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.

BACKGROUND:Magnesium can be degraded voluntarily in vivo, so a second surgery is avoided. However, its aloys have not been widely used in the clinical orthopedics because there is a lack of accurate and reliable methods to assess its degradationin vivo.
OBJECTIVE:To explore the degradation of micro-arc-oxidized AZ31 magnesium aloy in the femoral condyle of rabbits based on micro-CT images and relative data.
METHODS:Forty micro-arc-oxidized AZ31 magnesium aloys were implanted into the right femoral condyle of 40 New Zealand rabbits. Then 10 right femoral condyles were removed at 5, 10, 15 and 20 weeks after surgery, respectively, to quantitatively analyze and evaluate the degradation of AZ31 magnesium aloys by micro-CT images and relative data.
RESULTS AND CONCLUSION:The surface of AZ31 aloys was corroded progressively with dark color and distorted appearance at 5-20 weeks post implantation. Micro-CT images showed that in the first 5 weeks, the degradation was inactive, and at the 10th week, it turned active; at the 15th week, the corrosion pits were obviously increased in number, and the corrosion area and corrosion speed were enlarged and fastened, respectively. Up to the 20th week, the aloy surfaces were ful of corrosion pits besides roughness and discontinuity. Relevant data analysis showed that the volume fraction of magnesium aloy was 98.6%, 97.1% and 86.4% at the 5th, 10th and 20th weeks after implantation, respectively, and it had a significant decrease from the 10th to 15th week and from the 15th to 20th week (P < 0.05). Within 15-20 weeks, the volume fraction of magnesium aloy was decreased by 6.5% that was the maximum volume reduction per unit cycle. With the progress of corrosion, the surface continuously became rough and vague, and its surface area was enlarged; the ratio of surface area to volume continuously increased, and there was a significant difference at 15 and 20 weeks (P < 0.05). Because of the increasing number of corrosion pits, the cross-sectional radius decreased, which was reflected by the trabecular thickness decreasing from 1.00 to 0.87 mm. From the view of the slope of curve, the trabecular thickness decreased most rapidly at 10-15 weeks. The mineral density of magnesium aloy continuously decreased from 649.302 to 356.445 mg/cm3 during the whole experiment period (P< 0.05). In addition, the micro-CT image density decreased from 679.710 to 644.947 mg/cm3, but there was no significant difference. To conclude, the degradation speed is peaked at 10-20 weeks after implantation, and the content of magnesium aloys decrease with degradation, but the magnesium density has no significant change.

Objective To introduce and enhance an experimental technique for intraventricular drug delivery via an implantable osmotic pump.Methods Eight-week-old male SD rats were selected and the requisite equipment and reagents were prepared.The osmotic pump was assembled and brought to operational status before conducting the implantation surgery.Following anesthesia,the rats underwent skin preparation and the upper surface of the skull was surgically exposed.A point directly above the ventricle was located using a brain stereotaxic apparatus,and a small hole was drilled at that location with a high-speed cranial drill.The pump body was then implanted subcutaneously in the neck and the needle was inserted into the drilled hole,and secured with dental cement.Once solidified,the needle base was removed,the subcutaneous soft tissue and scalp were sutured in layers,and the animal was returned to its cage for rearing in isolation.Results The osmotic pump was successfully implanted subcutaneously in the rat's neck,the needle was securely fixed to the skull,and the catheter interface remained intact.The rats were sacrificed and the brain tissue was removed.Examination of the extracted brain tissue revealed no significant hematoma around the puncture site or needle tract,and the presence of blue dye in the ventricular and adjacent tissues indicated successful drug delivery to the ventricle.Conclusions The introduction of a brain stereotaxic apparatus to aid localization,coupled with enhancements to the operational procedure,may improve the accuracy and safety of the implantation process resulting in a high success rate for intraventricular drug administration.