Fragmin/protamine microparticles as cell carriers to enhance viability of adipose-derived stromal cells and their subsequent effect on in vivo neovascularization.

Abstract

We prepared fragmin/protamine microparticles (F/P MPs) as cell carriers to enhance cell viability. Use of material consisting of a low-molecular-weight heparin (fragmin) mixed with protamine resulted in water-insoluble microparticles (about 0.5-1 microm in diameter). In this study, we investigated the capability of F/P MPs to enhance the viabilities of human microvascular endothelial cells (HMVECs), human dermal fibroblasts (fibroblasts), and adipose tissue-derived stromal cells (ATSCs) in suspension culture. F/P MPs were bound to the surfaces of these cells, and the interaction of these cells with F/P MPs induced cells/F/P MPs-aggregate formations in vitro, and maintained viabilities of those cells for at least 3 days. The ATSCs/F/P MPs-aggregates adhered to and grew on suspension culture plates in a fashion similar to those on type I collagen-coated plates. The cultured ATSCs secreted significant amounts of angiogenic heparin-binding growth factors such as FGF-2. When the ATSCs/F/P MPs-aggregates were subcutaneously injected into the back of nude mice, significant neovascularization and fibrous tissue formation were induced near the site of injection from day 3 to week 2. The ATSCs/F/P MPs-aggregates were thus useful and convenient biomaterials for cell-therapy of angiogenesis.