Title:Identification of a Therapeutic Dose of Continuously Delivered Erythropoietin in the Eye Using An Inducible Promoter System
Volume: 13
Issue: 4
Author(s): Jessica Hines—Beard, Siddharth Desai, Rachel Haag, Noriko Esumi, Lauren D’Surney, Scott Parker, Cody Richardson and Tonia S. Rex
Affiliation:
Keywords:
Dose, erythropoietin, gene therapy, inducible promoter, intraocular, recombinant adeno-associated virus, retinal
degeneration.
Abstract: Erythropoietin (EPO) can protect the retina from acute damage, but long-term systemic treatment induces polycythemia.
Intraocular gene delivery of EPO is not protective despite producing high levels of EPO likely due to its bellshaped
dose curve. The goal of this study was to identify a therapeutic dose of continuously produced EPO in the eye. We
packaged a mutated form of EPO (EPOR76E) that has equivalent neuroprotective activity as wild-type EPO and attenuated
erythropoietic activity into a recombinant adeno-associated viral vector under the control of the tetracycline inducible
promoter. This vector was injected into the subretinal space of homozygous postnatal 5-7 day retinal degeneration slow
mice, that express the tetracycline transactivators from a retinal pigment epithelium specific promoter. At weaning, mice
received a single intraperitoneal injection of doxycycline and were then maintained on water with or without doxycycline
until postnatal day 60. Intraocular EPO levels and outer nuclear layer thickness were quantified and correlated. Control
eyes contained 6.1 ± 0.1 (SEM) mU/ml EPO. The eyes of mice that received an intraperitoneal injection of doxycycline
contained 11.8 ± 2.0 (SEM) mU/ml EPO-R76E. Treatment with doxycycline water induced production of 35.9 ± 2.4
(SEM) mU/ml EPO-R76E in the eye. The outer nuclear layer was approximately 8μm thicker in eyes of mice that received
doxycycline water as compared to the control groups. Our data indicates that drug delivery systems should be optimized
to deliver at least 36mU/ml EPO into the eye since this dose was effective for the treatment of a progressive retinal
degeneration.