Functional cell phenotype induction with TGF-β1 and collagen-polyurethane scaffold for annulus fibrosus rupture repair
1 AO Research Institute Davos, Davos, Switzerland
2 Icahn School of Medicine at Mount Sinai, New York, USA
3 Tokai University School of Medicine, Isehara, Japan
4 Inselspital, University of Bern, Bern, Switzerland
5 Shenzhen Key Laboratory of Anti-Aging and Regenerative Medicine, Department of Medical Cell Biology and Genetics, Health Sciences Centre, Shenzhen University, Shenzhen, China
6 Orthopaedic Institute, Medical College, Soochow University, Suzhou, Jiangsu, China
7 Collaborative Research Program Annulus Fibrosus Repair, AO Foundation, Davos, Switzerland
Abstract
Appropriate cell sources, bioactive factors and biomaterials for generation of functional and integrated annulus fibrosus (AF) tissue analogues are still an unmet need. In the present study, the AF cell markers, collagen type I, cluster of differentiation 146 (CD146), mohawk (MKX) and smooth muscle protein 22α (SM22α) were found to be suitable indicators of functional AF cell induction.In vitro2D culture of human AF cells showed that transforming growth factor β1 (TGF-β1) upregulated the expression of the functional AF markers and increased cell contractility, indicating that TGF-β1-pre-treated AF cells were an appropriate cell source for AF tissue regeneration. Furthermore, a tissue engineered construct, composed of polyurethane (PU) scaffold with a TGF-β1-supplemented collagen type I hydrogel and human AF cells, was evaluated within vitro3D culture andex vivopreclinical bioreactor-loaded organ culture models. The collagen type I hydrogel helped maintaining the AF functional phenotype. TGF-β1 supplement within the collagen I hydrogel further promoted cell proliferation and matrix production of AF cells withinin vitro3D culture. In theex vivoIVD organ culture model with physiologically relevant mechanical loading, TGF-β1 supplement in the transplanted constructs induced the functional AF cell phenotype and enhanced collagen matrix synthesis. In conclusion, TGF-β1-containing collagen-PU constructs can induce the functional cell phenotype of human AF cellsin vitroandin situ. This combined cellular, biomaterial and bioactive agent therapy has a great potential for AF tissue regeneration and rupture repair.
Graphical Abstract

Keywords
- Annulus fibrosus
- annular rupture repair
- tissue engineering
- transforming growth factor β1
- polyurethane scaffold
- collagen type I hydrogel
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