There are no clinically relevant treatments available that improve function in the growing population of very preterm infants (<32 weeks gestation) with neonatal brain injury. Diffuse white matter injury (DWMI) is a common finding in these children and results in chronic neurodevelopmental impairments1,2. As shown recently, failure in oligodendrocyte progenitor cell maturation contributes to DWMI3. In a previous study, we demonstrated that epidermal growth factor receptor (EGFR) plays an important role in oligodendrocyte development4. Here, we examine whether enhanced epidermal growth factor receptor (EGFR) signaling stimulates the endogenous response of EGFR-expressing progenitor cells during a critical period after brain injury, and promotes cellular and behavioral recovery in the developing brain. Using an established model of very preterm brain injury, we demonstrate that selective overexpression of human (h)EGFR in oligodendrocyte lineage cells or the administration of intranasal heparin binding EGF immediately after injury decreases oligodendroglia death, enhances generation of new oligodendrocytes from progenitor cells (OPCs) and promotes functional recovery. Furthermore, these interventions diminish ultrastructural abnormalities and alleviate behavioral deficits on white matter-specific paradigms. Inhibition of EGFR signaling with a molecularly targeted agent used for cancer therapy demonstrates that EGFR activation is an important contributor to oligodendrocyte regeneration and functional recovery after DWMI. Thus, our study provides direct evidence that targeting EGFR in OPCs at a specific time after injury is clinically feasible and applicable for the treatment of premature children with white matter injury.

Diffuse white matter injury (DWMI), a leading cause of neurodevelopmental disabilities in preterm infants, is characterized by reduced oligodendrocyte formation. Oligodendrocyte precursor cells (NG2-cells) are exposed to various extrinsic regulatory signals, including the neurotransmitter GABA. We investigated GABAergic signaling to cerebellar white matter NG2-cells in a mouse model of DWMI (chronic neonatal hypoxia). We found that hypoxia caused a loss of GABAA receptor-mediated synaptic input to NG2-cells, extensive proliferation of these cells and delayed oligodendrocyte maturation, leading to dysmyelination. Treatment of control mice with a GABAA receptor antagonist or deletion of the chloride-accumulating transporter NKCC1 mimicked the effects of hypoxia. Conversely, blockade of GABA catabolism or GABA uptake reduced NG2-cell numbers and increased the formation of mature oligodendrocytes both in control and hypoxic mice. Our results indicate that GABAergic signaling regulates NG2-cell differentiation and proliferation in vivo, and suggest that its perturbation is a key factor in DWMI.

Every year in the United States, an estimated 500,000 babies are born preterm (before 37 completed weeks of gestation), and this number is rising, along with the recognition of brain injuries due to preterm delivery. A common underlying pathogenesis appears to be perinatal hypoxia induced by immature lung development, which causes injury to vulnerable neurons and glia. Abnormal growth and maturation of susceptible cell types, particularly neurons and oligodendrocytes, in preterm babies with very low birth weight is associated with decreased cerebral and cerebellar volumes and increases in cerebral ventricular size. Here we reconcile these observations with recent studies using models of perinatal hypoxia that show perturbations in the maturation and function of interneurons, oligodendrocytes and astroglia. Together, these findings suggest that the global mechanism by which perinatal hypoxia alters development is through a delay in maturation of affected cell types, including astroglia, oligodendroglia and neurons.

Long-term potentiation (LTP) is a cellular model for persistent synaptic plasticity in the mammalian brain. Like several forms of memory, long-lasting LTP requires cAMP-mediated activation of protein kinase A (PKA) and is dependent on gene transcription. Consequently, activity-dependent genes such as c-fos that contain cAMP response elements (CREs) in their 5' regulatory region have been studied intensely. More recently, arg3.1/arc became of interest, because after synaptic stimulation, arg3.1/arc mRNA is rapidly induced and distributed to dendritic processes and may be locally translated there to facilitate synapse-specific modifications. However, to date nothing is known about the signaling mechanisms involved in the induction of this gene. Here we report that arg3.1/arc is robustly induced with LTP stimulation even at intensities that are not sufficient to activate c-fos expression. Unlike c-fos, the 5' regulatory region of arg3.1/arc does not contain a CRE consensus sequence and arg3.1/arc is unresponsive to cAMP in NIH3T3 and Neuro2a cells. However, in PC12 cells and primary cultures of hippocampal neurons, arg3.1/arc can be induced by cAMP and calcium. This induction requires the activity of PKA and mitogen-activated protein kinase, suggesting a neuron-specific pathway for the activation of arg3.1/arc expression.

The human cerebellum has a protracted developmental timeline compared to the neocortex, expanding the window of vulnerability to neurological disorders. As the cerebellum is critical for motor behavior, it is not surprising that most neurodevelopmental disorders share motor deficits as a common sequela. However, evidence gathered since the late 80's suggests that the cerebellum is involved in motor as well as non-motor function, including cognition and emotion. More recently, evidence indicates that major neurodevelopmental disorders such as intellectual disability, autism spectrum disorder, attention-deficit hyperactivity disorder, and Down syndrome have potential links to abnormal cerebellar development. Out of recent findings from clinical and preclinical studies the concept of the 'cerebellar connectome' has emerged that can be used as a framework to link the role of cerebellar development to human behavior, disease states, and the design of better therapeutic strategies.

We show that during formation of the mouse barrel cortex, NG2 cells receive glutamatergic synapses from thalamocortical fibers and preferentially accumulate along septa separating the barrels. Sensory deprivation reduces thalamocortical inputs on NG2 cells and increases their proliferation, leading to a more uniform distribution within the deprived barrels. Therefore, early sensory experience regulates thalamocortical innervation on NG2 cells, as well as their proliferation and distribution during development.

Diffuse white matter injury (DWMI) caused by hypoxia is associated with permanent neurodevelopmental disabilities in preterm infants. The cellular and molecular mechanisms producing DWMI are poorly defined. Using a mouse model of neonatal hypoxia, we demonstrate a biphasic effect on oligodendrocyte development, resulting in hypomyelination. Oligodendrocyte death and oligodendrocyte progenitor cell (OPC) proliferation during the week after hypoxia were followed by delayed oligodendrocyte differentiation and abnormal myelination, as demonstrated by electron microscopy. Cdk2 activation was essential for the regenerative OPC response after hypoxia and was accompanied by reduced FoxO1-dependent p27 Kip1 expression. p27 Kip1 was also reduced in OPCs in human infant white matter lesions after hypoxia. The negative effects of hypoxia on oligodendrogenesis and myelination were more pronounced in p27 Kip1-null mice; conversely, overexpression of FoxO1 or p27 Kip1 in OPCs after hypoxia promoted oligodendrogenesis. Our studies demonstrate for the first time that neonatal hypoxia affects the Foxo1/p27 Kip1 pathway during white matter development. We also show that molecular manipulation of this pathway enhances oligodendrocyte regeneration during a critical developmental time window after DWMI. Thus, FoxO1 and p27 Kip1 may serve as promising target molecules for promoting timely oligodendrogenesis in neonatal DWMI.

Background Neurodevelopmental delays in motor skills and white matter (WM) injury have been documented in congenital heart disease (CHD) and after pediatric cardiac surgery. The lack of a suitable animal model has hampered our understanding of the cellular mechanisms underlying WM injury in these patients. Our aim is to identify an optimal surgical strategy for WM protection to reduce neurological injury in CHD patients. Methods and Results We developed a porcine cardiopulmonary bypass (CPB) model, which displays area dependent WM maturation. In this model, WM injury was identified following CPB-induced ischemia-reperfusion injury. The degree of injury was inversely correlated with the maturation stage, indicating maturation-dependent vulnerability of WM. Within different oligodendrocyte (OL) developmental stages, we show selective vulnerability of O4+ pre-OLs, while OL progenitor cells (OPCs) were resistant to insults. This indicates that immature WM is vulnerable to CPB-induced injury, but has an intrinsic potential for recovery mediated by endogenous OPCs. OPC number decreased with age, suggesting that earlier repair allows successful WM development. OPC proliferation was observed within a few days after CPB-induced ischemia-reperfusion injury; however by four weeks arrested OL maturation and delayed myelination were detected. Logistic model confirmed that maintaining higher oxygenation and reducing inflammation were effective in minimizing the risk of injury at immature stages of WM development. Conclusions Primary repair in neonates and young infants potentially provides successful WM development in CHD patients. Cardiac surgery during this susceptible period should avoid ischemia-reperfusion injury and minimize inflammation to prevent long-term WM-related neurological impairment.