Role of the fetus in perinatal infection and neonatal brain damage

Implication of cord blood myeloperoxidase but not of soluble p-selectin levels in preterm deliveries

Although maternal amniotic and vaginocervical cytokines are known to play a role in triggering preterm delivery, the effects of activating fetal phagocytes and platelets are not clear. In an attempt to clarify this issue, we measured levels of myeloperoxidase (MPO), a phagocyte activation marker, and soluble p-selectin (sCD62p), a platelet activation marker, in umbilical cord blood samples from 2200 consecutive cord blood collections, 106 of which were from preterm infants. MPO and sCD62p levels were correlated to gestational age and preterm delivery. It was found that MPO levels were significantly higher in preterm infants and were not significantly correlated to gestational age. In contrast, sCD62p levels were lower in preterm infants and were negatively correlated to gestational age. In summary, we showed that fetal phagocyte activation as demonstrated by higher cord blood MPO levels is associated with preterm delivery, but platelet activation as shown by lower sCD62p levels is not. This suggests that fetal phagocyte activation may be implicated in preterm delivery, and subsequently in prematurity-related inflammatory insults.

Association of cord blood cytokines with prematurity and cerebral palsy

BACKGROUND

Many studies have shown that certain cytokines in amniotic fluids are correlated to premature labor and neonatal brain insults.

AIMS

We investigated whether different fetal phagocyte and vascular mediators including IL-8, myeloperoxidase (MPO), PGE(2) and soluble vascular cell adhesion molecule-1 (sVCAM-1) levels were correlated to prematurity and cerebral palsy (CP) of premature infants.

SUBJECTS

Umbilical cord blood samples from 96 preterm babies from 2250 cord blood collections were studied.

METHOD

The enzyme-linked immunoassay (ELISA) technique was used to determine concentrations of cord blood IL-8, MPO, PGE(2) and sVCAM-1.

RESULTS

Preterm babies with gestational age (GA) < or =32 weeks had significant higher cord blood IL-8, MPO and PGE(2) levels than full-term babies. These mediators, however, were not correlated to gestational age, suggesting that increases of these mediators are more related to preterm delivery but not fetal maturation. Further analysis showed that IL-8, a mediator mainly from monocytes, but not MPO, another mediator mostly from granulocytes, was correlated to cerebral palsy.

CONCLUSIONS

Taken together, these results suggest that both premature monocytes and granulocytes activation are involved in preterm delivery, but maybe only monocytes activation is correlated to premature infants' cerebral palsy. Selective manipulation of monocytes activation may be useful to prevent premature-related cerebral palsy.

Coagulation, inflammation, and the risk of neonatal white matter damage

Indicators of coagulation activation are sometimes increased in the blood of newborns and adults who have a systemic inflammatory response. These coagulation factors have the ability to exacerbate inflammation, which in turn can promote coagulation. Therapies directed solely at coagulation factors and therapies directed solely at inflammation factors have not proved effective in reducing mortality in adults with a systemic inflammatory response syndrome and multi-organ dysfunction (SIRS/MOD). On the other hand, the only therapy that has reduced mortality in SIRS/MOD is activated protein C, which has both anti-coagulation and anti-inflammatory effects. This and other observations support the view that activated coagulation factors enhance inflammation. Since newborns at risk of cerebral white matter damage and cerebral palsy are more likely than their peers to have a systemic inflammatory response, which is sometimes accompanied by elevated blood levels of coagulation factors, we suggest that activated coagulation factors contribute to the occurrence of cerebral white matter damage by exacerbating inflammatory phenomena, rather than by occluding cerebral blood vessels.

Severe umbilical cord inflammation-a predictor of periventricular leukomalacia in very low birth weight infants

Chorioamnionitis has been associated with periventricular leukomalacia (PVL) in very low birth weight (VLBW) infants. We examined the association between the pathological severity of chorioamnionitis and PVL in VLBW infants. Thirty-four VLBW infants with PVL and 34 control infants matched for gestational age without a diagnosis of PVL or intraventricular hemorrhage were obtained from the Women and Infants' Hospital of Rhode Island's Neonatal Follow-up Clinic database. Placental samples, including the amnion/chorion, chorionic plate, and umbilical cord, were examined microscopically. Statistical analysis included Mantel-Haenszel chi-square, and Student's t-test. Severe inflammation in the umbilical cord was observed in 53% of infants with PVL and 32% without PVL (p<0.05). Severe umbilical cord inflammation is one of the risk factors associated with the development of PVL in VLBW infants.

Animal models of hypoxic-ischemic brain damage in the newborn

Controversy continues over which animal model to use as a reflection of human disease states. With respect to perinatal brain disorders, scientists must contend with a disease in evolution. In that regard, the perinatal brain is at risk during a time of extremely rapid development and maturation, involving processes that are required for normal growth. Interfering with these processes, as part of therapeutic intervention must be efficacious and safe. To date, numerous models have provided tremendous information regarding the pathophysiology of brain damage to term and preterm infants. Our challenges will continue to be in identifying those infants at greatest risk for permanent injury, and adapting therapies that provide more benefit than harm. Using animal models to conduct these studies will bring us closer to that goal.

Bronchopulmonary dysplasia is not associated with ultrasound-defined cerebral white matter damage in preterm newborns

Bronchopulmonary dysplasia (BPD) and cerebral white matter damage (WMD) are neonatal disorders that occur most commonly in those who are born much before term. In a large multicenter database, we sought to determine whether the two disorders occur together more frequently than expected and whether BPD and other neonatal respiratory characteristics are more common among infants who develop ultrasound-defined WMD than among those who do not. In a sample of 904 infants who were born before the 30th week of gestation and survived until 36 wk postmenstrual age, we did not find a co-occurrence of BPD and WMD above what would be expected by chance. Confounding does not seem to account for this lack of association between WMD and BPD. In conclusion, our findings do not support the hypothesis that BPD contributes to the occurrence of sonographically defined WMD.

Second-trimester pregnancy loss at an urban hospital

OBJECTIVES

Second-trimester spontaneous pregnancy losses are less common than first-trimester losses, and are often associated with ascending infection and/or acute chorioamnionitis. A Medline search revealed only two large studies published in the recent literature, reporting incidences of chorioamnionitis of 39.3% and 58.2%, respectively. These studies did not address the use of histopathology for the identification of organisms. Since ascending infection is likely to be a significant cause of second-trimester loss in the inner-city population at the University Hospital in Newark, New Jersey, we sought to evaluate the usefulness of stains for microorganisms, which are rarely utilized on these specimens.

METHODS

Retrospective review of the medical records and pathologic material for cases of spontaneous abortions seen at the University Hospital in Newark between January 1999 and March 2001 was undertaken. Stains for microorganisms were performed on archival placental tissue for cases with histologic acute chorioamnionitis.

RESULTS

A total of 67 cases were available for review, of which 38 cases (56.7%) showed histologic acute chorioamnionitis, similar to the rates in one previous study, but significantly higher than those in the other (p = 0.01). Of 25 cases with histological chorioamnionitis for which appropriate fetal material was available, 13 cases (52%) showed polymorphonuclear leukocytes (PMNs) in the fetal lungs, one case (4%) showed PMNs in the fetal stomach, and seven cases (28%) showed PMNs in both the lung and the stomach. Of the 38 cases with chorioamnionitis, Gram stains showed Gram-positive cocci in six cases, two of which were culture positive for group B streptococcus. Warthin-Starry stains showed filamentous organisms consistent with Fusobacterium sp. in the placenta in three cases.

CONCLUSIONS

Acute chorioamnionitis is associated with second-trimester pregnancy loss at this inner-city hospital, and may be related to the high incidence of risk factors in this population. A small proportion of cases can be further characterized by the inclusion of Gram and Warthin-Starry stains in the evaluation. Selection of cases with histologic acute chorioamnionitis for further study with special stains may provide additional information on the causative organism.

Screening for infectious diseases

INTRODUCTION

Fetal brain injury is an essential cause of lifelong morbidity. Infection appears as a cause of brain damage. Apart from chorioamnionitis, screening for infectious diseases must be considered in pregnancies with a risk of congenital infection or cases with abnormal cerebral ultrasound findings.

DISCUSSION

Congenital infections include most of the major components of the TORCH complex: toxoplasmosis, rubella, cytomegalovirus, herpes, and varicella. Seronegative mothers can develop primary infection, which carries a risk of vertical transmission. The timing of the infection is a critical point, because fetal damage often depends on the gestational age at which acute maternal infection took place and occurs more likely in the first half of pregnancy. Antenatal ultrasound can detect brain abnormalities, like hydrocephalus, periventricular leukomalacia, calcifications or hemorrhage. Maternal serologic tests must be performed to look for an infectious etiology; the most frequent agents are the components of the TORCH complex. But additional serology must include parvovirus B19, HIV, and coxsackieviruses.

Effect of maternal antibiotic treatment on fetal periventricular white matter cell death in a rabbit intrauterine infection model

AIM

To evaluate the effects of maternal antibiotic treatment on fetal brain cell death in a rabbit intrauterine infection model.

METHODS

After Escherichia coli uterine-horn inoculation in 22 pregnant rabbits, followed at various times by ceftriaxone and caesarean section, cell death in white matter (histology and fragmented DNA staining) from fetuses killed at extraction was compared across groups using the Mantel-Haenszel test and Fisher's exact test for small numbers.

RESULTS

White matter cell death was consistently present at 48 h, with ceftriaxone initiation at 24 h (group 1), detectable at 84 but not 60 h, with ceftriaxone initiation at 12 h, and significantly reduced at 84 h with ceftriaxone initiation at 6 h (60% vs 100% in group 1, p < 0.001, Fisher's exact test).

CONCLUSION

Early maternal antibiotic therapy delays white matter cell death in rabbit fetuses exposed to intrauterine infection. This may provide a window for preventing white matter damage.

Chronic placental insufficiency and foetal growth restriction lead to long-term effects on postnatal retinal structure

The aim of this study was to determine the effects of foetal growth restriction on the retina after birth. Foetal growth restriction (FGR) was induced via umbilico-placental embolization (UPE) in ewes from 120 days of pregnancy until term (term approximately 147 days); controls were not exposed to UPE. Lambs were delivered and raised until 2 years of age when retinas were collected and processed for structural and neurochemical analysis. The foetuses exposed to UPE were hypoxemic and at birth were growth restricted. In 2-year-old FGR sheep, the total thickness of the retina and the number of tyrosine hydroxylase immunoreactive dopaminergic amacrine cells were reduced compared to controls (P < 0.05). It is concluded that restricted foetal growth leads to long-term structural and neurochemical changes in the retina. Of particular interest are the alterations to dopaminergic amacrine cell numbers, as alterations in this population may affect contrast sensitivity and have implications for the alterations in vision observed in very low birthweight infants.

Recombinant peroxiredoxin 5 protects against excitotoxic brain lesions in newborn mice

The pathophysiology of brain lesions associated with cerebral palsy is multifactorial and likely involves excess release of glutamate and excess production of free radicals, among other factors. Theoretically, antioxidants could limit the severity of these brain lesions. Peroxiredoxins are a family of peroxidases widely distributed in eukaryotes and prokaryotes. Peroxiredoxin 5 (PRDX5) is a recently discovered mammalian member of this family of antioxidant enzymes that is able to reduce hydrogen peroxide and alkyl hydroperoxides. The present study was designed to examine the neuroprotective effects of recombinant PRDX5 against neonatal excitotoxic challenge in both in vivo and in vitro experiments. For in vivo experiments, mice (postnatal day 5) were injected intraneopallially with ibotenate acting on NMDA and metabotropic receptors, or S-bromowillardiine acting on AMPA-kainate receptors to produce excitotoxic stress and brain lesions. Systemically administered recombinant PRDX5 provided protection against ibotenate-induced excitotoxic stress. Brain lesions of animals given ibotenate and PRDX5 were up to 63% smaller than that given ibotenate alone. However, PRDX5 provided no prevention from lesions induced with S-bromowillardiine. A mutated recombinant PRDX5 that is devoid of peroxidase activity was also tested and showed no protection against lesions induced by either ibotenate or S-bromowillardiine. Two classical antioxidants, N-acetylcysteine and catalase-PEG, provided the same neuroprotective effect as PRDX5. For in vitro experiments, neocortical neurons were exposed to 300 microM NMDA alone, NMDA plus recombinant PRDX5, or NMDA, recombinant PRDX5 and dithiothreitol, a classical electron donor for peroxiredoxins. Recombinant PRDX5 plus dithiothreitol displayed a synergistic neuroprotective effect on NMDA-induced neuronal death. These findings indicate that reactive oxygen species production participates in the formation of NMDA receptor-mediated brain lesions in newborn mice and that antioxidant compounds, such as PRDX5, provide some neuroprotection in these models.

Inflammatory mediators in perinatal asphyxia and infection

AIM

To determine serum levels of interleukin-6 (IL-6), IL-1beta, tumor necrosis factor-alpha (TNF-alpha), soluble intercellular adhesion molecule-1 (sICAM-1) and C-reactive protein (CRP) in asphyxiated neonates and compare these inflammatory factors with those found in neonates with perinatal infection.

METHODS

88 neonates were studied, of whom 36 were asphyxiated, 18 were infected and the remaining 34 were controls. Peripheral blood samples were obtained on the 1st, 3rd and 5th postnatal days.

RESULTS

Cytokines IL-6 and IL-1beta as well as sICAM-1 serum levels did not differ between asphyxiated and infected neonates; however, at most time periods, their values were significantly higher than controls. TNF-alpha was similar in the three groups of neonates. CRP serum values were significantly higher in the infected neonates than in the asphyxiated or control subjects. Among the 54 asphyxiated and infected neonates, 15 were considered as severe cases and 39 as mild. The severe cases, at most time periods, had significantly higher IL-6, IL-1beta and sICAM-1 levels compared with the mild ones. Through receiver operating characteristic curves the cut-off points, sensitivities, and specificities for distinguishing neonates at risk or at high risk for brain damage were established.

CONCLUSION

Similar increases in serum levels of IL-6, IL-1beta and sICAM-1 were found in perinatally asphyxiated and infected neonates. As these increases correlated with the severity of the perinatal insults, neonates at high risk for brain damage might be detected.

Antenatal causes of cerebral palsy: associations between inherited thrombophilias, viral and bacterial infection, and inherited susceptibility to infection

Cerebral palsy rates of 2 in every 1,000 births have varied little over the last 40 years, despite improvements in obstetric care. In the past, cerebral palsy was thought to be due to poor obstetric care and management; however, epidemiological studies have refuted this, suggesting that there is usually an antenatal timing to the neuropathology of cerebral palsy. There are many known risk factors for cerebral palsy, including multiple gestation, prematurity, and low birth weight. Recently, intrauterine infection, maternal pyrexia, and the presence of thrombophilic disorders (thrombophilia) have been identified as major risk factors for subsequent cerebral palsy. This review examines the links between intrauterine infection, the fetal inflammatory response, and thrombophilia as possible causes of cerebral palsy. The interactions of viral or bacterial infections during pregnancy, normal or abnormal fetal cytokine responses, and hereditary fetal thrombophilias as antenatal causes of the neuropathology of cerebral palsy are now areas of research priority.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the condition cerebral palsy, list the risk factors for the development of cerebral palsy, outline the ultrasound findings associated with cerebral palsy, and point out other conditions associated with cerebral palsy.

Disturbance of oligodendrocyte development, hypomyelination and white matter injury in the neonatal rat brain after intracerebral injection of lipopolysaccharide

Increasing data provide support for the hypothesis that brain inflammation plays an important role in injury to developing white matter. In the present study, inflammatory responses in the neonatal rat brain were investigated following lipopolysaccharide (LPS) administration at postnatal day 5. LPS-induced brain injury was examined in brain sections 24 h, 3 and 9 days after LPS injection. White matter rarefaction was observed in 50% of the rat brains (three out of six) 24 h after LPS injection. Lateral ventricle enlargement was found in 100% (four out of four) and 89% (eight out of nine) of rat brains 3 and 9 days after LPS administration, respectively. White matter necrosis was found in three out of nine brains injected with LPS on P14. None of these injuries was observed in any control rat brains. No histological changes in gray matter were noted in the LPS-injected rat brain. Proinflammatory cytokines, tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) in the rat brain were greatly induced after LPS administration. Activated astrocytes and microglia/macrophages were found in the affected rat brains. Double-labeling showed that IL-1beta and iNOS expressing cells were microglia/macrophages. Injury to or delayed development of immature oligodendrocytes (OLs) was evident by decreased immunostaining for both O4 and O1 antibodies, markers for developing immature OLs, in the LPS-injected as compared to the control rat brain. LPS also resulted in hypomyelination, as indicated by reduced myelin basic protein (MBP) immunostaining in the P8 rat brain. Co-administration of IL-1 receptor antagonist (IL-1Ra) with LPS reduced brain injury by improving myelination and subsequent reduction of lateral ventricle enlargement. These results indicate that developing OLs may be the target cells for LPS-induced brain injury and inflammatory cytokines are possible mediators of LPS-induced brain injury.

Antenatal mycoplasma infection, the fetal inflammatory response and cerebral white matter damage in very-low-birthweight infants

We address the question as to whether Ureaplasma urealyticum or Mycoplasma hominis, cultured from the placenta of very-low-birthweight (VLBW) infants, are associated with an increased risk of (a) fetal vasculitis and (b) ultrasonographic cerebral white matter echolucency. The sample consisted of 464 VLBW infants for whom (i) the surface of the chorion was cultured for U. urealyticum and M. hominis; (ii) the placenta was examined histologically; and (iii) a cranial ultrasound scan was obtained close to days 1, 7 or 21. Infants with echolucency were compared with controls in univariable and stratified analyses and in multivariable logistic regressions. Fifty-three per cent of placentas from infants with fetal vasculitis harboured U. urealyticum compared with 18% of controls (P </= 0.001). M. hominis was present in 14% of cases of fetal vasculitis and in 2% of controls (P </= 0.001). Among cases of echolucency, 22% had U. urealyticum compared with 30% of controls (P = 0.33), whereas 17% of these cases and 5% of controls had M. hominis (P = 0.08). Our findings support the hypothesis that U. urealyticum in the placenta of VLBW infants contributes to the fetal inflammatory response without contributing to white matter damage. Our finding that M. hominis in the placenta was associated with a not quite significant threefold risk increase for echolucency deserves further investigation.

Proinflammatory cytokines: a link between chorioamnionitis and fetal brain injury

OBJECTIVE

To review the etiology of impaired fetal neurodevelopment - in particular, the relationship between chorioamnionitis, cytokines, and cerebral palsy.

DATA SOURCES

A MEDLINE search was performed for all clinical and basic science studies published in the English literature from 1966 to 2002. Key words or phrases used were chorioamnionitis, cerebral palsy, fetal brain damage, fetal CNS injury, infection in pregnancy, proinflammatory cytokines in pregnancy, proinflammatory cytokines in infection, and preterm labour or birth. All relevant human and animal studies were included.

STUDY SELECTION

Fetal brain injury remains a major cause of lifelong morbidity, incurring significant societal and health care costs. It has been postulated that chorioamnionitis stimulates maternal/fetal proinflammatory cytokine release, which is damaging to the developing fetal nervous system. Elevated cytokine concentrations may interfere with glial cell development and proliferation in the late second trimester of pregnancy, when the central nervous system is most vulnerable. Increasing numbers of epidemiological and basic science studies found through MEDLINE searches support this hypothesis. Treatment options aimed at etiologic factors may lead to improved neurodevelopmental outcomes.

CONCLUSIONS

Clearly, some relationship exists between chorioamnionitis, cytokines, and the development of cerebral palsy, but the severity and duration of exposure required to produce fetal damage remains unknown. Future research addressing these issues may aid in clinical decision-making. As well, the elucidation of mechanisms of cytokine action may aid in early treatment options to prevent or limit development of fetal brain injury.

Sequelae of chorioamnionitis

Chorioamnionitis correlates to preterm delivery prior to 30 weeks of gestation. In most studies, proxies of intrauterine infection (clinical chorioamnionitis, histological chorioamnionitis, intra-amniotic increase in cytokines) are associated with acute neonatal morbidity and mortality and, at least to some degree, with neurological impairments (periventricular leukomalacia, intraventricular hemorrhage, cerebral palsy, polymicrogyria), chronic lung disease, and involution of the thymus in the preterm infant. The connection to visual impairment and cognitive deficits is uncertain or unknown. Full-term babies exposed to intrauterine infection often present with depressed Apgar scores and neonatal encephalopathy, and are at markedly increased risk of developing cerebral palsy. The infectious/inflammatory mechanisms involved are incompletely understood, and the types of microbes, as well as the genetic characteristics of the host adaptive and innate immune response, need to be better characterized.

Perinatal infection, fetal inflammatory response, white matter damage, and cognitive limitations in children born preterm

Only sparse information is available about a possible association between antenatal infection outside the brain and subsequent cognitive limitations among preterm infants. Based on published studies, we provide a theoretical schema that links them via the fetal inflammatory response and neonatal white matter damage. We conclude that the relationship between antenatal infection and cognitive limitations deserves much further attention by researchers interested in the prevention of this undesirable outcome of prematurity.

Public health issues related to infection in pregnancy and cerebral palsy

Cerebral palsy is the most common neuromotor developmental disability of childhood, affecting as many as 8,000 to 12,000 children born in the U.S. each year (corresponding to a prevalence rate of between 2 and 3 per 1000 children). Recent improvements in neonatal care have not resulted in a decline in the overall prevalence of cerebral palsy and, in fact, greater numbers of very preterm/very low birth weight infants are surviving with cerebral palsy and other developmental problems. Infection in pregnancy may be an important cause of the disorder. In preterm infants, there appears to be about a 2-fold increased risk for cerebral palsy from chorioamnionitis, and in term infants the estimated increased risk is about 4-fold. Provisionally, chorioamnionitis might account for 12% of spastic cerebral palsy in term infants and 28% of cerebral palsy in preterm infants. Studies of biochemical markers of fetal inflammation typically associated with infection also suggest that an inflammatory response may be an important independent etiologic factor. If a substantial proportion of cerebral palsy is attributable to acute amnionitis infection and/or neonatal sepsis, cerebral palsy should have decreased in the United States after administration of intrapartum antibiotics became widespread in response to publication of public health consensus guidelines for Group B streptococcus in 1996. However, failure to detect declines could have a number of explanations and these explanations illustrate the many public health challenges related to intrauterine infection and cerebral palsy. Given the gaps in our current knowledge about intrauterine infection and cerebral palsy, public health recommendations for timely and specific prevention activities are limited at this time.

Chorioamnionitis, mechanical ventilation, and postnatal sepsis as modulators of chronic lung disease in preterm infants

OBJECTIVE

This case-control study of chronic lung disease (CLD) evaluated the hypothesis that chorioamnionitis promotes CLD and interacts with other risk factors for CLD, including mechanical ventilation and postnatal infection.

STUDY DESIGN

We identified a population of 193 infants who met our case criteria for CLD whose birth weights were <or=1500 g. These infants were matched 1:1 with control infants for gestational age and hospital of birth.

RESULTS

Univariable analyses revealed decreased CLD risk associated with histologic chorioamnionitis and increased risk associated with mechanical ventilation >7 days and culture-documented sepsis. In multivariable analyses, infants were at greatest risk for CLD when they had exposure to both chorioamnionitis and either mechanical ventilation >7 days (odds ratio, 3.2; 95% confidence interval, 0.9-11) or postnatal infection (odds ratio, 2.9; 95% confidence interval, 1.1-7.4).

CONCLUSIONS

We conclude that prolonged mechanical ventilation or postnatal infection increases the risk of CLD among surviving preterm infants and that these 2 factors interact with antenatal infection to further increase the risk of CLD.

Temporal expression pattern of cerebrovascular endothelial cell alkaline phosphatase during human gestation

In premature human neonates, immaturity of cerebral vessels can contribute to clinical problems such as germinal matrix hemorrhage and white matter damage. Afferent cerebral vessels in the brain of term babies express alkaline phosphatase (AP), an ectoenzyme located on the surface of endothelial cells. Using AP enzyme histochemistry we have examined the cerebrovasculature of premature live-born human neonates to determine when cerebral afferent vessels begin to express AP. Brains were collected at autopsy and processed for histological examination. AP-stained vessel density in the periventricular white matter was quantified using digital imaging and automated morphometry. Babies born prior to 28 wk gestation display few AP-positive vessels in the periventricular white matter, whereas, babies born after 28 wk gestation exhibit an AP-positive vascular pattern that resembles the adult pattern. In contrast, immunostaining for collagen revealed an extensive vascular network in both early and late gestation infants. Our measurements indicate that neonates born prior to 28 wk gestation are characterized by immature cerebral white matter afferent vessels and raise the possibility that the immaturity compromises vascular function.

Do white cells matter in white matter damage?

Support is provided for the hypothesis that activated leukocytes, especially monocytes/macrophages, contribute to cerebral white matter damage in extremely low gestational age newborns. Much of the evidence is indirect and comes from analogies to brain diseases in adults, and from models of brain damage in adult and newborn animals. If the recruitment of circulating cells to the brain contributes to white matter damage in extremely low gestational age newborns, then minimizing the transendothelial migration of circulating cells by pharmacological manipulation might prevent or reduce the occurrence of neonatal white matter damage and the disabilities that follow.

Inflammatory mediators and neonatal brain damage

Inflammatory mediators are multifunctional cytokines that play important roles both in normal central nervous system (CNS) development and in the response of the brain to diverse forms of injury. Interleukin (IL)-1beta, tumor necrosis factor-alpha and IL-6 are among the best-characterized early-response cytokines. Recent data suggest that they may be synthesized and secreted by several CNS cell types, including microglia, astrocytes and neurons. Biological effects of these cytokines that could influence the progression of injury in the brain include stimulating the synthesis of other cytokines and neuronal injury mediators such as nitric oxide synthase, inducing leukocyte infiltration and the expression of adhesion molecules, influencing glial gene expression and damaging oligodendrocytes. In the immature brain, proinflammatory cytokines might lead to white matter damage during prenatal intrauterine infection and contribute to progressive neuronal damage in acute brain injury evoked by cerebral hypoxia-ischemia. Interrupting the proinflammatory cascade might limit the extent of irreversible injury.

Cerebral palsy and chorioamnionitis: the inflammatory cytokine link

Cerebral palsy remains a significant cause of perinatal morbidity in medically developed countries. Human epidemiologic data suggest a relationship between cerebral palsy and chorioamnionitis mediated by proinflammatory cytokines. This association has been confirmed by experimental data from human and animal research that demonstrate an increase in cytokine levels in the amniotic fluid of cases of white matter damage. Recent evidence suggests this damage is the result of a fetal inflammatory response initiated in response to placental inflammation. The strong association between cerebral palsy and chorioamnionitis warrants additional investigation into the mechanisms by which white matter damage is initiated and into possible neuroprotective treatments to prevent the development of cerebral palsy.

Neonatal brain injury

Complacency about long-term outcomes in newborns is being eroded rapidly with new information. We have examined developments in the area from an explicitly clinical approach, focusing on etiology, diagnostic modalities, and therapies. We attempt to discuss relevance from the preterm and the term perspective. Emerging evidence implicating chorioamnionitis as a significant contributor to neonatal brain injury is discussed. Therapeutic modalities such as magnetic resonance imaging and electrophysiological monitoring offer some potentially new tools for the clinician. An exploding series of basic advances suggest several potentially new strands of therapy. We discuss two that deserve further clinical exploration, namely anti-inflammatory strategies and thread hormone supplementation. In the arena of therapy, however, the paucity of large trials from which to guide therapies is a predominant theme, leaving a large reservoir of uncertainty for the clinician.

Possible strategies to protect the preterm brain against the fetal inflammatory response

The accruing evidence that a fetal inflammatory response is the link between antenatal infection and white matter damage in the preterm newborn infant offers room for speculation how this harmful sequence could be interrupted. Enhancement of endogenous protection, response modification, and damage limitation downstream could be helpful strategies for intervention design. Appropriate observational and experimental studies are needed before clinical interventions can be initiated.

Perinatal asphyxia: timing and mechanisms of injury in neonatal encephalopathy

This article summarizes the recent medical literature regarding perinatal asphyxia with respect to timing and mechanisms of injury for neonates who were clinically diagnosed with an encephalopathy in the newborn period. Multiple mechanisms of injury are reviewed, including genetic vulnerability, acquired inflammatory responses, and clotting defects that can lead to ischemic-induced brain damage. Before effective treatments for fetal and neonatal brain disorders can be developed, accurate and timely diagnoses of fetal or neonatal brain injury must be achieved. Specific subsets of children can then benefit from neuroprotective strategies that can target the specific developmental aspects of brain adaptation or plasticity relative to the specific etiology and timing of injury after asphyxia.

Mediators of fetal inflammation in extremely low gestational age newborns

To establish levels of mediators of inflammation in cord blood and postnatal serum from extremely low gestational age newborns (ELGANs, < or =28 weeks), we measured sixteen markers of inflammation by recycling immunoaffinity chromatography in 15 ELGANs who had serum sampled at days 2-5. Median levels of IL-1, IL-6, IL-8, IL-11, IL-13, TNF-alpha, G-CSF, M-CSF, GM-CSF, MIP-1alpha, and RANTES were considerably higher than published values of these inflammatory mediators from term newborns. In three of eight ELGANS who had serial measurements taken, levels of IL-1, IL-6, IL-8, IL-11, TNF-alpha, G-CSF, and MIP-1alpha declined from initially very high levels to reach an apparent baseline towards the end of the first postnatal week. In these same three infants, GM-CSF and TGF-beta1 levels increased continuously during the first week. In the other five ELGANs, no consistent changes were observed. We speculate, that in some ELGANs, a fetal systemic inflammatory response is characterized by an antenatal wave of pro-inflammatory cytokines, followed by a second, postnatal wave of anti-inflammatory cytokines. Large epidemiologic studies are needed to clarify relationships among inflammation markers and their expression in the fetal and neonatal circulation over time. Such studies would also add to our understanding of the possible role of inflammatory mediators in the pathophysiology of the major complications of extreme prematurity.

Brain damage in preterm newborns: biological response modification as a strategy to reduce disabilities

Substances that promote the growth and maturation of oligodendrocytes and their precursors might protect against white matter injury. We suggest that neuroprotection can also be provided by such modulators of fetal and neonatal inflammatory responses as antiinflammatory cytokines, cytokine-binding proteins, and cytokine-receptor blockers. We briefly describe inflammatory responses in the fetus and newborn and show how they might contribute to brain damage. We conclude with the possibility that so-called biological response modifiers, which are drugs that modulate these inflammatory responses, might reduce the risk of brain damage and disabilities.