Identification of key molecules in the brain of PSEN1 pigs to study Alzheimer's Disease

Abstract

Previously, a clinically relevant swine model (PSEN1ΔE9/+) has been established by utilizing genome editing system to study early onset Alzheimer's Disease (EO-AD). Cognitive assessments and MRI scans of their brain indicate that these pigs carry cognitive deficiencies and abnormal brain physiology, respectively, demonstrating their relevance to study AD. This study was conducted to characterize cell morphology and distributions in the brain cortex and hippocampus of PSEN1ΔE9/+ and wildtype (WT) pigs at 12-14 months of age. First, we quantified the level of APP, Tau, GFAP, and Iba1 proteins in their brain using western blotting. There were no statistically significant differences in Tau and GFAP concentrations in PSEN1 and WT pigs (n=3 per model) but there was a numerical increase in Tau and GFAP in PSEN1 pigs. Next, we examined if the localization of A[beta] and Tau proteins in the brain cortex and hippocampus were different between PSEN1 and WT pigs. Brains from PSEN1 and WT pigs (12-14 months old) were collected, fixed, then immunofluorescent staining was performed to identify Amyloid-beta protein plaques (A[beta]), Tau protein (Tau), reactive microglia (Iba1), astrocytes (GFAP), neurons (NeuN), and nuclei (DAPI) in age-matched PSEN1 and WT brains. PSEN1 pigs had statistically higher Amyloid-beta and Iba1 expression and number of microglia in the cortex than WT pigs. Tau signaling and numbers of neurons were numerically lower in PSEN1 animals than WT. The morphology and cell count of microglia and astrocytes showed early signs of gliosis and pro-inflammatory responses in the brain. The hippocampus analysis did not yield conclusive results, possible due to the animals not being aged long enough. This study demonstrates relevance of the PSEN1 pigs to study AD and suggests necessary refinements to study AD pathogenesis using the PSEN1 pigs.