ABSTRACT
BACKGROUND:Cartilage tissue engineering has been widely used to achieve cartilage regeneration in vitro and repair cartilage defects. Tissue-engineered cartilage mainly consists of chondrocytes, cartilage scaffold and in vitro environment. OBJECTIVE:To mimic the environment of articular cartilage development in vivo, in order to increase the bionic features of tissue-engineered cartilage scaffold and effectiveness of cartilage repair. METHODS: Knee joint chondrocytes were isolated from New Zealand white rabbits, 2 months old, and expanded in vitro. The chondrocytes at passage 2 were seeded onto a scaffold of articular cartilage extracelular matrix in the concentration of 1×106/L to prepare cel-scaffold composites. Cel-scaffold composites were cultivated in an Instron bioreactor with mechanical compression (1 Hz, 3 hours per day, 10% compression) as experimental group for 7, 14, 24, 28 days or cultured staticaly for 1 day as control group. RESULTS AND CONCLUSION:Morphological observations demonstrated that the thickness, elastic modulus and maximum load of the composite in the experimental group were significantly higher than those in the control group, which were positively related to time (P < 0.05). Histological staining showed the proliferation of chondrocytes, formation of cartilage lacuna and synthesis of proteoglycan in the experimental group through hematoxylin-eosin staining and safranin-O staining, which were increased gradualy with mechanical stimulation time. These results were consistent with the findings of proteoglycan kit. Real-time quantitative PCR revealed that mRNA expressions of colagen type I and colagen type II were significantly higher in the experimental group than the control group (P < 0.05). The experimental group showed the highest mRNA expression of colagen type I and colagen type II at 21 and 28 days of mechanical stimulation, respectively (P < 0.05). With the mechanical stimulation of bioreactor, the cel-scaffold composite can produce more extracelular matrix, such as colagen and proteoglycan, strengthen the mechanical properties to be more coincident with thein vivo environment of cartilage development, and increase the bionic features. With the progress of tissue engineering, the clinical bioregeneration of damaged cartilage wil be achieved.
ABSTRACT
Objective To compare the bone microstructure and osteoblast and osteoclast activity in different regions of osteonecrosis of the femoral head.Methods The osteonecrosis femoral heads were collected from 10 patients (Ficat Ⅳ) who had undergone total hip arthroplasty from March 2011 to May 2013.There were 6 males and 4 females.Their average age was 47.7 years old (range,40-57 years).The samples were divided into subchondral bone region,necrotic region,sclerosis region and healthy region according to radiographic results,then the bone microstructure,micro mechanism and osteoblasts/osteoclasts activity were analyzed byMicro-CT,RT-PCR,Nanoindentation,immunohistochemistry and Trap staining.Results According to the micro-CT results,the continuity of trabecular bone in necrotic region was damaged.The number of trabecular was increased and the gap was narrowed in sclerosis region.The shape and number of trabecular bone were normal in the healthy region.The elasticity moduli in different regions were:subchondral bone region 13.808±4.22 GPa,necrotic region 13.999±3.816 GPa,sclerosis region 17.266±3.533 GPa and healthy region 11.927±1.743 GPa.The hardness were subchondral bone region 0.425±0.173 GPa,necrotic region 0.331±0.173 GPa,sclerosis region 0.661±0.208 GPa,and healthy region 0.423±0.088 GPa.The trap staining of subchondral bone in healthy region and necrotic region were positive while other regions were negative.Immunohistochemistry staining showed that compared with necrotic region,the RANK and RANKL staining level increased significantly in subchondral bone and necrotic region,while Runx2 and BMP2 staining level increased significantly in sclerosis region.Conclusion The mechanical properties of trabecular have no significant difference between necrotic region and healthy region in the progress of the osteonecrosis,while the bone structure has obvious changes.An active bone resorption is observed in subchondral bone and necrotic region,while a higher bone formation activity is found in sclerosis region.