Indirect Printed Patient S pecific Scaffolds with a Bioactive Bottom Layer for Meniscus

Meniscus tissue exhibits a key role in the knee, acting as a shock absorber and preventing the deterioration and degeneration of articular cartilage. New tissue engineering (TE) strategies have been developed, where acellular scaffolds play a main role [1]. However, some strategies have failed in terms of implant fixation and anchorage [2]. In this work, indirect printed hierarchical scaffolds composed by a silk fibroin (SF) upper layer and an 80/20 (w/w) ratio of SF/ionic-doped β-tricalcium phosphate (TCP) bottom layer were produced. SF concentrations of 16% (w/v) (Hi16) and 8% (w/v) (Hi8) were used to produce the scaffolds. The ceramic-based bottom layer aimed to enhance the anchorage properties of the scaffolds by improving the bone-implant interface. The scaffolds presented adequate architecture and homogeneous porosity in both layers. Furthermore, suitable mechanical properties for meniscus TE were observed. Moreover, in vitro bioactivity studies revealed formation of apatite crystals onto the ceramic-based bottom layers of the scaffolds. These results are indicative that the presence of TCP in the bottom layer could be important in the anchorage of the scaffolds by enhancing the bone-implant interaction. Furthermore, human meniscus cells and human primary osteoblasts were seeded separately onto the top layer (SF8 and SF16) and bottom layer (SF8/TCP and SF16/TCP) of the scaffolds and revealed good adhesion and proliferation up to 7 days of culture. Lastly, a subcutaneous in vivo implantation in mice revealed weak inflammation and scaffold's integrity up to 8 weeks. As conclusion, the hierarchical indirect printed SF scaffolds presented promising features for meniscus regeneration, where the ceramic-based bottom layer can play a major role in the anchorage performance of the scaffolds. Despite these encouraging results, in vivo assays using a meniscus defect model in a larger animal should be performed.
Acknowledgments
The work was supported by Portuguese Foundation for Science and Technology (FCT) through the project B-FABULUS (PTDC/ BBB-ECT/2690/2014). FCT/MCTES is also acknowledged for the PhD scholarship attributed to J.B.C. (PD/BD/113803/2015) and the financial support provided to J.S.-C. (IF/00115/2015) and J.M.O. (IF/01285/2015) under the program “Investigador FCT”.
References
[1] Buma P, Ramrattan NN, van Tienen TG, Veth RP. Tissue engineering of the meniscus. Biomaterials 2004;25:1523-32.
[2] Gruchenberg K, Ignatius A, Friemert B, von Lübken F, Skaer N, Gellynck K, et al. In vivo performance of a novel silk fibroin scaffold for partial meniscal replacement in a sheep model. Knee Surg Sports Traumatol Arthrosc 2015;23:2218-29.