Identifying potential biomarkers related to pre-term delivery by proteomic analysis of amniotic fluid

Abstract

We sought to identify biomarkers in the amniotic fluid (AF) and specific signaling pathways related to spontaneous preterm delivery (SPTD, < 34 weeks) in women with preterm labor (PTL) without intra-uterine infection/inflammation (IUI). This was a retrospective cohort study of a total of 139 PTL women with singleton gestation (24 + 0 to 32 + 6 weeks) who underwent amniocentesis and who displayed no evidence of IUI. A nested case–control was conducted using pooled AF samples (n = 20) analyzed via label-free liquid chromatography-tandem mass spectrometry. In the total cohort, an ELISA validation study was performed for seven candidate proteins of interest. Proteomic analysis identified 77 differentially expressed proteins (DEPs, P < 0.05) in the AF from SPTD cases compared to term delivery controls. ELISA validation confirmed that women who had an SPTD before 34 weeks had significantly independently lower levels of VEGFR-1 and higher levels of lipocalin-2 and the Fc fragment of IgG binding protein in the AF. Five principle pathways associated with the 77 DEPs were identified, including glycolysis, gluconeogenesis, and iron homeostasis. The proteomic analysis data of AFs from women with PTL identified several novel biomarkers and specific protein pathways related to SPTD in the absence of IUI.

Proteomic identification of novel plasma biomarkers associated with spontaneous preterm birth in women with preterm labor without infection/inflammation

“…In the present study, we have demonstrated that LXR/RXR activation plays a significant role in the pathogenesis of PTL and SPTB without IAI. This is, in principle, in agreement with previous proteomic studies conducted using maternal blood or AF samples that demonstrated the role of diabetes/lipid metabolisms in the development of idiopathic SPTB [ 28 , 42 , 61 ]. Indeed, these observations are not unexpected because human and primate studies have corroborated that decreased maternal glucose levels and maternal dyslipidemia are directly linked to an increased risk of SPTB [ 63 , 64 ].…”

“…We could not find any data related to our findings in published literature. Nonetheless, we propose that the relationship between lower S100A9 levels in the plasma and SPTB without IAI may be explained by the findings reported by Averill et al [ 40 ], given that immune/inflammatory-related pathways may still be important common pathways that lead to term and preterm parturition, despite excluding the cases of IAI [ 41 , 42 ]. Averill et al showed that among three different myeloid cell populations (dendritic cells, macrophages, and neutrophils), S100A9-deficient dendritic cells exhibit an exacerbated release of cytokines (anti-inflammatory), whereas S100A9-deficient neutrophils show a reduced secretion of cytokines (pro-inflammatory) [ 40 ].…”

“…In the present study, we used label-free quantitative proteomics based on spectral counting to characterize maternal plasma proteins associated with SPTB among PTL women without IAI. Over the last decade, several investigators have employed this label-free proteomic technique to identify biomarkers of SPTB in the serum, AF, and cervicovaginal fluid [ 27 , 42 , 55 , 56 ], along with the biomarkers of other human diseases [ 57 ]. It demonstrates the following advantages: 1) cost-effectiveness; 2) requirement of minimal sample preparation; 3) yield high-proteome coverage; 4) does not require laborious labeling workflows; and 5) allows comparison across multiple experimental conditions, particularly compared to stable isotopic labeling methods [ 58 , 59 ].…”

The Role of Innate Immune System in the Human Amniotic Membrane and Human Amniotic Fluid in Protection Against Intra-Amniotic Infections and Inflammation

“…However, other molecules and pathways have been monitored in relation to IAI, preterm labor and preterm birth in order to find specific and reliable biomarkers to evaluate the risk of pregnancy complications. For instance, a study by Hong et al (178) identified several proteins and pathways with altered protein levels in the hAF, such as vascular endothelial growth factor receptor 1 and Fc fragment of IgG binding protein, and pathways of glycolysis, gluconeogenesis, and iron homeostasis (178). In line with this, glucose concentration in the hAF was lower in case of IAI, while hepcidina regulator of iron releasewas increased (203,204).…”

“…Human neutrophil (or alpha) defensins (HNPs)1-3, lysozyme and lactoferrin were also found in the hAF in women with non-complicated pregnancies ( 170 , 182 ). Moreover, HNP1-3, calgranulin/calprotectin, bactericidal permeability-increasing protein, lactoferrin, lipocalin 2 and cathelicidin family members are increased in the hAF of IAI or preterm labor ( 100 , 101 , 150 , 152 , 166 , 168 , 169 , 171 , 177 , 178 , 183 , 179 , 180 ) Overall, the presence and activation of numerous variable AMPs in normal pregnancy and in IAI imply an important role of AMPs in prevention and resolution of infections.…”