Parametric computational modelling of melt electrowritten scaffolds: Predicting the cellular micromechanical environment for gradient tissue engineering in rotator cuff repair

Surgical interventions of the rotator cuff (RC) tendons are failing at unacceptably high rates. This is primarily due to clinical strategies failing to regenerate the biomechanical junction between bone and tendon (enthesis). Tissue engineering approaches for RC repair involve attempts at increasing the acute strength of the repair and directing the healing cascade to regenerate the enthesis. Advances in bioprinting, specifically melt-electrowriting (MEW) allow precise fabrication of microarchitectures. Our group has utilized the functionality MEW offers to create a novel, single-material, gradient scaffold that approaches the mechanical gradients present in the RC. To characterize this novel geometry, high-throughput, parametric finite element analysis (FEA) models were generated: 1) determine how tunable print parameters such as the radius (R) of curvature of fibers, the fiber diameter (FD), and the fiber spacing (FS) alter the gradient present in the scaffold’s architecture and 2) predict, at the cellular level, what strain the scaffold generates regionally to ‘instruct’ the local cell milieu to producing healthy tissues (e.g. bone, tendon). FEA models predicted that mechanical gradients in the scaffold approached gradient levels seen in the RC (~2 orders of magnitude). In which global strain gradients were driven by R. Additionally, our novel architecture significantly affected regional mechanics, which could be optimized for tenocyte and osteoblastic bioactivity. The data presented demonstrates a novel, tunable architecture capable of approaching biologically relevant gradients observed in the RC with potential to address the clinical problems associated with tendon-bone repairs in other regions of the body using only a single material.