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 prepare the silk fibroin (SF)-chitosan (CS) scaffolds by adjusting the mass ratio between CS and SF, and test and compare the properties of the scaffolds at different mass ratios. Methods According to the mass ratios of 6 ∶ 4 (group A), 6 ∶ 8 (group B), and 6 ∶ 16 (group C) between SF and CS, CS-SF scaffolds were prepared by freeze-drying method, respectively. The material properties, porosity, the dissolubility in hot water, the modulus elasticity, and the water absorption expansion rate were measured; the aperture size and shape of scaffolds were observed by scanning electron microscope (SEM). Density gradient centrifugation method was used to isolate the bone marrow mesenchymal stell cells (BMSCs) of 4-week-old male Sprague Dawley rats. The BMSCs at passage 3 were seeded onto 3 scaffolds respectively, and then the proliferation of cells on the scaffolds was detected by MTS method. Results The results of fourier transform infrared spectroscopy proved that with the increased content of CS, the absorption peak of random coil/α helix structure (1 654 cm-1 and 1 540 cm-1) constantly decreased, but the absorption peak of corresponding to β-fold structure (1 628 cm-1 and 1 516 cm- 1) increased. The porosity was 87.36% ± 2.15% in group A, 77.82% ± 1.37% in group B, and 72.22% ± 1.37% in group C; the porosity of group A was significantly higher than that of groups B and C (P lt; 0.05), and the porosity of group B was significantly higher than that of group C (P lt; 0.05). The dissolubility in hot water was 0 in groups A and B, and was 3.12% ± 1.26% in group C. The scaffolds had good viscoelasticity in 3 groups; the modulus elasticity of 3 groups were consistent with the range of normal articular cartilage (4-15 kPa); no significant difference was found among 3 groups (F=5.523, P=0.054). The water absorption expansion rate was 1 528.52% ± 194.63% in group A, 1 078.22% ± 100.52% in group B, and 1 320.05% ± 179.97% in group C; the rate of group A was significantly higher than that of group B (P=0.05), but there was no significant difference between groups A and C and between groups B and C (P gt; 0.05). SEM results showed the aperture size of group A was between 50-250 μm, with good connectivity of pores; however, groups B and C had structure disturbance, with non-uniform aperture size and poor connectivity of pores. The growth curve results showed the number of living cells of group A was significantly higher than that of groups B and C at 1, 3, 5, and 7 days (P lt; 0.05); and there were significant differences between groups B and C at 3, 5, and 7 days (P lt; 0.05). Conclusion The CS-SF scaffold at a mass ratio of 6 ∶ 4 is applicable for cartilage tissue engineering.
Objective To investigate the application potential of alginate-strontium (Sr) hydrogel as an injectable scaffold material in bone tissue engineering. Methods The alginate-Sr/-calcium (Ca) hydrogel beads were fabricated by adding 2.0wt% alginate sodium to 0.2 mol/L SrCl2/CaCl2 solution dropwise. Microstructure, modulus of compression, swelling rate, and degradability of alginate-Sr/-Ca hydrogels were tested. Bone marrow mesenchymal stem cells (BMSCs) were isolated from femoral bones of rabbits by flushing of marrow cavity. BMSCs at passage 5 were seeded onto the alginate-Sr hydrogel (experimental group) and alginate-Ca hydrogel (control group), and the viability and proliferation of BMSCs in 2 alginate hydrogels were assessed. The osteogenic differentiation of cells embeded in 2 alginate hydrogels was evaluated by alkaline phosphate (ALP) activity, osteoblast specific gene [Osterix (OSX), collagen type I, and Runx2] expression level and calcium deposition by fluorescent quantitative RT-PCR and alizarin red staining, Von Kossa staining. The BMSCs which were embeded in alginate-Ca hydrogel and cultured with common growth medium were harvested as blank control group. Results The micromorphology of alginate-Sr hydrogel was similar to that of the alginate-Ca hydrogel, with homogeneous pore structure; the modulus of compression of alginate-Sr hydrogel and alginate-Ca hydrogel was (186.53 ± 8.37) and (152.14 ± 7.45) kPa respectively, showing significant difference (t=6.853, P=0.002); there was no significant difference (t=0.737, P=0.502) in swelling rate between alginate-Sr hydrogel (14.32% ± 1.53%) and alginate-Ca hydrogel (15.25% ± 1.64%). The degradabilities of 2 alginate hydrogels were good; the degradation rate of alginate-Sr hydrogel was significantly lower than that of alginate-Ca hydrogel on the 20th, 25th, and 30th days (P lt; 0.05). At 1-4 days, the morphology of cells on 2 alginate hydrogels was spherical and then the shape was spindle or stellate. When three-dimensional cultured for 21 days, the DNA content of BMSCs in experimental group [(4.38 ± 0.24) g] was significantly higher than that in control group [(3.25 ± 0.21) g ] (t=8.108, P=0.001). On the 12th day after osteogenic differentiation, the ALP activity in experimental group was (15.28 ± 1.26) U/L, which was significantly higher than that in control group [(12.07 ± 1.12) U/L] (P lt; 0.05). Likewise, the mRNA expressions of OSX, collagen type I, and Runx2 in experimental group were significantly higher than those in control group (P lt; 0.05). On the 21th day after osteogenic differentiation, alizarin red staining and Von Kossa staining showed calcium deposition in 2 groups; the calcium nodules and phosphate deposition in experimental group were significantly higher than those in control group (P lt; 0.05). Conclusion Alginate-Sr hydrogel has good physicochemical properties and can promote the proliferation and osteogenic differentiation of BMSCs, so it is an excellent injectable scaffold material for bone tissue engineering.
Objective To elucidate the latest research progress and application of tissue engineered meniscus. Methods The literature concerning the advance in tissue engineered meniscus was extensively reviewed, then closely-related issues including seed cells, scaffolds, and bioreactors were analyzed. Results With more and more attention being paid to meniscus tissue engineering, different approaches and strategies for seed cells, scaffolds, and bioreactors have contributed to the generation of meniscal constructs, which are capable of restoring meniscal lesions to some extent, but translating successes in basic science research to clinical application is still limited. Conclusion More research for the optimal combination of the appropriate cell source, the scaffold type, and the proper physical and chemical factors for the stimulation of cells differentiation into tissue with optimal phenotypes in tissue engineered meniscus is still in needed, but the overall future looks promising.
Objective To review the latest researches of Tenomodulin in tendon tissue engineering, to predict the progress of research and application of Tenomodulin. Methods The literature concerning Tenomodulin in tendon tissue engineering was collected and analyzed. Results Tenomodulin is a type II transmembrane glycoprotein that can regulate growth of tendon and contains a C-terminal anti-angiogenic domain. The human Tenomodulin gene spans approximately 1 360 bp and is mapped to Xq22.1. The expression of Tenomodulin is regulated by various biological factors, especially Scleraxis; and the nature and structure of scaffold material as well as the stain loading and cell passage, can modulate the expression of Tenomodulin. Conclusion Tenomodulin, as relatively specific molecule makers for tendon and containing a C-terminal anti-angiogenic domain, is expected to play a significant role in tendon tissue engineering.
Objective To review the research progress of cell-scaffold complex in the tendon tissue engineering. Methods Recent literature concerning cell-scaffold complex in the tendon tissue engineering was reviewed, the research situation of the cell-scaffold complex was elaborated in the aspects of seed cells, scaffolds, cell culture, and application. Results In tendon tissue engineering, a cell-scaffold complex is built by appropriate seed cells and engineered scaffolds. Experiments showed that modified seed cells had better therapeutic effects. Further, scaffold functionality could be improved through surface modification, growth factor cure, mechanical stimulation, and contact guidance. Among these methods, mechanical stimulation revealed the most significant results in promoting cell proliferation and function. Through a variety of defect models, it is demonstrated that the use of cell-scaffold complex could achieve satisfactory results for tendon regeneration. Conclusion The cell-scaffold complex for tendon tissue engineering is a popular research topic. Although it has not yet met the requirement of clinical use, it has broad application prospects.
Objective To review the current development in meniscus tissue engineering. Methods Recent literature concerning the development of the meniscus tissue engineering was extensively reviewed and summarized. Results Recent researches mainly focus on: selection of seed cells and research of their potential of differentiation into chondrocytes; selection of scaffold materials and research of their mechanical properties; cytokines and their mechanisms of action. Conclusion Many achievements have been made in meniscus tissue engineering. Most important topics in future research include: finding seed cells that are adapted to physiological process, are easy to culture, and have higher chondrogenic differentiation ability; looking for necessary cytokines and their mechanisms of action; finding scaffold meterials with b morphological plasticity, no antigenicity, good degradability, and mechanical property close to normal meniscus.
Objective To introduce the research progress on the technique of improving cell infiltration in electrospun scaffold. Methods The recent original articles about improving cell infiltration in electrospun scaffold were extensively reviewed and analyzed. Results The technique includes regulation of the electrospun parameters, modification of electrospun scaffold, and dynamic culture of scaffold-cells composite etc. The effect is limited and most of them need further optimization. Conclusion Cell infiltration in electrospun scaffold is of great significance in tissue engineering application. The relatively high compressed density and small pore size have become the bottleneck problem that prevents cell infiltration and tissue ingrowth into the scaffold. The combination of different techniques will be more effective to overcome this problem.
Objective To review the research progress of the seed cells, scaffolds, growth factors, and the prospects for clinical application of the intervertebral disc regeneration. Methods The recent literature concerning the regeneration strategies and tissue engineering for treatment of degenerative intervertebral disc disease was extensively reviewed and summarized. Results Seed cells based on mesenchymal stem cells (MSCs) and multiple-designed biomimetic scaffolds are the hot topic in the field of intervertebral disc regeneration. It needs to be further investigated how to effectively combine the interactions of seed cells, scaffolds, and growth factors and to play their regulation function. Conclusion The biological regeneration of intervertebral disc would have a very broad prospects for clinical application in future.
Objective To review the current research status and clinical application progress of extracellular matrix (ECM) material in tissue engineering. Methods The literature about the latest progress in the preparation, biocompatibility, mechanical property, degradability, and clinical application of ECM material was extensively reviewed. Results The improvement of the ECM preparation method and thorough understanding of the immunological properties have laid the foundation for the repair and reconstruction of the tissue. Moreover, a series of animal studies also confirm that the feasibility and effectiveness of the ECM such as small intestinal submucosa, bladder ECM grift, and acellular dermis which have been applied to the repair and reconstruction of the urethra, bladder, arteries, and skin tissue. It shows a wide prospect of clinical application in the future. Conclusion ECM material is a good bio-derived scaffold, which is expected to become an important source of alternative materials for the repair and reconstruction of the tissue.