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Michael Kozlowski; Evaluation of RPE cell senescence as a mechanism for age-related macular degeneration (AMD),. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5003.
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The purpose of this work is to assess whether or not the changes seen in retinal pigment epithelial (RPE) cells as they approach cell senescence are consistent with the pathological processes that occur in age-related macular degeneration (AMD).
In this study, ARPE-19 cells grown on membrane-containing multi-well plate inserts or in cell culture flasks were used to model the natural RPE cell layer. The cells were cultured to high population doubling levels (PDL’s) and several measures of cell growth and function were assessed including doubling rate, viability, morphology, terminal restriction fragment (TRF) length (as a measure of telomere erosion), trans-epithelial electrical resistance (TEER, as a measure of the quality of their tight junctions), and senescence associated beta-galactosidase activity (SABG).
As ARPE-19 cells reached high population doubling levels (PDL), which is one trigger for cell senescence, they experienced significant telomere erosion and displayed several senescence-associated changes. First, their staining for SABG, a marker for senescence which is related to lysosomal dysfunction, was elevated. Second, their shape became more rounded, possibly indicating a change in their adhesion characteristics. Finally, the depression of their TEER values by VEGF was significantly enhanced.
The changes seen in ARPE-19 cells that had reached high PDL’s are consistent with pathological processes that occur in AMD. For example, a change in RPE cell attachment characteristics, such as that seen in the present study, could lead to a compromise in the transport of materials across Bruch’s membrane and, thereby, to the development of drusen. Likewise, a change in lysosomal functioning, as was indicated in this study by the increased SABG staining, could cause a buildup of improperly process outer segment materials, which would also contribute to the development of drusen. In addition, increased responsiveness to VEGF in terms of loosening of tight junctions, as was indicated by the present TEER results, could be permissive to the development choroidal neovascularization in wet AMD. These finding demonstrate that RPE cell senescence could contribute to the occurrence of AMD.
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