The objective of this trial is to determine whether PBMNCs in diabetic patients with critical, non revascularizable limb ischemia can prevent major amputation and affect mortality and healing.

This is an interventional study with historical control group carried out to assess as primary outcome major amputations, overall mortality, number of healed patients in group of patients who received repetitive intra-muscular implant of PBMNCs (3 times; 4-week interval) in comparison to a historical internal control group with a 1:1 case-control ratio. Secondary outcomes are TCPO2, healing time and rest pain.

No-option critical limb ischaemia is defined by evidence of no run-off pedal vessels, failure after several percutaneous intervention and no longer possible re-intervention, failure after infra-genicular bypass grafting, no-walking capacity with severe comorbidities unfit for surgical or endovascular procedures.

Inclusion criteria are: a) ulcers with inadequate perfusion, as indicated by a transcutaneous oxygen pressure value (TcpO2) <30 mmHg; b) ulcers with grade I or II or III and stage C as defined by the Texas University Classification System or W1,2,3 - I 3 - FI 0,1 as defined by the WiFI Classification System c) not eligible for angioplasty or vascular surgery or following failed revascularization; d) possibility to save foot support.

Exclusion criteria are: a) lesion site above the tibial-tarsal joint; b) moderate or severe infection according by the WiFI classification system; c) NYHA class IV; d) Anemia (Hb<8g/dl); e) coagulation disorder/thrombocytopenia (PLT< 50,000 per microliter); f) active cancer/leukemia or lymphoma hematological disease.

Standard of care in both groups includes: diabetes control maximization by the diabetologist, comprehensive foot assessment by the nurse together with the diabetologist, including determination of vibration perception threshold, 10-g monofilament test and TcpO2 measurement, dressings, off-loading and systemic therapy according to the IWGDF guidelines .

Informed consent for participation in the study during the progress of the clinical trial is obtained from all subjects.

Concentration of PB-MNCs autologous cell therapy is produced by a filtration-based point-of-care device with the intended for use intra-operatively, from 120 mL of anticoagulated blood. All the procedures are performed in operatory room with anaesthesiologic support (propofol and/or peripheral block). Blood withdrawal (120 ml) is collected through a peripheral venous access, than loaded and gravity filtration is allowed in about 10 minutes. During filtration, MNCs are captured in the filter while plasma, platelets (PLTs) and red blood cells (RBCs) are not retained. After appropriate surgical debridement of the wound bed multiple perilesional and intramuscular injections of PBMNC cells suspension (0.2-0.3cc in boluses) are injected along the relevant axis below the knee, at intervals of 1-2 cm and to a mean depth of 1.5-2 cm, using a 21G needle. This procedure is repeated on each patient for three times, at intervals of 30-45 days from each other.

Foot-sparing surgery, the removal of all the unviable tissue and the reconstruction of the foot to allow a functional deambulation,is performed at the same time of the last implant in the patients with increased TcpO2 value above 30 mmHg. Between the implants, diabetologists together with nurses evaluated changing in pain, infection signs, wound size, demarcation of the necrosis, granulation tissue formation, perilesional tissue trophism and TcpO2 value to optimize standard of care. After the first treatment, a two years follow-up is registered, with evaluation at 1-3-6-12-18-24 months.

A baseline assessment is carried out, in order to estimate any differences among cases and controls before the treatment. Statistical evaluation includes non-parametric tests (Mann-Whitney U test for independent samples for continuous variables and Cochrane chi-square test for discrete variables), evaluation of Relative Risk (RR), Absolute Risk Reduction (ARR), Relative Risk Reduction (RRR) and Number Needed to Treat (NNT), multivariate survival analysis (Kaplan-Meier's survival analysis model).

Inclusion Criteria:

• ulcers with inadequate perfusion, as indicated by a transcutaneous oxygen pressure value (TcpO2) <30 mmHg;
• ulcers with grade I or II or III and stage C as defined by the Texas University Classification System or W1,2,3 - I 3 - FI 0,1 as defined by the WiFI Classification System
• not eligible for angioplasty or vascular surgery or following failed revascularization;
• possibility to save foot support.

Exclusion Criteria:

• lesion site above the tibial-tarsal joint;
• moderate or severe infection according by the WiFI classification system;
• NYHA class IV; d) Anemia (Hb<8g/dl);
• coagulation disorder/thrombocytopenia (PLT< 50,000 per microliter);
• active cancer/leukemia or lymphoma hematological disease.

data should not be shared before study completion and approvation by all the collaborators. Sharing data before this time would jeopardize the integrity of the clinical trial process and risk the scientific validity of the results.