Changes in the Fetal and Neonatal Cytokine Profile in Pregnancies Complicated by Fetal Growth Restriction

A prospective cohort study providing insights for markers of adverse pregnancy outcome in older mothers

Background

Advanced maternal age (≥35 years) is associated with increased rates of adverse pregnancy outcome. Better understanding of underlying pathophysiological processes may improve identification of older mothers who are at greatest risk. This study aimed to investigate changes in oxidative stress and inflammation in older women and identify clinical and biochemical predictors of adverse pregnancy outcome in older women.

Methods

The Manchester Advanced Maternal Age Study (MAMAS) was a multicentre, observational, prospective cohort study of 528 mothers. Participants were divided into three age groups for comparison 20–30 years (n = 154), 35–39 years (n = 222) and ≥ 40 years (n = 152). Demographic and medical data were collected along with maternal blood samples at 28 and 36 weeks’ gestation. Multivariable analysis was conducted to identify variables associated with adverse outcome, defined as one or more of: small for gestational age (< 10th centile), FGR (<5th centile), stillbirth, NICU admission, preterm birth < 37 weeks’ gestation or Apgar score < 7 at 5 min. Biomarkers of inflammation, oxidative stress and placental dysfunction were quantified in maternal serum. Univariate and multivariable logistic regression was used to identify associations with adverse fetal outcome.

Results

Maternal smoking was associated with adverse outcome irrespective of maternal age (Adjusted Odds Ratio (AOR) 4.22, 95% Confidence Interval (95%CI) 1.83, 9.75), whereas multiparity reduced the odds (AOR 0.54, 95% CI 0.33, 0.89). In uncomplicated pregnancies in older women, lower circulating anti-inflammatory IL-10, IL-RA and increased antioxidant capacity (TAC) were seen. In older mothers with adverse outcome, TAC and oxidative stress markers were increased and levels of maternal circulating placental hormones (hPL, PlGF and sFlt-1) were reduced (p < 0.05). However, these biomarkers only had modest predictive accuracy, with the largest area under the receiver operator characteristic (AUROC) of 0.74 for placental growth factor followed by TAC (AUROC = 0.69).

Conclusions

This study identified alterations in circulating inflammatory and oxidative stress markers in older women with adverse outcome providing preliminary evidence of mechanistic links. Further, larger studies are required to determine if these markers can be developed into a predictive model of an individual older woman’s risk of adverse pregnancy outcome, enabling a reduction in stillbirth rates whilst minimising unnecessary intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04178-6.

The role and mechanism of asymmetric dimethylarginine in fetal growth restriction via interference with endothelial function and angiogenesis

PURPOSE

Fetal growth restriction (FGR) is a high-risk pregnancy, and placental dysfunction is the main cause of FGR. The upregulation of asymmetric dimethylarginine (ADMA) is linked to FGR pathology, but the mechanism needs to be investigated.

METHODS

The levels of ADMA and other related molecules were measured in human biological samples. We further used human umbilical vein endothelial cells (HUVECs) to reveal the mechanism of ADMA-induced FGR in vitro.

RESULTS

Compared with the control group, FGR patients had higher placental resistance, and ADMA levels were increased in the maternal blood, cord blood, and placenta; additionally, nitric oxide (NO) production decreased, accompanied by a decreased expression of endogenous NO synthase (eNOS). The expression of vascular growth factor (VEGF) and placental growth factor (PLGF) in the maternal blood during the third trimester and umbilical cord of the FGR group was lower than the control group. The PLGF levels in the placentas of the FGR group were also reduced, while the expression of soluble fms-like tyrosine kinase-1 (sFlt-1) increased. In in vitro cell experiments, NO production was obviously lower when the cells were exposed to 100 μM of ADMA, with no difference in eNOS expression. There was a dose-dependent decrease in PLGF expression with increasing doses of ADMA, and the levels of sFlt-1 increased. Moreover, we confirmed that tube formation in HUVECs was lower after ADMA treatment compared with the control group.

CONCLUSION

The accumulation of ADMA during pregnancy has an adverse effect on fetal development via interference with placental endothelial function and angiogenesis.

Association between the fetal cerebroplacental ratio and biomarkers of hypoxia and angiogenesis in the maternal circulation at term

OBJECTIVES

A low fetal cerebroplacental ratio (CPR) in late pregnancy is a marker of a fetus that has failed to reach its growth potential and is associated with a variety of perinatal and pregnancy complications. It is not known if it is also correlated with aberrations in angiogenic, hypoxia-responsive or inflammatory cytokine levels in the maternal circulation. We investigated if there were any differences in levels of biomarkers of angiogenesis, endothelial cell dysfunction, hypoxia and/or inflammation in term pregnancies with a low fetal CPR compared to controls. We hypothesized that as the CPR is a marker of suboptimal growth, this would be reflected in a shift towards upregulation of hypoxia-responsive factors even in non-small for gestational age fetuses.

STUDY DESIGN

We used Multiplex ELISA to measure a panel of 28 candidate biomarkers of angiogenesis and/or hypoxia in pre-labour maternal plasma from 113 women at term, stratified for CPR <10th centile vs. CPR >10th centile. Plasma levels of the biomarkers were measured using 2 multiplex Luminex assays - a commercially available human angiogenesis/growth factor panel (R&D Systems®), comprising 15 analytes and an in-house custom panel of a further 13 candidate biomarkers.

RESULTS

Of the 28 candidate biomarkers investigated, we found significantly elevated levels of Carbonic Anhydrase 9 and soluble Fms-like tyrosine kinase (Vascular Endothelial Growth Factor Receptor 1), and lower levels of Placental Growth Factor in plasma from women with a low fetal CPR. The soluble Fms-like tyrosine kinase-1/Placental Growth Factor ratio was also markedly elevated in this cohort. We also demonstrated significant inverse correlations between the fetal CPR and Carbonic Anydrase 9, soluble Fms-like tyrosine kinase and Hepatocyte Growth Factor.

CONCLUSIONS

A low fetal CPR is associated with changes in some hypoxia-responsive and angiogenesis factors in the maternal circulation in pregnancies with normally grown fetuses.

Inflammatory Diseases and Growth: Effects on the GH-IGF Axis and on Growth Plate

This review briefly describes the most common chronic inflammatory diseases in childhood, such as cystic fibrosis (CF), inflammatory bowel diseases (IBDs), juvenile idiopathic arthritis (JIA), and intrauterine growth restriction (IUGR) that can be considered, as such, for the changes reported in the placenta and cord blood of these subjects. Changes in growth hormone (GH) secretion, GH resistance, and changes in the insulin-like growth factor (IGF) system are described mainly in relationship with the increase in nuclear factor-κB (NF-κB) and pro-inflammatory cytokines. Changes in the growth plate are also reported as well as a potential role for microRNAs (miRNAs) and thus epigenetic changes in chronic inflammation. Many mechanisms leading to growth failure are currently known; however, it is clear that further research in the field is still warranted.

Inflammation-induced fetal growth restriction in rats is associated with increased placental HIF-1α accumulation

Introduction

Hypoxia-inducible factor 1-alpha (HIF-1α) is the oxygen-sensitive subunit of the transcription factor HIF-1, and its expression is increased in placentas from pregnancies complicated by pre-eclampsia (PE). Fetal growth restriction (FGR) and PE often share a common pathophysiology; however, it is unknown whether increased placental HIF-1α occurs in FGR. We previously demonstrated that aberrant maternal inflammation in rats resulted in altered utero-placental perfusion and FGR, both of which were prevented by administration of the nitric oxide mimetic glyceryl trinitrate (GTN). Our aim here was to determine whether abnormal maternal inflammation causing FGR is linked to placental HIF-1α accumulation and whether GTN administration could prevent increases in placental HIF-1α.

Methods

Levels of inflammatory factors in maternal plasma were measured using a multiplex assay after an injection of low-dose lipopolysaccharide (LPS) to rats on gestational day (GD) 13.5. Following three additional daily LPS injections from GD14.5–16.5, GD17.5 placentas were harvested for HIF-1α immunolocalisation; serial sections were also stained for the hypoxia marker pimonidazole. A subset of rats received LPS injections along with GTN delivered continuously (25 μg/h via a transdermal patch) on GD12.5-GD17.5.

Results

Within two hours of LPS administration, levels of maternal pro-inflammatory cytokines were increased compared with saline-treated controls. GD17.5 placentas of growth-restricted fetuses exhibited increased HIF-1α accumulation; however, this did not correlate with pimonidazole staining for which no differences were observed between groups. Furthermore, the LPS-mediated increases in maternal inflammatory cytokine levels and placental HIF-1α accumulation did not occur in rats treated with GTN.

Discussion

Our results demonstrate that inflammation-induced FGR is associated with increased placental HIF-1α accumulation; however, expression of this transcription factor may not correlate with regions of hypoxia in late-gestation placentas. The GTN-mediated attenuation of placental HIF-1α accumulation in LPS-treated rats provides insight into the mechanism by which GTN improves inflammation-induced complications of pregnancy.

Characterizing Villitis of Unknown Etiology and Inflammation in Stillbirth

Villitis of unknown etiology (VUE) is an enigmatic inflammatory condition of the placenta associated with fetal growth restriction and stillbirth. Greater understanding of this condition is essential to understand its contribution to adverse outcomes. Our aim was to identify and quantify the cells in VUE in cases of stillbirth and to characterize immune responses specific to this condition. Immunohistochemistry was performed on placentas from stillborn infants whose cause of death was recorded as VUE to identify CD45(+) leukocytes, CD163(+) macrophages, CD4(+) and CD8(+) T cells, neutrophils, and proinflammatory and anti-inflammatory cytokines. Images were quantified with HistoQuest software. CD45(+) leukocytes comprised 25% of cells in VUE lesions: macrophages (12%) and CD4 T cells (11%) being predominant cell types; CD8 T cells were observed in all lesions. Leukocytes and macrophages were increased throughout the placenta in stillbirths; pan-placental CD4(+) and CD8(+) T cells outside VUE lesions were increased in stillbirth with VUE. There was increased IL-2 and IL-12 and reduced IL-4 immunostaining in VUE lesions. Our results suggest VUE in stillbirth has a similar immune cell profile to live birth. Pan-placental macrophages, CD4 and CD8 T cells indicate a wider inflammatory response unrestricted to VUE lesions. The cytokine profile observed suggests a skew towards inappropriate Th1 immune responses. Full characterisation VUE lesion phenotype confirms its immunological origins and provides foundations to develop novel investigations.