology (VUE) is a destructive villous inflammatory lesion that is characterized by the infiltration of maternal T cells (CD8+ cytotoxic T cells) into chorionic villi. Migration of maternal T cells into the villi is driven by the production of T-cell chemokines in the affected villi. Activation of macrophages in the villi has been implicated in the destruction of the villous architecture. VUE has been reported in association with preterm and term fetal growth restriction, preeclampsia, fetal death, and preterm labor. Infants whose placentas have VUE are at risk for death and abnormal neurodevelopmental outcome at the age of 2 years. Chronic chorioamnionitis is the most common lesion in late spontaneous preterm birth and is characterized by the infiltration of maternal CD8+ T cells into the chorioamniotic membranes. These cytotoxic T cells can induce trophoblast apoptosis and damage the fetal membranes. The lesion frequently is accompanied by VUE. Chronic deciduitis consists of the presence of lymphocytes or plasma cells in the basal plate of the placenta. This lesion is more common in pregnancies that result from egg donation and has been reported in a subset of patients with premature labor. Chronic placental inflammatory lesions can be due to maternal anti-fetal rejection, a process associated with the development of a novel form of fetal systemic inflammatory response. The syndrome is characterized by an elevation of the fetal plasma T-cell chemokine. The evidence that maternal anti-fetal rejection underlies the pathogenesis of many chronic inflammatory lesions of the placenta is reviewed. This article includes figures and histologic examples of all chronic inflammatory lesions of the placenta.