Protocol for "Neuromelanin accumulation drives endogenous synuclienopathy in non-human primates"

The authors report no competing interests

This study was aimed to develop and characterize

a non-human primate (NHP) model of Parkinson’s disease mimicking the known

neuropathological hallmarks of Parkinson’s disease to the best possible extent.

Accordingly, we sought to determine whether AAV-mediated enhanced expression of

human tyrosinase (hTyr) in the substantia nigra (SNpc) of non-human primates

(NHPs) is able to induce a time-dependent accumulation of neuromelanin (NMel)

in dopaminergic neurons, further triggering and endogenous synucleinopathy,

progressive cell death and a pro-inflammatory scenario, in keeping with what

was formerly reported in rats by taking advantage of a similar strategy (Carballo-Carbajal

et al., 2019). Furthermore, the potential prionoid spread of endogenous

alpha-synuclein (a-Syn) species towards the

prefrontal cortex was analyzed, in an attempt to evaluate to what extent there

is a propagation of endogenous a-Syn

by permissive trans-synaptic templating (e.g. the so-called Braak hypothesis).

Adult j Macaca fascicularis a fascicularis)

were injected with adeno-associated viral vectors (AAVs) encoding either the

hTyr gene (AAV-hTyr; delivered into the left SNpc) or a null construct for

control purposes (AAV-null; injected into the right SNpc). In order to

delineate a timeline for the underlying processes, one group of NHPs was

sacrificed four months post-AAV deliveries (animals M308F4 and M310M4), whereby

the follow-up timing for second experimental group was settled at eight months

post-AAVs surgeries (animals M307F8 and M309M8). Neuroimage studies (MRI and

Mic in vivo were conducted in vivo at

different time points. Upon animal sacrifices, brain tissue samples were

processed for histological analysis comprising intracellular NMel levels,

intracellular aggregates, nigrostriatal degeneration and neuroinflammation.

PROTOCOL.docx