Graft integration in autologous costal cartilage transplantation: a long-term study using chondrocyte-laden fibrin gel

Purpose Mosaicplasty of articular cartilage can be performed using costal cartilage due to its structural similarity. This method has been successfully applied in clinical practice for small joints; however, its use in large joints is limited, partly due to graft displacement. In this study, we used chondrocyte-laden fibrin gel to improve integration in a rat model of autologous costal cartilage transplantation into a knee joint defect and assessed long-term outcomes.Methods Costal cartilage was characterized histologically, immunohistochemically, and biomechanically. Autologous grafts were harvested from the tenth rib and implanted into knee defects pretreated with chondrocyte-laden fibrin gel. Controls included cell-free fibrin gel, defect-only control, and sham-operated animals. Graft integration, subchondral bone resorption, and graft composition were analyzed at 1, 6, and 12 months using micro-CT, histology, and immunostaining.Results Costal cartilage demonstrated histological and biomechanical properties comparable to articular cartilage. Chondrocyte-laden fibrin gel did not significantly improve integration but reduced subchondral bone resorption, a preliminary finding consistent with an anti-inflammatory effect. Retained grafts restored joint congruity, integrated with host tissue, and showed no resorption or loss of hyaline cartilage markers over 12 months, despite age-related osteoarthritis changes in surrounding tissue.Conclusions Although chondrocyte-laden fibrin gel did not enhance graft integration, this study demonstrates long-term structural preservation of costal cartilage grafts in a rat knee defect model. Further studies in larger animals are needed to optimize integration strategies and support translation into clinical practice, potentially expanding treatment options for patients with limited donor tissue.