<p>Knee pain is a common complaint among older Americans, nearly half of whom have developed or will develop painful osteoarthritis. Osteoarthritis is primarily a disease of articular cartilage, the low-friction, shock-absorbing connective tissue that lines long bones at their articulating surfaces. Within these joint tissues and within arthritis, the minor protein collagen VI plays an uncertain role, although it has been implicated in several muscle and ligament disorders. Determination of the collagen VI role in bone and cartilage of the knee is the focus of this dissertation.</p><p>Within articular cartilage, collagen VI exclusively localizes to and delimits the pericellular matrix (PCM), which differs from the extracellular matrix (ECM) in composition and structure. To interact with the cell, a molecule must first pass through the PCM. Fluorescent dextran diffusivities were quantified in the cartilage PCM using a newly developed model of scanning microphotolysis (SCAMP), a line photobleaching technique. Diffusion was slower in the PCM than in the ECM, although not in early-stage arthritic tissue. These results support the hypothesis that diffusivity is lower in the PCM than in the ECM of healthy articular cartilage, presumably due to differences in proteoglycan content. </p><p>Arthritic degradation is partly mediated by interleukin-1 (IL-1), a catabolic cytokine that affects the mechanical properties of articular cartilage and preferentially binds to cell-surface receptors in the surface zone. Since cells are the cartilage metabolic units, matrix degradation is hypothesized to influence molecular transport in the PCM before the ECM. Cartilage was cultured with or without IL-1, soaked in FITC-ovalbumin, and photobleached using SCAMP to measure diffusivity. Over 7 days of culture, IL-1 doubled the diffusivity in both zones (surface, middle) and matrices (PCM, ECM) of the cartilage. Diffusivity within the PCM was slightly lower than within the ECM. No increase in PCM diffusivity relative to ECM diffusivity was detected within either zone, suggesting that PCM-localized degradation either cannot be distinguished at these time points or cannot be detected by measures of ovalbumin diffusion.</p><p>To determine the effects of collagen VI absence on the morphometry and physical properties of the joint, knees of 2-, 9-, and 15-month-old Col6a1+/+ and Col6a1-/- mice were studied. Bone morphometry was evaluated using micro-computed tomography (microCT). Subchondral bone thickness, joint-capsule thickness, and cartilage degradation were assessed by histology. Cartilage elastic modulus, roughness, and coefficient of friction were measured by atomic force microscopy (AFM). Diffusion through the cartilage ECM was determined by SCAMP. Overall, collagen VI absence had profound effects on the morphometry of the proximal tibia and the overall histological structures of the mouse knee, yet minimal effects on the friction, roughness, elastic modulus, and diffusional properties of the articular cartilage. Musculoskeletal abnormalities at the knee do result from collagen VI absence.</p> / Dissertation

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18845号 / 理博第4103号 / 新制||理||1590(附属図書館) / 31796 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 濱田 穣, 准教授 平﨑 鋭矢, 教授 岡本 宗裕 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Introduction : La vitamine D (VitD) maintient la santé osseuse et influence le mouvement dentaire orthodontique (MDO). L’objectif était d’évaluer l’effet de la VitD sur la morphométrie osseuse, puis sur la vitesse et la stabilité du MDO. Méthode : 32 rats Sprague Dawley mâles ont été assignés à deux groupes expérimentaux, traités avec la VitD par gavage (systémique) ou par injection (locale), et deux groupes contrôles respectifs traités avec un tampon phosphate salin (PBS) pour 47 jours. Le MDO était effectué pendant 7 jours avec un ressort NiTi attaché entre la première molaire supérieure et les incisives. Un scan Micro-CT était réalisé à 5 temps : T0 (avant l’administration de VitD), T1 (début du MDO), T2 (fin du MDO), T3 (7 jours post-MDO), T4 (30 jours post-MDO). La vitesse et la stabilité du MDO étaient évaluées. La morphométrie osseuse a été analysée via la densité minérale osseuse (BMD), le pourcentage de volume d’os (BV/TV), la porosité totale (Po(tot)), le facteur du patron trabéculaire (Tb.Pf), l’index de structure du modèle (SMI) et la densité de connectivité (Conn.Dn). Résultats : Le groupe VitD systémique a montré une vitesse diminuée du MDO, mais une récidive inférieure au contrôle ainsi qu’une augmentation de la BMD et du BV/TV, et une diminution de la Po(tot) (p<0.05). La structure osseuse apparaissait plus fragmentée et présentait une Conn.Dn plus basse (p<0.05). Aucune différence n’a été trouvée entre le groupe administration locale de VitD et les autres groupes. Conclusion : L’administration systémique de VitD a engendré une diminution de vitesse du MDO en induisant plus de résistance, mais a aussi contribué à une meilleure stabilité grâce à une densité osseuse plus élevée. / Introduction: Vitamin D (VitD) maintains bone health and may influence the orthodontic tooth movement (OTM). The objective was to evaluate VitD effect on bone morphometry, and on the rate and stability of OTM. Methods: 32 male Sprague Dawley rats were assigned into two experimental groups, treated with VitD by gavage (systemic) or by injection (local), and two respective control groups treated with phosphate-buffered saline (PBS) for 47 days. OTM was performed for 7 days with a NiTi coil bonded between the upper first molar and incisors. Micro-CT scanning was performed at 5 time-points: T0 (before administration of VitD), T1 (start of OTM), T2 (end of OTM), T3 (7 days post-OTM) and T4 (30 days postOTM). Rate and stability of OTM were assessed. Bone morphometry was analyzed by bone mineral density (BMD), percent bone/volume (BV/TV), total porosity (Po(tot)), trabecular pattern factor (Tb.Pf), structure model index (SMI) and connectivity density (Conn.Dn). Results: The systemic VitD group showed a lower OTM rate, but also a lower relapse than control (p<0.05). It also demonstrated an increase of BMD and BV/TV, and a decrease of Po(tot) (p<0.05). The bone structure appeared more fragmented and presented lower Conn.Dn than the control (p<0.05). No statistical difference was found between VitD local administration and the other groups for the rate and stability of OTM, or for the bone morphometry. Conclusion: The systemic administration of VitD caused a decrease of OTM rate by generating more bone resistance, but also contributed to a greater stability due to a higher bone mineral density.