Neuroglia in the Diabetic Retina

In addition to vascular changes, alterations in retinal neurons and glial cells occur early during diabetic retinopathy. The glial reactivity includes all three types of retinal glial cells (microglia, astrocytes, and Müller cells) and is both a consequence of and a contributor to vascular abnormalities and neuronal dysfunction in the diabetic retina. Activated microglial cells and astrocytes contribute to neuronal apoptosis. Reactive astrocytes and Müller cells are implicated in the breakdown of the blood-retinal barrier and in neovascularization. Furthermore, glial cells are important constituents of the fibrovascular scar tissues formed during proliferative diabetic retinopathy. A crucial aspect is that activated Müller cells display a dysregulation of various neuron-supportive functions. This results in disturbances of retinal glutamate metabolism and K+ homeostasis and in the development of retinal edema, and finally aggravates the dysfunction and loss of neurons.