Assessing pilot vial material as a surrogate for functional and phenotypic stem cell markers in cryopreserved haematopoietic stem cell product

Poor mobilization of autologous CD34+ peripheral blood stem cells in haematology patients undergoing autologous stem cell transplantation is associated with the presence of variants in genes implicated in clonal haematopoiesis of indeterminant potential

Clonal haematopoiesis of indeterminant potential (CHIP) increases in frequency with age. The effect of CHIP on the mobilization of autologous CD34+ peripheral blood stem cells (PBSC) has not been reported. This study uses a DNA-based targeted candidate gene approach to identify the presence of somatic mutations in ASXL1, DNMT3A, JAK2, SF3B1, TET2 and TP53 in CD34+ haematopoietic progenitor cell-apheresis products of 96 patients who undergo PBSC mobilization for autologous stem cell transplantation (ASCT). Variants were identified in a significantly greater proportion of patients who experience poor CD34+ PBSC mobilization. A DNA-based targeted candidate gene array is able to predict poor CD34+ PBSC mobilization and may be deployed pre-emptively to minimize mobilization and graft failures.

Expression of Intracellular Reactive Oxygen Species in Hematopoietic Stem Cells Correlates with Time to Neutrophil and Platelet Engraftment in Patients Undergoing Autologous Bone Marrow Transplantation

Reactive oxygen species (ROS) play important roles in hematopoiesis and regulate the self-renewal, migration, and myeloid differentiation of hematopoietic stem cells (HSCs). This study was conducted to determine whether ROS levels in donor HSCs correlate with neutrophil and platelet engraftment in patients after bone marrow transplantation. Cryopreserved HSC samples from 51 patients who underwent autologous transplantation were studied. Levels of intracellular ROS were assessed by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate (H₂DCFDA) in the CD45⁺/CD34⁺ HSC population. Colony forming unit assays were performed on HSCs isolated from the ROS^high and ROS^low populations to assess the differentiation potential of these 2 cell subsets. Distinct populations of ROS^high and ROS^low cells were evident in all patient samples. The median percentage of ROS^high expressing HSCs in the study cohort was 75.8% (range, 2% to 95.2%). A significant correlation was identified between the percentage of ROS^high stem cells present in the hematopoietic progenitor cells collected by apheresis product infused and the time to neutrophil engraftment (P < .001, r = -.54), as well as time to plt20, plt50, and plt100 (P < 0.001; r = -.55, -.59, and -.56 respectively). The dose of CD34⁺/ROS^high/kg infused also inversely correlated with a shorter time to neutrophil engraftment; time to engraftment for patients receiving > or ≤3 × 10⁶ cells/kg was 11.5 days (range, 9 to 23) versus 14 days (range, 10 to 28), respectively (P = .02). The dose of ROS^high HSCs delivered did not correlate with platelet engraftment. Collectively, these data suggest that the dose of ROS^high stem cells delivered to patients may predict time to neutrophil engraftment after autologous transplantation.

Rescuing Self: Transient Isolation and Autologous Transplantation of Bone Marrow Mitigates Radiation-Induced Hematopoietic Syndrome and Mortality in Mice

The inflamed bone marrow niche shortly after total body irradiation (TBI) is known to contribute to loss of hematopoietic stem cells in terms of their number and function. In this study, autologous bone marrow transfer (AL-BMT) was evaluated as a strategy for mitigating hematopoietic form of the acute radiation syndrome by timing the collection phase (2 h after irradiation) and reinfusion (24 h after irradiation) using mice as a model system. Collection of bone marrow (BM) cells (0.5 × 10⁶ total marrow cells) 2 h after lethal TBI rescued different subclasses of hematopoietic stem and progenitor cells (HSPCs) from the detrimental inflammatory and damaging milieu in vivo. Cryopreservation of collected graft and its reinfusion 24 h after TBI significantly rescued mice from lethal effects of irradiation (65% survival against 0% in TBI group on day 30th) and hematopoietic depression. Transient hypometabolic state (HMS) induced 2 h after TBI effectively preserved the functional status of HSPCs and improved hematopoietic recovery even when BM was collected 8 h after TBI. Homing studies suggested that AL-BMT yielded similar percentages for different subsets of HSPCs when compared to syngeneic bone marrow transfer. The results suggest that the timing of collection, and reinfusion of graft is crucial for the success of AL-BMT.