The amniotic fluid proteome changes across gestation in humans and rhesus macaques

Abstract

Amniotic fluid is a complex biological medium that offers protection to the fetus and plays a key role in normal fetal nutrition, organogenesis, and potentially fetal programming. Amniotic fluid is also critically involved in longitudinally shaping the in utero milieu during pregnancy. Yet, the molecular mechanism(s) of action by which amniotic fluid regulates fetal development is ill-defined partly due to an incomplete understanding of the evolving composition of the amniotic fluid proteome. Prior research consisting of cross-sectional studies suggests that the amniotic fluid proteome changes as pregnancy advances, yet longitudinal alterations have not been confirmed because repeated sampling is prohibitive in humans. We therefore performed serial amniocenteses at early, mid, and late gestational time-points within the same pregnancies in a rhesus macaque model. Longitudinally-collected rhesus amniotic fluid samples were paired with gestational-age matched cross-sectional human samples. Utilizing LC–MS/MS isobaric labeling quantitative proteomics, we demonstrate considerable cross-species similarity between the amniotic fluid proteomes and large scale gestational-age associated changes in protein content throughout pregnancy. This is the first study to compare human and rhesus amniotic fluid proteomic profiles across gestation and establishes a reference amniotic fluid proteome. The non-human primate model holds promise as a translational platform for amniotic fluid studies.

Analysis of Crude, Diverse, and Multiple Advanced Glycation End-Product Patterns May Be Important and Beneficial

“…MALDI-MS and ESI-MS have promoted the investigation of proteomics since approximately 1990, and these instruments can be connected to liquid chromatography (LC) to produce LC-MALDI-MS and LC-ESI-MS [ 57 , 58 , 59 ]. Researchers have widely used LC-ESI-MS because of the ease of sample injection.…”

“…Researchers have widely used LC-ESI-MS because of the ease of sample injection. Based on the peptide sequence database, peptide ion peaks and their fragment ion peaks have been calculated, and proteins have been identified [ 57 , 58 , 59 ], contributing to the investigation of AGEs. MALDI-MS/ESI-MS and nuclear magnetic resonance (NMR) have been used to identify the structure of free-type AGEs, such as 3-deoxyglucosoine-derived lysine dimer (1,3-di( N ε -lysino)-4-2-(2,3,4-trihydroxybutyl)-imidazoium salt) (DOLD), glyoxal-lysine dimer (1,3-di( N ε -lysino) imidazolium salt) (GOLD), methylglyoxal-lysine dimer (1,3-di( N ε -lysino)-4-methyl-imidazolium salt) (MOLD), vesperlysne A, glucosepane, tetrahydropyrimidine, glycolaldehyde-pyridine, and crossline [ 60 , 61 , 62 ].…”

“…Analyzing AGE-modified peptides is challenging because typical databases do not contain glycation information, although information on methylation and acetylation is available [ 57 , 58 , 59 ]. When researchers analyze proteins, peptides can be identified using databases that can predict the possibility of methylation and acetylation.…”

“…Although information on glycosylation is normally unavailable, this modification can be removed from peptide sequences during ionization and does not inhibit peptide identification [ 59 ]. In contrast, glycation cannot be removed from peptides during the ionization step of MALDI-MS/ESI-MS analysis, and its information is unavailable; therefore, AGE-modified peptides cannot be identified ( Figure 3 ) [ 57 , 58 , 59 ]. However, many researchers have attempted to analyze AGE-modified proteins and succeeded in identifying amino acids (e.g., lysine and arginine) in AGE-modified proteins by comparing the ion peaks of normal and glycated peptides [ 22 , 30 , 31 , 51 , 66 , 67 , 68 ].…”

“…If researchers can input information on AGE modification against peptides in databases, AGE-modified proteins can be efficiently identified (Figure 3) [28]. Analyzing AGE-modified peptides is challenging because typical databases do not contain glycation information, although information on methylation and acetylation is available [57][58][59]. When researchers analyze proteins, peptides can be identified using databases that can predict the possibility of methylation and acetylation.…”