MEK-ERK and heparin-susceptible signaling pathways are involved in cell-cycle entry of the wound edge retinal pigment epithelium cells in the adult newt

• Published in: Pigment cell and melanoma research Vol. 25; no. 1; pp. 66 - 82
• Main Authors: Yoshikawa, Taro, Mizuno, Aki, Yasumuro, Hirofumi, Inami, Wataru, Vergara, Maria N., Del Rio-Tsonis, Katia, Chiba, Chikafumi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-01-2012
• Subjects: Animals; Cell Communication; cell cycle; Cells, Cultured; Contact Inhibition - physiology; ERK; Extracellular Matrix - physiology; Fibroblast Growth Factor 2 - physiology; Hedgehog Proteins - physiology; heparin; Heparin - pharmacology; MAP Kinase Signaling System - physiology; MEK; newt; Organ Culture Techniques; Regeneration - physiology; Retina - injuries; retinal pigment epithelium; Retinal Pigment Epithelium - metabolism; S Phase - drug effects; S Phase - physiology; Salamandridae; Serum; Signal Transduction - drug effects; Signal Transduction - physiology; Thrombin - physiology; Wnt Proteins - physiology; wound edge
• ISSN: 1755-1471; 1755-148X
• DOI: 10.1111/j.1755-148X.2011.00935.x

Summary
The onset mechanism of proliferation in mitotically quiescent retinal pigment epithelium (RPE) cells is still obscure in humans and newts, although it can be a clinical target for manipulating both retinal diseases and regeneration. To address this issue, we investigated factors or signaling pathways involved in the first cell‐cycle entry of RPE cells upon retinal injury using a newt retina‐less eye‐cup culture system in which the cells around the wound edge of the RPE exclusively enter the cell cycle. We found that MEK–ERK signaling is necessary for their cell‐cycle entry, and signaling pathways whose activities can be modulated by heparin, such as Wnt‐, Shh‐, and thrombin‐mediated pathways, are capable of regulating the cell‐cycle entry. Furthermore, we found that the cells inside the RPE have low proliferation competence even in the presence of serum, suggesting inversely that a loss of cell‐to‐cell contact would allow the cells to enter the cell cycle.