The data support the clinical reality of 1-step minimally invasive cartilage-reparative medicine with UPAL gel without harvesting donor cells.

(natural, toe-in, toe-out). The knee kinetics and kinematics during landing were evaluated 5 using a motion analysis system. Results under three toe conditions were compared using 6 a one-way repeated-measures analysis of variance and a post-hoc Bonferroni test. Results: Toe-in landing was associated with a significantly greater knee abduction angle, 8 tibial internal rotation angle, and knee abduction moment than the natural and toe-out 9 conditions. Toe-out landing was associated with significantly greater tibial internal 10 rotational angular velocity.

Background: Many tissue-engineered methods for meniscal repair have been studied, but their utility remains unclear. Hypothesis: Implantation of low-endotoxin, ultra-purified alginate (UPAL) gel without cells could induce fibrocartilage regeneration on meniscal defects in rabbits. Study Design: Controlled laboratory study. Methods: Forty-two mature Japanese White rabbits were divided into 2 groups of 21 animals each. In each animal, a cylindrical defect measuring 2 mm in diameter was created with a biopsy punch on the anterior horn of the medial meniscus. In the control group, no treatment was applied on the left medial meniscal defect. In the UPAL gel group, the right medial meniscal defect was injected with the UPAL gel and gelated by a CaCl2 solution. Samples were evaluated at 3, 6, and 12 weeks postoperatively. For biomechanical evaluation, 6 additional samples from intact animals were used for comparison. Results: The macroscopic score was significantly greater in the UPAL gel group than in the control group at 3 weeks (mean ± SE: 5.6 ± 0.82 vs 3.4 ± 0.83, P = .010), 6 weeks (5.9 ± 0.72 vs 2.5 ± 0.75, P = .026), and 12 weeks (5.2 ± 1.21 vs 1.0 ± 0.63, P = .020). The histological score was significantly greater in the UPAL group than in the control group at 3 weeks (2.1 ± 0.31 vs 1.2 ± 0.25, P = .029) and 12 weeks (2.2 ± 0.55 vs 0.3 ± 0.21, P = .016). The mean stiffness of the reparative tissue in the UPAL gel group was significantly greater than that in the control group at 6 weeks (24.325 ± 3.920 N/mm vs 8.723 ± 1.190 N/mm, P = .006) and at 12 weeks (27.804 ± 6.169 N/mm vs not applicable [because of rupture]). Conclusion: The UPAL gel enhanced the spontaneous repair of fibrocartilage tissues in a cylindrical meniscal defect in rabbits. Clinical Relevance: These results imply that the acellular UPAL gel may improve the repair of traumatic meniscal injuries.

Objective Osteoarthritis is a progressive joint disease characterized by cartilage degradation and synovial inflammation. Presence of cartilage fragments in the joint due to degradation of cartilage is thought to be associated with local inflammatory response and progressive osteoarthritic process. Understanding the mechanism by which cartilage fragments elicit this destructive process should aid in designing novel therapeutic approaches. Therefore, objective of current study is to establish an in vitro model to examine the cross-talk between chondrocytes and cartilage fragments–stimulated macrophages. Design Cartilage fragments were prepared from femoral head cartilages of mice and analyzed using a scanning electron microscope and particle size analyzer. Bone marrow–derived macrophages were co-cultured with cartilage fragments and chondrocytes using transwell co-culture system. Macrophage inflammatory mediators in supernatant of cultures were determined by ELISA and gene expression of macrophages and chondrocyte were quantified by qRT-PCR. Results Shapes of cartilage fragments were irregular with sizes ranged between 0.54 and 55 μm. Macrophages cultured with cartilage fragments released significantly higher concentrations of TNF-α, IL-6, and NO than those of mock and control. Consistently, gene expressions of TNF-α, IL-6, and MMP-9 were significantly increased in stimulated macrophages. The elevation in production of pro-inflammatory molecules in stimulated macrophages cultures were coincident with an increase in gene expression of chondrocyte MMP-13, iNOS, and IL-6. Conclusion We developed an in vitro co-culture model to study the impact of stimulation of macrophage by cartilage fragments on the expression of chondrocyte carbolic factors. Our results revealed that cartilage fragments triggered macrophages inflammatory response that enhanced the production of chondrocyte catabolic factors.

Background: One of the most important limitations of osteochondral autograft transplantation (OAT) is the adverse effect on donor sites in the knee. To decrease the number and/or size of osteochondral defects, we devised a method with biomaterial implantation after OAT. Hypothesis: OAT augmented by ultrapurified alginate (UPAL) gel enhances cartilage repair capacity. Study Design: Controlled laboratory study. Methods: Seventy-five osteochondral defects in rabbits were divided into 3 groups: osteochondral defects with OAT alone, defects with OAT augmented by UPAL gel (combined group), and defects without intervention as controls. Macroscopic and histological evaluations of the reparative tissues were performed at 4 and 12 weeks postoperatively. Histological evaluation of graft cartilage degradation was also performed. To evaluate the effects of UPAL gel on graft healing, repaired bone volumes and osseointegration of the graft were evaluated. Collagen orientation and the mechanical properties of the reparative tissue and graft cartilage were also evaluated qualitatively. Results: The macroscopic and histological evaluations of the combined group were significantly superior to the other groups at 12 weeks postoperatively. Regarding degenerative change of the graft, the histological scores of the combined group were significantly higher than those of the OAT-alone group. The values of repaired subchondral bone volumes and osseointegration of the graft were almost identical in both groups. Collagen orientation and the mechanical properties of the reparative tissue and graft cartilage were significantly better in the combined group than in the other groups. Conclusion: Administration of UPAL gel in OAT enhanced cartilage repair and protected graft cartilage without inhibiting subchondral bone repair and graft survival. Clinical Relevance: OAT augmented by UPAL gel decreases the number and/or size of osteochondral grafts, minimizing the risk of donor site morbidity. This combination technique has the potential to improve clinical outcomes and expand the surgical indications for OAT.

Juvenile tissue healing is capable of extensive scarless healing that is distinct from the scar-forming process of the adult healing response. Although many growth factors can be found in the juvenile healing process, the molecular mechanisms of juvenile tissue healing are poorly understood. Here we show that juvenile mice deficient in the chemokine receptor CCR7 exhibit diminished large-scale healing potential, whereas CCR7-depleted adult mice undergo normal scar-forming healing similar to wild type mice. In addition, the CCR7 ligand CCL21 was transiently expressed around damaged cartilage in juvenile mice, whereas it is rarely expressed in adults. Notably, exogenous CCL21 administration to adults decreased scar-forming healing and enhanced hyaline-cartilage repair in rabbit osteochondral defects. Our data indicate that the CCL21/CCR7 axis may play a role in the molecular control mechanism of juvenile cartilage repair, raising the possibility that agents modulating the production of CCL21 in vivo can improve the quality of cartilage repair in adults. Such a strategy may prevent post-traumatic arthritis by mimicking the self-repair in juvenile individuals.

Elucidation of the healing mechanisms in damaged tissues is a critical step for establishing breakthroughs in tissue engineering. Articular cartilage is clinically one of the most successful tissues to be repaired with regenerative medicine because of its homogeneous extracellular matrix and few cell types. However, we only poorly understand cartilage repair mechanisms, and hence, regenerated cartilage remains inferior to the native tissues. Here, we show that glycosylation is an important process for hypertrophic differentiation during articular cartilage repair. GM3, which is a precursor molecule for most gangliosides, was transiently expressed in surrounding damaged tissue, and depletion of GM3 synthase enhanced cartilage repair. Gangliosides also regulated chondrocyte hypertrophy via the Indian hedgehog pathway. These results identify a novel mechanism of cartilage healing through chondrocyte hypertrophy that is regulated by glycosylation. Manipulation of gangliosides and their synthases may have beneficial effects on articular cartilage repair.

Background: During meniscal tissue repair, the origin of the reparative cells of damaged meniscal tissue remains unclear. Hypothesis: Comparison of the influence between meniscal and synovial tissues on meniscal repair by the in vivo freeze-thaw method would clarify the origin of meniscal reparative cells. Study Design: Controlled laboratory study. Methods: A total of 48 mature Japanese white rabbits were divided into 4 groups according to the tissue (meniscal or synovial) that received freeze-thaw treatment. The meniscus of each group had a 2 mm–diameter cylindrical defect filled with alginate gel. Macroscopic and histologic evaluations of the reparative tissues were performed at 1, 3, and 6 weeks postoperatively. Additional postoperative measurements included cell density, which was the number of meniscal cells in the cut area per cut area (mm2) of meniscus; cell density ratio, which was the cell density of the sample from each group per the average cell density of the intact meniscus; and cell death rate, which was the number of cells stained by propidium iodide per the number of cells stained by Hoechst 33342 of the meniscal tissue adjacent to the defect. Results: The macroscopic and histologic evaluations of the non–synovium freeze-thaw groups were significantly superior to those of the synovium freeze-thaw groups at 3 and 6 weeks postoperatively. Additionally, the meniscal cell density ratio and cell death rate in the freeze-thaw groups were significantly lower than those in the non–meniscal freeze-thaw groups at 3 and 6 weeks postoperatively. Conclusion: The freeze-thawed meniscus recovered few cells in its tissue even after 6 weeks. However, the defect was filled with fibrochondrocytes and proteoglycan when the synovium was intact. On the basis of these results, it is concluded that synovial cells are the primary contributors to meniscal injury repair. Clinical Relevance: In meniscal tissue engineering, there is no consensus on the best cell source for meniscal repair. Based on this study, increasing the synovial activity and contribution should be the main objective of meniscal tissue engineering. This study can establish the foundation for future meniscal tissue engineering.