Investigation of the Roles of Brain Extracellular Matrix Aging in Alzheimer's Disease 'Independently of Cellular Senescence

Alzheimer's disease is a neurodegenerative disease characterized by a decrease in daily vital activities and impaired cognitive abilities, accompanied by neuropsychiatric symptoms and behavioral changes. It is the most common type of dementia. Age is the most effective risk factor affecting the prevalence of Alzheimer's disease. The main pathological findings in this disease are the accumulation of abnormally amyloid beta (Aβ) plaques outside the cell and the formation of neurofibrillary tangles with the phosphorylation of tau proteins accumulated inside the cell. These pathologies lead to disconnection of neuron connections, neuronal death and ultimately brain atrophy. Alzheimer's disease can develop by being affected by many factors, both genetic and environmental. In studies on genetically inherited Alzheimer's, mutations were frequently found in genes encoding amyloid precursor protein (APP) and presenilin-1 (PSEN1). Alzheimer's disease, which occurs with advancing age, is one of the diseases that are frequently studied. Studies usually involve cellular approaches.
This project proposal we have prepared divides the concept of aging into two as the cellular level and the extracellular matrix (ECM) level. This designed study is about the investigation of the roles of brain extracellular matrix (ECM) age in Alzheimer's disease, independent of cellular aging. Our study is a 3D cell culture model created to understand how brain ECM age changes Alzheimer's pathogenesis. Although there are many experimental models created for Alzheimer's disease, no model allows to examine the effects of ECM age in Alzheimer's disease independent of cellular aging. At this point, the model we propose is unique.

The project we propose consists of 3 basic stages. The first step involves obtaining the mutant stem cell line that will create the Alzheimer's phenotype. For this; Swedish (K670N / M671L) and London (V717I) mutations (APPIL) will be generated in the APP gene of ReNcell VM neural progenitor cells, and (ΔE9) mutation (PSEN1 (ΔE9)) in the PSEN1 gene. The second phase includes the creation of young and old ECM platforms. At this stage, brain extracellular matrices (dbECMs) will be produced by decellularization of the brains taken from donors. dbECMs will be obtained from both healthy (inbred Fischer 344 rats) and transgenic Alzheimer's (inbred TgF344-AD rats created with Fischer344 strain) young (6 months old) and old (16 months old) rats. The use of inbred rats at this stage is very important in preventing individual differences in the content of brain ECM. Finally, cells with Alzheimer's disease phenotype forming amyloid beta plaques and neurofibrillary tangles will be obtained by 8-week neurogenic differentiation of 3-dimensional (3D) dbECM hydrogel cultures to be created with mutant ReN cells (APPIL, PSEN1 (ΔE9 or both) in the same passage and population). At this stage, it is critical to use 3D dbECM hydrogels of cells in the same passage and population. In this way, cellular aging will be equalized in all experimental groups and the age difference will only be due to ECM in disease modeling.
Detailed investigations in these models will be transformed into data describing how ECM age affects Alzheimer's pathogenesis. The experimental model we will create to investigate the roles of ECM age in Alzheimer's disease has a structure that can be modified and used for many diseases that occur during the aging process. The proposed project has the potential to provide scientists who will study Alzheimer's disease with a different perspective on the mechanisms of the disease. This study, in which rejuvenation at ECM age causes changes in the pathogenesis of the disease, provides a model that can be used for new drug designs related to the matrix structure.