The Role of Growth Factors on Acceleration of Bone Regeneration During Distraction Osteogenesis

Alternated activation with relaxation of periosteum stimulates bone modeling and remodeling

Gradual elevation of the periosteum from the original bone surface, based on the principle of distraction osteogenesis, induces endogenous hard and soft tissue formation. This study aimed to assess the impact of alternating protocols of activation with relaxation (periosteal pumping) on bone modeling and remodeling. One hundred and sixty-two adult male Wistar rats were used in this study. Four test groups with different pumping protocols were created based on the relaxation applied. Two control groups underwent an activation period without relaxation or only a single activation. One group was sham-operated. Periosteal pumping without period of activation induced gene expression in bone and bone remodeling, and following activation period enhanced bone modeling. Four test groups and control group with activation period equaled the values of bone modeling at the end-consolidation period, showing significant downregulation of Sost in the bone and periosteum compared to that in the sham group (p < 0.001 and p < 0.001, respectively). When all test groups were pooled together, plate elevation from the bony surface increased bone remodeling on day 45 of the observation period (p = 0.003). Furthermore, bone modeling was significantly affected by plate elevation on days 17 and 45 (p = 0.047 and p = 0.005, respectively) and by pumping protocol on day 31 (p = 0.042). Periosteal pumping was beneficial for increasing bone repair when the periosteum remained in contact with the underlaying bony surface during the manipulation period. Following periosteal elevation, periosteal pumping accelerated bone formation from the bony surface by the modeling process.

Indications and surgical technique for distraction osteogenesis of the alveolar bone for augmentation prior to insertion of dental implants

When bone is limited, short, ultra-short, or narrow implants help to restore oral rehabilitation with an acceptable long-term outcome. This becomes more difficult with severe vertical bone loss. Guided bone regeneration, onlay block transplantation, or sandwich osteotomy have been established to build up these defects. The alternative to the alveolar distraction osteogenesis (ADO) has only been established in some centers, with a standardized protocol. On the one hand, ADO is a biological procedure that allows almost a "restitutio ad integrum" when building up hard and soft tissue. On the other hand, there are clear indications, limitations, and complications of the procedure in the literature. In addition to the literature, concept of Tissue Regeneration by Alveolar Callusdistraction Cologne (TRACC), which has been practiced successfully for over two decades, will be presented for different indications.

Cobalt-Doped Mesoporous Silica Coated Magnetic Nanoparticles Promoting Accelerated Bone Healing in Distraction Osteogenesis

Introduction

Large bone abnormalities are commonly treated using distraction osteogenesis (DO), but it is not suitable for a long-term application; therefore, there is an urgent need for adjuvant therapy that can accelerate bone repair.

Methods

We have synthesized mesoporous silica-coated magnetic nanoparticles doped with cobalt ions (Co-MMSNs) and assessed their capacity to quicken bone regrowth in a mouse model of DO. Furthermore, local injection of the Co-MMSNs significantly accelerated bone healing in DO, as demonstrated by X-ray imaging, micro-CT, mechanical tests, histological evaluation, and immunochemical analysis.

Results

In vitro, the Co-MMSNs exhibited good biocompatibility and induced angiogenic gene expression and osteogenic development in bone mesenchymal stem cells. And the Co-MMSNs can promote bone regeneration in a rat DO model.

Discussion

This study demonstrated the significant potential of Co-MMSNs to shorten the DO treatment duration and effectively reduce the incidence of complications.

High-fat diet causes undesirable bone regeneration by altering the bone marrow environment in rats

OBJECTIVE

Diet structure has changed greatly over the last few decades, and high-calorie diets have become an integral part of people's daily diet, as well as the important cause of obesity in society. Several organ systems, including the skeletal system, are seriously affected by high-fat-diets (HFD) in the world. There is, however, still a lack of knowledge about the effects of HFD on bone regeneration and the possible mechanisms involved. In this study, the difference in bone regeneration between rats under HFD and low-fat-diets (LFD) was evaluated by monitoring the process of bone regeneration in distraction osteogenesis (DO) model animals, as well as the possible mechanisms.

METHODS

A total of 40 Sprague Dawley (SD) rats (5 weeks old) were randomly divided into HFD group (n=20) and LFD group (n=20). Except for feeding methods, there were no differences between the two groups in terms of treatment conditions. All animals received the DO surgery eight weeks after starting to feed. After a delay of 5 days (latency phase), the active lengthening phase was performed for 10 days (0.25 mm/12 h), and the consolidation phase followed for 42 days. An observational study of bone included radioscopy (once a week), micro-computed tomography (CT), general morphology, biomechanics, histomorphometry, and immunohistochemistry.

RESULT

The results showed that HFD group had a higher body weight than LFD group after 8, 14, and 16 weeks of feeding. Furthermore, at the final observation, there were statistically significant differences between LFD group and HFD group in terms of total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels. Additionally, observations on bone regeneration showed a slower regeneration and a lower biomechanical strength in HFD group than LFD group, based on radiography, micro-CT, general morphology, biomechanics, histomorphometry, and immunohistochemistry.

CONCLUSION

In this study, HFD resulted in elevated blood lipids, increased adipose differentiation at the bone marrow level, and delayed bone regeneration. The pieces of evidence are beneficial to better understand the association between diet and bone regeneration and to adjust the diet optimally for fracture patients.

Dual drug delivery platforms for bone tissue engineering

The dual delivery platforms used in bone tissue engineering provide supplementary bioactive compounds that include distinct medicines and growth factors thereby aiding enhanced bone regeneration. The delivery of these compounds can be adjusted for a short or prolonged time based on the requirement by altering various parameters of the carrier platform. The platforms thus used are fabricated to mimic the niche of the bone microenvironment, either in the form of porous 3D structures, microspheres, or films. Thus, this review article focuses on the concept of dual drug delivery platform and its importance, classification of various platforms for dual drug delivery specific to bone tissue engineering, and finally highlights the foresight into the future direction of these techniques for better clinical applications.

Transverse Tibial Bone Transport Enhances Distraction Osteogenesis and Vascularization in the Treatment of Diabetic Foot

Objective

To investigate the effect of transverse tibial bone transport on the treatment of Wagner Stage 4 diabetic foot.

Methods

From January 2017 to October 2019, a total of 19 patients with Wagner Stage 4 diabetic foot ulcers were recruited. All patients were treated with transverse tibial bone transport. A detailed follow‐up was carried out at 1 week, 1 month, 3 months, 6 months, and 1 year after surgery. The wound healing rate and the limb salvage rate at 1 year after the surgery were evaluated. Preoperative and 3‐month postoperative digital subtraction angiography (DSA) were obtained. The level of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and platelet‐derived growth factor (PDGF) before surgery and on 1st, 4th, 11th, 18th, 28^th, and 35th days after surgery were measured. Operation time, intraoperative blood loss, postoperative complications, visual analog scale (VAS) pain score, skin temperature, Semmes‐weinstein monofilament (SWM), and ankle brachial index (ABI) were also assessed.

Results

The wound healing rate and the limb salvage rate were both 94.74% in the patients at 1 year after the surgery. DSA showed the thickening of the calf and foot arteries, clear visualization, and a rich vascular network. The levels of VEGF, bFGF, and PDGF on the 11th, 18th, 28^th, and 35th days after surgery were significantly higher than those before surgery (p < 0.05). The EGF level on the 18th, 28th, and 35th days after surgery was significantly higher than that before surgery (p < 0.05). Superficial wound complications occurred in one patient during the hospitalization. There was no movement area infection, skin flap necrosis, tibial fracture, loosening of the external fixator, or rupture in study.

Conclusion

Transverse tibial bone transport can improve the blood circulation of the affected limbs, promote the healing of diabetic foot wounds, and reduce the amputation rate of the affected limbs. Transverse tibial bone transport can promote the healing of Wagner Stage 4 diabetic foot.

Enhanced Bone Regeneration by Bone Morphogenetic Protein-2 after Pretreatment with Low-Intensity Pulsed Ultrasound in Distraction Osteogenesis

BACKGROUND

Bone morphogenetic protein 2 (BMP-2) and low-intensity pulsed ultrasound (LIPUS) have been used to enhance bone healing in distraction osteogenesis (DO). The aim of this study was to assess the synergistic effect of BMP-2 and LIPUS on bone regeneration in DO and to determine the optimal treatment strategy for enhanced bone regeneration.

METHODS

Rat mesenchymal stromal cells were treated with various application protocols of BMP-2 and LIPUS, and cell proliferation, alkaline phosphatase activity, and osteogenesis-related marker expression were evaluated. In vivo experiments were performed in a rabbit DO model according to the application protocols with different timings of BMP-2 and LIPUS application.

RESULTS

Application of BMP-2 after LIPUS pretreatment (BMP-2 after LIPUS) showed greater cell proliferation than LIPUS treatment alone, and higher ALP activity than all other treatment protocols. BMP-2 after LIPUS also exhibited increased gene expression levels of ALP, Cbfa1, and Osterix compared with LIPUS treatment alone. In vivo experiments revealed no significant differences in bone healing based on the timing of LIPUS treatment in DO. The combination of BMP-2 and LIPUS resulted in increased bone volume and bone mineral density compared with BMP-2 or LIPUS. Regarding the timing of BMP-2 application, the application of BMP-2 after LIPUS pretreatment led to greater bone volume than the application of BMP-2 before LIPUS.

CONCLUSION

The results of this study suggest that the combined treatment of BMP-2 and LIPUS can lead to enhanced bone healing in DO and that effective bone healing can be achieved through the application of LIPUS before BMP-2.

Pumping the Periosteum: A Feasibility Study: Periosteal Distraction Osteogenesis in a Rat Model

PURPOSE

Gradual elevation of periosteum from the bone surface is known to promote the adaptation of soft tissues and the formation of hard tissues. The aim of our study was to estimate the benefit of periosteal distraction osteogenesis (PDO) on de novo bone formation in a rat model.

MATERIALS AND METHODS

After device placement, animals were allowed for a latency period of 7 days. Animals in the PDO group were subjected to distraction at a rate of 0.1 mm/d for 10 days. In the periosteal pumping (PP) group, the animals were subjected to distraction at a rate of 0.1 mm/d. The direction of distraction was alternated every 2 days. The animals were euthanized at 17, 31, and 45 days after surgery, and the samples were analyzed histologically and by microcomputed tomography.

RESULTS

In both groups, the new bone was characterized as primary woven bone that was located at the leading edge of bone apposition. Bone volumes significantly increased throughout the observation period both in the PP group (P = 0.018) and in the PDO group (P < 0.001). The new bone was denser and more mature in the PP group than in the PDO group, and the difference was significant at the 31-day time point (P = 0.024). However, the volume of the new bone was higher in the PDO at the 45-day time point (P < 0.001).

CONCLUSIONS

We propose that the PP may be applied to enhance the osteogenic capacity of periosteum without plate elevation. Because this is only a proof-of-principle study, the alternated protocol of periosteal distraction warrants evaluation in the future studies.

Optimal timing for intermittent administration of parathyroid hormone (1-34) for distraction osteogenesis in rabbits

Background

To date, the usefulness of parathyroid hormone [PTH (1–34)] in distraction osteogenesis has been reported in several studies. We aimed to determine the optimal timing of PTH (1–34) administration in a rabbit distraction osteogenesis model.

Methods

The lower hind leg of a Japanese white rabbit was externally fixed, and tibial osteotomy was performed. One week after the osteotomy, bone lengthening was carried out at 0.375 mm/12 h for 2 weeks. After 5 weeks, the lower leg bone was collected. Bone mineral density (BMD), peripheral quantitative computed tomography (pQCT), micro-computed tomography (micro-CT), and mechanical tests were performed on the distracted callus. The rabbits were divided into three groups according to the timing of PTH (1–34) administration: 4 weeks during the distraction and consolidation phases (group D + C), 2 weeks of the distraction phase (group D), and the first 2 weeks of the consolidation phase (group C). A control group (group N) was administered saline for 4 weeks during the distraction and consolidation phases. Furthermore, to obtain histological findings, lower leg bones were collected from each rabbit at 2, 3, and 4 weeks after osteotomy, and tissue sections of the distracted callus were examined histologically.

Results

The BMD was highest in group C and was significantly higher than group D. In pQCT, the total cross-sectional area was significantly higher in groups D + C, D, and C than group N, and the cortical bone area was highest in group C and was significantly higher than group D. In micro-CT, group C had the highest bone mass and number of trabeculae. Regarding the mechanical test, group C had the highest callus failure strength, and this value was significantly higher compared to group N. There was no significant difference between groups D and N. The histological findings revealed that the distracted callus mainly consisted of endochondral ossification in the distraction phase. In the consolidation phase, the chondrocytes were almost absent, and intramembranous ossification was the main type of ossification.

Conclusion

We found that the optimal timing of PTH (1–34) administration is during the consolidation phase, which is mainly characterized by intramembranous ossification.

Regeneration of Craniofacial Bone Induced by Periosteal Pumping

A variety of surgical techniques and tissue engineering strategies utilizing osteogenic potential of the periosteum have been developed for the repair of extended bone deficiencies. The aim of the present study was to assess the impact of an alternating protocol of periosteal distraction osteogenesis (PDO) on bone regeneration in an intraoral model. Eight adult, male Beagle dogs were used for the study. Two distraction devices were placed on each side of the mandible. After a 7-day latency period, distraction devices in all animals were manipulated at the rate of 0.5 mm for a total of 8 days. The pumping protocol in two test groups proceeded twice daily by alternating activation with relaxation. In the periosteal pumping/distraction (PPDO) group, the distraction screws were activated two times (at 12 and 24 h) and then turned back (at 36 h), and in the periosteal pumping (PP) group repeatedly activated and turned back (at 12 h). In the PDO group, only activation was performed once daily (positive control). Devices were left inactivated in the negative control (NC) group. The samples were harvested after 8 weeks of consolidation period and investigated by micro-CT and histological analysis. New mature, lamellar bone was formed over the pristine bone in all groups. PPDO and PDO groups showed more new bone area (NBA) compared to the PP (p < 0.001 and p < 0.001, respectively) and to the NC group (p = 0.032 and p = 0.031, respectively). Furthermore, greater NBA was found in the PP group than the NC group (p = 0.006). PDO demonstrated higher relative connective tissue area than the PPDO group (p = 0.005) and lower relative new bone volume than the NC group (p = 0.025). Pumping protocol of periosteal distraction may successfully induce the endogenous regeneration of the mandibular bone in dogs. Impact Statement Repair of extended bone defects impose a significant challenge to oral and maxillofacial surgeons. In this article, a principle of distraction osteogenesis was applied to stimulate bone regeneration in the mandible. A periosteum-based regeneration approach may represent a valuable step toward creating a significant volume of hard and soft tissues, without need for autogenous bone harvesting or application of biomaterials.

Cyclic Distraction–Compression Dynamization Technique Enhances the Bone Formation During Distraction Osteogenesis

Background: Interfragmentary movements have benefits in the improvement of bone formation during distraction osteogenesis (DO). Although several clinical studies reported positive outcomes regarding the application of the cyclic distraction–compression (CDC) dynamization technique in cases with poor bone formation during DO, they are mostly anecdotal without a detailed description. The purpose of this study was to investigate the effectiveness and potential mechanism of different amplitudes and rates of the CDC technique on bone regeneration in a rat femur DO model.

Methods: A total of 60 adult male Sprague-Dawley rats underwent right femoral mid-diaphysis transverse osteotomy and were randomly and evenly divided into Control (no manipulation), Group1 (CDC therapy), Group2 (CDC therapy with larger amplitude), and Group3 (CDC therapy with a slower rate) after distraction. The CDC technique was performed during the middle phase of the consolidation period according to different protocols. Animals were sacrificed after 4 and 6 weeks of consolidation. The process of bone formation was monitored by digital radiographs, and the regenerate bone was evaluated by micro-computed tomography (micro-CT), biomechanical test, and histological analysis. The serum contents of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) were measured by enzyme-linked immunosorbent assay (ELISA).

Results: Bone regeneration after the CDC technique was improved significantly during DO. The digital radiograph, micro-CT, histomorphological analysis, and biomechanical evaluation showed better effects regarding volume, continuity, and mechanical properties of the regenerate bone in Group2 and Group3 when compared to Group1. The angiogenic and osteogenic markers were more highly expressed in Group2 and Group3 than in Group1 according to the immunohistochemical analysis. As for ELISA, the serum contents of HIF-1α and VEGF were also increased after the CDC technique, especially in Group2 and Group3.

Conclusion: The CDC dynamization technique has benefits on the improvement of bone formation during DO, and the mechanism may be due to tissue hypoxia activating the HIF pathway followed by the augmentation of osteogenic–angiogenic coupling. Better outcomes may be achieved by moderately increasing the amplitude and slowing down the rate of the CDC technique.

The RNA Methyltransferase METTL3 Promotes Endothelial Progenitor Cell Angiogenesis in Mandibular Distraction Osteogenesis via the PI3K/AKT Pathway

Distraction osteogenesis (DO) is used to treat large bone defects in the field of oral and maxillofacial surgery. Successful DO-mediated bone regeneration is dependent upon angiogenesis, and endothelial progenitor cells (EPCs) are key mediators of angiogenic processes. The N6-methyladenosine (m⁶A) methyltransferase has been identified as an important regulator of diverse biological processes, but its role in EPC-mediated angiogenesis during DO remains to be clarified. In the present study, we found that the level of m⁶A modification was significantly elevated during the process of DO and that it was also increased in the context of EPC angiogenesis under hypoxic conditions, which was characterized by increased METTL3 levels. After knocking down METTL3 in EPCs, m⁶A RNA methylation, proliferation, tube formation, migration, and chicken embryo chorioallantoic membrane (CAM) angiogenic activity were inhibited, whereas the opposite was observed upon the overexpression of METTL3. Mechanistically, METTL3 silencing reduced the levels of VEGF and PI3Kp110 as well as the phosphorylation of AKT, whereas METTL3 overexpression reduced these levels. SC79-mediated AKT phosphorylation was also able to restore the angiogenic capabilities of METTL3-deficient EPCs in vitro and ex vivo. In vivo, METTL3-overexpressing EPCs were additionally transplanted into the DO callus, significantly enhancing bone regeneration as evidenced by improved radiological and histological manifestations in a canine mandibular DO model after consolidation over a 4-week period. Overall, these results indicate that METTL3 accelerates bone regeneration during DO by enhancing EPC angiogenesis via the PI3K/AKT pathway.

Panax notoginseng Saponin Promotes Bone Regeneration in Distraction Osteogenesis via the TGF-β1 Signaling Pathway

Distraction osteogenesis (DO) is an efficient strategy that is employed for the treatment of large bone defects in craniomaxillofacial surgery. Despite its utility, however, DO is associated with a prolonged consolidation phase and a high complication rate that hinder its more widespread utilization. Panax notoginseng saponin (PNS) is a traditional Chinese medicine that is frequently administered for the treatment of a range of conditions. Herein, we explored the ability of PNS treatment to influence osteogenic differentiation using both rabbit bone marrow mesenchymal cells (BMSCs) and a model of mandibular DO. BMSC proliferation was assessed via CCK-8 assay, while osteogenic differentiation was monitored through ALP and alizarin red S staining. A PCR approach was used to evaluate the expression of genes associated with osteogenesis (ALP, Runx2, and OCN) and genes linked to the TGF pathway (TβR-II, SMAD2, SMAD3, and PPM1A). For in vivo experiments, treated BMSCs were locally injected into the DO gap, with PNS being injected into treated rabbits every other day throughout the experimental period. The quality of the regenerative process was assessed via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray imaging, and hematoxylin and eosin (H&E) staining. These analyses revealed that PNS was able to promote BMSC osteogenesis and mandibular generation, driving the upregulation of osteogenesis-related genes at the mRNA levels through the modulation of the TGF-β1/Smad pathway. Consistently, the overexpression or silencing of TβR-II in PNS-treated BMSCs was sufficient to modulate their osteogenic potential. Analyses of in vivo mandibular DO outcomes revealed significantly augmented new bone growth in the PNS-treated group relative to control animals, with maximal osteogenesis in the group overexpressing rabbit TβR-II. Together, these results highlight the PNS as a promising and cost-effective therapeutic tool with the potential to enhance bone regeneration in clinical contexts through the modulation of the TGF-β1/Smad pathway.

An In Vitro and In Vivo Comparison of Osteogenic Differentiation of Human Mesenchymal Stromal/Stem Cells

The use of stem cells in regenerative medicine, including tissue engineering and transplantation, has generated a great deal of enthusiasm. Mesenchymal stromal/stem cells (MSCs) can be isolated from various tissues, most commonly, bone marrow but more recently adipose tissue, dental pulp, and Wharton's jelly, to name a few. MSCs display varying phenotypic profiles and osteogenic differentiating capacity depending and their site of origin. MSCs have been successfully differentiated into osteoblasts both in vitro an in vivo but discrepancies exist when the two are compared: what happens in vitro does not necessarily happen in vivo, and it is therefore important to understand why these differences occur. The osteogenic process is a complex network of transcription factors, stimulators, inhibitors, proteins, etc., and in vivo experiments are helpful in evaluating the various aspects of this osteogenic process without distractions and confounding variables. With that in mind, the results of in vitro experiments need to be carefully considered and interpreted with caution as they do not perfectly replicate the conditions found within living organisms. This is where in vivo experiments help us better understand interactions that might occur in the osteogenic process that cannot be replicated in vitro. Potentially, these differences could also be exploited to develop an optimal MSC cell therapeutic product that can be used for bone disorders. There are many bone disorders, most of which cause a great deal of discomfort. Clinically acceptable protocols could be developed in which MSCs are used to aid in bone regeneration providing relief for patients with chronic pain. The aim of this review is to examine the differences between studies conducted in vitro and in vivo with regard to the osteogenic process to better define the gaps in current osteogenic research. By better understanding osteogenic differentiation, we can better define treatment strategies for various bone disorders.

Biodegradable magnesium combined with distraction osteogenesis synergistically stimulates bone tissue regeneration via CGRP-FAK-VEGF signaling axis

Critical size bone defects are frequently caused by accidental trauma, oncologic surgery, and infection. Distraction osteogenesis (DO) is a useful technique to promote the repair of critical size bone defects. However, DO is usually a lengthy treatment, therefore accompanied with increased risks of complications such as infections and delayed union. Here, we demonstrated that magnesium (Mg) nail implantation into the marrow cavity degraded gradually accompanied with about 4-fold increase of new bone formation and over 5-fold of new vessel formation as compared with DO alone group in the 5 mm femoral segmental defect rat model at 2 weeks after distraction. Mg nail upregulated the expression of calcitonin gene-related peptide (CGRP) in the new bone as compared with the DO alone group. We further revealed that blockade of the sensory nerve by overdose capsaicin blunted Mg nail enhanced critical size bone defect repair during the DO process. CGRP concentration-dependently promoted endothelial cell migration and tube formation. Meanwhile, CGRP promoted the phosphorylation of focal adhesion kinase (FAK) at Y397 site and elevated the expression of vascular endothelial growth factor A (VEGFA). Moreover, inhibitor/antagonist of CGRP receptor, FAK, and VEGF receptor blocked the Mg nail stimulated vessel and bone formation. We revealed, for the first time, a CGRP-FAK-VEGF signaling axis linking sensory nerve and endothelial cells, which may be the main mechanism underlying Mg-enhanced critical size bone defect repair when combined with DO, suggesting a great potential of Mg implants in reducing DO treatment time for clinical applications.

In ovariectomy-induced osteoporotic rat models, BMP-2 substantially reversed an impaired alveolar bone regeneration whereas PDGF-BB failed

OBJECTIVES

We previously suggested an ovariectomy (OVX)-induced osteoporotic rat model showing an impaired alveolar bone defect healing. This study aimed to evaluate and compare the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on alveolar bone defect healing in OVX-induced osteoporotic rats.

MATERIALS AND METHODS

A total of forty-one female rats were divided into four groups: a collagen group (n=10), a PDGF-BB group (n=11), a BMP-2 group (n=10), and a control group (n=10). Four months after OVX, alveolar bone drill-hole defects were created and grafted with collagen gel, rhPDGF-BB/collagen gel, or rhBMP-2/collagen gel. The defects in the control group were not grafted with any material. Defect healing was evaluated by histological, histomorphometric, and microcomputed tomographic (micro-CT) analyses at 2 and 4 weeks.

RESULTS

According to the micro-CT analysis, the BMP-2 group exhibited the greatest bone volume fraction among all groups, while the PDGF-BB group did not show significant differences compared with the collagen group. The histomorphometric analysis showed a significantly larger amount of new bone area in the BMP-2 group than in the control and collagen groups at 4 weeks; however, the PDGF-BB group did not reach significant superiority compared with the other groups.

CONCLUSIONS

Alveolar bone regeneration was significantly enhanced by the local use of rhBMP-2/collagen gel compared with the use of rhPDGF-BB/collagen gel in OVX-induced osteoporotic rats.

CLINICAL RELEVANCE

A treatment modality using rhBMP-2 may be a promising approach to promote alveolar bone regeneration in patients suffering from postmenopausal osteoporosis.

Overview of methods for enhancing bone regeneration in distraction osteogenesis: Potential roles of biometals

BACKGROUND

Distraction osteogenesis (DO) is a functional tissue engineering approach that applies gradual mechanical traction on the bone tissues after osteotomy to stimulate bone regeneration. However, DO still has disadvantages that limit its clinical use, including long treatment duration.

METHODS

Review the current methods of promoting bone formation and consolidation in DO with particular interest on biometal.

RESULTS

Numerous approaches, including physical therapy, gene therapy, growth factor-based therapy, stem-cell-based therapy, and improved distraction devices, have been explored to reduce the DO treatment duration with some success. Nevertheless, no approach to date is widely accepted in clinical practice due to various reasons, such as high expense, short biologic half-life, and lack of effective delivery methods. Biometals, including calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), manganese (Mn), and cobalt (Co) have attracted attention in bone regeneration attributed to their biodegradability and bioactive components released during in vivo degradation.

CONCLUSION

This review summarizes the current therapies accelerating bone formation in DO and the beneficial role of biometals in bone regeneration, particularly focusing on the use of biometal Mg and its alloy in promoting bone formation in DO. Translational potential: The potential clinical applications using Mg-based devices to accelerate DO are promising. Mg stimulates expression of multiple intrinsic biological factors and the development of Mg as an implantable component in DO may be used to argument bone formation and consolidation in DO.

Local administration of allogeneic or autologous bone marrow-derived mesenchymal stromal cells enhances bone formation similarly in distraction osteogenesis

BACKGROUND AIMS

Distraction osteogenesis (DO) is a surgical technique to promote bone regeneration that requires a long time for bone healing. Bone marrow-derived mesenchymal stromal cells (MSCs) have been applied to accelerate bone formation in DO. Allogeneic MSCs are attractive, as they could be ready to use in clinics. Whether allogeneic MSCs would have an effect similar to autologous MSCs with regard to promoting bone formation in DO is still unknown. This study compares the effect of autologous MSCs versus allogeneic MSCs on bone formation in a rat DO model.

METHODS

Rat bone marrow-derived MSCs were isolated, characterized and expanded in vitro. Adult rats were subjected to right tibia transverse osteotomy. On the third day of distraction, each rat received one injection of phosphate-buffered saline (PBS), autologous MSCs or allogeneic MSCs at the distraction site. Tibiae were harvested after 28 days of consolidation for micro-computed tomography examination, mechanical test and histological analysis.

RESULTS

Results showed that treatment with both allogeneic and autologous MSCs promoted bone formation, with significantly higher bone mass, mechanical properties and mineral apposition rate as well as expression of angiogenic and bone formation markers at the regeneration sites compared with the PBS-treated group. No statistical difference in bone formation was found between the allogeneic and autologous MSC treatment groups.

CONCLUSIONS

This study indicates that allogeneic and autologous MSCs have a similar effect on promoting bone consolidation in DO. MSCs from an allogeneic source could be used off-the-shelf with DO to achieve early bone healing.

Craniofacial and Long Bone Development in the Context of Distraction Osteogenesis

BACKGROUND

Bone retains regenerative potential into adulthood, and surgeons harness this plasticity during distraction osteogenesis. The underlying biology governing bone development, repair, and regeneration is divergent between the craniofacial and appendicular skeleton. Each type of bone formation is characterized by unique molecular signaling and cellular behavior. Recent discoveries have elucidated the cellular and genetic processes underlying skeletal development and regeneration, providing an opportunity to couple biological and clinical knowledge to improve patient care.

METHODS

A comprehensive literature review of basic and clinical literature regarding craniofacial and long bone development, regeneration, and distraction osteogenesis was performed.

RESULTS

The current understanding in craniofacial and long bone development and regeneration is discussed, and clinical considerations for the respective distraction osteogenesis procedures are presented.

CONCLUSIONS

Distraction osteogenesis is a powerful tool to regenerate bone and thus address a number of craniofacial and appendicular skeletal deficiencies. The molecular mechanisms underlying bone regeneration, however, remain elusive. Recent work has determined that embryologic morphogen gradients constitute important signals during regeneration. In addition, striking discoveries have illuminated the cellular processes underlying mandibular regeneration during distraction osteogenesis, showing that skeletal stem cells reactivate embryologic neural crest transcriptomic processes to carry out bone formation during regeneration. Furthermore, innovative adjuvant therapies to complement distraction osteogenesis use biological processes active in embryogenesis and regeneration. Additional research is needed to further characterize the underlying cellular mechanisms responsible for improved bone formation through adjuvant therapies and the role skeletal stem cells play during regeneration.

Exosomes Secreted by Young Mesenchymal Stem Cells Promote New Bone Formation During Distraction Osteogenesis in Older Rats

Distraction osteogenesis (DO) is a clinically effective procedure to regenerate large bone defects. However, the treatment duration is undesirably lengthy, especially in elderly patients. Exosomes derived from mesenchymal stem cells (MSC-Exos) could exert the beneficial effects while avoiding the possible complications of stem cell transplantation. This study aimed to evaluate the effects of MSC-Exos on bone regeneration during DO in older rats. Exosomes were isolated from the supernatants of young bone marrow mesenchymal stem cells (BMSCs) through ultra-centrifugation, and characterized using transmission electron microscopy, western blot, and tunable resistive pulse sensing analysis. The effects of MSC-Exos on the proliferation and differentiation of older BMSCs were evaluated using CCK-8 assay, ALP and ARS staining, and qRT-PCR. Unilateral tibial DO model was established on older Sprague-Dawley rats and MSC-Exos or phosphate buffer saline was locally injected into the distraction gaps after distraction weekly. Bone regeneration were evaluated using X-ray, Micro-CT, mechanical test, and histological staining. The MSC-Exos were round or cup-shaped vesicles ranging from 60 to 130 nm in diameter and expressed markers including CD9, CD63, and TSG101. The in vitro results indicated that MSC-Exos could enhance the proliferation and osteogenic differentiation of older BMSCs. Bone regeneration was markedly accelerated in rats treated with MSC-Exos according to the results of X-ray, micro-CT, and histological analysis. The distracted tibias from the MSC-Exos group also demonstrated better mechanical properties. These results suggest that MSC-Exos promote DO-mediated bone regeneration in older rats through enhancing the proliferation and osteogenic capacity of BMSCs.

Administration of allogeneic mesenchymal stem cells in lengthening phase accelerates early bone consolidation in rat distraction osteogenesis model

BACKGROUND

Distraction osteogenesis (DO) is a surgical technique to promote bone regeneration which may require long duration for bone consolidation. Bone marrow-derived mesenchymal stem cells (MSCs) have been applied to accelerate bone formation in DO. However, the optimal time point for cell therapy in DO remains unknown. This study sought to determine the optimal time point of cell administration to achieve early bone consolidation in DO. We hypothesized that the ratio of circulating MSCs to peripheral mononuclear cells and the level of cytokines in serum might be indicators for cell administration in DO.

METHODS

Unilateral tibial osteotomy with an external fixator was performed in adult Sprague Dawley rats. Three days after osteotomy, the tibia was lengthened at 0.5 mm/12 h for 5 days. At first, 5 rats were used to analyze the blood components at 6 different time points (3 days before lengthening, on the day lengthening began, or 3, 6, 10, or 14 days after lengthening began) by sorting circulating MSCs and measuring serum levels of stromal cell-derived factor 1 (SDF-1) and interleukin 1β. Then, 40 rats were used for cell therapy study. A single dose of 5 × 10⁵ allogeneic MSCs was locally injected at the lengthening site on day 3, 6, or 10 after lengthening began, or 3 doses of MSCs were injected at the three time points. Sequential X-ray radiographs were taken weekly. Endpoint examinations included micro-computed tomography analysis, mechanical testing, histomorphometry, and histology.

RESULTS

The number of circulating MSCs and serum level of SDF-1 were significantly increased during lengthening, and then decreased afterwards. Single injection of MSCs during lengthening phase (on day 3, but not day 6 or 10) significantly increased bone volume fraction, mechanical maximum loading, and bone mineralization of the regenerate. Triple injections of MSCs at three time points also significantly increased bone volume and maximum loading of the regenerates.

CONCLUSION

This study demonstrated that bone consolidation could be accelerated by a single injection of MSCs during lengthening when the ratio of peripheral MSCs to mononuclear cells and the serum SDF-1 presented at peak levels concurrently, suggesting that day 3 after lengthening began may be the optimal time point for cell therapy to promote early bone consolidation.

Bioengineering strategies for bone and cartilage tissue regeneration using growth factors and stem cells

Bone and cartilage tissue engineering is an integrative approach that is inspired by the phenomena associated with wound healing. In this respect, growth factors have emerged as important moieties for the control and regulation of this process. Growth factors act as mediators and control the important physiological functions of bone regeneration. Herein, we discuss the importance of growth factors in bone and cartilage tissue engineering, their loading and delivery strategies, release kinetics, and their integration with biomaterials and stem cells to heal bone fractures. We also highlighted the role of growth factors in the determination of the bone tissue microenvironment based on the reciprocal signaling with cells and biomaterial scaffolds on which future bone and cartilage tissue engineering technologies and medical devices will be based upon.

Regeneration of large bone defects using mesoporous silica coated magnetic nanoparticles during distraction osteogenesis

Distraction osteogenesis (DO) represents an effective but undesirably lengthy treatment for large bone defects. Both magnetic nanoparticles and silicon have been shown to induce osteogenic differentiation of mesenchymal stem cells (MSCs), the key participant in bone regeneration. We herein synthesized mesoporous silica coated magnetic (Fe₃O₄) nanoparticles (M-MSNs) and evaluated its potential for acceleration of bone regeneration in a rat DO model. The M-MSNs exhibited good biocompatibility and remarkable capability in promoting the osteogenic differentiation of MSCs via the canonical Wnt/β-catenin pathway in vitro. More importantly, local injection of M-MSNs dramatically accelerated bone regeneration in a rat DO model according to the results of X-ray imaging, micro-CT, mechanical testing, histological examination, and immunochemical analysis. This study demonstrates the notable potential of M-MSNs in promoting bone regeneration during DO by enhancing the osteogenic differentiation of MSCs, paving the way for clinical translation of M-MSNs in DO to repair large bone defects.

Efficacy of copolymer scaffolds delivering human demineralised dentine matrix for bone regeneration

Poly(L-lactide-co-ε-caprolactone) scaffolds were functionalised by 10 or 20 µg/mL of human demineralised dentine matrix. Release kinetics up to 21 days and their osteogenic potential on human bone marrow stromal cells after 7 and 21 days were studied. A total of 390 proteins were identified by mass spectrometry. Bone regeneration proteins showed initial burst of release. Human bone marrow stromal cells were cultured on scaffolds physisorbed with 20 µg/mL and cultured in basal medium (DDM group) or physisorbed and cultured in osteogenic medium or cultured on non-functionalised scaffolds in osteogenic medium. The human bone marrow stromal cells proliferated less in demineralised dentine matrix group and activated ERK/1/2 after both time points. Cells on DDM group showed highest expression of IL-6 and IL-8 at 7 days and expressed higher collagen type 1 alpha 2, SPP1 and bone morphogenetic protein-2 until 21 days. Extracellular protein revealed higher collagen type 1 and bone morphogenetic protein-2 at 21 days in demineralised dentine matrix group. Cells on DDM group showed signs of mineralisation. The functionalised scaffolds were able to stimulate osteogenic differentiation of human bone marrow stromal cells.

Assessment of the effect of systemic delivery of sclerostin antibodies on Wnt signaling in distraction osteogenesis

Sclerostin is a known inhibitor of the Wnt signaling pathway which is involved in osteogenesis and, when inactivated, stimulates bone formation. To our knowledge, this effect has not been studied in the context of distraction osteogenesis (DO). Tibial DO was conducted on a total of 24 wild-type mice, which were then divided into 2 groups-a saline injection group (control) and an anti-sclerostin (Scl-Ab) injection group (treatment). The mice in the treatment group received 100 mg/kg intravenous injections of the antibody weekly until killing. The 12 mice in each group were subdivided into four time points according to post-osteotomy time of killing-11 days (mid-distraction), 17 days (late distraction), 34 days (mid-consolidation) and 51 days (late consolidation), with 3 mice per subgroup. After killing, the tibia specimens were collected for immunohistochemical analysis. Our results show that the group injected with anti-sclerostin had an earlier peak (day 11) in the distraction phase of the osteogenic molecules involved in the Wnt signaling pathway in comparison to the placebo group. In addition, downregulation of the inhibitors of this pathway was noted in the treatment group when compared with the placebo group. Furthermore, LRP-5 showed a significant increase in expression in the treatment group. Sclerostin inhibition has a significant effect on the DO process through its effect on the Wnt pathway. This effect was evident through the decreased effect of sclerostin on LRP-5 and earlier upregulation of the osteogenic molecules involved in this pathway.

Prolonged release of bone morphogenetic protein-2 in vivo by gene transfection with DNA-functionalized calcium phosphate nanoparticle-loaded collagen scaffolds

In the combination of scaffolds immersed in growth factor solutions, the release of growth factors mainly depends on scaffold degradation. However, the release of bone morphogenetic protein (BMP)-2 at an appropriate concentration during the stage of tissue regeneration would enhance bone regeneration. To achieve this condition, the present study was performed to investigate the effects of scaffolds combined with gene transfection using non-viral vectors. Nanohydroxyapatite-collagen (nHAC) scaffolds cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or ascorbic acid/copper chloride, and a collagen scaffold (Terdermis®) were prepared, loaded with BMP-2-encoding plasmid DNA-functionalized calcium phosphate nanoparticles (CaP), naked plasmid DNA, or BMP-2 solution, and implanted in rats. The yield of released BMP-2 and its releasing period, respectively, were larger and longer from the scaffolds loaded with CaP than from those incubated with BMP-2 solution. In addition, the alkaline phosphatase activity induced by the CaP-loaded scaffolds was higher. Histological analysis showed that released BMP-2 could be observed on the macrophages or multinuclear giant cells surrounding the nHAC fragments or collagen fibres. TRAP-positive or OCN-positive sites were observed in all groups and a mineralization area was observed in the Terdermis®/CaP sample. The present study demonstrates that gene transfection by scaffold loaded with CaP gene transfer vectors induces a larger yield of BMP-2 for a longer period than by scaffolds loaded with BMP-2 solution or naked plasmid.

Role of TGF‑β1 expressed in bone marrow‑derived mesenchymal stem cells in promoting bone formation in a rabbit femoral defect model

Bone defects represent a major clinical and socioeconomic problem without suitable treatment options. Previous studies have shown that transforming growth factor β1 (TGF‑β1) is important in the development of various diseases. The present study aimed to investigate the therapeutic potential of rabbit bone marrow‑derived mesenchymal stem cells (BMSCs) expressing TGF‑β1 in the treatment of rabbit femoral defects. First, rabbit BMSCs were identified and cultured. TGF‑β1 was then stably overexpressed in the rabbit BMSCs by lentivirus transfection, which was expressed at a high level in the femoral defects treated with TGF‑β1‑overexpressing BMSCs, compared with PBS‑treated controls. In addition, the TGF‑β1‑overexpressing BMSCs promoted new bone formation in the rabbit femoral defect model, and increased the expression of bone‑related markers at week 2 and week 6. Therefore, the study demonstrated that BMSCs overexpressing TGF‑β1 may provide a novel therapeutic option for femoral defects.

Strategies of enhancing bone regenerate formation in distraction osteogenesis

Distraction osteogenesis (DO) is a commonly used technique in multiple orthopedic sub-specialties, including trauma, oncology and pediatrics. This technique aims to produce new bone formation in the distraction gap in a controlled manner. The issue with this technique has been the high risk of complications, one of which is poor regenerate formation during the distraction process. Although several factors (including patient and operative factors) and techniques (including surgical, mechanical and pharmacological) have been described to ensure successful regenerate formation during the process of DO, these factors are sometimes difficult to control clinically. Our aim from this review is to highlight the different factors that affect DO, modalities to assess the regenerate and review treatment options for poor regenerate in the distraction gap. In addition, we propose a management protocol derived from the available literature that can be used to facilitate the management of inadequate regenerate formation.

3-D mineralized silk fibroin/polycaprolactone composite scaffold modified with polyglutamate conjugated with BMP-2 peptide for bone tissue engineering

In the field of bone tissue engineering, an ideal three-dimensional (3-D) scaffold should not only structurally mimic the extracellular matrix (ECM) in large tissues but also mechanically support the bone healing process and provide biochemical cues to induce osteogenesis. In this study, we investigated the feasibility of functionalisation of scaffolds by coupling polyglutamate acid conjugated with BMP-2 peptide onto silk fibroin (SF)/polycaprolactone (PCL) (SF/PCL) blend nanofibers. The morphology, composition, and mineralisation, were confirmed by FE-SEM, XRD, and FT-IR spectroscopy. The FE-SEM images revealed that wet-electrospun nanofibrous scaffolds exhibited inter-connected nano/micro-pores at different levels, and a different morphology was observed on the 3-D SF/PCL scaffold after mineralisation. Furthermore, the binding property and release behaviour of the peptide were investigated on this mineralized structure, and adipose-derived stem cells were seeded on the composite scaffolds to assay their cytocompatibility and osteogenic differentiation capacities. Results suggest that the polyglutamate motif (repetitive glutamate amino acids) exhibited markedly improved binding properties to mineralized nanofibers, and the mineralized 3-D scaffolds with the conjugated with peptide enhances the mRNA expression of osteogenic genes. The sponge-like 3-D nanofibrous scaffold mechanically and biochemically mimics the regenerative process for applications in bone tissue engineering, including the regeneration of calvarial defects.

Enhancement of bone regeneration with the accordion technique via HIF-1α/VEGF activation in a rat distraction osteogenesis model

Axial micromotion of bone fragments promotes callus formation and bone healing during the process of distraction osteogenesis (DO). This study investigated the effects of the combined axial compression and distraction (accordion) technique on bone regeneration in rat DO model. Male Sprague-Dawley rats (n = 62) underwent right tibial transverse osteotomy and were randomly divided into four groups after lengthening: control (no manipulation) and three experimental groups assigned on the basis of the period of accordion manoeuvres in the consolidation phase (Groups 1, 2, and 3 with accordion technique applied at Weeks 1, 3, and 5, respectively). Animals were terminated at 1 week after each accordion phase (i.e., Weeks 2, 4, and 6). Callus formation was monitored by X-ray radiography; new bone quality was evaluated by microcomputed tomography, histological analysis, and mechanical testing. Serum levels of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) were measured. Callus formation after accordion manoeuvre at Week 3 (Group 2) increased significantly over time of consolidation. The microcomputed tomography and mechanical analysis revealed Group 2 had more newly formed bone and superior mechanical properties in contrast to the other groups at termination. Histomorphological and immunohistochemical analyses confirmed a greater degree of osteogenesis and angiogenesis corresponding to increased serum levels of HIF-1α and VEGF in Group 2. The accordion technique was effective in promoting bone consolidation via activation of HIF-1α/VEGF during DO. The accordion technique may be used in the middle phase of bone consolidation to promote bone formation in patients undergoing DO treatment.

Can Spatiotemporal Fluoride (18F-) Uptake be Used to Assess Bone Formation in the Tibia? A Longitudinal Study Using PET/CT

BACKGROUND

When a bone is broken for any reason, it is important for the orthopaedic surgeon to know how bone healing is progressing. There has been resurgence in the use of the fluoride (¹⁸F^-) ion to evaluate various bone conditions. This has been made possible by availability of positron emission tomography (PET)/CT hybrid scanners together with cyclotrons. Absorbed on the bone surface from blood flow, ¹⁸F^- attaches to the osteoblasts in cancellous bone and acts as a pharmacokinetic agent, which reflects the local physiologic activity of bone. This is important because it shows bone formation indicating that the bone is healing or no bone formation indicating no healing. As ¹⁸F^- is extracted from blood in proportion to blood flow and bone formation, it thus enables determination of bone healing progress.

QUESTIONS/PURPOSES

The primary objective of this study was to determine whether videos showing the spatiotemporal uptake of ¹⁸F^- via PET bone scans could show problematic bone healing in patients with complex tibia conditions. A secondary objective was to determine if semiquantification of radionuclide uptake was consistent with bone healing.

METHODS

This study investigated measurements of tibia bone formation in patients with complex fractures, osteomyelitis, and osteotomies treated with a Taylor Spatial Frame^TM (TSF) by comparing clinical healing progress with spatiotemporal fluoride (¹⁸F^-) uptake and the semiquantitative standardized uptake value (SUV). This procedure included static and dynamic image acquisition. For intrapatient volumes acquired at different times, the CT and PET data were spatially registered to bring the ends of the bones that were supposed to heal into alignment. To qualitatively observe how and where bone formation was occurring, time-sequenced volumes were reconstructed and viewed as a video. To semiquantify the uptake, the mean and maximum SUVs (SUVmean, SUVmax) were calculated for the ends of the bones that were supposed to heal and for normal bone, using a spherical volume of interest drawn on the registered volumes. To make the semiquantitative data comparable for all patients with multiple examinations, the SUVmean and SUVmax difference per day (SUVmeanDPD and SUVmaxDPD) between the first PET/CT scan and each subsequent one was calculated. Indicators of poor healing progress were (1) uneven distribution of the radionuclide uptake between ends of the bones that were supposed to heal as seen in the video or, (2) low absolute magnitude of the SUV difference data. Twenty-four patients treated between October 2013 and April 2015 with a TSF gave informed consent to be examined with ¹⁸F^- PET/CT bone scans. Twenty-two patients successfully completed treatment, one of whom had only one PET/CT scan.

RESULTS

Observation of ¹⁸F^- uptake was able to identify three patients whose healing progress was poor, indicated by uneven distribution of radionuclide uptake across the ends of the bones that were supposed to heal. An absolute magnitude of the SUVmaxDPD of 0.18 or greater indicated good bone formation progress. This was verified in 10 patients by the days between the operation to attach and to remove the TSF being less than 250 days, whereas other SUVmaxDPD values were ambiguous, with 11 patients achieving successful completion.

CONCLUSIONS

Observation of the spatiotemporal uptake of ¹⁸F^- appears to be a promising method to enable the clinician to assess the progress of bone formation in different parts of the bone. Bone uptake which is uneven across the ends of bone that were supposed to heal or very low bone uptake might indicate impaired bone healing where early intervention may then be needed. However, semiquantification of ¹⁸F^- uptake (SUVmaxDPD), SUVmeanDPD) was ambiguous in showing consistency with the bone-healing progress.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Does Sclerostin Depletion Stimulate Fracture Healing in a Mouse Model?

BACKGROUND

Sclerostin is a secreted glycoprotein that inhibits the intracellular Wnt signaling pathway, which, when inactivated, stimulates bone formation. This has been seen in fracture studies, which have shown larger and stronger calluses with accelerated fracture healing in sclerostin knockout and sclerostin antibody injection models. However, the effects of these two mechanisms have not been compared in the context of fracture healing.

QUESTIONS/PURPOSES

We sought to determine the degree to which sclerostin inhibition (Scl-Ab injection) and complete sclerostin depletion inhibit fracture healing in a mouse model as evaluated by (1) morphometric trabecular bone measures at the fracture site, and (2) fracture site structural strength.

METHODS

Ten-week-old male sclerostin knockout (n = 20) and wild type (n = 40) mice underwent insertion of a tibial intramedullary pin after which a midshaft tibial osteotomy was performed. The mice were divided in three groups: sclerostin knockout (n = 20), wild type with sclerostin antibody injection (intravenous dose of 100 mg/kg weekly) (n = 20), and wild type with saline injection (n = 20). The mice for each group where subdivided and euthanized at 14, 21, 28, and 35 days after surgery, at which time the fractured tibias were assessed with microCT (to assess morphometric trabecular bone measures: bone volume to total volume (BV/TV), trabecular thickness, trabecular number, and structural model index at the fracture site. Biomechanical testing in the form of three-point bending also was done to assess fracture site structural strength. A difference greater than 3.7% in our primary outcome (BV/TV) would be required to detect a difference between groups with a power of 80%, as per our power analysis.

RESULTS

The wild type with sclerostin antibody and the sclerostin knockout groups showed increased trabecular BV/TV at the fracture site compared with the wild type group with saline at all times, however no difference was seen between the treatment groups with the numbers available, except at 28 days postoperatively when the sclerostin knockout group showed greater BV/TV than the wild type sclerostin antibody group (47.0 ± 3.5 vs 40.1 ± 2.1; p < 0.05). On biomechanical testing the wild type sclerostin antibody showed increased stiffness at Days 14 and 28 compared with the wild type with saline group (70.9 ± 6.4 vs 14.8 ± 8.1; p = 0.001), (106.8 ± 24.3 vs 74.9 ± 16.0; p = 0.004); respectively. However, with the numbers available, no differences were detected between the wild type with sclerostin antibody and the sclerostin knockout groups in terms of whole-bone structural strength.

CONCLUSIONS

Sclerostin antibody injections showed promising results, which were not different with the numbers available, from results achieved with complete depletion of sclerostin, especially at earlier stages of the healing process, and therefore completed the healing process at an earlier time.

CLINICAL RELEVANCE

Sclerostin antibody injections appear to enhance fracture healing to a degree that is not different than complete sclerostin depletion, but larger animal studies are required to assess the accurate dosage and timing of administration in the fracture healing process to further evaluate its potential clinical utility to enhance fracture healing.

Influence of biomechanical and biochemical stimulation on the proliferation and differentiation of bone marrow stromal cells seeded on polyurethane scaffolds

The aim of the present investigation was to compare the effects of cyclic compression, perfusion, dexamethasone (DEX) and bone morphogenetic protein-7 (BMP-7) on the proliferation and differentiation of human bone marrow stromal cells (hBMSCs) in polyurethane scaffolds in a perfusion bioreactor. Polyurethane scaffolds seeded with hBMSCs were cultured under six different conditions, as follows: 10% Cyclic compression at 0.5 and 5 Hz; 10 ml/min perfusion; 100 nM DEX; 100 ng/ml BMP-7; and 1 ml/min perfusion without mechanical and biochemical stimulation (control). On days 7 and 14, samples were tested for the following data: Cell proliferation; mRNA expression of Runx2, COL1A1 and osteocalcin; osteocalcin content; calcium deposition; and the equilibrium modulus of the tissue specimen. The results indicated that BMP-7 and 10 ml/min perfusion promoted cell proliferation, which was inhibited by 5 Hz cyclic compression and DEX. On day 7, the 5 Hz cyclic compression inhibited Runx2 expression, whereas the 0.5 Hz cyclic compression and BMP-7 upregulated the COL1A1 mRNA levels on day 7 and enhanced the osteocalcin expression on day 14. The DEX-treated hBMSCs exhibited downregulated osteocalcin expression. After 14 days, the BMP-7 group exhibited the highest calcium deposition, followed by the 0.5 Hz cyclic compression and the DEX groups. The equilibrium modulus of the engineered constructs significantly increased in the BMP-7, 0.5 Hz cyclic compression and DEX groups. In conclusion, the present results suggest that BMP-7 and perfusion enhance cell proliferation, whereas high frequency cyclic compression inhibits the proliferation and osteogenic differentiation of hBMSCs. Low frequency cyclic compression is more effective than DEX, but less effective compared with BMP-7 on the osteogenic differentiation of hBMSCs seeded on polyurethane scaffolds.

Dual-controlled release system of drugs for bone regeneration

Controlled release systems have been noted to allow drugs to enhance their ability for bone regeneration. To this end, various biomaterials have been used as the release carriers of drugs, such as low-molecular-weight drugs, growth factors, and others. The drugs are released from the release carriers in a controlled fashion to maintain their actions for a long time period. Most research has been focused on the controlled release of single drugs to demonstrate the therapeutic feasibility. Controlled release of two combined drugs, so-called dual release systems, are promising and important for tissue regeneration. This is because the tissue regeneration process of bone formation is generally achieved by multiple bioactive molecules, which are produced from cells by other molecules. If two types of bioactive molecules, (i.e., drugs), are supplied in an appropriate fashion, the regeneration process of living bodies will be efficiently promoted. This review focuses on the bone regeneration induced by dual-controlled release of drugs. In this paper, various dual-controlled release systems of drugs aiming at bone regeneration are overviewed explaining the type of drugs and their release materials.

The Accordion Maneuver: A Noninvasive Strategy for Absent or Delayed Callus Formation in Cases of Limb Lengthening

The distraction osteogenesis (DO) technique has been used worldwide to treat many orthopaedic conditions. Although successful, absent or delayed callus formation in the distraction gap can lead to significant morbidities. An alternate cycle of distraction-compression (accordion maneuver) is one approach to accelerate bone regeneration. The primary aim of our study is to report our experience with the accordion maneuver during DO and to provide a detailed description of this technique, as performed in our center. The secondary aim is to present a review of the literature regarding the use of accordion maneuver. We reviewed the database of all patients undergoing limb lengthening from the year of 1997 to 2012. Four patients (6.15%) out of 65 showed poor bone regenerate in their tibiae and therefore accordion maneuver was applied for a mean of 6.75 weeks. Of these, three patients have had successful outcome with this technique. The literature showed that this technique is successful approach to trigger bone healing. However, details of how and when to apply this combination of distraction-compression forces were lacking. In conclusion, the accordion technique is safe noninvasive approach to promote bone formation, thus avoiding more invasive surgical procedures in cases of poor callus formation in limb lengthening.

Comprehensive Review of Adipose Stem Cells and Their Implication in Distraction Osteogenesis and Bone Regeneration

Bone is one of the most dynamic tissues in the human body that can heal following injury without leaving a scar. However, in instances of extensive bone loss, this intrinsic capacity of bone to heal may not be sufficient and external intervention becomes necessary. Several techniques are available to address this problem, including autogenous bone grafts and allografts. However, all these techniques have their own limitations. An alternative method is the technique of distraction osteogenesis, where gradual and controlled distraction of two bony segments after osteotomy leads to induction of new bone formation. Although distraction osteogenesis usually gives satisfactory results, its major limitation is the prolonged duration of time required before the external fixator is removed, which may lead to numerous complications. Numerous methods to accelerate bone formation in the context of distraction osteogenesis have been reported. A viable alternative to autogenous bone grafts for a source of osteogenic cells is mesenchymal stem cells from bone marrow. However, there are certain problems with bone marrow aspirate. Hence, scientists have investigated other sources for mesenchymal stem cells, specifically adipose tissue, which has been shown to be an excellent source of mesenchymal stem cells. In this paper, the potential use of adipose stem cells to stimulate bone formation is discussed.

Update on mandibular distraction osteogenesis

PURPOSE OF REVIEW

Mandibular distraction osteogenesis has become one of the most powerful reconstructive tools for addressing congenital lower jaw deformities. This review will focus on clinical and basic science contributions to the literature in the last year, which have shown innovations in mandibular distraction osteogenesis techniques and advances in outcomes.

RECENT FINDINGS

The longest phase of distraction is consolidation, when newly formed bone must fully heal. If consolidation could be accelerated, the length of time required for fixation would be less and complications associated with fixation devices would decline. In the last year, animal studies were conducted reporting the application of growth factors directly to distraction gaps to accelerate bone formation. Additional research in animal models showed success with the addition of bone marrow-derived mesenchymal stem cells to the distraction gap. Distraction devices are being piloted with automated, continuous formats compared with current devices that require manual activation. The use of surgical planning software programs to determine the location of osteotomies was another focus of current studies.

SUMMARY

Rates of activation can be accelerated with the addition of stem cells and growth factors to distraction sites, as could time to full consolidation. The addition of mesenchymal stem cells and deferoxamine and the use of low-intensity ultrasound during distraction are three of the most promising approaches reported in recent studies with potential for future translation from animal models. Computer-assisted presurgical planning offers added accuracy and potential time savings. Newer distraction devices using computer automation are still in preliminary phases, but show promise.

Biological strategies for improved osseointegration and osteoinduction of porous metal orthopedic implants

The biological interface between an orthopedic implant and the surrounding host tissue may have a dramatic effect upon clinical outcome. Desired effects include bony ingrowth (osseointegration), stimulation of osteogenesis (osteoinduction), increased vascularization, and improved mechanical stability. Implant loosening, fibrous encapsulation, corrosion, infection, and inflammation, as well as physical mismatch may have deleterious clinical effects. This is particularly true of implants used in the reconstruction of load-bearing synovial joints such as the knee, hip, and the shoulder. The surfaces of orthopedic implants have evolved from solid-smooth to roughened-coarse and most recently, to porous in an effort to create a three-dimensional architecture for bone apposition and osseointegration. Total joint surgeries are increasingly performed in younger individuals with a longer life expectancy, and therefore, the postimplantation lifespan of devices must increase commensurately. This review discusses advancements in biomaterials science and cell-based therapies that may further improve orthopedic success rates. We focus on material and biological properties of orthopedic implants fabricated from porous metal and highlight some relevant developments in stem-cell research. We posit that the ideal primary and revision orthopedic load-bearing metal implants are highly porous and may be chemically modified to induce stem cell growth and osteogenic differentiation, while minimizing inflammation and infection. We conclude that integration of new biological, chemical, and mechanical methods is likely to yield more effective strategies to control and modify the implant-bone interface and thereby improve long-term clinical outcomes.

An Update on Midface Advancement Using Le Fort II and III Distraction Osteogenesis

Le Fort II and III distraction osteogenesis (DO) is a powerful tool in the craniofacial armamentarium that is most often employed to treat patients with craniofacial syndromes such as Crouzon, Apert, or Pfeiffer syndrome who present with midfacial retrusion, shallow orbits, exorbitism, malocclusion, obstructive sleep apnea and facial imbalance. In this article, the authors will provide the reader with an update on techniques for the treatment of various forms of midfacial retrusion.

Synergistic induction of early stage of bone formation by combination of recombinant human bone morphogenetic protein-2 and epidermal growth factor

This study evaluates whether the combination of the rhBMP-2 and various types of growth factors including EGF, FGF, PDGF and VEGF increases osteoinductivity compared to the single use of rhBMP-2 through in vitro and in vivo study. Cultured human MSCs were treated with rhBMP-2 only or in combination with growth factors. For in vivo evaluation, rhBMP-2 only or with growth factors was implanted into the calvarial defect made on SD rats. Both EGF and PDGF significantly increased both ALP activity and expression level in hMSCs when treated in combination with rhBMP-2 at 3 and 7 days of differentiation and significantly raised the accumulation of the calcium at day 14. Furthermore, micro-CT scanning revealed that the EGF an FGF groups show significantly increased new bone surface ratio compared to the rhBMP-2 only group and, the EGF treatment significantly up regulated percent bone volume and trabecular number at two weeks after the surgery. VEGF treatment also significantly raised trabecular number and FGF treatment significantly increased the trabecular thickness. Histological examination revealed that the EGF combination group showed enhanced bone regeneration than the rhBMP-2 only group two weeks after the implantation. Even though the treatment of rhBMP-2 with PDGF and FGF failed to show enhanced osteogenesis in vitro and in vivo simultaneously, these results suggest that the positive effect of the combination of EGF and rhBMP-2 is expected to induce the bone formation earlier compared to the single use of rhBMP-2 in vitro and in vivo. © 2014 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons Ltd.

The effect of altering the mechanical loading environment on the expression of bone regenerating molecules in cases of distraction osteogenesis

Distraction osteogenesis (DO) is a surgical technique where gradual and controlled separation of two bony fragments following an osteotomy leads to the induction of new bone formation in the distracted gap. DO is used for limb lengthening, correction of bony deformities, and the replacement of bone loss secondary to infection, trauma, and tumors. Although DO gives satisfactory results in most cases, one major drawback of this technique is the prolonged period of time the external fixator has to be kept on until the newly formed bone consolidates thus leading to numerous complications. Numerous attempts at accelerating bone formation during DO have been reported. One specific approach is manipulation of the mechanical environment during DO by applying changes in the standard protocol of distraction. Attempts at changing this mechanical environment led to mixed results. Increasing the rate or applying acute distraction, led to poor bone formation in the distracted zone. On the other hand, the addition of compressive forces (such as weight bearing, alternating distraction with compression or by over-lengthening, and then shortening) has been reported to increase bone formation. It still remains unclear why these alterations may lead to changes in bone formation. While the cellular and molecular changes occurring during the standard DO protocol, specifically increased expression of transforming growth factor-β1, platelet-derived growth factor, insulin-like growth factor, basic fibroblast growth factor, vascular endothelial growth factor, and bone morphogenic proteins have been extensively investigated, the literature is sparse on the changes occurring when this protocol is altered. It is the purpose of this article to review the pertinent literature on the changes in the expression of various proteins and molecules as a result of changes in the mechanical loading technique in DO and try to define potential future research directions.

Growth factors in human serum during operative tibial lengthening with the Ilizarov method

Despite the widespread clinical use of distraction osteogenesis for limb lengthening, the cellular and molecular mechanisms by which this surgical treatment promotes new bone formation in humans are not well understood. The aim of the research was to study the levels of growth factors (GFs) in the serum of patients that were undergoing tibial lengthening with the Ilizarov method of distraction osteogenesis. Those were patients with unilateral congenital discrepancy of the tibia (n = 12), unilateral posttraumatic tibial shortening (n = 7), and healthy patients that underwent cosmetic bilateral tibial lengthening (n = 10). The study established that unlike the congenital group, the posttraumatic group and healthy subjects showed a significantly evident increase in the levels of angiogenic GFs in their serum on day 10 of distraction. In the congenital group, the changes were not significant at this time point. The levels of TGF-α, TGF-β1, and TGF-β2 tended to decrease on day 10 of distraction and on day 30 of the post-distraction period in the cosmetic and posttraumatic groups while they grew in the congenital group. Most dynamic changes in the GFs levels during tibial lengthening were noted in the subjects undergoing cosmetic lengthening, and the least ones were in the congenital group.