Differentiation of adipose stem cells seeded towards annulus fibrosus cells on a designed poly(trimethylene carbonate) scaffold prepared by stereolithography

Cell-based therapies could potentially restore the biomechanical function and enhance the self-repair capacity of annulus fibrosus (AF) tissue. However, choosing a suitable cell source and scaffold design are still key challenges. In this study, we assessed the in vitro ability of human adipose stem cells (hASCs), an easily available cell source to produce AF-like matrix in novel AF-mimetic designed scaffolds based on poly(trimethylene carbonate) and built by stereolithography. To facilitate efficient differentiation of hASCs towards AF tissue, we tested different culture medium compositions and cell seeding techniques. This is the first study to report that medium supplementation with transforming growth factor (TGF)-β3 is essential to support AF differentiation of hASCs while TGF-β1 has negligible effect after 21 days of culture. Fibrin gel seeding resulted in superior cell distribution, proliferation and AF-like matrix production of hASCs compared to direct and micromass seeding under TGF-β3 stimulation. Not only the production of sulphated glycosaminoglycans (sGAG) and collagen was significantly upregulated, but the formed collagen was also oriented and aligned into bundles within the designed pore channels. The differentiated hASCs seeded with fibrin gel were also found to have a comparable sGAG:collagen ratio and gene expression profile as native AF cells demonstrating the high potential of this strategy in AF repair