In Vivo Response to Electrocompacted Tendon-Derived Thread Scaffolds During Tendon Repair

Tendon injuries remain a major clinical challenge due to the tissue's limited regenerative capacity and poor remodeling of current allograft-based therapies. To address these limitations, we developed a tendon-derived thread (TDT) scaffold by electrocompacting decellularized tendon powder into aligned threads, which were subsequently woven into a porous overlay patch. Biochemical analyses of TDT confirmed efficient decellularization (DNA < 50 ng/mg) and the preservation of collagen and proteoglycans. Compared to en bloc human tendon graft (HTG), the TDT scaffold exhibited significantly higher swelling ratios and greater weight loss over 8 weeks in vitro, indicating greater porosity and faster degradation. In a rabbit infraspinatus partial-thickness fenestration injury model, the TDT scaffold and HTG were sutured over the injury and evaluated at 2 and 8 weeks to observe tissue infiltration and in vivo response to biomaterial degradation during early phases of healing. Biomechanical testing of shoulders showed no significant differences in load relaxation, ultimate tensile strength, and stiffness among intact, HTG, and TDT scaffold groups in this injury model, suggesting comparable mechanical restoration. Histological and gross observations indicated progressive resorption of TDT scaffolds, which were infiltrated by cells at 2 weeks, and neotissue formation was evident by 8 weeks. In contrast, cell infiltration into the allograft was limited at both time points, and there was no evidence of degradation in vivo. These findings support the potential of the TDT scaffold as a degradable scaffold to support tendon healing during injury.