Evaluation of Expansion and Maintenance of Umbilical Cord Blood CD34(+) Cells in The Co-Culture with Umbilical Cord Blood-Derived Mesenchymal Stem Cells in The Presence of Microcarrier Beads

OBJECTIVE: Umbilical cord blood (UCB) is an accessible and effective alternative source for hematopoietic stem cell (HSC) transplantation. Although the clinical application of UCB transplantation has been increased recently, quantitative limitation of HSCs within a single cord blood unit still remains a major hurdle for UCB transplantation. In this study we used microcarrier beads to evaluate the ex vivo expansion of UCB-derived HSCs in co-cultured with UCB-derived mesenchymal stem cells (MSC). MATERIALS AND METHODS: In this experimental study, we used microcarrier beads to expand UCB-derived MSCs. We investigated the simultaneous co-culture of UCB-derived CD34(+) cells and MSCs with microcarrier beads to expand CD34(+) cells. The colony forming capacity and stemness-related gene expression on the expanded CD34(+) cells were assessed to determine the multipotency and self-renewal of expanded cells. RESULTS: Our results indicated that the microcarrier-based culture significantly increased the total number and viability of UCB-derived MSCs in comparison with the monolayer cultures during seven days. There was a significant increase in the UCB-derived CD34(+) cells expanded in the presence of microcarrier beads in this co-culture system. The expanded UCB-derived CD34(+) cells had improved clonogenic capacity, as evidenced by higher numbers of total colony counts, granulocyte, erythrocyte, monocyte, megakaryocyte colony forming units (CFU-GEMM), and granulocyte–monocyte colony forming units (CFU-GM). There were significantly increased expression levels of key regulatory genes (CXCR4, HOXB4, BMI1) during CD34(+) cells self-renewal and quiescence in the microcarrier-based co-culture. CONCLUSION: Our results showed that the increase in the expansion and multipotency of CD34(+) cells in the microcarrierbased co-culture can be attributed to the enhanced hematopoietic support of UCB-derived MSCs and improved cell-cell interactions. It seems that this co-culture system could have the potential to expand primitive CD34(+) cells.