Headlines from a recent PNAS study showing that stem cells can reverse dementia in mice keep popping up in my inbox. Here’s the press release. The cells don’t actually become neurons but instead secrete a well-studied protein called brain-derived neurotrophic factor that stimulates neurons already in the brain to form new connections. The paper from UC Irvine scientists is supposedly out today, but I can’t find it on the PNAS site. I’d like to know how much cognitive performance improved. Also, the researchers used mice genetically engineered to have Alzheimer’s. That’s often the only way to study this, but I’d like to know how well the model represents human disease and also whether te researchers started “treating” the disease pathology long before any clinical signs of the disease became obvious, which would mean the strategy may not work for patients that have had Alzheimer’s for any significant time.