Fabrication of multi-component tissues for intervertebral disc tissue engineering

Abstract

BACKGROUND: Intervertebral-disc engineering is challenging because it involves the integration of multiple tissues with distinct structures and composition such as lamellar annulus fibrosus, gel-like nucleus pulposus and cartilage endplate. Each of them has different compositions and different structures. We demonstrated that integration of tissues can be enhanced with appropriate mechanical and biological stimuli. Meanwhile, we demonstrated torsion stimulus can lead to cell re-orientation in cell-collagen constructs. These findings can be used to fabricate bioengineered intervertebral-disc in the future. METHODS: Rabbit mesenchymal stem cells were used to fabricate cell-collagen constructs. Constructs were cultured in chondrogenic and osteogenic differentiation medium for 21 days. A layer of msc-collagen solution was added between chondrogenic and osteogenic differentiated constructs to form combined constructs. Combined constructs were then subjected to mechanical and biological stimulations. Samples were evaluated by histology and mechanical test. In a separate experiment, rMSC was used to fabricate cell-collagen lamellae formed hollow tubes, which were then subjected to torsion stimulation. Samples were histologically evaluated and cells alignment was investigated using ad-hoc MatLab program. RESULTS: Significant difference in ultimate tensile stress of the combined constructs was found among different treatment groups, suggesting that mechanical and biological stimulations strengthen interfacial strength between osteogenic and chondrogenic tissue layers. Histology evaluation indicated phenotypes in chondrogenic and osteogenic parts were preserved. Cells alignment evaluation suggested preferred cells alignment is significantly different between experimental and control groups. CONCLUSION: Mechanical and biological stimuli stabilized the interfacial strength between osteogenic and chondrogenic differentiated constructs. Torsion stimulus triggered re-orientation of MSCs in collagen lamellae and aligned along preferred angle.