Regenerative Effect of Injectable Collagen Loaded With Mesenchymal Stem Cell-Derived Extracellular Vesicles in a Collagenase-Induced Tendinopathy Rat Model.

Abstract

BACKGROUND: Tendinopathy remains a major clinical challenge due to the limited regenerative capacity of tendon tissue. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) show therapeutic promise; however, strategies to enhance their local retention and therapeutic efficacy remain necessary. PURPOSE: To evaluate the regenerative efficacy of an injectable collagen-EV system delivering human umbilical cord-derived MSC-EVs in a collagenase-induced supraspinatus tendinopathy rat model. STUDY DESIGN: Controlled laboratory study. METHODS: EVs were isolated from MSCs and characterized using nanoparticle tracking analysis. EVs were incorporated into an injectable collagen scaffold. In vivo fluorescence tracking of PKH26-labeled EVs was performed in a separate cohort (4 shoulders per group) to evaluate EV retention over 14 days. A collagenase-induced tendinopathy model was established in the supraspinatus tendons of 16 rats. Rats were randomly assigned to 4 treatment groups (control, collagen, EV, and collagen + EV) and received local injections (8 shoulders per group). Magnetic resonance imaging (MRI) was performed at weeks 3 and 4 to evaluate tendon signal intensity and thickness after treatment. At week 4, all rats were sacrificed for histological and immunofluorescence analysis. RESULTS: Fluorescence tracking revealed sustained retention of EVs within the tendon for 14 days via collagen scaffold delivery. MRI analysis at weeks 3 and 4 showed significantly reduced tendon signal intensity and thickness in the collagen + EV group compared with all other groups (< .001). Histological evaluation demonstrated superior collagen continuity, arrangement, and density, and significantly higher histological scores in the collagen + EV group (< .001). Immunofluorescence revealed reduced iNOS and increased CD206, Arg-1, and FOXP3 expression, indicating anti-inflammatory and regulatory immune modulation. CONCLUSION: Local delivery of MSC-EVs embedded within an injectable collagen scaffold enhanced tendon regeneration in a rat model of collagenase-induced tendinopathy. The collagen matrix provided sustained retention and bioactivity of the EVs, resulting in superior structural and histological recovery compared to either treatment alone. These findings support the therapeutic synergy between EVs and collagen and offer preclinical validation for a translatable, cell-free therapeutic strategy for tendinopathy. CLINICAL RELEVANCE: Combining EVs with collagen carriers is a promising strategy for biological augmentation of tendinopathy.