Viral and non-viral cellular therapies for neurodegeneration.

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) are characterized by progressive loss of neurons and still lack curative treatment options. In this review, we describe current and developing therapeutic strategies that include viral vector-based gene delivery, antisense oligonucleotide (ASO) and RNA interference methods, stem cell transplantation, and genome editing technologies. Adeno-associated viruses (AAVs) and lentiviruses have been used for gene delivery in preclinical and clinical studies, while ASOs are under development to reduce expression of pathogenic proteins such as tau, α-synuclein, and mutant huntingtin. Cellular therapies, including mesenchymal stem cell (MSC)-based paracrine support and transplantation of neurons derived from induced pluripotent stem cells (iPSCs), are being evaluated, particularly in PD and AD. We also discuss important gene targets such as APOE4, GBA1, SCNA, and MAPT, and how treatment strategies may differ between monogenic and polygenic forms of these disorders. Lastly, we highlight recent efforts focused on genes like TREM2, PINK1, and progranulin, and examine their role in the future development of gene- and cell-based interventions.