BackgroundThe fetal brain is particularly vulnerable to intrauterine growth restriction (IUGR) conditions evidenced by neuronal and white matter abnormalities and altered neurodevelopment in the IUGR infant. To further our understanding of neurodevelopment in the newborn IUGR brain, clinically relevant models of IUGR are required. This information is critical for the design and implementation of successful therapeutic interventions to reduce aberrant brain development in the IUGR newborn. We utilise the piglet as a model of IUGR as growth restriction occurs spontaneously in the pig as a result of placental insufficiency, making it a highly relevant model of human IUGR. The purpose of this study was to characterise neuropathology and neuroinflammation in the neonatal IUGR piglet brain.MethodsNewborn IUGR (< 5th centile) and normally grown (NG) piglets were euthanased on postnatal day 1 (P1; < 18 h) or P4. Immunohistochemistry was utilised to examine neuronal, white matter and inflammatory responses, and PCR for cytokine analysis in parietal cortex of IUGR and NG piglets.ResultsThe IUGR piglet brain displayed less NeuN-positive cells and reduced myelination at both P1 and P4 in the parietal cortex, indicating neuronal and white matter disruption. A concurrent decrease in Ki67-positive proliferative cells and increase in cell death (caspase-3) in the IUGR piglet brain was also apparent on P4. We observed significant increases in the number of both Iba-1-positive microglia and GFAP-positive astrocytes in the white matter in IUGR piglet brain on both P1 and P4 compared with NG piglets. These increases were associated with a change in activation state, as noted by altered glial morphology. This inflammatory state was further evident with increased expression levels of proinflammatory cytokines (interleukin-1β, tumour necrosis factor-α) and decreased levels of anti-inflammatory cytokines (interleukin-4 and -10) observed in the IUGR piglet brains.ConclusionsThese findings suggest that the piglet model of IUGR displays the characteristic neuropathological outcomes of neuronal and white matter impairment similar to those reported in the IUGR human brain. The activated glial morphology and elevated proinflammatory cytokines is indicative of an inflammatory response that may be associated with neuronal damage and white matter disruption. These findings support the use of the piglet as a pre-clinical model for studying mechanisms of altered neurodevelopment in the IUGR newborn.

An increase in the number of activated microglia in the brain is a key feature of neuroinflammation after a hypoxic-ischemic insult to the preterm neonate and can contribute to white matter injury in the brain. Minocycline is a potent inhibitor of microglia and may have a role as a neuroprotective agent that ameliorates brain injury after hypoxia-ischemia in neonatal animal models. However to date large doses, pre-insult administration and short periods of treatment after hypoxia-ischemia have mostly been investigated in animal models making it difficult to translate minocycline's potential applicability to protect the human preterm neonatal brain exposed to hypoxia-ischemia. We investigated whether repeated doses of minocycline can minimize white matter injury and neuroinflammation one week after hypoxia-ischemia (right carotid artery ligation and 30 min 6% O(2)) in the post-natal day 3 rat pup. Two dosage regimens of minocycline were administered for one week; a high dose of 45 mg/kg 2h after hypoxia-ischemia then 22.5 mg/kg daily or a low dose 22.5 mg/kg 2h after hypoxia-ischemia then 10 mg/kg. Post-natal day 3 hypoxia-ischemia significantly reduced myelin content, numbers of O1- and O4-positive oligodendrocyte progenitor cells and increased activated microglia one week later on post-natal day 10. The low dose minocycline regimen was as effective as the high dose in ameliorating neuroinflammation after post-natal day 3 hypoxia-ischemia. However only the high dose regimen significantly attenuated reductions in O1- and O4-positive oligodendrocyte progenitor cells and myelin content. The low dose only significantly attenuated the reduction in O1-positive oligodendrocyte cell counts. Repeated, daily, post-insult treatment with minocycline abolished neuroinflammation and may provide neuroprotection to white matter for up to one week after hypoxia-ischemia in a rodent preterm model. The present findings suggest the potential clinical relevance of a repeated, daily minocycline treatment strategy, administered after a hypoxia-ischemia insult, as a therapeutic intervention for hypoxia-ischemia-affected preterm neonates.

Minocycline is a second-generation tetracycline and a potential neuroprotective intervention following brain injury. However, despite the recognized beneficial effects of minocycline in a multitude of adult disease states, the clinical application of minocycline in neonates is contentious. Tetracyclines, as a class, are not usually administered to neonates, but there is compelling evidence that minocycline reduces brain injury after neonatal hypoxic-ischemic brain injury. This Review focuses on the evidence for minocycline use in neonates by considering aspects of pharmacology, drug regimens, functional outcomes, and mechanisms of action.

performed the experiments and along with Grant A. Ramm analyzed the data. Diego A. Calvopina and Gunter F. Hartel performed the more advanced statistical analyses. Louise E. Ramm collected clinical data and maintained the patient database. Peter J. Lewindon assisted in study design, enrollment of patients and collection of liver tissue specimens. Charlton Noble also helped enroll patients in the study and collected tissue specimens. Daniel H. Leung provided advice on study design.

Disruption to the maternal environment during pregnancy from events such as hypoxia, stress, toxins, inflammation, and reduced placental blood flow can affect fetal development. Intrauterine growth restriction (IUGR) is commonly caused by chronic placental insufficiency, interrupting supply of oxygen and nutrients to the fetus resulting in abnormal fetal growth. IUGR is a major cause of perinatal morbidity and mortality, occurring in approximately 5-10% of pregnancies. The fetal brain is particularly vulnerable in IUGR and there is an increased risk of long-term neurological disorders including cerebral palsy, epilepsy, learning difficulties, behavioural difficulties and psychiatric diagnoses. Few studies have focused on how growth restriction interferes with normal brain development in the IUGR neonate but recent studies in growth restricted animal models demonstrate increased neuroinflammation. This review describes the role of neuroinflammation in the progression of brain injury in growth restricted neonates. Identifying the mediators responsible for alterations in brain development in the IUGR infant is key to prevention and treatment of brain injury in these infants.

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Intrauterine growth restriction (IUGR) is a condition where the fetus does not achieve optimal growth, commonly caused by placental insufficiency. The chronic decrease in blood flow restricts oxygen and nutrient supply to the fetus, which can damage numerous organ systems, with the fetal brain being particularly vulnerable. Although white matter and neuronal injury are evident in IUGR infants, the specific mechanisms underlying these changes are poorly understood. Inflammation is considered to be a main driver in exacerbating brain injury. Using a spontaneous piglet model of IUGR, we aim to determine whether administration of the anti-inflammatory drug ibuprofen will decrease inflammation at postnatal day 4 (P4). The treatment group received ibuprofen (20 mg/kg/day on day 1 and 10 mg/kg/day on days 2 and 3) in piglet formula during the morning feed each day and brains examined on P4. Markers of inflammation, apoptosis, cell proliferation, neuronal injury, and white matter injury were examined. Ibuprofen treatment ameliorated the increase in numbers of microglia and astrocytes in the parietal cortex and white matter tracts of the IUGR piglet brain on P4 as well as decreasing proinflammatory cytokines. Ibuprofen treatment prevented the reduction in apoptosis, neuronal cell counts, and myelin index in the IUGR piglets. Our findings demonstrate ibuprofen reduces the inflammatory response in the IUGR neonatal brain and concurrently reduces neuronal and white matter impairment.

Traumatic brain injury results in an increased brain energy demand that is associated with profound changes in brain glycolysis and energy metabolism. Increased glycolysis must be met by increasing glucose supply that, in brain, is primarily mediated by two members of the facilitative glucose transporter family, Glut1 and Glut3. Glut1 is expressed in endothelial cells of the blood-brain barrier (BBB) and also in glia, while Glut3 is the primary glucose transporter expressed in neurons. However, few studies have investigated the changes in glucose transporter expression following traumatic brain injury, and in particular, the neuronal and glial glucose transporter responses to injury. This study has therefore focussed on investigating the expression of the glial specific 45-kDa isoform of Glut1 and neuronal specific Glut3 following severe diffuse traumatic brain injury in rats. Following impact-acceleration injury, Glut3 expression was found to increase by at least 300% as early as 4 h after induction of injury and remained elevated for at least 48 h postinjury. The increase in Glut3 expression was clearly evident in both the cerebral cortex and cerebellum. In contrast, expression of the glial specific 45-kDa isoform of Glut1 did not significantly change in either the cerebral cortex or cerebellum following traumatic injury. We conclude that increased glucose uptake after traumatic brain injury is primarily accounted for by increased neuronal Glut 3 glucose transporter expression and that this increased expression after trauma is part of a neuronal stress response that may be involved in increasing neuronal glycolysis and associated energy metabolism to fuel repair processes.