Long-Term Effect of Honeycomb β-Tricalcium Phosphate on Zygomatic Bone Regeneration in Rats

Effect of Scaffold Geometrical Structure on Macrophage Polarization during Bone Regeneration Using Honeycomb Tricalcium Phosphate

The polarization balance of M1/M2 macrophages with different functions is important in osteogenesis and bone repair processes. In a previous study, we succeeded in developing honeycomb tricalcium phosphate (TCP), which is a cylindrical scaffold with a honeycomb arrangement of straight pores, and we demonstrated that TCP with 300 and 500 μm pore diameters (300TCP and 500TCP) induced bone formation within the pores. However, the details of the influence of macrophage polarization on bone formation using engineered biomaterials, especially with respect to the geometric structure of the artificial biomaterials, are unknown. In this study, we examined whether differences in bone tissue formation due to differences in TCP geometry were due to the polarity of the assembling macrophages. Immunohistochemistry for IBA-1, iNOS, and CD163 single staining was performed. The 300TCP showed a marked infiltration of iNOS-positive cells, which are thought to be M1 macrophages, during the osteogenesis process, while no involvement of CD163-positive cells, which are thought to be M2 macrophages, was observed in the TCP pores. In addition, 500TCP showed a clustering of iNOS-positive cells and CD163-positive cells at 2 weeks, suggesting the involvement of M2 macrophages in the formation of bone tissue in the TCP pores. In conclusion, we demonstrated for the first time that the geometrical structure of the artificial biomaterial, i.e., the pore size of honeycomb TCP, affects the polarization of M1/2 macrophages and bone tissue formation in TCP pores.

Reconstruction of the orbitozygomatic framework: State of the art and perspectives

The reconstruction of the whole orbitozygomatic framework (OZF) is complex and can be encountered in cases of congenital midface deformity, after tumor ablative surgery and in severe facial trauma. Nowadays, surgeon has a wide range of available techniques that have continually grown over the past years, optimizing the surgical management and the aesthetical outcomes. Among them, the autologous bone graft (ABG) remains one of the most suitable options : ABG is easy to harvest and has optimal biological properties for bone healing. It can be tailored to the patient anatomy thanks to the recent advances in computer-assisted surgery. However, substantial drawbacks remain such as the early resorption of the non-vascularized graft, the need of a donor site and its potential morbidity. Alloplastic reconstruction is another option that can resolve both the resorption issue and the donor site morbidity. Moreover, the 3D-printing technologies also allows the manufacturing of patient specific implants. However, alloplastic materials have a variable success, especially due to the high risk of infection or exposure. Consequently, regenerative medicine is a promising field that aims to find a procedure without the disadvantages of ABG or alloplastic based reconstructions, but displaying similar or even higher success rate. Indeed, recent tissue engineering strategies have demonstrated encouraging results for bone regeneration using natural or synthetic biomaterials, patient cells and synthetic bioactive substances. The objective of this review is to present the etiologies of OZF defect, the available reconstruction procedures as well as the current state of the research.

Biodegradable Hydrogel Beads Combined with Calcium Phosphate Bone Cement for Bone Repair: In Vitro and In Vivo Characterization

This study evaluated the in vitro characterizations of biodegradable hydrogel beads with calcium phosphate bone cement (CPC). Commercial fast-setting CPC and hydrogel beads were compared with 25%-volume hydrogel in CPC (C/0.25) in vivo. The histological behaviors and absorption rates of CPC only, hydrogel beads, and hydrogel/CPC composite were measured and compared at 4, 8, and 12 weeks. The results indicated that the C/0.25 composite can be molded and does not disintegrate when immersed in the solution, but this delays the phase transition of the CPC into the product in the early reaction process. The osteoprogenitor D1 cell affinity of the C/0.25 composite was equally competitive with that of the CPC-only. Adding hydrogel beads to CPC did not inhibit cell proliferation as well as differentiation of osteoprogenitor cells. In vivo histological evaluations did not indicate any significant difference in the CPC-only, hydrogel-only, and C/0.25 composite after 4 weeks of implantation; however, significantly less residue was observed in the C/0.25 composite relative to the CPC-only after 8 weeks. After 12 weeks of hydrogel beads implantation, the hydrogel degraded substantially, creating vacancies that were subsequently occupied by a large amount of soft tissue. New bone was formed in large quantities in the C/0.25; therefore, the C/0.25 composite is a promising option for a wide range of dental, craniofacial, and orthopedic applications.

A Pilot Study of Seamless Regeneration of Bone and Cartilage in Knee Joint Regeneration Using Honeycomb TCP

The knee joint is a continuous structure of bone and cartilage tissue, making it difficult to regenerate using artificial biomaterials. In a previous study, we succeeded in developing honeycomb tricalcium phosphate (TCP), which has through-and-through holes and is able to provide the optimum microenvironment for hard tissue regeneration. We demonstrated that TCP with 300 μm pore diameters (300TCP) induced vigorous bone formation, and that TCP with 75 μm pore diameters (75TCP) induced cartilage formation. In the present study, we regenerated a knee joint defect using honeycomb TCP. 75TCP and 300TCP were loaded with transforming growth factor (TGF)-β alone or bone morphogenic protein (BMP)-2+TGF-β with or without Matrigel and transplanted into knee joint defect model rabbits. 75TCP showed no bone or cartilage tissue formation in any of the groups with TGF-β alone and BMP-2+TGF-β with/without Matrigel. However, for 300TCP and BMP-2+TGF-β with or without Matrigel, vigorous bone tissue formation was observed in the TCP holes, and cartilage tissue formation in the TCP surface layer was continuous with the existing cartilage. The cartilage area in the TCP surface was larger in the group without Matrigel (with BMP-2+TGF-β) than in the group with Matrigel (with BMP-2+TGF-β). Therefore, honeycomb TCP can induce the seamless regeneration of bone and cartilage in a knee joint.

Preparation of Absorption-Resistant Hard Tissue Using Dental Pulp-Derived Cells and Honeycomb Tricalcium Phosphate

In recent years, there has been increasing interest in the treatment of bone defects using undifferentiated mesenchymal stem cells (MSCs) in vivo. Recently, dental pulp has been proposed as a promising source of pluripotent mesenchymal stem cells (MSCs), which can be used in various clinical applications. Dentin is the hard tissue that makes up teeth, and has the same composition and strength as bone. However, unlike bone, dentin is usually not remodeled under physiological conditions. Here, we generated odontoblast-like cells from mouse dental pulp stem cells and combined them with honeycomb tricalcium phosphate (TCP) with a 300 μm hole to create bone-like tissue under the skin of mice. The bone-like hard tissue produced in this study was different from bone tissue, i.e., was not resorbed by osteoclasts and was less easily absorbed than the bone tissue. It has been suggested that hard tissue-forming cells induced from dental pulp do not have the ability to induce osteoclast differentiation. Therefore, the newly created bone-like hard tissue has high potential for absorption-resistant hard tissue repair and regeneration procedures.

Bone Regeneration Using PEVAV/β-Tricalcium Phosphate Composite Scaffolds in Standardized Calvarial Defects: Micro-Computed Tomographic Experiment in Rats

Bone regeneration using beta-tricalcium phosphate (β-TCP) can be practiced using a biocomposite scaffold. Poly(ethylene-co-vinylalcohol)/poly(δ-valerolactone)/β-tricalcium phosphate (PEVAV/β-TCP) composite scaffolds showed promising in vitro results. This study evaluated the bone regenerative potential of PEVAV/β-TCP biocomposite scaffolds in standardized calvarial defects in a rat model over 4 and 10 weeks. Bilateral calvarial defects (5 mm in diameter and about 1.5 mm thick, equivalent to the thickness of the calvaria) were created in 40 male Wistar albino rats. The defects were grafted with either commercially available β-TCP (positive control), PEVAV/β-TCP 70, or PEVAV/β-TCP 50, or left empty (negative control), depending on the group to which the animal was randomly assigned, to be covered before flap closure with resorbable collagen membrane (RCM). At 4 and 10 weeks post-surgery, the collected rat calvaria were evaluated using micro computed tomography (micro-CT) analysis, to assess the newly formed bone volume (NFBV), newly formed bone mineral density (NFBMD), and remaining graft volume (RGV). The results showed that calvarial defects grafted with the PEVAV/β-TCP biocomposite exhibited higher NFBV than did control defects, both at 4 and 10 weeks post-surgery. Furthermore, calvarial defects grafted with PEVAV/β-TCP 70 showed the highest NFBV among all grafting conditions, with a statistically significant difference recorded at 10 weeks post-surgery. The PEVAV/β-TCP composite scaffold showed potentiality for the regeneration of critical-sized calvarial bone defects in a rat model.