2017-11-27 00:30:03
One of the mysteries of science is why, on so many occasions, the experimental results obtained with laboratory mice are not relevant to the human case. For example, cancer has been cured many times in laboratory mice, but the same treatment rarely cures cancer in humans. However, the impressive advances made in the biomedical sciences would have been impossible without the experiments carried out with laboratory mice.
Science has discovered the importance of the intestinal microbiota thanks to research carried out with laboratory mice. In fact, all animals should be considered as a set of organisms, which has been called a metaorganism.
A metaorganism is composed of its eukaryotic cells (cells with a nucleus where DNA stored in chromosomes resides) and also its prokaryotic cells (cells without a nucleus), which live on epithelial surfaces, particularly the skin, the intestine, and respiratory tract. During the evolution of animals, both types of cells have evolved together, have established a symbiosis, and today neither can do well without the other.
Laboratory mice are kept under highly controlled conditions of humidity, temperature, and light cycles, and are provided with clean drinking water and a specific diet. This tight control also extends to the microorganisms in their environment. These living conditions are far removed from those of Nature, in which animals live together with a huge variety of microorganisms.
A group of researchers decided to compare the microbiota of laboratory mice with that of wild mice. Researchers studied the genetics of 21 different populations of mice around the world and found that wild-caught mice from the US state of Maryland are the most closely related to laboratory-used mice on the planet.
Next, the researchers captured around 800 wild mice, analyzed the microbiota of these animals, and compared it with the microbiota of a widely used laboratory mouse strain. As expected, they found significant differences between them.
To study whether these differences could affect the experimental results obtained with the animals, the experimenters carried out a microbiota transplant from wild mice to pregnant laboratory female mice that lacked microbiota. Four generations later, these animals still maintained the wild-type microbiota.
The scientists then analyzed the response of these animals to different treatments that implied a serious risk to their health. The results were amazing. Animals with wild-type microbiota survived to a greater extent at a high dose of influenza virus and resisted the progression of colorectal cancer much better.
These studies indicate, first of all, that a healthy microbiota is really important to help maintain good health. Second, that the conditions under which laboratory animals are housed must be seriously reviewed if we want the results of biomedical experiments using these animals to be more meaningful to the human situation. After all, most humans are certainly still somewhat “wild.”
Referencias: Rosshart et al., Wild Mouse Gut Microbiota Promotes Host Fitness and Improves Disease Resistance, Cell (2017),
More information on Jorge Laborda’s Blog: Wild and laboratory metaorganisms
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