The impact of the new SARS-CoV-2 coronavirus on skeletal muscle: morphological, biochemical and functional analysis

COVID-19 pandemic, a disease caused by the new coronavirus SARS-CoV-2, has been drastically affecting the lifestyle of millions of people in the past few months. Studies have shown that COVID-19 is a multiorgan disease that affects not only the respiratory tract of infected individuals, but it has considerable effects on the musculoskeletal system, causing excessive fatigue, myalgia, arthralgia, muscle weakness and damage to skeletal muscles. These symptoms can persist even after the infection ends, perduring for months and impacting the daily lives of individuals who, in theory, should have fully recovered. Some studies have indicated that the muscle weakness observed in COVID-19-positive individuals could be an effect of the deregulated immune response ("cytokine storm") that occurs during the course of the disease, and several pro-inflammatory interleukins have been found at high levels in the serum of studied patients. However, little is known about the effect of SARS-CoV-2 on skeletal muscles, especially of individuals who did not require hospitalization and/or ventilatory support. Therefore, we will analyze the contractile properties of fibers and myofibrils of skeletal muscles from individuals who presented the mild-to-moderate forms of COVID-19 and recovered from it, as well as the content of sarcomeric proteins and cytokines, relating this content to the possible effects of a deregulated immune response. We aim to contribute to a better understanding of the effects of COVID-19 on the musculoskeletal system.