Neonatal hypoxic-ischemic encephalopathy (HIE) occurs when the brain receives insufficient oxygen and blood supply before or during childbirth. HIE is a leading cause of neonatal mortality and morbidity that may also affect later brain development, specifically gyrification - folding of the cerebral cortex creating gyri and sulci. The nonhuman primate (NHP) brain is gyrified, similar to humans, making NHPs a highly translatable model to examine brain development after injury, which has not been well-studied in HIE. In our nonhuman primate (NHP) model of neonatal HIE, we induced injury through in utero umbilical cord occlusion (UCO) for 20 minutes, mimicking the cause of HIE in humans. Twenty-two term-equivalent pigtailed macaques (Macaca nemestrina) underwent UCO and were randomized to no treatment (n = 11) or treatment with therapeutic hypothermia and erythropoietin (TH + Epo [5x1000 U/kg]; n = 11), while non-UCO animals served as controls (n = 7). All animals were delivered via cesarian section. Injury severity was determined by physiological parameters (Apgar score), lactate, and pH levels after resuscitation. To evaluate the impact of injury on gyrification, we will utilize magnetic resonance imaging (MRI) taken 6-months post-injury to measure the gyrification index (GI). GI will be calculated by taking brain’s inner-to-outer hemispheric ratio; the inner trace following the contours of the gyri and sulci, and the outer trace following the circumference of the cerebral cortex. We hypothesize that global and regional GI will be altered in animals exposed to UCO, corresponding with decreased brain volume and greater injury. We also hypothesize that treatment will mitigate some of these changes, leading to a GI closer to control. These results will help determine whether hypoxia-ischemia alters the trajectory of cortical development, as well as the association between injury severity, brain volume, and gyrification.

Traumatic brain injury (TBI) results from a blow to the skull that causes shearing forces in the brain. Elevating intracranial pressure (ICP) at the moment of impact may protect the brain from TBI by stiffening the brain tissue and decreasing shearing. When they expect an impact, humans naturally brace and perform a Valsalva maneuver (exhaling against a closed airway), which momentarily elevates ICP. In a ferret TBI model, we conducted abdominal compression using a blood pressure cuff to induce a Valsalva-like response (VLR) and determine whether VLR resulted in neuroprotection. The ferret model was chosen for its gyrified brain structure and white to grey matter ratio that closely resembles the human. TBI was induced using a CHIMERA (Closed-Head Impact Model of Engineered Rotational Acceleration) device, which is designed to deliver high-energy, controlled skull impacts. Initial work showed that the abdominal compression procedures increased ICP. The TBI study involved a total of 36 adult ferrets of both sexes randomized into three groups: (1) a sham control group exposed to isoflurane with a cuff but no compression, (2) a TBI group with a cuff but no compression, and (3) a TBI group with a cuff and abdominal compression. Baseline behavioral assessments (CatWalk, Novel Object Recognition, Swim Test, and Open Field) were conducted one week prior to injury. Post-injury behavioral testing, using the same assessments, was performed at 24–48 hours and 8 days post-TBI to evaluate functional outcomes. On day 8, ferrets were euthanized, and their brain tissue was collected and assessed for neuropathological outcomes. We hypothesize that abdominal compression will mitigate deleterious TBI outcomes. If these findings are supported, this intervention could improve the lives of those at risk of TBI and contribute to ongoing research in the field.

Preterm birth is a leading cause of under-5 morbidity and mortality. No treatments exist to address the neurological complications of premature birth, which include loss of oligodendrocytes and activation of microglia, leading to white matter injury and inflammation, respectively. Our study explored repurposing azithromycin, an FDA-approved antibiotic with anti-inflammatory properties, to mitigate preterm brain injury caused by hypoxia-ischemia. We used a postnatal day (P)14 neonatal ferret model, equivalent to extremely preterm infants. We induced brain injury through a combination of inflammatory stimulus, bilateral carotid artery ligation, and oxygen fluctuations (hypoxia/hyperoxia). Ferrets were randomized into control, vehicle (saline)-treated, and azithromycin-treated groups. Littermate controls were not exposed to injury. Body weights and ex-vivo brain measurements (sulci and gyri widths) were recorded at P21, seven days after injury. Quantitative immunohistochemistry (qIHC) was performed to analyze microglia (Iba-1) and oligodendrocyte (Olig-2) density, and data were analyzed using Kruskal-Wallis tests. In our preliminary findings, post-surgical weights from the azithromycin-treated ferrets were similar to those of vehicle-treated animals. Azithromycin-treated ferrets also showed similar global microglia and oligodendrocyte staining compared to the vehicle group. The vehicle group had lower summed gyri measurements than controls (p=0.04), while azithromycin-treated ferrets had more similar gyri widths to controls (p=0.21). We will continue investigating microglial and oligodendrocyte density using qIHC across additional brain regions using pathology software (VisioPharm), including subregions of each gyrus (cortex, subcortical white matter, and coronal radiata), corpus callosum, hippocampus, and upper and lower thalamus. This will allow us to identify the brain regions most impacted by the injury and investigate if there are regional neuroprotective responses to azithromycin. By deepening our understanding of preterm brain injury and azithromycin-mediated neuroprotection, these findings could lay the groundwork for advancing azithromycin toward clinical trials, offering new hope for saving the lives of the tiniest neonates.

Traumatic brain injury (TBI), characterized by a physical impact to the skull, is a significant health concern among veterans, athletes, and the elderly, with over 200,000 TBI-related hospitalizations in 2020. TBI causes shearing forces and physical damage to the brain, resulting in increased risk of neurodegeneration and mental health problems. When they expect an impact, humans brace, exhaling against a closed airway in what is known as a Valsalva maneuver. This prevents venous return from the head, pressurizes the vascular network in the brain, and increases intracranial pressure (ICP) in a way that may protect the brain from TBI. We aim to mimic a Valsalva-like response (VLR) through external abdominal stimulation and measure corresponding ICP changes. First, we performed a 3mm-wide craniotomy in anesthetized ferrets and implanted a pressure transducer inside the brain to collect baseline pressure readings. After skull closure, VLR was performed both supine and upright (body at 45°), either physically (pVLR, 80-120mmHg by abdominal compression using a blood pressure cuff, n=4) or electrically (eVLR, bilateral 25-30mA stimulus of the rectus muscles, n=4). pVLR resulted in a 2-4mmHg increase in ICP over 2-5 sec. By comparison eVLR resulted in a larger and faster ICP increase - 3-7mmHg with an onset of 250-750ms. Consequently, we will utilize eVLR to modulate ICP in a TBI model to determine whether it is neuroprotective. Ferrets will be assigned to control or randomized to receive a TBI impact with either sham eVLR or eVLR. Animals will be subjected to baseline (pre-TBI), acute, and long-term behavioral testing. Additionally, we will perform brain cell specific histological staining. Results from behavioral testing and histology will inform us of the potential neuroprotective effects of eVLR against TBI and provide future direction towards translating the findings into a wearable device for at-risk individuals.

Hypoxic-ischemic encephalopathy (HIE) is a leading cause of neonatal morbidity and mortality worldwide. The ferret provides a highly translational model to investigate HIE; the gyrified ferret brain has a similar grey-to-white matter ratio to humans, allowing for better assessment of white matter injury and impairment of cortical development compared to rodents. Our previous work has suggested that ferret brains also show greater resilience to hypoxia-ischemia (HI) than rats. Ferrets tolerate exposure to much longer and more significant HI, and 100-fold larger doses of inflammatory stimuli, than rats do. We seek to identify signatures of the ferret's protective mechanisms by comparing differentially regulated genetic pathways in the ferret versus the rat when exposed to identical insults. Whole-hemisphere organotypic brain slices were obtained from term-equivalent ferrets and rats and cultured for 72 hours. Slices were randomly assigned to control or oxygen-glucose deprivation (OGD), an in-vitro model of HIE. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release, while global transcriptomics were analyzed via a 770-gene digital transcriptomics panel. Preliminary results show significantly lower LDH release in ferrets compared to rats, reaffirming the ferrets' resilience to OGD. We identified 90 differentially expressed genes in ferrets following OGD, and 11 genes in the rat. Ferrets upregulated CCL2 and LGALS, genes associated with inflammatory responses, and downregulated ADRB1 and NOS2, suggesting reduced oxidative stress. Rats downregulated KIR3DL1/2 and TGM1, which suppress natural killer cells and form the cell envelope, respectively. The experiment will be repeated with double the sample size and region-specific analysis of gene regulation. We hypothesize the ferret will display lower injury markers globally, which will be associated with regional differences in gene expression compared to the rat. We hope this will enable us to identify potential treatment targets for infants with HIE that can increase resilience and repair after injury. 

Hypoxic Ischemic Encephalopathy (HIE) is a brain injury caused by a lack of oxygen and blood flow in the peripartum period. Cardiac dysfunction occurs in up to 80% of infants with HIE and is associated with worse neurodevelopmental outcomes. The current standard of care for HIE is whole body therapeutic hypothermia (TH). The expected physiologic response to TH is a decrease in cardiac output by 10%, and heartrate (HR) by 10bpm, per 1-degree Celsius decrease in body temperature. However, neonates with cardiac dysfunction tend to have normal or elevated HR to compensate for decreased cardiac output. Therefore, normal or elevated HR during TH may indicate compromised cardiac function. We hypothesize that in neonates with HIE, HR trends during TH reflect cardiac function, and a sustained HR above 100bpm is indicative of cardiac dysfunction. Using echocardiograms performed within the first 2 days after birth in babies with HIE treated with TH at the Seattle Children's neonatal intensive care unit (NICU; n=19), we categorized neonates by cardiac function: normal, right ventricular (RV) dysfunction, and RV plus left ventricular (LV) dysfunction. We then extracted continuous HR data and compared median HR during TH across groups using linear regression during specific periods: 12-24h, 24-36h, and 36-48h after birth. Results showed that infants with RV+LV dysfunction had a higher HR than those with RV dysfunction only or normal function. Across all time periods, infants with any kind of cardiac dysfunction had an average HR above 100bpm, while those without dysfunction had average HRs less than 100bpm. Therefore, it appears that HR can be utilized as a proxy for cardiac dysfunction in neonates with HIE. Utilizing HR as screening biomarker for cardiac dysfunction may allow improve optimal resource utilization of echocardiograms as well as real-time, cost-effective monitoring and targeted treatment initiation.