PROJECT SUMMARY/ABSTRACT
Alzheimer’s disease (AD) is the most common and severe age-associated neurodegenerative dementia for
which finding a resolving cure is a pressing national priority. The discovery of resilient individuals who remain
cognitively intact despite the presence of AD neuropathology normally associated with fully symptomatic stages
of the disease, suggests that there is a way for the brain to evade dementia even in the face of AD. It follows
that understanding the mechanism(s) involved in such extraordinary resistance would reveal targets for the
development of a novel, effective therapeutic concept based on inducing cognitive resilience in anyone
challenged with AD neuropathology. With this goal in mind, we have discovered that brain synapses in these
unaffected individuals are resistant to the disrupting binding of toxic oligomers of both amyloid beta (Aß) and tau
(an event linked to onset of dementia in AD) and that this resistance is associated with the presence of higher
numbers of neural stem cells (NSC) in the hippocampus as compared to either AD patients and control subjects.
While these observations suggest a link between high NSC numbers and synaptic resistance to damaging
amyloid oligomers, the involved mechanism (an obvious treatment target) remains unknown. Based on exciting
new, compelling preliminary data involving exosomes specifically released from NSC as mediators of this
phenomenon, in this project we will test the hypothesis that NSC-derived exosomes (via delivering specific
microRNA cargoes to target neurons) render neuronal synapses resistant to the disrupting binding of
Aß and tau oligomers and thus protect from associated memory deficits. Employing both ex vivo and in
vivo models of Aß and tau oligomer-induced synaptic dysfunction and cognitive impairment, in Aim 1 we will test
the hypothesis that NSC-derived exosomes reduce synaptic susceptibility to amyloid oligomers binding and its
functional consequences. In Aim 2 we will characterize microRNAs uniquely present in NSC-exosomes
responsible for these effects. In Aim 3 we will document the translational value of this novel mechanism
employing human NSC and neurons derived from iPSCs. At the completion of the proposed studies we will have
documented a previously unappreciated phenomenon of synaptic resistance to Aß and tau oligomers mediated
by NSC-exosomes and discovered specific miRNAs that can promote it. Given the translational value of miRNAs
for drug development, this discovery will have a substantial impact in the field by illustrating targets for the
development of an innovative treatment concept for AD centered on promoting synaptic resistance to
toxic oligomers, a strategy expected to be effective in humans as suggested by the existence of NDAN subjects.
A uniquely qualified investigative team has been assembled to successfully accomplish this project, bringing
together expertise in AD molecular neurobiology (Taglialatela), NSC biology (Micci), biochemistry of amyloid
proteins (Kayed), miRNA sequencing and analysis (Widen), electrophysiology and animal behavior (Krishnan)
and neurobiology of NSC-derived exosomes and their miRNA cargoes (Cai, sub-contract PI).