Healing of rabbit calvarial critical-sized defects using autogenous bone grafts and fibrin glue

[Models of bone defects in rabbits used to evaluate the bone graft materials efficacy]

The review deals with the main types of experimental models of bone defects of the skull in rabbits. The information about the types of critical defects, methods of their modeling and the possibilities of application of the described models in the studies of bone graft materials in dentistry and maxillofacial surgery is systematized.

An Elastic Mineralized 3D Electrospun PCL Nanofibrous Scaffold for Drug Release and Bone Tissue Engineering

Complex shaped and critical-sized bone defects have been a clinical challenge for many years. Scaffold-based strategies such as hydrogels provide localized drug release while filling complex defect shapes, but ultimately possess weaknesses in low mechanical strength alongside a lack of macroporous and collagen-mimicking nanofibrous structures. Thus, there is a demand for mechanically strong, extracellular matrix (ECM) mimicking scaffolds that can robustly fit complex shaped critical sized defects and simultaneously provide localized, sustained, multiple growth factor release. We therefore developed a composite, bi-phasic PCL/hydroxyapatite (HA) 3D nanofibrous (NF) scaffold for bone tissue regeneration by using our innovative electrospun-based thermally induced self-agglomeration (TISA) technique. One intriguing feature of our ECM-mimicking TISA scaffolds is that they are highly elastic and porous even after evenly coated with minerals and can easily be pressed to fit different defect shapes. Furthermore, the bio-mimetic mineral deposition technique allowed us to simultaneously encapsulate different type of drugs, e.g., proteins and small molecules, on TISA scaffolds under physiologically mild conditions. Compared to scaffolds with physically surface-adsorbed phenamil, a BMP2 signaling agonist, incorporated phenamil composite scaffolds indicated less burst release and longer lasting sustained release of phenamil with subsequently improved osteogenic differentiation of cells in vitro. Overall, our study indicated that the innovative press-fit 3D NF composite scaffold may be a robust tool for multiple-drug delivery and bone tissue engineering.

Can the Combination of Simvastatin and Melatonin Create a Synergistic Effect on Bone Regeneration?

PURPOSE

The present study evaluated the potential bone regeneration capacity of combining melatonin and simvastatin, with a goal of producing more osteogenic bone substitutes.

MATERIALS AND METHODS

A total of 48 male Wistar rats were randomly divided into 4 groups. The following were administered into critical-sized calvarial defects of the rats: Group I-human allograft; Group II-human allograft + 10 mg melatonin; Group III-human allograft + 0.1 mg simvastatin; and Group IV-human allograft + 10 mg melatonin + 0.1 mg simvastatin. Histopathologic, histomorphometric, and microcomputed tomographic evaluations were performed postprocedurally at 4 and 8 weeks. A P value < .05 was considered significant for all evaluations.

RESULTS

Groups II and III had significantly superior regeneration compared to Group I at weeks 4 and 8. Group III had significantly superior regeneration compared to Group II, particularly in week 4. Group IV had significantly superior regeneration compared to all groups at week 8.

CONCLUSIONS

The local administration of melatonin and simvastatin resulted in increased new bone mass and quality of bone microstructure than was seen in the control group. Simvastatin shortened the defect regeneration time more effectively than melatonin did. The combined use of melatonin and simvastatin provided a synergic effect on bone regeneration, particularly in the late phase of healing.

Establishment and Characteristic Analysis of a Dog Model for Autologous Homologous Cranioplasty

Objective

The aim of this study is to establish a large animal (dog) model that can be referred clinically for autologous homologous cranioplasty.

Methods

Our large skull defect dog model was established by emulating the decompressive craniectomy with 22 adult beagle dogs. The autologous bones were taken out from the dogs and divided into two groups, the freeze-drying (FD) group and the single freezing (SF) group. They were then stored in the bone bank at -20°C after being irradiated with 25 KGy. Three months later, the bones were reimplanted. After operation, we closely watch the experimental objects for four more months examining the infection and survival of the bone graft.

Results

Through macroscopic observation, it was found that, among 44 cranial flaps (bilateral) from the rest of the 22 dogs, grade A cranial flaps accounted for 86.4% (19/22) in the SF group and only 31.8% (7/22) in the FD group. Although osteogenic osteoclast, Harvard tube, neovascularization, and angiogenic factors were found through the pathological results, including an electron microscope and calmodulin tracer, it could be verified by using X-CT and micro-CT that early bone resorption could be still found even in grade A bone flap.

Conclusion

By using the common clinical method to preserve the cranial flaps, we established an experimental dog model of autologous cranioplasty for a large area of cranial defect. It was proved that this model could reproduce the infections and bone resorption which typically happened in clinical autologous homologous cranioplasty. As a conclusion, the established model can be used as an effective experimental tool for further research to improve the success rate of autologous homologous cranioplasty.

Fibrin Sealant Derived from Human Plasma as a Scaffold for Bone Grafts Associated with Photobiomodulation Therapy

Fibrin sealants derived from human blood can be used in tissue engineering to assist in the repair of bone defects. The objective of this study was to evaluate the support system formed by a xenograft fibrin sealant associated with photobiomodulation therapy of critical defects in rat calvaria. Thirty-six rats were divided into four groups: BC (n = 8), defect filled with blood clot; FSB (n = 10), filled with fibrin sealant and xenograft; BCPBMT (n = 8), blood clot and photobiomodulation; FSBPBMT (n = 10), fibrin sealant, xenograft, and photobiomodulation. The animals were killed after 14 and 42 days. In the histological and microtomographic analysis, new bone formation was observed in all groups, limited to the defect margins, and without complete wound closure. In the FSB group, bone formation increased between periods (4.3 ± 0.46 to 6.01 ± 0.32), yet with lower volume density when compared to the FSBPBMT (5.6 ± 0.45 to 10.64 ± 0.97) group. It was concluded that the support system formed by the xenograft fibrin sealant associated with the photobiomodulation therapy protocol had a positive effect on the bone repair process.

A comparison of the bone regeneration and soft-tissue-formation capabilities of various injectable-grafting materials in a rabbit calvarial defect model

Restoring adequate blood supply is essential to the success of bone repair and augmentation procedures in craniofacial surgery. Nevertheless, the manner by which the incorporation of collagen gels (which can potentially induce angiogenesis), particulated deproteinized bovine bone grafts, or a combination of both can accelerate or delay bone regeneration in a clinical setting remains controversial. The objective of this study was to evaluate radiographically and histologically the capacity and functionality of particulated bone grafts and collagen gels on bone ossification and soft tissue formation in a rabbit calvarial defect. Bilateral calvarial defects in adult white New Zealand rabbits were filled or left either unfilled with bone grafts (DBBM), collagen gels (Gel), or a combination of both (DBBM + Gel). The defects were allowed to heal for 1, 2, and 6 months postoperatively before termination. Healing and regeneration patterns were assessed by 3D µCT and histological methods, and the biomechanical properties of regenerated tissue constructs were investigated and compared with autogenous calvarial bone. Results show that implanted DBBM and DBBM + Gel significantly enhanced immature bone formation compared with the empty and Gel groups; the latter treatment improved soft tissue formation and impeded immature bone formation but yielded no significant effect on mature bone formation. Implantation of DBBM not only effectively reconstructed 188.83 ± 25.25% of the tissue volume of the original defect, but it also regenerated bone tissue with similar tissue composition and biomechanical properties as the original autogenous bone. We also show that implanting different biomaterials can control the composition of soft and hard tissue in reconstructed tissue constructs in calvarial bone defects. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 529-544, 2019.

17β-estradiol improves the efficacy of exploited autologous bone marrow-derived mesenchymal stem cells in non-union radial defect healing: A rabbit model

Exploiting mesenchymal stem cells (MSCs) appears to be an appealing alternative to the traditional clinical approach in the treatment of non-union bone defects. It has been shown that 17β-estradiol improves the osteogenesis and proliferation potential of the MSCs via estrogen receptors. We investigated the effect of 17β-estradiol on exploiting autologous BMSCs (bone marrow-derived MSCs) for the purpose of healing of radial non-union segmental defect in rabbit. Twenty rabbits were divided into 4 experimental groups: 1. Control group; 2. MSC treatment group; 3. 17β-estradiol (E2) treatment group; and 4. E2+MSC treatment group. Isolated BMSCs were seeded in a critical-sized defect on radial mid-diaphysis that was filled with autologous fibrin clot differently in 4 groups: 1. intact fibrin clot (control); 2. Fibrin clot containing MSCs; 3. Estradiol; and 4. E₂ and MSCs. Defect healing was assessed by radiological (week 0, 2, 4, 6, 8 and 10) and histopathological evaluation (week 10). Radiological evaluation data demonstrated that quantities for the E2+MSC group were significantly the greatest in comparison with the other groups at week 4 to 10 inclusive. Moreover, Histopathological evaluation indicated that the E2+MSC group had the highest score which was significantly greater than the E2 group and the control group (P<0.05). In-vivo application of in situ 17β-estradiol provides the seeded BMSCs with improved osteogenic capacity in tandem with an accelerated rate of bone healing. This obviously more qualified approach that yields in a shorter time appears to be promising for the future cell-based clinical treatments of the non-union bone fractures. Exploiting mesenchymal stem cells (MSCs) appears to be an appealing alternative to the traditional clinical approach in the treatment of non-union bone defects. It has been shown that 17β-estradiol improves the osteogenesis and proliferation potential of the MSCs via estrogen receptors. We investigated the effect of 17β-estradiol on exploiting autologous BMSCs (bone marrow-derived MSCs) for the purpose of healing of radial non-union segmental defect in rabbit. Twenty rabbits were divided into 4 experimental groups: 1. Control group; 2. MSC treatment group; 3. 17β-estradiol (E2) treatment group; and 4. E2+MSC treatment group. Isolated BMSCs were seeded in a critical-sized defect on the radial mid-diaphysis that was filled with autologous fibrin clot differently in 4 groups: 1. intact fibrin clot (control); 2. Fibrin clot containing MSCs; 3. Estradiol; and 4. E₂ and MSCs. Defect healing was assessed by radiological (week 0, 2, 4, 6, 8 and 10) and histopathological evaluation (week 10). Radiological evaluation data demonstrated that quantities for the E2+MSC group were significantly the greatest in comparison with the other groups at week 4 to 10 inclusive. Moreover, Histopathological evaluation indicated that the E2+MSC group had the highest score which was significantly greater than the E2 group and the control group (P<0.05). In-vivo application of in situ 17β-estradiol provides the seeded BMSCs with improved osteogenic capacity in tandem with an accelerated rate of bone healing. This obviously more efficient approach that yields in a shorter time appears to be promising for future cell-based clinical treatments of the non-union bone fractures.

A review of fibrin and fibrin composites for bone tissue engineering

Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.

Micro-CT Analysis of Bone Healing in Rabbit Calvarial Critical-Sized Defects with Solid Bioactive Glass, Tricalcium Phosphate Granules or Autogenous Bone

Objectives

The purpose of the present study was to evaluate bone healing in rabbit critical-sized calvarial defects using two different synthetic scaffold materials, solid biodegradable bioactive glass and tricalcium phosphate granules alongside solid and particulated autogenous bone grafts.

Material and Methods

Bilateral full thickness critical-sized calvarial defects were created in 15 New Zealand white adult male rabbits. Ten defects were filled with solid scaffolds made of bioactive glass or with porous tricalcium phosphate granules. The healing of the biomaterial-filled defects was compared at the 6 week time point to the healing of autologous bone grafted defects filled with a solid cranial bone block in 5 defects and with particulated bone combined with fibrin glue in 10 defects. In 5 animals one defect was left unfilled as a negative control. Micro-computed tomography (micro-CT) was used to analyze healing of the defects.

Results

Micro-CT analysis revealed that defects filled with tricalcium phosphate granules showed new bone formation in the order of 3.89 (SD 1.17)% whereas defects treated with solid bioactive glass scaffolds showed 0.21 (SD 0.16)%, new bone formation. In the empty negative control defects there was an average new bone formation of 21.8 (SD 23.7)%.

Conclusions

According to findings in this study, tricalcium phosphate granules have osteogenic potential superior to bioactive glass, though both particulated bone with fibrin glue and solid bone block were superior defect filling materials.

Bone healing in rabbit calvarial critical-sized defects filled with stem cells and growth factors combined with granular or solid scaffolds

PURPOSE

In pediatric neurosurgery, decompressive craniectomy and correction of congenital cranial anomalies can result in major cranial defects. Corrective cranioplasty for the repair of these critical-sized defects is not only a cosmetic issue. The limited availability of suitable autogenous bone and the morbidity of donor site harvesting have driven the search for new approaches with biodegradable and bioactive materials. This study aimed to assess the healing of rabbit calvarial critical-sized defects filled with osteogenic material, either with bioactive glass scaffolds or tricalcium phosphate granules in various combinations with adipose stem cells or bone marrow stem cells, BMP-2, BMP-7, or VEGF to enhance osteogenesis.

METHODS

Eighty-two bicortical full thickness critical-sized calvarial defects were operated. Five defects were left empty as negative control defects. The remaining 77 defects were filled with solid bioactive glass scaffolds or tricalcium phosphate granules seeded with adipose or bone marrow derived stem cells in combination with BMP-2, BMP-7, or VEGF. The defects were allowed to heal for 6 weeks before histologic and micro-CT analyses.

RESULTS

Micro-CT examination at the 6-week post-operative time point revealed that defects filled with stem cell-seeded tricalcium phosphate granules resulted in new bone formation of 6.0 %, whereas defects with bioactive glass scaffolds with stem cells showed new bone formation of 0.5 to 1.7 %, depending on the growth factor used.

CONCLUSIONS

This study suggests that tricalcium phosphate granules combined with stem cells have osteogenic potential superior to solid bioactive glass scaffolds with stem cells and growth factors.