Mesenchymal Stromal Cell Delivery Via Cardiopulmonary Bypass Provides Neuroprotection in a Juvenile Porcine Model.

Oxidative/inflammatory stresses due to cardiopulmonary bypass (CPB) cause prolonged microglia activation and cortical dysmaturation, thereby contributing to neurodevelopmental impairments in children with congenital heart disease (CHD). This study found that delivery of mesenchymal stromal cells (MSCs) via CPB minimizes microglial activation and neuronal apoptosis, with subsequent improvement of cortical dysmaturation and behavioral alteration after neonatal cardiac surgery. Furthermore, transcriptomic analyses suggest that exosome-derived miRNAs may be the key drivers of suppressed apoptosis and STAT3-mediated microglial activation. Our findings demonstrate that MSC treatment during cardiac surgery has significant translational potential for improving cortical dysmaturation and neurological impairment in children with CHD.

CBP-HSF2 structural and functional interplay in Rubinstein-Taybi neurodevelopmental disorder.

Patients carrying autosomal dominant mutations in the histone/lysine acetyl transferases CBP or EP300 develop a neurodevelopmental disorder: Rubinstein-Taybi syndrome (RSTS). The biological pathways underlying these neurodevelopmental defects remain elusive. Here, we unravel the contribution of a stress-responsive pathway to RSTS. We characterize the structural and functional interaction between CBP/EP300 and heat-shock factor 2 (HSF2), a tuner of brain cortical development and major player in prenatal stress responses in the neocortex: CBP/EP300 acetylates HSF2, leading to the stabilization of the HSF2 protein. Consequently, RSTS patient-derived primary cells show decreased levels of HSF2 and HSF2-dependent alteration in their repertoire of molecular chaperones and stress response. Moreover, we unravel a CBP/EP300-HSF2-N-cadherin cascade that is also active in neurodevelopmental contexts, and show that its deregulation disturbs neuroepithelial integrity in 2D and 3D organoid models of cerebral development, generated from RSTS patient-derived iPSC cells, providing a molecular reading key for this complex pathology.

Impact of Cardiopulmonary Bypass on Neurogenesis and Cortical Maturation.

OBJECTIVE: Neurodevelopmental delays and frontal lobe cortical dysmaturation are widespread among children with congenital heart disease (CHD). The subventricular zone (SVZ) is the largest pool of neural stem/progenitor cells in the postnatal brain. Our aim is to determine the effects of cardiopulmonary bypass (CPB) on neurogenesis and cortical maturation in piglets whose SVZ development is similar to human infants. METHODS: Three-week-old piglets (n = 29) were randomly assigned to control (no surgery), mild-CPB (34°C full flow for 60 minutes) and severe-CPB groups (25°C circulatory-arrest for 60 minutes). The SVZ and frontal lobe were analyzed with immunohistochemistry 3 days and 4 weeks postoperatively. MRI of the frontal lobe was used to assess cortical development. RESULTS: SVZ neurogenic activity was reduced up to 4 weeks after both mild and severe CPB-induced insults. CPB also induced decreased migration of young neurons to the frontal lobe, demonstrating that CPB impairs postnatal neurogenesis. MRI 4 weeks after CPB displayed a decrease in gyrification index and cortical volume of the frontal lobe. Cortical fractional anisotropy was increased after severe CPB injury, indicating a prolonged deleterious impact of CPB on cortical maturation. Both CPB-induced insults displayed a significant change in densities of three major inhibitory neurons, suggesting excitatory-inhibitory imbalance in the frontal cortex. In addition, different CPB insults altered different subpopulations of inhibitory neurons. INTERPRETATION: Our results provide novel insights into cellular mechanisms contributing to CHD-induced neurological impairments. Further refinement of CPB hardware and techniques is necessary to improve long-term frontal cortical dysmaturation observed in children with CHD. ANN NEUROL 2021;90:913-926.

Impact of Mesenchymal Stromal Cell Delivery Through Cardiopulmonary Bypass on Postnatal Neurogenesis.

BACKGROUND: Neurodevelopmental impairment is an important challenge for survivors after neonatal surgery with cardiopulmonary bypass (CPB). The subventricular zone, where most neural stem/progenitors originate, plays a critical role in cortical maturation of the frontal lobe. Promoting neurogenesis in the subventricular zone is therefore a potential therapeutic target for preserving cortical growth. Mesenchymal stromal cells (MSCs) promote endogenous regeneration in the rodent brain. We investigated the impact of MSC delivery through CPB on neural stem/progenitor cells and neuroblasts (ie, young neurons) in the piglet subventricular zone. METHODS: Two-week-old piglets (n = 12) were randomly assigned to one of three groups: (1) control, (2) deep hypothermic circulatory arrest, and (3) circulatory arrest, followed by MSC administration. MSCs (10 × 106 per kg) were delivered through CPB during the rewarming period. Neural stem/progenitors, proliferating cells, and neuroblasts were identified with immunohistochemistry at 3 hours after CPB. RESULTS: CPB-induced insults caused an increased proliferation of neural stem/progenitors (P < .05). MSC delivery reduced the acute proliferation. MSC treatment increased the number of neuroblasts in the outer region of the subventricular zone (P < .05) where they form migrating chains toward the frontal lobe. Conversely, the thickness of the neuroblast-dense band along the lateral ventricle was reduced after treatment (P < .05). These findings suggest that MSC treatment changes neuroblast distribution within the subventricular zone. CONCLUSIONS: MSC delivery through CPB has the potential to mitigate effects of CPB on neural stem/progenitor cells and to promote migration of neuroblasts. Further investigation is necessary to determine the long-term effect of MSC treatment during CPB on postnatal neurogenesis.

Treatment With Tetrahydrobiopterin Improves White Matter Maturation in a Mouse Model for Prenatal Hypoxia in Congenital Heart Disease.

Background Reduced oxygen delivery in congenital heart disease causes delayed brain maturation and white matter abnormalities in utero. No treatment currently exists. Tetrahydrobiopterin (BH4) is a cofactor for neuronal nitric oxide synthase. BH4 availability is reduced upon NOS activation, such as during hypoxic conditions, and leads to toxin production. We hypothesize that BH4 levels are depleted in the hypoxic brain and that BH4 replacement therapy mitigates the toxic effects of hypoxia on white matter. Methods and Results Transgenic mice were used to visualize oligodendrocytes. Hypoxia was introduced during a period of white matter development equivalent to the human third trimester. BH4 was administered during hypoxia. BH4 levels were depleted in the hypoxic brain by direct quantification (n=7-12). The proliferation (n=3-6), apoptosis (n=3-6), and developmental stage (n=5-8) of oligodendrocytes were determined immunohistologically. Total oligodendrocytes increased after hypoxia, consistent with hypoxia-induced proliferation seen previously; however, mature oligodendrocytes were less prevalent in hypoxia, and there was accumulation of immature oligodendrocytes. BH4 treatment improved the mature oligodendrocyte number such that it did not differ from normoxia, and accumulation of immature oligodendrocytes was not observed. These results persisted beyond the initial period of hypoxia (n=3-4). Apoptosis increased with hypoxia but decreased with BH4 treatment to normoxic levels. White matter myelin levels decreased following hypoxia by western blot. BH4 treatment normalized myelination (n=6-10). Hypoxia worsened sensory-motor coordination on balance beam tasks, and BH4 therapy normalized performance (n=5-9). Conclusions Suboptimal BH4 levels influence hypoxic white matter abnormalities. Repurposing BH4 for use during fetal brain development may limit white matter dysmaturation in congenital heart disease.

Cortical Dysmaturation in Congenital Heart Disease.

Congenital heart disease (CHD) is among the most common birth defects. Children with CHD frequently display long-term intellectual and behavioral disability. Emerging evidence indicates that cardiac anomalies lead to a reduction in cerebral oxygenation, which appears to profoundly impact on the maturation of cerebral regions responsible for higher-order cognitive functions. In this review we focus on the potential mechanisms by which dysregulation of cortical neuronal development during early life may lead to the significant cognitive impairments that commonly occur in children with CHD. Further understanding of the mechanisms underlying cortical dysmaturation due to CHD will be necessary to identify strategies for neonatal neuroprotection and for mitigating developmental delays in this patient population.

ADAMTS-4 in oligodendrocytes contributes to myelination with an impact on motor function.

Myelination is a late developmental process regulated by a set of inhibitory and stimulatory factors, including extracellular matrix components. Accordingly, chondroitin sulfate proteoglycans (CSPGs) act as negative regulators of myelination processes. A disintegrin and metalloproteinase with thrombospondin motifs type 4 (ADAMTS-4) is an extracellular protease capable of degrading CSPGs. Although exogenous ADAMTS-4 has been proven to be beneficial in several models of central nervous system (CNS) injuries, the physiological functions of endogenous ADAMTS-4 remain poorly understood. We first used Adamts4/LacZ reporter mice to reveal that ADAMTS-4 is strongly expressed in the CNS, especially in the white matter, with a cellular profile restricted to mature oligodendrocytes. Interestingly, we evidenced an abnormal myelination in Adamts4-/- mice, characterized by a higher diameter of myelinated axons with a shifting g-ratio. Accordingly, lack of ADAMTS-4 is accompanied by motor deficits and disturbed nervous electrical activity. In conclusion, we demonstrate that ADAMTS-4 is a new marker of mature oligodendrocytes contributing to the myelination processes and thus to the control of motor capacities.

Tissue-type plasminogen activator exerts EGF-like chemokinetic effects on oligodendrocytes in white matter (re)myelination.

BACKGROUND: The ability of oligodendrocyte progenitor cells (OPCs) to give raise to myelin forming cells during developmental myelination, normal adult physiology and post-lesion remyelination in white matter depends on factors which govern their proliferation, migration and differentiation. Tissue plasminogen activator (tPA) is a serine protease expressed in the central nervous system (CNS), where it regulates cell fate. In particular, tPA has been reported to protect oligodendrocytes from apoptosis and to facilitate the migration of neurons. Here, we investigated whether tPA can also participate in the migration of OPCs during CNS development and during remyelination after focal white matter lesion. METHODS: OPC migration was estimated by immunohistological analysis in spinal cord and corpus callosum during development in mice embryos (E13 to P0) and after white matter lesion induced by the stereotactic injection of lysolecithin in adult mice (1 to 21 days post injection). Migration was compared in these conditions between wild type and tPA knock-out animals. The action of tPA was further investigated in an in vitro chemokinesis assay. RESULTS: OPC migration along vessels is delayed in tPA knock-out mice during development and during remyelination. tPA enhances OPC migration via an effect dependent on the activation of epidermal growth factor receptor. CONCLUSION: Endogenous tPA facilitates the migration of OPCs during development and during remyelination after white matter lesion by the virtue of its epidermal growth factor-like domain.