ARR3 and retinal degeneration: To further understand if altered microglial activation contributes to retinal degeneration in aged DKO mice, retinal explants from C57BL/6 J mice were cultured alone or co-cultured with microglia from Socs3fl/fl and DKO mice without and with M1 or M2 polarization (Fig. 9a), and the number of cone arrestin+ cells was evaluated in retinal flatmounts.