Enhancement of Rotator Cuff Regeneration via Injectable Spheroidal Adipose‐Derived Stem Cell Cluster‐Collagen Hydrogel Complex

ABSTRACT Background Rotator cuff repair often results in scar tissue rather than tendon regeneration, leading to inferior strength and high re‐tear risk. This study evaluated the regenerative efficacy of an injectable formulation combining adipose‐derived stem cell (ADSC) clusters with collagen in an animal model. Materials and Methods ADSCs from patients were formed into spheroids and mixed with collagen. Rats with surgically induced cuff injury received injections of (1) no treatment, (2) spheroid‐only, (3) collagen‐only, or (4) combined spheroid‐collagen. Tendon healing was assessed by histology (H&E, Masson's trichrome, Safranin O, picrosirius red) and biomechanical testing. Safety was verified through biodistribution, toxicity, and tumourigenicity studies in immunosuppressed mice. Results Gene expression analysis of the ADSCs and the spheroid‐collagen complex confirmed an upregulation of regeneration‐related transcription factors, indicating a potential for enhanced rotator cuff regeneration. Histological analysis showed that the combined group achieved significantly higher histological scores (11.33 ± 0.61 vs. 8.33 ± 1.33, p = 0.001) and tendon strength (16.57 ± 4.58 vs. 7.94 ± 1.44, p = 0.005) compared with controls. In terms of safety, No injected cells were found in other organs, and no toxicity or tumourigenesis was observed. Importantly, administered cells persisted at the injection site in the combined group for up to 16 weeks. Conclusion The combined injectable formulation of stem cells and collagen effectively enhanced the regeneration of injured rotator cuff tissue in an animal model. The demonstrated safety and persistence of the formulation suggest its potential applicability as a cell‐based therapeutic agent for clinical use.