Ferreting Out the Effects of Neonatal Hypoxia–Ischemia and Sex on Ferret Cortical Gyrification

Gyrification, the folding of the cerebral cortex, plays a crucial role in brain development and function. Perinatal hypoxia–ischemia (HI) is a leading cause of neonatal brain injury, affecting cortical folding that can be measured by the gyrification index (GI). Using a late-preterm ferret model, our objective was to explore the relationships between HI injury, GI changes, and behavior, as well as the potential moderating effects of sex and treatment. Animals received 3 mg/kg E. coli lipopolysaccharide and underwent bilateral carotid artery ligation followed by alternating hypoxia and hyperoxia (HIH) and were randomized to saline vehicle (n = 25), erythropoietin (n = 20), therapeutic hypothermia (6 h at 33.5 °C, n = 20), and uridine monophosphate (n = 6), with n = 20 unexposed littermates serving as controls. Early reflex testing, CatWalk gait analysis, open-field behavior, and an open-water swim test were performed. Average, peak, motor, and somatosensory strip GIs were then assessed using ex vivo MRI. In control animals, males had lower GI than females; however, HIH exposure resulted in male GI being more similar to females, where HIH animals had significantly higher average GI than controls (p = 0.02). Adjusting for brain volume and injury, GIs in motor and somatosensory areas were associated with faster reflex outcomes in males but not females. In female controls, motor and somatosensory GIs were associated with increased anxiety-like behaviors, such as spending less time in open water during the swim test. By comparison, in male controls, higher GI was associated with decreased anxiety-like behaviors, including higher exploration index in the swim test. These sex-specific relationships between GI and behavior were lost with HIH injury. Treatment did not meaningfully restore the relationship between GI and behavior after HIH, but targeting this outcome may be an important measure for use in future neuroprotection studies in the ferret.