Circadian Rhythm‐Regulated ADSC‐Derived sEVs and a Triphasic Microneedle Delivery System to Enhance Tendon‐to‐Bone Healing

Modulating the inflammatory microenvironment to reconstruct the fibrocartilaginous layer while promoting tendon repair is crucial for enhancing tendon‐to‐bone healing in rotator cuff repair (RCR), a persistent challenge in orthopedics. Small extracellular vesicles (sEVs) hold significant potential to modulate inflammation, yet the efficient production of highly bioactive sEVs remains a substantial barrier to their clinical application. Moreover, achieving minimally invasive local delivery of sEVs to the tendon‐to‐bone interface presents significant technical difficulties. Herein, the circadian rhythm of adipose‐derived stem cells is modulated to increase the yield and enhance the inflammatory regulatory capacity of sEVs. Circadian rhythm‐regulated sEVs (CR‐sEVs) enhance the cyclic adenosine monophosphate signaling pathway in macrophage (Mφ) via platelet factor 4 delivery, thereby inhibiting Mφ M1 polarization. Subsequently, a triphasic microneedle (MN) scaffold with a tip, stem, and base is designed for the local delivery of CR‐sEVs (CR‐sEVs/MN) at the tendon‐to‐bone junction, incorporating tendon‐derived decellularized extracellular matrix in the base to facilitate tendon repair. CR‐sEVs/MN mitigates inflammation, promotes fibrocartilage regeneration, and enhances tendon healing, thereby improving biomechanical strength and shoulder joint function in a rat RCR model. Combining CR‐sEVs with this triphasic microneedle delivery system presents a promising strategy for enhancing tendon‐to‐bone healing in clinical settings. Optimized circadian rhythms in ADSCs enhance the production and the inflammatory regulatory capacity of their secreted sEVs (CR‐sEVs). These CR‐sEVs inhibit macrophage M1 polarization by modulating the cAMP signaling pathway via PF4 delivery. Delivered via a triphasic microneedle in a rat rotator cuff repair model, CR‐sEVs/MN reduces inflammation, facilitates fibrocartilage regeneration, enhances tendon repair, and ultimately promotes tendon‐to‐bone healing.