Umbilical cord blood transplantation (UCBT) is increasingly used as an alternative stem cell source for therapy in place of bone marrow or peripheral blood stem cell transplantation. However, the low yield of transplantable cells limits the application of a single cord blood unit to patients, particularly with adults and high body weight children. Currently, different cytokines and serum-and-stroma-free medium are used to increase the number of hematopoietic stem/progenitor cells in a single cord blood unit. The ex vivo expanded cord blood transplantation results from phase I trials of clinical therapies have been reported. Here, we report our preliminary data using single HLA mismatched UCBT expanded ex vivo and transplanted for treatment of patients with hematological disease in China. Three patients suffering from chronic myelocytic leukemia (CML, accelerated phase), severe aplastic anemia (SAA, type II), or acute lymphocytic leukemia (ALL) (age range 10–35 years; Body weight range 37.0–76.5. kg) were given ex vivo expanded HLA mismatched (4/6 or 5/6) UCBT. Myeloablative conditioning regimens were used (busulfanum/cyclophosphamide (BU/CY), and anti-thymus globulin (ATG) for CML, cyclophosphamide and ATG for SAA-II, and BU/CY, ATG, and 1,3 -bis(2-chloroethyl)- 1- nitrosourea for ALL-CR2). All patients used cyclosporine A (CsA) and mycophenolate mofetil (MMF) for graft-versus-host disease (GVHD) prophylaxis. After thawing, a 5/6 fraction of the cord blood was infused on day 0 and the remaining 1/6 was expanded for 7 days in serum-and-stroma-free medium containing stem cell factor (SCF), thrombopoietin (TPO), Flt3-L, and IL3. This expaded fraction was infused on day 7. After incubation, the number of total nuclear cells (TNC) increased by 1.86-, 1.91-, 1.81- fold in the CML-Ap, SAA-II, and ALL patients, respectively, while CD34+ cells in these cord blood units increased 7.60-, 0-, 7.46- fold in the CML-Ap, SAA-II, and ALL patients, respectively. The TNC of the three grafts reached 2.4, 4.73, 3.72 ×107/kg; CD34+ cells reached 4.37, 2.69, 8.46×105/kg and colony-forming cells (CFC) reached 5.16, 2.43, 6.87×104/kg in the recipients respectively. One patient (CML-Ap) died of hepatic veno-occlusive disease (HVOD) and multi-organ failure (MOF). In the other two cases, neutrophils were engrafted on day 16 and day 17. In one patient (SAA-II), the cord blood was rejected on day 60. The genotype of 16 STR markers in the ALL patient changed on day 30, as detected by STR-PCR and the blood group changed on day 62. Platelet recovery (>20× 109/L) occurred on day 34. Both patients were still alive after 10–12 months follow up. We found that TNC and CD34+ cells were increased after incubation for seven days in the serum-and-stroma-free medium including SCF, TPO, Flt3-L, IL-3. After infusion of the expanded UCBT fraction, the time required for neutrophil recovery in the patients was significantly shortened, although there was no influence on platelet recovery. Therefore, these data indicate that it is safe and feasible to use a 1/6 expanded fraction of UCBT combined with a 5/6 unmanipulated fraction of UCBT for the treatment of hematological cancers.

Author notes

Disclosure: No relevant conflicts of interest to declare.