Characterization of pSer129-αSyn Pathology and Neurofilament Light-Chain Release across In Vivo, Ex Vivo, and In Vitro Models of Pre-Formed-Fibril-Induced αSyn Aggregation.

Protein aggregation is a predominant feature of many neurodegenerative diseases, including synucleinopathies, which are characterized by cellular inclusions containing α-Synuclein (αSyn) phosphorylated at serine 129 (pSer129). In the present study, we characterized the development of αSyn pre-formed fibril (PFF)-induced pSer129-αSyn pathology in F28tg mice overexpressing human wild-type αSyn, as well as in ex vivo organotypic cultures and in vitro primary cultures from the same mouse model. Concurrently, we collected cerebrospinal fluid (CSF) from mice and conditioned media from ex vivo and in vitro cultures and quantified the levels of neurofilament light chain (NFL), a biomarker of neurodegeneration. We found that the intra-striatal injection of PFFs induces the progressive spread of pSer129-αSyn pathology and microglial activation in vivo, as well as modest increases in NFL levels in the CSF. Similarly, PFF-induced αSyn pathology occurs progressively in ex vivo organotypic slice cultures and is accompanied by significant increases in NFL release into the media. Using in vitro primary hippocampal cultures, we further confirmed that pSer129-αSyn pathology and NFL release occur in a manner that correlates with the fibril dose and the level of the αSyn protein. Overall, we demonstrate that αSyn pathology is associated with NFL release across preclinical models of seeded αSyn aggregation and that the pharmacological inhibition of αSyn aggregation in vitro also significantly reduces NFL release.