Reduced white-matter integrity and lower speed of information processing in adolescents with mild and moderate neonatal hypoxic-ischaemic encephalopathy

Neuroprotection and neuroregeneration: roles for the white matter

Efficient strategies for neuroprotection and repair are still an unmet medical need for neurodegenerative diseases and lesions of the central nervous system. Over the last few decades, a great deal of attention has been focused on white matter as a potential therapeutic target, mainly due to the discovery of the oligodendrocyte precursor cells in the adult central nervous system, a cell type able to fully repair myelin damage, and to the development of advanced imaging techniques to visualize and measure white matter lesions. The combination of these two events has greatly increased the body of research into white matter alterations in central nervous system lesions and neurodegenerative diseases and has identified the oligodendrocyte precursor cell as a putative target for white matter lesion repair, thus indirectly contributing to neuroprotection. This review aims to discuss the potential of white matter as a therapeutic target for neuroprotection in lesions and diseases of the central nervous system. Pivot conditions are discussed, specifically multiple sclerosis as a white matter disease; spinal cord injury, the acute lesion of a central nervous system component where white matter prevails over the gray matter, and Alzheimer's disease, where the white matter was considered an ancillary component until recently. We first describe oligodendrocyte precursor cell biology and developmental myelination, and its regulation by thyroid hormones, then briefly describe white matter imaging techniques, which are providing information on white matter involvement in central nervous system lesions and degenerative diseases. Finally, we discuss pathological mechanisms which interfere with myelin repair in adulthood.

Neuroimaging in the term newborn with neonatal encephalopathy

Neuroimaging is widely used to aid in the diagnosis and clinical management of neonates with neonatal encephalopathy (NE). Yet, despite widespread use clinically, there are few published guidelines on neuroimaging for neonates with NE. This review outlines the primary patterns of brain injury associated with hypoxic-ischemic injury in neonates with NE and their frequency, associated neuropathological features, and risk factors. In addition, it provides an overview of neuroimaging methods, including the most widely used scoring systems used to characterize brain injury in these neonates and their utility as predictive biomarkers. Last, recommendations for neuroimaging in neonates with NE are presented.

[Effect of different melatonin treatment regimens on white matter damage in neonatal rats with hypoxic-ischemic brain damage]

OBJECTIVE

To study the effect of different melatonin treatment regimens on long-term behavior and white matter damage in neonatal rats with hypoxic-ischemic brain damage (HIBD), and to seek an optimal melatonin treatment regimen.

METHODS

Healthy Sprague-Dawley rats, aged 7 days, were randomly divided into four groups: sham-operation, HIBD, single-dose immediate treatment (SDIT), and 7-day continuous treatment (7DCT), with 8 rats in each group. A neonatal rat model of HIBD was prepared according to the classical Rice-Vannucci method. On day 21 after HIBD, the Morris water maze test was used to evaluate spatial learning and memory abilities. On day 70 after HIBD, immunofluorescence assay was used to measure the expression of neuronal nuclear antigen (NeuN) in the cerebral cortex and the hippocampal CA1 region of neonatal rats, and double-label immunofluorescence was used to measure the expression of myelin basic protein (MBP) and neurofilament 200 (NF200) in the corpus striatum and the corpus callosum.

RESULTS

The results of the Morris water maze test showed that the SDIT and 7DCT groups had a significantly shorter mean escape latency than the HIBD group, and the 7DCT group had a significantly shorter mean escape latency than the SDIT group (P < 0.05). The results of immunofluorescence assay for NeuN showed that the SDIT and 7DCT groups had a significantly higher number of NeuN⁺ cells in the cerebral cortex and the hippocampal CA1 region than the HIBD group, and the 7DCT group had a significantly higher number than the SDIT group (P < 0.05). MBP/NF200 double-label immunofluorescence showed that compared with the HIBD group, the SDIT group and the 7DCT group had significantly higher fluorescence intensities of MBP and NF200 in the corpus striatum, and the 7DCT group had significantly higher fluorescence intensities than the SDIT group (P < 0.05); the 7DCT group had significantly higher fluorescence intensities of MBP and NF200 in the corpus callosum than the SDIT and HIBD groups (P < 0.05).

CONCLUSIONS

Both SDIT and 7DCT can improve long-term behavior and reduce white matter damage in neonatal rats with HIBD, and 7DCT is more effective than SDIT.

Disrupted brain connectivity in children treated with therapeutic hypothermia for neonatal encephalopathy

Therapeutic hypothermia following neonatal encephalopathy due to birth asphyxia reduces death and cerebral palsy. However, school-age children without cerebral palsy treated with therapeutic hypothermia for neonatal encephalopathy still have reduced performance on cognitive and motor tests, attention difficulties, slower reaction times and reduced visuo-spatial processing abilities compared to typically developing controls. We acquired diffusion-weighted imaging data from school-age children without cerebral palsy treated with therapeutic hypothermia for neonatal encephalopathy at birth, and a matched control group. Voxelwise analysis (33 cases, 36 controls) confirmed reduced fractional anisotropy in widespread areas of white matter in cases, particularly in the fornix, corpus callosum, anterior and posterior limbs of the internal capsule bilaterally and cingulum bilaterally. In structural brain networks constructed using probabilistic tractography (22 cases, 32 controls), graph-theoretic measures of strength, local and global efficiency, clustering coefficient and characteristic path length were found to correlate with IQ in cases but not controls. Network-based statistic analysis implicated brain regions involved in visuo-spatial processing and attention, aligning with previous behavioural findings. These included the precuneus, thalamus, left superior parietal gyrus and left inferior temporal gyrus. Our findings demonstrate that, despite the manifest successes of therapeutic hypothermia, brain development is impaired in these children.