Enfermidade muito observada nas articulações dos equinos, o processo degenerativo articular crônico na articulação tibio-társica pode ser de origem primária, ou secundária à osteocondrose dissecante. A confirmação diagnóstica é feita por avaliação radiográfica. Importantes aliados diagnósticos são a avaliação do líquido sinovial, a avaliação ultrassonografia e a cirurgia de video-artroscopia, sendo esta última o tratamento para a enfermidade. Por sua evolução crônica e às vezes assintomática, a osteocondrose dissecante causa alterações no ambiente articular, como a perda de matriz cartilagínea, o que limita o potencial atlético do animal, acarretando em queda na performace e perdas econômicas. É comum o uso terapêutico intra-articular no periodo pós operatório recente de substâncias autólogas como o plasma rico em plaquetas (PRP), bem como o uso ácido hialurônico (HA), como adjuvante para o tratamento cirúrgico. O presente trabalho objetiva comparar e avaliar estes tratamentos. Foram utilizados 18 equinos, com idade variando entre 2 a 6 anos de idade, da raça Brasileiro de Hipismo, com peso corpóreo entre 400 e 650 kg, oriundos do mesmo criatório, com osteocondrose dissecante, na crista intermédia do osso tíbia. Estes animais no décimo dia pós operatório são dividos em três grupos experimentais: grupo AH, grupo PRP e grupo RCL como controle. Dados clínicos, ultrassonográficos e laboratoriais foram coletados em tempos definidos. Os resultados demonstraram que os animais do grupo controle - grupo RCL, que receberam solução de ringer com lactato intraarticular, apresentaram respostas clínicas e laboratoriais que indicaram menor indução do processo inflamatório ao ambiente articular quando comparado aos grupos PRP e AH. Os animais que receberam PRP apresentaram maior efusão sinovial e resposta positiva ao teste de flexão quando comparados aos animais que receberam AH; ao passo que a administração intra-articular de AH induziu maiores alteração citológica do líquido sinovial quando comparadas aos animais que receberam PRP. / One of the most commom diseases in the equine joint, the degenerative joint disease in the tibio tarsal joint could be a primary disease, or secondary to osteochondrosis dissecans. The diagnosis is made by radiographic study. Allies in diagnosing this disease includes sinovial fluid evaluation, ultrasonographic evaluation and video arthroscopy surgery, which is the way to treat this disease. The osteochondrosis dissecans has a chronic evolution, and several times asymptomatic, which causes an alteration on articular environment that contributes to a loss in the cartilage matrix. Resulting in the limited development of the athletic potential of the animal, poor performance and economic losses. Is common to use therapeutical autholog substances intra articular as the platelet rich plasma, and hialuronic acid, in the early post surgical treatment as an adjuvant therapy to the surgical treatment. This study reaches to compare and evaluate those treatments. Were used 18 horses, with ages between 2 to 6 years old, Brasileiro de Hipismo breed, weighting between 400 and 650 kg, from the same breeding center, with osteochondrosis dissecans fragments from the intermediate tibial crest. Those patients, 10 days after the video arthroscopy surgery, were divided in three experimental groups: AH group, PRP group, and RCL group as control group. Laboratorial data, clinical signs and ultrassonographic exam were performed. The results proved that RCL group had show less induction of inflamatory process on articular enviroment, when we compare with PRP group and AH group. The PRP group had shown more synovial effusion, and more sensibility to the flexion test when we compare to AH group; but the AH group had shown more laboratorial alterations when we compare to the PRP group.

Este projeto teve como finalidade fornecer informações sobre o contingente brasileiro de garanhões afetados pela osteocondrose dissecante (OCD), particularmente no estado de São Paulo. A OCD é uma doença ortopédica do desenvolvimento que acomete os humanos e os animais. É o distúrbio de desenvolvimento esquelético mais importante nos potros em crescimento. É uma falha no processo de ossificação endocondral, que compromete as cartilagens articular e de crescimento, principalmente a articulação tíbio-társica. É uma afecção importante pela incapacitação de atletas e é questão de caráter mundial para o bem-estar animal e para a eqüinocultura, implicando o seu tratamento e estratégias de controle. Há várias modalidades diagnósticas utilizadas na triagem da população acometida pela OCD, que se distinguem de acordo com a acurácia de cada uma. Entretanto, a radiologia, com imagens digitais, ainda se mantém como a ferramenta mais utilizada no campo. Os garanhões foram escolhidos considerando-se a idade, a sanidade, a maturidade, a docilidade e estavam obrigatoriamente registrados no stud-book da ABCCH. Os eqüinos foram submetidos a duas incidências radiográficas bilaterais das articulações tíbio-társicas. Os arquivos foram armazenados em sistema digital e os achados classificaram os animais em positivos e negativos para OCD. Os resultados demonstraram uma ocorrência de 7,7% (2/26) de OCD na população brasileira de garanhões, produtos de inseminação artificial com sêmen importado com a garantia OCD-Free de centrais européias de reprodução. Esta porcentagem se apresentou menor do que as relatadas por pesquisadores de outros países, indicando que o plantel brasileiro de garanhões se apresenta controlado para a OCD e abaixo da expectativa. A baixa ocorrência de OCD nos eqüinos no Brasil, em relação aos outros países, pode ser atribuída ao método de seleção dos reprodutores e também a fatores climáticos. / This project provides information about osteochondrosis dissecans (OCD) affection in Brazilian Warmblood stallions, particularly in the state of Sao Paulo. Osteochondrosis dissecans is a developmental orthopaedic disease, which can involve both humans and animals. It is the most important skeletal disorder in growing foals. It is a failure of the endochondral ossification, which affects both articular and growth-plate cartilages. The tibiotarsal joint is the primary region involved. It is a remarkably disabling condition for competing animals and a serious worldwide issue for animal welfare and the horse industry and involves various treatments and control strategies. There are several modalities of diagnosis used to investigate the OCD, which differ from each other according to their rate of accuracy. However, radiology utilizing digitized images remains the most appropriate tool in the field. The stallions were chosen by the criteria of age, official registration in the ABCCH (Brazilian Sport Horses Breeders\' Association), soundness, maturity and behaviour. The horses were submitted bilaterally to two radiographic views of their hocks. The images were stored in digital files for further individual classification into positive or negative diagnosis. The results yielded an incidence of 7.7% (2/26) of OCD within the Brazilian population of stallions, all of whom were artificial insemination drives offspring, sired from imported European stallions using \"OCD-free\" semen. These results show a lower incidence of OCD than obtained by other countries\' researchers, indicating that the Brazilian stallions are under control for OCD and below the expected mean. The low incidence of OCD in Brazil, in comparison with other countries may be due to the methods of selection established for choosing quality of the semen or to climate differences.

Les adaptations du fœtus aux stimuli intra-utérins ont des conséquences immédiates puis à long terme sur sa santé après la naissance. Chez l’équin, ce concept connu sous le nom de DOHaD (Developmental Origins of Health and Disease) a été validé à l’aide de croisements inter-races : la taille de la jument, qui conditionne l’environnement maternel pendant la gestation puis la lactation, a un impact crucial sur la croissance postnatale du poulain, mais aussi sur la sensibilité à l’insuline du nouveau-né. L’ostéochondrose, pathologie du cheval en croissance, est responsable de pertes financières majeures pour la filière équine. Elle a été reliée à des anomalies de l’homéostasie glucidique et son origine anténatale est fortement suspectée. Dans cette thèse, nous avons mesuré l’impact de perturbations expérimentales au cours du développement fœtal sur la croissance, l’homéostasie glucidique et la prédisposition à l’ostéochondrose du poulain jusqu’à l’âge de 1 an ½. Un premier modèle de croissance fœtale augmentée versus restreinte a été obtenu par transferts d’embryons inter-races (« poneys dans traits » versus « selles dans poneys », respectivement). L’environnement maternel « enrichi » de la jument de trait versus restreint de la ponette s’est révélé déterminant dans la régulation de la croissance des différents segments osseux, de l’axe thyréotrope, de la fonction des cellules β pancréatiques, de la sensibilité à l’insuline de l’organisme et de la santé ostéoarticulaire du poulain dès la naissance et jusqu’à 1 an ½. Tout en validant le concept de DOHaD chez l’équin, ce modèle souligne le soin qui doit être apporté à la sélection des juments receveuses dans la pratique du transfert d’embryons. En démontrant l’ampleur des effets post-nataux programmés in utero et pendant la lactation, ce modèle alerte aussi l’éleveur sur la gestion des poulinières et ses impacts à long terme. En ce sens, le second modèle est en adéquation avec les préoccupations d’élevage puisqu’une perturbation de l’environnement nutritionnel du fœtus a été induite en apportant un concentré (orge) dans la ration hivernale de la jument gravide versus des fourrages uniquement. A ce jour, l’impact de cette modification anténatale sur l’homéostasie glucidique du poulain avant sevrage semble limité à la période néonatale, tandis que sa croissance n’est pas du tout affectée. En revanche, sa prédisposition à l’ostéochondrose à l'âge de 6 mois semble être accrue, ce qui ne permet pas de présager de la suite car le statut ostéoarticulaire du poulain âgé de 6 mois reste susceptible d’évoluer jusqu’à 1 an ½. Ces travaux devraient permettre d’ajuster les recommandations nutritionnelles chez les poulinières. / Fetal adaptations to intra-uterine stimuli have immediate and long term effects on the offspring’s health after birth. In equids, this concept known as the DOHaD (Developmental Origins of Health and Disease) was validated using cross-breeding: the mare’s size which affects the fetal environment throughout gestation and then lactation, has a critical impact on the foal’s post-natal growth, as well as on the neonate’s sensitivity to insulin. Osteochondrosis, a pathology of the growing horse, induces heavy financial losses in the equine industry. It has been associated to abnormalities in glucose homeostasis and its antenatal origin is highly suspected. The present research aimed to evaluate the impact of experimental disturbances during fetal development on growth, glucose homeostasis and predisposition to osteochondrosis in the foal until age 1½ year. Increased versus restricted fetal growth was obtained using between-breed embryo transfers (“ponies in draft horses” versus “saddlebreds in ponies”, respectively). The lush environment of the draft mare versus the restricted environment of the pony mare turned out to be critical in the regulation of bone growth, thyroid hormones secretion, β-cells function, insulin sensitivity and the osteoarticular status of the foal from birth to 1½ year of age. This validates the concept of the DOHaD in equids and shows that recipient mares should be carefully selected in embryo transfer practice. By demonstrating the scope of post-natal effects which were programmed in utero and throughout the lactating period, it also alerts the breeder about the importance of broodmare management and its long term impacts. Thus, the second model was developed to address breeders' practices. A disturbance of the nutritional environment of the fetus was induced by supplementing mares in late pregnancy with concentrated feed (barley). So far, only the neonatal foal's glucose homeostasis was affected, whereas all other studied parameters, including growth, were not affected. The foal’s predisposition to osteochondrosis, however, was increased at 6 months of age, which does not preclude that it will affect the animals afterwards since the osteoarticular status of the 6-month-old foal will evolve beyond weaning time. This research could help adjust nutritional recommendations to broodmares.

[Truncated abstract] Articular cartilage has no vascular, neural, or lymphatic supply, and hence no intrinsic capacity to self-repair following injury. These physiological limitations, combined with the inability of local chondrocytes to contribute to the repair process, translate to poor structural and functional outcomes in these troublesome defects, and osteoarthritic deterioration with time. Subsequently, many surgical therapies have been trialed to stimulate cartilage repair, but none have produced reliable outcomes. Hence, cartilage repair research has been broadened, with many investigators now focused on cell-based treatment. Smith began a revolution of autologous cell research when in 1965 she isolated chondrocytes from articular cartilage and transplanted them into fresh cartilage nodules (Smith, 1965). Since, new technologies and improved techniques have seen autologous chondrocyte implantation (ACI) widely accepted for use in clinical orthopaedics (Bentley et al., 2003; Brittberg et al., 1994; Grande et al., 1989; Peterson et al., 2002). At present, matrix-induced autologous chondrocyte implantation (MACI) is the most surgically simple form of ACI, boasting clinical outcomes comparable to any technique on the market, and far less complications compared to the first generation of ACI - periosteal ACI (Bartlett et al., 2005; Behrens et al., 2006; Gigante et al., 2006; Henderson et al., 2004; Marlovits et al., 2005; Minas, 2001; Willers et al., 2007; Zheng et al., 2007). But whilst MACI has been adopted by the orthopaedic surgeon for articular cartilage repair, many of the molecular, histological, and clinical factors governing patient outcomes are still largely understudied. Firstly we assessed the bioactivity of fibrin sealant (FS - Tisseel®), a critical component of MACI, on the migration and proliferation of human articular chondrocytes in vitro. We also looked to elucidate the associated molecular mechanisms of thrombin, a key active ingredient in FS, by examining the expression and activation of proteaseactivated receptors (PARs), established thrombin receptors. All four PAR isoforms were detected in human chondrocytes, with PAR-1 being the major isoform expressed. '...' This thesis has demonstrated biological, histological, and clinical features of the MACI technique. Our in vitro has supported the use of fibrin sealant and collagen membrane as the major material components of MACI, illustrating improved chondrocyte proliferation, migration, and chondrogenic differentiation. We have evidenced that MACI stimulates successful production of hyaline-like cartilage by 6 months, while also showing that revised and clinically failed repair tissues are predominantly hyaline-like and fibrocartilage with inferior composition. Clinically, we have documented significant improvements in patient repair structure, function, symptoms, quality of life, and satisfaction, whilst concurrently confirming sentiment within the literature regarding the importance of exercise/ rehabilitation for maximising MACI outcome. In summary, the findings presented in this thesis suggest that MACI is a biologically sound and clinically efficacious cell-based treatment option for repairing articular cartilage defects.

Este projeto teve como finalidade fornecer informações sobre o contingente brasileiro de garanhões afetados pela osteocondrose dissecante (OCD), particularmente no estado de São Paulo. A OCD é uma doença ortopédica do desenvolvimento que acomete os humanos e os animais. É o distúrbio de desenvolvimento esquelético mais importante nos potros em crescimento. É uma falha no processo de ossificação endocondral, que compromete as cartilagens articular e de crescimento, principalmente a articulação tíbio-társica. É uma afecção importante pela incapacitação de atletas e é questão de caráter mundial para o bem-estar animal e para a eqüinocultura, implicando o seu tratamento e estratégias de controle. Há várias modalidades diagnósticas utilizadas na triagem da população acometida pela OCD, que se distinguem de acordo com a acurácia de cada uma. Entretanto, a radiologia, com imagens digitais, ainda se mantém como a ferramenta mais utilizada no campo. Os garanhões foram escolhidos considerando-se a idade, a sanidade, a maturidade, a docilidade e estavam obrigatoriamente registrados no stud-book da ABCCH. Os eqüinos foram submetidos a duas incidências radiográficas bilaterais das articulações tíbio-társicas. Os arquivos foram armazenados em sistema digital e os achados classificaram os animais em positivos e negativos para OCD. Os resultados demonstraram uma ocorrência de 7,7% (2/26) de OCD na população brasileira de garanhões, produtos de inseminação artificial com sêmen importado com a garantia OCD-Free de centrais européias de reprodução. Esta porcentagem se apresentou menor do que as relatadas por pesquisadores de outros países, indicando que o plantel brasileiro de garanhões se apresenta controlado para a OCD e abaixo da expectativa. A baixa ocorrência de OCD nos eqüinos no Brasil, em relação aos outros países, pode ser atribuída ao método de seleção dos reprodutores e também a fatores climáticos. / This project provides information about osteochondrosis dissecans (OCD) affection in Brazilian Warmblood stallions, particularly in the state of Sao Paulo. Osteochondrosis dissecans is a developmental orthopaedic disease, which can involve both humans and animals. It is the most important skeletal disorder in growing foals. It is a failure of the endochondral ossification, which affects both articular and growth-plate cartilages. The tibiotarsal joint is the primary region involved. It is a remarkably disabling condition for competing animals and a serious worldwide issue for animal welfare and the horse industry and involves various treatments and control strategies. There are several modalities of diagnosis used to investigate the OCD, which differ from each other according to their rate of accuracy. However, radiology utilizing digitized images remains the most appropriate tool in the field. The stallions were chosen by the criteria of age, official registration in the ABCCH (Brazilian Sport Horses Breeders\' Association), soundness, maturity and behaviour. The horses were submitted bilaterally to two radiographic views of their hocks. The images were stored in digital files for further individual classification into positive or negative diagnosis. The results yielded an incidence of 7.7% (2/26) of OCD within the Brazilian population of stallions, all of whom were artificial insemination drives offspring, sired from imported European stallions using \"OCD-free\" semen. These results show a lower incidence of OCD than obtained by other countries\' researchers, indicating that the Brazilian stallions are under control for OCD and below the expected mean. The low incidence of OCD in Brazil, in comparison with other countries may be due to the methods of selection established for choosing quality of the semen or to climate differences.

Enfermidade muito observada nas articulações dos equinos, o processo degenerativo articular crônico na articulação tibio-társica pode ser de origem primária, ou secundária à osteocondrose dissecante. A confirmação diagnóstica é feita por avaliação radiográfica. Importantes aliados diagnósticos são a avaliação do líquido sinovial, a avaliação ultrassonografia e a cirurgia de video-artroscopia, sendo esta última o tratamento para a enfermidade. Por sua evolução crônica e às vezes assintomática, a osteocondrose dissecante causa alterações no ambiente articular, como a perda de matriz cartilagínea, o que limita o potencial atlético do animal, acarretando em queda na performace e perdas econômicas. É comum o uso terapêutico intra-articular no periodo pós operatório recente de substâncias autólogas como o plasma rico em plaquetas (PRP), bem como o uso ácido hialurônico (HA), como adjuvante para o tratamento cirúrgico. O presente trabalho objetiva comparar e avaliar estes tratamentos. Foram utilizados 18 equinos, com idade variando entre 2 a 6 anos de idade, da raça Brasileiro de Hipismo, com peso corpóreo entre 400 e 650 kg, oriundos do mesmo criatório, com osteocondrose dissecante, na crista intermédia do osso tíbia. Estes animais no décimo dia pós operatório são dividos em três grupos experimentais: grupo AH, grupo PRP e grupo RCL como controle. Dados clínicos, ultrassonográficos e laboratoriais foram coletados em tempos definidos. Os resultados demonstraram que os animais do grupo controle - grupo RCL, que receberam solução de ringer com lactato intraarticular, apresentaram respostas clínicas e laboratoriais que indicaram menor indução do processo inflamatório ao ambiente articular quando comparado aos grupos PRP e AH. Os animais que receberam PRP apresentaram maior efusão sinovial e resposta positiva ao teste de flexão quando comparados aos animais que receberam AH; ao passo que a administração intra-articular de AH induziu maiores alteração citológica do líquido sinovial quando comparadas aos animais que receberam PRP. / One of the most commom diseases in the equine joint, the degenerative joint disease in the tibio tarsal joint could be a primary disease, or secondary to osteochondrosis dissecans. The diagnosis is made by radiographic study. Allies in diagnosing this disease includes sinovial fluid evaluation, ultrasonographic evaluation and video arthroscopy surgery, which is the way to treat this disease. The osteochondrosis dissecans has a chronic evolution, and several times asymptomatic, which causes an alteration on articular environment that contributes to a loss in the cartilage matrix. Resulting in the limited development of the athletic potential of the animal, poor performance and economic losses. Is common to use therapeutical autholog substances intra articular as the platelet rich plasma, and hialuronic acid, in the early post surgical treatment as an adjuvant therapy to the surgical treatment. This study reaches to compare and evaluate those treatments. Were used 18 horses, with ages between 2 to 6 years old, Brasileiro de Hipismo breed, weighting between 400 and 650 kg, from the same breeding center, with osteochondrosis dissecans fragments from the intermediate tibial crest. Those patients, 10 days after the video arthroscopy surgery, were divided in three experimental groups: AH group, PRP group, and RCL group as control group. Laboratorial data, clinical signs and ultrassonographic exam were performed. The results proved that RCL group had show less induction of inflamatory process on articular enviroment, when we compare with PRP group and AH group. The PRP group had shown more synovial effusion, and more sensibility to the flexion test when we compare to AH group; but the AH group had shown more laboratorial alterations when we compare to the PRP group.

L'ostéochondrose (OC) est une affection ostéo-articulaire juvénile caractérisée par une perturbation locale de la maturation du cartilage créant des zones de fragilité. L'OC a été décrite chez de nombreuses espèces dont l'Homme, le Chien, le Porc, le Poulet et le Cheval. Chez le cheval les lésions s'installent progressivement, sans symptômes, avant l'âge d'un an et les manifestations cliniques ne se manifestent que tardivement, souvent à l'entraînement. L'OC affecte 10 à 30 % de la population équine représentant ainsi un souci majeur pour la filière tant sur le plan du bien être animal que sur le plan économique. Son étiologie, multifactorielle, est encore mal comprise et implique des composantes génétiques et environnementales ainsi que traumatiques. Les objectifs des travaux présentés étaient d'améliorer la compréhension de la physiopathologie de l'OC équine et de mettre en évidence les processus biologiques perturbés. L'ensemble des résultats a permis de préciser la définition des différentes entités de l'OC et pourraient également être pertinentes dans l'amélioration du diagnostic et le dévelopement de nouveaux traitements. Un défaut constitutif de l'os et du cartilage a été mis en évidence chez les individus atteints d'OC, notamment associé à une perturbation du métabolisme énergénique et un stress du reticulum endoplasmique. De plus, selon le type de lésions, des mécanismes moléculaires sous-jacents différents sont impliqués dans leur développement. D'autre part, les microARNs (miRNAs) semblent également jouer un rôle dans la physiopathologie de l'OC et certains d'entre eux pourraient constituer de bonnes cibles thérapeutiques ou être utilisés comme biomarqueurs diagnostics. / Osteochondrosis (OC) is a juvenile osteo-articular disease characterized by a focal failure of cartilage maturation leading to weak areas. OC has been described in several species including Human, Dog, Swine, Poultry and Horse. In horse, lesions develop gradually without symptoms before one year old and clinical manifestations occur tardily during training. OC affects 10 to 30% of equine population and constitutes a major concern in terms of animal welfare and economy. Its multifactorial etiology remains poorly understood and involved several factors including genetics, environment and traumas. The aim of this current work was to improve the comprehension of equine OC physiopathology and highlight biological pathways disrupted. Taken together, our results made it possible to refine the definition of OC entities and our data could be relevant to improve diagnosis and develop new therapies. A constitutive defect was found in cartilage and bone of OC-affected horses and particularly a defective energy metabolism and a endoplasmic reticulum stress. Moreover, in function of lesion type, different underlying molecular mechanisms are involved in their development. Secondly, mircoRNAs (miRNAs) seem to take part in the OC physiopathology and some miRNAs could constitute a relevant therapeutic target or be used as diagnosis biomarkers.

L’ostéochondrite disséquante (OCD) est un défaut focal du processus d’ossification endochondrale en des sites spécifiques au niveau épiphysaire. Elle est caractérisée par la présence de fragments ostéochondraux pouvant se détacher de la surface articulaire. Cette maladie a un impact majeur sur les performances athlétiques des chevaux. Les deux hypothèses principales présentement véhiculées quant à sa pathogénie sont une nécrose ischémique du cartilage de croissance et une altération du métabolisme de la matrice de collagène de type II au sein du cartilage de croissance. Malgré de nombreuses années de recherche sur le sujet, plusieurs aspects de cette maladie demeurent inconnus. L’objectif de cette étude était de décrire le développement épiphysaire équin au niveau du membre pelvien à l’aide de l’imagerie médicale afin de déterminer si des variations du processus de maturation à certains sites pouvaient être un facteur prédisposant au développement de lésions d’OCD. Des membres pelviens de fœtus et de jeunes poulains ont été étudiés post-mortem. L’épiphyse du fémur distal, tibia distal et du talus ont été examinées par tomodensitométrie (CT) et résonnance magnétique 1.5 Tesla (IRM) dans le but de documenter le degré et le patron d’ossification, la régularité du front d’ossification, de même que le pourcentage du diamètre épiphysaire demeurant occupé par le complexe de cartilage articulaire-épiphysaire, et ce au niveau de certains sites prédéterminés. Les centres secondaires d’ossification (SOCs) ont été détectés pour la première fois à 7 mois de gestation (MOG) au niveau de l’épiphyse fémorale distale et à 8 MOG au niveau de l’épiphyse tibiale distale et du talus. À 8-9 MOG la lèvre latérale de la trochlée fémorale, la malléole médiale du tibia (MM) et la partie crâniale de la crête intermédiaire du tibia distal (DIRT(Cr)), tous des sites prédisposés à la maladie, avaient le plus haut pourcentage de cartilage de tous les sites évalués. Post-partum, le pourcentage de cartilage de la MM et de la DIRT(Cr) sont demeurés importants. Le CT et l’IRM ont su illustrer le développement épiphysaire équin et soutenir d’avantage le fait qu’un cartilage plus épais à certains sites articulaires pourrait avoir un rôle dans le développement de lésions d’OCD. / Osteochondrosis dissecans (OCD) is a focal failure of endochondral ossification of the epiphysis characterized by the presence of cartilage flaps and osteochondral fragments. This disease has a major impact on equine athletic performances. The two current principal hypotheses on etiopathogenesis are either an ischemic necrosis of growth cartilage or altered cartilage type II collagen metabolism. Despite years of research, many knowledge gaps on the etiology of this disease remain. The objective of this study was to image epiphyseal development in the equine pelvic limb to determine whether there was a variation in site maturation that could be a predisposing factor for OCD. Pelvic limbs (fetuses and foals) were studied post-mortem. The epiphyses of the distal femur, tibia and talus were scanned with computed tomography (CT) and 1.5 Tesla magnetic resonance imaging (MRI) to investigate the degree and pattern of ossification, the regularity of the ossification front and cartilage percentage (articular epiphyseal cartilage thickness as a percentage of total epiphyseal diameter) at predetermined sites. The secondary ossification centers (SOC) were first identified in the femoral epiphyses at 7 months of gestation (MOG), and both distal tibia and talus at 8 MOG. At 8-9 MOG the lateral trochlear ridge of the femur, medial malleolus of the tibia (MM), cranial part of the distal intermediate ridge of the tibia (DIRT(Cr)), all OCD susceptible sites, had the greatest cartilage percentage compared to all other sites assessed. Post-partum, the cartilage percentage of the MM and DIRT(Cr), common sites of OCD, remained high. CT and MRI images illustrate equine epiphyseal development and provide additional evidence that greater cartilage thickness at specific joint sites could play a role in the development of OCD.

L’ostéochondrite disséquante (OCD) est un défaut focal du processus d’ossification endochondrale en des sites spécifiques au niveau épiphysaire. Elle est caractérisée par la présence de fragments ostéochondraux pouvant se détacher de la surface articulaire. Cette maladie a un impact majeur sur les performances athlétiques des chevaux. Les deux hypothèses principales présentement véhiculées quant à sa pathogénie sont une nécrose ischémique du cartilage de croissance et une altération du métabolisme de la matrice de collagène de type II au sein du cartilage de croissance. Malgré de nombreuses années de recherche sur le sujet, plusieurs aspects de cette maladie demeurent inconnus. L’objectif de cette étude était de décrire le développement épiphysaire équin au niveau du membre pelvien à l’aide de l’imagerie médicale afin de déterminer si des variations du processus de maturation à certains sites pouvaient être un facteur prédisposant au développement de lésions d’OCD. Des membres pelviens de fœtus et de jeunes poulains ont été étudiés post-mortem. L’épiphyse du fémur distal, tibia distal et du talus ont été examinées par tomodensitométrie (CT) et résonnance magnétique 1.5 Tesla (IRM) dans le but de documenter le degré et le patron d’ossification, la régularité du front d’ossification, de même que le pourcentage du diamètre épiphysaire demeurant occupé par le complexe de cartilage articulaire-épiphysaire, et ce au niveau de certains sites prédéterminés. Les centres secondaires d’ossification (SOCs) ont été détectés pour la première fois à 7 mois de gestation (MOG) au niveau de l’épiphyse fémorale distale et à 8 MOG au niveau de l’épiphyse tibiale distale et du talus. À 8-9 MOG la lèvre latérale de la trochlée fémorale, la malléole médiale du tibia (MM) et la partie crâniale de la crête intermédiaire du tibia distal (DIRT(Cr)), tous des sites prédisposés à la maladie, avaient le plus haut pourcentage de cartilage de tous les sites évalués. Post-partum, le pourcentage de cartilage de la MM et de la DIRT(Cr) sont demeurés importants. Le CT et l’IRM ont su illustrer le développement épiphysaire équin et soutenir d’avantage le fait qu’un cartilage plus épais à certains sites articulaires pourrait avoir un rôle dans le développement de lésions d’OCD. / Osteochondrosis dissecans (OCD) is a focal failure of endochondral ossification of the epiphysis characterized by the presence of cartilage flaps and osteochondral fragments. This disease has a major impact on equine athletic performances. The two current principal hypotheses on etiopathogenesis are either an ischemic necrosis of growth cartilage or altered cartilage type II collagen metabolism. Despite years of research, many knowledge gaps on the etiology of this disease remain. The objective of this study was to image epiphyseal development in the equine pelvic limb to determine whether there was a variation in site maturation that could be a predisposing factor for OCD. Pelvic limbs (fetuses and foals) were studied post-mortem. The epiphyses of the distal femur, tibia and talus were scanned with computed tomography (CT) and 1.5 Tesla magnetic resonance imaging (MRI) to investigate the degree and pattern of ossification, the regularity of the ossification front and cartilage percentage (articular epiphyseal cartilage thickness as a percentage of total epiphyseal diameter) at predetermined sites. The secondary ossification centers (SOC) were first identified in the femoral epiphyses at 7 months of gestation (MOG), and both distal tibia and talus at 8 MOG. At 8-9 MOG the lateral trochlear ridge of the femur, medial malleolus of the tibia (MM), cranial part of the distal intermediate ridge of the tibia (DIRT(Cr)), all OCD susceptible sites, had the greatest cartilage percentage compared to all other sites assessed. Post-partum, the cartilage percentage of the MM and DIRT(Cr), common sites of OCD, remained high. CT and MRI images illustrate equine epiphyseal development and provide additional evidence that greater cartilage thickness at specific joint sites could play a role in the development of OCD.

Diverses lésions ostéochondrales peuvent affecter les articulations des jeunes chevaux et réduire leurs futures performances en course. L’objectif de cette thèse est d’identifier les régions du génome, appelées locus à caractère quantitatif (QTL), associées avec des caractères mesurant l’ostéochondrose (OC) enregistrés dans le programme GENEQUIN sur une population de Trotteurs Français. Le génotypage a été réalisé à l’aide de la puce SNP Illumina BeadChip EquineSNP50, qui est dense et permet d’exploiter le déséquilibre de liaison par des analyses d’association. Ces analyses sont sujettes à certains problèmes en présence d’une structure familiale des données. Dans la première partie de la thèse, une comparaison de la puissance et de la robustesse d’un choix restreint de méthodes d’analyses est effectuée. L’originalité de ce travail réside dans la dérivation algébrique des moments des distributions des statistiques de test comparées, donnant ainsi plus de généralité à nos résultats et permettant une meilleure compréhension des différences. Les résultats peuvent notamment servir à l’optimisation du dispositif expérimental. La deuxième partie est consacrée à la cartographie des régions QTL des caractères mesurant l’OC en différents sites articulaires dans une population de 583 Trotteurs Français. Cette étude a permis de mettre en évidence plusieurs régions QTL d’effets moyens et faibles à un niveau significatif mais pas hautement significatif. Nous montrons que l’OC est un caractère polygénique et qu’aucun QTL, ayant un effet à la fois sur l’OC du jarret et l’OC du boulet, n’est détectable dans ce protocole QTL, ce qui infirme l’hypothèse simple d’une cause génétique commune de la sensibilité à cette maladie sur les différents sites anatomiques. Suite à ces travaux, l’identification des gènes candidats et des mutations causales devrait clarifier la physiopathologie moléculaire de l’OC et ainsi permettre de développer des stratégies efficaces pour l’évaluation des risques. Pendant ce temps, les marqueurs peuvent être utilisés dans un contexte de sélection assistée par marqueurs afin d’améliorer la santé et le bien-être du cheval. / Osteochondral lesions are commonly observed in young horses and may be responsible for reduced performances in racing. The purpose of the PhD thesis was to identify genome regions, called quantitative trait loci (QTL), associated with various traits measuring osteochondrosis (OC) and recorded in the GENEQUIN program in a population of French Trotters horses. Genotyping was performed using the EquineSNP50 Illumina high density chip, which allows to exploit the linkage disequilibrium with genome-wide association studies. These analyses are subject to several problems in presence of family structure. We hence first proposed a comparison of power and robustness of a limited choice of models for this type of analysis. The originality of this work lies in the algebraic derivation of the distribution moments of the test statistics compared, making the outcome of this comparison more general and allowing a better understanding of differences. The results can be used to establish an experimental design. The second part was devoted to the QTL fine mapping of traits that measure OC in different joint sites. This study highlighted several significant QTL with low and medium effects but none of them were highly significant. We showed that OC is a polygenic trait and we were not able to identify QTL affecting both OC on the hock and the fetlock, rejecting the hypothesis of a single genetic determinism of susceptibility to this desease accross anatomical sites. Further studies will now focus on the identification of candidate genes and screening for mutation in an attempt to clarify the molecular physiopathology of OC and develop efficient strategies for risk assessment. Meanwhile, markers could be used in a marker-assisted selection context to improve horse health and welfare.