Objective To characterize aspects of triiodothyronine (T3) induced chondrocyte terminal maturation within the molecular osteoarthritis pathophysiology using the previously established T3 human ex... Show moreObjective To characterize aspects of triiodothyronine (T3) induced chondrocyte terminal maturation within the molecular osteoarthritis pathophysiology using the previously established T3 human ex vivo osteochondral explant model. Designs RNA-sequencing was performed on explant cartilage obtained from OA patients (n = 8), that was cultured ex vivo with or without T3 (10 ng/ml), and main fndings were validated using RT-qPCR in an independent sample set (n = 22). Enrichment analysis was used for functional clustering and comparisons with available OA patient RNAsequencing and GWAS datasets were used to establish relevance for OA pathophysiology by linking to OA patient genomic profles. Results Besides the upregulation of known hypertrophic genes EPAS1 and ANKH, T3 treatment resulted in diferential expression of 247 genes with main pathways linked to extracellular matrix and ossifcation. CCDC80, CDON, ANKH and ATOH8 were among the genes found to consistently mark early, ongoing and terminal maturational OA processes in patients. Furthermore, among the 37 OA risk genes that were signifcantly afected in cartilage by T3 were COL12A1, TNC, SPARC and PAPPA. Conclusions RNA-sequencing results show that metabolic activation and recuperation of growth plate morphology are induced by T3 in OA chondrocytes, indicating terminal maturation is accelerated. The molecular mechanisms involved in hypertrophy were linked to all stages of OA pathophysiology and will be used to validate disease models for drug testing. 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 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
Houtman, E.; Tuerlings, M.; Riechelman, J.; Suchiman, E.H.E.D.; Wal, R.J.P. van der; Nelissen, R.G.H.H.; ... ; Meulenbelt, I. 2021
Background Failing of intrinsic chondrocyte repair after mechanical stress is known as one of the most important initiators of osteoarthritis. Nonetheless, insight into these early mechano... Show moreBackground Failing of intrinsic chondrocyte repair after mechanical stress is known as one of the most important initiators of osteoarthritis. Nonetheless, insight into these early mechano-pathophysiological processes in age-related human articular cartilage is still lacking. Such insights are needed to advance clinical development. To highlight important molecular processes of osteoarthritis mechano-pathology, the transcriptome-wide changes following injurious mechanical stress on human aged osteochondral explants were characterized. Methods Following mechanical stress at a strain of 65% (65%MS) on human osteochondral explants (n(65%MS) = 14 versus n(control) = 14), RNA sequencing was performed. Differential expression analysis between control and 65%MS was performed to determine mechanical stress-specific changes. Enrichment for pathways and protein-protein interactions was analyzed with Enrichr and STRING. Results We identified 156 genes significantly differentially expressed between control and 65%MS human osteochondral explants. Of note, IGFBP5 (FC = 6.01; FDR = 7.81 x 10(-3)) and MMP13 (FC = 5.19; FDR = 4.84 x 10(-2)) were the highest upregulated genes, while IGFBP6 (FC = 0.19; FDR = 3.07 x 10(-4)) was the most downregulated gene. Protein-protein interactions were significantly higher than expected by chance (P = 1.44 x 10(-15) with connections between 116 out of 156 genes). Pathway analysis showed, among others, enrichment for cellular senescence, insulin-like growth factor (IGF) I and II binding, and focal adhesion. Conclusions Our results faithfully represent transcriptomic wide consequences of mechanical stress in human aged articular cartilage with MMP13, IGF binding proteins, and cellular senescence as the most notable results. Acquired knowledge on the as such identified initial, osteoarthritis-related, detrimental responses of chondrocytes may eventually contribute to the development of effective disease-modifying osteoarthritis treatments. Show less
Houtman, E.; Hoolwerff, M. van; Lakenberg, N.; Suchiman, E.H.D.; Zwaag, E.V.V. van der van der; Nelissen, R.G.H.H.; ... ; Meulenbelt, I. 2021
Introduction: Likely due to ignored heterogeneity in disease pathophysiology, osteoarthritis (OA) has become the most common disabling joint disease, without effective disease-modifying treatment... Show moreIntroduction: Likely due to ignored heterogeneity in disease pathophysiology, osteoarthritis (OA) has become the most common disabling joint disease, without effective disease-modifying treatment causing a large social and economic burden. In this study we set out to explore responses of aged human osteochondral explants upon different OA-related perturbing triggers (inflammation, hypertrophy and mechanical stress) for future tailored biomimetic human models.Methods: Human osteochondral explants were treated with IL-1 beta (10 ng/ml) or triiodothyronine (T3; 10 nM) or received 65% strains of mechanical stress (65% MS). Changes in chondrocyte signalling were determined by expression levels of nine genes involved in catabolism, anabolism and hypertrophy. Breakdown of cartilage was measured by sulphated glycosaminoglycans (sGAGs) release, scoring histological changes (Mankin score) and mechanical properties of cartilage.Results: All three perturbations (IL-1 beta, T3 and 65% MS) resulted in upregulation of the catabolic genes MMP13 and EPAS1. IL-1 beta abolished COL2A1 and ACAN gene expression and increased cartilage degeneration, reflected by increased Mankin scores and sGAGs released. Treatment with T3 resulted in a high and significant upregulation of the hypertrophic markers COL1A1, COL10A1 and ALPL. However, 65% MS increased sGAG release and detrimentally altered mechanical properties of cartilage.Conclusion: We present consistent and specific output on three different triggers of OA. Perturbation with the pro-inflammatory IL-1 beta mainly induced catabolic chondrocyte signalling and cartilage breakdown, while T3 initiated expression of hypertrophic and mineralization markers. Mechanical stress at a strain of 65% induced catabolic chondrocyte signalling and changed cartilage matrix integrity. The major strength of our ex vivo models was that they considered aged, preserved, human cartilage of a heterogeneous OA patient population. As a result, the explants may reflect a reliable biomimetic model prone to OA onset allowing for development of different treatment modalities. Show less
Objective: Inflammation and innate immune responses may contribute to development and progression of Osteoarthritis (OA). Chondrocytes are the sole cell type of the articular cartilage and produce... Show moreObjective: Inflammation and innate immune responses may contribute to development and progression of Osteoarthritis (OA). Chondrocytes are the sole cell type of the articular cartilage and produce extracellular-matrix molecules. How inflammatory mediators reach chondrocytes is incompletely understood. Previous studies have shown that chondrocytes express mRNA encoding complement proteins such as C1q, suggesting local protein production, which has not been demonstrated conclusively. The aim of this study is to explore C1q production at the protein level by chondrocytes.Design: We analysed protein expression of C1q in freshly isolated and cultured human articular chondrocytes using Western blot, ELISA and flow cytometry. We examined changes in mRNA expression of collagen, MMP-1 and various complement genes upon stimulation with pro-inflammatory cytokines or C1q. mRNA expression of C1 genes was determined in articular mouse chondrocytes.Results: Primary human articular chondrocytes express genes encoding C1q, C1QA, C1QB, C1QC, and secrete C1q to the extracellular medium. Stimulation of chondrocytes with pro-inflammatory cytokines upregulated C1QA, C1QB, C1QC mRNA expression, although this was not confirmed at the protein level. Extracellular C1q bound to the chondrocyte surface dose dependently. In a pilot study, binding of C1q to chondrocytes resulted in changes in the expression of collagens with a decrease in collagen type 2 and an increase in type 10. Mouse articular chondrocytes also expressed C1QA, C1QB, C1QC, C1R and C1S at the mRNA level.Conclusions: C1q protein can be expressed and secreted by human articular chondrocytes and is able to bind to chondrocytes influencing the relative collagen expression. (C) 2019 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved. Show less
Spoel, E. van der; Vliet, N.A. van; Heemst, D. van 2019
Specific hallmarks are thought to underlie the ageing process and age-related functional decline. In this viewpoint, we put forward the hypothesis that disturbances in the process of tissue... Show moreSpecific hallmarks are thought to underlie the ageing process and age-related functional decline. In this viewpoint, we put forward the hypothesis that disturbances in the process of tissue maintenance are an important common denominator that may lie in between specific hallmarks of ageing (i.e. damage and responses to damage) and their ultimate (patho)physiological consequences (i.e. functional decline and age-related disease). As a first step towards verifying or falsifying this hypothesis, it will be important to measure biomarkers of tissue maintenance in future studies in different study populations. The main aim of the current paper is to discuss potential biomarkers of tissue maintenance that could be used in such future studies. Among the many tissues that could have been chosen to explore our hypothesis, to keep the paper manageable, we chose to focus on a selected number of tissues, namely bone, cartilage, muscle, and the brain, which are important for mobility and cognition and affected in several common age-related diseases, including osteoporosis, osteoarthritis, sarcopenia, and neurodegenerative diseases. Furthermore, we discuss the advantages and limitations of potential biomarkers for use in (pre)clinical studies. The proposed biomarkers should be validated in future research, for example by measuring these in humans with different rates of ageing. 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
Measuring biomechanics of the knee with an acceptable degree of accuracy is difficult. When the in vivo knee joint motion is analyzed in all its six degrees-of-freedom without compromising on... Show moreMeasuring biomechanics of the knee with an acceptable degree of accuracy is difficult. When the in vivo knee joint motion is analyzed in all its six degrees-of-freedom without compromising on physiological loading conditions, the task becomes even more challenging. This thesis offers a brief overview of the development, validation and application of a non-invasive imaging methodology to capture the in vivo biomechanics of anterior cruciate ligament (ACL) deficient and posterior cruciate ligament (PCL) deficient knees. By combining dual fluoroscopy to capture the in vivo joint motion and magnetic resonance imaging to reconstruct the joint anatomy, we obtained a comprehensive insight in both tibiofemoral as well as patellofemoral kinematics and cartilage biomechanics of healthy knees under various loading conditions. These baseline measurements helped us comprehend the alterations in biomechanics seen in knees after injury of either ACL or PCL, which in turn generated clinically useful data for the improvement of our surgical reconstruction techniques. Show less
Caam, A. van; Madej, W.; Thijssen, E.; Vinuesa, A.G. de; Berg, W. van den; Goumans, M.J.; ... ; Kraan, P.M. van der 2016
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 view of the complex roles of the canonical Wnt signaling during skeletal devel-opment and disease, it is important to accurately distinguish the specific roles of this signaling cascade at... Show moreIn view of the complex roles of the canonical Wnt signaling during skeletal devel-opment and disease, it is important to accurately distinguish the specific roles of this signaling cascade at specific time windows during embryogenesis as well as postnatally in the maintenance of the skeleton. Moreover, a proper understanding of these multi-faceted roles will ultimately aid us in identifying new therapeutic targets for the treat-ment of growth disorders, osteoporosis and osteoarthritis. Most of the animal models that furnish our knowledge of the effects of canonical Wnt signaling during skeletal development and maintenance use the forced expression of a stabilized and thereby oncogenic _-catenin. The roles of intracellular _-catenin regulators and thereby of wild type _-catenin levels during skeletogenesis, bone mass accrual or AC maintenance are largely unknown. The research described in this thesis aimed at describing the role of two major intracellular regulators of _-catenin, namely Apc and Gsk3_ in regulation of SPC differentiation, bone mass accrual and cartilage maintenance. Show less
Osteoarthritis of the knee is a chronic progressive joint disease leading to pain and loss of function in a considerable proportion of patients with great impact and consequences in the ageing... Show moreOsteoarthritis of the knee is a chronic progressive joint disease leading to pain and loss of function in a considerable proportion of patients with great impact and consequences in the ageing population of the industrialized world. Clinical symptoms and radiographs of the knee are normally used to monitor osteoarthritic changes in the knee. However, the correlation between radiographic osteoarthritic findings and clinical features is poor. Does MR imaging of the knee tell us more about the relation between osteoarthritic structural findings and clinical features? According to the present thesis, the answer is “No”. Most of the data presented in this thesis is based on a 1.5T longitudinal MR study called the “Genetica, Artrose & Progressie” (GARP) study. In the GARP study MR imaging findings were associated with clinical features of patients with OA, and it was concluded that there were no strong associations between the most important OA imaging findings and clinical features of patients with OA. These controversial findings are important findings with regards to future clinical trials, as it urges conservatism with regards to the idea of BME being an outcome measure for progression of the disease. Therefore, the current theses also strongly recommend a further quest to identify ideal parameters to quantify the progression of the disease. Show less
