Spontaneous aging of mature amyloids alters structural stability, cytotoxicity, and susceptibility to biological clearanceDownload PDF Download PDF ArticleOpen accessPublished: 07 July 2026Maksim I. Sulatsky1 na1,Olga V. Stepanenko2 na1,Arina A. Kayda2,Olesya V. Stepanenko ORCID: orcid.org/0000-0003-3779-67112,Ekaterina V. Mikhailova2 &…Anna I. Sulatskaya ORCID: orcid.org/0000-0002-1207-33842 Cell Death Discovery (2026) Cite this article We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.SubjectsCell deathProtein aggregationProteolysisAbstractAccumulation of amyloid fibrils is a key factor in the pathogenesis of progressive diseases, including neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease, as well as systemic amyloidosis. Although amyloid deposits are known to persist in vivo for years or even decades, it remains unclear how the structure and biological properties of mature fibrils evolve during prolonged post-assembly residence. Here, we addressed this question using a simplified cell-free aqueous model designed to isolate the intrinsic time-dependent behavior of mature amyloid aggregates from the complexity of the biological milieu. Specifically, we investigated the long-term evolution of two polymorphs of lysozyme amyloid fibrils as model systems with distinct clustering propensities that mimic the diversity of amyloid deposits. We challenge the assumption of amyloid stability by demonstrating their spontaneous degradation over 16 months at physiological temperature, a process we define as amyloid “aging”. This process is characterized by aggregate declustering, fibril shortening, and progressive depolymerization into monomeric subunits, accompanied by a pronounced reduction in intrinsic toxicity across multiple human cell lines. Notably, “aged” fibrils were disassembled and degraded more efficiently than freshly prepared aggregates by the molecular chaperone α-B-crystallin and immune-associated proteases, including matrix metalloproteinase-9 and cathepsins B and D. However, this enhanced degradation revealed a paradox: accelerated processing of “aged” amyloids did not always reduce cytotoxicity and, in some cases, even exacerbated it, consistent with the generation of biologically active fibril-derived species rather than their complete conversion into non-toxic monomers. We provide the first systematic evidence that mature amyloids are dynamic structures undergoing spontaneous degradation that fundamentally alters their cytotoxicity and susceptibility to biological clearance. Our results introduce amyloid aging as a previously underappreciated dimension of amyloid biology and emphasize the need to account for fibril “age” when evaluating pathogenic potential and developing anti-amyloid therapeutic strategies.Spontaneous “aging” of amyloid fibrils leads to suprastructural remodeling: declustering, fibril shortening, and attenuated cytotoxicity. While “aged” aggregates are degraded more efficiently by immune-associated proteases and α-B-crystallin than “fresh” fibrils, this enhanced degradation does not reduce cytotoxicity and, in some cases, exacerbates it, highlighting the complex interplay between aggregate maturity and biological outcomes.FundingThe study was funded by the Russian Science Foundation (grant no. 23-74-10092).Author informationAuthor notesThese authors contributed equally: Maksim I. Sulatsky, Olga V. Stepanenko.Authors and AffiliationsLaboratory of cell morphology, Institute of Cytology Russian Academy of Sciences, St. Petersburg, RussiaMaksim I. SulatskyLaboratory of structural dynamics, stability and folding of proteins, Institute of Cytology Russian Academy of Sciences, St. Petersburg, RussiaOlga V. Stepanenko, Arina A. Kayda, Olesya V. Stepanenko, Ekaterina V. Mikhailova & Anna I. SulatskayaAuthorsMaksim I. SulatskyView author publicationsSearch author on:PubMed Google ScholarOlga V. StepanenkoView author publicationsSearch author on:PubMed Google ScholarArina A. KaydaView author publicationsSearch author on:PubMed Google ScholarOlesya V. StepanenkoView author publicationsSearch author on:PubMed Google ScholarEkaterina V. MikhailovaView author publicationsSearch author on:PubMed Google ScholarAnna I. SulatskayaView author publicationsSearch author on:PubMed Google ScholarCorresponding authorCorrespondence to Anna I. Sulatskaya.Ethics declarationsCompeting interestsThe authors declare no competing interests.Ethics approval and consent to participateThe study did not involve human participants, primary patient-derived material, identifiable personal data, or animal subjects. Therefore, ethics approval and informed consent to participate were not required.Additional informationPublisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Supplementary informationSupplemental material (download DOCX )Rights and permissionsOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Reprints and permissionsAbout this articleDownload PDF