Neonatal erythropoietin mitigates impaired gait, social interaction and diffusion tensor imaging abnormalities in a rat model of prenatal brain injury

Abstract

Children who are born preterm are at risk for encephalopathy of prematurity, a leading cause of cerebral palsy, cognitive delay and behavioral disorders. Current interventions are limited and none have been shown to reverse cognitive and behavioral impairments, a primary determinant of poor quality of life for these children. Moreover, the mechanisms of perinatal brain injury that result in functional deficits and imaging abnormalities in the mature brain are poorly defined, limiting the potential to target interventions to those who may benefit most. To determine whether impairments are reversible after a prenatal insult, we investigated a spectrum of functional deficits and diffusion tensor imaging (DTI) abnormalities in young adult animals. We hypothesized that prenatal transient systemic hypoxia-ischemia (TSHI) would induce multiple functional deficits concomitant with reduced microstructural white and gray matter integrity, and tested whether these abnormalities could be ameliorated using postnatal erythropoietin (EPO), an emerging neurorestorative intervention. On embryonic day 18 uterine arteries were transiently occluded for 60min via laparotomy. Shams underwent anesthesia and laparotomy for 60min. Pups were born and TSHI pups were randomized to receive EPO or vehicle via intraperitoneal injection on postnatal days 1 to 5. Gait, social interaction, olfaction and open field testing was performed from postnatal day 25-35 before brains underwent ex vivo DTI to measure fractional anisotropy, axial diffusivity and radial diffusivity. Prenatal TSHI injury causes hyperactivity, impaired gait and poor social interaction in young adult rats that mimic the spectrum of deficits observed in children born preterm. Collectively, these data show for the first time in a model of encephalopathy of prematurity that postnatal EPO treatment mitigates impairments in social interaction, in addition to gait deficits. EPO also normalizes TSHI-induced microstructural abnormalities in fractional anisotropy and radial diffusivity in multiple regions, consistent with improved structural integrity and recovery of myelination. Taken together, these results show behavioral and memory deficits from perinatal brain injury are reversible. Furthermore, resolution of DTI abnormalities may predict responsiveness to emerging interventions, and serve as a biomarker of CNS injury and recovery.

Repetitive Neonatal Erythropoietin and Melatonin Combinatorial Treatment Provides Sustained Repair of Functional Deficits in a Rat Model of Cerebral Palsy

“…Consistent with clinical data, the preclinical findings reported here reaffirm the concept that chorioamnionitis concomitant with placental insufficiency results in dynamic, multifactorial, and permanent changes to the CNS culminating in functional deficits in mature rats. Indeed, this prenatal insult causes significant chronic behavioral, social, executive function, and gait deficits in adult rats, similar to those observed in children with CP ( 46 , 62 , 71 ). This model that incorporates intrauterine chorioamnionitis is one of very few preclinical models to induce persistent gait and neurocognitive deficits in the mature CNS ( 40 , 70 ).…”

“…Therefore, through EPO and MLT together, it may be possible to cumulatively preserve more axon-myelin structural units, including those in major cerebral white matter and corticospinal tracts, by inhibiting detrimental protease expression, preserving structural connectivity, and restoring inhibitory neural networks. Indeed, it is through this action on structural and functional connectivity, neural conduction, and excitatory/inhibitory balance of fundamental circuitry that this combination of therapy likely improves motor and cognitive function into early adulthood (P90) following prenatal injury ( 46 – 48 , 71 ).…”

Extended Combined Neonatal Treatment With Erythropoietin Plus Melatonin Prevents Posthemorrhagic Hydrocephalus of Prematurity in Rats

“…Studies using DTI in children with hydrocephalus have shown alterations in white matter microstructural integrity ( Mangano et al, 2016 ; Zhao et al, 2016 ), similar to what we have shown here in toddler-equivalent P21 vehicle-treated CAM-IVH rats. In preclinical studies, extended neonatal EPO treatment mitigated widespread DTI abnormalities in white and gray matter ( Robinson et al, 2016 , 2017 ). Here, we showed that sustained neonatal treatment with EPO+MLT normalizes subacute DTI changes at 3 weeks after CAM-IVH.…”

Extended Erythropoietin Treatment Prevents Chronic Executive Functional and Microstructural Deficits Following Early Severe Traumatic Brain Injury in Rats

“…This process of random assignment followed by correlational analysis was repeated 5 times. Only those ROI that showed significant Pearson correlation on all 5 random assignments AND showed repair of EPO at P30 were considered robust ( 41 ). The correlations for a representative random assignment are shown in Table 1 .…”