Modulation of homing properties of primitive progenitor cells generated by ex vivo expansion.
OBJECTIVE
The maintenance of adequate interactions with the bone marrow (BM) microenvironment is critical to ensure efficient homing of ex vivo-expanded hematopoietic cells. This study was intended to assess adhesion and migration properties of long-term culture-initiating cells (LTC-IC) harvested after self-renewal division in ex vivo culture and to determine their susceptibility to growth-inhibitory signals mediated by adhesion to BM stromal ligands.


METHODS
We used cell tracking to isolate primitive LTC-IC that had accomplished 1 or 2 divisions ex vivo. Adhesion, migration and growth inhibition of divided LTC-IC were determined in the presence of purified BM ligands, and compared to the properties of uncultured LTC-IC.


RESULTS
As compared to undivided LTC-IC, adhesion and migration mediated by very late antigen (VLA)-4 integrin across both vascular cell adhesion molecule-1 (VCAM-1) and fibronectin (Fn) were downregulated in post-mitotic LTC-IC. Conversely, binding and motility via VLA-5 across Fn were stimulated. No changes occurred in LTC-IC interactions with intercellular adhesion molecule-1 (ICAM-1) or with E- or P-selectin. Proliferation of uncultured LTC-IC was inhibited by VLA-4-mediated binding to VCAM-1 and the CS-1 domain of Fn, as well as binding to P-selectin. Growth of ex vivo-generated LTC-IC became unresponsive to these 3 ligands but was suppressed through VLA-5 engagement by the cell binding domain of Fn.


CONCLUSIONS
The generation of LTC-IC in expansion culture is associated with functional alterations of adhesion receptors, modulating not only binding and migration in the BM but also responsiveness to adhesion-mediated growth inhibitory signals. Such changes may limit homing and engraftment of expanded primitive stem/progenitor cells.
Foguenne
Jacques
J
Department of Medicine/Hematology, University of Liège, Liège, Belgium.
Huygen
Sandra
S
Greimers
Roland
R
Beguin
Yves
Y
Gothot
André
A
D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000097:blood; D001853:Bone Marrow; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002455:Cell Division; D002465:Cell Movement; D002478:Cells, Cultured; D015536:Down-Regulation; D005353:Fibronectins / Q000378:metabolism; D006023:Glycoproteins / Q000097:blood; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D039041:Integrin alpha4beta1 / Q000502:physiology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008938:Mitosis / Q000502:physiology; D010455:Peptides / Q000097:blood; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D000071916:AC133 Antigen; D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D006023:Glycoproteins; D039041:Integrin alpha4beta1; D010455:Peptides; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1