Enhanced regeneration of critical bone defects using a biodegradable gelatin sponge and beta-tricalcium phosphate with bone morphogenetic protein-2

Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold

OBJECTIVE

In the present study, we aimed to assess whether gelatin/β-tricalcium phosphate (β-TCP) composite porous scaffolds could be used as a local controlled release system for vancomycin. We also investigated the efficiency of the scaffolds in eliminating infections and repairing osteomyelitis defects in rabbits.

METHODS

The gelatin scaffolds containing differing amounts of of β-TCP (0%, 10%, 30% and 50%) were prepared for controlled release of vancomycin and were labelled G-TCP0, G-TCP1, G-TCP3 and G-TCP5, respectively. The Kirby-Bauer method was used to examine the release profile. Chronic osteomyelitis models of rabbits were established. After thorough debridement, the osteomyelitis defects were implanted with the scaffolds. Radiographs and histological examinations were carried out to investigate the efficiency of eliminating infections and repairing bone defects.

RESULTS

The prepared gelatin/β-TCP scaffolds exhibited a homogeneously interconnected 3D porous structure. The G-TCP0 scaffold exhibited the longest duration of vancomycin release with a release duration of eight weeks. With the increase of β-TCP contents, the release duration of the β-TCP-containing composite scaffolds was decreased. The complete release of vancomycin from the G-TCP5 scaffold was achieved within three weeks. In the treatment of osteomyelitis defects in rabbits, the G-TCP3 scaffold showed the most efficacious performance in eliminating infections and repairing bone defects.

CONCLUSIONS

The composite scaffolds could achieve local therapeutic drug levels over an extended duration. The G-TCP3 scaffold possessed the optimal porosity, interconnection and controlled release performance. Therefore, this scaffold could potentially be used in the treatment of chronic osteomyelitis defects.Cite this article: J. Zhou, X. G. Zhou, J. W. Wang, H. Zhou, J. Dong. Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold. Bone Joint Res 2018;7:46-57. DOI: 10.1302/2046-3758.71.BJR-2017-0129.R2.

Adverse effect of beta-tricalcium phosphate with zeta potential control in repairing critical defects in rats' calvaria

Objective

To evaluate whether a new biphasic cement composed of calcium sulfate and beta tricalcium phosphate with zeta potential control could induce or lead to bone neoformation in critical defects.

Methods

A critical defect of diameter 8 mm was made in the calvaria of forty male Wistar rats. In the Test Group (n = 20), the defects were filled with cement. In the Control Group (n = 20), the defect was not filled and only coagulum was present. The animals were sacrificed 7, 14, 21 and 42 days after the operation. Calvaria specimens were subjected to microtomography and were then prepared for histological analysis. The analyses included morphological assessment on the histopathology of the repair; comparative morphometric evaluation of the area of formation of bone trabeculae between the groups; and histochemical staining by means of tartrate-resistant phosphatase (TRAP) in order to identify osteoclasts.

Results

Microtomographic images of the defects filled by the cement did not show any decrease in area over the course of postoperative evolution. In the Test Group, the material continued to present a foreign-body response until the last observational periods. Histomorphological analysis showed that there were more significant groupings of giant cells in the Test Group and greater maturity of neoformed bone in the Control Group. Exogenous material was also present. Histomorphometric analysis showed that in the Control Group, the total area of bone neoformation was significantly greater (p = 0.009) and grew progressively. The giant cells presented a positive reaction to TRAP but no osteoclasts were observed.

Conclusion

The ceramic cement did not induce or lead to bone neoformation from the microtomographic or histological point of view.

Sustained delivery of biomolecules from gelatin carriers for applications in bone regeneration

Local delivery of therapeutic biomolecules to stimulate bone regeneration has matured considerably during the past decades, but control over the release of these biomolecules still remains a major challenge. To this end, suitable carriers that allow for tunable spatial and temporal delivery of biomolecules need to be developed. Gelatin is one of the most widely used natural polymers for the controlled and sustained delivery of biomolecules because of its biodegradability, biocompatibility, biosafety and cost–effectiveness. The current study reviews the applications of gelatin as carriers in form of bulk hydrogels, microspheres, nanospheres, colloidal gels and composites for the programmed delivery of commonly used biomolecules for applications in bone regeneration with a specific focus on the relationship between carrier properties and delivery characteristics.

Controlled release of granulocyte colony-stimulating factor enhances osteoconductive and biodegradable properties of Beta-tricalcium phosphate in a rat calvarial defect model

Autologous bone grafts remain the gold standard for the treatment of congenital craniofacial disorders; however, there are potential problems including donor site morbidity and limitations to the amount of bone that can be harvested. Recent studies suggest that granulocyte colony-stimulating factor (G-CSF) promotes fracture healing or osteogenesis. The purpose of the present study was to investigate whether topically applied G-CSF can stimulate the osteoconductive properties of beta-tricalcium phosphate (β-TCP) in a rat calvarial defect model. A total of 27 calvarial defects 5 mm in diameter were randomly divided into nine groups, which were treated with various combinations of a β-TCP disc and G-CSF in solution form or controlled release system using gelatin hydrogel. Histologic and histomorphometric analyses were performed at eight weeks postoperatively. The controlled release of low-dose (1 μg and 5 μg) G-CSF significantly enhanced new bone formation when combined with a β-TCP disc. Moreover, administration of 5 μg G-CSF using a controlled release system significantly promoted the biodegradable properties of β-TCP. In conclusion, the controlled release of 5 μg G-CSF significantly enhanced the osteoconductive and biodegradable properties of β-TCP. The combination of G-CSF slow-release and β-TCP is a novel and promising approach for treating pediatric craniofacial bone defects.

Recent developments of functional scaffolds for craniomaxillofacial bone tissue engineering applications

Autogenous bone grafting remains a gold standard for the reconstruction critical-sized bone defects in the craniomaxillofacial region. Nevertheless, this graft procedure has several disadvantages such as restricted availability, donor-site morbidity, and limitations in regard to fully restoring the complicated three-dimensional structures in the craniomaxillofacial bone. The ultimate goal of craniomaxillofacial bone reconstruction is the regeneration of the physiological bone that simultaneously fulfills both morphological and functional restorations. Developments of tissue engineering in the last two decades have brought such a goal closer to reality. In bone tissue engineering, the scaffolds are fundamental, elemental and mesenchymal stem cells/osteoprogenitor cells and bioactive factors. A variety of scaffolds have been developed and used as spacemakers, biodegradable bone substitutes for transplanting to the new bone, matrices of drug delivery system, or supporting structures enhancing adhesion, proliferation, and matrix production of seeded cells according to the circumstances of the bone defects. However, scaffolds to be clinically completely satisfied have not been developed yet. Development of more functional scaffolds is required to be applied widely to cranio-maxillofacial bone defects. This paper reviews recent trends of scaffolds for crania-maxillofacial bone tissue engineering, including our studies.

A novel porous gelatin composite containing naringin for bone repair

As Gu-Sui-Bu (GSB) is a commonly used Chinese medical herb for therapeutic treatment of bone-related diseases, naringin is its main active component. This study elucidates how various concentrations of naringin solution affect the activities of bone cells, based on colorimetric, alkaline phosphatase activity, nodule formation, and tartrate-resistant acid phosphatase activity assays to determine the optimal concentration of naringin. GGT composite was obtained by combining genipin cross-linked gelatin and β-tricalcium phosphate. GGTN composite was prepared by mixing GGT composite with the predetermined concentration of naringin. Porous GGT and GGTN composites were then made using a salt-leaching procedure. The potential of the composites in repairing bone defects was evaluated and compared in vivo by using the biological response of rabbit calvarial bone to these composites. Consequently, the most effective concentration of naringin was 10 mg/mL, which significantly enhanced the proliferation of osteoblasts, osteoclast activity, and nodule formation without affecting the alkaline phosphatase activity of osteoblasts and mitochondrial activity of mixed-bone cells. Radiographic analysis revealed greater new bone ingrowth in the GGTN composite than in the GGT composite at the same implantation time. Therefore, the GGTN composite is highly promising for use as a bone graft material.

Repair of segmental bone defects in rabbit tibia promoted by a complex of β-tricalcium phosphate and hepatocyte growth factor

BACKGROUND

Segmental bone defect repair remains a clinical and scientific challenge with increasing interest focused on bone tissue engineering. Clinical studies are ongoing to address application of hepatocyte growth factor (HGF) for treatment of some diseases; however, the use of HGF in bone tissue engineering has not been addressed. This study was performed to evaluate the effect of HGF in a complex of β-tricalcium phosphate (β-TCP) and collagen in repairing segmental bone defects.

METHODS

Segmental bone defects 5 mm long were created in the middle of the tibial shafts of rabbits. The defect was stabilized with external fixators and implanted with a complex of β-TCP granules and collagen, with or without 100 μg recombinant human HGF. Biweekly, bone regeneration and β-TCP resorption were assessed radiographically and histologically. At 4 and 8 weeks, bone regeneration was evaluated by use of micro-computed tomography and mechanical tests.

RESULTS

Compared with the bone tissue treated with β-TCP and collagen, mineralization, angiogenesis, new bone formation, and absorption of β-TCP were promoted 4 weeks postoperatively by treatment with HGF in the β-TCP and collagen group. These changes were associated with promoting biomechanical regeneration. By 8 weeks, the formation of bone marrow in newly generated bone and absorption of the β-TCP granules were completed in a shorter period by combining HGF with β-TCP and collagen, compared with tissues without HGF.

CONCLUSIONS

The combined application of HGF in a β-TCP and collagen matrix promoted histological bone healing and augmented mechanical strength of the healing bone, particularly in the early stages. The combined use of HGF and β-TCP for treatment of bone defects made a substantial difference.

Studies of bone morphogenetic protein-based surgical repair

Over the past several decades, recombinant human bone morphogenetic proteins (rhBMPs) have been the most extensively studied and widely used osteoinductive agents for clinical bone repair. Since rhBMP-2 and rhBMP-7 were cleared by the U.S. Food and Drug Administration for certain clinical uses, millions of patients worldwide have been treated with rhBMPs for various musculoskeletal disorders. Current clinical applications include treatment of long bone fracture non-unions, spinal surgeries, and oral maxillofacial surgeries. Considering the growing number of recent publications related to clincal research of rhBMPs, there exists enormous promise for these proteins to be used in bone regenerative medicine. The authors take this opportunity to review the rhBMP literature paying specific attention to the current applications of rhBMPs in bone repair and spine surgery. The prospective future of rhBMPs delivered in combination with tissue engineered scaffolds is also reviewed.

The controlled release of vancomycin in gelatin/β-TCP composite scaffolds

Osteomyelitis remains a difficult infection to treat for orthopaedic surgeons regardless of the continuous advances in surgical techniques and antimicrobial agents. The controlled release of vancomycin from local delivery system is a promising method for eliminating infection. In this study, biodegradable gelatin sponge containing different contents of β-tricalcium phosphate ceramic (β-TCP) was prepared for the controlled-release of vancomycin. We aimed to confirm the composite scaffolds could be used as a vancomycin sustained-release system. Examinations of scanning electron microscopy, Fourier transform infrared spectroscopy, mechanical properties, and in vivo drug release were performed. The results showed that the composite scaffolds could achieve local therapeutic drug levels over an extended duration. Taking consideration of porosity, interconnection, mechanical properties, and controlled release performance, the composite gelatin scaffold containing 30% β-TCP granules may be a good candidate for the controlled release of vancomycin in the treatment of chronic osteomyelitis.

Positive effect on bone fusion by the combination of platelet-rich plasma and a gelatin β-tricalcium phosphate sponge: a study using a posterolateral fusion model of lumbar vertebrae in rats

We developed a novel method for bone fusion by combining platelet-rich plasma (PRP) and a gelatin β-tricalcium phosphate (β-TCP) sponge. The PRP is an autologous concentration of platelets that includes several growth factors. The gelatin β-TCP sponge comprises gelatin and β-TCP, thus enabling the sustained release of growth factors and osteoconduction. To evaluate this method, we generated a posterolateral fusion model of lumbar vertebrae in rats and divided it into five groups by implanting the following materials between transverse processes of vertebrae, (1) the gelatin β-TCP sponge with PRP (PRP sponge), (2) the gelatin β-TCP sponge with platelet-poor plasma, (3) gelatin hydrogel with PRP, (4) autologous iliac bone (autograft), and (5) no material was implanted as a control. The assessment of bone fusion by a radiographic assessment, a biomechanical test, microcomputed tomography, and histological evaluations demonstrated that there were no significant differences between the PRP sponge and the autograft groups regarding the osteogenic effect. Subsequent examinations revealed that no significant differences existed between the PRP sponge and the autograft groups in either biomechanical stiffness or the bone volume over time; whereas the radiographic and histological composition underwent similar changes in the fusion process. These results indicate that the PRP sponge could, therefore, be potentially useful as an attractive and less invasive method for bone fusion.

Evaluation of biomimetic scaffold of gelatin-hydroxyapatite crosslink as a novel scaffold for tissue engineering: biocompatibility evaluation with human PDL fibroblasts, human mesenchymal stromal cells, and primary bone cells

Biomimetic gelatin (gel)-hydroxyapatite (HA) composites have been prepared for studying hard tissue engineering scaffolds. However, the biocompatibility test of this form of material using these three cell types, which are periodontal ligament (PDL) fibroblast cells, human mesenchymal stromal cells (HMSc) and primary cells from human hip bone (HBc) has never been evaluated. The objective of this article is to prepare and evaluate the biocompatibility of gel-HA crosslinked scaffold for tissue engineering. Two different scaffolds were prepared: preparation (1), 2.5% gel/2.5% HA; preparation (2), 2.5% gel/5% HA. Three cell types including PDL, HMSc, and HBc were used. Assessment of biocompatibility and osteoblastic cellular responses was evaluated using a three-dimensional cell culture method and scanning electron microscopy (SEM). From SEM, it was observed that scaffold (1) exhibits stable porous formation with well-blended and dispersed HA powder. All three cell types were able to proliferate in both scaffolds. The HMSc and HBc got attached to the scaffolds to a significantly higher degree and subsequently proliferated more than PDL. The alkaline phosphatase (ALP) activities of HMSc and HBc were stronger when cultured in scaffold (S1) than (S2). It was seen that the two scaffold preparations show good biocompatibility with all three cell types tested. The better cellular responses with scaffold (S1) than (S2) might be due to the different structural and morphological characteristics, that is, scaffold (S1) retained more small-sized apatite crystals and a better developed pore configuration than scaffold (S2). Based on these findings, the biomimetically synthesized composite scaffolds have the potential to be used in hard tissue regeneration and tissue engineering fields.

Osteogenic protein-1 associated with mesenchymal stem cells promote bone allograft integration

Limited incorporation and modest bone remodeling can cause allograft failure. We investigated whether mesenchymal stem cells (MSCs) and osteogenic protein-1 (OP-1) can improve allograft integration. A 3-cm full-size intercalary bone defect was created in the mid-diaphysis of the metatarsal bone of the sheep and it was replaced with an allograft alone (control group), or with MSCs (MSC group), OP-1 (OP-1 group), or MSCs and OP-1 (MSC + OP-1 group). Radiographic results showed a faster and complete integration of the allograft in the MSC + OP-1 group. Histology demonstrated that the amount of new bone was significantly greater inside the graft and a longer vessel penetration in the MSC + OP-1 group than in others. Mechanical strength of the allograft was not compromised by the high rate of bone remodeling. These results demonstrated that the association of MSCs and OP-1 improve bone allograft integration promoting an almost complete bone restoring.

Application of autologous periosteal cells for the regeneration of class III furcation defects in Beagle dogs

The aim of this study was to evaluate the healing of class III furcation defects following transplantation of autogenous periosteal cells combined with beta-tricalcium phosphate (beta-TCP). Periosteal cells obtained from Beagle dogs' periosteum explant cultures, were inoculated onto the surface of beta-TCP. Class III furcation defects were created in the mandibular premolars. Three experimental groups were used to test the defects' healing: group A, beta-TCP seeded with periosteal cells were transplanted into the defects; group B, beta-TCP alone was used for defect filling; and group C, the defect was without filling materials. Twelve weeks post surgery, the tissue samples were collected for histology, immunohistology and X-ray examination. It was found that both the length of newly formed periodontal ligament and the area of newly formed alveolar bone in group A, were significantly increased compared with both group B and C. Furthermore, both the proportion of newly formed periodontal ligament and newly formed alveolar bone in group A were much higher than those of group B and C. The quantity of cementum and its percentage in the defects (group A) were also significantly higher than those of group C. These results indicate that autogenous periosteal cells combined with beta-TCP application can improve periodontal tissue regeneration in class III furcation defects.