ABSTRACT
The chemokine stromal-derived factor-1 (SDF-1) controls many aspects of stem cell function. Details of its regulation and sites of production are currently unknown. We report that in the bone marrow, SDF-1 is produced mainly by immature osteoblasts and endothelial cells. Conditioning with DNA-damaging agents (ionizing irradiation, cyclophosphamide, and 5-fluorouracil) caused an increase in SDF-1 expression and in CXCR4-dependent homing and repopulation by human stem cells transplanted into NOD/SCID mice. Our findings suggest that immature osteoblasts and endothelial cells control stem cell homing, retention, and repopulation by secreting SDF-1, which also participates in host defense responses to DNA damage.
Subject(s)
Chemokines, CXC/genetics , DNA Damage , Stem Cells/metabolism , Animals , Bone Marrow Cells/cytology , Bone Marrow Cells/metabolism , Cell Line , Cells, Cultured , Chemokine CXCL12 , Cyclophosphamide/pharmacology , Dose-Response Relationship, Radiation , Endothelium, Vascular/cytology , Endothelium, Vascular/metabolism , Flow Cytometry , Fluorouracil/pharmacology , Gene Expression Regulation/drug effects , Gene Expression Regulation/radiation effects , Humans , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, SCID , Osteoblasts/cytology , Osteoblasts/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Stem Cells/cytology , Tumor Cells, CulturedABSTRACT
Hematopoietic stem cell homing and engraftment require several adhesion interactions, which are not fully understood. Engraftment of nonobese/severe combined immunodeficiency (NOD/SCID) mice by human stem cells is dependent on the major integrins very late activation antigen-4 (VLA-4); VLA-5; and to a lesser degree, lymphocyte function associated antigen-1 (LFA-1). Treatment of human CD34(+) cells with antibodies to either VLA-4 or VLA-5 prevented engraftment, and treatment with anti-LFA-1 antibodies significantly reduced the levels of engraftment. Activation of CD34(+) cells, which bear the chemokine receptor CXCR4, with stromal derived factor 1 (SDF-1) led to firm adhesion and transendothelial migration, which was dependent on LFA-1/ICAM-1 (intracellular adhesion molecule-1) and VLA-4/VCAM-1 (vascular adhesion molecule-1). Furthermore, SDF-1-induced polarization and extravasation of CD34(+)/CXCR4(+) cells through the extracellular matrix underlining the endothelium was dependent on both VLA-4 and VLA-5. Our results demonstrate that repopulating human stem cells functionally express LFA-1, VLA-4, and VLA-5. Furthermore, this study implies a novel approach to further advance clinical transplantation.
Subject(s)
Chemokines, CXC/pharmacology , Endothelium, Vascular/physiology , Hematopoietic Stem Cell Transplantation , Hematopoietic Stem Cells/physiology , Integrins/physiology , Lymphocyte Function-Associated Antigen-1/physiology , Receptors, Fibronectin/physiology , Receptors, Lymphocyte Homing/physiology , Stromal Cells/physiology , Transplantation, Heterologous/immunology , Animals , Antibodies/pharmacology , Antigens, CD34 , Cell Adhesion , Cells, Cultured , Chemokine CXCL12 , Chemotaxis , Fetal Blood/cytology , Hematopoietic Stem Cells/drug effects , Hematopoietic Stem Cells/immunology , Humans , Infant, Newborn , Integrin alpha4beta1 , Integrin beta1/physiology , Integrins/antagonists & inhibitors , Lymphocyte Function-Associated Antigen-1/immunology , Mice , Mice, Inbred NOD , Mice, SCID , Models, Biological , Receptors, Fibronectin/antagonists & inhibitors , Receptors, Lymphocyte Homing/antagonists & inhibitorsABSTRACT
Stem cell homing and repopulation are not well understood. The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 were found to be critical for murine bone marrow engraftment by human severe combined immunodeficient (SCID) repopulating stem cells. Treatment of human cells with antibodies to CXCR4 prevented engraftment. In vitro CXCR4-dependent migration to SDF-1 of CD34+CD38-/low cells correlated with in vivo engraftment and stem cell function. Stem cell factor and interleukin-6 induced CXCR4 expression on CD34+ cells, which potentiated migration to SDF-1 and engraftment in primary and secondary transplanted mice. Thus, up-regulation of CXCR4 expression may be useful for improving engraftment of repopulating stem cells in clinical transplantation.