Enthesis Healing Is Dependent on Scaffold Interphase Morphology-Results from a Rodent Patellar Model

The use of multiphasic scaffolds to treat injured tendon-to-bone entheses has shown promising results in vitro. Here, we used two versions of a biphasic silk fibroin scaffold to treat an enthesis defect created in a rat patellar model in vivo. One version presented a mixed transition between the bony and the tendon end of the construct (S-MT) while this transition was abrupt in the second version (S-AT). At 12 weeks after surgery, the S-MT scaffold promoted better healing of the injured enthesis, with minimal undesired ossification of the insertion area. The expression of tenogenic and chondrogenic markers was sustained for longer in the S-MT-treated group and the tangent modulus of the S-MT-treated samples was similar to the native tissue at 12 weeks while that of the S-AT-treated enthesis was lower. Our study highlights the important role of the transition zone of multiphasic scaffolds in the treatment of complex interphase tissues such as the tendon-to-bone enthesis.