Abstract
Introduction: :
Background: Classically one thinks of erythropoietin (EPO) as a regulator of red blood cell production. Recent evidence points to EPO as a putative neuroprotective agent. EPO and its receptor are present in selected CNS neurons including retinal ganglion cells (RGCs). A modified form of EPO containing a single arginine to glutamate mutation (R103E) is neuroprotective while not triggering erythropoiesis. The goal of this study was to determine if systemic delivery of EPO-R103E would protect the RGCs from cell death in a mouse model of pigmentary dispersion glaucoma (DBA/2J mouse).
Methods: :
One month old DBA/2J mice received intramuscular injections of a recombinant adeno-associated virus (rAAV) carrying either eGFP, Epo or EpoR103E under the control of the cytomegalovirus promoter. Intraocular pressure was measured at six months to detect elevated pressure. At ten months, isolated retinas were stained with NueN, flat-mounted, and examined at 40X by confocal microscopy. Hematocrit levels were determined by capillary centrifugation of blood and serum EPO levels were determined by ELISA.
Results: :
Retinas from DBA/2J mice that received either rAAV.Epo or rAAV.EpoR103E had an average of 30% more cells present at the RGC layer then control mice (rAAV.eGFP). Hematocrit levels were not substantially increased in the rAAV.Epo R103E treated mice as compared to rAAV.Epo treated mice.
Conclusions: :
A single systemic injection of rAAV.Epo protects RGCs from glaucomatous cell death, but also increases the hematocrit to harmful levels. Treatment with rAAV.EpoR103E provides comparable levels of RGC protection but does not significantly increase the hematocrit. Thus, a single dose of rAAV.EpoR103E can provide long-term protection without the need for intraocular injections and without elevating the hematocrit.
Keywords: gene transfer/gene therapy • ganglion cells • neuroprotection