The establishing of myocardial tissue engineering techniques not only solve a series of issues that generate in cell and tissue transplantation after myocardial infarction, but also create a platform for selecting better materials and transplantation techniques. However, both experimental animal studies and recent clinical trials indicate that current transplantation techniques still have many defects, mainly including lack of suitable seed cells, low survival rate and low differentiation rate after transplantation. In this context, extracellular matrix （ECM）, as myocardial tissue engineering scaffold materials, has gained increasing attention and become a frontier and focus of medical research in recent years. ECM is no longer merely regarded as a scaffold or a tissue, but plays an important role in providing essential signals to influence major intracellular pathways such as cell proliferation, differentiation and metabolism. The involved models of ECM can be classified into following types：natural biological scaffold materials, synthetic polymer scaffold materials and composite scaffold materials with more balanced physical and biological properties. This review mainly introduces research progress of ECM in myocardial tissue engineering and ECM materials.
Objective To review the current status and problems in the developing scaffolds for the myocardial tissue engineering appl ication. Methods The l iterature concerning the myocardial tissue engineering scaffold in recent years was reviewed extensively and summarized. Results As one of three elements for tissue engineering, a proper scafold is veryimportant for the prol iferation and differentiation of the seeding cells. The naturally derived and synthetic extracellular matrix (ECM) materials aim to closely resemble the in vivo microenvironment by acting as an active component of the developing tissue construct in myocardial tissue engineering. With the advent and continuous refinement of cell removal techniques, a new class of native ECM has emerged with some striking advantages. Conclusion Through using the principle of composite scaffold, computers and other high-technology nano-polymer technology, surface modification of traditional biological materials in myocardial tissue engineering are expected to provide ideal myocardial scaffolds.
Objective To review the appl ication of collagen and biodegradable polymer composite scaffolds in vascular tissue engineering, and describe the multi-layering vascular scaffolds of collagen-based material in recent years. Methods The l iterature concerning collagen composite scaffold production for scaffold of vascular tissue engineering was extensively reviewed and summarized. Results As one of the structural proteins in natural blood vessel, collagen is widely used in vascular tissue engineering because of good biocompatibil ity, biodegradabil ity, and cell recognition signal. The vascular scaffolds with biological activity and good mechanical properties can be made by collagen-polymer composite materials. In addition, the structure and function of the natural blood vessel can be better simulated by multi-layering vascularscaffolds. Conclusion Collagen-polymer composite material is the hot spot in the research of vascular scaffolds, and multilayering vascular scaffolds have a brill iant future.
Objective To develop a novel porous three-dimensional scaffold and to investigate its physico-chemical properties for tissue engineering cartilage.Methods Refined 88% deacetylation degree chitosan was prepared and dissolved in 0.2 mol/L acetate acid and fully mixed with highly purified porcine type Ⅱcollagen in 0.5 mol/L acetate acid solution in a ratio of 4 to 1 (wt/wt). Freeze-drying process was employed to fabricate the composite scaffold. The construct wascross-linked by use of 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide (EDC) and Nhydroxysuccinimide (NHS). A mechanical tester was utilized to determine the tensilestrength change before and after cross-linking. The microstructure was observed via scanning electron microscopy (SEM). The lysozyme degradation was performedto evaluate the degradability of the scaffold in vitro. Results A bulk scaffold with desired configuration was obtained. The mechanical test showed that the crosslinking treatment could enhance the mechanical strength of the scaffold. The SEM results revealed that the two constituents evenly distributed in the scaffold and that the matrix was porous, sponge-like with interconnected pore sizing 100250 μm. In vitro lysozyme degradation indicated that crosslinked or uncross-linked composite scaffolds had faster degradation rate than the chitosan matrix. Conclusion Chitosan and typeⅡcollagen can be developed into a porous three-dimensional scaffold. The related physico-chemical tests suggest that the composite socaffold meets requirements for tissue engineered scaffold and may serve as an alternative cellcarrier for tissue engineering cartilage.
ObjectiveTo prepare composite scaffold of different quality ratio of silk fibroin to collagen,analyze the scaffold performance,and optimize the quality ratio for chondrocyte tissue engineering. MethodsThe silk fibroin/collagen composite scaffold was made using a freeze-drying technique in different quality ratios of silk fibroin to collagen:4:2(group A),4:4(group B),and 4:8(group C).The porosity,water absorption expansion rate,mechanical properties,and pore size of composite scaffold were detected.The bone marrow mesenchymal stem cells (BMSCs) were isolated from 4-week-old male Wistar rats by density gradient centrifugation,and the third generation BMSCs were seeded onto the scaffolds at 2×107 cells/mL density,and were cultured for 14 days.The cell proliferation was detected using MTT assay at 1,3,5,7,9,11,and 13 days,the cell morphology and distribution were observed by HE staining and scanning electron microscopy (SEM). ResultsThe porosity of groups A,B,and C was 94.6%±1.6%,80.6%±1.1%,and 60.6%±1.0% respectively;and significant differences were found between group A and groups B and C,and between group B and group C (P<0.05).The water absorption expansion rates of groups A,B,and C were 1 523.7%±186.6%,1 091.0%±151.6%,and 659.6%±161.4% respectively,showing no significant difference among 3 groups (F=6.67,P=0.08).The elasticity modulus of groups A,B,and C were (23.1±2.5),(25.1±2.3),and (29.8±2.6) kPa respectively,showing no significant difference among 3 groups (F=2.00,P=0.28).The pore size of groups A,B,and C was (103±12),(80±15),and (60±16)μm respectively,showing no significant difference among 3 groups (F=2.22,P=0.26).MTT results showed that the cell proliferation in the group A at 7,9,11,and 13 days were better than those in groups B and C (P<0.05);at 14 days after cultivation,even pore size,good intercommunicating of holes,and good cells growth on the scaffolds with full extension and more extracellular matrix were seen under SEM in group A,but small pore size,poor intercommunicating of holes and poor cell growth on the scaffolds in groups B and C.HE staining and SEM results showed that the cells on the scaffold in group A was obviously more than those in groups B and C. ConclusionThe scaffold prepared in a quality ratio 4:2 of silk fibroin to collagen has better porosity,water absorption expansion rate,elasticity modulus,and pore size,on which the cells can grow well,so it is more suitable for cartilage tissue engineering.
ObjectiveTo prepare the small intestinal submucosa (SIS)-silk composite scaffold for anterior cruciate ligament (ACL) reconstruction, and to evaluate its properties of biomechanics, biocompatibility, and the influence on synovial fluid leaking into tibia tunnel so as to provide a better choice in the clinical application of ACL reconstruction. MethodsThe silk was used to remove sericin and then weaved as silk scaffold, which was surrounded cylindrically by SIS to prepare a composite scaffold. The property of biomechanics was evaluated by biomechanical testing system. The cell biocompatibility of scaffolds was evaluated by live/dead staining and the cell counting kit 8 (CCK- 8). Thirty 6-week-old Sprague Dawley rats were randomly assigned to 2 groups (n=15). The silk scaffold (S group) and composite scaffold (SS group) were subcutaneously implanted. At 2, 4, and 8 weeks after implanted, the specimen were harvested for HE staining to observe the biocompatibility. Another 20 28-week-old New Zealand white rabbits were randomly assigned to the S group and SS group (n=20), and the silk scaffold and composite scaffold were used for ACL reconstruction respectively in 2 groups. Furthermore, a bone window was made on the tibia tunnel. At last, the electric resistance of tendon graft in the bone window was measured and recorded at different time points after 5 mL of 10% NaCl or 5 mL of ink solution was irrigated into the joint cavity recspectively. ResultsThe gross observation showed that the composite scaffold consisted of the helical silk bundle inside which was surrounded by SIS. The maximal load of silk scaffold and composite scaffold was respectively (138.62±11.41) N and (137.05±16.95) N, showing no significant difference (P>0.05); the stiffness was respectively (24.65±2.62) N/mm and (24.21±2.39) N/mm, showing no significant difference (P>0.05). The live/dead staining showed that the cells had good activity on both scaffolds. However, the cells on the composite scaffold had better extensibility. In addition, the cell proliferation curve indicated that no significant difference in the absorbance (A) values was founded between groups at various time points (P>0.05). HE staining showed less inflammatory cells and much more angiogenesis in SS group than in S group at 2, 4, and 8 weeks after subcutaneously implanted (P<0.05), indicating good biocompatibility. Additionally, the starting time points of electric resistance decrease and the ink leakage were both significantly later in SS group than in S group (P<0.05). The duration of ink leakage was significantly longer in SS group than in S group (P<0.05). ConclusionThe SIS-silk composite scaffold has excellent biomechanical properties and biocompatibility and early vacularization after in vivo implantation. Moreover, it can reducing the leakage of synovial fluid into tibia tunnel at the early stage of ACL reconstruction. So it is promising to be an ideal ACL scaffold.
ObjectiveTo investigate the effect of repairing radial bone defect with scaffold material of attapulgite/collagen type I/poly (caprolactone) (ATP/Col I/PCL) in rabbits and the possibility as bone graft substitutes. MethodsATP/Col I/PCL materials were prepared via adding ATP to hexafluoroisopropanol after dissolved Col I/PCL (3∶2), and Col I/PCL materials via dissolving Col I/PCL (3∶2) in hexafluoroisopropanol served as control. The structure of scaffolds was observed under scanning electron microscope (SEM). Twenty-four Japanese white rabbits (male, 2 months old) were used to establish the bilateral radius defect model of 15 mm in length, and randomly divided into group A (6 rabbits, 12 defects), group B (9 rabbits, 18 defects), and group C (9 rabbits, 18 defects); then the Col I/PCL scaffold was implanted in the bone defect area in group B, the ATP/Col I/PCL scaffold in group C, no treatment was done in group A as control. The general condition of rabbits was observed after operation, and bone defect repair was evaluated by X-ray at 4, 8, and 12 weeks. At 12 weeks, the tissue of defect area was harvested for the general, SEM, Micro-CT, histological, and immunohistochemical staining to observe defect repair and material degradation. ResultsSEM observation showed that two kinds of materials were porous structure, ATP/Col I/PCL structure was more dense than Col I/PCL. All animals survived to the end of experiment, and no incision infection occurred during repair process.X-ray films showed that the bone marrow cavity was re-opened in defect area of group C with time, the repair effect was superior to that of groups A and B. At 12 weeks after operation, general observation showed that scaffold material had good fusion with the surrounding tissue in groups B and C, defect was filled with connective tissue in group A. SEM indicated that the surface and pore of the scaffold were covered with a large number of cells and tissues in groups B and C. Micro-CT demonstrated that the new bone volume, bone mineral content, tissue mineral content, and connectivity density of group C were significantly higher than those of groups A and B (P<0.05). The observation of histology and immunohistochemical staining indicated that there were lots of connective tissues in defect area of group A, and ALP, Col I, and OPN were weakly expressed; there were many collagen fibers in scaffold degradation area in group B, and the expression levels of ALP, Col I, and OPN were higher than those of group A; there was few new bone in group C, the degradation rate of the scaffold was slower than that of group B, and the expression of Col I and OPN were enhanced, while ALP was weakened when compared with groups A and B. ConclusionATP/Col I/PCL composite scaffold material can degrade in vivo, and has dense three-dimensional porous structure, good biocompatibility, and high potentiality of bone repair, so it can be used as bone substitute material.