The Effect of a p38 Mitogen-Activated Protein Kinase Inhibitor on Cellular Senescence of Cultivated Human Corneal Endothelial Cells

PURPOSE. We have begun a clinical trial of a cell-based therapy for corneal endothelial dysfunction in Japan. The purpose of this study was to investigate the usefulness of a p38 MAPK inhibitor for prevention cellular senescence in cultivated human corneal endothelial cells (HCECs). METHODS. HCECs of 10 donor corneas were divided and cultured with or without SB203580 (a p38 MAPK inhibitor). Cell density and morphology were evaluated by phase-contrast microscopy. Expression of function-related proteins was examined by immunofluorescent staining. Cellular senescence was evaluated by SA-beta-gal staining and Western blotting for p16 and p21. Senescence-associated factors were evaluated by membrane blotting array, quantitative PCR, and ELISA. RESULTS. Phase-contrast microscopy showed a significantly higher cell density for HCECs cultured with SB203580 than without SB203580 (2623 6 657 cells/mm(2) and 1752 +/- 628 cells/mm(2), respectively). The HCECs cultured with SB203580 maintained a hexagonal morphology and expressed ZO-1, N-cadherin, and Na+/K+-ATPase in the plasma membrane, whereas the control HCECs showed an altered staining pattern for these marker proteins. HCECs cultured without SB203580 showed high positive SA-beta-gal staining, a low nuclear/cytoplasm ratio, and expression of p16 and p21. IL-6, IL-8, CCL2, and CXCL1 were observed at high levels in low cell density HCECs cultured without SB203580. CONCLUSIONS. Activation of p38 MAPK signaling due to culture stress might be a causative factor that induces cellular senescence; therefore, the use of p38 MAPK inhibitor to counteract senescence may achieve sufficient numbers of HCECs for tissue engineering therapy for corneal endothelial dysfunction.