Proteoglycans guide SDF-1-induced migration of hematopoietic progenitor cells

Stromal cell-derived factor-1 (SDF-1) is a chemoattractant involved in hematopoietic progenitor cell (HPC) trafficking to the bone marrow. We studied the role of bone marrow endothelial proteoglycans (PGs) in SDF-1-mediated migration of HPC using a transwell assay. A subclone of progenitor cell line KG-1 (KG-1v) was used, displaying CXCR4-dependent transmigration. Cell surface PGs on bone marrow endothelial cell line 4LHBMEC did not mediate SDF-1-induced transendothelial migration. In contrast, transwell filters precoated with various glycosaminoglycans (GAGs) enhanced migration toward SDF-1. SDF-1-induced migration was reduced by degradation of heparan sulfate in subendothelial matrix produced by 4LHBMEC. The stimulating effect of GAGs was caused by the formation of a stable haptotactic SDF-1 gradient, as SDF-1 bound to immobilized GAGs and triggered migration. Soluble heparan sulfate enhanced SDF-1-induced migration dose-dependently, suggesting that SDF-1-heparan sulfate complexes optimized SDF-1 presentation. In conclusion, we provide evidence that PGs in the subendothelial matrix establish an SDF-1 gradient guiding migrating HPC into the bone marrow.