Tendon repair is limited by the availability of replacement alternatives that adequately regenerate a tendon to its native biological and mechanical state. Tissue engineering strategies offer alternatives for successful tendon reconstruction. One approach has been the in vitro development of a functional tendon alternative utilizing natural extracellular matrices (bioscaffolds) seeded with exogenous cells. Functional replacements can be developed in vitro if appropriate biochemical and physical stimuli are present in the tissue culture environment. In this work we have investigated the effect of in vitro mechanical conditioning on small-intestine submucosa (SIS) augmented with primary tendon cells (tenocytes).

To achieve our objectives, the laboratory’s existing bioreactor reactor system was redesigned to increase oxygen delivery. To address oxygen transport limitations in long-term in vitro cultures, a mathematical model of oxygen diffusion through a cell-seeded scaffold was developed. From the model and experimental oxygen diffusivity data for several natural extracellular matrices, a practical limit on the size of cell-seeded constructs to be cultured long term in vitro was made. This estimate was then used to generate constructs for our loading experiments. In vitro cyclic loading significandy increased the biomechanical properties (e.g. stiffness) of cell-seeded SIS constructs (129.1 ± 10.2%) as compared to cyclic load constructs without cells (33.9 ± 13.8%) and no load or static load constructs (with or without cells) (-5.7 ± 10.7%, -7.5 ± 11.3%, 34.0 ± 15.2%, 33.4 ± 10.7% respectively). Using the mechanical loading regime from this work as a basis, alternate in vitro loading paradigms, cell types (e.g. mesenchymal stem cells), and growth factor conditioning could be explored as a means to further improve SIS construct mechanical properties.