Bone morphogenetic protein (BMPs) has been so far regarded as one of the highly potent osteoinductive growth factors. Recombinant human bone morphogenetic proteins have been utilized extensively in the disciplines of orthopedics, stomatology, etc. For clinical application, BMPs are usually loaded in carriers with a controlled-release system, to maintain concentration to induce de novo bone formation at the desired site. In this article, the research advancements of the carriers and release systems of BMP are reviewed.
Parathyroid hormone (PTH) exerts multiple effects such as regulating bone remodeling, promoting angiogenesis, etc., and it is an active factor with great application potential for bone repair. In recent years, with the development of scaffold material loading strategies and parathyroid hormone-related peptides (PTHrPs), in situ loading of PTH or PTHrPs on scaffold materials to promote bone defect healing gradually becomes possible. Based on the current status and challenges of intermittent PTH (iPTH) for bone tissue engineering, the review summarizes the in-situ application strategies of PTH and the construction of PTHrPs as well as current problems and further directions in this field, with a view to propel the clinical application of scaffold materials loaded with PTH or PTHrPs in situ.
OBJECTIVE To confirm membrane-guided tissue regeneration in the healing course of segmental bone defects and study the mechanism. METHODS Segmental, 1 cm osteoperiosteal defects were produced in both radii of 12 rabbits. One side was covered with hydroxyapatite/polylactic acid(HA/PLA) membrane encapsulated as a tube. The contralateral side served as an untreated control. Healing courses were detected by radiographic and histologic examinations. RESULTS All control sides showed nonunion, whereas there were consistent healing pattern in test sides. CONCLUSION Membrane technique can promote bone regeneration.
ObjectiveTo prepare a bone tissue engineering scaffold for repairing the skull defect of Sprague Dawley (SD) rats by combining exogenous transforming growth factor β1 (TGF-β1) with gelatin methacryloyl (GelMA) hydrogel.MethodsFirstly, GelMA hydrogel composite scaffolds containing exogenous TGF-β1 at concentrations of 0, 150, 300, 600, 900, and 1 200 ng/mL (set to groups A, B, C, D, E, and F, respectively) were prepared. Cell counting kit 8 (CCK-8) method was used to detect the effect of composite scaffold on the proliferation of bone marrow mesenchymal stem cells (BMSCs) in SD rats. ALP staining, alizarin red staining, osteocalcin (OCN) immunofluorescence staining, and Western blot were used to explore the effect of scaffolds on osteogenic differentiation of BMSCs, and the optimal concentration of TGF-β1/GelMA scaffold was selected. Thirty-six 8-week-old SD rats were taken to prepare a 5 mm diameter skull bone defect model and randomly divided into 3 groups, namely the control group, the GelMA group, and the GelMA+TGF-β1 group (using the optimal concentration of TGF-β1/GelMA scaffold). The rats were sacrificed at 4 and 8 weeks after operation, and micro-CT, HE staining, and OCN immunohistochemistry staining were performed to observe the repair effect of skull defects.ResultsThe CCK-8 method showed that the TGF-β1/GelMA scaffolds in each group had a promoting effect on the proliferation of BMSCs. Group D had the strongest effect, and the cell activity was significantly higher than that of the other groups (P<0.05). The results of ALP staining, alizarin red staining, OCN immunofluorescence staining, and Western blot showed that the percentage of ALP positive area, the percentage of alizarin red positive area, and the relative expressions of ALP and OCN proteins in group D were significantly higher than those of the other groups (P<0.05), the osteogenesis effect in group D was the strongest. Therefore, in vitro experiments screened out the optimal concentration of TGF-β1/GelMA scaffold to be 600 ng/mL. Micro-CT, HE staining, and OCN immunohistochemistry staining of rat skull defect repair experiments showed that the new bone tissue and bone volume/tissue volume ratio in the TGF-β1+GelMA group were significantly higher than those in the GelMA group and control group at 4 and 8 weeks after operation (P<0.05).ConclusionThe TGF-β1/GelMA scaffold with a concentration of 600 ng/mL can significantly promote the osteogenic differentiation of BMSCs, can significantly promote bone regeneration at the skull defect, and can be used as a bioactive material for bone tissue regeneration.
Objective To compare the effects of hypoxia-inducible drugs using deferoxamine (DFO) and accordion technique (AT) on activating the hypoxia-inducible factor 1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to promote bone regeneration and remodelling during consolidation phase of distraction osteogenesis (DO). Methods Forty-five specific-pathogen-free adult male Sprague-Dawley (SD) rats were randomly divided into the control group, DFO group, and AT group, with 15 rats in each group. All rats underwent osteotomy to establish a right femur DO model. Then, continuous distraction was started for 10 days after 5 days of latency in each group. During the consolidation phase after distraction, no intervention was performed in the control group; DFO was locally perfused into the distraction area in the DFO group starting at the 3rd week of consolidation phase; cyclic stress stimulation was given in the AT group starting at the 3rd week of consolidation phase. The general condition of rats in each group was observed. X-ray films were conducted at the end of the distraction phase and at the 2nd, 4th, and 6th weeks of the consolidation phase to observe the calcification in the distraction area. At the 4th and 6th weeks of the consolidation phase, peripheral blood was taken for ELISA detection (HIF-1α, VEGF, CD31, and Osterix), femoral specimens were harvested for gross observation, histological staining (HE staining), and immunohistochemical staining [HIF-1α, VEGF, osteopontin (OPN), osteocalcin (OCN)]. At the 6th week of the consolidation phase, Micro-CT was used to observe the new bone mineral density (BMD), bone volume/tissue volume (BV/TV), trabecular separation (Tb.Sp), trabecular number (Tb.N), and trabecular thickness (Tb.Th) in the distraction area, and biomechanical test (ultimate load, elastic modulus, energy to failure, and stiffness) to detect bone regeneration in the distraction area. Results The rats in all groups survived until the termination of the experiment. ELISA showed that the contents of HIF-1α, VEGF, CD31, and Osterix in the serum of the AT group were significantly higher than those of the DFO group and control group at the 4th and 6th weeks of the consolidation phase (P<0.05). General observation, X-ray films, Micro-CT, and biomechanical test showed that bone formation in the femoral distraction area was significantly better in the DFO group and AT group than in the control group, and complete recanalization of the medullary cavity was achieved in the AT group, and BMD, BV/TV, Tb.Sp, Tb.N, and Tb.Th, as well as ultimate load, elastic modulus, energy to failure, and stiffness in the distraction area, were better in the AT group than in the DFO group and control group, and the differences were significant (P<0.05). HE staining showed that trabecular bone formation and maturation in the distraction area were better in the AT group than in the DFO group and control group. Immunohistochemical staining showed that at the 4th week of consolidation phase, the expression levels of HIF-1α, VEGF, OCN, and OPN in the distraction area of the AT group were significantly higher than those of the DFO group and control group (P<0.05); however, at 6th week of consolidation phase, the above indicators were lower in the AT group than in the DFO group and control group, but there was no significant difference between groups (P>0.05). Conclusion Both continuous local perfusion of DFO in the distraction area and AT during the consolidation phase can activate the HIF-1α/VEGF signaling pathway. However, AT is more effective than local perfusion of DFO in promoting the process of angiogenesis, osteogenesis, and bone remodelling.
OBJECTIVE To investigate the effect of acid fibroblast growth factor (aFGF) on guided bone regeneration (GBR), to study whether aFGF can promote the repairing ability of GBR in bone defect. METHODS 10 mm long segmental defects were created in the diaphyses of both radii in 16 New Zealand rabbits. The defect was bridged with a silicon tube. Human recombinant aFGF was instilled into the tube on the experimental side, while the contralateral tube was instilled with saline as control group. The radiographic, gross and histologic examination of the samples were analyzed at 2, 4, 6 and 8 weeks after operation. RESULTS On the experimental side, there was new bone formation in the bone medullary cavity, the endosteum and the section surface of the cortex at 2 weeks. At 4 weeks, at the center of the blood clot in the tube there was new bone formation and bone defect was completely healed at 8 weeks. On the control side, new bone formation was less in every period compared with that of the experimental side. At 8 weeks, there was only partial healing of the bone defect. CONCLUSION It can be concluded that aFGF can promote new bone formation and facilitate GBR in bone defect.
Objective To evaluate the effect of internal fixation on the stability of pedicled fascial flap and the osteogenesis of exceed critical size defect (ECSD) of bone so as to provide theory for the clinical application by the radiography and histology observation. Methods The ECSD model of the right ulnar midshaft bone and periosteum defect of 1 cm in length was established in 32 New Zealand white rabbits (aged 4-5 months), which were divided into group A and group B randomly (16 rabbits in each group). The composite tissue engineered bone was prepared by seeding autologous red bone marrow (ARBM) on osteoinductive absorbing material (OAM) containing bone morphogenetic protein and was used repair bone defect. A pedicled fascial flap being close to the bone defect area was prepared to wrap the bone defect in group A (control group). Titanium miniplate internal fixation was used after defect was repair with composite tissue engineered bone and pedicled fascial flap in group B (experimental group). At 2, 4, 6, and 8 weeks, the X-ray films examination, morphology observation, and histology examination were performed; and the imaging 4-score scoring method and the bone morphometry analysis was carried out. Results All rabbits survived at the end of experiment. By X-ray film observation, group B was superior to group A in the bone texture, the space between the bone ends, the radiographic changes of material absorption and degradation, osteogenesis, diaphysis structure formation, medullary cavity recanalization. The radiographic scores of group B were significantly higher than those of group A at different time points after operation (P lt; 0.05). By morphology and histology observation, group B was superior to group A in fascial flap stability, tissue engineered bone absorption and substitution rate, external callus formation, the quantity and distribution area of new cartilage cells and mature bone cells, and bone formation such as bone trabecula construction, mature lamellar bone formation, and marrow cavity recanalization. The quantitative ratio of bone morphometry analysis in the repair area of group B were significantly larger than those of group A at different time points after operation (P lt; 0.05). Conclusion The stability of the membrane structure and the bone defect area can be improved after the internal fixation, which can accelerate bone regeneration rate of the tissue engineered bone, shorten period of bone defect repair, and improve the bone quality.
Objective To summarize the research progress of controlled release of angiogenic factors and osteogenic factors in bone tissue engineering. Methods The domestic and abroad literature on the controlled release structure of growth factors during bone regeneration in recent years was extensively reviewed and summarized. Results The sustained-release structure includes direct binding, microsphere-three-dimensional scaffold structure, core-shell structure, layer self-assembly, hydrogel, and gene carrier. A sustained-release system composed of different sustained-release structures combined with different growth factors can promote bone regeneration and angiogenesis. Conclusion Due to its controllability and persistence, the growth factor sustained-release system has become a research hotspot in bone tissue engineering and has broad application prospects.
OBJECTIVE To repair long bone segmental defects using biodegradable poly epsilon-caprolactone (PCL) and polylactic acid(PLA) co-polymer membranes, and explore its role and mechanism in guided bone regeneration (GBR). METHODS Rabbit radial segmental defects (1.2 cm in length, retain the periosteum) were created in this study, 24 animals were divided into 2 groups. The membranes were used to enclose the defects in experimental group, and no treatment in control group. After 3, 6, and 12 weeks of operation, X-ray, gross and histological examinations were observed. RESULTS The bone regeneration of experimental group was better than that of control group. Three weeks after operation, obvious external callus along the membrane were found in experimental group, and bony linking composed of external callus bridge were found in 6 weeks after operation. After 12 weeks of operation, callus bridge outside the membrane and bony reunion inside the membrane were achieved in experimental group. While in control group, typical nonunion was observed after 6 weeks of operation. CONCLUSION Guided bone regeneration can be achieved by using biodegradable membrane. The defects are repaired by the means of outside membrane callus and relatively late inside membrane callus. The membrane can prevent the ingrowth of fibrous tissue into defect area, thus nonunion are avoid, and keep a high concentration of nutritive elements, also serve as a frame for osteocyte growth to enhance bone healing.
With the in-depth research on bone repair process, and the progress in bone repair materials preparation and characterization, a variety of artificial bone substitutes have been fully developed in the treatment of bone related diseases such as bone defects. However, the current various natural or synthetic biomaterials are still unable to achieve the structure and properties of natural bone. Carbon nanotubes (CNTs) have provided a new direction for the development of new materials in the field of bone repair due to their excellent structural stability, mechanical properties, and functional group modifiability. Moreover, CNTs and their composites have broad prospects in the design of bone repair materials and as drug delivery carriers. This paper describes the advantages of CNTs related to bone tissue regeneration from the aspects of morphology, chemistry, mechanics, electromagnetism, and biosafety, as well as the application of CNTs in drug delivery carriers and reinforcement components of scaffold materials. In addition, the potential problems and prospects of CNTs in bone regenerative medicine are discussed.