Intra-arterial bone marrow cell transplantation induces angiogenesis in rat hindlimb ischemia

Modalities to Deliver Cell Therapy for Treatment of Chronic Limb Threatening Ischemia

Significance: Chronic limb threatening ischemia (CLTI) is a severe form of peripheral arterial disease (PAD) that is associated with high rates of morbidity and mortality, and especially limb loss. In patients with no options for revascularization, stem cell therapy is a promising treatment option. Recent Advances: Cell therapy directly delivered to the affected ischemic limb has been shown to be a safe, effective, and feasible therapeutic alternative for patients with severe PAD. Multiple methods for cell delivery, including local, regional, and combination approaches, have been examined in both pre-clinical studies and clinical trials. This review focuses on delivery modalities used in clinical trials that deliver cell therapy to patients with severe PAD. Critical Issues: Patients with CLTI are at high risk for complications of the disease, such as amputations, leading to a poor quality of life. Many of these patients do not have viable options for revascularization using traditional interventional or surgical methods. Clinical trials have shown therapeutic benefit for cell therapy in these patients, but methods of cell treatment are not standardized, including the method of cell delivery to the ischemic limb. Future Directions: The ideal delivery approach for stem cell therapy in PAD patients remains unclear. Further studies are needed to determine the best modality of cell delivery to maximize clinical benefits.

Systematic review and meta-analysis of the effect of bone marrow-derived cell therapies on hind limb perfusion

Preclinical and clinical studies on the administration of bone marrow-derived cells to restore perfusion show conflicting results. We conducted a systematic review and meta-analysis on preclinical studies to assess the efficacy of bone marrow-derived cells in the hind limb ischemia model and identify possible determinants of therapeutic efficacy. In vivo animal studies were identified using a systematic search in PubMed and EMBASE on 10 January 2022. 85 studies were included for systematic review and meta-analysis. Study characteristics and outcome data on relative perfusion were extracted. The pooled mean difference was estimated using a random effects model. Risk of bias was assessed for all included studies. We found a significant increase in perfusion in the affected limb after administration of bone marrow-derived cells compared to that in the control groups. However, there was a high heterogeneity between studies, which could not be explained. There was a high degree of incomplete reporting across studies. We therefore conclude that the current quality of preclinical research is insufficient (low certainty level as per GRADE assessment) to identify specific factors that might improve human clinical trials.

A Swine Hind Limb Ischemia Model Useful for Testing Peripheral Artery Disease Therapeutics

Currently, there is no large animal model of sustained limb ischemia suitable for testing novel angiogenic therapeutics for peripheral artery disease (PAD) such as drugs, genes, materials, or cells. We created a large animal model suitable for efficacy assessment of these therapies by testing 3 swine hind limb ischemia (HLI) variations and quantifying vascular perfusion, muscle histology, and limb function. Ligation of the ipsilateral external and bilateral internal iliac arteries produced sustained gait dysfunction compared to isolated external iliac or unilateral external and internal iliac artery ligations. Hyperemia-dependent muscle perfusion deficits, depressed limb blood pressure, arteriogenesis, muscle atrophy, and microscopic myopathy were quantifiable in ischemic limbs 6 weeks post-ligation. Porcine mesenchymal stromal cells (MSCs) engineered to express a reporter gene were visualized post-administration via positron emission tomography (PET) in vivo. These results establish a preclinical platform enabling better optimization of PAD therapies, including cellular therapeutics, increasing bench-to-bedside translational success. A preclinical platform for porcine studies of peripheral artery disease therapies including (1) a hind limb ischemia model and (2) non-invasive MSC viability and retention assessment via PET.

REX-001, a BM-MNC Enriched Solution, Induces Revascularization of Ischemic Tissues in a Murine Model of Chronic Limb-Threatening Ischemia

Background: Bone Marrow Mononuclear Cells (BM-MNC) constitute a promising alternative for the treatment of Chronic Limb-Threatening ischemia (CLTI), a disease characterized by extensive blockade of peripheral arteries, clinically presenting as excruciating pain at rest and ischemic ulcers which may lead to gangrene and amputation. BM-MNC implantation has shown to be efficient in promoting angiogenesis and ameliorating ischemic symptoms in CLTI patients. However, the variability seen between clinical trials makes necessary a further understanding of the mechanisms of action of BM-MNC, and moreover, to improve trial characteristics such as endpoints, inclusion/exclusion criteria or drug product compositions, in order to implement their use as stem-cell therapy.

Materials: Herein, the effect of REX-001, a human-BM derived cell suspension enriched for mononuclear cells, granulocytes and CD34+ cells, has been assessed in a murine model of CLTI. In addition, a REX-001 placebo solution containing BM-derived red blood cells (BM-RBCs) was also tested. Thus, 24 h after double ligation of the femoral artery, REX-001 and placebo were administrated intramuscularly to Balb-c nude mice (n:51) and follow-up of ischemic symptoms (blood flow perfusion, motility, ulceration and necrosis) was carried out for 21 days. The number of vessels and vascular diameter sizes were measured within the ischemic tissues to evaluate neovascularization and arteriogenesis. Finally, several cell-tracking assays were performed to evaluate potential biodistribution of these cells.

Results: REX-001 induced a significant recovery of blood flow by increasing vascular density within the ischemic limbs, with no cell translocation to other organs. Moreover, cell tracking assays confirmed a decrease in the number of infused cells after 2 weeks post-injection despite on-going revascularization, suggesting a paracrine mechanism of action.

Conclusion: Overall, our data supported the role of REX-001 product to improve revascularization and ischemic reperfusion in CLTI.

CXCR4 Overexpression in Human Adipose Tissue-Derived Stem Cells Improves Homing and Engraftment in an Animal Limb Ischemia Model

We investigated the effects of transplantation of CXCR4-overexpressing adipose tissue-derived stem cells (ADSCs) into a mouse diabetic hindlimb ischemia model on homing and engraftment as early as 48 h after transplant. CXCR4-overexpressing ADSCs were intramuscularly or intravenously injected into diabetic mice with hindlimb ischemia. After 48 h, muscle tissues in the femur and tibia were collected, and the CXCR4 expression pattern was analyzed by immunofluorescence staining. The homing and engraftment of transplanted CXCR4-overexpressing ADSCs into the ischemic area were significantly increased, and intravenous (systemic) injection resulted in the more effective delivery of stem cells to the target site 48 h posttransplantation. Furthermore, CXCR4-overexpressing ADSCs more efficiently contributed to long-term engraftment and muscle tissue regeneration than normal ADSCs in a limb ischemia model. In addition, the homing and engraftment of ADSCs were correlated with the CXCR4 transfection efficiency. These results demonstrated that enhanced CXCR4 signaling could significantly improve the early homing and engraftment of ADSCs into ischemic areas as well as the long-term engraftment and ultimate muscle tissue regeneration.

Interventional stem cell therapy

The ability to deliver cells in appropriate doses to their targeted site of action is a well-known obstacle to optimising stem cell therapy. Systemic administration of cells results in pulmonary "trapping," which significantly decreases the number of available circulating cells to impact underlying disorders. Directed delivery of stem cells in interventional radiology may provide an additional option for bypassing the lungs, as well as introduce novel potential avenues for decreasing doses required to effect cellular therapy, efficiently obtain local paracrine effects, and/or to simplify targeting strategies.

Effect of repetitive intra-arterial infusion of bone marrow mononuclear cells in patients with no-option limb ischemia: the randomized, double-blind, placebo-controlled Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra-arterial Supplementation (JUVENTAS) trial

BACKGROUND

Patients with severe limb ischemia may not be eligible for conventional therapeutic interventions. Pioneering clinical trials suggest that bone marrow-derived cell therapy enhances neovascularization, improves tissue perfusion, and prevents amputation. The objective of this trial was to determine whether repetitive intra-arterial infusion of bone marrow mononuclear cells (BMMNCs) in patients with severe, nonrevascularizable limb ischemia can prevent major amputation.

METHODS AND RESULTS

The Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra-arterial Supplementation (JUVENTAS) trial is a randomized, double-blind, placebo-controlled clinical trial in 160 patients with severe, nonrevascularizable limb ischemia. Patients were randomly assigned to repetitive (3 times; 3-week interval) intra-arterial infusion of BMMNC or placebo. No significant differences were observed for the primary outcome, ie, major amputation at 6 months, with major amputation rates of 19% in the BMMNC versus 13% in the placebo group (relative risk, 1.46; 95% confidence interval, 0.62-3.42). The safety outcome (all-cause mortality, occurrence of malignancy, or hospitalization due to infection) was not significantly different between the groups (relative risk, 1.46; 95% confidence interval, 0.63-3.38), neither was all-cause mortality at 6 months with 5% versus 6% (relative risk, 0.78; 95% confidence interval, 0.22-2.80). Secondary outcomes quality of life, rest pain, ankle-brachial index, and transcutaneous oxygen pressure improved during follow-up, but there were no significant differences between the groups.

CONCLUSIONS

Repetitive intra-arterial infusion of autologous BMMNCs into the common femoral artery did not reduce major amputation rates in patients with severe, nonrevascularizable limb ischemia in comparison with placebo. The general improvement in secondary outcomes during follow-up in both the BMMNC and the placebo group, as well, underlines the essential role for placebo-controlled design of future trials.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00371371.

Imaging techniques to evaluate cell therapy in peripheral artery disease: state of the art and clinical trials

Cell-based therapies, as potential approach to cure peripheral artery disease (PAD), have been clinically investigated after promising results in preclinical models. The so far published studies are very heterogeneous, as different cell sources, cell types, amounts of administered cells and delivering strategies have been used. Overall, cell therapies for PAD bring about a general improvement of patient's clinical condition, even though conclusions cannot be established due to the small size and non-randomized design of these trials. In this context, non-invasive imaging techniques, aimed to monitor angiogenesis and neovascularization after cell therapy, will help the follow-up of clinical studies. However, still much work is needed to establish advanced imaging procedure to overcome the limitation of the current techniques and to accumulate more data in large populations of patients. Here, we report the main imaging techniques employed to evaluate the outcome of the different cell-based therapies in PAD. Moreover, we focus on both published and ongoing clinical trials utilizing cell therapy in PAD.

Intra-arterial infusion of autologous bone marrow mononuclear cells in patients with moderate to severe middle cerebral artery acute ischemic stroke

Transplantation of autologous bone marrow mononuclear cells (BMMCs) has been proven safe in animal and human studies. However, there are very few studies in stroke patients. In this study, intra-arterial autologous BMMCs were infused in patients with moderate to severe acute middle cerebral artery infarcts. The subjects of this study included 20 patients with early or late spontaneous recanalization but with persistent deficits, in whom treatment could be initiated between 3 and 7 days after stroke onset. Mononuclear cells were isolated from bone marrow aspirates and infused at the proximal middle cerebral artery of the affected hemisphere. Safety analysis (primary endpoint) during the 6-month follow-up assessed death, any serious clinical events, neurological worsening with ≥ 4-point increase in National Institutes of Health Stroke Scale (NIHSS) scores, seizures, epileptogenic activity on electroencephalogram, and neuroimaging complications including new ischemic, hemorrhagic, or neoplastic lesions. Satisfactory clinical improvement (secondary endpoint) at 90 days was defined according to the pretreatment NIHSS scores as follows: modified Rankin Scale score of 0 in patients with NIHSS <8, modified Rankin Scale scores of 0-1 in patients with NIHSS 8-14, or modified Rankin Scale scores 0-2 in patients with NIHSS >14. Good clinical outcome was defined as mRS ≤2 at 90 days. Serial clinical, laboratory, electroencephalogram, and imaging evaluations showed no procedure-related adverse events. Satisfactory clinical improvement occurred in 6/20 (30%) patients at 90 days. Eight patients (40%) showed a good clinical outcome. Infusion of intra-arterial autologous BMMCs appears to be safe in patients with moderate to severe acute middle cerebral artery strokes. No cases of intrahospital mortality were seen in this pilot trial. Larger prospective randomized trials are warranted to assess the efficacy of this treatment approach.

No Difference in Intra-Arterial and Intramuscular Delivery of Autologous Bone Marrow Cells in Patients with Advanced Critical Limb Ischemia

Stem cell therapy has been proposed to be an alternative therapy in patients with critical limb ischemia (CLI), not eligible for endovascular or surgical revascularization. We compared the therapeutic effects of intramuscular (IM) and intra-arterial (IA) delivery of bone marrow cells (BMCs) and investigated the factors associated with therapeutic benefits. Forty-one patients (mean age, 66 ± 10 years; 35 males) with advanced CLI (Rutherford category, 5 and 6) not eligible for revascularization were randomized to treatment with 40 ml BMCs using local IM ( n = 21) or selective IA infusion ( n = 20). Primary endpoints were limb salvage and wound healing. Secondary endpoints were changes in transcutaneous oxygen pressure (tcpO2), quality-of-life questionnaire (EQ5D), ankle–brachial index (ABI), and pain scale (0–10). Patients with limb salvage and wound healing were considered to be responders to BMC therapy. At 6-month follow-up, overall limb salvage was 73% (27/37) and 10 subjects underwent major amputation. Four patients died unrelated to stem cell therapy. There was significant improvement in tcpO2 (15 ± 10 to 29 ± 13 mmHg, p < 0.001), pain scale (4.4 ± 2.6 to 0.9 ± 1.4, p < 0.001), and EQ5D (51 ± 15 to 70 ± 13, p < 0.001) and a significant decrease in the Rutherford category of CLI (5.0 ± 0.2 to 4.3 ± 1.6, p < 0.01). There were no differences among functional parameters in patients undergoing IM versus IA delivery. Responders ( n = 27) were characterized by higher CD34+ cell counts in the bone marrow concentrate (CD34+ 29 ± 15×106 vs. 17 ± 12×106, p < 0.05) despite a similar number of total nucleated cells (4.3 ± 1.4×109 vs. 4.1 ± 1.2×109, p = 0.66) and by a lower level of C-reactive protein (18 ± 28 vs. 100 ± 96 mg/L, p < 0.05) as well as serum leukocytes (8.3 ± 2.1×109/L vs. 12.3 ± 4.5×109/L, p < 0.05) as compared with nonresponders (10 patients). Both IM and IA delivery of autologous stem cells are effective therapeutic strategies in patients with CLI. A higher concentration of CD34+ cells and a lower degree of inflammation are associated with better clinical therapeutic responses.

Effect of cilostazol and pentoxifylline on gait biomechanics in rats with ischemic left hindlimb

OBJECTIVE

The purpose of this study was to determine the impact of pharmacologic treatment with cilostazol and pentoxifylline on gait biomechanics of ischemic rat hindlimbs compared with nonischemic controls.

METHODS

An experimental study was designed using 30 Wistar rats divided into five groups (n = 6): control (C); ischemia (I) - animals submitted to left common iliac artery interruption without pharmacologic treatment; pentoxifylline (Pen) - rats submitted to procedure and treated with pentoxifylline 3 mg/kg twice a day for 6 weeks; cilostazol (Cil) - animals submitted to procedure and treated with cilostazol 30 mg/kg twice a day for 6 weeks; and sham (S) - animals submitted to procedure without artery interruption. Gait analysis was performed using a computed treadmill. Time, number, and duration of each hindlimb contact were obtained. The total number of contacts (TNC) and the total duration of contacts (TDC) were compared between left and right hindlimb and among groups. Left hindlimb ischemic incapacitation index (LHII) was defined by the formula: LHII = (1-TNCleft x TDCleft / TNCright x TDCright) x 100.

RESULTS

Left hindlimb TNC values were twofold lower in I, Pen, and Cil groups than in C and S groups (P < .01). In I, Pen, and Cil groups, TNC values for the left hindlimb were half of the right hindlimb ones (P < .01). Left hindlimb TDC values were lower in I and Pen groups than the other groups (P < .01). Cil group presented twofold increased values, not different from C and S groups (P = 0.16). Right hindlimb TNC values were greater for I group (P < .01). LHII was around zero in C and S groups and 82 in both I and Pen groups (P < .01). Cil group presented a LHII of 42; higher than C and S groups, but lower than I and Pen groups (P < .01).

CONCLUSIONS

Cilostazol at a dose of 30 mg/kg twice a day promoted improvement in gait performance in rats submitted to chronic hindlimb ischemia. Pentoxifylline at a dose of 3 mg/kg twice a day did not show this effect.

Noninvasive management of the diabetic foot with critical limb ischemia: current options and future perspectives

Foot ulcers are a major complication in patients with diabetes mellitus and involve dramatic restrictions to quality of life and also lead to enormous socio-economical loss due to the high amputation rate. The poor and slow wound healing is often aggravated by the frequent comorbidity of foot ulcers with peripheral arterial disease, making the treatment of this condition even more complicated. While the local treatment of foot ulcers is mainly based on mechanical relief and prevention or treatment of infection, improving perfusion of the impaired tissue remains the major challenge in peripheral arterial disease. While focal arterial stenosis is the domain of interventional angioplasty or vascular surgery, patients with critical limb ischemia and lacking options for revascularization have a much worse prognosis, because current treatment options avoiding amputation are scarce. However, based on recent research efforts, there is rising hope for promising and more-effective therapeutic approaches for these patients. Here, we discuss the current improvements of established therapies aimed at an improvement of limb perfusion, as well as the development of novel cutting-edge therapies based on stem-cell technology. The experiences of a 'high-volume center' for treatment of diabetic foot syndrome with a current major amputation rate of 4% are discussed.

Intra-arterial injection of human embryonic stem cells in athymic rat hind limb ischemia model leads to arteriogenesis

Shear stress can enhance differentiation of human embryonic stem cells (hESC) to vascular cells. We tested the hypothesis that intra-arterial hESC injection will lead to arteriogenesis while intramuscular injection will have no effect on vascularization.

METHODS AND RESULTS

The superficial femoral arteries were excised on both hind limbs in athymic rats. hESC (2×10(6)) were injected intra-arterially (shear stress) or intramuscular (no shear stress) in one limb after arterial excision. Blood flow, muscle perfusion, and number of arteries/mm(2) muscle were studied at 10 and 21 days after injection. Blood flow in the common iliac artery improved significantly at 10 days after intra-arterial injection of hESC (22±9%, P<.02), and tight muscle perfusion improved significantly both at 10 and 21 days (9±2%, 16±5% respectively, both P<.02). In comparison, intramuscular injection of hESC did not affect blood flow at 10 and 21 days (-3±10% and 4±6%, respectively), while perfusion showed no significant effect of hESC injection after 10 days (1±8%) and was increased 21 days after hESC injection (11±5%, P=.03). Arterial density did not improve after intra-arterial hESC injection at 10 days (15±13%, P=.15) and significantly improved at 21 days (13±4%, P<.05). No significant change was demonstrated after intramuscular injection.

SUMMARY

Intra-arterial injection of hESC resulted in moderate improvement of flow and perfusion and increased number of arteries in the ischemic hind limb. No consistent change in perfusion, flow, and number of arteries was observed after intramuscular injection.

Rationale and design of the JUVENTAS trial for repeated intra-arterial infusion of autologous bone marrow-derived mononuclear cells in patients with critical limb ischemia

Critical limb ischemia (CLI) continues to form a substantial burden on Western healthcare. Many patients still face amputation as a last treatment option. Autologous bone marrow (BM)-derived cell administration has emerged as a potential new treatment, but proof for sustainable clinical effects of BM-derived cell therapy in CLI is still lacking. The JUVENTAS (reJUVenating ENdothelial progenitor cells via Transcutaneous intra-Arterial Supplementation) trial is the first randomized, placebo-controlled, double-blinded clinical trial on repeated intra-arterial BM mononuclear cell (MNC) infusion in 110 to 160 CLI patients, designed to provide definite proof for the efficacy of stem cell therapy. Primary outcome is the incidence of major amputation at 6 months. Inclusion of patients is well underway. If BM-MNC cells therapy is beneficial, it could become a novel treatment to prevent amputation in patients with CLI.

Safety and efficacy of therapeutic angiogenesis as a novel treatment in patients with critical limb ischemia

BACKGROUND

In some patients with critical limb ischemia (CLI) the possibility of revascularizing treatment does not exist. In this case therapeutic angiogenesis (TA) using autologous endothelial progenitor cell (EPC) transplantation could be an alternative. The objective of our study was to evaluate the safety and efficacy of TA using EPC.

METHODS

Twenty-eight patients with CLI who were not candidates for surgical or endovascular revascularization were included in a prospective study. To mobilize EPCs from the bone marrow, granulocyte colony-stimulating growth factor was injected subcutaneously at doses of 5 microg/kg/day for 5 days. Apheresis was performed, obtaining 50 mL of blood with a high rate of EPCs (CD34(+) and CD133(+) cells were counted). EPCs were implanted in the ischemic limb by intramuscular injections. Primary end points were the safety and feasibility of the procedure and limb salvage rate for amputation at 12 months. Other variables studied were improvement in rest pain, healing of ulcers, ankle-brachial pressure index (ABI), and digital plethysmography. All procedures were done pretreatment and every 3 months for a year on average. Postransplantation arteriography was done in selected cases.

RESULTS

No adverse effects were observed. Mean follow-up was 14 months. Before treatment, mean basal ABI was 0.35+/-0.2 and at 18 months postimplantation, 0.72+/-0.51 (p=0.009). There was a mean decrease of five points in pain scale: basal 8.7+/-1, after TA 3.8+/-2.9 (p=0.01). Seven patients required major amputation. Kaplan-Meier analysis revealed a limb salvage rate of 74.4% after 1 year.

CONCLUSION

Implantation of EPCs in CLI is a safe alternative, improves tissue perfusion, and obtains high amputation-free rates. Nevertheless, this is a small cohort and results should be tested with long randomized trials.

Treatment with bone marrow mononuclear cells induces functional recovery and decreases neurodegeneration after sensorimotor cortical ischemia in rats

We evaluated the beneficial effect of treatment with bone marrow mononuclear cells(BMMC) in a rat model of focal ischemia induced by thermocoagulation of the blood vessels in the left sensorimotor cortex. BMMC were obtained from donor rats and injected into the femoral vein one day after ischemia. BMMC-treated animals received approx. 3×10⁷ cells and control animals received PBS. Animals were evaluated for functional sensorimotor recovery weekly with behavioral tests and for changes in neurodegeneration and structural plasticity with histochemical and immunostaining techniques, respectively. The BMMC-treated group showed a significant recovery of function in the cylinder test 14, 21 and 28 days after ischemia. In the beam test, both groups showed improvement, with a tendency for faster recovery in the BMMC-treated group. In the adhesive test, both groups did not show significant recovery of function. FJC+ cell counting revealed significant decrease in the neurodegeneration in the periphery of the lesion in the BMMC-treated group. The analyses by immunoblotting revealed no significant difference in the expression of GAP-43 and synaptophysin between the groups. Thus, our results showed beneficial effects of the treatment with BMMC, which promoted significant functional recovery and decreased neurodegeneration. These results suggest that the therapy with BMMC is effective and might be a protocol of treatment for stroke in humans, alternative to the therapy proposed with the bone marrow-derived mesenchymal stem cells.

Study of growth parameters and potentialities of differentiation of multipotent mesenchymal stromal cells from rat bone marrow in vitro

The dynamics of growth and proliferative activity of the population of multipotent mesenchymal stromal cells from rat bone marrow was studied during 7 passages. The efficiency of colony formation, the morphology of multipotent mesenchymal stromal cells, and the possibility of spontaneous and induced differentiation were studied. The rat bone marrow fibroblast-like multipotent mesenchymal stromal cells are capable of clonal growth; their proliferative activity and the yield remained high until passage 4, but then decreased. Induction of osteo- or adipogenic differentiation of bone marrow multipotent mesenchymal stromal cells increased the percentage of morphologically modified cells carrying specific markers.

Therapeutic myocardial angiogenesis: past, present and future

One of the main goals in the treatment of myocardial ischemia is the development of effective therapy for angiogenesis and neovascularization. The first evidence demonstrating alleviation of myocardial ischemia and increased number of collateral blood vessels was reported in the early 90s following intra-coronary administration of basic fibroblast growth factor protein in canine. This study established the ground for extensive investigations to demonstrate the use of other angiogenic growth factor proteins, genes administered directly or incorporated in viruses, and more recently, endothelial progenitor stem cells (embryonic and adults). The positive results observed in animals failed, in most cases, to repeat themselves in clinical-trials in human patients. Therefore, additional experiments are warranted to allow full understanding of the mechanism underlying new blood vessel formation before further clinical studies are undertaken. This review will explore the milestones of angiogenic investigations and their clinical application.