The therapeutic effect of mesenchymal stem cell transplantation in experimental autoimmune encephalomyelitis is mediated by peripheral and central mechanisms

Stem cells are currently seen as a treatment for tissue regeneration in neurological diseases such as multiple sclerosis, anticipating that they integrate and differentiate into neural cells. Mesenchymal stem cells (MSCs), a subset of adult progenitor cells, differentiate into cells of the mesodermal lineage but also, under certain experimental circumstances, into cells of the neuronal and glial lineage. Their clinical development, however, has been significantly boosted by the demonstration that MSCs display significant therapeutic plasticity mainly occurring through bystander mechanisms. These features have been exploited in the effective treatment of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis where the inhibition of the autoimmune response resulted in a significant amelioration of disease and decrease of demyelination, immune infiltrates and axonal loss. Surprisingly, these effects do not require MSCs to engraft in the central nervous system but depend on the cells' ability to inhibit pathogenic immune responses both in the periphery and inside the central nervous system and to release neuroprotective and pro-oligodendrogenic molecules favoring tissue repair. These results paved the road for the utilization of MSCs for the treatment of multiple sclerosis.