Do Young Park

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.

Three dimensional plotted extracellular matrix scaffolds using a rapid prototyping for tissue engineering application

Naturally derived biomaterials are rarely used in advanced rapid prototyping technology despite their superior biocompatibility. The main problem of natural material plotting is the high sensitivity of materials concentration and viscosity on the plotting nozzle. The aim of the current study was to develop a three dimensional (3D) plotting system capable of dispensing extracellular matrix (ECM)-c (ECM powder blended collagen) and manufacture various shapes of ECM-c scaffolds to apply for irregular defects. We had adapted a powder-based plotting approach to print the stable 3D construct using only cartilage derived ECM materials. This study successfully developed the plotting method for high viscous ECM-c material and showed the 3D plotted scaffolds with high interconnected pores as well as complex shape. Furthermore, cell culture results proved that plotted ECM-c scaffolds were able to provide a suitable environment for cell attachment, proliferation and chondrogenesis. This study shows the 3D printing feasibility of ECM natural material has demonstrated as a first time. We believe our results will offer a meaningful step toward the 3D scaffold printing based on natural ECM materials for future organ printing.

A new era of cartilage repair using cell therapy and tissue engineering: turning current clinical limitations into new ideas

Caused by trauma or common joint disorders, cartilage degeneration can lead to major disability. Cartilage has little capacity in terms of self-regeneration due to its avascular nature. Current treatment for cartilage degeneration relies mainly on surgery, which usually generates fibrous tissue rather than hyaline cartilage. A number of studies have overcome the current limitations of existing therapies and have succeeded in cartilage tissue repair. Clinical trials have shifted from implementing autologous chondrocytes or grafts toward using more complex materials such as engineered cells, scaffolds, and growth factors as strategies. In this review, we focus on recent advances in cartilage tissue engineering utilizing cells and scaffolds.

The Degeneration of Meniscus Roots Is Accompanied by Fibrocartilage Formation, Which May Precede Meniscus Root Tears in Osteoarthritic Knees

Background: Fibrocartilage metaplasia in tendons and ligaments is an adaptation to compression as well as a pathological feature during degeneration. Medial meniscus posterior roots are unique ligaments that resist multidirectional forces, including compression. Purpose: To characterize the degeneration of medial meniscus posterior root tears in osteoarthritic knees, with an emphasis on fibrocartilage and calcification. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Samples of medial meniscus posterior roots were harvested from cadaveric specimens and patients during knee replacement surgery and grouped as follows: normal reference, no tear, partial tear, and complete tear. Degeneration was analyzed with histology, immunohistochemistry, and real-time polymerase chain reaction. Uniaxial tensile tests were performed on specimens with and without fibrocartilage. Quantifiable data were statistically analyzed by the Kruskal-Wallis test with the Dunn comparison test. Results: Thirty, 28, and 42 samples harvested from 99 patients were allocated into the no tear, partial tear, and complete tear groups, respectively. Mean modified Bonar tendinopathy scores for each group were 3.97, 9.31, and 14.15, respectively, showing a higher degree of degeneration associated with the extent of the tear (P < .05 for all groups). The characterization of root matrices revealed an increase in fibrocartilage according to the extent of the tear. Tear margins revealed fibrocartilage in 59.3% of partial tear samples and 76.2% of complete tear samples, with a distinctive cleavage-like shape. Root tears with a similar shape were induced within fibrocartilaginous areas during uniaxial tensile testing. Even in the no tear group, 56.7% of samples showed fibrocartilage in the anterior margin of the root, adjacent to the meniscus. An increased stained area of calcification and expression of the ectonucleotide pyrophosphatase/phosphodiesterase 1 gene were observed in the complete tear group compared with the no tear group (P < .0001 and P = .24, respectively). Conclusion: Fibrocartilage and calcification increased in medial meniscus posterior roots, associated with the degree of the tear. Both findings, which impair the ligament’s resistance to tension, may play a pivotal role during the pathogenesis of degenerative meniscus root tears in osteoarthritic knees. Fibrocartilage and calcification may be useful as diagnostic markers as well as markers of degeneration, which may aid in determining the treatment modality in meniscus root tears. The presence of fibrocartilage in intact roots may suggest an impending tear in osteoarthritic knees.

Polyethylene Wear Particles Play a Role in Development of Osteoarthritis via Detrimental Effects on Cartilage, Meniscus, and Synovium

OBJECTIVE While ultra-high molecular weight polyethylene (UHMWPE) wear particles are known to cause periprosthetic osteolysis, its interaction with other intra-articular tissues in the case of partial joint arthroplasties is not well understood. We hypothesized that UHMWPE particles per se would interact with intra-articular tissue, which by acting as inflammatory reservoirs, would subsequently induce osteoarthritic (OA) changes. Our goal was to assess the inflammatory response, phagocytic activity, as well as apoptosis of intra-articular cells in the presence of UHMWPE particles in vitro, and the in vivo response of those tissues after intra-articular injection of particles in a murine model. DESIGN Three cell types were used for the in vitro study; chondrocytes, meniscal fibrochondrocytes, and synoviocytes. Each cell type was cultured with two different concentrations of UHMWPE particles. Pro-inflammatory cytokine production, phagocytosis, and apoptosis were analyzed. In vivo experiments were done by injecting two concentrations of UHMWPE particles into normal and murine OA model knee joints. RESULTS In vitro experiments showed that UHMWPE particles increase pro-inflammatory cytokine and mediator (IL-1β, IL-6, TNF-α, Nitric Oxide, and Prostaglandin E2) production, phagocytosis of particles, and apoptosis in all cell types. In vivo experiment showed degeneration of cartilage and meniscus, as well as synovitis after particle injection. CONCLUSIONS UHMWPE wear particles per se exert detrimental effects in cartilage, synovium, and meniscus of the knee joint resulting in pro-inflammatory cytokine release, phagocytosis of particles and apoptosis. Particles induced and exacerbated OA changes in a murine model.

Repair of partial thickness cartilage defects using cartilage extracellular matrix membrane-based chondrocyte delivery system in human Ex Vivo model

Treatment options for partial thickness cartilage defects are limited. The purpose of this study was to evaluate the efficacy of the chondrocyte-seeded cartilage extracellular matrix membrane in repairing partial thickness cartilage defects. First, the potential of the membrane as an effective cell carrier was investigated. Secondly, we have applied the chondrocyte-seeded membrane in an ex vivo, partial thickness defect model to analyze its repair potential. After culture of chondrocytes on the membrane in vitro, cell viability assay, cell seeding yield calculation and cell transfer assay were done. Cell carrying ability of the membrane was also tested by seeding different densities of cells. Partial defects were created on human cartilage tissue explants. Cell-seeded membranes were applied using a modified autologous chondrocyte implantation technique on the defects and implanted subcutaneously in nude mice for 2 and 4 weeks. In vitro data showed cell viability and seeding yield comparable to standard culture dishes. Time dependent cell transfer from the membrane was observed. Membranes supported various densities of cells. Ex vivo data showed hyaline-like cartilage tissue repair, integrated on the defect by 4 weeks. Overall, chondrocyte-seeded cartilage extracellular membranes may be an effective and feasible treatment strategy for the repair of partial thickness cartilage defects.

Comparison of fetal cartilage-derived progenitor cells isolated at different developmental stages in a rat model

Fetal cartilage‐derived progenitor cells (FCPCs) could be a useful cell source in cell‐based therapies for cartilage disorders. However, their characteristics can vary depending on the developmental stages. The aim of this study was to compare the characteristics of rat FCPCs from the hind limb on embryonic day 14 (E14), E16 and E20 regarding proliferation, pluripotency, and differentiation. Morphologically, rat fetal cartilage tissue showed an increase in cartilaginous differentiation features (Safranin‐O, type II collagen) and decrease in pluripotency marker (Sox2) in the order of E14, E16 and E20. E14 FCPCs showed significantly higher doubling time compared to E16 and E20 FCPCs. While the E14 FCPCs expressed pluripotent genes (Sox2, Oct4, Nanog), the E16 and E20 FCPCs expressed chondrogenic markers (Sox9, Col2a1, Acan). E20 FCPCs showed the highest ability to both chondrogenic and adipogenic differentiation and E14 FCPCs showed relatively better activity in osteogenic differentiation. Further analysis showed that E20 FCPCs expressed both adipogenic (C/ebpß) and osteogenic (Runx2, Sp7, Taz) transcription factors as well as chondrogenic transcription factors. Our results show an inverse relationship overall between the expression of pluripotency genes and that of chondrogenic and lineage‐specific genes in FCPCs under development. Due to its exceptional proliferation and chondrogenic differentiation ability, fetal cells from epiphyseal cartilage (E20 in rats) may be a suitable cell source for cartilage regeneration.

Barefoot stubbing injuries to the great toe in children: a new classification by injury mechanism.

Objective: This study was conducted to categorize barefoot stubbing injuries to the great toe in children by injury mechanism to differentiate benign stubbing injuries from more complex injuries necessitating surgery. Design: Prospective clinical series of consecutively treated patients. Setting: Tertiary university hospital setting. Patients: Forty-one children who had sustained an indirect injury to the great toe during barefoot sports activities between January 2001 and December 2009 were included. Intervention: Conservative or surgical treatment was done according to clinical and radiological findings. Main Outcome Measurement: Information regarding injury mechanism was collected from patients, parents, and coaches using skeletal models and assessed by a pediatric orthopedic surgeon. Mechanisms of injury were identified and grouped as follows: hyperabduction–flexion, hyperflexion, hyperabduction–extension, hyperextension, and hyperextension–adduction. Results: Hyperabduction–flexion was the most common mechanism (n = 16), in which interphalangeal joint dislocation and skin disruption was noted in most cases. The second most common mechanism was hyperabduction–extension (n = 14) in which avulsion fracture of the lateral volar condyle of the proximal phalanx was noted in most cases. This avulsion fracture had the worst prognosis after conservative care. Conclusions: Based on these results, we have created a grading system and treatment protocol for indirect hallux sports injuries in children. Avulsion fracture of the lateral condyle of the proximal phalanx, a result of hyperabduction–extension, is a high-risk sign of nonunion and should be aggressively treated, contrary to previous guidelines. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Three Dimensional CT-based Virtual Patellar Resection in Female Patients Undergoing Total Knee Replacement: A Comparison between Tendon and Subchondral Method

Background Due to its small size, variable shape, and lack of distinct anatomical landmarks, osteoarthritic knees make a precise patellar resection extremely difficult. Methods We performed virtual patellar resection with digital software using three dimensional computed tomography scans of knees from 49 patients who underwent primary total knee replacement at our hospital. We compared 2 commonly used resection methods, the tendon method (TM) and the subchondral method, to determine an ideal resection plane with respect to the symmetry and thickness of the patellar remnant. Results The TM gave a thicker resected patella, and a less oval cut surface shape, which gives better coverage for a domed prosthesis. Both methods, however, gave a symmetric resection both superior-inferiorly, as well as mediolaterally. Conclusions Although TM appears statistically better with respect to the thickness and cut surface shape, only further intraoperative studies with long-term clinical follow-up may provide us with the most appropriate patellar resection method.

Three-Dimensional Spheroid Culture Increases Exosome Secretion from Mesenchymal Stem Cells

AbstractBackground: Mass production of exosomes is a prerequisite for their commercial utilization. This study investigated whether three-dimensional (3D) spheroid culture of mesenchymal stem cells (MSCs) could improve the production efficiency of exosomes and if so, what was the mechanism involved.Methods:We adopted two models of 3D spheroid culture using the hanging-drop (3D-HD) and poly(2-hydroxyethyl methacrylate) (poly-HEMA) coating methods (3D-PH). The efficiency of exosome production from MSCs in the 3D spheroids was compared with that of monolayer culture in various conditions. We then investigated the mechanism of the 3D spheroid culture-induced increase in exosome production.Results:The 3D-HD formed a single larger spheroid, while the 3D-PH formed multiple smaller ones. However, MSCs cultured on both types of spheroids produced significantly more exosomes than those cultured in conventional monolayer culture (2D). We then investigated the cause of the increased exosome production in terms of hypoxia within the 3D spheroids, high cell density, and non-adherent cell morphology. With increasing spheroid size, the efficiency of exosome production was the largest with the least amount of cells in both 3D-HD and 3D-PH. An increase in cell density in 2D culture (2D-H) was less efficient in exosome production than the conventional, lower cell density, 2D culture. Finally, when cells were plated at normal density on the poly-HEMA coated spheroids (3D-N-PH); they formed small aggregates of less than 10 cells and still produced more exosomes than those in the 2D culture when plated at the same density. We also found that the expression of F-actin was markedly reduced in the 3D-N-PH culture.Conclusion:These results suggested that 3D spheroid culture produces more exosomes than 2D culture and the non-adherent round cell morphology itself might be a causative factor. The result of the present study could provide useful information to develop an optimal process for the mass production of exosomes.