Amniotic fluid granulocyte colony-stimulating factor in preterm and term labor

The amniotic fluid proteome changes with term labor and informs biomarker discovery in maternal plasma

The intra-uterine components of labor, namely, myometrial contractility, cervical ripening, and decidua/membrane activation, have been extensively characterized and involve a local pro-inflammatory milieu of cellular and soluble immune mediators. Targeted profiling has demonstrated that such processes extend to the intra-amniotic space, yet unbiased analyses of the proteome of human amniotic fluid during labor are lacking. Herein, we utilized an aptamer-based platform to characterize 1,310 amniotic fluid proteins and found that the proteome undergoes substantial changes with term labor (251 proteins with differential abundance, q < 0.1, and fold change > 1.25). Proteins with increased abundance in labor are enriched for immune and inflammatory processes, consistent with prior reports of labor-associated changes in the intra-uterine space. By integrating the amniotic fluid proteome with previously generated placental-derived single-cell RNA-seq data, we demonstrated the labor-driven upregulation of signatures corresponding to stromal-3 and decidual cells. We also determined that changes in amniotic fluid protein abundance are reflected in the maternal plasma proteome. Collectively, these findings provide novel insights into the amniotic fluid proteome in term labor and support its potential use as a source of biomarkers to distinguish between true and false labor by using maternal blood samples.

G-CSF and Erythropoietin Stability in Amniotic Fluid during Simulated in vitro Digestion Conditions

Objective:

To determine the stability of granulocyte colony-stimulating factor (G-CSF) and erythropoietin (Epo) in human amniotic fluid and recombinant G-CSF (Neupogen) and Epo (Epogen) in simulated amniotic fluid to digestions at pH concentrations of 3.2, 4.5, and 5.8 to assess their bioavailability to the neonate.

Design:

A simulated amniotic fluid containing Neupogen and Epogen was subjected to in vitro conditions that mimicked preprandial and postprandial neonatal intestinal digestion. Human amniotic fluid was tested using identical digestion conditions as well as human amniotic fluid to which Epogen and Neupogen had been added.

Main Outcome Measures:

The percentages of G-CSF/Epo and Neupogen/Epogen remaining after 1 and 2 hours of simulated digestions were compared with those at time zero, and concentrations at 2 hours were compared with those at 1 hour and time zero.

Results:

In simulated amniotic fluid at pH 3.2, significant degradation of G-CSF was observed at 1 hour (p = 0.03). No differences were observed at 1 or 2 hours for either pH 4.5 (p = 0.30 and 0.11, respectively) or pH 5.8 (p = 0.20 and 0.49, respectively). Human amniotic fluid exhibited significant degradation pH 3.2 (p = 0.04) and pH 4.5 (p < 0.05) at 1 hour; no difference was noted at pH 5.8 at 1 hour (p = 0.34). When additional Neupogen was added to human amniotic fluid, significant degradation was observed at pH 3.2 (p < 0.05) and pH 4.5 (p = 0.03) at 1 hour; no difference was noted at 1 hour at pH 5.8 (p = 0.11). In simulated amniotic fluid at pH 3.2, significant degradation of Epo occurred at 1 hour (p < 0.05). There were no differences at 1 hour for pH 4.5 (p = 0.50) or pH 5.8 (p = 0.17). Human amniotic fluid exhibited significant degradation at pH 3.2 (p < 0.05) and pH 4.5 (p < 0.05) at 1 hour; no difference was noted at 1 hour at pH 5.8 (p = 0.34). When additional Epogen was added to human amniotic fluid, significant degradation was observed at pH 3.2 (p = 0.001) and pH 4.5 (p = 0.003); no difference was noted at 1 hour at pH 5.8 (p = 0.31).

Conclusions:

G-CSF/Epo in human amniotic fluid and Neupogen/Epogen in simulated amniotic fluid are preserved to varying degrees during simulated digestion conditions. The degree of degradation of both cytokines was time- and pH-dependent. Measurable quantities of G-CSF and Epo are biologically available when swallowed by the fetus or a preterm neonate.

Granulocyte colony-stimulating factor in amniotic fluid

OBJECTIVE

The purpose of this study was to determine if granulocyte colony-stimulating factor (G-CSF) is normally present in amniotic fluid and then to determine if amniotic-fluid G-CSF levels are affected by labor and intrauterine infection.

METHODS

Amniotic fluid was collected from 35 patients in 4 groups: no labor, early labor, late labor, and labor plus chorioamnionitis. G-CSF levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The mean amniotic-fluid G-CSF concentrations prior to labor were lower than during labor (0.49 +/- 0.25 ng/ml for prior to labor vs. 1.83 +/- 1.0 ng/ml for labor, P < 0.001). With chorioamnionitis, the mean levels were elevated compared with normal labor (25.0 +/- 4.8 ng/ml for chorioamnionitis vs. 1.83 +/- 1.0 ng/ml for normal labor, P < 0.0001). In early and late labor, G-CSF was higher than prior to labor (0.49 +/- 0.25 ng/ml for no labor vs. 1.48 +/- 1.0 ng/ml for early labor, P < 0.02, vs. 2.2 +/- 0.8 ng/ml for late labor, P < 0.0005). The mean concentrations in early and late labor were not different.

CONCLUSIONS

G-CSF is present in amniotic fluid and increased with labor. When labor is complicated by chorioamnionitis, G-CSF is significantly elevated.

Adiponectin in amniotic fluid in normal pregnancy, spontaneous labor at term, and preterm labor: a novel association with intra-amniotic infection/inflammation

OBJECTIVE

Adiponectin, an anti-inflammatory and anti-diabetogenic adipokine, has an important regulatory effect on both the innate and adaptive limbs of the immune response. The objective of this study was to determine whether adiponectin is present in amniotic fluid (AF) and if its concentration changes with gestational age, in the presence of labor, and in the presence of intra-amniotic infection (IAI) in patients with spontaneous preterm labor (PTL) and intact membranes.

STUDY DESIGN

This cross-sectional study included 468 patients in the following groups: (1) women in the mid-trimester of pregnancy (14-18 weeks) who underwent amniocentesis for genetic indications and delivered a normal neonate at term (n = 52); (2) normal pregnant women at term with (n = 49) and without (n = 41) spontaneous labor; (3) patients with an episode of PTL and intact membranes who were classified into: (a) PTL who delivered at term (n = 149); (b) PTL who delivered preterm (<37 weeks gestation) without IAI (n = 108); and (c) PTL with IAI (n = 69). Adiponectin concentration in AF was determined by ELISA.

RESULTS

(1) The median AF adiponectin concentration at term was significantly higher than in the mid-trimester (35.6 ng/ml, interquartile range [IQR] 26.4-52.7 vs. 29.9 ng/ml, IQR 19.9-35.2; p = 0.01); (2) among women with PTL and intact membranes, the median AF adiponectin concentration was significantly higher in patients with IAI than in those without IAI who delivered either at term (54.3 ng/ml, 39.0-91.8 vs. 50.1 ng/ml, 33.2-72.8; p = 0.02) or preterm (47.6 ng/ml, 32.6-74.6; p = 0.01); and (3) among women at term, there was no significant difference in the median AF adiponectin concentration between those with and without labor (33.7 ng/ml, IQR 21.7-53.9 vs. 35.6 ng/ml, IQR 26.4-52.7; respectively p = 0.5).

CONCLUSIONS

(1) Adiponectin is a physiologic constituent of AF; and (2) adiponectin concentrations in AF are increased significantly with advancing gestation and in the presence of IAI. Collectively, these findings suggest that adiponectin plays a dynamic role in normal gestation and in the presence of IAI.

Dysregulation of maternal serum adiponectin in preterm labor

OBJECTIVE

Intra-amniotic and systemic infection/inflammation have been causally linked to preterm parturition and fetal injury. An emerging theme is that adipose tissue can orchestrate a metabolic response to insults, but also an inflammatory response via the production of adipocytokines, and that these two phenomenons are interrelated. Adiponectin, an insulin-sensitising, anti-inflammatory adipocytokine, circulates in multimeric complexes including low-molecular weight (LMW) trimers, medium-molecular weight (MMW) hexamers and high-molecular weight (HMW) isoforms. Each of these complexes can exert differential biological effects. The aim of this study was to determine whether spontaneous preterm labor (PTL) with intact membranes and intra-amniotic infection/inflammation (IAI) is associated with changes in maternal serum circulating adiponectin multimers.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) normal pregnant women (n=158); (2) patients with an episode of preterm labor and intact membranes without IAI who delivered at term (n=41); (3) preterm labor without IAI who delivered preterm (n=27); and (4) preterm labor with IAI who delivered preterm (n=36). Serum adiponectin multimers (total, HMW, MMW and LMW) concentrations were determined by ELISA. Non-parametric statistics were used for analyses.

RESULTS

(1) Preterm labor leading to preterm delivery or an episode of preterm labor that does not lead to preterm delivery was associated with a lower median maternal serum concentration of total and HMW adiponectin, a lower median HMW/total adiponectin ratio and a higher median LMW/total adiponectin ratio than normal pregnancy; (2) among patients with preterm labor, those with IAI had the lowest median concentration of total and HMW adiponectin, as well as the lowest median HMW/total adiponectin ratio; (3) the changes in maternal adiponectin and adiponectin multimers remained significant after adjusting for confounding factors such as maternal age, BMI, gestational age at sampling and parity.

CONCLUSION

(1) Preterm labor is characterised by a change in the profile of adiponectin multimers concentrations and their relative isoforms. These changes were observed in patients with an episode of preterm labor not leading to preterm delivery, in patients with intra-amniotic inflammation, or in those without evidence of intra-amniotic inflammation. (2) The changes in adiponectin multimer concentrations reported in preterm labor are different from those previously reported in spontaneous labor at term, suggesting that there is a fundamental difference between preterm labor and labor at term. (3) The findings reported herein provide the first evidence for the participation of adiponectin multimer in preterm parturition. We propose that adiponectins and adipokines in general provide a mechanism to organise the metabolic demands generated by the process of preterm parturition regardless of the nature of the insult (intra-amniotic inflammation or not).

Visfatin/Pre-B cell colony-enhancing factor in amniotic fluid in normal pregnancy, spontaneous labor at term, preterm labor and prelabor rupture of membranes: an association with subclinical intrauterine infection in preterm parturition

OBJECTIVE

Visfatin, a novel adipokine originally discovered as a pre-B-cell colony enhancing factor, is expressed by amniotic epithelium, cytotrophoblast, and decidua and is over-expressed when fetal membranes are exposed to mechanical stress and/or pro-inflammatory stimuli. Visfatin expression by fetal membranes is dramatically up-regulated after normal spontaneous labor. The aims of this study were to determine if visfatin is detectable in amniotic fluid (AF) and whether its concentration changes with gestational age, spontaneous labor, preterm prelabor rupture of membranes (preterm PROM) and in the presence of microbial invasion of the amniotic cavity (MIAC).

METHODS

In this cross-sectional study, visfatin concentration in AF was determined in patients in the following groups: 1) mid-trimester (n=75); 2) term not in labor (n=27); 3) term in spontaneous labor (n=51); 4) patients with preterm labor with intact membranes (PTL) without MIAC who delivered at term (n=35); 5) patients with PTL without MIAC who delivered preterm (n=52); 6) patients with PTL with MIAC (n=25); 7) women with preterm PROM without MIAC (n=26); and 8) women with preterm PROM with MIAC (n=26). Non-parametric statistics were used for analysis.

RESULTS

1) The median AF concentration of visfatin was significantly higher in patients at term than in mid-trimester; 2) Among women with PTL who delivered preterm, the median visfatin concentration was significantly higher in patients with MIAC than those without MIAC; 3) Similarly, patients with PTL and MIAC had a higher median AF visfatin concentration than those with PTL who delivered at term; 4) Among women with preterm PROM, the median AF visfatin concentration was significantly higher in patients with MIAC than those without MIAC.

CONCLUSIONS

1) Visfatin is a physiologic constituent of AF; 2) The concentration of AF visfatin increases with advancing gestational age; 3) AF visfatin concentration is elevated in patients with MIAC, regardless of the membrane status, suggesting that visfatin participates in the host response against infection.

The role of inflammation and infection in preterm birth

Inflammation has been implicated in the mechanisms responsible for preterm and term parturition, as well as fetal injury. Out of all of the suspected causes of preterm labor and delivery, infection and/or inflammation is the only pathological process for which both a firm causal link with preterm birth has been established and a molecular pathophysiology defined. Inflammation has also been implicated in the mechanism of spontaneous parturition at term. Most cases of histopathological inflammation and histological chorioamnionitis, both in preterm and term labor, are sub-clinical in nature. The isolation of bacteria in the amniotic fluid, known as microbial invasion of the amniotic cavity, is a pathological finding; the frequency of which is dependent upon the clinical presentation and gestational age. This article reviews the role of inflammation in preterm and term parturition.

The preterm parturition syndrome

The implicit paradigm that has governed the study and clinical management of preterm labour is that term and preterm parturition are the same processes, except for the gestational age at which they occur. Indeed, both share a common pathway composed of uterine contractility, cervical dilatation and activation of the membranes/decidua. This review explores the concept that while term labour results from physiological activation of the components of the common pathway, preterm labour arises from pathological signalling and activation of one or more components of the common pathway of parturition. The term "great obstetrical syndromes" has been coined to reframe the concept of obstetrical disease. Such syndromes are characterised by: (1) multiple aetiology; (2) long preclinical stage; (3) frequent fetal involvement; (4) clinical manifestations that are often adaptive in nature; and (5) gene-environment interactions that may predispose to the syndromes. This article reviews the evidence indicating that the pathological processes implicated in the preterm parturition syndrome include: (1) intrauterine infection/inflammation; (2) uterine ischaemia; (3) uterine overdistension; (4) abnormal allograft reaction; (5) allergy; (6) cervical insufficiency; and (7) hormonal disorders (progesterone related and corticotrophin-releasing factor related). The implications of this conceptual framework for the prevention, diagnosis, and treatment of preterm labour are discussed.

Human developmental biology of granulocyte colony-stimulating factor

The availability of granulocyte colony-stimulating factor (G-CSF) has influenced the management of neonates with neutropenia. Since the first use of G-CSF in a neonate with neutropenia, much has been learned about the cellular sources and physiologic roles of G-CSF. This article reviews our present understanding of G-CSF and its cognate receptor in the fetus and neonate.

Endogenous production and peripheral blood levels of granulocyte-macrophage (GM-) and granulocyte (G-) colony-stimulating factors

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two important granulopoietic growth factors. This review will focus on the endogenous production of human GM-CSF and human G-CSF and its possible reflection in circulating levels in peripheral blood. When adequately stimulated a variety of cell-types such as monocytes/macrophages. T-lymphocytes, endothelial cells and fibroblasts can produce CSFs in vitro. G-CSF can increase to detectable levels in peripheral blood when there is a demand for granulocyte production such as acute neutropenic in conjunction with hematological disorders, chronic neutropenic conditions and acute infectious diseases in patients with or without underlying hematological disorders. G-CSF in peripheral blood is detected more often and in higher concentrations than GM-CSF. An independent regulation of GM-CSF and G-CSF secretion, quantitative differences in production and/or differences in elimination or distribution might be of importance.

Interleukin-4 and transforming growth factor-beta 1 modulate the production of interleukin-1 receptor antagonist and of prostaglandin E2 by decidual cells

OBJECTIVE

Increased production of prostaglandins is associated with parturition. The production of interleukin-1 is increased in preterm labor occurring in the setting of infection. Interleukin-1 receptor antagonist prevents the effects of interleukin-1. Interleukin-4 and transforming growth factor-beta inhibit the production of prostaglandin E2 by monocytes and amnion cells, respectively. In addition, these cytokines enhance the production of interleukin-1 receptor antagonist by monocytes. We investigated whether the production of prostaglandin E2 and interleukin-1 receptor antagonist by decidual cells is modulated by interleukin-4 and transforming growth factor-beta 1.

STUDY DESIGN

Human decidual cells in monolayer culture were treated for 44 hours with interleukin-4 (1 to 100 ng/ml), transforming growth factor-beta 1 (1 to 10 ng/ml), the combination of these cytokines, or vehicle. Production of prostaglandin E2 and interleukin-1 receptor antagonist was measured by radioimmunoassay and enzyme-linked immunosorbent assay, respectively. The Wilcoxon signed-rank test was used.

RESULTS

Both interleukin-4 and transforming growth factor-beta 1 inhibited prostaglandin E2 production by decidual cells (p < 0.01). Decidual cells produced interleukin-1 receptor antagonist at a basal rate of 26.4 +/- 6.7 pg/micrograms protein per 44 hours (n = 13). Interleukin-4 stimulated the production of interleukin-1 receptor antagonist by decidual cells (p < 0.01). Transforming growth factor-beta 1 potentiated the stimulatory effect of interleukin-4 on decidual cell interleukin-1 receptor antagonist production (p < 0.05).

CONCLUSION

By suppressing the production of prostaglandin E2 and enhancing the production of interleukin-1 receptor antagonist by decidual cells, interleukin-4 and transforming growth factor-beta may have a role in inhibiting preterm labor in the setting of infection.