Cord blood transplant: the glass is half full--can we do better?

Hematopoietic repopulating ability of CD34⁺ progenitor cells ex vivo expanded with different cytokine combinations

Ex-vivo expansion technologies were developed for application of hematopoietic stem cells (HSCs) derived from cord blood (CB). The cytokine combination was essential to expand HSCs ex vivo and maintain the function of expanded HSCs. However the optimal cytokine combination was not determined. In this study, two combinations of cytokines were applied in ex-vivo expansion of HSCs to investigate the effect on the hematopoietic repopulating ability of expanded HSCs. CB CD34(+) cells were expanded with SCF + TPO + FL (STF) or SCF + TPO + FL + IL-3 + IL-6 (STF36) for 7 days and got 30.3 ± 6.4 and 39.8 ± 7.3 folds of total cells, respectively. The cells cultured by both STF and STF36 could engraft and repopulate in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice effectively; however, the STF group achieved higher level of engraftment. These result demonstrated that the cytokine combination of STF36 favored the expansion of cells, while the cytokine combination of STF facilitated the engraftment and multi-lineage repopulating in vivo. These findings may have important implications for the cell therapy.

Umbilical cord blood transplantation supported by third-party donor cells: rationale, results, and applications

Low incidence of graft-versus-host disease provides the major rational for pursuing umbilical cord blood (UCB) stem cell transplantation (SCT). Considerable evidence also suggests a lower rate of recurrence after UCB SCT than after transplantation from adult donors. Recent advances in understanding of the human fetal immune development provide a rational underpinning for these clinical outcomes. The fetal immune system is geared toward maintaining tolerance to foreign antigens, particularly to the maternal antigens to which it is exposed throughout gestation. To this purpose it is dominated by a unique population of peripheral T regulatory cells that actively maintain tolerance. This and other features of the UCB lymphoid system explains the low incidence of graft-versus-host disease and superior outcomes of UCB SCT with noninherited maternal antigen-matched grafts. At the same time, highly sensitized maternal microchimeric cells are frequently detected in UCB and likely contribute to superior graft-versus-leukemia effects and low rates of disease recurrence in inherited paternal antigen-matched UCB recipients. However, historically erratic and slow hematopoietic recovery after UCB SCT leads to increased early morbidity and mortality, excessive hospitalization, and increased costs. This has held up the widespread utilization of UCB SCT in adults. Here we summarize recent data on UCB SCT with an emphasis on studies of co-infusion of adult CD34 selected hematopoietic stem cells with UCB SCT. This procedure, through transient engraftment of adult hematopoietic stem cells, largely overcomes the problem of delayed engraftment. It also results in predictable engraftment of a UCB with the desired characteristics. We also briefly discuss unresolved issues and possible future applications of this technology.

Reduced-intensity conditioning with combined haploidentical and cord blood transplantation results in rapid engraftment, low GVHD, and durable remissions

We conducted a 45 patient prospective study of reduced-intensity conditioning (RIC) and transplantation of unrelated umbilical cord blood (UCB) and CD34(+) stem cells from a haploidentical family member. Median age was 50 years; weight was 80 kg. Fifty-eight percent had active disease. Neutrophil engraftment occurred at 11 days (interquartile range [IQR], 9-15) and platelet engraftment at 19 days (IQR, 15-33). In the majority of patients, early haploidentical engraftment was replaced by durable engraftment of UCB by 100 days, with regular persistence of minor host and/or haplo-hematopoiesis. Percentage of haplochimerism at day 100 correlated with the haplo-CD34 dose (P = .003). Cumulative incidence of acute GVHD (aGVHD) was 25% and chronic GVHD (cGVHD) was 5%. Actuarial survival at 1 year was 55%, progression-free survival (PFS) was 42%, nonrelapse mortality (NRM) was 28%, and relapse was 30%. RIC and haplo-cord transplantation results in fast engraftment of neutrophils and platelets, low incidences of aGVHD and cGVHD, low frequency of delayed opportunistic infections, reduced transfusion requirements, shortened length of hospital stay, and promising long-term outcomes. UCB cell dose had no impact on time to hematopoietic recovery. Therefore, UCB selection can prioritize matching, and better matched donors can be identified rapidly for most patients. This study is registered at http://clinicaltrials.gov as NCI clinical trial no. NCT00943800.