Osteogenic evaluation of glutaraldehyde crosslinked gelatin composite with fetal rat calvarial culture model

Models of ex vivo explant cultures: applications in bone research

Ex vivo explant culture models are powerful tools in bone research. They allow investigation of bone and cartilage responses to specific stimuli in a controlled manner that closely mimics the in vivo processes. Because of limitations in obtaining healthy human bone samples the explant growth of animal tissue serves as a platform to study the complex physico-chemical properties of the bone. Moreover, these models enable preserving important cell-cell and cell-matrix interactions in order to better understand the behaviour of cells in their natural three-dimensional environment. Thus, the use of bone ex vivo explant cultures can frequently be of more physiological relevance than the use of two-dimensional primary cells grown in vitro. Here, we describe isolation and ex vivo growth of different animal bone explant models including metatarsals, femoral heads, calvaria, mandibular slices and trabecular cores. We also describe how these explants are utilised to study bone development, cartilage and bone metabolism, cancer-induced bone diseases, stem cell-driven bone repair and mechanoadaptation. These techniques can be directly used to understand mechanisms linked with bone physiology or bone-associated diseases.

Osteogenic Potential Using a Malleable, Biodegradable Composite Added Traditional Chinese Medicine: in vitro and in vivo Evaluations

The purpose of this investigation was to prepare and evaluate the feasibility and biocompatibility of a new composite as a large defect bone substitute. The new GTGG was mainly composed of tricalcium phosphate ceramic particles and glutaraldehyde crosslinked gelatin in which Gui-Lu-Jiao was added (a mixture of Cervi Colla Cornus and Colla Plastri Testudinis). In the in vitro study, rat's calvaria osteoblasts were used to study bone characteristics upon exposure to different concentrations of the Gui-Lu-Jiao solution. In the in vivo study, GTGG composites were implanted into the defects of calvarial bones in mature New Zealand rabbits to test their osteogenerative characteristics. As a result, we found that Gui-Lu-Jiao added to the culture could promote the proliferation of osteoblasts. In addition, GTGG could induce a large amount of new bone growth in the rabbit's calvarial bone defect. Therefore, the GTGG composite might be a potential bone substitute.

Evaluation of critical size defects of mouse calvarial bone: An organ culture study

Mouse calvarial organ culture has been used widely for the study of bone biology. The purpose of this study was to evaluate the healing potential of neonatal mouse parietal defects in different culture media. The critical size defect (CSD) was also investigated. The parietal bones of neonatal mice were used. Full-thickness, 0.8-mm circular defects were created through the bones from one litter of mice. The bones were divided into three groups: Dulbecco's Modified Eagle Medium (DMEM) group, DMEM/osteogenic medium (OM) group, and OM group. Cultures were analyzed with microcomputed-tomography, dissecting-microscope, phase-contrast-microscope, Von Kossa stain, scanning-electron-microscopy, and energy-dispersive-X-ray. Continuous bone formation of parietal bones was observed in all groups. Defects in the DMEM/OM group showed the highest healing potential and exhibited woven bone formation. Defects in the OM group showed limited bone healing at the defect edge. Defects in the DMEM group showed fibrous healing. The most effective culture medium (DMEM/OM) was used to determine the CSD of mouse calvaria in a separate experiment. Circular defects (diameters: 0.8, 1.0, and 1.5 mm) were made in the parietal bones from another litter of mice. The bones were analyzed with microcomputed-tomography, and phase-contrast-microscopy. The bone filling percentages of different size defects were statistically significant: 1.5-mm defects (4.49%), 1.0-mm defects (47.65%), and 0.8-mm defects (73.45%). In three culture conditions, DMEM/OM was the most effective approach to repair bone defects. A 1.5 mm in diameter, full-thickness parietal defect was found to be the CSD under the DMEM/OM culture conditions.

A novel bone substitute composite composed of tricalcium phosphate, gelatin and drynaria fortunei herbal extract

The Chinese herb, Gu-Sui-Bu (GSB) (Drynaria fortunei J. Sm.) has been anecdotally reported to enhance bone healing. We had previously confirmed in vitro the efficacy and safety of GSB in bone healing, and showed that it influenced both osteoblast and osteoclast activity. For clinically useful application of these bone regenerative effects, a satisfactory delivery system for GSB is required. In this study, we determined the optimal concentration of GSB for regenerative activity in rat bone cells via MTT, alkaline phosphatase (ALP), nodule formation and TRAP assays, and designed and tested a GSB-rich bone composite material. The composite was fabricated by mixing a biodegradable GGT composite, containing genipin cross-linked gelatin and tricalcium phosphate, with the predetermined concentration of GSB (GGT-GSB). Neonatal rat calvarial culture and animal implantation were employed to evaluate and compare in vitro and in vivo the potential of GGT-GSB and GGT in regeneration of defective bone tissue. The most effective concentration of GSB was 100 mug/mL, which significantly increased osteoblast numbers, intracellular ALP levels and nodule numbers, without influencing osteoclast activity. In vitro and in vivo tests also showed that GGT-GSB accelerated bone regeneration compared to GGT. GGT-GSB thus has great potential for improved bone repair.

Tricalcium phosphate and glutaraldehyde crosslinked gelatin incorporating bone morphogenetic protein--a viable scaffold for bone tissue engineering

Bone defects caused by various etiologies must be filled with suitable substances to promote bone repair. Autogenous iliac crest graft is most frequently used, but is often associated with morbidities. Several bone graft substitutes have been developed to provide osteoconductive matrices as well as to enhance osteoinductivity. A tricalcium phosphate and glutaraldehyde crosslinked gelatin (GTG) scaffold, incorporated with bone morphogenetic proteins (BMPs), was developed to provide an alternative mean of bone tissue engineering. This study investigated differences between GTG and BMP-4 immobilized GTG (GTG-BMP) scaffolds on neonatal rat calvaria osteoblast activities. The GTG scaffold possessed an average pore size of 200 microm and a porosity of 75%. HE staining revealed uniform cell distribution throughout the scaffold 24 h post cell seeding. Alkaline phosphatase (ALP) activity of the GTG samples increased initially and then stabilized at 3 weeks postseeding. ALP activity of the GTG-BMP samples was similar to that of the GTG samples in the second and third weeks, but it continued increasing and became significantly greater than that of the GTG samples by the fourth week. Gla-type osteocalcin (Gla-OC) activity of the GTG-BMP samples was initially lower, but also became significantly greater than that of the GTG samples by the fourth week. An HE stain revealed greater numbers of attached cells and a richer matrix deposits in the GTG-BMP samples. A von Kossa stain showed larger mineralizing nodules, in greater numbers, after 4 weeks of in vitro cultivation. These findings suggest that the GTG scaffold provides an excellent porous structure, conductive to greater cell attachment and osteoblast differentiation, and that utility can be significantly enhanced by the inclusion of BMPs. A GTG-BMP scaffold holds promise as a superior bioactive material for bone tissue engineering.

Calvarial bone response to a tricalcium phosphate-genipin crosslinked gelatin composite

A biodegradable composite which was composed of genipin cross-linked gelatin mixing with tricalcium phosphate ceramic particles (GGT) was developed as a bone substitute. This study was evaluated by the biological response of rabbit calvarial bone to assess the potential of the GGT composite as a biodegradable and osteoconductive bone substitute. Eighteen New Zealand white rabbits were used for cranial implantation. Bone defects (15 x 15 mm) of nine rabbits were filled with the GGT composites, while the others were filled with the de-proteinized bovine bones as controls. Three rabbits were examined for each group in every time period at 4, 8 and 12 weeks post-surgery. The assessment included serial post-operative gross examinations, radiographic analyses and histological evaluations. This study demonstrated that this composite is: (1) malleable, with easily molded to the calvarial bone defect without fracture; (2) biocompatible, with no evidence of adverse tissue reaction; (3) osteoconductive, with progressive growth of new bone into the calvarial bone defect; (4) biodegradable, with progressive replacement of the composite by new bone. Additionally, results of both radiographic analyses and histological evaluations revealed obviously greater new bone ingrowth in the GGT composite compared with the de-proteinized bovine bone at the same implantation time. Therefore, the GGT composite could serve as a useful bone substitute for repairing bone defects.

Biocompatibility and biodegradation of a bone composite containing tricalcium phosphate and genipin crosslinked gelatin

A biodegradable composite (GGT) containing tricalcium phosphate ceramic particles and genipin crosslinked gelatin was developed for use as a bone substitute. The objective of this study was to assess the biocompatibility and the osteoconductivity of the GGT composite on new bone formation in vitro. Additionally, biodegradation and biocompatibility of the GGT composite in animals were investigated. Results of the GGT composites cocultured with osteoblasts showed that the concentration of genipin used as a crosslinking agent should be <0.5 wt % to avoid cytotoxicity. For in vivo degradation studies, we found that when the concentration of genipin in the composite <0.5 wt % was not enough to fully crosslink the gelatin, it results in a rapid degradation of the gelatin-genipin mixture. However, we also found that the foreign body capsule surrounding the GGT composite containing 1.0 wt % of the genipin was much thicker than that in the other three groups, that is, the composites containing 0.05, 0.1, and 0.5 wt % of the genipin. We therefore concluded that the ideal concentration of genipin used in the GGT was 0.5 wt %. Finally, we examined the organ culture units, which were maintained in cultured medium for 5 weeks. Morphology of tissue was observed and the quantitative evaluation of the regenerated bone was determined. We found that the GGT composites containing 0.5 wt % of the genipin had an excellent biocompatibility and could produce osteoconduction for the regenerating bone tissues.