Local intramuscular transplantation of autologous bone marrow mononuclear cells for critical lower limb ischaemia

BACKGROUND

Peripheral arterial disease is a major health problem, and in about 1% to 2% of patients, the disease progresses to critical limb ischaemia (CLI), also known as critical limb-threatening ischaemia. In a substantial number of individuals with CLI, no effective treatment options other than amputation are available, with around a quarter of these patients requiring a major amputation during the following year. This is the second update of a review first published in 2011.

OBJECTIVES

To evaluate the benefits and harms of local intramuscular transplantation of autologous adult bone marrow mononuclear cells (BMMNCs) as a treatment for CLI.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 8 November 2021.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) of CLI in which participants were randomly allocated to intramuscular administration of autologous adult BMMNCs or control (either no intervention, conventional conservative therapy, or placebo).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes of interest were all-cause mortality, pain, and amputation. Our secondary outcomes were angiographic analysis, ankle-brachial index (ABI), pain-free walking distance, side effects and complications. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included four RCTs involving a total of 176 participants with a clinical diagnosis of CLI. Participants were randomised to receive either intramuscular cell implantation of BMMNCs or control. The control arms varied between studies, and included conventional therapy, diluted autologous peripheral blood, and saline. There was no clear evidence of an effect on mortality related to the administration of BMMNCs compared to control (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.15 to 6.63; 3 studies, 123 participants; very low-certainty evidence). All trials assessed changes in pain severity, but the trials used different forms of pain assessment tools, so we were unable to pool data. Three studies individually reported that no differences in pain reduction were observed between the BMMNC and control groups. One study reported that reduction in rest pain was greater in the BMMNC group compared to the control group (very low-certainty evidence). All four trials reported the rate of amputation at the end of the study period. We are uncertain if amputations were reduced in the BMMNC group compared to the control group, as a possible small effect (RR 0.52, 95% CI 0.27 to 0.99; 4 studies, 176 participants; very low-certainty evidence) was lost after undertaking sensitivity analysis (RR 0.52, 95% CI 0.19 to 1.39; 2 studies, 89 participants). None of the included studies reported any angiographic analysis. Ankle-brachial index was reported differently by each study, so we were not able to pool the data. Three studies reported no changes between groups, and one study reported greater improvement in ABI (as haemodynamic improvement) in the BMMNC group compared to the control group (very low-certainty evidence). One study reported pain-free walking distance, finding no clear difference between BMMNC and control groups (low-certainty evidence). We pooled the data for side effects reported during the follow-up, and this did not show any clear difference between BMMNC and control groups (RR 2.13, 95% CI 0.50 to 8.97; 4 studies, 176 participants; very low-certainty evidence). We downgraded the certainty of the evidence due to the concerns about risk of bias, imprecision, and inconsistency.

AUTHORS' CONCLUSIONS

We identified a small number of studies that met our inclusion criteria, and these differed in the controls they used and how they measured important outcomes. Limited data from these trials provide very low- to low-certainty evidence, and we are unable to draw conclusions to support the use of local intramuscular transplantation of BMMNC for improving clinical outcomes in people with CLI. Evidence from larger RCTs is needed in order to provide adequate statistical power to assess the role of this procedure.

Autologous cells derived from different sources and administered using different regimens for 'no-option' critical lower limb ischaemia patients

BACKGROUND

Revascularisation is the gold standard therapy for patients with critical limb ischaemia (CLI). In over 30% of patients who are not suitable for or have failed previous revascularisation therapy (the 'no-option' CLI patients), limb amputation is eventually unavoidable. Preliminary studies have reported encouraging outcomes with autologous cell-based therapy for the treatment of CLI in these 'no-option' patients. However, studies comparing the angiogenic potency and clinical effects of autologous cells derived from different sources have yielded limited data. Data regarding cell doses and routes of administration are also limited.

OBJECTIVES

To compare the efficacy and safety of autologous cells derived from different sources, prepared using different protocols, administered at different doses, and delivered via different routes for the treatment of 'no-option' CLI patients.

SEARCH METHODS

The Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE Ovid, Embase Ovid, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED), and trials registries (16 May 2018). Review authors searched PubMed until February 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving 'no-option' CLI patients comparing a particular source or regimen of autologous cell-based therapy against another source or regimen of autologous cell-based therapy.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed the eligibility and methodological quality of the trials. We extracted outcome data from each trial and pooled them for meta-analysis. We calculated effect estimates using a risk ratio (RR) with 95% confidence interval (CI), or a mean difference (MD) with 95% CI.

MAIN RESULTS

We included seven RCTs with a total of 359 participants. These studies compared bone marrow-mononuclear cells (BM-MNCs) versus mobilised peripheral blood stem cells (mPBSCs), BM-MNCs versus bone marrow-mesenchymal stem cells (BM-MSCs), high cell dose versus low cell dose, and intramuscular (IM) versus intra-arterial (IA) routes of cell implantation. We identified no other comparisons in these studies. We considered most studies to be at low risk of bias in random sequence generation, incomplete outcome data, and selective outcome reporting; at high risk of bias in blinding of patients and personnel; and at unclear risk of bias in allocation concealment and blinding of outcome assessors. The quality of evidence was most often low to very low, with risk of bias, imprecision, and indirectness of outcomes the major downgrading factors.Three RCTs (100 participants) reported a total of nine deaths during the study follow-up period. These studies did not report deaths according to treatment group.Results show no clear difference in amputation rates between IM and IA routes (RR 0.80, 95% CI 0.54 to 1.18; three RCTs, 95 participants; low-quality evidence). Single-study data show no clear difference in amputation rates between BM-MNC- and mPBSC-treated groups (RR 1.54, 95% CI 0.45 to 5.24; 150 participants; low-quality evidence) and between high and low cell dose (RR 3.21, 95% CI 0.87 to 11.90; 16 participants; very low-quality evidence). The study comparing BM-MNCs versus BM-MSCs reported no amputations.Single-study data with low-quality evidence show similar numbers of participants with healing ulcers between BM-MNCs and mPBSCs (RR 0.89, 95% CI 0.44 to 1.83; 49 participants) and between IM and IA routes (RR 1.13, 95% CI 0.73 to 1.76; 41 participants). In contrast, more participants appeared to have healing ulcers in the BM-MSC group than in the BM-MNC group (RR 2.00, 95% CI 1.02 to 3.92; one RCT, 22 participants; moderate-quality evidence). Researchers comparing high versus low cell doses did not report ulcer healing.Single-study data show similar numbers of participants with reduction in rest pain between BM-MNCs and mPBSCs (RR 0.99, 95% CI 0.93 to 1.06; 104 participants; moderate-quality evidence) and between IM and IA routes (RR 1.22, 95% CI 0.91 to 1.64; 32 participants; low-quality evidence). One study reported no clear difference in rest pain scores between BM-MNC and BM-MSC (MD 0.00, 95% CI -0.61 to 0.61; 37 participants; moderate-quality evidence). Trials comparing high versus low cell doses did not report rest pain.Single-study data show no clear difference in the number of participants with increased ankle-brachial index (ABI; increase of > 0.1 from pretreatment), between BM-MNCs and mPBSCs (RR 1.00, 95% CI 0.71 to 1.40; 104 participants; moderate-quality evidence), and between IM and IA routes (RR 0.93, 95% CI 0.43 to 2.00; 35 participants; very low-quality evidence). In contrast, ABI scores appeared higher in BM-MSC versus BM-MNC groups (MD 0.05, 95% CI 0.01 to 0.09; one RCT, 37 participants; low-quality evidence). ABI was not reported in the high versus low cell dose comparison.Similar numbers of participants had improved transcutaneous oxygen tension (TcO₂) with IM versus IA routes (RR 1.22, 95% CI 0.86 to 1.72; two RCTs, 62 participants; very low-quality evidence). Single-study data with low-quality evidence show a higher TcO₂ reading in BM-MSC versus BM-MNC groups (MD 8.00, 95% CI 3.46 to 12.54; 37 participants) and in mPBSC- versus BM-MNC-treated groups (MD 1.70, 95% CI 0.41 to 2.99; 150 participants). TcO₂ was not reported in the high versus low cell dose comparison.Study authors reported no significant short-term adverse effects attributed to autologous cell implantation.

AUTHORS' CONCLUSIONS

Mostly low- and very low-quality evidence suggests no clear differences between different stem cell sources and different treatment regimens of autologous cell implantation for outcomes such as all-cause mortality, amputation rate, ulcer healing, and rest pain for 'no-option' CLI patients. Pooled analyses did not show a clear difference in clinical outcomes whether cells were administered via IM or IA routes. High-quality evidence is lacking; therefore the efficacy and long-term safety of autologous cells derived from different sources, prepared using different protocols, administered at different doses, and delivered via different routes for the treatment of 'no-option' CLI patients, remain to be confirmed.Future RCTs with larger numbers of participants are needed to determine the efficacy of cell-based therapy for CLI patients, along with the optimal cell source, phenotype, dose, and route of implantation. Longer follow-up is needed to confirm the durability of angiogenic potential and the long-term safety of cell-based therapy.