Mild/asymptomatic COVID-19 in unvaccinated pregnant mothers impairs neonatal immune responses

Maternal SARS-CoV-2 infection triggers placental inflammation and alters cord blood immune cell composition. However, most studies focus on outcomes of severe maternal infection. Therefore, we analyzed cord blood and chorionic villi from newborns of unvaccinated mothers who experienced mild/asymptomatic SARS-CoV-2 infection during pregnancy. We investigated immune cell rewiring using flow cytometry, single-cell RNA sequencing, and functional readouts using ex vivo stimulation with TLR agonists and pathogens. Maternal infection was associated with increased frequency of memory T and B cells and nonclassical monocytes in cord blood. Ex vivo T and B cell responses to stimulation were attenuated, suggesting a tolerogenic state. Maladaptive responses were also observed in cord blood monocytes, where antiviral responses were dampened but responses to bacterial TLRs were increased. Maternal infection was also associated with expansion and activation of placental Hofbauer cells, secreting elevated levels of myeloid cell-recruiting chemokines. Moreover, we reported increased activation of maternally derived monocytes/macrophages in the fetal placenta that were transcriptionally primed for antiviral responses. Our data indicate that even in the absence of vertical transmission or symptoms in the neonate, mild/asymptomatic maternal COVID-19 altered the transcriptional and functional state in fetal immune cells in circulation and in the placenta.

Pulmonary Consequences of Prenatal Inflammatory Exposures: Clinical Perspective and Review of Basic Immunological Mechanisms

Chorioamnionitis, a potentially serious inflammatory complication of pregnancy, is associated with the development of an inflammatory milieu within the amniotic fluid surrounding the developing fetus. When chorioamnionitis occurs, the fetal lung finds itself in the unique position of being constantly exposed to the consequent inflammatory meditators and/or microbial products found in the amniotic fluid. This exposure results in significant changes to the fetal lung, such as increased leukocyte infiltration, altered cytokine, and surfactant production, and diminished alveolarization. These alterations can have potentially lasting impacts on lung development and function. However, studies to date have only begun to elucidate the association between such inflammatory exposures and lifelong consequences such as lung dysfunction. In this review, we discuss the pathogenesis of and fetal immune response to chorioamnionitis, detail the consequences of chorioamnionitis exposure on the developing fetal lung, highlighting the various animal models that have contributed to our current understanding and discuss the importance of fetal exposures in regard to the development of chronic respiratory disease. Finally, we focus on the clinical, basic, and therapeutic challenges in fetal inflammatory injury to the lung, and propose next steps and future directions to improve our therapeutic understanding of this important perinatal stress.

Randomized trial of the efficacy of intravaginal ulinastatin administration for the prevention of preterm birth in women with a singleton pregnancy and both cervical shortening and inflammation of lower genital tract

AIM

To assess the preventive effect on preterm birth of intravaginal ulinastatin (urinary trypsin inhibitor; UTI) administration during the mid-trimester in women with singleton pregnancy and both cervical shortening and lower genital infections.

METHODS

Pregnant women with a short cervical length < 25 mm between 16 and 26 weeks of gestation and who had been diagnosed with a lower genital infection were randomly assigned for intravaginal UTI administration or placebo. All of the women were screened for infection or inflammation of the lower genital tract, and women with negative results were excluded.

RESULTS

Of the 92 patients with a short cervical length who were assessed for eligibility for this study, 86 singleton patients were enrolled. All patients were randomized to one of two treatment groups: patients administered UTI (n = 35) and placebo (n = 35). There were no differences between the two groups in the incidence of preterm delivery before 28, 30, 32, 34 and 37 weeks of gestation and in perinatal outcomes.

CONCLUSION

For women diagnosed with a short cervical length < 25 mm) between 16 and 26 weeks of gestation and lower genital infection, who were at risk of preterm birth, administration of transvaginal UTI with vaginal irrigation showed no apparent benefit. Future research on the efficacy of UTI should evaluate modified modes of UTI application.

Serum cytokine concentrations, chorioamnionitis and the onset of bronchopulmonary dysplasia in premature infants

OBJECTIVE

To investigate the relationships between serum cytokine concentrations and chorioamnionitis (CAM) and CAM-related bronchopulmonary dysplasia (BPD) in premature infants.

METHODS

Serum was collected at 0 and 7 days after birth from 36 premature infants born at <32 weeks of gestation. We examined the relationships between 30 cytokine concentrations and CAM, BPD, and other perinatal factors.

RESULTS

On day 0, GM-CSF, IL-15, IL-17, IL-2, IL-2R, VEGF, and MIG concentrations were significantly higher in the CAM group (n = 17) than in the non-CAM group (n = 19). These concentrations had decreased by day 7 and were similar in both groups. The IL-12p70 concentration on day 0 was significantly lower in the BPD group (n = 16) than in the non-BPD group (n = 15). BPD incidence was similar between the CAM and non-CAM groups.

CONCLUSIONS

These data support the hypothesis that intrauterine inflammation is not a primary risk factor for BPD. The immunological environment at birth or soon after, rather than intrauterine fetal inflammation (e.g., CAM), is a primary risk factor for BPD onset in preterm infants. Decreased inflammatory responses are particularly relevant, as indicated by the relationship between BPD and low serum IL-12p70 concentrations on day 0.

Histologic Chorioamnionitis, Amniotic Fluid Interleukin 6, Krebs von den Lungen 6, and Transforming Growth Factor β1 for the Development of Neonatal Bronchopulmonary Dysplasia

Background:

Chorioamnionitis (CAM) is an important risk factor for the development of bronchopulmonary dysplasia (BPD) in preterm infants.

Objectives:

To evaluate the effects of CAM on the development of BPD using interleukin 6 (IL-6), Krebs von den Lungen 6 (KL-6), and transforming growth factor β₁ (TGF-β₁) in the amniotic fluid as markers for inflammation, lung injury, and fibrosis/remodeling, respectively.

Methods:

Amniotic fluid concentrations of IL-6, KL-6, and TGF-β₁ were measured with enzyme-linked immunosorbent assay or electrochemiluminescence immunoassay.

Results:

Of the 36 preterm infants, 18 were exposed to histologically confirmed CAM. Of these, 12 were later diagnosed as having BPD. The IL-6, KL-6, and TGF-β₁ levels in the amniotic fluid significantly increased with increasing histologic severity of CAM. Moreover, these markers were higher in the BPD group with histologic CAM than those without.

Conclusions:

Our study suggests that CAM is likely to induce inflammatory, injury, and remodeling processes in the fetal lung.

Chorioamnionitis is essential in the evolution of bronchopulmonary dysplasia--the case in favour

Bronchopulmonary dysplasia (BPD) is a major sequel of extremely premature birth. Multiple ante- and postnatal factors act in concert to injure the immature lung in the pathogenesis of the disease. Among them, chorioamnionitis--according to current evidence--plays a pivotal role. Pulmonary inflammatory processes seen in animal models of chorioamnionitis resemble those seen in premature infants who developed BPD. Chorioamnionitis can doubtlessly induce extremely preterm birth, thus contributing to a gestation-dependent risk of BPD. A gestation-independent association of chorioamnionitis with an increased risk of developing BPD has been demonstrated by a recent systematic review of clinical observational studies. Antenatal inflammation with signs of a systemic fetal response reduces the response to exogenous surfactant in infants with respiratory distress syndrome, leading to a longer need for mechanical ventilation. Moreover, chorioamnionitis increases the risk of early onset sepsis. Both mechanical ventilation and sepsis are, however, major postnatal risk factors for BPD.

Urinary ß2-microglobulin in very preterm neonates with chorioamnionitis

It is important to identify premature infants with prenatal inflammation as it contributes to short- and long-term complications. Our object was to study how prenatal inflammation affects the urinary β(2)-microglobulin (β(2)-MG) level. Preterm neonates were divided based on the presence of chorioamnionitis (CAM) into the CAM (n = 100) and non-CAM groups (n = 117). These were further subdivided into five groups each: 30 preterm neonates of 23-26; 42 neonates of 27-28; 54 neonates of 29-30; 51 neonates of 31-32; and 40 neonates of 33-34 weeks' gestation. The urinary β(2)-MG level within 48 h of birth was significantly higher in the CAM group than in the non-CAM group among the neonates of 23-26 weeks' gestation (18.3 ± 6.9 vs 10.0 ± 5.6 × 10(4) μg/gCr, p = 0.0018) and the neonates of 27-28 weeks' gestation (16.2 ± 10.8 vs 8.8 ± 3.3 × 10(4) μg/gCr, p = 0.0101). However, there was no difference in urinary β(2)-MG level between the CAM and the non-CAM group among the neonates ≥ 29 weeks 'gestation. Moreover, the elevated urinary β(2)-MG level in the neonates ≤ 28 weeks ' gestation with CAM had disappeared by 1 week after birth. The reasons for the increase in urinary β(2)-MG level within 48 h of birth in very preterm neonates (≤ 28 weeks' gestation) with CAM are believed to be not only prematurity, but also prenatal inflammation. It is suggested that the urinary β(2)-MG level during the early postnatal period can identify prenatal inflammation.

Evaluation of fetal lungs and stomach in the determination of amniotic sac infection

This study evaluated neutrophils in fetal lung/stomach, in association with chorioamnionitis. Reports/slides from fetuses 13-24 weeks with a confirmed histologic diagnosis of placental chorioamnionitis were reviewed. There were 94 cases with no neutrophils in the lungs or stomach, and 106 with neutrophils in lungs, stomach, or both (53%). Thirteen percent showed neutrophils in the lungs only. Fetuses with no neutrophils were older than those with neutrophils in the stomach only (p = 0.008). Neutrophils in fetal lungs/stomach are common, and may confirm chorioamnionitis when the placenta is not available. Submission of gastric sections increases identification of chorioamnionitis.

Soluble receptor for advanced glycation end products (sRAGE) in tracheobronchial aspirate fluid and cord blood of very low birth weight infants with chorioamnionitis and funisitis

BACKGROUND

A systemic fetal inflammatory response, reflected by histological funisitis is associated with pulmonary morbidity and increased mortality after premature birth. The receptor for advanced glycation end products (RAGE) is a membrane-bound multiligand receptor with a key role in inflammation. Soluble RAGE (sRAGE) is created by alternative mRNA splicing or shedding of the receptor's extracellular domain and can inhibit RAGE-activation.

AIMS

To assess the association of funisitis with airway and systemic concentrations of sRAGE in very premature infants.

METHODS

Forty-two ventilated infants (gestational age: 27.4 +/- 1.8weeks, birth weight: 1017 +/- 229 g [mean +/- SD]) were studied. sRAGE concentrations were measured in tracheobronchial aspirate fluid (TAF) on days of life 1, 3, 5, 7 and 10 and in umbilical cord serum of 28 infants by ELISA. The secretory component for IgA (SC) served as reference protein in TAF. Placental tissue, membranes and umbilical cords were examined microscopically to distinguish three groups: chorioamnionitis (n=9), funisitis (n=17) and controls (n=16).

RESULTS

The funisitis group had lower sRAGE concentrations than both other groups in cord blood serum (median: 0.52 ng/ml [25th-75th centile: 0.32-0.91]; control, 1.72 [1.02-2.69]; chorioamnionitis, 1.44 [0.92-1.63], p<0.01) and TAF on day 1 (290 ng/ngSC [140-400]; control, 2750 [1470-28920]; chorioamnionitis, 2150 [1220-7140], p<0.01). sRAGE in TAF remained lower in the funisitis than in the chorioamnionitis group on days 3 and 10, p<0.01 respectively.

CONCLUSIONS

Decreased sRAGE in airways and circulation after funisitis may contribute to an imbalance between pro- and anti-inflammatory factors priming very premature infants for pulmonary injury and increasing the risk of adverse outcome.

Response of leukocytes and nucleated red blood cells in very low-birth weight preterm infants after exposure to intrauterine inflammation

OBJECTIVES

To test the hypothesis if very immature preterm infants exposed to chorioamnionitis would exhibit increased numbers of leukocytes, neutrophils, and nucleated red blood cells (NRBC) in peripheral blood.

STUDY DESIGN

Preterm infants with birth weight <1500 g were prospectively evaluated. Blood cells were counted within the first hour of life in infants exposed to histological chorioamnionitis and controls.

RESULTS

Birth weight, gestational age, and sex did not differ between the groups (n = 71). Seventeen infants who were exposed to chorioamnionitis had significantly higher counts of leukocytes, neutrophils, and immature neutrophils after birth. However, there was no difference in the number of circulating NRBCs between both groups. In contrast, there was a tendency towards an increased NRBC count in the control group.

CONCLUSION

Preterm infants exposed to chorioamnionitis elicited a strong inflammatory response as reflected by increased numbers of leukocytes and neutrophils. However, chorioamnionitis did not induce an increase in numbers of NRBC.

The number of CD68(+) (Hofbauer) cells is decreased in placentas with chorioamnionitis and with advancing gestational age

Hofbauer cells are placental macrophages found in chorionic villous stroma; they express classic monocyte/macrophage markers, such as CD68. Little is known about their participation in placental disease and immunologic interactions at the placental interface. The aim of this study was to quantify the amount of Hofbauer cells in placentas complicated, or not, by chorioamnionitis and in placentas from different gestational ages. Fifty-eight 2nd- and 3rd-trimester placentas with the histologic diagnosis of acute chorioamnionitis were compared with 42 control placentas matched according to gestational age. Immunohistochemistry evaluation was performed with a monoclonal anti-CD68 antibody. Five areas of each placenta were photographed and 5 investigators, with the help of a computerized image analysis program, independently evaluated the number of CD68(+) cells. Our results showed that there are significantly fewer CD68(+) cells per villous area in placentas diagnosed with chorioamnionitis than in those of controls (P < 0.001). Moreover, there was a significant overall decrease in the number of these cells in 3rd as compared with 2nd trimester placentas (P  =  0.02), as well as in placentas from term as compared to preterm pregnancies (P  =  0.004). Our data indicate that CD68(+) Hofbauer cells may be involved in placental infection and possibly associated with the developmental maturation of the fetoplacental unit.

The importance of intra-amniotic inflammation in the subsequent development of atypical chronic lung disease

OBJECTIVE

To examine whether the intra-amniotic inflammation is a risk factor for the development of atypical chronic lung disease (CLD).

STUDY DESIGN

A retrospective cohort study was undertaken in 72 patients who delivered preterm neonates (gestational age: 24-32 weeks) within 5 days of amniocentesis and whose neonates subsequently developed CLD. Atypical CLD was defined as CLD without respiratory distress syndrome (RDS). Intra-amniotic inflammation was defined as an elevated amniotic fluid (AF) concentration of matrix metalloproteinase-8 (MMP-8) (>23 ng/ml).

RESULTS

(1) Atypical CLD was identified in 54.2% (39/72) of cases with CLD; (2) there were no significant differences in the median gestational age at birth and the rate of antenatal corticosteroid use between infants with atypical CLD and CLD with RDS; (3) preterm newborns with atypical CLD had a significantly higher median AF MMP-8 concentration (median 373.1 ng/ml vs. 8.6 ng/ml, p = 0.003) and median AF white blood cell count (median 450.0/mm(3)vs. 5.5/mm(3), p = 0.009), and a higher rate of intra-amniotic inflammation (74.4%vs. 45.5%, p = 0.012) than those with CLD with RDS.

CONCLUSION

Intra-amniotic inflammation confers a greater risk for atypical CLD than for typical CLD with initial RDS. This novel observation strengthens the importance of prenatal inflammation as a mechanism of lung injury.

Comparison of markers for fetal inflammatory response syndrome: fetal blood interleukin-6 and neonatal urinary beta(2)-microglobulin

AIM

Chronic lung disease (CLD) is a major component in the morbidity of premature infants suffering from fetal inflammatory response (FIRS). The aim of the present study was to compare the value of measuring neonatal urinary beta(2)-microglobulin (beta(2)-MG) levels with fetal blood interleukin (IL)-6 levels in premature infants at risk of developing CLD.

METHODS

Premature infants (gestational age <30 weeks) without CLD (n = 19) and with CLD (n = 10) were enrolled. We measured IL-6 levels in umbilical cord blood and beta(2)-MG levels in urine obtained within 48 h after birth.

RESULTS

IL-6 and beta(2)-MG levels were significantly higher in infants who developed CLD than in those who did not (median IL-6, 54.7 vs 7.6 pg/mL; P < 0.005; beta(2)-MG 17.7 vs 9.3 x 10(4) microg/gCr; P < 0.05). The sensitivity and negative predictive value of beta(2)-MG at the cut-off value at 10.0 x 10(4) microg/gCr (0.90 and 0.92) were comparable to IL-6 at 16 pg/mL (0.90 and 0.94).

CONCLUSION

We suggest that measuring urinary beta(2)-MG in premature infants soon after birth can monitor FIRS and may provide information on the risk of subsequent CLD development that is as clinically important as information derived from umbilical cord blood IL-6.

The association between intrauterine inflammation and spontaneous vaginal delivery at term: a cross-sectional study

Background

Different factors contribute to the onset of labor at term. In animal models onset of labor is characterized by an inflammatory response. The role of intrauterine inflammation, although implicated in preterm birth, is not yet established in human term labor. We hypothesized that intrauterine inflammation at term is associated with spontaneous onset of labor.

Methods/Results

In two large urban hospitals in the Netherlands, a cross-sectional study of spontaneous onset term vaginal deliveries and elective caesarean sections (CS), without signs of labor, was carried out. Placentas and amniotic fluid samples were collected during labor and/or at delivery. Histological signs of placenta inflammation were determined. Amniotic fluid proinflammatory cytokine concentrations were measured using ELISA. A total of 375 women were included. In term vaginal deliveries, more signs of intrauterine inflammation were found than in elective CS: the prevalence of chorioamnionitis was higher (18 vs 4%, p = 0.02) and amniotic fluid concentration of IL-6 was higher (3.1 vs 0.37 ng/mL, p<0.001). Similar results were obtained for IL-8 (10.93 vs 0.96 ng/mL, p<0.001) and percentage of detectable TNF-α (50 vs 4%, p<0.001).

Conclusions

This large cross-sectional study shows that spontaneous term delivery is characterized by histopathological signs of placenta inflammation and increased amniotic fluid proinflammatory cytokines.

The role of surfactant treatment in preterm infants and term newborns with acute respiratory distress syndrome

Surfactant treatment in preterm infants and term newborns with (acute respiratory distress syndrome) ARDS-like severe respiratory failure has become part of an individualized treatment strategy in many intensive care units around the world. These babies constitute heterogeneous groups of gestational ages, lung maturity, as well as of the underlying disease processes and postnatal interventions. The pathophysiology of respiratory failure in preterm infants is characterized by a combination of primary surfactant deficiency and surfactant inactivation as a result of plasma proteins leaking into the airways from areas of epithelial disruption and injury. Various pre- and postnatal factors, such as exposure to chorioamnionitis, pneumonia, sepsis and asphyxia, induce an injurious inflammatory response in the lungs of preterm infants, which may subsequently affect surfactant function, synthesis and alveolar stability. Surfactant inactivation--and dysfunction--is also a hallmark in newborns with meconium aspiration syndrome (MAS), pneumonia and other disorders affecting the pulmonary function. Although for the majority of suggested indications no data from randomized controlled trials exist, a surfactant replacement that counterbalances surfactant inactivation seems to improve oxygenation and lung function in many babies with ARDS without any apparent negative side effects. Newborns with MAS will definitely benefit from a reduced need for extracorporeal membrane oxygenation (ECMO). Clinical experience seems to justify surfactant treatment in neonates with ARDS.

MMP-9 and TIMP-1 in the cord blood of premature infants developing BPD

We investigated matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1) levels in the cord blood of 29 premature infants who were <30 weeks gestation. One, 8, and 14 infants developed severe, moderate and mild bronchopulmonary dysplasia (BPD), respectively, and 6 did not. MMP-9 and TIMP-1 levels in the cord blood were determined by ELISA. MMP-9/TIMP-1 ratios in the cord blood of infants who developed severe or moderate BPD (n = 9) were significantly higher than those who developed mild BPD or did not develop BPD (n = 20; P = 0.015). Multivariate linear regressions demonstrated that MMP-9 levels and MMP-9/TIMP-1 ratios in the cord blood of the premature infants correlated with the oxygen supplementation period (r = 0.58, P = 0.003 and r = 0.41, P = 0.030, respectively). The MMP-9 levels and MMP-9/TIMP-1 ratios correlated with the severity of maternal chorioamnionitis (both trend P = 0.006). The MMP-9 levels and MMP-9/TIMP-1 ratios in the cord blood may be related to the pathogenesis and severity of BPD and maternal chorioamnionitis.

Maternal exposure to endotoxin delays alveolarization during postnatal rat lung development

Maternal bacterial infections adversely affect lung development by crossing the placental barrier and infecting the developing fetus. The underlying mechanism negatively affecting pulmonary development remains unknown. Herein, we investigated whether a systemic maternal infection affects postnatal inflammation and alveolar development. Pregnant rats were injected with 2.5 mg/kg LPS on day 20 and 21 (term = 22 days). Postnatal (PN0-21) mRNA and protein expression of cytokines (IL-1beta, IL-6, IL-10, CXCL1/2, TNFalpha) and genes implicated in alveologenesis [tropoelastin, lysyl oxidase (LOX), lysyl oxidase-like (LOXL)1, tenascin-C (TNC), fibulin 5, vascular endothelial growth factor (VEGF-A), VEGF receptor (VEGFR)2, VEGFR1, platelet-derived growth factor (PDGF)A, PDGFB, and PDGFRalpha] were quantified by real-time PCR and beadlyte technology. Lung transcript and protein levels of IL-1beta, IL-6, and CXCL1/2 were significantly greater in LPS-exposed pups than those of control pups at PN0, 2, 6, 10, and 14. Bronchoalveolar lavage fluid (BALF) of LPS-exposed animals contained significantly more macrophages at PN2 and 14 than BALF of control pups. Morphometric analysis revealed that LPS-exposed animals had fewer and larger alveoli, fewer secondary septa, and decreased peripheral vessel density when compared with control pups. This morphological delay in alveolar development disappeared after PN14. Tropoelastin, LOXL1, VEGF, VEGFR2, and PDGFRalpha mRNA expression of LPS-exposed animals was significantly greater than those of control animals in PN2-14 lungs. TNC, LOX, fibulin 5, VEGFR1, PDGFA, and PDGFB expression was not affected by maternal LPS exposure. Together, the data demonstrate that maternal exposure to endotoxin results in a prolonged pulmonary inflammation postnatally, altered gene expression of molecules implicated in alveologenesis, and delayed morphological maturation of the lung.

Airway inflammatory cell responses to intra-amniotic lipopolysaccharide in a sheep model of chorioamnionitis

Chorioamnionitis, a risk factor for bronchopulmonary dysplasia in preterm infants, causes an influx of inflammatory cells into the fetal lung. Using a fetal sheep model, we evaluated the time course of activation, functional maturity, and apoptosis of the leukocytes recruited to the fetal air spaces by lipopolysaccharide (LPS). Time-mated sheep were given intra-amniotic injections with 10 mg of Escherichia coli LPS or saline 2 or 7 days before preterm delivery at 124 days of gestation (term is 150 days). Both neutrophils and monocytes in bronchoalveolar lavage fluid (BALF) had activated NF-kappaB after 2- and 7-day LPS exposures. These neutrophils and monocytes expressed the activation factor CD11b and the maturation factor PU.1 at 2 days, and increased PU.1 expression was detected in macrophages at 7 days. Leukocyte oxidative burst activity was greatest at 7 days. BALF lipid peroxidation increased fivefold at 2 days, while protein carbonyls increased eightfold at 7 days. Nitrative stress was not detected in the BALF, but leukocytes in the lung expressed nitric oxide synthase (NOS)II (inducible NOS). BALF leukocytes expressed the antioxidant peroxiredoxin V. Lung glutathione peroxidase was also increased with LPS exposure. There was minimal apoptosis of airway and lung leukocytes assessed by caspase-3 activation. Intra-amniotic LPS recruits leukocytes to the fetal air space that have a persistent activation. These results have implications for the pathogenesis of lung inflammatory disorders in the preterm.

Inflammatory mediators in the immunobiology of bronchopulmonary dysplasia

Inflammation is important in the development of bronchopulmonary dysplasia (BPD). Polymorphonuclear cells and macrophages and proinflammatory cytokines/chemokines denote early inflammation in clinical scenarios such as in utero inflammation with chorioamnionitis or initial lung injury associated with respiratory distress syndrome or ventilator-induced lung injury. The persistence and non-resolution of lung inflammation contributes greatly to BPD, including altering the lung's ability to repair, contributing to fibrosis, and inhibiting secondary septation, alveolarization, and normal vascular development. Further understanding of the role of inflammation in the pathogenesis of BPD, in particular, during the chronic inflammatory period, offers us the opportunity to develop inflammation-related prevention and treatment strategies of this disease that has long-standing consequences for very premature infants.

Antenatal inflammation and lung injury: prenatal origin of neonatal disease

INTRODUCTION

Antenatal inflammation in utero may be associated with lung injury and subsequent aberrant lung development resulting in bronchopulmonary dysplasia (BPD). BPD has become a developmental disease with a uniform arrest in lung development.

STUDY DESIGN

The role of antenatal inflammation in the induction of lung injury was explored in a sheep model suitable for the study of lung development with respect to human development. Chorioamnionitis was induced by a single injection of endotoxin into the amniotic cavity under ultrasound guidance.

RESULT

Endotoxin-induced chorioamnionitis caused a cascade of lung injury, pulmonary inflammation and remodeling in the fetal lung similar to lung injury previously described in adult animal models. The structural changes in the fetal lung after chorioamnionitis showed little to no fibrosis and alveolar/microvascular simplification similar to new BPD. The identified cytokine networks and regulators may explain the absence of fibrosis and lung simplification after strictly intra-uterine inflammation.

CONCLUSION

The mechanisms of antenatal inflammation in the fetal lung were multifactorial and could be antenatally modulated. Fetal pulmonary inflammation was temporarily suppressed by maternal glucocorticoid therapy. However, pulmonary inflammation could be augmented postnatally by resuscitation, oxygen toxicity, mechanical ventilation and pulmonary and systemic infection, which opens a broad window of clinical options.

Myelopoiesis in the Liver of Stillborns With Evidence of Intrauterine Infection

Context.—Chorioamnionitis is the maternal and fetal response to an ascending intrauterine infection. The fetal response is manifested by funisitis and chorionic vasculitis, or as neutrophils within pulmonary spaces. Human hematopoiesis occurs in the liver primarily during the 6th to 22nd weeks of gestation.

Objective.—To establish the relationship between the presence of an intrauterine infection and the degree of fetal hepatic myelopoiesis in second- and third-trimester fetuses.

Design.—Liver and lungs from 49 fetal autopsies, 20 to 41 weeks of gestational age, and their associated placentas and membranes were analyzed for evidence of intrauterine infection and hepatic myelopoiesis. Hematoxylin-eosin– stained sections from fixed tissues were evaluated for the presence of amnionic fluid infection, defined by the presence of acute chorioamnionitis or funisitis. The degree of portal hematopoiesis, myelopoiesis and intra-alveolar neutrophils was assessed semiquantitatively with hematoxylin-eosin–stained sections and immunohistochemically with antimyeloperoxidase. The Kruskal-Wallis 1-way analysis of variance and the Wilcoxon-Mann-Whitney test were used to determine the significance of any observed difference.

Results.—The degree of portal and lobular myelopoiesis was significantly greater with the presence of inflammation in both the membranes and umbilical cord, and correlated with the presence of intra-alveolar neutrophils (P &lt; .001). A high correlation between the hematoxylin-eosin and immunohistochemistry assessment of myeloid cells was noted.

Conclusions.—There is increased portal and lobular myelopoiesis in 20-week to 41-week gestational age fetal livers that is associated with intrauterine ascending infection. The presence of increased portal or lobular myelopoiesis suggests the presence of an active fetal response to an intrauterine ascending infection.

Pulmonary inflammation and bronchopulmonary dysplasia

Various pre- and postnatal risk factors, which act additively or synergistically induce an injurious inflammatory response in the airways and the pulmonary interstitium of preterm infants with bronchopulmonary dysplasia. This inflammatory response is characterized by an accumulation of neutrophils and macrophages as well as an arsenal of proinflammatory mediators that affect the endothelium and alveolar-capillary integrity. Besides proinflammatory cytokines and toxic oxygen radicals, lipid mediators as well as potent proteases may be responsible for acute lung injury. There is increasing evidence that an imbalance between pro- and anti-inflammatory factors, which should protect the alveoli and lung tissue, are key features in the pathogenesis of bronchopulmonary dysplasia. In addition, a subnormal generation of growth factors may affect alveolarization and vascular development in preterm infants with bronchopulmonary dysplasia. In this condensed review article, the current concepts on the possible role of inflammation in the evolution of bronchopulmonary dysplasia will be summarized.

The association between early tracheal colonization and bronchopulmonary dysplasia

OBJECTIVE

To evaluate the relationship between early tracheal colonization and bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This is a retrospective cohort study which included 308 inborn neonates admitted to the newborn intensive care unit at the University of Miami Jackson Memorial Medical Center between January 1997 and December 2000 with birthweight 500 to 1000 g, who required mechanical ventilation on the first day of life. Chorioamnionitis was diagnosed by maternal symptoms and histopathopathology. Tracheal cultures were obtained immediately after tracheal intubation. BPD was diagnosed in neonates who had supplemental oxygen requirement for more than 28 days. Pearson's chi(2) and Logistic Regression Analysis were used to evaluate the relationship between chorioamnionitis, positive initial tracheal cultures and BPD, after adjusting for confounding variables.

RESULTS

In patients with chorioamnionitis, the incidence of early positive tracheal cultures was 41% compared to 16% in those without chorioamnionitis, (p < 0.00001). In patients with birthweight 700 to 1000 g, a positive early tracheal culture increased the risk of BPD (OR = 2.42, CI 1.05 to 5.62, p < 0.05).

CONCLUSION

Preterm infants exposed to chorioamnionitis have an increased incidence of early tracheal colonization. This early tracheal colonization may predispose them to develop BPD.

Strategies for preventing bronchopulmonary dysplasia

PURPOSE OF REVIEW

Neonatologists and pulmonary biologists have long sought preventive treatments for bronchopulmonary dysplasia (BPD). The purpose of this review is to highlight recent reports of a number of potential treatments intended to prevent BPD and to discuss the controversies surrounding preventive strategies.

RECENT FINDINGS

The evolution of BPD from a disorder of pulmonary injury affecting moderately preterm infants, to one characterized by a developmental pulmonary arrest among survivors of extreme prematurity has important implications for BPD prevention. Recent recognition that the pathogenesis of BPD might have prenatal origins raises new challenges and opportunities for studies of BPD prevention; however, most current preventive strategies for BPD focus on respiratory management. Neither past nor current clinical trials have shown a conclusive benefit of a single preventive treatment strategy. Promising but still largely unproven preventive respiratory treatments include: high frequency oscillatory ventilation, permissive hypercapnea, and inhaled nitric oxide. Observational and recent laboratory data support the need for randomized clinical trials of continuous positive airway pressure versus mechanical ventilation. Additionally, clinical trials are needed to address the deficit in our knowledge of the potential benefits and risks of postnatal low dose corticosteroid treatment. Further study of superoxide dismutase, inositol, and alpha-1 proteinase inhibitor also are warranted on the basis of recent clinical trials or meta-analyses.

SUMMARY

Only Vitamin A has proven a safe and effective preventive treatment for BPD. Additional studies of respiratory technologies, management strategies, and protective molecules are needed. Directed cytokine and genetic therapies are on the horizon.

Activation of umbilical cord endothelial cells and fetal inflammatory response in preterm infants with chorioamnionitis and funisitis

Chorioamnionitis and funisitis are associated with preterm labor and postnatal morbidity. Activation of endothelium resulting in up-regulation of adhesion molecules seems to be a key mechanism in development of organ damage. We investigated whether chorioamnionitis with or without funisitis in preterm infants induced expression and shedding of adhesion molecules in the umbilical cord and resulted in increased concentrations of E-selectin, intercellular adhesion molecule (ICAM)-1, IL-1beta, IL-6, and IL-8 in the cord blood. Data were obtained by using immunohistochemistry and ELISA. Thirty-two preterm infants were divided into three groups according to histology: chorioamnionitis with funisitis, chorioamnionitis without funisitis, and controls without signs of inflammation. ICAM-1 expression on arterial endothelium was higher with funisitis compared with chorioamnionitis alone or with the control group. Similar results for ICAM-1 expression were found in venous endothelium, vascular walls, Wharton's jelly, and amnion epithelium. Endothelial E-selectin and vascular cell adhesion molecule (VCAM)-1 expression was only induced significantly with funisitis. Serum-concentrations of soluble ICAM-1 were higher with funisitis compared with chorioamnionitis alone or control group. Similarly, concentrations of soluble E-selectin, IL-1beta, IL-6, and IL-8 were increased exclusively with funisitis. In conclusion, only chorioamnionitis with funisitis was associated with systemic inflammation and endothelial activation with up-regulation and shedding of umbilical cord adhesion molecules. We speculate that this activation of endothelium may not be limited to the umbilical cord but may also involve other organs resulting in neonatal morbidity. This underlines the importance of funisitis as a risk factor for adverse outcome.

Modeling and Remodeling of the Lung in Neonatal Chronic Lung Disease

Neonatal chronic lung disease (CLD) is the major long-term pulmonary complication of preterm birth affecting about 20% of infants who need mechanical ventilation. CLD is the result of abnormal repair processes following inflammatory lung injury that lead to remodeling of the lung. Inflammation may be initiated by a variety of stimuli including mechanical ventilation, oxygen toxicity and infection. The resultant neutrophil chemotaxis and degranulation leads to the release of enzymes such as matrix metalloproteinases that can cause proteolysis of the lung extracellular matrix. Abnormal healing with remodeling leads to poorly compliant lungs with reduced capacity for gas exchange. Drugs can influence the normal process of lung modeling or remodeling. Fetal lung development can be influenced by glucocorticosteroids and inflammation. Both can cause abnormal lung modeling with fewer, larger alveoli and accelerated lung maturation, which confers benefits in terms of reduced morbidity and mortality from respiratory distress syndrome but potentially increases the risk of subsequent lung injury. Antioxidants, such as retinol (vitamin A), administered post-natally may reduce the effects of oxidative stress leading to a modest reduction in CLD but they require repeated intramuscular injections. Postnatal glucocorticosteroid therapy can modify the lung inflammatory response and reduce CLD but it can also have detrimental effects on the developing brain and lung, thereby creating a clinical dilemma for neonatologists. Proteinase inhibitors may be a rational therapy but more research is needed before they can be accepted as a treatment for preterm neonates.'Modeling' is defined as planning or forming that follows a set pattern. The term is used to describe the normal process of lung growth and development that culminates in mature branching alveolar air spaces surrounded by a network of capillaries. Normal lung modeling occurs under a variety of genetic and hormonal influences that can be altered, leading to abnormal patterns of growth. 'Remodeling' is defined as altering the structure of or re-making and, in the case of the lung, is used to describe the abnormal patterns of lung growth that occur after lung injury. Modeling and remodeling of the lungs occur to an extent throughout life but never more rapidly than during the fetal and early neonatal periods, and factors that influence this process may lead to development of neonatal CLD. Some of the factors involved in normal and abnormal lung modeling and inflammation and glucocorticosteroid-induced remodeling in the perinatal period, in the context of neonatal CLD, are reviewed with considerations of how various drugs may influence these processes.

Chorioamnionitis-induced changes of fetal extramedullar hematopoiesis in the second trimester of gestation. Is diagnosis from fetal autopsy possible?

Chorioamnionitis, as the most frequent cause of second trimester abortions, is commonly diagnosed by histomorphological examination of placental tissue. We determined whether chorioamnionitis induces a fetal extramedullary hematopoietic response and estimated whether chorioamnionitis can be diagnosed from fetal liver alone. Clinical data and morphological and histological findings of 39 second trimester abortions, caused by chorioamnionitis, were compared with 32 age-matched control cases. Using hematoxylin and eosin staining, naphtol-ASD-chloracetate esterase and "Berliner Blau" reaction, total hematopoiesis, erythropoiesis, myelopoiesis and intracytoplasmatic iron of fetal liver were examined. In the study group, total hematopoiesis was increased compared with the controls (94.9% versus 84.4%). The same was seen in erythropoiesis (69.2% versus 56.2%, P>0.05). Chorioamnionitis resulted in a significant increase of fetal myelopoiesis with clustering of leukocytes in 56.4% (P=0.001). Neutrophiles were located predominantly intrasinusoidal and periportal (74.4%), while an isolated periportal location was often observed in controls (50.0%). Isolated perivenous iron storing was more often seen with chorioamnionitis (28.3% versus 3.1%) and correlated with the increasing severity of chorioamnionitis. It can be stated that infectious diseases, such as chorioamnionitis, increase fetal intrahepatic myelopoiesis as one defense mechanism. The morphology of fetal intrahepatic hematopoiesis and iron storing might also be helpful in the diagnosis of chorioamnionitis, especially when the placenta is not available for examination.

Oral mucosal microvascular abnormalities: an early marker of bronchopulmonary dysplasia

An abnormal pulmonary vasculature has been reported as an important component of bronchopulmonary dysplasia (BPD). We tested the hypothesis of an early abnormal vascular network pattern in infants with BPD. Fifteen infants with BPD (nine boys and six girls; gestational age 27.5 +/- 2.0 wk; birth weight 850 +/- 125 g) and 15 sex- and gestational age-matched infants (nine boys and six girls; gestational age 27.6 +/- 2.6 wk; birth weight 865 +/- 135 g) were examined on postnatal days 1 and 28. BPD infants showed a significantly higher prevalence of histologic chorioamnionitis (p = 0.009), as well as higher intubation duration (p = 0.0004), oxygen supplementation (p < 0.0001), and initial illness severity (p = 0.0002) than the BPD-negative population. The lower gingival and vestibular oral mucosa was chosen as the study area. The blood vessel area was determined, and the oral vascular networks were characterized by analyzing their complexity (D, at two scales: D 1-46, D 1-15), tortuosity (Dmin), and randomness (L-Z) of the vascular loops. Infants with BPD showed a significantly lower blood vessel area as well as a higher vascular network complexity (D 1-46, D 1-15, and L-Z) than control subjects (p < 0.0001). Our findings provide a new early clinical sign in BPD and stress the importance of an early disorder in the oral mucosal vascularization process in the disease pathogenesis.

Interleukin-6, interleukin-8, and soluble tumor necrosis factor receptor-I in the cord blood as predictors of chronic lung disease in premature infants

OBJECTIVES

In order to predict the late-development of chronic lung disease of prematurity (CLD), cytokines in the cord blood were assessed in this study.

STUDY DESIGN

Eighteen premature infants with CLD were enrolled. Cord blood plasma levels of cytokines of these infants and 12 control infants without CLD were measured including interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, soluble TNF receptor-I, and soluble IL-6 receptor using a cytometric bead array and an enzyme-linked immunosorbent assay.

RESULTS

The cord blood IL-6, IL-8, and sTNFR-I levels were significantly elevated in CLD infants compared with those in control (P < .05). IL-1beta, IL-2, IL-4, IL-10, and IFN-gamma were undetectable in both groups. CLD infants with maternal chorioamnionitis had higher IL-6 than those without chorioamnionitis (P < .01). In CLD infants, IL-6 was higher in the infants who required prolonged oxygen therapy (P < .05).

CONCLUSION

Elevated inflammatory cytokines in the cord blood are associated with the progression to CLD.

Chorioamnionitis induced by subchorionic endotoxin infusion in sheep

OBJECTIVE

This study was undertaken to determine whether subchorionic endotoxin infusion causes chorioamnionitis and preterm lung maturation, as occurs after intra-amniotic endotoxin.

STUDY DESIGN

From day 118 of pregnancy, sheep received infusions of endotoxin (subchorionic 7.5 mg/d, n=11; intra-amniotic 2.5 mg/d, n=9) until delivery of lambs at 120 or 124 days. Other sheep received a single intra-amniotic injection of endotoxin (10 mg, n=7) at 118 days before delivery at 124 days. Controls (n=9) received equivalent saline solution treatments.

RESULTS

Chorioamnionitis accompanied all endotoxin treatments. Lung inflammation occurred after intra-amniotic endotoxin infusion or injection but not after subchorionic endotoxin. Umbilical arterial pH was lower and Pco(2) was higher than control after subchorionic endotoxin. Lung compliance and surfactant were increased after intra-amniotic endotoxin infusion or injection but not after subchorionic endotoxin.

CONCLUSION

Chorioamnionitis may result from inflammatory stimuli at various intrauterine sites, with different sites causing different fetal effects and not all cases of chorioamnionitis being accompanied by enhanced lung maturation.

Chorioamnionitis and increased neonatal lung lavage fluid matrix metalloproteinase-9 levels: implications for antenatal origins of chronic lung disease

OBJECTIVE

Matrix metalloproteinase-9 (MMP-9) degrades type IV collagen, the major constituent of lung basement membrane. We studied the effects of chorioamnionitis and antenatal corticosteroids on bronchoalveolar lavage (BAL) fluid levels of MMP-9, and its inhibitor, TIMP-1 in preterm infants.

STUDY DESIGN

A prospective study was performed on serial BAL samples from 79 ventilated preterm infants at less than 33 weeks' gestation, 18 of whom were from pregnancies complicated by chorioamnionitis. MMP-9 levels were measured by gelatin zymography and TIMP-1 by enzyme-linked immunosorbent assay, and the median value for each infant was calculated. The presence and severity of chorioamnionitis were defined histologically.

RESULTS

BAL fluid MMP-9 levels were higher in preterm infants in the chorioamnionitis group (86 [29-518] vs 13 [3-43] ng/mL, P =.001), and levels increased stepwise with the increasing severity of chorioamnionitis. Antenatal corticosteroids had no effect on median MMP-9 levels. Infants in the chorioamnionitis group were more likely to have chronic lung disease (CLD) develop (55% vs 28%, P <.05). TIMP-1 levels were no different between groups.

CONCLUSION

Chorioamnionitis is associated with increased lung type IV collagenase levels in the ventilated preterm infant. Antenatal lung inflammation with up-regulation of MMP-9 may be important in the pathogenesis of CLD.

Antenatal inflammation and infection in chronic lung disease of prematurity

In spite of improved neonatal care, chronic lung disease of prematurity (CLD) remains a major cause of morbidity and mortality in extremely preterm infants. Our current understanding is that antenatal infection can trigger intra-uterine inflammation which then promotes preterm labour. Recent studies suggest that antenatal infection and inflammation can also increase the preterm infant's susceptibility to develop CLD. It may be that exposure of the fetal lung to high concentrations of pro-inflammatory cytokines is the cause of this increased susceptibility. One candidate for initiating intra-uterine inflammation is ascending infection by the vaginal commensal Ureaplasma urealyticum (Uu). Antibiotics administered to mothers prior to delivery appear to improve the neonatal outcome in cases of preterm prolonged rupture of membranes, but not in cases of preterm labour with intact membranes. Uu can be transmitted vertically to the airways of the preterm infant, but the role of Uu in causing CLD remains uncertain. Small trials of antibiotics given to preterm infants after delivery have not shown any consistent benefit in reducing CLD. Although CLD remains a significant problem for the extremely preterm infant, it is likely that molecular biology techniques, such as the polymerase chain reaction, will enhance the detection of antenatal infection and further our understanding of the pathogenesis of CLD.

Small thymus at birth: a predictive radiographic sign of bronchopulmonary dysplasia

OBJECTIVE

Emerging evidence indicates a relationship between bronchopulmonary dysplasia (BPD) and chorioamnionitis. Recent data provide evidence of an acute thymic involution in very low birth weight (VLBW) preterm infants and fetuses with histologic chorioamnionitis. We tested the hypothesis that a small thymus detected at birth on the routine chest radiograph is a predictor of BPD in VLBW infants.

METHODS

A prospective study was conducted on 400 VLBW preterm infants who survived >4 weeks (mean gestational age: 27.5 weeks [range: 24-30]; mean birth weight: 1010 g [range: 450-1450]). Thymic size was measured on routine chest radiographs taken in the first 6 hours after birth and expressed as the ratio between the transverse diameter of the cardiothymic image at the level of the carina and that of the thorax (CT/T). The accuracy of CT/T for identifying infants with BPD was tested using receiver operating characteristic curve analyses and multivariate logistic regression.

RESULTS

Fifty-one VLBW infants (12.7%) subsequently developed BPD. A small thymus (CT/T <0.28) was observed in 94.1% of the infants with BPD versus 2.9% of the infants without BPD. A small thymus at birth identified infants with BPD with 94.1% sensitivity and 98.3% specificity (odds ratio: 17.8; 95% confidence interval: 5.7-55.4).

CONCLUSIONS

A small thymus at birth on the standard chest radiograph can accurately identify VLBW infants who subsequently develop BPD.