Modulation of microglia in the retina: new insights into diabetic retinopathy.

During last decades, the diagnosis of diabetes has been associated with several chronic complications such as diabetic retinopathy (DR). Recent studies of DR have revealed an inflammatory component, which precedes the detection of alterations in the visual function. During DR, the inflammatory process presents two opposite roles depending on the polarization of resident immune cells of the retina triggering proinflammatory (M1) or antiinflammatory (M2) actions. In an early stage of DR, the M2 response concurs with the M1 and is able to ameliorate inflammation and delay the progression of the disease. However, during the progression of DR, the M1 response is maintained whereas the M2 declines and, in this scenario, the classical proinflammatory signaling pathways are chronically activated leading to retinal neurodegeneration and the loss of visual function. The M1/M2 responses are closely related to the activation and polarization of microglial cells. This review aims to offer an overview of the recent insights into the role of microglial cells during inflammation in DR. We have focused on the possibility of modulating microglia polarization as a new therapeutic strategy in DR treatments.