Perinatal systemic inflammatory response syndrome and retinopathy of prematurity

Intra-amniotic IL-1β induces fetal inflammation in rhesus monkeys and alters the regulatory T cell/IL-17 balance

Very low birth weight preterm newborns are susceptible to the development of debilitating inflammatory diseases, many of which are associated with chorioamnionitis. To define the effects of chorioamnionitis on the fetal immune system, IL-1β was administered intra-amniotically at ~80% gestation in rhesus monkeys. IL-1β caused histological chorioamnionitis, as well as lung inflammation (infiltration of neutrophils or monocytes in the fetal airways). There were large increases in multiple proinflammatory cytokine mRNAs in the lungs at 24 h postadministration, which remained elevated relative to controls at 72 h. Intra-amniotic IL-1β also induced the sustained expression of the surfactant proteins in the lungs. Importantly, IL-1β significantly altered the balance between inflammatory and regulatory T cells. Twenty-four hours after IL-1β injection, the frequency of CD3(+)CD4(+)FOXP3(+) T cells was decreased in lymphoid organs. In contrast, IL-17A-producing cells (CD3(+)CD4(+), CD3(+)CD4(-), and CD3(-)CD4(-) subsets) were increased in lymphoid organs. The frequency of IFN-γ-expressing cells did not change. In this model of a single exposure to an inflammatory trigger, CD3(+)CD4(+)FOXP3(+) cells rebounded quickly, and their frequency was increased at 72 h compared with controls. IL-17 expression was also transient. Interestingly, the T cell profile alteration was confined to the lymphoid organs and not to circulating fetal T cells. Together, these results suggest that the chorioamnionitis-induced IL-1/IL-17 axis is involved in the severe inflammation that can develop in preterm newborns. Boosting regulatory T cells and/or controlling IL-17 may provide a means to ameliorate these abnormalities.

Thrown off balance: the effect of antenatal inflammation on the developing lung and immune system

In recent years, translational research with various animal models has been helpful to answer basic questions about the effect of antenatal inflammation on maturation and development of the fetal lung and immune system. The fetal lung and immune systems are very plastic and their development can be conditioned and influenced by both endogenous and/or exogenous factors. Antenatal inflammation can induce pulmonary inflammation, leading to lung injury and remodeling in the fetal lung. Exposure to antenatal inflammation can induce interleukin-1α production, which enhances surfactant protein and lipid synthesis thereby promoting lung maturation. Interleukin-1α is therefore a candidate for the link between lung inflammation and lung maturation, preventing respiratory distress syndrome in preterm infants. Antenatal inflammation can, however, cause structural changes in the fetal lung and affect the expression of growth factors, such as transforming growth factor-beta, connective tissue growth factor, fibroblast growth factor-10, or bone morphogenetic protein-4, which are essential for branching morphogenesis. These alterations cause alveolar and microvascular simplification resembling the histology of bronchopulmonary dysplasia. Antenatal inflammation may also affect neonatal outcome by modulating the responsiveness of the immune system. Lipopolysaccharide-tolerance (endotoxin hyporesponsiveness/immunoparalysis), induced by exposure to inflammation in utero, may prevent fetal lung damage, but increases susceptibility to postnatal infections. Moreover, prenatal exposure to inflammation appears to be a predisposition for the development of adverse neonatal outcomes, like bronchopulmonary dysplasia, if the preterm infant is exposed to a second postnatal hit, such as mechanical ventilation oxygen exposure, infections, or steroids.

Pregnancy disorders appear to modify the risk for retinopathy of prematurity associated with neonatal hyperoxemia and bacteremia

OBJECTIVE

To explore (1) whether extremely low gestational age newborns exposed to inflammation-associated pregnancy disorders differ in retinopathy of prematurity (ROP) risk from infants exposed to placenta dysfunction-associated disorders, and (2) whether ROP risk associated with postnatal hyperoxemia and bacteremia differs among infants exposed to these disorders.

METHODS

Pregnancy disorders resulting in preterm birth include inflammation-associated: preterm labor, prelabor premature rupture of membranes (pPROM), cervical insufficiency, and abruption and placenta dysfunction-associated: preeclampsia and fetal indication. The risk of severe ROP associated with pregnancy disorders was evaluated by multivariable analyses in strata defined by potential effect modifiers, postnatal hyperoxemia and bacteremia.

RESULTS

Compared to preterm labor, infants delivered after pPROM were at reduced risk of plus disease (Odds ratio = 0.4, 95% confidence interval: 0.2-0.8) and prethreshold/threshold ROP (0.5, 0.3-0.8). Infants delivered after abruption had reduced risk of zone I ROP (0.2, 0.1-0.8) and prethreshold/threshold ROP (0.3, 0.1-0.7). In stratified analyses, infants born after placenta dysfunction had higher risks of severe ROP associated with subsequent postnatal hyperoxemia and bacteremia than infants born after inflammation-associated pregnancy disorders.

CONCLUSION

Infants exposed to placenta dysfunction have an increased risk of severe ROP following postnatal hyperoxemia and bacteremia compared to infants exposed to inflammation-associated pregnancy disorders.

Evolution of in vitro cow's milk protein-specific inflammatory and regulatory cytokine responses in preterm infants with necrotising enterocolitis

BACKGROUND

We have previously reported evidence of in vitro sensitisation to cow's milk protein in peripheral blood mononuclear cells (PBMCs) in preterm infants with necrotising enterocolitis (NEC). In the present study, we document the changes in the PBMC responses to stimulation with mitogen (phytohaemagglutinin) and cow's milk proteins β-lactoglobulin (β-lg) and casein over time: from the acute presentation of NEC, to initial recovery (reinitiation of enteral feeds), to full recovery (full feeding).

METHODS

Of the 14 preterm infants recruited with acute NEC, 12 were followed until fully enterally fed (2 died during the acute phase). Cytokine secretion (interferon-γ [IFN-γ], interleukin 4, [IL-4], IL-10, and transforming growth factor-β1 [TGF-β1]) by PBMCs in response to stimulation by phytohaemagglutinin, β-lg, and casein was measured by enzyme-linked immunospot in the acute phase and subsequently at recovery and full recovery.

RESULTS

The high levels of cytokine secretion (IFN-γ, IL-4, IL-10, and TGF-β1) observed in response to β-lg and casein in the acute phase increased by a further 50% to 100% at recovery (P < 0.005). At full recovery (full feeding), however, IFN-γ, IL-4, and IL-10 secretion response had returned to, or below, acute-phase levels, whereas the augmented TGF-β1 response was maintained (P = 0.005 vs acute level). This response pattern was similar for casein, and did not appear to be influenced by the nature of the feed used following NEC (breast milk/formula/hydrolysed formula).

CONCLUSIONS

The evolution of the cytokine response profile in parallel with the clinical recovery from NEC is consistent with a putative role for TGF-β1 in regulation of inflammation, and possibly also oral tolerance.

A new way of thinking about complications of prematurity

The morbidity and mortality of preterm infants are impacted by their ability to maintain physiologic homeostasis using metabolic, endocrine, and immunologic mechanisms independent of the mother's placenta. Exploring McEwen's allostatic load model in preterm infants provides a new way to understand the altered physiologic processes associated with frequently occurring complications of prematurity such as bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis, and retinopathy of prematurity. The purpose of this article is to present a new model to enhance understanding of the altered physiologic processes associated with complications of prematurity. The model of allostatic load and complications of prematurity was derived to explore the relationship between general stress of prematurity and complications of prematurity. The proposed model uses the concepts of general stress of prematurity, allostasis, physiologic response patterns (adaptive-maladaptive), allostatic load, and complications of prematurity. These concepts are defined and theoretical relationships in the proposed model are interpreted using the four maladaptive response patterns of repeated hits, lack of adaptation, prolonged response, and inadequate response. Empirical evidence for cortisol, inflammation, and oxidative stress responses are used to support the theoretical relationships. The proposed model provides a new way of thinking about physiologic dysregulation in preterm infants. The ability to describe and understand complex physiologic mechanisms involved in complications of prematurity is essential for research. Advancing the knowledge of complications of prematurity will advance clinical practice and research and lead to testing of interventions to reduce negative outcomes in preterm infants.

Cytokine profiles of preterm neonates with fungal and bacterial sepsis

BACKGROUND

Information on cytokine profiles in fungal sepsis (FS), an important cause of mortality in extremely low birthweight (ELBW) infants, is lacking. We hypothesized that cytokine profiles in the first 21 d of life in ELBW infants with FS differ from those with bacterial sepsis (BS) or no sepsis (NS).

METHODS

In a secondary analysis of the National Institute of Child Health and Human Development Cytokine study, three groups were defined-FS (≥1 episode of FS), BS (≥1 episode of BS without FS), and NS. Association between 11 cytokines assayed in dried blood spots obtained on days 0-1, 3 ± 1, 7 ± 2, 14 ± 3, and 21 ± 3 and sepsis group was explored.

RESULTS

Of 1,066 infants, 89 had FS and 368 had BS. As compared with BS, FS was more likely to be associated with lower birthweight, vaginal delivery, patent ductus arteriosus, postnatal steroids, multiple central lines, longer respiratory support and hospital stay, and higher mortality (P < 0.05). Analyses controlling for covariates showed significant group differences over time for interferon-γ (IFN-γ), interleukin (IL)-10, IL-18, transforming growth factor-β (TGF-β), and tumor necrosis factor-α (TNF-α) (P < 0.05).

CONCLUSION

Significant differences in profiles for IFN-γ, IL-10, IL-18, TGF-β, and TNF-α in FS, BS, or NS in this hypothesis-generating secondary study require validation in rigorously designed prospective studies and may have implications for diagnosis and treatment.

Effect of carotenoid supplementation on plasma carotenoids, inflammation and visual development in preterm infants

OBJECTIVE

Dietary carotenoids (lutein, lycopene and β-carotene) may be important in preventing or ameliorating prematurity complications. Little is known about carotenoid status or effects of supplementation.

STUDY DESIGN

This randomized controlled multicenter trial compared plasma carotenoid levels among preterm infants (n=203, <33 weeks gestational age) fed diets with and without added lutein, lycopene and β-carotene with human milk (HM)-fed term infants. We assessed safety and health.

RESULT

Plasma carotenoid levels were higher in the supplemented group at all time points (P<0.0001) and were similar to those of term HM-fed infants. Supplemented infants had lower plasma C-reactive protein (P<0.001). Plasma lutein levels correlated with the full field electroretinogram-saturated response amplitude in rod photoreceptors (r=0.361, P=0.05). The supplemented group also showed greater rod photoreceptor sensitivity (least squares means 6.1 vs 4.1; P<0.05).

CONCLUSION

Carotenoid supplementation for preterm infants raises plasma concentrations to those observed in HM-fed term infants. Carotenoid supplementation may decrease inflammation. Our results point to protective effects of lutein on preterm retina health and maturation.

The association between respiratory tract Ureaplasma urealyticum colonization and severe retinopathy of prematurity in preterm infants ≤1250 g

AIM

To evaluate the association between respiratory tract Ureaplasma urealyticum (Uu) colonization and development of retinopathy of prematurity (ROP) requiring treatment.

METHODS

The infants with birthweight (BW) ≤1250 g born in a third-level neonatal intensive care unit between March 2009 and May 2010 were prospectively identified. Nasopharyngeal swabs for Uu colonization were taken in postnatal first 3 days. Culture-positive patients were reevaluated on the twelfth day by nasopharyngeal swabs for Uu. The primary outcome was to define whether there was an association between respiratory tract Uu colonization and severe ROP requiring treatment. Independent sample's t-test or Mann-Whitney U-test was used to compare continuous variables and Chi-square test or Fisher's exact test for categorical variables. Multivariate (backward) logistic regression analysis was performed to simultaneously measure the influence of the independent variables with ROP as the dependent variable.

RESULTS

A total of 25 (12.1%) infants developed severe ROP requiring treatment among 206 infants who underwent ROP screening. Mean BW and gestational age of total cohort were 1013±159 g and 27.9±1.6 weeks, respectively. Multivariate analysis demonstrated that BW (OR: 0.64 (95% Cl 0.47-0.88); P=0.006), duration of mechanical ventilation (OR: 1.17 (95% Cl 1.06-1.28); P=0.001), premature rupture of membrane >18 h (OR: 3.83 (95% Cl 1.2-12.2); P=0.02), and Uu positivity in both cultures (OR: 5.02 (95% Cl 1.8-13.9); P=0.002) were independent risk factors for the development of severe ROP requiring treatment.

CONCLUSIONS

Respiratory tract colonization with Uu was independently associated with severe ROP requiring treatment.

Perinatal infection, inflammation, and retinopathy of prematurity

The major known risk factors for retinopathy of prematurity (ROP) are extremely low gestational age, exposure to high levels of oxygen early after birth (phase I) and relatively lower oxygen levels later (phase II). In this review, we summarize recent data suggesting that exposure to perinatal infection/inflammation is associated with an increased risk for ROP. Part of this effect might be due to direct exposure of the developing retina to circulating products of infection and/or inflammation. Another potential mechanism that deserves exploration is that inflammation and/or oxidative stress can modify the known increased risk of oxygen-associated ROP. Taken together, accumulating evidence suggests that prenatal, perinatal, and postnatal systemic inflammation contribute to a 'pre-phase', sensitizing the pre-ROP retina for subsequent insults, setting the stage for what are now called phase I and phase II of ROP pathogenesis. Strategies targeting inflammatory responses might help reduce the risk for ROP in extremely low gestational age newborns.

Cytokines and neurodevelopmental outcomes in extremely low birth weight infants

OBJECTIVE

To determine if selected pro-inflammatory and anti-inflammatory cytokines and/or mediators of inflammation reported to be related to the development of cerebral palsy (CP) predict neurodevelopmental outcome in extremely low birth weight infants.

STUDY DESIGN

Infants with birth weights ≤1000 g (n = 1067) had blood samples collected at birth and on days 3 ± 1, 7 ± 1, 14 ± 3, and 21 ± 3 to examine the association between cytokines and neurodevelopmental outcomes. The analyses were focused on 5 cytokines (interleukin [IL] 1β; IL-8; tumor necrosis factor-α; regulated upon activation, normal T-cell expressed, and secreted (RANTES); and IL-2) reported to be most predictive of CP in term and late preterm infants.

RESULTS

IL-8 was higher on days 0-4 and subsequently in infants who developed CP compared with infants who did not develop CP in both unadjusted and adjusted analyses. Other cytokines (IL-12, IL-17, tumor necrosis factor-β, soluble IL rα, macrophage inflammatory protein 1β) were found to be altered on days 0-4 in infants who developed CP.

CONCLUSIONS

CP in former preterm infants may, in part, have a late perinatal and/or early neonatal inflammatory origin.

The role of granulocyte colony-stimulating factor in the neutrophilia observed in the fetal inflammatory response syndrome

OBJECTIVES

Fetal neutrophilia is present in two-thirds of cases with the fetal inflammatory response syndrome (FIRS). The mechanisms responsible for this finding have not been elucidated. Granulocyte colony-stimulating factor (G-CSF) is the primary physiologic regulator of neutrophil production and plays a key role in the rapid generation and release of neutrophils in stressful conditions (i.e., infection). The objective of this study was to determine: 1) whether FIRS was associated with changes in fetal plasma G-CSF concentrations; and 2) if fetal plasma G-CSF concentrations correlated with fetal neutrophil counts, chorioamnionitis, neonatal morbidity/mortality and cordocentesis-to-delivery interval.

STUDY DESIGN

Percutaneous umbilical cord blood sampling was performed in a population of patients with preterm labor (n=107). A fetal plasma interleukin-6 (IL-6) concentration >11 pg/mL was used to define FIRS. Cord blood G-CSF was measured by a sensitive and specific immunoassay. An absolute neutrophil count was determined and corrected for gestational age. Receiver operating characteristic (ROC) curve, survival analysis and Cox proportional hazard model were employed.

RESULTS

1) G-CSF was detected in all fetal blood samples; 2) fetuses with FIRS had a higher median fetal plasma G-CSF concentration than those without FIRS (P<0.001); 3) a fetal plasma G-CSF concentration ≥134 pg/mL (derived from an ROC curve) was associated with a shorter cordocentesis-to-delivery interval, a higher frequency of chorioamnionitis (clinical and histological), intra-amniotic infection, and composite neonatal morbidity/mortality than a fetal plasma concentration below this cut-off; and 4) a fetal plasma G-CSF concentration ≥134 pg/mL was associated with a shorter cordocentesis-to-delivery interval (hazard ratio 3.2; 95% confidence interval 1.8-5.8) after adjusting for confounders.

CONCLUSIONS

1) G-CSF concentrations are higher in the peripheral blood of fetuses with FIRS than in fetuses without FIRS; and 2) a subset of fetuses with FIRS with elevated fetal plasma G-CSF concentrations are associated with neutrophilia, a shorter procedure-to-delivery interval, chorio-amnionitis and increased perinatal morbidity and mortality.

Mediators involved in retinopathy of prematurity and emerging therapeutic targets

Retinopathy of prematurity (ROP) is a potentially blinding disease of premature infants and despite timely treatment some infants develop retinal detachment and sight loss. Current treatment utilises laser therapy which causes destruction of treated retinal tissue resulting in field loss. There is considerable research work ongoing on neovascular eye disease which is likely to result in antiangiogenic approaches that will arrest the development of ROP by specifically targeting the involved molecular mediators. Some of these new therapeutic interventions have entered clinical trials. This article reviews new information available on the molecular pathogenesis of ROP which may result in novel treatments for ROP; it does not discuss the well-known role of oxygen in the development of ROP.

Placenta microbiology and histology and the risk for severe retinopathy of prematurity

PURPOSE

To test the hypothesis that the presence of bacteria and/or histologic inflammation in the placenta of infants born preterm is associated with an increased risk for severe retinopathy of prematurity (ROP).

METHODS

This was a prospective cohort study. Exploratory and multivariable data analyses were used, including logistic regression models with interaction terms. Main outcomes were four definitions of severe ROP: stage 3 or higher, any ROP in zone I, prethreshold/threshold, and plus disease.

RESULTS

Individually, placenta bacteria and histologic inflammation were not associated with severe ROP in univariable analyses among 1064 infants with gestational age <28 weeks or among 715 infants with gestational age <27 weeks (we excluded infants with a gestational age of 27 weeks because of the very small number of ROP cases). However, the co-occurrence of bacteria and inflammation was associated with an increased risk for ROP in zone I (odds ratio, 3.1; 95% confidence interval, 1.02-9.5). Among 339 infants with any placental bacteria, the co-occurrence of (1) inflammation and a gestational age of 23 to 24 weeks and (2) inflammation and hyperoxia were associated with prominent increases in risk for all definitions of severe ROP.

CONCLUSIONS

While antenatal exposure to infection or inflammation alone does not appear to convey risk information for severe ROP, their co-occurrence does. This finding supports the hypothesis that a fetal inflammatory response to antenatal infection might be part of the etiology of severe ROP.

Effects of maternal and placental inflammation on retinopathy of prematurity

PURPOSE

To identify maternal and placental risk factors for the occurrence and progression of retinopathy of prematurity (ROP).

METHODS

This was a retrospective cohort study. The study cohort consisted of 246 infants with gestational age ≤ 32 weeks, with histologic examinations of their placentas. Medical records of eligible preterm infants were retrospectively reviewed. A regression model was constructed with control for known or potential factors associated with ROP. Occurrences of ROP, severe ROP (≥ stage 3), and clinically significant ROP requiring laser treatment were assessed.

RESULTS

ROP was diagnosed in 82 of 246 infants (33.3%), including 49 with mild ROP and 33 with severe ROP. Laser treatment was performed on 27 infants (11%: 27/246). Multivariate regression analysis indicated clinical chorioamnionitis and elevated maternal WBC count on admission to be associated with ROP occurrence [odds ratio (OR) = 4.370, P = 0.046; and OR = 1.104 per 1,000 cells/mm(3) incremental increase, P = 0.019, respectively], while the use of tocolytics was associated with reduced occurrence of ROP (OR = 0.278, P = 0.006). Elevated maternal WBC count on admission was also independently associated with ROP progression requiring laser treatment (OR = 1.171 per 1,000 cells/mm(3) incremental increase, P = 0.026). However, neither histologic chorioamnionitis nor funisitis was associated with the occurrence or progression of ROP.

CONCLUSIONS

Clinical chorioamnionitis and elevated maternal WBC count, but not histologic chorioamnionitis, were significantly and independently associated with ROP. These findings support the hypothesis that maternal systemic inflammation may play a role in the pathogenesis of ROP.

Understanding retinopathy of prematurity: update on pathogenesis

Retinopathy of prematurity (ROP), an ocular disease characterized by the onset of vascular abnormalities in the developing retina, is the major cause of visual impairment and blindness in premature neonates. ROP is a complex condition in which various factors participate at different stages of the disease leading to microvascular degeneration followed by neovascularization, which in turn predisposes to retinal detachment. Current ablative therapies (cryotherapy and laser photocoagulation) used in the clinic for the treatment of ROP have limitations and patients can still have long-term effects even after successful treatment. New treatment modalities are still emerging. The most promising are the therapies directed against VEGF; more recently the use of preventive dietary supplementation with ω-3 polyunsaturated fatty acid may also be promising. Other than pharmacologic and nutritional approaches, cell-based strategies for vascular repair are likely to arise from advances in regenerative medicine using stem cells. In addition to all of these, a greater understanding of other factors involved in regulating pathologic retinal angiogenesis continues to emerge, suggesting potential targets for therapeutic approaches. This review summarizes an update on the current state of knowledge on ROP from our and other laboratories, with particular focus on the role of nitro-oxidative stress and notably trans-arachidonic acids in microvascular degeneration, semaphorin 3 operating as vasorepulsive molecules in the avascular hypoxic retina and in turn impairing revascularization, succinate and its receptor GPR91 in neuron-mediated retinal neovascularization, and ω-3 lipids as modulators of preretinal neovascularization.