Hyaluronidase and Hyaluronan Oligosaccharides Promote Neurological Recovery after Intraventricular Hemorrhage.

Intraventricular hemorrhage (IVH) in premature infants results in inflammation, arrested oligodendrocyte progenitor cell (OPC) maturation, and reduced myelination of the white matter. Hyaluronan (HA) inhibits OPC maturation and complexes with the heavy chain (HC) of glycoprotein inter-α-inhibitor to form pathological HA (HC-HA complex), which exacerbates inflammation. Therefore, we hypothesized that IVH would result in accumulation of HA, and that either degradation of HA by hyaluronidase treatment or elimination of HCs from pathological HA by HA oligosaccharide administration would restore OPC maturation, myelination, and neurological function in survivors with IVH. To test these hypotheses, we used the preterm rabbit model of glycerol-induced IVH and analyzed autopsy samples from premature infants. We found that total HA levels were comparable in both preterm rabbit pups and human infants with and without IVH, but HA receptors--CD44, TLR2, TLR4--were elevated in the forebrain of both humans and rabbits with IVH. Hyaluronidase treatment of rabbits with IVH reduced CD44 and TLR4 expression, proinflammatory cytokine levels, and microglia infiltration. It also promoted OPC maturation, myelination, and neurological recovery. HC-HA and tumor necrosis factor-stimulated gene-6 were elevated in newborns with IVH; and depletion of HC-HA levels by HA oligosaccharide treatment reduced inflammation and enhanced myelination and neurological recovery in rabbits with IVH. Hence, hyaluronidase or HA oligosaccharide treatment represses inflammation, promotes OPC maturation, and restores myelination and neurological function in rabbits with IVH. These therapeutic strategies might improve the neurological outcome of premature infants with IVH. Significance statement: Approximately 12,000 premature infants develop IVH every year in the United States, and a large number of survivors with IVH develop cerebral palsy and cognitive deficits. The onset of IVH induces inflammation of the periventricular white matter, which results in arrested maturation of OPCs and myelination failure. HA is a major component of the extracellular matrix of the brain, which regulates inflammation through CD44 and TLR2/4 receptors. Here, we show two mechanism-based strategies that effectively enhanced myelination and neurological recovery in preterm rabbit model of IVH. First, degrading HA by hyaluronidase treatment reduced CD44 and TLR4 expression, proinflammatory cytokines, and microglial infiltration, as well as promoted oligodendrocyte maturation and myelination. Second, intraventricular injection of HA oligosaccharide reduced inflammation and enhanced myelination, conceivably by depleting HC-HA levels.

Neurogenesis continues in the third trimester of pregnancy and is suppressed by premature birth.

Premature infants exhibit neurodevelopmental delay and reduced growth of the cerebral cortex. However, the underlying mechanisms have remained elusive. Therefore, we hypothesized that neurogenesis in the ventricular and subventricular zones of the cerebral cortex would continue in the third trimester of pregnancy and that preterm birth would suppress neurogenesis. To test our hypotheses, we evaluated autopsy materials from human fetuses and preterm infants of 16-35 gestational weeks (gw). We noted that both cycling and noncycling Sox2(+) radial glial cells and Tbr2(+) intermediate progenitors were abundant in human preterm infants until 28 gw. However, their densities consistently decreased from 16 through 28 gw. To determine the effect of premature birth on neurogenesis, we used a rabbit model and compared preterm [embryonic day 29 (E29), 3 d old] and term (E32, <2 h old) pups at an equivalent postconceptional age. Glutamatergic neurogenesis was suppressed in preterm rabbits, as indicated by the reduced number of Tbr2(+) intermediate progenitors and the increased number of Sox2(+) radial glia. Additionally, hypoxia-inducible factor-1α, vascular endothelial growth factor, and erythropoietin were higher in term than preterm pups, reflecting the hypoxic intrauterine environment of just-born term pups. Proneural genes, including Pax6 and Neurogenin-1 and -2, were higher in preterm rabbit pups compared with term pups. Importantly, neurogenesis and associated factors were restored in preterm pups by treatment with dimethyloxallyl glycine, a hypoxia mimetic agent. Hence, glutamatergic neurogenesis continues in the premature infants, preterm birth suppresses neurogenesis, and hypoxia-mimetic agents might restore neurogenesis, enhance cortical growth, and improve neurodevelopmental outcome of premature infants.

Bedside lung mechanics predict survival in hypoplastic lung disease.

Newer bedside pulmonary mechanics using conventional ventilators allow for CONTINUOUS serial determinations of tidal volume (V(T)). We sought to determine whether the degree of pulmonary hypoplasia could be measured using bedside pulmonary graphics and whether survival could be predicted in potential extracorporeal membrane oxygenation (ECMO) candidates. Data on all neonates considered for or treated with ECMO at our center between April 2000 and March 2005 were collected. The "maximal bedside V(T)" was measured daily at the peak pressure where "beaking" began with a peak end expiratory pressure of 4 cm H(2)O. Twenty-two patients were reviewed: eight ECMO plus fourteen similar patients in whom the threshold for ECMO intervention was not achieved. Independent of need for ECMO, any patient with V(T) of < 3 mL/kg or < 0.2 mL/cm length died ( N = 4). All other measures of lung capacity or blood gas assessments were less valuable than V(T) in predicting survival. We conclude that bedside V(T) can be easily measured and that values < 3 mL/kg or < 0.2 mL/cm length demarcate severe lung hypoplasia, which in our patient population was incompatible with survival. We speculate that bedside V(T) may assist in evaluating the utility of ECMO.

Neuroprotection in a rabbit model of intraventricular haemorrhage by cyclooxygenase-2, prostanoid receptor-1 or tumour necrosis factor-alpha inhibition.

Intraventricular haemorrhage is a major complication of prematurity that results in neurological dysfunctions, including cerebral palsy and cognitive deficits. No therapeutic options are currently available to limit the catastrophic brain damage initiated by the development of intraventricular haemorrhage. As intraventricular haemorrhage leads to an inflammatory response, we asked whether cyclooxygenase-2, its derivative prostaglandin E2, prostanoid receptors and pro-inflammatory cytokines were elevated in intraventricular haemorrhage; whether their suppression would confer neuroprotection; and determined how cyclooxygenase-2 and cytokines were mechanistically-linked. To this end, we used our rabbit model of intraventricular haemorrhage where premature pups, delivered by Caesarian section, were treated with intraperitoneal glycerol at 2 h of age to induce haemorrhage. Intraventricular haemorrhage was diagnosed by head ultrasound at 6 h of age. The pups with intraventricular haemorrhage were treated with inhibitors of cyclooxygenase-2, prostanoid receptor-1 or tumour necrosis factor-α; and cell-infiltration, cell-death and gliosis were compared between treated-pups and vehicle-treated controls during the first 3 days of life. Neurobehavioural performance, myelination and gliosis were assessed in pups treated with cyclooxygenase-2 inhibitor compared to controls at Day 14. We found that both protein and messenger RNA expression of cyclooxygenase-2, prostaglandin E2, prostanoid receptor-1, tumour necrosis factor-α and interleukin-1ß were consistently higher in the forebrain of pups with intraventricular haemorrhage relative to pups without intraventricular haemorrhage. However, cyclooxygenase-1 and prostanoid receptor 2-4 levels were comparable in pups with and without intraventricular haemorrhage. Cyclooxygenase-2, prostanoid receptor-1 or tumour necrosis factor-α inhibition reduced inflammatory cell infiltration, apoptosis, neuronal degeneration and gliosis around the ventricles of pups with intraventricular haemorrhage. Importantly, cyclooxygenase-2 inhibition alleviated neurological impairment, improved myelination and reduced gliosis at 2 weeks of age. Cyclooxygenase-2 or prostanoid receptor-1 inhibition reduced tumour necrosis factor-α level, but not interleukin-1ß. Conversely, tumour necrosis factor-α antagonism did not affect cyclooxygenase-2 expression. Hence, prostanoid receptor-1 and tumour necrosis factor-α are downstream to cyclooxygenase-2 in the inflammatory cascade induced by intraventricular haemorrhage, and cyclooxygenase-2-inhibition or suppression of downstream molecules--prostanoid receptor-1 or tumour necrosis factor-α--might be a viable neuroprotective strategy for minimizing brain damage in premature infants with intraventricular haemorrhage.

Role of Ca2+ in induction of neurotransmitter-related gene expression by butyrate.

We examined the effect of butyrate on neurotransmitter-related gene expression and calcium homeostasis in PC12 cells. Pretreatment with Ca2+ chelators (EGTA or BAPTA-AM) attenuated the butyrate-triggered accumulation of TH and ppEnk mRNA indicating that Ca2+ plays a role in butyrate-induced regulation of neuronal genes. Butyrate alone did not alter intracellular Ca2+ levels as determined by Fura-PE3 fluorescence; however, pretreatment with butyrate (18-24 h) reduced the first Ca2+ peak and prevented the second sustained rise in [Ca2+]i as induced by nicotine or ryanodine. In contrast, butyrate had no effect on Ca2+ transients when added shortly before or during nicotine or ryanodine stimulation. These results suggest that chronic butyrate exposure can modulate cell responses by affecting intracellular Ca2+ signaling.