Tendon injury is one of the most common sports injuries, including local tissue degeneration at the tendon insertion site following inflammation caused by long-term joint movement, friction, or strain, as well as acute traumatic tendon tears and defects of varying degrees due to sports. It is a recognized therapeutic challenge in orthopedics and sports medicine. With the increase in people's physical activities and changes in work styles, tendon injuries have become increasingly prevalent, with at least 30 million tendon injury cases annually. Meanwhile, tendon injuries pose a significant threat to the careers of many elite athletes. Currently, clinical treatments for tendon injuries mainly remain at the stages of physical therapy, surgical suture, and transplantation. Although these treatments have certain effects, their efficacy is limited-primarily because adult tendons lack complete regenerative capacity. As a result, the quality of repaired tendons is far inferior to that of normal tendons, making them prone to tendon adhesion, poor structural and mechanical properties, and frequent re-rupture. Even autologous tendon transplantation can only achieve approximately 40% of the mechanical properties of normal tendons, accompanied by excessive scar tissue formation. Current therapeutic and tissue engineering approaches can only partially improve tendon repair quality, failing to induce complete tendon repair and regeneration. Therefore, exploring new and efficient strategies for the treatment and regeneration of tendon injuries is of great significance.

In recent years, cell therapy has brought new opportunities for improving the repair quality of soft tissues such as tendons. Tendon-derived cells are isolated and extracted from tendons. These cells not only possess stem cell characteristics similar to bone marrow mesenchymal stem cells but also highly express tendon-specific genes and proteins. Therefore, this study intends to first culture and expand tendon stem/progenitor cells (TSPCs) to form therapeutic agents, then apply TSPC-enhanced therapy intraoperatively to patients with rotator cuff tendinopathy, and evaluate its clinical safety and efficacy.

Inclusion Criteria:

1. Aged between 18 and 70 years, regardless of gender;
2. Tear size classified as small (< 1 cm) or medium-sized (1 cm to 3 cm) according to the DeOrio and Cofield classification system;
3. Persistent shoulder pain or functional limitations despite at least 3 months of non-surgical treatment, with indications for arthroscopic rotator cuff repair;
4. Willing to sign the informed consent form and agree to participate in this study.

Exclusion Criteria:

1. Tear size classified as large (3 cm to 5 cm) or massive (> 5 cm) according to the DeOrio and Cofield classification, or Patte grade 3 tendon retraction;
2. Subscapularis tendon tear;
3. Complicated with anterior, posterior, or multidirectional shoulder joint instability;
4. Indications for repair of anterior or posterior labral injury;
5. Intra-articular injection of hyaluronic acid or corticosteroids within 3 months prior to the planned surgery;
6. Comorbidities that contraindicate arthroscopic shoulder surgery;
7. Local (shoulder, abdomen, buttocks) or systemic infection, osteomyelitis, or sepsis;
8. Diabetes mellitus, untreated thyroid disease, chronic kidney disease, or rheumatoid arthritis;
9. Immunodeficiency;
10. Chronic diseases involving coagulation or platelet aggregation, or severe coagulopathy;
11. Severe cardiovascular disease;
12. Stroke or acute cardiovascular event within 6 months prior to the planned surgery;
13. Weight loss > 30 kg for any reason within 12 months, or unexplained weight loss > 10 kg within 12 months;
14. Eating disorder or body dysmorphic disorder;
15. Alcohol/drug addiction or mental illness that may affect compliance with postoperative protocols;
16. Pregnant or lactating women;
17. Refusal to sign the informed consent form;
18. Other conditions deemed inappropriate by the investigators.

In phase II clinical trial, blinding will be applied to the participants, those measuring the intervention effects, and the statistician responsible for the analysis. The operating surgeons will not be blinded. Sequentially numbered, sealed opaque envelopes containing group allocation information will be provided to the operating surgeons. Group allocation concealment will be ensured through the use of a central automated randomization system, and security measures will be implemented to prevent those blinded from accessing or influencing the allocation data. Objective measurements of rotator cuff structural changes and pain will be performed by trained assessors unaware of the group assignments. The statistician conducting the statistical analysis will also remain blinded.