Objective: To investigate the changes of vascular endothelial cell tight junction protein (occludin) and glial cell morphology as well as their relationship with blood-retinal barrier (BRB) in the retina of diabetic rats.
Methods: The distribution of occludin and GFAP were explored by immunofluorescence histochemical studies in the retina of streptozotocin (STZ)-diabetic rats and age-matched control rats. Evans blue was used to evaluate the impairment of BRB.
Results: GFAP immunoreactivity was limited to ganglion cell layer and nerve fiber layer in the control retina. GFAP immunoreactivity was significantly increased in ganglion cell layer and nerve fiber layer in one month diabetic rats. GFAP positive Müller cells were increased in three months and six months diabetic rats. Occludin immunoreactivity progressively decreased in three months and six months diabetic rats but not in the one month diabetic rats. Evans blue injection showed a progressive impairment of BRB.
Conclusions: Astrocytes activation in the early stage of diabetes plays an important role in the maintaining of the BRB function. But the activation of Müller cells in the later stage destroyed the BRB eventually. These changes are consistent with the concept that BRB changes caused by altered glial-endothelial cell interactions contributes to the occurrence of diabetic retinopathy.