Hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF) is a severe disease with high mortality. Our previous study have demonstrated that peripheral infusion of bone marrow-derived mesenchymal stromal cells (MSCs) weekly for 4 times is safe and improves 24 weeks survival rate of ACLF patients. In this study, we intend to assess the safety and efficacy of umbilical cord blood derived MSCs for HBV-related ACLF patients.

Inclusion Criteria:

1. Patients with ACLF-which is characterized by acute hepatic insult manifesting as jaundice (serum total bilirubin ≥ 10×ULN umol/L) and coagulopathy (international normalized ratio≥ 1.5 or prothrombin activity < 40%), complicated within 4 weeks by ascites and/or encephalopathy as determined by physical examination, in patients with previously diagnosed or undiagnosed chronic liver disease;
2. Positive serum hepatitis B surface antigen (HBsAg) for more than 6 months;
3. End-stage liver disease scores ranging from 17-30,; 4.18-65 years of age.

Exclusion Criteria:

1. Serious complications within the previous 2 months (e.g. gastrointestinal bleeding, serious infection );
2. Concomitant autoimmune disease;
3. Superinfection with other hepatitis viruses;
4. Important organ dysfunctions not due to liver disease or malignancies;
5. Pregnancy and lactation;
6. Liver tumor or nodules secondary to cirrhosis proven by ultrasound, computerized tomography (CT), or magnetic resonance (MR) imaging;
7. Bioartificial liver support therapy;
8. Previous liver transplantation.