Hypoxic-ischemic encephalopathy (HIE), a brain injury that occurs when infants do not get enough blood flow or oxygen to the brain, is a leading cause of neonatal mortality and morbidity worldwide. Therapeutic hypothermia (TH) is the current standard of care for newborns with HIE, but TH is only available in high-resource settings and only provides partial neuroprotection. Thus, the search for additional neuroprotective treatments is critical. The ferret provides an excellent model for investigating novel treatments for HIE as, unlike rodents, it has a gyrified brain and gray-to-white matter ratio that is like humans. Previous research has shown that the ferret brain is resilient to brain injury, requiring additional hypoxia periods and increased pro-inflammatory stimuli to create the same injury as in rats. However, no previous studies have evaluated why the ferret brain is so resilient. This study will use live rat and ferret organotypic brain slices to investigate this resiliency. Whole hemisphere brain slices from postnatal day (P)10-12 rats and P21-23 ferret, equivalent to term gestation in humans, will be collected. The slices will be randomized to oxygen-glucose deprivation (OGD) injury, to mimic HIE, or control groups. OGD slices will be in 0% oxygen for 2 hours, resulting in partial, but not total, cell death. Subsequent analyses will assess transcriptomics using NanoString nCounter technology, which provides a neuropathology panel of 770 genes, as well as cell-specific regional death in brain regions affected by HIE: hippocampus, cortex, corpus callosum, subcortical white matter, basal ganglia, and thalamus. Preliminary results show that genes such as UCHL1 and TLR4, both associated with injury, are upregulated in ferret OGD slices, but rat data are currently incomplete. Identifying the pathways associated with the resiliency of the ferret brain to injury at the transcriptome level could inform future therapies to treat infants at risk for HIE.

The period around birth is when neonates are at the highest risk of neurological injury or death. A common neonatal neurological injury is hypoxic-ischemic encephalopathy (HIE), which occurs after the brain does not receive enough oxygen or blood flow. There is a large disparity in the severity and long-term neurodevelopmental outcomes of HIE between high-income countries (HICs) and low-and-middle income countries (LMICs). In HICs, HIE occurs in 1-4 neonates per 1,000 births. In LMICs, the instance of HIE is at least 2-3 times higher. Furthermore, cases of HIE seen in LMICs suggest a different type of injury - a more prolonged intermittent injury resulting in white matter injury - compared to HIE in high-income countries that is more acute and affects the deep grey matter. Therapeutic hypothermia (TH) has been the standard of care for HIE in HICs; however, TH is not an effective treatment for HIE in LMICs. Thus, the creation of alternative and accessible therapies for HIE in LMICs is crucial. This study will seek to model HIE as seen in LMICs through an in vitro ferret model that may be used to pilot therapies before applying them to in vivo models. Organotypic brain slices from postnatal day (P) 21 ferrets, equivalent to a term neonate, will be cultured and randomized to receive increasing intervals of oxygen glucose deprivation (OGD), with and without serum deprivation. Serum deprivation is defined as culturing in 2.5% serum as opposed to the standard 5% to mimic certain aspects of malnutrition that may be more common in LMICs. Cell death and white matter injury will be assessed 24 hours after OGD. We hypothesize that slices with more rounds of intermittent OGD and serum deprivation will display relatively more cell death and white matter injury, thus serving as a model of HIE in LMICs.