The purpose of this study is to assess the feasibility, safety and clinical efficacy of the novel clonal fetal mesenchymal stem cell (cfMSC) therapy in patients with type II diabetes mellitus.

Type II diabetes mellitus is a chronic metabolic disease with progressive islet β-cell dysfunction and insulin resistance as the core pathogenesis, leading to persistent hyperglycemia and a series of microvascular and macrovascular complications. Conventional treatments including lifestyle intervention, oral hypoglycemic agents and insulin injection can only control blood glucose levels, but cannot reverse the loss and dysfunction of islet β-cells, the root cause of the disease.

At present, the clinical treatment of diabetes is mainly based on lifestyle intervention, oral hypoglycemic drugs and insulin injection, which can only control blood glucose and cannot fundamentally repair the damaged islet function and reverse the disease process. Mesenchymal stem cells have the characteristics of multi-directional differentiation potential, immune modulation, anti-inflammatory, allogeneic tolerance and paracrine effects. MSCs could have diverse sources. The fetal tissue-derived clonal MSCs (cfMSCs) have extended expansion potential, high purity and can generate rich levels of various growth factors, and can achieve high quality consistency. The cfMSCs may modulate islet-like cells' differentiation, repair the damaged islet tissue, improve insulin resistance, and regulate the abnormal immune response of the body, which is a potential new strategy for the treatment of diabetes.

This study aims to adopt intravenous infusion of cfMSCs to treat patients with type II diabetes who have poor curative effect from the conventional treatment. The goal is to evaluate the safety, feasibility and preliminary clinical efficacy of this novel therapy, and provide important clinical evidence for the clinical transformation and application of cfMSC therapy for diabetes, so as to bring new treatment options for diabetic patients.

Inclusion Criteria:

1. Ability to understand the study protocol and voluntarily sign the written informed consent form;
2. A clear diagnosis of type II diabetes mellitus for more than 3 years, with poor blood glucose control under conventional treatment (HbA1c ≥ 7.5% for 3 consecutive months);
3. Age 18-75 years old, with a body mass index (BMI) of 18.5-35 kg/m²;
4. Fasting C-peptide level 0.3-1.5 ng/mL, indicating residual islet function;
5. Karnofsky performance score (KPS) ≥ 70, with good daily living ability;
6. Life expectancy > 5 years;
7. Normal liver and kidney functions (bilirubin < 1.5×ULN, ALT/AST < 2.5×ULN, creatinine < 1.5×ULN); normal blood routine (absolute neutrophil count ≥ 1.8×10^9/L, platelets ≥ 100×10^9/L);
8. No serious heart, brain, lung and other important organ diseases, and stable vital signs;
9. Women of childbearing age have a negative pregnancy test within 7 days before enrollment, and all subjects of childbearing age agree to take effective contraceptive measures during the study and within 1 year after the end of the study; Willing to cooperate with the whole course of follow-up and complete all examination and observation indicators.

Exclusion Criteria:

1. Type 1 diabetes mellitus or other special types of diabetes;
2. Severe diabetes-related complications, such as end-stage renal disease, severe proliferative retinopathy, diabetic foot with ulcer and infection, etc.;
3. A history of malignant tumors within 5 years, or current suspicious malignant tumor lesions;
4. HIV, hepatitis B, hepatitis C and other infectious diseases with positive pathogen indicators;
5. Active autoimmune diseases, or long-term use of glucocorticoids and immunosuppressants (except for small dose hormone replacement therapy);
6. A history of severe allergic reactions, or allergy to the components of the study cell preparation;
7. Pregnant or lactating women;
8. Actively participating in other clinical research projects at the same time;
9. Mental diseases or poor compliance that cannot cooperate with the study; Other conditions that the investigator deems unsuitable for participating in the study.