Defining Longer-Term Outcomes in an Ovine Model of Moderate Perinatal Hypoxia-Ischemia

Abstract

Hypoxic-ischemic encephalopathy (HIE) is the leading cause of neonatal morbidity and mortality worldwide. Approximately 1 million infants born with HIE each year survive with cerebral palsy (CP) and/or serious cognitive disabilities. While infants born with mild and severe HIE frequently result in predictable outcomes, infants born with moderate HIE exhibit variable outcomes that are highly unpredictable. Here, we describe an umbilical cord occlusion (UCO) model of moderate HIE with a 6-day follow-up. Near term lambs (n=27) are resuscitated after the induction of 5 minutes of asystole. Following recovery, lambs are assessed to define neurodevelopmental outcomes. At the end of this period, lambs are euthanized, and brains harvested for histological analysis. Compared with prior models that typically follow lambs for 3 days, the observation of neurobehavioral outcomes for 6 days enables identification of animals that recover significant neurological function. Approximately 35 % of lambs exhibited severe motor deficits throughout the entirety of the 6-day course and, in the most severely affected lambs, developed spastic diparesis similar to that observed in infants who survive severe neonatal HIE (severe, UCOs). Importantly, and similar to outcomes in human neonates, while initially developing significant acidosis and encephalopathy, the remainder of the lambs in this model recovered normal motor activity and exhibited normal neurodevelopmental outcomes by 6 days of life (improved, UCOi). The UCOs group exhibited gliosis and inflammation in both white and gray matter, oligodendrocyte loss, and neuronal loss and cellular death in the hippocampus and cingulate cortex. While the UCOi group exhibited more cellular death and gliosis in the parasagittal cortex and demonstrated more preserved white matter markers, along with reduced markers of inflammation and lower cellular death and neuronal loss in Ca3 of the hippocampus compared with UCOs lambs. Our large animal model of moderate HIE with prolonged follow-up will help further define pathophysiologic drivers of brain injury while enabling identification of predictive biomarkers that correlate with disease outcomes and ultimately help support development of therapeutic approaches to this challenging clinical scenario.

Perinatal Azithromycin Provides Limited Neuroprotection in an Ovine Model of Neonatal Hypoxic-Ischemic Encephalopathy

“…Serial arterial blood gasses were drawn at baseline preUCO, immediately before initiation of CPR and at 10, 20, 30, and 60 minutes after ROSC. Consistent with our prior studies, 23 the UCO protocol produced a clinically significant combined metabolic and respiratory acidosis ( Table S3 , 1A). Azithromycin-treated lambs were slightly more acidic at the end of asphyxia just before CPR compared with the placebo group as evidenced by lower pH values ( P =0.006).…”

“…Hemodynamic data were analyzed using grouped analysis of the individual group’s means for a specific time point. AZM: n=18; placebo: n=13; control: n=6 (controls data were used with permission from Mike et al 23 ). D , The incidence of second dose of epinephrine and dextrose administration was similar between the groups.…”

“…Structural and inflammatory changes at 6 days after UCO were measured using qualitative and morphological assessment of gray and white matter structures in a blinded manner, as described previously. 23 Analysis included the average of 3 images from one anatomic area of interest. We assessed 3 regions of white matter represented by periventricular white matter (PVWM), subcortical white matter of the cingulate and first parasagittal gyrus, and 6 regions of gray matter represented by cortex of the cingulate and first parasagittal gyrus (Ctx1 and Ctx2), caudate, putamen (Put), and hippocampal areas (Ca1/2 and Ca3).…”

“…Structural and inflammatory changes at 6 days after UCO were measured using qualitative and morphological assessment of gray and white matter structures in a blinded manner, as described previously. 23 Analysis included the average of 3 images from one anatomic area of interest. We assessed…”

A Novel Murine Multi-Hit Model of Perinatal Acute Diffuse White Matter Injury Recapitulates Major Features of Human Disease

“…Given the evident paucity of human pathologic specimens from affected infant brains available for research, reliance on experimental models that reproduce key features of human disease is even greater than in other areas of study. Numerous mammalian models (mouse, rat, sheep, and non-human primate) have been developed to study white matter injury disease mechanisms and potential therapeutic interventions [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Many of these models have been developed to model the focal cystic necrosis produced by earlier WMI.…”