<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

<p>Human joints are able to withstand millions of loading cycles with loads regularly more than 3 times an individual's body weight in large part due to the unique bearing properties of articular cartilage, a strong, slippery tissue that covers the ends of long bones. PRG4 is a boundary lubricating glycoprotein present on the cartilage surface and in the synovial fluid surrounding it. While evidence that PRG4 lubricates and preserves normal joint function is strong, little is known of its effect on cartilage surface properties, the mechanism by which it lubricates, or its postulated role of preventing wear on joints. The effect of PRG4 on cartilage friction, wear, structure, morphology, and the mechanisms by which it mediates these factors are studied here. Methods to study these parameters at the microscale using atomic force microscopy are also developed. </p><p>Cartilage of mice with the Prg4 gene (which expresses PRG4) deleted is shown to be different in a number of ways from wild type cartilage. The uppermost layer is thicker and less uniform and the surface is rougher and softer. There is also a loss of proteoglycans, structural components of cartilage, from the underlying superficial tissue, and apparent tissue damage in some cases. Wear in the presence of PRG4 in shown to be significantly lower than in its absence, a finding which may have direct implications for prevention and treatment of osteoarthritis. It appears that PRG4 needs to be present in solution, not merely on the cartilage surface to have this effect, indicating that adsorption properties are important for wear prevention.</p> / Dissertation

Pigs, mice and human beings are all vertebrate mammals. More than 90% of genomes in pigs and mice are the same as human beings. Experiment pigs and mice are with advantages in purebloods, small size, high reproductive capacity and short life cycle, etc. The tissue structure and metabolism of physiology in pig and mice are similar to human as well. Therefore, laboratory pigs and mice are often used to substitute human beings for biomedical engineering test. The research topics of this thesis are in the area of biomechanical properties of bones in mammal. The objectives of the study are to reveal the biomechanical properties of various types of bones and discuss its implication to human development. The entire thesis is divided into three parts. The first topic used micro-indentation test and FEM analysis for the determination of biomechanical properties of controlled cartilages in pigs. The second topic applied (a) three-point-bend failure test to study the age-related radius strength in mice, (b) tensile test to study the mechanical response of cranial sutures in mice, and (c) optical interferometry for 3D profile determination of mouse cranium. The third topic is for quantitative analysis of patterns in cranial sutures using DFT (Discrete Fourier Transform). The mechanism of diseases (such as osteoporosis, craniosynostosis, etc.) and the complexity of patterns in human cranial sutures in different age groups are discussed.

名古屋大学博士学位論文 学位の種類 : 博士(医学)(課程) 学位授与年月日:平成6年4月5日 西田佳弘氏の博士論文として提出された

Thèse de doctorat : Biomécanique : Paris 12 : 2007. / Titre provenant de l'écran-titre. Pagination : XII-247 p. Bibliogr. : 152 réf.

Reproduction de : Thèse de doctorat : Odontologie. Biologie cellulaire et ingénierie tissulaire : Nantes : 2007. / Bibliogr.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves [202]-230). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves [202]-230). Also available online.

Habilitation-Thesis--Cologne. / Includes bibliographical references (p. 45-48) and index.

Due to the limited intrinsic healing ability of mature cartilage tissue, stem cell therapies offer the potential to restore cartilage lost due to trauma or arthritis. Mesenchymal stem cells (MSCs) are a promising cell source due to their ability to differentiate into various adult tissues under specific biochemical and physical cues. Current MSC chondrogenic differentiation strategies employ large pellets, however, we have previously developed a high-throughput technique to form small MSC aggregates (500-1,000 cells) that may reduce diffusion barriers while maintaining a multicellular structure that is analogous to cartilaginous condensations. The objective of this study was to examine the effects on chondrogenesis of incorporating chondroitin sulfate methacrylate (CSMA) microparticles (MPs) within these small MSC spheroids when cultured in the presence of transforming growth factor-β1 (TGF-β1) over 21 days. Spheroids +MP induced earlier increases in collagen II and aggrecan gene expression (chondrogenic markers) than spheroids -MP, although no large differences in immunostaining for these matrix molecules were observed by day 21. Collagen I and X was also detected in the ECM of all spheroids by immunostaining. Interestingly, histology revealed that CSMA MPs clustered together near the center of the MSC spheroids and induced circumferential alignment of cells and ECM around the material core. Because chondrogenesis was not hindered by the presence of CSMA MPs, this study demonstrates the utility of this culture system to further examine the effects of matrix molecules on MSC phenotype, as well as potentially direct differentiation in a more spatially controlled manner that better mimics the architecture of specific target tissues.