15 18-02-2020; 30-01-2020 to 31-03-2020 1–2Recruiting ChiCTR2000029990;http://www.chictr.org.cn/showproj.aspx?proj=49674 Clinical trials of mesenchymal stem cells for the treatment of pneumonitis caused by novel coronavirus pneumonia (COVID-19) MSCs 120 Experimental group: MSCsControl group: saline