Mice as Models
As I was reading for this article, I couldn't help but recall the title of Steinbeck's novel Of Mice and Men. While it would have been a nice title for this post, the connection is no deeper than those four words.
In medical research, mice are frequently used as genetic models. The mouse has been identified as a model, a stand in for humans, if you will, because it is a mammal with "close genetic and physiological similarities to humans." The mouse is easy to handle, easy to manipulate on a genetic level, cheap to maintain and multiplies rapidly. They have a short life-cycle and can express the desired traits or symptoms only months into their lives as opposed to the decades it takes to see the same symptoms in humans. All of these factors have contributed to its widespread use in research. While mice do not naturally get Alzheimer's, their genes can be manipulated to cause them to experience some of the hall markers of Alzheimer's such as cognitive decline or plaque tangles in their brains.
A mouse model does not refer to a single mouse. It refers to a line of modified mice which share the same genetic changes. There are thousands of mice models which have been developed and maintained for use in the research of such topics as cancer and Alzheimer's. There are so many, in fact, that scientists have to carefully consider which mouse model is best suited for their research based upon the traits found in the available lines. Some mice may show an early cognitive decline; some not. Some may have plaque tangles; others may not. As a result, no one mouse model can serve for all of the research needs.
This complicates the research because what works on one mouse model may not work on another. However, this is also beneficial because it allows the scientists to eliminate variables and narrow the focus of their research. Even two of the newest mouse models are incomplete views into Alzheimer's.
So, why does this matter? It matters because we see headlines heralding the latest study which shows promise in mice. But, it is not in all mice. It is not in just any old mouse. It is in mice which have a particular set of genetic changes which allows them to express some of the hall markers of Alzheimer's. It is hopeful and exciting. However, it is still a long way from the solution working in humans. We've seen before that the possible new solution doesn't make it beyond the one model used to benefit humans with actual Alzheimer's.
I'm in no way against using mice as models. I understand the reasons behind their use. I just want us to realize that the headlines which crow "Cures X in Mice" should be read with a critical eye. We cannot declare a soccer game won by just the first goal regardless of what my youngest thinks and we cannot declare a cure from just one mouse model.