Role of Stem Cells and Derived Exosomes as a Novel Therapeutic Agent against Alzheimer’s and Parkinson’s Disease

The significant rise in the global incidence of neurological diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), has been attributed to the aging population. There are no efficient therapies for these disorders, regardless of medical improvements. Therefore, there is an urgent need for innovative treatments for these diseases. Over the years, stem cell-based therapy has transformed regenerative medicine by providing crucial and compelling possibilities to treat a variety of diseases (e.g., cancer), including neurological diseases. Stem cell therapy, referred to as regenerative therapy, uses stem cells or their derivatives to enhance the curative response of dysfunctional and injured tissue. Hence, mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs) are two stem cell types that are used. Recent evidence supports stem cell transplantation as promising therapeutic potential, which could be regarded as stem cells' mechanistic actions. In addition to stem cells, exosomes are a type of nanovesicles with a wide range of functionalities and possibilities for diagnosing and treating. It is shown that exosomes are implicated in cell-cell communication and have been explored as candidates for possible biomarkers, which are particularly relevant in AD and PD. Exosomes are also employed as a drug delivery vehicle at a target site; thus, their inherent ability to cross the blood-brain barrier and selectively adorn it with the ligand depends on the treatments of the targeted brain regions. This chapter aims to shed light on the different roles of stem cells and derived exosomes as therapeutic agents in the treatment of neurodegenerative disorders.