A System to Measure Maximal Isometric Torque of the Mouse Quadriceps to Assess Functional Recovery of Skeletal Muscle in a Volumetric Muscle Loss Injury
VanderLaan, Skylar A.
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Volumetric muscle loss (VML) is an injury characterized by the traumatic or surgical loss of skeletal muscle and a severe loss of function to the affected limb. Due to the injury’s size and complexity, the body is unable to regenerate sufficient muscle tissue after a VML injury, causing a functional deficit to the affected limb. To better analyze functionality of limb recovery after VML, we have created a protocol and custom built apparatus to measure peak isometric torque conducted by the quadriceps muscle of our mouse model. To complete this process and analyze the data, we have also created a custom in situ apparatus and novel MATLAB code for data analysis of the functional force data. One mouse underwent isometric torque testing immediately after receiving a surgically induced volumetric muscle loss injury. Maximum and average torque values of the injured leg saw a respective 53.2% and 55.6% drop when compared to the uninjured leg. After this preliminary testing, three mice received VML injuries and were allowed to heal for a 28-day period before isometric torque testing was conducted. All three mice showed decreases in both maximum and average torque readings across the injured legs, with maximum and average torque values of the uninjured leg being significantly greater than the injured leg (p values of 0.0325 and 0.0264 respectively). Our findings are promising and indicate that our testing method can quantify isometric torque readings and detect functional differences between injured and uninjured muscles. In the future we will apply this technique to studies in which regenerative therapies targeting muscle recovery, or even alternative injury models are explored.