Vascular burden attenuates the TDP-43-TMEM106B pathological relationship in neurodegenerative disease with and without Alzheimer disease neuropathological change

TMEM106B, a lysosomal transmembrane protein, is a risk factor for neurodegenerative diseases, including Alzheimer disease (ad) and TDP-43 proteinopathies. TMEM106B pathology occurs in normal aging and is increased in TDP-43 proteinopathy but its role in dementia remains unclear. Cerebrovascular disease (CVD) is a driver and co-pathology of dementia, yet its contribution to TMEM106B accumulation in the context of TDP-43 and ad neuropathological changes (ADNC) has not been explored. We analyzed post-mortem human hippocampal sections spanning not-, low-, intermediate-, and high-ADNC. In secondary analyses, cases ≥65 years were stratified by TDP-43 immunopositivity and CVD severity; cases <65 years were included to contextualize age-associated effects. TMEM106B immunoreactivity was quantified using digital pathology. Linear regression models demonstrated that age and sex (higher in females) were independent predictors of TMEM106B immunopositivity whereas Braak stage, CERAD-NP score, and Thal phase were not. The positive TDP-43-TMEM106B association was attenuated with increased CVD pathology severity, suggesting that vascular burden modifies this relationship. Sensitivity analyses restricted to LATE-NC attenuated several associations, indicating that pooled TDP-43 findings should be interpreted cautiously given possible disease heterogeneity. TMEM106B immunoreactivity was most strongly associated with age and sex, while vascular burden, rather than ADNC level, modified its relationship with TDP-43 proteinopathy.