Discovering novel players in mechanisms of extracellular vesicle release, cargo loading, and early pathogenesis of late-onset Alzheimer's Disease

Cheng, Linzhao; MacHairaki, Vasiliki; Witwer, Kenneth

Abstract

Alzheimer?s disease (AD) is a public health crisis that continues to grow as the population ages, demanding new insights into pathophysiology. AD, a progressive neurodegenerative disease, is now the sixth-leading cause of death in the United States, places a burden of nearly half a trillion dollars per year on caregivers and taxpayers, and is expected to double in prevalence within the next decade. The pathophysiology of AD includes the loss of synaptic connections through neurodegeneration and the prion-like spread of proteinopathies including extracellular deposition of ?-amyloid peptides (A?). In sporadic AD, variants of the apolipoprotein E gene (APOE) have emerged as the greatest apparent risk factor, and AD has an outsized effect on aging women. Extracellular vesicles (EVs), including exosomes, have recently emerged as important players in AD pathophysiology (26?28). Comprising a diversity of double-leaflet membrane-bound particles, EVs have been reported by several groups including ours to spread proteins implicated in pathogenesis both in vitro and in vivo. Certain types of EVs have also been suggested to alleviate AD symptoms and may serve as therapeutic options. However, much remains to be learned and exploited in the relationship of AD and EVs in APOE- and gender-associated contexts. We plan to address this need, focusing innovative techniques and tools on the problem. We hypothesize firstly (Aims 1-3) that powerful induced pluripotent stem cell models of neurons and astrocytes, two cell types of central importance in AD, will facilitate screens of factors likely involved in AD pathogenesis via EVs. Secondly (Aims 2 and 3), membrane trafficking and membrane surface proteins will contribute to EV release, AD-related cargo loading, and effects on recipient. Thirdly and finally, (Aim 4), modulating EVs in novel organoid and animal models will also modulate disease-related markers and processes.

Public Health Relevance

Extracellular vesicles are small pieces of cells that can transmit proteins and other factors involved in the development of Alzheimer?s disease, a degenerative disease of the brain with devastating personal and financial costs to affected families and the general public. In this study, powerful biological tools including patient-derived induced pluripotent stem cells that are differentiated into neurons and astrocytes are used to generate a better understanding at the molecular and cellular level of the contributions of extracellular vesicles to Alzheimer?s. By identifying and describing the pathways of extracellular vesicle release and loading, and by probing the consequences when neurons are exposed to extracellular vesicles, our findings are expected to point the way to much-needed new therapeutic possibilities.