Microglial changes in healthy mice retina in an early aging stage

Abstract

AbstractPurposeTo quantify different morphological signs of microglial cells activation, as well as to analyze the P2RY12, MHC‐II and CD68 expression in 15‐month old mice , an early stage of aging (aged naïve) in comparison with a young adult mice (young naïve).MethodsYoung naïve (n = 6) and aged naïve (n = 6) mice were analyzed. Retinal whole‐mounts were immunolabeled with: 1) anti Iba‐1 to quantify: i) Iba‐1 + cells number (Ibacn) in outer segments (OS), outer plexiform layer (OPL) and inner plexiform layer (IPL); ii) area of retina occupied by Iba‐1 + cells (Iba‐1 RA) in the nerve fiber layer‐ ganglion cell layer (NFL‐GCL) iii) cell body area of Iba‐1+ cells (CbIbac) in OPL, IPL and NFL‐GCL; iv) arbor area of Iba‐1+ cells (AAIbac) in OPL and IPL; number of vertical processes of Iba‐1+ cells (VPIbac) beetween the OS and OPL. 2) anti‐P2RY12 to identify resident microglia, anti‐CD68 and anti‐MHC‐II as a microglial activation marker.ResultsIn aged naïve with respect to young naïve the quantitative analysis showed: i) a non‐significant increase in the Ibacn in OS; ii) a non‐significant decrease in the AAIbac in OPL; iii) a significant increase in the CbIbac in OPL, IPL and NFL‐GCL and iv) a significant increase in the VPIbac. When we analyzed the expression of P2RY12, CD68 and MHC‐II we observed: i) in young naïve all Iba‐1+ cells were P2RY12+, except perivascular and dendritic cells, but in the aged naïve some cells were Iba‐1+/P2RY12‐; ii) in aged naïve numerous amoeboid‐like CD68+ cells were found while in the young naïve the expression of CD68 practically was absent, and iii) in both young naïve and aged naïve no expression of MHC‐II was observed.ConclusionsIn 15‐month‐old mice, morphological changes and in the expression of P2RY12, CD68 and MHC‐II occurs in the microglial cells compared to young adult mice. These signs show a non‐pathological state of microglial activation that could influence of retinal age‐related disorders.