Activation of ephrin A proteins influences hematopoietic stem cell adhesion and trafficking patterns
Received 21 June 2009; received in revised form 9 July 2010; accepted 14 July 2010. published online 26 July 2010. Uncorrected Proof
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-Fc 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-Fc 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 mg/cm2 EphA3-Fc extracellular molecule alone). Injection of the antagonist soluble EphA3-Fc 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-Fc 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.
aLeukaemia Foundation of Queensland Research Unit, Queensland Institute of Medical Research, Brisbane, Australia
bSchool of Medicine, Faculty of Health Sciences, University of Queensland, Brisbane, Australia
Offprint requests to: Michael J. Ting, Ph.D., University of Queensland Centre for Clinical Research, Tissue Repair and Inflammation Laboratory (Level 8), Building 71/918, RWBH Herston Campus, Herston, Queensland 4029, Australia
ABSTRACT