An Alzheimer-associated neuronal model to study APP processing and mitochondrial homeostasis

Abnormal amyloid precursor protein (APP) metabolism and mitochondrial dysfunction are implicated in Alzheimer's disease (AD) pathogenesis. The Swedish mutation (APPSwe), which causes early-onset familial AD, enhances β-secretase cleavage, shifting APP processing toward the amyloidogenic pathway. Previous results in APPSwe patient-derived brain organoids show selective mitochondrial vulnerability under oxidative conditions, suggesting a direct link between APP and mitochondrial homeostasis. We developed glutamatergic neurons (i3N) from wild type (WT) and APPSwe patient-derived iPSCs as a model to study the molecular mechanisms underlying mitochondrial homeostasis alterations in AD. APP distribution was assessed by immunofluorescence with N- and C-terminal APP antibodies revealing an increase in the N-/C-terminal ratio in APPSwe i3N. Neuronal polarization evaluated by quantifying neurite length and morphological progression showed an increased neurites number with longer projections in APPSwe i3N compared with WT i3N. Mitochondrial morphology was characterized by analyzing length and width (MitoTracker-Green) and membrane depolarization was analyzed by TMRE intensity. These findings suggest that APPSwe alters APP metabolism and early neuronal morphological development, providing a useful system to study their relationship with mitochondrial homeostasis and oxidative vulnerability in AD.