1. ¹Department of Hematology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands
2. ²Department of Molecular Cell Biology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands
3. ³CLB, Sanquin Blood Supply Foundation, and Laboratory for Experimental and Clinical Immunology, Amsterdam, The Netherlands

Correspondence: A M Dräger, Department of Hematology, BR246, Vrije Universiteit Medical Center, PO Box 7057, 1007 MB Amsterdam, The Netherlands; Fax: (31)-20-4442601

Received 26 October 2001; Accepted 1 July 2002.

Abstract

Recognition events between hematopoietic progenitor cells (HPC) and bone marrow endothelial cells (BMEC) initiate homing of HPC to the bone marrow. The chemokine SDF-1 is present on BMEC and plays a crucial role in bone marrow engraftment. We studied the role of proteoglycans (PGs) on BMEC in binding and presentation of SDF-1. SDF-1 mRNA was present in three human BMEC cell lines. Competition experiments showed that ¹²⁵I-SDF-1 binding to the BMEC cell line 4LHBMEC was inhibited by heparins, heparan sulfate (HS) intestinal mucosa, chondroitin and dermatan sulfate (CS/DS), but not by HS bovine kidney. Pretreatment of 4LHBMEC with glycosaminoglycan (GAG)-degrading enzymes or sodium chlorate demonstrated that SDF-1 bound to both HSPGs and CS/DSPGs in a sulfation-dependent manner, as determined with an SDF-1 antibody recognizing the CXCR4-binding site. 4LHBMEC bound four-fold more SDF-1 than HUVEC. Isolated endothelial PGs did not bind SDF-1 in a filter or microplate-binding assay, suggesting the necessity of membrane association. In flow adhesion experiments, endothelial arrest of CXCR4⁺ KG-1 and not of CXCR4^- KG-1a cells increased significantly when SDF-1 was presented on 4LHBMEC. In conclusion, SDF-1 is produced by BMEC and binds to the BMEC cell surface via HS and CS/DS-GAGs, thereby presenting its CXCR4 binding site to HPC contributing to their arrest.