ALBERT

Description: Umbilical cord blood (UCB) is an alternative donor source for allogeneic hematopoietic stem cell transplantation. However, transplantation in adults is frequently limited by the small number of cells available in a unit. We have previously developed the technology to expand hematopoietic stem cells (HSC) and stromal/mesenchymal stem cells (SMSC) from all UCB frozen samples (13, 3). The incubation of thawed UCB mononuclear cells (MNC) in the presence of SCF (25ng/ml), FLt-3 (25ng/ml), MGDF (10ng/ml) & IL-6 (20ng/ml) and 10% human serum in stroma-free liquid culture not only generated long term expansion of transplantable UCB HSC (non-adherent). Also, long-term expansion of SMSC (adherent cells) was successful. In order to upscale the expansion to use for clinical applications, we analyzed 3 frozen UCB comparing the expansion from 24-well plates (previous) versus expansion in bags (VueLife™) after 10 and 14 days of culture. Results show substantial expansion in total cell count (TCC, 4.8, 10.9: 2.4, 3.8 fold) at d10 and d14 from wells & bags respectively. TCC increased further in the presence of SMSC (38% & 33% in CD34+ cell count cultured in wells). CD133+CD34+CD38- HSC multiplied (11, 25 fold, d10/d14 & colony forming cells (CFC) 19 fold at d14 bags respectively). Heterogeneous cell populations were detected after d 14 in bags: T and B -lymphoid (%CD3/%CD19; 65/4:50w/3), megakaryocytic (%CD61; 7:4) and myeloid (%CD33; 31:43) at d0/d14 respectively. Further, expanded cells (250,000) containing a small number of CD133+CD34+CD38- (15,000–30,000) were injected into the liver of sub-lethally irradiated newborn Balb/C Rag2-Cγ−/− mice. Our preliminary data show no engraftment from cells expanded in wells and bags after 6 weeks of transplantation from d10 cultures (human CD45 + 90%. Following repeated trypsinization, SMSC count increased 41–96 folds. CFU-Fibroblast colonies (92–173) were generated from 104 SMSC after 2 weeks in MesenCult medium. We have previously differentiated SMSC into hepatocytes. Now we also generated adipocytes in an induction medium containing, Insulin, dexamethasone & indomethacin. SMSC formed Oil-droplet vacuoles in the cytoplasm in 3 weeks. The culture conditions we defined to maintain UCB PRC should be developed clinically. SMSC described herein exhibit in vitro properties of multipotent stem cells.