Researchers at Tokyo Metropolitan University have turned to concepts from polymer physics to better understand a central feature of Alzheimer's disease (AD), the university informs. They examined the formation of tau protein fibrils—structures that play a key role in the degradation of neurons—and heir work revealed that these fibrils do not appear suddenly.

The results of the study were published in the journal Science Direct.

Instead, these fibrils emerge after large clusters of tau proteins begin to gather in solution, a process that resembles polymer crystallization. When the scientists disrupted these early clusters, the fibrils failed to form, suggesting a promising direction for new strategies against neurodegenerative conditions.

Led by Professor Rei Kurita, the research team applied ideas from how polymers organize into crystals.

Polymers, which are long chains of repeating molecular units, often do not crystallize by simply adding one chain at a time. Instead, they pass through intermediate precursor structures before forming an ordered crystal.

Drawing on this concept, the scientists examined tau proteins in solution and found that fibril formation (fibrillization) is also preceded by a precursor stage. In this case, the precursor is a loose assembly of tau proteins measuring only tens of nanometers. Techniques including small angle X-ray scattering and fluorescence-based analyses confirmed the presence of these structures.

A key discovery was that these precursors are not rigid but instead are soft, temporary clusters. The researchers were able to dissolve them by altering sodium chloride levels in the presence of heparin, a naturally occurring anticoagulant. When the clusters were disrupted or prevented from forming, the solution produced almost no tau fibrils. The team suggested that this effect occurs because increased concentrations of charged ions reduce how strongly tau proteins interact with heparin. According to their explanation, this change enhances electrostatic "screening," making it more difficult for the molecules to find each other and form clusters.

These findings point to a potential shift in how scientists approach AD treatments. Instead of trying to break apart the final fibrils, therapies could aim at stopping the reversible precursor stage before harmful structures develop. This approach could influence not only AD research but also efforts to understand other neurodegenerative diseases, including Parkinson's disease.