Growing up in the 1990′s, I was familiar with the usefulness of laboratory mice from a very young age, thanks to my hours spent watching Pinky and the Brain. Since that time, however, lab mouse technology has improved quite a bit–scientists have found a way to make mice function more like humans. If you’re feeling skeptical about how a mouse could become man, not to worry, these lab mice won’t look like people any time soon. Rather, scientists have discovered a way to replicate the human immune system in mice, enabling them to figure out how an individual immune system will respond under various medical conditions.
Though mice have traditionally been used for testing medications and response to treatment–essentially anything scientists can come up with–mice with modified immune systems have huge implications for cancer treatment and the development of pharmaceuticals. Studies have been done to determine how similar the immune systems of mice and humans are, and these studies suggest that while there are a number of similarities, there are many differences as well. These differences could explain why tests conducted on mice in the laboratory don’t always translate to humans the way that they are expected to. By reprogramming mice with the immune systems of individual people, however, scientists have learned that discrepancies can be eliminated.
The specifics are relatively complicated but, essentially, mice can be injected in certain parts of the body with human cells, which allows a small-scale replica of a human immune system to develop. The genetically modified mice that are injected, called SCID mice, do not have immune systems of their own, which is why they are able to accept and grow stem cells or white blood cells from humans. This process is so exceptional because it requires genetic material directly from humans to work, meaning that the exact immune system of a sick individual can be duplicated in a low-risk manner. For example, once the immune system of a cancer patient has been replicated, scientists can inject the mice with the cancer as well, before trying any treatment combination desired. Though the cancer can take several months to grow in the injected mice, studies suggest that the wait is well worth it. In one study by Manuel Hidalgo, SCID mice with human immune systems were used to find treatments for 94% of the participants. Treatment reactions observed in the patients mirrored reactions first seen in the mice.
Such mouse technology may not be readily accessible, and it certainly requires patience from those who are able to use it, but the science is rapidly progressing, and researchers are hopeful for the future. An assortment of obstacles are present–some cancers will not grow in mice at all, while organs like the liver in mice can respond to drugs differently than they do in humans–but scientists have not been deterred. In fact, many are working on recreating human organs in lab mice as well, to make testing more accurate. The scientific road ahead might be a long one, but this technology could help us to understand and treat ailments from HIV to arthritis to diabetes. Considering the work that has already been done with man-mice, the future impact of these studies is likely to be substantial.