Hierarchically structured biphasic scaffolds mimicking osteochondral tissue
Final Report Abstract
Main goal of the interdisciplinary project was to develop artificial osteochondral tissue which mimics the hierarchical architecture of the natural one as close as possible. For this purpose, biphasic materials consisting of alginate and constituents of the extracellular matrices of bone (hydroxyapatite/HAP) and cartilage (hyaluronic acid/HYA), respectively, should be developed applying the principle of diffusion controlled directed ionotropic gelation where – simultaneously to the gelation – parallel aligned pores are formed, running through the whole lengths of the scaffold. Therefore, parameters like the influence of the alginate concentration, concentration of different gelling ions, biopolymer additives and sterilization methods of the precursor powders on pore formation and mechanical properties of the scaffolds were systematically analyzed. Incorporation of cells into the biphasic scaffolds is crucial to finally mimic osteochondral tissue in the lab and to understand the biological response to scaffold composition and properties. To enable the incorporation of cells as early as during gel and channel pore formation, sterile and nearly physiological fabrication conditions are required while maintaining the channel pore formation and stability of the final scaffold. Therefore, the following aspects where additionally considered to adapt the process to cell compatible conditions: temperature during gelation; comparison of different media for suspending the precursor powders; addition of a sacrificial layer to protect cells from the crosslinking agent. Primary human mesenchymal stem cells as well as chondrocytes were embedded into the chondral layer of the scaffolds and cultured in presence and absence of chondrogenic supplements. Chondrogenically stimulated cells showed higher viability and could be successfully (re)differentiated as indicated by gene expression of Col2 and aggrecan. Additionally, expression of collagen type 2 could be verified on protein level. Protein expression of collagen type 2 was in the same range but even superior for mesenchymal stem cells compared to chondrocytes which is a very positive aspect with regard to the use of easily available mesenchymal stem cells instead of chondrocytes for defect regeneration. Perfusion of the biphasic scaffolds led to an increase of the viability of embedded cells and could potentially also increase chondrogenic differentiation. Incorporation of cells into the bony layer is more challenging compared to the chondral part. After embedding, cells showed round morphology indication the missing potential of the matrix for cell adhesion. Therefore, further modifications are required to increase attractiveness of the scaffold matrix for cell adhesion.
Publications
- Biphasic scaffolds for the regeneration of osteochondral tissue. Euro Bio-inspired Materials, Potsdam, 20-23 March 2012
Schütz, K., Despang, F., Halm, C., Lode, A., Gelinsky, M.
- Designing anisotropic biomaterials for engineering anisotropic tissues. Invited keynote lecture, Strategies in Tissue Engineering Conference, Würzburg, 23.-25. May 2012
Gelinsky, M.
- From alginate hydrogels to composites to bioceramics: Novel processing routes to biomimetic anisotropic materials. E-MRS Spring Meeting, Strasbourg (France), 14.-18. May 2012
Gelinsky, M., Dittrich, R., Bernhardt, A., Lode, A., Schütz, K., John, A., Despang, F.
- Tissue-specific integration of cells in anisotropic bilayered hydrogels for treatment of osteochondral defects. Jahrestagung der Deutschen Gesellschaft für Biomaterialien (DGBM), Erlangen, 26.-28. September 2013
Schütz, K., Despang, F., Bernhardt, A., Lode, A., Gelinsky, M.
- Cell-laden biphasic scaffolds with anisotropic structure for the regeneration of osteochondral tissue. J. Tissue Eng. Regen. Med., 2014, published online
Schütz, K., Despang, F., Lode, A., Gelinsky, M.
(See online at https://doi.org/10.1002/term.1879) - Embedding of small cell microaggregates into anisotropic biphasic alginate constructs mimicking chondrons in articular cartilage. Euro Bio-inspired Materials, Potsdam, 18-21 March 2014
Schütz, K., Milan, F., Gelinsky, M.
- Towards tissue engineered constructs mimicking osteochondral tissue: embedding of hMSC as single cells and small microaggregates into anisotropic alginate scaffolds. Tissue Engineering & Regenerative Medicine International Society (TERMIS-EU) Congress, Genova (Italy), 10-13 June 2014
Schütz, K., Milan, F., Gelinsky, M.
