Application of hUC-MSCs in Treating Acute Lung Injury: a Single Center Prospective Clinical Research

Inclusion Criteria: * 1.≤ 3 days (72h) * 2.Age ≥18 years, ≤65 years * 3.200\<PaO2/FiO2 ≤ 300 * 4.Chest X-ray/chest CT : infiltrates of both lungs * 5.Need assisted ventilation (ventilation or high flow oxygen therapy) * 6.No left heart failure, pulmonary edema * 7.Agree to participate and signe an informed consent Exclusion Criteria: * 1.Life expectancy \<3 months due to non-respiratory failure * 2.Patients receiving extracorporeal membrane oxygenation support therapy(ECMO),high frequency oscillatory ventilation * 3.History of HIV, malignant tumors, or impaired immune function * 4.Patients accepted major surgery in the past 14 days (such as tumor removal, thoracotomy, heart surgery, abdominal surgery, intracranial surgery, or surgery for more than 3 hours, etc.) * 5.Pregnancy * 6.Have a serious concomitant disease * 7.Unable to follow-up * 8.History of severe allergic reactions or allergy to saline and serum * 9.Already participated in another clinical study within 12 weeks * 10.Pulmonary edema caused by other underlying diseases