oa Biphasic nanofibrillar matrices for valve tissue engineering

Our strategy for heart valve tissue engineering uses autologous cells to populate appropriate template matrices.The goal is to create a suitable scaffold supporting proper cell growth while reproducing the specific mechanical properties of native heart valves extracellular matrix (ECM). Accordingly, aligned and non-aligned nanofibrillar structures of different porosities were prepared and evaluated with regards to their mechanical properties and their ability to support human adipose derived stem cell (hADSC) colonization and growth. Nanofibrillar structures were obtained by jet-spraying poly (ε-caprolactone) dissolved in chloroform at different concentrations (0.0733, 0.0833 and 0.1033 mg/ml). Morphological evaluations of the structures were performed using scanning electron microscopy and porosity calculated. hADSCs (600,000) were top and rotary seeded on nanofibrillar discs (diameter 1 cm and thickness 0.8 mm) and cultured in 10 ml of complete medium under rotation (10 rpm) for 20 days. Histology (DAPI staining) and DNA quantification characterized the resulting cellularized structures. Jet-spraying polymers resulted in biphasic structures composed of both a dense and a nanofibrillar layer (Fig. 1-A). The nanofibers could either be of random orientation (isotropic) or well aligned (anisotropic). Isotropic matrices showed an increase in porosity when increasing polymer solution (96 to 97 %). Mechanical properties were inversely related to matrice porosities. Anisotropic matrices were stiffer than isotropic ones (elastic modulus up to 22 and 2 MPa respectively). hADSC proliferated significantly over 20 days within the scaffolds (up to 5-fold DNA increase), regardless of structure and porosity. The constructs dense polymer layer was favored by the cells up to 10 culture days, but after 20 days, the cells tended to bridge the entire scaffolds thicknesses (Fig. 1-B). This study highlights the potential of biphasic nanofibrillar matrices as substrate for valve engineering, particularly with regards to their elevated mechanical properties and capacity to support cellular population and proliferation.