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
Houtman, E.; Tuerlings, M.; Suchiman, H.E.D.; Lakenberg, N.; Cornelis, F.M.F.; Mei, H.L.; ... ; Meulenbelt, I. 2022
Objectives To investigate whether the deiodinase inhibitor iopanoic acid (IOP) has chondroprotective properties, a mechanical stress induced model of human aged explants was used to test both... Show moreObjectives To investigate whether the deiodinase inhibitor iopanoic acid (IOP) has chondroprotective properties, a mechanical stress induced model of human aged explants was used to test both repeated dosing and slow release of IOP. Methods Human osteochondral explants subjected to injurious mechanical stress (65%MS) were treated with IOP or IOP encapsulated in poly lactic-co-glycolic acid-polyethylene glycol nanoparticles (NP-IOP). Changes to cartilage integrity and signalling were determined by Mankin scoring of histology, sulphated glycosaminoglycan (sGAG) release and expression levels of catabolic, anabolic and hypertrophic markers. Subsequently, on a subgroup of samples, RNA sequencing was performed on 65%MS (n = 14) and 65%MS+IOP (n = 7) treated cartilage to identify IOP's mode of action. Results Damage from injurious mechanical stress was confirmed by increased cartilage surface damage in the Mankin score, increased sGAG release, and consistent upregulation of catabolic markers and downregulation of anabolic markers. IOP and, though less effective, NP-IOP treatment, reduced MMP13 and increased COL2A1 expression. In line with this, IOP and NP-IOP reduced cartilage surface damage induced by 65%MS, while only IOP reduced sGAG release from explants subjected to 65%MS. Lastly, differential expression analysis identified 12 genes in IOP's mode of action to be mainly involved in reducing metabolic processes (INSIG1, DHCR7, FADS1 and ACAT2) and proliferation and differentiation (CTGF, BMP5 and FOXM1). Conclusion Treatment with the deiodinase inhibitor IOP reduced detrimental changes of injurious mechanical stress. In addition, we identified that its mode of action was likely on metabolic processes, cell proliferation and differentiation. Show less
In dit proefschrift worden de moleculaire mechanismen behandeld die onderliggend zijn aan artrose. Specifiek wordt genoomwijd onderzocht welke genen anders tot expressie komen in aangedaan... Show moreIn dit proefschrift worden de moleculaire mechanismen behandeld die onderliggend zijn aan artrose. Specifiek wordt genoomwijd onderzocht welke genen anders tot expressie komen in aangedaan vergeleken met gezond kraakbeen van artrose patienten. Dit in de context van epigenetische regulatie van gen expressie, specifiek door DNA methylatie in het licht van de lokale genetische context in de vorm van puntmutaties. 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
Huetink, K.; Voort, P. van der; Bloem, J.L.; Nelissen, R.G.H.H.; Meulenbelt, I. 2016
Osteoarthritis (OA) is a prevalent and complex disorder with a high hereditary probability. Previous genetic research into OA has yielded several common gene variants contributing to joint... Show moreOsteoarthritis (OA) is a prevalent and complex disorder with a high hereditary probability. Previous genetic research into OA has yielded several common gene variants contributing to joint specific OA phenotypes. Only a few studies allowed an examination of multiple joint sites in the patients included. In this thesis, we have focused, on the identification and investigation of OA susceptibility of rare and common generalised OA (GOA) in family based studies and common OA in the population. We investigated previously reported relationships between two candidate genes (FRZB and MATN3) with OA in a random sample from the population-based Rotterdam study and in siblings from the Genetics Osteoarthritis and Progression (GARP) study. A functional variant in FRZB indeed associates to OA but this seems not confined to hip only. Associations of MATN3 variants suggest that genetic variation in this gene determines susceptibility to spinal disc degeneration and OA of the first carpometacarpal joint. Different linkage areas were identified for early and late onset GOA. We mapped a major locus for OA at multiple joint sites on 14q32.11 in middle aged siblings from the GARP study and on 2q33.3 in seven early onset families. From our studies so far, DIO2, IDH1 and NRP2 may be new OA loci. Show less
