Activation of ephrin A proteins influences hematopoietic stem cell adhesion and trafficking patterns

Objective To determine if Eph receptors and ephrins can modulate the homing of hematopoietic cells in a murine bone marrow transplantation model Materials and Methods EphA and ephrin A gene expression by mouse hematopoietic stem cells and the progenitor cell line FDCP 1 was determined by real-time reverse transcription polymerase chain reaction and flow cytometry The effect of ephrin A activation on adhesion of hematopoietic progenitors was determined by in vitro adhesion assays in which cells were exposed to fibronectin or vascular cell adhesion molecule - 1 (VCAM-1) and an increasing gradient of immobilized EphA3-Fc Adhesion to fibronectin and VCAM-1 was further investigated using soluble preclustered EphA3 Fc We used soluble unclustered EphA3 Fc as an antagonist to block endogenous EphA - ephrin A interactions in vivo The effect of injecting soluble EphA3 Fe on the mobilization of hematopoietic progenitor cells was examined We determined the effect on short-term homing by pretreating bone marrow cells with EphA3 Fc or the control IgG before infusion Into lethally irradiated mice Results Preclustered and immobilized EphA3 Fe Increased adhesion of progenitor cells and FDCP 1 to fibronectin and VCAM-1 (1 6 to 2-fold higher adhesion, p < 0 05) relative to control (0 mu/cm(2) EphA3 Fe extracellular molecule alone) Injection of the antagonist soluble EphA3 Fe increased progenitor cell and colony forming unit-spleen cells in the peripheral blood (42% greater colony forming unit in culture, p < 0 05,3 8 fold higher colony forming unit - spleen) relative to control Conclusion Treating bone marrow cells with EphA3 Fe resulted in a reduction by 31 % in donor stem cells homing to the bone marrow and accumulation of donor cells in recipient spleens (50% greater than control) and greater recovery of donor stem cells from the peripheral blood Crown Copyright (C) 2010 Published by Elsevier Inc on behalf of the ISEH Society for Hematology and Stem Cells All rights reserved