TNF-α modulates Hippo and Wnt/β-catenin signaling pathways in retinal Müller cells in experimental glaucoma

Hippo and Wnt/β-catenin signaling are associated with retinal Müller cell proliferation and dedifferentiation into stem cells (precursor cells). However, in mammals, Müller cells are difficult to dedifferentiate into stem cells in retinal injury and diseases, which may be related to the altered retinal microenvironment. TNF-α is a major inflammatory cytokine released by activated retinal glial cells in glaucoma. Here, we investigated the roles and underlying mechanisms of TNF-α on Hippo and Wnt/β-catenin signaling in chronic ocular hypertension (COH) experimental glaucoma and primary cultured Müller cells. The activities of β-catenin and YAP, the key effective factors of Wnt and Hippo signaling, were inhibited by TNF-α in COH retinas. In activated Müller cells, TNF-α inhibited the activity of β-catenin and YAP. Following intervention with the TNFR1 antagonist R7050, Wnt3a protein levels increased, β-catenin, Stat3, and YAP phosphorylation decreased, and the activities of GSK3β and MST1 were suppressed. Additionally, R7050 elevated Müller cell proliferation and increased cyclin D1/D2 and Nestin protein expression. In COH retinas, intravitreal injection of R7050 increased Nestin and Ascl1 expression in Müller cells. These results demonstrate that TNF-α inhibits the proliferation and reprogramming of Müller cells by awakening the Hippo pathway and inhibiting the Wnt/β-catenin pathway in COH retinas.