Alzheimer's disease (AD) is the most common dementia, and is hallmarked by deposition of amyloid- peptides as 'senile' -amyloid plaques, neurofibrillary tangles comprised of abnormally phosphorylated tau protein, and neuronal dysfunction and loss. Currently available AD treatments have a quantitatively minor impact on the disease, doing little to improve the quality or duration of life of patients suffering from thi debilitating illness, which is clinically characterized by loss of pneumonic and higher cortical functions. A critical lynchpin for the development of an AD treatment that is both effective and safe is model systems that faithfully recapitulate the human syndrome. In this regard, transgenic mice harboring mutations in one or more genes that cause early-onset familial AD (fAD) have been enormously helpful, both in terms of interrogating potential therapeutic targets and also for understanding pathological mechanisms of disease. Yet, these models are necessarily limited due to their species, and it remains an open question as to whether the mouse will ever be able to faithfully model AD neuropathology as it occurs in the human. The central theme of our R21 grant application is to use an emerging technology with great promise for modeling human diseases: human induced pluripotent stem (hiPS) cells. The basic steps involve culturing skin fibroblasts from individuals bearing mutations in genes that cause fAD or from age-matched control relatives lacking disease, and reprogramming them into hiPS cells that are later differentiated into forebrain glutamatergic neurons. Once differentiated, these forebrain neurons will be functionally interrogated to specifically assess pathologic hallmarks of human AD. We propose to carry out this work in two parts. The focus of Specific Aim 1 is to establish iPS cell lines from four fAD mutant and four related control fibroblast cell lines. We will draw fibroblastsfrom ~175 lines derived from individuals bearing fAD mutations and age-matched control relatives, maintained through the NIH/NIA Aging Cell Culture Repository at the Coriell Institute for Medical Research. The main goal of Specific Aim 2 is to interrogate Alzheimer phenotypes in fAD mutant vs. control forebrain neurons differentiated from reprogrammed iPS cells. In Sub-Aim 2a, we hypothesize that Alzheimer disease phenotypes will occur and be exacerbated by experimental induction of excitotoxicity in fAD mutant vs. non-mutant hiPS-derived forebrain neurons. Sub-Aim 2b will test proof-of-concept for whether the current standard of care AD drug, memantine, will at least partially rescue Alzheimer phenotype(s) in differentiated fAD mutant forebrain neurons. Completion of this exploratory work is expected to lead to a 'disease-in-a-dish' model of human fAD. Such a model could pave the way toward understanding both basic pathologic mechanisms of the disease as well as potential therapeutic approaches.
There are now over 3 million Americans afflicted with Alzheimer's disease, a figure that is projected to increase to 9 million by 2050, underscoring a rapidly developing public health crisis. We propose to utilize cutting-edge human induced pluripotent stem (hiPS) cell technology to model this devastating disease in cultured neurons. If successful, this exciting disease-in-a-dish model could allow pre-clinical testing of therapeutic approaches.
