Autogenous bone particle/titanium fiber composites for bone regeneration in a rabbit radius critical-size defect model

Challenges and tissue engineering strategies of periodontal guided tissue regeneration

Periodontitis is a chronic infectious oral disease with a high prevalence rate in the world, and is a major cause of tooth loss. Nowadays, people have realized that the local microenvironment that includes proteins, cytokines, and extracellular matrix has a key influence on the functions of host immune cells and periodontal ligament stem cells during a chronic infectious disease such as periodontitis. The above pathological process of periodontitis will lead to a defect of periodontal tissues. Through the application of biomaterials, biological agents, and stem cells therapy, guided tissue regeneration (GTR) makes it possible to reconstruct healthy periodontal ligament tissue after local inflammation control. To date, substantial advances have been made in periodontal guided tissue regeneration. However, the process of periodontal remodeling experiences complex microenvironment changes, and currently periodontium regeneration still remains to be a challenging feat. In this review, we summarized the main challenges in each stage of periodontal regeneration, and try to put forward appropriate biomaterial treatment mechanisms or potential tissue engineering strategies that provide a theoretical basis for periodontal tissue engineering regeneration research.

Effect of vascularized periosteum on revitalization of massive bone isografts: An experimental study in a rabbit model

INTRODUCTION

In the last years, limb salvage has become the gold standard treatment over amputation. Today, 90% of extremity osteogenic sarcomas can be treated with limb salvage surgery. However, these reconstructions are not exempt from complications. Massive allografts have been associated to high risk of nonunion (12-57%), fracture (7-30%) and infection (5-21%). Association of vascularized periosteum flap to a massive bone allograft (MBA) has shown to halve the average time of allograft union in clinical series, even compared to vascularized fibular flap. Creeping substitution process has been reported in massive allograft when periosteum flap was associated. However, we have little data about whether it results into allograft revitalization. We hypothesize that the association of a periosteum flap to a bone isograft promotes isograft revitalization, defined as the colonization of the devitalized bone by new-form vessels and viable osteocytes, turning it vital.

MATERIALS AND METHODS

Forty-four New Zealand white male rabbits underwent a 10 mm segmental radial bone defect. In 24 rabbits the bone excision included the periosteum (controls); in 20 rabbits (periosteum group) bone excision was performed carefully detaching periosteum in order to preserve it. Cryopreserved bone isograft from another rabbit was trimmed and placed to the defect gap and was fixed with a retrograde intramedullar 0.6 mm Kirschner wire. Rabbits were randomized and distributed in 3 subgroups depending on the follow-up (control group: 5 rabbits in 5-week follow up group, 8 rabbits in 10-week follow-up group, 7 rabbits in 20-week follow-up group; periosteum group: 5 rabbits in 5-week follow up group, 7 rabbits in 10-week follow-up group, 7 rabbits in 20-week follow-up group). Fluoroscopic images of rabbit forelimb were taken after sacrifice to address union. Each specimen was blindly evaluated in optical microscope (magnification, ×4) after hematoxylin and eosin staining to qualitative record: presence of new vessels and osteocytes in bone graft lacunae (yes/no) to address revitalization, presence of callus (yes/no) and woven bone and cartilage tissue area (mm2 ) to address remodeling (osteoclast resorption of old bone and substitution by osteoblastic new bone formation).

RESULTS

No isograft revitalization occurred in any group, but it was observed bone graft resorption and substitution by new-formed bone in periosteum group. This phenomenon was accelerated in 5-week periosteum group (control group: 49.5 ± 9.6 mm2 vs. periosteum group: 34.9 ± 10.4 mm2 ; p = .07). Remodeled lamellar bone was observed in both 20-week groups (control group: 6.1 ± 6.3 mm2 vs. periosteum group: 5.8 ± 3.0 mm2 , p = .67). Periosteum group showed complete integration and graft substitution, whereas devitalized osteons were still observed in 20-week controls. All periosteum group samples showed radiographic union through a bone callus, whereas controls showed nonunion in eight specimens (Union rate: control group 60% vs. periosteum group 100%, p = .003).

CONCLUSIONS

Association of vascularized periosteum to a massive bone isograft has shown to accelerate bone graft substitution into a newly formed bone, thus, no bone graft revitalization occurs.

Autogenous bone particles combined with platelet-rich plasma can stimulate bone regeneration in rabbits

Long-term bone defects are a key clinical problem. Autogenous bone graft remains the gold standard for the treatment of these defects; however, improving the osteogenic properties and reducing the amount of autogenous bone is challenging. Autologous platelet-rich plasma (PRP) has been widely considered for treatment, due to its potentially beneficial effect on bone regeneration and vascularization. The aim of the present study was to explore the effects of autogenous bone particles combined with PRP on repairing segmental bone defects in rabbits. Briefly, a critical-size diaphyseal radius defect was established in 45 New Zealand White rabbits. Animals were randomly divided into four groups, according to the different implants: Group A, empty bone defect; group B, PRP; group C, autogenous bone particles + bone mesenchymal stem cells (BMSCs) on the left radius; group D, autogenous bone particles + PRP + BMSCs on the right radius. Bone samples were collected and further analyzed using X-ray, histology and histomorphometry 4, 8 and 12 weeks post-surgery. In addition, the effect of PRP on cell proliferation was detected by Cell Counting Kit-8 and the concentrations of growth factors (GFs), transforming GF (TGF)-β1 and platelet-derived GF (PDGF), in PRP were verified by ELISA. X-ray, histology and histomorphometry data revealed that the fraction area of the newly formed bone was larger in group D. In addition, PRP could improve cell proliferation, osteogenic differentiation and the release of GFs, TGF-β1 and PDGF-AB. In conclusion, these findings indicated that an autogenous bone particle + PRP + BMSC scaffold may be used as a potential treatment strategy for segmental defects in humans.

Magnesium-alloy rods reinforced bioglass bone cement composite scaffolds with cortical bone-matching mechanical properties and excellent osteoconductivity for load-bearing bone in vivo regeneration

Various therapeutic platforms have been developed for repairing bone defects. However, scaffolds possess both cortical bone-matching mechanical properties and excellent osteoconductivity for load-bearing bone defects repair is still challenging in the clinic. In this study, inspired by the structure of the ferroconcrete, a high-strength bifunctional scaffold has been developed by combining surface-modified magnesium alloy as the internal load-bearing skeleton and bioglass-magnesium phosphate bone cement as the osteoconductive matrix. The scaffold combines the high mechanical strength and controllable biodegradability of surface-modified magnesium alloy with the excellent biocompatibility and osteoconductivity of bioglass-magnesium phosphate bone cement, thus providing support for load-bearing bone defects and subsequently bone regeneration. The scaffolds generate hydroxyapatite (HA) during the degrading in simulated body fluid (SBF), with the strength of the scaffold decreasing from 180 to 100 MPa in 6 weeks, which is still sufficient for load-bearing bone. Moreover, the scaffolds showed excellent osteoconductivity in vitro and in vivo. In a New Zealand White Rabbit radius defect model, the scaffolds degrade gradually and are replaced by highly matured new bone tissues, as assessed by image-based analyses (X-ray and Micro-CT) and histological analyses. The bone formation-related proteins such as BMP2, COL1a1 and OCN, all showed increased expression.

Scaffold-Mediated Gene Delivery for Osteochondral Repair

Osteochondral defects involve both the articular cartilage and the underlying subchondral bone. If left untreated, they may lead to osteoarthritis. Advanced biomaterial-guided delivery of gene vectors has recently emerged as an attractive therapeutic concept for osteochondral repair. The goal of this review is to provide an overview of the variety of biomaterials employed as nonviral or viral gene carriers for osteochondral repair approaches both in vitro and in vivo, including hydrogels, solid scaffolds, and hybrid materials. The data show that a site-specific delivery of therapeutic gene vectors in the context of acellular or cellular strategies allows for a spatial and temporal control of osteochondral neotissue composition in vitro. In vivo, implantation of acellular hydrogels loaded with nonviral or viral vectors has been reported to significantly improve osteochondral repair in translational defect models. These advances support the concept of scaffold-mediated gene delivery for osteochondral repair.

Ursolic acid loaded-mesoporous bioglass/chitosan porous scaffolds as drug delivery system for bone regeneration

Bioglass scaffolds have great application potentials in orthopedics, and Ursolic acid (UA) can effectively promote in vivo new bone formation. Herein, we for the first time developed the mesoporous bioglass/chitosan porous scaffolds loaded with UA (MBG/CS/UA) for enhanced bone regeneration. The MBG microspheres with particle sizes of ~300 nm and pore sizes of ~3.9 nm were uniformly dispersed on the CS films. The mesoporous structure within the MBG microspheres and the hydrogen bonding between the scaffolds and UA drugs made the MBG/CS/UA scaffolds have controlled drug release performances. The as-released UA drugs from the scaffolds increased remarkably the alkaline phosphatase activity, osteogenic differentiation related gene type I collagen, runt-related transcription factor 2 expression, and osteoblast-associated protein expression. Moreover, the results of micro-CT images, histomorphological observations demonstrated that the MBG/CS/UA scaffolds improved new bone formation ability. Therefore, the MBG/CS/UA porous scaffolds can be used as novel bone tissue engineering materials.

Osseointegration of titanium scaffolds manufactured by selective laser melting in rabbit femur defect model

The aim of this study was to assess the osseointegration of two series of titanium (Ti) scaffolds with 0.8 and 1 mm cell size obtained by Selective Laser Melting (SLM) technique. One of the series had the Ti surface unmodified, while the other had the Ti surface coated with silicon-substituted nano-hydroxyapatite (nano-HapSi). The scaffolds were implanted in the femur bone defects of 6 White Californian male rabbits: three animals were implanted with 0.8 mm cell size scaffolds and three animals with 1 mm cell size scaffolds, respectively. The bone fragments and scaffolds harvested at 2, 4 and 6 months were histologically analyzed using conventional light microscopy (LM) and scanning electron microscopy (SEM) for the qualitative evaluation of the bone tissue formed in contact with the scaffold. Both LM and SEM images indicated a better osseointegration for nano-HapSi coated Ti scaffolds. LM revealed that the compact bone formed in the proximity of nano-HapSi-coated scaffolds was better organized than spongy bone associated with unmodified scaffolds. Moreover, Ti scaffolds with meshes of 0.8 mm showed higher osseointegration compared with 1 mm. SEM images at 6 months revealed that the bone developed not only in contact with the scaffolds, but also proliferated inside the meshes. Nano-HapSi-coated Ti implants with 0.8 mm meshes were completely covered and filled with new bone. Ti scaffolds osseointegration depended on the mesh size and the surface properties. Due to the biocompatibility and favorable osseointegration in bone defects, nano-HapSi-coated Ti scaffolds could be useful for anatomical reconstructions.