Bone marrow-derived mesenchymal stem cell therapy as a candidate disease-modifying strategy in Parkinson's disease and multiple system atrophy

Parkinson's disease (PD) and multiple system atrophy (MSA) are neurodegenerative diseases representative of alpha-synucleinopathies characterized pathologically by alpha-synuclein-abundant Lewy bodies and glial cytoplasmic inclusions, respectively. Embryonic stem cells, fetal mesencephalic neurons, and neural stem cells have been introduced as restorative strategies in PD animals and patients, but ethical and immunological problems as well as the serious side effects of tumorigenesis and disabling dyskinesia have limited clinical application of these stem cells. Meanwhile, cell therapy using mesenchymal stem cells (MSCs) is attractive clinically because these cells are free from ethical and immunological problems. MSCs are present in adult bone marrow and represent <0.01% of all nucleated bone marrow cells. MSCs are themselves capable of multipotency, differentiating under appropriate conditions into chondrocytes, skeletal myocytes, and neurons. According to recent studies, the neuroprotective effect of MSCs is mediated by their ability to produce various trophic factors that contribute to functional recovery, neuronal cell survival, and stimulation of endogenous regeneration and by immunoregulatory properties that not only inhibit nearly all cells participating in the immune response cell-cell-contact-dependent mechanism, but also release various soluble factors associated with immunosuppressive activity. However, the use of MSCs as neuroprotectives in PD and MSA has seldom been studied. Here we comprehensively review recent advances in the therapeutic roles of MSCs in PD and MSA, especially focusing on their neuroprotective properties and use in disease-modifying therapeutic strategies.