This trial is to evaluate the efficacy and safety of umbilical cord-derived mesenchymal stromal cells (Amimestrocel ) in study subjects with progressive diabetic kidney disease (DKD), to investigate whether Amimestrocel can improve renal function or proteinuria of DKD patients.

Inclusion Criteria: -

1. Men and women who are ≥18 and ≤ 80 years old.
2. Diagnosed with type 2 diabetes mellitus.
3. Diagnosed with diabetic kidney disease based on renal pathology within the past 10 years.
4. The 24-hour urine protein quantification is continuously ≥ 3.5 g, or the urine albumin-to-creatinine ratio (UACR) > 1000 mg/g.
5. The estimated glomerular filtration rate (eGFR) ≥ 15 ml/min/1.73m² (calculated according to the CKD-EPI formula).
6. The blood pressure can be controlled at BP ≤ 160/100 mmHg.
7. Glycated hemoglobin (HbA1c) < 9%.
8. Willing and able to provide written informed consent.

Exclusion Criteria:

1. Patients with kidney diseases not caused by diabetes mellitus.
2. Patients who have received treatment with systemic immunosuppressants (such as cyclosporine A, tacrolimus, mycophenolate mofetil, etc.) within 30 days before enrollment and the duration of treatment exceeds one week.
3. Severe cardiovascular diseases, such as congenital heart diseases, atrial fibrillation, NYHA class Ⅲ-IV, unstable angina pectoris, etc.
4. A history of cerebral hemorrhage or cerebral infarction within the past six months (except for those with a history of lacunar cerebral infarction without residual limb movement disorders, cognitive and language function disorders).
5. Patients with severe hyperlipidemia: (serum triglyceride ≥ 6.2 mmol/L, serum low-density lipoprotein cholesterol ≥ 4.1 mmol/L).
6. Hyperkalemia that cannot be controlled through diet or potassium-lowering treatment.
7. Patients with active infections of hepatitis B or hepatitis C viruses (the copy number of HBV DNA or HCV RNA exceeds the upper limit of the normal value); patients with active tuberculosis; patients with severe immunodeficiency diseases, human immunodeficiency virus (HIV) infection, etc.
8. Patients with a history of malignant tumors within the past five years.
9. Patients with a known history of severe allergy to component blood or blood products, or patients with a history of allergy to heterologous proteins.
10. Lactating women, or female patients who have a pregnancy plan or an egg donation plan from the start of the study to the follow-up period, and male patients (or their partners) who have a childbearing plan or a sperm donation plan from the start of the study to the follow-up period and are unwilling to take contraceptive measures.
11. Active infection within one week before enrollment and requiring treatment with intravenous antibiotics.
12. Patients who have participated in other interventional clinical trials within three months before enrollment.
13. The research physician deems that the patient's condition is not suitable for participating in this clinical study.