Umbilical cord blood CD34+ stem cells and other mononuclear cell subtypes processed up to 96 h from collection and stored at room temperature maintain a satisfactory functionality for cell therapy

Background and Objectives Umbilical cord blood ( UCB ) is a good stem cell source for cell therapy. We recently demonstrated that cord blood mononuclear cell ( MNC s) subtypes were viable and functional until 96 h after collection, even stored at room temperature. Now, we analyzed the viability and functionality of the cells before and after cryopreservation. Materials and Methods Twenty UCB units were analyzed at 24 and 96 h after collection, frozen for 6 months, thawed and re‐evaluated. MNC s were analyzed by flow cytometry, viability by 7‐ AAD and clonogenic assays ( CFU ) were performed. Results After 96 h of storage, no substantial loss of MNC was found (median 7·320 × 10 6 × 6·305 × 10 6 ). Percentage and viability CD 34 + cells, B‐cell precursors and mesenchymal stem cells were not affected. However, mature B and T lymphocytes as well as granulocytes had a substantial loss. CFU growth was observed in all samples. Prefreezing storage of 96 h was associated with a relative loss of colony formation (median 12%). Postthaw, this loss had a median of 49% (24 h samples) to 56% (96 h samples). Conclusion The delay of 96 h before UCB processing is possible, without a prohibitive impairment of CD 34 + loss in number and functionality.