Robust Revascularization, Despite Impaired VEGF Production, After Meniscus Allograft Transplantation in Rabbits

Background: Little is known about vascularization restoration and vascular circulation after allogenic graft transplantation, which are both important prerequisites for optimal use of allograft meniscus transplantation. Purpose: To study vascularization restoration through autograft and allograft meniscus models in Oryctolagus cuniculus. Study Design: Controlled laboratory study. Methods: Forty-eight rabbits at mature bone age were randomized to receive either an autograft or allograft after the meniscus of the left knee was completely resected. Vascularization, blood circulation, histological characteristics of the grafted meniscus and surrounding tissues, and vascular endothelial growth factor (VEGF) expression in the meniscus were assessed at 4, 8, and 12 weeks after allograft or autologous transplantation. Results: The grafted meniscus was in good condition and was well connected to the surrounding joint capsule, and no obvious damage of the joint cartilage at the tibial plateau was observed. Even though the revascularization pattern was similar in the 2 groups, the meniscus body showed vessel growth mainly at the adhesion margin for less than one-third of the meniscus transverse diameter, and no significant vascular distribution was found at the free margin. Blood circulation peaked after 8 weeks at the anterior and posterior horns and declined thereafter. This was mimicked by VEGF expression, which showed a progressive decrease with time, even though the vascular endothelial cells gradually increased over time. There were no statistical differences in the various assessments between the allograft and autograft groups. Conclusion: At 12 weeks after meniscus allografting, the vascular circulation had almost recovered and gradual reconstruction of cells and fibers had begun, mimicking similar observations in the autograft group. Clinical Relevance: Our data provide test reference for clinical rehabilitation after meniscus autograft.