The potential of anisotropic matrices as substrate for heart valve engineering

Cells environment is increasingly recognized as an important function regulator through cell-matrix interactions. Extracellular matrix (ECM) anisotropy being a key component of heart valves properties, we have devised a method to create highly porous anisotropic nanofibrillar scaffolds and studied their suitability as cell-support and interactions with human adipose derived stem cells (hADSCs) and human valve interstitial cells (hVICs). Anisotropic nanofibrillar scaffolds were produced by a modified jet-spraying method that allows the formation of aligned nanofibres (600 nm) through air-stream diffraction of a polymer solution (poly (ε-caprolactone, PCL) and collection onto a variably rotating drum. The resulting matrices of high porosity (99%) mimicked valve mechanical anisotropy. Dynamically seeded hADSC and hVIC cultured on scaffolds up to 20 days revealed that hADSC and hVIC penetration within the matrices was improved by anisotropic organization. Within 10 days, cells populated the entire scaffolds thickness and produced ECM (collagen I, III and elastin). As a result, mechanical properties of the constructs were improved over culture, while remaining anisotropic. In contrast to isotropic matrices, anisotropy induced elongated hADSCs and hVICs morphology that followed nanofibres orientation. Interestingly, these morphological changes did not induce hADSC differentiation towards the mesoderm lineages while hVIC recovered a physiological phenotype over culture in the biomimetic matrices. Overall, this study indicates that highly porous anisotropic jet-sprayed matrices are interesting candidates for valve tissue engineering, through anisotropic mechanical properties, efficient cell population, conservation of stem cells phenotype and recovery of hVIC physiological phenotype.