Paralysis is the loss of ability to move, often coupled with the loss of ability to feel. This immobility can be caused by illness, such as multiple sclerosis, or by spinal cord injuries. Paralysis can have a devastating effect on quality of life, as it limits the independence of the affected person and can put pressure on family to provide appropriate support around the clock.
It is therefore exciting that scientists have taken a step closer to helping paralysed patients achieve control of their hands again. A recent study at Kings College London found that gene therapy was capable of repairing damage to the spinal cord of rats, with the test subjects regaining the ability to pick up and eat sugar cubes with their paws.
For those who don’t know, gene therapy is using genes to treat or prevent disease. This could be done by;
- Replacing a mutated copy of the gene which has caused the disease with that of a ‘healthy’ copy.
- Inactivating or knocking out a defective gene.
- Introducing a new gene with advantageous properties.
In the future, gene therapy could be used by doctors to treat disorders which are currently incurable. The technique is still under study as there are associated risks, but results such as these are promising.
For this study, the scientists inserted a gene which encodes an enzyme (a protein that assists with reactions) called chondroitinase. They used an inactive virus to deliver the gene to the cells in the spinal cord so that the encoded enzyme could dissolve components of the scar tissue, which is formed as a result of damage to the spinal cord. Without the scar tissue, the nerves can grow again, form new connections and muscle movement can be restored.
Leading the study was Professor Elizabeth Bradbury. She said to Sky News that “In some of the tests we looked at – such as gripping the rungs of a ladder – the treatment worked within one to two weeks”. She also said that tests requiring more complex movement, such as those with reaching, gripping and turning the wrist, showed results within five to six weeks.
Some footage of the lab-ulous subjects can be seen by clicking this link: https://www.bbc.co.uk/news/av/embed/p06b26xf/44484901
After this offload of information, one question you may feel embarrassed asking is – why do we use rats and mice for all these experiments? Admittedly, I was only given a valid explanation for this within the third year of my degree. There are actually quite a few reasons;
- It’s convenient. Rodents are small and their social nature means that they can be housed and maintained fairly easily.
- Anyone who has had a pest problem will know that they breed like mad within their relatively short life span, which means that many generations can be observed in a shorter period of time.
- Many strains are inbred, so that they are close to being genetically identical. This allows the results of medical studies to be more uniform.
- Although we aren’t similar to mice (some people may be ‘rats’…), their genetic, biological and behaviour characteristics resemble those of humans, and many symptoms of human conditions can be replicated in mice and rats.
We’ve also reached a point in research where we now have SCID (Severe Combined Immune Deficiency) mice, which are born without an immune system. Their responses are able to replicate those of humans with a immunodeficiency, such as HIV, and this is useful for developing non-invasive treatments. Transgenic (genetically-altered) mice can be manipulated to carry genes that are similar to those that cause human diseases. Scientists can then turn off or inactivate genes (creating Knockout mice) to evaluate the effects of carcinogens (cancer-causing chemicals) and assess drug safety.
For many patients with spinal cord injuries, the ability to regain function in their hands is the priority. From having a cup of tea to brushing teeth, the movement of our hands is valuable and research as promising as this gives hope to those longing for that independence again. This also forms a supportive argument for the use of rodents in scientific research. However, this does not come without controversy, as many activist groups are strongly against research with rodents on the grounds of animal cruelty. Is it worth it to treat human diseases? I could write a whole blog post on this topic; I may do just that…
What do you think? Please feel free to leave a comment!