Objective: To advance molecular and cellular therapy into the clinic for peripheral nerve injury, modification of neural scaffolds with the extracellular matrix (ECM) of peripheral nerves has been established as a promising alternative to direct inclusion of support cells and/or growth factors within a neural scaffold, while the cell-derived ECM proves to be superior to the tissue-derived ECM in modification of neural scaffolds. Based on the fact that bone marrow mesenchymal stem cells (BMSCs), just like Schwann cells, are adopted as support cells within a neural scaffold, in this study, we used BMSCs as parent cells to generate ECM for application in peripheral nerve tissue engineering.
Methods: A chitosan nerve guidance conduit (NGC) and silk fibroin filamentous fillers were respectively prepared for co-culture with purified BMSCs respectively, followed by decellularization to stimulate ECM deposition. The ECM modified NGC and lumen fillers were then assembled into a chitosan/silk fibroin-based, BMSC-derived ECM modified neural scaffold, which was implanted into rats to bridge a 10-mm long sciatic nerve gap. After nerve grafting 12 weeks, a series of histological and functional assessments were conducted to compare the regenerative outcomes between MSC-ECM and Scaffold groups.
Results: (1) Light and electron micrography were used to observe the topological structure of the BMSC-derived ECM, and immunostaining was performed to identify the protein composition of the BMSC-derived ECM. These results showed that the ECM ultrastructure consistied of a dense meshwork of filamentous and granular materials.
(2)A animal model of peripheral nerve injury was adopted in this study to investigate the performances of the BMSC-derived ECM modified neural scaffolds. Anti-NF immunostaining demonstrated that the length or the number of regenerating nerve fibers was significantly greater in MSC-ECM group than in Scaffold group.
Electrophysiological assessments were used to evaluate the effects of BMSC-derived ECM modified neural scaffolds on functional recovery.
In this study, we noted that the regenerative outcomes were significantly larger in MSC-ECM group than in Scaffold group, suggesting that BMSC-derived ECM had promoting effects on motor function restoration. Finally, morphological observation of regenerated nerve fibers under TEM and the related morphometric analysis revealed that myelin sheath formation was promoted by BMSC-derived ECM modified scaffolds as compared to that by plain scaffolds. Collectively, the comprehensive data from histological and functional examinations suggest that regenerative outcomes achieved by our engineered neural scaffold were better than those by a plain chitosan/silk fibroin scaffold, and suggested the benefits of BMSC-derived ECM for peripheral nerve repair.
Conclusion: We have prepared a novel neural scaffold for peripheral nerve repair. A chitosan NGC and silk fibroin filamentous fillers were respectively prepared, and then co-cultured with purified BMSCs respectively, followed by decellularization to stimulate ECM deposition. The ECM modified NGC and lumen fillers were assembled into a chitosan/SF-based, BMSC-derived ECM modified neural scaffold, which was used to bridge a 10 mm long sciatic nerve gap in rats. Histological and functional assessments after scaffold grafting showed that regenerative outcomes achieved by our developed scaffold were better than those by a plain chitosan/silk fibroin scaffold.
National Natural Science Foundation of China (Grant Nos. 81200932 and 81471255); Basic Research Program of Jiangsu Education Department (Grant No. 14KJA310004)
References:
[1] Gu Y, Zhu J, Xue C, Li Z, Ding F, Yang Y and Gu X 2014b; Chitosan/silk fibroin-based, Schwann cell-derived extracellular matrix-modified scaffolds for bridging rat sciatic nerve gaps. Biomaterials 35: 2253-2263
[2] Gu X, Ding F and Williams DF 2014a; Neural tissue engineering options for peripheral nerve regeneration. Biomaterials 35: 6143-6156
[3] Burdick JA, Mauck RL, Gorman JH, 3rd and Gorman RC 2013; Acellular biomaterials: an evolving alternative to cell-based therapies. Sci Transl Med 5: 176ps174
[4] Lu H, Hoshiba T, Kawazoe N, Koda I, Song M and Chen G 2011; Cultured cell-derived extracellular matrix scaffolds for tissue engineering. Biomaterials 32: 9658-9666