Fig. 7
Lack of IgM is associated with RPE stress and barrier dysfunction in aged mice. Retinas were dissected out of aged (24mo) WT and µs-/- mice; one eye was used for H&E and one eye was used for RNA extraction. (A) Representative image of H&E RPE flat mount from an aged WT mouse compared to (B) representative image of that from an aged µs-/- mouse. (C) RPE cells from the peripheral/equatorial region of the retina were counted and averaged to be either (1) mononucleate (only 1 nucleus/cell) or (2) multinucleate (≥2 nuclei/cell). (D) H&E retinal sections from an aged WT mouse compared to (E) the aged µs-/- retina shows signs of retinal degeneration in the neural retina and RPE layer including extensive vacuolation (labeled as “V” in (E)). (F) RNA was isolated from the RPE of both young and aged retinas, and qPCR was performed to determine expression level of the inflammatory cytokine IL-6. (G&H) Cytoskeleton changes are seen in RPE from aged µs-/- mice (H) as compared to aged WT mice (G) through examination of F-actin. Both aging WT and µs-/- RPE show typical age-related changes with increase in RPE size and changes in regular polygonal geometry and shape. However, µs-/- aged mice (H) show further evidence of RPE stress and barrier dysfunction such irregular morphology (1), the presence to intracellular stress fibers, with fraying and thickening (2), and fragmentation of the RPE cytoskeleton (3). Results based on three independent experiments. Statistics used: unpaired, two-tailed Mann-Whitney U test. ***p < 0.001. Animals used: Young WT n = 10; Young µs-/- n = 12; Aged WT n = 7; Aged µs-/- n = 5. Scale bar = 50 μm