Objective To establ ish a porcine model of articular full-thickness cartilage defect characterized byremaining cartilage calcified zone on femoral trochlea, so as to provide a considerable and comparative control group forinvestigating repair effects of tissue engineered scaffolds in articular cartilage defects with cartilage calcified zone remaining.Methods The full-thickness cartilage column defects (6 mm in diameter, 0.2-0.5 mm in depth) without damage on calcifiedcartilage zone were made on the femoral trochlea in 9 clean-grade 6-month-old Guizhou mini pigs by standard cartilage-defectmakingsuites. Microscopical observation was performed after modeling. Scanning were made by 3.0T MRI at 4 weeks. Thengeneral observation, stereomicroscope, and histological staining were used to observe cartilage repair. Results All animals wereal ive. No infection of incisions or patellar dislocations occurred; they were able to walk with partial weight-bearing immediatelyafter surgery and could move freely without limp at 1 week. Obvious signal discontinuity in trochlea and subchondral bone couldbe observed in MRI, without deep signal change in defects surrounding. Microscopical observation showed a few repair tissueand petechia at base of the defect with clear boundary. Nearly intact calcified zone of cartilage and zonal collapse of subchondralbone in defects could be observed with stereomicroscope. Under common microscope, no chondrocytes was found in defects,as well as negative staining of fast green-safranin O and alcian blue. Under polarized microscope, the bottom of defects werefilled with a l ittle of fibrous tissue presenting continuous and b l ight-refraction by sirius red staining. Conclusion Theanimal model of articular full-thickness cartilage defect on femoral trochlea by standard cartilage-defect-making suites can beapplied for the research of cartilage disease in early human osteoarthritis and function of calcified cartilage zone in pig.
To explore the shape and structure of calcified cartilage zone and its interface between the non-calcified articular cartilage and subchondral bone plate. Methods The normal human condyles of femur (n=20) were obtained from the tissue bank donated by the residents, 10 males and 10 females, aged 17-45 years. The longitudinal and transverse paraffin sections were prepared by the routine method. The shape and structure of calcified cartilage zone were observed with theSafranin O/fast green and von kossa stain method. The interface conjunction among zones of cartilage was researched by SEM and the 3D structural model was establ ished by serial sections and model ing technique. Results Articular bone-cartilage safranin O/fast green staining showed that cartilage was stained red and subchondral bone was stained blue. The calcified cartilage zone was located between the tidemark and cement l ine. Von kossa staining showed that calcified cartilage zone was stained black and sharpness of structure border. Upper interface gomphosised tightly with the non-calcified cartilage by the wave shaped tidemark and lower interface anchored tightly with the subchondral bone by the uneven comb shaped cement l ine. The noncalcified cartilage zone was interlocked tightly in the manner of “ravine-engomphosis” by the calcified cartilage zone as observed under SEM, and the subchondral bone was anchored tightly in the manner of “comb-anchor” by the in the calcified cartilage zone 3D reconstruction model. Conclusion The calcified cartilage zone is an important structure in the articular cartilage. The articular cartilage is fixed firmly into subchondral bone plate by the distinctive conjunct interfaces of calcified cartilage zone.