Attached segment has higher CD34+ cells and CFU-GM than the main bag after thawing.

A contiguous segment attached to the cord blood unit (CBU) is required for verifying HLA types, cell viability, and, possibly, potency before transplantation since such a segment is considered to be representative of the CBU. However, little is known regarding the characteristics of contiguous segments in comparison to main bag units due to the difficulty experienced in accessing a large number of cryopreserved CBUs. In this study, we used 245 nonconforming CBUs for allogeneic transplantation. After thawing the cryopreserved CBU, the number of total nucleated cells (TNCs), CD34(+) cells, and CFUs in CB from main bags and segments, as well as cell viability and apoptosis, were examined. The comparative analysis showed that the number of TNCs was significantly higher in CB from main bags, whereas the numbers of CD34(+) cells and CFU-GM were significantly higher in CB from segments. While the cell viability of TNCs in segments was higher, the proportion of apoptotic TNCs was also higher. In contrast, no difference was observed between the proportion of apoptotic CD34(+) cells in main bags and segments. In the correlation analysis, the numbers of TNCs, CD34(+) cells, and CFU-GM in main bags were highly correlated with those in segments, indicating that CB from segments is indeed representative of CB in main bags. Taken together, we conclude that segments have higher CD34(+) cells and CFU-GM and lower TNCs than the main cryopreserved bag, although the two compartments are highly correlated with each other.