Novel cell markers with altered expression in brain aging and Alzheimer's disease: A review
Aging and Alzheimer's disease are complex processes marked by continuous neuronal loss, disrupted neural networks, and cognitive decline. The past decade has seen advances in genomics, proteomics, and single-cell RNA sequencing, enabling the discovery of cellular markers with distinct gene expression patterns. This review aims to compile recent markers of aging and Alzheimer’s disease in immune, glial, and neuronal cells, which are increasingly vital for enhancing diagnostic precision and monitoring disease progression. Markers such as Triggering receptor expressed on myeloid cells 2 (TREM2) and Cluster of differentiation 33 (CD33) facilitate immune responses and function as indicators of neuroinflammation and amyloid-beta clearance; Glial fibrillary acidic protein (GFAP) and aquaporin-4 serve as indicators of gliosis and impaired interstitial fluid drainage; Postsynaptic density protein 95 (PSD-95), Synaptosomal-associated protein 25 (SNAP25), and aberrant tau phosphorylation signify synaptic degradation and cytoskeletal instability characteristic of Alzheimer's pathology. The breakdown of the blood-brain barrier is associated with endothelial nitric oxide synthase (eNOS) and vascular cell adhesion molecule 1 (VCAM-1). The markers were identified using cutting-edge technologies that unveiled variations in gene expression across cell types, brain regions, and disease stages. This cellular heterogeneity improves understanding of Alzheimer's disease (AD) progression and brain aging, clarifies molecular pathways, and may be used for prognostic and diagnostic purposes after thorough validation. Novel cellular markers with altered expression profiles are still being identified through ongoing research, which could be crucial for improving our understanding of and ability to treat neurodegenerative diseases.