Long-term coordinated microstructural disruptions of the developing neocortex and subcortical white matter after early postnatal systemic inflammation.

Severe postnatal systemic infection is highly associated with persistent disturbances in brain development and neurobehavioral outcomes in survivors of preterm birth. However, the contribution of less severe but prolonged postnatal infection and inflammation to such disturbances is unclear. Further, the ability of modern imaging techniques to detect the underlying changes in cellular microstructure of the brain in these infants remains to be validated. We used high-field ex-vivo MRI, neurohistopathology, and behavioral tests in newborn rats to demonstrate that prolonged postnatal systemic inflammation causes subtle, persisting disturbances in brain development, with neurodevelopmental delays and mild motor impairments. Diffusion-tensor MRI and neurite orientation dispersion and density imaging (NODDI) revealed delayed maturation of neocortical and subcortical white matter microstructure. Analysis of pyramidal neurons showed that the cortical deficits involved impaired dendritic arborization and spine formation. Analysis of oligodendrocytes showed that the white matter deficits involved impaired oligodendrocyte maturation and axonal myelination. These findings indicate that prolonged postnatal inflammation, without severe infection, may critically contribute to the diffuse spectrum of brain pathology and subtle long-term disability in preterm infants, with a cellular mechanism involving oligodendrocyte and neuronal dysmaturation. NODDI may be useful for clinical detection of these microstructural deficits.

Genetic and microstructural differences in the cortical plate of gyri and sulci during gyrification in fetal sheep.

Gyrification of the cerebral cortex is a developmentally important process, but the mechanisms that drive cortical folding are not fully known. Theories propose that changes within the cortical plate (CP) cause gyrification, yet differences between the CP below gyri and sulci have not been investigated. Here we report genetic and microstructural differences in the CP below gyri and sulci assessed before (at 70 days of gestational age [GA] 70), during (GA 90), and after (GA 110) gyrification in fetal sheep. The areal density of BDNF, CDK5, and NeuroD6 immunopositive cells were increased, and HDAC5 and MeCP2 mRNA levels were decreased in the CP below gyri compared with sulci during gyrification, but not before. Only the areal density of BDNF-immunopositive cells remained increased after gyrification. MAP2 immunoreactivity and neurite outgrowth were also increased in the CP below gyri compared with sulci at GA 90, and this was associated with microstructural changes assessed via diffusion tensor imaging and neurite orientation dispersion and density imaging at GA 98. Differential neurite outgrowth may therefore explain the localized changes in CP architecture that result in gyrification.

Protocol of changes induced by early Hand-Arm Bimanual Intensive Therapy Including Lower Extremities (e-HABIT-ILE) in pre-school children with bilateral cerebral palsy: a multisite randomized controlled trial.

BACKGROUND: Cerebral palsy (CP), which is the leading cause of motor disability during childhood, can produce sensory and cognitive impairments at different degrees. Most recent therapeutic interventions for these patients have solely focused on upper extremities (UE), although more than 60% of these patients present lower extremities (LE) deficits. Recently, a new therapeutic concept, Hand-arm Bimanual Intensive Therapy Including Lower Extremities (HABIT-ILE), has been proposed, involving the constant stimulation of UE and LE. Based on motor skill learning principles, HABIT-ILE is delivered in a day-camp setting, promoting voluntary movements for several hours per day during 10 consecutive week days. Interestingly, the effects of this intervention in a large scale of youngsters are yet to be observed. This is of interest due to the lack of knowledge on functional, neuroplastic and biomechanical changes in infants with bilateral CP. The aim of this randomized controlled study is to assess the effects of HABIT-ILE adapted for pre-school children with bilateral CP regarding functional, neuroplastic and biomechanical factors. METHODS: This international, multicentric study will include 50 pre-school children with CP from 12 to 60 months of age, comparing the effect of 50 h (2 weeks) of HABIT-ILE versus regular motor activity and/or customary rehabilitation. HABIT-ILE presents structured activities and functional tasks with continuous increase in difficulty while the child evolves. Assessments will be performed at 3 period times: baseline, two weeks later and 3 months later. The primary outcome will be the Gross Motor Function Measure 66. Secondary outcomes will include Both Hands Assessment, Melbourne Assessment-2, Semmes-Weinstein Monofilament Test, algometry assessments, executive function tests, ACTIVLIM-CP questionnaire, Pediatric Evaluation of Disability Inventory (computer adaptative test), Young Children's Participation and Environment Measure, Measure of the Process of Care, Canadian Occupational Performance Measure, neuroimaging and kinematics. DISCUSSION: The results of this study should highlight the impact of a motor, intensive, goal-directed therapy (HABIT-ILE) in pre-school children at a functional, neuroplastic and biomechanical level. In addition, this changes could demonstrated the impact of this intervention in the developmental curve of each child, improving functional ability, activity and participation in short-, mid- and long-term. NAME OF THE REGISTRY: Evaluation of Functional, Neuroplastic and Biomechanical Changes Induced by an Intensive, Playful Early-morning Treatment Including Lower Limbs (EARLY-HABIT-ILE) in Preschool Children With Uni and Bilateral Cerebral Palsy (HABIT-ILE). TRIAL REGISTRATION: NCT04017871 REGISTRATION DATE: July 12, 2019.

Magnetic Resonance Imaging Correlates of White Matter Gliosis and Injury in Preterm Fetal Sheep Exposed to Progressive Systemic Inflammation.

Progressive fetal infection/inflammation is strongly associated with neural injury after preterm birth. We aimed to test the hypotheses that progressively developing fetal inflammation leads to neuroinflammation and impaired white matter development and that the histopathological changes can be detected using high-field diffusion tensor magnetic resonance imaging (MRI). Chronically instrumented preterm fetal sheep at 0.7 of gestation were randomly assigned to receive intravenous saline (control; n = 6) or a progressive infusion of lipopolysaccharide (LPS, 200 ng intravenous over 24 h then doubled every 24 h for 5 days to induce fetal inflammation, n = 7). Sheep were killed 10 days after starting the infusions, for histology and high-field diffusion tensor MRI. Progressive LPS infusion was associated with increased circulating interleukin (IL)-6 concentrations and moderate increases in carotid artery perfusion and the frequency of electroencephalogram (EEG) activity (p < 0.05 vs. control). In the periventricular white matter, fractional anisotropy (FA) was increased, and orientation dispersion index (ODI) was reduced (p < 0.05 vs. control for both). Histologically, in the same brain region, LPS infusion increased microglial activation and astrocyte numbers and reduced the total number of oligodendrocytes with no change in myelination or numbers of immature/mature oligodendrocytes. Numbers of astrocytes in the periventricular white matter were correlated with increased FA and reduced ODI signal intensities. Astrocyte coherence was associated with increased FA. Moderate astrogliosis, but not loss of total oligodendrocytes, after progressive fetal inflammation can be detected with high-field diffusion tensor MRI.

Multimodal MRI Imaging of Apoptosis-Triggered Microstructural Alterations in the Postnatal Cerebral Cortex.

Prematurely born children often develop neurodevelopmental delay that has been correlated with reduced growth and microstructural alterations in the cerebral cortex. Much research has focused on apoptotic neuronal cell death as a key neuropathological features following preterm brain injuries. How scattered apoptotic death of neurons may contribute to microstructural alterations remains unknown. The present study investigated in a rat model the effects of targeted neuronal apoptosis on cortical microstructure using in vivo MRI imaging combined with neuronal reconstruction and histological analysis. We describe that mild, targeted death of layer IV neurons in the developing rat cortex induces MRI-defined metabolic and microstructural alterations including increased cortical fractional anisotropy. Delayed architectural modifications in cortical gray matter and myelin abnormalities in the subcortical white matter such as hypomyelination and microglia activation follow the acute phase of neuronal death and axonal degeneration. These results establish the link between mild cortical apoptosis and MRI-defined microstructure changes that are reminiscent to those previously observed in preterm babies.

Lactoferrin and prematurity: a promising milk protein?

Lactoferrin (Lf) is the major whey protein in milk, with multiple beneficial health effects including direct antimicrobial activities, anti-inflammatory effects, and iron homeostasis. Oral Lf supplementation in human preterm infants has been shown to reduce the incidence of sepsis and necrotizing enterocolitis. In preclinical models of antenatal stress and perinatal brain injury, bovine Lf protected the developing brain from neuronal loss, improved connectivity, increased neurotrophic factors, and decreased inflammation. It also supported brain development and cognition. Further, Lf can prevent preterm delivery by reducing proinflammatory factors and inhibiting premature cervix maturation. We review here the latest research on Lf in the field of neonatology.

Fingolimod protects against neonatal white matter damage and long-term cognitive deficits caused by hyperoxia.

Cerebral white matter injury is a leading cause of adverse neurodevelopmental outcome in prematurely born infants involving cognitive deficits in later life. Despite increasing knowledge about the pathophysiology of perinatal brain injury, therapeutic options are limited. In the adult demyelinating disease multiple sclerosis the sphingosine-1-phosphate (S1P) receptor modulating substance fingolimod (FTY720) has beneficial effects. Herein, we evaluated the neuroprotective potential of FTY720 in a neonatal model of oxygen-toxicity, which is associated with hypomyelination and impaired neuro-cognitive outcome. A single dose of FTY720 (1mg/kg) at the onset of neonatal hyperoxia (24h 80% oxygen on postnatal day 6) resulted in improvement of neuro-cognitive development persisting into adulthood. This was associated with reduced microstructural white matter abnormalities 4 months after the insult. In search of the underlying mechanisms potential non-classical (i.e. lymphocyte-independent) pathways were analysed shortly after the insult, comprising modulation of oxidative stress and local inflammatory responses as well as myelination, oligodendrocyte degeneration and maturation. Treatment with FTY720 reduced hyperoxia-induced oxidative stress, microglia activation and associated pro-inflammatory cytokine expression. In vivo and in vitro analyses further revealed that oxygen-induced hypomyelination is restored to control levels, which was accompanied by reduced oligodendrocyte degeneration and enhanced maturation. Furthermore, hyperoxia-induced elevation of S1P receptor 1 (S1P1) protein expression on in vitro cultured oligodendrocyte precursor cells was reduced by activated FTY720 and protection from degeneration is abrogated after selective S1P1 blockade. Finally, FTY720s' classical mode of action (i.e. retention of immune cells within peripheral lymphoid organs) was analysed demonstrating that FTY720 diminished circulating lymphocyte counts independent from hyperoxia. Cerebral immune cell counts remained unchanged by hyperoxia and by FTY720 treatment. Taken together, these results suggest that beneficial effects of FTY720 in neonatal oxygen-induced brain injury may be rather attributed to its anti-oxidative and anti-inflammatory capacity acting in concert with a direct protection of developing oligodendrocytes than to a modulation of peripheral lymphocyte trafficking. Thus, FTY720 might be a potential new therapeutic option for the treatment of neonatal brain injury through reduction of white matter damage.

MRI of animal models of developmental disorders and translation to human imaging.

PURPOSE OF REVIEW: In order to understand the pathophysiological mechanisms leading to the specific brain alterations observed in immature newborn babies, preclinical studies on animal models mimicking clinical reality are mandatory and are ideally coupled with imaging modalities transferable to the human scenario. The availability of MRI techniques on both clinical and animal scanners allows this methodological transfer from bench to bedside. The aim of this review is to give an overview of the recent findings in MRI of animal models of developmental disorders and emphasize what we can learn from MRI on these models. RECENT FINDINGS: Progress in newborn medicine has allowed the survival of increasingly immature newborns that is often associated with specific morbidities. The brain in particular shows developmentally linked vulnerability leading to specific brain injury and subsequent developmental disorders. MRI delivers a large amount of anatomical, microstructural and functional information and has been widely used to monitor cerebral development and characterize the specificity of brain lesions in the immature brain in humans and animal models. SUMMARY: In this review, we will present the different animal models assessed by magnetic resonance techniques and the histopathological correlations observed, as well as the implications for human imaging.

Definition and quantification of acute inflammatory white matter injury in the immature brain by MRI/MRS at high magnetic field.

BACKGROUND: Lipopolysaccharide (LPS) injection in the corpus callosum (CC) of rat pups results in diffuse white matter injury similar to the main neuropathology of preterm infants. The aim of this study was to characterize the structural and metabolic markers of acute inflammatory injury by high-field magnetic resonance imaging (MRI) magnetic resonance spectroscopy (MRS) in vivo. METHODS: Twenty-four hours after a 1-mg/kg injection of LPS in postnatal day 3 rat pups, diffusion tensor imaging and proton nuclear magnetic spectroscopy ((1)H NMR) were analyzed in conjunction to determine markers of cell death and inflammation using immunohistochemistry and gene expression. RESULTS: MRI and MRS in the CC revealed an increase in lactate and free lipids and a decrease of the apparent diffusion coefficient. Detailed evaluation of the CC showed a marked apoptotic response assessed by fractin expression. Interestingly, the degree of reduction in the apparent diffusion coefficient correlated strongly with the natural logarithm of fractin expression, in the same region of interest. LPS injection further resulted in increased activated microglia clustered in the cingulum, widespread astrogliosis, and increased expression of genes for interleukin (IL)-1, IL-6, and tumor necrosis factor. CONCLUSION: This model was able to reproduce the typical MRI hallmarks of acute diffuse white matter injury seen in preterm infants and allowed the evaluation of in vivo biomarkers of acute neuropathology after inflammatory challenge.

Protective effects of maternal nutritional supplementation with lactoferrin on growth and brain metabolism.

BACKGROUND: Intrauterine growth restriction (IUGR) is a major risk factor for both perinatal and long-term morbidity. Bovine lactoferrin (bLf) is a major milk glycoprotein considered as a pleiotropic functional nutrient. The impact of maternal supplementation with bLf on IUGR-induced sequelae, including inadequate growth and altered cerebral development, remains unknown. METHODS: IUGR was induced through maternal dexamethasone infusion (100 µg/kg during last gestational week) in rats. Maternal supplementation with bLf (0.85% in food pellet) was provided during both gestation and lactation. Pup growth was monitored, and Pup brain metabolism and gene expression were studied using in vivo (1)H NMR spectroscopy, quantitative PCR, and microarray in the hippocampus at postnatal day (PND)7. RESULTS: Maternal bLf supplementation did not change gestational weight but increased the birth body weight of control pups (4%) with no effect on the IUGR pups. Maternal bLf supplementation allowed IUGR pups to recover a normalized weight at PND21 (weaning) improving catch-up growth. Significantly altered levels of brain metabolites (γ-aminobutyric acid, glutamate, N-acetylaspartate, and N-acetylaspartylglutamate) and transcripts (brain-derived neurotrophic factor (BDNF), divalent metal transporter 1 (DMT-1), and glutamate receptors) in IUGR pups were normalized with maternal bLf supplementation. CONCLUSION: Our data suggest that maternal bLf supplementation is a beneficial nutritional intervention able to revert some of the IUGR-induced sequelae, including brain hippocampal changes.

Changes Induced by Early Hand-Arm Bimanual Intensive Therapy Including Lower Extremities in Young Children With Unilateral Cerebral Palsy: A Randomized Clinical Trial.

Importance: Intensive interventions are provided to young children with unilateral cerebral palsy (UCP), classically focused on the upper extremity despite the frequent impairment of gross motor function. Hand-Arm Bimanual Intensive Therapy Including Lower Extremities (HABIT-ILE) effectively improves manual dexterity and gross motor function in school-aged children. Objective: To verify if HABIT-ILE would improve manual abilities in young children with UCP more than usual motor activity. Design, Setting, and Participants: This prospective randomized clinical trial (November 2018 to December 2021), including 2 parallel groups and a 1:1 allocation, recruitment took place at European university hospitals, cerebral palsy specialized centers, and spontaneous applications at 3 sites: Brussels, Belgium; Brest, France; and Pisa, Italy. Matched (age at inclusion, lesion type, cause of cerebral palsy, and affected side) pairs randomization was performed. Young children were assessed at baseline (T0), 2 weeks after baseline (T1), and 3 months after baseline (T2). Health care professionals and assessors of main outcomes were blinded to group allocation. At least 23 young children (in each group) aged 12 to 59 months with spastic/dyskinetic UCP and able to follow instructions were needed. Exclusion criteria included uncontrolled seizures, scheduled botulinum toxin injections, orthopedic surgery scheduled during the 6 months before or during the study period, severe visual/cognitive impairments, or contraindications to magnetic resonance imaging. Interventions: Two weeks of usual motor activity including usual rehabilitation (control group) vs 2 weeks (50 hours) of HABIT-ILE (HABIT-ILE group). Main Outcomes and Measures: Primary outcome: Assisting Hand Assessment (AHA); secondary outcomes: Gross Motor Function Measure-66 (GMFM-66), Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT), and Canadian Occupational Performance Measure (COPM). Results: Of 50 recruited young children (26 girls [52%], median age; 35.3 months for HABIT-ILE group; median age, 32.8 months for control group), 49 were included in the final analyses. Change in AHA score from T0 to T2 was significantly greater in the HABIT-ILE group (adjusted mean score difference [MD], 5.19; 95% CI, 2.84-7.55; P < .001). Changes in GMFM-66 (MD, 4.72; 95% CI, 2.66-6.78), PEDI-CAT daily activities (MD, 1.40; 95% CI, 0.29-2.51), COPM performance (MD, 3.62; 95% CI, 2.91-4.32), and satisfaction (MD, 3.53; 95% CI, 2.70-4.36) scores were greater in the HABIT ILE group. Conclusions and Relevance: In this clinical trial, early HABIT-ILE was shown to be an effective treatment to improve motor performance in young children with UCP. Moreover, the improvements had an impact on daily life activities of these children. Trial registration: ClinicalTrials.gov Identifier: NCT04020354.

Investigation of field and diffusion time dependence of the diffusion-weighted signal at ultrahigh magnetic fields.

Over the last decade, there has been a significant increase in the number of high-magnetic-field MRI magnets. However, the exact effect of a high magnetic field strength (B0 ) on diffusion-weighted MR signals is not yet fully understood. The goal of this study was to investigate the influence of different high magnetic field strengths (9.4 T and 14.1 T) and diffusion times (9, 11, 13, 15, 17 and 24 ms) on the diffusion-weighted signal in rat brain white matter. At a short diffusion time (9 ms), fractional anisotropy values were found to be lower at 14.1 T than at 9.4 T, but this difference disappeared at longer diffusion times. A simple two-pool model was used to explain these findings. The model describes the white matter as a first hindered compartment (often associated with the extra-axonal space), characterized by a faster orthogonal diffusion and a lower fractional anisotropy, and a second restricted compartment (often associated with the intra-axonal space), characterized by a slower orthogonal diffusion (i.e. orthogonal to the axon direction) and a higher fractional anisotropy. Apparent T2 relaxation time measurements of the hindered and restricted pools were performed. The shortening of the pseudo-T2 value from the restricted compartment with B0 is likely to be more pronounced than the apparent T2 changes in the hindered compartment. This study suggests that the observed differences in diffusion tensor imaging parameters between the two magnetic field strengths at short diffusion time may be related to differences in the apparent T2 values between the pools.

Brain imaging and human nutrition: which measures to use in intervention studies?

The present review describes brain imaging technologies that can be used to assess the effects of nutritional interventions in human subjects. Specifically, we summarise the biological relevance of their outcome measures, practical use and feasibility, and recommended use in short- and long-term nutritional studies. The brain imaging technologies described consist of MRI, including diffusion tensor imaging, magnetic resonance spectroscopy and functional MRI, as well as electroencephalography/magnetoencephalography, near-IR spectroscopy, positron emission tomography and single-photon emission computerised tomography. In nutritional interventions and across the lifespan, brain imaging can detect macro- and microstructural, functional, electrophysiological and metabolic changes linked to broader functional outcomes, such as cognition. Imaging markers can be considered as specific for one or several brain processes and as surrogate instrumental endpoints that may provide sensitive measures of short- and long-term effects. For the majority of imaging measures, little information is available regarding their correlation with functional endpoints in healthy subjects; therefore, imaging markers generally cannot replace clinical endpoints that reflect the overall capacity of the brain to behaviourally respond to specific situations and stimuli. The principal added value of brain imaging measures for human nutritional intervention studies is their ability to provide unique in vivo information on the working mechanism of an intervention in hypothesis-driven research. Selection of brain imaging techniques and target markers within a given technique should mainly depend on the hypothesis regarding the mechanism of action of the intervention, level (structural, metabolic or functional) and anticipated timescale of the intervention's effects, target population, availability and costs of the techniques.

Low-molecular weight sulfated marine polysaccharides: Promising molecules to prevent neurodegeneration in mucopolysaccharidosis IIIA?

Mucopolysaccharidosis IIIA is a hereditary disease caused by mutations in the sulfamidase enzyme that participates in catabolism of heparan sulfate (HS), leading to HS fragment accumulation and multisystemic failure. No cure exists and death occurs around the second decade of life. Two low molecular weight highly sulfated compounds derived from marine diabolican and infernan exopolysaccharides (A5_3 and A5_4, respectively) with heparanase inhibiting properties were tested in a MPSIIIA cell line model, resulting in limited degradation of intracellular HS. Next, we observed the effects of intraperitoneal injections of the diabolican derivative A5_3 from 4 to 12 weeks of age on MPSIIIA mice. Brain metabolism and microstructure, levels of proteins and genes involved in MPSIIIA brain pathophysiology were also investigated. 1H-Magnetic Resonance Spectroscopy (MRS) indicated deficits in energetic metabolism, tissue integrity and neurotransmission at both 4 and 12 weeks in MPSIIIA mice, with partial protective effects of A5_3. Ex-vivo Diffusion Tensor Imaging (DTI) showed white matter microstructural damage in MPSIIIA, with noticeable protective effects of A5_3. Protein and gene expression assessments displayed both pro-inflammatory and pro-apoptotic profiles in MPSIIIA mice, with benefits of A5_3 counteracting neuroinflammation. Overall, derivative A5_3 was well tolerated and was shown to be efficient in preventing brain metabolism failure and inflammation, resulting in preserved brain microstructure in the context of MPSIIIA.

In vivo assessment of myelination by phase imaging at high magnetic field.

The present study evaluated the potential of using the phase of T2* weighted MR images to characterize myelination during brain development and pathology in rodents at 9.4 T. Phase contrast correlated with myelin content assessed by histology and suggests that most contrast between white and cortical gray matter is modulated by myelin. Ex vivo experiments showed that gray-white matter phase contrast remains unchanged after iron extraction. In dysmyelinated shiverer mice, phase imaging correlated strongly with myelin staining, showing reduced contrast between white and gray matter when compared to healthy controls. We conclude that high-resolution phase images, acquired at high field, allow assessment of myelination and dysmyelination.

Delayed cortical impairment following lipopolysaccharide exposure in preterm fetal sheep.

OBJECTIVE: Preterm infants exhibit chronic deficits in white matter (WM) and cortical maturation. Although fetal infection/inflammation may contribute to WM pathology, the factors contributing to cortical changes are largely unknown. We examined the effect of fetal lipopolysaccharide (LPS) exposure on WM and cortical development as assessed by magnetic resonance imaging (MRI), electroencephalography (EEG), and histopathology in fetal sheep at preterm human equivalent age. METHODS: LPS was administered to fetal sheep at 102.5 ± 0.5 days of gestation. Continuous biophysical recordings were analyzed for 10 days after LPS. At postmortem, measurement of cerebral WM and cortical tissue volumes was achieved by stereological techniques. Specific effects of LPS on MRI-assessed T(1)-weighted and T(2)-weighted images, and immunohistochemical expression of oligodendrocytes, proliferating cells, cortical NeuN-positive and Nurr1-positive neurons (subplate marker), and cell death mechanisms were examined. RESULTS: We observed reductions in WM (~21%; LPS, 1.19 ± 0.04 vs control, 1.51 ± 0.07 cm(3); p < 0.001) and cortical (~18%; LPS, 2.34 ± 0.10 vs control, 2.85 ± 0.07 cm(3); p < 0.001) volumes, associated with overt and diffuse WM injury, T(1)-/T(2) -weighted signal alterations, and reduced numbers of WM oligodendrocytes (LPS, 485 ± 31 vs control, 699 ± 69 cells/mm(2); p = 0.0189) and NeuN-positive (LPS, 421 ± 71 vs control 718 ± 92 cells/mm(2); p = 0.04) and Nurr1-positive (control, 2.5 ± 0.6 vs LPS, 0.6 ± 0.1 cells/mm(2); p = 0.007) cortical neurons after LPS. Moreover, there was loss of the normal maturational increase in cortical EEG amplitude, which correlated with reduced cortical volumes. INTERPRETATION: Fetal exposure to LPS prior to myelination onset can impair both white matter and cortical development in a preclinical large animal model, supporting a role for maternal/fetal infection in the pathogenesis of preterm brain injury.

High-field diffusion tensor imaging characterization of cerebral white matter injury in lipopolysaccharide-exposed fetal sheep.

BACKGROUND: In gyrencephalic species such as sheep, precise anatomical and microstructural characterization of the consequences of fetal inflammation remains scarce. The goal of this study was to characterize changes in white matter (WM) structure using advanced magnetic resonance imaging (MRI) following lipopolysaccharide (LPS) exposure in the preterm-equivalent fetal sheep. METHODS: Preterm (0.7 gestation) fetal sheep received vehicle (Sham group) or LPS (LPS group), and fetal brains were collected 10 d later for subsequent ex vivo MRI. T1-weighted (T(1)W), T2-weighted (T(2)W), and diffusion tensor imaging (DTI) data were collected. RESULTS: Fetuses exposed to LPS exhibited reductions in WM volume and corpus callosum thickness at 10 d recovery. Characteristic patterns of diffuse and focal WM lesions (necrosis or cysts) could be identified by various T1, T2, and DTI signal changes. CONCLUSION: Fetal LPS exposure induces a pattern of injury characterized by diffuse and focal WM injury that closely reproduces that observed clinically in preterm infants. This work provides anatomical and microstructural MRI assessment, as well as histopathological correlates, of the consequences of LPS exposure in an animal model with a WM structure similar to that of the human brain. This work will help to further our understanding of MRI changes in preterm infants.

Early neurodevelopmental reflex impairments in a rodent model of cerebral palsy.

Cerebral palsy (CP) causes sensorimotor disabilities due to injury to the developing brain. Experimental models do not always induce the CP phenotype completely. Early neurological assessment predicts future impairments and is valuable during development. Using a rodent model characterized by brain injury caused by maternal inflammation and perinatal anoxia, and sensorimotor restriction (experimental cerebral palsy [ECP]), we describe early neurodevelopmental delays by assessing reflexes in a stage corresponding to the brain development of term infants (Postnatal Day [P] 8 in rats). Pregnant Wistar rats were injected with lipopolysaccharide (LPS; 200 µg/kg) (n = 6) or saline (n = 4) on Embryonic Days 18/19. Following delivery, 87 male and female pups were used. At P0, injured animals were exposed to anoxia for 20'. From P2 to P21, ECP rats were subjected to hindlimb movement restriction for 16 h/day. ECP group had impaired righting reflex and negative geotaxis and, interestingly, performed home bedding test better than controls. From P7, ECP animals showed decreased body weight compared with controls. Overall, data provide evidence showing that this CP model based on the association of brain damage followed by sensorimotor restriction mimics CP delays and highlights the valuable information given by early neurological assessment during the establishment of the CP phenotype.

Altered trajectory of neurodevelopment associated with fetal growth restriction.

Fetal growth restriction (FGR) is principally caused by suboptimal placental function. Poor placental function causes an under supply of nutrients and oxygen to the developing fetus, restricting development of individual organs and overall growth. Estimated fetal weight below the 10th or 3rd percentile with uteroplacental dysfunction, and knowledge regarding the onset of growth restriction (early or late), provide diagnostic criteria for fetuses at greatest risk for adverse outcome. Brain development and function is altered with FGR, with ongoing clinical and preclinical studies elucidating neuropathological etiology. During the third trimester of pregnancy, from ~28 weeks gestation, neurogenesis is complete and neuronal complexity is expanding, through axonal and dendritic outgrowth, dendritic branching and synaptogenesis, accompanied by myelin production. Fetal compromise over this period, as occurs in FGR, has detrimental effects on these processes. Total brain volume and grey matter volume is reduced in infants with FGR, first evident in utero, with cortical volume particularly vulnerable. Imaging studies show that cerebral morphology is disturbed in FGR, with altered cerebral cortex, volume and organization of brain networks, and reduced connectivity of long- and short-range circuits. Thus, FGR induces a deviation in brain development trajectory affecting both grey and white matter, however grey matter volume is preferentially reduced, contributed by cell loss, and reduced neurite outgrowth of surviving neurons. In turn, cell-to-cell local networks are adversely affected in FGR, and whole brain left and right intrahemispheric connections and interhemispheric connections are altered. Importantly, disruptions to region-specific brain networks are linked to cognitive and behavioral impairments.

Longitudinal MR assessment of hypoxic ischemic injury in the immature rat brain.

Extremely preterm infants commonly show brain injury with long-term structural and functional consequences. Three-day-old (P3) rat pups share some similarities in terms of cerebral development with the very preterm infant (born at 24-28 weeks of gestation). The aim of this study was to assess longitudinally the cerebral structural and metabolic changes resulting from a moderate neonatal hypoxic ischemic injury in the P3 rat pup using high-field (9.4 T) MRI and localized (1) H magnetic resonance spectroscopy techniques. The rats were scanned longitudinally at P3, P4, P11, and P25. Volumetric measurements showed that the percentage of cortical loss in the long term correlated with size of damage 6 h after hypoxia-ischemia, male pups being more affected than female. The neurochemical profiles revealed an acute decrease of most of metabolite concentrations and an increase in lactate 24 h after hypoxia-ischemia, followed by a recovery phase leading to minor metabolic changes at P25 in spite of an abnormal brain development. Further, the increase of lactate concentration at P4 correlated with the cortical loss at P25, giving insight into the early prediction of long-term cerebral alterations following a moderate hypoxia-ischemia insult that could be of interest in clinical practice.