A communication from Dr Tamir Ben-Hur (Tedx Jaffa 2014) :

"A major conceptual shift in the field : from that of cell replacing therapy to neurotrophic and neuroprotective support by transplanted stem cells"

Trying to rebuild damaged axon myelin in mice brain, Tamir's team has introduced specific stem cells to generate oligodendrocytes to precisely regenerate the myelin deficient ... and it has been noticed, marking them ... that they didn't contributed directly to it but they attenuated inflammation, protecting the other cells and promoting their own stem cells present there to regenerate myelin. So, the initial asumption wasn't confirmed, the transplanted cells did not act as they thought they did ... but the discovery was even more impressive: the transplanted stem cells activated the immune system, preventing myelin, reducing inflammation and promoting the proliferation of the precursor cells which at the end regenerated myelin.
And better than all this: they have realized that they could assert other stem cells coming from other body parts could do the job and in particular, some of the bone marrow could did it as well !!!