Patients were transferred to designated hospitals for treatment as needed, the clinical trials cannot be conducted.

The 2019 novel coronavirus pneumonia outbroken in Wuhan, China, which spread quickly to 26 countries worldwide and presented a serious threat to public health. It is mainly characterized by fever, dry cough, shortness of breath and breathing difficulties. Some patients may develop into rapid and deadly respiratory system injury with overwhelming inflammation in the lung. Currently, there is no effective treatment in clinical practice. The present clinical trial is to explore the safety and efficacy of Human Umbilical Cord Mesenchymal Stem Cells (UC-MSCs) therapy for novel coronavirus pneumonia patients.

Since late December 2019, human pneumonia cases infected by a novel coronavirus (2019-nCoV) were firstly identified in Wuhan, China. As the virus is contagious and of great epidemic, more and more cases have found in other areas of China and abroad. Up to February 24, a total of 77, 779 confirmed cases were reported in China. At present, there is no effective treatment for patients identified with novel coronavirus pneumonia. Therefore, it's urgent to explore more active therapeutic methods to cure the patients.

Recently, some clinical researches about the 2019 novel coronavirus pneumonia published in The Lancet and The New England Journal of Medicine suggested that massive inflammatory cell infiltration and inflammatory cytokines secretion were found in patients' lungs, alveolar epithelial cells and capillary endothelial cells were damaged, causing acute lung injury. It seems that the key to cure the pneumonia is to inhibit the inflammatory response, resulting to reduce the damage of alveolar epithelial cells and endothelial cells and repair the function of the lung.

Mesenchymal stem cells (MSCs) are widely used in basic research and clinical application. They are proved to migrate to damaged tissues, exert anti-inflammatory and immunoregulatory functions, promote the regeneration of damaged tissues and inhibit tissue fibrosis. Studies have shown that MSCs can significantly reduce acute lung injury in mice caused by H9N2 and H5N1 viruses by reducing the levels of proinflammatory cytokines and the recruitment of inflammatory cells into the lungs. Compared with MSCs from other sources, human umbilical cord-derived MSCs (UC-MSCs) have been widely applied to various diseases due to their convenient collection, no ethical controversy, low immunogenicity, and rapid proliferation rate. In our recent research, we confirmed that UC-MSCs can significantly reduce inflammatory cell infiltration and inflammatory factors expression in lung tissue, and significantly protect lung tissue from endotoxin (LPS) -induced acute lung injury in mice.

The purpose of this clinical study is to investigate safety and efficiency of UC-MSCs in treating pneumonia patients infected by 2019-nCoV. The investigators planned to recruit 48 patients aged from 18 to 75 years old and had no severe underlying diseases. In the cell treatment group, 24 patients received 0.5*10E6 UC-MSCs /kg body weight intravenously treatment 4 times every other day besides conventional treatment. In the control group, other 24 patients received conventional treatment plus 4 times of placebo intravenously. The lung CT, blood biochemical examination, lymphocyte subsets, inflammatory factors, 28-days mortality, etc will be evaluated within 24h and 1, 2, 4, 8 weeks after UC-MSCs treatment.

Inclusion Criteria:

1. Male or female, 18 years old ≤ age ≤ 75years old;
2. CT image is characteristic of 2019 novel coronavirus pneumonia;
3. Laboratory confirmation of 2019-nCoV infection by reverse-transcription polymerase chain reaction (RT-PCR);
4. In compliance with the 2019-nCoV pneumonia diagnosis standard (according to the novel coronavirus infection pneumonia diagnosis and treatment program (Trial Implementation Version 6) issued by the National Health and Medical Commission, and WHO 2019 new coronavirus guidelines standards): (A) increased breathing rate (≥30 beats / min), difficulty breathing, cyanosis of the lips; (B) in resting state, means oxygen saturation ≤93%; (C) partial pressure of arterial oxygen (PaO2) / Fraction of inspired oxygen (FiO2) ≤300 mmHg (1mmHg = 0.133kPa);

Exclusion Criteria:

1. Patients with severe allergies or allergies to stem cells;
2. Patients with serious basic diseases that affect survival, including: blood diseases, cachexia, active bleeding, severe malnutrition, etc.;
3. Patients with pulmonary obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis, allergic alveolitis, and other known viral pneumonia or bacterial pneumonia;
4. Continuous use of immunosuppressive agents or organ transplants in the past 6 months;
5. In vitro life support (ECMO, ECCO2R, RRT);
6. Expected deaths within 48 hours, uncontrolled infections;
7. Patients with malignant blood-borne diseases such as HIV or syphilis;
8. Patient with pregnancy, are planning to become pregnant or breastfeeding;
9. Patients with poor compliance and unable to complete the full study;
10. The investigator determines that there may be increased risk of the subject or other conditions that interfere with the clinical trial and the judgment of the results (such as excessive stress, sensitivity or cognitive impairment, etc.);
11. There are other situations that the researchers think are not suitable to participate in this clinical study