There have previously been attempts to treat AD with stem cells....

There have previously been attempts to treat AD with stem cells. researchers radiolabelled the cells before injecting them into the spinal canal. being radiolabelled, their migration could be tracked. Whilst they did tend to migrate to those parts of the brain that had been damaged by AD, they differentiated into glial (connective tissue) cells, not neurons.

Even if this problem has now been overcome, I'd question the point of delivering a new, healthy neuron into a toxic environment.

Seems to me analogous to an environmental disaster, where you've got a coastline ruined by oil, damaging the wildlife, then planning to address that damage by shipping in more wildlife!