Functional role of mesenchymal stem cells in the treatment of chronic neurodegenerative diseases

Mesenchymal stem cells (MSCs) can differentiate into not only cells of mesodermal lineages, but also into endodermal and ectodermal derived elements, including neurons and glial cells. For this reason, MSCs have been extensively investigated to develop cell-based therapeutic strategies, especially in pathologies whose pharmacological treatments give poor results, if any. As in the case of irreversible neurological disorders characterized by progressive neuronal death, in which behavioral and cognitive functions of patients inexorably decline as the disease progresses. In this review, we focus on the possible functional role exerted by MSCs in the treatment of some disabling neurodegenerative disorders such as Alzheimer's Disease, Amyotrophic Lateral Sclerosis, Huntington's Disease, and Parkinson's Disease. Investigations have been mainly performed in vitro and in animal models by using MSCs generally originated from umbilical cord, bone marrow, or adipose tissue. Positive results obtained have prompted several clinical trials, the number of which is progressively increasing worldwide. To date, many of them have been primarily addressed to verify the safety of the procedures but some improvements have already been reported, fortunately. Although the exact mechanisms of MSC-induced beneficial activities are not entirely defined, they include neurogenesis and angiogenesis stimulation, antiapoptotic, immunomodulatory, and anti-inflammatory actions. Most effects would be exerted through their paracrine expression of neurotrophic factors and cytokines, mainly delivered at damaged regions, given the innate propensity of MSCs to home to injured sites. Hopefully, in the near future more efficacious cell-replacement therapies will be developed to substantially restore disease-disrupted brain circuitry.