Mesenchymal stromal cells for the treatment of critical limb ischemia: context and perspective

Spinal Neuromodulation for Peripheral Arterial Disease of Lower Extremities: A Ten-Year Retrospective Analysis

OBJECTIVE

This long-term retrospective study evaluated the survival and amputation outcome of subjects who received neuromodulation therapy for the management of peripheral arterial disease (PAD).

MATERIALS AND METHODS

The study reviews the health data of a single cohort of 51 patients who received spinal neuromodulation (spinal cord stimulation [SCS] or dorsal root ganglion stimulation [DRG-S]) for PAD from 2007 to 2022 in a single German center. Survival rate and major amputation rate were determined. Pain, quality of life, walking distance, and opioid usage were assessed before implantation (baseline), one, six, and 12 months (M) after implantation, and then annually (during a follow-up visit). Implant-related complications also were documented.

RESULTS

In total, 51 patients (37 men [mean age 68.9 ± 10.2 years], 14 women [mean age (68.7 ± 14.6 years]) underwent SCS (n = 49) or DRG-S (n = 2) implantation owing to persistent ischemic pain. The follow-up mean years ± SD is 4.04 ± 2.73. At baseline, patients were classified as Rutherford's category 3 (n = 23), category 4 (n = 15) or category 5 (n = 9). At 24 M, 42 of 47 patients did not require a major amputation after the implant. All the patients reported nearly complete pain relief from pain at rest. A total of 75% of patients were able to walk >200 m, and 87% of patients who used opioids at baseline were off this medication at 24 M. Overall, 93% of patients reported an improvement in their overall health assessment. These improved outcomes were sustained through years three to 10 for patients who have reported outcomes.

CONCLUSIONS

Our single-center data support the efficacy of spinal neuromodulation for improvements in limb salvage, pain relief, mobility, and quality of life. The data also show that neuromodulative therapy has a long-term therapeutic effect in patients with chronic limb pain with Rutherford category 3, 4, and 5 PAD.

Peripheral Vascular Disease and Kidney Transplant Outcomes: Rethinking an Important Ongoing Complication

Peripheral vascular disease (PVD) is highly prevalent in patients on the waiting list for kidney transplantation (KT) and after transplantation and is associated with impaired transplant outcomes. Multiple traditional and nontraditional risk factors, as well as uremia- and transplant-related factors, affect 2 processes that can coexist, atherosclerosis and arteriosclerosis, leading to PVD. Some pathogenic mechanisms, such as inflammation-related endothelial dysfunction, mineral metabolism disorders, lipid alterations, or diabetic status, may contribute to the development and progression of PVD. Early detection of PVD before and after KT, better understanding of the mechanisms of vascular damage, and application of suitable therapeutic approaches could all minimize the impact of PVD on transplant outcomes. This review focuses on the following issues: (1) definition, epidemiological data, diagnosis, risk factors, and pathogenic mechanisms in KT candidates and recipients; (2) adverse clinical consequences and outcomes; and (3) classical and new therapeutic approaches.

Comparative analysis of mouse bone marrow and adipose tissue mesenchymal stem cells for critical limb ischemia cell therapy

INTRODUCTION

Critical limb ischemia (CLI) is the most advanced form of peripheral arterial disease (PAD) characterized by ischemic rest pain and non-healing ulcers. Currently, the standard therapy for CLI is the surgical reconstruction and endovascular therapy or limb amputation for patients with no treatment options. Neovasculogenesis induced by mesenchymal stem cells (MSCs) therapy is a promising approach to improve CLI. Owing to their angiogenic and immunomodulatory potential, MSCs are perfect candidates for the treatment of CLI. The purpose of this study was to determine and compare the in vitro and in vivo effects of allogeneic bone marrow mesenchymal stem cells (BM-MSCs) and adipose tissue mesenchymal stem cells (AT-MSCs) on CLI treatment.

METHODS

For the first step, BM-MSCs and AT-MSCs were isolated and characterized for the characteristic MSC phenotypes. Then, femoral artery ligation and total excision of the femoral artery were performed on C57BL/6 mice to create a CLI model. The cells were evaluated for their in vitro and in vivo biological characteristics for CLI cell therapy. In order to determine these characteristics, the following tests were performed: morphology, flow cytometry, differentiation to osteocyte and adipocyte, wound healing assay, and behavioral tests including Tarlov, Ischemia, Modified ischemia, Function and the grade of limb necrosis scores, donor cell survival assay, and histological analysis.

RESULTS

Our cellular and functional tests indicated that during 28 days after cell transplantation, BM-MSCs had a great effect on endothelial cell migration, muscle restructure, functional improvements, and neovascularization in ischemic tissues compared with AT-MSCs and control groups.

CONCLUSIONS

Allogeneic BM-MSC transplantation resulted in a more effective recovery from critical limb ischemia compared to AT-MSCs transplantation. In fact, BM-MSC transplantation could be considered as a promising therapy for diseases with insufficient angiogenesis including hindlimb ischemia.

The Importance of HLA Assessment in "Off-the-Shelf" Allogeneic Mesenchymal Stem Cells Based-Therapies

The need for more effective therapies of chronic and acute diseases has led to the attempts of developing more adequate and less invasive treatment methods. Regenerative medicine relies mainly on the therapeutic potential of stem cells. Mesenchymal stem cells (MSCs), due to their immunosuppressive properties and tissue repair abilities, seem to be an ideal tool for cell-based therapies. Taking into account all available sources of MSCs, perinatal tissues become an attractive source of allogeneic MSCs. The allogeneic MSCs provide "off-the-shelf" cellular therapy, however, their allogenicity may be viewed as a limitation for their use. Moreover, some evidence suggests that MSCs are not as immune-privileged as it was previously reported. Therefore, understanding their interactions with the recipient's immune system is crucial for their successful clinical application. In this review, we discuss both autologous and allogeneic application of MSCs, focusing on current approaches to allogeneic MSCs therapies, with a particular interest in the role of human leukocyte antigens (HLA) and HLA-matching in allogeneic MSCs transplantation. Importantly, the evidence from the currently completed and ongoing clinical trials demonstrates that allogeneic MSCs transplantation is safe and seems to cause no major side-effects to the patient. These findings strongly support the case for MSCs efficacy in treatment of a variety of diseases and their use as an "off-the-shelf" medical product.

Cost-Effective, Safe, and Personalized Cell Therapy for Critical Limb Ischemia in Type 2 Diabetes Mellitus

Cell therapy is a progressively growing field that is rapidly moving from preclinical model development to clinical application. Outcomes obtained from clinical trials reveal the therapeutic potential of stem cell-based therapy to deal with unmet medical treatment needs for several disorders with no therapeutic options. Among adult stem cells, mesenchymal stem cells (MSCs) are the leading cell type used in advanced therapies for the treatment of autoimmune, inflammatory and vascular diseases. To date, the safety and feasibility of autologous MSC-based therapy has been established; however, their indiscriminate use has resulted in mixed outcomes in preclinical and clinical studies. While MSCs derived from diverse tissues share common properties depending on the type of clinical application, they markedly differ within clinical trials in terms of efficacy, resulting in many unanswered questions regarding the application of MSCs. Additionally, our experience in clinical trials related to critical limb ischemia pathology (CLI) shows that the therapeutic efficacy of these cells in different animal models has only been partially reproduced in humans through clinical trials. Therefore, it is crucial to develop new research to identify pitfalls, to optimize procedures and to clarify the repair mechanisms used by these cells, as well as to be able to offer a next generation of stem cell that can be routinely used in a cost-effective and safe manner in stem cell-based therapies targeting CLI.

Long-Term Outcomes of BMMSC Compared with BMMNC for Treatment of Critical Limb Ischemia and Foot Ulcer in Patients with Diabetes

We first compared long-term clinical outcomes in treating critical limb ischemia (CLI) and foot ulcer in patients with diabetes between autologous bone marrow mesenchymal stem cell (BMMSC) and bone-marrow-derived mononuclear cell (BMMNC) transplants. Forty-one patients were enrolled and followed up for 3 years. They received an 18-day standard treatment before stem cell transplantation. Patients with bilateral CLI and foot ulcer were injected intramuscularly or basally with BMMSC, BMMNC, or normal saline (NS). Cox model analysis showed significant differences in the hazard ratio (HR) for amputation with treatment by BMMSC (HR 0.21 [95% CI (0.05, 0.95)], P = 0.043), infection of foot (HR 5.30 [95% CI (1.89, 14.92)], P = 0.002), and age ≥64 (HR 3.01 [95% CI (1.11, 8.15)], P = 0.030), but no significant differences by BMMNC at 9 months after transplantation. Regarding ulcer healing and recurrence rate, the BMMSC group demonstrated a significant difference from the NS group during the 3-6 months after transplantation or healing, but the BMMNC group did not. This trial suggests that, compared with BMMNC treatment, BMMSC treatment leads to a longer time of limb salvage and blood flow improvement, and, when compared with conventional therapy, it can promote limb blood flow and ulcerative healing, and reduce ulcer recurrence and amputation within 9 months.

Cell Therapy for Chronic Limb-Threatening Ischemia: Current Evidence and Future Directions

Cell‐based therapies have gained interest as a potential treatment method in cardiovascular disease in the past two decades, peripheral artery disease amongst others. Initial pre‐clinical and small pilot clinical studies showed promising effects of cell therapy in peripheral artery disease and chronic limb‐threatening ischemia in particular. However, these promising results were not corroborated in larger high quality blinded randomized trials. This has led to a shift of the field towards more sophisticated cell products, especially mesenchymal stromal cells. Mesenchymal stromal cells have some important benefits, making these cells ideal for regenerative medicine, e.g., potential for allogeneic application, loss of disease‐mediated cell dysfunction, reduced production costs, off‐the‐shelf availability. Future high quality and large clinical studies have to prove the efficacy of mesenchymal stromal cells in the treatment of peripheral artery disease. Stem Cells Translational Medicine2018;7:842–846

Mesenchymal Stromal Cell Characteristics and Regenerative Potential in Cardiovascular Disease: Implications for Cellular Therapy

Administration of mesenchymal stromal cells (MSCs) is a promising strategy to treat cardiovascular disease (CVD). As progenitor cells may be negatively affected by both age and comorbidity, characterization of MSC function is important to guide decisions regarding use of allogeneic or autologous cells. Definitive answers on which factors affect MSC function can also aid in selecting which MSC donors would yield the most therapeutically efficacious MSCs. Here we provide a narrative review of MSC function in CVD based on a systematic search. A total of 41 studies examining CVD-related MSC (dys)function were identified. These data show that MSC characteristics and regenerative potential are often affected by CVD. However, studies presented conflicting results, and directed assessment of MSC parameters relevant to regenerative medicine applications was lacking in many studies. The predictive ability of in vitro assays for in vivo efficacy was rarely assessed. There was no correlation between quality of study reporting and study findings. Age mismatch was also not associated with study findings or effect size. Future research should focus on assays that assess regenerative potential in MSCs and parameters that relate to clinical success.

Rationale and design of the SAIL trial for intramuscular injection of allogeneic mesenchymal stromal cells in no-option critical limb ischemia

BACKGROUND

Critical limb ischemia (CLI) represents the most severe form of peripheral artery disease and has an immense impact on quality of life, morbidity, and mortality. A considerable proportion of CLI patients are ineligible for revascularization, leaving amputation as the only option. Mesenchymal stromal cells (MSCs), because of their vasculoregenerative and immunomodulatory characteristics, have emerged as a potential new treatment.

METHODS

The primary objective of this trial is to investigate whether intramuscular administration of allogeneic bone marrow (BM)-derived MSCs is safe and potentially effective. The SAIL (allogeneic mesenchymal Stromal cells for Angiogenesis and neovascularization in no-option Ischemic Limbs) trial is a double-blind, placebo-controlled randomized clinical trial to investigate the effect of allogeneic BM-MSCs in patients with CLI who are not eligible for conventional revascularization. A total of 66 patients will be included and randomized (1:1) to undergo 30 intramuscular injections with either BM-MSCs (5 × 10⁶ MSCs per injection) or placebo in the ischemic lower extremity. Primary outcome, that is, therapy success, a composite outcome consisting of mortality, limb status, clinical status, and changes in pain score, will be assessed at 6 months. All study-related procedures will take place in the University Medical Center Utrecht in The Netherlands.

CONCLUSIONS

If our results indicate that intramuscular allogeneic BM-MSC therapy for CLI is safe and potentially effective, this will have important consequences for treatment of patients with CLI. A large multicenter clinical trial with longer follow-up focusing on hard end points should then be initiated to confirm these findings.

Exosomes secreted by human-induced pluripotent stem cell-derived mesenchymal stem cells attenuate limb ischemia by promoting angiogenesis in mice

Introduction

‘Patient-specific’ induced pluripotent stem cells (iPSCs) are attractive because they can generate abundant cells without the risk of immune rejection for cell therapy. Studies have shown that iPSC-derived mesenchymal stem cells (iMSCs) possess powerful proliferation, differentiation, and therapeutic effects. Recently, most studies indicate that stem cells exert their therapeutic effect mainly through a paracrine mechanism other than transdifferentiation, and exosomes have emerged as an important paracrine factor for stem cells to reprogram injured cells. The objective of this study was to evaluate whether exosomes derived from iMSCs (iMSCs-Exo) possess the ability to attenuate limb ischemia and promote angiogenesis after transplantation into limbs of mice with femoral artery excision.

Methods

Human iPSCs (iPS-S-01, C1P33, and PCKDSF001C1) were used to differentiate into iMSCs in a modified one-step method. iMSCs were characterized by flow cytometry and multipotent differentiation potential analysis. Ultrafiltration combined with a purification method was used to isolate iMSCs-Exo, and transmission electron microscopy and Western blotting were used to identify iMSCs-Exo. After establishment of mouse hind-limb ischemia with excision of femoral artery and iMSCs-Exo injection, blood perfusion was monitored at days 0, 7, 14, and 21; microvessel density in ischemic muscle was also analyzed. In vitro migration, proliferation, and tube formation experiments were used to analyze the ability of pro-angiogenesis in iMSCs-Exo, and quantitative reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay were used to identify expression levels of angiogenesis-related molecules in human umbilical vein endothelial cells (HUVECs) after being cultured with iMSCs-Exo.

Results

iPSCs were efficiently induced into iMSC- with MSC-positive and -negative surface antigens and osteogenesis, adipogenesis, and chondrogenesis differentiation potential. iMSCs-Exo with a diameter of 57 ± 11 nm and expressed CD63, CD81, and CD9. Intramuscular injection of iMSCs-Exo markedly enhanced microvessel density and blood perfusion in mouse ischemic limbs, consistent with an attenuation of ischemic injury. In addition, iMSCs-Exo could activate angiogenesis-related molecule expression and promote HUVEC migration, proliferation, and tube formation.

Conclusion

Implanted iMSCs-Exo was able to protect limbs from ischemic injury via the promotion of angiogenesis, which indicated that iMSCs-Exo may be a novel therapeutic approach in the treatment of ischemic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt546) contains supplementary material, which is available to authorized users.

Neovascularization capacity of mesenchymal stromal cells from critical limb ischemia patients is equivalent to healthy controls

Critical limb ischemia (CLI) is often poorly treatable by conventional management and alternatives such as autologous cell therapy are increasingly investigated. Whereas previous studies showed a substantial impairment of neovascularization capacity in primary bone-marrow (BM) isolates from patients, little is known about dysfunction in patient-derived BM mesenchymal stromal cells (MSCs). In this study, we have compared CLI-MSCs to healthy controls using gene expression profiling and functional assays for differentiation, senescence and in vitro and in vivo pro-angiogenic ability. Whereas no differentially expressed genes were found and adipogenic and osteogenic differentiation did not significantly differ between groups, chondrogenic differentiation was impaired in CLI-MSCs, potentially as a consequence of increased senescence. Migration experiments showed no differences in growth factor sensitivity and secretion between CLI- and control MSCs. In a murine hind-limb ischemia model, recovery of perfusion was enhanced in MSC-treated mice compared to vehicle controls (71 ± 24% versus 44 ± 11%; P < 1 × 10(-6)). CLI-MSC- and control-MSC-treated animals showed nearly identical amounts of reperfusion (ratio CLI:Control = 0.98, 95% CI = 0.82-1.14), meeting our criteria for statistical equivalence. The neovascularization capacity of MSCs derived from CLI-patients is not compromised and equivalent to that of control MSCs, suggesting that autologous MSCs are suitable for cell therapy in CLI patients.

Efficacy of autologous bone marrow mononuclear cell therapy in patients with peripheral arterial disease

AIM

Peripheral arterial disease (PAD), particularly critical limb ischemia (CLI), is a severe cause of amputation and mortality. More than 50% of diabetic patients with CLI die within four to five years. The development of novel stem cell therapies may bring new hope to these patients. We aimed to assess the efficacy of autologous bone marrow cell therapy for treating CLI using a meta-analysis.

METHODS

We searched the literature in PubMed, the Cochrane Central Registry of Controlled Trials, the Elsevier database and EBSCO for trials of autologous cell therapy in patients with severe PAD published before October 30, 2013. We chose objective clinical endpoints to assess the efficacy of therapy in the meta-analysis, including changes in the ankle-brachial index (ABI), transcutaneous oxygen tension (TcO2), pain scale (0-10 scale) and amputation-free survival (AFS).

RESULTS

Thirty-one articles reporting clinical trials involving a total of 1,214 patients treated with bone marrow stem cell-based therapy were collected for the meta-analysis, in which the randomized controlled trials (RCTs) and other trials (non-RCTs) were classified into two groups. Regarding the efficacy of stem cell therapy, the ABI showed significant increases (P＜0.05) at 12 , 24 and 48 weeks after therapy in the non-RCT and RCT groups, but not after four to eight weeks in the non-RCT group. The TcO2 values also increased in the RCT group at four to eight weeks after therapy and 24 weeks after therapy (P＜0.001) and in the non-RCT group at four to eight weeks after therapy (P= 0.01), although no significant increases were observed in the RCT group at 12 weeks after therapy or the non-RCT group at 24 weeks after therapy. Meanwhile, pain was significantly reduced (P＜0.05) at four to eight weeks and 24 weeks after therapy in both the non-RCT and RCT groups, but not at four to eight weeks or 12 weeks after therapy in the RCT group. In addition, the long-term clinical trials demonstrated that the AFS rate improved after therapy with bone marrow stem cells (one-year AFS, P＜0.00001; three-year AFS, P=0.0003).

CONCLUSIONS

The present results suggest that autologous bone marrow stem cells have an advantageous therapy effect in PAD patients who are not eligible for revascularization.