Obstetrics & Gynecology:
Using Proteomic Analysis of the Human Amniotic Fluid to Identify Histologic Chorioamnionitis
Buhimschi, Irina A. MD1; Zambrano, Eduardo MD2; Pettker, Christian M. MD1; Bahtiyar, Mert Ozan MD1; Paidas, Michael MD1; Rosenberg, Victor A. MD1; Thung, Stephen MD1; Salafia, Carolyn M. MD3; Buhimschi, Catalin S. MD1
From the Departments of 1Obstetrics, Gynecology and Reproductive Sciences and 2Pathology, Yale University School of Medicine, New Haven, Connecticut; and the 3Department of Epidemiology, Mailman School of Public Health, Columbia University College of Physicians and Surgeons, New York, New York.
Supported by the Department of Health and Human Services, National Institutes of Health RO1 HD 047321-01 (IAB).
Corresponding author: Irina A. Buhimschi, MD, Yale University School of Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, 333 Cedar Street, LLCI 804, New Haven, CT 06520; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors have no potential conflicts of interest to disclose.
OBJECTVE: To estimate the relationship between histologic chorioamnionitis and four amniotic fluid proteomic biomarkers characteristic of inflammation (defensins 2 and 1, calgranulins C and A).
METHODS: One hundred fifty-eight women with singleton pregnancies had a clinically indicated amniocentesis to rule out inflammation and infection in the context of preterm labor or preterm premature rupture of membranes. A proteomic fingerprint (Mass Restricted score) was generated from amniotic fluid using surface-enhanced laser desorption ionization time-of-flight mass spectrometry. The Mass Restricted score ranges from 0 to 4 (none to all four biomarkers present) in direct relationship with severity of intra-amniotic inflammation. Presence or absence of biomarkers was analyzed in relationship to placental pathology. Criteria for severity of histologic chorioamnionitis were 3 stages and 4 grades of inflammation of the amnion, choriodecidua and chorionic plate.
RESULTS: The prevalence of histologic chorioamnionitis was 64% (stage I 12%, stage II 16%, and stage III 37%). The Mass Restricted score significantly correlated with stages of histologic chorioamnionitis (r=0.539, P<.001), grades of choriodeciduitis (r=0.465, P<.001), and amnionitis (r=0.536, P<.001). African-American women were overrepresented in the group with severe inflammation (Mass Restricted score 3–4, P=.022). Of the four biomarkers of the Mass Restricted score, calgranulin C had the strongest relationship with presence of stage III chorioamnionitis, independent of race, amniocentesis-to-delivery interval, and gestational age.
CONCLUSION: Proteomic analysis of amniotic fluid provides an opportunity for early recognition of histologic chorioamnionitis. This methodology may in the future identify candidates for antenatal therapeutic interventions.
LEVEL OF EVIDENCE: II
Spontaneous preterm birth is one of the most important problems in maternal-child health, worldwide. In 2005 the rate of preterm birth in the United States reached 12.7%, the highest rate yet reported for the nation.1 Short- and long-term neurodevelopmental outcome studies provide compelling evidence that prematurity is responsible for 75% of infant mortality and 50% of long-term handicaps, including blindness, deafness, developmental delay, cerebral palsy, and chronic lung disease.2–6 Although only 10% of all infant hospitalizations are related to prematurity, preterm birth-related expenses reach $10 billion to $15.5 billion per year.7,8
A recurring motif in modern perinatology is that preterm birth carries an increased risk of cerebral palsy, and that each weekly increase in gestational age is associated with a decreasing risk of neonatal death and neurologic impairment.9 Although it is clear that prolongation of pregnancy might be beneficial for very premature fetuses, consideration for a variety of other confounders suggests that the poor outcome observed in many children born prematurely is not entirely dependent on their gestational age at birth or birth weight.10,11 In such cases, prematurity may be inappropriately cited as the only cause of perinatal mortality or morbidity when other factors such as an inflammatory intrauterine process may contribute to poor outcome.12
It is commonly hypothesized that inflammatory conditions of the placenta and fetal membranes correlate with an increased risk for the fetus. However, while several studies noted a relationship between intra-amniotic inflammation, histologic chorioamnionitis and cerebral palsy,13–15 others have not.16,17 One possible explanation may rest with the wide range of criteria used to diagnose chorioamnionitis, intraamniotic inflammation, gradings of the placental histologic inflammation and means of identifying early neonatal sepsis at the time of delivery.
We have previously shown that proteomic mapping of the amniotic fluid reveals a profile, designated as the Mass Restricted score, that is highly characteristic of intraamniotic inflammation.18,19 The presence of four protein biomarkers (neutrophil defensins-2 and -1 and calgranulins C and A) was highly predictive of preterm birth, funisitis—a hallmark of fetal inflammatory syndrome—and early neonatal sepsis.20 In previous studies we sought to grade the severity of inflammation based on our observation that appearance of the biomarkers in the amniotic fluid of women with intraamniotic inflammation or infection was not random, but rather sequential (from defensins to calgranulins). In the present study we sought to estimate the relationships between presence in the amniotic fluid of the four proteomic biomarkers (human neutrophil defensins 2 and 1, calgranulins C and A) characteristic of intraamniotic inflammation and the likelihood and severity of histologic chorioamnionitis.
MATERIALS AND METHODS
We conducted a prospective study that included 158 women recruited between May 2004 to January 2007. All women presented with symptoms of either preterm labor or preterm premature rupture of membranes (PROM) and were enrolled immediately after admission to the Labor and Birth unit or High Risk antepartum unit at Yale New Haven Hospital.
At Yale New Haven Hospital, amniocentesis for microbiologic studies and for evaluation of the inflammatory status of the amniotic fluid is offered routinely. Management of the patients was left to the clinical team who recommended or performed amniocentesis independent of our study protocol. For research purpose, women were enrolled consecutively based on the availability of one of the investigators (C.S.B.). The Human Investigation Committee of Yale University approved our study protocol, and written informed consent for research purpose was obtained from all participants before the procedure. After consent, amniotic fluid was retrieved by ultrasound-guided amniocentesis for all the participants, and each woman was followed prospectively to the point of delivery.
Eligible subjects met the following criteria: singleton fetus at less than 37 weeks gestational age with a clinically indicated amniocentesis to rule out intraamniotic infection. Exclusion criteria included anhydramnios, human immunodeficiency virus (HIV) or hepatitis infections, and nonreassuring fetal status. Gestational age was established based on an ultrasonographic examination before 20 weeks of gestation in all instances. Preterm labor was defined as the presence of regular uterine contractions and documented cervical effacement and/or dilatation in patients of less than 37 weeks gestational age. The diagnosis of preterm PROM was confirmed by vaginal amniotic fluid “pooling,” “nitrazine,” “ferning,” or by a positive amniocentesis dye-positive test. Digital examinations were not permitted in women with confirmed preterm PROM. In the absence of signs or symptoms of clinical chorioamnionitis (fever more than 37.8°C, uterine tenderness, fetal tachycardia), amniotic fluid laboratory results suggestive of infection, nonreassuring fetal heart, and/or abruption, preterm PROM was managed expectantly. Patients received corticosteroids for lung maturity if less than 32 weeks gestational age and antibiotic therapy was clinically indicated.21 Per institutional protocol, fetal monitoring was performed at least twice daily followed by biophysical profile if indicated. Induction of labor or a surgical delivery was performed for such clinical indications as amniotic fluid laboratory results traditionally considered to indicate intraamniotic inflammation or infection, fetal lung maturity, prolapsed umbilical cord, and/or gestational age 34 weeks or more in the context of preterm PROM.22
Amniotic fluid was cultured for aerobic and anaerobic bacteria, Ureaplasma, and Mycoplasma species. The clinical laboratory tests performed for the purpose of diagnosing inflammation or infection were glucose, lactate dehydrogenase activity (LDH), Gram stain, and white (WBC) and red blood cell (RBC) counts. In clinical management, an amniotic fluid glucose cutoff of 15 mg/dL or less and LDH levels 419 International Units/L or more were considered suggestive of intraamniotic inflammation or infection.23,24 Amniotic fluid not used for diagnostic purposes was spun at 3,000g at 4°C for 20 minutes., aliquoted, and immediately stored at –80°C until analysis.
After retrieval, fresh amniotic fluid was used to generate the Mass Restricted score. These results were not available for clinical management. The methodology for generation of the Mass Restricted score has been previously described.18,19 The Mass Restricted score provides qualitative information regarding the presence or absence of intraamniotic inflammation.18 The Mass Restricted score ranges from 0 to 4, depending upon the presence or absence of each of the four protein biomarkers.18 A categorical value of 1 was assigned if a biomarker peak was present and 0 if absent. Intraamniotic inflammation was characterized by a degree of severity, which varied from a Mass Restricted score 0 (“absent” inflammation), to Mass Restricted score 1–2 (“minimal” inflammation), to Mass Restricted score 3–4 (“severe” inflammation).19 One investigator (I.A.B.) performed all the surface-enhanced laser desorption ionization assays and scored the surface-enhanced laser desorption ionization tracings without knowledge of the clinical presentation, clinical outcome, or results of the placental histologic examination.
Enzyme-linked immunosorbent assay for human interleukin (IL)-6 (Pierce-Endogen, Rockford, IL) was performed in duplicate according to manufacturer's instructions by investigators unaware of the sample origin. The minimal detectable concentration was 1 pg/mL, and the interassay and intraassay coefficients of variation were less than 10%.
At Yale New Haven Hospital, histologic evaluation of the placenta is performed routinely in women who deliver prematurely. In all 158 cases, a membrane roll extending from the area of membrane rupture to the placental margin and samples of chorionic plate with at least two chorionic vessels per sample were taken. Sections of tissue blocks were stained with hematoxylin-eosin and examined systematically for inflammation by a perinatal pathologist unaware of the proteomic results of the amniotic fluid. Severity of histologic chorioamnionitis was scored on two semiquantitative scales based on the extent of neutrophil infiltration in the chorionic plate (stages) and membrane roll section (grades). Thus, the histologic stages of chorioamnionitis25 (stage I intervillositis, stage II chorionic inflammation, and stage III full-thickness inflammation of both chorion and amnion) were complemented by the histologic grading system devised by Salafia et al,26 which includes four grades of inflammation of the amnion and chorion-decidua.
Neonatal hematologic indices and sepsis categorization were assessed as previously described from blood specimens and cultures obtained after delivery as described earlier.19,20 Briefly, of the 158 pregnant women included in the study, 125 had their newborns admitted to the Newborn Special Care Unit. Neonatal sepsis was defined as the presence of confirmed or suspected sepsis at 3 days or less after birth. A diagnosis of early neonatal sepsis was based on clinical symptoms corroborated with hematologic laboratory results.27,28 Early-onset neonatal sepsis was dichotomized into present (when sepsis was either confirmed or suspected) or absent. All neonates with confirmed or suspected sepsis received antibiotic therapy, per institutional protocol.
Result reporting was in accordance with “REporting recommendations for tumor MARKer prognostic studies” (REMARK) guidelines of the Consolidated Standards of Reporting Trials (CONSORT) group.29 Statistical analyses were performed with Sigma Stat 23 (SPSS Inc., Chicago, IL) and MedCalc (Broekstraat, Belgium) statistical software. Data were compared with Mann-Whitney U test, one-way analysis of variance (ANOVA) followed by Dunnet's tests or Kruskal-Wallis on ranks, followed by Dunn's tests, to adjust for multiple comparisons as appropriate. Pearson or Spearman correlations were used to measure colinearity between the selected independent variables as well as other relevant relationships between dependent and independent variables. Comparisons between proportions were done with χ2 tests. Odds ratios are reported, along with true-positive fractions (probability [marker positive/outcome positive]), false-positive fractions (probability [marker positive/outcome negative]),30 and concordance statistic, an index of predictive discrimination based on the rank correlation between predicted and observed outcomes.31 The concordance statistic is exactly equivalent to the area under a receiver operating characteristic curve with respect to true disease outcome. Potential values of the concordance statistic range from 0.5 (the model performs no better than chance) to 1.0 (perfect predictive power). P values were adjusted with the use of multiple logistic or linear regression analysis as appropriate. P<.05 was considered significant.
The clinical characteristics of the women at amniocentesis are presented in Table 1. We determined that women with “severe” inflammation (Mass Restricted score 3–4) of the amniotic fluid were of lower gestational age at the time of amniocentesis and more often presented with preterm PROM and clinical signs of chorioamnionitis. There was a significant difference in race distribution among groups, with an overrepresentation of African-American women in the group with “severe” inflammation (χ2 7.6, P=.022). Women with Mass Restricted score 3–4 had more often clinical chorioamnionitis and shorter amniocentesis-to-delivery interval and delivered at earlier gestational ages. Overall, five neonates had proven sepsis. All were delivered by mothers with intraamniotic inflammation (Mass Restricted score 1–2, n=2 and Mass Restricted score 3–4, n=3). Newborns delivered by mothers with “severe” intraamniotic inflammation (Mass Restricted score 3–4) more frequently had a sepsis workup suggestive of early neonatal sepsis (P=.001). We present the results of the amniotic fluid analysis in Table 2. We determined that women with Mass Restricted score 3–4 had lower glucose levels, higher LDH activity, higher WBC counts, and a higher prevalence of a positive Gram stain or positive microbial culture result compared with women with Mass Restricted score 0 or 1–2.
The prevalence of histologic chorioamnionitis (stage 1–3) in our study population was 64% (102 of 158; stage I 12%, stage II 16%, and stage III 37%), with a racial distribution of 72% (38 of 53) in African Americans, 71% (20 of 28) in Hispanics, and 60% (39 of 65) in whites (χ2=2.2, P=.336). There was an overall poor correlation between clinical chorioamnionitis and presence (Spearman r=0.073, P=.360) or severity (Spearman r=0.141, P=.078) of histologic chorioamnionitis, underscored by the 88% (90 of 102) of women with histologic chorioamnionitis who lacked signs or symptoms of clinical chorioamnionitis. Women with abnormal Mass Restricted score 3–4 were more likely to have histologic chorioamnionitis and of a higher stage (Table 3). Moreover, neonates with early neonatal sepsis were more often delivered by mothers with evidence of histologic chorioamnionitis (χ2=13.4, P<.001) and of more advanced stages (r=0.443, P<.001), whereas clinical chorioamnionitis was not significantly associated with early neonatal sepsis (χ2=0.2, P=.659) (Fig. 1).
Placental histology micrographs illustrating histologic chorioamnionitis of increasing severity and the corresponding amniotic fluid Mass Restricted scores are presented in Figure 1, while the quantitative aspects of the relationship are depicted in Figure 2. There was a significant correlation between amniotic fluid inflammation as estimated by the Mass Restricted score and the presence (Spearman r=0.475, P<.001) or stage (Spearman r=0.539, P<.001) of histologic chorioamnionitis (Fig. 2A). This indicates that patients with a Mass Restricted score 3–4 are more likely to have marked neutrophil infiltration of the chorionic plate. Multivariable logistic regression analysis revealed that a diagnosis of histologic chorioamnionitis (any stage) occurred independent of the amniocentesis-to-delivery interval or status of the membranes (intact compared with ruptured) and was best predicted by the combination of a Mass Restricted score 3–4 (odds ratio 10.4, 95% confidence interval [CI] 3.3–32.1], P<.001) and an earlier gestational age at delivery (odds ratio 0.8, 95% CI 0.7–0.9, P<.001). The concordance statistic of the model was 0.789 while true-positive fractions and false-positive fractions values were 81.6% and 30.6%, respectively. The amniotic fluid WBC count, mode of delivery (vaginal or cesarean), steroid, antibiotic exposures, demographic characteristics such as maternal age or race, and results of other rapid laboratory tests of amniotic fluid used clinically (glucose concentration, LDH, or Gram stain) did not show significance in the model, suggesting these variables had less value in predicting histologic chorioamnionitis compared with the Mass Restricted score. For comparison, concordance statistic values for an amniotic fluid-positive Gram stain, a glucose concentration of 15 mg/dL or less, or a LDH activity of 419 International Units/L or more ranged from 0.644 (Gram stain), to 0.667 (LDH), to 0.686 (glucose). True-positive fractions values of the same tests were 33.3%, 39.3%, and 51.5%, whereas false-positive fractions values were 3.6%, 5.9%, and 14.3%, respectively.
To exclude the possibility of a prolonged amniocentesis-to-delivery interval affecting or confounding the presence or emergence of histologic chorioamnionitis, we then restricted our analysis to cases delivered within 48 hours from the time of the amniocentesis (n=89).32 Again, a Mass Restricted score 3–4 and gestational age at delivery were the only predictors retained in our model for this subset (concordance statistic 0.778, true-positive fractions 88.9%, false-positive fractions 36.4%; odds ratios Mass Restricted score 10.0 [95% CI 2.5–40.2], P=.001 and gestational age at delivery 0.8 [95% CI 0.7–0.9], P=.005). The direct and significant correlation of the Mass Restricted score with the stages of histologic chorioamnionitis was also maintained for this analysis (Spearman r=0.505, P<.001).
Next, we analyzed the relationship between intraamniotic inflammation and grades of choriodeciduitis and amnionitis. There was a direct relationship between the Mass Restricted score and severity of inflammation in the choriodecidua (Spearman r=0.465, P<.001) (Fig. 2B) and in amnion (Spearman r=0.536, P<.001) (Fig. 2C). Again, these relationships were independent of the amniocentesis-to-delivery interval, mode of delivery, and steroid or antibiotic exposure.
In a prior study we demonstrated that the appearance of the biomarkers of the Mass Restricted score in amniotic fluid is not random but rather sequential.19 The conversion from “mild” (Mass Restricted score 1–2) to “severe” inflammation (Mass Restricted score 3–4) is marked by the appearance in the amniotic fluid of the peak corresponding to calgranulin C (S100A12) protein followed by that of calgranulin A (S100A8). For clinical relevance we were interested in the relationships between the component biomarkers of the Mass Restricted score and severity of histologic chorioamnionitis. We found that the presence of calgranulin C had the strongest relationship with the presence of a stage III chorioamnionitis (concordance statistic: 0.762; true-positive fractions: 71%; false-positive fractions: 19%; odds ratio: 10.2 [95%CI: 4.8–21.6], P<.001), independent of race, amniocentesis-to-delivery interval or gestational age at amniocentesis or delivery.
This study provides evidence that there is a direct correlation between the degree of intraamniotic inflammatory response (as estimated by the Mass Restricted score) and the severity of chorioamnionitis, choriodeciduitis and amnionitis. This relationship is maintained independent of the amniocentesis-to-delivery interval, mode of delivery, and steroid or antibiotic exposure. Lastly, the presence in amniotic fluid of the biomarker corresponding to calgranulin C (S100A12 protein biomarker) is strongly associated with neutrophil infiltration of the chorionic plate. Calgranulin C is a member of the S100 protein family (S100A12) and a potent ligand for the receptor for advanced glycation end-products (RAGE), activity for which it has been designated as ENRAGE (extracellular newly identified RAGE-binding protein).33
This research was motivated by prior studies which suggested that histologic chorioamnionitis is an important risk factor for neonatal sepsis and poor long-term neurodevelopmental outcome.34–36 The finding that newborns delivered by mothers with “severe” intraamniotic inflammation (Mass Restricted score 3–4) and advanced stage of chorioamnionitis more frequently had a sepsis work-up suggestive of early neonatal sepsis, seems to support for this theory, bearing in mind that early neonatal sepsis is a risk factor for neonatal disease, early death and adverse neurologic events.37 The importance of this model is predicated on the idea that inflammation, a highly orchestrated process designed to fight infection or tissue injury, can turn maladaptive and contribute to the fetal neurologic damage by virtue of the effects of proinflammatory cytokines on blood vessels, astrocytes and neurons.38
The prior description of stages and grades of histologic chorioamnionitis, choriodeciduitis and amnionitis represented a significant step forward by development of pathologic criteria which allowed scientists to provide a uniform description of the distribution of acute placental inflammation in women with preterm birth.26 However, description of a relationship between the intensity of histologic inflammation (based on stages and grades) and that of intraamniotic inflammation (based on cytokines and matrix metalloproteinase cut-offs) proved to be difficult.39,40 Some of the explanations for the imperfect correlation between histologic inflammation and cytokines may be inherent in pathology practice which relies on analysis of tissues rather than biologic fluids. Differences in tissue sampling relative to the lower uterine segment (and the initial site of ascending infection), variation in the integrity of the decidual capillary bed, restricting neutrophil exposure to cytokine gradients may account for the significant regionalization of the inflammatory infiltrate. Perhaps most important is that the current pathology practice still follows the recommendations espoused by Kurt Benirschke in 1961,41 assessing neutrophil number in the different tissues that bound, or are contained in, the amniotic fluid space, while the intervening decades have demonstrated the range of inflammatory effects on connective tissue integrity (via matrix metalloproteinases), cell cycle (cell proliferation and apoptosis). Neutrophil number may also not be the most reliable scale to assess intraamniotic cytokines, nor to measure the risks for infection-associated sequelae such as cerebral palsy. Perhaps, along with other variables (fetal genotype, integrity of the blood brain barrier, gestational age at delivery), this may be an explanation for why 76% of the fetuses exposed to elevated amniotic fluid cytokine concentration do not develop cerebral palsy.42
While some researchers have not found a racial/ethnic difference for chorioamnionitis others have found that clinically diagnosed intraamniotic infection occurs more commonly in African-American women than in other groups.43 Recognizing that clinical signs and symptoms of chorioamnionitis are unreliable, Dammann et al found a significant relationship between histologic chorioamnionitis and African-American ancestry.44 In the present study we found that African-American women were more likely to have “severe” intraamniotic inflammation as indicated by the Mass Restricted score, which proved to be a stronger predictor of histologic chorioamnionitis in multivariable analysis than race per se. Moreover, our data also indicate that a significant proportion of women with histologic chorioamnionitis and/or “severe” intraamniotic inflammation lacked clinical signs of inflammation underscoring the limited value of clinical symptoms in predicting histologic inflammation in the placenta. This is especially important in the context where histologic (but not clinical) chorioamnionitis is a significant predictor of neonatal brain injury.45
From a pathophysiologic perspective, the biomarkers comprising the Mass Restricted score (defensins and calgranulins) are anti-microbial/anti-inflammatory proteins released following neutrophil activation.46 Our study provides evidence in support of the view that there is a direct relationship between stages and grades of placental histologic inflammation and the intensity of the intraamniotic inflammation as determined by the Mass Restricted score. The clinical implication is that the severity of histologic chorioamnionitis can be potentially predicted at the time of amniocentesis and before histologic evaluation of the placenta.
The use of subclinical biomarkers for individual-level prediction and classification in the context of personalized medicine has expanded significantly in recent years with cancer markers at the forefront.30 However, the practical utility of such markers remains to be judged entirely in the context where they are to be used. For instance, when screening for prostate cancer in a healthy population, Baker et al47 recommends a false-positive fractions of less than 2% and a true-positive fractions of 50% or more. These values are significantly different for prognostic markers measured in people with disease. A true-positive fractions of 92% and a false-positive fractions of 42% are quoted by one study which evaluated a gene expression profile in patients with breast cancer as a prognostic marker of distant metastases within 5 years.48 The study also emphasized on the importance of a high true-positive fractions for prognostic markers of poor outcome. Although there are no preset numbers for what should be acceptable or not, we appreciate this scenario resembles more closely to our clinical setting. Our predictive model based on a Mass Restricted score 3–4 in amniocentesis samples from symptomatic women had a true-positive fractions of 82%-89% as compared with 33%-51% for the other clinically implemented tests of amniotic fluid. However, whether it would be acceptable for 30% of women with preterm labor or preterm PROM to undergo additional unnecessary therapy remains to be further evaluated.
A major hypothesis to explain the relationship between adverse neonatal outcomes and histologic chorioamnionitis is that in utero, cytokines, activated inflammatory cells, and other mediators of the innate immune response are released by the placenta into the fetal circulation where they can directly affect the integrity of the fetus.49 Members of our research team (CMS) previously described that acute inflammation of the chorionic plate was the most sensitive indicator of infection and hence inflammation.50 Taken together, these data suggest that vascular pathologic features (arthritis and phlebitis) in the chorionic plate and choriodecidua may be important variables to control for the cytokine exchange between the placental and fetal compartment. The observations reported herein suggest that a more advanced degree of inflammation, as reflected by the presence of calgranulin C (S100A12/ENRAGE) in the amniotic fluid, had the strongest relationship with the presence of a stage III chorioamnionitis. We previously determined that histologic chorioamnionitis was associated with increased placental expression of S100A12/ENRAGE paralleled by a decrease in mRNA levels of its antagonist, soluble RAGE.33 Based on recent data suggesting an important role of this biomarker in vascular remodeling,51 we propose that in women with advanced stages of histologic chorioamnionitis, S100A12/ENRAGE may participate directly in vascular inflammation, promoting access of inflammatory mediators into the fetal circulation. This paradigm requires further testing to clarify the role of S100A12/ENRAGE in placental vascular tissue injury.
In summary, our results provide insight into the relationship between severity of histologic chorioamnionitis and amniotic fluid of biomarkers characteristic for intraamniotic inflammation. Additionally, we propose a novel paradigm related to a direct role for one of the biomarkers, S100A12/ENRAGE, in endothelial cellular activation and placental tissue injury secondary to inflammation and infection.
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