Endothelial-Derived Signatures of Neurodegenerative Progression

PROJECT SUMMARY/ABSTRACT Amyotrophic Lateral Sclerosis (ALS), Frontotemporal Dementia (FTD) are devastating progressive neurodegenerative diseases characterized by neuronal dysfunction and loss. Dysfunction of the vascular endothelium precedes and likely contributes to cognitive decline by impairing blood-brain barrier (BBB) integrity. However, the exact timing of endothelial dysfunction, neuroinflammation, and cognitive decline has not been determined, in part due to the challenges associated with reliably detecting and characterizing endothelial changes in vivo. Our lab identified a unique transcriptional state in capillary endothelium, marked by nuclear TDP-43 depletion, in human donors with ALS-FTD. TDP-43, encoded by the TARDBP gene, is an RNA-binding protein implicated in both familial and sporadic forms of ALS-FTD. Nuclear loss of TDP-43 leads to pathological protein aggregation. Mouse models of nuclear TDP-43 depletion show endothelial dysfunction and increased BBB permeability, with significant transcriptional overlap between these models and human patients. Understanding how vascular alterations, including endothelial dysfunction and BBB breakdown, evolve during disease progression remains a critical gap. To gain an understanding of molecular changes preceding vascular dysfunction, this project aims to leverage cerebrovascular endothelial extracellular vesicles (cEC-EVs) to sample the capillary brain endothelium, given their unique ability to preserve RNA and protein cargo. In Aim 1, we will identify markers of nuclear TDP-43 depletion in cEC-EVs using a brain endothelial cell-specific TDP-43 deletion mouse model combined with BirA-mediated biotinylation to selectively isolate brain-endothelial-derived secreted proteins and cEC-EVs. Complementary in vitro studies will validate EV content via RNA sequencing and proteomics. Aim 2 focuses on longitudinal characterization of EV composition in a TDP-43 knock-in mutation mouse model, which partially recapitulates molecular features of human ALS-FTD. These analyses will assess EV-derived RNA and protein markers as indicators of endothelial dysfunction across neurodegenerative disease progression. This research seeks to establish a novel approach for in vivo sampling of the BBB and to establish a timeline linking endothelial dysfunction to neuroinflammation and cognitive dysfunction. The approaches developed could offer valuable insights into vascular dysfunction in ALS-FTD and inform future diagnostic strategies.