Erythropoietin Stimulates GABAergic Maturation in the Mouse Hippocampus

Several neurodevelopmental disabilities are strongly associated with alterations in GABAergic transmission, and therapies to stimulate its normal development are lacking. Erythropoietin (EPO) is clinically used in neonatology to mitigate acute brain injury, and to stimulate neuronal maturation. Yet it remains unclear whether EPO can stimulate maturation of the GABAergic system. Here, with the use of a transgenic mouse line that constitutively overexpresses neuronal EPO (Tg21), we show that EPO stimulates postnatal GABAergic maturation in the hippocampus. We show an increase in hippocampal GABA-immunoreactive neurons, and postnatal elevation of interneurons expressing parvalbumin (PV), somatostatin (SST) and neuropeptide Y (NPY). Analysis of perineuronal net formation and innervation of glutamatergic terminals onto PV+ cells, shows to be enhanced early in postnatal development. Additionally, an increase in GABA(A) ergic synapse density and inhibitory postsynaptic currents (IPSCs) in CA1 pyramidal cells from Tg21 mice is observed. Detection of erythropoietin receptor (EPOR) mRNA was observed to be restricted to glutamatergic pyramidal cells and increased in Tg21 mice at postnatal day 7, along with reduced apoptosis. Our findings show that EPO can stimulate postnatal GABAergic maturation in the hippocampus, by increasing neuronal survival, modulating critical plasticity periods, and increasing synaptic transmission. Our data supports EPO's clinical use to balance GABAergic dysfunction. Significance Statement Using a mouse model that overexpresses recombinant human EPO in the CNS, we observed stimulation of the postnatal maturation of GABAergic transmission in the hippocampus, notably accelerated maturation of PV+ interneurons, enhanced glutamatergic inputs onto these interneurons, and enhanced inhibitory postsynaptic currents (IPSCs) onto pyramidal cells. We show that EPORs are expressed on pyramidal cells, therefore the impact of EPO on GABAergic maturation is likely to be indirect. Our data show that EPO can modulate hippocampal network maturation and support ongoing trials of the use of EPO in clinical neonatology to stimulate neuronal maturation after perinatal brain injury.

Automated summary

EPO stimulates postnatal maturation of GABAergic transmission in the hippocampus of mice, increasing neuronal survival, modulating critical plasticity periods, and enhancing synaptic transmission. EPORs are expressed on pyramidal cells, suggesting indirect impact of EPO on GABAergic maturation.