Diabetic Peripheral Neuropathy (DPN) is one of the most common chronic complications in type 2 diabetes, conventional drug therapy can only target a single pathogenesis but not treat Diabetic Peripheral Neuropathy (DPN) fundamentally. As a novel technique, stem cell transplantation provides a new option for patients with DPN. In 2012, Wuhan Central Hospital, took the lead in carrying out clinical research on the treatment of DPN with autologous bone marrow stem cells in China, and patients were significantly relieved. Based on this research, our clinical trial is to evaluate the safety and efficacy of HUC-MSCs in the treatment of refractory diabetic peripheral neuropathy (DPN) by formulating standard operating procedures (SOP) and quality standards (QS) to explore the possible mechanism of HUC-MSCs in the treatment of DPN.

As Diabetes is becoming a health problem of global concern rapidly, DPN, one of the common chronic complications in Diabetes is also getting more and more attention. The result of a survey of 5 regions in Southeast Asia showed that 39-72% of patients with DPN had severe or very severe impact on their quality of life. For the treatment of DPN, conventional drug therapy can almost only target a single pathogenesis and cannot treat it fundamentally. Therefore, new safe and effective treatment options for DPN are particularly important.

Both here and abroad, large number of experimental studies have shown that Bone Marrow or Umbilical Cord Mesenchymal Stem Cells have a significant therapeutic effect on diabetic peripheral neuropathy. In 2012, the Department of Endocrinology of Wuhan Central Hospital took the lead in conducting a clinical study of Autologous Bone Marrow Stem Cells in the treatment of DPN in China. The results of the study showed that the nerve conduction velocity of the lower extremities in most patients was improved within 3 months after treatment compared with before treatment. No serious adverse events occurred during the period. Based on this research of our own. The clinical trial is to evaluate the safety and efficacy of HUC-MSCs in the treatment of refractory diabetic peripheral neuropathy (DPN) by formulating standard operating procedures (SOP) and quality standards (QS) to explore the possible mechanism of HUC-MSCs in the treatment of DPN.

The investigators will do a Single center, randomization, open trial, controlled clinical trials design to assess treatment with the MSCs compared with the control group. 42 patients with DPN will be recruited in China. 21 patients receive i. m. HUC-MSCs both lower extremities (5 × 10^6 cells/mL, 1 mL per injection, each injection point is 2 cm apart ,1.0-1.5 cm deep, total amount of injection is estimated based on the surface area of the patient's lower limbs). 21 patients in the control group received i.v. Lipoic Acid Injection (600 mg/d for 15 consecutive days). Both efficacy and Adverse Event (AE) during the 96 weeks follow up.

Inclusion Criteria:

• Ages at 18-55 years (including 18 and 55 years), regardless of gender;
• Understand and sign the ICF before proceeding with any steps related to this study, comply with the requirements, and do not to participate in other clinical studies during this research;
• T2DM patients defined by the 2013 American Diabetes Association (ADA) standards;
• Meet the diagnostic criteria for diabetic peripheral neuropathy: ① A clear history of diabetes; ② Neuropathy that occurs on or after the diagnosis of diabetes; ③Clinical symptoms and signs are consistent with DPN; ④ People with clinical symptoms (pain, numbness, abnormal sensation, etc.), had any 1 of the 5 items of ankle reflex, acupuncture pain, vibration, pressure and temperature in abnormal; people without clinical symptoms had any 2 of the 5 items were abnormal;
• The evaluation of symptoms and signs of neuropathy is at severe level (TCSS score ≥12);
• For conventional standard drug treatment (combined use of Lipoic Acid Capsules, Methyl cobalamin Tablets, and Epalrestat Tablets) at least 6 months and TCSS score decrease ≤30%;

Exclusion Criteria:

• Diseases that the investigator believes that it may interfere with subject compliance, including any uncontrolled diseases like in urinary, circulatory, respiratory, nervous, mental, digestive, endocrine, immune, and other system;
• Pregnant women, breastfeeding women or those who have a childbearing plan soon;
• Patients who are known to be allergic to cell products;
• People with various types of malignancies or hematological diseases;
• Complicated with severe lower extremity arterial disease (ankle-brachial index < 0.9)
• Complicated with foot ulcers, infections, or lower extremity amputation;
• Combined with neuropathy caused by other causes, such as lumbar spondylosis, cerebral infarction, Guillain-Barre Syndrome, excluding severe arteriovenous vascular disease, application of some chemotherapy drugs or renal insufficiency, etc. Nerve damage disease;
• Those who are unable or unwilling to provide informed consent or fail to comply with research requirements;
• Participated in other stem cell clinical researches before enrollment;
• Participated in other clinical trials within 3 months before enrollment.
• Patients with positive serum HIV antibodies;
• Patients with a history of alcohol and drug abuse and failed to abstain effectively

After approval from the steering committee and the Human Genetic Resources Administration of China, this trial data can be shared with qualifying researchers who submit a proposal with a valuable research question. A contract should be signed.