Objective To investigate the way and process of degradation behavior of acellular porcine aortic valve in vitro. Methods Acellular porcine aortic valve（n=90）were randomly divided into 3 groups （collagenase group, elastase group, control group）, 30 piece in each group . Behavior of acellular porcine aortic valve was degradated with 0.05mg/ml collagenase Ⅰ, 0. 05mg/ml elastase, phosphate buffered solution in collagenase group, elastase group and control group. The histomorphology, weight loss, value of protein and hydroxyproline were observed at 3,6,9, 12, 15 and 30d after degradation. Results The behavior of acellular porcine aortic valve of collagenase group and elastase group became poorer, looser and broken gradually in degradation. The weight loss of valve, the value of protein and hydroxyproline in vehiculum became greater gradually in collagenase group and elastase group（P〈0. 01）. Furthermore the effect of collagenase Ⅰ was b than elastase in degradation. Conclusion The effect of collagenase Ⅰ and elastase can degradate the acellular porcine aortic valve in vitro. Collagenase Ⅰ is b than elastase in degradation.
Objective To develop an experimental model of abdominal aorta transplantation with nano-biomimetictissue engineered blood vessel (NBTEBV) and to investige the change of histomorphology in evolutionary process of degradation and remodel ing. Methods Twenty 6-month-old New Zealand rabbits were included, weighing 2-3 kg, male or female. The autologous seed cells of rabbits were harvested to build NBTEBV in vitro. After the branch of abdominal aorta under kidney was l igated, about 10 mm abdominal aorta was cut and replaced by NBTEBV; the anastomotic stoma was marked by Ti cl ips. NBTEBV’s evolutionary processes of degradation and rebuilding were observed. Twelve weeks after operation, DSA and color Doppler examinations were made. At 1, 4 and 12 weeks after operation, the gross and histological observations were made and 14C binding in PLGA was detected with X-ray photon spectroscopy. Results Of 20 rabbits, 17 showed that the NBTEBV was patency; 3 died from NBTEBV occlusion 36 or 72 hours after operation. The results of DAS and color Doppler showed the blood flow was patency, the blood flow rate was normal and there was no angiectasis. The lumen of transplanted blood vessel was covered with monolayer endothel ial cells. At 1 week, smooth muscle cells (SMCs) arranged regularly and much PLGA distributed in the EMCs. At 4 weeks, SMCs arranged in a layer, ECM was forming, mimic ECM degraded partly; PLGA decreased obviously. At 12 weeks, the SMCs arranged regularly, ECM formed, mimic ECM degraded, no PLGA was seen in the wall, the shape of graft was similar to the natural vessel. The decreasing crest value of 14C in specimen showed the degradation of PLGA. Conclusion NBTEBV has a good surgical maneuverabil ity and histocompatibil ity, its remodel ing evolutionary process fits in with tissue engineering specification. Building NBTEBV with ELSP is feasible.
Objective To investigate the feasibility of a new kind of porous β tricalcium phosphate (β-TCP) as a scaffold for the bone tissue engineering Methods The inverted phase contrast microscope was used to observe the growth of the marrow mesenchymal stem cells (MSCs) in the experimentalgroup and the control group at 10 days.In the experimental group, the MSCs were cultured with β-TCP(3 mm×3 mm×3 mm) in the 24-hole cultivation board, and in the control to control group, only MSCs were cultivated. The scanning electron microscope was used to observe growth of MSCs at 6 days. Cultivated with β-TCP at 3, 6, 9, 12 days, the MTT assay was used to judge the biocompatibility. The cytotoxicity was analyzed with the method that used the different density(100%， 50%， 10%， 1%，0%) leaching liquor gained from β-TCP to raise MSCs. MSCs were induced into the osteoblasts and were mixed with β-TCP, and the composite was used to repair a large radius bone defect in the rabbit. The specimens were made at 2,6,12 weeks. The histology imageology, and the radionuclide bone scan were used to analyze the bone formation. Results Some MSCs had a good adherence 4 hours after MSCs were inoculated and had a complete adherence at 12 hours. The cells were shaped like polyangle, spindle or converge monolayer after 8-10 days. The cells in the two groups had no difference. The cell adhesion was good, when observed by the inverted phase contrast microscope and the scanning electron microscope at 6 days. MTT showed that the absorbance (A)was not statistically different between the experimental group and the control group (P＞0.05); the different density leaching liquor had no cytotoxicity at the different time points. Histology, X-ray, and CT tomograph showed that itcould repair the large radius bone defect in the rabbit and its in vivo degradationrate was the same as the bone formation rate. Conclusion The new porous β-TCP has a unique three dimensional (3D) stereochemical structure and superordinary physicochemical property, and so it is a good scaffold for the bone tissue engineering.
Objective To choose the best procedure on preparation of acellularbovine pericardium (ABP) guided bone regeneration (GBR) material. Methods The BP was decellularized with 0.25% Trypsin+0.5% Triton X-100. The acellular bovine pericardiums (ABPs) were treated with phosphatebuffered saline(PBS) (group A), 95% glycerol (group B), EDAC (group C), and EDAC and 95% glycerol (group D) respectively. The treated ABPs were implanted subcutaneously in the back of SD rats respectively at random and no material was implanted as control. Seven rats were sacrificed at 2 weeks, twelve at 4 weeks, twelve at 8 weeks, seven at 16 weeks. Local reaction was studied grossly. The amount of antigen presenting cell (APC) and the percentage of ABP degeneration were reckoned by images analysis system. Results The ABPs were replaced by fibroblasts completely in group A at 8 weeks， in group C at 16 weeks, but only less than 50% till 16 weeks in groups B and D. In all groups, the depth of surrounding fibres attenuated timedependingly. The APC amount of the groups B and D was higher than that of the control group, and the ABP of the groups B and D degraded partly at 16 weeks. Conclusion The ABP treated with EDAC can be replaced by the surrounding tissues and has good biocompatibility.
Objective To study degradation of the antigen-extracted meniscus in PBS solution with no enzyme or with different enzymes. Methods Four types of enzymes (collagenase, hyaluronidase, trypsin, papain) were used to enzymolyze the antigen-extracted meniscus and the fresh meniscus for 3, 7, 15 and 30 days (37℃). The antigenextracted meniscus and the fresh meniscus were immersed in PBS solution (37℃) for 30 days. Weight loss measurement, UV spectrophotometry, and scanning electron microscopy (SEM) were used to characterize the degraded materials. Results The two types of the materials were remarkably digested under the enzymes, especially under trypsin. The degradation curves showed that the antigen-extracted meniscus was enzymolyzed less than the fresh meniscus. The degradation products were grouped as amino, peptide, and polyose by the analysis. Both of the materials could hardly behydrolyzed in PBS solution without the enzymes. The four different enzymes had different surface morphologies under the examination of SEM. Conclusion The antigen-extracted meniscus is enzymolyzed more slowly than the fresh meniscus in vitro, and the result can be used as a guideline to the further research.
Objective To study the degradable properties of 3D-SC artificial skin in vitro. Methods The 3D-SC artificial skin materials wererespectively immersed into the solutions of 0.9% normal saline (control group), pancreatic tissue liquid (experimental group 1), physiological buffer (Hanks balanced salt solution，experimental group 2) and 0.2 mol/L phosphate buffer (pH 7.4，experimentalgroup 3), and the degradation was carried out at 37℃. The quality lost ratioswere determined on the 3rd day, the 5th day, the 7th day, the 9th day, 11th dayand 14th day in the experimental group 1, while on the 3rd day, 7th day, 14th day, 15th day, 21st day and 30th day in the other groups. Results The 3D-SC artificial skin was degraded completely in pancreatic tissue liquid about within 14 days in the experimental group 1; in the control group, and in the experimental groups 2 and 3, the degradation ratios were 868%±2.30%,28.51%±10.68% and 7.35%±0.61% on the 14th day; 71.83%±2.58%, 91.32%±1.87% and 75.64%±6.13% on the 15th day, being significant difference between the control group and the experimental group 2(Plt;0.01); and 91.87%±8.15%, 95.62%±1.36% and 92.10%±2.26% on the 30th day, being no significant differences between these 3 groups(Pgt;0.05), respectivelies. Conclusion The 3D-SC artificial skin materials have good degradable properties. The trend of degradation speed is from slow to quick and then to slow without enzyme.
OBJECTIVE: To study the histocompatibility and degradation in vivo of a new artificial material, calcium polyphosphate fiber (CPPF), and to provide some experimental basis for further study in tendon tissue engineering. METHODS: CPPF and carbon fiber (CF) as control material were implanted in symmetry part in subcutaneous layer, muscle and Achilles tendon of 20 SD rats. The day of operation, the 4th, 8th, 12th, 16th, and 20th weeks after operation, X-ray examination was performed to detect the density change of materials. Local tissue and materials were observed grossly, and pathological examination was made with HE staining 4, 8, 12, 16 weeks after operation. RESULTS: CPPF degraded completely within 16 weeks in muscle, and in 20 weeks after implantation in Achilles tendon and subcutaneous layer according to X-ray and pathological examination. No calcium phosphate crystal deposit was observed in local tissue. No obviously degradation of CF was found within 20 weeks. Local infiltration of lymphocytes and macrophagocytes around CPPF were much fewer than that of CF. CPPF combined compactly with surrounding hyperplastic tissue. CONCLUSION: CPPF degrade thoroughly from 16 to 20 weeks without sediment of crystal of calcium phosphate in vivo. CPPF has good histocompatibility and can be used as a scaffold material of tissue engineering.
ObjectiveTo explore the degradation of AZ31 magnesium alloy and poly (lactic-co-glycolic acid) (PLGA) in the femoral condyle, and then evaluate the laws of degradation of AZ31 magnesium alloy by Micro-CT images and data. MethodsForty 3-month-old male New Zealand white rabbits (weighing, 2.5 kg) were randomly divided into 4 groups, 10 rabbits each group. Forty micro-arc-oxidized AZ31 magnesium alloy pins and 40 PLGA pins were implanted into the right and left femoral condyle, respectively. Micro-CT images and data analysis were used to evaluate the degradation at 4, 8, 12, and 16 weeks after operation (n=10). Degradation was evaluated by weight difference between pre-and post-implantation. The inflammatory response was observed around the implants by HE staining. The weight loss of magnesium alloy and Micro-CT results were compared. ResultsThe Micro-CT images showed that PLGA pins had gray low signal, which was similar to the soft tissue around. At 4 weeks after operation, no signs of degradation were observed, and there were little corrosion pitting on the magnesium alloy. At 8 weeks, corrosion pitting gradually expanded, the boundary between the longitudinal axis and the cross section became blurred; at 16 weeks, corrosion pitting became bigger, and the boundary was discontinuous. Micro-CT quantitative analysis showed that the volume fraction of magnesium pins decreased slowly at 4 and 8 weeks; it was significantly lower at 12 and 16 weeks than 4 and 8 weeks (P < 0.05). The magnesium cylinder mineral density continuously decreased during the study period, it had a rapidly speed from 12 to 16 weeks (P < 0.05). However, the magnesium CT image density showed a slight change (P>0.05). The surface-to-volume ratio of the pins constantly increased, and the ratio was significantly larger at 12 and 16 weeks than 4 and 8 weeks, and at 16 weeks than 12 weeks (P < 0.05). There was more and more corrosion pitting on the surface with time, which resulted in a decrease in the radius that mean trabecular thickness gradually decreased, showing significant difference between different time points after 8 weeks (P < 0.05). The weight loss detection showed that the degradation of magnesium pin and PLGA gradually increased with time (P < 0.05), and the degradation rate of magnesium pin was significantly lower than that of PLGA at 8-12 weeks (P < 0.05), but the degradation rate of magnesium pin was higher than that of PLGA at 16 weeks. At each time point, the weight loss of magnesium alloy was similar to that by Micro-CT, but mass fraction was lower than volume fraction and had significant differences at 8, 12, and 16 weeks (P < 0.05). HE staining revealed that slight inflammatory response was observed around the magnesium pins at 4 weeks, and inflammatory reaction gradually reduced with time and disappeared at 16 weeks, but no inflammatory reaction was seen around PLGA. ConclusionMicro-CT has the advantages of non-trauma, in vivo detection, quantitative analysis, and precise data in evaluating the degradation of AZ31 magnesium alloy. Regarding the degradation of the magnesium alloy and PLGA in vivo, the degradation rate is slow in the early stage, and then increases with time. The degradation of PLGA is faster and earlier but it is then overtaken by AZ31 magnesium alloy at 16 weeks. During the degradation, the density of the magnesium has almost no change. The biomaterials can not firmly attach to the surrounding tissues due to inadequate holding forces.
ObjectiveTo summarize the research and application progress of magnesium and magnesium alloys implants in the orthopedics. MethodsThe domestic and foreign related literature about the research progress and application of magnesium and magnesium alloys implants in the orthopedics was reviewed. ResultsCurrently approved and commonly used metallic implants in orthopedics include stainless steels, titanium alloys, and chromium alloys having many disadvantages of poor biocompatibility, mismatch with the biomechanical properties of the bone tissue, and need of second surgical procedure to remove. Compared with traditional implants, magnesium and magnesium alloys have biomechanical properties closer to natural bone tissue, and in vivo degradation, which have the potential to serve as new biocompatible and degradable implants. Although magnesium and magnesium alloy materials have their own advantages, but the degradation rate is still too fast and so on. At present, the research and development of medical magnesium and magnesium alloy materials are to improve their corrosion resistance and control the rate of degradation. ConclusionMagnesium and magnesium alloys have great potential as a implant material in the orthopedics, through further systematic and in-depth study, it is expected to become a new generation of degradation biological implant materials.