Hypoxic-Ischaemic Encephalopathy and the Blood-Brain Barrier in Neonates

This review aims to highlight a possible relationship between hypoxic-ischaemic encephalopathy (HIE) and the disruption of the blood-brain barrier (BBB). Inflammatory reactions perpetuate a large proportion of cerebral injury. The extent of injury noted in HIE is not only determined by the biochemical cascades that trigger the apoptosis-necrosis continuum of cell death in the brain parenchyma, but also by the breaching of the BBB by pro-inflammatory factors. We examine the changes that contribute to the breakdown of the BBB that occur during HIE at a macroscopic, cellular, and molecular level. The BBB is a permeability barrier which separates a large majority of brain areas from the systemic circulation. The concept of a physiological BBB is based at the anatomical level on the neurovascular unit (NVU). The NVU consists of various cellular components that jointly regulate the exchanges that occur at the interface between the systemic circulation and the brain parenchyma. There is increased understanding of the contribution of the components of the NVU, e.g., astrocytes and pericytes, to the maintenance of this physiological barrier. We also explore the development of therapeutic options in HIE, such as harnessing the transport systems in the BBB, to enable the delivery of large molecules with molecular Trojan horse technology, and the reinforcement of the physical barrier with cell-based therapy which utilizes endothelial progenitor cells and stem cells.