Objective To review the recent progress of the researches in the field of cartilage tissue engineering, and to discuss the challenges in construction of tissue engineered cartilage. Methods Literature related with cartilage tissue engineering was reviewed and analyzed. Results Some techniques have been appl ied in cl inical. As far as the seeding cells, induced pluripotent stem cells have attracted much more attention. Current strategies of scaffold designing are trying to imitate both component and structure of natural extracellular matrix. Cartilage regeneration through the autologous cell homing technique el iminate the transplantation of exotic cells and has become the hot topic. Conclusion Successful treatment of the damaged cartilage using tissue engineering method will depend on the advances of stem cell technology development, biomimetic scaffolds fabrication and proper appl ication of growth factors.
Objective To study the mechanism of ectopic osteogenesis of nacre/Polylactic acid (N/P) artificial bone combined with allogenic osteoblasts, and to explore the possibility as a scaffold material of bone tissue engineering. Methods The allogenic- osteoblasts seeded onto N/P artificial bone were co-cultured in vivo 1 week.The N/P artificial bone with allogenic osteoblasts were implanted subcutaneously into the left back sites of the New Zealand white rabbits in the experimental group and the simple N/P artificial bone into the right ones in the control group. The complexes were harvested and examined by gross observation, histologic analysis and immunohistochemical investigation 2, 4 and 8 weeks after implantation respectively.Results In experimental group, the osteoid formed after 4 weeks, and the mature bone tissue withbone medullary cavities formed after 8 weeks; but in control group there was nonew bone formation instead of abundant fibrous tissue after 4 weeks, and more fibrous tissue after 8 weeks.Conclusion N/P artificial bone can be used as an optical scaffold material of bone tissue engineering.
Objective To establish a scaffold model from heterogeneoussmall blood vessels. Methods Caudal arteries from 34 Wistar rats( average length 12.08±1.69 cm) were made into acellular blood vessel scaffolds. Some scaffoldswere observed by electron microscope, and others were transplanted to the cut ends of ear central arteries of male Japanese big ear white rabbits. Results Average external diameter was 0.74±0.08 mm in proximal, and 0.55±0.08 mm in distal end of rat caudal arteries. The small blood vessel scaffolds had shin wall whichwas white and soft, composed of fibrous tissues without cells. On the intima surface the fibrous tissues were arrayed densely in a grid-like pattern. After transplantation, the blood flow was reserved, and kept flowing freely in 24 hours. The pulsation of the transplanted artery was accessible and no blood leakage wasfound.Conclusion The natural scaffolds are composed of fibrous tissues, and can sustain the artery pulse pressure for 24 hours. It is better to suture the blood vessels by sleeve anastomosis.
Objective To prepare collagen-chitosan /nano-hydroxyapatite-collagen-polylactic acid (Col-CS/ nHAC-PLA) biomimetic scaffold and to examine its biocompatibility so as to lay the foundation for its application on the treatment of osteochondral defect. Methods PLA was dissolved in dioxane for getting final concentration of 8%, and the nHAC power was added at a weight ratio of nHAC to PLA, 1 ∶ 1. The solution was poured into a mold and frozen. CS and Col were dissolved in 2% acetum for getting the final concentrations of 2% and 1% respectively, then compounded at a weight ratio of CS to Col, 20 ∶ 1. The solution was poured into the frozen mold containing nHAC-PLA, and then biomimetic osteochondral scaffold of Col-CS/nHAC-PLA was prepared by freeze-drying. Acute systemic toxicity test, intracutaneous stimulation test, pyrogen test, hemolysis test, cytotoxicity test, and bone implant test were performed to evaluate its biocompatibility. Results Col-CS/nHAC-PLA had no acute systemic toxicity. Primary irritation index was 0, indicating that Col-CS/nHAC-PLA had very slight skin irritation. In pyrogen test, the increasing temperature of each rabbit was less than 0.6℃, and the increasing temperature sum of 3 rabbits was less than 1.3℃, which was consistent with the evaluation criteria. Hemolytic rate of Col-CS/nHAC-PLA was 1.38% (far less than 5%). The toxicity grade of Col-CS/nHAC-PLA was classified as grade I. Bone implant test showed that Col-CS/nHAC-PLA had good biocompatibility with the surrounding tissue. Conclusion Col-CS/ nHAC-PLA scaffold has good biocompatibility, which can be used as an alternative osteochondral scaffold.
Objective To study the influence of in vitro force-vascularization on in vivo vascularization of porous polylactic glycolic acid copolymer(PLGA) scaffolds with internal network channels (PPSINC). Methods After the in vitro forcevascula ization of PPSINCs covered with microvessel endothelial cells (MVEC) of mice, they were divided into two groups: the force-vascularization group (group A) and the control group with only PSINCs (group B). All the PPSINCs were planted in the mesentery of 12 mice for 2 and 4 weeks, the PPSINCs were cut out, the vascular ization of PPSINCs was investigated by histology and immunohistochemistry, and the vascularization area of the histologic section of the PPSINCswas measured with the computer-assistant image analysis system. Result After the in vitro forcevascularization of PPSINCs, the MVEC of the mice sticking on the channel wall could be seen. After the scaffold was im planted into the mice for 2 weeks, the vascularization area of the histologic section of PPSINCs (VA) in group A (2 260.91±242.35 μm2) was compared with that in group B (823.64±81.29 μm2)，and the difference was sig nificant in statistics（P＜0.01).The VA for 4 weeks in group A (17 284.36 ±72.67 μm2) was compared with that in group B (17 041.14±81.51 μm2), and the difference was not significant in statistics（P＞0.05）.The area of the actin positivestaining (AA) in the histologi c section of PPSINCs for 2 weeks’ implantation in group A (565.22±60.58 μm2) was compared with that in group B (205.91±16.25 μm2), and the difference was signi ficant in statistics（P＜0.01). After the implantation for 4 weeks, the VA in group A (4 321.09±19.82 μm2) was compared with group B (4 260.28±27.17 μm2), and the difference was not significant in statistics（P＞0.05）. Conclusion The PPSINC is a good simple scaffold model of vasculariazation. The in vitro force-vascularization can increase the in vivo vascularization of PPSINCs in the early stage.
Objective To study the cellular biocompatibility, adhesion and proliferation of endothelial outgrowth cells (EOCs) isolated and expanded from rabbit peripheral blood cultured with aligned poly-L-lactic acid (PLLA) nanofibrous scaffolds in vitro so as to provide a basis for the applications of scaffolds biomaterials in tissue repair. Methods Nanofibrous scaffolds of PLLA by electrostatic spinning were modified by hypothermal plasmas body and type Ⅰ collagen was coated onto the materials physically. In vitro, EOCs were cultured on the modified PLLA scaffold. Adhesion and proliferation were surveyed and morphological changes and biocompatibility of seeding cells on PLLA scaffold were observed by growth curves of the cells, fluorescent microscope and scanning electron microscope respectively. Results Fibers with diameters ranging from 300 nm to 400 nm were included in the nanofibrous scaffolds, whose porosities were more than 90%. Absorbance (A) of each scaffold increased gradually after EOCs grew in the absence or presence of random, aligned, or super-aligned PLLA nanofibrous scaffold. Although there was no detectable effect of the random PLLA scaffold on the growth EOCs (Pgt;0.05), both aligned and super-aligned PLLA nanofibrous scaffold had significantly enhanced their growth since the 5th day (P＜0.05). The rates of adhesion in both aligned and super-aligned PLLA nanofibrous scaffold were significantly higher than those of random PLLA scaffold after 12 h and 24 h incubation (P＜0.01). The rates of proliferation after 1 d, 3 d and 7 d incubation in aligned and super-aligned PLLA nanofibrous scaffold were significantly higher than those of random PLLA nanofibrous scaffold (P＜0.05, P＜0.01). EOCs grew well with PLLA scaffold, yet confused and disorderly in random nanofibers. EOCs could attach, extend and proliferate following fibrous orientation in aligned and super-aligned PLLA nanofibrous scaffold, in majority of the fibers were oriented along the longitudinal axis so that a unique aligned topography was formed. Especially super-aligned PLLA nanofibrous had advantageous to keep well on cell morphology. Conclusion EOCs are ideal seeding cells for tissue engineering. EOCs can be adhered well to aligned and super-aligned PLLA nanofibrous scaffold and proliferate, keep well on cell morphology. So this type of PLLA nanofibrous scallfold is proposed to be an optimal candidate material for EOCs transplantation in tissue repair.
Objective To explore a novel nanometer biomaterial which could induce the regeneration of tooth tissues intell igently, and to evaluate the feasibil ity of using this kind of biomaterial as the scaffold for tooth tissue engineering by investigating the role it plays in tooth tissue engineering. Methods The scaffold for tooth tissue engineering containing recombinant human bone morphogenetic protein 2 (rhBMP-2) was prepared by mixing nanoscale β tricalcium phosphate (β-TCP)/collagen particles. Forty-six 8-10 weeks old specific pathogen free Sprague Dawley (SD)rats, including 34 females and 12 males, weighing 250-300 g, were involved in this study. Tooth germs were removed under a stereomicroscope from the mandible of newborn SD rat, then digested and suspended. Scanning electronic microscope (SEM), adhesion rate of cells, and MTT assay were used to evaluate the effects of the scaffold on the tooth germ cells cultured in vitro. The tissue engineered tooth germ which was constructed by tooth germ cells and scaffold was transplanted under SD rat’s kidney capsule as the experimental group (n=12); the tooth germ cells (cell-control group, n=12) or scaffold without cells (material-control group, n=4) were transplanted separately as control groups Specimens were harvested to perform general and histological observations at 4 and 8 weeks after transplantation. Results β-TCP/collagen showed a loose and porous appearance with soft texture and excellent hydrophil icity. Tooth germ cells grew well and could attach to the scaffold tightly 3 days after coculture. The adhesion rates of tooth germ cells were 27.20% ± 2.37%, 44.52% ± 1.87%, and 73.81% ± 4.15% when cocultured with scaffold for 4, 8, and 12 hours, respectively. MTT assay showed that the cell prol iferation status of experimental group was similar to that of the control group, showing no significant difference (P gt; 0.05). Some white calcified specimens could be harvested at 4-8 weeks after transplantation. At 4 weeks after transplantation some typical structures of dental cusp and enamel-dentin l ike tissues could be seen in the experimental group. Enamel-dentin l ike tissues also formed in some specimens of cell-control group, but they arranged irregularly. At 8 weeks after transplantation the enamel-dentin l ike tissue of experimental group exhibited a mature appearance and organized structure in comparison with that at 4 weeks. And mature enamel or dentin l ike tissue also could be seen in cell-control group. In contrast, there was no enamel or dentin l ike tissue in material-control group at 4 or 8 weeks after transplantation. Conclusion rhBMP-2 decorated β-TCP/collagen scaffold has good biocompatibil ity and can be used as a novel nanometer biomaterial, so it is a good choice in scaffolds for tooth tissue engineering.
Objective To fabricate a nanohydroxyapatite-chitosan(nano-HA-CS) scaffold with high porosity by a simple and effective technique and to evaluate the physical and chemical properties and the cytocompatibility of the composite scaffold. Methods The threedimensional nano-HA-CS scaffolds with high porosity were prepared by the in situ hybridization-freeze-drying method. The microscopic morphology and components of the composite scaffolds were analyzed by the scanning electron microscopy (SEM), the transmission electron microscopy（TEM）, the X-ray diffraction（XRD）examination, and the Fourier transformed infrared spectroscopy（FTIR）. The calvarial osteoblasts were isolated from the neonatal Wistar rats. The serial subcultured cells (3rd passage) were respectively seeded onto the nanoHACS scaffold and the CS scaffold, and then were cocultured for 2, 4, 6 and 8 hours. At each time point,four specimens from each matrix were taken to determine the celladhesion rate. The cell morphology was observed by the histological staining and SEM. Results The macroporous nanoHACS scaffolds had a feature of high porosity with a pore diameter from 100 to 500 μm (mostly 400500 μm). The scaffolds had a high interval porosity; however, the interval porosity was obviously decreased and the scaffold density was increased with an increase in the contents of CS and HA. The SEM and TEM results showed that the nanosized HA was synthesized and was distributed on the pore walls homogeneously and continuously. The XRD and FTIR results showed that the HA crystals were carbonatesubstituded and not wellcrystallized. The cytocompatibility test showed that the seeded osteoblasts could adhere the scaffolds, proliferating and producing the extracellular matrix on the scaffolds. The adherence rate for the nanoHACS scaffolds was obviously higher than that for the pure CS scaffolds. Conclusion The nano-HA-CS scaffolds fabricated by the in situ hybridization-freeze-drying method have a good physical and chemical properties and a good cytocompatibility; therefore, this kind of scaffolds may be successfully used in the bone tissue engineering.
Objective?To review the recent progress of the researches in construction of tissue engineered osteochondral composites, and to discuss the challenges in construction of tissue engineered osteochondral composites.?Methods?The recent literature on the construction of tissue engineered osteochondral composites was extensively reviewed and analyzed.?Results?The studies on the construction of tissue engineered osteochondral composites are relatively more in vivo, the current focus is that different tissues derived mesenchymal stem cells are widely used to be seed cells; single-phase scaffold has been limited, studies on biphase scaffold and triphase scaffold are new trends; the design and performance of bioreactor need to be further optimized in the future.?Conclusion?The construction of tissue engineered osteochondral composites will be a promising method for the treatment of cartilage defects.
Objective To review the appl ication of electrospinning in preparation of tendon tissue engineered scaffolds, to describe its appl ication effect and prospects. Methods Recent l iterature was extensively reviewed and summarized from various aspects, concerning the appl ication of electrospinning in preparing tendon tissue engineered scaffolds. Results Because of its huge surface and high porosity, the electrospun fibers prepared by electrospinning technology have been widely used in the manufacture of tendon tissue engineered scaffolds in recent years. A variety of materials, including polylactic acid, have been successfully electrospun into various types of tendon tissue engineered scaffolds, and goodresults in the repair of tendon defect were achieved. Conclusion The electrospinning technology has provide a new way for the preparation of the tendon tissue engineered scaffolds, with the perfection of the technology they will have broad application prospects in the field of tendon tissue engineering.