Cell therapy for the treatment of cardiovascular disease has been hindered by low cell engraftment, poor survival, and inadequate phenotype and function. In this study, we added chitosan to a previously developed injectable collagen matrix, with the aim of improving its properties for cell therapy and neovascularization. Different ratios of collagen and chitosan were mixed and chemically crosslinked to produce hydrogels. Swell and degradation assays showed that chitosan improved the stability of the collagen hydrogel. In culture, endothelial cells formed significantly more vascular-like structures on collagen–chitosan than collagen-only matrix. While the differentiation of circulating progenitor cells to CD31+ cells was equal on all matrices, vascular endothelial-cadherin expression was increased on the collagen–chitosan matrix, suggesting greater maturation of the endothelial cells. In addition, the collagen–chitosan matrix supported a significantly greater number of CD133+ progenitor cells than the collagen-only matrix. In vivo, subcutaneously implanted collagen–chitosan matrices stimulated greater vascular growth and recruited more von Willebrand factor (vWF+) and CXCR4+ endothelial/angiogenic cells than the collagen-only matrix. These results indicate that the addition of chitosan can improve the physical properties of collagen matrices, and enhance their ability to support endothelial cells and angiogenesis for use in cardiovascular tissue engineering applications.

Background-Blood-derived circulatory angiogenic cells (CACs) and resident cardiac stem cells (CSCs) have both beenshown to improve cardiac function after myocardial infarction. The superiority of either cell type has long been an area of speculation with no definitive head-to-head trial. In this study, we compared the effect of human CACs and CSCs, alone or in combination, on myocardial function in an immunodeficient mouse model of myocardial infarction. Methods and Results-CACs and CSCs were cultured from left atrial appendages and blood samples obtained from patients undergoing clinically indicated heart surgery. CACs expressed a broader cytokine profile than CSCs, with 3 cytokines in common. Coculture of CACs and CSCs further enhanced the production of stromal cell-derived factor-1α and vascular endothelial growth factor (P≤0.05). Conditioned media promoted equivalent vascular networks and CAC recruitment with superior effects using cocultured conditioned media. Intramyocardial injection of CACs or CSCs alone improved myocardial function and reduced scar burdens when injected 1 week after myocardial infarction (P≤0.05 versus negative controls). Cotransplantation of CACs and CSCs together improved myocardial function and reduced scar burdens to a greater extent than either stem cell therapy alone (P≤0.05 versus CAC or CSC injection alone). Conclusions-CACs

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