Biomarkers.

Area of Science:

• Neuroscience
• Biomarker Discovery
• Molecular Biology

Background:

• Distinguishing Dementia with Lewy Bodies (DLB) from Alzheimer's Disease (AD) is crucial due to differing prognoses, risk factors, and treatments.
• Current radioisotope-based imaging biomarkers for DLB are not widely accessible, highlighting the need for blood-based diagnostic markers.
• Chronic microglial activation is implicated in AD pathology but absent in DLB, suggesting microglial-derived biomarkers could aid differentiation.

Purpose of the Study:

• To identify and validate blood-based biomarkers for accurate differentiation between DLB and AD.
• To investigate the utility of plasma small extracellular vesicle (SEV) RNA, particularly microglial-derived RNA, as a diagnostic marker for DLB.
• To refine a prototype multiplex RNA assay for improved diagnostic accuracy.

Main Methods:

• Plasma samples were collected from individuals with DLB, AD, and controls (N=30).
• Small extracellular vesicles (SEVs) were isolated from plasma and enriched for microglial origin using TMEM119 immunoprecipitation.
• RNA was extracted from enriched SEVs, and differential gene expression was analyzed using next-generation RNA sequencing.

Main Results:

• A novel protocol for enriching microglial-origin plasma SEVs was established, enabling measurement of low-input RNA.
• Next-generation RNA sequencing identified 28 differentially expressed RNAs in DLB patients compared to AD patients, including MAPK6, IRAK1, and MIR28.
• Functional enrichment analysis revealed downregulation of pathways associated with Galactosyltransferase activity and inflammation in DLB.

Conclusions:

• Plasma SEV RNA, focused on neuroinflammation markers, can accurately distinguish DLB from AD.
• The identified differentially expressed RNAs will be used to develop a multiplex plasma SEV RNA assay.
• The diagnostic accuracy of the developed assay will be evaluated in an independent cohort.