Single-layer periosteum progenitor cell sheet significantly promotes tendon-bone healing in comparison with acellular collagen sheet in anterior cruciate ligament reconstruction

Purpose: Successful tendon-bone healing in anterior cruciate ligament reconstruction can be achieved by introducing a suitable medium into the tendon-bone junction. Two new feasible media, periosteum progenitor cell sheet (PPCS) and acellular collagen sheet (ACS), were utilized to promote tendon-bone healing. This study aimed to compare the effects of these two media on tendon-bone healing in a rabbit model. Methods: Periosteum progenitor cells were harvested from rabbit tibial periosteum, cultivated on polymerized fibrin-coated dishes, and obtained as PPCS. ACS was prepared from rabbit small intestinal submucosa. Twenty rabbits were used in this study. Tendon grafts wrapped in cell sheet were pulled into a bone tunnel in a model of anterior cruciate ligament reconstruction. Rabbits were sacrificed at 8 weeks postoperatively for histological, immunohistochemical, and biomechanical assay. Results: The monolayer PPCS that had been wrapped around the tendon before surgery was analysed. Histological staining revealed that PPCS gave rise to higher collagen and glycosaminoglycan deposition with fibrocartilage formation than ACS at the tendon-bone junction at 8 weeks. In addition, PPCS produced significantly better mechanical results compared with ACS, including increased maximum load, stiffness, and maximum load per length of bone tunnel. Conclusions: Single-layer PPCS significantly enhanced tendon-bone healing compared with ACS, with fibrocartilage formation at the tendon interface and superior biomechanical strength.