Immobilization, stabilization, and activation of human stem cell factor (SCF) on fragmin/protamine microparticle (F/P MP)-coated plates.

Fragmin (low-molecular-weight heparin)/protamine microparticles (F/P MPs) immobilize to culture plates, thereby retaining the binding of heparin-binding cytokines such as human stem cell factor (SCF). The purpose of this study was to evaluate the ability of F/P MP-coating to immobilize, stabilize, and enhance SCF-activity. Cell assays showed that SCF and preimmobilized SCF on F/P MP-coated plates significantly stimulated the proliferation of human erythroleukemia cell line TF-1 in a concentration-dependent manner. Heparin and fragmin enhanced SCF-induced proliferation of chlorate-treated TF-1 cells, in which the biosynthesis of endogenous sulfated polysaccharides was blocked, on noncoated plates at a range of concentrations (2-8 microg/mL). However, heparin and fragmin had no effect on SCF-induced proliferation of chlorate-treated TF-1 cells on F/P MP-coated plates. The interaction of SCF with fragmin and F/P MPs prolonged the half-life of SCF bioactivity, and immobilized and protected SCF from inactivation, such as from heat and proteolysis. These results suggest that F/P MP-coated plates protect SCF and enhance its activity, and F/P MP-coating provides an excellent biomaterial to immobilize and retain heparin-binding cytokines, including SCF, in bioactive form for optimal expansion of hematopoietic cells.