Abstract

ENGINEERING A JOINT-ON-CHIP FOR EVALUATION OF NEW DRUGS FOR TREATMENT OF DEGENERATIVE JOINT DISEASES

Marcel Karperien, Head Department of Developmental BioEngineering, TechMed Centre, University of Twente

Degenerative joint diseases such as osteoarthritis are a major and rising health care problem which still cannot be effectively treated.  Consequently there is still a large unmet need for disease modifying treatments, with many attempts failed at phase 2 and 3 clinical trials due to lack of efficacy in recent years. This is in part due to the lack of translational power of frequently used animal models. To address this issue we have engineered the first prototypes of a cartilage-on-chip and a synovial membrane-on-chip which can be combined in a multi-organ on-chip device; the Joint-on-Chip (JoC). The cartilage-on-chip model comprises a mechanical actuation unit, a cell-hydrogel chamber, which can be filled with chondrocyte-laden hydrogel, and a perfusion channel. Uniquely, the cell-hydrogel chamber can be exposed to mechanical loading emulating the rolling motion of the moving knee joint. For this the mechanical stimulation unit consisted of 3 units which can be independently actuated. The synovial membrane-on-chip comprises two compartments separated by a thin non-porous membrane. The upper chamber is used for culturing synovial fibroblasts and macrophages constituting the synovial lining of the intima, while the bottom chamber is used for culturing endothelial cells emulating the subintima. In our cartilage-on-chip model we showed that emulating the rolling motion of the joint resulted in the deposition of more cartilaginous matrix composed of glycosaminoglycans and collagen 2 and 6. It also induced the formation of a pericellular matrix. Matrix formation was much more abundant than in the devices exposed to compression only and to static culture in which there was virtually no matrix formation. This suggests that a combination of compression and shear stress such as uniquely seen during a rolling motion is beneficial for cartilage formation. We furthermore showed that in our device iPS cells could be differentiated into chondrocytes and that mechanical loading increased differentiation as evidenced by improved cartilage matrix deposition and marker expression. In the synovial membrane-on-chip we showed that the presence of endothelial cells is required for macrophage integration into the synoviocyte layer and the subsequent polarization into the M2 phenotype emulating the intima in healthy conditions. Challenging this intima with proinflammatory cytokines evoked a classical inflammatory response with increased mRNA expression of matrix degrading enzymes and pro-inflammatory cytokines and chemokines and upregulation of markers typically present in rheumatoid arthritis. In conclusion, we have successfully engineered cartilage and synovial membrane on-chip models which will allow us to emulate healthy and diseased conditions in a JoC. Presently we are using this model for studying pathophysiological mechanisms of disease and its application in drug development programs.