Multi-Modal Assessment of Long-Term Erythropoietin Treatment after Neonatal Hypoxic-Ischemic Injury in Rat Brain

Abstract

Erythropoietin (EPO) has been recognized as a neuroprotective agent. In animal models of neonatal brain injury, exogenous EPO has been shown to reduce lesion size, improve structure and function. Experimental studies have focused on short course treatment after injury. Timing, dose and length of treatment in preterm brain damage remain to be defined. We have evaluated the effects of high dose and long-term EPO treatment in hypoxic-ischemic (HI) injury in 3 days old (P3) rat pups using histopathology, magnetic resonance imaging (MRI) and spectroscopy (MRS) as well as functional assessment with somatosensory-evoked potentials (SEP). After HI, rat pups were assessed by MRI for initial damage and were randomized to receive EPO or vehicle. At the end of treatment period (P25) the size of resulting cortical damage and white matter (WM) microstructure integrity were assessed by MRI and cortical metabolism by MRS. Whisker elicited SEP were recorded to evaluate somatosensory function. Brains were collected for neuropathological assessment. The EPO treated animals did not show significant decrease of the HI induced cortical loss at P25. WM microstructure measured by diffusion tensor imaging was improved and SEP response in the injured cortex was recovered in the EPO treated animals compared to vehicle treated animals. In addition, the metabolic profile was less altered in the EPO group. Long-term treatment with high dose EPO after HI injury in the very immature rat brain induced recovery of WM microstructure and connectivity as well as somatosensory cortical function despite no effects on volume of cortical damage. This indicates that long-term high-dose EPO induces recovery of structural and functional connectivity despite persisting gross anatomical cortical alteration resulting from HI.

The Akt/mTOR/p70S6K Pathway Is Involved in the Neuroprotective Effect of Erythropoietin on Hypoxic/Ischemic Brain Injury in a Neonatal Rat Model

“…EPO and its receptor are expressed in organs throughout the body, including neurons and glia during development, where EPO has been shown to exert neuroprotection in animal models [16]. EPO plays a crucial role in protecting neuron-mediated cell injury following H/I insult in the developing brain.…”

Erythropoietin for the Repair of Cerebral Injury in Very Preterm Infants (EpoRepair)

“…Administration of rEPO even several days after the insult can enhance neurogenesis and oligodendrogenesis and promotes the recovery of neurological function weeks to months after the insult [21]. Of interest, long-term treatment with rEPO after an insult in the very immature rat brain induced the recovery of WM microstructures and of connectivity as well as somatosensory cortical function without effects on the total brain volume [22]. Observational data from preterm infants who suffered from IVH and who were treated with rEPO to prevent red blood cell transfusions showed improved long-term neurodevelopmental outcomes when assessed at 3 years of age or more [23].…”

Neuroprotective Treatments after Perinatal Hypoxic-Ischemic Brain Injury Evaluated with Magnetic Resonance Spectroscopy

“…Epo has been studied by means of 1 H MRS during the subacute phase (at 24-72 h of age in nonhuman primates) and at longterm follow-up (at 9 months in nonhuman primates and at 25 days of age in rats). The metabolic profile of the rat cortex was similar in pups treated with Epo and those treated with saline for 3 weeks after hypoxic-ischemic injury, and both groups had reduced NAA compared to the sham-controls [72] . In contrast, a combination therapy of hypothermia and Epo in a term nonhuman primate model of perinatal asphyxia improved the NAA/Cr ratio and reduced the Cho levels in the first 72 h after birth [73] .…”