Tissue-engineered mitral valve: morphology and biomechanics †

OBJECTIVES: The present study aimed at developing tissue-engineered mitral valves based on cell-free ovine mitral allografts. METHODS: The ovine mitral valves (OMVs) (n= 46) were harvested in the local slaughter house. They were decellularized using detergent solutions and DNase. The effectiveness of decellularization was assessed by histological (haematoxylin-eosin, Movat’s pentachrome) and immunofluorescent staining (for DNA and α-Gal), and DNA-quantification. To reveal the receptiveness of decellularized tissue to endothelial cells (ECs), the valve leaflets were reseeded with ovine ECs, derived from endothelial progenitor cells in vitro. For assessment of biomechanical properties, uniaxial tensile tests were carried out. RESULTS: Histology and immunofluorescent staining revealed absence of cell nuclei in decellularized leaflets, chordae and papillary muscles. According to the software for immunofluorescence analysis, reduction in DNA and α-Gal was 99.9 and 99.6%, respectively. DNAquantification showed 71.2% reduction in DNA content without DNase and 96.4% reduction after DNase treatment. Decellularized leaflets were comparable with native in ultimate tensile strain (native, 0.34 ± 0.09 mm/mm, vs decellularized, 0.44 ± 0.1 mm/mm; P= 0.09), and elastin modulus (native, 0.39 ± 0.27, vs decellularized, 0.57 ± 0.55, P= 0.46), had increased ultimate tensile stress (native, 1.23 ± 0.35 MPa, vs decellularized 2.12 ± 0.43 MPa; P= 0.001) and collagen modulus (native, 5.5 ± 1.26, vs decellularized, 8.29 ± 2.9; P= 0.04). After EC seeding, immunofluorescent staining revealed a monolayer of CD31-, eNOS- and vWF-positive cells on the surface of the leaflet, as well as a typical cobble-stone morphology of those cells.