OBJECTIVETo compare the effect of bone regeneration with two different ratios of nano-hydroxyapatite(nHA)/collagen(Col) (nHAC) after tooth extraction in canine.

METHODSTwo kinds of nHAC grafts were prepared with different nHA/collagen ratio of 3∶7 and 5∶5. Eighteen male healthy adult dogs had been randomly divided into three groups. Immediately after extraction of the mandibular second premolars, each kind of nHAC was implanted into extraction sockets as follow: Group A, nHA/Col=3∶7(12 sites); Group B, nHA/Col=5∶5(12 sites); Group C, blank control group(12 sites). The bone repairing abilities of the two grafts such as vertical distance of alveolar, CT values, general observation, histological observation, trabecular volume fraction and porosity were separately analyzed at 1st, 3rd and 6th month, respectively (each group had 4 sites in different time periods).

RESULTSnHAC were absorbed gradually after they were implanted into alveolar bone defect and were replaced by new bone. The vertical distance of alveolar bone in Group A([15.76±0.28] mm) was significant higher than that in Group B([14.88±0.36] mm), and CT values of Group A([879±31] HU) were higher than those in Group B([718±29] HU) (P<0.05). The trabecular bone volume percentage of Group A([22.2±0.4]%) was higher than that in Group B([20.3±0.4]%), and the bone porosity of Group A([23.6±0.9]%) was lower than that in Group B([27.6±0.6]%) (P<0.05). In addition, the vertical distance, CT values and the trabecular bone volume percentage of Group C was lower than those in Group A and B, but the bone porosity of Group C was higher.

CONCLUSIONSThe nHAC with nHA/collagen ratio of 3∶7 could better promote bone regeneration than nHAC with the nHA/collagen ratio of 5∶5 did.

Animals ; Bone Regeneration ; Collagen ; administration & dosage ; pharmacokinetics ; Dogs ; Durapatite ; administration & dosage ; pharmacokinetics ; Male ; Nanoparticles ; Random Allocation ; Tissue Engineering ; Tooth Extraction

Objective:To study the feasibility of a new composite mineralized collagen membrane in alveolar ridge preservation.Methods:The third mandibular premolars on both sides were extracted from 12 dogs,the 24 alveolar sockets were randomly assigned into A,B and C groups(n =8).The distal alveolar sockets of group A was immediately implanted with the new composite mineralized collagen membrane and bone graft material,those of group B with bone graft material,group C was the blank control.The healing of sockets was evaluated by gross observation,morphological measurements,X-ray microscope and photographs of spiral CT.Results:The horizontal width of the alveolar process of group A was bigger than that of group B (P ＜ 0.05),that of group B was bigger than that of group C (P ＜ 0.05).The region of extraction interest in spiral CT value was higher in group A than that in group B and C (P ＜ 0.05).The extraction sockets were generated new bone and the degree of reconstruction measurements was higher in group A than that in group B and C (P ＜ 0.05).Conclusion:The new composite mineralized collagen membrane can induce the regeneration of new bone,and preserve the alveolar.

OBJECTIVETo explore the effect of different functional groups on self-assembled monolayers on the biological characteristics of rabbit skeletal muscle cells in vitro.

METHODSRabbit skeletal muscle cells were cultured on self-assembled monolayers of gold on which different terminal chemical groups including methyl groups (-CH(3)), amino(-NH(2)), hydroxyl(-OH) and carboxyl (-COOH ) were anchored with self-assembled methods. Contact angle measurements and atomic force microscopy were employed to confirm the similar density of different functional groups occupation. Fluorescence microscopy, MTT assay, flow cytometry, and scanning electron microscopy (SEM) were used to analyze the morphological and biological alterations of the cells.

RESULTSSEM results revealed that the chemical groups on the surface of the monolayer modulated the structure of skeletal muscle cells and the cell morphology. Skeletal muscle cells cultured on the monolayer with -CH3 exhibited the smallest contact area with a spherical morphology, while the cells on the monolayers with -NH(2), -OH and -COOH showed much larger contact area and flatter morphology. The functional groups -NH(2) and -COOH obviously promoted cell adhesion and proliferation, while -CH(3) group produced significantly greater toxicity than -NH(2), -OH and -COOH groups to inhibit the cell growth and adhesion and promote cell death. Cell attachment and growth was enhanced, in the order the magnitude of the effect, by -NH(2)>-COOH>-OH>-CH(3), and the toxicity decreased in the order of -NH(2)>-COOH>-OH>-CH(3).

CONCLUSIONThe terminal chemical groups can obviously affect the phenotype of skeletal muscle cells in vitro, and this finding provides a theoretical basis for surface design of biomaterials.

Animals ; Cell Adhesion ; Cell Proliferation ; Cells, Cultured ; Microscopy, Atomic Force ; Microscopy, Electron, Scanning ; Microscopy, Fluorescence ; Muscle Fibers, Skeletal ; cytology ; Rabbits

BACKGROUND:Titanium implants as a safe biological material have been used to produce the artificial Russian titanium cornea, but complications stil exist, including artificial cornea shift, leakage, corneal tissue melting and artificial cornea discharge.
OBJECTIVE:To evaluate in vivo biocompatibility of hydroxyapatite modified titanium skirt for keratoprosthesis in alkali burn cornea.
METHODS:A total of 30 alkali burned New Zealand white rabbit corneas were divided into three group groups. Hydroxyapatite modified titanium skirt (experimental group) and titanium skirt (control group) were respectively inserted into the corneal stroma of rabbits. In the blank control group, only a lamel ar corneal incision was made.
RESULTS AND CONCLUSION:Al skirts were stable without necrosis, melting and exclusion during the observation period. The number of inflammatory cells in the experimental and control groups was significantly higher than that in the blank control group at 2 and 8 weeks postoperatively (P<0.05), but there was no difference in inflammatory cellinfiltration among different groups by the 16th week. The number of corneal fibroblasts increased significantly in the experimental group compared with the control and blank control group after 2, 8, 16 weeks (P<0.05). The extracellular matrix deposited on the surface of hydroxyapatite modified titanium skirt was denser and tighter than that on the surface of titanium skirt. It indicates that hydroxyapatite modified titanium skirt for keratoprosthesis can promote the interfacial biointegration of skirt and host cornea.

Objective To establish a new canine model of ureter trauma to observe the protective effect of biodegradable ureteral stent on renal function following traumatic ureter injury. Methods A self-made device was used to make firearm fragment wounds unilaterally on the ureters in nine Beagle dogs (model group). The wounds were debrided and sutured and the results were evaluated by using intravenous pyelography (IVP) and radioactive renography at 40, 80 and 120 days postoperatively. Firearm fragment wounds were made to the bilateral ureters of nine Beagle dogs in the positive control group, in which a biodegradable stent was placed in one side and a double-J stent placed in the other side. Results In model group, hydronephrosis and hydroureter occurred and got worse postoperatively on the wounded side in all nine Beagle dogs, while none of these symptoms were found in any animals in the control group. The ratios of biodegradable stent side to double-J stent side were increased in renal patial concertration index and half time of kidney washout, but neither showed significant differences. However,vesicoureteral reflux (VUR) was not found in the biodegradable stent side, but in the double -J stent side. Conclusions A new canine model of firearm fragment wounds is successfully developed. Both the biodegradable and double-J stent play important roles in support and drainage and show no significant difference in aspects of renal uptake and half time of kidney washout. The biodegradable stent can effectively prevent VUR.

Objective To compare the effectiveness of nano-hydroxyapatite/collagen (nHAC)and autologous mesenchymal stem cells (AMSCs) for the repair of femoral defect in a rabbit model with femoral defect under the monitoring of the synchrotron radiation hard X-ray. Methods The rabbit models of traumatic bone defect were established and completely randomized into three groups. The femoral defects filled with nothing were used as control group (Group A) , the femoral defects filled with nHAC as Group B and the femoral defects filled with nHAC + AMSCs as Group C. Phase-contrast imaging with synchrotron radiation hard X-ray was applied to detect the degradation and repair process of each group at postoperative weeks 4, 8 and 12, respectively. Results Phase-contrast imaging with synchrotron radiation hard X-ray could display the reparative process. Four weeks after operation, there was collapse in some defect areas in Group A, and the degradation of nHAC and new bone formation were observed in Groups B and C. Eight weeks after operation, fibrous tissues were observed in the defect area in Group A, while osteogenesis and nHAC degradation were more obvious in Groups B and C. Twelve weeks after operation, the defect areas were still unhealed and were substituted by fibrous tissues in Group A, tissue densities of defect areas in Group C were identical with periphery areas, and trabecular bones were formed in Group C. There were statistical differences in the osteogenesis between Group A and Groups B and C,with Group C the best. Conclusion Phase-contrast imaging with synchrotron X-ray can detect the reparative process at a micro-level and plays an important role in the development of tissue engineering.

Biodegradable magnesium-alloy stents have been employed in animal experiments and clinical researches in recent years. Magnesium-alloy stents have been reported to be biocompatible, and degradable due to corrosion after being implanted into blood vessel. However, magnesium alloy is brittle compared with stainless steel. This may cause strut break under large deformation. In this paper, a finite element model of magnesium-alloy stent was set up, with reference to pictures from Biotronik Corporation, to simulate the expanding and bending processes. The results of analysis show that the maximum strain during expanding reaches 20%, being greater than the elongation limit of the commercially available magnesium alloys. Therefore, to avoid strut breakage during expanding, the magnesium alloys should be custom-made. The plasticity of the material should be improved by grain refinement processes before practicable magnesium-alloy stents could be developed.
Absorbable Implants ; Alloys ; Angioplasty, Balloon, Coronary ; instrumentation ; Finite Element Analysis ; Humans ; Magnesium ; Materials Testing ; Prosthesis Design ; Stents ; Stress, Mechanical ; Surface Properties

BACKGROUND:Selection of proper bone transplantation materials to substitute autogenous bone for treatment of jaw bone defect in patients has become the focus of current researches.OBJECTIVE:To observe the ability of tissue engineered bone constructed with nano-hydroxyapatite/collagen/poly(L-lactic acid)(nHAC/PLA)co-cultured with bone marrow stromal cells(BMSCs)in treatment of rabbit mandibular defect.and to make a comparison with autogenous bone and simple nHAC/PLA.DESIGN.TIME AND SETTING:A randomized controlled animal experiment was performed at the Animal Laboratory of Jinzhou Central Hospital between March and October 2007.MATERIALS:A total of 40 New Zealand rabbits were randomized to 4 groups.with 10 rabbits per group:nHAC/PLA co-cultured with rabbit BMSCs(BMSCs/nHAC/PLA),autogenous bone,nHAC/PLA,and control.METHODS:A 15 mm×15 mm full-thickness bone defect was created in rabbit mandible body.In the BMSCs/nHAC/PLA group.bone defect was repaired by nHAC/PLA co-cultured with BMSCs for 14 days in vitro;the bone defect in the autogenous bone and nHAC/PLA groups was treated by autogenous iliac bone and nHAC/PLA.respectively;while the control group received no any treatment.MAIN OUTCOME MEASURES:At 1,3,and 6 months after surgery,bone mineral density(BMD)measurement and histological examination were performed to evaluate the repairing effects of bone defect.RESULTS:The BMSCs/nHAC/PLA group exhibited the BMD similar to the autogenous bone group(P＞0.05),but it was significantly higher compared to the nHAC/PLA group and the blank control group(P＜0.01).At 6 months after surgery.newly formed bone tissue grew towards large bulk and bridged defected stumps.and the seaffold materials were hardly seen in the BMSCs/nHAC/PLA and autogenous bone groups;simultaneously.the nHAC/PLA group exhibited increased trabecular bone with many fibrous tissues and incompletely degraded seaffold materials.CONCLUSION:BMSCs/nHAC/PLA seaffold exhibits the effects similar to autogenous bone.but superior to nHAC/PLA seaffold in the treatment of mandibular defects.

Objective To explore the possibility of repairing injured facial nerve with tissue engineering technology and neural stem cells(NSCs).The complex consisted of NSCs,scaffold and NT-3.NSCs were immature cells with the potential of self-renewal and multiple differentiation to neurons and glial cells.The scaffold with porous surface was made of hyaluronic acid and collagen(HA-Col gel) which degenerate in vivo after transplantation.NT-3 is the signal to promote neurons survival in vitro.Methods NSCs of S-D rat were co-cultured with scaffold and NT-3 in vitro.The two stumps of disconnected facial nerve of rabbit were re-connected with the complex.Electrophysiology and morphology tests were used to examine functional and morphological changes.Results Result] NSCs adhered to the HA-Col gel and survived.Injured facial nerve fixed by NSCs-HA-Col gel-NT-3 complex showed significant improvement in function and anatomical structure.Conclusion Combinative implant of NSCs,HA-Col gel and NT-3 may promote the regeneration of injured facial nerve.

Objective To observe the repairing effects of bone after nano-hydroxyapatite/collagen (nHAC)being implanted in and to study its prospect in clinical application.Methods Nano-hydroxyapatite/collagen composite was developed by biomimetic method. The material was used in clinical operation,the healing effects of bone defects were assessed by methods of radiography.Results The composite showed some features of natural bone in both composition and microstructure.After implanting,the patients were not hyperpyrexial,did not have extravasate and immunoreaction,the bone defects were healing well.Conclusion The composite can serve as one of the promising materials for bone repairing.