Chaperone-mediated production of active homodimer human bone morphogenetic protein - 2 in E. coli.

Human bone morphogenetic protein 2 (hBMP-2) plays a leading role in the process of osteogenesis and is one of the key components of osteoplastic materials, ensuring their high osteoinduction. In order to obtain a homodimeric form hBMP-2 using the E. coli expression system, a number of problems associated with refolding in vitro and purification from monomer and oligomeric forms must be solved. The developed method for co-expression of the target protein with chaperone proteins makes it possible to obtain the biologically active homodimeric form of hBMP-2 in vivo. Purification with simple ion-exchange sorbents without the use of denaturing reagents affecting the structure of the protein molecule provides a chromatographic purity of the product of at least 97%. The expressed hBMP-2 was identified by Western blotting and the LC-ESI-TOF mass spectrometry confirmed its molecular weight of 26052.72 Da. Circular dichroism spectroscopy showed that recombinant hBMP-2 has a native secondary structure.

Assessment of Escherichia coli-derived Recombinant Human Bone Morphogenic Protein-2 on Fertilization and Early Embryonic Development in Rats.

OBJECTIVE: Bone morphogenetic protein-2 (BMP-2) impacts fertility in women by affecting the menstrual cycle and embryonic development. We aimed to determine the reproductive toxicity of Escherichia coli (E. coli)-derived recombinant human BMP-2 (rhBMP-2) by measuring changes in the reproductive performance and organs in rhBMP-2-treated rats. METHODS: Overall, 88 male and female rats each were categorized into one control and three experimental groups. rhBMP-2 was intravenously administered to the experimental groups at 0.05, 0.15, and 0.50 mg/kg/day, respectively. The male rats were administered rhBMP-2 daily, starting from 28 days before mating until the day of necropsy (48 days), after which they were euthanized and necropsied. The female rats were administered rhBMP-2 daily, starting from 14 days before mating until 7 days after fertilization (22-36 days), after which they were necropsied 13 days after fertilization. RESULTS: No rhBMP-2-related death occurred throughout the study period. All rhBMP-2-treated groups showed swelling in the tail at the site of rhBMP-2 administration. In the high-dose rhBMP-2 group, the male rats showed a slight reduction in body weight and food consumption, whereas the female rats showed a reduction in the weights of the ovary and oviduct. Examining the fertilization status and necropsy showed no effect of rhBMP-2 on fertility and early embryonic development. The no-observed-adverse-effect level of rhBMP-2 was 0.50 mg/kg/day in all rats. CONCLUSION: rhBMP-2 had no reproductive toxicity on the reproductive performance and organs in female and male rats. Therefore, these results provide new toxicology information on E. coli-derived rhBMP-2 as a therapeutic protein.

Current Trends in Recombinant Human Bone Morphogenetic Protein 2 (rhBMP2) Usage for Spinal Fusion Surgery.

(1) Background: Since first approved by the FDA, on-label and off-label usage of recombinant human bone morphogenetic protein 2 (rhBMP2) for spinal fusion surgeries has become widespread. While many studies have investigated the safety and efficacy of its use, as well as its economic impact, few have looked at the current trends in its on- and off-label use. The goal of this study is to evaluate the current trends of on- and off-label rhBMP2 use for spinal fusion surgery. (2) Methods: A deidentified survey was created and electronically distributed to members of two international spine societies. Surgeons were asked to report their demographic information, surgical experience, and current usage of rhBMP2. They were then presented with five spinal fusion procedures and asked to report if they use rhBMP2 for these indications in their current practice. Responses were stratified between rhBMP2 users vs. non-users and on-label vs. off-label use. Data were analyzed using chi-square with Fisher's exact test for categorical data. (3) Results: A total of 146 respondents completed the survey with a response rate of 20.5%. There was no difference in overall rhBMP2 usage based on specialty, experience, or number of cases per year. Fellowship-trained surgeons and those who practice in the United States were more likely to use rhBMP2. Surgeons who were trained in the Southeast and Midwest regions reported the highest usage rates. rhBMP2 use was more common among fellowship-trained and US surgeons for ALIFs; non-US surgeons for multilevel anterior cervical discectomy and fusions; and fellowship-trained and orthopedic spine surgeons for lateral lumbar interbody fusions. Non-US surgeons were more likely to use rhBMP2 for off-label indications compared to surgeons from the US. (4) Conclusions: While various demographics of surgeons report different rates of rhBMP2 use, off-label use remains relatively commonplace amongst practicing spine surgeons.

Treatment of two Asiatic black bears (Ursus thibetanus) with severe injuries and their subsequent release into the wild: a case report.

BACKGROUND: The rehabilitation of injured wildlife and their subsequent release into the wild is a humane act as well as important in wildlife conservation. However, little is known about the animals' fate after release. Therefore, to address these uncertainties, it is essential to adequately describe how the injured animals were treated and managed before releasing into the wild; moreover, post-release monitoring should also be performed. Herein, we document for the first time the process of rescue, surgery, and rehabilitation of severely injured Asiatic black bears (Ursus thibetanus; endangered species in South Korea) and their fate after returning to the wild. CASE PRESENTATION: A six-year-old female (bear-01) and a three-year-old male (bear-02) bears were injured by an illegal snare and collision with a bus, respectively. Bear-01 had broad muscle necrosis and ruptures from the snared ankle on the right thoracic limb, with myiasis, and elbow disarticulation was performed. In bear-02, a non-reducible comminuted fracture of the left humerus was confirmed radiologically, and the operation was performed by using dual plate fixation with hydroxyapatite and recombinant human bone morphogenetic protein-2. The bear-01 and -02 were completely healed approximately 30 and 60 days after surgery, respectively. After that, they underwent rehabilitation for 8 and 25 days, respectively, in an outdoor enclosure similar to their natural habitat. Bear-01 and -02 were released into the wild after 45 and 99 days after surgery, respectively, and their mean daily movement distance during the first 30 days after releasing was 2.9 ± 2.1 and 1.3 ± 1.6 km, respectively. The annual mean 95% Kernel home-range size of bear-01 and bear-02 was 265.8 and 486.9 km2, respectively. They hibernated every winter, gained weight, gave birth to cubs (bear-01), were not found to have any abnormalities in the veterinary tests, and were not involved in any conflicts with humans after returning to the wild. CONCLUSIONS: Bears without one leg or those with dual plates could adapt well in their natural habitat, which shows that our surgical and post-operative treatments were effective. Additionally, minimizing human contact and observing/evaluating behavior during the rehabilitation is essential in reducing human-bear conflicts after release.

Use of rhBMP-2 for adult spinal deformity surgery: patterns of usage and changes over the past decade.

OBJECTIVE: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to increase fusion rates; however, cost, limited FDA approval, and possible complications impact its use. Decisions regarding rhBMP-2 use and changes over time have not been well defined. In this study, the authors aimed to assess changes in rhBMP-2 use for adult spinal deformity (ASD) surgery over the past decade. METHODS: A retrospective review of the International Spine Study Group prospective multicenter database was performed to identify ASD patients treated surgically from 2008 to 2018. For assessment of rhBMP-2 use over time, 3 periods were created: 2008-2011, 2012-2015, and 2016-2018. RESULTS: Of the patients identified, 1180 met inclusion criteria, with a mean age 60 years and 30% of patients requiring revision surgery; rhBMP-2 was used in 73.9% of patients overall. The mean rhBMP-2 dose per patient was 23.6 mg. Patients receiving rhBMP-2 were older (61 vs 58 years, p < 0.001) and had more comorbidities (Charlson Comorbidity Index 1.9 vs 1.4, p < 0.001), a higher rate of the Scoliosis Research Society-Schwab pelvic tilt modifier (> 0; 68% vs 62%, p = 0.026), a greater deformity correction (change in pelvic incidence minus lumbar lordosis 15° vs 12°, p = 0.01), and more levels fused (8.9 vs 7.9, p = 0.003). Over the 3 time periods, the overall rate of rhBMP-2 use increased and then stabilized (62.5% vs 79% vs 77%). Stratified analysis showed that after an overall increase in rhBMP-2 use, only patients who were younger than 50 years, those who were smokers, those who received a three-column osteotomy (3CO), and patients who underwent revision sustained an increased rate of rhBMP-2 use between the later two periods. No similar increases were noted for older patients, nonsmokers, primary surgery patients, and patients without a 3CO. The total rhBMP-2 dose decreased over time (26.6 mg vs 24.8 mg vs 20.7 mg, p < 0.001). After matching patients by preoperative alignment, 215 patients were included, and a significantly lower rate of complications leading to revision surgery was observed within the 2012-2015 period compared with the 2008-2011 (21.4% vs 13.0%, p = 0.029) period, while rhBMP-2 was increasingly used (80.5% vs 66.0%, p = 0.001). There was a trend toward a lower rate of pseudarthrosis for patients in the 2012-2015 period, but this difference did not reach statistical significance (7% vs 4.2%, p = 0.283). CONCLUSIONS: The authors found that rhBMP-2 was used in the majority of ASD patients and was more commonly used in those with greater deformity correction. Additionally, over the last 10 years, rhBMP-2 was increasingly used for ASD patients, but the dose has decreased.

Prognosis of single tooth implants following alveolar ridge preservation with two recombinant human bone morphogenetic protein-2 delivery systems.

BACKGROUND: We previously reported similar efficacies of alveolar ridge preservation (ARP) on single extraction socket with two different E. coli derived recombinant human bone morphogenetic protein-2 (rhBMP-2) delivery systems (Cowell BMP, Cowell medi Co, Busan, Korea; ß-tricalcium phosphate and hydroxyapatite particle & O-BMP, Osstem Implant Co, Busan, Korea; absorbable collagen sponge). After the trial, we completed implant therapy and observed over an average of 3 years. This follow-up study was performed retrospectively to compare result of implant treatment at the preserved alveolar ridge site. METHODS: Patients who underwent extraction of single tooth and received ARP with one of two rhBMP-2 delivery systems from October 2015 to October 2016 were enrolled. Twenty-eight patients (Group 1: Cowell BMP 14; Group 2: O-BMP 14) who underwent implant therapy and prosthetic treatment were included in study. Stability and marginal bone loss (MBL) of each implant were collected from medical charts and radiographs, and analyzed. The survival and success rates of implants were calculated. RESULTS: The primary implant stability represented by implant stability quotient (ISQ) for Groups 1 and 2 was 69.71 and 72.86, respectively. The secondary implant stability for Groups 1 and 2 was 78.86 and 81.64, respectively. Primary and secondary stabilities were not statistically different (P = 0.316 and 0.185, respectively). MBL at the latest follow-up was 0.014 mm in Group 1 over 33.76 ± 14.31 months and 0.021 mm in Group 2 over 40.20 ± 9.64 months, with no significant difference (P = 0.670). In addition, the success rate of implants was 100% (14/14) in Group 1 and 92.9% (13/14) in Group 2, with survival rate of 100% (14/14) in Group 1 and 92.9% (13/14) in Group 2. CONCLUSIONS: We confirmed good prognosis in both groups as a result of implant therapy after ARP with each of two rhBMP-2 carriers.

PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence.

OBJECTIVE: The authors have provided a review of radiographic subsidence after lateral lumbar interbody fusion (LLIF) as a comparative analysis between titanium and polyetheretherketone (PEEK) cages. Many authors describe a reluctance to use titanium cages in spinal fusion secondary to subsidence concerns due to the increased modulus of elasticity of metal cages. The authors intend for this report to provide observational data regarding the juxtaposition of these two materials in the LLIF domain. METHODS: A retrospective review of a prospectively maintained database identified 113 consecutive patients undergoing lateral fusion for degenerative indications from January to December 2017. The surgeons performing the cage implantations were two orthopedic spine surgeons and two neurosurgeons. Plain standing radiographs were obtained at 1-2 weeks, 8-12 weeks, and 12 months postoperatively. Using a validated grading system, interbody subsidence into the endplates was graded at these time points on a scale of 0 to III. The primary outcome measure was subsidence between the two groups. Secondary outcomes were analyzed as well. RESULTS: Of the 113 patients in the sample, groups receiving PEEK and titanium implants were closely matched at 57 and 56 patients, respectively. Cumulatively, 156 cages were inserted and recombinant human bone morphogenetic protein-2 (rhBMP-2) was used in 38.1%. The average patient age was 60.4 years and average follow-up was 75.1 weeks. Subsidence in the titanium group in this study was less common than in the PEEK cage group. At early follow-up, groups had similar subsidence outcomes. Statistical significance was reached at the 8- to 12-week and 52-week follow-ups, demonstrating more subsidence in the PEEK cage group than the titanium cage group. rhBMP-2 usage was also highly correlated with higher subsidence rates at all 3 follow-up time points. Age was correlated with higher subsidence rates in univariate and multivariate analysis. CONCLUSIONS: Titanium cages were associated with lower subsidence rates than PEEK cages in this investigation. Usage of rhBMP-2 was also robustly associated with higher endplate subsidence. Each additional year of age correlated with an increased subsidence risk. Subsidence in LLIF is likely a response to a myriad of factors that include but are certainly not limited to cage material. Hence, the avoidance of titanium interbody implants secondary solely to concerns over a modulus of elasticity likely overlooks other variables of equal or greater importance.

Alveolar Cleft Reconstruction Using Morphogenetic Protein (rhBMP-2): A Systematic Review and Meta-Analysis.

OBJECTIVE: This study aimed to review the existing evidence regarding reconstruction of the alveolar cleft using recombinant human bone morphogenetic protein-2 (rhBMP-2) in terms of bone volume and bone height. DESIGN: Systematic review and meta-analysis. PATIENTS­PARTICIPANTS: A systematic search was done. Randomized and nonrandomized clinical trials, where rhBMP-2 was used in the reconstruction of human alveolar cleft were included. INTERVENTIONS: Reconstruction of alveolar cleft with rhBMP-2. MAIN OUTCOME MEASURES: Average bone volume formation and average bone height formation in the alveolar cleft. Mean difference was calculated and pooled by meta-analysis. RESULTS: Of 709 identified articles, 5 studies met the inclusion criteria. The average bone volume formation was higher in the rhBMP-2 group than in the control group (61.11% vs 59.12%). The average bone height formation was higher in the control group compared to the rhBMP-2 group (75.4% vs 61.5%). The risk of bias in the selected articles was high. The meta-analysis showed that rhBMP-2 treatment may benefit bone formation compared to iliac crest graft (low certainty evidence; mean difference: -208.76; 95% confidence interval: -253.59 to -163.93; -I2 = 0%). CONCLUSIONS: The results obtained in primary articles are promising but have a high risk of bias and have low quality of evidence; therefore, it is necessary to conduct controlled clinical trials with a greater number of patients to recommend the use of rhBMP-2 in the treatment of the alveolar cleft. PROSPERO registration number: CRD42018077741.

The adjunctive effect of rhBMP-2 on the regeneration of peri-implant bone defects after experimental peri-implantitis.

OBJECTIVES: The aim was to evaluate the degree of bone regeneration and re-osseointegration attained when combining a xenogeneic bone replacement graft plus rhBMP-2 and a collagen membrane in ligature-induced peri-implantitis osseous defects in dogs. MATERIAL AND METHODS: Thirty-six implants were placed in a total of 6 Beagle dogs, 3 months after tooth extraction. Once experimental peri-implantitis was induced, defects were randomly allocated into two treatment groups: in the test group guided bone regeneration was applied using de-proteinized bovine bone mineral with 10% collagen soak loaded with rhBMP2 covered with a natural collagen membrane. In the control group, the same scaffold and membrane were used but saline was used to soak the grafting material. After a period of 8 weeks of healing, a submerged environment clinical measurements were taken and histological outcomes were evaluated once the animals were euthanized. Histological bone defect regeneration (BR) was considered as the primary outcome variable, and dog was selected as the unit of analysis. RESULTS: Partial defect resolution was observed in both treatment groups. The histometric analysis showed a higher degree of bone regeneration for the test group, although differences were not statistically significant, both in terms of histological bone gain and percentage of re-osseointegration. CONCLUSIONS: (a) The addition of rhBMP2 to a bovine xenograft/collagen vehicle carrier failed to provide a significant added value in terms of bone regeneration or re-osseointegration, (b) partial re-osseointegration of a previously contaminated surface was achieved, although (c) a complete defect resolution and re-osseointegration to the level previous to the induction of the disease failed to occur in any of the treatment groups.

Insights into complication rates, reoperation rates, and healthcare utilization associated with use of recombinant human bone morphogenetic protein-2 in patients with spine infections.

OBJECTIVEUse of recombinant human bone morphogenetic protein-2 (rhBMP-2) in patients with spine infections is controversial. The purpose of this study was to identify long-term complications, reoperations, and healthcare utilization associated with rhBMP-2 use in patients with spine infections.METHODSThis retrospective study extracted data using ICD-9/10 and CPT codes from MarketScan (2000-2016). Patients were dichotomized into 2 groups (rhBMP-2, no rhBMP-2) based on whether rhBMP-2 was used during fusion surgery for spinal infections. Outcomes of interest were reoperation rates (index level, other levels), readmission rates, discharge disposition, length of stay, complications, and healthcare resource utilization at the index hospitalization and 1, 3, 6, 12, and 24 months following discharge. Outcomes were compared using nonparametric 2-group tests and generalized linear regression models.RESULTSThe database search identified 2762 patients with > 24 months' follow-up; rhBMP-2 was used in 8.4% of their cases. The patients' median age was 53 years, 52.43% were female, and 15.11% had an Elixhauser Comorbidity Index ≥ 3. Patients in the rhBMP-2 group had higher comorbidity indices, incurred higher costs at index hospitalization, were discharged home in most cases, and had lower complication rates than those in the no-rhBMP-2 group. There was no statistically significant between-groups difference in complication rates 1 month following discharge or in reoperation rates at 3, 6, 12, and 24 months following the procedure. Patients in the no-rhBMP-2 group incurred higher utilization of outpatient services and medication refill costs at 1, 3, 6, 12, and 24 months following surgery.CONCLUSIONSIn patients undergoing surgery for spine infection, rhBMP-2 use was associated with lower complication rates and higher median payments during index hospitalization compared to cases in which rhBMP-2 was not used. There was no significant between-groups difference in reoperation rates (index and other levels) at 3, 6, 12, and 24 months after the index operation. Patients treated with rhBMP-2 incurred lower utilization of outpatient services and overall payments. These results indicate that rhBMP-2 can be used safely in patients with spine infections with cost-effective utilization of healthcare resources and without an increase in complications or reoperation rates.

Endoscopic transforaminal lumbar interbody fusion without general anesthesia: operative and clinical outcomes in 100 consecutive patients with a minimum 1-year follow-up.

OBJECTIVEOpen spinal fusion surgery is often associated with significant blood loss, postoperative pain, and prolonged recovery times. Seeking to minimize surgical and perioperative morbidity, the authors adopted an endoscopic minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) technique performed without general anesthesia. In this report, they present data on the first 100 patients treated with this procedure.METHODSThe authors conducted a retrospective review of the first 100 patients who underwent awake endoscopic MIS-TLIF at a single institution between 2014 and 2017. Surgery was performed while the patient was sedated but without intubation or the use of general anesthetic or narcotic agents. Long-lasting (liposomal) bupivacaine was used for local analgesia. The discectomy and placement of an expandable interbody graft were performed endoscopically, followed by percutaneous pedicle screw implantation. Inclusion criteria for the procedure consisted of diagnosis of degenerative disc disease with grade I or II spondylolisthesis and evidence of spinal stenosis or nerve impingement with intractable symptomatology.RESULTSOf the first 100 patients, 56 were female and 44 were male. Single-level fusion was performed in 84 patients and two-level fusion in 16 patients. The most commonly fused level was L4-5, representing 77% of all fused levels. The mean (± standard deviation) operative time was 84.5 ± 21.7 minutes for one-level fusions and 128.1 ± 48.6 minutes for two-level procedures. The mean intraoperative blood loss was 65.4 ± 76.6 ml for one-level fusions and 74.7 ± 33.6 ml for two-level fusions. The mean length of hospital stay was 1.4 ± 1.0 days. Four deaths occurred in the 100 patients; all four of those patients died from complications unrelated to surgery. In 82% of the surviving patients, 1-year follow-up Oswestry Disability Index (ODI) data were available. The mean preoperative ODI score was 29.6 ± 15.3 and the mean postoperative ODI score was 17.2 ± 16.9, which represents a significant mean reduction in the ODI score of -12.3 using a two-tailed paired t-test (p = 0.000001). In four cases, the surgical plan was revised to include general endotracheal anesthesia intraoperatively and was successfully completed. Other complications included two cases of cage migration, one case of osteomyelitis, and one case of endplate fracture; three of these complications occurred in the first 50 cases.CONCLUSIONSThis series of the first 100 patients to undergo awake endoscopic MIS-TLIF demonstrates outcomes comparable to those reported in our earlier papers. This procedure can provide a safe and efficacious option for lumbar fusion with less morbidity than open surgery. Further refinements in surgical technique and technologies will allow for improved success.

Overaugmentation to compensate for postextraction ridge atrophy using a putty-type porcine bone substitute material with recombinant bone morphogenetic protein-2: 4 weeks of healing in a canine model.

OBJECTIVES: The aims of the present study were (i) to determine the short-term effects of putty-type porcine bone substitute material (PB) with recombinant bone morphogenetic protein-2 (rhBMP-2) for alveolar ridge preservation (ARP) and (ii) evaluate the early healing of labial overaugmentation. MATERIALS AND METHODS: Two groups were randomly assigned to the extraction sockets in mandibular incisors of eight dogs: labial overaugmentation with (i) PB (control) or (ii) rhBMP-2-loaded PB (BMP). Microcomputed tomography (micro-CT), and histologic and histomorphometric analyses were performed after 4 weeks. RESULTS: Micro-CT revealed that some of the overaugmented PB was dispersed in both groups. The new bone volume was significantly larger in the BMP group than in the control group (18.4 ± 3.3 vs. 15.5 ± 3.0 mm3, mean ± SD, P < 0.05). Labial bone resorption was generally found histologically. No signs of mineralization were observed in the overaugmented area despite significantly increased ridge width, as compared to the adjacent tooth area. The area of new bone formation was larger in the BMP group than in the control group overall (23.7 ± 18.8 vs. 18.3 ± 21.2 mm2) and in three parts (apical, middle, and coronal), although the difference was statistically significant only in the coronal part (7.7 ± 7.9 vs. 4.6 ± 6.4 mm2, P < 0.05). CONCLUSIONS: The addition of rhBMP-2 enhanced ossification in the coronal part of the extraction socket relative to using PB alone. Overaugmentation increased the ridge dimension with no evidence of ossification in situ at 4 weeks. CLINICAL RELEVANCE: In early healing following ARP, rhBMP-2 enhances bone formation within the socket, but ossification in the overaugmented area needs to be studied further.

Outcomes of Alveolar Graft With Rhbmp-2 in CLP: Influence of Cleft Type and Width, Canine Eruption, and Surgeon.

OBJECTIVE: To evaluate the influence of cleft type and width, canine eruption stage, and surgeon on the outcomes of alveolar graft with rhBMP-2. DESIGN: Cross-sectional. SETTING: Tertiary craniofacial center. PARTICIPANTS: Ninety individuals submitted to alveolar graft in late mixed or early permanent dentition. INTERVENTIONS: The 90 individuals (mean age: 16.8 years) were submitted to alveolar graft with rhBMP-2. Periapical radiographs were obtained before and 6 months after surgery. Surgeries were performed by 4 experienced maxillofacial surgeons. The alveolar grafts were assigned as success or failure by 3 blinded raters based on the modified Bergland and Chelsea scales. Permanent canines adjacent to the defect were assigned as erupted and not erupted. The greatest cleft width was measured on preoperative periapical radiographs. MAIN OUTCOME MEASURES: The influence of 4 independent variables (cleft type, cleft width, canine eruption phase, and surgeon) on the outcome of alveolar graft was analyzed by multivariate logistic regression ( P < .05). RESULTS: All independent variables presented significant influence on alveolar graft outcome. The subgroup of unerupted maxillary canines demonstrated better outcomes than erupted canines ( P = .001). The group with cleft lip and alveolus (CL/A) demonstrated better outcomes than complete cleft lip and palate (CLP; P < .001). The greater the alveolar cleft width, the less favorable were the graft outcomes ( P = .027). The surgeon also had a significant influence on the surgery success ( P = .003 and .001). CONCLUSION: The type and width of CLP, the eruption of permanent canines, and the surgeon influenced the outcome of alveolar graft surgeries performed with rhBMP-2.

Demineralized Dentin Matrix (DDM) As a Carrier for Recombinant Human Bone Morphogenetic Proteins (rhBMP-2).

A bone graft and bone graft substitute should have at least one of the following properties: it should be (1) osteogenic, (2) osteoinductive and/or (3) osteoconductive. In addition, bone graft substitutes should be biocompatible and bioresorbable as well as easy to use and cost effective. Autologous cancellous bone is the clinical gold standard in bone grafting procedures1, 4 and it has osteogenic, osteoinductive, and osteoconductive properties. Because of disadvantages associated with harvesting autologous bone graft material, such as requiring an additional operation and possible donor site morbidity, there is a need for an alternative in terms of enhancing the bone healing for the treatment of large bony defects. One possible option is a newly developed biomaterial, the demineralized dentin matrix (DDM). It is based on autogenous tooth dentin and is produced through demineralization. It is osteoconductive and osteoinductive due to the fact that dentin contains extracellular Type I collagen and various growth factors. Based on the demineralization process the factors stay available to the host environment. In 1965, Urist already showed the formation of ectopic bone after implanting DDM into muscle pouches in rodents. DDM is used for example in dental surgery in the treatment of extraction socket preservation and guided bone regenerations. It functions as a scaffold to support bone regeneration, but can also be used as a carrier for rhBMP-2. When DDM serves as a carrier, it combines the properties of the grafting material with those of the delivered substances. This chapter will present the experimental and clinical studies of DDM for rhBMP-2 carrier as well as alternatives of bone graft substitute.

In vitro and in vivo evaluation of osteoinductivity and bone fusion ability of an activin a/BMP2 chimera (AB204): a comparison study between AB204 and rhBMP-2.

This study compared osteoinductivity and osteogenic capacity between AB204 and rhBMP-2 using hMSCs in vitro and a beagle's posterolateral spinal fusion model. Cultured hMSCs were treated with AB204 or rhBMP-2 with low to high doses. Three male beagles were performed posterolateral spinal fusion with biphasic calcium phosphate (2 ml) + AB204 or rhBMP-2 (20, 50 or 200 µg). They were euthanized after 8 weeks. The fusion rate and bone formation of spine samples were examined. AB204 had higher alkaline phosphatase activity, mineralization and osteogenic-related gene expression than rhBMP-2. Fusion rates in all rhBMP-2 groups were 0. They were 100% for 50 µg and 200 µg AB204 groups. Therefore, AB204 showed higher osteogenicity than rhBMP-2. It could be a better bone graft substitute.

Recombinant bone morphogenetic protein-2 and platelet-derived growth factor-BB for localized bone regeneration. Histologic and radiographic outcomes of a rabbit study.

OBJECTIVES: Improvement in localized bone regeneration is needed to avoid the use of autogenous tissue. For that purpose, the use biologic mediators was proposed. The aim was to test whether or not one of two biologic mediators, recombinant human bone morphogenetic protein-2 (rhBMP-2) or recombinant platelet-derived growth factor (rhPDGF-BB), is superior to the other and to control groups for localized bone regeneration. MATERIALS AND METHODS: Four cylinders (height: 5 mm; diameter: 7 mm) were screwed on the parietal and frontal bones at the cranium in 12 rabbits. The cylinders either received (i) deproteinized bovine bone mineral (DBBM) mixed rhBMP-2 (DBBM/BMP-2), (ii) DBBM mixed with rhPDGF-BB (DBBM/PDGF), (iii) DBBM (DBBM), and (iv) empty control (control). Rabbits were euthanized at 2 and 8 weeks (n = 6, respectively). Conventional histomorphometric and micro-CT analyses were performed. Parametric linear mixed models were applied for the analyses with Bonferroni correction for the multiple group comparisons. RESULTS: The area of bone regeneration (histology; AAHisto ) at 2 weeks peaked for DBBM (41.91%) with statistically significantly greater values compared to DBBM/PDGF and the control group (P < 0.05). At 8 weeks, mean AAHisto values were 96.29% (DBBM/BMP-2), 46.37% (DBBM/PDFG), 39.66% (DBBM), and 35.98% (control) (DBBM/BMP-2 vs. all groups (P < 0.05)). At 8 weeks, bone regeneration was greatest for DBBM/BMP-2 (35.62%) with statistically significant differences compared to all other groups (P < 0.05). The area of bone regeneration (micro-CT; AAm-CT ) at 2 weeks amounted to 43.87% (DBBM/BMP-2), 42.81% (DBBM/PDFG), 48.71% (DBBM), and 0.96% (control). The control group demonstrated statistically significantly less AAm-CT compared to all groups (P < 0.05). At 8 weeks, mean AAm-CT values were 63.65% (DBBM/BMP-2), 50.21% (DBBM/PDFG), 44.81% (DBBM), and 4.57% (control) (P > 0.05). CONCLUSIONS: The use of rhBMP-2 significantly enhanced bone regeneration compared to all other groups including the group with rhPDGF-BB.

Implant-guided supracrestal alveolar bone growth using scaffolds, BMP-2, and novel scaffold-retaining device.

OBJECTIVE: To evaluate the efficacy of various scaffold systems and a Ti scaffold-retaining device with and without non-glycosylated rhBMP-2 (BMP-2) for increasing the vertical alveolar bone growth in the intra-oral mini-pig model. METHODS: Forty-eight Straumann Bone Level implants with hydrophilic (SLActive) surfaces were partially embedded in mandibles of 12 adult mini-pigs with the shoulder of the implant located 3 mm above the bone crest. Twenty-four implants were placed in conjunction with BMP-2 (50 µg) incorporated within resorbable scaffolds. Twenty-four additional control implants were placed with scaffolds only. Scaffolds were placed around the implant and stabilized with a newly developed Ti "umbrella" scaffold retainer. Scaffolds included (i) HA-coated collagen (Healos); (ii) biphasic HA/ß-TCP crystals (Straumann Bone Ceramic, SBC); and (iii) SBC crystals infused with polyethylene glycol (PEG) hydrogel. Eight test and control pairs for each scaffold group were implanted. At 9 weeks, soft tissue healing was assessed and the extent of new vertical bone was evaluated with microCT and histomorphometry. RESULTS: microCT analysis revealed a mean of 167 ± 47 mm3 new supracrestal mineralized tissue volume formation around the test sites where BMP-2 was released from the scaffold whereas the control group (no BMP-2) showed a significantly lower mineralized tissue volume of 106 ± 55 mm3 . The SBC+BMP-2 group had the highest mineralized tissue volume of 189 ± 36 mm3 . Histomorphometry showed bone-to-implant contact of 54.5% for the test groups and 33.3% for the control groups and new vertical bone growth of 2.2 ± 1.0 and 1.0 ± 0.9 mm, respectively. The SBC+BMP-2 group again demonstrated the best outcome (2.7 ± 0.4 mm). The qualitative scoring of soft tissue dehiscence showed that the presence of BMP-2 yielded far superior outcomes, 0.63 vs. 1.75 for all control implant sites (with scores ranging from 0, reflecting no soft dehiscence, to 4, showing a completely exposed umbrella). CONCLUSION: The release of BMP-2 from a SBC scaffold adjacent to a hydrophilic, rough Ti implant and scaffold retention umbrella consistently regenerated the greatest volume and height of new vertical bone along the length of the implant.

Effect of Oxy133, an osteogenic oxysterol, on new bone formation in rat two-level posterolateral fusion model.

PURPOSE: The aim of our study was to determine the effect of Oxy133 and rhBMP2 on fusion rates and new bone formation in a rat posterolateral fusion (PLF) model. Furthermore, we examined whether Oxy133 could inhibit the adipogenesis that is often present in rhBMP2-induced fusions. METHODS: Sixty-four male Lewis rats underwent two levels PLF (L3-L5). All animals were randomly divided into eight groups based on the test compound that they received: control (DMSO), low-dose rhBMP2 (0.5 µg), high-dose rhBMP2 (5 µg), low-dose Oxy133 (5 mg), high-dose Oxy133 (20 mg), low rhBMP2 + high Oxy133, high rhBMP2 + high Oxy133, and low rhBMP2 + low Oxy133. Fusion rates were assessed 8 weeks after surgery with manual palpation and plain radiographs. Bone parameters were measured using microCT. Histology was used to evaluate adipogenesis. RESULTS: No fusion was observed in the control group. Based on the manual palpation, 100% fusion was observed in all other groups except in the low-dose rhBMP2 group (69%). At 8 weeks based on X-rays, 100% fusion was observed in the following groups: high-dose rhBMP2, low-dose Oxy133, and low rhBMP2 + low Oxy133. In the other groups, the fusion rates were between 95 and 97%, except for the low rhBMP2 group (72%). We observed similar values in BV/TV ratio at L3-4 when Oxy133 groups were compared to rhBMP2 groups alone (44.62% in high-dose Oxy133 vs. 41.47% in high-dose rhBMP2 and 47.18% in low-dose Oxy133 vs. 54.98% in low-dose rhBMP2). Trabecular thickness was slightly lower in Oxy133 groups compared to rhBMP2 when comparing low- and high-dose groups from each group (118.44 µm for high-dose Oxy133 vs. 122.39 µm for high-dose rhBMP2 and 123.51 µm for low-dose Oxy133 vs. 135.74 µm for low-dose rhBMP2). At the same time, trabecular separation was lower in Oxy133 groups compared to rhBMP2 groups. Similar trends in bone parameters were observed at the L4-5 levels. Fusion masses with low- and high-dose Oxy133 had significantly less adipocytes than rhBMP2 groups that showed robust adipocyte formation. CONCLUSION: In our study, both low-dose and high-dose Oxy133 produced solid fusions with bone densities similar or higher than in the BMP2 groups. High-dose Oxy133 group had significantly less adipocytes than high- or low-dose rhBMP2 groups. Furthermore, high-dose Oxy133 was able to significantly inhibit high-dose BMP2-induced adipogenesis when combined together. Consistent with the previous reports, our preliminary findings suggest that Oxy133 has a significant potential as an alternative to rhBMP2 in spine fusion.

Minimally invasive direct pars repair with cannulated screws and recombinant human bone morphogenetic protein: case series and review of the literature.

OBJECTIVE The objective of this study was to describe the use of a minimally invasive surgical treatment of lumbar spondylolysis in athletes by a fluoroscopically guided direct pars screw placement with recombinant human bone morphogenetic protein-2 (rhBMP-2) and to report on clinical and radiographic outcomes. METHODS A retrospective review was conducted of all patients treated surgically for lumbar spondylolysis via a minimally invasive direct pars repair with cannulated screws. Demographic information, clinical features of presentation, perioperative and intraoperative radiographic imaging, and postoperative data were collected. A 1-cm midline incision was performed for the placement of bilateral pars screws utilizing biplanar fluoroscopy, followed by placement of a fully threaded 4.0-mm-diameter titanium cannulated screw. A tubular table-mounted retractor was utilized for direct pars fracture visualization and debridement through a separate incision. The now-visualized pars fracture could then be decorticated, with care taken not to damage the titanium screw when using a high-speed drill. Local bone obtained from the curettage was then placed in the defect with 1.05 mg rhBMP-2 divided equally between the bilateral pars defects. RESULTS Nine patients were identified (mean age 17.7 ± 3.42 years, range 14-25 years; 6 male and 3 female). All patients had bilateral pars fractures of L-4 (n = 4) or L-5 (n = 5). The mean duration of preoperative symptoms was 17.22 ± 13.2 months (range 9-48 months). The mean operative duration was 189 ± 29 minutes (range 151-228 minutes). The mean intraoperative blood loss was 17.5 ± 10 ml (range 10-30 ml). Radiographic follow-up was available in all cases; the mean length of time from surgery to the most recent imaging study was 30.8 ± 23.3 months (range 3-59 months). The mean hospital length of stay was 1.13 ± 0.35 days (range 1-2 days). There were no intraoperative complications. CONCLUSIONS Lumbar spondylolysis treatment with a minimally invasive direct pars repair is a safe and technically feasible option that minimizes muscle and soft-tissue dissection, which may particularly benefit adolescent patients with a desire to return to a high level of physical activity.

Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) with Additional Protein Domain Synthesized in E. coli: In Vivo Osteoinductivity in Experimental Models on Small and Large Laboratory Animals.

Recombinant human bone morphogenetic protein-2 with an additional s-tag domain (s-tag-BMP-2) synthesized in E. coli is characterized by higher solubility and activity than the protein without additional s-tag domain, which increases the yield during purification and simplifies protein introduction into the osteoplastic materials. The high osteoinductivity of the demineralized bone matrix with s-tag-BMP-2 was shown on the model of regeneration of cranial defects of a critical size in mice and on the model of implantation of porous titanium matrix into defects of femoral and tibial bones in rabbits.