Proteomics technology for the accurate diagnosis of inflammation in twin pregnancies

Changes in lipid transport-involved proteins of epicardial adipose tissue associated with coronary artery disease

OBJECTIVE

Recent studies have focused on the potential role of epicardial adipose tissue (EAT) in the physiopathology of several metabolic and cardiovascular diseases, especially coronary artery disease (CAD). We aimed to study whether there are differences in the proteome and the secretome between epicardial and subcutaneous adipose tissue (SAT) from patients with and without CAD.

METHODS

EAT and SAT samples were collected from 64 patients undergoing elective cardiac surgery either for coronary artery bypass grafting or valve surgery. One or two-dimensional electrophoresis were performed on tissue samples and media collected at 3, 6, 24 or 48 of tissue culture. Protein identification was performed with mass spectrometry, and the results were then validated with Western blot or enzyme immunoassay. mRNA expression levels were analysed by real time polymerase chain reaction.

RESULTS

The release of several proteins was found to be higher in EAT that in SAT. Remarkably, there were higher levels of apolipoprotein A-I and glutation S-transferase P release, whereas mRNA expression of fatty acid binding protein 4 was lower in EAT. Although apolipoprotein A-I protein quantity in EAT was similar between CAD and non CAD patients, its released levels from this fat pad were lower in CAD.

CONCLUSION

EAT and SAT show different profiles of protein release and a different pattern was also found in samples from patients with CAD. These findings might support the hypothesis that EAT plays an interesting role in the physiopathology of atherosclerosis and CAD.

Using SELDI-TOF mass spectrometry on amniotic fluid and for clinical proteomics and theranostics in disorders of pregnancy

Clinical proteomics encompasses a multitude of experimental approaches, tools, and techniques based on proteomics technology which are directly aimed to accelerate and improve diagnosis and treatment of human diseases. Surface-enhanced laser desorption ionization time-of-flight (SELDI-TOF) mass spectrometry is a variant of matrix-enhanced laser desorption ionization (MALDI) that makes use of chemically-modified surfaces to reduce the complexity of biological samples prior to separation in the mass analyzer. Compared to other proteomic techniques, SELDI has several important advantages such as ability to analyze complex biological samples with minimal pre-processing, ease of handling and high throughput. Importantly, once the biomarker or combination of biomarkers with potential clinical value has been established, validation analyses can be conducted in close proximity to clinical settings which is important for establishing the utility of new diagnostics in clinical decision making and perhaps future theranostic interventions. This chapter provides protocols for experimental design and methodology aimed at (1) discovering biologically relevant biomarkers in amniotic fluid using SELDI-TOF; (2) validating the clinical utility of the biomarkers as new diagnostics; (3) translating the biomarker findings into pathophysiological phenomena to provide further insight and extend the current understanding of the disease process. Many of the principles described herein for amniotic fluid could be generalized to studies involving other types of biological samples and other clinical questions.

Bioinformatics approaches in the discovery and understanding of reproduction-related biomarkers

The emerging field of bioinformatics in proteomics is introducing new algorithms in order to handle large and heterogeneous datasets and improve the knowledge-discovery process. Management systems, software construction and application, database population and leverage, as well as computed prediction, have crafted bioinformatics into a valuable tool for basic research. Human reproduction is one of many fields proteomics has been extensively studying over the last decade, accumulating complex experimental data at a rate far exceeding the ability to assimilate them. Transformation of the rapidly proliferating quantities of experimental information into a usable form in order to facilitate their analysis is a challenging task. On this track, bioinformatics, an essential part of proteomics research, aspires to amend inquiries into a better manipulated, a better handled and a better understood form so as to enhance existing knowledge expansion.

Different protein profile in amniotic fluid with nervous system malformations by surface-enhanced laser desorption-ionization/time-of-flight mass spectrometry (SELDI-TOF-MS) technology

AIM

To detect the distinct proteins in amniotic fluid (AF) between nervous system malformations fetuses and normal fetuses.

MATERIAL AND METHODS

Surface-enhanced laser desorption-ionization/time-of-flight mass spectrometry was used to characterize AF peptides in AF between nervous system malformations fetuses and normal fetuses. WCX2 protein chips were used to characterize AF peptides in AF. Protein chips were examined in a PBSIIC protein reader, the protein profiling was collected by ProteinChip software version 3.1 (Ciphergen Biosystems, Fremont, CA, USA) and analyzed by Biomarker Wizard software (Ciphergen Biosystems). Nine distinct proteins were identified in AF between nervous system malformations fetuses and normal fetuses.

RESULTS

Compared with the control group, three proteins with m/z 4967.5 Da, 5258.0 Da, and 11,717.0 Da were down-regulated, and six proteins with m/z 2540.4 Da, 3107.1 Da, 3396.8 Da, 4590.965 Da, 5589.2 Da and 6429.4 Da up-regulated in nervous system malformations fetuses.

CONCLUSION

The results suggest that there are distinct proteins in protein profiling of AF between nervous system malformations fetuses and normal fetuses.

Evidence for activation of Toll-like receptor and receptor for advanced glycation end products in preterm birth

OBJECTIVE

Individuals with inflammation have a myriad of pregnancy aberrations including increasing their preterm birth risk. Toll-like receptors (TLRs) and receptor for advanced glycation end products (RAGE) and their ligands were all found to play a key role in inflammation. In the present study, we reviewed TLR and RAGE expression, their ligands, and signaling in preterm birth.

RESEARCH DESIGN AND METHODS

A systematic search was performed in the electronic databases PubMed and ScienceDirect up to July 2010, combining the keywords "preterm birth," "TLR", "RAGE", "danger signal", "alarmin", "genomewide," "microarray," and "proteomics" with specific expression profiles of genes and proteins.

RESULTS

This paper provides data on TLR and RAGE levels and critical downstream signaling events including NF-kappaB-dependent proinflammatory cytokine expression in preterm birth. About half of the genes and proteins specifically present in preterm birth have the properties of endogenous ligands "alarmin" for receptor activation. The interactions between the TLR-mediated acute inflammation and RAGE-mediated chronic inflammation have clear implications for preterm birth via the TLR and RAGE system, which may be acting collectively.

CONCLUSIONS

TLR and RAGE expression and their ligands, signaling, and functional activation are increased in preterm birth and may contribute to the proinflammatory state.

Metabolomics in the assessment of chemical-induced reproductive and developmental outcomes using non-invasive biological fluids: application to the study of butylbenzyl phthalate

This study was conducted to evaluate the use of metabolomics for improving our ability to draw correlations between early life exposures and reproductive and/or developmental outcomes. Pregnant CD rats were exposed by gavage daily during gestation to vehicle or to butylbenzyl phthalate (BBP) in vehicle at a level known to induce effects in the offspring and at a level previously not shown to induce effects. Urine was collected for 24 h (on dry ice using all glass metabolism chambers) from dams on gestational day 18 (during exposure) and on post natal day (pnd) 21, and from pnd 25 pups. Traditional phenotypic anchors were measured in pups (between pnd 0 and pnd 26). Metabolomics of urine collected from dams exposed to vehicle or BBP exhibited different patterns for endogenous metabolites. Even three weeks after gestational exposure, metabolic profiles of endogenous compounds in urine could differentiate dams that received the vehicle, low dose or high dose of BBP. Metabolic profiles could differentiate male from female pups, pups born to dams receiving the vehicle, low or high BBP dose, and pups with observable adverse reproductive effects from pups with no observed effects. Metabolites significant to the separation of dose groups and their relationship with effects measured in the study were mapped to biochemical pathways for determining mechanistic relevance. The application of metabolomics to understanding the mechanistic link between low levels of environmental exposure and disease/dysfunction holds huge promise, because this technology is ideal for the analysis of biological fluids in human populations.

Using proteomics in perinatal and neonatal sepsis: hopes and challenges for the future

PURPOSE OF REVIEW

Particularities of the fetal immune response to infection cause a heightened inflammatory state that acts synergistically with microbial insult to induce damage. Proteomics offers the opportunity for detecting fetuses at risk of sepsis and neurological injury.

RECENT FINDINGS

Molecular tools (16S-rRNA) demonstrate that the diversity of microbial agents of intra-amniotic infection exceeds what is suspected clinically or is documented by cultures. The resulting inflammatory process has the potential to damage the fetus in utero. Stepwise algorithms (mass restricted score) have been developed to extract proteomic profiles characteristic of amniotic fluid inflammation. The mass restricted score includes four proteomic biomarkers: defensin-2, defensin-1, S100A12, and S100A8 proteins. Other amniotic fluid biomarkers relevant for preterm birth are S100A9 and insulin-like growth factor-binding protein 1. S100A12 - ligand for the receptor of advanced glycation end products - has the strongest association with histological chorioamnionitis and funisitis. Presence of S100A12 and S100A8 in amniotic fluid is predictive of early-onset neonatal sepsis and poor neurodevelopmental outcome.

SUMMARY

Presence of amniotic fluid proteomic biomarkers of inflammation is associated with increased inflammatory status of the fetus at birth. Future challenges are to find biomarkers that provide insight into molecular mechanisms of chronic fetal and neonatal cellular damage and to identify candidates for early neuroprotection strategies.

Application of proteomics for diagnosis of fetal aneuploidies and pregnancy complications

Proteomic technologies represent new strategies towards high-throughput, simultaneous analysis of thousands of biological molecules leading to the discovery of biomarkers for early diagnosis, prognosis and prediction of pregnancy outcome. Proteomics have additional relevance in understanding pathophysiology and the development of molecularly targeted therapeutics. Comparison of normal human amniotic fluid proteome with that coming from pregnancies carrying fetuses with chromosomal abnormalities facilitated the detection of panels of potential biomarkers for prenatal detection of fetal aneuploidies. Candidate biomarkers for the early prediction of preeclampsis are also available, while four biomarkers (defensins-2 and -1, calgranulin-C, and calgranulin-A), which were called the "MR score", can quickly and accurately detect potentially dangerous infections and predict premature birth. Researchers remain hopeful that proteomic studies will allow for the identification of either one protein marker or of a panel of markers for prenatal detection of fetal aneuploidies and pregnancy complications that could be usefully employed for diagnostic purposes or improvement of the current screening methods. For maximum predictive power however, biomarkers should be selected for further comparative analysis of expression and structural modifications in large numbers of samples from chromosomally normal and abnormal pregnancies obtained from different populations.

Mass spectrometry-based proteomics in reproductive medicine

The emergence of powerful mass spectrometry-based proteomic techniques has added a new dimension to the field of biomedical research. Application of these high throughput methodologies in pregnancy-related pathology has contributed to the comprehension of the underlying pathophysiologies and the successful identification of relevant protein biomarkers that can potentially change early diagnosis and treatment of several medical conditions related to human pregnancy. Most of the existing research on human reproduction and gestation has focused on follicular fluid, cervical/vaginal fluid, and amniotic fluid. Although proteome technologies in reproductive medicine research are not as yet widely applied, characterization of the proteome of reproductive fluids can be expected to significantly improve maternal healthcare. This article aims to summarize the applications of mass spectrometry based technology on the most important and specific biological fluids related to reproduction and gestation.

Proteomic profiling of urine identifies specific fragments of SERPINA1 and albumin as biomarkers of preeclampsia

OBJECTIVE

The cause of preeclampsia remains unknown and the diagnosis can be uncertain. We used proteomic-based analysis of urine to improve disease classification and extend the pathophysiologic understanding of preeclampsia.

STUDY DESIGN

Urine samples from 284 women were analyzed by surface-enhanced laser desorption/ionization. In the exploratory phase, 59 samples were used to extract the proteomic fingerprint characteristic of severe preeclampsia requiring mandated delivery and to develop a diagnostic algorithm. In the challenge phase, we sought to prospectively validate the algorithm in 225 women screened for a variety of high- and low-risk conditions, including preeclampsia. Of these, 19 women were followed longitudinally throughout pregnancy. The presence of biomarkers was interpreted relative to clinical classification, need for delivery, and other urine laboratory measures (ratios of protein to creatinine and soluble fms-like tyrosine kinase-1 to placental growth factor). In the translational phase, biomarker identification by tandem mass spectrometry and validation experiments in urine, serum, and placenta were used to identify, quantify, and localize the biomarkers or related proteins.

RESULTS

We report that women with preeclampsia appear to present a unique urine proteomic fingerprint that predicts preeclampsia in need of mandated delivery with highest accuracy. This characteristic proteomic profile also has the ability to distinguish preeclampsia from other hypertensive or proteinuric disorders in pregnancy. Pregnant women followed longitudinally who developed preeclampsia displayed abnormal urinary profiles more than 10 weeks before clinical manifestation. Tandem mass spectrometry and de novo sequencing identified the biomarkers as nonrandom cleavage products of SERPINA1 and albumin. Of these, the 21 amino acid C-terminus fragment of SERPINA1 was highly associated with severe forms of preeclampsia requiring early delivery. In preeclampsia, increased and aberrant SERPINA1 immunoreactivity was found in urine, serum, and placenta, in which it localized predominantly to placental villi and placental vascular spaces adherent to the endothelium. In addition, significant perivascular deposits of misfolded SERPINA1 aggregates were exclusively identified in preeclamptic placentae.

CONCLUSION

Proteomics-based characterization of urine in preeclampsia identified a proteomic fingerprint composed of SERPINA1 and albumin fragments, which can accurately diagnose preeclampsia and shows promise to discriminate it from other hypertensive proteinuric diseases. These findings provide insight into a novel pathophysiological mechanism of preeclampsia related to SERPINA1 misfolding, which may offer new therapeutic opportunities in the future.

Identification of proteomic biomarkers of preeclampsia in amniotic fluid using SELDI-TOF mass spectrometry

OBJECTIVE

To identify proteomic biomarkers in amniotic fluid (AF) that can distinguish preeclampsia (PE) from chronic hypertension (CHTN) and normotensive controls (CTR).

METHODS

AF from women with PE, CHTN, and CTR were subjected to proteomic analysis by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

Proteomic profiling of AF identified 2 biomarkers: peak X (17399.11 Da), which distinguished PE from CTR, and peak Y (28023.34 Da), which distinguished PE and CHTN from CTR. High performance liquid chromatography fractions containing the biomarkers were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in-gel tryptic digestion. The biomarkers were matched to proapolipoprotein A-I (peak Y) and a functionally obscure peptide, SBBI42 (peak X). Western blot analysis confirmed that AF from PE and CHTN had higher proapolipoprotein A-I levels than CTR.

CONCLUSION

Proteomic analysis of AF can distinguish PE from CHTN and CTR. The discriminatory proteins were identified as proapolipoprotein A-I and SBBI42.

Proteomics of the amniotic fluid in assessment of the placenta. Relevance for preterm birth

Proteomics is the study of expressed proteins and has emerged as a complement to genomic research. The major advantage of proteomics over DNA-RNA based technologies is that it more closely relates to phenotypes and not the source code. Proteomics thus holds the promise of providing a direct insight into the true mechanisms of human diseases. Historically, examination of the placenta has been the first modality to subclassify pathogenetic entities responsible for preterm birth. Because placenta is a key pathophysiological participant in several major obstetrical syndromes (preterm birth, pre-eclampsia, intrauterine growth restriction) identification of relevant biomarkers of placental function can profoundly impact on the prediction of fetal outcome and treatment efficacy. Since proteomics is a young science and studies that associate proteomic patterns with long-term outcome require follow-up of children up to school age, using placental pathological footprints of cellular injury as intermediate outcomes can be useful in the interim. Furthermore, knowledge on the identity of the dysregulated proteins may provide the needed breakthrough insight into novel pathophysiological pathways and unravel possible targets for therapeutical intervention that could not have been envisioned through hypothesis-driven approaches.

MYOMETRIAL ACTIVATION – COORDINATION, CONNECTIVITY AND CONTRACTILITY

One of the most important stages of pregnancy is the activation of uterine contractions that result in the expulsion of the fetus. The timely onset of labour is clearly important for a healthy start to life but incomplete understanding of the precise mechanisms regulating labour onset have prohibited the development of effective and safe treatments for preterm labour. This review explores the activation of the myometrium at labour onset, focussing on mechanisms of uterine contractility, including those proteins that play an important role in smooth muscle contractility. The review primarily focuses on human work but in the absence of human data describes animal studies. A broad overview of myometrial contraction mechanisms is provided before discussing more detailed aspects and identifying areas where uncertainty remains. Also discussed is the recent application of ‘omics’ based approaches to parturition research, which has facilitated an increase in the understanding of myometrial activation.

Value of placental microbial evaluation in diagnosing intra-amniotic infection

OBJECTIVE

To evaluate the ability of microbiologic and pathologic examination of the placenta to accurately diagnose intraamniotic infection and inflammation.

METHODS

One hundred eighty-three women with a clinically indicated amniocentesis were enrolled prospectively. We applied our analysis to 56 women with evidence of preterm labor or preterm premature rupture of membranes who delivered within 48 hours of amniotic fluid testing results. Twenty-three patients, assessed for fetal lung maturity in the third trimester, served as controls. Amniotic fluid was cultured for aerobic, anaerobic, Ureaplasma, and Mycoplasma species. We used mass spectrometry to assess the degree of intraamniotic inflammation (Mass Restricted scoring). After delivery, microbiologic and histologic studies of the placenta were performed. These results were interpreted in comparison with the direct microbiologic and inflammatory analysis of the amniotic fluid. A sample size of 45 patients was required to show a test accuracy of 80% or more.

RESULTS

Ninety-two percent of women with positive amniotic fluid cultures tested with at least one positive placenta culture. Eighty percent of women who had negative amniotic fluid cultures also tested with a positive placenta culture. The accuracy of placental cultures in predicting amniotic fluid infection varied from 44% to 57%. Placental pathology showed an accuracy of only 58% in diagnosing intraamniotic inflammation.

CONCLUSION

Placental microbiologic and histologic studies poorly reflect the infectious and inflammatory status of the amniotic fluid. Results of such studies should be interpreted with caution in the management and future counseling of women with preterm labor or preterm premature rupture of membranes.

LEVEL OF EVIDENCE

II.

Proteomic biomarkers of intra-amniotic inflammation: relationship with funisitis and early-onset sepsis in the premature neonate

Our goal was to determine the relationship between 4 amniotic fluid (AF) proteomic biomarkers (human neutrophil defensins 2 and 1, calgranulins C and A) characteristic of intra-amniotic inflammation, and funisitis and early-onset sepsis in premature neonates. The mass restricted (MR) score was generated from AF obtained from women in preterm labor (n = 123). The MR score ranged from 0-4 (none to all biomarkers present). Funisitis was graded histologically and interpreted in relation to the MR scores. Neonates (n = 97) were evaluated for early-onset sepsis. There was significant correlation between the severity of AF inflammation and the presence (53/123) and grades of funisitis (p < 0.001). Funisitis occurred independently of the amniocentesis-to-delivery interval or status of the membranes and was best predicted by an MR score 3-4 and an earlier gestational age (GA) at delivery. Neonates born to women with an MR score 3-4 had an increased incidence of suspected/confirmed sepsis, even after adjusting for GA at birth. Calgranulin C had the highest association with clinically significant funisitis, while calgranulin A had the strongest association with early-onset sepsis. To conclude, AF proteomic analysis shows that women with MR scores 3-4 are more likely to have histologic funisitis, and deliver neonates with early-onset sepsis.

Biomarker discovery in infectious diseases using SELDI

Surface enhanced laser desorption ionization–time of flight is a mass spectrometric-based method that requires a minimal amount of sample for analysis and can be used for high-throughput screening. It has been used to discover serum or tissue protein signatures and biomarkers for infectious diseases in the fields of virology (hepatitis B and C viruses, severe acute respiratory syndrome, HIV-1, human T-cell leukemia virus-1 and BK virus), parasitology (trypanosomiasis) and bacteriology (intra-amniotic inflammation, tuberculosis and bacterial endocarditis). The protein signatures, or biomarkers, can be used to diagnose infection, predict disease states and to inform on disease processes. Careful attention to experimental design, sample handling and storage, and the use of appropriate internal controls is crucial to success.

The receptor for advanced glycation end products (RAGE) system in women with intraamniotic infection and inflammation

OBJECTIVE

Receptor for advanced glycation end products (RAGE) is a multiligand cell-surface receptor part of the immunoglobulin superfamily with crucial roles in inflammation. S100A12/ENRAGE, a biomarker of amniotic fluid (AF) inflammation, is a ligand for RAGE. sRAGE, a competitive soluble RAGE receptor, inhibits RAGE ligands. Here we aimed to investigate the presence and changes in components of the RAGE system in women with intra-amniotic infection and inflammation.

STUDY DESIGN

AF was retrieved by amniocentesis in 113 women stratified as follows: (1) positive AF culture (+AFC; GA = 27 [20-33] wk; n = 27); (2) negative AF culture (-AFC; GA = 30 [20-36] wk; n = 27); (3) second trimester control (2T-CRL; GA = 19 [15-25] wk; n = 31); (4) third trimester control (3T-CRL; GA = 36 [31-38] wk; n = 28). We used mass spectrometry (SELDI) to detect S100A12/ENRAGE in AF. sRAGE levels were measured using specific immunoassays. Placental pathology was interpreted in relationship to the presence or absence of histologic acute inflammation and immunoreactivity of S100A12/ENRAGE and RAGE. mRNA expression of S100A12/ENRAGE, sRAGE, and RAGE in amniochorion and placental villous tissue was investigated using quantitative real-time polymerase chain reaction (PCR).

RESULTS

Presence of the S100A12/ENRAGE biomarker SELDI peak was confirmed in 70% of the +AFC but in only 10% of the -AFC samples (P < .001). The inflammatory biomarker was absent in all control samples. We further determined that the competitive inhibitor sRAGE is temporally regulated during gestation and that its AF levels are not influenced by the presence of either intra-amniotic infection or inflammation. Histologic choriamnionitis associated with intense staining for S100A12/ENRAGE, particularly in inflammatory cells. The immunoreactivity for extracellular domain of RAGE was localized exclusively to amnion epithelial, decidual, and extravillous trophoblast cells. Yet, acute histologic chorioamnionitis was related to increased gene expression of S100A12/ENRAGE in fetal membranes and decreased sRAGE and RAGE in the placenta.

CONCLUSION

The S100A12/ENRAGE system is markedly upregulated in women with intra-amniotic infection and correlates with the degree of inflammation. Further studies remain to elucidate whether the gestational age dependence of the inhibitor molecule sRAGE may explain the higher incidence of infection-related preterm deliveries and especially rupture of the membranes at earlier gestational age.

Proteomic profiling of the amniotic fluid to detect inflammation, infection, and neonatal sepsis

BACKGROUND

Proteomic analysis of amniotic fluid shows the presence of biomarkers characteristic of intrauterine inflammation. We sought to validate prospectively the clinical utility of one such proteomic profile, the Mass Restricted (MR) score.

METHODS AND FINDINGS

We enrolled 169 consecutive women with singleton pregnancies admitted with preterm labor or preterm premature rupture of membranes. All women had a clinically indicated amniocentesis to rule out intra-amniotic infection. A proteomic fingerprint (MR score) was generated from fresh samples of amniotic fluid using surface-enhanced laser desorption ionization (SELDI) mass spectrometry. Presence or absence of the biomarkers of the MR score was interpreted in relationship to the amniocentesis-to-delivery interval, placental inflammation, and early-onset neonatal sepsis for all neonates admitted to the Newborn Special Care Unit (n = 104). Women with "severe" amniotic fluid inflammation (MR score of 3 or 4) had shorter amniocentesis-to-delivery intervals than women with "no" (MR score of 0) inflammation or even "minimal" (MR score of 1 or 2) inflammation (median [range] MR 3-4: 0.4 d [0.0-49.6 d] versus MR 1-2: 3.8 d [0.0-151.2 d] versus MR 0: 17.0 d [0.1-94.3 d], p < 0.001). Nonetheless, a "minimal" degree of inflammation was also associated with preterm birth regardless of membrane status. There was a significant association between the MR score and severity of histological chorioamnionitis (r = 0.599, p < 0.001). Furthermore, neonatal hematological indices and early-onset sepsis significantly correlated with the MR score even after adjusting for gestational age at birth (OR for MR 3-4: 3.3 [95% CI, 1.1 to 9.2], p = 0.03). When compared with other laboratory tests routinely used to diagnose amniotic fluid inflammation and infection, the MR score had the highest accuracy to detect inflammation (white blood cell count > 100 cells/mm3), whereas the combination of Gram stain and MR score was best for rapid prediction of intra-amniotic infection (positive amniotic fluid culture).

CONCLUSIONS

High MR scores are associated with preterm delivery, histological chorioamnionitis, and early-onset neonatal sepsis. In this study, proteomic analysis of amniotic fluid was shown to be the most accurate test for diagnosis of intra-amniotic inflammation, whereas addition of the MR score to the Gram stain provides the best combination of tests to rapidly predict infection.

Proteomics, Part II: The Emerging Role of Proteomics Over Genomics in Spontaneous Preterm Labor/Birth

Conventional wisdom holds that complications of immature organ systems such as respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia are the primary causes of the high neonatal morbidity and mortality attendant preterm delivery. However, recent evidence suggests that a major cause of prematurity-associated neonatal pathology is the fetal and neonatal response to inflammation/infection. Although functional genomics offered the promise of providing answers to many of these questions, the identification of the genes intrinsic to human parturition proved to be a difficult task. Proteomic profiling of the amniotic fluid (AF) provides a precise means for detection of inflammation by revealing the presence of 4 biomarkers (defensins-2 and -1, calgranulin-C, and calgranulin-A) that are highly predictive of intrauterine inflammation (MR score). The MR score is especially useful as it presents a gradient of disease activity progressing from "absent" to "mild" to "severe" inflammation. Thus, it provides the ability to identify patients who may benefit from interventions in utero in a modern diagnostic-therapeutic framework.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to explain that the cause or causes of preterm delivery are still unknown, recall that functional genomics has not given the answer to these causes, and state that proteomic profiling of amniotic fluid, through mass-restricted (MR) scoring, may be predictive of intrauterine inflammation and allow for potential diagnosis and potential therapy.

Proteomic but not enzyme-linked immunosorbent assay technology detects amniotic fluid monomeric calgranulins from their complexed calprotectin form

Four proteomic biomarkers (human neutrophil peptide 1 [HNP1], HNP2 [defensins], calgranulin C [Cal-C], and Cal-A) characterize the fingerprint of intra-amniotic inflammation (IAI). We compared proteomic technology using surfaced-enhanced laser desorption-ionization-time of flight (SELDI-TOF) mass spectrometry to enzyme-linked immunosorbent assay (ELISA) for detection of these biomarkers. Amniocentesis was performed on 48 women enrolled in two groups: those with intact membranes (n = 27; gestational age [GA], 26.0 +/- 0.8 weeks) and those with preterm premature rupture of the membranes (PPROM; n = 21; GA, 28.4 +/- 0.9 weeks). Paired abdominal amniotic fluids (aAFs)-vaginal AFs (vAFs) were analyzed in PPROM women. Quantitative aspects of HNP1-3, Cal-C, Cal-A, and calprotectin (a complex of Cal-A with Cal-B) were assessed by ELISA. SELDI-TOF mass spectrometry tracings from 16/48 (33.3%) aAFs and 13/17 (88.2%) vAFs were consistent with IAI (three or four biomarkers present). IAI (by SELDI-TOF mass spectrometry) was associated with increased HNP1-3 and Cal-C measured by ELISA. However, immunoassays detected Cal-A in only 4 of the AFs even though its specific SELDI-TOF mass spectrometry peak was identified in 19/48 AFs. Calprotectin immunoreactivity was decreased in AFs retrieved from women with IAI (P = 0.01). In conclusion, IAI is associated with increased HNP1-3 levels. In the absence of isoform-specific ELISAs, mass spectrometry remains the only way to discriminate the HNP biomarker isoforms. Monomeric Cal-A is not reliably estimated by specific ELISA as it binds to Cal-B to form the calprotectin complex. Cal-C was reliably measured by SELDI-TOF mass spectrometry or specific ELISA.