Artificial intelligence-based 3D segmentation of tangle-associated TDP-43 in neurodegeneration

Area of Science:

• Neuroscience
• Neuropathology
• Biochemistry

Background:

• TAR DNA-binding protein 43 (TDP-43) inclusions are frequently observed alongside hyperphosphorylated tau, forming neurofibrillary tangles characteristic of Alzheimer's disease (AD) and primary age-related tauopathy (PART).
• While the association of TDP-43 with cognitive impairment in AD is known, its precise localization, cellular characteristics, and inclusion maturation patterns remain incompletely understood.
• Investigating these aspects is crucial for deciphering the complex neuropathological processes in tauopathies.

Purpose of the Study:

• To investigate the intricate relationships between TDP-43 inclusions and the continuum of neurofibrillary tangle maturation in AD, PART, and co-pathological conditions.
• To elucidate the regional distribution, cellular characteristics, and maturation stages of TDP-43 inclusions across different brain regions.
• To apply advanced AI-based segmentation for precise quantification and spatial analysis of these pathological hallmarks.

Main Methods:

• Multiplex immunostaining was employed to label phosphorylated TDP-43 and various phosphorylated tau epitopes (AT8, pS396, TauC3, MN423, GT38) in brain tissue from controls, PART-TDP, AD-TDP, and AD-TDP-LBD cases.
• Confocal imaging was performed on eight specific brain regions: amygdala (basolateral and centromedial), hippocampus (CA1-4, DG, subiculum), and entorhinal cortex.
• Artificial intelligence (AI)-based segmentation was utilized for object recognition, 3D reconstruction, and quantification to analyze spatial relationships and TAT inclusion maturity, complemented by Thioflavin S (ThioS) histochemistry.

Main Results:

• Mature TDP-43 and tau (TAT) inclusions labeled by pS396 predominated across all examined regions in both PART and AD cases.
• The amygdala, specifically the basolateral and centromedial nuclei, exhibited the highest overall counts of both pre-TAT and mature TAT inclusions.
• While mature TATs were homogenously distributed in the hippocampus, the CA4 and dentate gyrus (DG) showed the greatest mature TAT composition. The entorhinal cortex displayed comparable numbers of pre-TAT and mature TATs, with mature forms predominating.

Conclusions:

• The study successfully demonstrated unique aggregation and maturation patterns of TDP-43 and tau inclusions using an unbiased AI-driven pipeline.
• Region-specific dynamics in the neurodegenerative processes of PART and AD were highlighted, emphasizing the differential distribution and maturation of TAT inclusions.
• These findings provide critical insights into the spatiotemporal progression of tauopathies and the role of TDP-43 in these diseases.