Muscles of the head
Patrick J. Lynch, CC BY 2.5
When skeletal muscles in elderly people are seriously injured, the tissue often fails to regenerate properly. The muscles of people with Duchenne muscular dystrophy degenerate and become weak due to a genetic problem. In both of these cases, injecting MuSCs into damaged or weakened muscles to replace missing tissue sounds like a great idea. It presents challenges, however. The cells must stay alive in the body, attach to the right area, and then produce new muscle cells.
The term “muscular dystrophy” refers to a group of diseases in which muscles degenerate. Unfortunately, the diseases are progressive. The muscles become weaker as their mass decreases. The illnesses are caused by a genetic problem. Duchenne muscular dystrophy or DMD is the most common disorder in the group.
DMD starts in childhood and generally occurs in boys. It’s a sex-linked disease, which means that it’s controlled by a gene on the sex chromosomes. It’s possible for a girl to get the disease, but the condition is rare in females. There is no cure for the disorder at the moment. Doctors have methods to help people deal with DMD, though.
The lifespan of patients with DMD is increasing due to better treatments. The weakening of respiratory muscles eventually results in the death of many patients, however. Due to the gene problem, the patients lack a protein called dystrophin. This protein protects muscle cells. Gene therapy is an active area of research for the disorder.
Under normal conditions, temporary inflammation in the body is useful. Cells of the immune system and the chemicals that they release repair the damaged area and destroy pathogens. After the area has been repaired, inflammation subsides. Extreme or chronic inflammation can be harmful, however. The excessive or continued production of inflammatory chemicals can create pain and damage tissue. The immune system is very active in the damaged and inflamed muscles found in elderly people with serious injuries. Inflammation is also involved in DMD. In both cases, the immune system attacks and destroys any stem cells that are injected.
Bruce Blaus, CC BY 3.0
The researchers have created a hydrogel to enclose muscle stem cells. The gel consists of a net of molecules suspended in water. The net forms a matrix that traps and protects the stem cells.
In mice with a condition resembling the two illnesses described above, the gel was injected directly into muscles that weren’t regenerating. The gel protected the stem cells from inflammatory chemicals and stopped them from being destroyed. In addition, the stem cells were able to heal the damaged tissue. Without the hydrogel, only 1% to 20% of the injected stem cells survived and many of the surviving cells were weak.
The researchers say that the stem cells multiply within the biocompatible and biodegradable hydrogel that they’ve created. When the gel attaches to tissues it hardens and forms a glue that holds the cells in place. The “glue” gradually disintegrates, leaving the healthy stem cells attached to the damaged area. The stem cells then divide and form new muscle cells.
A Potential Treatment
Regenerating the damaged muscle cells of elderly people could be very useful for mobility and quality of life. Regenerating the diaphragm (the main muscle of respiration) could be a life saver for people with Duchenne muscular dystrophy. The hydrogel treatment is not ready for clinical trials in humans yet, but the researchers are working towards this goal.
One problem is that the muscle stem cells may have to come from someone with healthy muscles. With a few exceptions, when cells from another person’s body are placed in our own, the immune system attacks and destroys the cells. This means that researchers will have to solve the donor cell rejection problem in humans before the treatment can be tested. The results of their research could be very worthwhile, though.
Facts about muscular dystrophy from the Mayo Clinic
Duchenne muscular dystrophy information from the Muscular Dystrophy Association
A matrix delivers healing stem cells from the ScienceDaily new service