Effects of Erythropoietin-Dextran Microparticle-Based PLGA/PLA Microspheres on RGCs

Abstract

PURPOSE. We explored the neuroprotective effects of erythropoietin (EPO)-loaded dextran microparticle-based Poly(DLlactide-co-glycolide)/Poly(DL-lactide) (PLGA/PLA) microspheres (EPO-dextran PLGA/PLA microspheres) on retinal ganglion cells (RGCs) in optic nerve crush rats for a prolonged period of time.METHODS. EPO-dextran PLGA/PLA microspheres were prepared first by a novel solid-in-oil-in-water (S/O/W) technique. Then, the in vitro EPO release profile was assessed. Afterward, the bioactive effect of EPO released from EPO-dextran PLGA/PLA microspheres was explored in vitro on the retinal explants. Lastly, the neuroprotective effects of EPO-dextran PLGA/PLA microspheres on RGCs were evaluated in optic nerve crush rats with TUNEL staining for apoptotic RGCs. The level of glial fibrillary acidic protein (GFAP) expressed in retina was explored by immunohistochemistry staining. Survival RGCs were observed by DiI retrograde labeling using a DiI fluorescent tracer (1,1 0 -dioctadecyl-3,3,3 0 ,3 0 -tetramethylindocarbocyanine perchlorate). RESULTS.The results demonstrated that a sustained release of EPO from PLGA/PLA microspheres could last for at least 60 days. EPO released from the microspheres showed as efficaciously neuroregenerative as EPO protein solution on retinal explants (P ¼ 0.2554 for neurite density, P ¼ 0.1004 for neurite length). TUNEL staining revealed that EPO-dextran PLGA/PLA microspheres remarkably reduced RGCs death when compared to the control (untreated) group (P < 0.01 at five days and one week post-crush, P < 0.05 at two weeks post-crush). Increased GFAP expression in retina was reduced greatly in EPO-dextran PLGA/PLA microspheres-administrated rats two weeks post optic nerve crush. DiI retrograde labeling revealed that a single injection of EPO-dextran PLGA/PLA microspheres significantly promoted RGCs survival (P < 0.01 at four and eight weeks post-crush). CONCLUSIONS.A single intravitreal injection of EPO-dextran PLGA/PLA microspheres appeared to have a prolonged protective effect on RGCs in optic nerve crush rats. The PLGA/PLA microspheres may be a feasible protein delivery system, such as EPO, to intravitreal injection for retinal degeneration diseases. (Invest Ophthalmol Vis Sci. 2012; 53:6025-6034)

Identification of a Therapeutic Dose of Continuously Delivered Erythropoietin in the Eye Using An Inducible Promoter System

“…A recent publication demonstrated protection of retinal ganglion cells using intraocular delivery of nanoparticles carrying EPO for up to 60 days post-injection [41]. Unfortunately, they did not perform quantification of the amount of EPO delivered to the eye by the nanoparticles.…”

Safety evaluation of poly(lactic-co-glycolic acid)/poly(lactic-acid) microspheres through intravitreal injection in rabbits

“…13,14 Previous studies conducted by the present researchers have demonstrated the neuroprotective effects of the intravitreal protein drug delivery system (erythropoietin [EPO]-dextran PLGA/PLA microspheres) on retinal ganglion cells in rats. 15 The microspheres were first prepared by a unique system of stabilized aqueous-aqueous ''emulsion'' to formulate EPOdextran particles. The particles were then encapsulated into PLGA/PLA by the solid-in-oil-in-water (S/O/W) method.…”

“…6,15 In this study, EPO was used as an example of protein drugs. First, a temperature-induced phase separation method was applied to prepared EPO-dextran particles.…”

“…16 The microspheres possessed a spherical shape, smooth surface, and diameter of 40-100 μm, with an in vitro release profile of more than 60 days, as analyzed in the previous studies. 6,15 PLGA-and/or PLA-sustained drug release systems applied in the eye have shown prolonged release of drugs 21,22 and have facilitated effective treatments for chronic ocular disorders such as proliferative vitreoretinopathy, retinal diseases, glaucoma, and neovascularization. The present researchers' previous studies have revealed that a single intravitreal injection of EPO-dextran PLGA/PLA microspheres could significantly protect retinas damaged from optic nerve crush in rats.…”

“…The present researchers' previous studies have revealed that a single intravitreal injection of EPO-dextran PLGA/PLA microspheres could significantly protect retinas damaged from optic nerve crush in rats. 15 However, whether intravitreally injected PLGA/PLA microspheres and their degraded products could cause inflammatory reactions and damage to retinas and vision function have not been systemically investigated.…”