title: Identification of a therapeutic dose of continuously delivered erythropoietin in the eye using an inducible promoter system.
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 8 μm 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 36 mU/ml EPO into the eye since this dose was effective for the treatment of a progressive retinal degeneration.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt University, 11435 MRBIV, 2213 Garland Ave, Nashville, TN 37232-8808, USA. tonia.rex@vanderbilt.edu.
authors.forename: Jessica
authors.initials: J
authors.lastname: Hines-Beard
authors.forename: Siddharth
authors.initials: S
authors.lastname: Desai
authors.forename: Rachel
authors.initials: R
authors.lastname: Haag
authors.forename: Noriko
authors.initials: N
authors.lastname: Esumi
authors.forename: Lauren
authors.initials: L
authors.lastname: D'Surney
authors.forename: Scott
authors.initials: S
authors.lastname: Parker
authors.forename: Cody
authors.initials: C
authors.lastname: Richardson
authors.forename: Tonia S
authors.initials: TS
authors.lastname: Rex
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D004921:Erythropoietin / Q000008:administration & dosage* / Q000235:genetics; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000627:therapeutic use; D006801:Humans; D051379:Mice; D011401:Promoter Regions, Genetic / Q000235:genetics; D012160:Retina / Q000187:drug effects / Q000473:pathology; D012162:Retinal Degeneration / Q000235:genetics / Q000628:therapy
chemical_list: D004921:Erythropoietin