ObjectiveTo review the current treatment status of osteochondral defects (OCD) of the knee joint. MethodsRecent literature concerning treatment of OCD of the knee joint was extensively reviewed and summarized. ResultsOCD affect both the articular cartilage and the underlying subchondral bone, whereas OCD caused by different etiologies require various treatments. OCD repair is available by conventional clinical methods or the advanced tissue engineering strategies. Current clinical treatment outcomes remain uncertain; tissue engineering has emerged as a potential option as it can be efficiently applied to regenerate bone, cartilage, and the bone-cartilage interface, as well as effectively restore normal function and mechanical properties of the cartilage and subchondral bone. ConclusionOCD management and repair remain a great challenge in orthopedic surgery, thus cartilage and subchondral bone should be promoted as an interdependent functional unit considering treatment strategies to provide the best solution for the treatment of osteochondral defects.
ObjectiveTo explore the relationship between subchondral bone reconstruction and articular cartilage regeneration in a rabbit model of spontaneous osteochondral repair. MethodsTwenty-four 6-month-old New Zealand white rabbits were included. The osteochondral defects (4 mm in diameter and 3 mm in depth) were created in the trochlear groove of the unilateral femur, which penetrated the subchondral bone without any treatment. The rabbits were sacrificed at 1, 4, 12, and 24 weeks after operation, respectively. The specimens were obtained for macroscopic, histological, and immunohistochemical observations. According to the International Cartilage Repair Society (ICRS) histological scoring, the effect of cartilage repair was assessed. The histomorphometrical parameters of subchondral bone were analyzed by micro-CT scan and reconstruction, and the relationship between cartilage repair and the histomorphometrical parameters of the subchondral bone were also analyzed. ResultsOsteochondral defects could be repaired spontaneously in rabbit model. With time, defect was gradually filled with repaired tissue, subchondral bone plate under the defect region gradually migrated upward. Bone mineral density, bone volume fraction, tissue mineralized density, trabecula number, and trabecula thickness were increased, while trabecula spacing was decreased. Significant difference was found in the other parameters between different time points (P<0.05) except for trabecula thickness between at 4 and 12 weeks after operation (P>0.05). Histological examination showed that fibrous repair was predominant with rare hyaline cartilage. With time, ICRS scores increased gradually, showing significant differences between other time points (P<0.05) except for between at 4 and 12 weeks after operation (P>0.05). Among the histomorphometrical parameters of subchondral bone, the trabecula spacing was negatively correlated with ICRS score (r=-0.584, P=0.039), and the other histomorphometrical parameters were positively correlated with ICRS score (r=0.680-0.891). ConclusionThere is relevant correlation as well as independent process between cartilage regeneration and subchondral bone reconstruction in the rabbit model of spontaneous osteochondral repair, and fast subchondral bone remodeling may adversely affect articular cartilage repair.
ObjectiveTo investigate the effect of three-dimensional cultivation with dynamic compressive stimulation on promotion of cartilage growth in vitro, by constructing tissue engineered cartilage with three-dimensional porous articular cartilage extracellular matrix (ECM) scaffolds laden with rabbit chondrocytes and performing mechanical stimulation by compressive stress in bioreactor. MethodsChondrocytes of healthy adult New Zealand rabbits were isolated, and passage 2 chondrocytes were seeded onto three-dimensional porous articular cartilage ECM scaffolds for 5 days pre-cultivation, and then were divided into 2 groups:Group A continued static culture as control; group B (dynamic culture condition) underwent dynamic compressive strain stimulation (compressive strain of 15%, frequence of 1 Hz) in a bioreactor. Cell viability and distribution in scaffolds were observed; the glycosaminoglycan (GAG) content, collagen content, and total DNA content were measured after 3 weeks of culturing; and elastic modulus was evaluated by mechanical test. ResultsLaser scanning confocal microscopy indicated that cells grew well and evenly distributed in the scaffold of group B, while poor cells growth and loss of staining in the central region of the scaffolds were observed in group A. Scanning electron microscopy showed that chondrocytes possessed good adhesion, proliferation, and growth on the scaffolds of group B; while the number of chondrocytes was significantly reduced, and cells scattered in group A. Biochemical composition analysis showed that collagen, GAG, and DNA contents of cell-scaffold constructs were (675.85±27.93) μg/mg, (621.72±26.75) μg/mg, and (16.98±3.23) μg/sample in group B, and were (438.72±6.35) μg/mg, (301.63±30.51) μg/mg, and (10.18±4.39) μg/sample in group A respectively, which were significantly higher in group B than in group A (t=18.512, P=0.000;t=17.640, P=0.000;t=2.790, P=0.024). Mechanical testing indicated that the elastic modulus of group B[(0.67±0.09) MPa] was significantly higher than that of group A[(0.49±0.16) MPa] and cell-free scaffolds[(0.43±0.12) MPa] (P < 0.05). ConclusionMimetic compressive stress with three-dimensional dynamic conditions created in the bioreactor is superior to the ordinary static three-dimensional cultivation, it can provide the optimal environment for chondrocytes on the ECM scaffolds, which may be a good way to construct tissue engineered cartilage in vitro.