Mechanism of Interleukin-17A Regulation of Mesenchymal Stroma/Stem Cell Osteogenic Differentiation

The immune and musculoskeletal systems closely interplay in bone repair and regeneration. After bone injury, the body produces high levels of cytokines and signaling molecules to balance bone formation and resorption. Interleukin (IL)-17A, a cytokine expressed early in the inflammatory process, profoundly influences osteoprogenitor cell fate, thereby contributing to bone homeostasis. In addition, mesenchymal stromal/stem cells (MSCs) can differentiate into osteoblasts, contributing to bone repair and regeneration. Although IL-17A can influence MSCs to become early osteoprogenitor cells, it also can inhibit bone formation. However, the reasons for these dual roles are not yet fully understood. This review overviews IL-17A signaling and the mechanisms that govern MSCs' osteogenic differentiation and summarizes relevant data from the literature on IL-17A's pro- and anti-osteogenic roles.