The molecular basis for the cytokine-induced defect in homing and engraftment of hematopoietic stem cells.
OBJECTIVE
Hematopoietic stem cell homing and engraftment is dramatically altered by cytokine exposure. These studies address the molecular mechanisms responsible for the observed changes in transplantation biology.


METHODS
Primitive murine hematopoietic stem cells were isolated by fluorescence-activated cell sorting of lineage depleted (Lin(-)) cells exhibiting low staining of Hoechst 33342 and rhodamine 123 dyes or Lin(-) cells bearing Sca. Adhesion receptor expression was examined by immunofluorescence and reverse transcriptase polymerase chain reaction. In vitro adhesion assays were employed to define binding interactions between stem cells and stroma or extracellular matrix proteins.


RESULTS
Adhesion of Lin(-)Sca+ cells to Dexter stroma could be blocked by about 90% with antibodies to PECAM-1, alphaa(4), or beta(1), and partially blocked by antibodies to alpha(5), CD44, or L-selectin. By immunofluorescence, about 30% of purified Lin(-)Ho(lo)Rho(lo) cells expressed alpha(4), alpha(5), beta(1), and L-selectin, about 15% expressed alpha(L) and alpha(6), half expressed PECAM-1, and none expressed alpha(1) or alpha(2). After 48 hours in expansion cytokines, only 9% of the cells expressed alpha(4) and none expressed beta(1), whereas alpha(L) expression was fully restored, PECAM-1 and L-selectin partially restored, CD44 expression was newly induced, and adhesion to both fibronectin and laminin was reduced. Adhesion to purified collagen, fibronectin, or laminin enhanced expression of beta(1) integrins.


CONCLUSIONS
Expansion cytokines that move quiescent primitive hematopoietic stem cells into S phase markedly altered adhesion receptor expression and reduced their functional binding to extracellular matrix, which could reduce engraftment after transplant.
Berrios
V M
VM
Division of Gene Therapy, Department of Medicine, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
Dooner
G J
GJ
Nowakowski
G
G
Frimberger
A
A
Valinski
H
H
Quesenberry
P J
PJ
Becker
P S
PS
D000818:Animals; D001562:Benzimidazoles; D001853:Bone Marrow / Q000473:pathology; D002448:Cell Adhesion; D002453:Cell Cycle / Q000187:drug effects; D019070:Cell Lineage; D002465:Cell Movement / Q000187:drug effects; D003094:Collagen; D016207:Cytokines / Q000494:pharmacology; D005353:Fibronectins; D005456:Fluorescent Dyes; D005786:Gene Expression Regulation / Q000187:drug effects; D006085:Graft Survival; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects*; D018960:Hyaluronan Receptors / Q000032:analysis; D016023:Integrins / Q000096:biosynthesis / Q000235:genetics; D007375:Interleukin-1 / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D019041:L-Selectin / Q000032:analysis; D007797:Laminin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D019038:Platelet Glycoprotein GPIb-IX Complex; D011994:Recombinant Proteins / Q000494:pharmacology; D020112:Rhodamine 123; D013194:Staining and Labeling; D019089:Stem Cell Factor / Q000494:pharmacology; D017154:Stromal Cells / Q000166:cytology
D001562:Benzimidazoles; D016207:Cytokines; D005353:Fibronectins; D005456:Fluorescent Dyes; D018960:Hyaluronan Receptors; D016023:Integrins; D007375:Interleukin-1; D007377:Interleukin-3; D015850:Interleukin-6; D007797:Laminin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D019038:Platelet Glycoprotein GPIb-IX Complex; D011994:Recombinant Proteins; D019089:Stem Cell Factor; C094990:adhesion receptor; D019041:L-Selectin; D020112:Rhodamine 123; D003094:Collagen; C017807:bisbenzimide ethoxide trihydrochloride