In Vitro Bioactivity Evaluation of <scp>IL</scp>‐4 and <scp>SDF</scp>‐1 Mimicking Peptides Engineered to Enhance Skeletal Muscle Reconstruction

Skeletal muscle regeneration depends on satellite cells, which, in response to injury, activate, proliferate, and reconstruct damaged tissue. However, under certain conditions, such as large injuries or myopathies, this process may not be properly executed, and muscle function may be affected. Thus, pro-regenerative actions, such as the use of various factors or cells, are widely tested as a tool to improve muscle regeneration. In the current study, we designed peptides derived from the IL-4 and SDF-1 proteins, namely IL-4-X, IL-4-Y, SDF-1-X, and SDF-1-Y. We showed that these peptides can bind to appropriate receptors and can adopt proper structure in solution. Importantly, we documented, using in vitro culture, that they do not negatively affect the cells that are present and active in skeletal muscles, such as myoblasts and fibroblasts, bone marrow stromal cells, as well as induced pluripotent stem cells, which can serve as a source of myoblasts. The presence of peptides did not affect cell proliferation compared to untreated cells. In vitro culture and differentiation protocols documented that selected IL-4 and SDF-1 peptides increased cell migration and inhibited undesirable adipogenic differentiation. Thus, we proved that these peptides are safe to use in in vivo studies aimed at improving skeletal muscle regeneration.