Oligodendrocytes Play a Critical Role in White Matter Damage of Vascular Dementia

With the deepening of population aging, the treatment of cognitive impairment and dementia is facing increasing challenges. Vascular dementia (VaD) is a cognitive dysfunction caused by brain blood flow damage and one of the most common causes of dementia after Alzheimer's disease. White matter damage in patients with chronic ischemic dementia often occurs before cognitive impairment, and its pathological changes include leukoaraiosis, myelin destruction and oligodendrocyte death. The pathophysiology of vascular dementia is complex, involving a variety of neuronal and vascular lesions. The current proposed mechanisms include calcium overload, oxidative stress, nitrative stress and inflammatory damage, which can lead to hypoxia-ischemia and demyelination. Oligodendrocytes are the only myelinating cells in the central nervous system and closely associated with VaD. In this review article, we intend to further discuss the role of oligodendrocytes in white matter and myelin injury in VaD and the development of anti-myelin injury target drugs.

A damaged periventricular white matter damage model in neonatal rats

OBJECTIVES

To investigate the function of circMyt1l/rno-let-7d-5p/BDNF in the white matter damage of premature rats.

METHODS

Bioinformatic analysis was used to analyze the differential expression of circMyt1l and its interacting miRNAs and mRNAs in rats with periventricular white matter damage. Rats at postnatal day 3 had their right common carotid artery permanently ligated, and were then exposed for 2 h to 6 % O2, or sham surgery and exposure to normal O2 levels (sham). CircMyt1l and rno-let-7d-5p expression was detected and BDNF protein levels were analyzed at 24, 48, and 72 h post hypoxia-ischemia.

RESULTS

Bioinformatic analysis suggested that circMyt1l, rno-let-7d-5p and BDNF interact. CircMyt1l expression decreased significantly relative to the sham-operated rats (p<0.01) in an exposure time-dependent manner. Contrastingly, rno-let-7d-5p increased significantly relative to the sham-operated rats (p<0.01) in an exposure time dependent manner. BDNF protein levels decreased significantly relative to the sham-operated rats (p<0.05) in an exposure time dependent manner.

CONCLUSIONS

The expression levels of circMyt1l/rno-let-7d-5p/BDNF are interrelated in periventricular white matter damage. Decreased circMyt1l expression of promoted the effect of rno-let-7d-5p and decreased the level of its target, BDNF.

Ethoxyquin, a Lipid Peroxidation Inhibitor, Has Protective Effects against White Matter Lesions in a Mouse Model of Chronic Cerebral Hypoperfusion

White matter lesions induced by chronic cerebral hypoperfusion can cause vascular dementia; however, no appropriate treatments are currently available for these diseases. In this study, we investigated lipid peroxidation, which has recently been pointed out to be associated with cerebrovascular disease and vascular dementia, as a therapeutic target for chronic cerebral hypoperfusion. We used ethoxyquin, a lipid-soluble antioxidant, in a neuronal cell line and mouse model of the disease. The cytoprotective effect of ethoxyquin on glutamate-stimulated HT-22 cells, a mouse hippocampal cell line, was comparable to that of a ferroptosis inhibitor. In addition, the administration of ethoxyquin to bilateral common carotid artery stenosis model mice suppressed white matter lesions, blood-brain barrier disruption, and glial cell activation. Taken together, we propose that the inhibition of lipid peroxidation may be a useful therapeutic approach for chronic cerebrovascular disease and the resulting white matter lesions.

Growth variables and obstetrical risk factors in newborns are associated with psychomotor development at preschool age

BACKGROUND

Low birthweight resulting from preterm birth or fetal growth restriction is associated with poor neurocognitive development and child psychopathology affecting school performance and educational success. Prediction of developmental performance may therefore serve as a basis for early intervention strategies to improve educational success and mental health of our children in a timely manner.

OBJECTIVE

This study aimed to explore the predictive capacity of morphometric variables taken at birth and that of obstetrical risk factors to predict developmental performance at 4.3 (standard deviation, 0.8) years preschool age. We examined predicted Total psychomotor development score, predicted Developmental disability index, calculated Morphometric vitality index, and predicted Intelligence quotient, Maze test, and Neurologic examination optimality score in a large prospective screening (cranial ultrasound screening, n=5,301) and validation cohort (n=508,926).

STUDY DESIGN

In a single-center cohort observational study design (data collection done from 1984-1988, analysis done in 2022), a prospective cranial ultrasound screening study (1984-1988) was carried out on 5,301 live-born infants, including 571 (10.8%) preterm infants (≤36 weeks gestation), on the day of discharge of the mother at 5 to 8 days postpartum from a level 3 perinatal center. Predicted psychomotor development as assessed by predicted Total psychomotor development score, predicted Developmental disability index, calculated Morphometric vitality index, and predicted Intelligence quotient, Maze test, and Neurologic examination optimality score, was calculated. We related growth variables and obstetrical risk factors to Psychomotor development indices, and calculated Morphometric vitality index using odds ratios, receiver operating characteristics, analysis of variance, and multivariate analysis of variance.

RESULTS

The key result of our study is the observation that simple morphometric measures from newborns at birth like weight/head circumference ratio predict overall psychomotor development at 4.3 years (standard deviation, 0.8) of preschool age. Psychomotor development was assessed by predicted Total psychomotor development score, predicted Intelligence quotient, Maze test, and Neurologic examination optimality score, and related to weight/head circumference ratio in linear regression (P<.001) and ROC curve analyses (P<.001). Further, white matter damage strongly predicted adverse outcome in predicted Developmental disability index (P<.001). There was also a close correlation between calculated Morphometric vitality index and predicted Developmental disability index (P<.001). Finally, brain body weight ratio, weight/head circumference ratio, preterm birth, reduced Apgar at 10 minutes, weight/length ratio, and white matter damage yielded highest odds ratios for adverse outcome in predicted Total psychomotor development score and in predicted Developmental disability index (P<.001) and high effect sizes in reduced predicted Intelligence quotient, Maze test, and Neurologic examination optimality scores.

CONCLUSION

Simple morphometric data, birth variables, and obstetrical risk factors bear predictive capacity for neurocognitive performance in children at 4.3 years (standard deviation, 0.8) of age and hence provide a basis for parental consultation and early intervention to improve school performance, educational success, and mental health in developed and developing countries.

Acute Blood Levels of Neurofilament Light Indicate One-Year White Matter Pathology and Functional Impairment in Repetitive Mild Traumatic Brain Injured Mice

Mild traumatic brain injury (mTBI) mostly causes transient symptoms, but repeated (r)mTBI can lead to neurodegenerative processes. Diagnostic tools to evaluate the presence of ongoing occult neuropathology are lacking. In a mouse model of rmTBI, we investigated MRI and plasma biomarkers of brain damage before chronic functional impairment arose. Anesthetized adult male and female C57BL/6J mice were subjected to rmTBI or a sham procedure. Sensorimotor deficits were evaluated up to 12 months post-injury in SNAP and Neuroscore tests. Cognitive function was assessed in the novel object recognition test at six and 12 months. Diffusion tensor imaging (DTI) and structural magnetic resonance imaging (MRI) were performed at six and 12 months to examine white matter and structural damage. Plasma levels of neurofilament light (NfL) were assessed longitudinally up to 12 months. Brain histopathology was performed at 12 months. Independent groups of mice were used to examine the effects of 2-, 7- and 14-days inter-injury intervals on acute plasma NfL levels and on hyperactivity. Twelve months after an acute transient impairment, sensorimotor functions declined again in rmTBI mice (p < 0.001 vs sham), but not earlier. Similarly, rmTBI mice showed memory impairment at 12 (p < 0.01 vs sham) but not at 6 months. White matter damage examined by DTI was evident in rmTBI mice at both six and 12 months (p < 0.001 vs sham). This was associated with callosal atrophy (p < 0.001 vs sham) evaluated by structural MRI. Plasma NfL at one week was elevated in rmTBI (p < 0.001 vs sham), and its level correlated with callosal atrophy at 12 months (Pearson r = 0.72, p < 0.01). Histopathology showed thinning of the corpus callosum and marked astrogliosis in rmTBI mice. The NfL levels were higher in mice subjected to short (2 days) compared with longer (7 and 14 days) inter-injury intervals (p < 0.05), and this correlated with hyperactivity in mice (Pearson r = 0.50; p < 0.05). These findings show that rmTBI causes white matter pathology detectable by MRI before chronic functional impairment. Early quantification of plasma NfL correlates with the degree of white matter atrophy one year after rmTBI and can serve to monitor the brain's susceptibility to a second mTBI, supporting its potential clinical application to guide the return to practice in sport-related TBI.

Whole-brain DTI parameters associated with tau protein and hippocampal volume in Alzheimer's disease

The causes of the neurodegenerative processes in Alzheimer's disease (AD) are not completely known. Recent studies have shown that white matter (WM) damage could be more severe and widespread than whole-brain cortical atrophy and that such damage may appear even before the damage to the gray matter (GM). In AD, Amyloid-beta (Aβ₄₂ ) and tau proteins could directly affect WM, spreading across brain networks. Since hippocampal atrophy is common in the early phase of disease, it is reasonable to expect that hippocampal volume (HV) might be also related to WM integrity. Our study aimed to evaluate the integrity of the whole-brain WM, through diffusion tensor imaging (DTI) parameters, in mild AD and amnestic mild cognitive impairment (aMCI) due to AD (with Aβ₄₂ alteration in cerebrospinal fluid [CSF]) in relation to controls; and possible correlations between those measures and the CSF levels of Aβ₄₂ , phosphorylated tau protein (p-Tau) and total tau (t-Tau). We found a widespread WM alteration in the groups, and we also observed correlations between p-Tau and t-Tau with tracts directly linked to mesial temporal lobe (MTL) structures (fornix and hippocampal cingulum). However, linear regressions showed that the HV better explained the variation found in the DTI measures (with weak to moderate effect sizes, explaining from 9% to 31%) than did CSF proteins. In conclusion, we found widespread alterations in WM integrity, particularly in regions commonly affected by the disease in our group of early-stage disease and patients with Alzheimer's disease. Nonetheless, in the statistical models, the HV better predicted the integrity of the MTL tracts than the biomarkers in CSF.

Alterations in white matter fiber density associated with structural MRI and metabolic PET lesions following multimodal therapy in glioma patients

BACKGROUND

In glioma patients, multimodality therapy and recurrent tumor can lead to structural brain tissue damage characterized by pathologic findings in MR and PET imaging. However, little is known about the impact of different types of damage on the fiber architecture of the affected white matter.

PATIENTS AND METHODS

This study included 121 pretreated patients (median age, 52 years; ECOG performance score, 0 in 48%, 1-2 in 51%) with histomolecularly characterized glioma (WHO grade IV glioblastoma, n=81; WHO grade III anaplastic astrocytoma, n=28; WHO grade III anaplastic oligodendroglioma, n=12), who had a resection, radiotherapy, alkylating chemotherapy, or combinations thereof. After a median follow-up time of 14 months (range, 1-214 months), anatomic MR and O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET images were acquired on a 3T hybrid PET/MR scanner. Post-therapeutic findings comprised resection cavities, regions with contrast enhancement or increased FET uptake and T2/FLAIR hyperintensities. Local fiber density was determined from high angular-resolution diffusion-weighted imaging and advanced tractography methods. A cohort of 121 healthy subjects selected from the 1000BRAINS study matched for age, gender and education served as a control group.

RESULTS

Lesion types differed in both affected tissue volumes and relative fiber densities compared to control values (resection cavities: median volume 20.9 mL, fiber density 16% of controls; contrast-enhanced lesions: 7.9 mL, 43%; FET uptake areas: 30.3 mL, 49%; T2/FLAIR hyperintensities: 53.4 mL, 57%, p<0.001). In T2/FLAIR-hyperintense lesions caused by peritumoral edema due to recurrent glioma (n=27), relative fiber density was as low as in lesions associated with radiation-induced gliosis (n=13, 48% vs. 53%, p=0.17). In regions with pathologically increased FET uptake, local fiber density was inversely related (p=0.005) to the extent of uptake. Total fiber loss associated with contrast-enhanced lesions (p=0.006) and T2/FLAIR hyperintense lesions (p=0.013) had a significant impact on overall ECOG score.

CONCLUSIONS

These results suggest that apart from resection cavities, reduction in local fiber density is greatest in contrast-enhancing recurrent tumors, but total fiber loss induced by edema or gliosis has an equal detrimental effect on the patients' performance status due to the larger volume affected.

Proteomic analysis of the effects of caffeine in a neonatal rat model of hypoxic-ischemic white matter damage

Aim

White matter damage (WMD) is the main cause of cerebral palsy and cognitive impairment in premature infants. Although caffeine has been shown to possess neuroprotective effects in neonatal rats with hypoxic‐ischemic WMD, the mechanisms underlying these protective effects are unclear. Herein, proteins modulated by caffeine in neonatal rats with hypoxic‐ischemic WMD were evaluated.

Methods

We identified differential proteins and performed functional enrichment analyses between the Sham, hypoxic‐ischemic WMD (HI), and HI+caffeine‐treated WMD (Caffeine) groups. Confirmed the changes and effect of proteins in animal models and determined cognitive impairment via water maze experiments.

Results

In paraventricular tissue, 47 differential proteins were identified between the Sham, HI, and Caffeine groups. Functional enrichment analyses showed that these proteins were related to myelination and axon formation. In particular, the myelin basic protein (MBP), proteolipid protein, myelin‐associated glycoprotein precursor, and sirtiun 2 (SIRT2) levels were reduced in the hypoxic‐ischemic WMD group, and this effect could be prevented by caffeine. Caffeine alleviated the hypoxic‐ischemic WMD‐induced cognitive impairment and improved MBP, synaptophysin, and postsynaptic density protein 95 protein levels after hypoxic‐ischemic WMD by preventing the HI‐induced downregulation of SIRT2; these effects were subsequently attenuated by the SIRT2 inhibitor AK‐7.

Conclusion

Caffeine may have clinical applications in the management of prophylactic hypoxic‐ischemic WMD; its effects may be mediated by proteins related to myelin development and synapse formation through SIRT2.

Sex-Specific Causes and Consequences of White Matter Damage in a Middle-Aged Cohort

Objective

To evaluate potential sex-specific effects of multiple cardiovascular risk factors on white matter pathology in normal aging men and women, as well as potential sex-differences in the association of white matter pathology and cognitive functions.

Methods

We analyzed cross-sectional data of 581 participants (median age: 53 years, 54% women) of the population-based cohort of the BiDirect Study who completed clinical examinations, five neuropsychological tests, and an 3T MRI examination. White matter pathology was determined by the extent of white matter hyperintensities (WMH) on FLAIR images as well as the magnitude of global fractional anisotropy (FA) based on diffusion tensor imaging. Main effects, interaction as well as sex-stratified generalized linear regression models were used to evaluate the moderating effect of sex on the association of hypertension, diabetes mellitus, smoking, and obesity with WMH and FA, respectively. Associations of imaging markers with cognitive test results were determined with linear regression models.

Results

Hypertension showed stronger associations with more extensive WMH and less FA in women compared to men. Current smoking was associated with more severe WMH in women only. Adjusted for age and education, WMH were not significantly associated with cognitive tests, but higher FA was associated with better performance in motor function in both sexes and with executive functions in men, even after adjustment for cardiovascular risk factors.

Conclusion

We observed a stronger association of hypertension and smoking with white matter damage in women, suggesting a higher susceptibility for vascular pathology in women. However, there was no association of WMH with cognition, and FA was associated with executive function tests only in men, suggesting a higher cognitive reserve in women.

White matter damage in patients with mild cognitive impairment in Parkinson's disease

BACKGROUND

This study investigates the correlation between white matter structural damage and cognitive impairment in patients with Parkinson's disease (PD) and mild cognitive impairment (MCI).

METHODS

A total of 40 patients with PD were divided into two groups, i.e., a mild cognitive impairment (PD-MCI) and a normal cognitive (PDN) group, and 20 healthy patients were enrolled as the control group. Changes in the white matter structure of patients with PD were evaluated using diffusion tensor imaging (DTI), and cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA) scale and Mini-Mental State Examination (MMSE). Finally, the correlations between the two groups were analyzed.

RESULTS

The Unified Parkinson's Disease Rating Scale score was significantly higher in the PD-MCI than in the PDN group (P=0.008). The total MoCA and MMSE scores in the PD-MCI group were significantly lower than in the PDN and control groups (P<0.01). Patients in PDMCI group were tested by MMSE scale, and the abnormal score rate was 60.0%. Among them, 8 PD patients with normal MMSE total score were found to have mild cognitive impairment by MoCA evaluation. When compared with the PDN and control groups, the MoCA scores for visual space, which is assessed as part of the MoCA scale and generally represents bilateral parietal function; naming; memory; and attention were significantly lower in the PD-MCI group (P<0.001). When compared with the PDN group, the fractional anisotropy (FA) values for the right parietal and left occipital lobes were significantly lower in the PD-MCI group (P=0.005; P=0.018). The relationship between MoCA value and right parietal white matter and left occipital white matter was 0.555, 0.474, respectively. A Pearson's correlation test was conducted to compare the FA values and MoCA scores of the various brain areas in the PD-MCI group and revealed a significant positive correlation between the MoCA score and the white matter of the right parietal and left occipital lobes (P<0.01).

CONCLUSIONS

Patients with PD experience early cognitive impairment, and the MoCA scale can be used for early screening. In addition, the DTI of white matter can highlight early white matter damage. In the current study, the damaged brain areas displayed by DTI were consistent with areas showing decreased MoCA scores and were positively correlated with the severity of PD.

Chronic Kidney Disease Associated with Worsening White Matter Disease and Ventricular Enlargement

BACKGROUND

Chronic kidney disease (CKD), a growing public health issue in the elderly, is associated with increased risk of cognitive impairment.

OBJECTIVE

To investigate the mechanisms through which CKD impacts brain health using longitudinal imaging.

METHODS

We identified 97 participants (74 CKD and 23 non-CKD) from the BRINK (BRain IN Kidney Disease), a longitudinal study of CKD with two MRI scans (baseline and 3-year follow-up). We measured the associations between baseline and change in kidney disease biomarkers of estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR), considered a measure of microvascular inflammation, and imaging outcomes of cortical thickness and ventricular volume from structural MRI, white matter hyperintensities (WMH) volume from FLAIR images, and fractional anisotropy of the corpus callosum (FACC).

RESULTS

There were white matter-specific changes as observed by increased WMH volume and decreased FACC in CKD participants, as well as ventricular volume increase in both CKD and non-CKD groups reflective of aging-related changes. Decline in eGFR was associated with decrease in the FACC, suggesting that subtle early white matter changes due to kidney disease can be captured using DTI. An increase in UACR was associated with increase in ventricular volume.

CONCLUSION

Our results support the role of eGFR as a measure of kidney microvascular disease which is associated with concurrent white matter damage in CKD. Future work is needed to investigate the possible link between endothelial microvascular inflammation (as measured by an increased UACR) and ventricular volume increase.

Adverse neural effects of delayed, intermittent treatment with rEPO after asphyxia in preterm fetal sheep

KEY POINTS

We have previously shown that high-dose constant infusion of recombinant human erythropoietin (rEPO) from 30 min to 72 h after asphyxia in preterm fetal sheep reduced histological injury and improved electrophysiological recovery. This study shows that a high-dose infusion of rEPO from 6 to 72 h after asphyxia did not improve EEG recovery, oligodendrocyte and neuronal survival at 1 week post-asphyxia. Of concern, intermittent rEPO boluses started 6 h after asphyxia were associated with impaired EEG recovery and bilateral cystic injury of temporal lobe intragyral white matter. Intermittent boluses of rEPO were associated with significantly increased cerebral vascular resistance and hypoperfusion, particularly after the first dose, but did not affect seizures, suggesting mismatch between perfusion and brain activity.

ABSTRACT

Recombinant human erythropoietin (rEPO) is a promising treatment for hypoxic-ischaemic brain injury. Disappointingly, a large randomized controlled trial in preterm infants found that prophylactic, repeated high-dose rEPO boluses started within 24 h of birth did not improve neurodevelopmental outcomes. We examined whether initiation of a continuous infusion of rEPO at the end of the latent phase after hypoxic-ischaemia (HI) might improve outcomes compared with intermittent bolus injections. Chronically instrumented preterm (0.7 gestation) fetal sheep received sham asphyxia or asphyxia induced by complete umbilical cord occlusion for 25 min. Six hours after asphyxia, fetuses received either a continuous infusion of rEPO (loading dose 2000 IU, infusion at 520 IU/h) from 6 to 72 h post-asphyxia or intravenous saline or 5000 IU rEPO, with repeated doses every 48 h for 5 days. Continuous infusion of rEPO did not improve EEG recovery, oligodendrocyte and neuronal survival at 1 week post-asphyxia. By contrast, intermittent rEPO boluses were associated with impaired EEG recovery and bilateral cystic injury of temporal lobe intragyral white matter in 6/8 fetuses. These studies demonstrate for the first time that initiation of intermittent rEPO boluses 6 h after HI, at a dose comparable with recent clinical trials, exacerbated neural injury. These data reinforce the importance of early initiation of many potential neuroprotective therapies.

Contribution of Gray Matter Atrophy and White Matter Damage to Cognitive Impairment in Mildly Disabled Relapsing-Remitting Multiple Sclerosis Patients

Cognitive impairment (CI) is frequently present in multiple sclerosis patients. Despite ongoing research, the neurological substrates have not been fully elucidated. In this study we investigated the contribution of gray and white matter in the CI observed in mildly disabled relapsing-remitting multiple sclerosis (RRMS) patients. For that purpose, 30 patients with RRMS (median EDSS = 2), and 30 age- and sex-matched healthy controls were studied. CI was assessed using the symbol digit modalities test (SDMT) and the memory alteration test. Brain magnetic resonance imaging, diffusion tensor imaging (DTI), voxel-based morphometry (VBM), brain segmentation, thalamic vertex analysis, and connectivity-based thalamic parcellation analyses were performed. RRMS patients scored significantly lower in both cognitive tests. In the patient group, significant atrophy in the thalami was observed. Multiple regression analyses revealed associations between SDMT scores and GM volume in both hemispheres in the temporal, parietal, frontal, and occipital lobes. The DTI results pointed to white matter damage in all thalamocortical connections, the corpus callosum, and several fasciculi. Multiple regression and correlation analyses suggested that in RRMS patients with mild disease, thalamic atrophy and thalamocortical connection damage may lead to slower cognitive processing. Furthermore, white matter damage at specific fasciculi may be related to episodic memory impairment.

[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.

[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.

Development and Validation of a Dynamic Nomogram to Predict the Risk of Neonatal White Matter Damage

Purpose

White matter damage (WMD) was defined as the appearance of rough and uneven echo enhancement in the white matter around the ventricle. The aim of this study was to develop and validate a risk prediction model for neonatal WMD.

Materials and Methods

We collected data for 1,733 infants hospitalized at the Department of Neonatology at The First Affiliated Hospital of Zhengzhou University from 2017 to 2020. Infants were randomly assigned to training (n = 1,216) or validation (n = 517) cohorts at a ratio of 7:3. Multivariate logistic regression and least absolute shrinkage and selection operator (LASSO) regression analyses were used to establish a risk prediction model and web-based risk calculator based on the training cohort data. The predictive accuracy of the model was verified in the validation cohort.

Results

We identified four variables as independent risk factors for brain WMD in neonates by multivariate logistic regression and LASSO analysis, including gestational age, fetal distress, prelabor rupture of membranes, and use of corticosteroids. These were used to establish a risk prediction nomogram and web-based calculator (https://caowenjun.shinyapps.io/dynnomapp/). The C-index of the training and validation sets was 0.898 (95% confidence interval: 0.8745-0.9215) and 0.887 (95% confidence interval: 0.8478-0.9262), respectively. Decision tree analysis showed that the model was highly effective in the threshold range of 1-61%. The sensitivity and specificity of the model were 82.5 and 81.7%, respectively, and the cutoff value was 0.099.

Conclusion

This is the first study describing the use of a nomogram and web-based calculator to predict the risk of WMD in neonates. The web-based calculator increases the applicability of the predictive model and is a convenient tool for doctors at primary hospitals and outpatient clinics, family doctors, and even parents to identify high-risk births early on and implementing appropriate interventions while avoiding excessive treatment of low-risk patients.

A Narrative Review of Circular RNAs in Brain Development and Diseases of Preterm Infants

Circular RNAs (circRNAs) generated by back-splicing are the vital class of non-coding RNAs (ncRNAs). Circular RNAs are highly abundant and stable in eukaryotes, and many of them are evolutionarily conserved. They are blessed with higher expression in mammalian brains and could take part in the regulation of physiological and pathophysiological processes. In addition, premature birth is important in neurodevelopmental diseases. Brain damage in preterm infants may represent the main cause of long-term neurodevelopmental disorders in surviving babies. Until recently, more and more researches have been evidenced that circRNAs are involved in the pathogenesis of encephalopathy of premature. We aim at explaining neuroinflammation promoting the brain damage. In this review, we summarize the current findings of circRNAs properties, expression, and functions, as well as their significances in the neurodevelopmental impairments, white matter damage (WMD) and hypoxic-ischemic encephalopathy (HIE). So we think that circRNAs have a direct impact on neurodevelopment and brain injury, and will be a powerful tool in the repair of the injured immature brain. Even though their exact roles and mechanisms of gene regulation remain elusive, circRNAs have potential applications as diagnostic biomarkers for brain damage and the target for neuroprotective intervention.

Corrigendum: Comprehensive Evaluation of White Matter Damage and Neuron Death and Whole-Transcriptome Analysis of Rats With Chronic Cerebral Hypoperfusion

[This corrects the article DOI: 10.3389/fncel.2019.00310.].

Damage in the Thalamocortical Tracts is Associated With Subsequent Thalamus Atrophy in Early Multiple Sclerosis

Background: In early multiple sclerosis (MS), thalamus atrophy and decreased integrity of the thalamocortical white matter (WM) tracts have been observed.

Objective: To investigate the temporal association between thalamus volume and WM damage in the thalamocortical tract in subjects with early MS.

Methods: At two time points, 72 subjects with early MS underwent T1, FLAIR and diffusion tensor imaging. Thalamocortical tracts were identified with probabilistic tractography using left and right thalamus as seed regions. Regression analysis was performed to identify predictors of annual percentage change in both thalamus volumes and integrity of the connected tracts.

Results: Significant atrophy was seen in left and right thalamus (p < 0.001) over the follow-up period (13.7 ± 4.8 months), whereas fractional anisotropy (FA) and mean diffusivity (MD) changes of the left and right thalamus tracts were not significant, although large inter-subject variability was seen. Annual percentage change in left thalamus volume was significantly predicted by baseline FA of the left thalamus tracts F_(1.71) = 4.284, p = 0.042; while no such relation was found for the right thalamus. Annual percentage change in FA or MD of the thalamus tracts was not predicted by thalamus volume or any of the demographic parameters.

Conclusion: Over a short follow-up time, thalamus atrophy could be predicted by decreased integrity of the thalamic tracts, but changes in the integrity of the thalamic tracts could not be predicted by thalamus volume. This is the first study showing directionality in the association between thalamus atrophy and connected WM tract damage. These results need to be verified over longer follow-up periods.

Bone Fracture Enhanced Blood-Brain Barrier Breakdown in the Hippocampus and White Matter Damage of Stroke Mice

Background: Tibia fracture (BF) before stroke shortly causes long-term post-stroke memory dysfunction in mice. The mechanism is unclear. We hypothesize that BF enhances neuroinflammation and blood brain barrier (BBB) breakdown in the hippocampus and white matter (WM) damage. Methods: Mice were assigned to groups: BF, stroke, BF+stroke (BF 6 h before stroke) and sham. BBB integrity was analyzed 3 days after the surgeries and WM injury was analyzed 3 days and 8 weeks after the surgeries. Results: Stroke and BF+stroke groups had more activated microglia/macrophages and lower levels of claudin-5 in the ipsilateral hippocampi than the BF group. BF+stroke group had the highest number microglia/macrophages and the lowest level of claudin-5 among all groups and had fewer pericytes than BF group. Stroke and BF+stroke groups had smaller WM areas in the ipsilateral basal ganglia than the sham group 8 weeks after the injuries. The BF+stroke group also had smaller WM areas in the ipsilateral than sham and BF groups 3 days after the injuries and in the contralateral basal ganglia than stroke and BF groups 8 weeks after the injuries. Conclusions: BF exacerbates neuroinflammation and BBB leakage in the hippocampus and WM damage in basal ganglia, which could contribute to the long-lasting memory dysfunction in BF+stroke mice.

The Role of Amyloid-β in White Matter Damage: Possible Common Pathogenetic Mechanisms in Neurodegenerative and Demyelinating Diseases

Just as multiple sclerosis (MS) has long been primarily considered a white matter (WM) disease, Alzheimer's disease (AD) has for decades been regarded only as a grey matter disorder. However, convergent evidences have suggested that WM abnormalities are also important components of AD, at the same extent as axonal and neuronal loss is critically involved in MS pathophysiology since early clinical stages. These observations have motivated a more thorough investigation about the possible mechanisms that could link neuroinflammation and neurodegeneration, focusing on amyloid-β (Aβ). Neuroimaging studies have found that patients with AD have widespread WM abnormalities already at the earliest disease stages and prior to the presence of Aβ plaques. Moreover, a correlation between cerebrospinal fluid (CSF) Aβ levels and WM lesion load was found. On the other hand, recent studies suggest a predictive role for CSF Aβ levels in MS, possibly due in the first instance to the reduced capacity for remyelination, consequently to a higher risk of WM damage progression, and ultimately to neuronal loss. We undertook a review of the recent findings concerning the involvement of CSF Aβ levels in the MS disease course and of the latest evidence of AD related WM abnormalities, with the aim to discuss the potential causes that may connect WM damage and amyloid pathology.

Long Longitudinal Tract Lesion Contributes to the Progression of Alzheimer's Disease

Background: The degenerative pattern of white matter (WM) microstructures during Alzheimer's disease (AD) and its relationship with cognitive function have not yet been clarified. The present research aimed to explore the alterations of the WM microstructure and its impact on amnestic mild cognitive (aMCI) and AD patients. Mechanical learning methods were used to explore the validity of WM microstructure lesions on the classification in AD spectrum disease.

Methods: Neuropsychological data and diffusion tensor imaging (DTI) images were collected from 28 AD subjects, 31 aMCI subjects, and 27 normal controls (NC). Tract-based spatial statistics (TBSS) were used to extract diffusion parameters in WM tracts. We performed ANOVA analysis to compare diffusion parameters and clinical features among the three groups. Partial correlation analysis was used to explore the relationship between diffusion metrics and cognitive functions controlling for age, gender, and years of education. Additionally, we performed the support vector machine (SVM) classification to determine the discriminative ability of DTI metrics in the differentiation of aMCI and AD patients from controls.

Results: As compared to controls or aMCI patients, AD patients displayed widespread WM lesions, including in the inferior longitudinal fasciculus, inferior fronto-occipital fasciculi, and superior longitudinal fasciculus. Significant correlations between fractional anisotropy (FA), mean diffusivity (MD), and radial diffusion (RD) of the long longitudinal tract and memory deficits were found in aMCI and AD groups, respectively. Furthermore, through SVM classification, we found DTI indicators generated by FA and MD parameters can effectively distinguish AD patients from the control group with accuracy rates of up to 89 and 85%, respectively.

Conclusion: The WM microstructure is extensively disrupted in AD patients, and the WM integrity of the long longitudinal tract is closely related to memory, which would hold potential value for monitoring the progression of AD. The method of classification based on SVM and WM damage features may be objectively helpful to the classification of AD diseases.

Relevance of Porcine Stroke Models to Bridge the Gap from Pre-Clinical Findings to Clinical Implementation

In the search of animal stroke models providing translational advantages for biomedical research, pigs are large mammals with interesting brain characteristics and wide social acceptance. Compared to rodents, pigs have human-like highly gyrencephalic brains. In addition, increasingly through phylogeny, animals have more sophisticated white matter connectivity; thus, ratios of white-to-gray matter in humans and pigs are higher than in rodents. Swine models provide the opportunity to study the effect of stroke with emphasis on white matter damage and neuroanatomical changes in connectivity, and their pathophysiological correlate. In addition, the subarachnoid space surrounding the swine brain resembles that of humans. This allows the accumulation of blood and clots in subarachnoid hemorrhage models mimicking the clinical condition. The clot accumulation has been reported to mediate pathological mechanisms known to contribute to infarct progression and final damage in stroke patients. Importantly, swine allows trustworthy tracking of brain damage evolution using the same non-invasive multimodal imaging sequences used in the clinical practice. Moreover, several models of comorbidities and pathologies usually found in stroke patients have recently been established in swine. We review here ischemic and hemorrhagic stroke models reported so far in pigs. The advantages and limitations of each model are also discussed.

Increased CSF NFL in Non-demented Parkinson's Disease Subjects Reflects Early White Matter Damage

Parkinson's disease (PD) is a chronic neurodegenerative disorder with various underlying pathological processes. Until now, no fluid biomarkers have been established for PD. Given recent biochemical and neuroimaging evidence for the presence of white matter damage in PD, which may even precede neuronal loss, we investigated whether neurofilament light (NFL) was increased in the cerebrospinal fluid (CSF) of PD patients in comparison to controls. NFL is located mainly in large myelinated axons, and increased CSF levels of this protein reflect axonal injury. CSF levels of NFL in 58 early PD patients and 28 controls were quantified by ELISA (Uman Diagnostics). Measures of PD severity included disease duration, UPDRS-III, and Hoehn-Yahr stage. Statistically significant differences in CSF NFL levels were found between PD patients and controls [median with interquartile range 524.82 (393.28-678.34) vs. 271.84 (198.09-335.24) ng/l; p < 0.05)]. In PD patients, there were no correlations between CSF NFL level and the measures of disease severity. The CSF NFL turned out to have a high discriminatory value (AUC 0.850) for differentiating between PD subjects and healthy controls, with 84% sensitivity and 85.2% specificity. The study indirectly demonstrates that axonal damage is present in early PD in addition to neuronal loss. Interestingly, white matter damage was observed in non-demented PD patients. In the light of the results of recent MRI studies which confirm early white matter damage in PD, our data may turn out to be potentially useful in the diagnosis of early, or even preclinical, stages of the disease.

Elevation of stromal cell-derived factor 1 and C-X-C chemokine receptor type 4 in white matter damage treatment with recombinant human erythropoietin and human umbilical cord mesenchymal stem cells in a rat model of preterm birth

OBJECTIVES

To investigate the role of stromal cell-derived factor 1 (SDF-1) and C-X-C chemokine receptor type 4 (CXCR-4) in the premature brain with white matter damage (WMD) undergoing treatment with human umbilical cord mesenchymal stem cells (hUC-MSCs) and recombinant human erythropoietin (rhEPO).

EXPERIMENTAL DESIGN

Three-day-old Sprague-Dawley (SD) rats were randomly divided into sham operation group, hypoxia-ischemia (HI) group, rhEPO treated HI group, hUC-MSCs treated HI group, and rhEPO + hUC-MSCs treated HI group. WMD was established in all groups except the Sham group. SDF-1 and CXCR-4 levels in each group were detected at postnatal day (P) 5, P7, and P14. Pathological changes were assessed via HE staining at P14 and neuroethological tests were performed at P28.

OBSERVATIONS AND CONCLUSIONS

The rhEPO and hUC-MSCs intervention reduced injury area, increased body weight at P7, and improved neurobehavioral scores at P28. Furthermore, their combined use proved even more beneficial. SDF-1 levels in the rhEPO group were higher than those in the other groups and highest in the hUC-MSCs + rhEPO group (all p < .01). SDF-1 levels in the hUC-MSCs + rhEPO and rhEPO groups were increased at P5 and reached a peak at P7. CXCR-4 levels in the hUC-MSCs group were higher than those in the other groups and highest in the hUC-MSCs + rhEPO group (all p < .01). CXCR-4 levels were also increased at P5 and highest at P14.

SIGNIFICANCE

hUC-MSCs + rhEPO might reduce nerve cell damage and improve neurobehavioral development, in connection with increased SDF-1 and CXCR-4 expression, in premature rats with WMD due to hypoxic-ischemic injury.

The role of myelin damage in Alzheimer's disease pathology

Although Alois Alzheimer described myelin disruption in Alzheimer's disease (AD) as early as in 1911, his observation has escaped the attention of researchers since that time. Alzheimer's disease has been mainly considered as a grey matter disorder; nevertheless, recent evidence suggests that myelin impairment may play an important role in AD pathology. Classical neuropathological changes in AD, e.g. the accumulation of aggregated Aβ 42 and the presence of neurofibrillary tangles, are responsible for neuronal loss, but they may also induce death of oligodendrocytes and myelin damage. There is also evidence that myelin pathology may even precede Aβ and tau pathologies in AD. The state of the art does not allow us to determine whether myelin damage is a primary or a secondary injury in AD subjects. The article presents an overview of current knowledge on the role of myelin in AD pathology and its interactions with Aβ and tau pathologies.

Heterogeneity of microglia and their differential roles in white matter pathology

Microglia are resident immune cells that play multiple roles in central nervous system (CNS) development and disease. Although the classical concept of microglia/macrophage activation is based on a biphasic beneficial‐versus‐deleterious polarization, growing evidence now suggests a much more heterogenous profile of microglial activation that underlie their complex roles in the CNS. To date, the majority of data are focused on microglia in gray matter. However, demyelination is a prominent pathologic finding in a wide range of diseases including multiple sclerosis, Alzheimer's disease, and vascular cognitive impairment and dementia. In this mini‐review, we discuss newly discovered functional subsets of microglia that contribute to white matter response in CNS disease onset and progression. Microglia show different molecular patterns and morphologies depending on disease type and brain region, especially in white matter. Moreover, in later stages of disease, microglia demonstrate unconventional immuno‐regulatory activities such as increased phagocytosis of myelin debris and secretion of trophic factors that stimulate oligodendrocyte lineage cells to facilitate remyelination and disease resolution. Further investigations of these multiple microglia subsets may lead to novel therapeutic approaches to treat white matter pathology in CNS injury and disease.

Genomic deletion of TLR2 induces aggravated white matter damage and deteriorated neurobehavioral functions in mouse models of Alzheimer's disease

Toll-like receptor-2 (TLR2), a member of the TLR family, plays an important role in the initiation and regulation of immune/inflammation response, which is a critical mechanism underlying Alzheimer’s disease (AD). To clarify the role of TLR2 in the pathological process of AD, in the present study, TLR2 knockout plus APPswe/PSEN1dE9 transgenic mice (AD-TLR2KO) were generated. Neurobehavioral tests and brain MRI scan were conducted on mice at the age of 12 months. Additionally, neuron loss was evaluated using NeuN staining. Amyloid β protein (Aβ), glial fibrillary acidic protein (GFAP), endogenous ligands for TLR2, and the activation of downstream signaling of TLR2 in mouse brains were detected by immunohistochemistry and Western blots. The results demonstrated that TLR2 deficit induced learning disabilities, decreased spontaneous activity, increased anxiety and depression, and led to white matter damage (WMD), brain atrophy, loss of neurons, and glial activation. Moreover, TLR2 deficit aggravated impaired neurobehavioral functions and WMD in AD mice, but did not affect the Aβ deposition in mouse brains. Our data indicate that the genomic deletion of TLR2 impairs neurobehavioral functions, induces WMD and brain atrophy, and increases the activation of astrocytes, which in turn aggravate the symptoms of AD through a non-Aβ mechanism.

Comprehensive Evaluation of White Matter Damage and Neuron Death and Whole-Transcriptome Analysis of Rats With Chronic Cerebral Hypoperfusion

Background/Aims

Chronic cerebral hypoperfusion (CCH) is induced by chronic deficit of brain perfusion, contributes to a persistent or progressive cognitive dysfunction, which is characterized by diverse neuropathological manifestations. There are currently no effective medications available. White matter damage (WMD) and cortical neuron death may be caused by CCH, which are related to cognitive impairment, while the underlying molecular mechanisms remain unclear. In the study, a database of the transcriptome level was built to determine potential biomarkers in cortex of CCH.

Methods

CCH was induced in male Sprague-Dawley rats by permanent occlusion of the bilateral common carotid arteries. Rats were randomly divided into three groups: Sham-operated group (n = 24), the 4th and 8th week of CCH groups (total = 56, n = 28 for each group). Cognitive function was evaluated using the Morris water maze task. WMD and neuron damage were detected using diffusion tensor imaging and histological analysis, respectively. Western blotting analysis of various markers was used to examine neuronal death. Whole-transcriptome microarray was performed to assess mRNA, circRNA, and lncRNA expression profiles at 4th and 8th weeks after CCH. Diversified bioinformatic tools were performed to analyze and predict the key biological processes and signaling pathways of differentially expressed RNAs and co-expressed potential target genes. Co-expression networks of mRNA–circRNA–miRNA and lncRNA–mRNA were constructed.

Results

Compared to the sham group, cognitive impairment, disintegration of white matter, blood-brain barrier damage and neuron death were induced by CCH. Neuron death including apoptosis and necroptosis might occur in the cortex of CCH. We constructed the regulatory networks of whole-transcriptomic including differentially expressed mRNAs, circRNAs, and lncRNAs, and related biological functions and pathways involved in neurological disease, cell death and survival, energy and metabolism, et al. Our results also indicated that Cyr61 mRNA may play a role in the CCH-related cortical neuronal death.

Conclusion

WMD and cortical neuronal death are worthy of attention in the pathogenesis of CCH. Additionally, the present results provide potential evidence at the whole-transcription level for CCH, offering candidate biomarkers and therapeutic targets.

Protective Role of Levetiracetam Against Cognitive Impairment And Brain White Matter Damage in Mouse prolonged Cerebral Hypoperfusion

White matter lesions due to cerebral hypoperfusion may be an important pathophysiology in vascular dementia and stroke, although the inherent mechanisms remain to be fully elucidated. The present study, using a mouse model of chronic cerebral hypoperfusion, examined the white matter protective effects of levetiracetam, an anticonvulsant, via the signaling cascade from the activation of cAMP-responsive element binding protein (CREB) phosphorylation. Mice underwent bilateral common carotid artery stenosis (BCAS), and were separated into the levetiracetam group (injected once only after BCAS [LEV1] or injected on three consecutive days [LEV3]), the vehicle group, or the anti-epileptic drugs with different action mechanisms phenytoin group (PHT3; injected on three consecutive days with the same condition as in LEV3). Cerebral blood flow analysis, Y-maze spontaneous alternation test, novel object recognition test, immunohistochemical and Western blot analyses, and protein kinase A assay were performed after BCAS. In the LEV3 group, SV2A expression was markedly increased, which preserved learning and memory after BCAS. Moreover, as the protein kinase A level was significantly increased, pCREB expression was also increased. The activation of microglia and astrocytes was markedly suppressed, although the number of oligodendrocyte precursor cells (OPCs) and GST-pi-positive-oligodendrocytes was markedly higher in the cerebral white matter. Moreover, oxidative stress was significantly reduced. We found that 3-day treatment with levetiracetam maintained SV2A protein expression via interaction with astrocytes, which influenced the OPC lineage through activation of CREB to protect white matter from ischemia.

Clinical efficacy of gangliosides on premature infants suffering from white matter damage and its effect on the levels of IL-6, NSE and S100β

This study investigated the clinical efficacy of gangliosides on premature infants suffering from white matter damage and its effect on the levels of IL-6, neuron-specific enolase (NSE) and S100β. Seventy-six cases of premature infants suffering from white matter damage admitted to the Tianjin Central Hospital of Obstetrics and Gynecology from February 2016 to March 2017 were enrolled in this study. They were randomly divided into the control group and the observation group with 38 cases in each group. Control group was given conventional treatment, while the observation group was given ganglioside treatment on the basis of the treatment given to the control group. Craniocerebrum ultrasonic detection was used to observe the condition of white matter around the ventricle of child patients in the two groups, before and after treatment. ELISA was used to detect the levels of IL-6, NSE and S100β. Gesell developmental scale was used to compare the developmental quotient (DQ) of various function regions of the children. The total effective rate of the observation group was higher than that of the control group (P<0.05). The gray value of craniocerebrum ultrasonic detection in the observation group was significantly lower than that in the control group (P<0.05). IL-6, S100β and NSE levels of the child patients in the two groups were significantly declined at 7 and 14 days after birth (P<0.05). After 1 year, the observation group scored significantly higher DQ than the control group in the aspects of social adaptation, gross motor, fine motor, language and personal social contact. The sequel incidence of patients in the observation group was significantly lower than that of the control group (P<0.05). In conclusion, the intervention treatment with ganglioside for premature infants suffering from white matter damage was beneficial and provided a protective effect. It also reduced sequel and produced some promising results.

Neuroimaging in amyotrophic lateral sclerosis: current and emerging uses

INTRODUCTION

Several neuroimaging techniques have been used to define in vivo markers of pathological alterations underlying amyotrophic lateral sclerosis (ALS). Growing evidence supports the use of magnetic resonance imaging (MRI) and positron emission tomography (PET) for the non-invasive detection of central nervous system involvement in patients with ALS. Areas covered: A comprehensive overview of structural and functional neuroimaging applications in ALS is provided, focusing on motor and extra-motor involvement in the brain and the spinal cord. Implications for pathogenetic models, patient diagnosis, prognosis, monitoring, and the design of clinical trials are discussed. Expert commentary: State-of-the-art neuroimaging techniques provide fundamental instruments for the detection and quantification of upper motor neuron and extra-motor brain involvement in ALS, with relevance for both pathophysiologic investigation and clinical practice. Network-based analysis of structural and functional connectivity alterations and multimodal approaches combining several neuroimaging measures are promising tools for the development of novel diagnostic and prognostic markers to be used at the individual patient level.

[Neuroprotective effects of oligodendrocyte precursor cells on white matter damage in preterm infants]

White matter damage, characterized by demyelination due to the damage of oligodendrocyte precursor cells (OPCs), is the most common type of brain damage in preterm infants. Survivors are often subject to long-term neurodevelopmental sequelae because of the lack of effective treatment. In recent years, it has been found that cell transplantation has the potential for the treatment of white matter damage. OPCs are frequently used cells in cell transplantation therapy. With abilities of migration and myelinization, OPCs are the best seed cells for the treatment of white matter damage. Several studies have found that OPCs may not only replace impaired cells to reconstruct the structure and function of white matter, but also inhibit neuronal apoptosis, promote the proliferation of endogenous neural stem cells, and enhance the repairment of the blood-brain barrier. However, the clinical application of OPC transplantation therapy faces many challenges, such as the effectiveness, risk of tumorigenesis and immune rejection. With reference to these studies, this article reviewed the development of myelination, the obtainment of OPCs, the therapeutic mechanism as well as application research, and analyzed the current challenges of OPC transplantation, in order to provide a new direction for clinical treatment of white matter damage in preterm infants.

Explaining the heterogeneity of functional connectivity findings in multiple sclerosis: An empirically informed modeling study

To understand the heterogeneity of functional connectivity results reported in the literature, we analyzed the separate effects of grey and white matter damage on functional connectivity and networks in multiple sclerosis. For this, we employed a biophysical thalamo‐cortical model consisting of interconnected cortical and thalamic neuronal populations, informed and amended by empirical diffusion MRI tractography data, to simulate functional data that mimic neurophysiological signals. Grey matter degeneration was simulated by decreasing within population connections and white matter degeneration by lowering between population connections, based on lesion predilection sites in multiple sclerosis. For all simulations, functional connectivity and functional network organization are quantified by phase synchronization and network integration, respectively. Modeling results showed that both cortical and thalamic grey matter damage induced a global increase in functional connectivity, whereas white matter damage induced an initially increased connectivity followed by a global decrease. Both white and especially grey matter damage, however, induced a decrease in network integration. These empirically informed simulations show that specific topology and timing of structural damage are nontrivial aspects in explaining functional abnormalities in MS. Insufficient attention to these aspects likely explains contradictory findings in multiple sclerosis functional imaging studies so far.

Pretreatment with magnesium sulfate attenuates white matter damage by preventing cell death of developing oligodendrocytes

AIM

Antenatal maternal administration of magnesium sulfate (MgSO₄ ) reduces cerebral palsy in preterm infants. However, it remains controversial as to whether it also reduces occurrence of white matter damage, or periventricular leukomalacia. We assessed the effect of MgSO₄ against white matter damage induced by hypoxic-ischemic insult using a neonatal rat model and culture of premyelinating oligodendrocytes (pre-OL).

METHODS

Rat pups at postnatal day (P) 6 were administered either MgSO₄ or vehicle intraperitoneally before hypoxic-ischemic insult (unilateral ligation of the carotid artery followed by 6% oxygen for 1 h). The population of oligodendrocyte (OL) markers and CD-68-positive microglia at P11, and TdT-mediated biotin-16-dUTP nick-end labeling (TUNEL)-positive cells at P8 were evaluated in pericallosal white matter. Primary cultures of mouse pre-OL were subjected to oxygen glucose deprivation condition, and the lactate dehydrogenase release from culture cells was evaluated to assess cell viability.

RESULTS

Pretreatment with MgSO₄ attenuated the loss of OL markers, such as myelin basic protein and Olig2, in ipsilateral pericallosal white matter and decreased the number of CD-68-positive microglia and TUNEL-positive cells in vivo. Pretreatment with MgSO₄ also inhibited lactate dehydrogenase release from pre-OL induced by oxygen glucose deprivation in vitro.

CONCLUSION

Pretreatment with MgSO₄ attenuates white matter damage by preventing cell death of pre-OL.

Implications of white matter damage in amyotrophic lateral sclerosis (Review)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, which involves the progressive degeneration of motor neurons. ALS has long been considered a disease of the grey matter; however, pathological alterations of the white matter (WM), including axonal loss, axonal demyelination and oligodendrocyte death, have been reported in patients with ALS. The present review examined motor neuron death as the primary cause of ALS and evaluated the associated WM damage that is guided by neuronal‑glial interactions. Previous studies have suggested that WM damage may occur prior to the death of motor neurons, and thus may be considered an early indicator for the diagnosis and prognosis of ALS. However, the exact molecular mechanisms underlying early‑onset WM damage in ALS have yet to be elucidated. The present review explored the detailed anatomy of WM and identified several pathological mechanisms that may be implicated in WM damage in ALS. In addition, it associated the pathophysiological alterations of WM, which may contribute to motor neuron death in ALS, with similar mechanisms of WM damage that are involved in multiple sclerosis (MS). Furthermore, the early detection of WM damage in ALS, using neuroimaging techniques, may lead to earlier therapeutic intervention, using immunomodulatory treatment strategies similar to those used in relapsing‑remitting MS, aimed at delaying WM damage in ALS. Early therapeutic approaches may have the potential to delay motor neuron damage and thus prolong the survival of patients with ALS. The therapeutic interventions that are currently available for ALS are only marginally effective. However, early intervention with immunomodulatory drugs may slow the progression of WM damage in the early stages of ALS, thus delaying motor neuron death and increasing the life expectancy of patients with ALS.

Lysophosphatidyl Choline Induced Demyelination in Rat Probed by Relaxation along a Fictitious Field in High Rank Rotating Frame

In this work a new MRI modality entitled Relaxation Along a Fictitious Field in the rotating frame of rank 4 (RAFF4) was evaluated in its ability to detect lower myelin content in lysophosphatidyl choline (LPC)-induced demyelinating lesions. The lesions were induced in two areas of the rat brain with either uniform or complex fiber orientations, i.e., in the corpus callosum (cc) and dorsal tegmental tract (dtg), respectively. RAFF4 showed excellent ability to detect demyelinated lesions and good correlation with myelin content in both brain areas. In comparison, diffusion tensor imaging metrices, fractional anisotropy, mean diffusivity and axonal and radial diffusivity, and magnetization transfer (MT) metrices, longitudinal relaxation during off-resonance irradiation and MT ratio, either failed to detect demyelination in dtg or showed lower correlation with myelin density quantified from gold chloride stained histological sections. Good specifity of RAFF4 to myelin was confirmed by its low correlation with cell density assesed from Nissl stained sections as well as its lack of sensitivity to pH changes in the physiological range as tested in heat denaturated bovine serum albumin phantoms. The excellent ability of RAFF4 to detect myelin content and its insensitivity to fiber orientation distribution, gliosis and pH, together with low specific absorption rate, demonstrates the promise of rotating frame of rank n (RAFFn) as a valuable MRI technique for non-invasive imaging of demyelinating lesions.

Alterations of Caspr2 and Nav1.6 on myelinated axon damage in a rat model of chronic cerebral hypoperfusion

Myelinated axons require the correct localization of key proteins that are essential for nerve conduction and cognitive function. Little is known regarding the altered expression of contactin-associated protein 2 (Caspr2) at the juxtaparanodal regions and Nav1.6 at the node of Ranvier in response to chronic cerebral hypoperfusion (CCH). The aim of the present study was to examine the alterations in the key protein of myelinated axons and the potential mechanisms that may follow CCH. We established a rat model of CCH by controllable partial narrowing of bilateral common carotid arteries. Then, we detected cerebral blood flow (CBF) after surgery. We also evaluated motor-evoked potentials (MEPs), assessed the Morris water maze test, analyzed Caspr2 expression through immunohistochemistry and Nav1.6 protein expression through western blot analysis at 2, 4 and 12 weeks. The results revealed that the mean CBF value was significantly decreased to 33.90±5.48%. The MEP latencies and the escaping latencies were significantly prolonged. There was also an elongation of the first time passing of the hidden platform with a reduction of crossing platform times in spatial probing. Furthermore, the Caspr2 immunoreactivity demonstrated that the Caspr2 level was significantly downregulated with abnormal locations in the corpus callosum. The western blot analysis of Nav1.6 protein revealed that the level was reduced significantly over time. The results demonstrate that CCH leads to central conductive function loss, cognitive function damage and alterations in the key protein of myelinated axons, which may provide a molecular basis and key link for white matter damage.

Rodent Hypoxia-Ischemia Models for Cerebral Palsy Research: A Systematic Review

Cerebral palsy (CP) is a complex multifactorial disorder, affecting approximately 2.5-3/1000 live term births, and up to 22/1000 prematurely born babies. CP results from injury to the developing brain incurred before, during, or after birth. The most common form of this condition, spastic CP, is primarily associated with injury to the cerebral cortex and subcortical white matter as well as the deep gray matter. The major etiological factors of spastic CP are hypoxia/ischemia (HI), occurring during the last third of pregnancy and around birth age. In addition, inflammation has been found to be an important factor contributing to brain injury, especially in term infants. Other factors, including genetics, are gaining importance. The classic Rice-Vannucci HI model (in which 7-day-old rat pups undergo unilateral ligation of the common carotid artery followed by exposure to 8% oxygen hypoxic air) is a model of neonatal stroke that has greatly contributed to CP research. In this model, brain damage resembles that observed in severe CP cases. This model, and its numerous adaptations, allows one to finely tune the injury parameters to mimic, and therefore study, many of the pathophysiological processes and conditions observed in human patients. Investigators can recreate the HI and inflammation, which cause brain damage and subsequent motor and cognitive deficits. This model further enables the examination of potential approaches to achieve neural repair and regeneration. In the present review, we compare and discuss the advantages, limitations, and the translational value for CP research of HI models of perinatal brain injury.

Aging in Down Syndrome and the Development of Alzheimer's Disease Neuropathology

Chromosome 21, triplicated in Down Syndrome, contains several genes that are thought to play a critical role in the development of AD neuropathology. The overexpression of the gene for the amyloid precursor protein (APP), on chromosome 21, leads to early onset beta-amyloid (Aβ) plaques in DS. In addition to Aβ accumulation, middle-aged people with DS develop neurofibrillary tangles, cerebrovascular pathology, white matter pathology, oxidative damage, neuroinflammation and neuron loss. There is also evidence of potential compensatory responses in DS that benefit the brain and delay the onset of dementia after there is sufficient neuropathology for a diagnosis of AD. This review describes some of the existing literature and also highlights gaps in our knowledge regarding AD neuropathology in DS. It will be critical in the future to develop networked brain banks with standardized collection procedures to fully characterize the regional and temporal pathological events associated with aging in DS. As more information is acquired regarding AD evolution in DS, there will be opportunities to develop interventions that are age-appropriate to delay AD in DS.

Protective effects of carnosine on white matter damage induced by chronic cerebral hypoperfusion

Carnosine is a dipeptide that scavenges free radicals, inhibits inflammation in the central nervous system, and protects against ischemic and hypoxic brain damage through its anti-oxidative and anti-apoptotic actions. Therefore, we hypothesized that carnosine would also protect against white matter damage caused by subcortical ischemic injury. White matter damage was induced by right unilateral common carotid artery occlusion in mice. The animals were treated with 200, 500 or 750 mg/kg carnosine by intraperitoneal injection 30 minutes before injury and every other day after injury. Then, 37 days later, Klüver-Barrera staining, toluidine blue staining and immunofluorescence staining were performed. Carnosine (200, 500 mg/kg) substantially reduced damage to the white matter in the corpus callosum, internal capsule and optic tract, and it rescued expression of myelin basic protein, and alleviated the loss of oligodendrocytes. However, carnosine at the higher dose of 750 mg/kg did not have the same effects as the 200 and 500 mg/kg doses. These findings show that carnosine, at a particular dose range, protects against white matter damage caused by chronic cerebral ischemia in mice, likely by reducing oligodendroglial cell loss.

Oligodendroglial maldevelopment in the cerebellum after postnatal hyperoxia and its prevention by minocycline

According to recent research, brain injury after premature birth often includes impaired growth of the cerebellum. However, causes of cerebellar injury in this population are poorly understood. In this study, we analyzed whether postnatal hyperoxia perturbs white matter development of the cerebellum, and whether cerebellar glial damage can be prevented by minocycline. We used a hyperoxia model in neonatal rats providing 24 h exposure to fourfold increased oxygen concentration (80% O2) from P6 to P7, followed by recovery in room air until P9, P11, P15, P30. Injections with minocycline were performed at the beginning and 12 h into hyperoxia exposure. Hyperoxia induced oxidative stress in the cerebellum at P7 as evidenced by increased nitrotyrosine concentrations. Numbers of proliferating, NG2+Ki67+ oligodendroglial precursor cells were decreased at P7 after hyperoxia and at P11 following recovery in room air. Numbers of mature, CC1+ oligodendrocytes were diminished in recovering hyperoxia rats, and myelin basic protein expression was still decreased at P30. Electron microscopy analysis of myelinated fibers at P30 revealed thinner myelin sheath after hyperoxia. Long-term injury of the cerebellum by neonatal hyperoxia was confirmed by reduced volumes in MRI measurements at P30. In response to 80% O2, expression of platelet-derived growth factor (PDGF)-A was largely reduced in cerebellar tissue and also in cultured cerebellar astrocytes. Treatment with minocycline during hyperoxia prevented oxidative stress, attenuated oligodendroglial injury, and improved astroglial PDGF-A levels. In conclusion, early hyperoxia causes white matter damage in the cerebellum with astroglial dysfunction being involved, and both can be prevented by treatment with minocycline. Neonatal exposure to hyperoxia causes hypomyelination of the cerebellum. Reduced astroglial growth factor production but not microglial inflammation seems to contribute to oligodendroglial damage, and minocycline rescues oligodendroglia development in the cerebellum after hyperoxia.

White matter microstructure abnormalities in pediatric migraine patients

BACKGROUND

Diffusion tensor (DT) magnetic resonance imaging (MRI) provides several quantities with the potential to disclose white matter (WM) microstructural abnormalities. We explored alterations of WM architecture in pediatric migraine patients using DT MRI and two different methods of analysis.

METHODS

Dual-echo and DT MRI scans were acquired from 15 pediatric migraine patients and 15 age-matched controls. Whole-brain voxel-wise comparisons of WM DT MRI abnormalities were performed using tract-based-spatial-statistics (TBSS). A DT probabilistic tractography analysis was also run.

RESULTS

Both TBSS and DT tractography analysis showed that, compared to controls, pediatric migraine patients had significant lower mean (MD), axial (AD) and radial (RD) diffusivity of WM tracts located in the brainstem, thalamus and fronto-temporo-occipital lobes, bilaterally. Patients also experienced increased fractional anisotropy (FA) of the optic radiations. No correlation was found between WM tract abnormalities and disease duration and attack frequency.

CONCLUSIONS

Pediatric migraine patients harbor diffuse brain WM microstructural abnormalities. High FA and low MD, AD and RD in these patients might be explained by repeated neuronal activation, which may lead to cell swelling and stimulate activity-dependent myelin-modulation, or by increased fiber and dendritic densities. Both these mechanisms might reflect a hyperexcitability of the brain in migraineurs.

Diffuse and focal corticospinal tract disease and its impact on patient disability in multiple sclerosis

BACKGROUND AND PURPOSE

We investigated the impact of focal and diffuse corticospinal tracts damage on sensory-motor disability in multiple sclerosis (MS) patients.

METHODS

Twenty-five MS patients underwent 3.0 Tesla (3T) magnetic resonance imaging with diffusion tensor imaging (DTI). The Expanded Disability Status Scale (EDSS) and the Timed 25-Foot Walk test (T25FW) quantified patient physical disability. Fractional anisotropy (FA) and mean diffusivity (MD) of the corticospinal tracts, whole brain and corticospinal tracts lesion volume were also computed. Spearman rank correlation analyses measured the associations between DTI-derived metrics and other measures of disease. Partial correlation analyses between DTI and disability measures were performed and corrected for lesion volumes as appropriate.

RESULTS

Significant associations were seen between FA of the corticospinal tracts and EDSS (r = -.500, P = .0011), motor-EDSS (r = -.519, P = .008), and T25WF (r = -.637, P = .001) scores and MD of the corticospinal tracts and motor-EDSS (r = .469, P = .018) and T25WF (r = .428, P = .033) scores. When correcting for lesion volumes, only the association between FA of the corticospinal tracts and EDSS (r ≤ -.516, p ≤ .01) or motor-EDSS score (r ≤ -.516, p ≤ .01) persisted.

CONCLUSIONS

DTI at 3T shows that the impact of diffuse corticospinal tracts disease on sensory-motor disability is greatly mediated by focal lesions in MS.

Enterovirus infections are associated with white matter damage in neonates

AIM

To explore the imaging findings of neonatal infants infected with enteroviruses.

METHODS

A retrospective study was conducted on 12 patients who were diagnosed with encephalitis caused by enterovirus. Clinical presentation, cranial ultrasonography (cUS), magnetic resonance imaging (MRI) findings and neurodevelopment outcome of 12 cases were analysed.

RESULTS

Twelve infants, with a gestational age of 35 to 39 weeks, presented at 36 to 41 weeks postmenstrual age with clinical symptoms of enterovirus infections. Ten of 12 neonatal infants had a fever and 4 of 12 presented with a sepsis-like illness. cUS in one preterm infant showed periventricular echogenicity. Neonatal MRI confirmed white matter changes in 12 infants. Follow-up of infants were 18 months. Outcome was variable with cerebral palsy in 2 infants and normal neurodevelopment outcome in 10 infants.

CONCLUSIONS

Enterovirus may cause severe central nervous system infection in the neonatal period. The neuroimaging studies are informative and should be a part of care for infants with enteroviruses.

Strategies for myelin regeneration: lessons learned from development

Myelin regeneration is indispensably important for patients suffering from several central nervous system (CNS) disorders such as multiple sclerosis (MS) and spinal cord injury (SCI), because it is not only essential for restoring neurophysiology, but also protects denuded axons for secondary degeneration. Understanding the cellular and molecular mechanisms underlying remyelination is critical for the development of remyelination-specific therapeutic approaches. As remyelination shares certain common mechanisms with developmental myelination, knowledge from study of developmental myelination contributes greatly to emerging myelin regeneration therapies, best evidenced as the recently developed human anti-Nogo receptor interacting protein-1 (LINGO-1) monoclonal antibodies to treat MS patients in clinical trials.

Abnormal heart rate characteristics are associated with abnormal neuroimaging and outcomes in extremely low birth weight infants

OBJECTIVE

Brain injury in preterm infants may lead to an inflammatory response and central nervous system dysfunction reflected by abnormal heart rate characteristics (HRC). We hypothesized that a continuously monitored HRC index reflecting reduced HR variability and decelerations correlates with abnormal neuroimaging and outcomes in extremely low birth weight infants (ELBW).

STUDY DESIGN

We analyzed the average HRC index within 28 days after birth (aHRC28) and head ultrasound (HUS) in 384 ELBW infants. In 50 infants with brain magnetic resonance imaging (MRI) and 70 infants with Bayley neurodevelopmental testing at 1 year of age, we analyzed the relationship between aHRC28, MRI abnormalities and low Bayley scores.

RESULT

aHRC28 was higher in infants with severe HUS abnormalities (2.65±1.27 for Grade III-IV intraventricular hemorrhage (IVH) or cystic periventricular leukomalacia (cPVL) versus 1.72±0.95 for normal or Grade I-II IVH, P<0.001). Higher aHRC28 was also associated with white matter damage on MRI and death or Bayley motor or mental developmental index <70. Associations persisted after adjusting for gestational age, birth weight and septicemia. For every one point increase in aHRC28, the odds ratio of death or Bayley score <70 was 2.45 (95% CI 1.46, 4.05, P<0.001).

CONCLUSION

A continuously monitored HRC index provides an objective, noninvasive measure associated with abnormal brain imaging and adverse neurologic outcomes in ELBW infants.

Mechanism underlying the protective effect of Kaixin Jieyu Fang on vascular depression following cerebral white matter damage

The Chinese compound Kaixin Jieyu Fang can be used to treat vascular depression; however, the underlying mechanism remains unclear. This study established a rat model of chronic cerebral ischemia-caused white matter damage by ligation of the bilateral common carotid arteries. Rats received daily intragastric administration of a suspension of Kaixin Jieyu Fang powder. After 3, 7 and 21 days of treatment, the degree of white matter damage in the cerebral ischemia rat model was alleviated, Bcl-2 protein and mRNA expression in brain tissue increased, and Bax protein and mRNA expression decreased. These results indicate that Kaixin Jieyu Fang can alleviate cerebral white matter damage, and the underlying mechanism is associated with regulation of Bcl-2/Bax protein and mRNA expression, which is one of possible mechanism behind the protective effect of Kaixin Jieyu Fang against vascular depression.

Inhaled NO prevents hyperoxia-induced white matter damage in neonatal rats

White matter damage (WMD) and bronchopulmonary dysplasia (BPD) are the two main complications occurring in very preterm infants. Inhaled nitric oxide (iNO) has been proposed to promote alveolarization in the developing lung, and we have reported that iNO promotes myelination and induces neuroprotection in neonatal rats with excitotoxic brain damage. Our hypothesis is that, in addition to its pulmonary effects, iNO may be neuroprotective in rat pups exposed to hyperoxia. To test this hypothesis, we exposed rat pups to hyperoxia, and we assessed the impact of iNO on WMD and BPD. Rat pups were exposed to either hyperoxia (80% FiO2) or to normoxia for 8 days. Both groups received iNO (5 ppm) or air. We assessed the neurological and pulmonary effects of iNO in hyperoxia-injured rat pups using histological, molecular and behavioral approaches. iNO significantly attenuated the severity of hyperoxia-induced WMD induced in neonatal rats. Specifically, iNO decreased white matter inflammation, cell death, and enhanced the density of proliferating oligodendrocytes and oligodendroglial maturation. Furthermore, iNO triggered an early upregulation of P27kip1 and brain-derived growth factor (BDNF). Whereas hyperoxia disrupted early associative abilities, iNO treatment maintained learning scores to a level similar to that of control pups. In contrast to its marked neuroprotective effects, iNO induced only small and transient improvements of BPD. These findings suggest that iNO exposure at low doses is specifically neuroprotective in an animal model combining injuries of the developing lung and brain that mimicked BPD and WMD in preterm infants.

Mild cognitive impairment in Parkinson's disease is associated with a distributed pattern of brain white matter damage

This study assesses the patterns of gray matter (GM) and white matter (WM) damage in patients with Parkinson's disease and mild cognitive impairment (PD-MCI) compared with healthy controls and cognitively unimpaired PD patients (PD-Cu). Three-dimensional T1-weighted and diffusion tensor (DT) magnetic resonance imaging (MRI) scans were obtained from 43 PD patients and 33 healthy controls. Cognition was assessed using a neuropsychological battery. Tract-based spatial statistics was applied to compare DT MRI indices between groups on a voxel-by-voxel basis. Voxel-based morphometry was performed to assess GM atrophy. Thirty PD patients were classified as MCI. Compared with healthy controls, PD-Cu and PD-MCI patients did not have GM atrophy. No region of WM damage was found in PD-Cu patients when compared with healthy controls. Relative to healthy controls and PD-Cu patients, PD-MCI patients showed a distributed pattern of WM abnormalities in the anterior and superior corona radiata, genu, and body of the corpus callosum, and anterior inferior fronto-occipital, uncinate, and superior longitudinal fasciculi, bilaterally. Subtle cognitive decline in PD is associated with abnormalities of frontal and interhemispheric WM connections, and not with GM atrophy. DT MRI might contribute to the identification of structural changes in PD-MCI patients prior to the development of dementia.