• Tribology and Lubricants
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• v.29 no.1
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• pp.46-50
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• 2013

In this study, the frictional behaviors of articular cartilage against a Co-Cr alloy in two types of kinematic motions were compared. Cartilage pins were punched from the femoral condyles of porcine knee joints, and Co-Cr alloy disks were machined from orthopedic-grade rods and polished to a surface roughness ($R_a$) of 0.002. Friction tests were conducted by using a pin-on-disk-type tribotester in phosphate buffered saline (PBS) under pressures of 0.5, 1, and 2 MPa. All tests were performed in the repeat pass rotational (ROT) and the linear reciprocal (RCP) sliding motions with the same sliding distance and speed of 50 mm/s. The coefficients of friction of the cartilage against the Co-Cr alloy increased with the sliding time in both kinematic motions for all contact pressures. The maximum coefficients of friction in RCP motion were 1.08, 2.82, and 1.96 times those in ROT motion for contact pressures of 0.5, 1, and 2 MPa, respectively. As the contact pressure increased, the coefficients of friction gradually increased in RCP motion, whereas they decrease and then increased in ROT motion. The interaction between the directional change of the shear stress and the orientation of collagen fiber in the superficial layer of the cartilage could affect the change in the frictional behaviors of the cartilage. A large difference in the coefficients of friction between the two kinematic motions could be interpreted as differences in the directional change of shear stress at the contact surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1205-1206
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1605-1606
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1425-1426
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• 2011

• Archives of Plastic Surgery
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• v.40 no.6
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• pp.676-686
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• 2013

Background To overcome the potential drawbacks of a short half-life and dose-related adverse effects of using active transforming growth factor-beta 1 for cartilage engineering, a cell-mediated latent growth factor activation strategy was developed incorporating latent transforming growth factor-${\beta}$1 (LTGF) into an electrospun poly(L-lactide) scaffold. Methods The electrospun scaffold was surface modified with NH3 plasma and biofunctionalised with LTGF to produce both random and orientated biofunctionalised electrospun scaffolds. Scaffold surface chemical analysis and growth factor bioavailability assays were performed. In vitro biocompatibility and human nasal chondrocyte gene expression with these biofunctionalised electrospun scaffold templates were assessed. In vivo chondrogenic activity and chondrocyte gene expression were evaluated in athymic rats. Results Chemical analysis demonstrated that LTGF anchored to the scaffolds was available for enzymatic, chemical and cell activation. The biofunctionalised scaffolds were non-toxic. Gene expression suggested chondrocyte re-differentiation after 14 days in culture. By 6 weeks, the implanted biofunctionalised scaffolds had induced highly passaged chondrocytes to re-express Col2A1 and produce type II collagen. Conclusions We have demonstrated a proof of concept for cell-mediated activation of anchored growth factors using a novel biofunctionalised scaffold in cartilage engineering. This presents a platform for development of protein delivery systems and for tissue engineering.

• Archives of Plastic Surgery
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• v.32 no.5
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• pp.599-606
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• 2005

Clinical application of the cartilage formed by tissue engineering is of no practical use due to the failure of long-term structural integrity maintenance. One of the important factors for integrity maintenance is the biomaterial for a scaffold. The purpose of this study is to evaluate the difference between polylactic-co-glycolic acids (PLGA) and chitosan as scaffolds. Human auricular chondrocytes were isolated, cultured, and seeded on the scaffolds, which were implanted in the back of nude mice. Eight animals were sacrificed at 4, 8, 12, 16, and 24 weeks after implantation respectively. In gross examination and histological findings, the volume of chondrocyte-PLGA complexes was decreased rapidly. The volume of chondrocyte-chitosan complexes was well maintained with a slow decrease rate. The expression of type II collagen protein detected by immunohistochemistry and western blots became weaker with time in the chondrocyte-PLGA complexes. However, the expression in the chondrocyte-chitosan complexes was strong for the whole period. Collagen type II gene expressions using RT-PCR showed a similar pattern. In conclusion, these results suggest that chitosan is a superior scaffold in cartilage tissue engineering in terms of structural integrity maintenance. It is expected that chitosan scaffold may become one of the most useful scaffolds for cartilage tissue engineering.

• Archives of Plastic Surgery
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• v.33 no.6
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• pp.723-731
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• 2006

Purpose: Collagen is the principal structural biomolecule in cartilage extracellular matrix, which makes it a logical target for cartilage engineering. In this study, porous type I collagen scaffolds were cross-linked using dehydrothermal(DHT) treatment and/or 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide(EDC), in the presence and absence of chondroitin-6-sulfate(CS) for cartilage regeneration. Methods: Cartilage defects were created in the proximal part of the ear of New Zealand rabbits. Four types of scaffolds(n=4) were inserted. The types included DHT cross-linked(Group 1), DHT and EDC cross- linked(Group 2), CS added DHT cross-linked(Group 3), and CS added DHT and EDC cross-linked(Group 4). Histomorphometric analysis and cartilage-specific gene expression of the reconstructed tissues were evaluated respectively 4, 8, and 12 weeks after implantation. Results: The largest quantity of regenerated cartilage was found in DHT cross-linked groups 1 and 3 in the 8th week and then decreased in the 12th week, while calcification increased. Calcification was observed from the 8th week and the area increased in the 12th week. Group 4 was treated with EDC cross-linking and CS, and the matrix did not degrade in the 12th week. Cartilage-specific type II collagen mRNA expression increased with time in all groups. Conclusion: CS did not increase chondrogenesis in all groups. EDC cross-linking may prevent chondrocyte infiltration from the perichondrium into the collagen scaffold.

• Journal of the Optical Society of Korea
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• v.12 no.2
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• pp.98-102
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• 2008

Optical Coherence Tomography (OCT) is an important noninvasive medical imaging technique that can reveal subsurface structures of biological tissue. OCT has demonstrated a good correlation with histology in sufficient resolution to identify morphological changes in articular cartilage to differentiate normal through progressive stages of degenerative joint disease. Current OCT systems provide individual cross-sectional images that are representative of the tissue directly under the scanning beam, but they may not fully demonstrate the degree of degeneration occurring within a region of a joint surface. For a full understanding of the nature and degree of cartilage degeneration within a joint, multiple OCT images must be obtained and an overall assessment of the joint surmised from multiple individual images. This study presents frequency domain three-dimensional (3-D) OCT imaging of degenerative joint cartilage extracted from bovine knees. The 3-D OCT imaging of articular cartilage enables the assembly of 126 individual, adjacent, rapid scanned OCT images into a full 3-D image representation of the tissue scanned, or these may be viewed in a progression of successive individual two-dimensional (2-D) OCT images arranged in 3-D orientation. A fiber-based frequency domain OCT system that provides cross-sectional images was used to acquire 126 successive adjacent images for a sample volume of $6{\times}3.2{\times}2.5\;mm^3$. The axial resolution was $8\;{\mu}m$ in air. The 3-D OCT was able to demonstrate surface topography and subsurface disruption of articular cartilage consistent with the gross image as well as with histological cross-sections of the specimen. The 3-D OCT volumetric imaging of articular cartilage provides an enhanced appreciation and better understanding of regional degenerative joint disease than may be realized by individual 2-D OCT sectional images.

• Archives of Plastic Surgery
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• v.32 no.1
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• pp.1-4
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• 2005

Previous sucessful results of neocartilage formation using tissue engineering technique in immunocompromised nude mouse xenograft model were reported. For clinical application, autogenous cell is preferrable to allogenic or xenogenic cell for circumvention of immune rejection. This study evaluates the feasibility of producing a engineered cartilage using autogenous chondrocytes. Chondrocytes were isolated from the auricular catilage of New Zealand White rabbit and seeded onto PGA polymer coated with polylactic acid in round pattern(diameter 0.7 cm, thickness 0.1 cm) at a concentration $7{\times}10^7$ chondrocytes per $cm^3$. Each Autogenous Cell-polymer constructs were implanted subcutaneously into the left side of dorsum of twelve Rabbits. Polymer templates not containg cells were implanted into the right side as a control. Fifteen rabbits were sacrificed at the following intervals: 5 rabbits at nine weeks, 7 rabbits at twelve weeksNew autogenous cartilage formation which retained the approximate dimensions of origianl round polymer template in 11 of 12 cell seeded implants. Histological examination using hematoxyline and eosin stain revealed vast majority of implants developed into mature cartilage. This study opens up the possibility of autologus cell transplant to construct autogenous cartilge.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.75-81
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• 2010

The segmentation of cartilage is crucial for the diagnose and treatment of osteoarthritis (OA), and has mostly been done manually by an expert, requiring a considerable amount of time and effort due to the thin shape and vague boundaries of the cartilage in MR (magnetic resonance) images. In this paper, we propose a fully automatic method to segment cartilage in a knee joint on MR images. The proposed method is based on a small number of manually segmented images as the training set and comprised of an initial per patch segmentation process and a global refinement process on the cumulative per patch results. Each patch for per patch segmentation is positioned by classifying the bone-cartilage interface on the pre-segmented bone surface. Next, the shape and intensity priors are constructed for each patch based on information extracted from reference patches in the training set. The ratio of influence between the shape and intensity priors is adaptively determined per patch. Each patch is segmented by graph cuts, where energy is defined based on constructed priors. Finally, global refinement is conducted on the global cartilage using the results of per patch segmentation as the shape prior. Experimental evaluation shows that the proposed framework provide accurate and clinically useful segmentation results.