AA2P-mediated DNA demethylation synergizes with stem cell agonists to promote expansion of hematopoietic stem cells

Reduction in cord blood graft potency due to processing delay can be prevented by trehalose supplementation

BACKGROUND AND OBJECTIVES

Maximizing the potency of cord blood (CB) units (CBU) is a goal of all CB banks. Low transplant cell dose in CB transplantation is one of several contributors to the slower engraftment. Processing delays could also be at play because CBU can be stored at room temperature (RT) for up to 48 h before cryopreservation. We hypothesized that prolonged storage at RT reduces the potency and engraftment activities of CBU due to the loss of haematopoietic stem cells (HSCs) and progenitor cells.

MATERIALS AND METHODS

CBU were split in half, with one half processed shortly after collection and the other half after 40 h of storage at RT. Viabilities and potencies were compared post thaw, and engraftment activity was tested in xenotransplants. Bioinformatic analysis was carried out to identify pathways modulated by prolonged storage at RT.

RESULTS

Prolonged storage at RT reduced the viability of CB cells and potency of grafts based on in vitro and in vivo assays. Transcriptomic analyses revealed that paracrine factors released in CBU induce several changes in gene expression programmes in CD34+ cells. These included the activation of the senescence gene CDKN1B and down-regulation of cell cycle and autophagy genes. Supplementation of CBU with trehalose prevented the loss in cell viability and potency. The latter was associated with the restoration of autophagy and suppression of the senescence gene CDKN1B.

CONCLUSION

These results stress the importance of rapid processing of CBU and support further investigations on trehalose as a natural supplement to protect CBU' potency during storage.

Homing and Engraftment of Hematopoietic Stem Cells Following Transplantation: A Pre-Clinical Perspective

Hematopoietic stem-cell (HSC) transplantation (HSCT) is used to treat various hematologic disorders. Use of genetically modified mouse models of hematopoietic cell transplantation has been critical in our fundamental understanding of HSC biology and in developing approaches for human patients. Pre-clinical studies in animal models provide insight into the journey of transplanted HSCs from infusion to engraftment in bone-marrow (BM) niches. Various signaling molecules and growth factors secreted by HSCs and the niche microenvironment play critical roles in homing and engraftment of the transplanted cells. The sustained equilibrium of these chemical and biologic factors ensures that engrafted HSCs generate healthy and durable hematopoiesis. Transplanted healthy HSCs compete with residual host cells to repopulate stem-cell niches in the marrow. Stem-cell niches, in particular, can be altered by the effects of previous treatments, aging, and the paracrine effects of leukemic cells, which create inhospitable bone-marrow niches that are unfavorable for healthy hematopoiesis. More work to understand how stem-cell niches can be restored to favor normal hematopoiesis may be key to reducing leukemic relapses following transplant.