For the first time ever, human stem cells have been shown to have a significant effect on restoring memory in animals suffering from Alzheimer's disease. The breakthrough could have profound implications for the treatment of the age-related disorder, which affects as many as 5.3 million Americans and threatens to affect many more as the population continues to age.
To make their discovery, a team of researchers from UC Irvine and StemCells Inc. worked to alleviate the cognitive deficits found in animal models of Alzheimer's disease. When setting up the experiment, the scientists wanted to make sure that they were replicating the severe effects of Alzheimer's. To that end, they only tested on mice who were exhibiting a considerable degree of neural pathology. They also created two different models, those bred to model the effects of Alzheimer's and those bred to model the loss of neurons.
Targeting learning and memory
The researchers focused their efforts on the hippocampus, the area of the brain that is responsible for learning and memory. They injected human stem cells in both sides of the brain and then waited for a month. The researchers then reinvestigated the memory capabilities of these mice, comparing their performances to their previous levels, and those of a control group. Specifically, the mice were tested on a battery of behavioral tasks followed by histological and biochemical analysis.
And what they found was nothing short of remarkable. The animals that received stem cells performed as well as mice without any previous neural pathology. By applying this particular strategy, they had statistically increased memory in their two animal models.
Restoring synaptic health
Looking at the science of what they had accomplished, the researchers speculate that the stem cells went to work by alleviating the detrimental effects of protein build-up in the brain, particularly beta-amyloid plaques (what's often considered to be the most proximate cause of Alzheimer's) and neurofibrillay tangles.
These buildups cause the brain to lose the connections its neurons make with each other. Thus, the best correlates for the damage being done by Alzheimer's is the amount of synaptic loss that is experienced. The researchers observed that the mice that received the stem cells had substantially more of these synapses between connections — at times as much as a 75% increase. The researchers speculate that this is very likely the explanation behind the success of their treatment.
The next step for this team is to translate their work to a human therapy. Specifically, they're hoping to evaluate human stem cells to determine if they'll work in the same way they do in animal models.
The data was presented on July 17 at the Alzheimer's Association International Conference 2012 in Vancouver, Canada.