Cathepsin B pH-Dependent Activity Is Involved in Lysosomal Dysregulation in Atrophic Age-Related Macular Degeneration

Abstract EN

Age-related macular degeneration (AMD) is characterized by retinal pigment epithelial (RPE) cell dysfunction beginning at early stages of the disease.

The lack of an appropriate in vitro model is a major limitation in understanding the mechanisms leading to the occurrence of AMD.

This study compared human-induced pluripotent stem cell- (hiPSC-) RPE cells derived from atrophic AMD patients (77 y/o±7) to hiPSC-RPE cells derived from healthy elderly individuals with no drusen or pigmentary alteration (62.5 y/o±17.5).

Control and AMD hiPSC-RPE cell lines were characterized by immunofluorescence, flow cytometry, and electronic microscopy.

The toxicity level of iron after Fe-NTA treatment was evaluated by an MTT test and by the detection of dichloro-dihydro-fluorescein diacetate.

Twelve hiPSC-RPE cell lines (6 AMD and 6 controls) were used for the experiment.

Under basal conditions, all hiPSC-RPE cells expressed a phenotypic profile of senescent cells with rounded mitochondria at passage 2.

However, the treatment with Fe-NTA induced higher reactive oxygen species production and cell death in hiPSC-RPE AMD cells than in hiPSC-RPE Control cells.

Interestingly, functional analysis showed differences in lysosomal activity between the two populations.

Indeed, Cathepsin B activity was higher in hiPSC-RPE AMD cells compared to hiPSC-RPE Control cells in basal condition and link to a pH more acidic in this cell population.

Moreover, oxidative stress exposure leads to an increase of Cathepsin D immature form levels in both populations, but in a higher proportion in hiPSC-RPE AMD cells.

These findings could demonstrate that hiPSC-RPE AMD cells have a typical disease phenotype compared to hiPSC-RPE Control cells.