Regenerative medicine for neurodegenerative diseases: history, strategies, and clinical advances

In the context of global ageing, the prevalence of neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), is rapidly increasing. However, current symptomatic treatments have achieved limited benefits in clinical settings and fundamentally fail to reverse the progressive loss of specific neuronal populations. Halting neurodegeneration and restoring impaired cognitive, motor or visual functions through nerve regeneration and circuit reconstruction represent the clinically meaningful goals for treatments of NDDs. Regenerative medicine has emerged as a promising paradigm to address this unmet need. In this review, we trace the historical evolution of regenerative therapies for NDDs - from early exploratory cell transplantation to modern approaches involving pluripotent stem cells (PSCs) and in vivo direct reprogramming. Furthermore, we elucidate the core strategies of regenerative medicine within an integrated framework encompassing "Replacement", "Regeneration", and "Rejuvenation". Finally, we highlight recent advances in clinical research, particularly milestone trials in cell replacement therapy for PD, as well as the application of mesenchymal stem cells (MSCs) in AD and ALS.