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.

Calcium phosphate ceramics combined with rhBMP6 within autologous blood coagulum promote posterolateral lumbar fusion in sheep

Posterolateral spinal fusion (PLF) is a procedure used for the treatment of degenerative spine disease. In this study we evaluated Osteogrow-C, a novel osteoinductive device comprised of recombinant human Bone morphogenetic protein 6 (rhBMP6) dispersed in autologous blood coagulum with synthetic ceramic particles, in the sheep PLF model. Osteogrow-C implants containing 74-420 or 1000-1700 µm ceramic particles (TCP/HA 80/20) were implanted between L4-L5 transverse processes in sheep (Ovis Aries, Merinolaandschaf breed). In the first experiment (n = 9 sheep; rhBMP6 dose 800 µg) the follow-up period was 27 weeks while in the second experiment (n = 12 sheep; rhBMP6 dose 500 µg) spinal fusion was assessed by in vivo CT after 9 weeks and at the end of the experiment after 14 (n = 6 sheep) and 40 (n = 6 sheep) weeks. Methods of evaluation included microCT, histological analyses and biomechanical testing. Osteogrow-C implants containing both 74-420 and 1000-1700 µm ceramic particles induced radiographic solid fusion 9 weeks following implantation. Ex-vivo microCT and histological analyses revealed complete osseointegration of newly formed bone with adjacent transverse processes. Biomechanical testing confirmed that fusion between transverse processes was complete and successful. Osteogrow-C implants induced spinal fusion in sheep PLF model and therefore represent a novel therapeutic solution for patients with degenerative disc disease.

Comparison of synthetic ceramic products formulated with autologous blood coagulum containing rhBMP6 for induction of bone formation

PURPOSE

Osteogrow, an osteoinductive device containing recombinant human Bone Morphogenetic Protein 6 (rhBMP6) in autologous blood coagulum, is a novel therapeutic solution for bone regeneration. This study aimed to evaluate different commercially available calcium phosphate synthetic ceramic particles as a compression-resistant matrix (CRM) added to Osteogrow implants to enhance their biomechanical properties.

METHODS

Osteogrow implants with the addition of Vitoss, ChronOs, BAM, and Dongbo ceramics (Osteogrow-C, where C stands for ceramics) were evaluated in the rodent subcutaneous ectopic bone formation assay. Osteogrow-C device was prepared as follows: rhBMP6 was added to blood, and blood was mixed with ceramics and left to coagulate. Osteogrow-C was implanted subcutaneously in the axillary region of Sprague-Dawley rats and the outcome was analyzed 21 days following implantation using microCT, histology, morphometric analyses, and immunohistochemistry.

RESULTS

Osteogrow-C implants with all tested ceramic particles induced the formation of the bone-ceramic structure containing cortical bone, the bone between the particles, and bone at the ceramic surfaces. The amount of newly formed bone was significant in all experimental groups; however, the highest bone volume was measured in Osteogrow-C implants with highly porous Vitoss ceramics. The trabecular number was highest in Osteogrow-C implants with Vitoss and ChronOs ceramics while trabeculae were thicker in implants containing BAM and Dongbo ceramics. The immunological response and inflammation were comparable among ceramic particles evaluated in this study.

CONCLUSION

Osteogrow-C bone regenerative device was effective with a broad range of commercially available synthetic ceramics providing a promising therapeutic solution for the regeneration of long bone fracture nonunion, large segmental defects, and spinal fusion surgeries.

Anti-inflammatory, but not osteoprotective, effect of the TRAF6/CD40 inhibitor 6877002 in rodent models of local and systemic osteolysis

NFκB plays a key role in inflammation and skeletal disorders. Previously, we reported that pharmacological inhibition of NFκB at the level of TRAF6 suppressed RANKL, CD40L and IL1β-induced osteoclastogenesis and attenuated cancer-induced bone disease. TNFα is also known to regulate TRAF6/NFκB signalling, however the anti-inflammatory and osteoprotective effects associated with inhibition of the TNFα/TRAF6/NFκB axis have not been investigated. Here, we show that in vitro and ex vivo exposure to the verified small-molecule inhibitor of TRAF6, 6877002 prevented TNFα-induced NFκB activation, osteoclastogenesis and calvarial osteolysis, but it had no effects on TNFα-induced apoptosis or growth inhibition in osteoblasts. Additionally, 6877002 disrupted T-cells support for osteoclast formation and synoviocyte motility, without affecting the viability of osteoblasts in the presence of T-cells derived factors. Using the collagen-induced arthritis model, we show that oral and intraperitoneal administration of 6877002 in mice reduced joint inflammation and arthritis score. Unexpectedly, no difference in trabecular and cortical bone parameters were detected between vehicle and 6877002 treated mice, indicating lack of osteoprotection by 6877002 in the arthritis model described. Using two independent rodent models of osteolysis, we confirmed that 6877002 had no effect on trabecular and cortical bone loss in both osteoporotic rats or RANKL- treated mice. In contrast, the classic anti-osteolytic alendronate offered complete osteoprotection in RANKL- treated mice. In conclusion, TRAF6 inhibitors may be of value in the management of the inflammatory component of bone disorders, but may not offer protection against local or systemic bone loss, unless combined with anti-resorptive therapy such as bisphosphonates.

Zoledronate Bound to Ceramics Increases Ectopic Bone Volume Induced by rhBMP6 Delivered in Autologous Blood Coagulum in Rats

Autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (ABC) with synthetic ceramics is a novel therapeutic solution for bone repair. The aim of this study was to investigate whether the application of Zoledronate (ZOL) with ABGS might enhance the properties of newly formed bone. The effect of ZOL on bone induction was tested in a rat subcutaneous implant model. ZOL bound to synthetic ceramics was added into ABGS implants, and the quantity, quality, and longevity of the induced bone were assessed by micro-CT, histomorphometry, and histology over a period of 365 days. Local use of ZOL in the ABGS implants with ceramics had no influence on the bone volume (BV) on day 14 but subsequently significantly increased BV on days 35, 50, 105, 140, and 365 compared to the control implants. Locally applied ZOL had a similar effect in all of the applied doses (2–20 µg), while its systemic use on stimulating the BV of newly induced bone by ABGS depended on the time of application. BV was increased when ZOL was applied systemically on day 14 but had no effect when applied on day 35. The administration of ZOL bound to ceramics in ABGS increased and maintained the BV over a period of one year, offering a novel bone tissue engineering strategy for treating bone defects and spinal fusions.

Iron overload in aging Bmp6‑/‑ mice induces exocrine pancreatic injury and fibrosis due to acinar cell loss

The relationship between hemochromatosis and diabetes has been well established, as excessive iron deposition has been reported to result in impaired function of the endocrine and exocrine pancreas. Therefore, the objective of the present study was to analyze the effects of iron accumulation on the pancreata and glucose homeostasis in a bone morphogenetic protein 6-knockout (Bmp6^−/−) mouse model of hemochromatosis. The sera and pancreatic tissues of wild-type (WT) and Bmp6^−/− mice (age, 3 and 10 months) were subjected to biochemical and histological analyses. In addition, ¹⁸F-fluorodeoxyglucose biodistribution was evaluated in the liver, muscle, heart, kidney and adipose tissue of both animal groups. The results demonstrated that 3-month-old Bmp6^−/− mice exhibited iron accumulation preferentially in the exocrine pancreas, with no signs of pancreatic injury or fibrosis. No changes were observed in the glucose metabolism, as pancreatic islet diameter, insulin and glucagon secretion, blood glucose levels and glucose uptake in the liver, muscle and adipose tissue remained comparable with those in the WT mice. Aging Bmp6^−/− mice presented with progressive iron deposits in the exocrine pancreas, leading to pancreatic degeneration and injury that was characterized by acinar atrophy, fibrosis and the infiltration of inflammatory cells. However, the aging mice exhibited unaltered blood glucose levels and islet structure, normal insulin secretion and moderately increased α-cell mass compared with those in the age-matched WT mice. Additionally, iron overload and pancreatic damage were not observed in the aging WT mice. These results supported a pathogenic role of iron overload in aging Bmp6^−/− mice leading to iron-induced exocrine pancreatic deficiency, whereas the endocrine pancreas retained normal function.

A novel autologous bone graft substitute containing rhBMP6 in autologous blood coagulum with synthetic ceramics for reconstruction of a large humerus segmental gunshot defect in a dog: The first veterinary patient to receive a novel osteoinductive therapy

Background

Management of large segmental defects is one of the most challenging issues in bone repair biology. Autologous bone graft substitute (ABGS) containing rhBMP6 within autologous blood coagulum (ABC) with synthetic ceramics is a novel biocompatible therapeutic solution for bone regeneration.

Case presentation

A 2-year old dog was brought to the veterinary clinics due to pain and bleeding from the right front leg after being unintendedly hit by a gunshot. Radiological examination revealed a large, 3 cm long multisegmental defect of the humerus on the right front leg with a loss of anatomical structure in the distal portion of the bone. The defect was treated surgically and an external fixator was inserted to ensure immobilization. Complete lack of bone formation 3 months following surgery required a full reconstruction of the defect site with a novel ABGS (rhBMP6 in ABC with ceramic particles) to avoid front leg amputation. The healing was then followed for the next 16 months. The callus formation was observed on x-ray images 2 months following ABGS implantation. The bone segments progressively fused together leading to the defect rebridgment allowing removal of the external fixator by 4 months after the reconstruction surgery. At the end of the observation period, the function of the leg was almost fully restored while analyses of the humeral CT sections revealed restoration and cortices rebridgment with a renewal of uniform medullary canal including structural reconstruction of the distal humerus.

Conclusion

This large humeral gunshot segmental defect of the front leg in a dog was saved from amputation via inducing bone regeneration using a novel ABGS osteoinductive device containing BMP6 in ABC.

Biology of bone morphogenetic protein in bone repair and regeneration: A role for autologous blood coagulum as carrier

BMPs were purified from demineralized bone matrix based on their ability to induce new bone in vivo and they represent a large member of the TGF-β superfamily of proteins. BMPs serve as morphogenic signals for mesenchymal stem cell migration, proliferation and subsequently differentiation into cartilage and bone during embryonic development. A BMP when implanted with a collagenous carrier in a rat subcutaneous site is capable of inducing new bone by mimicking the cellular events of embryonic bone formation. Based on this biological principle, BMP2 and BMP7 containing collagenous matrix as carrier have been developed as bone graft substitutes for spine fusion and long bone fractures. Here, we describe a novel autologous bone graft substitute that contains BMP6 delivered within an autologous blood coagulum as carrier and summarize the biology of osteogenic BMPs in the context of bone repair and regeneration specifically the critical role that carrier plays to support osteogenesis.

Autologous bone graft substitute containing rhBMP6 within autologous blood coagulum and synthetic ceramics of different particle size determines the quantity and structural pattern of bone formed in a rat subcutaneous assay

Bone morphogenetic proteins (BMPs) are potent osteoinductive agents for bone tissue engineering. In order to define optimal properties of a novel autologous bone graft substitute (ABGS) containing rhBMP6 within the autologous blood coagulum (ABC) and ceramic particles as a compression resistant matrix (CRM), we explored the influence of their amount, chemical composition and particle size on the quantity and quality of bone formation in the rat subcutaneous assay. Tested ceramic particles included tricalcium phosphate (TCP), hydroxyapatite (HA) and biphasic calcium phosphate ceramic (BCP), containing TCP and HA in 80/20 ratio of different particle sizes (small 74-420 μm, medium 500-1700 μm and large 1000-4000 μm). RhBMP6 was either mixed with ABC or lyophilized on CRM prior to use with ABC. The experiments were terminated on day 21 and implants were analysed by microCT, histology and histomorphometry. Addition of CRM to ABGS containing rhBMP6 in ABC significantly increased the amount of newly formed bone and the optimal CRM/ABC ratio was found to be around 100 mg/500 μL. MicroCT analyses revealed that all tested ABGS formulations induced an extensive new bone formation and there were no differences between the two methods of rhBMP6 application as determined by the bone volume. However, the particle size played a significant role in the quantity and quality of newly formed bone. ABGS containing small particles induced new bone forming a dense trabecular network, cortical bone at the rim, bone and bone marrow in apposition to and in between ceramic particles. ABGS containing medium and large particles also resulted in new bone on the surface of particles as well as inside the pores. Histomorphometric analysis revealed that the ceramics particle size correlated with the quality of trabecular pattern of newly formed bone, bone/bone marrow ratio as observed in apposition and between particles, and the ratio between the cortical and trabecular bone. By employing rat subcutaneous implant assay, we showed for the first time that the size of synthetic ceramics particles affected the osteogenesis as defined by both the quantity and quality of ectopic bone.

A novel autologous bone graft substitute comprised of rhBMP6 blood coagulum as carrier tested in a randomized and controlled Phase I trial in patients with distal radial fractures

Bone morphogenetic proteins (BMPs) are known to induce new bone formation in vivo but treating trabecular bone defects with a BMP based therapeutic remains controversial. Here, we evaluated the safety and efficacy of a novel Autologous Bone Graft Substitute (ABGS) comprised of recombinant human BMP6 (rhBMP6) dispersed within an autologous blood coagulum (ABC) as a physiological natural carrier in patients with a closed distal radial fracture (DRF). We enrolled 32 patients in a randomized, standard of care (SoC) and placebo (PBO) controlled, double-blinded Phase I First in Human (FiH) clinical trial. ABGS was prepared from peripheral blood as 250 μg rhBMP6/mL ABC or PBO (1 mL ABC containing excipients only) and was administered dorsally via a syringe injection into the fracture site following closed fracture fixation with 3 Kirschner wires. Patients carried an immobilization for 5 weeks and were followed-up for 0 to 26 weeks by clinical examination, safety, serial radiographic analyses and CT. During the 13 weeks follow-up and at 26 weeks post study there were no serious adverse reactions recorded. The results showed that there were no detectable anti-rhBMP6 antibodies in the blood of any of the 32 patients at 13- and 26-weeks following treatment. Pharmacokinetic analyses of plasma from patients treated with ABGS showed no detectable rhBMP6 at any time point within the first 24 h following administration. The CT image and radiographic analyses score from patients treated with AGBS showed significantly accelerated bone healing as compared to PBO and SoC at 5 and 9 weeks (with high effect sizes and P = 0.027), while at week 13 all patients had similar healing outcomes. In conclusion, we show that intraosseous administration of ABGS (250 μg rhBMP6/mL ABC) into the distal radial fracture site demonstrated a good tolerability with no serious adverse reactions as well as early accelerated trabecular bone healing as compared to control PBO and SoC patients.

Synthetic ceramic macroporous blocks as a scaffold in ectopic bone formation induced by recombinant human bone morphogenetic protein 6 within autologous blood coagulum in rats

PURPOSE

We have recently developed an autologous bone graft substitute (ABGS) containing recombinant human bone morphogenetic protein 6 (rhBMP6) in autologous blood coagulum (ABC) that induces new bone formation in vivo. In order to improve biomechanical properties of the implant, compression resistant matrix (CRM) consisting of synthetic ceramics in the form of macroporous cylinders was added to the ABGS and we evaluated the biomechanical properties and the quantity and quality of bone formation following subcutaneous implantation in rats.

METHODS

ABGS implants containing rhBMP6 in ABC with cylindrical ceramic blocks were implanted subcutaneously (n = 6 per time point) in the axillary region of Sprague-Dawley rats and removed at specified time points (7, 14, 21, 35, and 50 days). The quantity and quality of newly formed bone were analyzed by microCT, histology, and histomorphometric analyses. Biomechanical properties of ABGS formulations were determined by employing the cut test.

RESULTS

MicroCT analyses revealed that ABGS implants induced formation of new bone within ceramic blocks. Histological analysis revealed that on day seven following implantation, the endochondral ossification occupied the peripheral part of implants. On days 14 and 21, newly formed bone was present both around the ceramic block and through the pores inside the block. On both days 35 and 50, cortical bone encircled the ceramic block while inside the block, bone covered the ceramic surface surrounding the pores. Within the osseous circles, there were few trabeculae and bone marrow containing adipocytes. ABGS containing cylindrical ceramic blocks were more rigid and had significantly increased stiffness compared with implants containing ceramic particles as CRM.

CONCLUSION

We demonstrated that macroporous ceramic blocks in a form of cylinders are promising CRMs with good handling and enhanced biomechanical properties, supporting bone formation with ABGS containing rhBMP6 within autologous blood coagulum. Hence, ABGS containing ceramic blocks should be tested in preclinical models including diaphyseal segmental defects and non-unions in larger animals.

Recombinant Human BMP6 Applied Within Autologous Blood Coagulum Accelerates Bone Healing: Randomized Controlled Trial in High Tibial Osteotomy Patients

Bone morphogenetic proteins (BMPs) are potent osteogenic proteins that induce new bone formation in vivo. However, their effect on bone healing in the trabecular bone surfaces remains challenging. We evaluated the safety and efficacy of recombinant human BMP6 (rhBMP6) applied within an autologous blood coagulum (ABC) in a surgically created wedge defect of the proximal tibia in patients undergoing high tibial osteotomy (HTO) for varus deformity and medial osteoarthritis of the knee. We enrolled 20 HTO patients in a randomized, placebo-controlled, double-blinded phase I/II clinical trial. RhBMP6/ABC (1.0 mg/10 mL ABC prepared from peripheral blood) or placebo (10 mL ABC containing excipients) was administered into the tibial wedge defects. Patients were followed for 0 to 24 months by clinical examination (safety) and computed tomography (CT) and serial radiographic analyses (efficacy). The results show that there were no detectable anti-rhBMP6 antibodies in the blood of any of the 20 patients at 14 weeks after implantation. During the 24 months of follow-up, there were no serious adverse reactions recorded. The CT scans from defects of patients treated with rhBMP6/ABC showed an accelerated bone healing compared with placebo at 9 weeks (47.8 ± 24.1 versus 22.2 ± 12.3 mg/cm³ ; p = 0.008) and at 14 weeks (89.7 ± 29.1 versus 53.6 ± 21.9 mg/cm³ ; p = 0.006) follow-up. Radiographic analyses at weeks 6 and 24 and months 12 and 24 suggested the advanced bone formation and remodeling in rhBMP6/ABC-treated patients. In conclusion, we show that rhBMP6/ABC at a dose of 100 μg/mL accelerated bone healing in patients undergoing HTO without serious adverse events and with a good tolerability compared with placebo alone. Overall, for the first time, a BMP-based osteogenic implant was examined against a placebo for bone healing efficacy in the trabecular bone surface, using an objective bone mineral density measurement system. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

A cell-based combination product for the repair of large bone defects

Regenerative cell-based implants using periosteum-derived stem cells were developed for the treatment of large 3 cm fresh and 4.5 centimeter biological compromised bone gaps in a tibial sheep model and compared with an acellular ceramic-collagen void filler. It was hypothesized that the latter is insufficient to heal large skeletal defects due to reduced endogenous biological potency. To this purpose a comparison was made between the ceramic dicalciumphosphate scaffold (CopiOs®) as such, the same ceramic coated with clinical grade Bone Morphogenetic Protein 2 and 6 (BMP) only or a BMP coated cell-seeded combination product. These implants were evaluated in 2 sheep models, a fresh 3 cm critical size tibial defect and a 4.5 cm biologically exhausted tibial defect. For the groups in which growth factors were applied, BMP-6 was chosen at a dose of 344 μg for 3 cm and 1.500 μg or 3.800 μg for 4.5 cm defects. An additional group in the 4.5 cm defect was tested using BMP-2 in a dose of 1.500 μg. For all the cell based implants autologous periosteum-derived cells were used which were cultured in monolayer during 6 weeks. For the fresh defect 408 million cells and for the biologically exhausted tibial defect 612 million cells were drop-seeded on the BMP coated scaffolds. Bone healing was studied during 16 weeks postimplantation, using standard radiographs. While fresh defects responded to all treatments, regardless the use of cells, the biologically hampered defects responded in half of the cases and only if the BMP-cell combination product was used, supporting the concept that cell-based therapies may become attractive in treating defects with a compromised biological status.

Autologous blood coagulum containing rhBMP6 induces new bone formation to promote anterior lumbar interbody fusion (ALIF) and posterolateral lumbar fusion (PLF) of spine in sheep

In the present study, we evaluated an autologous bone graft substitute (ABGS) composed of recombinant human BMP6 (rhBMP6) dispersed within autologous blood coagulum (ABC) used as a physiological carrier for new bone formation in spine fusion sheep models. The application of ABGS included cervical cage for use in the anterior lumbar interbody fusion (ALIF), while for the posterolateral lumbar fusion (PLF) sheep model allograft devitalized bone particles (ALLO) were applied with and without use of instrumentation. In the ALIF model, ABGS (rhBMP6/ABC/cage) implants fused significantly when placed in between the L4-L5 vertebrae as compared to control (ABC/cage) which appears to have a fibrocartilaginous gap, as examined by histology and micro CT analysis at 16 weeks following surgery. In the PLF model, ABGS implants with or without ALLO showed a complete fusion when placed ectopically in the gutter bilaterally between two decorticated L4-L5 transverse processes at a success rate of 88% without instrumentation and at 80% with instrumentation; however the bone volume was 50% lower in the instrumentation group than without, as examined by histology, radiographs, micro CT analyses and biomechanical testing at 27 weeks following surgery. The newly formed bone was uniform within ABGS implants resulting in a biomechanically competent and histologically qualified fusion with an optimum dose in the range of 100 μg rhBMP6 per mL ABC, while in the implants that contained ALLO, the mineralized bone particles were substituted by the newly formed remodeling bone via creeping substitution. These findings demonstrate for the first time that ABGS (rhBMP6/ABC) without and with ALLO particles induced a robust bone formation with a successful fusion in sheep models of ALIF and PLF, and that autologous blood coagulum (ABC) can serve as a preferred physiological native carrier to induce new bone at low doses of rhBMP6 and to achieve a successful spinal fusion.

Copresentation of BMP-6 and RGD Ligands Enhances Cell Adhesion and BMP-Mediated Signaling

We report on the covalent immobilization of bone morphogenetic protein 6 (BMP-6) and its co-presentation with integrin ligands on a nanopatterned platform to study cell adhesion and signaling responses which regulate the transdifferentiation of myoblasts into osteogenic cells. To immobilize BMP-6, the heterobifunctional linker MU-NHS is coupled to amine residues of the growth factor; this prevents its internalization while ensuring that its biological activity is maintained. Additionally, to allow cells to adhere to such platform and study signaling events arising from the contact to the surface, we used click-chemistry to immobilize cyclic-RGD carrying an azido group reacting with PEG-alkyne spacers via copper-catalyzed 1,3-dipolar cycloaddition. We show that the copresentation of BMP-6 and RGD favors focal adhesion formation and promotes Smad 1/5/8 phosphorylation. When presented in low amounts, BMP-6 added to culture media of cells adhering to the RGD ligands is less effective than BMP-6 immobilized on the surfaces in inducing Smad complex activation and in inhibiting myotube formation. Our results suggest that a local control of ligand density and cell signaling is crucial for modulating cell response.

Autologous blood coagulum is a physiological carrier for BMP6 to induce new bone formation and promote posterolateral lumbar spine fusion in rabbits

In the present study, we describe autologous blood coagulum (ABC) as a physiological carrier for BMP6 to induce new bone formation. Recombinant human BMP6 (rhBMP6), dispersed within ABC and formed as an autologous bone graft substitute (ABGS), was evaluated either with or without allograft bone particles (ALLO) in rat subcutaneous implants and in a posterolateral lumbar fusion (PLF) model in rabbits. ABGS induced endochondral bone differentiation in rat subcutaneous implants. Coating ALLO by ABC significantly decreased the formation of multinucleated foreign body giant cells (FBGCs) in implants, as compared with ALLO alone. However, addition of rhBMP6 to ABC/ALLO induced a robust endochondral bone formation with little or no FBGCs in the implant. In rabbit PLF model, ABGS induced new bone formation uniformly within the implant resulting in a complete fusion when placed between two lumbar transverse processes in the posterolateral gutter with an optimum dose of 100‐μg rhBMP6 per ml of ABC. ABGS containing ALLO also resulted in a fusion where the ALLO was replaced by the newly formed bone via creeping substitution. Our findings demonstrate for the first time that rhBMP6, with ABC as a carrier, induced a robust bone formation with a complete spinal fusion in a rabbit PLF model. RhBMP6 was effective at low doses with ABC serving as a physiological substratum providing a permissive environment by protecting against foreign body reaction elicited by ALLO.

Analysis and quantification of bone healing after open wedge high tibial osteotomy

Background

The aim of this study was to analyze radiographic imaging techniques and to quantify bone ossification in the osteotomy gap after high tibial osteotomy.

Material and methods

Study phase 1: high tibial osteotomy was performed on six lower extremities of human body donors and experimental X‑rays and computed tomography (CT) scans were applied. Different techniques were evaluated by three specialists for best representation of the osteotomy gap.

Study phase 2: optimized radiological techniques were used for follow-up on 12 patients. The radiographs were examined by 3 specialists measuring 10 different parameters. The CT scans were analyzed with semiautomatic computer software for quantification of bone ossification.

Results

The osteotomy gap was best represented in 30° of flexion in the knee and 20° internal rotation of the leg. There were significant changes of the medial width over time (p < 0.019) as well as of the length of fused osteotomy, the Schröter score, sclerosis, trabecular structure and zone area measurements. Sclerosis, medial width of the osteotomy and area measurements were detected as reproducible parameters. Bone mineral density was calculated using CT scans, showing a significantly higher value 12 weeks postoperatively (112.5 mg/cm³) than at baseline (54.6 mg/cm³). The ossification of the gap was visualized by color coding.

Conclusion

Sclerosis and medial width of the osteotomy gap as well as area measurements were determined as reproducible parameters for evaluation of bone healing. Quantification of bone ossification can be calculated with CT scans using a semiautomatic computer program and should be used for research in bone healing.

A novel role of bone morphogenetic protein 6 (BMP6) in glucose homeostasis

AIMS

Bone morphogenetic proteins (BMPs) are involved in the development and homeostasis of multiple organs and tissues. There has been a significant focus on understanding the role of BMPs in pancreatic β-cell dysfunction associated with type 2 diabetes (T2D). Our objective was to investigate the relationship between BMP6 and glucose homeostasis.

METHODS

Ob/ob mice were treated with BMP6 for 6 days and analyzed for insulin release, body weight, lipid parameters and glucose tolerance. Quantitative real-time PCR, chromatin immunoprecipitation and glucose output assays were used to assess BMP6 effect on gluconeogenesis in rat hepatoma H4IIE cells. Specificity of BMP6 receptors was characterized by the utilization of various receptor Fc fusion proteins in luciferase reporter gene and glucose output assays in INS1 and H4IIE cells.

RESULTS

Treatment of ob/ob mice with BMP6 for 6 days resulted in a reduction of circulating glucose and lipid levels, followed by a significantly elevated plasma insulin level in a dose-dependent manner. In addition, BMP6 improved the glucose excursion during an oral glucose tolerance test, lowering the total glycemic response by 21%. In rat H4IIE hepatoma cells, BMP6 inhibited gluconeogenesis and glucose output via downregulation the PepCK expression. Moreover, BMP6 inhibited glucose production regardless of the presence of cAMP, antagonizing its glycogenolytic effect. BMP6 acted on pancreatic and liver cells utilizing Alk3, Alk6 and ActRIIA serine/threonine kinase receptors.

CONCLUSIONS

Collectively, we demonstrate that BMP6 improves glycaemia in T2D mice and regulates glucose metabolism in hepatocytes representing an exciting prospect for future treatments of diabetes.

Antiviral activity of bone morphogenetic proteins and activins

Understanding the control of viral infections is of broad importance. Chronic hepatitis C virus (HCV) infection causes decreased expression of the iron hormone hepcidin, which is regulated by hepatic bone morphogenetic protein (BMP)/SMAD signalling. We found that HCV infection and the BMP/SMAD pathway are mutually antagonistic. HCV blunted induction of hepcidin expression by BMP6, probably via tumour necrosis factor (TNF)-mediated downregulation of the BMP co-receptor haemojuvelin. In HCV-infected patients, disruption of the BMP6/hepcidin axis and genetic variation associated with the BMP/SMAD pathway predicted the outcome of infection, suggesting that BMP/SMAD activity influences antiviral immunity. Correspondingly, BMP6 regulated a gene repertoire reminiscent of type I interferon (IFN) signalling, including upregulating interferon regulatory factors (IRFs) and downregulating an inhibitor of IFN signalling, USP18. Moreover, in BMP-stimulated cells, SMAD1 occupied loci across the genome, similar to those bound by IRF1 in IFN-stimulated cells. Functionally, BMP6 enhanced the transcriptional and antiviral response to IFN, but BMP6 and related activin proteins also potently blocked HCV replication independently of IFN. Furthermore, BMP6 and activin A suppressed growth of HBV in cell culture, and activin A inhibited Zika virus replication alone and in combination with IFN. The data establish an unappreciated important role for BMPs and activins in cellular antiviral immunity, which acts independently of, and modulates, IFN.

Prognostic significance of bone morphogenetic protein 6 (BMP6) expression, clinical and pathological factors in clinically node-negative oral squamous cell carcinoma (OSCC)

Bone morphogenetic protein 6 (BMP6) has unique properties regarding structure and function in supporting bone formation during development and adult life. Despite its known role in various malignant tumors, the prognostic significance of BMP6 expression in oral squamous cell carcinoma (OSCC) remains unknown. The aim of the study was to investigate immunohistochemical expression of BMP6 in OSCC in correlation with clinical and pathological parameters, disease recurrence and survival. In addition, we investigated other parameters in order to identify prognosticators of neck metastases and final outcome. The study included 120 patients with clinically T1-3N0 OSCC who were primarily surgically treated between 2003 and 2008. There were 99 (82.5%) male and 21 (17.5%) female patients. The five-year disease-specific survival for the whole cohort was 79.7%. Tumors smaller than 2 cm in diameter showed higher incidence of strong BMP6 expression. No statistical correlation was observed between other clinico-pathological factors and BMP6 expression. Expression of BMP6 was not associated with disease recurrence and survival. BMP6 may not serve as prognosticator of final outcome or recurrence in clinically node-negative OSCC subjects. In multivariate analysis predictors of poorer survival were positive surgical margin, moderate tumor cell differentiation and pathological involvement of levels IV and/or V.

Recombinant Human Bone Morphogenetic Protein 6 Delivered Within Autologous Blood Coagulum Restores Critical Size Segmental Defects of Ulna in Rabbits

BMP2 and BMP7, which use bovine Achilles tendon-derived absorbable collagen sponge and bovine bone collagen as scaffold, respectively, have been approved as bone graft substitutes for orthopedic and dental indications. Here, we describe an osteoinductive autologous bone graft substitute (ABGS) that contains recombinant human BMP6 (rhBMP6) dispersed within autologous blood coagulum (ABC) scaffold. The ABGS is created as an injectable or implantable coagulum gel with rhBMP6 binding tightly to plasma proteins within fibrin meshwork, as examined by dot-blot assays, and is released slowly as an intact protein over 6 to 8 days, as assessed by ELISA. The biological activity of ABGS was examined in vivo in rats (Rattus norvegicus) and rabbits (Oryctolagus cuniculus). In a rat subcutaneous implant assay, ABGS induced endochondral bone formation, as observed by histology and micro-CT analyses. In the rabbit ulna segmental defect model, a reproducible and robust bone formation with complete bridging and restoration of the defect was observed, which is dose dependent, as determined by radiographs, micro-CT, and histological analyses. In ABGS, ABC scaffold provides a permissive environment for bone induction and contributes to the use of lower doses of rhBMP6 compared with BMP7 in bovine bone collagen as scaffold. The newly formed bone undergoes remodeling and establishes cortices uniformly that is restricted to implant site by bridging with host bone. In summary, ABC carrier containing rhBMP6 may serve as an osteoinductive autologous bone graft substitute for several orthopedic applications that include delayed and nonunion fractures, anterior and posterior lumbar interbody fusion, trauma, and nonunions associated with neurofibromatosis type I.

Systemic inhibition of BMP1-3 decreases progression of CCl4-induced liver fibrosis in rats

Liver fibrosis is a progressive pathological process resulting in an accumulation of excess extracellular matrix proteins. We discovered that bone morphogenetic protein 1-3 (BMP1-3), an isoform of the metalloproteinase Bmp1 gene, circulates in the plasma of healthy volunteers and its neutralization decreases the progression of chronic kidney disease in 5/6 nephrectomized rats. Here, we investigated the potential role of BMP1-3 in a chronic liver disease. Rats with carbon tetrachloride (CCl₄)-induced liver fibrosis were treated with monoclonal anti-BMP1-3 antibodies. Treatment with anti-BMP1-3 antibodies dose-dependently lowered the amount of collagen type I, downregulated the expression of Tgfb1, Itgb6, Col1a1, and Acta2 and upregulated the expression of Ctgf, Itgb1, and Dcn. Mehanistically, BMP1-3 inhibition decreased the plasma levels of transforming growth factor beta 1(TGFβ1) by prevention of its activation and lowered the prodecorin production further suppressing the TGFβ1 profibrotic effect. Our results suggest that BMP1-3 inhibitors have significant potential for decreasing the progression of fibrosis in liver cirrhosis.

Expression of Bone Morphogenetic Proteins in Stromal Cells from Human Bone Marrow Long-term Culture

Highly purified primitive hemopoietic stem cells express BMP receptors but do not synthesize bone morphogenetic proteins (BMPs). However, exogenously added BMPs regulate their proliferation, differentiation, and survival. To further explore the mechanism by which BMPs might be involved in hemopoietic differentiation, we tested whether stromal cells from long-term culture (LTC) of normal human bone marrow produce BMPs, BMP receptors, and SMAD signaling molecules. Stromal cells were immunohistochemically characterized by the presence of lyzozyme, CD 31, factor VIII, CD 68, S100, alkaline phosphatase, and vimentin. Gene expression was analyzed by RT-PCR and the presence of BMP protein was confirmed by immunohistochemistry (IHC). The supportive role of the stromal cell layer in hemopoiesis in vitro was confirmed by a colony assay of clonogenic progenitors. Bone marrow stromal cells express mRNA and protein for BMP-3, -4, and -7 but not for BMP-2, -5, and -6 from the first to the eighth week of culture. Furthermore, stromal cells express the BMP type I receptors, activin-like kinase-3 (ALK-3), ALK-6, and the downstream transducers SMAD-1, -4, and -5. Thus, human bone marrow stromal cells synthesize BMPs, which might exert their effects on hemopoietic stem cells in a paracrine manner through specific BMP receptors.

Constitutively Elevated Blood Serotonin Is Associated with Bone Loss and Type 2 Diabetes in Rats

Reduced peripheral serotonin (5HT) in mice lacking tryptophan hydroxylase (TPH1), the rate limiting enzyme for 5HT synthesis, was reported to be anabolic to the skeleton. However, in other studies TPH1 deletion either had no bone effect or an age dependent inhibition of osteoclastic bone resorption. The role of 5HT in bone therefore remains poorly understood. To address this issue, we used selective breeding to create rat sublines with constitutively high (high-5HT) and low (low-5HT) platelet 5HT level (PSL) and platelet 5HT uptake (PSU). High-5HT rats had decreased bone volume due to increased bone turnover characterized by increased bone formation and mineral apposition rate, increased osteoclast number and serum C-telopeptide level. Daily oral administration of the TPH1 inhibitor (LX1032) for 6 weeks reduced PSL and increased the trabecular bone volume and trabecular number of the spine and femur in high-5HT rats. High-5HT animals also developed a type 2 diabetes (T2D) phenotype with increased: plasma insulin, glucose, hemoglobin A1c, body weight, visceral fat, β-cell pancreatic islets size, serum cholesterol, and decreased muscle strength. Serum calcium accretion mediated by parathyroid hormone slightly increased, whereas treatment with 1,25(OH)2D3 decreased PSL. Insulin reduction was paralleled by a drop in PSL in high-5HT rats. In vitro, insulin and 5HT synergistically up-regulated osteoblast differentiation isolated from high-5HT rats, whereas TPH1 inhibition decreased the number of bone marrow-derived osteoclasts. These results suggest that constitutively elevated PSL is associated with bone loss and T2D via a homeostatic interplay between the peripheral 5HT, bone and insulin.

Bone morphogenetic proteins in inflammation, glucose homeostasis and adipose tissue energy metabolism

Bore morphogenetic proteins (BMPs) are members of the transforming growth factor (TGF)-β superfamily, a group of secreted proteins that regulate embryonic development. This review summarizes the effects of BMPs on physiological processes not exclusively linked to the musculoskeletal system. Specifically, we focus on the involvement of BMPs in inflammatory disorders, e.g. fibrosis, inflammatory bowel disease, anchylosing spondylitis, rheumatoid arthritis. Moreover, we discuss the role of BMPs in the context of vascular disorders, and explore the role of these signalling proteins in iron homeostasis (anaemia, hemochromatosis) and oxidative damage. The second and third parts of this review focus on BMPs in the development of metabolic pathologies such as type-2 diabetes mellitus and obesity. The pancreatic beta cells are the sole source of the hormone insulin and BMPs have recently been implicated in pancreas development as well as control of adult glucose homeostasis. Lastly, we review the recently recognized role of BMPs in brown adipose tissue formation and their consequences for energy expenditure and adiposity. In summary, BMPs play a pivotal role in metabolism beyond their role in skeletal homeostasis. However, increased understanding of these pleiotropic functions also highlights the necessity of tissue-specific strategies when harnessing BMP action as a therapeutic target.

Molecular background and physiological consequences of altered peripheral serotonin homeostasis in adult rats perinatally treated with tranylcypromine

Serotonin (5-hydroxytryptamine, 5-HT) is a biologically active molecule present in mammals in the brain and peripheral tissues where it exerts many physiological functions. Developmental exposure to 5-HT-enhancing agents has been reported to induce long-lasting changes in the brain, but the long-term effects of perinatal 5-HT enhancement on 5-HT balance and function in the peripheral compartment have not been explored. Perinatal treatment of rats with monoamine oxidase (MAO) inhibitor tranylcypromine (TCP), leads to persistent imbalance in central (increased 5-HT degradation and decreased 5-HT concentrations in the brain) and peripheral (increased platelet and decreased plasma 5-HT concentrations) 5-HT homeostasis. In this study, we explored the molecular background of peripheral 5-HT imbalance, and its possible consequences on bone remodeling and hematopoiesis. Jejunum, liver and blood samples were collected from TCP- and saline-treated rats on post-natal day 70. Relative mRNA levels for tryptophan hydroxylase 1 (TPH1) and MAO A were analyzed using quantitative RT-PCR, femoral trabecular bone parameters were measured using microcomputed tomography, while peripheral blood cell number was determined by cell counter. TCP-treated rats displayed significant decrease in expression of Tph1, and significant increase in percentage of bone volume, trabecular number, connectivity density, and leukocyte number. In addition, significant negative correlation was observed between relative concentrations of TPH1 mRNA and trabecular bone parameters. Our results: a) show that perinatal exposure to tranylcypromine leads to long-lasting compensatory decrease in Tph1 expression in the peripheral compartment, accompanied with alterations in bone remodeling and hematopoiesis, b) suggest that peripheral and central 5HT compartment use different strategies to compensate for 5-HT imbalances of the same cause, and c) indicate dominant role of peripheral over central 5-HT in the regulation of bone maintenance, as well as possible negative in vivo influence of peripheral 5-HT on leukocyte development and/or sustainment.

The rational use of animal models in the evaluation of novel bone regenerative therapies

Bone has a high potential for endogenous self-repair. However, due to population aging, human diseases with impaired bone regeneration are on the rise. Current strategies to facilitate bone healing include various biomolecules, cellular therapies, biomaterials and different combinations of these. Animal models for testing novel regenerative therapies remain the gold standard in pre-clinical phases of drug discovery and development. Despite improvements in animal experimentation, excessive poorly designed animal studies with inappropriate endpoints and inaccurate conclusions are being conducted. In this review, we discuss animal models, procedures, methods and technologies used in bone repair studies with the aim to assist investigators in planning and performing scientifically sound experiments that respect the wellbeing of animals. In the process of designing an animal study for bone repair investigators should consider: skeletal characteristics of the selected animal species; a suitable animal model that mimics the intended clinical indication; an appropriate assessment plan with validated methods, markers, timing, endpoints and scoring systems; relevant dosing and statistically pre-justified sample sizes and evaluation methods; synchronization of the study with regulatory requirements and additional evaluations specific to cell-based approaches. This article is part of a Special Issue entitled "Stem Cells and Bone".

Soluble type III TGFβ receptor in diagnosis and follow-up of patients with breast cancer

Type III transforming growth factor (TGFβ) receptor (TGFβrIII) modulates TGFβ superfamily signaling. Its tumor tissue expression is downregulated in human breast cancer. We determined (indirect ELISA) plasma levels of the soluble receptor (sTGFβrIII) in 47 women with breast cancer (AJCC stages 0-IIB) (cases) pre-surgery and over two months after the surgery, and in 36 healthy women (controls). Plasma sTBFβrIII was lower in cases than in the controls (age-adjusted difference -29.7 ng/mL, p < 0.001), and discriminated between disease and health (sensitivity and specificity 100% at 16.6 ng/mL). With adjustment for age, AJCC stage, lymph node involvement, HER2 and hormone receptor status, higher pre-surgery sTBFβrIII was associated with better progression-free survival (HR = 0.68, 95%CI 0.49-0.89, p = 0.004). An increasing trend in plasma sTBFβrIII was observed over 2 months after the surgery (0.6% increase/day, p < 0.001), consistently across the patient subsets. Data suggest a high potential of plasma sTBFβrIII as a novel diagnostic and prognostic biomarker in breast cancer.

Exogenous BMP7 corrects plasma iron overload and bone loss in Bmp6-/- mice

PURPOSE

Iron overload accelerates bone loss in mice lacking the bone morphogenetic protein 6 (Bmp6) gene, which is the key endogenous regulator of hepcidin, iron homeostasis gene. We investigated involvement of other BMPs in preventing haemochromatosis and subsequent osteopenia in Bmp6-/- mice.

METHODS

Iron-treated wild-type (WT) and Bmp6-/- mice were analysed for hepcidin messenger RNA (mRNA) and tissue and blood BMP levels by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR), immunohistochemistry, Western blot, enzyme-linked immunosorbent assay (ELISA) and proximity extension assay. BMPs labeled with technetium-99m were used in pharmacokinetic studies.

RESULTS

In WT mice, 4 h following iron challenge, liver Bmp6 and hepcidin expression were increased, while expression of other Bmps was not affected. In parallel, we provided the first evidence that BMP6 circulates in WT mice and that iron increased the BMP6 serum level and the specific liver uptake of (99m)Tc-BMP6. In Bmp6-/- mice, iron challenge led to blunted activation of liver Smad signaling and hepcidin expression with a delay of 24 h, associated with increased Bmp5 and Bmp7 expression and increased Bmp2, 4, 5 and 9 expression in the duodenum. Liver Bmp7 expression and increased circulating BMP9 eventually contributed to the late hepcidin response. This was further supported by exogenous BMP7 therapy resulting in an effective hepcidin expression followed by a rapid normalisation of plasma iron values and restored osteopenia in Bmp6-/- mice.

CONCLUSION

In Bmp6-/- mice, iron activated endogenous compensatory mechanisms of other BMPs that were not sufficient for preventing hemochromatosis and bone loss. Administration of exogenous BMP7 was effective in correcting the plasma iron level and bone loss, indicating that BMP6 is an essential but not exclusive in vivo regulator of iron homeostasis.

Possible target for preventing fibrotic scar formation following acute myocardial infarction

Bone morphogenetic protein 1 (BMP1) was originally isolated from bone with other BMPs due to its affinity for heparin. While all other BMPs are members of the Transforming Growth Factor β (TGFβ) superfamily of growth factors, BMP1 is not an authentic member of the BMP protein family. Together with mammalian Tolloid Like protein 1 (mTLL-1) and mTLL-2, BMP1 comprise a small group of zinc- and calcium-dependent proteinases. Acute myocardial infarction (AMI) is the leading cause of death in developed countries which accounts for 13% of deaths worldwide. It was recently shown that inhibition of BMP1-3 reduces progression of fibrosis in chronic kidney disease and suggested that BMP1-3 is an important molecule for fibrogenesis. We hypothesize that inhibition of BMP1-3 represents future of therapeutic interventions in the heart tissue fibrosis following AMI. This novel approach aims to acquire the first candidate specific treatment for recuperating the heart function in patients with AMI.

TSH prevents bone resorption and with calcitriol synergistically stimulates bone formation in rats with low levels of calciotropic hormones

Thyroid-stimulating hormone exerts both antiresorptive and anabolic effects on bone remodeling in aged ovariectomized rats and thyroid stimulating hormone-receptor null mice, supported by clinical results demonstrating that low thyroid-stimulating hormone level is associated with increased bone loss. To further explore the effect of thyroid-stimulating hormone on bone metabolism we introduced here a rat model with removed thyroid and parathyroid glands to obtain low serum concentrations of thyroid and parathyroid hormone, calcitonin and 1,25(OH)2D3. Surgery resulted in hypocalcemia, low parathyroid and thyroid hormone, 1,25(OH)2D3, C-telopeptide, and osteocalcin serum level. Intermittent administration of thyroid-stimulating hormone resulted in a further decrease of serum calcium and decreased level of serum C-telopeptide due to the suppression of bone resorption, while in the same animals osteocalcin in serum was higher indicating an increased bone formation rate. A combination of thyroid-stimulating hormone and 1,25(OH)2D3 significantly increased the serum Ca2+, C-telopeptide and serum osteocalcin values. MicroCT analyses of the distal femur and proximal tibia showed that rats treated with 1,25(OH)2D3 alone or in a combination with thyroid-stimulating hormone had an increased trabecular bone volume, and enhanced trabecular bone quality. Biomechanical testing of the trabecular bone showed an increased maximal load for 105% and 235%, respectively, in rats treated with 1,25(OH)2D3 alone, or in a combination with thyroid-stimulating hormone. We suggest that thyroid-stimulating hormone independently of calciotropic hormones suppressed bone resorption and stimulated bone formation, while in combination with 1,25(OH)2D3 acted synergistically on bone formation resulting in an increased bone volume.

BMP7 activates brown adipose tissue and reduces diet-induced obesity only at subthermoneutrality

Background/Aims

Brown adipose tissue (BAT) dissipates energy stored in triglycerides as heat via the uncoupling protein UCP-1 and is a promising target to combat hyperlipidemia and obesity. BAT is densely innervated by the sympathetic nervous system, which increases BAT differentiation and activity upon cold exposure. Recently, Bone Morphogenetic Protein 7 (BMP7) was identified as an inducer of BAT differentiation. We aimed to elucidate the role of sympathetic activation in the effect of BMP7 on BAT by treating mice with BMP7 at varying ambient temperature, and assessed the therapeutic potential of BMP7 in combating obesity.

Methods and Results

High-fat diet fed lean C57Bl6/J mice were treated with BMP7 via subcutaneous osmotic minipumps for 4 weeks at 21°C or 28°C, the latter being a thermoneutral temperature in which sympathetic activation of BAT is largely diminished. At 21°C, BMP7 increased BAT weight, increased the expression of Ucp1, Cd36 and hormone-sensitive lipase in BAT, and increased total energy expenditure. BMP7 treatment markedly increased food intake without affecting physical activity. Despite that, BMP7 diminished white adipose tissue (WAT) mass, accompanied by increased expression of genes related to intracellular lipolysis in WAT. All these effects were blunted at 28°C. Additionally, BMP7 resulted in extensive ‘browning’ of WAT, as evidenced by increased expression of BAT markers and the appearance of whole clusters of brown adipocytes via immunohistochemistry, independent of environmental temperature. Treatment of diet-induced obese C57Bl6/J mice with BMP7 led to an improved metabolic phenotype, consisting of a decreased fat mass and liver lipids as well as attenuated dyslipidemia and hyperglycemia.

Conclusion

Together, these data show that BMP7-mediated recruitment and activation of BAT only occurs at subthermoneutral temperature, and is thus likely dependent on sympathetic activation of BAT, and that BMP7 may be a promising tool to combat obesity and associated disorders.

Differential expression of proteins with heparin affinity in patients with rheumatoid and psoriatic arthritis: a preliminary study

OBJECTIVES

Using proteomic approach in this study, we sought to identify proteins with heparin affinity associated with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and non-inflammatory arthritis (NIA).

METHODS

Plasma samples from adult RA, PsA and NIA patients, 20 of each, were collected. After enrichment of proteins with heparin affinity, SDS-PAGE and in-gel digestion with trypsin were performed. Peptides were concentrated, micro-purified, separated and measured by nano-scale HPLC system coupled to a mass spectrometer. Peak lists were generated from raw spectra and searched against human complete proteome set by MaxQuant software. Statistical analysis of protein relative expression levels was done in IPython interactive Python shell using NumPy and Matplotlib libraries. Individual protein impact on the whole dataset correlation was done by excluding one protein at a time and calculating the correlation coefficient of remaining data points.

RESULTS

Three hundred and eighty-four different proteins were identified keeping false discovery rate to 1%, from which 163 were identified in all three conditions. The plasma proteome showed a good correlation between rheumatoid (RA) and psoriatic arthritis (PsA). Out of 10 proteins whose impact on the correlation coefficient fell outside of two standard deviations from the mean, four were up-regulated (complement factor I, complement component C8 beta, glyceraldehyde-3-phosphate dehydrogenase and inter-alpha-trypsin inhibitor heavy chain H1), and two were down-regulated (immunoglobulin heavy chain V-III region BRO, and immunoglobulin J chain), both in PsA and RA by a similar ratio when compared to NIA. The remaining four proteins (Serpin A11, complement factor H-related protein 5, cartilage acidic protein 1 and coagulation factor IX) were down-regulated in PsA and up-regulated in RA when compared to NIA.

CONCLUSIONS

We found differently expressed proteins in patients with inflammatory and non-inflammatory rheumatic conditions. Out of 384 proteins with heparin affinity four proteins should be further validated as potential diagnostic biomarkers in patients with RA and PsA.

Exogenous heparin binds and inhibits bone morphogenetic protein 6 biological activity

PURPOSE

The purpose of this study was to explore the effect of heparin on bone morphogenetic protein 6 (BMP6) osteogenic activity.

METHODS

Western blot analysis was used to confirm the binding of BMP6 to heparin and to observe its effect on BMP6 signaling in C2C12-BRE-Luc myoblasts. Real-time RT-PCR was performed for the expression analysis of alkaline phosphatase (ALP) and osteocalcin (OC) in C2C12 myoblasts treated with BMP6 and heparin for 72 hours. Rat ectopic bone formation assay was performed to explore the effect of heparin on BMP6 osteogenic activity. Two weeks following implantation the implants were analysed morphologically and histologically. A mouse osteoporotic model was used to test the ability of BMP6 to improve the bone quality in vivo in the presence of heparin, followed by DEXA and μCT analyses. Blood coagulation was tested in rats previously treated with BMP6.

RESULTS

BMP6 specifically bound to heparin and induced Smad1/5/8 phosphorylation which was inhibited by heparin. After 48 and 72 hours of treatment, heparin inhibited BMP6-induced ALP and OC expression in C2C12 cells. Heparin dose dependently inhibited BMP6-induced new bone and cartilage formation in the rat ectopic bone formation assay, while in osteoporotic mice heparin inhibited the BMP6 potential to improve the bone quality as evidenced by decreased bone mineral density and trabecular bone parameters. Interestingly, BMP6 prevented the effect of heparin on the blood coagulation parameters.

CONCLUSION

The interaction of BMP6 with heparin might contribute to the heparin-induced osteoporosis and blood coagulation.

BMP signaling in rats with TNBS-induced colitis following BMP7 therapy

Beyond stimulating bone formation, bone morphogenetic proteins (BMPs) are important in development, inflammation, and malignancy of the gut. We have previously shown that BMP7 has a regenerative, anti-inflammatory, and antiproliferative effect on experimental inflammatory bowel disease (IBD) in rats. To further investigate the BMP signaling pathway we monitored the effect of BMP7 therapy on the BMP signaling components in the rat colon during different stages of experimentally induced colitis by 2,4,6-trinitrobenzene sulfonic acid (TNBS). The results showed a significantly decreased BMP7 expression in the acute phase, followed by a significantly increased BMP2 and decreased BMP6 expression during the chronic phase of colitis. BMP7 therapy influenced the expression of several BMPs with the most prominent effect on downregulation of BMP2 and upregulation of BMP4 in the chronic phase of colitis. Importantly, connective tissue growth factor and noggin expression were elevated in the acute stage and significantly decreased upon BMP7 therapy. BMP receptor I expression was unchanged, whereas BMP receptor II was decreased at day 2 and increased at days 14 and 30 of TNBS inflammation. However, an opposite pattern of expression following BMP7 therapy has been observed. BMP7 increased the expression of BR-Smad including Smad3 and Smad4. Inhibitory Smads were increased in colitis and significantly decreased following BMP7 therapy at later stages of the disease. We suggest that BMP signaling was altered during TNBS-induced colitis and was recovered with BMP7 administration, suggesting that IBD is a reversible process.

Effects of 3 years of lasofoxifene treatment on bone turnover markers in women with postmenopausal osteoporosis

The aims of this study were to describe the changes in bone turnover markers (BTMs) in response to lasofoxifene therapy; to describe the changes in BTMs in the individual; and to examine the relationships between BTM levels on treatment and treatment outcomes. Women (n=1126) aged 59-80years with femoral neck or spine bone mineral density T-scores ≤-2.5 were randomized to lasofoxifene 0.25mg/d, 0.5mg/d, or placebo for 5years. We measured serum C-telopeptide of type I collagen (CTX) and serum procollagen I N-propeptide (PINP), osteocalcin, and bone alkaline phosphatase (ALP) at baseline and at 1, 3, 6, 12, 24, and 36months. Lasofoxifene therapy resulted in a decrease in the concentrations of bone resorption and bone formation markers compared with placebo; the decrease was maximal between 6 and 24months. The effect of lasofoxifene 0.5mg/d was similar to that of lasofoxifene 0.25mg/d. The decrease in bone ALP was less than the decreases in CTX, osteocalcin, and PINP. Lasofoxifene therapy 0.5mg/d resulted in BTM-defined response rates for CTX (decrease in concentration from baseline >60%), PINP (>50%), and bone ALP (>30%) of 35%, 45%, and 43% of women at month 12, respectively, compared with placebo responses of 4%, 4%, and 7%. In contrast, the increase in BMD took longer (50% responded after 36months of lasofoxifene 0.5mg/d) and was not as specific (15% of placebo group responded). Bone density change was weakly inversely correlated with change in the concentrations of BTMs. BTMs may prove useful in the monitoring of the response to lasofoxifene treatment for women with postmenopausal osteoporosis early in the course of treatment.

The proteome and gene expression profile of cementoblastic cells treated by bone morphogenetic protein-7 in vitro

AIM

Regenerative periodontal therapy is often unpredictable and limited. Cementum regeneration is necessary for the proper repair of a periodontal ligament. The precise mechanism how bone morphogenetic protein-7 (BMP7) induces differentiation and mineralization of cementoblasts remains undetermined. The purpose of this study was to evaluate the effect of BMP7 on early proteome and gene expression profile of cementoblastic OCCM.30 cells in vitro.

MATERIALS AND METHODS

Immortalized murine cementoblasts (OCCM.30) were exposed to BMP7 and evaluated for: (1) proliferation; (2) mineralization; (3) early proteome profile using liquid chromatography-mass spectrometry (LC-MS); and (4) gene expression by quantitative RT-PCR.

RESULTS

Bone morphogenetic protein-7 increased the cell proliferation at 24 h and 48 h, while higher doses suppressed the cell proliferation at 48 h. BMP7 induced the mineralization of cementoblasts following 8 days of therapy. Using LC-MS we identified 1117 proteins from the cell lysate. Many belonged to extracellular matrix formation such as PCPE1, collagens, annexins and integrin receptors. RT-PCR analyses revealed a BMP7 dose-dependent upregulation of BMP1, TGFβ1, osterix, osteoprotegerin, procollagen I and II, PCPE1, and noggin, while BMP6 and chordin expression were decreased. The high BMP7 dose down regulated most of the genes 24 h following therapy.

CONCLUSION

Bone morphogenetic protein-7 promotes differentiation and mineralization of cementoblasts via inducing PCPE1 and BMP1 responsible for processing of type I collagen.

Circulating bone morphogenetic protein 1-3 isoform increases renal fibrosis

Bone morphogenetic proteins (BMPs) participate in organ regeneration through autocrine and paracrine actions, but the existence and effects of these proteins in the systemic circulation is unknown. Using liquid chromatography-mass spectrometry, we identified BMP6, GDF15, and the BMP1-3 isoform of the Bmp1 gene in plasma samples from healthy volunteers and patients with CKD. We isolated the endogenous BMP1-3 protein and demonstrated that it circulates as an active enzyme, evidenced by its ability to cleave dentin matrix protein-1 in vitro. In rats with CKD, administration of recombinant BMP1-3 increased renal fibrosis and reduced survival. In contrast, administration of a BMP1-3-neutralizing antibody reduced renal fibrosis, preserved renal function, and increased survival. In addition, treating with the neutralizing antibody was associated with low plasma levels of TGFβ1 and connective tissue growth factor. In HEK293 cells and remnant kidneys, BMP1-3 increased the transcription of collagen type I, TGFβ1, β-catenin, and BMP7 via a BMP- and Wnt-independent mechanism that involved signaling through an integrin β1 subunit. The profibrotic effect of BMP1-3 may, in part, be a result of the accompanied decrease in decorin (DCN) expression. Taken together, inhibition of circulating BMP1-3 reduces renal fibrosis, suggesting that this pathway may be a therapeutic target for CKD.

Bone morphogenetic protein (BMP)1-3 enhances bone repair

Members of the astacin family of metalloproteinases such as human bone morphogenetic protein 1 (BMP-1) regulate morphogenesis by processing precursors to mature functional extracellular matrix (ECM) proteins and several growth factors including TGFβ, BMP2, BMP4 and GFD8. We have recently discovered that BMP1-3 isoform of the Bmp-1 gene circulates in the human plasma and is significantly increased in patients with acute bone fracture. We hypothesized that circulating BMP1-3 might have an important role in bone repair and serve as a novel bone biomarker. When administered systemically to rats with a long bone fracture and locally to rabbits with a critical size defect of the ulna, recombinant human BMP1-3 enhanced bone healing. In contrast, neutralization of the endogenous BMP1-3 by a specific polyclonal antibody delayed the bone union. Invitro BMP1-3 increased the expression of collagen type I and osteocalcin in MC3T3-E(1) osteoblast like cells, and enhanced the formation of mineralized bone nodules from bone marrow mesenchymal stem cells. We suggest that BMP1-3 is a novel systemic regulator of bone repair.