When it comes to research for Duchenne muscular dystrophy (DMD), mouse models are a critical tool used to investigate potential treatment options and study disease progression. In particular, mdx mice are a very popular model used in this field.
From examining the physiology of DMD to evaluating potential gene therapies, mdx models have contributed significantly to our understanding of the disease.
What is the mdx mouse model?
Mdx mice were first discovered in the 1980s, when a colony of mice exhibited signs of muscle weakness. Genetic analysis revealed that these mice had a mutation in the gene that codes for the protein dystrophin, which is mutated in patients with DMD.
Read more about DMD signs and symptoms
Interestingly, the original mdx mice didn’t display the same characteristics as patients with DMD. They had a longer relative lifespan with very few noticeable symptoms.
Since the discovery of these mice, though, researchers have engineered a number of new mdx models that better represent the clinical signs of DMD in humans. For example, a newer model known as D2.mdx displays more severe symptoms of muscle disease than the original mdx mice.
Why are mdx mice used in research?
When it’s unethical or logistically difficult to include human participants in studies, mdx mice offer an alternative for studying DMD. They have fairly short lifespans of two to three years, allowing researchers to fast-track studies of disease progression. They’re also relatively easy to breed and aren’t too difficult to take care of.
Genetically, humans and mice are also very similar: Around 85% of the mouse and human genomes are identical, with some genes being up to 99% identical between the two species. When studying genetic diseases, this similarity is very useful for predicting the potential impact of a treatment in humans who carry the same or similar mutations.
Mouse models are often used during preclinical studies, which test the safety and efficacy of a drug before it is given to humans. The mdx model has also been used to study cognitive function, understand the role of the gut microbiome, identify potential biomarkers of DMD and many more areas of research.
What are the downsides of using mdx mice in research?
Although mdx mice have played a critical role in DMD research, they aren’t perfect. Some of the limitations of the model include:
- Different gene sequences: Although the mouse and human DMD genes are similar, they aren’t identical. Using mdx mice to test gene therapies, therefore, isn’t an exact representation of the effect the treatment may have in humans.
- Varying disease symptoms: Improvements have been made to create mdx models that more closely represent the human experience of DMD. Even so, no single mdx model perfectly mimics all aspects of the disease.
- Ethical concerns: While many practices are in place to ensure that animal experimentation is done humanely, any type of animal research will naturally raise ethical concerns. In the future, advanced techniques such as digital modeling of diseases may be able to replace animal research, but the field isn’t at that point just yet.
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