A BMP/activin A chimera is superior to native BMPs and induces bone repair in nonhuman primates when delivered in a composite matrix

The Phase-Transited Lysozyme Coating Modified Small Intestinal Submucosa Membrane Loaded with Calcium and Zinc Ions for Enhanced Bone Regeneration

Bone defects caused by severe trauma, tumors, infections and diseases remain a global challenge due to limited natural regeneration capacity of bone tissue in large-scale or complex injuries. Guided bone regeneration (GBR) has emerged as a pivotal technique in addressing these issues, relying on barrier membranes to facilitate osteoprogenitor cell infiltration. Current clinical GBR membranes function solely as physical barriers, lacking antibacterial and osteoinductive properties, which underscores the need for advanced alternatives. This study focuses on resorbable GBR membranes made from small intestinal submucosa (SIS), known for biocompatibility and tissue regeneration but hindered by low mechanical strength and rapid degradation. In addition, SIS lacks both antibacterial properties and strong osteogenic capabilities. Enhancements involve crosslinking treatment and dual incorporation of calcium (Ca2+) and zinc (Zn2+), which address the physical property shortcomings and synergistically boost osteoinductivity by activating osteogenic signaling pathways. Additionally, phase-transited lysozyme (PTL) nanofilm technique enables efficient ion loading and controlled release, while offering antibacterial properties. In this study, a multifunctional SIS membrane is constructed by PTL-ions layers, providing a potential solution to the challenge of clinical bone defects.

[Genetic variants associated with the development of stress disorders: A systematic review of GWAS]

Studying the genetic basis of post-traumatic stress disorder (PTSD) can be useful in predicting its risk in a person with a history of severe traumatic stress and in facilitating earlier diagnosis and referral to a specialist. The aim of the study is to review all GWAS studies related to PTSD. In total, 20 studies were included, of which 5 meta-analyses and 9 included war veterans. The functions of genes and their associations were considered, which included single-cell polymorphisms in different groups of genes involved in embryogenesis, neuron formation, and cell functioning, as well as many DNA sequences with non-coding RNA transcribed. The repeatability of the results between studies and replicative samples was studied. Between the studies, the associations were repeated in the CAMKV, CDHR4, DCC, FAM120A, FOXP2 (3 studies), MAD1L1 (3 studies), MAPT, NCAM1, NOS1, SP4, ZMYM4, TCF4 genes. A new large-scale study with many found associations was considered individually. Studies regarding polygenic risk were also studied, and several studies showed genetic comorbidity with anxiety and bipolar disorder. However, the models developed by the authors explain a small percentage of variance and are weakly repeated in other samples. It may be possible to solve this problem by using larger samples and clearer homogeneous inclusion criteria. Thus, at the moment, there are few GWAS studies of PTSD; they are ambiguous and uninformative compared to the same studies for other mental disorders, but they have further potential for assessing the risks of developing the disease.

Investigating the potential effect of Holothuria scabra extract on osteogenic differentiation in preosteoblast MC3T3-E1 cells

The present medical treatments of osteoporosis come with adverse effects. It leads to the exploration of natural products as safer alternative medical prevention and treatment. The sea cucumber, Holothuria scabra, has commercial significance in Asian countries with rising awareness of its properties as a functional food. This study aims to investigate the effects of the inner wall (IW) extract isolated from H. scabra on extracellular matrix maturation, mineralization, and osteogenic signaling pathways on MC3T3-E1 preosteoblasts. The IW showed the expression of several growth factors. Molecular docking revealed that H. scabra BMP2/4 binds specifically to mammal BMP2 type I receptor (BMPR-IA). After osteogenic induction, the viability of cells treated with IW extract was assessed and designated with treatment of 0.1, 0.5, 1, and 5 µg/ml of IW extract for 21 consecutive days. On days 14 and 21, treatments with IW extract at 1 and 5 µg/ml showed increased alkaline phosphatase (ALP) activity and calcium deposit levels in a dose-dependent manner compared to the control group. Moreover, the transcriptomic analysis of total RNA of cells treated with 5 µg/ml of IW extract exhibited upregulation of TGF-β, PI3K/Akt, MAPK, Wnt and PTH signaling pathways at days 14. This study suggests that IW extract from H. scabra exhibits the potential to enhance osteogenic differentiation and mineralization of MC3T3-E1 preosteoblasts through TGF-β, PI3K/Akt, MAPK, Wnt and PTH signaling pathways. Further investigation into the molecular mechanisms underlying the effect of IW extract on osteogenesis is crucial to support its application as a naturally derived supplement for prevention or treatment of osteoporosis.

Bone regeneration using activin A/BMP2 chimera (AB204) with collagen membrane in rats with calvarial defects

PURPOSE

Collagen has long been recognized as an excellent carrier for growth factors, and membrane-type collagen has been widely applied in dentistry for guided bone regeneration. This study was conducted to examine the effects of an activin A/BMP2 chimera (AB204) combined with a collagen membrane (CM) on bone repair in a rat calvarial defect model.

METHODS

A unilateral calvarial defect measuring 5.0 mm was surgically created in 32 Sprague-Dawley rats. The rats were then randomly assigned to 1 of 4 groups, each consisting of 8 animals: control (untreated), CM (treated with a CM only), CM/bone morphogenetic protein 2 (BMP2) (treated with a CM and 1.0 μg of BMP2), and CM/AB204 (treated with a CM and 1.0 μg of AB204). Bone regeneration was evaluated using micro-computed tomography (CT) and histological analysis at 2 and 4 weeks following surgery.

RESULTS

Micro-CT analysis revealed that bone formation in the CM/BMP2 and CM/AB204 groups was superior to that observed in the control and CM groups at both 2 and 4 weeks postoperatively. BMP2 induced greater bone regeneration than AB204 at 2 weeks; however, AB204 resulted in a greater bone volume at 4 weeks, achieving the highest values recorded. No significant differences were found between the CM/BMP2 and CM/AB204 groups at either time point (P>0.05). On histological examination, new bone formation was evident in both CM/BMP2 and CM/AB204 groups.

CONCLUSIONS

Within the limitations of this study, the findings indicate that AB204 may enhance osteogenic potential when used in combination with CM for bone regeneration.

Clinical management and innovation in fracture non-union

INTRODUCTION

With the introduction and continuous improvement in operative fracture fixation, even the most severe bone fractures can be treated with a high rate of successful healing. However, healing complications can occur and when healing fails over prolonged time, the outcome is termed a fracture non-union. Non-union is generally believed to develop due to inadequate fixation, underlying host-related factors, or infection. Despite the advancements in fracture fixation and infection management, there is still a clear need for earlier diagnosis, improved prediction of healing outcomes and innovation in the treatment of non-union.

AREAS COVERED

This review provides a detailed description of non-union from a clinical perspective, including the state of the art in diagnosis, treatment, and currently available biomaterials and orthobiologics.Subsequently, recent translational development from the biological, mechanical, and infection research fields are presented, including the latest in smart implants, osteoinductive materials, and in silico modeling.

EXPERT OPINION

The first challenge for future innovations is to refine and to identify new clinical factors for the proper definition, diagnosis, and treatment of non-union. However, integration of in vitro, in vivo, and in silico research will enable a comprehensive understanding of non-union causes and correlations, leading to the development of more effective treatments.

Shear Stress and Sub-Femtomolar Levels of Ligand Synergize to Activate ALK1 Signaling in Endothelial Cells

Endothelial cells (ECs) respond to concurrent stimulation by biochemical factors and wall shear stress (SS) exerted by blood flow. Disruptions in flow-induced responses can result in remodeling issues and cardiovascular diseases, but the detailed mechanisms linking flow-mechanical cues and biochemical signaling remain unclear. Activin receptor-like kinase 1 (ALK1) integrates SS and ALK1-ligand cues in ECs; ALK1 mutations cause hereditary hemorrhagic telangiectasia (HHT), marked by arteriovenous malformation (AVM) development. However, the mechanistic underpinnings of ALK1 signaling modulation by fluid flow and the link to AVMs remain uncertain. We recorded EC responses under varying SS magnitudes and ALK1 ligand concentrations by assaying pSMAD1/5/9 nuclear localization using a custom multi-SS microfluidic device and a custom image analysis pipeline. We extended the previously reported synergy between SS and BMP9 to include BMP10 and BMP9/10. Moreover, we demonstrated that this synergy is effective even at extremely low SS magnitudes (0.4 dyn/cm2) and ALK1 ligand range (femtogram/mL). The synergistic response to ALK1 ligands and SS requires the kinase activity of ALK1. Moreover, ALK1's basal activity and response to minimal ligand levels depend on endocytosis, distinct from cell-cell junctions, cytoskeleton-mediated mechanosensing, or cholesterol-enriched microdomains. However, an in-depth analysis of ALK1 receptor trafficking's molecular mechanisms requires further investigation.

3D-Printed Osteoinductive Polymeric Scaffolds with Optimized Architecture to Repair a Sheep Metatarsal Critical-Size Bone Defect

The reconstruction of critical-size bone defects in long bones remains a challenge for clinicians. A new osteoinductive medical device is developed here for long bone repair by combining a 3D-printed architectured cylindrical scaffold made of clinical-grade polylactic acid (PLA) with a polyelectrolyte film coating delivering the osteogenic bone morphogenetic protein 2 (BMP-2). This film-coated scaffold is used to repair a sheep metatarsal 25-mm long critical-size bone defect. In vitro and in vivo biocompatibility of the film-coated PLA material is proved according to ISO standards. Scaffold geometry is found to influence BMP-2 incorporation. Bone regeneration is followed using X-ray scans, µCT scans, and histology. It is shown that scaffold internal geometry, notably pore shape, influenced bone regeneration, which is homogenous longitudinally. Scaffolds with cubic pores of ≈870 µm and a low BMP-2 dose of ≈120 µg cm-3 induce the best bone regeneration without any adverse effects. The visual score given by clinicians during animal follow-up is found to be an easy way to predict bone regeneration. This work opens perspectives for a clinical application in personalized bone regeneration.

Complementary modulation of BMP signaling improves bone healing efficiency

The bone morphogenetic protein (BMP) signaling pathway plays a crucial role in bone development and regeneration. While BMP-2 is widely used as an alternative to autograft, its clinical application has raised concerns about adverse side effects and deteriorated bone quality. Therefore, there is a need to develop more sophisticated approaches to regulate BMP signaling and promote bone regeneration. Here, we present a novel complementary strategy that targets both BMP antagonist noggin and agonist Trb3 to enhance bone defect repair without the application of exogenous BMP-2. In vitro studies showed that overexpression of Trb3 with simultaneous noggin suppression significantly promotes osteogenic differentiation of mesenchymal stem cells. This was accompanied by increased BMP/Smad signaling. We also developed sterosome nanocarriers, a non-phospholipid liposomal system, to achieve non-viral mediated noggin suppression and Trb3 overexpression. The gene-loaded sterosomes were integrated onto an apatite-coated polymer scaffold for in vivo calvarial defect implantation, resulting in robust bone healing compared to BMP-2 treatments. Our work provides a promising alternative for high-quality bone formation by regulating expression of BMP agonists and antagonists.

Formation and characterization of BMP2/GDF5 and BMP4/GDF5 heterodimers

BACKGROUND

Proteins of the TGFβ family, which are largely studied as homodimers, are also known to form heterodimers with biological activity distinct from their component homodimers. For instance, heterodimers of bone morphogenetic proteins, including BMP2/BMP7, BMP2/BMP6, and BMP9/BMP10, among others, have illustrated the importance of these heterodimeric proteins within the context of TGFβ signaling.

RESULTS

In this study, we have determined that mature GDF5 can be combined with mature BMP2 or BMP4 to form BMP2/GDF5 and BMP4/GDF5 heterodimer. Intriguingly, this combination of a BMP2 or BMP4 monomer, which exhibit high affinity to heparan sulfate characteristic to the BMP class, with a GDF5 monomer with low heparan sulfate affinity produces a heterodimer with an intermediate affinity. Using heparin affinity chromatography to purify the heterodimeric proteins, we then determined that both the BMP2/GDF5 and BMP4/GDF5 heterodimers consistently signaled potently across an array of cellular and in vivo systems, while the activities of their homodimeric counterparts were more context dependent. These differences were likely driven by an increase in the combined affinities for the type 1 receptors, Alk3 and Alk6. Furthermore, the X-ray crystal structure of BMP2/GDF5 heterodimer was determined, highlighting the formation of two asymmetric type 1 receptor binding sites that are both unique relative to the homodimers.

CONCLUSIONS

Ultimately, this method of heterodimer production yielded a signaling molecule with unique properties relative to the homodimeric ligands, including high affinity to multiple type 1 and moderate heparan binding affinity.

Structural analysis of the interaction between human cytokine BMP-2 and the antagonist Noggin reveals molecular details of cell chondrogenesis inhibition

Bone morphogenetic proteins (BMPs) are secreted cytokines belonging to the transforming growth factor-β superfamily. New therapeutic approaches based on BMP activity, particularly for cartilage and bone repair, have sparked considerable interest; however, a lack of understanding of their interaction pathways and the side effects associated with their use as biopharmaceuticals have dampened initial enthusiasm. Here, we used BMP-2 as a model system to gain further insight into both the relationship between structure and function in BMPs and the principles that govern affinity for their cognate antagonist Noggin. We produced BMP-2 and Noggin as inclusion bodies in Escherichia coli and developed simple and efficient protocols for preparing pure and homogeneous (in terms of size distribution) solutions of the native dimeric forms of the two proteins. The identity and integrity of the proteins were confirmed using mass spectrometry. Additionally, several in vitro cell-based assays, including enzymatic measurements, RT-qPCR, and matrix staining, demonstrated their biological activity during cell chondrogenic and hypertrophic differentiation. Furthermore, we characterized the simple 1:1 noncovalent interaction between the two ligands (K_Dca. 0.4 nM) using bio-layer interferometry and solved the crystal structure of the complex using X-ray diffraction methods. We identified the residues and binding forces involved in the interaction between the two proteins. Finally, results obtained with the BMP-2 N102D mutant suggest that Noggin is remarkably flexible and able to accommodate major structural changes at the BMP-2 level. Altogether, our findings provide insights into BMP-2 activity and reveal the molecular details of its interaction with Noggin.

Targeting of bone morphogenetic protein complexes to heparin/heparan sulfate glycosaminoglycans in bioactive conformation

Bone morphogenetic proteins (BMP) are powerful regulators of cellular processes such as proliferation, differentiation, and apoptosis. However, the specific molecular requirements controlling the bioavailability of BMPs in the extracellular matrix (ECM) are not yet fully understood. Our previous work showed that BMPs are targeted to the ECM as growth factor-prodomain (GF-PD) complexes (CPLXs) via specific interactions of their PDs. We showed that BMP-7 PD binding to the extracellular microfibril component fibrillin-1 renders the CPLXs from an open, bioactive V-shape into a closed, latent ring shape. Here, we show that specific PD interactions with heparin/heparan sulfate glycosaminoglycans (GAGs) allow to target and spatially concentrate BMP-7 and BMP-9 CPLXs in bioactive V-shape conformation. However, targeting to GAGs may be BMP specific, since BMP-10 GF and CPLX do not interact with heparin. Bioactivity assays on solid phase in combination with interaction studies showed that the BMP-7 PD protects the BMP-7 GF from inactivation by heparin. By using transmission electron microscopy, molecular docking, and site-directed mutagenesis, we determined the BMP-7 PD-binding site for heparin. Further, fine-mapping of the fibrillin-1-binding site within the BMP-7 PD and molecular modeling showed that both binding sites are mutually exclusive in the open V- versus closed ring-shape conformation. Together, our data suggest that targeting exquisite BMP PD-binding sites by extracellular protein and GAG scaffolds integrates BMP GF bioavailability in a contextual manner in development, postnatal life, and connective tissue disease.

Bioheterojunction-Engineered Polyetheretherketone Implants With Diabetic Infectious Micromilieu Twin-Engine Powered Disinfection for Boosted Osteogenicity

Diabetic infectious micromilieu (DIM) leads to a critical failure rate of osseointegration by virtue of two main peculiarities: high levels of topical glucose and inevitable infection. To tackle the daunting issue, a bioheterojunction-engineered orthopedic polyetheretherketone (PEEK) implant consisting of copper sulfide/graphene oxide (CuS/GO) bioheterojunctions (bioHJs) and glucose oxidase (GOx) is conceived and developed for DIM enhanced disinfection and boosted osseointegration. Under hyperglycemic micromilieu, GOx can convert surrounding glucose into hydrogen peroxide (H₂ O₂ ). Then, upon infectious micromilieu, the bioHJs enable the catalyzation of H₂ O₂ to highly germicidal hydroxyl radical (·OH). As a result, the engineered implants massacre pathogenic bacteria through DIM twin-engine powered photo-chemodynamic therapy in vitro and in vivo. In addition, the engineered implants considerably facilitate cell viability and osteogenic activity of osteoblasts under a hyperglycemic microenvironment via synergistic induction of copper ions (Cu²⁺ ) and GO. In vivo studies using bone defect models of diabetic rats at 4 and 8 weeks further authenticate that bioHJ-engineering PEEK implants substantially elevate their osseointegration through biofilm elimination and vascularization, as well as macrophage reprogramming. Altogether, the present study puts forward a tactic that arms orthopedic implants with DIM twin-engine powered antibacterial and formidable osteogenic capacities for diabetic stalled osseointegration.

Zinc-doped ferric oxyhydroxide nano-layer enhances the bactericidal activity and osseointegration of a magnesium alloy through augmenting the formation of neutrophil extracellular traps

Implant-associated infections (IAI) and osseointegration disorders are the most common complications in orthopedics. Studies have shown that neutrophils surrounding implants play a vital role in regulating these complications. Although magnesium (Mg) and its alloys are considered promising biodegradable bone implants, their role in neutrophil-mediated antibacteria has not yet been examined. Considering the rapid corrosion of Mg, it is necessary to develop methods to inhibit its corrosion. To solve these issues, a zinc-doped ferric oxyhydroxide nano-layer modified plasma electrolytic oxidation (PEO)-coated Mg alloy (PEO-FeZn) was developed in this study, and its antibacterial, immune anti-infective, and osteogenic ability were systematically evaluated. The results showed that PEO-FeZn nano-layer enhanced the corrosion resistance, biocompatibility, bactericidal activity, and osteoblastic differentiation activity of the Mg alloy. Moreover, PEO-FeZn nano-layer inhibited immune evasion-related gene expression and contributed to the formation of neutrophil extracellular traps (NETs) by activating the extracellular release of DNA fibers and granule proteins, and thereby suppressing bacterial invasion and promoting osseointegration in vivo in Staphylococcus aureus (S. aureus)-infected rat femurs. Overall, the findings of this study could serve as a reference for the fabrication of highly biocompatible and corrosion resistant Mg alloys to address the challenges of IAI and osseointegration disorders. STATEMENT OF SIGNIFICANCE: The widely used metallic biomaterials usually come with the risk of IAI. As the first responder around the biomaterials, neutrophils could form NETs to defense against microorganism and promote tissue remodeling. Therefore, biomaterials addressing antibacterial and neutrophils-modulatory strategies are highly necessary in reducing IAI. To solve these issues, we grew PEO-FeZn nano-layers in situ on Mg alloy using a simple and green technique. The nano-layer not only enhanced the corrosion resistance and biocompatibility of Mg alloy, but also elevated the antibacterial and osteogenesis capability. Moreover, nano-layer contributed to NETs formation, thereby suppressing bacterial invasion and even promoting osseointegration in S.aureus-infected femurs. Accordingly, this functionalized multilayer coating with antibacterial immunity represents a novel therapeutic strategy for IAI and weak osseointegration.

Reversely immortalized mouse salivary gland cells presented a promising metabolic and fibrotic response upon BMP9/Gdf2 stimulation

The submandibular gland (SMG) and the sublingual gland (SLG) are two of the three major salivary glands in mammals. In mice, they are adjacent to each other and open into the oral cavity, producing saliva to lubricate the mouth and aid in food digestion. Though salivary gland dysfunction accompanied with fibrosis and metabolic disturbance is common in clinic, in-depth mechanistic research is lacking. Currently, research on how to rescue salivary function is challenging, as it must resort to using terminally differentiated acinar cells or precursor acinar cells with unknown differentiation. In this study, we established reversely immortalized mouse primary SMG cells (iSMGCs) and SLG cells (iSLGCs) on the first postnatal day (P0). The iSMGCs and iSLGCs grew well, exhibited many salivary gland characteristics, and retained the metabolism-related genes derived from the original tissue as demonstrated using transcriptome sequencing (RNA-seq) analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of these two cell lines, which overlapped with those of the SMG and SLG, were enriched in cysteine and methionine metabolism. Furthermore, we investigated the role of bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), on metabolic and fibrotic functions in the SMG and SLG. We demonstrated that iSMGCs and iSLGCs presented promising adipogenic and fibrotic responses upon BMP9/Gdf2 stimulation. Thus, our findings indicate that iSMGCs and iSLGCs faithfully reproduce characteristics of SMG and SLG cells and present a promising prospect for use in future study of salivary gland metabolism and fibrosis upon BMP9/Gdf2 stimulation.

The context-dependent, combinatorial logic of BMP signaling

Cell-cell communication systems typically comprise families of ligand and receptor variants that function together in combinations. Pathway activation depends on the complex way in which ligands are presented extracellularly and receptors are expressed by the signal-receiving cell. To understand the combinatorial logic of such a system, we systematically measured pairwise bone morphogenetic protein (BMP) ligand interactions in cells with varying receptor expression. Ligands could be classified into equivalence groups based on their profile of positive and negative synergies with other ligands. These groups varied with receptor expression, explaining how ligands can functionally replace each other in one context but not another. Context-dependent combinatorial interactions could be explained by a biochemical model based on the competitive formation of alternative signaling complexes with distinct activities. Together, these results provide insights into the roles of BMP combinations in developmental and therapeutic contexts and establish a framework for analyzing other combinatorial, context-dependent signaling systems.

Biodegradable Microparticles for Regenerative Medicine: A State of the Art and Trends to Clinical Application

Tissue engineering and cell therapy are very attractive in terms of potential applications but remain quite challenging regarding the clinical aspects. Amongst the different strategies proposed to facilitate their implementation in clinical practices, biodegradable microparticles have shown promising outcomes with several advantages and potentialities. This critical review aims to establish a survey of the most relevant materials and processing techniques to prepare these micro vehicles. Special attention will be paid to their main potential applications, considering the regulatory constraints and the relative easiness to implement their production at an industrial level to better evaluate their application in clinical practices.

Fabrication and evaluation of a BMP-2/dexamethasone co-loaded gelatin sponge scaffold for rapid bone regeneration

Improving the osteogenic activity of BMP-2 in vivo has significant clinical application value. In this research, we use a clinical gelatin sponge scaffold loaded with BMP-2 and dexamethasone (Dex) to evaluate the osteogenic activity of dual drugs via ectopic osteogenesis in vivo. We also investigate the mechanism of osteogenesis induced by BMP-2 and Dex with C2C12, a multipotent muscle-derived progenitor cell. The results show that the gelatin scaffold with Dex and BMP-2 can significantly accelerate osteogenesis in vivo. It is indicated that compared with the BMP-2 or Dex alone, 100 nM of Dex can dramatically enhance the BMP-2-induced alkaline phosphatase activity (ALP), ALP mRNA expression and mineralization. Further studies show that 100 nM of Dex can maintain the secondary structure of BMP-2 and facilitate recognition of BMP-2 with its receptors on the surface of C2C12 cells. We also find that in C2C12, Dex has no obvious effect on the BMP-2-induced Smad1/5/8 protein expression and the STAT3-dependent pathway, but Runx2-dependent pathway is involved in the Dex-stimulated osteoblast differentiation of BMP-2 both in vitro and in vivo. Based on these results, a potential mechanism model about the synergistic osteoinductive effect of Dex and BMP-2 in C2C12 cells via Runx2 activation is proposed. This may provide a theoretical basis for the pre-clinical application of Dex and BMP-2 for bone regeneration.

Case Report: Reconstruction of a Large Maxillary Defect With an Engineered, Vascularized, Prefabricated Bone Graft

The reconstruction of complex midface defects is a challenging clinical scenario considering the high anatomical, functional, and aesthetic requirements. In this study, we proposed a surgical treatment to achieve improved oral rehabilitation and anatomical and functional reconstruction of a complex defect of the maxilla with a vascularized, engineered composite graft. The patient was a 39-year-old female, postoperative after left hemimaxillectomy for ameloblastic carcinoma in 2010 and tumor-free at the 5-year oncological follow-up. The left hemimaxillary defect was restored in a two-step approach. First, a composite graft was ectopically engineered using autologous stromal vascular fraction (SVF) cells seeded on an allogenic devitalized bone matrix. The resulting construct was further loaded with bone morphogenic protein-2 (BMP-2), wrapped within the latissimus dorsi muscle, and pedicled with an arteriovenous (AV) bundle. Subsequently, the prefabricated graft was orthotopically transferred into the defect site and revascularized through microvascular surgical techniques. The prefabricated graft contained vascularized bone tissue embedded within muscular tissue. Despite unexpected resorption, its orthotopic transfer enabled restoration of the orbital floor, separation of the oral and nasal cavities, and midface symmetry and allowed the patient to return to normal diet as well as to restore normal speech and swallowing function. These results remained stable for the entire follow-up period of 2 years. This clinical case demonstrates the safety and the feasibility of composite graft engineering for the treatment of complex maxillary defects. As compared to the current gold standard of autologous tissue transfer, this patient’s benefits included decreased donor site morbidity and improved oral rehabilitation. Bone resorption of the construct at the ectopic prefabrication site still needs to be further addressed to preserve the designed graft size and shape.

The Potential Use of Novel Plant-Derived Recombinant Human Collagen in Aesthetic Medicine

SUMMARY

Recombinant human type I collagen, identical in structure and functionality to human type I collagen, was successfully expressed and extracted from genetically modified tobacco plants. Contrarily to tissue extracted protein, rhCollagen is not immunogenic and not allergenic and has an intact triple helix structure showing superior biological functionality. A photocurable rhCollagen was developed by chemically modifying the protein to allow cross-linking under illumination at various wavelengths, maintaining the protein structural and biological functions. The use of the photocurable rhCollagen in aesthetic medicine, especially as a dermal filler and as a bioink for 3D-printed breast implant is discussed in this article.

Nutrient Element Decorated Polyetheretherketone Implants Steer Mitochondrial Dynamics for Boosted Diabetic Osseointegration

As a chronic metabolic disease, diabetes mellitus (DM) creates a hyperglycemic micromilieu around implants, resulting inthe high complication and failure rate of implantation because of mitochondrial dysfunction in hyperglycemia. To address the daunting issue, the authors innovatively devised and developed mitochondria-targeted orthopedic implants consisted of nutrient element coatings and polyetheretherketone (PEEK). Dual nutrient elements, in the modality of ZnO and Sr(OH)2 , are assembled onto the sulfonated PEEK surface (Zn&Sr-SPEEK). The results indicate the synergistic liberation of Zn2+ and Sr2+ from coating massacres pathogenic bacteria and dramatically facilitates cyto-activity of osteoblasts upon the hyperglycemic niche. Intriguingly, Zn&Sr-SPEEK implants are demonstrated to have a robust ability to recuperate hyperglycemia-induced mitochondrial dynamic disequilibrium and dysfunction by means of Dynamin-related protein 1 (Drp1) gene down-regulation, mitochondrial membrane potential (MMP) resurgence, and reactive oxygen species (ROS) elimination, ultimately enhancing osteogenicity of osteoblasts. In vivo evaluations utilizing diabetic rat femoral/tibia defect model at 4 and 8 weeks further confirm that nutrient element coatings substantially augment bone remodeling and osseointegration. Altogether, this study not only reveals the importance of Zn2+ and Sr2+ modulation on mitochondrial dynamics that contributes to bone formation and osseointegration, but also provides a novel orthopedic implant for diabetic patients with mitochondrial modulation capability.

A BMP/Activin A Chimera Induces Posterolateral Spine Fusion in Nonhuman Primates at Lower Concentrations Than BMP-2

BACKGROUND

Supraphysiologic bone morphogenetic protein (BMP)-2 concentrations are required to induce spinal fusion. In this study, a BMP-2/BMP-6/activin A chimera (BV-265), optimized for BMP receptor binding, delivered in a recombinant human collagen:CDHA [calcium-deficient hydroxyapatite] porous composite matrix (CM) or bovine collagen:CDHA granule porous composite matrix (PCM), engineered for optimal BV-265 retention and guided tissue repair, was compared with BMP-2 delivered in a bovine absorbable collagen sponge (ACS) wrapped around a MASTERGRAFT Matrix (MM) ceramic-collagen rod (ACS:MM) in a nonhuman primate noninstrumented posterolateral fusion (PLF) model.

METHODS

In vivo retention of 125I-labeled-BV-265/CM or PCM was compared with 125I-labeled-BMP-2/ACS or BMP-2/buffer in a rat muscle pouch model using scintigraphy. Noninstrumented PLF was performed by implanting CM, BV-265/CM, BV-265/PCM, or BMP-2/ACS:MM across L3-L4 and L5-L6 or L3-L4-L5 decorticated transverse processes in 26 monkeys. Computed tomography (CT) images were acquired at 0, 4, 8, 12, and 24 weeks after surgery, where applicable. Manual palpation, μCT (microcomputed tomography) or nCT (nanocomputed tomography), and histological analysis were performed following euthanasia.

RESULTS

Retention of 125I-labeled-BV-265/CM was greater than BV-265/PCM, followed by BMP-2/ACS and BMP-2/buffer. The CM, 0.43 mg/cm3 BMP-2/ACS:MM, and 0.05 mg/cm3 BV-265/CM failed to generate PLFs. The 0.15-mg/cm3 BV-265/CM or 0.075-mg/cm3 BV-265/PCM combinations were partially effective. The 0.25-mg/cm3 BV-265/CM and 0.15 and 0.3-mg/cm3 BV-265/PCM combinations generated successful 2-level PLFs at 12 and 24 weeks.

CONCLUSIONS

BV-265/CM or PCM can induce fusion in a challenging nonhuman primate noninstrumented PLF model at substantially lower concentrations than BMP-2/ACS:MM.

CLINICAL RELEVANCE

BV-265/CM and PCM represent potential alternatives to induce PLF in humans at substantially lower concentrations than BMP-2/ACS:MM.

The Role of BMP Signaling in Endothelial Heterogeneity

Bone morphogenetic proteins (BMPs), which compose the largest group of the transforming growth factor-β (TGF-ß) superfamily, have been implied to play a crucial role in diverse physiological processes. The most intriguing feature of BMP signaling is that it elicits heterogeneous responses from cells with equivalent identity, thus permitting highly context-dependent signaling outcomes. In endothelial cells (ECs), which are increasingly perceived as a highly heterogeneous population of cells with respect to their morphology, function, as well as molecular characteristics, BMP signaling has shown to elicit diverse and often opposite effects, illustrating the innate complexity of signaling responses. In this review, we provide a concise yet comprehensive overview of how outcomes of BMP signaling are modulated in a context-dependent manner with an emphasis on the underlying molecular mechanisms and summarize how these regulations of the BMP signaling promote endothelial heterogeneity.

High-throughput measurements of bone morphogenetic protein/bone morphogenetic protein receptor interactions using biolayer interferometry

Bone morphogenetic proteins (BMPs) are an important family of growth factors playing a role in a large number of physiological and pathological processes, including bone homeostasis, tissue regeneration, and cancers. In vivo, BMPs bind successively to both BMP receptors (BMPRs) of type I and type II, and a promiscuity has been reported. In this study, we used biolayer interferometry to perform parallel real-time biosensing and to deduce the kinetic parameters (ka, kd) and the equilibrium constant (KD) for a large range of BMP/BMPR combinations in similar experimental conditions. We selected four members of the BMP family (BMP-2, 4, 7, 9) known for their physiological relevance and studied their interactions with five type-I BMP receptors (ALK1, 2, 3, 5, 6) and three type-II BMP receptors (BMPR-II, ACTR-IIA, ACTR-IIB). We reveal that BMP-2 and BMP-4 behave differently, especially regarding their kinetic interactions and affinities with the type-II BMPR. We found that BMP-7 has a higher affinity for the type-II BMPR receptor ACTR-IIA and a tenfold lower affinity with the type-I receptors. While BMP-9 has a high and similar affinity for all type-II receptors, it can interact with ALK5 and ALK2, in addition to ALK1. Interestingly, we also found that all BMPs can interact with ALK5. The interaction between BMPs and both type-I and type-II receptors in a ternary complex did not reveal further cooperativity. Our work provides a synthetic view of the interactions of these BMPs with their receptors and paves the way for future studies on their cell-type and receptor specific signaling pathways.

3D-printed scaffold combined to 2D osteoinductive coatings to repair a critical-size mandibular bone defect

The reconstruction of large bone defects (12 cm³) remains a challenge for clinicians. We developed a new critical-size mandibular bone defect model on a minipig, close to human clinical issues. We analyzed the bone reconstruction obtained by a 3D-printed scaffold made of clinical-grade polylactic acid (PLA), coated with a polyelectrolyte film delivering an osteogenic bioactive molecule (BMP-2). We compared the results (computed tomography scans, microcomputed tomography scans, histology) to the gold standard solution, bone autograft. We demonstrated that the dose of BMP-2 delivered from the scaffold significantly influenced the amount of regenerated bone and the repair kinetics, with a clear BMP-2 dose-dependence. Bone was homogeneously formed inside the scaffold without ectopic bone formation. The bone repair was as good as for the bone autograft. The BMP-2 doses applied in our study were reduced 20- to 75-fold compared to the commercial collagen sponges used in the current clinical applications, without any adverse effects. Three-dimensional printed PLA scaffolds loaded with reduced doses of BMP-2 may be a safe and simple solution for large bone defects faced in the clinic.

BMP heterodimers signal via distinct type I receptor class functions

TGF-β family heterodimeric ligands show increased or exclusive signaling compared to homodimeric ligands in both vertebrate and insect development as well as in therapeutically relevant processes, like osteogenesis. However, the mechanisms that differentiate heterodimer and homodimer signaling remain uncharacterized. We show that BMP antagonists do not account for the exclusive signaling of Bmp2/7 heterodimers in zebrafish development. We found that overexpressed homodimers can signal but surprisingly require two distinct type I receptors, like heterodimers, indicating a required activity of the heteromeric type I receptor complex. We further demonstrate that a canonical type I receptor function has been delegated to only one of these receptors, Acvr1. Our findings should inform both basic and translational research in multiple TGF-β family signaling contexts.

Heterodimeric TGF-β ligands outperform homodimers in a variety of developmental, cell culture, and therapeutic contexts; however, the mechanisms underlying this increased potency remain uncharacterized. Here, we use dorsal–ventral axial patterning of the zebrafish embryo to interrogate the BMP2/7 heterodimer signaling mechanism. We demonstrate that differential interactions with BMP antagonists do not account for the reduced signaling ability of homodimers. Instead, we find that while overexpressed BMP2 homodimers can signal, they require two nonredundant type I receptors, one from the Acvr1 subfamily and one from the Bmpr1 subfamily. This implies that all BMP signaling within the zebrafish gastrula, even BMP2 homodimer signaling, requires Acvr1. This is particularly surprising as BMP2 homodimers do not bind Acvr1 in vitro. Furthermore, we find that the roles of the two type I receptors are subfunctionalized within the heterodimer signaling complex, with the kinase activity of Acvr1 being essential, while that of Bmpr1 is not. These results suggest that the potency of the Bmp2/7 heterodimer arises from the ability to recruit both Acvr1 and Bmpr1 into the same signaling complex.

Activation of Bone Remodeling Compartments in BMP-2-Injected Knees Supports a Local Vascular Mechanism for Arthritis-Related Bone Changes

BACKGROUND

Synovial membrane-derived factors are implicated in arthritis-related bone changes. The route that synovial factors use to access subchondral bone and the mechanisms responsible for these bone changes remain unclear. A safety study involving intra-articular injection of bone morphogenetic protein-2 (BMP-2)/calcium phosphate matrix (CPM) or CPM addresses these issues.

METHODS

Knee joints in 21 monkeys were injected with CPM or 1.5 or 4.5 mg/mL BMP-2/CPM and were evaluated at 1 and 8 weeks. Contralateral joints were injected with saline solution. Knee joints in 4 animals each were injected with 1.5 or 4.5 mg/mL BMP-2/CPM. Contralateral joints were injected with corresponding treatments at 8 weeks. Both joints were evaluated at 16 weeks. Harvested joints were evaluated grossly and with histomorphometry. Knee joints in 3 animals were injected with 125I-labeled BMP-2/CPM and evaluated with scintigraphy and autoradiography at 2 weeks to determine BMP-2 distribution.

RESULTS

All treatments induced transient synovitis and increased capsular vascularization, observed to anastomose with metaphyseal venous sinusoids, but did not damage articular cartilage. Both treatments induced unanticipated activation of vascular-associated trabecular bone remodeling compartments (BRCs) restricted to injected knees. Bone volume increased in BMP-2/CPM-injected knees at 8 and 16 weeks. Scintigraphy demonstrated metaphyseal 125I-labeled BMP-2 localization restricted to injected knees, confirming local rather than systemic BMP-2 release. Autoradiography demonstrated that BMP-2 diffusion through articular cartilage into the metaphysis was blocked by the tidemark. The lack of marrow activation or de novo bone formation, previously reported following metaphyseal BMP-2/CPM administration, confirmed BMP-2 and synovial-derived factors were not free in the marrow. The 125I-labeled BMP-2/CPM, observed within venous sinusoids of injected knees, confirmed the potential for capsular and metaphyseal venous portal communication.

CONCLUSIONS

This study identifies a synovitis-induced venous portal circulation between the joint capsule and the metaphysis as an alternative to systemic circulation and local diffusion for synovial membrane-derived factors to reach subchondral bone. This study also identifies vascular-associated BRCs as a mechanism for arthritis-associated subchondral bone changes and provides additional support for their role in physiological trabecular bone remodeling and/or modeling.

CLINICAL RELEVANCE

Inhibition of synovitis and accompanying abnormal vascularization may limit bone changes associated with arthritis.

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.

Learning from BMPs and their biophysical extracellular matrix microenvironment for biomaterial design

It is nowadays well-accepted that the extracellular matrix (ECM) is not a simple reservoir for growth factors but is an organization center of their biological activity. In this review, we focus on the ability of the ECM to regulate the biological activity of BMPs. In particular, we survey the role of the ECM components, notably the glycosaminoglycans and fibrillary ECM proteins, which can be promoters or repressors of the biological activities mediated by the BMPs. We examine how a process called mechano-transduction induced by the ECM can affect BMP signaling, including BMP internalization by the cells. We also focus on the spatio-temporal regulation of the BMPs, including their release from the ECM, which enables to modulate their spatial localization as well as their local concentration. We highlight how biomaterials can recapitulate some aspects of the BMPs/ECM interactions and help to answer fundamental questions to reveal previously unknown molecular mechanisms. Finally, the design of new biomaterials inspired by the ECM to better present BMPs is discussed, and their use for a more efficient bone regeneration in vivo is also highlighted.

Structural perspective of BMP ligands and signaling

The Bone Morphogenetic Proteins (BMPs) are the largest class signaling molecules within the greater Transforming Growth Factor Beta (TGFβ) family, and are responsible for a wide array of biological functions, including dorsal-ventral patterning, skeletal development and maintenance, as well as cell homeostasis. As such, dysregulation of BMPs results in a number of diseases, including fibrodysplasia ossificans progressiva (FOP) and pulmonary arterial hypertension (PAH). Therefore, understanding BMP signaling and regulation at the molecular level is essential for targeted therapeutic intervention. This review discusses the recent advances in the structural and biochemical characterization of BMPs, from canonical ligand-receptor interactions to co-receptors and antagonists. This work aims to highlight how BMPs differ from other members of the TGFβ family, and how that information can be used to further advance the field. Lastly, this review discusses several gaps in the current understanding of BMP structures, with the aim that discussion of these gaps will lead to advancements in the field.

BMP gene delivery for skeletal tissue regeneration

Musculoskeletal disorders are common and can be associated with significant morbidity and reduced quality of life. Current treatments for major bone loss or cartilage defects are insufficient. Bone morphogenetic proteins (BMPs) are key players in the recruitment and regeneration of damaged musculoskeletal tissues, and attempts have been made to introduce the protein to fracture sites with limited success. In the last 20 years we have seen a substantial progress in the development of various BMP gene delivery platforms for several conditions. In this review we cover the progress made using several techniques for BMP gene delivery for bone as well as cartilage regeneration, with focus on recent advances in the field of skeletal tissue engineering. Some methods have shown success in large animal models, and with the global trend of introducing gene therapies into the clinical setting, it seems that the day in which BMP gene therapy will be viable for clinical use is near.

An "all-in-one" scaffold targeting macrophages to direct endogenous bone repair in situ

Scaffolds for tissue repair are designed in an increasingly complicated manner to meet multi-facet biological needs during the healing process. However, overly sophisticated design, especially the use of multiple components and delivery of exogenous cells, hampers the bench-to-bedside translation. Here, a multi-functional - yet mono-compositional - bioactive scaffold is devised to mediate the full-range, endogenous bone repair. Based on immunoactivity screening, a chemically-modified glucomannan polysaccharide is selected and processed into an anisotropic porous scaffold, which accurately stimulates macrophages to produce pro-regenerative cytokines. These cytokines effectively enhance the recruitment ("R") and induced osteogenesis ("IO") of the bone progenitor cells in situ. Meanwhile, the anisotropic porosity and carbohydrate signal of the scaffold facilitate differential adhesion ("A") and distribution ("D") of the macrophages and bone progenitor cells - enabling the former's accumulation at the surface while encouraging the latter's infiltration into the scaffold. Implanted in a rat calvarial defect model, this "RADIO" system effectively promotes healing over 12 weeks, with the obvious formation of hard callus through the scaffold. In summary, RADIO integrates multiple functions into one single scalable system ("all-in-one") to govern the dynamic bone-repair process, by harnessing the power of host macrophages. RADIO represents an open platform to solving the long-lasting complexity-versus-simplicity dilemma in biomaterials design. STATEMENT OF SIGNIFICANCE: Biomaterials as versatile tools for tissue repair are becoming increasingly complicated, yet overly sophisticated design - especially the use of multiple components, exogenous cells, and overdosed growth factors - hampers their clinical application. The pre-requisite for designing a successful integrative scaffold is to identify an inherent biological target responding to biomaterial signals, thereby efficiently and safely promoting tissue repair via the endogenous healing capability instead of extra multifarious biochemical components. For bone regeneration, the pivotal regulator is macrophages. Through activating host macrophages, our single-component scaffold system coordinates the entire bone regenerative cascade in situ and induces successful bone regeneration in a calvarial defect model. This scaffold represents a scalable and multi-functional approach to effectively simplify the sophisticated design in regenerative medicine.

Precision Medicine in Tissue Engineering on Bone

With the rapidly development of clinical treatments, precision medicine has come to people eyes with the requirement according to different people and different disease situation. So precision medicine is called personalized medicine which is a new frontier of healthcare. Bone tissue engineering developed from traditional bone graft to precise medicine era. So scientists seek approaches to harness stem cells, scaffolds, growth factors, and extracellular matrix to promise enhanced and more reliable bone formation. This review provides an overview of novel developments on precision medicine in tissue engineering of bone hoping it can open new perspectives of strategies on bone treatment.

Bio-orthogonal, Site-Selective Conjugation of Recombinant Proteins to Microporous Annealed Particle Hydrogels for Tissue Engineering

Protein conjugation to biomaterial scaffolds is a powerful approach for tissue engineering. However, typical chemical conjugation methods lack site-selectivity and can negatively impact protein bioactivity. To overcome this problem, a site-selective strategy is reported here for installing tetrazine groups on terminal poly-histidines (His-tags) of recombinant proteins. These tetrazine groups are then leveraged for bio-orthogonal conjugation to poly(ethylene glycol) (PEG) hydrogel microparticles, which are subsequently assembled into microporous annealed particle (MAP) hydrogels. Efficacy of the strategy is demonstrated using recombinant, green fluorescent protein with a His tag (His-GFP), which enhanced fluorescence of the MAP hydrogels compared to control protein lacking tetrazine groups. Subsequently, to demonstrate efficacy with a therapeutic protein, recombinant human bone morphogenetic protein-2 (His-BMP2) was conjugated. Human mesenchymal stem cells growing in the MAP hydrogels responded to the conjugated BMP2 and significantly increased mineralization after 21 days compared to controls. Thus, this site-selective protein modification strategy coupled with bio-orthogonal click chemistry is expected to be useful for bone defect repair and regeneration therapies. Broader application to the integration of protein therapeutics with biomaterials is also envisioned.

Specification of BMP Signaling

Bone Morphogenetic Proteins (BMPs) together with the Growth and Differentiation Factors (GDFs) form the largest subgroup of the Transforming Growth Factor (TGF)β family and represent secreted growth factors, which play an essential role in many aspects of cell communication in higher organisms. As morphogens they exert crucial functions during embryonal development, but are also involved in tissue homeostasis and regeneration in the adult organism. Their involvement in maintenance and repair processes of various tissues and organs made these growth factors highly interesting targets for novel pharmaceutical applications in regenerative medicine. A hallmark of the TGFβ protein family is that all of the more than 30 growth factors identified to date signal by binding and hetero-oligomerization of a very limited set of transmembrane serine-threonine kinase receptors, which can be classified into two subgroups termed type I and type II. Only seven type I and five type II receptors exist for all 30plus TGFβ members suggesting a pronounced ligand-receptor promiscuity. Indeed, many TGFβ ligands can bind the same type I or type II receptor and a particular receptor of either subtype can usually interact with and bind various TGFβ ligands. The possible consequence of this ligand-receptor promiscuity is further aggravated by the finding that canonical TGFβ signaling of all family members seemingly results in the activation of just two distinct signaling pathways, that is either SMAD2/3 or SMAD1/5/8 activation. While this would implicate that different ligands can assemble seemingly identical receptor complexes that activate just either one of two distinct pathways, in vitro and in vivo analyses show that the different TGFβ members exert quite distinct biological functions with high specificity. This discrepancy indicates that our current view of TGFβ signaling initiation just by hetero-oligomerization of two receptor subtypes and transduction via two main pathways in an on-off switch manner is too simplified. Hence, the signals generated by the various TGFβ members are either quantitatively interpreted using the subtle differences in their receptor-binding properties leading to ligand-specific modulation of the downstream signaling cascade or additional components participating in the signaling activation complex allow diversification of the encoded signal in a ligand-dependent manner at all cellular levels. In this review we focus on signal specification of TGFβ members, particularly of BMPs and GDFs addressing the role of binding affinities, specificities, and kinetics of individual ligand-receptor interactions for the assembly of specific receptor complexes with potentially distinct signaling properties.

Tyrosine kinase Eph receptor A6 sensitizes glioma-initiating cells towards bone morphogenetic protein-induced apoptosis

Bone morphogenetic protein (BMP) signaling plays important roles in glioblastoma multiforme (GBM), a lethal form of brain tumor. BMP reduces GBM tumorigenicity through its differentiation‐ and apoptosis‐inducing effects on glioma‐initiating cells (GIC). However, some GIC do not respond to the tumor suppressive effects of BMP. Using a phosphoreceptor tyrosine kinase array, we found that EPHA6 (erythropoietin‐producing hepatocellular carcinoma receptor A6) phosphorylation was regulated by BMP‐2 signaling in some GIC. Analysis of The Cancer Genome Atlas showed that EPHA6 expression was lower in patients with GBM than in the normal brain, and that high EPHA6 expression was correlated with better prognosis. EPHA6 receptor increased the susceptibility of both sensitive and resistant GIC to BMP‐2‐induced apoptosis. The cooperative effect on apoptosis induction depended on the kinase activity of BMP type I receptor but was independent of EPHA6 kinase function. Overexpression of the EPHA6 receptor in GIC resulted in the formation of a protein complex of EPHA6 receptor and the BMP type I receptor ALK‐2, which was associated with BMP‐induced apoptosis in GIC. Intracranial injection of GIC into nude mice showed that gain‐of‐function of EPHA6 together with BMP‐2 pretreatment slowed GBM tumor progression in the mouse brain and promoted mouse survival. In summary, EPHA6 together with BMP‐2 signaling led to apoptotic cell death in GIC, and thus is a putative tumor suppressor in GBM.