White matter damage and chemokine induction in developing rat brain after intrauterine infection

Neurocognitive and social-communicative function of children born very preterm at 10 years of age: Associations with microorganisms recovered from the placenta parenchyma

OBJECTIVE

Infection of the placenta has been associated with preterm birth as well as neurocognitive impairment. This study aimed to determine whether specific bacterial species in the placenta of extremely preterm pregnancies are associated with neurological deficits later in life.

STUDY DESIGN

Using data from 807 children in the ELGAN study the risks of a low score on six neurological assessments in relation to 15 different microbes were quantified with odds ratios.

RESULTS

The presence of certain microbial species in the placenta was associated with lower scores on numerical and oral language assessments. Lactobacillus sp. was associated with decreased risk of a low oral language score and a composite measure of IQ and executive function.

CONCLUSION

Placental microorganisms were associated with neurocognitive, but not social-communicative, outcomes at age 10. In contrast, the presence of the anti-inflammatory Lactobacillus sp. in the placenta was associated with a lower risk of impaired neurocognitive functions.

Systemic inflammation combined with neonatal cerebellar haemorrhage aggravates long-term structural and functional outcomes in a mouse model

BACKGROUND

Despite the increased recognition of cerebellar injury in survivors of preterm birth, the neurodevelopmental consequences of isolated cerebellar injury have been largely unexplored and our current understanding of the functional deficits requires further attention in order to translate knowledge to best practices. Preterm infants are exposed to multiple stressors during their postnatal development including perinatal cerebellar haemorrhage (CBH) and postnatal infection, two major risk factors for neurodevelopmental impairments.

METHODS

We developed a translational mouse model of CBH and/or inflammation to measure the short- and long-term outcomes in cerebellar structure and function.

RESULTS

Mice exposed to early combined insults of CBH and early inflammatory state (EIS) have a delay in grasping acquisition, neonatal motor deficits and deficient long-term memory. CBH combined with late inflammatory state (LIS) does not induce neonatal motor problems but leads to poor fine motor function and long-term memory deficits at adulthood. Early combined insults result in poor cerebellar growth from postnatal day 15 until adulthood shown by MRI, which are reflected in diminished volumes of cerebellar structures. There are also decreases in volumes of gray matter and hippocampus. Cerebellar microgliosis appears 24h after the combined insults and persists until postnatal day 15 in the cerebellar molecular layer and cerebellar nuclei in association with a disrupted patterning of myelin deposition, a delay of oligodendrocyte maturation and reduced white matter cerebellar volume.

CONCLUSIONS

Together, these findings reveal poor outcomes in developing brains exposed to combined cerebellar perinatal insults in association with cerebellar hypoplasia, persistence of microgliosis and alterations of cerebellar white matter maturation and growth.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

A Critical Review of Models of Perinatal Infection

One of the central, unanswered questions in perinatology is why preterm infants continue to have such poor long-term neurodevelopmental, cognitive and learning outcomes, even though severe brain injury is now rare. There is now strong clinical evidence that one factor underlying disability may be infection, as well as nonspecific inflammation, during fetal and early postnatal life. In this review, we examine the experimental evidence linking both acute and chronic infection/inflammation with perinatal brain injury and consider key experimental determinants, including the microglia response, relative brain and immune maturity and the pattern of exposure to infection. We highlight the importance of the origin and derivation of the bacterial cell wall component lipopolysaccharide. Such experimental paradigms are essential to determine the precise time course of the inflammatory reaction and to design targeted neuroprotective strategies to protect the perinatal brain from infection and inflammation.

A "multi-hit" model of neonatal white matter injury: cumulative contributions of chronic placental inflammation, acute fetal inflammation and postnatal inflammatory events

OBJECTIVE

We sought to determine whether cumulative evidence of perinatal inflammation was associated with increased risk in a "multi-hit" model of neonatal white matter injury (WMI).

METHODS

This retrospective cohort study included very preterm (gestational ages at delivery <32 weeks) live-born singleton neonates delivered at Hutzel Women's Hospital, Detroit, MI, from 2006 to 2011. Four pathologists blinded to clinical diagnoses and outcomes performed histological examinations according to standardized protocols. Neurosonography was obtained per routine clinical care. The primary indicator of WMI was ventriculomegaly (VE). Neonatal inflammation-initiating illnesses included bacteremia, surgical necrotizing enterocolitis, other infections, and those requiring mechanical ventilation.

RESULTS

A total of 425 live-born singleton neonates delivered before the 32nd week of gestation were included. Newborns delivered of pregnancies affected by chronic chorioamnionitis who had histologic evidence of an acute fetal inflammatory response were at increased risk of VE, unlike those without funisitis, relative to referent newborns without either condition, adjusting for gestational age [odds ratio (OR) 4.7; 95% confidence interval (CI) 1.4-15.8 vs. OR 1.3; 95% CI 0.7-2.6]. Similarly, newborns with funisitis who developed neonatal inflammation-initiating illness were at increased risk of VE, unlike those who did not develop such illness, compared to the referent group without either condition [OR 3.6 (95% CI 1.5-8.3) vs. OR 1.7 (95% CI 0.5-5.5)]. The greater the number of these three types of inflammation documented, the higher the risk of VE (P<0.0001).

CONCLUSION

Chronic placental inflammation, acute fetal inflammation, and neonatal inflammation-initiating illness seem to interact in contributing risk information and/or directly damaging the developing brain of newborns delivered very preterm.

The persistent effects of maternal infection on the offspring's cognitive performance and rates of hippocampal neurogenesis

Accumulating evidence indicates that perinatal infection is a major cause of neonatal neurologic morbidity. Here we explored the effects of maternal infection on the offspring's cognitive performance and hippocampal neurogenesis. Pregnant rats were treated with Escherichia coli suspension and allowed to deliver. Proliferating cells in the hippocampus were examined at postnatal (P) 3, 7, 14, and 28 days and neuronal survival/differentiation was assessed at P28. Additionally, we examined the expressions of BDNF, TrkB and Akt. The cognitive performance of the offspring was assessed by the Morris water maze test. We found that maternal infection significantly impaired the offspring's spatial learning ability and spatial memory, thus could delay the cognitive performance development. Maternal infection significantly increased the number of proliferating cells in the offspring's hippocampus at postnatal 3, 7 and 14 days, accompanied by significantly increased expressions of BDNF, TrkB and p-Akt at postnatal 3 and 7 days. On postnatal 28 days, maternal infection did not significantly affect the neuronal and glial differentiation, nor any significant changes in the expression levels of BDNF and TrkB in the hippocampus. Our result suggests that the hippocampal neurogenesis level may increase during early postnatal period after maternal infection. Increase of BDNF/TrkB expression and Akt activity may be the contributing molecular mechanism.

Infection-induced vulnerability of perinatal brain injury

A growing body of evidence demonstrates that susceptibility and progression of both acute and chronic central nervous system disease in the newborn is closely associated with an innate immune response that can manifest from either direct infection and/or infection-triggered damage. A common feature of many of these diseases is the systemic exposure of the neonate to bacterial infections that elicit brain inflammation. In recent years, the importance of innate immune receptors in newborn brain injury, the so-called Toll-like receptors, has been demonstrated. In this paper we will discuss how neonatal sepsis, with particular emphasis on Escherichia coli, coagulase-negative staphylococci, and group B streptococcal infections in preterm infants, and Toll-like receptor-mediated inflammation can increase the vulnerability of the newborn brain to injury.

Ciprofloxacin prevents myelination delay in neonatal rats subjected to E. coli sepsis

OBJECTIVE

Perinatal infections and the systemic inflammatory response to them are critical contributors to white matter disease (WMD) in the developing brain despite the use of highly active antibiotics. Fluoroquinolones including ciprofloxacin (CIP) have intrinsic anti-inflammatory effects. We hypothesized that CIP, in addition to its antibacterial activity, could exert a neuroprotective effect by modulating white matter inflammation in response to sepsis.

METHODS

We adapted an Escherichia coli sepsis model to 5-day-old rat pups (P5), to induce white matter inflammation without bacterial meningitis. We then compared the ability of CIP to modulate inflammatory-induced brain damage compared with cefotaxime (CTX) (treatment of reference).

RESULTS

Compared with CTX, CIP was associated with reduced microglial activation and inducible nitric oxide synthase (iNOS) expression in the developing white matter in rat pups subjected to E. coli sepsis. In addition to reducing microglial activation, CIP was able to prevent myelination delay induced by E. coli sepsis and to promote oligodendroglial survival and maturation. We found that E. coli sepsis altered the transcription of the guidance molecules semaphorin 3A and 3F; CIP treatment was capable of reducing semaphorin 3A and 3F transcription levels to those seen in uninfected controls. Finally, in a noninfectious white matter inflammation model, CIP was associated with significantly reduced microglial activation and prevented WMD when compared to CTX.

INTERPRETATION

These data strongly suggest that CIP exerts a beneficial effect in a model of E. coli sepsis-induced WMD in rat pups that is independent of its antibacterial activity but likely related to iNOS expression modulation.

Notch signaling: key role in intrauterine infection/inflammation, embryonic development, and white matter damage?

The mechanisms or pathophysiologies that lead to cerebral white matter damage during development are complex and not fully understood. It is postulated that exposure of the preterm brain to inflammatory cytokines during intrauterine infection/inflammation contributes to brain white matter damage, and this damage may affect the function and differentiation of progenitor oligodendrocyte cells under physiological conditions. The Notch pathway, an important signaling pathway controlling various cells' differentiation, functions in the timing of oligodendrocyte differentiation, and Notch signaling may contribute to white matter damage and may mediate neurogenesis in a pathophysiological phase. Recent studies have led to recognition of the role of the Notch pathway in neurogenesis in cerebral ischemic damage and in myelination and axonal damage of neurodegenerative diseases. Moreover, Notch plays a critical role in steering an immune response toward inflammation by regulating expression of various cytokines and proinflammatory cytokines resulting in the activation of Notch signaling. Thus, the Notch signaling pathway likely plays a key role in intrauterine infection/inflammation, brain development, and white matter damage, and future research directed toward understanding its role will be important. Insofar as Notch signaling could have an important effect on neurogenesis, mobilization of progenitor cells is one strategy for compensating for the neuronal losses seen in white matter damage after intrauterine infection/inflammation.

Microbiologic and histologic characteristics of the extremely preterm infant's placenta predict white matter damage and later cerebral palsy. the ELGAN study

Inflammatory phenomena seem to contribute to the occurrence of perinatal cerebral white matter damage and CP. The stimulus that initiates the inflammation remains obscure. One thousand two hundred forty-six infants born before the 28th postmenstrual week had a protocol ultrasound scan of the brain read concordantly by two independent sonologists. Eight hundred ninety-nine of the children had a neurologic examination at approximately 24-mo postterm equivalent. The placenta of each child had been biopsied under sterile conditions and later cultured. Histologic slides of the placenta were examined specifically for this study. Recovery of a single microorganism predicted an echolucent lesion, whereas polymicrobial cultures and recovery of skin flora predicted both ventriculomegaly and an echolucent lesion. Diparetic CP was predicted by recovery of a single microorganism, multiple organisms, and skin flora. Histologic inflammation predicted ventriculomegaly and diparetic CP. The risk of ventriculomegaly associated with organism recovery was heightened when accompanied by histologic inflammation, but the risk of diparetic CP was not. Low-virulence microorganisms isolated from the placenta, including common skin microflora, predict ultrasound lesions of the brain and diparetic CP in the very preterm infant. Organism recovery does not seem to be needed for placenta inflammation to predict diparetic CP.

Intrauterine infection induced oligodendrocyte injury and inducible nitric oxide synthase expression in the developing rat brain

AIMS

In order to investigate the neuropathological effect on the developing rat brain after intrauterine infection, 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and inducible nitric oxide synthase (iNOS) were evaluated.

METHODS

Escherichia coli (E. coli) was inoculated into the uterine cervix of the time-pregnant rats and controls were injected with normal saline. Immunohistochemical staining for CNPase was performed to assess oligodendrocyte injury in pup brains at postnatal day 1, 3 and 7 (P1, P3, and P7). Immunohistochemistry was used to evaluate iNOS expression and quantitative reverse transcriptase PCR to analyze iNOS mRNA expression in pup brains at P1, P3 and P7. Nitrate reductase method was used for detection of nitric oxide (NO) concentration in pup brains at P1, P3 and P7.

RESULTS

The immunohistochemical staining for CNPase in the E. coli-treated group showed a decrease compared with the control in periventricular white matter at P7. Obvious immunohistochemical staining of iNOS was observed in periventricular white matter of the E. coli-treated pup brains at P1. The expression of iNOS mRNA in the E. coli-treated pup brains increased at P1 and P3, but there was no significant difference at P7 compared with controls. Similarly, the NO concentration increased in the E. coli-treated pup brains at P1 and P3, and no significant difference was found at P7 compared with controls.

CONCLUSIONS

The alteration of CNPase expression indicates that intrauterine infection could cause oligodendrocyte injury in the developing brain. Moreover, the increased expression of iNOS followed by the increasing NO concentration after intrauterine infection suggests that iNOS might be a key mediator between the intrauterine infection and oligodendrocyte injury in the developing brain.