Osteoclastogenic activity during mandibular distraction osteogenesis

Activated FGFR3 suppresses bone regeneration and bone mineralization in an ovariectomized mouse model

BACKGROUND

Postmenopausal osteoporosis is a widespread health concern due to its prevalence among older adults and an associated high risk of fracture. The downregulation of bone regeneration delays fracture healing. Activated fibroblast growth factor receptor 3 (FGFR3) accelerates bone regeneration at juvenile age and downregulates bone mineralization at all ages. However, the impact of FGFR3 signaling on bone regeneration and bone mineralization post-menopause is still unknown. This study aimed to evaluate the impact of FGFR3 signaling on bone regeneration and bone mineralization during menopause by developing a distraction osteogenesis (DO) mouse model after ovariectomy (OVX) using transgenic mice with activated FGFR3 driven by Col2a1 promoter (Fgfr3 mice).

METHODS

The OVX or sham operations were performed in 8-week-old female Fgfr3 and wild-type mice. After 8 weeks of OVX surgery, DO surgery in the lower limb was performed. The 5-day-latency period followed by performing distraction for 9 days. Bone mineral density (BMD) and bone regeneration was assessed by micro-computed tomography (micro-CT) scan and soft X-ray. Bone volume in the distraction area was also evaluated by histological analysis after 7 days at the end of distraction. Osteogenic differentiation and mineralization of bone marrow-derived mesenchymal stem cells (BMSCs) derived from each mouse after 8 weeks of the OVX or sham operations were also evaluated with and without an inhibitor for FGFR3 signaling (meclozine).

RESULTS

BMD decreased after OVX in both groups, and it further deteriorated in Fgfr3 mice. Poor callus formation after DO was also observed in both groups with OVX, and the amount of regenerated bone was further decreased in Fgfr3 mice. Similarly, histological analysis revealed that Fgfr3 OVX mice showed lower bone volume. Osteogenic differentiation and mineralization of BMSCs were also deteriorated in Fgfr3 OVX mice. An inhibitor for FGFR3 signaling dramatically reversed the inhibitory effect of OVX and FGFR3 signaling on BMSC mineralization.

CONCLUSION

Upregulated FGFR3 decreased newly regenerated bone after DO and BMD in OVX mice. FGFR3 signaling can be a potential therapeutic target in patients with postmenopausal osteoporosis.

Immunomodulatory effects and mechanisms of distraction osteogenesis

Distraction osteogenesis (DO) is widely used for bone tissue engineering technology. Immune regulations play important roles in the process of DO like other bone regeneration mechanisms. Compared with others, the immune regulation processes of DO have their distinct features. In this review, we summarized the immune-related events including changes in and effects of immune cells, immune-related cytokines, and signaling pathways at different periods in the process of DO. We aim to elucidated our understanding and unknowns about the immunomodulatory role of DO. The goal of this is to use the known knowledge to further modify existing methods of DO, and to develop novel DO strategies in our unknown areas through more detailed studies of the work we have done.

Systemic Administration of G-CSF Accelerates Bone Regeneration and Modulates Mobilization of Progenitor Cells in a Rat Model of Distraction Osteogenesis

Granulocyte colony-stimulating factor (G-CSF) was shown to promote bone regeneration and mobilization of vascular and osteogenic progenitor cells. In this study, we investigated the effects of a systemic low dose of G-CSF on both bone consolidation and mobilization of hematopoietic stem/progenitor cells (HSPCs), endothelial progenitor cells (EPCs) and mesenchymal stromal cells (MSCs) in a rat model of distraction osteogenesis (DO). Neovascularization and mineralization were longitudinally monitored using positron emission tomography and planar scintigraphy. Histological analysis was performed and the number of circulating HSPCs, EPCs and MSCs was studied by flow cytometry. Contrary to control group, in the early phase of consolidation, a bony bridge with lower osteoclast activity and a trend of an increase in osteoblast activity were observed in the distracted callus in the G-CSF group, whereas, at the late phase of consolidation, a significantly lower neovascularization was observed. While no difference was observed in the number of circulating EPCs between control and G-CSF groups, the number of MSCs was significantly lower at the end of the latency phase and that of HSPCs was significantly higher 4 days after the bone lengthening. Our results indicate that G-CSF accelerates bone regeneration and modulates mobilization of progenitor cells during DO.

Effects of 12-week combined exercise on RANKL/RANK/OPG signaling and bone-resorption cytokines in healthy college females

[Purpose]

The OPG/RANK/RANKL signaling is a new family of bone metabolism biomarkers belonging to the immune system. However, the bone metabolism response to long-term exercise in the RANKL/RANK/OPG signaling is less evident. The purpose of this study was to examine these biomarkers in healthy college females after 12-weeks combined exercise intervention.

[Methods]

Participants (N=22, 22.4±1.3yrs) were randomly divided in two different group: 12 in the control group and 10 in the exercise group performing combined exercise program that interventions was conducted 3 times per week for 12 weeks. The outcome measures included serum concentrations of RANKL, OPG and bone metabolic cytokines such as TNF-α and IL-6, and mRNA expressions of same variables from PBMC. VO_2max and bone mineral density (BMD) were measured at before and after exercise intervention.

[Results]

There were no significant differences in the serum RANKL, OPG concentrations and all RANKL/RANK/OPG signaling mRNA expression on interaction effect between group and time (NS). Also no significant differences were found in the serum TNF-α and IL-6 concentrations and mRNA expression (NS). The IL-6 mRNA expression only showed significant difference in the main effect of groups (p<.05). There were also no significant differences in the VO_2max and BMD on interaction effect between group and time (NS).

[Conclusion]

These results suggested that there were no effects on bone mineral density and RANKL/RANK/OPG signaling without the effect of 8-weeks combined exercise on cardiovascular endurance fitness.

Biomolecular phases in transverse palatal distraction: A review

Transverse palatal distraction is a biological process of regenerating new bone and enveloping soft tissues in the maxillary palate region. This technique is similar to Osteo-distraction (OD) procedure for bone lengthening in which gradual and controlled traction forces are applied on the osteotomy gaps to produce new bone in between the surgically separated bone segments. This review describes the different phases after osteotomy and the biological process involved during the new bone and soft tissue formation. The mechanical environment formed in the distraction area is due to the traction forces by the distractor appliance. This environment stimulates differentiation of pluripotent cells, neovascularization, osteogenesis and remodeling of newly formed bone. The role of different pro-inflammatory cytokines, interleukins, bone morphogenic proteins, transforming growth factors, fibroblast growth factors-2) and extracellular matrix proteins (osteonectin, osteopontin) during the distraction phases has been described in detail. Also, an important note on the nutritional aspect during Osteo-distraction will benefit the clinicians to guide their patients after osteotomy throughout the distraction process.

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.

The effects of a single bout pilates exercise on mRNA expression of bone metabolic cytokines in osteopenia women

[Purpose]

The purpose of this study was to examine the effect of a single bout pilates exercise on mRNA expression of bone metabolic cytokines in elderly osteopenia women.

[Methods]

We selected 11 people of elderly osteopenia women and loaded a single bout pilates exercise about RPE 10-14 level. The blood samples were collected before, immediately after and 60 minute after pilates exercise, then examined calcium metabolic markers in serum and extracted peripheral blood mononuclear cell (PBMC) from whole blood and confirmed mRNA expression of bone metabolic cytokines from PBMC. To clarify the changes during exercise, we designed repeated measure ANOVA as the control group to perform blood sampling without exercise.

[Results]

As a result, serum P showed significant interaction effect between group and time (p<.001), the pilates exercise group decreased about 9% at immediately after exercise and 13% during recovery after exercise (p<.05), while the control group showed a tendency to increase. Serum CK also showed a significant interaction between group and time (p<.05), the pilates group significantly increased at immediately after exercise and during recovery after exercise (p<.05) but the control group didn’t have changes. TNF-α and IL-6 mRNA expression in PBMC was significantly increased in the pilates group (p<.01, p<.05), although INF-γ mRNA expression didn’t show statistically significant difference, it tended to increase in the pilates group (NS).

[Conclusion]

These results suggested that a single bout pilates exercise of elderly osteopenia women cause hypophosphatemia with temporary muscle damage, and it leading high turnover bone metabolic state with to activate both of bone formation and bone resorption.

The Molecular and Cellular Events That Take Place during Craniofacial Distraction Osteogenesis

Summary:

Gradual bone lengthening using distraction osteogenesis principles is the gold standard for the treatment of hypoplastic facial bones. However, the long treatment time is a major disadvantage of the lengthening procedures. The aim of this study is to review the current literature and summarize the cellular and molecular events occurring during membranous craniofacial distraction osteogenesis. Mechanical stimulation by distraction induces biological responses of skeletal regeneration that is accomplished by a cascade of biological processes that may include differentiation of pluripotential tissue, angiogenesis, osteogenesis, mineralization, and remodeling. There are complex interactions between bone-forming osteoblasts and other cells present within the bone microenvironment, particularly vascular endothelial cells that may be pivotal members of a complex interactive communication network in bone. Studies have implicated number of cytokines that are intimately involved in the regulation of bone synthesis and turnover. The gene regulation of numerous cytokines (transforming growth factor-β, bone morphogenetic proteins, insulin-like growth factor-1, and fibroblast growth factor-2) and extracellular matrix proteins (osteonectin, osteopontin) during distraction osteogenesis has been best characterized and discussed. Understanding the biomolecular mechanisms that mediate membranous distraction osteogenesis may guide the development of targeted strategies designed to improve distraction osteogenesis and accelerate bone regeneration that may lead to shorten the treatment duration.

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.

A collagenated porcine bone substitute for augmentation at Neoss implant sites: a prospective 1-year multicenter case series study with histology

BACKGROUND

The presence of localized defects and/or small amounts of bone below the maxillary sinus is a common finding, which may compromise implant placement. There is therefore a need for predictable techniques for bone augmentation in such situations.

PURPOSE

The study aims to clinically and histologically evaluate a porcine bone (PB) substitute used for augmentation of the alveolar crest or the maxillary sinus floor prior to or in conjunction with implant placement.

MATERIALS AND METHODS

Nineteen patients were treated with a porcine bone substitute and barrier membranes (OsteoBiol, Tecnoss Dental, Turin, Italy) for lateral bone augmentation (Group 1a) and healing of bone defects (Group 1b) or for augmentation of the maxillary sinus floor using either a replaceable (Group 2a) or an infractured bone window (Group 2b). A total of 34 implants (Neoss Ltd., Harrogate, UK) were placed in conjunction or 5 to 7 months after the procedure. Implants were followed with implant stability measurements at placement and abutment connection, and with intraoral radiographs at abutment connection and after at least 1 year of loading. A biopsy for histology and morphometry was taken at the first reentry operation.

RESULTS

All but one of the procedures was successful (94.7%) as one maxillary sinus procedure (Group 2a) resulted in insufficient bone for implant placement. One of the 34 implants failed, giving an implant survival rate of 97.1% after 1 year. Implant stability measurements showed a mean stability of 71.9 ± 7.7 implant stability quotient (ISQ) at placement, which significantly increased to 75.3 ± 6.8 ISQ at abutment connection (p = .03). The average bone loss was 0.5 ± 0.7 mm during 1 year. Histology revealed new bone formation at the PB surface, which formed bridges between particles and between particles and preexisting bone. The presence of scalloped resorption lacunae and new osteons inside the particles indicated ongoing resorption/remodeling of the particles. The histomorphometric analyses showed that the total specimen area consisted of, in average, 56.5 ± 15.7% mineralized tissue of which 24.8 ± 13.9% of the total area was PB particles.

CONCLUSION

This study showed good clinical results when using a PB substitute and barrier membranes for augmentation of the alveolar crest and maxillary sinus. Histology revealed bone condensation properties and indicated that the material can be resorbed with time.

The Effects of Hyperbaric Oxygen on Tooth Movement into the Regenerated Area after Distraction Osteogenesis

Objective

To analyze the effect of hyperbaric oxygen on newly formed bone in distracted areas surrounding the root of a moving tooth by histological and radiological analysis. It was hypothesized that the application of hyperbaric oxygen to a tooth moving into the distracted area would accelerate ossification and vascularization of newly formed bone in the distracted space.

Design

Ten dogs were used. After creating a 10-mm-long bone defect, a bony segment was prepared and translocated into the defect area at a rate of 1 mm/d for 10 days. Following the distraction period, tooth movement was started and the dogs were divided into two groups. The HBO group received hyperbaric oxygen; whereas, the control group did not. At 150 days after tooth movement, the distracted area around the moving tooth was evaluated radiologically and histologically. Differences between groups were confirmed by a Mann-Whitney U test.

Results

Trabecular bone density and cortical and subcortical bone areas measured by peripheral quantitative computed tomography in the HBO group were significantly higher than those in the control group. Histological observations revealed regenerated bone and blood vessels formation in the tension site of the moving tooth in the HBO group. The regenerated bone structure measured by bone histomorphometry was larger and more active in bone formation in the HBO group than in the control group.

Conclusions

Applying hyperbaric oxygen to tooth movement into a distracted area appears to accelerate ossification and vascularization of regenerated bone in the that area.

Molecular mechanisms controlling bone formation during fracture healing and distraction osteogenesis

Fracture healing and distraction osteogenesis have important applications in orthopedic, maxillofacial, and periodontal treatment. In this review, the cellular and molecular mechanisms that regulate fracture repair are contrasted with bone regeneration that occurs during distraction osteogenesis. While both processes have many common features, unique differences are observed in the temporal appearance and expression of specific molecular factors that regulate each. The relative importance of inflammatory cytokines in normal and diabetic healing, the transforming growth factor beta superfamily of bone morphogenetic mediators, and the process of angiogenesis are discussed as they relate to bone repair. A complete summary of biological activities and functions of various bioactive factors may be found at COPE (Cytokines & Cells Online Pathfinder Encyclopedia), http://www.copewithcytokines.de/cope.cgi.

Trigeminal nitric oxide synthase expression correlates with new bone formation during distraction osteogenesis

Nitric oxide synthase (NOS) has been reported to be involved with both bone healing and bone metabolism. The aim of this study was to test the null hypothesis that there is no correlation between new bone formation during mandibular distraction osteogenesis and NOS expression in the trigeminal ganglion of rats. Newly formed tissue during distraction osteogenesis and trigeminal NOS expression measured by the NADPH-diaphorase (NADPH-d) reaction were evaluated in 72 male Wistar rats by histomorphometric and histochemical methods. In animals submitted to 0.5 mm/day distraction osteogenesis, the percentage of bone tissue was higher in the basal area of the mandibles compared with the center and significantly increased through the experimental periods (P < 0.05). At the sixth postoperative week, the difference in bone formation between the continuous and acute distraction osteogenesis groups was the highest. Significant correlation between new bone formation by distraction osteogenesis and NADPH-d-reactive neurons was found, varying according to neuronal cell size (r = -0.6, P = 0.005, small cells strongly stained; r = 0.5, P = 0.018, large cells moderately stained). The results suggest that NOS may play a role in the bone healing process via neurogenic pathways, and the phenomenon seems to be neuronal cell morphotype-dependent. Further studies are now warranted to investigate the mechanistic link between the expression of trigeminal NOS and mandibular new bone formation by distraction osteogenesis.

Molecular Mechanisms Controlling Bone Formation during Fracture Healing and Distraction Osteogenesis

Fracture healing and distraction osteogenesis have important applications in orthopedic, maxillofacial, and periodontal treatment. In this review, the cellular and molecular mechanisms that regulate fracture repair are contrasted with bone regeneration that occurs during distraction osteogenesis. While both processes have many common features, unique differences are observed in the temporal appearance and expression of specific molecular factors that regulate each. The relative importance of inflammatory cytokines in normal and diabetic healing, the transforming growth factor beta superfamily of bone morphogenetic mediators, and the process of angiogenesis are discussed as they relate to bone repair. A complete summary of biological activities and functions of various bioactive factors may be found at COPE (Cytokines & Cells Online Pathfinder Encyclopedia), http://www.copewithcytokines.de/cope.cgi .

The bone tissue responses to prehydrated and collagenated cortico-cancellous porcine bone grafts: a study in rabbit maxillary defects

BACKGROUND

Bone substitutes should have osteoconductive properties and be completely replaced with new bone with time. Adding collagen gel to prehydrated and collagenated porcine bone (PCPB) particles results in a sticky and moldable material which facilitates clinical handling. However, the possible influence of the gel on the bone tissue response is not known.

PURPOSE

The objective of the study was to evaluate the bone tissue responses to PCPB graft with or without collagen gel and to evaluate the resorption/degradation properties of the biomaterials.

MATERIALS AND METHODS

Fourteen rabbits were used in the study. Bilateral bone defects, 5 x 8 x 3 mm, were created in the maxilla and filled with PCPB + collagen gel (test) or with PCPB only (control) and covered with a collagen membrane. Animals were killed after 2 (n = 3), 4 (n = 3), and 8 weeks (n = 8) for histological and morphometrical evaluations.

RESULTS

There were no differences between test and control defects. Both materials showed bone formation directly on the particles by typical osteoblastic seams. The bone area increased with time (2-8 weeks) for both sides, from 16.2% (control) and 19.2% (test) to 42.7 and 43.8%, respectively. The PCPB, whether mixed with collagen gel or not, was resorbed by osteoclasts as well as part of remodeling with the formation of osteons within the particles. Morphometry showed a decrease of PCPB area from 19.4% (control) and 23.8% (test) after 2 weeks to 3.7 and 9.3% after 8 weeks, respectively.

CONCLUSIONS

Mixing collagen gel and PCPB to facilitate the clinical handling does not influence the bone tissue responses to the material, which exhibited osteoconductive properties and was resorbed with time.