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neutrophil recovery on each of post-transplant days 8 (P=0.009), 12 (P<0.0001), and 18 (P=0.01), achieving an effect quite similar to that of accelerating a 500,000 donor cell transplant with (+)-SW209415 (Figure 5). Notably though, treatment with (+)-SW209415 significantly fur- ther accelerated hematopoietic recovery even in mice transplanted with the higher cell dose. Indeed, mice receiving 2x106 donor cells plus (+)-SW209415 showed greater neutrophil recovery than corresponding mice receiving vehicle control on each of post-HSCT days 8 (P=0.04), 12 (P=0.0019), and 18 (P=0.04) (Figure 5). Furthermore, in mice transplanted with 2x106 donor bone marrow cells, added treatment with (+)-SW209415 increased post-HSCT day 18 numbers of marrow SKL cells by 55%, which is approximately the same proportion as the corresponding day 18 increase in neutrophil counts (Online Supplementary Figure S8). These data demonstrate that (+)-SW209415 continues to provide acceleration of hematopoietic recovery from HSCT even when the inocu- lum of transplanted donor cells is markedly increased.
(+)-SW209415 promotes bone marrow homing
of human umbilical cord and human bone marrow hematopoietic stem cells
To further model the potential efficacy of (+)-SW209415 in human HSCT, we examined the effects of (+)- SW209415 in accelerating bone marrow homing of xeno- transplanted human bone marrow and human umbilical
cord blood cells. In these studies, lethally irradiated immunodeficient NSG mice received inocula of CFSE- labeled total human cells, and the frequency of the labeled cells was determined at 16 h after transplantation in recip- ient mouse femora and tibiae. We found that administer- ing (+)-SW209415 increased homing of human bone mar- row aspirate-derived cells by ~1.78-fold (P=0.0008) in a pooled analysis of two donors and increased homing of human umbilical cord blood-derived cells by ~1.71-fold (P=0.0001) in a pooled analysis of three donors (Figure 6A). A similar ~2-fold effect of (+)-SW209415 on increas- ing homing of purified human CD34+ cells was obtained in mice that were transplanted with CFSE-labeled isolated human CD34+ cells from two bone marrow aspirate donors (Online Supplementary Figure S9). Beneficial effects of (+)-SW209415 were maintained in follow-up studies assessing 12-week engraftment of human cells. In these experiments, NSG mice were transplanted with 1x106 mononuclear cells/mouse from total bone marrow aspi- rates of 2 donors and effects of (+)SW209415 human engraftment were assessed 84 days later. Treatment with (+)-SW209415 on days 1-21 days after BMT resulted in a 3.16-fold increase in day 84 human CD45+ bone marrow cells (P=0.024) (Online Supplementary Figure S10) and a sim- ilar 2- to 3-fold sustained increase in human peripheral blood chimerism from days 30-84 (P<0.03) (Figure 6B). CD45+ human-derived cells were identified in each of the myeloid, T-cell, and B-cell compartments, at frequencies
Figure 5. (+)-SW209415 accelerates hematopoietic recovery in hematopoietic stem cell transplantation (HSCT) recipient mice that receive “high-dose” donor cell inoculum. Lethally irradiated (11 Gy) 8-week old female C57/BL6J mice were transplanted with either 500 x103 (blue bars) or 2x106 (red bars) total bone marrow cells and treated with either vehicle (V), or 2.5 mg/kg (+)- SW209415 (S). Graphs display means and Standard Error of Mean of peripheral blood neutrophil counts as measured on days 8, 12, and 18 after BMT (12 mice/arm). *Student t-test P<0.05.
haematologica | 2018; 103(6)