RESUMO
BACKGROUND: Mesenchymal stem cells (MSCs) have emerged as living biodrugs for myocardial repair and regeneration. Recent randomized controlled trials (RCTs) have reported that MSC-based therapy is safe and effective in heart failure patients; however, its dose-response relationship has yet to be established. We aimed to determine the optimal MSC dose for treating HF patients with reduced ejection fraction (EF) (HFrEF). METHODS: The preferred reporting items for systematic reviews and meta-analyses (PRISMA) and Cochrane Handbook guidelines were followed. Four databases and registries, i.e., PubMed, EBSCO, clinicaltrials.gov, ICTRP, and other websites, were searched for RCTs. Eleven RCTs with 1098 participants (treatment group, n = 606; control group, n = 492) were selected based on our inclusion/exclusion criteria. Two independent assessors extracted the data and performed quality assessments. The data from all eligible studies were plotted for death, major adverse cardiac events (MACE), left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and 6-minute walk distance (6-MWD) as safety, efficacy, and performance parameters. For dose-escalation assessment, studies were categorized as low-dose (< 100 million cells) or high-dose (≥ 100 million cells). RESULTS: MSC-based treatment is safe across low and high doses, with nonsignificant effects. However, low-dose treatment had a more significant protective effect than high-dose treatment. Subgroup analysis revealed the superiority of low-dose treatment in improving LVEF by 3.01% (95% CI; 0.65-5.38%) compared with high-dose treatment (-0.48%; 95% CI; -2.14-1.18). MSC treatment significantly improved the 6-MWD by 26.74 m (95% CI; 3.74-49.74 m) in the low-dose treatment group and by 36.73 m (95% CI; 6.74-66.72 m) in the high-dose treatment group. The exclusion of studies using ADRCs resulted in better safety and a significant improvement in LVEF from low- and high-dose MSC treatment. CONCLUSION: Low-dose MSC treatment was safe and superior to high-dose treatment in restoring efficacy and functional outcomes in heart failure patients, and further analysis in a larger patient group is warranted.