Matrix Glycoproteins May Regulate the Local Concentrations of Different Hemopoietic Growth Factors
We compared the binding properties of granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin (epo) and interleukin-3 (IL-3) to test the hypothesis that binding to extracellular matrix (ECM) governs growth factor distribution in the marrow microenvironment. Since mitogens for cells of mesodermal and neuroectodermal origin bind to heparin , heparin-like molecules (e.g. heparan sulphate) are candidate growth factor-binding structures in the ECM associated with marrow-derived stromal cells. In contrast to the heparin-binding fibroblast growth factor (FGF), GM-CSF did not bind to heparin-sepharose beads. However, most recombinant (r), human (h), gibbon (g) and murine (m) IL-3 bound to the beads; intermediate levels of binding were shown by epo and native mIL-3. Like GM-CSF , epo and h/gIL-3 did not bind to intact marrow-derived stromal layers but more than 85% of mIL-3 (native and recombinant) bound under these conditions. Murine IL-3 and GM-CSF  bind to marrow-derived ECM but epo does not. The different binding properties of haemopoietic growth factors vis-a-vis matrix glycoproteins suggests that their distributions and concentrations may be determined by the local composition of the ECM.
KeywordsHeparan Sulphate Stromal Layer Bone Marrow Cell Culture Haemopoietic Cell Haemopoietic Growth Factor
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