Osteoarthritis (OA) is a prevalent age-related joint disease, determined by diverse changes in pathways maintaining articular cartilage and subchondral bone. This thesis aimed to identify and study... Show moreOsteoarthritis (OA) is a prevalent age-related joint disease, determined by diverse changes in pathways maintaining articular cartilage and subchondral bone. This thesis aimed to identify and study gene networks driving interacting etiopathophysiological OA processes in cartilage and subchondral bone. Hereto, characterization of the molecular landscape of bone and cartilage of OA patients showed 305 genes with similar direction of effect, including IL11 and CHADL. Moreover, to capture biological complexity and decipher underlying OA disease mechanisms a variety of human 3D cartilage and bone organoids models were exploited and a human osteochondral construct-on-a-chip was developed. Herein, we showed that the robust OA risk gene WWP2 may initiate OA, via aberrant responses in hypoxia-associated genes and a decrease in anabolic markers. Additionally we showed, as reflected by upregulation of SPP1 and downregulation of WNT16 in cartilage, that treatment of ex vivo human osteochondral explants with human recombinant IL11 does not necessarily has a beneficial outcome. Finally, to allow implementation of knowledge on diverse OA pathophysiological processes, the potency of circulating miRNAs to report on ongoing OA pathophysiological process in joint tissues was established. Such insights are crucial to stratify respective OA patients that require different therapeutic mode of action, towards precision medicine. Show less
Bone and joint disorders have an enormous personal- and societal impact. Diagnosis and treatment of these disorders are most efficient if targeted screening, accurate diagnosis, and targeted... Show moreBone and joint disorders have an enormous personal- and societal impact. Diagnosis and treatment of these disorders are most efficient if targeted screening, accurate diagnosis, and targeted treatment are available. To enable targeted screening, the population at risk must be well-defined, and categorized if required. Subsequently, screening- and diagnostic methods must have good, or excellent predictive value and finally, treatment must target the disease, thus spare healthy tissues and processes and thereby avoid adverse events.The aim of this thesis is to gain new insights about the diagnostic process- and treatment of pathological conditions of the bone and joints, namely male urological cancer-induced bone loss and inflammatory arthritis. Show less
Osteoarthritis is one of the most common musculoskeletal disorders. Despite its high prevalence, the pathogenesis of osteoarthritis is incompletely understood. A major risk factor for... Show moreOsteoarthritis is one of the most common musculoskeletal disorders. Despite its high prevalence, the pathogenesis of osteoarthritis is incompletely understood. A major risk factor for osteoarthritis is obesity. Not only due to increased mechanical stress, but also due to systemic factors such as lipids. Our knowledge on how lipids are involved in osteoarthritis is limited. Therefore, this thesis focusses on the association of lipids with hand and knee osteoarthritis. Firstly, we investigated the reproducibility of lipid measurements to guide future lipidomic research. Subsequently, comparison of the lipid profile of osteoarthritis patients in different disease stages showed that the lipid profile explained disease severity to a limited extent. We observed the strongest association of the lipid profile with hand pain, and no association with knee osteoarthritis. This suggests that lipotoxicity may play a larger role in the hand, while in the knee mechanical stress is more relevant. In addition, treatment with anti-inflammatory medication resulted in a change in lipid concentrations in patients with hand osteoarthritis, suggesting that lipids are involved in inflammation and/or pain processes. These insights may increase our understanding of osteoarthritis pathophysiology and lead to new targets for future development of disease modifying osteoarthritis medication. Show less
Diseases and injuries related to bone and cartilage severely affect the function of the musculoskeletal system. They affect the life quality of patients and make them unable to move. The... Show moreDiseases and injuries related to bone and cartilage severely affect the function of the musculoskeletal system. They affect the life quality of patients and make them unable to move. The peculiarities of bone and cartilage structures mean that the therapeutic and surgical treatments that have been developed till date have a lot of disadvantages and limitations. Consequently, the development of new strategies for administering drugs that favor localized delivery is very important to achieve increasingly better treatments.The design and preparation of platforms for this purpose is a constant challenge, and for this reason three types of matrices were designed and prepared in the thesis. The drugs encapsulated in these matrices were cefazolin sodium, betamethasone, dexamethasone sodium phosphate, and Etanercept (anti-TNF-α drug). We were able to show that our matrices modified the release of the incorporated molecules and the composition of the prepared materials played an important role in the kinetics of the release process. Physicochemical characterizations were carried out on all the materials, obtaining that in each case the morphology varied once modifications in the matrix composition had been introduced. Biological studies in vitro and in vivo showed the cytocompatibility of the materials and also the ability to help repair damaged cartilage. Show less
To advance development of effective disease modifying OA treatments, a better understanding of its pathophysiological mechanisms is necessary. By studyinga family with early onset OA and high... Show moreTo advance development of effective disease modifying OA treatments, a better understanding of its pathophysiological mechanisms is necessary. By studyinga family with early onset OA and high cartilage mineralization, a likely causal mutation in the TNF receptor superfamily member 11b (TNFRSF11B) encoding for osteoprotegerin (OPG) was identified. This mutation causes a 19 amino acid extension in the C-terminal domain of OPG (OPG-XL). OPG is a decoy receptor that competes with receptor activator of the nuclear KB factor (RANK) for the binding of nuclear factor KB ligand (RANKL). This triad is known for regulating the formation of osteoclasts, hence playing a critical role in bone remodeling. Given that TNFRSF11B is also one of the highest upregulated genes in OA lesioned cartilage as compared to preserved, this gene is likely underlying OA development and progression but its implication in cartilage homeostasis is as of yet unknown.Altogether, this thesis highlights the role of OPG in OA development by generating an OPG overexpression system in primary chondrocytes and by studying a rare mutation in TNFRSF11B. By further generating neo-cartilage, neo-bone and osteoclasts from the OPG-XL family members, we showed a bidirectional interplay of OPG-XL characterized by higher bone resorption and higher cartilage mineralization. Novel treatments for this family and extrapolation to common OA could be addressed on highly differentially expressed genes such as MGP and DIO2. Finally, the pleiotropy that OPG-XL showed indicates a beneficial or detrimental stage depending on the tissue, making OPG-XL, and likely OPG, a double-edged sword in OA development. Show less
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
The studies described in this thesis provides the field with valuable data on the potential therapeutic effects of fatty acids and specialized pro-resolving lipid mediators in rheumatoid arthritis... Show moreThe studies described in this thesis provides the field with valuable data on the potential therapeutic effects of fatty acids and specialized pro-resolving lipid mediators in rheumatoid arthritis and osteoarthritis. The omega-6 fatty acid AdA shows potent pro-resolving effects on the production of pro-inflammatory chemoattractantLTB4 with great promise to limit RA disease progression. In contrast to the promising potential therapeutic effects of AdA in RA, the evidence for pro-resolving effects in OA is still scarce. The results of the studies from this thesis show that neither LXA4, LXB4, RvE2 or Mar-1 were able to reduce OA disease activity in the experimental set-up we used. Finally, the studies described in this thesis show the utmost critical importance of the right sample preparation and storage for the intended subsequent analysis. Show less
The aim of this thesis was to combine transcriptomics, genetics and human disease modelling to obtain further insight into molecular processes underlying osteoarthritis. More specifically, we aimed... Show moreThe aim of this thesis was to combine transcriptomics, genetics and human disease modelling to obtain further insight into molecular processes underlying osteoarthritis. More specifically, we aimed to elucidate the role of long noncoding RNAs expression changes as aberrant epigenetic mechanism in regulating gene expression in chondrocytes. We identified previously unknown long noncoding RNAs associated with the osteoarthritic process and showed enrichment for cis¬-regulation of these long noncoding RNAs with target messenger RNAs.To provide insight in the etiology of osteoarthritis, causal pathways can be identified by unravelling the substantial genetic component. To this end, we investigated the biological functionality of the high-impact, pathogenic mutation identified in the gene fibronectin1 in an early-onset osteoarthritis family. We demonstrated that the identified causal missense mutation in the gelatin-binding domain of the extracellular matrix protein fibronectin resulted in significant decreased binding capacity to collagen type II.Finally, the common function of fibronectin1 was investigated in cartilage and what changes occur at the transcript level of fibronectin1 with osteoarthritis. Down-regulation of full-length fibronectin was unbeneficial for in vitro chondrogenesis, we hypothesize that this was caused by decreased availability of the classical integrin binding site of fibronectin. Show less
In this thesis several aspects of complement proteins are described, from circulating levels in blood to their intracellular presence and from autoimmunity to the infectious disease tuberculosis.... Show moreIn this thesis several aspects of complement proteins are described, from circulating levels in blood to their intracellular presence and from autoimmunity to the infectious disease tuberculosis. We explored the local production of complement and we describe in Chapter 2 the production of C1q by chondrocytes. Additionally, studies addressing the potential intracellular C3 role are described in Chapter 3. The potential role of the complement system as biomarker was investigated by addressing the presence and concentrations of C1q in serum of patients with active tuberculosis and controls in Chapter 4. Like C1q, we also investigated the expression and concentration of the natural inhibitor C1-INH in Chapter 5. C1q protein was further analysed as biomarker for tuberculosis in experimental non-human primate models in Chapter 6. In this thesis, a newly identified case of a lupus patient is described with a complex medical history and a compound heterozygous deficiency of C1q in Chapter 7. To better comprehend a possible role of a prominent post-translational modification associated rheumatic disease, carbamylation, the interaction between carbamylated IgG was investigated in relation to the ability to activate the complement system. These studies are described in Chapter 8. Show less
The aims of this thesis were:1. To investigate associations between radiographic OA severity, knee instability, pain and function prior to and after THA and/or TKA.2. To evaluate factors... Show moreThe aims of this thesis were:1. To investigate associations between radiographic OA severity, knee instability, pain and function prior to and after THA and/or TKA.2. To evaluate factors influencing physical activities in patients with end-stage hip or knee OA.3. To identify determinants of return to work after THA or TKA.The research in this thesis showed that the combination of preoperative radiographic OA severity and pain perception of the patient are important predictors for the expected postoperative pain/function outcome due to effect modification. Furthermore, the initial clinical recovery after arthroplasty surgery and preoperative scores can be used during the postoperative recovery period to identify patients at risk for an unfavourable one-year outcome. Besides, it showed that kneeinstability could be considered as an easy identifiable surrogate outcome for poor pain relief and poor function. Furthermore, pain and functional limitations were not associated with an objective technical measurement of physical activity in patients with end-stage hip or knee OA. Finally, we found that preoperative occupational information (more specifically preoperative absence from work) and work-related expectations are important predictors for return to work after THA or TKA. Show less
This thesis has provided more knowledge on the disease course and its determinants of outcome in hand osteoarthritis. The role of joint-specific factors and coping styles on disability, the... Show moreThis thesis has provided more knowledge on the disease course and its determinants of outcome in hand osteoarthritis. The role of joint-specific factors and coping styles on disability, the prevelance of aesthetic dissatisfaction, its impact on daily life and their determinants were evaluated. Additionally, the association between MR Imaging features with hand pain and the association of MR Imaging features with radiographic progression were investigated. Another part of the thesis focused on the association between osteoarthritis and mortality. Show less
Total hip-and total knee arthroplasties (THA/TKA) are effective treatments for end-stage hip/knee osteoarthritis, leading to satisfactory improvement of pain/function in 80-90% of the patients... Show moreTotal hip-and total knee arthroplasties (THA/TKA) are effective treatments for end-stage hip/knee osteoarthritis, leading to satisfactory improvement of pain/function in 80-90% of the patients within 12-months after surgery. Overall, knowledge regarding clinical outcomes reflecting the process of recovery in patients undergoing THA/TKA over a prolonged period is scarce. First, this thesis addressed the successfull feasibility of collecting a comprehensive set of outcomes relevant for the process of recovery. Second, it was found that the decrease in pain/improvement in function after 1 -year in THA-patients, but not in TKA-patients, was positively associated with more preoperative radiographic severity of OA. Thirdly, most patients’ preoperative expectations of outcomes of THA/TKA regarding functioning were met, unfortunately more frequently not in TKA-patients. Finally, 90%/52% of THA/TKA-patients return after surgery after 12-weeks on average. However, despite high return-to-work rates, a considerable proportion of the patients who return-to-work, worked less hours than preoperatively. Concluding, although overall favourable outcomes were seen, this thesis identified a number of areas for improvement: better identification of subgroups with a likely perceived unsuccessful outcome or recovery process, if not preoperatively then early after surgery. Early identification and subsequent interventions may change the course of recovery of THA/TKA for such patients, leading to added value in this subgroup. 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
Immunometabolism focusses on the interplay between immunological and metabolic processes, both at a systemic and a cellular level. This thesis is divided into two parts based on these two... Show moreImmunometabolism focusses on the interplay between immunological and metabolic processes, both at a systemic and a cellular level. This thesis is divided into two parts based on these two levels. The first part focusses on the infrapatellar fat pad (IFP), an adipose tissue located in the knee, and the potential role in the pathophysiology of osteoarthritis. Therefore, we characterized the IFP based on a cellular and molecular level and found that the inflammatory state of the joint does affect the cellular load of the IFP, however, the secretory profile of the IFP does not seem to be affected. Furthermore, obesity-related changes normally found in adipose tissue were not present in the IFP. When characterizing the IFP we found two interesting cell populations, IL-6-secreting T cells and macrophages with an anti-inflammatory phenotype secreting pro-inflammatory cytokines. Both populations could be involved in the pathophysiology of the osteoarthritic joint. Furthermore, in the second part we focussed on cellular metabolism where we determined the mechanism by which fatty acids exert their effect on T cells. We found that fatty acids are not served as energy, however, whether it is used for daughter cells or influencing cell signalling remains to be elucidated. 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
The pathogenesis of OA is largely unknown; however, several risk factors are known to contribute to disease development. Treatment modalities are currently limited to alleviation of symptoms. In... Show moreThe pathogenesis of OA is largely unknown; however, several risk factors are known to contribute to disease development. Treatment modalities are currently limited to alleviation of symptoms. In order to develop better treatment modalities, increase of the understanding of the underlying mechanisms leading to OA development may provide targets for disease modification. Furthermore, knowledge regarding appropriate outcome measures that can be applied in OA research has to be increased for adequate assessment of potential treatment effects. Therefore, part I of this thesis describes studies aiming to increase the understanding of mechanisms underlying the association between known risk factors and OA, especially focussing on obesity in relation to OA in weight-bearing and non-weight-bearing joints. Furthermore, it was investigated which specific structural abnormalities on specific locations within the knee joint could best discriminate presence of symptomatic OA, and impact of knee OA and its modifiable or preventable risk on health-related quality of life was evaluated. Part II of this thesis describes two systematic reviews, assessing available instruments for measurement of the domains pain, physical function, patient global assessment and imaging in hand OA in order to enable recommendations for use in clinical trials. Show less
Although osteoarthritis is a common disease, there are currently no disease-modifying availible. For a long time osteoarthritis was considered a purely degenerative disease without inflammation of... Show moreAlthough osteoarthritis is a common disease, there are currently no disease-modifying availible. For a long time osteoarthritis was considered a purely degenerative disease without inflammation of the synovium (synovitis). However, recent research has shown that synovitis is of importance in patients with osteoarthritis. Therefore, this thesis aimed to understand the role synovitis in ossteoarthritis. In the first part of this thesis, we investigated the nature of synovitis by examining the synovium of osteoarthritis patients using differnt laboratory techniques. Furthermore, we validated a new synovitis scoring system on MRI with contrast. In the second part of this thesis, we investigated role of synovitis in relation to clinical characteristics such as pain and structural damage. This thesis shows that synovial inflammation in osteoarthritis is not only frequently present, but may also play a role in the pathophysiology of osteoarthritis and development of clinical features. Results presented in this thesis provide insight into different aspects of synovial inflammation aimed at increasing our understanding of the pathophysiology of OA and aiding to the development of disease-modifying drugs in OA. Show less
Osteoarthritis (OA) is an age related disorder of the joints characterized by pain, crepitus, and stiffness resulting in decreased mobility. Pathophysiology consists of cartilage degeneration and... Show moreOsteoarthritis (OA) is an age related disorder of the joints characterized by pain, crepitus, and stiffness resulting in decreased mobility. Pathophysiology consists of cartilage degeneration and bone remodeling, however, knowledge of OA etiology is still limited. Due to the growing population of elderly, OA prevalence rapidly increases. The fact that no reliable clinical markers are available for diagnosis, monitoring and progression is a major impediment in OA disease management and incurs high costs in drug development and clinical trials. Molecular markers were studied in OA affected cartilage compared to unaffected cartilage of the same joint (chapter 2) and in blood of OA patients (chapter 3). Perturbation of the application of traditional biochemical markers sCOMP and uCTX2 in the clinic due to genetic factors that, independent of OA, affect innate levels was investigated (chapter 4). Furthermore, we have tried to go beyond the results of molecular epidemiological studies to increase insights into underlying mechanisms (chapter 6 & 7). This shows how functional genomics can be achieved by combining genetic and functional data and will facilitate translation of knowledge of genetic variants to the needs of OA patients and thus to application in the clinic. Show less
In the first part an update of a guideline for the physiotherapy treatment of patients with hip and knee OA is described. Then a set of quality indicators for the physiotherapy management is... Show moreIn the first part an update of a guideline for the physiotherapy treatment of patients with hip and knee OA is described. Then a set of quality indicators for the physiotherapy management is developed to be used as an instrument to measure guideline adherence. Subsequently the effect of educational strategies to enhance their uptake by physiotherapists in daily clinical practice is investigated. An interactive approach with patient colaboration and following a proces of clinical reasoning has shown to be the most effective strategy. The second part describes the extent of the provision of physiotherapy before and after joint replacement surgery from the physiotherapists__ and patients__ perspective. Results showed a large variation in provided interventions before and after surgery, although evidence for physiotherapy before joint replacement surgery is lacking. This indicates that more research is necessary focussing on effectiveness for specific groups of patients. In addition it was concluded that the presence of severe back pain in THA and dizziness in THA and TKA, should maybe ascertained before surgery and if present be treated if possible in order to decrease the chance of unfavourable outcome, although the predictive value of dizziness should be confirmed in a study with a prospective design. Show less
Osteoarthritis is a prevalent disease causing pain and disability. It__s aetiology is unknown and no curative treatment is available. Osteoarthritis research is complicated due to heterogeneity of... Show moreOsteoarthritis is a prevalent disease causing pain and disability. It__s aetiology is unknown and no curative treatment is available. Osteoarthritis research is complicated due to heterogeneity of the disease, slow progression and poor association of clinical features with radiographic abnormalities, imaging modality of choice until now. In this thesis the role of synovitis in osteoarthritis is studied in relationship with clinical features and structural damage. The studies described made especially use of data derived a prospective follow-up study in symptomatic hand osteoarthritis patients. Synovitis detected on ultrasound was associated with clinical features and with progression of structural damage after 2.3 years in hand osteoarthritis. In erosive osteoarthritis, a subtype of hand osteoarthritis, more synovitis was found in all hand joints, even in non-erosive joints, when compared to joints of patients without erosive osteoarthritis. Also, associations were found between synovitis and erosive development at follow-up. All analyses were performed on joint level, using GEE analyses, thereby taking into account patient effects. Associations were poor/absent when analyses were done on patient level. This is important for further research. These results indicate that synovitis plays a role in pain and in development of structural damage in osteoarthritis and could be a therapeutic target. Show less
