(131b) Bioactive 3d Gel Matrices in Tissue Engineering

Cellular behavior differs in three dimensions from that in two dimensions in multiple ways, including in complicated physiological processes such as stem cell differentiation and tissue regeneration. Our group has developed two such scaffolds for studies of cellular differentiation and application in tissue engineering and regenerative medicine. In one hydrogel scaffold material, fibrin gels are used as a scaffold, and exogenous bioactive materials are grafted into the scaffold during coagulation under the enzymatic activity of factor XIIIa; the exogenous biomolecules are either synthesized or expressed as fusion peptides or proteins with a domain that acts as a substrate for this enzyme. This can be carried out with growth factors (engineered variants of vascular endothelial growth factor, VEGF, will be shown) or with adhesion ligands (engineered variants of the 9th and 10th type-III repeat of fibronectin, containing the RGD and PHSRN sequences respectively, will be shown). In a second approach, one leading to hydrogel scaffolds that are completely synthetic, chemically reactive polyethylene glycol) (PEG) is formed by vinylsulfide functionalization. Peptides are synthesized with a matrix-metalloproteinase (MMP) substrate flanked by cysteine residues, and mixture of the two components results in formation of a crosslinked hydrogel, comprising multifunctional PEG crosslinked by MMP-sensitive peptides. Cysteine-containing adhesion peptides can be crosslinked into the system by incorporation as a comonomer. Cells are able to migrate within these three-dimensional scaffolds by locally degrading the matrix via membrane-localized MMPs. The use of such materials in mesenchymal stem cell differentiation and bone regeneration will be shown.