Injectable Fibrin/Polyethylene Oxide Semi-IPN Hydrogel for a Segmental Meniscal Defect Regeneration

Background: Meniscal deficiency from meniscectomy is a common situation in clinical practices. Regeneration of the deficient meniscal portion, however, is still not feasible. Purpose: To develop an injectable hydrogel system consisting of fibrin (Fb) and polyethylene oxide (PEO) and to estimate its clinical potential for treating a segmental defect of the meniscus in a rabbit meniscal defect model. Study Design: Controlled laboratory study. Methods: The Fb/PEO hydrogel was fabricated by extruding 100 mg·mL -1 of fibrinogen solution and 2,500 U·mL -1 of thrombin solution containing 100 mg·mL -1 of PEO through a dual-syringe system. The hydrogels were characterized by rheological analysis and biodegradation tests. The meniscal defects of New Zealand White male rabbits were generated by removing 60% of the medial meniscus from the anterior side. The removed portion included the central portion. The Fb/PEO hydrogel was injected into the meniscal defect of the experimental knee through the joint space between the femoral condyle and tibial plateau at the anterior knee without a skin incision. The entire medial menisci from both knees of each rabbit were collected and photographed before placement in formalin for histological processing. Hematoxylin and eosin, safranin O, and immunohistochemical staining for type II collagen was performed. The biomechanical property of the regenerated meniscus was evaluated using a universal tensile machine. Results: The Fb/PEO hydrogel was fabricated by an in situ gelation process, and the hydrogel displayed a semi-interpenetrating polymer network structure. We demonstrated that the mechanical properties of Fb-based hydrogels increased in a PEO-dependent manner. Furthermore, the addition of PEO delayed the biodegradation of the hydrogel. Our in vivo data demonstrated that, as compared with Fb hydrogel, Fb/PEO hydrogel injection into the meniscectomy model showed improved tissue regeneration. The regenerated meniscal tissue by Fb/PEO hydrogel showed enhanced tissue quality, which was supported by the histological and biomechanical properties. Conclusion: The Fb/PEO hydrogel had an effective tissue-regenerative ability through injection into the in vivo rabbit meniscal defect model. Clinical Relevance: This injectable hydrogel system can promote meniscal repair and be readily utilized in clinical application.