Safety and feasibility of umbilical cord mesenchymal stem cells in patients with COVID‐19 pneumonia: A pilot study

OBJECTIVES: We aim to explore the safety and feasibility of umbilical cord mesenchymal stem cells (UC‐MSCs) transplantation in patients with severe and critically severe coronavirus disease‐2019 (COVID‐19). METHODS: We conducted a small sample, single arm, pilot trial. In addition to standard therapy, we performed four rounds of transplantation of UC‐MSCs in sixteen patients with severe and critically severe COVID‐19. We recorded adverse events from enrolment to Day 28. We evaluated the oxygenation index, inflammatory biomarkers, radiological presentations of the disease and lymphocyte subsets count on the 7th day (D7 ± 1 day), the 14th day (D14 ± 1 day) and the 28th day (D28 ± 3 days). RESULTS: There were no infusion‐related or allergic reactions. The oxygenation index was improved after transplantation. The mortality of enrolled patients was 6.25%, whereas the historical mortality rate was 45.4%. The level of cytokines estimated varied in the normal range, the radiological presentations (ground glass opacity) were improved and the lymphocyte count and lymphocyte subsets (CD4(+) T cells, CD8(+) T cells and NK cells) count showed recovery after transplantation. CONCLUSIONS: Intravenous transplantation of UC‐MSCs was safe and feasible for treatment of patients with severe and critically severe COVID‐19 pneumonia.