An interfacial hydrogel compartment within a multicompartment tendon-to-bone scaffold influences cell behavior under cyclic tensile loading

Abstract Injuries to spatially graded insertional tissues such as the tendon-to-bone enthesis in the rotator cuff present unique challenges for regenerative engineering. To address these, tissue engineering approaches are increasingly considering the use of biomaterials that display spatially graded properties to mimic aspects of the tendon, bone, and connecting fibrocartilage enthesis zones. Mechanical loading introduces an additional opportunity to locally deliver disparate mechanical signals to cells across a biomaterial that contains spatial changes in composition, structure, or mechanical properties. Here, we demonstrate the significance of in vitro mechanical stimulation via a cyclic tensile strain bioreactor on progenitor cell activity in a collagen scaffold that contains tendon and bone specific compartments linked by a continuous gelatin hydrogel interface. We demonstrate that inclusion of a hydrogel interfacial architecture modulates local patterns of strain across the biomaterial as well as differences in mesenchymal stem cell activity, secretion of pro-regenerative cytokines, and expression of enthesis-associated genes. Further, we report region-specific shifts in gene expression in response to mechanical loading, presence of a hydrogel interface, and their cross-interaction. Broadly, these findings demonstrate the importance of considering mechanical stimulation when designing spatially graded biomaterials for regeneration of interfacial tissue, such as the tendon-to-bone enthesis, providing insight into how environmental factors and material design can shape spatial and temporal trajectories of pro-regenerative activity.