Background: COVID-19 is a highly infectious respiratory disease. No therapeutics have yet been proven effective for treating severe COVID-19. Objectives: To determine whether human umbilical cord mesenchymal stem cell infusion may be effective and safe for the treatment of severe COVID-19. Methods: Patients with severe COVID-19 were randomly divided into 2 groups: the standard treatment group and the standard treatment plus hUC-MSC infusion group. The incidence of progression from severe to critical illness, 28-day mortality, clinical symptom improvement, time to clinical symptom improvement, hematologic indicators including C-reactive protein, lymphocyte number, and interleukin 6, and imaging changes were observed and compared between the two groups. Measurements and main results: The incidence of progression from severe to critical illness and the 28-day mortality rate were 0 in the hUC-MSC treatment group, while 4 patients in the control group deteriorated to critical condition and received invasive ventilation; 3 of them died, and the 28-day mortality rate was 10.34%. In the hUC-MSC treatment group, the time to clinical improvement was shorter than that in the control group. Clinical symptoms of weakness and fatigue, shortness of breath, and low oxygen saturation obviously improved beginning on the third day of stem cell infusion and reached a significant difference on day 7. CRP and IL-6 levels were significantly lower from day 3 of infusion, the time for the lymphocyte count to return to the normal range was significantly faster, and lung inflammation absorption was significantly shorter on CT imaging in the hUC-MSC group than in the control group. Conclusions: Intravenous transplantation of hUC-MSCs is a safe and effective method that can be considered a salvage and priority treatment option for severe COVID-19.

Background COVID-19 is a highly infectious respiratory disease. No effective therapeutics have yet been proved for treating of severe COVID-19. Objectives To determine whether human Umbilical Cord Mesenchymal Stem Cells infusion may be effectiveness and safety in the treatment of severe COVID-19. Methods The severe COVID-19 randomly divided into 2 groups, standard treatment group and standard treatment plus hUC-MSCs infusion group. The incidence of severe patients aggravated to critically illness, 28-day mortality, clinical symptoms improvement, time to clinical symptoms improvement, hematologic indicators including C-reaction protein, lymphocyte number, interleukin 6 and imaging changes were observed and compared between two groups. Measurements and Main Results The incidence of severe patients aggravated to critically illness and 28-day mortality were 0 in hUC-MSCs treatment group, while 4 patients in control group were deteriorated to critical illness and been used invasive ventilation, 3 of them died, and 28-day mortality was 10.34%. In hUC-MSCs treatment group, the time to clinical improvement was shorter, clinical symptoms of weakness and fatigue, shortness of breath, and low oxygen saturation had improved obviously began the third day of stem cells infusion, and reached the significant difference on the day 7, CRP and IL-6 were significantly decreased from day 3 of infusion, the time for lymphocyte count returned to normal range was significant faster, and lung inflammation absorption was significantly shorter from CT imaging. Conclusions Intravenous transplantation of hUC-MSCs is a safe and effective way that can be considered as salvage and priority choice in the treatment of severe COVID-19.

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