Exosomes in Alzheimer's Disease: From Pathological Mechanisms to Biomarker Potential and Therapeutic Applications.

Exosomes are small extracellular vesicles that mediate communication between cells by carrying proteins, lipids, nucleic acids, and other biologically active molecules. In Alzheimer's disease (AD), their role appears to be complex and context-dependent. Evidence suggests that exosomes may contribute to disease progression by supporting the intercellular spread of amyloid-β and tau pathology. At the same time, they are increasingly being investigated as blood-based biomarkers and as potential therapeutic delivery systems. This review summarizes current evidence on the involvement of exosomes in AD biology. Particular attention is given to their role in amyloid-β and tau propagation, microglia-driven neuroinflammation, and the Pellino-1 (Peli1)-related communication between microglia and astrocytes. The review also discusses the diagnostic value of neuron- and astrocyte-derived exosomes as minimally invasive biomarkers. In addition, the therapeutic potential of mesenchymal stem cell-derived exosomes is evaluated, especially in relation to amyloid clearance, neuroinflammation, synaptic repair, and blood-brain barrier crossing. Although preclinical and early clinical findings are encouraging, several barriers still limit clinical translation. These include the lack of standardized isolation methods, cargo heterogeneity, large-scale production difficulties, and insufficient long-term safety and efficacy data. Overall, exosome-based strategies represent a promising but still developing field in AD research, with potential relevance for early diagnosis, disease monitoring, and future therapeutic applications.