The effect of recombinant human bone morphogenetic protein-4 on the osteoblastic differentiation of mouse calvarial cells affected by Porphyromonas gingivalis

G protein-coupled receptor 91 activations suppressed mineralization in Porphyromonas gingivalis-infected osteoblasts

Succinate receptor GPR91 is one of the G protein-coupled receptors (GPCRs) that interacts with various proteins to regulate diverse cellular functions such as cell morphology, apoptosis, and differentiation. In this study, we investigated whether the GPR91-mediated signaling pathway regulates mineralization in Porphyromonas gingivalis (P. gingivalis)-treated osteoblasts and to determine its potential role in osteoclast differentiation. Primary mouse osteoblasts from wild-type (WT) and GPR91 knockout (GPR91-/-) mice infected with P. gingivalis were used for in vitro experiments. The results showed that inhibition by 4C, a specific inhibitor, and GPR91 knockout promoted mineralization in P. gingivalis-infected osteoblasts. Surprisingly, GPR91 knockdown decreased the migration ability of osteoblasts. Moreover, compared with P. gingivalis-infected WT osteoblasts, GPR91-/- osteoblasts exhibited decreased RANKL production, and conditioned media (CM) from bacteria-infected GPR91-/- osteoblasts suppressed the formation of osteoclast precursors. Moreover, P. gingivalis mediated the role of GPR91 in osteoblast mineralization by activating the NF-κB pathway. These findings suggest that GPR91 activation reduces mineralization of P. gingivalis-infected osteoblasts and promotes osteoclastogenesis in macrophages. Therefore, targeting GPR91 may mitigate the loss of alveolar bone during bacterial infection.

Aptamer Based SPREETA Sensor for the Detection of Porphyromonas gingivalis G-Protein

We have developed an aptamer that specifically binds to Porphyromonas gingivalis to reduce the cellular damage caused by P. gingivalis infection and applied it as a biosensor. P. gingivalis is one of the major pathogens causing destructive periodontal disease among the periodontal microorganisms constituting complex biofilms. Porphyromonas gingivalis G-protein (PGP) known to play an important role in the transmission of germs was used as a target protein for the screening of aptamer. The aptamer that has binds to the G-protein of P. gingivalis, was screened and developed through the Systemic Evolution of Ligands by Exponential Energy (SELEX) method. Modified-Western blot analysis was performed with the aptamer which consisted of 38 single-stranded DNA to confirm the selectivity. ELONA (enzyme linked oligonucleotide assay) used to confirm that the aptamer was sensitive to PGP even at low concentration of 1 μg/ml. For the rapid detection of P. gingivalis, we constructed a surface plasmon resonance biosensor with SPREETA using the PGP aptamer. It was confirmed that PGP could be detected as low concentration as at 0.1 pM, which is the minimum concentration of aptamer sensor within 5 min. Based on these results, we have constructed a SPREETA biosensor based on aptamer that can bind to P. gingivalis G-protein. It can be used as an infection diagnosis system to rapidly diagnose and analyze oral diseases caused by P. gingivalis.

Effects of rhBMP-2 with various carriers on maxillofacial bone regeneration through computed tomography evaluation

BACKGROUND

rhBMP-2 is regarded as the most potent osteoinductive growth factor, and it has been used in the oral cavity with different carriers. The purpose of this study is to evaluate the bone-regenerative effect of rhBMP-2 delivered with different carrier systems through three-dimensional cone beam computed tomography analysis.

METHOD

A total of 112 patients underwent oral surgery with rhBMP-2 application (Group 1, n = 53) or without rhBMP-2 application (Group 2, n = 59). Group 1 was divided into 3 groups according to carriers, rhBMP-2 with allograft (Group 1-1, n = 34), rhBMP-2 with xenograft (Group 1-2, n = 5), and rhBMP-2 with absorbable collagen sponge (Group 1-3, n = 14). Cone beam computed tomography scans were taken before surgery (T0) 6 months after surgery (T1). The volume of defects was measured through the three-dimensional image analysis tool.

RESULTS

The average bone regeneration rate of Group 1 was significantly greater than that of Group 2. Within Group 1, the group that used allograft as a carrier (Group 1-1) showed significantly higher bone regeneration rates than the group that used absorbable collagen sponge as a carrier (Group 1-3).

CONCLUSION

The use of rhBMP-2 after oral surgery results in a superior bone regeneration rate compared to not using rhBMP-2, and its efficacy depends on the carriers it is used with. Allograft affects bone regeneration more than absorbable collagen sponge when it is carried with rhBMP-2. Therefore, the appropriate use of rhBMP-2 with suitable bone grafting materials is useful for promoting postoperative bone regeneration in oral surgery.

Fibrin Glue/Fibronectin/Heparin-Based Delivery System of BMP2 Induces Osteogenesis in MC3T3-E1 Cells and Bone Formation in Rat Calvarial Critical-Sized Defects

Bone morphogenetic proteins (BMPs) have been used to promote bone formation in many clinical scenarios. However, the BMPs are inherently unstable in vivo and therefore need to be combined with carriers for controlled delivery. In this study, an innovative and efficient fibrin glue/fibronectin/heparin (FG/Fn/Hep)-based delivery system was developed for controlled release of BMP2. The incorporation of heparin can significantly slow the release of BMP2 without substantially affecting the structure and stiffness of the FG/Fn. The BMP2 release from the FG/Fn/Hep-BMP2 hydrogel is largely dominated by hydrogel degradation rather than simple diffusion. In vitro release experiments and MC3T3-E1 cell induction experiments showed that BMP2 can be released steadily and can induce MC3T3-E1 cells to differentiate into osteoblasts efficiently. This process is characterized by the significantly increased expression of calcium deposits, alkaline phosphatase, runt-related transcription factor-2, osteopontin, osteocalcin, and collagen I in comparison with the negative control. In vivo assessments revealed that the FG/Fn/Hep-BMP2 hydrogel significantly promotes bone regeneration in a rat calvarial critical-sized defect model. Our investigation indicates that FG/Fn/Hep-BMP2 hydrogel holds promise to be used as an alternative biomaterial for the repair of bone defects.

Bone regenerative efficacy of biphasic calcium phosphate collagen composite as a carrier of rhBMP-2

OBJECTIVES

This study compared the bone regenerative effects of a recombinant human bone morphogenetic protein 2 (rhBMP-2)-loaded collagen-based biphasic calcium phosphate composite (BCPC) and rhBMP-2-loaded biphasic calcium phosphate (BCP).

MATERIAL AND METHODS

The in vitro release profiles of rhBMP-2-loaded BCP and BCPC were measured. The animal surgery was performed on ten rabbits. Four 8-mm-diameter circular calvarial defects were made and filled with BCP, BCPC, rhBMP-2-loaded BCP (BMP + BCP) and rhBMP-2-loaded BCPC (BMP + BCPC). The animals were euthanized either 2 or 8 weeks after surgery.

RESULTS

The initial burst release of rhBMP-2 was greater for BCP than for BCPC, and both presented a slow release pattern thereafter. In rabbit calvarial defects, the space maintaining capability and graft resorption of all experimental groups did not show statistical differences at 2 and 8 weeks. New bone formation in the rhBMP-2-loaded groups was greater than in the non-loaded groups at both weeks, but the amount of new bone was comparable between both rhBMP-2-loaded groups at both weeks. There was a distinct histologic difference between the BMP + BCP and BMP + BCPC groups at 2 weeks; the new bone formation occurred more in the intergranular spaces and the BCP-to-bone contact was greater in the BMP + BCPC group, but these differences were no longer discernible at 8 weeks.

CONCLUSIONS

BCP- and BCPC-loaded rhBMP-2 significantly improved bone regeneration and BCPC led to a dense network of new bone and bone particles during the early healing period. BCPC can therefore be considered as a promising candidate for carrying rhBMP-2.

The efficacy of BMP-2 preloaded on bone substitute or hydrogel for bone regeneration at peri-implant defects in dogs

OBJECTIVES

The objective of this experiment was to test whether or not a synthetic bone substitute (SBS) was more effective than a polyethylene glycol hydrogel as a carrier material for bone morphogenetic protein-2 (BMP-2) when attempting to regenerate bone.

MATERIAL AND METHODS

Two identical, box-type dehiscence defects (4 × 4 mm buccolingually and apicocoronally, and 8 mm mesiodistally) were surgically prepared on buccal sides of the left and right edentulous ridge in five beagle dogs. Following implant placement, the defects either received (i) no graft, (ii) SBS+hydrogel, (iii) SBS+BMP-2 loaded hydrogel, and (iv) BMP-2-loaded SBS+hydrogel. The animals were euthanized at 8 weeks postsurgery. Radiographic and histomorphometric analyses were performed.

RESULTS

The hydrogel alone was not able to stabilize the grafted bone particles at 8 weeks, and SBS+hydrogel group did not significantly differ from the control group in all volumetric measurements. On the other hand, extensively regenerated new bone was connected with most of the remaining SBS particles in the BMP-2 groups. The BMP-2 groups exhibited significantly greater new bone formation (10.65 mm(3) and 1.47 mm(2) in the SBS+BMP-2-loaded hydrogel group; 14.17 mm(3) and 0.93 mm(2) in the BMP-2-loaded SBS+hydrogel) than non-BMP-2 groups (1.27 mm(3) and 0.00 mm(2) in the control group; 2.01 mm(3) and 0.19 mm(2) in the SBS+hydrogel group) in volumetric and histomorphometric analyses (P < 0.001). However, there were no significant differences between both BMP-2 groups.

CONCLUSION

BMP-2 could yield enhanced bone regeneration in the critical-size peri-implant defects regardless of whether SBS or hydrogel is used for preloading, although the outcomes seem to be more reproducible with BMP-2 preloaded on SBS.

Porphyromonas gingivalis infection increases osteoclastic bone resorption and osteoblastic bone formation in a periodontitis mouse model

Background

Porphyromonas gingivalis has been shown to invade osteoblasts and inhibit their differentiation and mineralization in vitro. However, it is unclear if P. gingivalis can invade osteoblasts in vivo and how this would affect alveolar osteoblast/osteoclast dynamics. This study aims to answer these questions using a periodontitis mouse model under repetitive P. gingivalis inoculations.

Methods

For 3-month-old BALB/cByJ female mice, 10⁹ CFU of P. gingivalis were inoculated onto the gingival margin of maxillary molars 4 times at 2-day intervals. After 2 weeks, another 4 inoculations at 2-day intervals were applied. Calcein was injected 7 and 2 days before sacrificing animals to label the newly formed bone. Four weeks after final inoculation, mice were sacrificed and maxilla collected. Immunohistochemistry, micro-CT, and bone histomorphometry were performed on the specimens. Sham infection with only vehicle was the control.

Results

P. gingivalis was found to invade gingival epithelia, periodontal ligament fibroblasts, and alveolar osteoblasts. Micro-CT showed alveolar bone resorption and significant reduction of bone mineral density and content in the infected mice compared to the controls. Bone histomorphometry showed a decrease in osteoblasts, an increase in osteoclasts and bone resorption, and a surprisingly increased osteoblastic bone formation in the infected mice compared to the controls.

Conclusions

P. gingivalis invades alveolar osteoblasts in the periodontitis mouse model and cause alveolar bone loss. Although P. gingivalis appears to suppress osteoblast pool and enhance osteoclastic bone resorption, the bone formation capacity is temporarily elevated in the infected mice, possibly via some anti-microbial compensational mechanisms.

Porphyromonas gingivalis invades osteoblasts and inhibits bone formation

Porphyromonas gingivalis is etiologically associated with adult periodontitis, but it is unclear how P. gingivalis long-term interactions with bone cells contribute to this disease. This study investigates P. gingivalis interactions with osteoblasts over an extended time course. A primary mouse calvarial osteoblast culture was established and inoculated with P. gingivalis 33277 repeatedly every other day for up to four weeks. Invasion of osteoblasts by P. gingivalis, and the resulting effects on the proliferation, differentiation, and mineralization of osteoblasts were evaluated. P. gingivalis was found to invade osteoblasts in a dose-dependent manner, and repetitive inoculation increased the percentage of osteoblasts with internalized P. gingivalis. P. gingivalis did not affect osteoblast proliferation, but inhibited their differentiation and mineralization, partially via an inhibition of the differentiation regulatory transcription factors Cbfa-1 and osterix. In conclusion, P. gingivalis invades osteoblasts and inhibits bone formation, which likely contributes to alveolar bone loss in chronic periodontitis.

The Effect of Varying the Particle Size of Beta Tricalcium Phosphate Carrier of Recombinant Human Bone Morphogenetic Protein-4 on Bone Formation in Rat Calvarial Defects

BACKGROUND

Beta tricalcium phosphate (beta-TCP) has been developed as one of the carriers of recombinant human bone morphogenetic protein (rhBMP). However, it is not known whether the particle size of beta-TCP is related to its resorption rate and the degree of bone formation. The purpose of this study was to evaluate the effect of using beta-TCP with different particle sizes on the ability of rhBMP-4 to enhance bone formation in the rat calvarial defect model.

METHODS

Calvarial, 8-mm-diameter, critical-size defects were created in 100 male Sprague-Dawley rats. Five groups of 20 animals each received either rhBMP-4 (2.5 microg) using beta-TCP with a particle size of 50 to 150 microm, rhBMP-4 (2.5 microg) using beta-TCP with a particle size of 150 to 500 microm, a beta-TCP control with a particle size of 50 to 150 microm, a beta-TCP control with a particle size of 150 to 500 microm, or a sham-surgery control, respectively, and were evaluated by measuring their histologic and histometric parameters following a 2- and 8-week healing interval.

RESULTS

There were no significant differences in the defect closure, new bone area, or augmented area between either the two rhBMP-4/beta-TCP groups or between the two beta-TCP control groups at 2 and 8 weeks.

CONCLUSIONS

rhBMP-4 combined with either small- or large-particle beta-TCP had a significant effect on the induction of bone formation compared to either a small- or large-particle beta-TCP control or a sham-surgery control. Within the parameters of this study, varying the particle size of beta-TCP did not seem to have a significant effect on bone formation.

Effect of a Fibrin-Fibronectin Sealing System as a Carrier for Recombinant Human Bone Morphogenetic Protein-4 on Bone Formation in Rat Calvarial Defects

BACKGROUND

Bone morphogenetic proteins (BMPs) have been shown to play an important role in bone formation during development and wound healing. Despite there being good prospects for BMP applications, an ideal carrier system for BMPs has yet to be determined. The purpose of this study was to evaluate the possibility of a fibrin-fibronectin sealing system (FFSS) as a carrier for recombinant human BMP-4 (rhBMP-4) and to evaluate the genuine osteoconductive potential of the FFSS in a rat calvarial defect model.

METHODS

An 8-mm, calvarial, critical-size osteotomy defect was created in each of 30 male Sprague-Dawley rats. Three groups of 10 animals each received rhBMP-4 (0.025 mg/ml) in the FFSS, FFSS control, or sham-surgery control. The groups were evaluated using histologic and histometric parameters following 2- and 8-week healing intervals (five animals per group per healing interval).

RESULTS

Surgical implantation of rhBMP-4/FFSS resulted in enhanced local bone formation at 2 and 8 weeks. New bone formation was also evident in the FFSS control; however, the amount of defect closure, new bone area, and bone density was significantly greater in the rhBMP-4/FFSS group (P < 0.05). At 8 weeks, the quantity of the new bone was greater than that observed at 2 weeks, and the specimens showed a more advanced stage of remodeling and consolidation in both groups (P < 0.05). Only very limited bone formation was observed in the sham-surgery control.

CONCLUSION

The results of the present study indicated that the FFSS has osteoconductive potential and may be employed as a carrier for BMPs.

Role of Bovine Bone Morphogenetic Proteins in Bone Matrix Protein and Osteoblast-Related Gene Expression During Rat Bone Marrow Stromal Cell Differentiation

Bone morphogenetic proteins (BMPs) are known to promote osteogenesis, and clinical trials are currently underway evaluating the ability of certain BMPs to promote bone graft and fracture healing. To observe the mechanism of osteoinductive and bone formation, 100 microg of bovine BMP was tested during osteogenic differentiation of rat bone marrow stromal cells (MSCs) and C2C12 line culture for 14 and 28 days. We examined alkaline phosphatase (ALP) by assay, immunohistochemical studies for bone matrix proteins, and mRNA expression of bone matrix proteins and osteoblast-related analysis by reverse-transcription polymerase chain reaction. ALP activity in MSC cultures was elevated by bovine BMP by two to fivefold (P < 0.05-0.001). DNA and protein content increased over 14 days. BMP significantly increased the mRNA expression of type I collagen, ALP, osterix, osteocalcin, osteopontin, vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF)-A, and parathyroid hormone receptor time dependently during the osteoblastic differentiation. There was no markedly enhanced mRNA expression of bone sialoprotein (BSP) and glyceraldehyde-3-phosphate dehydrogenase compared with that of control. Immunohistochemical results also showed BMP increased immunoreactive positivity of type I collagen, osteocalcin, osteonectin, osteopontin, and BSP during the C2C12 differentiation. These data indicated that BMP enhances our ability to stimulate the differentiation of osteoblast-like cells and increases osteoinductivity, bone matrix protein formation and mineralization, angiogenesis, and chondrogenesis during osteoblast progenitor cell differentiation in vitro and that the role of chondrogenic is weak.

Effect of Recombinant Human Bone Morphogenetic Protein-2, -4, and -7 on Bone Formation in Rat Calvarial Defects

BACKGROUND

Currently, more than 20 bone morphogenetic proteins (BMPs) have been identified, and many trials have been carried out using recombinant human BMPs (rhBMPs) for bone tissue engineering. However, comparative analyses on bone formative activities of rhBMP using a preclinical model have been limited. Therefore, the aim of this study was to evaluate and compare the osteogenic potential of rhBMP-2, -4, and -7 delivered with absorbable collagen sponge (ACS) upon early (2 weeks) and complete (8 weeks) wound healing phases in a critical sized rat calvarial defect model.

METHODS

Eight-millimeter critical sized calvarial defects were created in 30 male Sprague-Dawley rats. The animals were divided into three groups of 10 animals each. The defects were treated with 0.025 mg/ml rhBMP-2/ACS, rhBMP-4/ACS, or rhBMP-7/ACS. The rats were sacrificed at either 2 (five rats) or 8 (five rats) weeks after surgery, and the results were evaluated histologically, histomorphometrically, and immunohistometrically.

RESULTS

The surgical implantation of rhBMP-2/ACS, rhBMP-4/ACS, or rhBMP-7/ACS resulted in enhanced local bone formation in the rat calvarial defect model at both 2 and 8 weeks. The amount of defect closure, new bone area, and bone density were similar in the three groups at each time point (P > 0.05). In terms of bone density and new bone area, there were statistically significant differences between results obtained at 2 weeks and those obtained at 8 weeks in all groups (P < 0.05). Two-way analysis of variance (ANOVA) revealed that there was no correlation between the time and conditions (P > 0.05), but time was found to have a strong influence on defect closure, new bone area, and bone density (P < 0.05). Irrespective of rhBMP type, positive immunoreactions of osteopontin (OPN) and osteocalcin (OCN) were evident at 2 and 8 weeks. Intense OPN and OCN staining was observed near the newly formed bone as well as in some cells within the new bone.

CONCLUSIONS

Within the rhBMP types used, rhBMP concentration, and the observation interval, there appears to be no specific differences in bone regenerative potential. All rhBMPs used in this study may be considered effective factors for inducing bone formation.

Ectopic bone formation associated with recombinant human bone morphogenetic proteins-2 using absorbable collagen sponge and beta tricalcium phosphate as carriers

The ectopic bone formation of recombinant human bone morphogenetic protein-2(rhBMP-2) was evaluated using absorbable collagen sponges (ACS) and beta tricalcium phosphate (beta-TCP) as carriers in a rat subcutaneous assay model. Subcutaneous pockets were created on the back of rats. The pockets were implanted with rhBMP-2/ACS, rhBMP-2/beta-TCP, ACS alone, and beta-TCP alone. The rats were sacrificed at 2 or 8 weeks for histological and immunohistochemical evaluation. At 2 weeks, bone formation was evident in both the rhBMP-2/ACS and rhBMP-2/beta-TCP sites. At 8 weeks, the quantity of the new bone with a more advanced stage of remodeling had increased further in the rhBMP-2/beta-TCP sites. However, the newly formed bone observed at 2 weeks was not found in the rhBMP-2/ACS sites. On immunohistochemical observation, osteopontin staining was observed on both the rhBMP-2/ACS (2 weeks) and rhBMP-2/beta-TCP (2 and 8 weeks) sites. Osteocalcin was not detected in any of the samples. The lack of space-providing capacity of ACS may be one of the major factors responsible for its failure to maintain the newly induced bone. Therefore, a carrier for BMPs should provide space for bone formation and maturation during the more advanced healing stages.

Effect of recombinant human bone morphogenetic protein-4 dose on bone formation in a rat calvarial defect model

BACKGROUND

Bone morphogenetic proteins (BMPs) are being evaluated for periodontal and bone regenerative therapy. The objective of this study was to evaluate the effect of recombinant human bone morphogenetic protein-4 (rhBMP-4) dose on local bone formation in a rat calvaria defect model.

METHODS

Calvarial, 8 mm diameter, critical-size osteotomy defects were created in 140 male Sprague-Dawley rats. Seven groups of 20 animals each received either 1) rhBMP-4 (2.5 microg) in an absorbable collagen sponge (ACS) carrier, 2) rhBMP-4 (5 microg)/ACS, 3) rhBMP-4 (2.5 microg) in a beta-tricalcium phosphate (beta-TCP) carrier, 4) rhBMP-4 (5 microg)/beta-TCP, 5) ACS or 6) beta-TCP carrier controls, or 7) a sham-surgery control, and were evaluated by histologic and histometric parameters following a 2- or 8-week healing interval (10 animals/group/healing interval).

RESULTS

Surgical implantation of rhBMP-4/ACS and rhBMP-4/beta-TCP resulted in enhanced local bone formation at both 2 and 8 weeks. Within the dose range examined, rhBMP-4 did not exhibit an appreciable dose-dependent response. Defect closure was not significantly different between the rhBMP-4/ACS and rhBMP-4/beta-TCP groups. New bone area of the rhBMP-4/ beta-TCP group was significantly greater than that of the rhBMP-4/ ACS group; however, bone density in the rhBMP-4/ACS group was significantly greater than that in the rhBMP-4/beta-TCP group at 8 weeks (P < 0.05).

CONCLUSIONS

rhBMP-4 combined with ACS or beta-TCP has a significant potential to induce bone formation in the rat calvaria defect model. Within the selected rhBMP-4 dose range and observation interval, there appeared to be no meaningful differences in bone formation.