Micromechanical homogenisation of a hydrogel-filled electrospun scaffold for tissue-engineered epicardial patching of the infarcted heart

This study aimed at developing a formulation to link microscopic structure and macroscopic mechanics of a fibrous scaffold filled with a hydrogel for use as a tissue-engineered patch for local epicardial support of the infarcted heart. Mori-Tanaka mean field homogenisation, closed-cell foam mechanics and finite element (FE) methods were used to represent the macroscopic elastic modulus of the filled fibrous scaffold. The homogenised constitutive description of the scaffold was implemented for an epicardial patch in a FE model of a human cardiac left ventricle (LV) to assess effects of patching on myocardial mechanics and ventricular function in presences of an infarct. The macroscopic elastic modulus of the scaffold was predicted to be 0.287 MPa with the FE method and 0.290 MPa with the closed-cell model for the realistic fibre structure of the scaffold, and 0.108 and 0.540 MPa with mean field homogenization for randomly oriented and completely aligned fibres. Epicardial patching was predicted to reduce maximum myocardial stress in the infarcted LV from 19 kPa (no patch) to 9.5 kPa (patch), and to increase the ventricular ejection fraction from 40% (no patch) to 43% (patch). The predictions of the macroscopic elastic modulus of the realistic scaffold with the FE and the closed-cell model agreed well, and were bound by the mean field homogenisation prediction for random and fully aligned fibre orientation of the scaffold. This study demonstrates the feasibility of homogenization techniques to represent complex multiscale structural features in an simplified but meaningful manner.