Background: We aim to explore the safety and feasibility of umbilical cord mesenchymal stem cells (UC-MSCs) transplantation in severe and critically severe type Coronavirus disease 2019 (COVID-19) patients. Methods: In addition to normal therapy, we performed four times transplantation of UC-MSCs in 16 severe and critically severe type COVID-19 patients. We observed adverse events from enrollment to D28. We evaluated the oxygenation index, inflammatory biomarkers, chest imaging, lymphocyte subsets count et al 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%. The level of cytokines estimated was varied in normal range, the chest imaging was improved, the lymphocyte count and lymphocyte subsets count were recovered after transplantation. Conclusions: Intravenous transplantation of UC-MSCs was safe and feasible for treatment in patients with COVID-19 pneumonia.Trial registration: Clinical Trial, NCT04269525. Registered 7 February 2020. https://clinicaltrials.gov/ct2/show/NCT04269525
Safety and Feasibility of Umbilical Cord Mesenchymal Stem Cells in Patients with COVID-19 Pneumonia: A Pilot Study