Stem cell-attracting tissue engineered heart valve

Introduction: Currently available heart valve replacements are limited in long-term performance or fail due to lack of growth or remodeling potential. In order to address these issues, it is necessary to mimic multiple factors of the native valvular extracellular matrix (ECM) such as architecture, mechanical behavior and biochemical signals. Electrospinning is a suitable method to mimic the fibrous structure of the ECM1. For an easy translation into clinics, cell-free products with the potential of self-seeding are preferable. Circulating progenitor cells in the blood present the receptors CXCR4 as well as VEGFR2, which bind to stromal cell-derived factor 1 (SDF-1)2 and decorin3, respectively. Therefore, we aimed to generate a nature-mimicking scaffold via electrospinning and protein coating, which is able to attract circulating stem or progenitor cells from blood. Materials and methods: A polymeric scaffold was generated via electrospinning based on the structural and mechanical characteristics of native heart valve leaflets. After SDF-1 and decorin coating, the scaffolds were dynamically cultured on a shaker with a suspension of endothelial progenitor cells (EPCs). Protein mediated cell adhesion was determined using scanning electron microscopy and DAPI staining. EPC viability was assessed by applying a MTT-assay and flow cytometry analysis. Furthermore, immunostaining was used in order to visualize scaffold bound protein as well as to characterize adhered EPCs on the scaffolds. Results: Using electrospinning, we successfully generated a biocompatible polymeric scaffold, which showed similar structural and mechanical properties as porcine heart valve leaflets. Despite the high hydrophilicity, it was possible to functionalize the surface with SDF-1 and decorin. After a 2 day dynamic culture of EPCs in suspension, a significantly higher number of EPCs were detected on the coated scaffolds when compared to uncoated controls. The captured cells on the scaffold were viable since they metabolized MTT and were negative for 7-AAD, a dye that identifies dead cells. Furthermore, immunostaining confirmed CXCR4, VEGFR2, von Willebrand Factor and CD34 positive cells both, before and after substrate contact. These results indicate that SDF-1 and decorin are promising proteins to attract circulating EPCs. Discussion and conclusions: We successfully demonstrated that SDF-1 and the proteoglycan decorin are suitable proteins for EPC adhesion and therefore excellent for tissue engineered heart valve functionalization. The generated nature-mimicking polymeric scaffold coated with these proteins is a promising off-the shelf material with cell-capturing potential. Acknowledgments: This study was financially supported by a Fraunhofer-Gesellschaft internal program (Attract 692263 to KSL). Disclosure: The authors have nothing to disclose.