Autologous living chondrocytes contained in the meniscal matrix play an important role in in vivo meniscus regeneration induced by in situ meniscus fragment implantation

Introduction: Implantation of autogenous meniscal fragments wrapped with a fascia sheath significantly enhances fibrocartilage regeneration in vivo in defect cases at 12 weeks after implantation. The specific effects of the implanted autologous living chondrocytes and meniscal matrix have not been elucidated, however. The aim of this study was to clarify the role of autologous living chondrocytes contained in the meniscal matrix in in vivo meniscus regeneration induced by in situ meniscus fragment implantation. Hypothesis: Implantation of meniscus fragments containing autologous living chondrocytes may result in significant in vivo meniscus regeneration. Materials and methods: Seventy-five rabbits were used in this study. A partial meniscectomy of the anterior one-third of the medial meniscus including the part of the anterior horn was performed. The rabbits were divided into 3 groups. In Group I, no treatment was applied to the defect. In Group II, the autogenous meniscal fragments devitalized by freeze-thaw treatment were reimplanted into the defect. In Group III, the autogenous meniscal fragments were reimplanted. In each group, the defect was covered with a fascia. Five rabbits from each group were subjected to morphologic and histologic evaluations at 3, 6, and 12 weeks, and 5 rabbits from each group were subjected to biomechanical evaluations at 6 and 12 weeks. Results: Histologically, no cells were seen in the grafted meniscal fragments at 3 weeks in Group II, whereas chondrocytes in the grafted meniscal fragments were alive at 3 weeks in Group III. Histologic and biomechanical data for Group II were slightly but significantly better than those of Group I at 12 weeks after implantation (p = 0.007 and p = 0.002, respectively), whereas the data for Group III were significantly superior to those of Groups I and II at 12 weeks (p < 0.0014 and p < 0.0029, respectively). Discussions: Grafted autologous living chondrocytes contained in the meniscal matrix play an important role in in vivo meniscus regeneration induced by in situ meniscus fragment implantation. Study design: II, Controlled laboratory study. (C) 2019 Elsevier Masson SAS. All rights reserved.