Electrospun Elastomeric Leaflet Substrates that Structurally and Mechanically Mimic Human Aortic Valve Leaflets

Abstract

Creating leaflet substrates that accurately mimic the trilayered structure, anisotropic tensile characteristics, and elastomeric features of native human heart valve leaflets is essential to the success of heart valve tissue engineering. Earlier leaflet substrates have successfully replicated the mechanical properties of animal (porcine) heart valve leaflets. However, not one of them has been able to simultaneously replicate the trilayered structure and the highly anisotropic and elastomeric mechanical properties of human aortic heart valve leaflets. In this study, we employed a combination of polymers – polycaprolactone (PCL), poly(trimethylene carbonate-co-l-lactide) (PTMC-LA), and poly(trimethylene carbonate-co-caprolactone) (PTMC-CL) – in an electrospinning system to create elastomeric trilayer PCL/PTMC leaflet substrates that possess mechanical, flexural, and anisotropic properties similar to those of human native heart valve leaflets. We then compared these substrates with non-elastomeric trilayer PCL leaflet substrates to determine their effect on leaflet tissue engineering. Porcine valvular interstitial cells (PVICs) were cultured on these substrates for 1 month in static conditions to develop trilayer PCL and PCL/PTMC cell-cultured constructs. The PCL/PTMC substrates exhibited lower crystallinity and hydrophobicity than the PCL substrate, resulting in better cell adhesion and infiltration. The PCL/PTMC substrates demonstrated significantly greater cell proliferation, extracellular matrix production, and preferable gene and protein expression than the PCL substrates. Furthermore, in an osteogenic environment, the PCL/PTMC substrates showed superior resistance to calcification compared to the PCL substrates. The development of trilayer PCL/PTMC substrates with mechanical and structural characteristics resembling native tissue enhances leaflet tissue engineering.