Abstract 12558: Treatment of Limb Ischemia Using Hydrogels With Tunable Mechanical Properties for Endothelial Cell Transplantation

IntroductionPeripheral arterial disease (PAD) affects over 8 million people in the US. It is associated with narrowing the peripheral arteries and restricts the blood flow to peripheral limbs. Cell-based approaches to enhance revascularization by delivery of therapeutic endothelial cells are promising, but are limited by low transplant viability.HypothesisSince extracellular matrix (ECM) interactions are critical to cell survival and function, we hypothesized that optimal mechanical properties of the ECM can modulate endothelial survival and angiogenic function.MethodsA family of engineered elastin-like proteins (ELP) was developed using recombinant protein technology. Three-dimensional (3D) ELP-polyethylene glycol (PEG) hydrogels were fabricated with interacting hydrazine-modified ELP with either aldehyde- or benzaldehyde-modified PEG (PEG-ALD or PEG-BZA), resulting in hydrogels with independently tunable mechanical stiffness and stress relaxation rates. We characterized the elastic modulus and stress relaxation rates of RGD-ELP/PEG-BZA and RGD-ELP/PEG-ALD by dynamic oscillatory rheology. Human umbilical vein endothelial cells were encapsulated within 3D gels for 7 days for cell viability by confocal fluorescence imaging.ResultsRheology measurements of the RGD-ELP/PEG-BZA and RGD-ELP/PEG-ALD hydrogels demonstrated a storage modulus of 850 and 1300Pa, respectively. Measurement of stress relaxation rate showed significantly higher rate (>2x) in RGD-ELP/PEG-ALD compared to RGD-ELP/PEG-BZA. Live/Dead cell viability assay demonstrated that both hydrogels could support high cell viability (>90%) at 7 days. However, cell spreading increased in RGD-ELP/PEG-BZA hydrogels and tubular networks appeared inside the gels, whereas the cells did not form elongated morphology in RGD-ELP/PEG-ALD hydrogels, suggesting that a lower stress relaxation rate and storage modulus (~850Pa) improved the formation of endothelial cell network.ConclusionsInjectable ELP/PEG-ALD/BZA has controllable mechanical stiffness, stress relaxation rate and bioactivity, which all make this hydrogel system a promising candidate for cell transplantation in tissue regeneration.