A Randomized Controlled Trial on the Efficacy and Safety of Umbilical Cord Mesenchymal Stem Cell Therapy in Subjects With Moderate to Severe Diabetic Peripheral Neuropathy

Inclusion Criteria: 1. Males or females aged 18-80 years; 2. Meeting the 2023 ADA diagnostic criteria for type 2 diabetes; 3. Presence of symptoms and signs of diabetic neuropathy in lower extremities: For symptomatic patients: At least one abnormal finding among ankle reflex, pinprick sensation, vibration sense, pressure perception, or temperature sensation, accompanied by clinical symptoms (e.g., symmetric lower limb numbness, pain, or tingling); For asymptomatic patients: At least two abnormal findings in the above five examinations; 4. Confirmed neurophysiological dysfunction: Reduced nerve conduction velocity (≥2 standard deviations) in at least one lower extremity nerve (common peroneal, posterior tibial, or deep peroneal nerve), with or without decreased amplitude; Moderate to severe neuropathy severity: 5. Toronto Clinical Scoring System (TCSS) score ≥9; 6. Inadequate response to conventional therapy: Persistent symptoms (reduction of TCSS score \<2 points from baseline) despite ≥3 months of conventinal treatment; 7. Capacity to understand and voluntarily complete all study procedures and interventions, with signed informed consent. Exclusion Criteria: 1. Non-diabetic neuropathy or pain conditions in lower limbs that may confound DPN assessment per investigator's judgment; 2. Poorly controlled diabetes (HbA1c \>12%); 3. Severe hematological, hepatic, or renal dysfunction, meeting any of the following laboratory criteria: Hematology: Neutrophils \<1.5×10⁹/L, platelets \<90×10⁹/L, or hemoglobin \<80 g/L; Liver function: ALT or AST \>3× upper limit of normal (ULN), or total bilirubin \>1.5× ULN; Renal function: eGFR \<30 mL/min/1.73m² (calculated by MDRD formula) or requiring renal replacement therapy; Creatine kinase \>2× ULN; 4. Known allergy to stem cells, stem cell-derived products, or components of stem cell preparations; 5. Current use of prohibited medications within 5 half-lives prior to enrollment (may be reconsidered after ≥5 half-lives washout); 6. Uncontrolled systemic diseases, including but not limited to: Severe uncontrolled systemic infections (bacterial, fungal, or viral); Severe autoimmune disorders; Hematological diseases; Heart failure (NYHA class ≥III); 7. Clinically significant arrhythmia on 12-lead ECG; 8. Conditions requiring amputation (e.g., severe diabetic foot or lower limb ulcers) that preclude local stem cell injection; 9. Other diseases unsuitable for trial participation (e.g., active malignancy, cognitive impairment, depression, or psychiatric disorders); 10. Participation in any interventional clinical trial within 3 months prior to screening; 11. Pregnancy, lactation, or planning pregnancy within 2 years; 12. Any other condition deemed by the investigator to compromise trial suitability.