Stem cell discovery in fruit flies may help understand muscle disorders in humans

Indian researchers are trying to understand the mystery of muscle related problems like Muscle Dystrophy, a progressive muscle disorder where muscles fail to recover after damage, using advances in stem cell science.

At the National Center for Biological Sciences-TIFR, Bangalore, researchers have discovered a new population of stem cells in muscles of Drosophila flies involved in repair of injured tissue.

Exercise such as running and lifting weights causes muscles damage, but they recover and are suitable for work again. How is this achieved? “We thought we can study this in the most easily accessible model i.e. fly. These are small flying insects, we see hovering on the ripened banana. We were puzzled about how an insect can fly for so long, much like we, humans run and walk throughout our life. It is a simple question with vast implication to understand about muscles in general. Fruit fly came as an easy model,” says Rajesh Gunage, a senior author of the new study published this week.

Researchers designed a simple Pin Prick Assay as an experimental strategy. The ‘pin prick' assay involves a tiny metal pin with dimensions close to an adult’s eyebrow hair. “Using this we could induce non-life threating damage to tiny flight muscles of fly and observe for recovery of flight,” says Dr. Gunage.

Flight muscles, as the name suggests, are involved in flying and they are equated to human muscles of leg or arm. Much like the recovery of damaged muscles in case of a runner who recovers from it and starts to run again, researchers were surprised to see fruit fly flying once again after a brief period of recovery. Detailed analysis led to the discovery of novel stem cells. Team members observed that pin injury activates stem cells and they multiply in number. These newly formed cells then become part of injured muscles to help them recover from the injury. These results were published in the journal eLife Science.

“Anybody can do this experiment even at home. All you need is a small pin and a banana. Banana attracts small flying insects named Drosophila. All you need to do is prick them in the thorax with a pin to injure their muscles. Initially, they fail to fly due to injury but soon due to stem cells, the damage is reversed, are set into action again. Within no time you can see them resume their normal flight,” says Dr. Gunage.

Researchers said, “Just imagine small flying insects with stem cells. We were skeptical for a very long time. Insect muscles are very small and to confirm the presence of stem cells, we used electron microscopy. Using this we could clearly see these small stem cells next to muscles, much like a number of satellites around the planets.”

“Using the knowledge gained from the current findings, one can understand how in old animals, muscles fail to work or show less recovery following accidental damage. Questions such as how different diet, regular exercise affect muscles or even a possible drug expected to enhance muscle function affect can now be tested. It just makes many difficult experiments easy to perform with much less effort,” said Gunage and Chaturvedi.

The research team included Rajesh Gunage, Dhananjay Chaturvedi (Heinrich Reichert, Switzerland) and K. VijayRaghavan (Department of Biotechnology).