Research Status of the Safety and Efficacy of Mesenchymal Stem Cells in the Treatment of COVID-19-Related Pneumonia: A Systematic Review and Meta-Analysis

Mesenchymal stem cell (MSC) therapy is considered one of the most promising treatments in the context of the coronavirus disease 2019 (COVID-19) pandemic. However, the safety and effectiveness of MSCs in the treatment of COVID-19-associated pneumonia patients need to be systematically reviewed and analyzed. Two independent researchers searched for relevant studies published between October 2019 and April 2021 in the PubMed, Embase, Cochrane Library, WAN FANG, and CNKI databases. All relevant randomized controlled trials, clinically controlled studies, retrospective studies, case reports, letters (with valid data), and case series were included in this meta-analysis. A fixed-effects model and 95% confidence interval (CI) were used to analyze the results. A total of 22 studies involving 371 patients were included in the present study. Allogeneic MSCs from umbilical cord, adipose tissue, menstrual blood, placental tissue, Wharton's jelly, or unreported sources were administered in 247 participants. Combined results revealed that MSC therapy significantly reduced the incidence of adverse events [AEs; odds ratio (OR) = 0.43, 95% CI = 0.22-0.84, P = 0.01] and mortality (OR = 0.17, 95% CI = 0.06-0.49, P < 0.01), and the difference compared with control group was statistically significant. No serious MSC treatment-related AEs were reported. Lung function, radiographic outcomes, and inflammation- and immunity-related biomarker levels all showed improving trends. Therefore, MSC therapy is an effective and safe method for the treatment of COVID-19-associated pneumonia and shows advantages in reducing AEs and mortality. However, a standard and effective MSC treatment program must be developed.