Umbilical Cord Mesenchymal Stem Cells Therapy for Diabetic Nephropathy

Enrollment criteria: * Adult patients (age 18-60 years) who met the WHO 1999 diagnostic criteria for type 2 diabetes, regardless of gender; * Concomitant proteinuria ,3500 mg/day≥24h urinary protein excretion ≥500 mg/day, and uncontrolled disease course; * Pathological examination of puncture biopsy resulting in diagnosis of type IIa, IIb, III, or IV diabetic nephropathy. (In 2010, an international expert group led by Bruijn of Leiden University in the Netherlands published a pathological classification system for diabetic nephropathy); * eGFR between 30 ml/min/1.732 m2 and 60 ml/min/1.732 m2; * Diabetes treatment according to guidelines and norms before the umbilical cord mesenchymal stem cell therapy; * If there is a possibility of pregnancy in female, must be negative pregnancy test, not in lactation, and confirm that is receiving the method of contraception recognized by the researchers, and agree to maintain the method of contraception throughout the study. Sexually active male patients must agree to the use of an appropriate contraceptive method for birth control from the first administration of the study treatment until 24 weeks after the last administration. * participate in all visits, examinations, and treatments as required by the experimental protocol. Exclusion criteria: * Patients with kidney biopsy diagnosis of type I diabetic nephropathy or a diagnosis of another glomerular disease; * Patients with abnormal renal function (serum creatinine ≥ the upper limit of normal); * Patients with HbA1c ≥10%; * Patients with active liver disease or abnormal liver function test results (ALT or AST ≥2 times the upper limit of normal); * Patients with blood leukocyte count \<3.0 × 109/L, hemoglobin \<90 g/L, platelet count \<100 × 109/L, or those who have other hematologic diseases (severe anemia, idiopathic thrombocytopenic purpura, splenomegaly, coagulation dysfunction, etc.); * Patients with serious and unstable cardiovascular or cerebrovascular diseases (unstable angina pectoris, coronary artery disease, cerebrovascular disease, transient ischemic attack, congestive heart failure, etc.), acute and difficult to control the disease, after treatment has not been effectively controlled severe hypertension (blood pressure \>160/100 mm Hg), or organ transplantation; * Patients with increased use of hypotensive drugs in the past 3 months; * Patients with uncontrolled infection; * Patients with tumors or abnormal tumor marker levels; * Patients with blood-borne diseases (i.e., HIV, syphilis, hepatitis B, and hepatitis C); * Pregnancy, the potential for pregnancy, or lactation; * Patients receiving immunosuppressive therapy; * Patients with a history of allergy, especially patients allergic to human blood albumin; * Patients with mental illness affecting their voluntarism, ability to make decisions, and ability to communicate； * A history of alcoholism or known drug addiction in the last 2 years; * Participation in another clinical trial within the last 3 months; * Patients judged inappropriate for this study by the physicians.