Recent observations have demonstrated that Insulin-like Growth Factors (IGFs) are able to form complexes with the extracellular matrix protein Vitronectin (VN). These complexes of VN:IGFBP:IGF-I significantly enhance the proliferation and migration of various cell lines including skin and corneal epithelial cells, as well as primary cells derived from human skin and corneal tissue. These enhanced effects arise from co- activation of the IGF-binding type-1 IGF receptor (IGF-1R) as well as activation of the VN-binding αv-integrins. Further studies suggest that these complexes can replace the requirement for serum in the ex vivo expansion of cells. In order to translate the VN:IGFBP:IGF-I technology into techniques for the improved culture of cells, we have designed, expressed and purified synthetic chimeric molecules, consisting of various domains of VN and mature IGF-I, using a baculovirus based expression system. The recombinant VN:IGF-I (rVN:IGF-I) chimeras were secreted into conditioned media of transfected Sf9 insect cells. Purification of the chimeras was achieved via methods including heparin-sepharose chromatography, Q-sepharose ion-exchange chromatography and Ni2+-NTA affinity chromatography. The rVN:IGF-I chimeras were detectable by Western blot analysis using a poly-clonal anti-VN antibody. Functional characterisation studies indicate that the chimeras promote cellular growth and migration to a similar extent as the VN:IGFBP:IGF-I complexes at 10x and 30x molar ratios. Additionally, function blocking antibodies directed to the IGF-1R and the VN binding αv-integrin were able to abolish this effect indicating that co-activation of these receptors is critical to the migratory effect of the chimeras. A functional chimera may lead to the development of cell culture techniques and methodologies that are devoid of xenogeneic or allogeneic support systems, thus paving the way to approved tissue engineering therapeutics that incorporate ex vivo expanded adult stem and progenitor cells
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