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2013|14 Annual Report Fraunhofer IGB

78 The challenge of regenerating articular cartilage Because of the lack of circulation articular cartilage has no access to regenerative cell populations. Cartilage damage is therefore close to irreversible and frequently results in progressive destruction of the joint affected. One promis- ing therapy is matrix-associated autologous chondrocyte transplantation (MACT), in which a suitable material (matrix) is seeded with the patient’s cartilage cells (chondrocytes) and then implanted into the damaged cartilage. However, the cultivation of the chondrocytes of the generally used collagen- based matrices can lead to dedifferentiation, i.e. a loss of cel- lular function. Reproduction of tissues by modifying natural tissue components In order to preserve the function of chondrocytes it seems highly significant to create a reproduction of the native extra- cellular matrix (ECM) that is as natural as possible. Articular cartilage has outstanding properties in regard to strength and water content. These are due to the composition of its ECM, of collagen fibers and hydrophilic polysaccharide units (glucosaminoglycans). In order to represent cartilage-like hydrogel systems, researchers at the IGB modified biological molecules of the natural ECM by means of a chemical reaction with methacrylic acid, thereby making crosslinking possible. A two-component system made of gelatin (denatured collagen) and chondroitin sulphate (glucosaminoglycan) can thereby be chemically crosslinked into ECM-mimicking hydrogels in a controlled way. By varying the degree of crosslinking and solid content we were able to produce gelatin hydrogels with strengths of about 5 kPa to 370 kPa. This approximately corresponds to the strength of soft fatty tissue and nasal cartilage, respec- tively [1]. The integration of chondroitin sulphate enables the swelling ability of the matrices to continue being increased, while retaining their strength. Thus we could improve the hy- drogel properties and increase the similarity to native articular cartilage. Stabilization of chondrocytes: the right matrix composition provides biofunctionality A distinct effect of the composition of the hydrogel on the morphology and proliferative behavior of the cells was found during the encapsulation of chondrocytes in three-dimen- sional hybrid hydrogels. By contrast with hydrogels containing collagen or pure gelatin, chondrocytes in hydrogels contain- ing chondroitin sulphate showed a cell type-specific spherical morphology and low cell division activity. Our biomimetic hydrogels, which imitate the natural cartilage environment, therefore represent a promising 3D system for the construc- tion of replacement cartilage tissue. Cell matrix systems as bio-inks to print tissues Like many other native tissues, hyaline cartilage has a charac- teristic micro- and macro-structure. For example, the content of proteoglycans continually increases from the joint line to the bone. Also, there are zones with high cell density as well as cell-free zones. Precise dosing techniques are necessary to be able to reconstruct the internal structures of tissues; inkjet printing is one such technique. In order to make the material systems presented here suitable for inkjet printing, the gelling PRINTABLE 3D MATRICES FOR THE ENGINEERING OF BIOARTIFICIAL CARTILAGE Dr. rer. nat. Eva Hoch, Dr. rer. nat. Kirsten Borchers 1 2 3 MEDICINE 200 μm 200 μm

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