Novel strategies for induction of aging in human PSC-derived lineages for modeling Alzheimer's Disease

Sloan-Kettering Inst Can Research, New York NY

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Abstract

Project Summary Alzheimer’s disease (AD) represents an increasing medical and societal problem affecting > 6 million patients in the US, with numbers continuing to grow due to the increase in average age and lifespan. Despite the urgent need, there are still only few therapeutic options available to date, and many fundamental questions about AD pathology and mechanisms remain unresolved. Human pluripotent stem cells (hPSCs) offer a novel strategy to tackle AD, as they allow the study of AD directly in human neurons and glia, at scale, and in a patient-specific manner. Furthermore, there has been considerable progress in generating AD patient-specific or genetically engineered stem cells, in directing their differentiation into neuronal and glial lineages and in devising strategies to study many hPSC lines in parallel, including hPSCs from annotated patient cohorts to match in vitro behavior, human genetics and longitudinal clinical data. However, an unresolved issue is that hPSC derived cells resemble a fetal rather than adult-like or aged state, which represents an age mismatch for the neurons used for AD modeling versus the neurons affected in the brain of patients suffering from AD. Over the last 5 years, supported by R01AG054720, we made considerable progress in devising strategies to measure and manipulate neuronal age in vitro, and we have developed culture systems that can model neuroinflammatory interactions present in the AD brain. Most recently, we developed two novel paradigms to identify age-modifying factors : i) based on a genome wide CRISPR loss-of-function screen we identified genetic disease modifiers in hPSC-derived APPSwe cortical neurons that trigger late-onset phenotypes in AD but not isogenic control neurons, including inhibitors of neddylation s ii) We developed RNAge as a tool to measure cellular age in hPSC-derived cortical neurons, and we performed an in-silico screen using RNAge as a probe set in L1000 perturbation data. Validated hits from the study can trigger neuronal age signatures and late-onset neurodegenerative phenotypes in AD neurons. Here, we will extend in Aim 1, our ability to measure and score cellular age at the single cell level with a particular focus on glial aging and on tracking dynamic experimental systems that either reset, retain, or rejuvenate the age of neurons. In Aim 2, we will assess and compare the performance of novel aging paradigms and ask to what extent aging trajectories and endpoints are shared or distinct. We will further address the role of glial cells and glial aging in an effort to capture both cell autonomous and non-autonomous components of the aging process. Finally, in Aim 3, we will apply the most promising induced aging paradigms to modeling AD. These studies will include neuronal, astrocyte, microglial and combined tri-culture systems; and introduction of AD-related mutations that capture neuronal vs glial AD vulnerabilities. The ultimate goal is to devise aging paradigms that mimic physiological age and AD progression and to establish a new class of disease models to capture a decade long process in a defined in vitro culture system.