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Research in tissue engineering has been focused on articular cartilage repair for more than a decade. Some pioneristic studies involved the use of hydrogels such as alginate and fibrin glue which still possess valuable potential for cartilage regeneration. One of the main issues in cartilage tissue engineering is represented by the ideal maturation of the construct, before in vivo implantation, in order to optimize matrix quality and integration. The present study was focused on the effect of in vitro culture on a fibrin glue hydrogel embedding swine chondrocytes. We performed an evaluation of the immunohistochemical and biochemical composition and of the biomechanical properties of the construct after 1 and 5 weeks of culture. We noticed that chondrocytes survived in the fibrin glue gel and enhanced their synthetic activity. In fact, DNA content remained stable, while all indices of cartilage matrix production increased (GAGs content, immunohistochemistry for collagen II and safranin-o staining). On the other hand, the biomechanical properties remained steady, indicating a gradual substitution of the hydrogel scaffold by cartilaginous matrix. This demonstrates that an optimal preculture could provide the surgeon with a better engineered cartilage for implantation. However, whether this more mature tissue will result in a more efficient regeneration of the articular surface still has to be evaluated in future investigations.

Menisci represent fundamental structures for the maintenance of knee homeostasis, playing a key role in knee biomechanics. However, their intrinsic regenerative potential is poor. As a consequence, when a lesion occurs and the meniscus is partially removed by surgery, knee mechanics is subject to dramatic changes. These have been demonstrated to lead often to the development of early osteoarthritis. Therefore, menisci should be repaired whenever possible. In the last decades, tissue engineering approaches have been advocated to improve the reparative processes of joint tissues. In this study, the bonding capacity of an articular chondrocytes-fibrin glue hydrogel was tested as a biologic glue to improve the bonding between two swine meniscal slices in a nude mouse model. The composites were wrapped with acellular fibrin glue and implanted in subcutaneous pouches of nude mice for 4 weeks. Upon retrieval, a firm gross bonding was observed in the experimental samples while none of the control samples, prepared with acellular fibrin glue at the interface, presented any sign of bonding. This was consistent with the histological and scanning electron microscope findings. In particular, a fibrocartilaginous tissue was found at the interface between the meniscal slices, partially penetrating the native meniscus tissue. In order to overcome the lack of regenerative properties of the meniscus, the rationale of using cellular fibrin glue is that fibrin provides immediate stability while carrying cells in the site of lesion. Moreover, fibrin gel is recognized as an optimal scaffold for cell embedding and for promoting fibrocartilaginous differentiation of the cells which synthesize matrix having healing property. These results demonstrated the potential of this model for improving the meniscal bonding. However, further orthotopic studies in a large animal model are needed to evaluate its potential for clinical application.