Pharmacological Inhibition of Rac1 Activity Prevents Pathological Calcification and Enhances Tendon Regeneration.

Tendinopathy is a common disease, which is characterized by pain, swelling, and dysfunction. At the late stage of tendinopathy, pathological changes may occur, such as tendon calcification. Previously, we have shown that in situ tendon stem/progenitor cells (TSPCs) underwent osteogenesis in the inflammatory niche in diseased tendons. In this study, we demonstrate that this process is accompanied by the activation of Ras-related C3 botulinum toxin substrate 1 (Rac1) signaling. A specific inhibitor NSC23766 significantly downregulated catabolic factors and calcification-related genes and rescued the tenogenesis gene expression of TSPCs under the influence of Interleukin (IL)-1β in vitro. For in vivo evaluation, we further developed a drug delivery system to encapsulate Rac1 inhibitor NSC23766. Chitosan/β-glycerophosphate hydrogel encapsulated NSC23766 effectively impeded tendon calcification and enhanced tendon regeneration in rat Achilles tendinosis. Our findings indicated that inhibiting Rac1 signaling could act as an effective intervention for tendon pathological calcification and promote tendon regeneration, thus providing a new therapeutic strategy.