Muscle stem cell on a muscle fiber (IMAGE) The Ottawa Hospital Caption When a muscle fiber is damaged, stem cells (in pink) start producing and coating themselves with hyaluronic acid (pale green outline). Once the coating gets thick enough, it causes the muscle stem cells to wake up. Credit Dr. Kiran Nakka Usage Restrictions Only to be used in content related to this research study License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.