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.


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 μ/cm(2) 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.


CONCLUSIONS
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.
Ting
Michael J
MJ
Leukaemia Foundation of Queensland Research Unit, Queensland Institute of Medical Research, Brisbane, Australia. m.ting@uq.edu.au
Day
Bryan W
BW
Spanevello
Mark D
MD
Boyd
Andrew W
AW
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016026:Bone Marrow Transplantation; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D036384:Ephrin-A3 / Q000235:genetics / Q000378:metabolism; D036342:Ephrins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D005434:Flow Cytometry; D015870:Gene Expression; D019650:Hematopoietic Stem Cell Mobilization; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051379:Mice; D020297:Mice, Congenic; D008810:Mice, Inbred C57BL; D036121:Receptor, EphA3 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D036081:Receptors, Eph Family / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D000906:Antibodies; D036384:Ephrin-A3; D036342:Ephrins; D005353:Fibronectins; D019010:Vascular Cell Adhesion Molecule-1; D036121:Receptor, EphA3; D036081:Receptors, Eph Family