Bone Defect Site Research Articles

CD271 antibody-functionalized microspheres capable of selective recruitment of reparative endogenous stem cells for in situ bone regeneration

In the strategy of in situ bone regeneration, it used to be difficult to specifically recruit bone marrow mesenchymal stem cells (BM-MSCs) by a single marker. Recently, CD271 has been considered to be one of the most specific markers to isolate BM-MSCs; however, the effectiveness of CD271 antibodies in recruiting BM-MSCs has not been explored yet. In this study, we developed novel CD271 antibody-functionalized chitosan (CS) microspheres with the aid of polydopamine (PDA) coating to recruit endogenous BM-MSCs for in situ bone regeneration. The CS microspheres were sequentially modified with PDA and CD271 antibody through dopamine self-polymerization and bioconjugation, respectively. In vitro studies showed that the CD271 antibody-functionalized microspheres selectively captured significantly more BM-MSCs from a fluorescently labeled heterotypic cell population than non-functionalized controls. In addition, the PDA coating was critical for supporting stable adhesion and proliferation of the captured BM-MSCs. Effective early recruitment of CD271+ stem cells by the functionalized microspheres at bone defect site of SD rat was observed by the CD271/DAPI immunofluorescence staining, which led to significantly enhanced new bone formation in rat femoral condyle defect over long term. Together, findings from this study have demonstrated, for the first time, that the CD271 antibody-functionalized CS microspheres are promising for in situ bone regeneration.

Efficacy of apolipoprotein 2-Jifusheng in the treatment of osteomyelitis in rabbits

To evaluate the effect of one-stage treatment of bone morphogenetic protein 2 combined with Jifusheng in the experimental model of osteomyelitis in rabbits. The model of chronic osteomyelitis of tibia was established in 30 3-month-old male New Zealand white rabbits with a body weight of (2.0±0.5) kg, and the model was verified 4 weeks after operation. Thirty rabbits with osteomyelitis were randomly divided into 3 groups with 10 rabbits in each group (n= 10). The model group did not do any treatment after focal debridement, treatment group A was implanted with musculosheng at the site of focal debridement and bone defect, and treatment group B was implanted with apolipoprotein 2-Jifusheng at the site of focal debridement and bone defect. The therapeuticeffect was evaluated by blood biochemical, microbiological, imaging, pathological and immunohistochemical examination 8 weeks after operation. At 4 weeks after operation, 30 rabbits with osteomyelitis were successfully validated. The results of serological examination showed that the hypersensitive C-reactive protein (CRP) and white blood cell count(WBC)in the model group were significantly higher than those in the blank group at 2 and 4 weeks after operation. Eight weeks after treatment, the detection of blood indexes showed that the white blood cell count (WBC)and hypersensitive C reactive protein (CRP)in treatment group A and treatment group B were significantly lower than those in the model group (P<0.05), but there was no significant difference between treatment group An and treatment group B (P>0.05). Eight weeks after treatment, the bone defect area was measured. The bone volume/total volume (BV/TV) and bone mineral density (BMD)in treatment group A and B were significantly higher than those in the model group (P<0.05), and the bone volume/total volume (BV/TV) and bone mineral density(BMD)in treatment group B were significantly higher than those in treatment group A (P<0.05), the repair of bone defect was almost complete, and the bone volume and bone mineral density increased significantly. At 8 weeks after treatment, the number of osteoblasts/bone tissue area (N.Ob/T.Ar) and the number of osteoblasts/bone tissue perimeter (N.Ob/B.Pm) in treatment group A and B were significantly higher than those in model group, and the N.Ob/T.Ar and N.Ob/B.Pm in treatment group B were significantly higher than those in treatment group A. The immunohistochemical staining of TNF- α and IL-6 around bone tissue in treatment group A and treatment group B was significantly less than that in model group, but there was no significant difference between treatment group B and treatment group A. The combined application of apolipoprotein 2-Jifusheng can promote bone repair and reduce the inflammation of the focus. it can treat rabbits with osteomyelitis in one stage, provide objective basis for the formulation of clinical treatment strategy of osteomyelitis and further promote clinical research.

Development of hierarchical porous bioceramic scaffolds with controlled micro/nano surface topography for accelerating bone regeneration

Mimicking hierarchical porous architecture of bone has been considered as a valid approach to promote bone regeneration. In this study, hierarchical porous β-tricalcium phosphate (β-TCP) scaffolds were constructed by combining digital light processing (DLP) printing technique and in situ growth crystal process. Macro/micro hierarchical scaffolds with designed macro pores for facilitating the ingrowth of bone tissue were fabricated by DLP printing. Three types of micro/nano surface topography were obtained by in situ growth crystal process to regulate stem cells behavior. The attachment and proliferation of rat bone marrow mesenchymal stem cells (rBMSCs) were strongly dependent on the surface roughness and the specific surface area. The micro/nano surface topography distinctly facilitated the differentiation of rBMSCs by targeting MAPK, STAT and AKT signaling pathways, in which the sodium hydroxide treatment group showed the highest promoting effect. Furthermore, in vivo results of skull defect repair model of rats indicated that hierarchical scaffolds with micro/nano topographies exhibited appealing bone regeneration capacity. The hierarchical porous bioceramic scaffolds constructed by integrating structural design and physical stimulation of the external surface topography have great potential for rapid bone repair via modulation of microenvironmental regulatory pathways at the bone defect site.

Bioactive Scaffolds Integrated with Liposomal or Extracellular Vesicles for Bone Regeneration.

With population aging and increased life expectancy, an increasing number of people are facing musculoskeletal health problems that necessitate therapeutic intervention at defect sites. Bone tissue engineering (BTE) has become a promising approach for bone graft substitutes as traditional treatments using autografts or allografts involve clinical complications. Significant advancements have been made in developing ideal BTE scaffolds that can integrate bioactive molecules promoting robust bone repair. Herein, we review bioactive scaffolds tuned for local bone regenerative therapy, particularly through integrating synthetic liposomal vesicles or extracellular vesicles to the scaffolds. Liposomes offer an excellent drug delivery system providing sustained release of the loaded bioactive molecules. Extracellular vesicles, with their inherent capacity to carry bioactive molecules, are emerging as an advanced substitute of synthetic nanoparticles and a novel cell-free therapy for bone regeneration. We discuss the recent advance in the use of synthetic liposomes and extracellular vesicles as bioactive materials combined with scaffolds, highlighting major challenges and opportunities for their applications in bone regeneration. We put a particular focus on strategies to integrate vesicles to various biomaterial scaffolds and introduce the latest advances in achieving sustained release of bioactive molecules from the vesicle-loaded scaffolds at the bone defect site.

Core/Shell Glycine-Polyvinyl Alcohol/Polycaprolactone Nanofibrous Membrane Intended for Guided Bone Regeneration: Development and Characterization

Glycine (Gly), which is the simplest amino acid, induces the inflammation response and enhances bone mass density, and particularly its β polymorph has superior mechanical and piezoelectric properties. Therefore, electrospinning of Gly with any polymer, including polyvinyl alcohol (PVA), has a great potential in biomedical applications, such as guided bone regeneration (GBR) application. However, their application is limited due to a fast degradation rate and undesirable mechanical and physical properties. Therefore, encapsulation of Gly and PVA fiber within a poly(ε-caprolactone) (PCL) shell provides a slower degradation rate and improves the mechanical, chemical, and physical properties. A membrane intended for GBR application is a barrier membrane used to guide alveolar bone regeneration by preventing fast-proliferating cells from growing into the bone defect site. In the present work, a core/shell nanofibrous membrane, composed of PCL as shell and PVA:Gly as core, was developed utilizing the coaxial electrospinning technique and characterized morphologically, mechanically, physically, chemically, and thermally. Moreover, the characterization results of the core/shell membrane were compared to monolithic electrospun PCL, PVA, and PVA:Gly fibrous membranes. The results showed that the core-shell membrane appears to be a good candidate for GBR application with a nano-scale fiber of 412 ± 82 nm and microscale pore size of 6.803 ± 0.035 μm. Moreover, the wettability of 47.4 ± 2.2° contact angle (C.A) and mechanical properties of 135 ± 3.05 MPa average modulus of elasticity, 4.57 ± 0.04 MPa average ultimate tensile stress (UTS), and 39.43% ± 0.58% average elongation at break are desirable and suitable for GBR application. Furthermore, the X-ray diffraction (XRD) and transmission electron microscopy (TEM) results exhibited the formation of β-Gly.

Bone formation recovery with gold nanoparticle-induced M2 macrophage polarization in mice

The prevention of fractures induced by inflammatory bone disease remains a clinical challenge. This is because of a lack of bone formation to fill in the bone defects, which are believed to be due in part to persistent inflammation caused by the imbalance of M1 over M2 macrophages. In this study, gold nanoparticles (AuNPs) were synthesized to shift the balance of macrophages at the site of bone damage to improve osteanagenesis in a mouse model of LPS-induced inflammatory bone erosion. Specifically, the AuNPs treatment improved bone structure and increased bone mineral density (BMD) by ~14% compared with model group. Macrophages recruited by LPS treatment were reduced by ~11% after AuNPs injection. Compared to LPS treatment only, the percentage of M2 macrophages increased threefold by AuNPs, while the proportion of M1 macrophages decreased by 59%. This promoted the regeneration of bone matrix proteins in the bone defect site, which finally leads to increased bone mass and improved bone structure in model mice. These data suggest that AuNPs could be a novel candidate therapeutic for inflammatory bone disease rather than a drug carrier.

Directional homing of glycosylation-modified bone marrow mesenchymal stem cells for bone defect repair

BackgroundOne of the greatest challenges for tissue-engineered bone is the low survival rate of locally grafted cells. The cell homing technology can effectively increase the number of these grafted cells, therefore, enhancing the repair of bone defects. Here we explore the effect of fucosylation modification on the directional homing of bone marrow mesenchymal stem cells (BMSCs) and their ability to repair bone defects.ResultsGlycosylated BMSCs expressed high levels of the Sialyl Lewis-X (sLeX) antigen, which enabled the cells to efficiently bind to E- and P-selectins and to home to bone defect sites in vivo. Micro-CT and histological staining results confirmed that mice injected with FuT7-BMSCs showed an improved repair of bone defects compared to unmodified BMSCs.ConclusionsThe glycosylation modification of BMSCs has significantly enhanced their directional homing ability to bone defect sites, therefore, promoting bone repair. Our results suggest that glycosylation-modified BMSCs can be used as the source of the cells for the tissue-engineered bone and provide a new approach for the treatment of bone defects.Graphic

Facilitated and Controlled Strontium Ranelate Delivery Using GCS-HA Nanocarriers Embedded into PEGDA Coupled with Decortication Driven Spinal Regeneration.

Background and PurposeStrontium ranelate (SrR) is an oral pharmaceutical agent for osteoporosis. In recent years, numerous unwanted side effects of oral SrR have been revealed. Therefore, its clinical administration and applications are limited. Hereby, this study aims to develop, formulate, and characterize an effective SrR carrier system for spinal bone regeneration.MethodsHerein, glycol chitosan with hyaluronic acid (HA)-based nanoformulation was used to encapsulate SrR nanoparticles (SrRNPs) through electrostatic interaction. Afterward, the poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels were used to encapsulate pre-synthesized SrRNPs (SrRNPs-H). The scanning electron microscope (SEM), TEM, rheometer, Fourier-transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS) were used to characterize prepared formulations. The rabbit osteoblast and a rat spinal decortication models were used to evaluate and assess the developed formulation biocompatibility and therapeutic efficacy.ResultsIn vitro and in vivo studies for cytotoxicity and bone regeneration were conducted. The cell viability test showed that SrRNPs exerted no cytotoxic effects in osteoblast in vitro. Furthermore, in vivo analysis for new bone regeneration mechanism was carried out on rat decortication models. Radiographical and histological analysis suggested a higher level of bone regeneration in the SrRNPs-H-implanted groups than in the other experimental groups.ConclusionLocal administration of the newly developed formulated SrR could be a promising alternative therapy to enhance bone regeneration in bone-defect sites in future clinical applications.

Masquelet-Induced Membrane Characteristics in Chicken Radii Bone Defects.

This study evaluated the formation of a Masquelet-induced membrane created through the formation of segmental bone defects in the radii of 15 healthy domestic chickens. When the chickens were in a surgical plane of anesthesia, a 1.5-cm segmental bone defect was produced in the left radius, which was subsequently filled with a bone cement spacer during its pasty polymerization phase. The bone defects were evaluated through radiographic imaging immediately after surgery and at 7, 15, 21, and 30 days after the creation of the bone defect. Five birds were euthanatized at 15, 21, and 30 days postoperatively for histological evaluation of the bone defect site. Immediate postoperative radiographic examination of the radii showed the presence of bone cement, which occupied the segmental bone defect. Thirty days after the surgical procedure, the presence of new bone formation at the fractured extremities was evident in the 5 remaining chickens. Histologically, the induced-membrane had 3 distinct zones at 15 days postoperatively, including 1 cell layer in contact with the bone cement spacer, 1 layer with collagen fibers, and 1 layer in contact with muscle, which was composed of disorganized connective tissue, active fibroblasts, and blood vessels. Twenty-one days after surgery, the zones were less defined, and there were metaplastic areas comprising cartilage and bone. Postoperative, diffuse mineralization of the membrane was observed 30 days after the surgical procedure. Formation of the induced membrane was observed during all periods of evaluation. The best histological characteristics for the Masquelet-induced membrane were detected 15 days after the formation of the bone defect, suggesting this would be the optimal time for second-stage surgery for bone reconstruction.

Implantable blood clot loaded with BMP-2 for regulation of osteoimmunology and enhancement of bone repair

The treatment of large-area bone defects still faces many difficulties and challenges. Here, we developed a blood clot delivery platform loaded with BMP-2 protein (BMP-2@BC) for enhanced bone regeneration. Blood clot gel platform as natural biomaterials can be engineered from autologous blood. Once implanted into the large bone defect site, it can be used for BMP-2 local delivery, as well as modulating osteoimmunology by recruiting a great number of macrophages and regulating their polarization at different stages. Moreover, due to the deep-red color of blood clot gel, mild localized hyperthermia under laser irradiation further accelerated bone repair and regeneration. We find that the immune niche within the bone defect microenvironment can be modulated in a controllable manner by the blood clots implantation and laser treatment. We further demonstrate that the newly formed bone covered almost 95% of the skull defect area by our strategy in both mice and rat disease models. Due to the great biocompatibility, photothermal potential, and osteoimmunomodulation capacity, such technology shows great promise to be used in further clinical translation.

Efficacy of extracellular vesicles from dental pulp stem cells for bone regeneration in rat calvarial bone defects

BackgroundExtracellular vesicles (EVs) are known to be secreted by various cells. In particular, mesenchymal stem cell (MSC)-derived EVs (MSC-EVs) have tissue repair capacity and anti-inflammatory properties. Dental pulp stem cells (DPSCs), which are MSCs isolated from pulp tissue, are less invasive to the body than other MSCs and can be collected from young individuals. In this study, we investigated the efficacy of EVs secreted by DPSCs (DPSC-EVs) for bone formation.MethodsDPSC-EVs were isolated from the cell culture medium of DPSCs. DPSC-EVs were unilaterally injected along with collagen (COL), beta-tricalcium phosphate (β-TCP) or hydroxyapatite (HA) into rat calvarial bone defects. The effects of DPSC-EVs were analyzed by micro-computed tomography (micro-CT) and histological observation.ResultsMicro-CT showed that administration of DPSC-EVs with the abovementioned scaffolds resulted in bone formation in the periphery of the defects. DPSC-EVs/COL specifically resulted in bone formation in the center of the defects. Histological observation revealed that DPSC-EVs/COL promoted new bone formation. Administration of DPSC-EVs/COL had almost the same effect on the bone defect site as transplantation of DPSCs/COL.ConclusionsThese results suggest that DPSC-EVs may be effective tools for bone tissue regeneration.

Acceleration of bone formation using insitu-formed hyaluronan-hydrogel containing bone morphogenetic protein-2 in a mouse critical size bone defect model.

An enzymatic crosslinking strategy using hydrogen peroxide and horseradish peroxidase is receiving increasing attention for application with in situ-formed hydrogels (IFHGs). IFHGs may also be ideal carrier materials for bone repair, although their ability to carry bone morphogenetic protein-2 (BMP2) has yet to be examined. We examined the effectiveness of an IFHG made of hyaluronan (IFHG-HA) containing BMP2 for promoting bone formation in a mouse critical size bone defect model. C57/BL6J mice received a 2-mm femoral critical-sized bone defect before being randomly assigned to one of the following treatment groups (n =6): control (no treatment), IFHG-HA only, PBS with BMP2, and IFHG-HA with BMP2. X-ray radiographs were utilized to track new bone formation, and micro-computed tomography and histological examination were performed on new bone formed at the bone defect site two weeks after surgery. Mice treated with PBS with BMP2 and IFHG-HA with BMP2 had greater bone volume (BV) and bone mineral content (BMC) than those receiving control, and successfully achieved consolidation. Mice treated with IFHG-HA with BMP2 had significantly higher BV and BMC than those treated with PBS with BMP2. IFHG-HA may be an effective carrier for BMP2 to enable delivery for bone defect repair.

DOPA-derived electroactive copolymer and IGF-1 immobilized poly(lactic-co-glycolic acid)/hydroxyapatite biodegradable microspheres for synergistic bone repair

Abstract Owing to defect features (irregular shape and size) and local environments (e.g., pulsation of dura matter and proximity of the brain), the skull is one of the most difficult to repair. Electroactive microsphere systems with good injectability, adjustable size, high surface-to-volume ratio and surface modifiability, exhibit excellent bone regeneration potential. Herein, the electroactive microspheres were prepared by immobilizing aniline tetramer (AT) on poly(lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA) microspheres. Subsequently, the 3,4-hydroxyphenalyalanine-containing recombinant insulin-like growth-factor-1 (DOPA-IGF-1) inspired by bioorthogonal chemistry was designed by combining the recombinant DNA technology and tyrosinase treatment, and modified on electroactive scaffolds surface. The as-prepared microspheres exhibited excellent sphericity and homogeneity with an average diameter of 329.2 ± 16.5 μm. Interestingly, the electroactive microsphere exhibits significant cell proliferation and enhanced osteogenic differentiation, and combining with DOPA-IGF-1 can further synergistically induce mineralization and osteogenic differentiation. Rat calvarial defect repair experiments showed excellent repairability in forming mineralized collagen deposition within the transplanted composite microspheres scaffold in the bone defect site. Thus, biomimetic composite microsphere with electroactivity and bioactivity exhibits considerable potential for calvarial defect repair.

Masquelet technique for reconstructing bone defects in open lower limb fracture: Analysis of the relationship between bone defect and bone graft.

The aim of this study was to retrospectively analyze the experience of treating long segmental bone defects. Bone union was used as the criteria for the assessment of the quantitative relationship between tibial bone defects and bone grafts, which could help reduce the complication incidence in patients. A total of 45 patients with tibial bone defects treated with the Masquelet technique at the Ninth People's Hospital of Wuxi Affiliated to Soochow University between February 2013 and December 2017 were recruited. The age, sex, body mass index (BMI), complications, site of bone defect, length of bone defect, time from the first to the second stage of operation, and postoperative complications (including deep infection, absorption of bone graft, and bone union) were assessed. Forty-two patients, including 17 males (40.5%) and 25 females (59.5%), with segmental bone defect, met the inclusion criteria. The mean age of the patients was 38.5 years (22-55 years). Nineteen patients (45.2%) underwent multiple traumas. The mean length of the bone defect was 6.3cm. Six patients experienced complications, resulting in the incidence of complications of 14.3%. The relationship between the length of bone defect and volume of bone grafts was Y=7.210+6.954×X in patients treated with steel plates; Y=10.962+5.029×X for patients treated with intramedullary nails, and Y=11.498+5.474×X regardless of methods of internal fixation. Masquelet technique is effective and safe for the treatment of long segmental tibial bone defects. The present study revealed the quantitative relationship between the size of bone defects and bone grafts, thus providing evidence for the selection of treatment strategies for long segmental bone defects in clinical practices, as well as helping to reduce the incidence of complications in Masquelet technique.

BMP-2 and hMSC dual delivery onto 3D printed PLA-Biogel scaffold for critical-size bone defect regeneration in rabbit tibia

3D printing technology has various advantages, and the incorporation of bioactive substances into the 3D printed scaffold provides the biological and architectural characteristics of the scaffolds, which is very important for obtaining a good osseointegration effect. In this relation, this study prepared a novel porous hollow cage poly(lactic acid) (PLA) 3D printed scaffold and combined recombinant human bone morphogenetic protein-2 (rhBMP-2) and/or mesenchymal stem cells (MSCs) with Biogel composed of gelatin and alginate. Then, the scaffolds were used to evaluate the resulting bone regeneration through both in vitro and in vivo tests. The experimental group was divided into four groups as follows: only PLA scaffold (PLA); PLA scaffold filled with BMP-2 loaded on Biogel (P-BG-B2); PLA scaffold filled with MSCs encapsulated Biogel (P-BG-M); PLA scaffold filled with both BMP-2 and MSCs loaded on Biogel (P-BG-B2-M). Then in vitro results showed that the PLA-Biogel-based scaffold increased cell proliferation, and the P-BG-B2-M group showed a higher alkaline phosphatase activity and bone-related gene expression than was seen with the P-BG-M group at all the time points. It was shown that four weeks post-operative micro-CT analysis showed that within the defect site the P-BG-B2 group had a significantly higher percent bone volume (BV/TV) than the PLA group and P-BG-M group. And, out of the defect site, the P-BG-B2-M group BV/TV was shown significantly higher than the PLA group (p < 0.05). Histologically, defects in the P-BG-B2-M group showed a homogeneous new bone distribution, however the P-BG-B2 group and P-BG-M group presented a notably higher bone formation in the internal region than in the proximal region of the bone defect site. In conclusion, the 3D PLA-Biogel-based scaffold adapted rhBMP-2 and MSCs with carrier PLA showed good biocompatibility and high possibility as an effective and satisfactory bone graft material.

Custom-Made Horizontal and Vertical Maxillary Augmentation with Smartbone® On Demand™: A Seven-Year Follow-Up Case

The presence of non-sufficient bone height and width requires an increase in the amount of bone available to insert an implant. Different materials are described in the literature, and the “custom-made bone graft approach” is a modern option which currently requires a preoperative stage of studying the bone defect and designing the implant. SmartBone® (SB®) mimics the characteristics of healthy human bone. Thanks to the strong performance, high workability, resistance and shape retention of SB®, it is possible to obtain SmartBone® on DemandTM, a bone graft uniquely shaped exactly to patient specifications, produced by following the data precisely and contoured to the bone defect site. The aim of this study was to determine the success over 7 years following a customized SmartBone® on DemandTM, a xeno-hybrid bone graft and installation of implants in a maxillary horizontal and vertical atrophy. This case study presents the diagnosis for a 60-year-old male patient requesting the rehabilitation of his edentulous maxilla with dental implants. Preoperative evaluation included the study of photographs, a radiological examination and 3D reconstruction to assess the missing bone, implant size, positioning of implants and anatomical landmarks. Rehabilitation included the insertion of a custom-made xeno-hybrid bone block into the maxilla in order to restore the anatomy prior to the implants’ placement. The newly developed bone substitute SB® is a safe and effective material, and its custom-made variant SmartBone® on DemandTM has been shown to be a valid alternative to traditional autologous bone grafting techniques in terms of accuracy, absence of infection/rejection and overall clinical outcome.

Poly(POG)n loaded with recombinant human bone morphogenetic protein-2 accelerates new bone formation in a critical-sized bone defect mouse model

BackgroundDelivery of bone morphogenetic protein-2 (BMP-2) via animal-derived absorbable collagen materials is used for the treatment of large bone defects. However, the administration of bovine proteins to humans is associated with the risk of zoonotic complications. We therefore examined the effect of combining BMP-2 with collagen-like peptides, poly(POG)n, in a critical-sized bone defect mouse model.MethodsA 2-mm critical-sized bone defect was created in the femur of 9-week-old male C57/BL6J mice. Mice were randomly allocated into one of four treatment groups (n = 6 each): control (no treatment), poly(POG)n only, 0.2 μg, or 2.0 μg BMP-2 with poly(POG)n. New bone formation was monitored using soft X-ray radiographs, and bone formation at the bone defect site was examined using micro-computed tomography and histological examination at 4 weeks after surgery.ResultsAdministration of 2.0 μg of BMP-2 with poly(POG)n promoted new bone formation and resulted in greater bone volume and bone mineral content than that observed in the control group and successfully achieved consolidation. In contrast, bone formation in all other groups was scarce.ConclusionsOur findings suggest the potential of BMP-2 with poly(POG)n as a material, free from animal-derived collagen, for the treatment of large bone defects.

Characterization of Tissue-Engineered Human Periosteum and Allograft Bone Constructs: The Potential of Periosteum in Bone Regenerative Medicine

Delayed-union or non-union between a host bone and a graft is problematic in clinical treatment of segmental bone defects in orthopedic cases. Based on a preliminary study of human periosteum allografts from this laboratory, the present work has extensively investigated the use of human cadaveric tissue-engineered periosteum-allograft constructs as an approach to healing such serious orthopedic surgical situations. In this current report, human cadaveric periosteum-wrapped bone allografts and counterpart controls without periosteum were implanted subcutaneously in athymic mice (nu/nu) for 10, 20, and, for the first time, 40 weeks. Specimens were then harvested and assessed by histological and gene expression analyses. Compared to controls, the presence of new bone formation and resorption in periosteum-allograft constructs was indicated in both histology and gene expression results over 40 weeks of implantation. Of several genes also examined for the first time, RANKL and SOST expression levels increased in a statistically significant manner, data suggesting that bone formation and the presence of increasing numbers of osteocytes in bone matrices had increased with time. The tissue-engineering strategy described in this study provides a possible means of improving delayed-union or non-union at the healing sites of segmental bone defects or bone fractures. The potential of periosteum and its resident cells could thereby be utilized effectively in tissue-engineering methods and tissue regenerative medicine.

Periosteum progenitors could stimulate bone regeneration in aged murine bone defect model.

Periosteal stem cells are critical for bone regeneration, while the numbers will decrease with age. This study focused on whether Prx1+ cell, a kind of periosteal stem cell, could stimulate bone regeneration in aged mice. Four weeks and 12 months old Prx1CreER‐GFP; Rosa26tdTomato mice were used to reveal the degree of Prx1+ cells participating in the femoral fracture healing procedure. One week, 8 weeks, 12 and 24 months old Prx1CreER‐GFP mice were used to analyse the real‐time distribution of Prx1+ cells. Twelve months old C57BL/6 male mice (n = 96) were used to create the bone defect model and, respectively, received hydrogel, hydrogel with Prx1− mesenchymal stem cells and hydrogel with Prx1+ cells. H&E staining, Synchrotron radiation‐microcomputed tomography and mechanical test were used to analyse the healing results. The results showed that tdTomato+ cells were involved in bone regeneration, especially in young mice. At the same time, GFP+ cells decreased significantly with age. The Prx1+ cells group could significantly improve bone regeneration in the murine bone defect model via directly differentiating into osteoblasts and had better osteogenic differentiation ability than Prx1− mesenchymal stem cells. Our finding revealed that the quantity of Prx1+ cells might account for decreased bone regeneration ability in aged mice, and transplantation of Prx1+ cells could improve bone regeneration at the bone defect site.

Evaluation of Resorption and Osseointegration of Autogenous Bone Ring Grafting in Vertical Bone Defect With Simultaneous Implant Placement in Dogs.

The aim of this research was to evaluate the resorption and osseointegration of an autogenous bone ring, which was grafted in a local vertical alveolar defect with simultaneous implant placement. Six Beagle dogs were enrolled in the study; their 4 nonadjacent mandibular premolars were extracted, and the buccal plate was removed to create bone defects in 2 of the 4 sites. Three months after extraction, Straumann implants (Ø 3.3 mm, length of 8 mm) were placed in the bone defect sites with simultaneous autogenous bone ring grafting and in the conventional extraction sites. After a 3-month healing period and a 3-month loading period, the animals were euthanized. The harvested samples were analyzed using micro-computed tomography (CT) scanning and histological analysis. From the micro-CT measurements, the average vertical bone resorption of the bone ring was 0.23 ± 0.03 mm, which was not significantly different from that around the conventional implant, 0.24 ± 0.12 mm (P > .05). The ratio of the bone volume to the total volume of the bone ring group was 91.11 ± 0.02, which was higher than that of the control group, 88.38 ± 2.34 (P < .05). From the hard tissue section, the bone rings developed fine osseointegration with the implants and the base alveolar bone. The results suggest autogenous bone ring grafting with simultaneous implant placement can survive in a local vertical bone defect with little bone resorption and good osseointegration in dogs with strict management. A bone ring graft must be compared with guided bone regeneration, and a larger and longer observation must be confirmed in clinical patients.