Human Osteogenic Protein-1 Research Articles

The induction of bone formation: From bone morphogenetic proteins to the transforming growth factor-β3 protein - Redundancy, pleiotropy and the induction of cementogenesis

This review proposes to translate organogenesis and the induction of bone formation by the recombinant human transforming growth factor-β3 (hTGF-β3 ) in the Chacma baboon Papio ursinus to periodontal tissue induction and regeneration. Naturally derived highly purified osteogenic proteins of the transforming growth factor-β (TGF-β) supergene family were implanted in Class II furcation defects of the first and second mandibular molars. Additional defects in P.ursinus were treated with recombinant human osteogenic protein-1 (hOP-1, also known as bone morphogeneticprotein-7, hBMP-7) and hBMP-2, singly or in binary applications. In different studies defects were also implanted with hTGF-β3singly or in binary application with hOP-1. Harvested specimens on day 60 and 180 were processed for undecalcified histology using tungsten-carbide knives mounted on Polycut sledge’ micro-tomes or the Exakt precision cutting and grinding system.Highly purified osteogenic proteins showed the induction of Sharpey’s fibres into newly formed cementoid with foci of mineralization. hOP-1 induced substantial cementogenesis whilst hBMP-2 preferentially induced alveolar bone. Intramuscular implantation of hTGF-β3 absorbed onto coral-derived macroporous bioreactors engineered large heterotopic multicellular bone organoids. Gene expression pathways by quantitative Reverse Transcription Polymerases Chain Reaction (qRT-PCR) show that the induction of bone is via several profiled BMPs and TGF-βs expressed upon implantation of hTGF-β3 recapitulating the synergistic induction of bone as shown by binary applications of low doses of hTGF-β1 and hTGF-β3with hOP-1. The rapid induction of bone by hTGF-β3 provides theframework for a paradigmatic shift from recombinanthBMPs to hTGF-β3 in clinical contexts, provocatively operational in periodontal tissue regeneration with substantial induction of cementogenesis in angiogenesis.

The synergistic induction of bone formation by the osteogenic proteins of the TGF-β supergene family.

The momentum to compose this Leading Opinion on the synergistic induction of bone formation suddenly arose when a simple question was formulated during a discussion session on how to boost the often limited induction of bone formation seen in clinical contexts. Re-examination of morphological and molecular data available on the rapid induction of bone formation by the recombinant human transforming growth factor-β3 (hTGF-β3) shows that hTGF-β3 replicates the synergistic induction of bone formation as invocated by binary applications of hOP-1:hTGF-β1 at 20:1 by weight when implanted in heterotopic sites of the rectus abdominis muscle of the Chacma baboon, Papio ursinus. The rapid induction of bone formation in primates by hTGF-β3 may stem from bursts of cladistic evolution, now redundant in lower animal species but still activated in primates by relatively high doses of hTGF-β3. Contrary to rodents, lagomorphs and canines, the three mammalian TGF-β isoforms induce rapid and substantial bone formation when implanted in heterotopic rectus abdominis muscle sites of P.ursinus, with unprecedented regeneration of full thickness mandibular defects with rapid mineralization and corticalization. Provocatively, thus providing potential molecular and biological rationales for the apparent redundancy of osteogenic molecular signals in primates, binary applications of recombinant human osteogenic protein-1 (hOP-1) with low doses of hTGF-β1 and -β3, synergize to induce massive ossicles in heterotopic rectus abdominis, orthotopic calvarial and mandibular sites of P.ursinus. The synergistic binary application of homologous but molecularly different soluble molecular signals has indicated that per force several secreted molecular signals are required singly, synchronously and synergistically to induce optimal osteogenesis. The morphological hallmark of the synergistic induction of bone formation is the rapid differentiation of large osteoid seams enveloping haematopoietic bone marrow that forms by day 15 in heterotopic rectus abdominis sites. Synergistic binary applications also induce the morphogenesis of rudimentary embryonic growth plates indicating that the "memory" of developmental events in embryo can be redeployed postnatally by the application of morphogen combinations. Synergistic binary applications or single relatively high doses of hTGF-β3 have shown that hTGF-β3 induces bone by expressing a variety of inductive morphogenetic proteins that result in the rapid induction of bone formation. Tissue induction thus invocated singly by hTGF-β3 recapitulates the synergistic induction of bone formation by binary applications of hTGF-β1 and -β3 isoforms with hOP-1. Both synergistic strategies result in the rapid induction and expansion of the transformed mesenchymal tissue into large corticalized heterotopic ossicles with osteoblast-like cell differentiation at the periphery of the implanted reconstituted specimens with "tissue transfiguration" invivo. Molecularly, the rapid induction of bone formation by binary applications of hOP-1 and hTGF-β3 or by hTGF-β3 applied singly resides in the up-regulation of selected genes involved in tissue induction and morphogenesis, Osteocalcin, RUNX-2, OP-1, TGF-β1 and -β3 with however the noted lack of TGF-β2 up-regulation.

Nano-hydroxyapatite/fibrin glue/recombinant human osteogenic protein-1 artificial bone for repair of bone defect in an animal model

Nano-hydroxyapatite (nano-HA), with similar components of human bone tissues and good biomechanical properties, is considered as the most promising bioactive material. Its application, however, is still limited because of its lack of bone induction effect. To assess the ability of polypro nano-HA/fibrin glue/recombination human osteogenic protein-1 (nano-HA/FG/rhOP-1) for bone defect reconstruction. After the unilateral radius bone defect was established at the 45 New Zealand white rabbits, they were randomly divided into the nano-HA/FG/rhOP-1 (Group A), nano-HA/FG (Group B) and control groups (Group C; without repair), each with 15 rabbits. The ability of bone defect repair was evaluated by gross observation, X-ray radiography, scanning electronic microscope, radionuclide bone imaging and biomechanical analysis at 4, 8 and 12 weeks after repair. The radio graphically score, bone formation, radionuclide intake ratio and biomechanical strength were higher in the nano-HA/FG/rhOP-1 group than the nano-HA/FG and control groups at 4, 8 and 12 weeks (P<0.05). There were no bone connection at the defect site and the bone defect was reconstructed in the control group. It is indicated that the nano-HA/FG/rhOP-1 artificial bone has good osteoconductibility and is a promising material for repair of bone defect.

Synergistic induction of periodontal tissue regeneration by binary application of human osteogenic protein‐1 and human transforming growth factor‐β3 in Class II furcation defects of Papio ursinus

Binary applications of recombinant human osteogenic protein-1 (hOP-1) and transforming growth factor-β3 (hTGF-β3) synergize to induce pronounced bone formation. To induce periodontal tissue regeneration, binary applications of hOP-1 and hTGF-β(3) were implanted in Class II furcation defects of the Chacma baboon, Papio ursinus. Defects were created bilaterally in the furcation of the first and second mandibular molars of three adult baboons. Single applications of 25 μg hOP-1 and 75 μg hTGF-β(3) in Matrigel(®) matrix were compared with 20:1 binary applications, i.e. 25 μg hOP-1 and 1.25 μg hTGF-β(3). Morcellated fragments of autogenous rectus abdominis striated muscle were added to binary applications. Sixty days after implantation, the animals were killed and the operated tissues harvested en bloc. Undecalcified sections were studied by light microscopy, and regenerated tissue was assessed by measuring volume and height of newly formed alveolar bone and cementum. The hOP-1 and hTGF-β(3) induced periodontal tissue regeneration and cementogenesis. Qualitative morphological analysis of binary applications showed clear evidence for considerable periodontal tissue regeneration. Quantitatively, the differences in the histomorphometric values did not reach statistical significance for the group size chosen for this primate study. The addition of morcellated muscle fragments did not enhance tissue regeneration. Binary applications showed rapid expansion of the newly formed bone against the root surfaces following fibrovascular tissue induction in the centre of the treated defects. Binary applications of hOP-1 and hTGF-β(3) in Matrigel(®) matrix in Class II furcation defects of P. ursinus induced substantial periodontal tissue regeneration, which was tempered, however, by the anatomy of the furcation defect model, which does not allow for the rapid growth and expansion of the synergistic induction of bone formation, particularly when additionally treated with responding myoblastic stem cells.

The optimal dose of recombinant human osteogenic protein-1 enhances differentiation of mouse osteoblast-like cells: An in vitro study

ObjectiveThere is no certain conclusion on the effect of recombinant human Osteogenic Protein-1 (OP-1, BMP-7) on the proliferation of the osteoblast-like cell line, MC3T3-E1. Furthermore, the optimal dose of rhOP-1 on cell differentiation still needs to be elucidated. This investigation aims to delineate the biofunctional characteristics of rhOP-1 in inducing osteoblastogenesis of MC3T3-E1 through in vitro time-course and dose–response studies. DesignMC3T3-E1 cells were cultured for 1, 4, 7 days with the addition of different rhOP-1 concentrations (0, 10, 20, 50, 100, 200, 400ng/ml), and cell proliferation and cell differentiation were examined. ResultsMC3T3-E1 cell proliferation was stimulated by rhOP-1 in a dose-dependent manner (0–400ng/ml) on day 1, whereas on day 4 and 7, it was still stimulated at low concentrations (10, 20, 50ng/ml) but inhibited at high ones (200, 400ng/ml). The alkaline phosphatase (ALP) activity, osteocalcin (OC) production, collagen deposition and extracellular matrix mineralization were dramatically elevated by rhOP-1 treatment, as a function of culture time and rhOP-1 concentration, and all of them reached a plateau at the concentration of 200ng/ml. Real-time quantitative RT-PCR results showed Runx2, AKP-2, OC and Nog mRNA expressions increased in a dose- and time-dependent manner, and their expressions were significantly higher at high rhOP-1 concentrations than that of low ones. No significant differences were found between the effects of 200ng/ml rhOP-1 and 400ng/ml rhOP-1 on the differentiation of MC3T3-E1 cells, except the expression of Nog mRNA, whose expression level was much higher at 400ng/ml than that at 200ng/ml. ConclusionsThese results suggest that cell proliferation of MC3T3-E1 is depended on culture time and rhOP-1 concentration, rhOP-1 could stimulate the differentiation of MC3T3-E1 cells and the optimal concentration could be 200ng/ml.

Bone Morphogenetic Protein Binding Peptide Mechanism and Enhancement of Osteogenic Protein-1 Induced Bone Healing

In vitro and in vivo evaluation of BBP interactions with BMP. To explore bone morphogenetic protein-binding peptide (BBP)'s mechanism of action, investigate an extended repertoire for BBP applications, and evaluate the usefulness of BBP as a surgical adjuvant when used with recombinant human osteogenic protein-1 (rhOP-1). Bone morphogenetic proteins (BMPs) are osteoinductive proteins that provide a potential alternative to autograft. Their utility is limited by cost, and potential dose-dependent risks, such as local inflammatory reactions and ectopic bone formation. BBP, a cyclized synthetic peptide, avidly binds recombinant human BMP-2(rhBMP-2) and has been shown to accelerate and enhance its osteogenic qualities. BBP binding with 4 growth factors from the transforming growth factor -beta family were assessed using surface plasmon resonance. The in vivo retention of rhBMP-2 was quantified by comparing the percentage of retained [¹²⁵I]-labeled rhBMP-2 in absorbable collagen sponge implants with or without BBP at 1, 3, and 7 days postimplantation. The adjunctive effect of BBP with rhOP-1-induced bone growth was evaluated by comparing time to fusion and fusion rates in a rodent posterolateral fusion model with 2 different doses of rhOP-1 with or without BBP. BBP bound all 4 growth factors with an intermediate affinity. The in vivo retention of rhBMP-2 alone ranged from about 40% on day 1 to about 30% on day 7, whereas, the retention of rhBMP-2 in the presence of BBP was about 85% on day 1 and about 55% on day 7. The addition of BBP to rhOP-1 resulted in significantly earlier and greater fusion rates than achieved with rhOP-1 alone. The mechanism of the BBP enhanced osteoinductive properties of BMPs involves the binding and retention of the growth factor, resulting in a prolonged exposure of BMP to the desired fusion site. The use of BBP in conjunction with BMPs may prove to provide satisfactory fusion outcomes, while reducing the costs and side effects associated with BMP use.

Immunogenicity of osteogenic protein 1: results from a prospective, randomized, controlled, multicenter pivotal study of uninstrumented lumbar posterolateral fusion

The aim in this study was to detect and quantify antibody responses against recombinant human osteogenic protein 1 (OP-1) and to compare these responses to patient clinical outcomes and safety information. A controlled, open-label, randomized, prospective, multicenter pivotal study was performed in which patients with single-level Grade I or II degenerative lumbar spondylolisthesis (Meyerding classification) and spinal stenosis underwent decompression and uninstrumented posterolateral spinal arthrodesis. Three hundred thirty-six patients were randomized in a 2:1 fashion to receive either OP-1 Putty or autogenous iliac crest bone graft. Patients were evaluated at regular postoperative intervals for radiographic results, clinical outcomes, and safety parameters for more than 36 months. Serum samples were collected over this period and evaluated for the presence of anti–OP-1 antibodies and neutralizing activity by using a battery of in vitro binding assays (including enzyme-linked immunosorbent assay [ELISA]) and cell-based bioassays, respectively. Antibodies were predominantly seen in the OP-1–treated patients, although some responses were recorded preoperatively and in patients receiving autograft alone. Antibody production peaked in the 6-week to 3-month postoperative time frame and diminished thereafter. Neutralizing antibodies (Nabs) were detected at 1 time point at least in 25.6% of the patients treated with OP-1 Putty, but were not found in any patient following the 24-month postoperative time period. A single autograft patient (1.2%) also presented with OP-1 Nabs. An anti–OP-1 antibody status did not correlate with any measure of patient outcomes or adverse events. Recombinant human OP-1 (bone morphogenetic protein 7), like many recombinant human proteins, induces an immune response following its use as a bone graft alternative. This response was transient and diminished over time, and there was no statistical evidence to suggest an association between Nab status and any of the efficacy or safety criteria that were examined.

Synergistic induction of bone formation by hOP-1, hTGF-β3 and inhibition by zoledronate in macroporous coral-derived hydroxyapatites

Thirty coral-derived calcium carbonate-based macroporous constructs with limited hydrothermal conversion to hydroxyapatite (7% HA/CC) were implanted in the rectus abdominis of three adult non-human primate Papio ursinus to investigate the intrinsic induction of bone formation. Macroporous constructs with 125μg human recombinant osteogenic protein-1 (hOP-1) or 125μg human recombinant transforming growth factor-β3 (hTGF-β3) were also implanted. The potential synergistic interaction between morphogens was tested by implanting binary applications of hOP-1 and hTGF-β3 5:1 by weight, respectively. To evaluate the role of osteoclastic activity on the implanted macroporous surfaces, coral-derived constructs were pre-loaded with 0.24mg of bisphosphonate zoledronate (Zometa®). To correlate the morphology of tissue induction with osteogenic gene expression and activation, harvested specimens on day 90 were analyzed for changes in OP-1 and TGF-β3 mRNA synthesis by quantitative real-time polymerase chain reaction (qRT-PCR). The induction of bone formation in 7% HA/CC solo correlated with OP-1 expression. Massive bone induction formed by binary applications of the recombinant morphogens. Single applications of hOP-1 and hTGF-β3 also resulted in substantial bone formation, not comparable however to synergistic binary applications. Zoledronate-treated macroporous constructs showed limited bone formation and in two specimens bone formation was altogether absent; qRT-PCR showed a prominent reduction of OP-1 gene expression whilst TGF-β3 expression was far greater than OP-1. The lack of bone formation by zoledronate-treated specimens indicates that osteoclastic activity on the implanted coral-derived constructs is critical for the spontaneous induction of bone formation. Indirectly, zoledronate-treated samples showing lack of OP-1gene expression and absent or very limited bone formation by induction confirm that the spontaneous induction of bone formation by coral-derived macroporous constructs is initiated by secreted BMPs/OPs, in context the OP-1 isoform.

Alveolar ridge augmentation using implants coated with recombinant human bone morphogenetic protein‐7 (rhBMP‐7/rhOP‐1): histological observations

Pre-clinical studies have shown that recombinant human bone morphogenetic protein-2 (rhBMP-2) coated onto purpose-designed titanium porous-oxide surface implants induces clinically relevant bone formation and osseointegration. The objective of this study was to examine the potential of rhBMP-7, also known as recombinant human osteogenic protein-1 (rhOP-1), coated onto titanium porous-oxide surface implants to support vertical alveolar ridge augmentation and implant osseointegration. Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in six young adult Hound Labrador mongrel dogs. The animals received implants coated with rhBMP-7 at 1.5 or 3.0 mg/ml randomized to contra-lateral jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at 3, 4, 7, and 8 weeks post-surgery when they were euthanized for histological evaluation. Without striking differences between treatments, the implant sites exhibited a swelling that gradually regressed to become hard to palpation disguising the implant contours. The histological evaluation showed robust bone formation; the newly formed bone assuming characteristics of the contiguous resident bone, bone formation (height and area) averaging 4.1+/-1.0 versus 3.6+/-1.7 mm and 3.6+/-1.9 versus 3.1+/-1.8 mm(2); and bone density 56%versus 50% for implants coated with rhBMP-7 at 1.5 and 3.0 mg/ml, respectively. Both treatments exhibited clinically relevant osseointegration, the corresponding bone-implant contact values averaging 51% and 47%. Notable peri-implant resident bone remodelling was observed for implants coated with rhBMP-7 at 3.0 mg/ml. rhBMP-7 coated onto titanium porous-oxide surface implants induces clinically relevant local bone formation including osseointegration and vertical augmentation of the alveolar ridge, the higher concentration/dose associated with some local side effects.

Post-Operative Dressing of Total HIP and KNEE Replacements: Comparison of the Jubilee Dressing Method to a standard adhesive dressing

Post-Operative Dressing of Total HIP and KNEE Replacements: Comparison of the Jubilee Dressing Method to a standard adhesive dressing

Immunogenicity of bone morphogenetic proteins

The object of this paper is to review the immunogenicity of bone morphogenetic proteins (BMPs) and to compare the results of the immunogenicity characterization and clinical consequences between recombinant human (rh)BMP-2 and recombinant human osteogenic protein-1 (rhOP-1/BMP-7). The immunogenicity of therapeutic proteins and its clinical effects were reviewed. The characteristics of BMPs were also described in terms of immunogenicity. The methods and results of antibody detection in various clinical trials of rhBMP-2 and rhOP-1 were compared, including the most recent studies using a systematic characterization strategy with both a binding assay and bioassay. Similar to all recombinant human proteins, rhBMPs induce immune responses in a select subgroup of patients. Adverse effects from this response in these patients, however, have not been reported with antibody formation to either rhBMP-2 or rhOP-1. Overall, the incidence of antibody formation was slightly higher in rhOP-1 trials than in rhBMP-2 trials. Although they occur in a subgroup of patients, the immune responses against rhBMPs have no correlation with any clinical outcome or safety parameter. Clinicians, however, must be aware of the potential complications caused by the immunogenicity of BMPs until more studies clearly elucidate their safety.

Production of human osteogenic protein-1 in tobacco seeds

Production of human osteogenic protein-1 in tobacco seeds

Alveolar ridge augmentation using implants coated with recombinant human bone morphogenetic protein‐7 (rhBMP‐7/rhOP‐1): radiographic observations

The objective of this study was to radiographically evaluate the potential of a purpose-designed titanium porous-oxide implant surface coated with recombinant human bone morphogenetic protein-7 (rhBMP-7), also known as recombinant human osteogenic protein-1 (rhOP-1), to stimulate alveolar ridge augmentation. Six young-adult Hound Labrador mongrel dogs were used. Three 10 mm titanium oral implants per jaw quadrant were placed 5 mm into the alveolar ridge in the posterior mandible following surgical extraction of the pre-molar teeth and reduction of the alveolar ridge leaving 5 mm of the implants in a supra-alveolar position. The implants had been coated with rhBMP-7 at 1.5 or 3.0 mg/ml and were randomized to contralateral jaw quadrants using a split-mouth design. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants. Radiographic registrations were made immediately post-surgery (baseline), and at weeks 4 and 8 (end of study). rhBMP-7-coated implants exhibited robust radiographic bone formation. At 8 weeks, bone formation averaged 4.4 and 4.2 mm for implants coated with rhBMP-7 at 1.5 and 3.0 mg/ml, respectively. There were no significant differences between the rhBMP-7 concentrations at any observation interval. A majority of the implant sites showed voids within the newly formed bone at week 4 that generally resolved by week 8. The newly formed bone assumed characteristics of the resident bone. The titanium porous-oxide implant surface serves as an effective carrier for rhBMP-7 showing a clinically significant potential to stimulate local bone formation.

OP-1 application in bone allograft integration: preliminary results in sheep experimental surgery

Massive bone allografts are frequently used in orthopaedic reconstructive surgery. However the failure rate at long term follow-up is around 25%. Stimulation of allograft incorporation. In order to stimulate bone remodeling of an allograft we applied recombinant human osteogenic protein-1 (rh-OP-1, also know as bone morphogenetic protein-7, BMP-7) to a long bone critical size defect sheep model. In nine sheep we created a 3 cm osteoperiosteal metatarsal defect replaced with a structural allograft alone (control group, 4 animals), or an allograft added with rh-BMP-7 (BMP group, 5 animals). Radiographic, mechanical, histological and histomorphometric analysis were performed. X-rays in the BMP group showed a better and faster callus formation, compared to the control group within the first 8 weeks after surgery. After 16 weeks there was a higher evidence of bone remodeling in the BMP group. Radiographic healing at junction sites was more evident in the BMP group at 4, 8 and 16 weeks. Mechanical testing on screw extraction showed no statistical differences between the two groups and histomorphometry showed no difference in terms of newly formed bone inside the allograft as well. The resorption rate of the graft was higher in the BMP group in comparison to the control group. The penetration of newly formed vessels was significantly higher in the BMP group. These findings indicate that BMP-7 added to a structural bone allograft inducing early remodeling of the graft through stimulation of neo-angiogenesis and osteoclastic activity, without negative effects in mechanical strength and clinical outcome.

Human osteogenic protein-1 induces osteogenic differentiation of adipose-derived stem cells harvested from mice

Objective Osteogenic protein-1 (OP-1) has been shown to stimulate undifferentiated cells to produce mineralized tissue. Adipose tissue is a rich source of undifferentiated cells for tissue engineering purposes. The purpose of this study was to investigate the effect of OP-1 on osteogenic differentiation of adipose-derived stem cells and the production of bony tissue in vitro. Design Adipose-derived stem cells (ADSCs) were isolated from inguinal fat pads of adult mice. Following cell expansion the cells were plated in 8-well chambered slides. The cells received one of four treatments: Group 1 cells were maintained in control medium, Group 2 cells were cultured in a common osteogenic medium, Group 3 cells were cultured in osteogenic medium supplemented with 250 ng/mL of OP-1, and Group 4 cells were cultured with 250 ng/mL of OP-1 added to control medium. Osteogenic differentiation of ADSCs was determined by estimating the number and size of mineralized nodules, and the amount of extracellular osteopontin secreted into cell culture medium. Mineralized nodule production was assessed at day 21 with von Kossa staining. Extracellular osteopontin release was measured after 8 and 21 days by enzyme-linked immunosorbant assay (ELISA). ANOVA/Tukey tests were used to identify differences among the four treatment groups for mineralized nodule production and osteopontin release ( p ≤ 0.05). Results Deposition of calcified nodules and osteopontin secretion was significantly greater for cell cultures incubated with OP-1 ( p ≤ 0.05). At day 21, no significant differences in osteopontin secretion were noted among groups incubated with osteogenic nutrients and/or OP-1 ( p > 0.05), which were significantly higher than the group incubated in cell growth medium only ( p ≤ 0.05). No significant differences in osteopontin secretion were noted between 8 and 21 days for any group ( p > 0.05). Linear regression analysis demonstrated a linear relationship was present between the presence of calcified nodules and the amount of osteopontin released ( p ≤ 0.05). Conclusions OP-1 is a powerful inducer of osteogenic differentiation of adult adipose-derived stem cells.

Effect of osteogenic protein‐1 on the matrix metabolism of bovine tendon cells

Tendon rupture is a common sports injury in adults. However, the mechanical properties of repair tissue are inferior to those of normal tissue. To accelerate tendon healing, an in vivo approach using growth factors has been applied and has shown evidence for the efficacy of biological stimulation of the repair process. Recombinant human osteogenic protein-1 (rhOP-1) has been shown to be effective in stimulating matrix production by various connective tissues. To test the effect of rhOP-1 on the matrix metabolism of tendon cells in vitro, bovine tendon cells were cultured in monolayer with various doses of rhOP-1 for 7 days. The addition of rhOP-1 to cell culture media resulted in significant increases in cell proliferation, DNA content, and the synthesis of proteoglycans (PGs) and collagen, compared to control cultures. The relative percentage of large PGs in the OP-1 culture was higher than that in the control culture. In conclusion, we show for the first time that rhOP-1 stimulates the proliferation of tendon cells and their ability to synthesize and accumulate PGs and collagen in their extracellular matrix. These biological properties may be used in the tissue-engineering of tendon tissues.

Clinical applications of BMP-7/OP-1 in fractures, nonunions and spinal fusion

Since the identification of the osteogenic protein-1 (OP-1) gene, also called bone morphogenetic protein-7 (BMP-7), almost 20 years ago, OP-1 has become one of the most characteristic members of the BMP family. The biological activity of recombinant human OP-1 has been defined using a variety of animal models. These studies have demonstrated that local implantation of OP-1 in combination with a collagen matrix results in the repair of critical size defects in long bones and in craniofacial bones and the formation of bony fusion masses in spinal fusions. Clinical trials investigating long bone applications have provided supportive evidence for the use of OP-1 in the treatment of open tibial fractures, distal tibial fractures, tibial nonunions, scaphoid nonunions and atrophic long bone nonunions. Clinical studies investigating spinal fusion applications have provided supportive evidence for the use of OP-1 in posterolateral lumbar models and compromised patients as an adjunct or as a replacement for autograft. Both long bone repair and spinal fusion studies have demonstrated the efficacy and safety of OP-1 by clinical outcomes and radiographic measures. Future clinical investigations will be needed to better define variables, such as dose, scaffold and route of administration. Clearly the use of BMPs in orthopaedics is still in its formative stage, but the data suggest an exciting and promising future for the development of new therapeutic applications.

Extracortical Bone-Bridging Fixation with Use of Cortical Allograft and Recombinant Human Osteogenic Protein-1

Prosthetic reconstruction with extracortical bone-bridging fixation is an effective method for the treatment of massive bone loss. We evaluated the effect of the use of recombinant human osteogenic protein-1 (rhOP-1) combined with allogenic cortical bone strips as a substitute for an autogenous bone graft for extracortical bone-bridging. Eight skeletally mature adult male dogs underwent a bilateral resection of a 6-cm segment of the femoral diaphysis and reconstruction with a porous segmental prosthesis. On the experimental side, an allogenic cortical onlay graft in the form of bone strips combined with rhOP-1 mixed with bovine type-I-collagen putty (OP-1 putty) was applied. On the control side, allogenic cortical bone strips augmented with autogenous cancellous bone chips and bone marrow were used. The reconstructions were followed for twelve weeks with biweekly evaluations of load-bearing gait and radiographs. The animals were killed twelve weeks after the surgery, and the reconstructed femora were studied biomechanically, histologically, and with microradiographs. One animal was excluded from the analysis because a fracture of the proximal part of the femur on the control side was observed radiographically twelve weeks after the surgery. There were no significant differences in load-bearing gait between the experimental and control sides throughout the experimental period. Serial radiographs revealed a 1.9-fold (p<0.04), 2.7-fold (p<0.01), and 2.4-fold (p<0.03) increase in mineralized area on the experimental side at two, four, and six weeks, respectively. The torsional stiffness and strength of the fixation attributed to the extracortical bridging bone alone were 2.3-fold (p<0.03) and 2.2-fold (p=0.058) greater on the experimental side, respectively. The allograft porosity on the experimental side was 3.8-fold (p<0.02) greater than that on the control side. With the number of samples available, there was no significant difference in mineral apposition rate between the experimental and control sides. In an animal model of segmental bone-replacement prosthetic fixation with use of the extracortical bone-bridging principle, an allogenic onlay cortical graft combined with rhOP-1 was an effective substitute for autogenous bone graft.

Extracortical Bone-Bridging Fixation with Use of Cortical Allograft and Recombinant Human Osteogenic Protein-1

Background: Prosthetic reconstruction with extracortical bone-bridging fixation is an effective method for the treatment of massive bone loss. We evaluated the effect of the use of recombinant human osteogenic protein-1 (rhOP-1) combined with allogenic cortical bone strips as a substitute for an autogenous bone graft for extracortical bone-bridging. Methods: Eight skeletally mature adult male dogs underwent a bilateral resection of a 6-cm segment of the femoral diaphysis and reconstruction with a porous segmental prosthesis. On the experimental side, an allogenic cortical onlay graft in the form of bone strips combined with rhOP-1 mixed with bovine type-I-collagen putty (OP-1 putty) was applied. On the control side, allogenic cortical bone strips augmented with autogenous cancellous bone chips and bone marrow were used. The reconstructions were followed for twelve weeks with biweekly evaluations of load-bearing gait and radiographs. The animals were killed twelve weeks after the surgery, and the reconstructed femora were studied biomechanically, histologically, and with microradiographs. Results: One animal was excluded from the analysis because a fracture of the proximal part of the femur on the control side was observed radiographically twelve weeks after the surgery. There were no significant differences in load-bearing gait between the experimental and control sides throughout the experimental period. Serial radiographs revealed a 1.9-fold (p < 0.04), 2.7-fold (p < 0.01), and 2.4-fold (p < 0.03) increase in mineralized area on the experimental side at two, four, and six weeks, respectively. The torsional stiffness and strength of the fixation attributed to the extracortical bridging bone alone were 2.3-fold (p < 0.03) and 2.2-fold (p = 0.058) greater on the experimental side, respectively. The allograft porosity on the experimental side was 3.8-fold (p < 0.02) greater than that on the control side. With the number of samples available, there was no significant difference in mineral apposition rate between the experimental and control sides. Conclusions: In an animal model of segmental bone-replacement prosthetic fixation with use of the extracortical bone-bridging principle, an allogenic onlay cortical graft combined with rhOP-1 was an effective substitute for autogenous bone graft. Clinical Relevance: The allogenic onlay cortical graft combined with rhOP-1 may be useful for fixation of segmental bone and joint prostheses implanted for the treatment of massive defects of long bones.

Restoration of Disc Height Loss by Recombinant Human Osteogenic Protein-1 Injection Into Intervertebral Discs Undergoing Degeneration Induced by an Intradiscal Injection of Chondroitinase ABC

In vivo study of the effect of an injection of recombinant human osteogenic protein-1 into degenerated discs induced by chondroitinase ABC. To investigate the efficacy of an injection of recombinant human osteogenic protein-1 to induce the recovery of disc height, and biochemical and histologic repair, in discs degenerated through enzymatic digestion by chondroitinase ABC. Chondroitinase ABC is currently proposed as a chemonucleolysis agent; however, postchemonucleolysis degeneration is currently unavoidable. Recombinant human OP-1 has been shown to promote extracellular matrix repair in vitro and in vivo. Fifty-four adolescent New Zealand white rabbits were used. Four weeks after an initial injection of chondroitinase ABC (10 mU/disc), 5% lactose (10 microL/disc) or recombinant human osteogenic protein-1 (100 microg in 10 microL lactose/disc) was injected. Disc heights were monitored radiographically at 2-week intervals, and rabbits were killed at 6, 8, 12, and 16 weeks after the initial chondroitinase ABC injections. The intervertebral discs were subjected to histologic and biochemical analyses. Significant disc space narrowing was observed in both groups 2 weeks after the injection of chondroitinase ABC. In the chondroitinase ABC/lactose group, this narrowing progressed after the vehicle injection and was sustained for up to 16 weeks. In the chondroitinase ABC/recombinant human osteogenic protein-1 group, the disc height index showed a significant increase at 6 weeks (lactose vs. recombinant human osteogenic protein-1; P < 0.01); this recovery was sustained for up to 16 weeks. The proteoglycan content was higher in the chondroitinase ABC/recombinant human osteogenic protein-1 group than in the chondroitinase ABC/lactose group. However, histologic changes, after the recombinant human osteogenic protein-1 injection, were not observed. A single injection of recombinant human osteogenic protein-1 into a rabbit disc dramatically reversed the decrease in disc height induced by chondroitinase ABC chemonucleolysis. The recovery was significant and sustained over the next 12 weeks. The therapeutic effects of both chondroitinase ABC chemonucleolysis and recombinant human osteogenic protein-1 injections should be further explored in higher animals before it is applied to humans.