Restoring mitochondrial function promotes hematopoietic reconstitution from cord blood following cryopreservation-related functional decline

Umbilical cord blood (UCB) showcases substantial roles in hematopoietic stem cells (HSCs) transplantation and regenerative medicine. UCB is usually cryopreserved for years before use. Whether and how cryopreservation affects its function remain unclear. We constructed single-cell transcriptomic profile of CD34+ hematopoietic stem and progenitor cells (HSPCs) and mononuclear cells (MNCs) from fresh and cryopreserved UCB stored for 1-, 5-, 10-, and 19- years. Compared to fresh UCB, cryopreserved HSCs and multipotent progenitors (MPPs) exhibited more active cell cycle and lower HSC/MPP signature gene expressions. Hematopoietic reconstitution of cryopreserved HSPCs gradually decreased during the first 5 years but stabilized thereafter, aligning with the negative correlation between clinical neutrophil engraftment and cryopreservation duration of UCB. Cryopreserved HSPCs also showed reduced megakaryocyte generation. In contrast, cryopreserved natural killer (NK) cells and T cells maintained cytokine production and cytotoxic ability comparable to fresh cells. Mechanistically, cryopreserved HSPCs exhibited elevated reactive oxygen species, reduced ATP synthesis, and abnormal mitochondrial distribution, which collectively led to attenuated hematopoietic reconstitution. These effects could be ameliorated by sulforaphane. Together, we elucidated the negative impact of cryopreservation on UCB HSPCs and provided sulforaphane as a mitigation strategy, broadening the temporal window and scope for clinical applications of cryopreserved UCB. .