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Farhad Farjood, Elizabeth Vargis; Mechanical Stress in RPE Cells Induces VEGF Expression and Promotes in vitro Angiogenesis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2472.
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Retinal pigment epithelium (RPE) is exposed to increasing levels of mechanical stress when drusen are formed during non-exudative age-related macular degeneration (AMD). Using two novel devices, specific levels of mechanical stress was applied to RPE cells in vitro to test the hypothesis that mechanical stress can induce angiogenesis via elevating vascular endothelial growth factor (VEGF) expression in RPE cells.
Polydimethylsiloxane (PDMS) was used to fabricate a mechanical stress device (PDMS device) to apply continuous mechanical stress to ARPE-19 cells (n=6) over 24 hours. Another device was developed to apply acute mechanical stress to ARPE-19 cells (n=6) grown on porous polyester membranes (Transwell membranes; pore size=0.4 µm). VEGF expression in the used media of control and mechanically stressed cells was measured using enzyme-linked immunosorbent assays (ELISA). An in vitro tube formation assay was also performed by incubating human umbilical vein endothelial cells (HUVECs) with conditioned media from mechanically stressed and control ARPE-19 cultures (n=3). MATLAB software was used to measure the length of endothelial tubes. Two-tailed Student's t-test was performed for statistical analysis with p<0.05 considered statistically significant.
Exposing ARPE-19 cells to continuous mechanical stress over 24 hours using the PDMS device significantly increased VEGF expression by 12.3% compared to control groups (p=0.015). Also, mechanical stress elevated both apical and basal VEGF expression in ARPE-19 cells grown on Transwell membranes by 17.2% (p=0.016) and 30.4% (p=0.039), respectively. Adding continuous mechanical stress to ARPE-19 cultures using the PDMS device increased the length of endothelial tubes by 27.9 % (p=0.041). While the apical media from mechanically stressed Transwell cultures did not significantly increase tube length (11.3%; p=0.074), the basal media significantly increased the length of endothelial tubes by 34.0% (p=0.039).
VEGF expression in RPE cells increases in response to both acute and continuous mechanical stress. Elevated VEGF levels are associated with increased in vitro angiogenesis. These results support our hypothesis that mechanical stress in RPE cells can induce angiogenesis and suggest that mechanical stress may be involved in the initiation and progression of neovascularization in AMD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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