Clinical Research Directory

Inclusion Criteria: 1. History of long-term bed rest: continuous bed rest for ≥4 weeks, with causes including neurological injury (such as brain death, stroke, or spinal cord injury), recovery after major orthopedic surgery, intensive care unit stay, or activity limitation due to chronic diseases. 2. Evidence of muscle atrophy: a significant reduction in muscle mass or muscle strength confirmed by clinical assessment and imaging. According to dual-energy X-ray absorptiometry (DXA), appendicular skeletal muscle mass index (ASM/height²) \< 7.0 kg/m² in men and \< 5.4 kg/m² in women, in accordance with EWGSOP2 criteria. 3. Stable underlying medical conditions, with no acute exacerbation, and an APACHE II score of 0-20. 4. Absence of severe comorbidities that would contraindicate surgical or transplantation interventions. 5. Written informed consent obtained from the patient, an immediate family member, or a legal guardian, agreeing to muscle biopsy, with general health status adequate to permit subcutaneous transplantation. Exclusion Criteria: 1. History of malignant tumors. 2. Coagulation disorders or current use of anticoagulant therapy. 3. Active infection or immunodeficiency. 4. Severe cardiac or renal insufficiency (estimated glomerular filtration rate \< 60 mL/min/1.73 m²; New York Heart Association \[NYHA\] class III-IV heart failure). 5. Muscle-related diseases, including hereditary myopathies (such as muscular dystrophy) or acquired myositis (creatine kinase \> 3 times the upper limit of normal). 6. Severe local skin lesions or a history of allergic reactions at the injection site. 7. Use of muscle growth-modulating medications (such as testosterone or growth hormone) within the past 6 months. 8. Long-term use of corticosteroids or immunosuppressive therapy, including anti-rejection medications following organ transplantation. 9. Other exclusion criteria: participation in other interventional clinical trials (excluding observational studies). 10. Any other medical or ethical conditions deemed by the investigator to make the participant unsuitable for enrollment.