PATHOLOGICAL EVALUATION OF NEONATAL FERRET MODELS OF INFLAMMATION‐SENSITIZED HYPOXIA‐ISCHEMIA
Authors: Snyder Jessica M , Wood Thomas , Corry Kylie , Parikh Pratik , Moralejo Daniel , Traudt Christopher , Juul Sandra 
Published: June 2021

Background

There is a need for relevant animal models for encephalopathy of prematurity and neonatal encephalopathy, and the ferret, with a gyrified brain and similar white:gray matter ratio to humans, is an appealing potential model species. The P10 ferret is approximately equivalent to a human infant at 23–26 weeks gestation, and the P21 ferret corresponds to approximately 40 weeks human gestation.

Methods

Four different protocols to create ferret models of ischemia related preterm and term injury were evaluated: (1) intraperitoneal lipopolysaccharide (LPS; 5 mg/kg) administration at postnatal day (P)11 followed by consecutive hypoxia/hyperoxia/hypoxia (60min at 9%, 120min at 60%, 30min at 9%) in a humidified chamber with a target intra‐hypoxic rectal temperature of 37°C; (2) carotid artery ligation at P11 in combination with LPS administration and hypoxia/hyperoxia/hypoxia; (3) bilateral carotid artery ligation at P21 with LPS administration and hypoxia/hyperoxia/hypoxia (4) bilateral carotid artery ligation at P17 with LPS administration and hypoxia/hyperoxia/hypoxia, followed by 5 hours of prolonged temperature management to prevent anapyrexia. Control animals received saline vehicle followed by normoxia. Ferrets were followed to P42 or P70 and underwent weekly behavioral testing consisting of negative geotaxis, cliff aversion, and righting, as well as assessment of gait coordination on an automated catwalk. At end point, hematoxylin and eosin (HE) histology, immunohistochemistry (GFAP, MBP, and Olig2), and ex vivo magnetic resonance imaging (MRI) analyses were performed.

Results

No abnormalities were observed on HE stained sections of P11 ferrets subjected to LPS and hypoxia/hyperoxia/hypoxia, although MRI at P70 showed widespread white matter hyperintensity on T2‐weighted images, and white matter changes within the internal capsule and corpus callosum were also present on MBP and Olig2 immunohistochemistry. Behavioral testing in these animals revealed slower overall reflex development between P28 and P40, smaller hind paw areas consistent with “toe walking”, and significantly greater lateral movement and reduced gait co‐ordination. More pronounced pathology was found in animals that underwent carotid artery ligation, LPS, and hypoxia/hyperoxia/hypoxia at P17 or P21. Gross abnormalities included thinned gyri in the temporal and/or occipital lobes and widening of the longitudinal fissure, with frank areas of cystic tissue loss in the most severely affected animals. Histological abnormalities included neuronal necrosis, vacuolation and cavitation of the neuropil, and gliosis.

Conclusions

Ferret kits treated with LPS and hypoxia/hyperoxia/hypoxia showed pathological and motor deficits consistent with white matter injury, and more severe injury including neuronal necrosis was observed in animals subjected to bilateral carotid artery ligation. These newborn ferret models may provide an additional platform to assess potential therapies in human encephalopathy of prematurity and neonatal encephalopathy.

Support or Funding Information

NIH grant 5R21NS093154‐02 (NICHD)

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.