In this study, it was demonstrated that EPO reached the retinal ganglion cell layers when administered subconjunctivally. EPO reached the retina 24 h after the subconjunctival administration, and was still present 60 h after the administration. Furthermore, it was also proved that EPO subconjunctival administration did not cause any haematopoietic significant side-effects. The subconjunctival route was shown to be a promising alternative for EPO ocular delivery.

Keywords Erythropoietin · Glaucoma · Subconjunctival route · Retinal ganglion cells · RatAbstract Purpose: The present study aimed to assess functional and structural benefits of erythropoietin (EPO) when administered subconjunctivally in the retina of glaucomatous rats using electroretinography (ERG) and retinal thickness (RT) measurements. Methods: Glaucoma was experimentally induced in 26 Wistar Hannover albino rats. Animals were divided into 2 groups of 13 animals each: a treated group receiving a unique subconjunctival injection of 1,000 IU of EPO and a control group receiving a saline solution. In each group, 7 animals were used for retinal function evaluation (ERG) and 6 animals were used for retinal structural evaluation (histology). RT was measured, dorsally and ventrally, at 500 μm (RT1) and at 1,500 μm (RT2) from the optic nerve. Results: Retinal function evaluation: for both scotopic and photopic conditions, ERG wave amplitudes increased in the treated group. This increase was statistically significant (p < 0.05) in photopic conditions. Structural evaluation: for both locations RT1 and RT2, the retinas were significantly (p < 0.05) thicker in the treated group. Conclusion: Sub- What Is It about?Glaucoma is the leading cause of irreversible blindness worldwide. Erythropoietin (EPO) has revealed neuroprotective properties on the retina, preserving visual function in several glaucoma models. The present study assesses functional and structural benefits of EPO when administered subconjunctivally in the retina of glaucomatous albino rats using electroretinography and retinal thickness measurements. Subconjunctival EPO administration, a mini-invasive and safe periocular route, showed beneficial effects both on retinal structure and on retinal function. This neuroprotective effect should be applied in other animal species, and more studies should be performed to assess EPO kinetics when administered via a subconjunctival route in glaucoma conditions. conjunctival EPO administration showed beneficial effects both on retinal structure and on retinal function in induced glaucoma in albino rats. This neuroprotective effect should be applied in other animal species.

The aim of this study is to test the permeation of human recombinant erythropoietin (rHuEPO) across conjunctiva, cornea, and sclera in an ex vivo model. Thirty fresh pig eyes were collected from a slaughterhouse. Conjunctivas (n = 10), corneas (n = 10), and scleras (n = 10) were surgically dissected from surrounding tissues. Ocular membranes were placed into Franz diffusion cells and rHuEPO was administered into the donor phase of each cell, except for control samples. Samples were collected from the receptor phase at seven time points, from 30 min to 6 h of incubation. Erythropoietin (EPO) was quantified by enzyme-linked immunosorbent assay (ELISA) technique. Ocular membranes immunohistochemistry was also performed at the end of the study. EPO was detected in all test samples. After 6 h of incubation, conjunctiva was the most permeable membrane to rHuEPO (509.3 ± 89.8 mIU/cm, corresponding to 0.52% of the total rHuEPO administered on the donor phase), followed by sclera (359.1 ± 123.7 mIU/cm, corresponding to 0.35%) and finally cornea (71.0 ± 31.8 mIU/cm, corresponding to 0.07%). Differences between ocular membranes' permeation were statistically significant (p < 0.001). EPO immunostaining signal was positive for the three ocular membranes. We have demonstrated in an ex vivo model that porcine conjunctiva, cornea, and sclera are permeable to rHuEPO protein. These are promising results concerning ocular EPO administration.

Purpose: The present study aimed to determine whether the subconjunctival administration of recombinant human erythropoietin (rHuEPO) reached the retina in glaucoma conditions. After subconjunctival rHuEPO administration, in a rat glaucoma model, erythropoietin (EPO) distribution in the rat's retina was studied by immunohistochemistry. Methods: Female Wistar Hannover albino rats (n = 15) were divided into 2 groups, control (n = 3) and treated (n = 12). The animals' unilateral glaucoma was induced by coagulation of episcleral veins, under general anaesthesia. After vein coagulation, 1,000 IU of rHuEPO were administered by the subconjunctival route to the treated group (n = 12). The control group (n = 3) received only a subconjunctival saline injection. The contralateral eye of each animal remained untouched. Treated group animals were euthanized at different time points, i.e. days 1, 3, 7 and 14. Bilateral enucleation was performed, and EPO distribution in the rat's retina was assessed by immunohistochemistry. Results: Glaucoma was confirmed by results of repeated intraocular pressure measurements over the experimental period. In the test group, EPO was identified in different neuroretinal cells, showing a stronger immunostaining signal during the first 2 time points in the retinal ganglion cell (RGC) layer. EPO protein was still present on day 14 after the subconjunctival injection. EPO was not detected in any of the control eyes or in any contralateral eye of the treated group. Conclusion: When administered subconjunctivally to glaucomatous eyes, rHuEPO reached the RGC layer and was still present at least 14 days after administration. The subconjunctival route was shown to be a promising alternative for ocular EPO delivery in glaucomatous conditions in a rat animal model.

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