B.-H. Min

Establishment of a reliable and reproducible murine osteoarthritis model

OBJECTIVE Many osteoarthritis (OA) models have been developed in mice to understand OA progression and evaluate new OA therapies. However, the individual variation of the joint lesions remains a critical problem in most of the current OA models. We established an OA model in C57BL/6 mice that is more reproducible and amenable to therapeutic intervention by controlling their movement. DESIGN OA was induced in 9-week-old C57BL/6 mice by destabilizing the medial meniscus. The mice were then raised in the standard cage for free movement or in a confined cage customized to restrict movement. Mice in the confined cage were subjected to no exercise or exercise of 400, 800, and 1200 m/day. RESULTS OA lesions of mice in the confined cage were more severe in the exercise group and showed much less variation. However, the patterns of OA lesions over time were quite different depending on the amount of daily exercise; the patterns increased linearly until 8 weeks in 400 m/day exercise group, but showed plateauing after 4 weeks in 800 m/day and 1200 m/day groups. The validity of our novel OA model with movement control was proven by successfully discriminating the therapeutic effect of hyaluronic acid (HA) in histological scores, while the OA model using standard caging showed a statistically insignificant difference. CONCLUSION The mouse OA model using the confine cage and enforced periodic exercise of mice is more reproducible and reliable than standard caging methods.

Quantitative analysis of water distribution in human articular cartilage using terahertz time-domain spectroscopy

The water distribution in human osteoarthritic articular cartilage has been quantitatively characterized using terahertz time-domain spectroscopy (THz TDS). We measured the refractive index and absorption coefficient of cartilage tissue in the THz frequency range. Based on our measurements, the estimated water content was observed to decrease with increasing depth cartilage tissue, showing good agreement with a previous report based on destructive biochemical methods.

Effect of Continuous-Wave Low-Intensity Ultrasound in Inflammatory Resolution of Arthritis-Associated Synovitis.

Background Low-intensity ultrasound (LIUS) can reduce pain and improve function in arthritic joints. Neutrophils are first-line actors in host defense that recruit macrophages. Dead neutrophils are removed during resolution of inflammation. Delayed neutrophil clearance can lead to extended inflammation or even chronic autoimmune disease. Although neutrophil extracellular traps (NETs) in arthritic tissue are involved in the pathogenesis of arthritis, their functional role has not been clarified. Objectives This study aimed to investigate the effect of LIUS on synovial inflammation and its resolution via neutrophil clearance. Methods Synovitis was induced by intra-articular injection of complete Freunds adjuvant (CFA) into the left knee joint of 58 adult male Sprague-Dawley rats. Low-intensity ultrasound (1 MHz, 200 mW/cm2) was applied for 10 minutes daily. Neutrophil clearance was assessed with the expression of myeloperoxidase (MPO). In addition, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and NET formation in the synovium were observed. In neutrophil and macrophage cultures from peripheral blood, the effect of NET clearance by LIUS was investigated. Results In CFA-induced synovitis, MPO-positive neutrophils peaked after 2 to 3 days, filling the inflammatory core. Monocytes and macrophages in the periphery later infiltrated the core and were reduced thereafter. Low-intensity ultrasound reduced synovial hyperplasia and induced earlier MPO clearance. Neutrophils in the core of the inflamed synovium exhibited NET formation, which LIUS increased. Low-intensity also induced NETs in peripheral polymorphonuclear cells in an intensity-dependent manner and potentiated phorbol myristate acetate (PMA)-induced NETosis. The PMA-induced NETs were cleared by macrophages; clearance was enhanced by LIUS. Limitations The effect of LIUS on CFA-induced inflammation was observed only during the acute phase. Although the effect of LIUS on NETosis in the in vitro neutrophil culture system was clear, the in vivo NETosis cannot be quantified. Conclusions Neutrophil extracellular traps act in inflammatory synovitis, and LIUS enhanced the NETs and resulted in neutrophil clearance by enhancing the phagocytosis of macrophages, which might be a factor underlying the therapeutic effect of LIUS in arthritic synovium.

THz spectroscopic estimation of water content in human articular cartilage

Water distribution of human osteoarthritic articular cartilage has been characterized using terahertz time domain spectroscopy. The evaluation of water content in cartilage tissue can be helpful to diagnose the early degenerative joint diseases. The estimated water content in our measurement decreases along the depth of the cartilage tissue and shows a good agreement with the previous results acquired by destructive biochemical methods.

Terahertz Pulse Imaging of Human Articular Cartilage

Terahertz (THz) time-domain spectroscopy (TDS) provides powerful means to image biomedical structures that cannot be obtained by other imaging techniques. In this work, we report THz imaging of human cartilage by using THz TDS. In general, degeneration of cartilage is accompanied by alteration of structural, compositional and molecular level in cartilage matrix. We performed THz pulse imaging experiments for human articular cartilage tissues. Each THz image distinguishes between the normal and abnormal cartilage tissues and demonstrates the possibility of THz pulse imaging as a diagnostic tool in biomedicine.

P381 MECHANO-ACTIVE CARTILAGE TISSUE ENGINEERING USING A HIGHLY ELASTIC SCAFFOLD AND BONE MARROW STEM CELLS

Conclusions: In summary, we have characterized a novel targeting peptide and showed its specificity as well as its competetive binding to articular cartilage. Surface functionalisation of PPS nanoparticles was carried out and showed similar binding at 10% surface functionalisation as the free peptide. After further optimisation, the functionalized nanoparticles will be labeled and loaded with small molecule drugs to determine the in vivo targeting of the articular cartilage and their capability of sustained intra-articular drug release in the cartilage matrix.