Altered neurodevelopmental DNA methylation status after fetal growth restriction with brain-sparing.

It is under debate how preferential perfusion of the brain (brain-sparing) in fetal growth restriction (FGR) relates to long-term neurodevelopmental outcome. Epigenetic modification of neurotrophic genes by altered fetal oxygenation may be involved. To explore this theory, we performed a follow-up study of 21 FGR children, in whom we prospectively measured the prenatal cerebroplacental ratio (CPR) with Doppler sonography. At 4 years of age, we tested their neurodevelopmental outcome using the Wechsler Preschool and Primary Scale of Intelligence, the Child Behavior Checklist, and the Behavior Rating Inventory of Executive Function. In addition, we collected their buccal DNA to determine the methylation status at predefined genetic regions within the genes hypoxia-inducible factor-1 alpha (HIF1A), vascular endothelial growth factor A (VEGFA), erythropoietin (EPO), EPO-receptor (EPOR), brain-derived neurotrophic factor (BDNF), and neurotrophic tyrosine kinase, receptor, type 2 (NTRK2) by pyrosequencing. We found that FGR children with fetal brain-sparing (CPR <1, n = 8) demonstrated a trend (0.05 < p < 0.1) toward hypermethylation of HIF1A and VEGFA at their hypoxia-response element (HRE) compared with FGR children without fetal brain-sparing. Moreover, in cases with fetal brain-sparing, we observed statistically significant hypermethylation at a binding site for cyclic adenosine monophophate response element binding protein (CREB) of BDNF promoter exon 4 and hypomethylation at an HRE located within the NTRK2 promoter (both p <0.05). Hypermethylation of VEGFA was associated with a poorer Performance Intelligence Quotient, while hypermethylation of BDNF was associated with better inhibitory self-control (both p <0.05). These results led us to formulate the hypothesis that early oxygen-dependent epigenetic alterations due to hemodynamic alterations in FGR may be associated with altered neurodevelopmental outcome in later life. We recommend further studies to test this hypothesis.

Cerebral Autoregulation in Sick Infants: Current Insights.

Cerebrovascular autoregulation is the ability to maintain stable cerebral blood flow within a range of cerebral perfusion pressures. When cerebral perfusion pressure is outside the limits of effective autoregulation, the brain is subjected to hypoperfusion or hyperperfusion, which may cause vascular injury, hemorrhage, and/or hypoxic white matter injury. Infants born preterm, after fetal growth restriction, with congenital heart disease, or with hypoxic-ischemic encephalopathy are susceptible to a failure of cerebral autoregulation. Bedside assessment of cerebrovascular autoregulation would offer the opportunity to prevent brain injury. Clinicians need to know which patient populations and circumstances are associated with impaired/absent cerebral autoregulation.