Graduate student University of Missouri - Columbia, United States
Introduction:: Valvular heart disease (VHD) is expected to cause 23.6 million deaths by 2030. Valve replacement is the primary treatment, but current valve replacements have limitations as they can't grow and remodel after implantation. Tissue-engineered heart valves (TEHVs) offer a promising alternative, but creating leaflet substrates that accurately mimic the trilayer extracellular matrix (ECM) and mechanical anisotropy of human native heart valve leaflets is challenging. If the substrates fail to replicate the properties of native leaflets, valvular interstitial cells (VICs) can become activated, and maladaptive remodeling can cause valve failure. In this study, we developed trilayer polycaprolactone (PCL)/poly(L-lactide-co-ε-caprolactone) (PLCL) substrates that have tensile properties, anisotropicity, and a trilayer structure with fiber orientations similar to native leaflet
Materials and Methods:: Trilayer PCL (control) and PCL/PLCL substrates were fabricated using the electrospinning technique with optimized parameters. We measured the hydrophobicity, chemical composition, crystallinity, and mechanical properties and assessed the structure of the trilayer PCL and PCL/PLCL substrates. Then, valvular interstitial cells (VICs) were seeded onto the trilayer PCL and PCL/PLCL substrates and cultured to produce the trilayer PCL and PCL/PLCL cell-cultured constructs. We evaluated and compared the constructs' mechanical properties, cell proliferation, cell viability, extracellular matrix (ECM) production, and cell gene expression to assess their suitability as heart valve leaflets.
Results, Conclusions, and Discussions:: We utilized electrospinning to produce trilayer PCL/PLCL substrates, using different polymer blends for the circumferential, radial, and random layers (Figure: a-d). Compared to PCL substrates, PCL/PLCL substrates had lower crystallinity and hydrophobicity but displayed native-like tensile properties, flexibility, and anisotropy. Specifically, the PCL/PLCL substrates exhibited comparable radial (1.23 ± 0.21 MPa) and circumferential (8.31 ± 0.81 MPa) tensile moduli to the radial (1.26 ± 0.30 MPa) and circumferential (8.33 ± 2.41 MPa) elastic moduli of native aortic valve leaflets (Figure: e). Additionally, the PCL/PLCL constructs exhibited 11% more cells, 22% more collagen, and 35% more GAG than the PCL constructs (Figure: f-g). The increased gene expression of ECM growth markers and growth factors by the valvular interstitial cells (VICs) in the PCL/PLCL constructs indicated a higher number of cells in a growth state than those in the PCL constructs.
In this study, trilayer PCL/PLCL substrates were produced through electrospinning and optimized to mimic the structural, tensile, and anisotropic properties of native aortic valve leaflets. Compared to the PCL substrates, the PCL/PLCL substrates exhibited lower hydrophobicity, which facilitated better cell adhesion. After cell culture, the resulting PCL/PLCL cell-cultured constructs maintained their mechanical anisotropy and flexural properties similar to the PCL/PLCL original substrate and native leaflets. Additionally, the PCL/PLCL constructs showed higher levels of cell proliferation, infiltration, ECM production, and superior gene expression of critical markers for cell growth compared to the PCL constructs.
