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A principal challenge in wound healing is a lack of cell recruitment, cell infiltration, and vascularization, which occurs in the absence of temporal and spatial cues. We hypothesized that a scaffold that expands due to local changes in pH may alter oxygen and nutrient transport and the local cell density, leading to enhanced cell deposition and survival. In this study, we present a pH-responsive scaffold that increases oxygen transport, as confirmed by our finite element model analysis, and cell proliferation relative to a non-responsive scaffold. In vivo, responsive scaffolds induce a pro-healing gene expression profile indicative of enhanced angiogenesis, granulation tissue formation, and tissue remodeling. Scaffolds that stretch in response to their environment may be a hallmark for tissue regeneration.

Background RNAi technology is a promising tool for gene therapy of vascular disease. However, the biological heterogeneity between endothelial (EC) and vascular smooth muscle cells (SMC) and within different vascular beds make them differentially susceptible to siRNA. This is further complicated by the task of choosing the right transfection reagent that leads to consistent gene silencing across all cell types with minimal toxicity. The goal of this study was to investigate the intrinsic RNAi susceptibility of primary human aortic and coronary artery endothelial and vascular smooth muscle cells (AoEC, CoEC, AoSMC and CoSMC) using adherent cell cytometry. Methods Cells were seeded at a density of 5000 cells/well of a 96well plate. Twenty four hours later cells were transfected with either non-targeting unlabeled control siRNA (50 nM), or non-targeting red fluorescence labeled siRNA (siGLO Red, 5 or 50 nM) using no transfection reagent, HiPerFect or Lipofectamine RNAiMAX. Hoechst nuclei stain was used to label cells for counting. For data analysis an adherent cell cytometer, Celigo was used. Results Red fluorescence counts were normalized to the cell count. EC displayed a higher susceptibility towards siRNA delivery than SMC from the corresponding artery. CoSMC were more susceptible than AoSMC. In all cell types RNAiMAX was more potent compared to HiPerFect or no transfection reagent. However, after 24 h, RNAiMAX led to a significant cell loss in both AoEC and CoEC. None of the other transfection conditions led to a significant cell loss. Conclusion This study confirms our prior observation that EC are more susceptible to siRNA than SMC based on intracellular siRNA delivery. RNAiMax treatment led to significant cell loss in AoEC and CoEC, but not in the SMC populations. Additionally, this study is the first to demonstrate that coronary SMC are more susceptible to siRNA than aortic SMC.