Osteogenic efficacy of BMP-2 mixed with hydrogel and bone substitute in peri-implant dehiscence defects in dogs: 16 weeks of healing

OBJECTIVES

The objective of this study was to determine the effect of bone morphogenetic protein-2 (BMP-2) mixed with either polyethylene glycol hydrogel or synthetic bone substitute (SBS) on new bone formation in peri-implant dehiscence defects after 16 weeks of healing.

MATERIALS AND METHODS

A guided bone regeneration procedure was performed in box-type peri-implant defects that were surgically prepared in six beagle dogs. The following four experimental groups were used (i) control (no graft), (ii) SBS+hydrogel, (iii) SBS+BMP-2/hydrogel and (iv) BMP-2/SBS+hydrogel. Volumetric analysis using micro-computed tomography and histomorphometric analysis was performed at 16 weeks post-operatively.

RESULTS

The amount of new bone and the total augmented volume did not differ significantly between both BMP-treated groups and the SBS+hydrogel group (p > .05). Likewise, no histometric differences were observed in the values of new bone area and bone-to-implant contact ratio among the three augmentation groups (new bone area: 0.06 ± 0.08, 0.19 ± 0.20, 0.48 ± 0.37 and 0.56 ± 0.60 mm² [mean ± standard deviation] in groups 1-4, respectively; bone-to-implant contact: 9.44 ± 11.51%, 19.91 ± 15.19%, 46.31 ± 29.82% and 42.58 ± 26.27% in groups 1-4, respectively).

CONCLUSION

The osteogenic efficacy of BMP-2 on the regeneration of peri-implant bone defects was not detectable after 16 weeks regardless of the carrier materials.

Dose reduction of bone morphogenetic protein-2 for bone regeneration using a delivery system based on lyophilization with trehalose

Introduction

To induce sufficient new bone formation, high doses of bone morphogenetic protein-2 (BMP-2) are applied in regenerative medicine that often induce serious side effects. Therefore, improved treatment strategies are required. Here, we investigate whether the delivery of BMP-2 lyophilized in the presence of trehalose reduced the dose of BMP-2 required for bone regeneration.

Materials and methods

A new growth factor delivery system was fabricated using BMP-2-loaded TiO₂ nanotubes by lyophilization with trehalose (TiO₂-Lyo-Tre-BMP-2). We measured BMP-2 release characteristics, bioactivity, and stability, and determined the effects on the osteogenic differentiation of bone marrow stromal cells in vitro. Additionally, we evaluated the ability of this formulation to regenerate new bone around implants in rat femur defects by micro-computed tomography (micro-CT), sequential fluorescent labelling, and histological analysis.

Results

Compared with absorbed BMP-2-loaded TiO₂ nanotubes (TiO₂-BMP-2), TiO₂-Lyo-Tre-BMP-2 exhibited sustained release, consistent bioactivity, and higher stability of BMP-2, and resulted in greater osteogenic differentiation of BMSCs. Eight weeks post-operation, TiO₂-Lyo-Tre-BMP-2 nanotubes, with various dosages of BMP-2, regenerated larger amounts of new bone than TiO₂-BMP-2 nanotubes.

Conclusion

Our findings indicate that delivery of BMP-2 lyophilized with trehalose may be a promising method to reduce the dose of BMP-2 and avoid the associated side effects.

* Calvarial Bone Regeneration Is Enhanced by Sequential Delivery of FGF-2 and BMP-2 from Layer-by-Layer Coatings with a Biomimetic Calcium Phosphate Barrier Layer

A drug delivery coating for synthetic bone grafts has been developed to provide sequential delivery of multiple osteoinductive factors to better mimic aspects of the natural regenerative process. The coating is composed of a biomimetic calcium phosphate (bCaP) layer that is applied to a synthetic bone graft and then covered with a poly-l-Lysine/poly-l-Glutamic acid polyelectrolyte multilayer (PEM) film. Bone morphogenetic protein-2 (BMP-2) was applied before the coating process directly on the synthetic bone graft and then, bCaP-PEM was deposited followed by adsorption of fibroblast growth factor-2 (FGF-2) into the PEM layer. Cells access the FGF-2 immediately, while the bCaP-PEM temporally delays the cell access to BMP-2. In vitro studies with cells derived from mouse calvarial bones demonstrated that Sca-1 and CD-166 positive osteoblast progenitor cells proliferated in response to media dosing with FGF-2. Coated scaffolds with BMP-2 and FGF-2 were implanted in mouse calvarial bone defects and harvested at 1 and 3 weeks. After 1 week in vivo, proliferation of cells, including Sca-1+ progenitors, was observed with low dose FGF-2 and BMP-2 compared to BMP-2 alone, indicating that in vivo delivery of FGF-2 activated a similar population of cells as shown by in vitro testing. At 3 weeks, FGF-2 and BMP-2 delivery increased bone formation more than BMP-2 alone, particularly in the center of the defect, confirming that the proliferation of the Sca-1 positive osteoprogenitors by FGF-2 was associated with increased bone healing. Areas of bone mineralization were positive for double fluorochrome labeling of calcium and alkaline phosphatase staining of osteoblasts, along with increased TRAP+ osteoclasts, demonstrating active bone formation distinct from the bone-like collagen/hydroxyapatite scaffold. In conclusion, the addition of a bCaP layer to PEM delayed access to BMP-2 and allowed the FGF-2 stimulated progenitors to populate the scaffold before differentiating in response to BMP-2, leading to improved bone defect healing.

[Experimental study on accelerated healing of jaw fracture using gelatin sponge compound growth factor]

OBJECTIVE

To explore the role and mechanism of drug delivery systems using growth factor combined with gelatin sponge on accelerating the healing of jaw fracture and to seek better treatment of accelerating the maxillofacial fracture.

METHODS

About 100 μg recombinant human bone morphogenetic protein (BMP)-2 was completely dissolved in 1 mL recombinant bovine basic fibroblast growth factor (bFGF), and the solution (40 μL) was dropped in gelatin sponge (0.5 cm×0.5 cm×1.0 cm). Then, it was freeze dried and prepared into bFGF/BMP/gelatin sponge delivery systems. The mandibular fracture model on two sides were prepared in 12 New Zealand rabbits and randomly divided into two groups. The left side was the control group, which was only fixed with titanium plates. The right side was the experimental group, in which bFGF/BMP/gelatin sponge delivery systems were put under the titanium plates. General observation, X-ray, and histological examination were taken at 2, 4, and 12 weeks after surgery.

RESULTS

After 2 weeks, more fibrous tissues were seen between the fracture ends in the experimental group than in the control group. After 4 weeks, fibrous fracture callus were seen in the fracture gap in the experimental group. The ingrowths of fibrous tissue and blood vessels were seen in the control group. The fracture healing of the experimental group was significantly faster than the control group at 2 and 4 weeks. After 12 weeks, the experimental and control groups all healed completely.

CONCLUSIONS

bFGF/BMP/gelatin sponge can accelerate and improve fracture healing; thus, it has better clinical application prospect.

Dual growth factor-immobilized asymmetrically porous membrane for bone-to-tendon interface regeneration on rat patellar tendon avulsion model

Insufficient repair of the bone-to-tendon interface (BTI) with structural/compositional gradients has been a significant challenge in orthopedics. In this study, dual growth factor (platelet-derived growth factor-BB [PDGF-BB] and bone morphogenetic protein-2 [BMP-2])-immobilized polycaprolactone (PCL)/Pluronic F127 asymmetrically porous membrane was fabricated to estimate its feasibility as a potential strategy for effective regeneration of BTI injury. The growth factors immobilized (via heparin-intermediated interactions) on the membrane were continuously released for up to ∼80% of the initial loading amount after 5 weeks without a significant initial burst. From the in vivo animal study using a rat patellar tendon avulsion model, it was observed that the PDGF-BB/BMP-2-immobilized membrane accelerates the regeneration of the BTI injury, probably because of the continuous release of both growth factors (biological stimuli) and their complementary effect to create a multiphasic structure (bone, fibrocartilage, and tendon) like a native structure, as well as the role of the asymmetrically porous membrane as a physical barrier (nanopore side; prevention of fibrous tissue invasion into the defect site) and scaffold (micropore side; guidance for tissue regeneration). © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 115-125, 2018.

Effect of dopamine on bone morphogenesis protein-2 expression in human retinal pigment epithelium

AIM

To investigate the effect of dopamine on bone morphogenesis protein-2 (BMP-2) expression in retinal pigment epithelium (RPE) cells in vitro.

METHODS

ARPE-19 cells as a human RPE cell line were cultured with dopamine for different times (2, 4, 6, 8, 12, 16 and 24h) or with different concentrations (0.1, 1, 2, 5, 10, 20, and 100 µg/mL) in vitro. BMP-2 mRNA expression level in ARPE-19 cells was analyzed with real-time polymerase chain reaction (PCR) analysis and BMP-2 protein level was measured with Western blot analysis. The active form of BMP-2 in the culture medium was measured with enzyme-linked immunosorbent assay (ELISA).

RESULTS

The expression level of BMP-2 increased significantly cultured with 20 µg/mL dopamine, at different time points (P<0.05). BMP-2 mRNA level peaked 2h and the protein level peaked at 6 and 8h after treatment. The concentrations of secreted BMP-2 elevated at 12h and peaked at 24h (P<0.05) in a time-dependent manner. Treated with 100 µg/mL dopamine for 6h, the expression levels of BMP-2 mRNA and protein in ARPE-19 cells were enhanced significantly compared to that in the untreated cells (P<0.05). And secreted BMP-2 protein in the cell culture supernatant was also increased (P<0.05).

CONCLUSION

Dopamine up-regulate BMP-2 expression in RPE cells, and this may be associated with its inhibitive effect on myopia development.

Celecoxib inhibits osteoblast differentiation independent of cyclooxygenase activity

Non-steroidal anti-inflammatory drugs (NSAIDs) exert their effects primarily by inhibiting the activity of cyclooxygenase (COX), thus suppressing prostaglandin synthesis. Some NSAIDs are known to perform functions other than pain control, such as suppressing tumour cell growth, independent of their COX-inhibiting activity. To identify NSAIDs with COX-independent activity, we examined various NSAIDs for their ability to inhibit osteoblastic differentiation using the mouse pre-osteoblast cell line MC3T3-E1. Only celecoxib and valdecoxib strongly inhibited osteoblastic differentiation, and this effect was not correlated with COX-inhibiting activity. Moreover, 2,5-dimethyl (DM)-celecoxib, a celecoxib analogue that does not inhibit COX activity, also inhibited osteoblastic differentiation. Celecoxib and DM-celecoxib inhibited osteoblastic differentiation induced by bone morphogenetic protein (BMP)-2 in C2C12 mouse myoblast cell line. Although celecoxib suppresses the growth of some tumour cells, the viability and proliferation of MC3T3-E1 cells were not affected by celecoxib or DM-celecoxib. Instead, celecoxib and DM-celecoxib suppressed BMP-2-induced phosphorylation of Smad1/5, a major downstream target of BMP receptor. Although it is well known that COX plays important roles in osteoblastic differentiation, these results suggest that some NSAIDs, such as celecoxib, have targets other than COX and regulate phospho-dependent intracellular signalling, thereby modifying bone remodelling.

Sinus augmentation using a mini-pig model: Effect of ceramic and allogeneic bone biomaterials

BACKGROUND

Present clinical practice broadly relies on off-the-shelf allogeneic, xenogeneic or synthetic bone biomaterials in support of sinus augmentation. Also, recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge carrier (rhBMP-2/ACS) has been shown to support clinically relevant bone formation when used to augment the maxillary sinus.

OBJECTIVES

To evaluate local bone formation/dental implant osseointegration following implantation of two particulate bone biomaterials using the mini-pig sinus augmentation model.

METHODS

Nine adult Göttingen mini-pigs were used for evaluation of a biphasic ceramic (15%/85% HA/ß-TCP) and an allogeneic mineralized bone biomaterial. Treatments randomized to contralateral sinus sites included sham-surgery (control) and biomaterials. Two threaded dental implants (ø4.0 × 11.5 mm) were placed at each sinus site. The animals were euthanized at 8 weeks for histologic analysis.

RESULTS

Execution of the surgical protocol and healing was unremarkable. Limited infraorbital swelling was observed until suture removal. The biphasic ceramic and allogeneic bone biomaterials produced significantly increased bone formation (5.2 ± 1.9 mm and 4.9 ± 1.6 mm vs. 2.6 ± 0.5 mm, p < 0.05) and osseointegration (18.0 ± 6.0% and 25.1 ± 18.2% vs. 10.1 ± 8.0%, p < 0.05) over the sham-surgery control. No significant differences were observed between biomaterials.

CONCLUSIONS

Implantation of biphasic ceramic or allogeneic bone biomaterials enhances bone formation in the mini-pig maxillary sinus, however, dental implant bone support is incomplete resulting in overall limited osseointegration.

Biscarbamate Cross-Linked Low-Molecular-Weight Polyethylenimine for Delivering Anti-chordin siRNA into Human Mesenchymal Stem Cells for Improving Bone Regeneration

Small-interfering RNA (siRNA) provides a rapid solution for drug design and provides new methods to develop customizable medicines. Polyethyleneimine 25 kDa (PEI25kDa) is an effective transfection agent used in siRNA delivery. However, the lack of degradable linkage causes undesirable toxicity, hindering its clinical application. We designed a low-molecular-weight cross-linked polyethylenimine named PEI-Et (Mn:1220, Mw:2895) by using degradable ethylene biscarbamate linkage with lower cytotoxicity and higher knockdown efficiency than PEI25kDa in delivery Chordin siRNA to human bone mesenchymal stem cells (hBMSCs). Suppression of Chordin by using anti-Chordin siRNA delivered by PEI-Et improved bone regeneration in vitro and in vivo associated with the bone morphogenetic protein-2 (BMP-2) mediated smad1/5/8 signaling pathway. Results of this study suggest that Chordin siRNA can be potentially used to improve osteogenesis associated with the BMP-2-mediated Smad1/5/8 signaling pathway and biodegradable biscarbamate cross-linked low-molecular-weight polyethylenimine (PEI-Et) is a therapeutically feasible carrier material to deliver anti-Chordin siRNA to hBMSCs.

[Effect of naringin combined with bone morphogenetic protein-2 on the proliferation and differentiation of MC3T3-E1 cells]

OBJECTIVE

This study evaluates the biological effects of naringin (NAR) joint bone morphogenetic protein (BMP)-2 on the proliferation, alkaline phosphatase (ALP) activity, and expression of osteoblastogenic genes, such as Runt-related transcription factor 2 (Runx2), collagen Ⅰ (ColⅠ), ALP, and osteocalcin (OCN) of pre-osteoblasts.

METHODS

Three different NAR concentrations (10, 100, and 1 000 μmol·L⁻¹) were applied, alone or combined with BMP-2(50 ng·mL⁻¹), to restore the osteoblastogenesis of pre-osteoblasts (MC3T3-E1 cell line). Cell numbers (proliferation) were evaluated at first, fourth, and seventh days by Alamar blue assay. ALP activity and the expression of osteoblastogenic genes, such as Runx2, ColⅠ, ALP, and OCN were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) at fourth and seventh day.

RESULTS

Stimulation by NAR alone and in combination with BMP-2 for 1 day and 4 days could promote cell proliferation, which peaked at a concentration of 100 μmol·L⁻¹ NAR combined with BMP-2 could promote cell proliferation significantly (P<0.05). Stimulation by NAR alone and in combination with BMP-2 for 4 and 7 days could promote ALP activity and bone-related gene(ALP, OCN, Runx2, ColⅠ) expression. ALP expression was significantly promoted after stimulation of 100 μmol·L⁻¹ NAR and BMP-2 (P<0.05).

CONCLUSIONS

NAR exhibits promising potential for improving MC3T3-E1 proliferation and differentiation, and appropriate concentrations of NAR and BMP-2 show synergistic effect.
.

Hyaluronic Acid Promotes the Osteogenesis of BMP-2 in an Absorbable Collagen Sponge

(1) Background: We tested the hypothesis that hyaluronic acid (HA) can significantly promote the osteogenic potential of BMP-2/ACS (absorbable collagen sponge), an efficacious product to heal large oral bone defects, thereby allowing its use at lower dosages and, thus, reducing its side-effects due to the unphysiologically-high doses of BMP-2; (2) Methods: In a subcutaneous bone induction model in rats, we first sorted out the optimal HA-polymer size and concentration with micro CT. Thereafter, we histomorphometrically quantified the effect of HA on new bone formation, total construct volume, and densities of blood vessels and macrophages in ACS with 5, 10, and 20 μg of BMP-2; (3) Results: The screening experiments revealed that the 100 µg/mL HA polymer of 48 kDa molecular weight could yield the highest new bone formation. Eighteen days post-surgery, HA could significantly enhance the total volume of newly-formed bone by approximately 100%, and also the total construct volume in the 10 μg BMP-2 group. HA could also significantly enhance the numerical area density of blood vessels in 5 μg BMP-2 and 10 μg BMP-2 groups. HA did not influence the numerical density of macrophages; and (4) Conclusions: An optimal combined administration of HA could significantly promote osteogenic and angiogenic activity of BMP-2/ACS, thus potentially minimizing its potential side-effects.

Adenovirus-mediated bone morphogenetic protein-2 promotes osteogenic differentiation in human mesenchymal stem cells in vitro

Delayed and failed bone union following fracture is a common clinical complication that requires treatment in orthopedics. Cell-based therapies and tissue-engineering approaches are potential therapeutic strategies for bone repair and fracture healing. However, the effect of adenovirus expressing bone morphogenetic protein-2 (Ad-BMP-2) on the osteogenic ability of human mesenchymal stem cells (hMSCs) has remained to be fully elucidated. Therefore, in the present study, hMSCs were transduced using Ad-BMP-2 to assess the effects of its application and to determine whether Ad-BMP-2 promotes the osteogenic differentiation of hMSCs. The purity of the hMSC cultures was assessed using flow cytometric analysis. In order to assess the osteogenic activity, alkaline phosphatase activity (ALP) was measured and to estimate the osteoblastic mineralization and calcification, von Kossa staining for phosphates was performed. Cells positive for Src homology 2 domain were determined to be hMSCs and the presence of CD34 was used to distinguish hematopoietic lineages. Following treatment, the Ad-BMP-2 and control group had significantly increased ALP levels (P<0.05). Compared to the blank group and the group transfected with adenoviral vector containing LacZ, the phosphate deposition in the Ad-BMP-2 group and the positive control group treated with dexamethasone was markedly increased. The results of the present study suggested that Ad-BMP-2 promotes osteogenic differentiation in hMSCs and may have a potential application in treating delayed union and nonunion following bone fracture.

Dual growth factor delivery from biofunctionalized allografts: Sequential VEGF and BMP-2 release to stimulate allograft remodeling

Autografts have been shown to stimulate osteogenesis, osteoclastogenesis, and angiogenesis, and subsequent rapid graft incorporation. Large structural allografts, however, suffer from limited new bone formation and remodeling, both of which are directly associated with clinical failure due to non-unions, late graft fractures, and infections, making it a priority to improve large structural allograft healing. We have previously shown the osteogenic ability of a polymer-coated allograft that delivers bone morphogenetic protein-2 both in vitro and in vivo through both burst release and sustained release kinetics. In this study, we have demonstrated largely sequential delivery of bone morphogenetic protein-2 and vascular endothelial growth factor from the same coated allograft. Release data showed that loading both growth factors onto a polymeric coating with two different techniques resulted in short-term (95% release within 2 weeks) and long-term (95% release within 5 weeks) delivery kinetics. We have also demonstrated how released VEGF, traditionally associated with angiogenesis, can also provide a stimulus for allograft remodeling via resorption. Bone marrow derived mononuclear cells were co-cultured with VEGF released from the coated allograft and showed a statistically significant (p < 0.05) and dose dependent increase in the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclasts. Functionality of these osteoclasts was assessed quantitatively and qualitatively by evaluating resorption pit area from both osteo-assay plates and harvested bone. Data indicated a statistically significant higher resorption area from the cells exposed to VEGF released from the allografts over controls (p < 0.05). These results indicate that by using different loading protocols temporal control can be achieved when delivering multiple growth factors from a polymer-coated allograft. Further, released VEGF can also stimulate osteoclastogenesis that may enhance allograft incorporation, and thus mitigate long-term clinical complications. © 2017 Orthopedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1086-1095, 2017.

Potentiating bioactivity of BMP-2 by polyelectrolyte complexation with sulfonated polyrotaxanes to induce rapid bone regeneration in a mouse calvarial defect

Bone reconstruction is a challenging issue in the regeneration of surgically removed bone and disease-related bone defects. Although bone morphogenetic protein-2 (BMP-2) has received considerable attention as a bone regeneration inducer, a high dose of BMP-2 is typically required due to its short life-time under in vivo conditions. We have proposed a method to enhance the osteogenetic differentiation ability of BMP-2 in vitro that is based on supramolecular polyelectrolyte complexation with sulfonated polyrotaxanes (PRXs) consisting of sulfopropyl ether (SPE)-modified α-cyclodextrins threaded along a poly(ethylene glycol) chain capped with terminal bulky stopper molecules. In this study, we evaluated the in vivo bone regeneration ability of the SPE-PRX/BMP-2 complexes in a mouse calvarial defect model in comparison to free BMP-2 and heparin/BMP-2 complexes. The regenerated bone area was determined by X-ray computed microtomography, and the mice implanted with sulfonated PRX/BMP-2 complexes exhibited rapid and significant bone regeneration compared to those implanted with free BMP-2 and heparin/BMP-2 complexes. We concluded that the sulfonated PRX/BMP-2 complexes are a promising candidate for clinical bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1355-1363, 2017.

A Comparative Study of the Bone Regenerative Effect of Chemically Modified RNA Encoding BMP-2 or BMP-9

Employing cost-effective biomaterials to deliver chemically modified ribonucleic acid (cmRNA) in a controlled manner addresses the high cost, safety concerns, and lower transfection efficiency that exist with protein and gene therapeutic approaches. By eliminating the need for nuclear entry, cmRNA therapeutics can potentially overcome the lower transfection efficiencies associated with non-viral gene delivery systems. Here, we investigated the osteogenic potential of cmRNA-encoding BMP-9, in comparison to cmRNA-encoding BMP-2. Polyethylenimine (PEI) was used as a vector to increase in vitro transfection efficacy. Complexes of PEI-cmRNA (encoding BMP-2 or BMP-9) were fabricated at an amine (N) to phosphate (P) ratio of 10 and characterized for transfection efficacy in vitro using human bone marrow stromal cells (BMSCs). The osteogenic potential of BMSCs treated with these complexes was determined by evaluating the expression of bone-specific genes as well as through the detection of bone matrix deposition. It was found that alkaline phosphatase (ALP) expression 3 days post transfection in the group treated with BMP-9-cmRNA was significantly higher than that in the group that received BMP-2-cmRNA treatment. Alizarin red staining and atomic absorption spectroscopy demonstrated enhanced osteogenic differentiation as evidenced by increased bone matrix production by the BMSCs treated with BMP-9-cmRNA when compared to cells treated with BMP-2-cmRNA. In vivo studies showed increased bone formation in calvarial defects treated with the BMP-9-cmRNA and BMP-2-cmRNA collagen scaffolds when compared to empty defects. The connectivity density of the regenerated bone was higher (2-fold-higher) in the group that received BMP-9-cmRNA compared to BMP-2-cmRNA. Together, these findings suggest that cmRNA-activated matrix encoding osteogenic molecules can provide a powerful strategy for bone regeneration with significant clinical translational potential.

Osteoblastic differentiation and cell calcification of adamantinomatous craniopharyngioma induced by bone morphogenetic protein-2

BACKGROUND

The calcification of adamantinomatous craniopharyngioma (ACP) often creates difficulties for surgical therapy. Nevertheless, the mechanism of ACP calcification is unclear. Our previous studies demonstrated that osteoblastic factors might play important roles in ACP calcification.

OBJECTIVE

We examined the effects of recombinant human Bmp2 on ACP cell differentiation by testing osteoblastic proteins and calcium deposition.

METHODS

The expression of osteoblastic factors including osteopontin (OPN), Runx2, and osterix in Bmp2-treated ACP cells was examined by western blot and/or real time PCR. ALP activity and calcium deposition after Bmp2 induction were also tested.

RESULTS

Bmp2 significantly amplified the expression of Runx2, Osterix and OPN, as well as ALP activity. Both of these effects could be repressed by noggin treatment. Bmp2 also significantly induced the calcification of ACP, and noggin inhibited this calcium deposition.

CONCLUSION

Our study demonstrated for the first time that ACP cells could differentiate into an osteoblastic lineage via induction by Bmp2. The mechanism of ACP calcification likely involves osteoblastic differentiation modulated by Bmp2. Further studies targeting Bmp2 cascades could result in novel therapeutic interventions for recurrent ACP.

MicroRNA-98 regulates osteogenic differentiation of human bone mesenchymal stromal cells by targeting BMP2

To study the effects of microRNA‐98 (miR‐98) on human bone mesenchymal stromal cells (hBMSCs). The patients undergoing hip arthroplasty were selected by inclusion/exclusion criteria for this study. The extracted hBMSCs were detected of osteogenic differentiation by alizarin red S staining, and of cell phenotype by flow cytometry. Bioinformatics, dual luciferase report, western blotting, RT‐PCR and immunoblotting were used in our study. The hBMSCs were divided into miR‐98 mimics, miR‐98 negative control (NC), miR‐98 inhibitors, Mock and miR‐98 inhibitors + siBMP2 groups. Human bone mesenchymal stromal cells were extracted and purified in vitro and had specific cytological morphology, surface markers and abilities of self‐renewal and differentiation. Compared with the NC group and Mock group, the miR‐98 mimics group showed increased miR‐98 level while the miR‐98 inhibitors group decreased miR‐98 level (both P < 0.01). Dual luciferase reporter showed BMP2 was the target gene of miR‐98. The levels of mRNA and protein expression of BMP2, protein expression of RUNX2, alkaline phosphatase activity and osteocalcin content significantly decreased in the miR‐98 mimics group while increased in the miR‐98 inhibitors group and showed no changes in the NC group and Mock group (all P < 0.05). The miR‐98 mimics group showed obviously declined stained red particles and the miR‐98 inhibitors group showed opposite result. After lowering the expression of miR‐98, osteogenic differentiation ability of hBMSCs rose, which was weakened by the transfection with siBMP2. miR‐98 may regulate osteogenic differentiation of hBMSCs by targeting BMP2.

Localized bone regeneration around dental implants using recombinant bone morphogenetic protein-2 and platelet-derived growth factor-BB in the canine

OBJECTIVES

To test whether or not one of two biological mediators (recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human platelet-derived growth factor (rhPDGF-BB)) is superior to the other and compared with control groups for bone regeneration around implants based on histomorphometrical outcome measures.

MATERIALS AND METHODS

Box-type defects (10 × 5 × 5 mm) were prepared on the buccal sides of the left and right edentulous ridge in ten mongrel dogs. Implants were placed at each site, the defects either received (i) bovine-derived particulated bone mineral (DBBM) mixed with rhBMP-2 and a collagen membrane (CM) (DBBM/BMP-2), (ii) DBBM mixed with rhPDGF-BB and CM (DBBM/PDGF), (iii) DBBM and CM (DBBM) and (iv) empty control (control). Animals were euthanized post-surgery at 8 weeks and 16 weeks. Histomorphometrical analyses were performed.

RESULTS

The mean percentages of regenerated area within total defect area amounted to 56.95% for DBBM/BMP-2, 48.86% for DBBM/PDFG, 33.44% for DBBM and 1.59% for control at 8 weeks, and 26.79% for DBBM/BMP-2, 23.78% for DBBM/PDFG, 30.21% for DBBM and 5.07% for control at 16 weeks with no statistically significant differences between the groups (P > 0.05). The mean amount of regenerated bone was 26.97% for DBBM/BMP-2, 22.02% for DBBM/PDFG, 5.03% for DBBM and 1.25% for control at 8 weeks, and at 16 weeks, these values were lower in the two groups with biological mediators (DBBM/BMP-2 = 13.35%; DBBM/PDGF = 6.96%) and only slightly increased in group DBBM (10.68%) and the control group (4.95%) compared with 8 weeks. The first bone-to-implant contact values on the buccal side were minimal for DBBM/BMP-2 (0.57 mm) and maximal for control (3.72 mm) at 8 weeks.

CONCLUSIONS

The use of biological mediators (rhBMP-2 and rhPDGF-BB) can increase the amount of bone regeneration at dehiscence-type defects compared with controls at 8 weeks, but not at 16 weeks due to enhanced hard tissue remodeling processes.

Bone Morphogenetic Protein-2 Promotes Human Mesenchymal Stem Cell Survival and Resultant Bone Formation When Entrapped in Photocrosslinked Alginate Hydrogels

There is a substantial need to prolong cell persistence and enhance functionality in situ to enhance cell-based tissue repair. Bone morphogenetic protein-2 (BMP-2) is often used at high concentrations for osteogenic differentiation of mesenchymal stem cells (MSCs) but can induce apoptosis. Biomaterials facilitate the delivery of lower doses of BMP-2, reducing side effects and localizing materials at target sites. Photocrosslinked alginate hydrogels (PAHs) can deliver osteogenic materials to irregular-sized bone defects, providing improved control over material degradation compared to ionically cross-linked hydrogels. It is hypothesized that the delivery of MSCs and BMP-2 from a PAH increases cell persistence by reducing apoptosis, while promoting osteogenic differentiation and enhancing bone formation compared to MSCs in PAHs without BMP-2. BMP-2 significantly decreases apoptosis and enhances survival of photoencapsulated MSCs, while simultaneously promoting osteogenic differentiation in vitro. Bioluminescence imaging reveals increased MSC survival when implanted in BMP-2 PAHs. Bone defects treated with MSCs in BMP-2 PAHs demonstrate 100% union as early as 8 weeks and significantly higher bone volumes at 12 weeks, while defects with MSC-entrapped PAHs alone do not fully bridge. This study demonstrates that transplantation of MSCs with BMP-2 in PAHs achieves robust bone healing, providing a promising platform for bone repair.

Enhanced osteogenesis on biofunctionalized poly(ɛ-caprolactone)/poly(m-anthranilic acid) nanofibers

Biofunctionalized nanofibers with a desired biological function can be used as a tissue engineering scaffold due to their small fiber diameters and porous structure. In the present study, poly(ɛ-caprolactone)/poly(m-anthranilic acid) nanofibers were biofunctionalized with covalent immobilization of bone morphogenetic protein-2 (BMP-2) through 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide activation. Fourier transform infrared analysis of the nanofiber surfaces confirmed the successful immobilization. The amount of immobilized BMP-2 was determined with bicinchoninic acid protein assay. The nanofibers before and after BMP-2 immobilization were non-cytotoxic and enhanced the attachment and proliferation of Saos-2 cells. Biofunctionalization of nanofibers with BMP-2 promoted in vitro osteogenic activity. The alkaline phosphatase activity and calcium mineralizatio of cells after 14 days of in vitro culture were enhanced on nanofibers with immobilized BMP-2.

Bone morphogenetic protein-2 expression in an intraductal papillary mucinous neoplasm with marked ossification: A case report

Intratumoral ossification has been reported in a number of epithelial tumors, but its presence in intraductal papillary mucinous neoplasms (IPMNs) is very rare. Herein, we present a rare case of IPMN with marked ossification. A 56-year-old Japanese man was under follow-up for a previously diagnosed IPMN. Seven years later, he was found to have dilatation of the main pancreatic duct and an enlarged solid mass, for which pancreaticoduodenectomy was performed. Macroscopically, multiple and cystically dilated pancreatic branch ducts, as well as a dilated main pancreatic duct, were identified. There was a solid, polypoid hard mass measuring 15 × 12 mm in the cystically dilated branch of the duct in the pancreatic head. Histological examination revealed papillary proliferation of atypical cuboidal or columnar epithelial cells in the dilated main and branch pancreatic ducts. The solid mass included an invasive adenocarcinoma component with a tubular or trabecular structure that showed pronounced ossification. We diagnosed the patient with invasive IPMN accompanied by marked ossification. Immunohistochemically, tumor cells in both the non-invasive and invasive lesions expressed bone morphogenetic protein-2 (BMP-2). While the mechanism of intratumoral ossification is unclear, it may have involved BMP-2 in the present case.

Evaluating the effects of recombinant human bone morphogenetic protein-2 on pain-associated behaviors in a rat model following implantation near the sciatic nerve

OBJECTIVE It has been hypothesized that the recombinant human bone morphogenetic protein-2 (rhBMP-2) amplification of the host inflammatory response interacts with nerves in the spine and contributes to the occurrence of new, postoperative complaints of radiculitis. This in vivo rat study was conducted to assess the capacity for rhBMP-2/ACS (rhBMP-2 applied to absorbable collagen sponge [ACS]) to stimulate pain-associated behaviors in the rat chronic constriction injury (CCI) model. METHODS Rats were randomly assigned to one of 14 treatment groups. Half of the animals underwent a sham procedure in which the left sciatic nerve was exposed and manipulated but no ligature was placed (Sham cohort), while the remaining animals had chromic gut sutures tied around the sciatic nerve to induce CCI (CCI cohort). The following test articles were applied to the sciatic nerve in each cohort: saline alone, saline applied to ACS, 0.1 mg/ml rhBMP-2 applied to ACS, or 1.0 mg/ml rhBMP-2 applied to ACS. The ACS was either wrapped around the sciatic nerve or implanted adjacent to the nerve. Thermal withdrawal latency was assessed on Days 7, 14, 21, and 28 postoperatively. Isolated nerves from selected rats in each group were examined and assessed for histopathological changes on Days 3, 7, 14, and 28. RESULTS CCI produced a significant pain behavioral response for all treatment groups at all time points. In the Sham cohort, 0.1 mg/ml rhBMP-2/ACS wrapped around the nerve (WRP) decreased thermal withdrawal on Day 28, and 1.0 mg/ml rhBMP-2/ACS placed adjacent to the nerve (ADJ) decreased thermal withdrawal on Days 21 and 28. Conversely, in the CCI cohort, 0.1 mg/ml rhBMP-2/ACS ADJ increased thermal withdrawal latencies on Day 7; 1.0 mg/ml rhBMP-2/ACS ADJ increased thermal withdrawal latencies on Day 7; and 1.0 mg/ml rhBMP-2/ACS WRP increased thermal withdrawal on Days 7 and 14. Histologically, the effect of rhBMP-2 on nerve inflammation was unclear, as inflammatory cell infiltration was similar in the rhBMP-2/ACS and saline/ACS groups. rhBMP-2 was variably associated with bone formation within the epineurium at 14 days, and more prevalently at 28 days, with no clear relationship between dose or ACS positioning. CONCLUSIONS In this study, rhBMP-2/ACS did not appear to induce pain independent of grossly visible ectopic bone formation. At the earliest time points, rhBMP-2 appeared to have a neuroprotective effect as evidenced by decreased pain exhibited by the rhBMP-2-treated animals in the CCI cohort, but this effect diminished over time, and by Day 28, the pain behavioral responses in the rhBMP-2-treated group were comparable to those in the group in which saline was applied to the nerve. In the Sham cohort, there was a dose-independent induction of pain at later time points, presumably due to new bone formation mechanically irritating the nerve. Histological examination revealed nerve lesions that appeared to be caused by mechanical trauma associated with surgical manipulation of the nerve during placement of the ACS and/or CCI sutures.

Autologous implantation of BMP2-expressing dermal fibroblasts to improve bone mineral density and architecture in rabbit long bones

Cell-mediated gene therapy may treat bone fragility disorders. Dermal fibroblasts (DFb) may be an alternative cell source to stem cells for orthopedic gene therapy because of their rapid cell yield and excellent plasticity with bone morphogenetic protein-2 (BMP2) gene transduction. Autologous DFb or BMP2-expressing autologous DFb were administered in twelve rabbits by two delivery routes; a transcortical intra-medullar infusion into tibiae and delayed intra-osseous injection into femoral drill defects. Both delivery methods of DFb-BMP2 resulted in a successful cell engraftment, increased bone volume, bone mineral density, improved trabecular bone microarchitecture, greater bone defect filling, external callus formation, and trabecular surface area, compared to non-transduced DFb or no cells. Cell engraftment within trabecular bone and bone marrow tissue was most efficiently achieved by intra-osseous injection of DFb-BMP2. Our results suggested that BMP2-expressing autologous DFb have enhanced efficiency of engraftment in target bones resulting in a measurable biologic response by the bone of improved bone mineral density and bone microarchitecture. These results support that autologous implantation of DFb-BMP2 warrants further study on animal models of bone fragility disorders, such as osteogenesis imperfecta and osteoporosis to potentially enhance bone quality, particularly along with other gene modification of these diseases.

Vascular endothelial growth factor/bone morphogenetic protein-2 bone marrow combined modification of the mesenchymal stem cells to repair the avascular necrosis of the femoral head

Vascular endothelial cell growth factor (VEGF) combined with bone morphogenetic protein (BMP) was used to repair avascular necrosis of the femoral head, which can maintain the osteogenic phenotype of seed cells, and effectively secrete VEGF and BMP-2, and effectively promote blood vessel regeneration and contribute to formation and revascularization of tissue engineered bone tissues. To observe the therapeutic effect on the treatment of avascular necrosis of the femoral head by using bone marrow mesenchymal stem cells (BMSCs) modified by VEGF-165 and BMP-2 in vitro. The models were avascular necrosis of femoral head of rabbits on right leg. There groups were single core decompression group, core decompression + BMSCs group, core decompression + VEGF-165/BMP-2 transfect BMSCs group. Necrotic bone was cleared out under arthroscope. Arthroscopic observation demonstrated that necrotic bone was cleared out in each group, and fresh blood flowed out. Histomorphology determination showed that blood vessel number and new bone area in the repair region were significantly greater at various time points following transplantation in the core decompression + VEGF-165/BMP-2 transfect BMSCs group compared with single core decompression group and core decompression + BMSCs group (P < 0.05). These suggested that VEGF-165/BMP-2 gene transfection strengthened osteogenic effects of BMSCs, elevated number and quality of new bones and accelerated the repair of osteonecrosis of the femoral head.

Novel mouse model of spinal cord injury-induced heterotopic ossification

Heterotopic ossification (HO) develops in about 20% to 30% of patients with spinal cord injury (SCI) and significantly impairs their rehabilitation. There is no effective prevention or treatment for this condition at this time. Our current understanding of its etiology and pathophysiology is limited partially due to the lack of clinically relevant animal models. In this study, we report a novel mouse model of SCI-induced HO by administering a subthreshold dose of bone morphogenetic protein (BMP)-2 to muscles in mice after SCI. Micro-computed tomography scanning showed that an intramuscular injection of 0.25 micrograms of BMP-2 causes significant HO in mice with SCI but not in control (sham surgery) mice. Our analysis of gene expression showed significantly increased BMP signaling in quadriceps following SCI, suggesting that BMP signaling may play a role in SCI-induced HO. Administering 0.25 micrograms of BMP-2 to the front arms of the mice with SCI also results in the development of significant HO but not in control mice. This suggests that SCI causes a systematic osteogenic effect, which is not limited to paralyzed limbs. This novel mouse model will serve as a powerful tool in exploring the molecular mechanisms of SCI-induced HO, which may lead to novel treatment for this disease.