Neurotrophic Regulation by Erythropoietin in Diabetic Retinas and Müller Cells Cultured in High Glucose Medium

Abstract

Purpose: : To explore whether erythropoietin (EPO) promotes neurotrophic factors in diabetic retinas.

Methods: : A single intravitreal injection of EPO (8 mU/eye) was given to streptozotocin-induced diabetic rats at 1 month after the onset of diabetes. Four days later, neurosensory retinas of normal and diabetic rats treated with or without EPO were used as the sources of Q-PCR and WB for the detection of ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF), and glial fibrillary acidic protein (GFAP). Immunofluorescence was used to show the distribution pattern of these neurothrophic factors in diabetic retinas. Rat Müller cell (rMc-1 cell line) in high glucose was used to mimic diabetic conditions. After EPO (1-4 U/mL) treatment, the changes of nuerothorphic factorswere measured by Q-PCR and ELISA at different time points.

Results: : Both mRNA and protein levels of BDNF and CNTF were mildly up regulated in diabetic retinas, which were further increased with EPO treatment (N=4; P<0.05). The similar changes were also observed in rMc-1 cells in high glucose. The time-dependent neurotrophic factors with EPO was observed both in RNA and protein levels. The protein level of GFAP was significantly up regulated in 1-month diabetic retina, which was down regulated by EPO. The change of GFAP was confirmed by the immunofluorescence.

Conclusions: : EPO could promote the production of neurotrophic factors both in vivo and in vitro. The down regulation of GFAP by. EPO indcates that EPO may target Müller cells to protect neurons through induced neurotrophic factors and to suppress the process of gliosis in diabetic retinopathy.

Keywords: diabetic retinopathy • Muller cells • protective mechanisms