Le cartilage articulaire est un tissu avasculaire ayant une faible capacité de régénération. Ce tissu est essentiellement constitué d’un type cellulaire, les chondrocytes, inclus dans une matrice extracellulaire abondante et de composition très spécifique. L’arthrose, la maladie touchant le cartilage la plus fréquente, est caractérisée par la perte progressive de cette matrice extracellulaire, ce qui conduit à l’érosion des surfaces articulaires. Les causes sont multiples et encore mal comprises: inflammation, génétique, mécanique etc... Plusieurs études ont récemment mis en évidence l’implication des mécanismes épigénétiques dans la réponse des chondrocytes aux cytokines inflammatoires (contribuant au catabolisme du tissu).Notre but a été d’étudier le rôle encore peu exploré de ces mécanismes dans la synthèse de la matrice extracellulaire du cartilage (contribuant à l'anabolisme). En utilisant des chondrocytes articulaires humains en culture primaire, nous avons identifié des marques de méthylation de l'ADN étroitement associées à l’expression de gènes codant les principaux composants de la matrice cartilagineuse. Ceci apporte un nouvel éclairage sur l’instabilité du phénotype chondrocytaire. De plus, nous décrivons pour la première fois l'implication de la lysine déméthylase LSD1 (une enzyme modifiant l'état de la chromatine dont l’expression est augmentée dans le cartilage arthrosique), dans la régulation génique d'un collagène du cartilage, le collagène de type IX. L’ensemble des résultats met en évidence de nouveaux mécanismes de régulation génique dans les chondrocytes articulaires, qui pourraient être impliqués dans le développement de l’arthrose / The articular cartilage is an avascular tissue displaying a very limited regenerative capacity. This tissue is mainly composed of one cell type, the chondrocytes, which are embedded within an abundant and highly specialized extracellular matrix. Osteoarthritis, which is the most common joint disease, is characterized by the progressive loss of that matrix, leading to the erosion of articular surface. The causes of this pathology are multiple (genetic, biomechanical, inflammatory…) and are still not fully understood. Several studies have recently highlighted the involvement of epigenetic mechanisms in the chondrocyte response to inflammatory cytokines (contributing to cartilage catabolism).The aim of our work was to investigate the unexplored role of the epigenetic mechanisms in the ability of chondrocytes to synthesize the cartilage-specific matrix (contributing to cartilage anabolism). Using primary culture of human articular chondrocytes, we identified a DNA methylation profile closely associated with the expression of the genes encoding the main structural components of the extracellular matrix. These findings bring new insights in the comprehension of chondrocyte phenotype instability. Moreover, we report for the first time the involvement of the lysine demethylase LSD1, a chromatin-modifying enzyme highly expressed in osteoarthritic tissue, in the gene regulation of COL9A1, a cartilage-specific collagen. Altogether, these results highlight new mechanisms of gene regulation in articular chondrocytes, which may be involved in the development of osteoarthritis

DCC est un récepteur transmembranaire ayant pour ligand la nétrine-1. DCC appartient à la famille des récepteurs à dépendance, qui ont la particularité de ne pas rester inactifs en absence de ligand mais, au contraire, d'induire activement l'apoptose lorsqu'ils sont dans un état non lié, ce qui explique leur fonction suppresseur de tumeur. Mon travail de thèse s'est articulé autour de deux axes de recherche: Axe 1 : Implication du couple DCC/nétrine-1 dans la lymphomagenèse. Nous avons montrer que l'expression du couple DCC/nétrine-1 est dérégulée dans les lymphomes du manteau (LM) ainsi que dans les lymphomes diffus à grandes cellules B (LDGC-B) : l'expression de la nétrine-1 est augmentée dans les LM et les LDGC-B de type ABC, alors que l'expression de DCC est diminuée dans les LDGC-B de type GC. Sur le plan thérapeutique, rétablir l'apoptose induite par DCC en bloquant l'interaction avec son ligand nétrine-1 induit une diminution du volume tumoral dans un modèle de xénogreffe. Le couple DCC/nétrine-1 pourrait également jouer un rôle dans le développement des lymphomes extranodaux. Axe 2 : Caractérisation fonctionnelle de la protéine ADAMTSL-1.L'orthologue de DCC chez C. elegans, UNC-40 interagit fonctionnellement avec la protéine MADD-4 lors de la mise en place des jonctions neuromusculaires. Nous n'avons pas établi l'existence d'une telle connexion entre DCC et l'orthologue de MADD-4 chez les Mammifères, ADAMTSL1. La fonction d'ADAMTSL1 étant inconnue, nous avons utilisé différents systèmes in vitro et in vivo, dont un modèle murin invalidé constitutivement pour ce gène, pour déterminer la fonction de cette protéine matricielle, notamment dans les tissus musculaires et cartilagineux / DCC is a tramsmembrane protein, receptor of netrin-1. DCC belongs to the dependence receptor family, which have a dual functionality. Indeed, they are not inactive when not bound by their ligand but instead they actively induce apoptosis thus explaining that they are tumor suppressors. My PhD project contains 2 axes :Axe 1 : Involvement of DCC/netrin-1 during lymphomagenesis. We demonstrated that the gene expression of DCC and netrin-1 is deregulated in mantle cell lymphoma (MCL) and in diffuse large b cell lymphoma (DLBCL) : netrin-1 expression is upregulated in MCL and Activated B-Cell DLBCL. On the opposit, DCC expression is downregulated in Germinal Centre DLBCL. From a therapeutical point of view, reinducing DCC's apoptotis by blocking its interaction with netrin-1 triggers tumor volum in a xenograft model. DCC-netrin-1 might also be involved in extra-nodal lymphoma development. Axe 2 : Functional caracterization of ADAMTSL1.DCC's ortholog in C. elegans, UNC-40, functionnaly interacts with the protein MADD-4 during the setting up of neuromuscular junctions. We did not find any such connexion between DCC and MADD-4's ortholog in mammals, ADAMTSL1. The function of ADAMTSL1 is unknown and we used different in vitro and in vivo models including a mouse model invalidated for this gene to unravel the function of this matricial protein, notably in muscular and cartilaginous tissus

Articular cartilage injuries occur frequently in the knee joint. Several methods have been implemented clinically, to treat osteochondral defects but none have been able to produce a long term, durable solution. Photopolymerizable cartilage tissue engineering approaches appear promising; however, fundamentally, forming a stable interface between the tissue engineered cartilage and native tissue, mainly subchondral bone and native cartilage, remains a major challenge. The overall objective of this research is to find a solution for the current problem of dislodgment of tissue engineered cartilage at the defect site for the treatment of degraded cartilage that has been caused due to knee injuries or because of mild to moderate level of osteoarthritis. For this, an in-vitro model was created to analyze the integration of tissue engineered cartilage with the bone, healthy and diseased cartilage over time. We investigated the utility of hydroxyapatite (HA) nanoparticles to promote controlled bone-growth across the bone-cartilage interface in an in vitro engineered tissue model system using bone marrow derived stem cells. We also investigated the application of HA nanoparticles to promote enhance integration between tissue engineered cartilage and native cartilage both in healthy and diseased states. Samples incorporated with HA demonstrated significantly higher interfacial shear strength (at the junction between engineered cartilage and engineered bone and also with diseased cartilage) compared to the constructs without HA (p < 0.05), after 28 days of culture. These findings indicate that the incorporation of HA nanoparticles permits more stable anchorage of the injectable hydrogel-based engineered cartilage construct via augmented integration between bone and cartilage.

L'Osteoarthrose (OA) est la maladie articulaire la plus répandue avec un impact socio-économique croissant en raison du vieillissement de la population, de l’augmentation de l'obésité et surtout de l'absence d'un traitement efficace. En effet, l’OA est caractérisée par la dégradation inéluctable du cartilage articulaire, l'apoptose des chondrocytes, un remodelage osseux sous-chondral et une inflammation de la synovie. La matrice extracellulaire (MEC) du cartilage est constituée de collagènes et de protéoglycanes (PG) eux-mêmes composés de glycosaminoglycanes (GAG) liés à un corps proteique, présents dans l'ECM ou à la surface cellulaire. Les GAG sont des chaînes polysaccharidiques linéaires sulfatées comprenant les Héparine/Héparan Sulfate (Hep/HS), Chondroitin Sulfate (CS) et Keratan Sulfate (KS). L'acide hyaluronique (AH) est un GAG non sulfaté particulier, non associé à un corps proteique. Dans le cartilage, l'un des principaux composants de la MEC est l'aggrécan, un CS/KS PG qui forme des aggrégats par interaction avec de l’AH. Au cours du vieillissement, des changements dans la qualité des PG ouvrent la voie à l’OA et les études depuis 60 ans se concentrent sur les aggrécans et le catabolisme des CS. En effets, les niveaux d'expression des CS, la taille de leurs chaînes, leurs profils de sulfatation évoluent, affectant les propriétés mécaniques de la MEC. Cependant, les traitements actuels de visco-supplémentation à base d’injections locales de CS ont démontré leur limite puisque la réparation du cartilage n'est pas induite. Même si ils sont rares dans le cartilage adulte, les HSPG sont associés aux chondrocytes et leurs rôles a été démontrée lors du développement osseux. Or les HS sont des régulateurs de l’homéostasie très importants car ils peuvent lier et réguler l'activité de protéines liant l'héparine (HBP) (facteurs de croissance, cytokines, chimiokines, morphogènes), les protégeant contre la protéolyse et potentialisant leur liaison à leurs récepteurs. Tous ces effets sont contrôlés par les profils de sulfatation complexes des chaînes d’HS.Dans ce contexte les objectifs de cette thèse sont de caractériser l'évolution de la signature chimique et de la fonctionnalité des HS au cours de l’OA. En collaboration avec les Rhumatologistes et Orthopédistes de l’Hopital Henri Mondor, une évaluation quantitative des HS dans des échantillons de cartilage humain contrôle versus OA a été corrélée à la gravité des dommages. Grace à la plateforme glycomic du CRRET, des modifications dans les profils de sulfatation des disaccharides de HS ont été observées et confirmées par des analyses de l'expression des enzymes de la biosynthèse des GAG. Ces caractéristiques structurales ont été corrélées à des changements fonctionnels de l’affinité des GAG pour des HBP, telles que FGF-2, VEGF et PTN. Enfin, les GAG OA ont des capacités différentes à moduler les propriétés (prolifération, adhésion, phénotype) de cellules souches mésenchymateuses, chondrocytes, fibroblastes et cellules endothéliales. Ces résultats démontrent que des modifications des structures et fonctions des HS pourraient être impliquées dans l'évolution de l'homéostasie du cartilage vers des processus pathologiques au cours de l’OA. Ce projet se positionne clairement comme une recherche fondamentale et translationnelle qui permettra d'acquérir des connaissances sur les mécanismes régulant les interactions cellules/matrice au cours de l'OA. De plus, les outils développés au cours de ce projet ont permis de réaliser 2 projets collaboratifs sur l'hypertension artérielle pulmonaire et une pathologie éosophagique. Enfin, ces données confirment l'intérêt d’identifier de nouvelles cibles glycaniques basées sur la chimie des HS. Cela permettra de proposer une nouvelle stratégie thérapeutique basée sur des composes à même de contrôler les profils de sulfatation de la MEC, dans le but d'améliorer les propriétés de cellules souches thérapeutiques endogènes ou exogènes, associées. / Osteoarthritis (OA) is the most prevalent joint disease with increasing socio-economic impact due to population aging, obesity , and absence of an efficient medical treatment that can repair cartilage. OA is characterized by degradation of articular cartilage, hypertrophy and apoptosis of chondrocytes, subchondral bone remodeling and joint synovial inflammation. Cartilage extracellular matrix (ECM) consists of collagens, glycoproteins and proteoglycans (PGs) that are composed of Glycosaminoglycans (GAGs) linked to core proteins, presents in the ECM or at the cell surface. GAGs are linear polysaccharidic sulfated chains including Heparine/Heparan Sulfate (Hep/HS), Chondroitin Sulfate (CS) and Keratan Sulfate (KS) families. Hyaluronic acid (HA) is a particular un-sulfated GAG no associated to core protein. In cartilage, one of the major ECM component is aggrecan, a CS/KS PG that form aggregate through HA interaction. During the aging process, changes in PGs quality pave the way for OA and studies are focus on aggrecans and CS catabolism since 60 years. CS expression levels, chain size, sulfation patterns evolved during OA, affecting the mechanical properties of ECM. However, treatments based on visco-supplementation with CS local injections have demonstrated their limit since cartilage repair is not induced. Even if rare in adult cartilage, HSPG are present associated to chondrocytes also and their relevance was demonstrated mainly during bone development. HS chains are very important homeostatic regulators because they are able to bind and regulate the activity of several heparin binding proteins (HBP) (growth factors, cytokines, chemokines, morphogens), protecting them against proteolysis and potentiating their binding to their receptors. These interactions provide a stock of regulatory factors that can be release by selective degradation of the HS chains too. All these regulatory effects are mediated through the complex sulfation/acetylation pattern of HS chains but no data are available on this aspect during OA.In this context, the goals of this Thesis were to characterize the evolution of HS chemical signature and functionality during OA. In collaboration with Rheumatology and Orthopedic clinical teams from Henri Mondor Hospital, a quantitative evaluation of HS and CS amount in control versus OA human cartilage samples was correlated to the structural damage severity. According to the tools of the CRRET’s lab glycomic platform, structural changes on HS and CS sulfated disaccharides compositions was observed using HPLC, confirmed by RQ-PCR analyzes of the expression of enzymes involved in GAG biosynthesis. These structural features were correlated to functional changes on HBP affinities, such as FGF-2, VEGF and PTN, through ELISA based competition assay. Finally, GAGs from OA have different abilities to modulate properties (adhesion proliferation, phenotype…) of Mesenchymal Stem Cells, chondrocytes, fibroblast and endothelial cells. These results clearly make the proof that modifications of HS structures and functions could be involved in the evolution of cartilage homeostasis and pave the way for altered pathological processes during OA. This project is clearly positioned as a fundamental and translational research that will permit to gain knowledge on the mechanisms regulating cartilage cells/matrix interactions during OA. All these results are summarized in 2 scientific and 1 review articles. Moreover, all the tools developed during this project have permit to realize 2 collaborative projects and associated articles on Pulmonary Hypertension and Eosophagic pathology also. Finally, all these data confirmed the interest of the team to identify new glycanic targets based on HS chemistry. This will permit to propose new therapeutic strategy based on HS compounds associated to endogenous or exogenous therapeutic stem cells, with the aim of improving cell properties according to HS ability to control sulfation panels of ECM.

Focal damage to cartilage sustained in serious joint injuries typically goes unrepaired and may progress to post-traumatic osteoarthritis. However, in a bovine explant model we found that cartilage damage provoked the emergence of highly migratory cells that homed to the site of injury and appeared to re-populate dead zones. We hypothesized that the migrating population were chondrogenic progenitor cells engaged in cartilage repair. The surfaces of bovine osteochondral explants injured by blunt impact were serially imaged to follow cell migration. Migrating cells harvested from cartilage surfaces were tested for clonogenic, side population, chemotactic activities and multipotency in in vitro assays. Gene expression in migrating cells was evaluated by microarray and their potential for spontaneous cartilage regeneration was assessed in a chondral defect model. Migrating cells emerged from superficial zone cartilage and efficiently repopulated areas where chondrocyte death had occurred. In confocal examination with high magnification, we could clearly observe the morphology of elongated progenitor cells which were migrating toward cartilage defect area and these cells were distinguishable from round chondrocytes. The cells were also activated to migrate in cartilage defect model. Most migrated cells in fibrin were morphologically elongated and a few cells were differentiating to chondrocyte-like cells with the deposit of proteoglycans. These cells proved to be highly clonogenic and capable of chondrogenesis and osteogenesis, but not adipogenesis. They were more active in chemotaxis assays than chondrocytes, showed a significantly larger side population, and over-expressed progenitor cell markers and genes involved in migration, chemotaxis, and proliferation. To active migration of chondrogenic progenitor cells (CPCs) short-term enzymatic method was used around edge of cartilage defect. Surprisingly, CPCs migrated into fibrin defect and were differentiating into chondrocytes with abundant deposit of proteoglycans. This result strongly supports that progenitor cells are activated in traumatic cartilage injury and have great potential for cartilage repair. In conclusion, migrating cells on injured explant surfaces are chondrogenic progenitors from the superficial zone that were activated by cartilage damage to attempt repair. Facilitating this endogenous process could allow repair of focal defects that would otherwise progress to post-traumatic osteoarthritis.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23417号 / 医博第4762号 / 新制||医||1052(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 松田 秀一特定拠点, 教授 妻木 範行, 教授 安達 泰治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

A polyconvex continuum-level proteoglycan Cauchy stress function was developed based on the continuum electromechanical Poisson-Boltzmann unit cell model for proteoglycan interactions. The resulting proteoglycan model was combined with a novel collagen fibril model and a ground substance matrix material to create a polyconvex constitutive finite element model of articular cartilage. The true collagen fibril modulus , and the ground substance matrix shear modulus , were varied to obtain the best fit to experimental tension, confined compression, and unconfined compression data for native explants and explants cultured in insulin-like growth factor-1 (IGF-1) and transforming growth factor-β1 (TGF-β1). Results indicate that culture in IGF-1 results in a weakening of the COL fibers compared to native explants, and culture in TGF-β1 results in a strengthening of the COL fibers compared to native explants. These results elucidate the biomechanical changes in collagen fibril modulus, and ground matrix shear modulus following in vitro culture with IGF-1 and TGF-β1. Understanding the constitutive effects of growth factor stimulated culture may have applications in AC repair and tissue engineering.

Les lésions cartilagineuses survenant majoritairement dans un contexte de traumatisme, ne se réparent pas spontanément. Les traitements chirurgicaux et les techniques d'ingénierie cellulaire, utilisés en clinique, donnent des résultats perfectibles. L'ingénierie tissulaire du cartilage fait l'objet de nombreux travaux dans le but de produire au sein de la lésion un tissu de réparation dont les caractéristiques structurales et fonctionnelles sont similaires à celles du cartilage natif. Le diagnostic précoce de ces lésions et l'évaluation du tissu de réparation sont également des enjeux majeurs en orthopédie. L'IRM est une technique d'imagerie non invasive et à haute résolution permettant une évaluation du cartilage tant d'un point de vue architectural que biochimique en utilisant des séquences dédiées. En raison de leurs potentialités chondrogéniques, les cellules souches, provenant de différents tissus, sont une piste encourageante pour induire la régénération du cartilage lésé par des traumatismes articulaires. Des cellules provenant de différents tissus (moelle osseuse, membrane synoviale) ainsi que des chondrocytes dédifférenciés ont été ensemencés dans une structure tridimensionnelle poreuse à base de collagène I (éponge de collagène I) et soumis à un environnement chondrogénique afin de produire un implant fonctionnalisé. L'évaluation de la qualité de la synthèse matricielle in vitro dans l'implant a démontré le potentiel chondrogénique des différents contingents. La faisabilité d'un marquage de cellules souches mésenchymateuses (CSM) par des particules d'oxyde de fer superparamagnétiques (SPIO), diminuant le signal en IRM a été démontrée in vitro à 3 Teslas (3T) et 7 Teslas (7T). Des concentrations inférieures à 25 µg Fe/mL peuvent être utilisées sans endommager massivement la synthèse d'une matrice cartilagineuse par des CSM osté-médullaires. L'implantation des biomatériaux fonctionnalisés en site ectopique chez la souris nude a conduit à une dérive phénotypique ostéoïde de l'implant. En revanche, en site articulaire, chez le rat nude, les implants induisent la production d'un tissu de réparation comblant l'intégralité de la lésion et présentant des caractéristiques proche du cartilage sain environnant / Cartilaginous lesions mainly occur from a traumatic background and do not heal spontaneously. The chirurgical treatment and the cellular engineering techniques, usually used in clinic, produce perfectible results. Cartilage tissue engineering is the subject of many works in order to produce a repair tissue into the lesion. This repair tissue aims to have the same structural an functional characteristics as the native cartilage. In orthopaedic field, the early diagnostic of chondral lesions and the evaluation of the repair tissue are major issues. MRI is a high resolution and non invasive imaging technique that could be used to evaluate the architectural and biochemical structures of the cartilage by using dedicated sequences. Because of their chondrogenic capacities, stem cells provide a promising avenue to regenerate damaged cartilage in articular traumas. The stem cells from various origins (bone marrow, synovium) and the dedifferentiated chondrocytes were seeded into a porous 3D scaffold in collagen I (collagen I sponge). These cells were cultivated in chondrogenic conditions to produce a functionalized implant. The quality of the matrix synthesis was evaluated in vitro and demonstrated the chondrogenic potential of these various cell types. Superparamagnetic iron oxid particle (SPIO) labelling of the mesenchymal stem cells (MSC) is feasible in vitro at 3 Teslas (3T) and 7 Teslas (7T). A SPIO concentration lower than 25 ?g Fe/mL could be used without reducing the cartilaginous matrix synthesis by bone marrow MSC. The functionalized biomaterial implantation in an ectopic site in a nude mouse model showed an osseous split. However, in articular site in a nude rat model, the implants produced a repair tissue filling the totality of the lesion. This tissue seems to have similar characteristics of the surrounding healthy cartilage

. / Articular cartilage is made up of dense, connective tissue localized at the junction of several locations in the skeleton. It covers the surface of the joints to ensure that bones can move. It is an avascular tissue that is not innervated and is composed primarily of a single cell type, the chondrocyte, which synthesizes an abundant extracellular matrix (ECM). Osteoarthritis (OA), a degenerative disease of articular cartilage, is characterized by the degradation of the ECM, associated with increased secretion of matrix metalloproteinases (MMPs) and aggrecanases. In addition, the OA process induces chondrocyte dedifferentiation characterized at least in part by increased synthesis of type I collagen, an atypical isoform in articular cartilage. Moreover, due to the poor intrinsic healing capacity of articular cartilage, there is currently no treatment to restore the chondrocyte phenotype and, in the most advanced stages of OA, the joint must be replaced with a prosthesis, requiring surgery. Therefore, various drug and surgical treatments have been developed in an attempt to prevent the destruction of cartilage which, in light of their relative success, then lead to new, improved therapeutic strategies. One of the most promising approaches is the cartilage tissue engineering based on the procedure described by Brittberg using autologous chondrocyte implantation (ACI). Applied in the earliest stages of OA or chondral lesions, ACI is based on the use of chondrocytes from a healthy, non-bearing region of the diseased joint. The cells are then amplified in monolayer culture and then re-implanted in the lesion. However, amplification of autologous chondrocytes in two-dimensional culture mimics, at least in part, some of the characteristics of the OA process and is accompanied by cell dedifferentiation leading to the formation of nonfunctional fibrocartilage. The numerous pharmaceutical approaches and surgical techniques developed to repair cartilage lesions have revealed their limitations. Ideally, traumatic cartilage lesions should be treated earlier to prevent OA and postpone prosthetic surgery. In the interest of preventing OA, cartilage cell therapy has proven to be a pivotal approach for repairing damaged tissue. Cell therapy consists not only in filling the cartilage lesion with healthy chondrocytes, but also in reconstituting the structure, the physico-chemical properties and the functionality of the hyaline matrix. The transplantation of autologous chondrocytes is the foundation of cell therapy and cartilage tissue engineering and there have been several generations of ACI, each improving on the previous one. However, even the most recent ACI techniques are showing limitations and consequently, research efforts are now focused on improving this technique in order to obtain, after amplification, a differentiated and stable chondrocyte phenotype. This is to be achieved by using new types of biomaterials that can fill more important lesions, molecules and growth factors to better control the chondrogenic differentiation and more suitable cell sources that avoid morbidity at the donor site as it is the case with articular chondrocytes. Today, MSCs hold much promise for biomedical research because they are able to recapitulate many tissues, including cartilage. However, for future advances in the field of regeneration and tissue engineering it is important to know the exact nature of these cells. With this goal, in this work, we first fully characterized 4 categories of serum free amplified mesenchymal stem cells extracted from adipose tissue (AT), bone marrow (BM), dental pulp (DP) and Wharton’s jelly (WJ) of the umbilical cord. The cells were characterized in terms of efficiency of isolation, amplification kinetics and according to an extensive immunophenotyping using flow cytometry... [etc]

Knee pain can alter lower-extremity neuromechanics and often results in functional disability. The relationship between lower-extremity neuromechanical alterations, due to anterior knee pain, and articular cartilage condition is unclear. The purpose of this study was to determine the independent effect of anterior knee pain during running on articular cartilage condition, as reflected by serum cartilage oligomeric matrix protein concentrations and muscle cocontraction duration. Seven men and five women completed a 30-min run in three different sessions: control (no infusion), sham (isotonic saline infusion), and pain (hypertonic saline infusion). Saline was infused into the right infrapatellar fat pad for the duration of the run. Subject-perceived pain was recorded every 3 min on a 100-mm visual analog scale. During the run, bilateral electromyography was recorded for five leg muscles, and heel and toe markers were used to track foot position. During the 30-min run of the pain session average subject-perceived pain was 27.8 (SD = 2.3 mm) and 19.7 (SD = 1.9) mm greater than during the control (0.0 mm) and sham (8.1 mm) session, respectively (p < 0.01). Knee pain while running did not result in changes in muscular cocontraction duration (p = 0.13). Blood samples were drawn prior to the run, immediately following the run, and 60 min following the run. Samples were analyzed using enzyme-linked immunosortbent assay to determine serum cartilage oligomeric matrix protein concentration. Average serum cartilage oligomeric matrix protein concentration was 14% greater at immediate post run (132.19 ± 158.61 ng/ml; Range = 22.61-290.81 ng/ml) relative to pre run (116.02 ± 118.87 ng/ml; Range = 19.81-234.89 ng/ml) (p < 0.01), and 18% less at 60 min post run (108.45 ± 171.78 ng/ml; Range = 20.84-280.23 ng/ml) relative to immediate post run (Figure 4; p < 0.01). Serum cartilage oligomeric matrix protein did not significantly differ between baseline and 60 min post-exercise (p = 0.29). There was not a difference in cartilage oligomeric matrix protein concentration between sessions. Knee pain while running does not cause an increase in serum cartilage oligomeric matrix protein concentration (p = 0.29). There are two important findings from this study. First, anterior knee pain during a 30 min running session does not appear to independently affect cartilage oligomeric matrix protein concentrations. This implies other factors, aside from anterior knee pain alone, influence articular cartilage degradation during movement that occurs while individuals are experiencing anterior knee pain. Second, the present experimental anterior knee pain model can be used to evaluate the independent effects of anterior knee pain over an extended duration while subjects perform a dynamic activity like running.