What Can Gene Therapy Do For Parkinson’s and Muscular Dystrophy?
There are two ways we can apply a gene therapy: in vivo and ex vivo. In the first case, the desired genes are delivered to the target cells directly.
In the second case, we remove a target cell from a body. Then we insert the desired gene into this cell. The changed cell is eventually returned to our body. The problem with ex vivo gene therapy is to come up with the reliable and effective gene delivery solutions.
For these purposes, the viruses or vectors are commonly used. Of course, we're talking about the "naked" or altered viruses that are harmless to our bodies. Their initial role and capacity to penetrate cells and deliver the desirable genes are preserved.
We have high hopes when it comes to gene therapy and its potential. We are eager to see what it can do in challenging fields, such as Parkinson’s or Muscular Dystrophy.
Parkinson’s and Gene Therapy
The scientists have come up with a delivery system that has a capacity to deliver an essential enzyme called the AADC, which can decrease the progress of Parkinson's disease. The initial experiments were conducted on rodents. However, their dopaminergic system is quite different from ours.
These biochemical differences made the scientists to treat the monkeys for a change. They’ve been using the AAV vector in order to deliver the AADC genes into the monkeys. The initial results have shown that is possible to restore the enzyme levels in the monkeys’ brains up to four times compared to the regular levels.
We have to be careful while interpreting these results. That’s the main reason, the scientists have been closely following the progress with the treated monkeys for a couple of years. The positive signs just couldn’t be ignored.
Thanks to this gene therapy it has become possible to treat the Parkinson’s symptoms with only one-tenth of the usual L-dopa dose used for this disease. The most important thing worth emphasizing is that thanks to this particular gene transfer, all side effects associated with L-dopa were eliminated or significantly diminished. In simple words, L-dopa just got the second huge change to treat Parkinson’s more effectively thanks to gene therapy.
Muscular Dystrophy and Gene Therapy
The scientists believe that some of the most common types of muscular dystrophy are very suitable candidates to be treated with gene therapy. Why? Well, it turns out that muscular dystrophy has been triggered by the faulty muscle proteins that can be fixed through gene therapy. In theory, an appropriate copy of the broken gene can solve or ease the troubles associated with some forms of the muscular dystrophy.
For these purposes a high-capacity vector was designed. The harmful parts of the virus are removed while the capacity to carry and deliver the full-length dystrophin genes is increased. This is how an ideal gene therapy vector is supposed to look like. All negativities eliminated and cell penetration capacities increased.
For the purpose of experiments, the mice were used because some species have a tendency to lack dystrophin as humans. The current delivery system makes sure that the full-length dystrophin genes are delivered to a treated mouse. The dystrophin then protects the muscle surface membrane integrity. Now, we know that if the integrity of this membrane is compromised, it is very likely that the muscular dystrophy may occur.
The Challenges and Perspectives of Treating Parkinson’s and Muscular Dystrophy With Gene Therapy
It is easy and understandable to get carried away with the promises of gene therapy. However, we have to take every breakthrough in this field with a grain of salt. There are immunity and delivery issues associated with gene therapy that are standing in the way of the full-scale clinical application.
For instance, it has been noticed that some vectors when being introduced for the first time in mice can trigger the B cells, which have the capacity to create the neutralizing antibodies. The trouble is that these antibodies will work against the vector (virus) you are trying to reach the target cells with, in the first place.
The additional problem is that the dystrophin can be identified as a foreign body and therefore eliminated by our immunity system. Once our body’s protection system is set in motion, it won’t attack only the vector and transferred genes, but the treated cells, as well.
As long as we don’t solve these problems, gene therapy treatment of Parkinson’s and muscular dystrophy is going to be reserved for experiments and laboratories only. The clinical applications will have to wait. However, these problems shouldn’t discourage the scientists on their quest of finding the long-term and reliable solutions. The ultimate prize of saved and improved lives is definitely worth all the time and resources invested in the research.
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