Could stem cells offer the cure for muscular dystrophy?

by etoledo / Tuesday, 04 August 2015 / Published in Corporate News / Blog

The term muscular dystrophy is used for referring to a group of disorders in which the muscles responsible for controlling movement get weaker, and muscle mass is lost as a result of a genetic abnormality. These inherited diseases usually affect the voluntary muscles (skeletal muscles), but the weakness can also extend to the muscles that control respiration or swallowing.

Given that the genetic mutations triggering this condition interfere with the normal production of proteins, the body is not able to reverse the muscle weakening or the loss of mass, so even if the ailment progresses slowly, it eventually affects one’s ability to walk in a more or less significant manner.

Who is affected by muscular dystrophy?

In most cases the condition appears in infancy, but it’s not uncommon for symptoms to start manifesting in teens or adults. Although the manifestations are similar, their severity varies depending on the age at which the ailment occurs. In some, the symptoms are mild and allow the sufferers to continue their lives almost normally, while in others the ailment is disabling and can lead to muscle wasting, loss of the walking ability and even death.

There are different kinds of muscular dystrophy, the most known form of this disorder being Duchenne muscular dystrophy. Caused by defective or flawed genes, this condition affects about 1 in every 3,500 boys worldwide, being more common in males than in females [1].

Duchenne muscular dystrophy has its onset between the ages of 2 and 6, and evolves slowly but surely, the muscles becoming weaker year after year and the spine and limbs becoming progressively deformed. In most cases, kids affected by this form of the disease need a wheelchair by the age of 12.

People suffering from this ailment often die in their 20s, and if they survive, they usually experience some degree of cognitive impairment. The shortening of tendons and muscles limits the mobility of sufferers even more, and breathing and heart problems can occur.

Why muscles can’t repair themselves in Duchenne muscular dystrophy

There is no known cure for DMD for the moment, but there are treatments that help in reducing some of the symptoms and in strengthening the patients’ muscles to some degree.

Physiotherapy is commonly used for slowing down the loss of muscle mass and for maintaining the flexibility or reducing the stiffness of muscles. Also, steroids are used for slowing down muscle wasting, but they often cause more harm than good, as they come with severe side effects, such as the weakening of bones or cardiovascular problems.

In a healthy organism, damaged muscles repair themselves thanks to a series of cells among which the muscle stem cells, called satellite cells. In Duchene muscular dystrophy, the muscles lack dystrophin, the protein needed for maintaining the integrity of fibers. Without this protein, the burden placed on muscle stem cells is too big, so these cells become unable to repair the damaged tissues or to generate new muscle mass for replacing the wasted one [6].

For this reason, scar tissue and fat cells take the place of damaged muscle tissue. This contributes to the weakening of muscles and in time causes them to lose their functional ability. But would it be possible for the damaged muscle fibers to regain their regeneration ability with help from transplanted stem cells?

Research suggests stem cells could be a potential solution for muscle wasting

Different strategies involving stem cells for muscular dystrophy may become available in the future, research suggests. Scientists have been using stem cells isolated from muscles, bone marrow and blood vessels for regenerating muscle fibers that are deficient in dystrophin in laboratory animals [3] with encouraging results.

In 2006, researchers managed to restore the mobility of two dogs using stem cells isolated from muscle blood vessels [4], and in 2007 scientists managed to treat DMD in research mice using a combination of genetic correction and stem cells [3]. The latter study showed that it is possible to correct the genetic error in the cells that no longer produce dystrophin protein, and then inject those cells into mice, for stimulating the regeneration of muscles.

Researchers at the Harvard Stem Cell Institute obtained similar results, demonstrating that transplanted muscle stem cells can improve function in mice with MD, while replenishing the stem cell population in the muscle fibers [5].

Although it’s still early to say whether stem cells can cure Duchenne muscular dystrophy in humans, it’s clear that there are different stem-cell-based approaches for this issue. A fist solution would be to replace the defective stem cells with healthy ones, as these may be able to generate working muscle fibers for replacing the damaged ones.

A second solution would be to reduce the inflammation that speeds up the loss and weakening of muscle using certain types of stem cells [2]. Combined treatments such as those mixing stem cell therapy with gene therapy are also being tested and may prove successful in the near future.

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