mTORC1 activity is up-regulated in the aged, degenerating human RPE. (A) p21 and p27 expression was detected in the primary RPE isolated from young and elderly donors by Western blots. Statistical result is shown at the right panel (n = 3, *P<0.05, mean ± standard deviation). (B) RPE markers, including MERTK, CK18, and LRAT, were detected by Western blots in the primary RPE isolated from the young and elderly donors. Statistical result is on the right panel (n = 3, *P<0.05, mean ± standard deviation). (C) Phosphorylation levels of S6 Ser235/236 and p70s6K Thr389 protein were detected in the primary RPE isolated from the young and elderly donors. Statistical result is shown at the right panel (n = 3, *P<0.05, mean ± standard deviation).