Cyclic stretch induced-retinal pigment epithelial cell apoptosis and cytokine changes

The pathogenesis of age-related macular degeneration (AMD) is complex. It has been shown that vitreomacular traction (VMT) plays a role in the pathogenesis of AMD. We speculate that the continuous stretch induced by VMT might impair the function of retinal pigment epithelium (RPE) cells and it might also be involved in the progression of AMD.

Cultured ARPE-19 cells were subjected to cyclic stretch on the Flexcell Strain system at a level of 25% increment on the surface area for 8 h, 14 h, 20 h, 24 h. In another group, the stretch was withdrawn at 14 h and the cell cultured for another 6 h. Then, we observed the changes in morphology, apoptosis and expression of interleukin 6 (IL6) and vascular endothelial growth factor (VEGF) in RPE cells under stretch.

We found that stretch induced the RPE cells to change from a spreading shape into a rounded shape, and that the morphological changes were positively correlated with the duration of the stretch. The expression of pFAK397 and pRac1/cdc42 were elevated in a time-dependent fashion. The stretch resulted in an increase in the apoptosis ratio, with Bcl2, Bax and p53 also showing time-dependent changes. In addition, up-regulation of IL6 and VEGF expression levels was also observed. After withdrawal of the stretch, all of these changes were significantly diminished.

Stretch may induce morphological, cell apoptosis, and up-regulation of cytokines changes in RPE cells, indicating that cyclic stretching may participate in the progression of AMD by impeding the functions of the RPE.