Fetal-origin cells in maternal circulation correlate with placental dysfunction, fetal sex, and severe hypertension during pregnancy.

Fetal microchimerism (FMc) arises when fetal cells enter maternal circulation, potentially persisting for decades. Increased FMc is associated with fetal growth restriction, preeclampsia, and anti-angiogenic shift in placenta-associated proteins in diabetic and normotensive term pregnancies. The two-stage model of preeclampsia postulates that placental dysfunction causes such shift in placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLt-1), triggering maternal vascular inflammation and endothelial dysfunction. We investigated whether anti-angiogenic shift, fetal sex, fetal growth restriction, and severe maternal hypertension correlate with FMc in hypertensive disorders of pregnancy with new-onset features (n = 125). Maternal blood was drawn pre-delivery at > 25 weeks' gestation. FMc was detected by quantitative polymerase chain reaction targeting paternally inherited unique fetal alleles. PlGF and sFlt-1 were measured by immunoassay. We estimated odds ratios (ORs) by logistic regression and detection rate ratios (DRRs) by negative binomial regression. PlGF correlated negatively with FMc quantity (DRR = 0.2, p = 0.005) and female fetal sex correlated positively with FMc prevalence (OR = 5.0, p < 0.001) and quantity (DRR = 4.5, p < 0.001). Fetal growth restriction no longer correlated with increased FMc quantity after adjustment for correlates of placental dysfunction (DRR = 1.5, p = 0.272), whereas severe hypertension remained correlated with both FMc measures (OR = 5.5, p = 0.006; DRR = 6.3, p = 0.001). Our findings suggest that increased FMc is independently associated with both stages of the two-stage preeclampsia model. The association with female fetal sex has implications for microchimerism detection methodology. Future studies should target both male and female-origin FMc and focus on clarifying which placental mechanisms impact fetal cell transfer and how FMc impacts the maternal vasculature.

Poor glucose control and markers of placental dysfunction correlate with increased circulating fetal microchimerism in diabetic pregnancies.

Fetal microchimerism (FMc) arises during pregnancy as fetal cells enter maternal circulation and remain decades postpartum. Circulating FMc is increased in preeclampsia, fetal growth restriction, and as we recently showed, is associated with biomarkers of placental dysfunction in normotensive term pregnancies. Diabetes mellitus (DM) also correlates with placental dysfunction. We hypothesize that poor glucose control and markers of placental dysfunction are associated with increased circulating FMc in diabetic pregnancies. We included 122 pregnancies preceding active labor (pregestational DM, n = 77, gestational DM (GDM), n = 45) between 2001 and 2017. Maternal and fetal samples were genotyped for various human leukocyte antigen (HLA) loci, and other polymorphisms to identify fetus-specific alleles. We used validated polymerase chain reaction (PCR) assays to quantify FMc in maternal peripheral blood buffy coat. Negative binomial regression with adjustment for confounders was used to assess FMc quantity. In pregestational DM, increased circulating FMc correlated with elevation of HbA1c (≥ 6.0 %) (detection rate ratio (DRR) = 4.9, p = 0.010) and a 1000 pg/mL rise in the anti-angiogenic biomarker soluble fms-like tyrosine kinase-1 (sFlt-1) (DRR = 1.1, p = 0.011). In GDM, increased FMc correlated with elevated 2-hour oral glucose tolerance test results (DRR = 2.3, p = 0.046) and birthweight < 10th or > 90th percentile (DRR = 4.2, p = 0.049). These findings support our novel hypothesis that FMc correlates with poor glucose control and various aspects of placental dysfunction in DM. Whether increased FMc in pregnancies with poor glucose control and placental dysfunction contributes to the risk of preeclampsia in diabetic pregnancies and to the increased risk of chronic cardiovascular disease later in life remains to be investigated.

Markers of placental function correlate with prevalence and quantity of nucleated fetal cells in maternal circulation in normotensive term pregnancies.

INTRODUCTION: Transplacental fetal cell transfer results in the engraftment of fetal-origin cells in the pregnant woman's body, a phenomenon termed fetal microchimerism. Increased fetal microchimerism measured decades postpartum is implicated in maternal inflammatory disease. Understanding which factors cause increased fetal microchimerism is therefore important. During pregnancy, circulating fetal microchimerism and placental dysfunction increase with increasing gestational age, particularly towards term. Placental dysfunction is reflected by changes in circulating placenta-associated markers, specifically placental growth factor (PlGF), decreased by several 100 pg/mL, soluble fms-like tyrosine kinase-1 (sFlt-1), increased by several 1000 pg/mL, and the sFlt-1/PlGF ratio, increased by several 10 (pg/mL)/(pg/mL). We investigated whether such alterations in placenta-associated markers correlate with an increase in circulating fetal-origin cells. MATERIAL AND METHODS: We included 118 normotensive, clinically uncomplicated pregnancies (gestational age 37+1 up to 42+2 weeks' gestation) pre-delivery. PlGF and sFlt-1 (pg/mL) were measured by Elecsys® Immunoassays. We extracted DNA from maternal and fetal samples and genotyped four human leukocyte antigen loci and 17 other autosomal loci. Paternally inherited, unique fetal alleles served as polymerase chain reaction (PCR) targets for detecting fetal-origin cells in maternal buffy coat. Fetal-origin cell prevalence was assessed by logistic regression, and quantity by negative binomial regression. Statistical exposures included gestational age (weeks), PlGF (100 pg/mL), sFlt-1 (1000 pg/mL) and the sFlt-1/PlGF ratio (10 (pg/mL)/(pg/mL)). Regression models were adjusted for clinical confounders and PCR-related competing exposures. RESULTS: Gestational age was positively correlated with fetal-origin cell quantity (DRR = 2.2, P = 0.003) and PlGF was negatively correlated with fetal-origin cell prevalence (odds ratio [OR]100 = 0.6, P = 0.003) and quantity (DRR100 = 0.7, P = 0.001). The sFlt-1 and the sFlt-1/PlGF ratios were positively correlated with fetal-origin cell prevalence (OR1000 = 1.3, P = 0.014 and OR10 = 1.2, P = 0.038, respectively), but not quantity (DRR1000 = 1.1, P = 0.600; DRR10 = 1.1, P = 0.112, respectively). CONCLUSIONS: Our results suggest that placental dysfunction as evidenced by placenta-associated marker changes, may increase fetal cell transfer. The magnitudes of change tested were based on ranges in PlGF, sFlt-1 and the sFlt-1/PlGF ratio previously demonstrated in pregnancies near and post-term, lending clinical significance to our findings. Our results were statistically significant after adjusting for confounders including gestational age, supporting our novel hypothesis that underlying placental dysfunction potentially is a driver of increased fetal microchimerism.

Increased fetal microchimerism in immune and stem cell subsets in preeclampsia.

PROBLEM: Preeclampsia (PE) is associated with an increased risk of maternal cardiovascular disease (CVD), however, it is unclear whether this is due to shared underlying physiology or changes which occur during the disease process. Fetal microchimerism (FMc) within the maternal circulation can durably persist decades after pregnancy, is known to occur at greater frequency in PE, and can potentially affect local and systemic immune programming, thus changes in cellular FMc may provide a mechanism for long-term health outcomes associated with PE. METHOD OF STUDY: We investigated whether PE is associated with alterations in FMc immune and stem cell populations. We analyzed maternal peripheral blood mononuclear cells (PBMC) from PE cases (n = 16) and matched controls from normal pregnancies (n = 16), from which immune and stem cell subsets were isolated by flow cytometry. Genomic DNA was extracted from total PMBC and individual cell subsets, and FMc frequency was quantified by quantitative polymerase chain reaction assays targeting a fetal-specific non-shared polymorphism identified from family genotyping. RESULTS: There was a significant increase in FMc concentration in immune cell subsets in PE cases compared to controls, predominantly in B cell, and NK cell lymphocyte populations. There was no significant difference in FMc frequency or concentration within the stem cell population between PE and controls. CONCLUSIONS: The altered concentrations of immune cells within FMc in the maternal blood provides a potential mechanism for the inflammation which occurs during PE to induce long-lasting changes to the maternal immune system and may potentially promote chronic maternal disease.

Umbilical Cord Maternal Microchimerism in Normal and Preeclampsia Pregnancies.

Bidirectional exchange of cells between mother and fetus establishes microchimerism (Mc). Mc can persist for decades and is associated with later-life health and disease. Greater fetal Mc is detected in the maternal compartment in preeclampsia (PE), but whether maternal Mc (MMC) in umbilical cord blood (CB) is altered in PE is unknown. We evaluated MMc in CB from normal and PE pregnancies. DNA from CB mononuclear cells following placental delivery (n = 36 PE, n = 37 controls) and maternal blood was extracted and genotyped. MMc, quantified by qPCR assays targeting maternal-specific nonshared polymorphisms in CB, was compared using logistic and negative binomial regression models. Clinically and statistically relevant confounders were included, and included the total number of cell equivalents tested, gravidity, mode of delivery, birthweight, and fetal sex. PE participants delivered at earlier gestational ages, with higher Cesarean rates, and lower infant birthweights. CB MMc detection was similar between PE and controls (52.8% vs. 51.3%, respectively, p = 0.90) and unchanged after adjustment for confounders. MMc concentration was not different between groups (mean 73.7 gEq/105 gEq in PE vs. mean 22.8 gEq/105 in controls, p = 0.56), including after controlling for confounders (p = 0.64). There was no difference in CB MMc detection or concentration between PE and normal pregnancies, despite previously noted greater fetal Mc in the maternal compartment. This suggests possible differential transfer of cells at the maternal fetal interface in PE. Phenotypic evaluation of Mc cells may uncover underlying mechanisms for differential cellular exchange between mother and fetus in PE.