The Effect of stem cell mobilisation with granulocyte colony-stimulating factor on the morphology of the haematopoietic organs in mice

The cellular mobilisation of mice with granulocyte colony-stimulating factor (G-CSF) results in an egress of haematopoietic stem/progenitor cells from the bone marrow and an increase in their level in the peripheral blood. While the mobilisation process with different agents is widely studied, little is known about the morphology of the murine haematopoietic organs during the mobilisation. The purpose of this study was to examine the morphology of the bone marrow, spleen and liver in mice mobilised with G-CSF. To address this issue mice were injected subcutaneously with G-CSF for 6 consecutive days. Morphological analysis revealed an increase in the number of mature neutrophils close to the wall of sinusoids in the bone marrow as well as hypertrophy of the red pulp in the spleen. At the same time no morphological changes were noticed in the livers of G-CSF-mobilised mice. In conclusion, G-CSF induces discrete ultrastructural changes in the bone marrow, which intensify the transendothelial traverse of haematopoietic stem and progenitor cells from it. The changes in the spleen are related to repopulation of this organ by mobilised early haematopoietic cells circulating in the peripheral blood. We also noticed that the process of migration of haematopoietic cells from the bone marrow into the peripheral blood began on day 2 and was most pronounced on day 4 after stimulation with G-CSF

Signal One and Two Blockade Are Both Critical for Non-Myeloablative Murine HSCT across a Major Histocompatibility Complex Barrier

Non-myeloablative allogeneic haematopoietic stem cell transplantation (HSCT) is rarely achievable clinically, except where donor cells have selective advantages. Murine non-myeloablative conditioning regimens have limited clinical success, partly through use of clinically unachievable cell doses or strain combinations permitting allograft acceptance using immunosuppression alone. We found that reducing busulfan conditioning in murine syngeneic HSCT, increases bone marrow (BM):blood SDF-1 ratio and total donor cells homing to BM, but reduces the proportion of donor cells engrafting. Despite this, syngeneic engraftment is achievable with non-myeloablative busulfan (25 mg/kg) and higher cell doses induce increased chimerism. Therefore we investigated regimens promoting initial donor cell engraftment in the major histocompatibility complex barrier mismatched CBA to C57BL/6 allo-transplant model. This requires full myeloablation and immunosuppression with non-depleting anti-CD4/CD8 blocking antibodies to achieve engraftment of low cell doses, and rejects with reduced intensity conditioning (≤75 mg/kg busulfan). We compared increased antibody treatment, G-CSF, niche disruption and high cell dose, using reduced intensity busulfan and CD4/8 blockade in this model. Most treatments increased initial donor engraftment, but only addition of co-stimulatory blockade permitted long-term engraftment with reduced intensity or non-myeloablative conditioning, suggesting that signal 1 and 2 T-cell blockade is more important than early BM niche engraftment for transplant success