Development of a 3D bioprinted hydrogel model to study Hedgehog signalling in Chondrocytes

Osteoarthritis (OA) is a chronic degenerative joint disease caused by the breakdown of joint cartilage. Patients suffering from OA may experience severe joint pain, inflammation, and limited range of motion. The disease is generally progressive and no treatment is as of yet available, only palliative care to relieve symptoms, and for late stage cases of the disease, surgical replacement of the joint might be required. Chondrocytes are a specialised cell type which can only be found in cartilage, where they are the only cell type under healthy conditions. Their main role is to maintain the cartilage by secreting type II collagen and proteoglycans, which form the majority of cartilage. Chondrocytes have been demonstrated to be highly susceptible to environmental changes, and their internal balance can be thrown off either by external factors such as mechanical shock sustained in an injury to the joint, or via biochemical signalling. The Sonic Hedgehog (SHH) signalling pathway is among other things known to play a role in the development and subsequently the regulation of joint cartilage. The precise mechanisms leading to chondrocyte dysregulation and subsequent progression of OA are largely unknown however, and progress towards elucidating the precise role of SHH and its related components Smoothened (SMO) and glioma-associated oncogene homolog 1 (GLI1) in cartilage degradation has been slow. Research into chondrocytes and their related diseases has utilised both standard 2D cell models, as well as a more novel and innovative 3D culturing, with the latter showing more promise and more closely resembling the gene expression of in vivo chondrocytes. Recent research has found that cells grown in a 3D matrix share more similarities with chondrocytes directly extracted from cartilage. In this thesis, attempts are made at establishing methods that implement 3D cell cultivation and bioprinting, which can be used for a wide selection of chondrocyte related research.