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.