Combination of Atelocollagen Gel With Induced Pluripotent Stem Cell-Derived Tenocyte for Rotator Cuff Tendon Regeneration in a Rat Model.

BACKGROUND: Despite successful mechanical rotator cuff repair, the intrinsic quality of the tendon often remains poor, thereby increasing the risk of retear. PURPOSE: To investigate a proper differentiation of tenocytes from induced pluripotent stem cells (iPSCs) and a regenerative approach using iPSC-derived tenocytes (iPSC-TCs) combined with atelocollagen gel to enhance tendon healing after rotator cuff repair. STUDY DESIGN: Controlled laboratory study. METHODS: Tenogenic differentiation was induced in vitro from the human iPSC line 1231A3, with differentiation confirmed by cell morphology, flow cytometry, and immunofluorescence staining. The viability of iPSC-TC within 3% atelocollagen gel was analyzed. The Sprague Dawley rats were divided into 4 groups (n = 16 per group). Group 1 acted as the control without damage; group 2 with surgical repair of the fully torn supraspinatus; group 3 with additional injection of atelocollagen after the repair; and group 4 with additional injection of iPSC-TC embedded on atelocollagen after the repair. After tissue harvest at postoperative 6 weeks, quantitative evaluation of gene expression (messenger ribonucleic acid levels), immunohistochemistry (percentage of stained area), and Western blot (relative protein expression) was performed. All experimental results are reported as mean and error, and analyzed using the Student t test, the Mann-Whitney U test, and analysis of variance. RESULTS: Differentiation to iPSC-TC was confirmed on day 19 of passage 3 with positive expression of cell surface markers and positive expression of tenogenic markers on immunofluorescence staining. Differentiated iPSC-TC showed significantly higher expression of tendon-related genes when compared with nondifferentiated iPSC. After the tissue harvest, PKH16-labeled iPSC-TC was identified only in group 4 under confocal microscopy. The Masson trichrome stain showed significantly greater collagen intensity in group 4 compared with the other repair groups (P < .05). Higher expression of type I collagen in group 4 was identified in both immunohistochemistry (P < .05) and Western blot analysis (group 1: 0.39 ± 0.07 vs group 4: 0.96 ± 0.27; P < .05). CONCLUSION: Our study demonstrates that an injection of atelocollagen containing iPSC-TCs into the lesion after rotator cuff repair produced excellent residual effects. The addition of iPSC-TCs embedded in atelocollagen to a surgically repaired rotator cuff could improve tendon quality by increasing type I collagen production. CLINICAL RELEVANCE: The combination of atelocollagen with induced pluripotent stem cell-derived tenocytes could help tendon healing and thus potentially reduce retear. This approach may have the potential to improve the biological quality of repaired rotator cuffs, reduce the risk of retear, and ultimately enhance long-term surgical outcomes in patients with tendon injuries.