Ex vivo fucosylation improves human cord blood engraftment in NOD-SCID IL-2Rγnull mice

Abstract

Delayed engraftment remains a major hurdle following cord blood (CB) transplantation. It may be due, at least in part, to low fucosylation of cell surface molecules important for homing to the BM microenvironment. Since fucosylation of specific cell surface ligands is required before effective interaction with selectins expressed by the BM microvasculature can occur, a simple 30 minute ex vivo incubation of CB HPC with fucosyltransferase (FT) - VI and its substrate (GDP-fucose) was performed to increase levels of fucosylation. The physiologic impact of CB HPC hypo-fucosylation was investigated in vivo in NOD-SCID IL-2Rγnull (NSG) mice. By isolating fucosylated and non-fucosylated CD34+ cells from CB we show that only fucosylated CD34+ cells are responsible for engraftment in NSG mice. Further, since the proportion of CD34+ cells that are fucosylated in CB is significantly less than in BM and PB, we hypothesize that these combined observations might explain, at least in part, the delayed engraftment observed following CB transplantation. Since engraftment appears to be correlated with the fucosylation of CD34+ cells, we hypothesized that increasing the proportion of CD34+ cells that are fucosylated would improve CB engraftment. Ex vivo treatment with fucosyltransferase (FT)-VI significantly increases the levels of CD34+ fucosylation and, as hypothesized, this was associated with improved engraftment. Ex vivo fucosylation did not alter the biodistribution of engrafting cells, or pattern of long-term, multi-lineage, multi-tissue engraftment. We propose that ex vivo fucosylation will similarly improve the rate and magnitude of engraftment for CB transplant recipients in a clinical setting.

Umbilical cord blood graft engineering: challenges and opportunities

“…A rapid decline in NK cell function occurs when IL-2 is removed from medium. 41 In vivo dependence on IL-2 for persistence is greater with ex vivo expanded cells than fresh, activated cells. 131 In vivo use of IL-2 (which can expand NK cell numbers) can lead to severe toxicity and also to Treg expansion which limits NK cell activation.…”

“…Levels of fucosylation can be increased by incubation with α1-3 fucosyltransferase (FT)-VI. 38,40,42 Robinson et al 41 showed that fucosylation of CB HPCs can be increased from a baseline of~15% to 495% with a 30-min incubation with FT-VI at room temperature and that only the fucosylated fraction of CD34 + HPCs contributes to engraftment in NOD scid gamma mice. In addition, appearance of human CD45 + cells in the peripheral blood of NOD scid gamma mice was more rapid in mice receiving fucosylated grafts than those receiving untreated grafts and both myeloid and B-lymphoid engraftment in marrow and spleen were threefold greater than in recipients of unfucosylated grafts.…”

Modalities to Improve Cord Blood Engraftment

“…Robinson and colleagues [70] have tried a simple 30-minute ex vivo incubation of UCB hemotopoietic progenitor cells with fucosyltransferase-VI (a1-3 fucosyltransferase) and its substrate (Guanosine diphosphate -fucose/ GDP) to increase levels of fucosylation. In their study they observed a concomitant improvement in engraftment with increased number of fucosylated CD34 cells in a NSG mouse model.…”

Background and Future Considerations for Human Cord Blood Hematopoietic Cell Transplantation, Including Economic Concerns

“…Such approaches have assessed fucosylation [36], pretreatment of cells with a modifi ed prostaglandin (PG) E2 [37 -39], or pretreatment of cells with an inhibitor of the enzyme dipeptidylpeptidase (DPP) 4 [40,41,51]. Fucosylation of CB cells has enhanced the homing and engrafting capability of these treated cells in sublethally irradiated NS2 mice [36].…”

“…Such approaches have assessed fucosylation [36], pretreatment of cells with a modifi ed prostaglandin (PG) E2 [37 -39], or pretreatment of cells with an inhibitor of the enzyme dipeptidylpeptidase (DPP) 4 [40,41,51]. Fucosylation of CB cells has enhanced the homing and engrafting capability of these treated cells in sublethally irradiated NS2 mice [36]. Pretreatment of mouse BM or human CB cells for minutes with a modifi ed PGE2 molecule has, respectively, enhanced the engraftment of these cells into lethally irradiated congenic mice and sublethally irradiated immune -defi cient mice [37,38], with efforts in nonhuman primates [39] and humans [52] showing safety, with a modest decrease to the time to engraftment seen in a human study in context of a double -CB transplant including one manipulated and one unmanipulated CB unit [52].…”