Hyaluronan/Collagen Hydrogels with Sulfated Glycosaminoglycans Maintain VEGF₁₆₅ Activity and Fine-Tune Endothelial Cell Response

In order to restore the regeneration capacity of large-size vascularized tissue defects, innovative biomaterial concepts are required. Vascular endothelial growth factor (VEGF(165)) is a key factor of angiogenesis interacting with sulfated glycosaminoglycans (sGAG) within the extracellular matrix. As this interplay mainly controls and directs the biological activity of VEGF(165), we used chemically modified sGAG derivatives to evaluate the structural requirements of sGAG for controlling and tuning VEGF(165) function and to translate these findings into the design of biomaterials. The in-depth analysis of this interaction by surface plasmon resonance and ELISA studies in combination with molecular modeling stressed the relevance of the substitution position, degree of sulfation, and carbohydrate backbone of GAG. Acrylated hyaluronan (HA-AC)/collagen (coll)-based hydrogels containing cross-linked acrylated, sulfated hyaluronan (sHA-AC) derivatives with different substitution patterns or an acrylated chondroitin sulfate (CS-AC) derivative function as multivalent carbohydrate-based scaffolds for VEGF(165) delivery with multiple tuning capacities. Depending on the substitution pattern of sGAG, the release of biologically active VEGF(165) was retarded in a defined manner compared to pure HA/toll gels, which further controlled the VEGF(165)-induced stimulation of endothelial cell proliferation and extended morphology of cells. This indicates that sGAG can act as modulators of protein interaction profiles of HA/coll hydrogels. In addition, sHA-AC-containing gels with and even without VEGF(165) strongly stimulate endothelial cell proliferation compared to gels containing only CS-AC or HA-AC. Thus, HA/toll-based hydrogels containing cross-linked sHA-AC are biomimetic materials able to directly influence endothelial cells in vitro, which might translate into an improved healing of injured vascularized tissues.