Background: The prion-like misfolding and aggregation of
-synuclein (-syn) is involved in the pathophysiology of
Parkinson’s disease and other synucleinopathies. Seed amplification assays (SAAs)
are biophysical tools that take advantage on the peculiar properties of prion
proteins by amplifying small amounts of aggregates in biological fluids at the
expense of recombinant monomeric protein added in solution. SAAs have emerged as
the most promising tools for the diagnosis of synucleinopathies in vivo.
However, the diagnostic outcome of SAAs depends on the aggregation kinetics of
-syn, which in turn is influenced by several experimental variables.
Methods: In our work, we analysed the impact on SAAs of some of the most
critical experimental factors by considering models that describe the aggregation
kinetics of -syn. Results: We started our analysis by making
simulations to understand which kinetic models could explain the aggregation
kinetics of -syn during incubation/shaking cycles. Subsequently, under
shaking/incubation cycles similar to the ones commonly used in SAAs, we tested
the influence of some analytical variables such as monomer concentration,
presence/absence of glass beads, pH, addition of human cerebrospinal fluid, and
use of detergents on -syn aggregation. Conclusions: Our
investigation highlighted how optimization and standardization of experimental
procedures for -syn SAAs is of utmost relevance for the ultimate goal
of applying these assays in clinical routine. Although these aspects have been
evaluated with specific SAA protocols, most of the experimental variables
considered influenced very general aggregation mechanisms of -syn, thus
making most of the results obtained from our analyses extendable to other
protocols.