gms | German Medical Science

Objectives: Large meniscal defects or loss of meniscus substance after subtotal meniscectomies are still a problem in traumatology and predisposes the knee for early onset of osteoarthritis. Meniscal substitutes e.g. on a polyurethane basis are already in clinical use to replace lost parts of the meniscus. However there is still a lack of information about the timeline and quality of remodeling of these meniscal substitutes and the repair tissue. The aim of this study was to enhance the quality of meniscal healing by biological augmentation of a polyurethane scaffold with mesenchymal stem cells in a Tissue Engineering approach.

Methods: A full size meniscal defect was created by resection of the complete pars intermedia of the lateral menisci of New Zealand White Rabbits according to a published and validated animal model. The defects were treated by a polyurethane scaffold loaded with autologous mesenchymal stem cells without preculture of the cell matrix composites. Treatment of meniscal defects with a cellfree polyurethane matrix in the contralateral knee served as a control. All the composites were placed in the meniscal tears with a 5-0 suture. After 6 and 12 weeks, all menisci were analysed macroscopically, histologically and immunohistochemically according to a validated meniscal scoring system regarding defect-filling, stability, quality of the surface area, integration, cellularity, cell morphology and content proteoglycan and collagen II. Vascularisation was visualized with CD31 immunostaining.

Results and Conclusion: After 6 weeks in vivo treatment with a polyurethane matrix loaded with autologous mesenchymal stem cells showed significantly improved meniscal healing with differentiated meniscal repair tissue compared to cellfree scaffolds. Especially integration of the repair tissue in the native meniscus and the content of proteoglycan were increased. After 12 weeks no difference between the stem cell loaded and cellfree group could be detected with development of differentiated repair tissue in both groups. Vascularisation was seen throughout the whole remodeled area also reaching the central parts of the meniscal repair tissue.

Biological augmentation of a polyurethane scaffold with autologous mesenchymal stem cells promotes earlier differentiation of meniscal repair tissue and faster integration in the surrounding native meniscus. Faster stabilization of the repair tissue with mesenchymal stem cells might be a promising approach to support meniscus remodeling and improve clinical outcome after meniscal substitution.