This thesis aims to increase the understanding of human osteoarthritis pathophysiology by developing reliable biomimetic ex vivo human osteochondral explant models and focussing on the role of... Show moreThis thesis aims to increase the understanding of human osteoarthritis pathophysiology by developing reliable biomimetic ex vivo human osteochondral explant models and focussing on the role of osteoarthritis-relevant triggers (mechanical stress) and interacting genetic factors for developing treatment targets. Human aged joint tissues were collected in the Research in Articular Osteoarthritis Cartilage (RAAK) biobank. To add knowledge of the osteoarthritis pathophysiological processes, aged human ex vivo osteochondral explants were subject to three osteoarthritis-relevant triggers, being inflammation, hypertrophy and injurious mechanical stress. Next, knowledge on early initiating processes occurring in mechano-pathology was investigated by applying RNA-sequencing to cartilage of aged human osteochondral explants subjected to mechanical stress. In addition, to show that the human osteochondral explant model could also be used for genetic interaction studies, we investigated expression of the osteoarthritis risk gene MGP in relation to rs1800801 genotypes. By combining information from RNA-sequencing datasets of cartilage and bone with osteoarthritis-relevant triggers in cartilage and bone explants we investigated the role of MGP and vitamin K in osteoarthritis. Lastly, the injurious mechanical explant model was exploited to determine the effectivity of inhibiting the osteoarthritis risk gene DIO2 by iopanoic acid treatment either by burst or prolonged release from PLGA-PEG nanoparticles. Show less
In the field of Osteoarthritis (OA) research the step from genetics to biological functionality, also named ‘functional genomics’, is necessary to allow valorisation of genetic findings, thereby... Show moreIn the field of Osteoarthritis (OA) research the step from genetics to biological functionality, also named ‘functional genomics’, is necessary to allow valorisation of genetic findings, thereby augmenting the need for functional data of disease relevant tissues. Even so, it was estimated that pursuing druggable targets directed by genetic studies are twice as often successful as compared to those without it. In this thesis we apply the functional genomics methodology, to proceed from a genetic association to mechanistic understanding of the effect of genetic variation on gene expression and epigenetic regulation contributing to OA susceptibility. Particularly we set out to characterize and validate the pathophysiological processes that underlie the role of DIO2/thyroid hormone signalling in the onset of OA after identifying the DIO2 gene as a OA susceptibility locus. The results in this thesis show that intracellular T3 levels should be strictly regulated via DIO2 upon mechanical loading of the cartilage, to ensure cartilage tissue homeostasis. Future endeavours should be designed to demonstrate that local inhibition of DIO2 by intra-articular admission of a deiodinase-inhibitor (Iopanoic acid), could be an effective therapy to alleviate the burden of OA thereby increasing mobility, well-being and quality of life particularly among elderly. Show less
