Application of the biological principle of induced osteogenesis for craniofacial defects

Mesenchymal stem cells in craniofacial reconstruction: a comprehensive review

Craniofacial reconstruction faces many challenges, including high complexity, strong specificity, severe injury, irregular and complex wounds, and high risk of bleeding. Traditionally, the "gold standard" for treating craniofacial bone defects has been tissue transplantation, which involves the transplantation of bone, cartilage, skin, and other tissues from other parts of the body. However, the shape of craniofacial bone and cartilage structures varies greatly and is distinctly different from ordinary long bones. Craniofacial bones originate from the neural crest, while long bones originate from the mesoderm. These factors contribute to the poor effectiveness of tissue transplantation in repairing craniofacial defects. Autologous mesenchymal stem cell transplantation exhibits excellent pluripotency, low immunogenicity, and minimally invasive properties, and is considered a potential alternative to tissue transplantation for treating craniofacial defects. Researchers have found that both craniofacial-specific mesenchymal stem cells and mesenchymal stem cells from other parts of the body have significant effects on the restoration and reconstruction of craniofacial bones, cartilage, wounds, and adipose tissue. In addition, the continuous development and application of tissue engineering technology provide new ideas for craniofacial repair. With the continuous exploration of mesenchymal stem cells by researchers and the continuous development of tissue engineering technology, the use of autologous mesenchymal stem cell transplantation for craniofacial reconstruction has gradually been accepted and promoted. This article will review the applications of various types of mesenchymal stem cells and related tissue engineering in craniofacial repair and reconstruction.

Self-Assembled Nanocomposite Hydrogels as Carriers for Demineralized Bone Matrix Particles and Enhanced Bone Repair

Demineralized bone matrix (DBM) has been widely used as an allogeneic alternative to autologous bone graft for bone repair. However, more extensive use of DBM is limited due to its particulate nature after demineralization and rapid particle dispersion following irrigation, resulting in unpredictable osteoinductivity. Here, a new design of injectable hydrogel carriers for DBM that combine self-healing ability and osteogenic properties based on the self-assembly of guanidinylated hyaluronic acid and silica-rich nanoclays is reported. The nanoclays serve as reversible linkages to form a dynamic hydrogel network with the guanidine moieties on the polymer chains. Gelation kinetics and mechanical properties can be controlled by altering nanoclay content in the hydrogel. The resulting hydrogel exerts self-healing ability due to its dynamic crosslinks and well retains its overall performance with high DBM loading. The hydrogel exhibits great cytocompatibility and osteogenic effects mediated by the nanoclays. In vivo delivery of DBM using the nanocomposite hydrogel further demonstrates robust bone regeneration in a mouse calvarial defect model in comparison to DBM delivered with aqueous HA. This work suggests a promising hydrogel platform for many applications including therapeutic delivery and tissue engineering.

Boosting osteogenic potential and bone regeneration by co-cultured cell derived extracellular matrix incorporated porous electrospun scaffold

Implants for bone regeneration to remedy segmental bone defects, osteomyelitis, necrotic bone tissue and non-union fractures have worldwide appeal. Although biomaterials offer most of the advantages by improving tissue growth but developments are more commonly achieved via biologically derived molecules. To aid site specific bone tissue regeneration by synthetic scaffold, cell derived extracellular matrix (ECM) can be a crucial component. In this study, co-cultured bone marrow mesenchymal stem cell and osteoblastic cells derived ECM incorporated electrospun polycaprolactone (PCL) membranes were assessed for bone tissue engineering application. The preliminary experimental details indicated that, co-culture of cells supported enhanced in vitro ECM synthesis followed by successful deposition of osteoblastic ECM into electrospun membranes. The acellular samples revealed retention of ECM related biomacromolecules (collagen, glycosaminoglycan) and partial recovery of pores after decellularization. In vitro biocompatibility tests ensured improvement of proliferation and osteoblastic differentiation of MC3T3-E1 cells in decellularized ECM containing membrane (PCL-ECM) compared to bare membrane (PCL-B) which was further confirmed by osteogenic marker proteins expression analysis. The decellularized PCL-ECM membrane allowed great improvement of bone regeneration over the bare membrane (PCL-B) in 8 mm size critical sized rat skull defects at 2 months of post implantation. In short, the outcome of this study could be impactful in development and application of cell derived ECM based synthetic electrospun templates for bone tissue engineering application.[Formula: see text].

Allogeneic Demineralized Dentin Matrix Graft for Guided Bone Regeneration in Dental Implants

Autogenous and allogeneic demineralized dentin matrices (Auto-DDM and Allo-DDM, respectively) are currently used for guided bone regeneration (GBR). Buccal marginal bone (BMB) resorption is critical for successful implant integration. This study analyzed BMB resorption around dental implants for GBR between the control group (Auto-DDM graft) and experimental group (Allo-DDM graft). From 2014 to 2019, we enrolled 96 patients (59 males, 37 females, average 57.13 years) who received GBR (52 and 44 using Allo-DDM and Auto-DDM, respectively,) without a barrier membrane and a simultaneous single dental implantation (54 in the maxilla and 42 in the mandible). BMB height was measured immediately after GBR, at prosthetic loading, and 12 months after loading. BMB resorption was classified as initial resorption (between GBR and prosthetic loading) and functional resorption (during 12 months after prosthetic loading). The differences in the BMB levels of Auto-DDM and Allo-DDM were analyzed between the initial and functional resorption stages by independent sample t-test. Auto-DDM and Allo-DDM showed similar BMB changes in initial resorption (0.73 ± 0.97 and 0.72 ± 0.77 mm, respectively) and functional resorption (0.69 ± 0.81 and 0.48 ± 0.58 mm, respectively) without a significant difference between the maxilla and mandible. For GBR, Allo-DDM is comparable to Auto-DDM in terms of BMB resorption.

Epileptic Syndrome and Cranioplasty: Implication of Reconstructions in the Electroencephalogram

BACKGROUND

In the presence of a skull deformity after large decompressive craniectomy (DC), neurologic deterioration manifesting as epileptic syndrome (ES) may occur independently of the primary disease or spontaneous improvement may be unduly impaired, and these unfavorable outcomes have sometimes been reversed by cranioplasty. The objective of this study was to analyze the influence of cranioplasty on the presence of ES in patients who underwent DC.

METHODS

A prospective study was performed from October 2016 to October 2017 involving patients who underwent DC and subsequent cranioplasty. Electroencephalographic (EEG) status before and after cranioplasty was analyzed in the presence of seizures and was compared with results after DC.

RESULTS

The sample included 52 patients. Male sex (78.8%) and traumatic brain injury (82.7%) were common indications for DC. ES after DC was verified in 26.9% of patients, and 50% of patients presented with abnormal EEG status. ES after cranioplasty was noted in 21.2% and 36.3% of patients followed by abnormal EEG status. All patients with precranioplasty epileptogenic paroxysms showed better EEG tracings after the procedure.

CONCLUSIONS

In routine clinical practice, altered amplitudes were observed in the region of bone defects. Although cranioplasty reduced pathologic EEG status (epileptogenic paroxysms), it was not able to produce new EEG tracings that could predict changes in seizure discharge or reduce ES.

Polyelectrolyte Complexes between Polycarboxylates and BMP-2 for Enhancing Osteogenic Differentiation: Effect of Chemical Structure of Polycarboxylates

Bone morphogenetic protein 2 (BMP-2) has received considerable attention because of its osteoinductivity, but its use is limited owing to its instability and adverse effects. To reduce the dose of BMP-2, complexation with heparin is a promising approach, because heparin enhances the osteoinductivity of BMP-2. However, the clinical use of heparin is restricted because of its anticoagulant activity. Herein, to explore alternative polymers that show heparin-like activity, four polycarboxylates, poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(aspartic acid) (PAsp), and poly(glutamic acid) (PGlu), were selected and their capability to modulate the osteoinductivity of BMP-2 was evaluated. Dynamic light scattering indicated that these polycarboxylates formed polyelectrolyte complexes with BMP-2. The osteogenic differentiation efficiency of MC3T3-E1 cells treated with the polycarboxylate/BMP-2 complexes was investigated in comparison to that of the heparin/BMP-2 complex. As a result, PGlu/BMP-2 complex showed the highest activity of alkaline phosphatase, which is an early-stage marker of osteogenic differentiation, and rapid mineralization. Based on these observations, PGlu could serve as an alternative to heparin in the regenerative therapy of bone using BMP-2.

Radiographic Evaluation of Low-Level Laser Therapy-Enhanced Maxillary Sinus Augmentation with Simultaneous Dental Implant Placement

Background

To evaluate the effect of low-level laser therapy (LLLT) on bone healing in patients undergoing bilateral sinus lifting and simultaneous dental implant application.

Methods

Twelve patients with total/partial posterior maxillary edentulism who needed bilateral sinus bone augmentation were included in the study. Dental implants were inserted in the same session. LLLT (λ = 630-660 nm, 25 mW/cm², 6 min) was used for one operation side on the 1^st, 3^rd, 5^th, and 7^th days, whereas contralateral side served as control side. Preoperative and postoperative 1^st, 3^rd, and 6^th month orthopantomograms were obtained using the aluminum step-wedge technique. Optic density analyses were performed using a Cardinal Health Digital Densitometer (Fluke Biomedical 07-443) with 1 mm diameter. Digital densitometry results were obtained as the equivalent aluminum thickness for each radiograph. These data were used to evaluate the changes in optical bone density and to compare the treatment side with the control side for each patient.

Results

The LLLT side showed better results than the control side according to the densitometry results. Increase in the bone density at all the postoperative intervals was statistically significant (P < 0.05).

Conclusions

LLLT enhances bone regeneration in sinus augmentation with simultaneous dental implant placement.

Antibiotic-loaded bone void filler accelerates healing in a femoral condylar rat model

AIMS

Demineralised bone matrix (DBM) is rarely used for the local delivery of prophylactic antibiotics. Our aim, in this study, was to show that a graft with a bioactive glass and DBM combination, which is currently available for clinical use, can be loaded with tobramycin and release levels of antibiotic greater than the minimum inhibitory concentration for Staphylococcus aureus without interfering with the bone healing properties of the graft, thus protecting the graft and surrounding tissues from infection.

MATERIALS AND METHODS

Antibiotic was loaded into a graft and subsequently evaluated for drug elution kinetics and the inhibition of bacterial growth. A rat femoral condylar plug model was used to determine the effect of the graft, loaded with antibiotic, on bone healing.

RESULTS

We found that tobramycin loaded into a graft composed of bioglass and DBM eluted antibiotic above the minimum inhibitory concentration for three days in vitro. It was also found that the antibiotic loaded into the graft produced no adverse effects on the bone healing properties of the DBM at a lower level of antibiotic.

CONCLUSION

This antibiotic-loaded bone void filler may represent a promising option for the delivery of local antibiotics in orthopaedic surgery. Cite this article: Bone Joint J 2016;98-B:1126-31.

Bone Regeneration Using Dentin Matrix Depends on the Degree of Demineralization and Particle Size

Objectives

This study aimed to examine the influence of particle size and extent of demineralization of dentin matrix on bone regeneration.

Materials and Methods

Extracted human teeth were pulverized and divided into 3 groups according to particle size; 200, 500, and 1000 μm. Each group was divided into 3 groups depending on the extent of demineralization; undemineralized dentin (UDD), partially demineralized dentin matrix (PDDM), and completely demineralized dentin matrix (CDDM). The dentin sample was implanted into rat calvarial bone defects. After 4 and 8 weeks, the bone regeneration was evaluated with micro-CT images, histomorphometric and immunohistochemical analyses. Osteoblasts were cultured on UDD and DDM to evaluate the cell attachment using electron microscope.

Results

Micro-CT images and histological observation revealed that CDDM had largely resorbed but UDD had not, and both of them induced little bone formation, whereas all particle sizes of PDDM induced more new bone, especially the 1000 μm. Electron microscopic observation showed osteoblasts attached to DDM but not to UDD.

Conclusions

PDDM with larger particle size induced prominent bone regeneration, probably because PDDM possessed a suitable surface for cell attachment. There might be an exquisite balance between its resorption and bone formation on it. PDDM could be considered as a potential bone substitute.

Milestones Contributing to the Evolution of Craniofacial Surgery

Craniofacial surgery (CFS) has a rich history of collaboration with a wide variety of surgical and nonsurgical specialties. This has resulted in a large volume of publications across this spectrum of subspecialties cataloging the advancements across the field. The authors aim to analyze the characteristics of the most cited articles in CFS. A literature search was performed using the Thomson/Reuters Web of Knowledge database to identify the top 50 most cited articles in CFS. The articles were analyzed for journal distribution, total citations, year of publication, citations per year, number of authors, type of article, institution, departmental affiliation, national affiliation, and top contributors. The articles were extracted from an assortment of 21 journals. The number of citations per article ranged from 115 to 1092 (average of 185). Forty-eight percent of articles were published in the 1990s, and 22% in the 2000s. The average number of years since publication until the present time was 21.34 (range 6-45 y). The most cited article (1092 citations and 52 citations/y) was an article by McCarthy et al on human mandible lengthening via gradual distraction. Departmental distribution indicated that the majority were attributable to departments of Plastic and Reconstructive Surgery for 21 articles (42%). Twenty articles were categorized under cranial defect/bone substitutes, 12 under craniosynostosis, 7 under surgical modeling, 6 under distraction osteogenesis, and the remaining 5 under other. These articles qualitatively represent important milestones in CFS. This study affirms the potential value of "number of citations" as a meaningful metric when assessing the importance of an article within CFS.

On the feasibility of utilizing allogeneic bone blocks for atrophic maxillary augmentation

Purpose. This systematic review was aimed at assessing the feasibility by means of survival rate, histologic analysis, and causes of failure of allogeneic block grafts for augmenting the atrophic maxilla. Material and Methods. A literature search was conducted by one reviewer in several databases. Articles were included in this systematic review if they were human clinical trials in which outcomes of allogeneic bone block grafts were studied by means of survival rate. In addition other factors were extracted in order to assess their influence upon graft failure. Results. Fifteen articles fulfilled the inclusion criteria and subsequently were analyzed in this systematic review. A total of 361 block grafts could be followed 4 to 9 months after the surgery, of which 9 (2.4%) failed within 1 month to 2 months after the surgery. Additionally, a weighed mean 4.79 mm (95% CI: 4.51–5.08) horizontal bone gain was computed from 119 grafted sites in 5 studies. Regarding implant cumulative survival rate, the weighed mean was 96.9% (95% CI: 92.8–98.7%), computed from 228 implants over a mean follow-up period of 23.9 months. Histologic analysis showed that allogeneic block grafts behave differently in the early stages of healing when compared to autogenous block grafts. Conclusion. Atrophied maxillary reconstruction with allogeneic bone block grafts represents a reliable option as shown by low block graft failure rate, minimal resorption, and high implant survival rate.

Use of lincomycin-impregnated demineralized freeze-dried bone allograft in the periodontal defect after third molar surgery

PURPOSE

The aim of the present study was to evaluate the periodontal regenerative capacity of demineralized freeze-dried bone allograft (DFDBA) alone or used with local lincomycin.

MATERIALS AND METHODS

In the present single-blind, randomized, controlled clinical trial, 20 subjects 26 years old or older, requiring extraction of bilateral third molars (M3s), were included. Each subject was randomly assigned to receive either DFDBA or DFDBA plus lincomycin therapy. Within the subjects, 1 M3 site was randomly selected to be the experimental site and the contralateral served as the control and was permitted to heal without intervention. The primary variables were changes in the probing depth (PD), clinical alveolar bone levels (ABLs), and radiographic alveolar bone density (ABD) on the distal aspect of second molar between baseline (immediately postoperatively) and 26 weeks postoperatively (T26). Appropriate sample sizes and descriptive, bivariate, and multivariate statistics were computed.

RESULTS

For both treatment and control sites, between T0 and T26, statistically significant improvements were seen in the ABLs and ABD (P < .05). Within-subject comparisons showed no significant differences in PD, ABL, or ABD between the treatment and control M3 sites at T0 or T26 (P > .05). Also, no significant differences were found in the PD, ABL, or ABD between the 2 treatment M3 sites at T26 (P > .05).

CONCLUSIONS

The results of the present study have revealed that the PD, ABL, and ABD improved after M3 removal in subjects 26 years old or older, irrespective of the treatment or control group. Reconstructive procedures (e.g., DFDBA with or without lincomycin therapy) did not offer predictable benefits compared with a no-treatment protocol in patients younger than 30 years old.

Cartilage tissue engineering of nasal septal chondrocyte-macroaggregates in human demineralized bone matrix

Tissue Engineering is an important method for generating cartilage tissue with isolated autologous cells and the support of biomaterials. In contrast to various gel-like biomaterials, human demineralized bone matrix (DBM) guarantees some biomechanical stability for an application in biomechanically loaded regions. The present study combined for the first time the method of seeding chondrocyte-macroaggregates in DBM for the purpose of cartilage tissue engineering. After isolating human nasal chondrocytes and creating a three-dimensional macroaggregate arrangement, the DBM was cultivated in vitro with the macroaggregates. The interaction of the cells within the DBM was analyzed with respect to cell differentiation and the inhibitory effects of chondrocyte proliferation. In contrast to chondrocyte-macroaggregates in the cell-DBM constructs, morphologically modified cells expressing type I collagen dominated. The redifferentiation of chondrocytes, characterized by the expression of type II collagen, was only found in low amounts in the cell-DBM constructs. Furthermore, caspase 3, a marker for apoptosis, was detected in the chondrocyte-DBM constructs. In another experimental setting, the vitality of chondrocytes as related to culture time and the amount of DBM was analyzed with the BrdU assay. Higher amounts of DBM tended to result in significantly higher proliferation rates of the cells within the first 48 h. After 96 h, the vitality decreased in a dose-dependent fashion. In conclusion, this study provides the proof of concept of chondrocyte-macroaggregates with DBM as an interesting method for the tissue engineering of cartilage. The as-yet insufficient redifferentiation of the chondrocytes and the sporadic initiation of apoptosis will require further investigations.

Demineralized bone particle impregnated poly(l-lactide-co-glycolide) scaffold for application in tissue-engineered intervertebral discs

Demineralized bone particle (DBP) contains powerful bioactive molecules that facilitate new bone or cartilage growth. We developed hybrid scaffolds of poly(l-lactide-co-glycolide) (PLGA) with various concentrations of DBP (DBP/PLGA), of which phenotypes on intervertebral disc (IVD) cells were investigated. The hybrid scaffold has a cylindrical donut shape with two distinct parts; the inner is for the nucleus pulposus (NP) and the outer is for annulus fibrosus (AF). Rabbit NP and AF cells were seeded into the inner and outer regions of the DBP/PLGA scaffolds separately. Disc cell viability in DBP/PLGA scaffolds was superior to pure PLGA scaffold and increased with increasing DBP concentration. In vitro- and in vivo-formed tissues were characterized by RT-PCR, Safranin-O, Masson's trichrome staining and immunohistochemi- cal staining for type-I and type-II collagen. DBP/PLGA hybrid scaffolds revealed more active expression of disc phenotypes, as characterized by protein and mRNA expression, than the PLGA control. This study provides valuable information for potential disc replacement using DBP and PLGA.

Osteoconductivity and osteoinductivity of NanoFUSE(®) DBM

Bone graft substitutes have become an essential component in a number of orthopedic applications. Autologous bone has long been the gold standard for bone void fillers. However, the limited supply and morbidity associated with using autologous graft material has led to the development of many different bone graft substitutes. Allogeneic demineralized bone matrix (DBM) has been used extensively to supplement autograft bone because of its inherent osteoconductive and osteoinductive properties. Synthetic and natural bone graft substitutes that do not contain growth factors are considered to be osteoconductive only. Bioactive glass has been shown to facilitate graft containment at the operative site as well as activate cellular osteogenesis. In the present study, we present the results of a comprehensive in vitro and in vivo characterization of a combination of allogeneic human bone and bioactive glass bone void filler, NanoFUSE(®) DBM. NanoFUSE(®) DBM is shown to be biocompatible in a number of different assays and has been cleared by the FDA for use in bone filling indications. Data are presented showing the ability of the material to support cell attachment and proliferation on the material thereby demonstrating the osteoconductive nature of the material. NanoFUSE(®) DBM was also shown to be osteoinductive in the mouse thigh muscle model. These data demonstrate that the DBM and bioactive glass combination, NanoFUSE(®) DBM, could be an effective bone graft substitute.

Clinical evaluation of demineralized bone allograft for sinus lifts in humans: a clinical and histologic study

PURPOSE

Severe alveolar bony resorption in the edentulous posterior maxilla and pneumatization of the maxillary sinus wall make traditional implant placement impossible in the posterior maxilla. To reconstruct the severely resorbed maxilla for dental implant placement, 1 successful technique is to elevate the maxillary sinus floor using demineralized bone matrix (DBM) grafts. The purpose of this study was to evaluate a histologic and histomorphometric evaluation of DBM grafts in the human maxilla.

PATIENTS AND METHODS

Nine months after grafting, at the time of dental implantation, biopsy samples were taken from the grafted areas of 8 patients and were analyzed histologically.

RESULTS

All the sinus lifts were successful in the clinical study conducted after implantation. Resorption of the graft materials and new bone formation were observed, and there was direct deposition of bone on the surface of the graft particles.

CONCLUSION

The results of this study indicate that limited maxillary sinus lift with DBM graft material is a clinically reliable preimplant procedure.

Osteoconductivity and Osteoinductivity of Puros® DBM Putty

Bone graft substitutes have been developed due to the limited supply and morbidity associated with using autogenous graft material. Allogeneic demineralized bone matrix (DBM) has been used extensively as a clinical graft material because of its inherent osteoinductive and osteoconductive properties. Differential enhancement of these properties may optimize the performance of these products for various orthopedic and craniofacial applications. Commercially available bone paste products consist of formulations that combine DBM with a carrier to facilitate handling and containment. In the present study, we present results of a comprehensive in vitro and in vivo characterization of a 100% human DBM putty product, Puros DBM Putty. Results indicate the DBM particles are completely dispersed in the putty. Data are presented showing the porosity of and cell attachment to Puros DBM Putty, thereby demonstrating the osteoconductive properties of this DBM. Puros DBM Putty was also shown to be osteoinductive in the rat ectopic pouch model. We demonstrate here for the first time that Puros DBM Putty maintains its activity to markedly stimulate or induce bone formation over the entire period of its shelf life. Taken together, these data demonstrate that the 100% human allograft derived Puros DBM Putty could be an effective bone graft substitute.

Direct chemical cross-linking of platelet-derived growth factor-BB to the demineralized bone matrix improves cellularization and vascularization

In previous studies, we have described the use of demineralized bone matrix (DBM) as a carrier for the localized delivery system of growth factors in vitro and in vivo. The aim of the present work was to develop a direct chemical approach to immobilize the platelet-derived growth factor-BB (PDGF-BB) on DBM with cross-linking reagents. The amount of PDGF-BB covalently immobilized on DBM was significantly increased. The increased proliferation of fibroblasts demonstrated that the biological activity of PDGF-BB was not significantly reduced by cross-linking. Compared with control groups, there was a statistically significant increase in blood vessel density in the PDGF-C-DBM group after having been subcutaneously implanted into the dorsal side of the rats. The surface bioactivity of scaffolds on stimulation cell and new blood vessel invasion was improved. Therefore, the direct chemical cross-linking approach could be used to retain growth factors on collagen scaffolds effectively to develop functional biomaterials.

No influence of alimentary zinc on the healing of calvarial defects filled with osteopromotive substances in rats

Zinc has been demonstrated to play an important role in bone metabolism and is required for normal growth. However, no studies have investigated the influence of zinc on calvarial bone healing in aged or adult rats. The aim of the study was to evaluate whether alimentary zinc supplementation and depletion affect bone healing of calvarial defects implanted with osteopromotive substances in adult rats. Two 5 mm full thickness critical size bone defects were trephined in the central part of each parietal bone of 60 six-month-old male Wistar rats. The bone defects were filled with demineralized bone matrix (DBM), autogenous bone chips, or were left as unfilled controls. The rats were divided into three groups of 20 rats each and received a semi-synthetic diet containing 20, 60, or 120 mg zinc/kg. After 4 months, the biomechanical integrity of the healing defects was evaluated by a punch out test and the healed defects were examined with histomorphometry. Statistical analysis of the data was carried out by two-way analysis of variance and Wilcoxon's non-parametric signed rank test. Biomechanical testing revealed that the maximum load was significantly higher in DBM-filled defects than in those filled with autogenous bone, and that the defects filled with autogenous bone were stronger than the unfilled controls. The biomechanical findings indicated that the alimentary zinc content did not influence the healing of calvarial defects. No significant difference in maximum load could be established between the three diet groups for any of the filling materials, whereas the highest zinc supplement resulted in an increase in the relative extension on mineralizing surfaces in the control group. Thus, healing of adult rat calvarial defects is not influenced by alimentary zinc supplementation or depletion. Defects filled with DBM were significantly stronger and exhibited significantly more new bone formation than defects filled with autogenous bone or unfilled controls.

Loading of VEGF to the heparin cross-linked demineralized bone matrix improves vascularization of the scaffold

Deficient vascularization is one of the prominent shortcomings of porous tissue-engineering scaffolds, which results in insufficient oxygen and nutrients transportation. Here, heparin cross-linked demineralized bone matrices (HC-DBM) pre-loaded with vascular endothelial growth factor (VEGF) were designed to promote cells and new microvessels invasion into the matrices. After being chemical crosslinked with heparin by N-hydroxysuccinimide and N-(3-di-methylaminopropyl)-N'-ethylcarbodiimide, the scaffold could bind more VEGF than the non-crosslinked one and achieve localized and sustained delivery. The biological activity of VEGF binding on heparinized collagen was demonstrated by promoting endothelial cells proliferation. Evaluation of the angiogenic potential of heparinized DBM loaded with VEGF was further investigated by subcutaneous implantation. Improved angiogenesis of heparinized DBM loaded with VEGF was observed from haematoxylin-eosin staining and immunohistochemistry examination. The results demonstrated that heparin cross-linked DBM binding VEGF could be a useful strategy to stimulate cells and blood vessels invasion into the scaffolds.

Effects of e-beam radiation, storage, and hydration on osteoinductivity of DBM/AM composite

E-beam irradiation is often used to sterilize medical devices including demineralized bone matrix (DBM) products. In this study, the effect of e-beam on osteoinductivity of a DBM product in hydrous and anhydrous configurations has been evaluated at 0-, 6- and 12-month ambient storage using a nude rat muscle pouch model. The thermal and structural stabilities of DBM and acellular dermal matrix (AM) composites were analyzed using differential scanning calorimetry (DSC) and trypsin digestion assay. Both hydrous and anhydrous DBM/AM composites exhibited osteoinductivity after e-beam irradiation of 15 kGy. After 12-month ambient storage, the osteoinductivity of hydrous DBM/AM was diminished, whereas the anhydrous DBM/AM retained its osteoinductive potential. However, the DSC and trypsin analysis revealed that the DBM in anhydrous DBM/AM was more vulnerable to damage from e-beam irradiation than its hydrous counterpart. This study has found that although the anhydrous DBM has more structural damage than hydrous DBM from e-beam irradiation, it has retained its osteoinductivity better after 1-year ambient storage.

Evaluation of bone matrix and demineralized bone matrix incorporated PLGA matrices for bone repair

The aim of this study was to evaluate the composite matrices prepared using Poly(lactic-co-glycolic acid)- PLGA (85:15) by incorporating human bone matrix (BM) powder or demineralized bone matrix (DBM) powder with the weight ratio of polymer: BM or DBM (75:25) to apply for bone repair. Murine Bone Marrow Stromal Cell (BMSC) attachment was studied with different time points at 30 min, 1 h, 2 h, 4 h, and 6 h for BM/PLGA, DBM/PLGA and PLGA control matrices. All types of matrices were linearly increased the BMSC attachment with the increase of time. Significantly higher number of BMSCs was attached to the both BM/PLGA and DBM/PLGA matrices after 2 h compared to the controls. If BM or DBM is incorporated into biodegradable PLGA matrices and cultured with BMSCs, those composite matrices could be potentially used for bone tissue engineering applications. In addition, particle migration and handling difficulties in DBM powder in clinical applications eliminate using a PLGA matrix. Furthermore, we have observed that DBM/PLGA matrices were structurally stronger compared to the BM/PLGA or control PLGA matrices when they exposed to physiological environment for 72 days.

Effects of gamma-irradiation, storage and hydration on osteoinductivity of DBM and DBM/AM composite

This study investigated the effect of gamma-irradiation dose, irradiation temperature, hydration and storage condition on osteoinductivity of demineralized bone matrix (DBM) and demineralized bone matrix/acellular dermal matrix (DBM/AM) composite. DBM and DBM/AM in dry and hydrated form were treated with gamma-irradiation of 15-40 kGy at ambient or low temperature (-40 degrees C approximately -70 degrees C) and then stored at ambient condition for 6 months. The athymic rat muscle implant model was used to evaluate the osteoinductive potential of the DBM and DBM/AM composites. Histological and alkaline phosphatase (ALPase) activity assessments were carried out at 28 days after implantation to determine the new bone formation and ALPase activity. Both histological and ALPase activity analysis showed that the osteoinductivity of DBM decreased with the increase of gamma-irradiation dose at ambient temperature, whereas no decrease occurred when treated with gamma-irradiation at low temperature. However, the hydrated DBM showed diminishing osteoinductivity after 6-month storage at ambient condition, whereas the DBM in dry form retained their osteoinductivity after the 6-months storage. The findings in this study indicate that DBM and DBM/AM composites could retain their osteoinductivity when they are in dry configuration and are irradiated at low temperature (-40 degrees C approximately -70 degrees C) using the custom-made cold gamma-irradiation system.

Acceleration of biomimetic mineralization to apply in bone regeneration

The delivery of growth factors and therapeutic drugs into bone defects is a major clinical challenge. Biomimetically prepared bone-like mineral (BLM) containing a carbonated apatite layer can be used to deliver growth factors and drugs in a controlled manner. In the conventional biomimetic process, BLM can be deposited on the biodegradable polymer surfaces by soaking them in simulated body fluid (SBF) for 16 days or more. The aim of this study was to accelerate the biomimetic process of depositing BML in the polymer surfaces. We accelerated the deposition of mineral on 3D poly(lactic-co-glycolic acid) (PLGA) porous scaffolds to 36-48 h by modifying the biomimetic process parameters and applying surface treatments to PLGA scaffolds. The BLM was coated on scaffolds after surface treatments followed by incubation at 37 degrees C in 15 ml of 5x SBF. We characterized the BLM created using the accelerated biomineralization process with wide angle x-ray diffraction (XRD), Fourier transform infrared (FTIR) microscopy, and scanning electron microscopy (SEM). The FTIR and XRD analyses of mineralized scaffolds show similarities between biomimetically prepared BLM, and bone bioapatite and carbonated apatite. We also found that the BLM layer on the surface of scaffolds was stable even after 21 days immersed in Tris buffered saline and cell culture media. This study suggests that BLM was stable for at least 3 weeks in both media, and therefore, BLM has a potential for use as a carrier for biological molecules for localized release applications as well as bone tissue engineering applications.

Haemopoietic growth factors: their relevance in osteoclast formation and function

The major recent advance in our knowledge of the haemopoietic system has been the purification and characterization of a family of haemopoietic growth factors, and their availability in recombinant form. In the bone marrow the sequences of differentiation and proliferation leading to the production of mature cells that these factors regulate may be determined by the relative availability of the factors in microenvironmental domains. The observation that growth factor-producing cells and haemopoietic progenitor cells are not evenly distributed in the bone marrow leads us to expect that the overall effect of growth factors (and other regulatory molecules) on the production and function of macrophages and osteoclasts may differ when in vivo or in vitro assays are used as end-points and, in the latter case, when whole marrow or purified cell populations are tested. The availability of an in vitro assay in which osteoclast-like cells are generated will allow these concepts to be tested.

Impaired osteoinduction in a rat model for chronic alcohol abuse

Alcohol abuse is a risk factor for bone fractures. Following a fracture, alcoholics have a higher risk for impaired fracture healing. However, the specific alcohol-induced defect(s) in bone healing are not known. Alcohol is a potent inhibitor of bone formation during bone growth and turnover. Thus, the purpose of this study was to determine the effects of alcohol consumption on induction of new bone formation. Demineralized allogeneic bone matrix (DABM) cylinders were used to model osteoinduction in a rat model for chronic alcohol abuse. DABM cylinders, prepared from femurs and tibiae of rats fed a normal diet, were implanted into sexually mature male rats adapted to alcohol (ethanol contributed 35% of caloric intake) or control liquid diets. Food intake in the control rats was restricted to match food intake of alcohol-fed animals. The implants were recovered 6 weeks later and analyzed by histology, muCT and chemical analysis. Histological evaluation revealed a robust osteoinductive response, resulting in mature bone ossicle formation, in DABM implants in rats fed the control diet. Alcohol consumption affected bone mass and architecture of the DABM implants but not volumetric density or mineral composition. Specifically, alcohol consumption resulted in significant decreases in DABM-induced bone volume, bone volume/mg original cylinder weight, connectivity density, trabecular number and thickness, ash weight and % ash weight. There were no changes in mineral (ash) density nor in the relative amounts of calcium, magnesium, iron, selenium and zinc (microg/mg ash), indicating that alcohol consumption did not impair mineralization. Taken together, these results show that alcohol abuse resulted in decreased bone formation within the DABM implant. We conclude that reduced osteoinduction may contribute to impaired bone healing in alcoholics.

Biological Assessment of Porous-Implant Hydroxyapatite Combined With Periosteal Grafting in Maxillary Defects

PURPOSE

To investigate the use of porous hydroxyapatite (HA) combined with periosteal graft to repair an induced maxillary bone defect.

MATERIALS AND METHODS

A defect was produced in the premaxillary bone of rats. Four groups were used: 1) those treated with the mucoperiosteal graft from the premaxilla; 2) those treated with HA combined with mucoperiosteal graft from the premaxilla; 3) those treated with HA combined with periosteal graft from the femur; and 4) those treated with periosteal graft from the femur.

RESULTS

The radiographic aspects from all groups showed no signs of bone formation after 2 weeks. After 16 weeks, there was evidence of points of radiolucency inside the HA implants. Cell proliferation occurred from the periosteum covering the defect. Bone tissue grew from the defect margin to inside the defect in all cases. Mature bone was seen around the HA implants after 8 and 16 weeks.

CONCLUSION

The periosteal graft provides satisfactory support to the HA implant, allowing the growth of new bone.

Clinical results of localized alveolar ridge augmentation with bone grafts harvested from symphysis in comparison with ramus

Background and aims

Autogenous onlay bone grafting is a common procedure for alveolar ridge augmentation. It has been suggested that the amount of healed bone after this technique would be significantly less than the initial quantity. The aim of this study was to determine the relationship between the various parameters influencing the outcome of ridge augmentation procedures.

Materials and methods

Thirty-two patients, 17 males and 15 females (mean age 40 ± 8.66), requiring lateral ridge augmentation in the anterior maxilla were recruited. Bone grafts obtained from either the mandibular ramus or symphysis were grafted on the recipient site and the buccolingual dimensions of the edentulous ridge before and six months after the procedure were measured and the difference between them was considered as ridge augmentation (RA). Parameters including graft thickness (GT), graft area (GA) and donor site (DS) were also recorded.

Results

Onlay bone grafts, taken from mandibular and symphysis areas, significantly increased the buccolingual dimension of the alveolar ridge (mean 1.98 ± 1.22 mm, p< 0.001). However, the mean RA by symphysis grafts was significantly greater than ramus grafts (2.49 mm vs. 1.48 mm). There was also a significant correlation between graft thickness, surface area and the amount of bone augmentation.

Conclusion

Symphysis area provides thicker and larger grafts, which may result in a better clinical outcome in alveolar ridge augmentation.

Safety and efficacy of use of demineralised bone matrix in orthopaedic and trauma surgery

Demineralised bone matrix (DBM) acts as an osteoconductive, and possibly as an osteoinductive, material. It is widely used in orthopaedic, neurosurgical, plastic and dental areas. More than 500,000 bone grafting procedures with DBM are performed annually in the US. It does not offer structural support, but it is well suited for filling bone defects and cavities. The osteoinductive nature of DBM is presumably attributed to the presence of matrix-associated bone morphogenetic proteins (BMPs) and growth factors, which are made available to the host environment by the demineralisation process. Clinical results have not been uniformly favourable; however, a variable clinical response is attributed partly to nonuniform processing methods found among numerous bone banks and commercial suppliers. DBMs remain reasonably safe and effective products. The ultimate safe bone-graft substitute, one that is osteoconductive, osteoinductive, osteogenic and mechanically strong, remains elusive.

Evaluation of bone regeneration at critical-sized calvarial defect by DBM/AM composite

This study investigated the bone-regenerative potential of a demineralized bone and acellular matrix (DBM/AM) composite (AlloCraft DBM) in comparison with autologous bone using an in vivo model. Critical-sized calvarial defects (5 mm) were created in athymic rats. The defects were grafted with either the DBM/AM composite or the acellular human dermal matrix (AM), and compared with the defects filled with autologous bone (positive control) and the empty defect (negative control). Histological and radiographic assessments were carried out at 4 and 8 weeks after surgery to determine the biological healing, the amount and type of new bone formation and the percentage of new bone filled in the critical defects. At 4 weeks, DBM/AM composite group had the highest percentage of the defect filled with new bone (84%), which was significantly greater than autologous bone (62%), AM (41%), and untreated control (32%) groups. At 8 weeks, the DBM/AM continued to have the highest percentage of the defect filled with new bone (91%). The autologous bone group increased the percentage of bone fill to 83%. The defects either filled with AM or left untreated still had less of the defect filled with new bone, 57% and 33%, respectively. The total healing of defects grafted with DBM/AM was comparable with autologous bone group at 8 weeks. The results demonstrated that the DBM/AM composite promoted new bone formation more rapidly than autologous bone at calvarial defect in athymic rats. The study supports that DBM/AM is a potential substitute of autologous bone for bone repair.

Prefabrication of Vascularized Bone Flap by Demineralized Bone Matrix

Demineralized bone matrix (DBM) has been reported to have osteoconductive and osteoinductive properties and has been clinically used as a bone graft alternative. In the present study we attempted to generate a vascularized bone flap by subcutaneous implantation of DBM with a vascular loop to provide blood supply in a rat model. Thirty male Sprague-Dawley rats were divided into two groups according to the presence or absence of blood supply. In the experimental group, the bone flap was created by application of 0.4 mL of DBM onto two pieces of gelatin sponge sheets between which a vascular loop was sandwiched. A prefabricated flap without a vascular loop served as the control. The flaps were biopsied at three different time intervals postoperatively (2, 4, and 6 weeks). The results showed that DBM induced subcutaneous bone formation in both of the groups. However, in the nonvascularized group, the amount of bony tissue had decreased at four postoperative weeks and continued to do so afterwards. In contrast, bone formation was active at four weeks in the vascularized group. Our study indicated that implantation of DBM can prefabricate a bone flap. Blood supply to the flap is considered a key factor of the success of this prefabrication.

An alternative sinus floor elevation procedure: trephine osteotomy

Today, the sinus floor elevation procedure is not only being used on a routine basis, but clinicians are reporting high success rates. The sinus floor graft has become an important option in the treatment of the edentulous posterior maxilla, where vertical bone height is less than ideal. A review of maxillary sinus floor elevation as an integral part of restoring the posterior maxillary is discussed. The related anatomy of the area and current osteotomy techniques are reviewed. This article describes a trephine osteotomy, which is an alternative technique to the existing lateral antrostomy approach currently being used.

Vascular endothelial growth factor augments the healing of demineralized bone matrix grafts

AIM

To produce a totally allogeneic graft material that would eliminate the need for harvesting the autogenous bone from patients.

MATERIALS AND METHODS

Thirty-six (10x5mm) defects were created in the parietal bones of 18 rabbits. Two experimental groups of 12 defects each were grafted with DBM(IM) alone and VEGF+DBM(IM), respectively. The remaining 12 defects were left empty as controls, and sacrificed on days 14, 30 and 60. Two rabbits, with four defects, of each group were sacrificed on day 14, 30 and 60 post grafting. The defects were retrieved for histological evaluation and quantitative analysis.

RESULTS

No bone formed across the defect in the controls. The difference in the amount of new bone formation between experimental groups was significant especially 30 and 60days post grafting (p<0.0001), which were 149% and 100% respectively.

CONCLUSION

VEGF+DBM(IM) powder is a promising graft material, and warrants further clinical investigation.

Effects of bone protein extract on human mesenchymal stem cells proliferation and differentiation

Since its osteoinductive capacity has been established, demineralized bone matrix is considered a suitable alternative to bone autograft in the healing of osseous defects. The mechanisms of bone formation induction are still not fully understood. In this study we assessed the effects of a dispersion of bovine bone extract COLLOSS (BPE) with regard to proliferation and differentiation of a human mesenchymal stem cell line overexpressing human telomerase reverse transcriptase (hMSC-TERT). Proliferation rate was determined by (3)H-thymidine incorporation. The differentiation of hMSC-TERT cells to osteoblastic cells was assessed by means of measuring alkaline phosphatase activity and collagen synthesis in vitro. Both undifferentiated and osteoblast-differentiated hMSC-TERT cells were investigated for response to BPE. The metabolic responses to BPE were compared to unstimulated cells and cells stimulated with bovine collagen (COL). Undifferentiated hMSC-TERT cells responded to BPE with increased proliferation and decreased alkaline phosphatase activity. Osteoblastic differentiated hMSC-TERT cells had a diminished proliferative response and an increased alkaline phosphatase activity and collagen synthesis. Our study demonstrated significant metabolic effects of BPE on hMSC-TERT cells, which were highly dependant on the differentiated state of the cells.

Bone morphogenetic proteins for spinal fusion

BACKGROUND CONTEXT

In 1965, Marshall Urist discovered that the extracellular matrix of bone contains the ability to induce new bone formation. This substance was later named bone morphogenetic protein (BMP). Since that time, BMPs have been extensively studied. Molecular clones have since been characterized and expressed as complementary DNAs (cDNAs). BMPs have recently been used in a multitude of mammalian clinical studies, including many recent human studies, for the purpose of evaluating their function in bone healing and spinal arthrodesis. BMPs are currently the most effective substitute available for bone graft as a means to eliminate the morbidity of iliac crest bone graft harvest and increase the rate of successful spinal arthrodesis.

PURPOSE

The purpose of this article is to review the history and recent advancements in the use of BMPs in spinal arthrodesis models, as well as discuss the possible future use of BMPs in this clinical setting.

STUDY DESIGN/SETTING

The setting of this review article is centered on classic and recent literature of BMPs with emphasis on anterior as well as posterolateral spinal arthrodesis.

METHODS

The classic and recent primary literature about BMPS and their clinical use in human and nonhuman mammals for spinal fusion was reviewed. Special emphasis is placed on animal and human studies of both recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human osteogenic protein-1 (rhOP-1, rhBMP-7).

RESULTS

BMPs are able to promote solid fusion in the spine in both the anterior and the posterolateral environments in animal studies and early human trials. Human trials to date have also shown an acceptable safety profile with the clinical use of these proteins.

CONCLUSIONS

Animal studies and early human trials of BMPs support the ability of these growth factors to enhance or replace autograft bone for spinal arthrodesis. Studies have shown this promotion of fusion in both the anterior interbody and the posterolateral environments. Future use of these factors is likely to continue to expand in clinical as well as research arenas.

Demineralized bone promotes chondrocyte or osteoblast differentiation of human marrow stromal cells cultured in collagen sponges

Demineralized bone implants have been used for many types of craniomaxillofacial, orthopedic, periodontal, and hand reconstruction procedures. In previous studies, we showed that demineralized bone powder (DBP) induces chondrogenesis of human dermal fibroblasts in a DBP/collagen sponge system that optimized interactions between particles of DBP and target cells in cell culture. In this study, we test the hypothesis that DBP promotes chondrogenesis or osteogenesis of human marrow stromal cells (hMSCs) in 3-D collagen sponge culture, depending upon the culture conditions. We first confirmed that hMSCs have chondrogenic potential when treated with TGF-beta, either in 2-D monolayer cultures or in 3-D porous collagen sponges. Second, we found that DBP markedly enhanced chondrogenesis in hMSCs in 3-D sponges, as assessed by metachromasia and expression of chondrocyte-specific genes AGGRECAN, COL II, and COL X. Human dermal fibroblasts (hDFs) were used to define mechanisms of chondroinduction because unlike hMSCs they have no inherent chondrogenic potential. In situ hybridization revealed that hDFs vicinal to DBPs express chondrocyte-specific genes AGGRECAN or COL II. Macroarray analysis showed that DBP activates TGF-beta/BMP signaling pathway genes in hDFs. Finally, DBP induced hMSCs to express the osteoblast phenotype when cultured with osteogenic supplements. These studies show how culture conditions can influence the differentiation pathway that human marrow stromal cells follow when stimulated by DBP. These results support the potential to engineer cartilage or bone in vitro by using human bone marrow stromal cells and DBP/collagen scaffolds.

A review of osteoinductive testing methods and sterilization processes for demineralized bone

Allogeneic demineralized bone has been used extensively as a clinical graft material because it has osteoinductive and osteoconductive properties. Concerns over processing and terminal sterilization procedures that may reduce performance have led clinicians to call for assurances of product potency. There is extensive experience on effects of demineralized bone in animal and cell culture models with the possibility for future evidence-based standards for release of products. Evaluation of the current state of knowledge leads to the fact that we cannot conclude that performance of different lots of demineralized bone allografts in in vivo or in vitro test systems can be used as a measure of clinical performance. It may be possible to adopt an osteoinductivity standard for release-to-market, but it should be followed by clinical monitoring and further research.

DBM induced ectopic bone formation in the rat: the importance of surface area

Demineralized bone matrix (DBM) has been shown to induce ectopic endochondral bone formation, when intramuscularly implanted in rats. In earlier studies we have found a variation in bone formation capacity of this DBM. This might be due to the properties of the DBM itself, but the use of DBM blocks could be of influence as well. Therefore, this study was designed to investigate whether increasing the surface area of the DBM by morsellizing, influences the bone formation capacity. In view of this, DBM implants and morsellized DBM (MDBM) implants were placed intramuscularly in a rat model. At six weeks the implants were retrieved and evaluated by histology and histomorphometry. The results demonstrated that significant amounts of newly formed bone were present in some DBM as well as some MDBM implants while in others no, or very little new bone was found. Histomorphometric analysis showed an average bone formation of 2.6% in DBM implants and an average of 1.9% in MDBM implants. Still, the amount of bone formation was limited compared with previous studies. It is concluded that enlargement of the surface area by morsellizing DBM implants is not an important factor in bone forming capacity.