Stringent requirement for spatial arrangement of extracellular matrix in supporting cell morphogenesis and differentiation

BACKGROUND: In vitro experiments on the functional roles of extracellular matrix (ECM) components usually involve the culture of cells on surfaces coated with purified ECM components. These experiments can seldom recuperate the spatial arrangement of ECM found in vivo. In this study, we have overcome this obstacle by using histological sections of bovine Achilles tendon as cell culture substrates. RESULTS: We found that tendon sections can be viewed as a pre-formed block of ECM in which the collagen fibrils exhibited a spatial regularity unraveled in any artificially constructed scaffold. By carving the tendon at different angles relative to its main axis, we created different surfaces with distinct spatial arrangements of collagen fibrils. To assess the cellular responses to these surfaces, human mesenchymal stem cells (MSCs) were directly cultured on these sections, hence exposed to the collagen with different spatial orientations. Cells seeded on longitudinal tendon sections adopted a highly elongated and aligned morphology, and expressed an increased level of tenomodulin, suggesting that the collagen fibrils present in this section provide a microenvironment that facilitates cell morphogenesis and differentiation. However, MSC elongation, alignment and induction of tenomodulin diminished dramatically even as the sectioned angle changed slightly. CONCLUSION: Our results suggest that cell functions are influenced not only by the type or concentration of ECM components, but also by the precise spatial arrangements of these molecules. The method developed in this study offers a simple and robust way for the studying of cell-ECM interactions, and opens many research avenues in the field of matrix biology.published_or_final_versio

One-year clinical outcomes of patients implanted with a Resolute Onyx™ zotarolimus-eluting stent

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Factors contributing to the psychological well-being for Hong Kong Chinese children from low-income families: a qualitative study

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Reduction of corrosion behavior of magnesium alloy by PCL surface treatment

Poster no. 2282INTRODUCTION: Metallic implants are often used for fracture fixation. However, stress-shielding effect may be resulted in some cases and thereby leading to bone loss around the implant1. Therefore those metallic implants may need to be removed after the tissues have healed. The use of degradable metallic materials such as magnesium alloy is a promising candidate that may avoid second surgery. Hence, it helps reduce costs to health care system and morbidity to the patients. However, the major obstacles are the rapid degradation inside the human body and hydrogen gas release upon degradation. The corrosion rate has to be carefully controlled so as to make the alloys available for orthopaedic implantation. Surface modification is used since this method will not alter the bulk properties of magnesium alloy. Various surface treatments such as Plasma Immersion Ion Implantation and Deposition (PIII&D)2 and plasma anodisation3 are applied so that the corrosion resistance of material can be enhanced. Our group has recently developed a unique method to deposit a biodegradable polymer named polycaprolactone (PCL) on the magnesium surface. Previous in-vitro studies suggested that the rate …postprin

Profiling biomolecules at cell-biomaterial interface by quantitative proteomics

Session: Controlling Microenvironment and Cell Fate: abstract no. 789INTRODUCTION: Implant surface structure and chemistry determines the contacting cell’s fate. Therefore, the fate of those cells directly affect bone-implant incorporation in clinical practice1-5. However, how these chemical and mechanical signals translating to cellular responses are not yet known. The major drawback is a lack of systematic study of cellbiomaterial interaction in terms of protein expression, specifically, at the attachment interface between the cell and biomaterial (adherence surface, AS). Therefore, we have proposed to unbiasedly identify the biomolecules at the interface by proteomics. This method combines the use of a subcellular fractionation with quantitative mass …postprintThe 2010 North America Conference of the Tissue Engineering and Regenerative Medicine International Society (TERMIS-NA 2010), Orlando, FL., 5-8 December 2010

Helping cancer patients quit smoking using brief advice based on risk communication: A randomized controlled trial

This randomized controlled trial aimed to examine the effectiveness of a smoking cessation intervention using a risk communication approach. A total of 528 smoking cancer patients were randomly allocated either into an intervention group (n = 268) to receive brief advice based on risk communication by a nurse counselor or a control group (n = 260) to receive standard care. Subjects in both groups received a smoking cessation booklet. Patient follow-ups were at 1 week and at 1, 3, 6, 9 and 12 months. No significant differences were found in self-reported point-prevalence 7-day abstinence between the intervention and control groups at 6 months (15.7% vs 16.5%; OR 0.94, 95% CI 0.59-1.50). The rate of at least 50% self-reported reduction of smoking at 6 months, was higher in the intervention group than in the control group (16.8% vs 12.3%; OR 1.43, 95% CI 0.88-2.35). The biochemically validated quit rate at the 6-month follow-up was higher in the intervention group than in the control group (5.2% vs 3.8%; OR 1.38, 95% CI 0.60-3.16). These data suggest that advice based on risk communication was not effective for quitting but improved the rate of smoking reduction among smoking cancer patients.published_or_final_versio

Nickel ion level in scoliotic patients implanted with nitrogen plasma surface modified nickel-titanium superelastic spinal implant

published_or_final_versionThe 3rd International NanoElectronics Conference (INEC), Hong Kong, 3-8 January 2010. In Proceedings of the 3rd INEC, 2010, p. 136

A biodegradable polymer-based coating to control the performance of magnesium alloy orthopaedic implants

Magnesium and its alloys may potentially be applied as degradable metallic materials in orthopaedic implantations due to their degradability and resemblance to human cortical bone. However, the high corrosion rate and accumulation of hydrogen gas upon degradation hinders its clinical application. In this study, we adopt a new approach to control the corrosion rate by coating a controllable polymeric membrane fabricated by polycaprolactone and dichloromethane onto magnesium alloys, in which the pore size was controlled during the manufacturing process. The addition of the polymeric membrane was found to reduce the degradation rate of magnesium, and the bulk mechanical properties were shown to be maintained upon degradation. The in-vitro studies indicated good cytocompatibility of eGFP and SaOS-2 osteoblasts with the polymer-coated samples, which was not observed for the uncoated samples. The in-vivo study indicated that the uncoated sample degraded more rapidly than that of the polymer-coated samples. Although new bone formation was found on both samples, as determined by Micro-CT, higher volumes of new bone were observed on the polymer-coated samples. Histological analysis indicated no inflammation, necrosis or hydrogen gas accumulation on either of the samples during degradation. Collectively, these data suggest that the use of polymeric membrane may be potentially applied for future clinical use. © 2009 Elsevier Ltd. All rights reserved.postprin

New plasma surface-treated memory alloys: Towards a new generation of "smart" orthopaedic materials

This paper describes the corrosion resistance, surface mechanical properties, cyto-compatibility, and in-vivo performance of plasma-treated and untreated NiTi samples. Nickel-titanium discs containing 50.8% Ni were treated by nitrogen and carbon plasma immersion ion implantation (PIII). After nitrogen plasma treatment, a layer of stable titanium nitride is formed on the NiTi surface. Titanium carbide is also found at the surface after carbon plasma implantation. Compared to the untreated samples, the corrosion resistances of the plasma PIII samples are better by a factor of five and the surface hardness and elastic modulus are better by a factor of two. The concentration of Ni leached into the simulated body fluids from the untreated samples is 30 ppm, whereas that from the plasma-treated PIII are undetectable. Although there is no significant difference in the ability of cells to grow on either surface, bone formation is found to be better on the nitrogen and carbon PIII sample surfaces at post-operation 2 weeks. All these improvements can be attributed to the formation of titanium nitride and titanium carbide on the surface. © 2007 Elsevier B.V. All rights reserved.postprin