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.