Bone morphogenetic proteins: from structure to clinical use

In vitro caries-preventive effect of a mineralization-promoting peptide combined with fluoride gel on sound primary teeth

BACKGROUND

Mineralization-promoting peptide-3 (MPP3) is a new biomimetic remineralization agent.

AIM

To assess the remineralization efficiency of MPP3, either alone or in combination with fluoride gel.

DESIGN

The samples were divided into four groups: control, 1.23% fluoride gel, 10% MPP3 gel, and 1.23% fluoride gel + 10% MPP3. Following the application of remineralization agents (4 min), the samples remained in a pH-cycling model (37°C, 4 weeks). Microhardness, microcomputed tomography (micro-CT), polarized light microscopy (PLM), and field emission scanning electron microscopy (FE-SEM) analysis were conducted. RM-ANOVA, one-way ANOVA, and intraclass correlation coefficient (ICC) were used for statistical analysis, and a significance level of p < .05 was employed.

RESULTS

Mineralization-promoting peptide 3 and fluoride gel + MPP3 increased the microhardness of the enamel compared with initial values in each group (p < .05). Mineralization-promoting peptide 3 successfully maintained the mineral density of enamel, although the cariogenic pH-cycling and PLM results indicated that the lesion depth (μm) was significantly lower in the fluoride gel + MPP3 group (27.0336 ± 12.53650) than in the control group (37.3907 ± 12.76002, p < .05).

CONCLUSION

The combined use of MPP3 with fluoride gel enhanced the caries-protective and mineralization-promoting effects of fluoride. Mineralization-promoting peptide 3 may be a potential agent that can be employed to improve the physical properties of enamel.

Repair of Rat Calvarial Critical-Sized Defects Using Heparin-Conjugated Fibrin Hydrogel Containing BMP-2 and Adipose-Derived Pericytes

The repair of critical-sized calvarial defects is a challenging problem for orthopedic surgery. One of the promising strategies of bone bioengineering to enhance the efficacy of large bone defect regeneration is the combined delivery of stem cells with osteoinductive factors within polymer carriers. The purpose of the research was to study the regenerative effects of heparin-conjugated fibrin (HCF) hydrogel containing bone morphogenetic protein 2 (BMP-2) and adipose-derived pericytes (ADPs) in a rat critical-sized calvarial defect model. In vitro analysis revealed that the HCF hydrogel was able to control the BMP-2 release and induce alkaline phosphatase (ALP) activity in neonatal rat osteoblasts. In addition, it was found that eluted BMP-2 significantly induced the osteogenic differentiation of ADPs. It was characterized by the increased ALP activity, osteocalcin expression and calcium deposits in ADPs. In vivo studies have shown that both HCF hydrogel with BMP-2 and HCF hydrogel with pericytes are able to significantly increase the regeneration of critical-sized calvarial defects in comparison with the control group. Nevertheless, the greatest regenerative effect was found after the co-delivery of ADPs and BMP-2 into a critical-sized calvarial defect. Thus, our findings suggest that the combined delivery of ADPs and BMP-2 in HCF hydrogel holds promise to be applied as an alternative biopolymer for the critical-sized bone defect restoration.

Off-label: The results of adjunctive bone morphogenetic protein for challenging femur fractures; a review of two cases

Background

Although bone morphogenetic proteins (BMPs) are used as an adjunct to promote healing, they may have unintended effects such as heterotopic ossification (HO). The literature is limited regarding the effect of using off-label BMPs for femur fractures.

Case presentation

We report two outcomes after off-label use of BMPs for the treatment of femur fractures and propose a possible explanation for the difference.

Conclusions

BMPs are critical osteoinductive factors in injured bone and muscle that facilitate bony healing. However, it may be important to recognize the potentially negative effects of adding BMP to bone graft material in certain cases to stimulate bone repair. We hope this case series helps surgeons consider the risks and benefits of using BMP for femur fractures, and therefore to decide with caution when BMP is indicated.

Histological and Immunohistochemical Evaluation of Rh-BMP2: Effect on Gingival Healing Acceleration and Proliferation of Human Epithelial Cells

This study aims to histologically and immunohistochemically evaluate the effect recombinant human bone morphogenetic protein (rh-BMP2) injected in gingival tissue has on the acceleration of the epithelial migration from the wound edges and epithelial cell proliferation after implant surgery.

MATERIAL AND METHODS

The study includes 20 patients who underwent bilateral implant surgeries in the premolar-molar region of the mandible, followed by guided bone regeneration. Each patient received an implant in both locations, but rh-BMP2 was only on the right side. At 9 days from the surgery, a gingival biopsy was performed 3 mm distally to the last implant. In total, 20 samples were collected from the left side (control group #1) and 20 from right (test group #1). This was repeated at a 4-month interval during healing abutment placements. Tissues were processed and stained with hematoxylin-eosin and then immunohistochemically for the expression of Ki-67 and further histological examination.

RESULT

Complete closure of the epithelium with new cell formation was observed in the 55% test group and 20% control group after 9 days. At 4 months, although 100% samples of all groups had complete epithelial closure, the test group showed that the epithelial cells were more organized and mature due to the increased number of blood vessels. The average number of new epithelial cells was 17.15 ± 7.545 and 16.12 ± 7.683 cells per mm in test group, respectively, at 9 days and 4 months and 10.99 ± 5.660 and 10.95 ± 5.768 in control groups.

CONCLUSION

Evident from histological observations, rh-BMP-2 can accelerate the closure of gingival wounds, the healing process of epithelial gingival tissue, and the formation of epithelial cells in patients undergoing dental implant treatment.

rhBMP6 in autologous blood coagulum is a preferred osteoinductive device to rhBMP2 on bovine collagen sponge in the rat ectopic bone formation assay

Osteoinductive BMPs require a suitable delivery system for treating various pathological conditions of the spine and segmental bone defects. INFUSE, the only commercially available BMP-based osteoinductive device, consisting of rhBMP2 on bovine absorbable collagen sponge (ACS) showed major disadvantages due to serious side effects. A novel osteoinductive device, OSTEOGROW, comprised of rhBMP6 dispersed within autologous blood coagulum (ABC) is a promising therapy for bone regeneration, subjected to several clinical trials for diaphysial bone repair and spinal fusion. In the present study, we have examined the release dynamics showing that the ABC carrier provided a slower, more steady BMP release in comparison to the ACS. Rat subcutaneous assay was employed to evaluate cellular events and the time course of ectopic osteogenesis. The host cellular response to osteoinductive implants was evaluated by flow cytometry, while dynamics of bone formation and maintenance in time were evaluated by histology, immunohistochemistry and micro CT analyses. Flow cytometry revealed that the recruitment of lymphoid cell populations was significantly higher in rhBMP6/ABC implants, while rhBMP2/ACS implants recruited more myeloid populations. Furthermore, rhBMP6/ABC implants more efficiently attracted early and committed progenitor cells. Dynamics of bone formation induced by rhBMP2/ACS was characterized by a delayed endochondral ossification process in comparison to rhBMP6/ABC implants. Besides, rhBMP6/ABC implants induced more ectopic bone volume in all observed time points in comparison to rhBMP2/ACS implants. These results indicate that OSTEOGROW was superior to INFUSE due to ABC's advantages as a carrier and rhBMP6 superior efficacy in inducing bone.

The Therapeutic Potential of Pericytes in Bone Tissue Regeneration

Pericytes, as perivascular cells, are present in all vascularized organs and tissues, and they actively interact with endothelial cells in capillaries and microvessels. Their involvement includes functions like blood pressure regulation, tissue regeneration, and scarring. Studies have confirmed that pericytes play a crucial role in bone tissue regeneration through direct osteodifferentiation processes, paracrine actions, and vascularization. Recent preclinical and clinical experiments have shown that combining perivascular cells with osteogenic factors and tissue-engineered scaffolds can be therapeutically effective in restoring bone defects. This approach holds promise for addressing bone-related medical conditions. In this review, we have emphasized the characteristics of pericytes and their involvement in angiogenesis and osteogenesis. Furthermore, we have explored recent advancements in the use of pericytes in preclinical and clinical investigations, indicating their potential as a therapeutic resource in clinical applications.

Treatment of Human Intraosseous Periodontal Defects Using Recombinant Human Bone Morphogenetic Protein-2: A Randomized Controlled Clinical Trial

Aim The purpose of this research was to assess the clinical and radiographic outcomes of recombinant human bone morphogenetic protein-2 (rhBMP-2) for the treatment of intraosseous abnormalities after periodontal flap surgery. Material and methods Patients aged 35-55 years who had undergone periodontal treatment at Shree Bankey Bihari Dental College and Research Centre, Ghaziabad, and had a total of 14 intraosseous abnormalities were included in the research. Those in the control group had open flap debridement with alloplast, whereas those in the experimental group underwent the same procedure with the addition of rhBMP-2. Clinical indicators, such as plaque index (PI), gingival index, probing pocket depth (PPD), clinical attachment level, and radiographic defect fill, were collected at baseline at three months, six months, and nine months. Results The findings demonstrated that following periodontal treatment, both sets of patients had considerable improvements in their PI, gingival index, and PPD. The degree of relative connection improved significantly in both groups. When comparing the two groups radiographically, we saw that the test group had significantly better defect fill than the control group. Conclusion According to this research, there was a statistically significant decrease in PI, gingival index, PPD, clinical attachment level, and radiographic bone fill in patients who received rhBMP-2. Open flap debridement with rhBMP-2 and alloplastic bone grafts showed better reduction than open flap debridement with alloplastic bone grafts group in the radiographic defect fill.

Shear loaded osteocyte-like-cells affect epithelial and mesenchymal gene expression in DU145 prostate cancer cells, while decreasing their invasion in vitro

Once prostate cancer (PC) metastasizes towards bone the 5-year survival rates drop with 70%, but it is largely unknown why. Bone is continuously mechanically loaded, which likely modulates the paracrine signaling from osteocytes towards PC cells to affect tumor behavior. We hypothesize that shear loaded osteocytes affect PC cell proliferation, invasion and epithelial and mesenchymal-related gene and protein expression. We cultured human DU145 cells, a commonly used cell line for prostate cancer metastases, in the conditioned medium (CM) from shear loaded or unloaded human osteocyte-like-cells (OCYLCs) for 1 and 3 days and assessed their number by staining nuclei with DAPI, their invasion by performing an invasion assay, and epithelial-to-mesenchymal (EMT)-related gene and protein expression by qPCR and immunocytochemistry. CM of shear loaded OCYLCs did not affect DU145 cell number compared to CM of static cultured OCYLCs, but decreased their invasion 1.34-fold. CM of shear loaded OCYLCs enhanced expression of epithelial genes: SYND1 and CDH1 after day 1, while it also enhanced CDH1 after day 3. CM of shear loaded osteocytes enhanced mesenchymal genes: VMN, Snail and MIP2 after day 1, while it decreased expression of mesenchymal CYR61 after day 3. We conclude that CM of shear loaded OCYLCs does not affect DU145 cell proliferation, but decreases their invasion, and differentially affects their EMT-related gene expression. Identifying paracrine signals from shear loaded osteocytes that decrease PC cell invasion may provide novel leads in developing treatments for bone metastases from PC.

Biomimetic approaches and materials in restorative and regenerative dentistry: review article

Biomimetics is a branch of science that explores the technical beauty of nature. The concept of biomimetics has been brilliantly applied in famous applications such as the design of the Eiffel Tower that has been inspired from the trabecular structure of bone. In dentistry, the purpose of using biomimetic concepts and protocols is to conserve tooth structure and vitality, increase the longevity of restorative dental treatments, and eliminate future retreatment cycles. Biomimetic dental materials are inherently biocompatible with excellent physico-chemical properties. They have been successfully applied in different dental fields with the advantages of enhanced strength, sealing, regenerative and antibacterial abilities. Moreover, many biomimetic materials were proven to overcome significant limitations of earlier available generation counterpart. Therefore, this review aims to spot the light on some recent developments in the emerging field of biomimetics especially in restorative and regenerative dentistry. Different approaches of restoration, remineralisation and regeneration of teeth are also discussed in this review. In addition, various biomimetic dental restorative materials and tissue engineering materials are discussed.

Effects of Chemical Additives in Refolding Buffer on Recombinant Human BMP-2 Dimerization and the Bioactivity on SaOS-2 Osteoblasts

Bone morphogenetic protein-2 (BMP-2) is a promising osteogenic agent in tissue engineering. BMP-2 is usually expressed in Escherichia coli owing to the high yield and low cost, but the protein is expressed as inclusion bodies. Thus, the bottleneck for BMP-2 production in E. coli is the refolding process. Here, we explored the effects of the refolding buffer composition on BMP-2 refolding. The BMP-2 inclusion body was solubilized in urea and subjected to refolding by the dilution method. Various additives were investigated to improve the BMP-2 refolding yield. Nonreducing SDS-PAGE showed that BMP-2 dimers, the presumably biologically active form, were detected at approximately 25 kDa. The highest yield of the BMP-2 dimers was observed in the refolding buffer that contained ionic detergents (sarkosyl and cetylpyridinium chloride) followed by zwitterionic and nonionic detergents (NDSB-195, NP-40, and Tween 80). In addition, sugars (glucose, sorbitol, and sucrose) in combination with anionic detergents (sodium dodecyl sulfate and sarkosyl) reduced BMP-2 oligomers and increased the BMP-2 dimer yield. Subsequently, the refolded BMP-2s were tested for their bioactivity using the alkaline phosphatase assay in osteogenic cells (SaOS-2), as well as the luciferase reporter assay and the calcium assays. The refolded BMP-2 showed the activities in the calcium deposition assay and the luciferase reporter assay but not in the alkaline phosphatase activity assay or the intracellular calcium assay even though the dimers were clearly detected. Therefore, the detection of the disulfide-linked dimeric BMP-2 in nonreducing SDS-PAGE is an inadequate proxy for the bioactivity of BMP-2.

The regulatory role of BMP4 in testicular Sertoli cells of Tibetan sheep

This study aimed to determine the regulatory mechanism of bone morphogenetic protein 4 (BMP4) gene in the testes of Tibetan sheep and its role in the blood-testis barrier (BTB). First, we cloned BMP4 gene for bioinformatics analysis, and detected the mRNA and protein expression levels of BMP4 in the testes of Tibetan sheep pre-puberty (3-mo-old), during sexual maturity (1-yr-old), and in adulthood (3-yr-old) by qRT-PCR and Western blot. In addition, the subcellular localization of BMP4 was analyzed by immunohistochemical staining. Next, BMP4 overexpression and silencing vectors were constructed and transfected into primary Sertoli cells (SCs) to promote and inhibit the proliferation of BMP4, respectively. Then, CCK-8 was used to detect the proliferation effect of SCs. The expression of BMP4 and downstream genes, pathway receptors, tight junction-related proteins, and cell proliferation and apoptosis-related genes in SCs were studied using qRT-PCR and Western blot. The results revealed that the relative expression of BMP4 mRNA and protein in testicular tissues of 1Y group and 3Y group was dramatically higher than that of 3M group (P < 0.01), and BMP4 protein is mainly located in SCs and Leydig cells at different development stages. The CDS region of the Tibetan sheep BMP4 gene was 1,229 bp. CCK-8 results demonstrated that the proliferation rate of BMP4 was significantly increased in the overexpression group (pc-DNA-3.1(+)-BMP4; P < 0.05). In addition, the mRNA and protein expressions of SMAD5, BMPR1A, and BMPR1B and tight junction-related proteins Claudin11, Occludin, and ZO1 were significantly increased (P < 0.05). The mRNA expression of cell proliferation-related gene Bcl2 was significantly enhanced (P < 0.05), and the expression of GDNF was enhanced (P > 0.05). The mRNA expression of apoptosis-related genes Caspase3 and Bax decreased significantly (P < 0.05), while the mRNA expression of cell cycle-related genes CyclinA2 and CDK2 increased significantly (P < 0.05). It is worth noting that the opposite results were observed after transfection with si-BMP4. In summary, what should be clear from the results reported here is that BMP4 affects testicular development by regulating the Sertoli cells and BTB, thereby modulating the spermatogenesis of Tibetan sheep.

The Influence of rhBMP-7 Associated with Nanometric Hydroxyapatite Coatings Titanium Implant on the Osseointegration: A Pre-Clinical Study

Background: Bioceramic nanometer coatings have been regarded as potential substitutes for plasma-sprayed hydroxyapatite coatings, and the association with bone morphogenetic protein (BMP) is an attempt to achieve faster osseointegration to hasten oral rehabilitation. Objective: This study aimed to investigate the effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) on the osseointegration of titanium implants coated with a thin film surface of hydroxyapatite (HA). Methods: Two implants (n = 24) were placed in each white New Zealand rabbits’ femur (n = 6). Implants were placed in the right femur after standard instrumentation (A and B) and in the left femur after an over-instrumentation (C and D), preventing bone-implant contact. The distal implants were installed associated with rhBMP-7 (groups B [regular instrumentation] and D [over-instrumentation]) and, also, in the absence of without BMP (control groups A [regular instrumentation] and C [over-instrumentation]). After 4 weeks, the animals were euthanized. The bone blocks containing the implants were embedded in methyl methacrylate and sectioned parallel to the long axis of the implant, which were analyzed by image segmentation. The data were analyzed using a nonparametric statistical method. Results: We observed that Group A had a mean bone formation of 35.6% compared to Group B, which had 48.6% (p > 0.05). Moreover, this group showed 28.3% of connective tissue compared to Group A, with 39.3%. In the over-instrumented groups, rhBMP-7 (Group D) showed an enhanced and significant increase in bone formation when compared with the group without rhBMP-7 (Group C). Conclusion: We concluded that the association of rhBMP-7 to thin nanostructure HA-coated implants promoted greater new bone area than the same implants in the absence of rhBMP-7, mainly in cases of over-instrumented implant sites.

Biomaterial-Mediated Protein Expression Induced by Peptide-mRNA Nanoparticles Embedded in Lyophilized Collagen Scaffolds

In our aging society, the number of patients suffering from poorly healing bone defects increases. Bone morphogenetic proteins (BMPs) are used in the clinic to promote bone regeneration. However, poor control of BMP delivery and thus activity necessitates high doses, resulting in adverse effects and increased costs. It has been demonstrated that messenger RNA (mRNA) provides a superior alternative to protein delivery due to local uptake and prolonged expression restricted to the site of action. Here, we present the development of porous collagen scaffolds incorporating peptide-mRNA nanoparticles (NPs). Nanoparticles were generated by simply mixing aqueous solutions of the cationic cell-penetrating peptide PepFect14 (PF14) and mRNA. Peptide-mRNA complexes were uniformly distributed throughout the scaffolds, and matrices fully preserved cell attachment and viability. There was a clear dependence of protein expression on the incorporated amount of mRNA. Importantly, after lyophilization, the mRNA formulation in the collagen scaffolds retained activity also at 4 °C over two weeks. Overall, our results demonstrate that collagen scaffolds incorporating peptide-mRNA complexes hold promise as off-the-shelf functional biomaterials for applications in regenerative medicine and constitute a viable alternative to lipid-based mRNA formulations.

Potential bioactive coating system for high-performance absorbable magnesium bone implants

Magnesium alloys are considered the most suitable absorbable metals for bone fracture fixation implants. The main challenge in absorbable magnesium alloys is their high corrosion/degradation rate that needs to be controlled. Various coatings have been applied to magnesium alloys to slow down their corrosion rates to match their corrosion rate to the regeneration rate of the bone fracture. In this review, a bioactive coating is proposed to slow down the corrosion rate of magnesium alloys and accelerate the bone fracture healing process. The main aim of the bioactive coatings is to enhance the direct attachment of living tissues and thereby facilitate osteoconduction. Hydroxyapatite, collagen type I, recombinant human bone morphogenetic proteins 2, simvastatin, zoledronate, and strontium are six bioactive agents that show high potential for developing a bioactive coating system for high-performance absorbable magnesium bone implants. In addition to coating, the substrate itself can be made bioactive by alloying magnesium with calcium, zinc, copper, and manganese that were found to promote bone regeneration.

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Bioactive-coated magnesium implant could accelerate bone fracture healing time to match with magnesium degradation.

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Hydroxyapatite, collagen type I, recombinant human bone morphogenetic proteins 2, simvastatin, zoledronate, and strontium are high potential bioactive coating materials.

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The incorporation of Ca, Zn, Cu, Sr, and Mn in Mg base-metal could further enhance bone formation.

Long-read whole genome sequencing reveals HOXD13 alterations in synpolydactyly

Synpolydactyly 1, also called syndactyly type II (SDTY2), is a genetic limb malformation characterized by polydactyly with syndactyly involving the webbing of the third and fourth fingers, and the fourth and fifth toes. It is caused by heterozygous alterations in HOXD13 with incomplete penetrance and phenotypic variability. In our study, a five-generation family with an SPD phenotype was enrolled in our Rare Disease Genomics Protocol. A comprehensive examination of three generations using Illumina short-read whole-genome sequencing (WGS) did not identify any causative variants. Subsequent WGS using Pacific Biosciences (PacBio) long-read HiFi Circular Consensus Sequencing (CCS) revealed a heterozygous 27-bp duplication in the polyalanine tract of HOXD13. Sanger sequencing of all available family members confirmed that the variant segregates with affected individuals. Reanalysis of an unrelated family with a similar SPD phenotype uncovered a 21-bp (7-alanine) duplication in the same region of HOXD13. Although ExpansionHunter identified these events in most individuals in a retrospective analysis, low sequence coverage due to high GC content in the HOXD13 polyalanine tract makes detection of these events challenging. Our findings highlight the value of long-read WGS in elucidating the molecular etiology of congenital limb malformation disorders.

The Role of BMP Signaling in Female Reproductive System Development and Function

Bone morphogenetic proteins (BMPs) are a group of multifunctional growth factors that belong to the transforming growth factor-β (TGF-β) superfamily of proteins. Originally identified by their ability to induce bone formation, they are now known as essential signaling molecules that regulate the development and function of the female reproductive system (FRS). Several BMPs play key roles in aspects of reproductive system development. BMPs have also been described to be involved in the differentiation of human pluripotent stem cells (hPSCs) into reproductive system tissues or organoids. The role of BMPs in the reproductive system is still poorly understood and the use of FRS tissue or organoids generated from hPSCs would provide a powerful tool for the study of FRS development and the generation of new therapeutic perspectives for the treatment of FRS diseases. Therefore, the aim of this review is to summarize the current knowledge about BMP signaling in FRS development and function.

Fabricating a novel HLC-hBMP2 fusion protein for the treatment of bone defects

Treating serious bone trauma with an osteo-inductive agent such as bone morphogenetic proteins (BMPs) has been considered as an optimized option when delivered via a collagen sponge (CS). Previous works have shown that the BMP concentration and release rate from approved CS carriers is difficult to control with precision. Here we presented the fabrication of a recombinant fusion protein from recombinant human-like collagen (HLC) and human BMP-2 (hBMP2). The fusion protein preserved the characteristic of HLC allowing the recombinant protein to be expressed in Yeast (such as Pichia pastoris GS115) and purified rapidly and easily with mass production after methanol induction. It also kept the stable properties of HLC and hBMP2 in the body fluid environment with good biocompatibility and no cytotoxicity. Moreover, the recombinant fusion protein fabricated a vertical through-hole structure with improved mechanical properties, and thus facilitated migration of bone marrow mesenchymal stem cells (MSCs) into the fusion materials. Furthermore, the fusion protein degraded and released hBMP-2 in vivo allowing osteoinductive activity and the enhancement of utilization rate and the precise control of the hBMP2 release. This fusion protein when applied to cranial defects in rats was osteoinductively active and improved bone repairing enhancing the repairing rate 3.5- fold and 4.2- fold when compared to the HLC alone and the control, respectively. There were no visible inflammatory reactions, infections or extrusions around the implantation sites observed. Our data strongly suggests that this novel recombinant fusion protein could be more beneficial in the treatment of bone defects than the simple superposition of the hBMP2/collagen sponge.

Nanostructured Carbonated Hydroxyapatite Associated to rhBMP-2 Improves Bone Repair in Rat Calvaria

Many biomaterials are used for Bone Morphogenetic Proteins (BMPs) delivery in bone tissue engineering. The BMP carrier system's primary function is to hold these growth factors at the wound's site for a prolonged time and provide initial support for cells to attach and elaborate the extracellular matrix for bone regeneration. This study aimed to evaluate the nanostructured carbonated hydroxyapatite microspheres (nCHA) as an rhBMP-2 carrier on rats calvaria. A total of fifteen male Wistar rats were randomly divided into three groups (n = 5): clot (control group), rhBMP-2 associated with collagen membrane (COL/rhBMP-2) or associated with the microspheres (nCHA/rhBMP-2). After 45 days, the calvaria defect samples were evaluated through histological, histomorphometric, and SR-µCT analyses to investigate new-formed bone and connective tissue volume densities. The descriptive histological analysis showed that nCHA/rhBMP-2 improved bone formation compared to other groups. These results were confirmed by histomorphometric and SR-µCT analysis that showed substantially defect area filling with a higher percentage of newly formed (36.24 ± 6.68) bone than those with the COL/rhBMP-2 (0.42 ± 0.40) and Clot (3.84 ± 4.57) (p < 0.05). The results showed that nCHA is an effective carrier for rhBMP-2 encouraging bone healing and an efficient alternative to collagen membrane for rhBMP-2 delivery.

Research Progress of Hair Cell Protection Mechanism

How to prevent and treat hearing-related diseases through the protection of hair cells (HCs) is the focus in the field of hearing in recent years. Hearing loss caused by dysfunction or loss of HCs is the main cause of hearing diseases. Therefore, clarifying the related mechanisms of HC development, apoptosis, protection, and regeneration is the main goal of current hearing research. This review introduces the latest research on mechanism of HC protection and regeneration.

BMP and TGFβ use and release in bone regeneration

A fracture that does not unite in nine months is defined as nonunion. Nonunion is common in fragmented fractures and large bone defects where vascularization is impaired. The distal third of the tibia, the scaphoid bone or the talus fractures are furthermore prone to nonunion. Open fractures and spinal fusion cases also need special monitoring for healing. Bone tissue regeneration can be attained by autografts, allografts, xenografts and synthetic materials, however their limited availability and the increased surgical time as well as the donor site morbidity of autograft use, and lower probability of success, increased costs and disease transmission and immunological reaction probability of allografts oblige us to find better solutions and new grafts to overcome the cons. A proper biomaterial for regeneration should be osteoinductive, osteoconductive, biocompatible and mechanically suitable. Cytokine therapy, where growth factors are introduced either exogenously or triggered endogenously, is one of the commonly used method in bone tissue engineering. Transforming growth factor β (TGFβ) superfamily, which can be divided structurally into two groups as bone morphogenetic proteins (BMPs), growth differentiation factors (GDFs) and TGFβ, activin, Nodal branch, Mullerian hormone, are known to be produced by osteoblasts and other bone cells and present already in bone matrix abundantly, to take roles in bone homeostasis. BMP family, as the biggest subfamily of TGFβ superfamily, is also reported to be the most effective growth factors in bone and development, which makes them one of the most popular cytokines used in bone regeneration. Complications depending on the excess use of growth factors, and pleiotropic functions of BMPs are however the main reasons of why they should be approached with care. In this review, the Smad dependent signaling pathways of TGFβ and BMP families and their relations and the applications in preclinical and clinical studies will be briefly summarized.

Opposing and potentially antagonistic effects of BMP and TGF-β in multiple sclerosis: The "Yin and Yang" of neuro-immune Signaling

Bone Morphogenetic Proteins (BMP) and Transforming Growth Factor-beta (TGF-β) are cytokines with similar receptors and messengers. They are important for immune cell function, with BMPs exerting mainly proinflammatory but also anti-inflammatory effects, and TGF-β suppressing inflammation. Patients with Multiple Sclerosis exhibit BMP overactivity and suppressed TGF-β signaling. This dysregulated signaling participates in the crosstalk between infiltrating immune cells and glia, where BMP inhibits remyelination. Reciprocal antagonism between the two pathways takes place via a variety of mechanisms. Although this antagonism has not been studied in the setting of Multiple Sclerosis, it could inform further research and treatment discovery.

Bone Generation Following Repeated Administration of Recombinant Bone Morphogenetic Protein 2

BACKGROUND

The delivery of recombinant human bone morphogenetic protein 2 (rhBMP2) by using various carriers has been used to successfully induce bone formation in many animal models. However, the effect of multiple administration of rhBMP2 on bone formation and BMP2 antibody production has not been determined. Our aim was to examine the bone formation activity of rhBMP2 and serum levels of anti-BMP2 antibodies following the repeated administration of rhBMP2 in mice.

METHODS

Absorbable collagen sponges or polyphosphazene hydrogels containing rhBMP2 were subcutaneously implanted or injected into one side on the back of six-week-old C57BL/6 mice. Three or 4 weeks later, the same amount of rhBMP2 was administered again with the same carrier into the subcutaneous regions on the other side of the back or into calvarial defects. The effects of a single administration of rhBMP2 on the osteoinductive ability in the ectopic model were compared with those of repeated administrations. In vivo ectopic or orthotopic bone formation was evaluated using microradiography and histological analyses. Serum concentrations of anti-rhBMP2 antibodies were measured by ELISAs.

RESULTS

Re-administration of the same amount of rhBMP2 into the subcutaneous area showed a comparable production of ectopic bone as after the first administration. The bone forming ability of repeated rhBMP2 administrations was equal to that of single rhBMP2 administration. The administration of rhBMP2 into calvarial defects, following the first subcutaneous administration of rhBMP2 on the back, completely recovered the defect area with newly regenerated bone within 3 weeks. Repeated administration of rhBMP2 at 4-week intervals did not significantly alter the serum levels of anti-BMP2 antibodies and did not induce any inflammatory response. The serum obtained from rhBMP2-exposed mice had no effect on the ability of rhBMP2 to induce osteogenic gene expressions in MC3T3-E1.

CONCLUSION

We suggest that the osteoinductive ability of rhBMP2 is not compromised by repeated administrations. Thus, rhBMP2 can be repeatedly used for bone regeneration at various sites within a short duration.

Effect of bone morphogenetic protein-2/hydroxyapatite on ankle fusion with bone defect in a rabbit model: a pilot study

Background

Revision ankle-fusion surgery after a failure of total ankle arthroplasty has a problem with bone-defect management by implant removal. For the reconstruction of bone defects, autogenous bone often causes minor and major complications. Recombinant human-bone morphogenetic protein-2 (rhBMP-2) plays essential roles in bone regeneration strategies, and hydroxyapatite (HA) is beneficial as the rhBMP-2 carrier. In this study, we evaluate whether rhBMP-2/HA can replace autogenous bone in a rabbit ankle-fusion model with distal tibia bone defect.

Methods

The bone defect was created in the distal tibia. The ankle fusion was performed by a cannulated screw from lateral malleolus and various treatments on bone defect. Thirty male white New Zealand rabbits were divided into three groups of 10 animals on each group dependent on treatment methods as control group (no treatment into defect), auto-bone group (autogenous bone treatment), and rhBMP-2/HA group (40 μL of 1 μg/mL rhBMP-2/100 μL HA). Bone formation on defect and the union of the ankle joint were evaluated by X-ray, micro-CT, and histological analysis at 8 weeks and 12 weeks, postoperatively.

Results

Radiographic assessment found the control and auto-bone groups still had the bone defect present, but rhBMP-2/HA group showed complete replacement of the defect with newly formed bone at 12 weeks. Micro-CT showed significantly higher new bone formation within the defect in the rhBMP-2/HA group than in the auto-bone and control groups at 8 weeks (p > 0.05 and p < 0.01, respectively) and 12 weeks (p < 0.05, p < 0.001, respectively). Fusion rate (%) analysis of micro-CT showed a higher percentage of union in the rhBMP-2/HA group than in the auto bone and control groups at 8 weeks (p > 0.05, p < 0.001, respectively) and 12 weeks (p < 0.001 and p < 0.001, respectively). The histological showed the highest osteointegration between distal tibia and talus in the rhBMP-2/HA group at 12 weeks.

Conclusions

This study indicated that rhBMP-2/HA showed much better bone fusion than did the autogenous bone graft and was effective in promoting fusion rate and improving the quality of the ankle joint fusion.

Activin A and BMP chimera (AB204) induced bone fusion in osteoporotic spine using an ovariectomized rat model

BACKGROUND CONTEXT

Recombinant human bone morphogenic protein 2 (rhBMP2) has been used to induce bone fusion in patients with spinal fusion surgery. However, the effectiveness of rhBMP2 in the bone fusion process is limited in osteoporosis patients, and a high dose of rhBMP2 for enough bone fusion sometimes provokes side effects. Therefore, substitutes for rhBMP2 with a higher therapeutic potency are needed, and already several studies have published the effectiveness of Activin A/BMP2 chimera (AB204) in new bone formation process in vitro and in vivo.

PURPOSE

In the present study, we provide evidence that bone fusion activity of AB204 is superior to that of rhBMP2 in osteoporotic rat models.

STUDY DESIGN/SETTINGS

An in vivo animal study was carried out.

METHODS

A total of 40 Sprague-Dawley rats underwent bilateral ovariectomy. At 6 weeks after ovariectomy, a lumbar spinal bone fusion model of bilateral intertransverse process was performed. All rats were randomly divided into four groups as follows: rats receiving 5 µg of rhBMP2 (Group I), rats receiving 10 µg of rhBMP2 (Group II), rats receiving 5 µg of AB204 (Group III), and rats receiving 10 µg of AB204 (Group IV). Simple radiographs were performed at 6 and 12 weeks after bone fusion, and direct palpation, micro-CT, and immunohistochemistry (hematoxylin-eosin stain and Masson's trichrome stain) were performed at 12 weeks after bone fusion. The qualitative degree of bone fusion was assessed as manual fusion score from direct palpation, and radio-histologic fusion score from simple radiographs, micro-CT, and immunohistochemistry. Also, the quantitative degree of bone fusion was assessed using fusion bone volume by micro-CT and serum osteocalcin level as bone turnover markers.

RESULTS

The change of body weight was not different among the groups during follow-up. The qualitative degree of bone fusion assessed by direct palpation, simple radiographs, micro-CT, and histologic evaluation was significantly different among the four groups. Also, the quantitative degree of bone fusion including fusion bone volume and serum osteocalcin was significantly different among the groups. Especially, in manual fusion score, radio-histologic fusion score, and fusion bone volume, the AB204 group revealed superior results to the rhBMP2 group when using the same dose. Furthermore, even the low-dose AB204 group (Group III) showed superior results to the high-dose rhBMP2 group (Group II) in radio-histologic fusion score and fusion bone volume.

CONCLUSION

The effect of bone fusion in osteoporotic rats was significantly higher in the AB204 group than in the rhBMP2 group.

CLINICAL SIGNIFICANCE

If further organized animal studies and clinical trials are provided, AB204 may be a good substitute for rhBMP2 in osteoporotic spinal fusion surgery, as a superior osteogenesis inducer.

Drug Delivery Systems Based on Titania Nanotubes and Active Agents for Enhanced Osseointegration of Bone Implants

TiO2 nanotubes (TNTs) are attractive nanostructures for localized drug delivery. Owing to their excellent biocompatibility and physicochemical properties, numerous functionalizations of TNTs have been attempted for their use as therapeutic agent delivery platforms. In this review, we discuss the current advances in the applications of TNT-based delivery systems with an emphasis on the various functionalizations of TNTs for enhancing osteogenesis at the bone-implant interface and for preventing implant-related infection. Innovation of therapies for enhancing osteogenesis still represents a critical challenge in regeneration of bone defects. The overall concept focuses on the use of osteoconductive materials in combination with the use of osteoinductive or osteopromotive factors. In this context, we highlight the strategies for improving the functionality of TNTs, using five classes of bioactive agents: growth factors (GFs), statins, plant derived molecules, inorganic therapeutic ions/nanoparticles (NPs) and antimicrobial compounds.

The Role of Bone Morphogenetic Protein 7 (BMP-7) in Inflammation in Heart Diseases

Bone morphogenetic protein-7 is (BMP-7) is a potent anti-inflammatory growth factor belonging to the Transforming Growth Factor Beta (TGF-β) superfamily. It plays an important role in various biological processes, including embryogenesis, hematopoiesis, neurogenesis and skeletal morphogenesis. BMP-7 stimulates the target cells by binding to specific membrane-bound receptor BMPR 2 and transduces signals through mothers against decapentaplegic (Smads) and mitogen activated protein kinase (MAPK) pathways. To date, rhBMP-7 has been used clinically to induce the differentiation of mesenchymal stem cells bordering the bone fracture site into chondrocytes, osteoclasts, the formation of new bone via calcium deposition and to stimulate the repair of bone fracture. However, its use in cardiovascular diseases, such as atherosclerosis, myocardial infarction, and diabetic cardiomyopathy is currently being explored. More importantly, these cardiovascular diseases are associated with inflammation and infiltrated monocytes where BMP-7 has been demonstrated to be a key player in the differentiation of pro-inflammatory monocytes, or M1 macrophages, into anti-inflammatory M2 macrophages, which reduces developed cardiac dysfunction. Therefore, this review focuses on the molecular mechanisms of BMP-7 treatment in cardiovascular disease and its role as an anti-fibrotic, anti-apoptotic and anti-inflammatory growth factor, which emphasizes its potential therapeutic significance in heart diseases.

Effects of recombinant human bone morphogenetic protein-2 compared to other biomaterials in the treatment of intrabony defects in periodontitis patients: A systematic review

Background:

Bone morphogenetic proteins have a powerful osteoinductive capacity and have been used as a new adjunct to graft materials for bone regeneration. The objectives of this systematic review are to assess the amount of radiographic bone fill, clinical attachment level (CAL) gain, and reduction in pocket depth (PD) in patients with intrabony defects in periodontitis patients following the use of recombinant human bone morphogenetic protein-2 (rhBMP-2).

Materials and Methods:

Electronic bibliographic databases search of Medline, Science Direct, and Google Scholar was made from January 1980 to December 2017. Studies using rhBMP-2 to treat periodontal intrabony defects of the maxillary or mandibular region with follow-up period of at least 6 months were searched. Two reviewers performed the systematic review using the PRISMA Statement for reporting and the Cochrane risk-of-bias tool was used for quality assessment.

Results:

It was found that rhBMP-2 showed statistically significant results with respect to radiographic defect resolution, CAL, and PD reduction at 9 months compared to open-flap debridement but showed statistically significant results only with respect to radiographic bone fill when compared with platelet-rich fibrin at 6 months.

Conclusion:

The rhBMP-2 may provide a promising alternative to traditional grafting procedures therapy that can enhance periodontal regeneration in patients having intrabony defects. Due to limited human studies, it can be concluded that no definitive evidence exists to ascertain the effectiveness of rhBMP-2 in the treatment of intrabony defects in periodontal diseases.

Bmp4 inhibits goose granulosa cell apoptosis via PI3K/AKT/Caspase-9 signaling pathway

Bone morphogenetic protein 4 (BMP4) has an important role in regulating cellular proliferation, differentiation and apoptosis. It, however, is still unclear as to the mechanisms by which BMP4 regulates the apoptosis of granulosa cells (GCs) in geese. In the present study, there was cloning of the full-length coding sequence of goose BMP4 gene, which consisted of 1212 nucleotides encoding 403 amino acids. Its deduced amino acid sequence comprised one signal peptide, one TGFβ pro-peptide and one mature peptide domain. Results from conducting the quantitative real-time PCR (qPCR) indicated the relative abundances of BMP4 mRNA in geese GCs increased gradually from the relative abundances in pre-hierarchical follicles that were 4 to 6 mm in diameter to that in the fifth largest (F5) follicle and then relative abundances of BMP4 mRNA decreased with further development as the largest (F1) follicle. Results from use of the TUNEL assay indicated that overexpression of the goose BMP4 gene suppressed GC apoptosis and this was confirmed when relative abundances of the CAD, Caspase-9 and Caspase-3 proteins were determined using western blotting. In addition, overexpression of the BMP4 gene induced phosphorylation of AKT, which was inhibited with use of the PI3K inhibitor, LY294002. Co-transfection of BMP4 and LY294002 resulted in increased relative abundances of Caspase-9 and CAD proteins but had no effect on that of Caspase-3. Taken together, these results suggested that expression of the BMP4 gene resulted in a reduction in Caspase-9 protein leading to inhibition of GC apoptosis via the PI3K/AKT signaling pathway in geese.

Formulation, Delivery and Stability of Bone Morphogenetic Proteins for Effective Bone Regeneration

Bone morphogenetic proteins (BMPs) are responsible for bone formation during embryogenesis and bone regeneration and remodeling. The osteoinductive action of BMPs, especially BMP-2 and BMP-7, has led to their use in a range of insurmountable treatments where intervention is required for effective bone regeneration. Introduction of BMP products to the market, however, was not without reports of multiple complications and side effects. Aiming for optimization of the therapeutic efficacy and safety, efforts have been focused on improving the delivery of BMPs to lower the administered dose, localize the protein, and prolong its retention time at the site of action. A major challenge with these efforts is that the protein stability should be maintained. With this review we attempt to shed light on how the stability of BMPs can be affected in the formulation and delivery processes. We first provide a short overview of the current standing of the complications experienced with BMP products. We then discuss the different delivery parameters studied in association with BMPs, and their influence on the efficacy and safety of BMP treatments. In particular, the literature addressing the stability of BMPs and their possible interactions with components of the delivery system as well as their sensitivity to conditions of the formulation process is reviewed. In summary, recent developments in the fields of bioengineering and biopharmaceuticals suggest that a good understanding of the relationship between the formulation/delivery conditions and the stability of growth factors such as BMPs is a prerequisite for a safe and effective treatment.

Recombinant Human Bone Morphogenetic Protein-2 in Development and Progression of Oral Squamous Cell Carcinoma

Bone morphogenetic proteins (BMPs), belonging to the transforming growth factor-β superfamily, regulate many cellular activities including cell migration, differentiation, adhesion, proliferation and apoptosis. Use of recombinant human bone morphogenic protein?2 (rhBMP?2) in oral and maxillofacial surgery has seen a tremendous increase. Due to its role in many cellular pathways, the influence of this protein on carcinogenesis in different organs has been intensively studied over the past decade. BMPs also have been detected to have a role in the development and progression of many tumors, particularly disease-specific bone metastasis. In oral squamous cell carcinoma - the tumor type accounting for more than 90% of head and neck malignancies- aberrations of both BMP expression and associated signaling pathways have a certain relation with the development and progression of the disease by regulating a range of biological functions in the altered cells. In the current review, we discuss the influence of BMPs -especially rhBMP-2- in the development and progression of oral squamous cell carcinoma.

Fluoride affects bone repair differently in mice models with distinct bone densities

We grouped mice [strains: C57BL/6J (n=32) and C3H/HeJ (n=32)] to address the influence of bone density on fluoride's (F's) biological effects. These animals received low-fluoride food and water containing 0 (control group) or 50ppm of F for up to 28days. The upper left central incisor was extracted, and the left maxilla was collected at 7, 14, 21, and 28days for histological and histomorphometric analysis to estimate bone neoformation. Our results showed bone neoformation in all of the evaluated groups, with the presence of bone islets invading the center of the alveoli when replacing the existing connective tissue. Curiously, this biological phenomenon was more evident in the C57BL/6J strain. The histomorphometric analysis confirmed the histological findings in relation to the amount of new bone tissue and showed a decrease in C3H/HeJ mice (control group). Altogether, our results showed differential effects of fluoride bone metabolism, confirming a genetic component in susceptibility to the effects of fluoride.

Bone Morphogenetic Proteins: Promising Molecules for Bone Healing, Bioengineering, and Regenerative Medicine

Bone morphogenetic proteins (BMPs), glycoproteins secreted by some cells, are members of the TGF-β superfamily that have been implicated in a wide variety of roles. Currently, about 20 different BMPs have been identified and grouped into subfamilies, according to similarities with respect to their amino acid sequences. It has been shown that BMPs are secreted growth factors involved in mesenchymal stem cell differentiation, also being reported to control the differentiation of cancer stem cells. BMPs initiate signaling from the cell surface by binding to two different receptors (R: Type I and II). The heterodimeric formation of type I R and II R may occur before or after BMP binding, inducing signal transduction pathways through SMADs. BMPs may also signal through SMAD-independent pathways via mitogen-activated protein kinases (ERK, p38MAPKs, JNK). BMPs may act in an autocrine or paracrine manner, being regulated by specific antagonists, namely: noggin and chordin. Genetic engineering allows the production of large amounts of BMPs for clinical use, and clinical trials have shown the benefits of FDA-approved recombinant human BMPs 2 and 7. Several materials from synthetic to natural sources have been tested as BMP carriers, ranging from hydroxyapatite, and organic polymers to collagen. Bioactive membranes doped with BMPs are promising options, acting to accelerate and enhance osteointegration. The development of smart materials, mainly based on biopolymers and bone-like calcium phosphates, appears to provide an attractive alternative for delivering BMPs in an adequately controlled fashion. BMPs have revealed a promising future for the fields of Bioengineering and Regenerative Medicine. In this chapter, we review and discuss the data on BMP structure, mechanisms of action, and possible clinical applications.

Bone Regeneration Using Bone Morphogenetic Proteins and Various Biomaterial Carriers

Trauma and disease frequently result in fractures or critical sized bone defects and their management at times necessitates bone grafting. The process of bone healing or regeneration involves intricate network of molecules including bone morphogenetic proteins (BMPs). BMPs belong to a larger superfamily of proteins and are very promising and intensively studied for in the enhancement of bone healing. More than 20 types of BMPs have been identified but only a subset of BMPs can induce de novo bone formation. Many research groups have shown that BMPs can induce differentiation of mesenchymal stem cells and stem cells into osteogenic cells which are capable of producing bone. This review introduces BMPs and discusses current advances in preclinical and clinical application of utilizing various biomaterial carriers for local delivery of BMPs to enhance bone regeneration.

TGF-β/BMP signaling and other molecular events: regulation of osteoblastogenesis and bone formation

Transforming growth factor-beta (TGF-β)/bone morphogenetic protein (BMP) plays a fundamental role in the regulation of bone organogenesis through the activation of receptor serine/threonine kinases. Perturbations of TGF-β/BMP activity are almost invariably linked to a wide variety of clinical outcomes, i.e., skeletal, extra skeletal anomalies, autoimmune, cancer, and cardiovascular diseases. Phosphorylation of TGF-β (I/II) or BMP receptors activates intracellular downstream Smads, the transducer of TGF-β/BMP signals. This signaling is modulated by various factors and pathways, including transcription factor Runx2. The signaling network in skeletal development and bone formation is overwhelmingly complex and highly time and space specific. Additive, positive, negative, or synergistic effects are observed when TGF-β/BMP interacts with the pathways of MAPK, Wnt, Hedgehog (Hh), Notch, Akt/mTOR, and miRNA to regulate the effects of BMP-induced signaling in bone dynamics. Accumulating evidence indicates that Runx2 is the key integrator, whereas Hh is a possible modulator, miRNAs are regulators, and β-catenin is a mediator/regulator within the extensive intracellular network. This review focuses on the activation of BMP signaling and interaction with other regulatory components and pathways highlighting the molecular mechanisms regarding TGF-β/BMP function and regulation that could allow understanding the complexity of bone tissue dynamics.

Recombinant human bone morphogenetic protein type 2 in the reconstruction of atrophic maxilla: Case report with long-term follow-up

Autologous bone is reported by scientific literature as the gold standard for the replacement of the bone loss in maxillary atrophic area. Notwithstanding, this grafting type shows several disadvantages as: The procedure morbidity, limited size of the graft and longer recovering time. Recombinant human bone morphogenetic protein type 2 (rhBMP-2) has been used as bone substitute for the reconstruction of large bone defects. The aim of this case was to report a clinical case exhibiting the reconstruction of the atrophic maxilla through using rhBMP-2 as grafting material associated with absorbable collagen sponge (ACS). At 8 months of following-up, osseointegrated implants were placed. After 2 years and 5 months of following-up, it could be observed an appropriate aesthetical and functional rehabilitation.

Bone Morphogenetic Proteins: structure, biological function and therapeutic applications

Bone Morphogenetic Proteins (BMPs) are multifunctional secreted cytokines, which belong to the TGF-β superfamily. These glycoproteins act as a disulfide-linked homo- or heterodimers, being potent regulators of bone and cartilage formation and repair, cell proliferation during embryonic development and bone homeostasis in the adult. BMPs are promising molecules for tissue engineering and bone therapy. The present review discusses this family of proteins, their structure and biological function, their therapeutic applications and drawbacks, their effects on mesenchymal stem cells differentiation, and the cell signaling pathways involved in this process.

Cellular behavior as a dynamic field for exploring bone bioengineering: a closer look at cell-biomaterial interface

Bone is a highly dynamic and specialized tissue, capable of regenerating itself spontaneously when afflicted by minor injuries. Nevertheless, when major lesions occur, it becomes necessary to use biomaterials, which are not only able to endure the cellular proliferation and migration, but also to substitute the original tissue or integrate itself to it. With the life expectancy growth, regenerative medicine has been gaining constant attention in the reconstructive field of dentistry and orthopedy. Focusing on broadening the therapeutic possibilities for the regeneration of injured organs, the development of biomaterials allied with the applicability of gene therapy and bone bioengineering has been receiving vast attention over the recent years. The progress of cellular and molecular biology techniques gave way to new-guided therapy possibilities. Supported by multidisciplinary activities, tissue engineering combines the interaction of physicists, chemists, biologists, engineers, biotechnologist, dentists and physicians with common goals: the search for materials that could promote and lead cell activity. A well-oriented combining of scaffolds, promoting factors, cells, together with gene therapy advances may open new avenues to bone healing in the near future. In this review, our target was to write a report bringing overall concepts on tissue bioengineering, with a special attention to decisive biological parameters for the development of biomaterials, as well as to discuss known intracellular signal transduction as a new manner to be explored within this field, aiming to predict in vitro the quality of the host cell/material and thus contributing with the development of regenerative medicine.

Composite chitosan and calcium sulfate scaffold for dual delivery of vancomycin and recombinant human bone morphogenetic protein-2

A biodegradable, composite bone graft, composed of chitosan microspheres embedded in calcium sulfate, was evaluated in vitro for point-of-care loading and delivery of antibiotics and growth factors to prevent infection and stimulate healing in large bone injuries. Microspheres were loaded with rhBMP-2 or vancomycin prior to mixing into calcium sulfate loaded with vancomycin. Composites were evaluated for set time, drug release kinetics, and bacteriostatic/bactericidal activity of released vancomycin, induction of ALP expression by released rhBMP-2, and interaction of drugs on cells. Results showed the composite set in under 36 min and released vancomycin levels that were bactericidal to S. aureus (>MIC 8-16 μg/mL) for 18 days. Composites exhibited a 1 day-delayed release, followed by a continuous release of rhBMP-2 over 6 weeks; ranging from 0.06 to 1.49 ng/mL, and showed a dose dependent release based on initial loading. Released rhBMP-2 levels were, however, too low to induce detectable levels of ALP in W20-17 cells, due to the affinity of rhBMP-2 for calcium-based materials. With stimulating amounts of rhBMP-2 (>50 ng/mL), the ALP response from W-20-17 cells was inhibited when exposed to high vancomycin levels (1,800-3,600 μg/mL). This dual-delivery system is an attractive alternative to single delivery or preloaded systems for bone regeneration since it can simultaneously fight infection and deliver a potent growth factor. Additionally, this composite can accommodate a wide range of therapeutics and thus be customizable for specific patient needs, however, the potential interactive effects of multiple agents must be investigated to ensure that functional activity is not altered.

Genetic association for caries susceptibility among cleft lip and/or palate individuals

AIM

To evaluate the association of the polymorphisms in the TGFB3 gene (rs2268626), and the BMP4 gene (rs17563) with dental caries in two different groups (noncleft group and oral cleft group) from a cleft center located at Rio de Janeiro, Brazil.

MATERIALS AND METHODS

A total of 486 unrelated children and adolescents with or without caries were evaluated using a cohort design. Data on oral health habits was obtained through a questionnaire and caries data was collected by clinical examination. Genotyping of the selected polymorphisms for TGFB3 and BMP4 were carried out by real-time PCR using the TaqMan assay method from a genomic DNA isolated from buccal epithelial cells of all children and adolescents.

RESULTS

No association was found between BMP4 polymorphism and caries among individuals from both groups. For TGFB3 polymorphism, significant differences were observed for allele and genotype frequencies between caries free and caries affected individuals in oral cleft group (p = 0.013 and 0.006 for allele and genotype frequencies respectively).

CONCLUSION

Our findings provide evidence suggesting that TGFB3 may be involved in caries susceptibility in oral cleft group.

CLINICAL SIGNIFICANCE

In the future, the possibility of identifying genes related to caries susceptibility can lead to counseling of the individual that carries gene alterations, with the aim of working on preventive measures for caries as well as bioengineering treatments.

Cell therapy of pseudarthrosis

Objective

To assess the safety and efficiency of cell therapy for pseudarthrosis. Implant of the bone marrow aspirate was compared to mononuclear cells purified extemporaneously using the Sepax^® equipment.

Methods

Six patients with nonunion of the tibia or femur were treated. Four received a percutaneous infusion of autologous bone marrow aspirated from the iliac crest, and two received autologous bone marrow mononuclear cells separated from the aspirate with the Sepax^®. The primary fixation method was unchanged, and the nonunion focus was not exposed. Physical examination and radiographies were performed 2, 4 and 6 months after the treatment by the same physician. After consolidation of the fracture the satisfaction of the patients was estimated using the adapted QALY scale.

Results

No complications occurred as a result of the referred procedures. Bone consolidation was obtained in all cases within 3 to 24 weeks. The degree of patient satisfaction before and after bone consolidation was assessed, with the average value increasing from two to nine (p=0.0156).

Conclusion

We conclude that the proposed method is effective and safe for the treatment of nonunion of long bones regardless of the stabilization method used. Level of Evidence II, Prospective Comparative Study

Cell therapy of pseudarthrosis

OBJECTIVE

To assess the safety and efficiency of cell therapy for pseudarthrosis. Implant of the bone marrow aspirate was compared to mononuclear cells purified extemporaneously using the Sepax(®) equipment.

METHODS

Six patients with nonunion of the tibia or femur were treated. Four received a percutaneous infusion of autologous bone marrow aspirated from the iliac crest, and two received autologous bone marrow mononuclear cells separated from the aspirate with the Sepax(®). The primary fixation method was unchanged, and the nonunion focus was not exposed. Physical examination and radiographies were performed 2, 4 and 6 months after the treatment by the same physician. After consolidation of the fracture the satisfaction of the patients was estimated using the adapted QALY scale.

RESULTS

No complications occurred as a result of the referred procedures. Bone consolidation was obtained in all cases within 3 to 24 weeks. The degree of patient satisfaction before and after bone consolidation was assessed, with the average value increasing from two to nine (p=0.0156).

CONCLUSION

We conclude that the proposed method is effective and safe for the treatment of nonunion of long bones regardless of the stabilization method used. Level of Evidence II, Prospective Comparative Study.

Bone morphogenetic proteins: facts, challenges, and future perspectives

Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily, acting as potent regulators during embryogenesis and bone and cartilage formation and repair. Cell and molecular biology approaches have unveiled the great complexity of BMP action, later confirmed by transgenic animal studies. Genetic engineering allows for the production of large amounts of BMPs for clinical use, but they have systematically been associated with a delivery system, such as type I collagen and calcium phosphate ceramics, to ensure controlled release and to maximize their biological activity at the surgical site, avoiding systemic diffusion. Clinical orthopedic studies have shown the benefits of FDA-approved recombinant human BMPs (rhBMPs) 2 and 7, but side effects, such as swelling, seroma, and increased cancer risk, have been reported, probably due to high BMP dosage. Several studies have supported the use of BMPs in periodontal regeneration, sinus lift bone-grafting, and non-unions in oral surgery. However, the clinical use of BMPs is growing mainly in off-label applications, with robust evidence to ascertain rhBMPs' safety and efficacy through well-designed, randomized, and double-blind clinical trials. Here we review and discuss the critical data on BMP structure, mechanisms of action, and possible clinical applications.