published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 159-190). Also available in print.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.

Abstract The study was undertaken to determine effects of unilateral masticatory function on craniofacial growth and temporomandibular joint structures in young rabbits. Right-side maxillary and mandibular molars were ground out of occlusion under general anesthesia. Macroscopic measurements were made using the skulls and mandibular halves. Articular surface inclinations were determined using photographs. Positions of articular eminences on crania were determined using machine-vision technique. Changes to extracellular matrix of condylar cartilage were studied histochemically and biochemically. Unilateral masticatory function resulted in changes in the shapes and dimensions of the mandible, maxilla and glenoid fossa. Maxillary widths, lengths of half-mandibles, and angles between the ramus and corpus were lower on the right than on the left side of each animal that had been subjected to right-side molar grinding, and in comparison with controls. As the rabbits grew, there was no recovery from the changes that had been brought about by the asymmetric function, even after occlusal function was reversed or left unmodified after a period of unilateral function. Inclinations of articular surfaces became shallower and positions of articular eminences and glenoid fossae more anterior in animals that had been subjected to molar grinding than in controls. Proteoglycan contents of condylar cartilage extracellular matrix were also affected by molar grinding: amounts of the aggregated proteoglycans in particular were low. We concluded, that the shape and the sagittal and vertical position of the articular eminence is highly adaptive to the function of the condyle process, and that there were associated alterations in the dimensions and shapes of mandible and maxilla. Unilateral masticatory function resulted in significant changes in condylar cartilage extracellular matrix. Normal occlusion and bilaterally symmetric masticatory function during early phases of growth is important for normal development of the maxilla, mandible and articular cartilage.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Arthritis is a pathological condition whereby a persistent inflammatory response leads to breakdown of articular cartilage in synovial joints. Cartilage is a specialised avascular tissue containing chondrocytes embedded in an extracellular matrix. The cartilage matrix is composed of collagen to provide strength with aggregated proteoglycan to facilitate hydration. Cartilage has been reported to loose proteoglycans with concordant loss of integrity observed in arthritic disease pathology. Proteoglycans loss from cartilage has also been reported in in vitro models. Application of interleukin-1 (lL-1β) to cartilage in vitro has been demonstrated to increase loss of proteoglycans and modulate production of inflammatory mediators such as Nitric Oxide (NO) and Prostaglandin-E2 (PGE2). NO and PGE2 have also been associated with cartilage breakdown. Other cytokines such as colony stimulating factors (CSFs) may regulate cartilage function. The aim of this study was to select a cartilage explant system and compare the effects of interleukin-1 (lL-1) with those of colony stimulating factors (CSFs) by measuring the production of NO and PGE2 and release of proteoglycans. It was found that IL-1β increased PGE2 and NO production, but not loss of proteoglycans from rat cartilage explants. Granulocyte-CSF (G-CSF) and lL-3 increased production of NO and PGE2, respectively. When combined, IL-1β / Granulocyte-Macrophage (GM-CSF) increased production of PGE2 and G-CSF / IL-1β produced increased proteoglycan loss from explants. The model was then modified by integrating Swiss 3T3 Fibroblasts monolayers with explants. Fibroblasts were initially screened to determine their separate response to these cytokines. Fibroblasts did not release proteoglycans into the culture media, but produced elevated concentrations of NO and PGE2 in response to IL-lβ.·Fibroblast-cartilage co-cultures treated with IL-lβ produced increased NO, PGE2 and proteoglycan release. G-CSF, GM-CSF and IL-3 caused increased levels of PGE2 in co-cultures, however, IL-1β was required to generate significant proteoglycan loss from cartilage explants. Finally, extra-cellular signal related protein kinases I and 2 (ERK 1&2) and p38 intracellular signalling pathways were shown to be involved in IL-1β mediated production of NO fibroblasts and explants. These studies show that IL-1β has increased potential to mediate cartilage breakdown when interacting with other cytokines, such as G-CSF, and other cell types, such as Swiss 3T3 fibroblasts. IL-1β has defined intracellular signalling pathways that may produce a range of responses in cartilage explants and fibroblasts. These studies may relate to production of inflammatory processes and loss of cartilage integrity and function in pathological conditions.

Animal and clinical studies have shown an acceleration of bone healing by the application of pulsed low-intensity ultrasound (PLIUS). Several studies have reported that pulsed low-intensity ultrasound increase the synthesis of proteoglycan and type II collagen of cultured animal chondrocytes. The objectives of this study were to exam the bioeffect of pulsed low-intensity ultrasound on in vitro cultured human chondrocytes. Human chondrocytes were isolated from the amputated polydactyly digit of six different 1 to 10 years patients and cultured in agarose suspension for 3 days before treatment. PLIUS with intensities of 3.6, 18, 48, 72 and 98 mW/cm2was respectively applied to human chondrocytes for a single 10-min per day treatment. A control group was treated without PLIUS. The results demonstrated that PLIUS-treated human chondrocytes increased the proteoglycan synthesis compared with the control in a time-dependent manner. It is shown that the effect of 48 mW/cm2 is the most potent among a variety of PLIUS intensities tested determined by ELISA method. PLIUS at 48 mW/cm2 also increased type II collagen synthesis by up to 48.5+8.0% of the control determined by western blotting analysis. However, PLIUS has no significant influence on the cell proliferation of human chondrocytes compared with the control. It revealed that the PLIUS can enhance extracellular matrix synthesis. The response to PLIUS of chondrocytes harvested from 1 year old donor was significantly better than that of chondrocytes of 10 years old patient. These observations may lead to a better understanding of the bioeffect of PLIUS on in vitro cultured human chondrovytes.

Syndecan-1 is a cell surface proteoglycan which participates in cell adhesion, differentiation, motility, morphogenesis and intracellular signaling. The two glycosaminoglycans heparan sulfate and chondroitin sulfate are covalently attached to the ectodomain of syndecan-1 via a tetra saccharide linkage sequence. However, the ectodomain can be modified having only one or neither of the glycosaminglycans attached. The glycosaminoglycans are capable of binding ligands such as fibroblast growth factors (FGFs) and support activation of receptors. The ectodomain is proteolytically cleaved from the cell surface by metalloproteinases in a process known as shedding. Shedding turns the ectodomain into a soluble effector which can stimulate other cells in the surroundings by delivering growth factors and also translocate into cells through endocytosis. In this study the aim was to find out if a modified ectodomain, which only contains chondroitin sulfate, could support intracellular signaling in the absence of heparan sulfate. The aim was also to find out whether a modified ectodomain could translocate into the cell. The methods used were cell culturing, isolation and purification of syndecan-1 ectodomain, cell signaling and immunohistochemistry. It was found that modified shed syndecan-1 ectodomain was able to support intracellular signaling almost to the same degree as wild type syndecan-1 ectodomain. This may suggest that heparan sulfate does not have to be present on the ectodomain to support intracellular signaling, although the signal is slightly higher when present. When trying to detect translocation of the ectodomain the results were too uncertain and further research is required.