Postnatal Erythropoietin Mitigates Impaired Cerebral Cortical Development Following Subplate Loss from Prenatal Hypoxia–Ischemia

Abstract

Preterm birth impacts brain development and leads to chronic deficits including cognitive delay, behavioral problems, and epilepsy. Premature loss of the subplate, a transient subcortical layer that guides development of the cerebral cortex and axonal refinement, has been implicated in these neurological disorders. Subplate neurons influence postnatal upregulation of the potassium chloride co-transporter KCC2 and maturation of γ-amino-butyric acid A receptor (GABAAR) subunits. We hypothesized that prenatal transient systemic hypoxia-ischemia (TSHI) in Sprague-Dawley rats that mimic brain injury from extreme prematurity in humans would cause premature subplate loss and affect cortical layer IV development. Further, we predicted that the neuroprotective agent erythropoietin (EPO) could attenuate the injury. Prenatal TSHI induced subplate neuronal loss via apoptosis. TSHI impaired cortical layer IV postnatal upregulation of KCC2 and GABAAR subunits, and postnatal EPO treatment mitigated the loss (n ≥ 8). To specifically address how subplate loss affects cortical development, we used in vitro mechanical subplate ablation in slice cultures (n ≥ 3) and found EPO treatment attenuates KCC2 loss. Together, these results show that subplate loss contributes to impaired cerebral development, and EPO treatment diminishes the damage. Limitation of premature subplate loss and the resultant impaired cortical development may minimize cerebral deficits suffered by extremely preterm infants.

Preclinical Models of Encephalopathy of Prematurity

“…In this model following injury, O4-immunoreactive immature oligodendrocytes are most affected and their loss correlates with decreased survival and maturation[69], with the most notable reductions in O4+ and O1+ stages of the lineage[35], consistent with previous reports by other investigators[70]. This model also demonstrates premature loss of the subplate, reduced KCC2 expression, and a lower seizure threshold and impaired gait[25,26,55]. Detailed analyses of other components of EoP including loss of thalamic and GABAergic neurons, and the contribution of placental pathology is underway.…”

Erythropoietin attenuates loss of potassium chloride co-transporters following prenatal brain injury

“…For samples obtained at P28, CA3 from individual pups were used (n=8-14). Membrane and whole cell proteins were isolated using a sucrose containing homogenization buffer, sonication and differential centrifugation (Jantzie et al, 2014). Following extraction of the whole cell fraction and reconstitution of membrane proteins in lysis buffer, a Bradford protein assay was performed.…”

Preschool Assessment of Preterm Infants Treated With Darbepoetin and Erythropoietin

“…The neuroprotective mechanisms of ESAs include decreased neuronal apoptosis, decreased inflammation, promotion of oligodendrocyte differentiation and maturation, and improved white matter survival. [1][2][3][4][5][6][7][8][9] These biological mechanisms of neuroprotection may be revealed through MRI. 26 All children enrolled in the BRITE study underwent MRI, and analyses of total and regional brain volume, cortical thickness, surface area, spectroscopy, total and regional cerebral blood flow, and diffusion tensor imaging are nearing completion.…”

“…Recent studies in animals and humans evaluating the nonhematopoietic effects of erythropoiesis-stimulating agents (ESAs) suggest a neuroprotective potential via such mechanisms as increased oligodendrogenesis, decreased inflammation, decreased oxidative injury, and decreased apoptosis. [1][2][3][4][5][6][7][8][9] We previously reported 18-to 22-month outcomes on our prospective, randomized, masked study in preterm infants randomly assigned to receive ESAs or placebo 10 and hypothesized that ESA recipients would have higher composite cognitive scores measured by using the Bayley Scales of Infant Development III (BSID-III). 11 Indeed, those very low birth weight infants receiving erythropoietin or darbepoetin alfa (hereafter "darbepoetin") had significantly higher composite cognitive scores, including higher scores on a scale of executive function.…”