Cancer risk after use of recombinant bone morphogenetic protein-2 for spinal arthrodesis

Novel Osteobiologics and Biomaterials in the Treatment of Spinal Disorders

Spinal osteobiologics have evolved substantially in this century after the development of many product categories such as growth factors, allograft, and stem cells. The indications for the use of novel biologics within spine surgery are rapidly expanding as the mechanism of each is elucidated. While the knowledge base of bone morphogenetic protein increases with each subsequent year, the application of new nanotechnology and cell-based strategies are being reported. This review will discuss the most recent data in novel osteobiologics, and where we could use future study.

Comparison of the osteogenesis and fusion rates between activin A/BMP-2 chimera (AB204) and rhBMP-2 in a beagle's posterolateral lumbar spine model

BACKGROUND CONTEXT

Activin A/BMP-2 chimera (AB204) could promote bone healing more effectively than recombinant bone morphogenetic protein 2 (rhBMP-2) with much lower dose in a rodent model, but there is no report about the effectiveness of AB204 in a large animal model.

PURPOSE

The purpose of this study was to compare the osteogenesis and fusion rate between AB204 and rhBMP-2 using biphasic calcium phosphate (BCP) as a carrier in a beagle's posterolateral lumbar fusion model.

STUDY DESIGN

This is a randomized control animal study.

METHODS

Seventeen male beagle dogs were included. Bilateral posterolateral fusion was performed at the L1-L2 and L4-L5 levels. Biphasic calcium phosphate (2 cc), rhBMP-2 (50 µg)+BCP (2 cc), or AB204 (50 µg)+BCP (2 cc) were implanted into the intertransverse space randomly. X-ray was performed at 4 and 8 weeks. After 8 weeks, the animals were sacrificed, and new bone formation and fusion rate were evaluated by manual palpation, computed tomography (CT), and undecalcified histology.

RESULTS

The AB204 group showed significantly higher fusion rate (90%) than the rhBMP-2 group (15%) or the Osteon group (6.3%) by manual palpation. On x-ray and CT assessment, fusion rate and the volume of newly formed bone were also significantly higher in AB204 group than other groups. In contrast, more osteolysis was found in rhBMP-2 group (40%) than in AB204 group (10%) on CT study. In histologic results, new bone formation was sufficient between transverse processes in AB204 group, and obvious trabeculation and bone remodeling were observed. But in rhBMP-2 group, new bone formation was less than AB204 group and osteolysis was observed between the intertransverse spaces.

CONCLUSIONS

A low dose of AB204 with BCP as a carrier significantly promotes the fusion rate in a large animal model when compared with the rhBMP-2. These findings demonstrate that AB204 could be an alternative to rhBMP-2 to improve fusion rate.

Trends Analysis of rhBMP Utilization in Single-Level Posterior Lumbar Interbody Fusion in the United States

STUDY DESIGN

Retrospective study.

OBJECTIVES

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely used in spinal fusion surgery, but there is little information on rhBMP-2 utilization in single-level posterior lumbar interbody fusion (PLIF). The purpose of our study was to evaluate the trends and demographics of rhBMP-2 utilization in single-level PLIF.

METHODS

Patients who underwent single-level PLIF from 2005 to 2011 were identified by searching ICD-9 diagnosis and procedure codes in the PearlDiver Patient Records Database, a national database of orthopedic insurance records. The year of procedure, age, gender, and region of the United States were recorded for each patient. Results were reported for each variable as the incidence of procedures identified per 100 000 patients searched in the database.

RESULTS

A total of 2735 patients had single-level PLIF. The average rate of single-level PLIF with rhBMP-2 maintained at a relatively stable level (28% to 31%) from 2005 to 2009, but decreased in 2010 (9.9%) and 2011 (11.8%). The overall incidence of single-level PLIF without rhBMP-2 (0.68 cases per 100 000 patients) was statistically higher (P < .01) compared to single-level PLIF with rhBMP-2 (0.21 cases per 100 000 patients). The average rate of single-level PLIF with rhBMP-2 utilization was the highest in West (30.1%), followed by Midwest (26.9%), South (20.5%), and Northeast (17.8%). The highest incidence of single-level PLIF with rhBMP-2 was observed in the age group <65 years (0.3 per 100 000 patients).

CONCLUSIONS

To our knowledge, this is the first study to report on the demographics associated with rhBMP-2 use in single-level PLIF. There was a 3-fold increase in the rate of PLIF without rhBMP-2 compared to PLIF with rhBMP-2, with both procedures being mainly done in patients less than 65 years of age.

Bone morphogenetic protein use in spine surgery in the United States: how have we responded to the warnings?

BACKGROUND CONTEXT

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely adopted as a fusion adjunct in spine surgery since its approval in 2002. A number of concerns regarding adverse effects and potentially devastating complications of rhBMP-2 use led to a Food and Drug Administration (FDA) advisory issued in 2008 cautioning its use, and a separate warning about its potential complications was published by The Spine Journal in 2011.

PURPOSE

To compare trends of rhBMP-2 use in spine surgery after the FDA advisory in 2008 and The Spine Journal warning in 2011.

STUDY DESIGN

Retrospective cross-sectional study using a national database.

PATIENT SAMPLE

All patients from 2002 to 2013 who underwent spinal fusion surgery at an institution participating in the Nationwide Inpatient Sample (NIS).

OUTCOME MEASURES

Proportion of spinal fusion surgeries using rhBMP-2.

METHODS

We queried the NIS from 2002 to 2013 and used International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes to identify spinal fusion procedures and those that used rhBMP-2. Procedures were subdivided into primary and revision fusions, and by region of the spine. Cervical and lumbosacral fusions were further stratified into anterior and posterior approaches. The percentage of cases using BMP was plotted across time. A linear regression was fit to the data from quarter 3 of 2008 (FDA advisory) through quarter 1 of 2011, and a separate regression was fit to the data from quarter 2 of 2011 (The Spine Journal warning) onward. The slopes of these regression lines were statistically compared to determine differences in trends. No funding was received to conduct this study, and no authors had any relevant conflicts of interest.

RESULTS

A total of 4,167,079 patients in the NIS underwent spinal fusion between 2002 and 2013. We found a greater decrease in rhBMP-2 use after The Spine Journal warning compared with the FDA advisory for all fusion procedures (p=.006), primary fusions (p=.006), and revision fusions (p=.004). Lumbosacral procedures also experienced a larger decline in rhBMP-2 use after The Spine Journal article as compared with the FDA warning (p=.0008). This pattern was observed for both anterior and posterior lumbosacral fusions (p≤.0001 for both). Anterior cervical fusion was the only procedure that demonstrated a decline in rhBMP-2 use after the FDA advisory that was statistically greater than after The Spine Journal article (p=.02).

CONCLUSIONS

Warnings sanctioned through the spine literature may have a greater influence on practice of the spine surgery community as compared with advisories issued by the FDA.Comprehensive guidelines regarding safe and effective use of rhBMP-2 must be established.

Use of recombinant human bone morphogenetic protein-2 in spine surgery

Bone morphogenetic proteins are osteoinductive factors which have gained popularity in orthopaedic surgery and especially in spine surgery. The use of recombinant human bone morphogenetic protein-2 has been officially approved by the United States Food and Drug Administration only for single level anterior lumbar interbody fusion, nevertheless it is widely used by many surgeons with off-label indications. Despite advantages in bone formation, its use still remains a controversial issue and several complications have been described by authors who oppose their wide use.

Orthobiologics in Pediatric Orthopedics

Orthobiologics are biologic devices or products used in orthopedic surgery to augment or enhance bone formation. The use of orthobiologics in pediatric orthopedics is less frequent than in other orthopedic subspecialties, mainly due to the naturally abundant healing potential and bone formation in children compared with adults. However, orthobiologics are used in certain situations in pediatric orthopedics, particularly in spine and foot surgery. Other uses have been reported in conjunction with specific procedures involving the tibia and pelvis. The use of bioabsorable implants to stabilize children's fractures is an emerging concept but has limited supporting data.

Is the Cage an Additional Hardware in Lumbar Interbody Fusion for Low Grade Spondylolisthesis? A Prospective Study

INTRODUCTION

Lumbar interbody fusion has become the standard of care for the management of lumbar instability, where fusion is achieved using bone grafts, cages, etc.

AIM

The aim of the study was to compare the outcomes of the interbody fusion using interbody cage technique and stand alone local bone graft technique.

MATERIALS AND METHODS

A total of 30 patients, operated for single level instability with low grade lytic and degenerative spondylolisthesis of L4-5/L5-S1, were selected and grouped into two groups: Group I (stand alone grafts) and Group II (interbody cage and graft) based on computer generated random numbers. All patients who underwent interbody fusion through conventional open posterior approach were included in the study. Data regarding the time taken for interbody fusion, formaninal height maintenance, disc height restoration, translation, functional scores (VAS,ODI) and operative complications were analysed using in both the groups was collected and a student's-t test was performed to evaluate the difference.

RESULTS

The mean age of patients in Group I was 46.7 years whereas, the mean age of patients in Group II was 43.5 years with mean age of 46.7 years and 43.5 years respectively. Interbody fusion, was achieved in seven and eight months in Group I and II respectively (p>0.05). The clinical results of both groups were comparable and there was no significant difference between the two groups in VAS score (p-0.147) and ODI score (p-0.983). Radiological parameters were also comparable and there was no significant difference between the postoperative measurements of the two groups (p=0.348 for translation, p=0.310 for intervertebral disc height and p=0.135 for foraminal height). One patient in Group I had transient foot drop which recovered, while one in Group II had infection, wound was managed with wound wash and antibiotics and another patient in Group II had pseudoarthrosis.

CONCLUSION

Lumbar interbody fusion with standalone local bone grafts is sufficient in single level low grade spondylolisthesis treated by conventional open surgery.

Neuroforaminal Bone Growth Following Minimally Invasive Transforaminal Lumbar Interbody Fusion With BMP: A Computed Tomographic Analysis

STUDY DESIGN

Computed tomographic analysis.

OBJECTIVE

To identify radiographic patterns of symptomatic neuroforaminal bone growth (NFB) in patients who have undergone a single-level minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) augmented with bone morphogenetic proteins (BMP) utilizing computed tomography (CT).

SUMMARY OF BACKGROUND DATA

BMP induces osteoblast differentiation leading to new bone formation. The association of BMP utilization and heterotopic bone formation after an MIS-TLIF has been described. However, studies have been limited in their patient population and details regarding diagnosis and treatment of NFB.

MATERIALS AND METHODS

Postoperative CT scans of the symptomatic and asymptomatic patients were analyzed to identify patterns of heterotopic bone growth on axial and sagittal views. The area of bone growth at the disk level, lateral recess, adjacent foramen, and retrovertebral area were measured. Mann-Whitney U test was used to compare the areas of bone growth between cohorts.

RESULTS

Postoperative CT images between 18 symptomatic and 13 asymptomatic patients were compared. On axial views, the symptomatic patients demonstrated greater areas of bone growth at the disk level (164.0±92.4 vs. 77.0±104.9 mm), and lateral recess (69.6±70.5 and 5.9±12.5 mm) as well as in the total cross-sectional area (290.3±162.1 vs. 119.4±115.6 mm). On sagittal imaging, the mean bone growth at the subarticular level (148.7±185.1 vs. 35.8±37.4 mm) and the total cross-sectional area (298.4±324.4 vs. 85.8±76.3 mm) were greater in symptomatic patients (P<0.01). Amount of BMP utilized and operative levels were no different between cohorts.

CONCLUSIONS

The findings of the present study suggest that an anatomic association exists between recalcitrant postoperative radiculopathy and NFB following an MIS-TLIF with BMP. Increased total bone growth as measured on serial axial and sagittal sections was associated with postoperative radiculopathy. The association between radiculopathy and the extension of BMP-induced bone growth toward the traversing nerve root appeared the most significant.

Heterotopic ossification related to the use of recombinant human BMP-2 in osteonecrosis of femoral head

Despite the wide use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in bone defect, its application in treating osteonecrosis of femoral head (ONFH) is yet to be elucidated. The heterotopic ossification (HO) after rhBMP-2 usage in some orthopedic surgeries has been reported previously; however, only a few studies describe this complication in the treatment of ONFH.The present study investigated whether the rhBMP-2 application would increase the risk of HO formation in selected ONFH patients with nonvascularized bone grafting surgery and enhance the surgical results of nonvascularized bone grafting as compared to patients who did not receive intraoperative rhBMP-2.A retrospective analysis was performed on 94 patients (141 hips) who, with Association Research Circulation Osseous (ARCO) stages IIb, IIc, and IIIa ONFH, underwent nonvascularized bone grafting surgery. The first 46 patients (66 hips) received intraoperative rhBMP-2. The postoperative radiographic results (X-ray and CT scan) and Harris hip score (HHS) were reviewed in each patient to record the incidence of HO formation and evaluate the clinical efficacy of rhBMP-2, respectively.HO formation frequently occurred in patients receiving intraoperative rhBMP-2 (8/66 hips) than those not receiving the protein (1/75 hips) (P = .02). HHS improved from preoperatively at the final follow-up (P < .01) in the BMP-positive group, with a survival rate of 83.3%. In the BMP-negative group, the HHS improved from preoperatively at the end of the follow-up (P < .01), and the survival rate was 72.0%.rhBMP-2 has osteoinductive property and might serve as an adjuvant therapy in the surgical treatment of ONFH. However, the incidence of HO formation might increase when used in high doses.

Bone Morphogenetic Protein: Is There Still a Role in Orthopedic Trauma in 2017?

Approximately 10 years ago bone morphogenic protein (BMP) was seen as a miraculous adjuvant to assist with bone growth. However, in the face of an increasing number of complications and a lack of understanding its long-term effects, it is unclear what role BMP has in the current treatment of orthopedic trauma patients. This article reviews the current recommendations, trends, and associated complications of BMP use in fracture care.

The Good the Bad and the Ugly of Glycosaminoglycans in Tissue Engineering Applications

High sulfation, low cost, and the status of heparin as an already FDA- and EMA- approved product, mean that its inclusion in tissue engineering (TE) strategies is becoming increasingly popular. However, the use of heparin may represent a naïve approach. This is because tissue formation is a highly orchestrated process, involving the temporal expression of numerous growth factors and complex signaling networks. While heparin may enhance the retention and activity of certain growth factors under particular conditions, its binding 'promiscuity' means that it may also inhibit other factors that, for example, play an important role in tissue maintenance and repair. Within this review we focus on articular cartilage, highlighting the complexities and highly regulated processes that are involved in its formation, and the challenges that exist in trying to effectively engineer this tissue. Here we discuss the opportunities that glycosaminoglycans (GAGs) may provide in advancing this important area of regenerative medicine, placing emphasis on the need to move away from the common use of heparin, and instead focus research towards the utility of specific GAG preparations that are able to modulate the activity of growth factors in a more controlled and defined manner, with less off-target effects.

Enhancing Vascularization through the Controlled Release of Platelet-Derived Growth Factor-BB

Using delivery systems to control the in vivo release of growth factors (GFs) for tissue engineering applications is extremely desirable as the clinical use of GFs is limited by their fast in vivo turnover. Hence, the development of effective platforms that are able to finely control the release of GFs in vivo remains a challenge. Herein, we investigated the ability of multiscale microspheres, composed by a nanostructured silicon multistage vector (MSV) core and a poly(dl-lactide-co-glycolide) acid (PLGA) forming outer shell (PLGA-MSV), to release functional platelet-derived growth factor-BB (PDGF-BB) to induce in vivo localized neovascularization. The in vitro release of PDGF-BB was assessed by enzyme-linked immunosorbent assay (ELISA) over 2 weeks and showed a sustained, zero-order release kinetics. The ability to promote in vivo localized neovascularization was investigated in a subcutaneous injection model in BALB/c mice and followed by intravital microscopy up to 2 weeks. Fully functional newly formed vessels were found within the area where PLGA-MSVs were localized and covered 3.0 ± 0.9 and 19 ± 5.1% at 7 and 14 days, respectively, showing a 6-fold increase in 1 week. The distribution of CD31⁺ and α-SMA⁺ cells was detected by immunofluorescence on harvested tissues. CD31 was significantly more expressed (4-fold increase) compared to the untreated control. Finally, the level of up-regulation of angiogenesis-associated genes (Vegfa, Vwf, and Col3a1) was assessed by q-PCR, resulting in a significantly higher expression where PLGA-MSVs were localized (Vegfa: 2.32 ± 0.50 at 7 days and 4.37 ± 0.75 at 14 days; Vwf: 4.13 ± 0.82 and 7.74 ± 0.91; Col3a1: 5.43 ± 0.37 and 6.66 ± 0.89). Altogether, our data supported the conclusion that the localized delivery of PDGF-BB from PLGA-MSVs induced the localized de novo formation of fully functional vessels in vivo. With this study, we demonstrated that PLGA-MSV holds promise for accomplishing the controlled localized in vivo release of GFs for the design of innovative tissue engineering strategies.

Teriparatide attenuates scarring around murine cranial bone allograft via modulation of angiogenesis

Nearly all bone fractures in humans can deteriorate into a non-union fracture, often due to formation of fibrotic tissue. Cranial allogeneic bone grafts present a striking example: although seemingly attractive for craniofacial reconstructions, they often fail due to fibrosis at the host-graft junction, which physically prevents the desired bridging of bone between the host and graft and revitalization of the latter. In the present study we show that intermittent treatment with recombinant parathyroid hormone-analogue (teriparatide) modulates neovascularization feeding in the graft surroundings, consequently reducing fibrosis and scar tissue formation and facilitates osteogenesis. Longitudinal inspection of the vascular tree feeding the allograft has revealed that teriparatide induces formation of small-diameter vessels in the 1st week after surgery; by the 2nd week, abundant formation of small-diameter blood vessels was detected in untreated control animals, but far less in teriparatide-treated mice, although in total, more blood capillaries were detected in the animals that were given teriparatide. By that time point we observed expression of the profibrogenic mediator TGF-β in untreated animals, but negligible expression in the teriparatide-treated mice. To evaluate the formation of scar tissue, we utilized a magnetization transfer contrast MRI protocol to differentiate osteoid tissue from scar tissue, based on the characterization of collagen fibers. Using this method we found that significantly more bone matrix was formed in animals given teriparatide than in control animals. Altogether, our findings show how teriparatide diminishes scarring, ultimately leading to superior bone graft integration.

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

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

Core decompression and biotechnologies in the treatment of avascular necrosis of the femoral head

Avascular necrosis (AVN) of the femoral head (FH) causes 5% to 12% of total hip arthroplasties (THA). It especially affects active male adults between the third and fifth decades of life. The exact worldwide incidence is unknown. There are only few data related to each country, but most of it relates to the United States.Non-surgical management has a very limited role in the treatment of AVN of the FH and only in its earliest stages. Core decompression (CD) of the hip is the most common procedure used to treat the early stages of AVN of the FH. Recently, surgeons have considered combining CD with autologous bone-marrow cells, demineralised bone matrix or bone morphogenetic proteins or methods of angiogenic potential to enhance bone repair in the FH.Manuscripts were deemed eligible for our review if they evaluated treatment of early stage AVN of the FH with biotechnology implanted via CD. After application of eligibility criteria, we selected 19 reports for final analysis.The principal results showed that only by correctly mastering the therapeutic principles and adopting proper methods specifically oriented to different stages can the best therapeutic effect be achieved. Combining CD with biotechnology could result in a novel long-lasting hip- preserving treatment option.Furthermore, more refined clinical studies are needed to establish the effectiveness of biotechnology treatments in AVN of the FH. Cite this article: EFORT Open Rev 2017;2:41-50. DOI: 10.1302/2058-5241.2.150006.

Complications Associated With Bone Morphogenetic Protein in the Lumbar Spine

Complications associated with the use of recombinant human bone morphogenetic protein in the lumbar spine include retrograde ejaculation, ectopic bone formation, vertebral osteolysis and subsidence, postoperative radiculitis, and hematoma and seroma. These complications are controversial and remain widely debated. This article discusses the reported complications and possible implications for the practicing spine surgeon. Understanding the complications associated with the use of recombinant human bone morphogenetic protein and the associated controversies allows for informed decision making by both the patient and the surgeon. [Orthopedics. 2017; 40(2):e229-e237.].

Nano-Hydroxyapatite Bone Substitute Functionalized with Bone Active Molecules for Enhanced Cranial Bone Regeneration

The aim of this study was to synthesize and characterize a nano-hydroxyapatite (nHAP) and calcium sulfate bone substitute (NC) for cranioplasty. The NC was functionalized with low concentrations of bone morphogenetic protein-2 (BMP-2) and zoledronic acid (ZA) and characterized both in vitro and in vivo. In vitro studies included MTT, ALP assays, and fluorescent staining of Saos-2 (human osteoblasts) and MC3T3-E1 (murine preosteoblasts) cells cultured on NC. An in vivo study divided 20 male Wistar rats into four groups: control (defect only), NC, NC + ZA, and NC + ZA + rhBMP-2. The materials were implanted in an 8.5 mm critical size defect in the calvarium for 12 weeks. Micro-CT quantitative analysis was carried out in vivo at 8 weeks and ex vivo after 12 weeks. Mineralization was highest in the NC + ZA + rhBMP-2 group (13.0 ± 2.8 mm³) compared to the NC + ZA group (9.0 ± 3.2 mm³), NC group (6.4 ± 1.9 mm³), and control group (3.4 ± 1.0 mm³) after 12 weeks. Histological and spectroscopic analysis of the defect site provided a qualitative confirmation of neo-bone, which was in agreement with the micro-CT results. In conclusion, NC can be used as a carrier for bioactive molecules, and functionalization with rhBMP-2 and ZA in low doses enhances bone regeneration.

Encapsulation of Adenovirus BMP2-Transduced Cells with PEGDA Hydrogels Allows Bone Formation in the Presence of Immune Response

Gene therapy approaches have been difficult to implement due to pre-existing immunity against the virus used for delivery. To circumvent this problem, a cell-based approach was developed that avoided the use of free virus within the animal. However, even cells transduced in vitro with E1- to E3-deleted adenovirus encoding bone morphogenetic protein 2 (AdBMP2) resulted in the production of virus-neutralizing antibodies in mice. Furthermore, when mice received an intramuscular injection of nonencoding adenovirus (AdEmpty)-transduced cells, AdBMP2-transduced cells were unable to launch bone formation when an intramuscular injection of these BMP2-producing cells was delivered 1 week later. This phenomenon was not observed in NOD/SCID mice, and could be overcome in C57BL/6 mice by encapsulating the adenovirus-transduced cells in a nondegradable hydrogel poly(ethylene glycol) diacrylate (PEGDA). Data collectively suggest that PEGDA hydrogel encapsulation of AdBMP2-transduced cells prevents pre-existing immunity from suppressing BMP2-induced bone formation.

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

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

Bone morphogenetic protein-2 and tumor growth: Diverse effects and possibilities for therapy

Concern regarding safety with respect to the clinical use of human bone morphogenetic protein-2 (BMP-2) has become an increasingly controversial topic. The role of BMP-2 in carcinogenesis is of particular concern. Although there have been many studies of this topic, the results have been contradictory and confusing. We conducted a systematic review of articles that are relevant to the relationship or effect of BMP-2 on all types of tumors and a total of 97 articles were included. Studies reported in these articles were classified into three major types: "expression studies", "in vitro studies", and "in vivo studies". An obvious pattern was that those works that hypothesize an inhibitory effect for BMP-2 most often examined only the proliferative properties of the tumor cells. This subset of studies also contained an extraordinary number of contradictory findings which made drawing a reliable general conclusion impossible. In general, we support a pro-tumorigenesis role for BMP-2 based on the data from these in vitro cell studies and in vivo animal studies, however, more clinical studies should be carried out to help make a firm conclusion.

A Comparative Study of the Bone Regenerative Effect of Chemically Modified RNA Encoding BMP-2 or BMP-9

Employing cost-effective biomaterials to deliver chemically modified ribonucleic acid (cmRNA) in a controlled manner addresses the high cost, safety concerns, and lower transfection efficiency that exist with protein and gene therapeutic approaches. By eliminating the need for nuclear entry, cmRNA therapeutics can potentially overcome the lower transfection efficiencies associated with non-viral gene delivery systems. Here, we investigated the osteogenic potential of cmRNA-encoding BMP-9, in comparison to cmRNA-encoding BMP-2. Polyethylenimine (PEI) was used as a vector to increase in vitro transfection efficacy. Complexes of PEI-cmRNA (encoding BMP-2 or BMP-9) were fabricated at an amine (N) to phosphate (P) ratio of 10 and characterized for transfection efficacy in vitro using human bone marrow stromal cells (BMSCs). The osteogenic potential of BMSCs treated with these complexes was determined by evaluating the expression of bone-specific genes as well as through the detection of bone matrix deposition. It was found that alkaline phosphatase (ALP) expression 3 days post transfection in the group treated with BMP-9-cmRNA was significantly higher than that in the group that received BMP-2-cmRNA treatment. Alizarin red staining and atomic absorption spectroscopy demonstrated enhanced osteogenic differentiation as evidenced by increased bone matrix production by the BMSCs treated with BMP-9-cmRNA when compared to cells treated with BMP-2-cmRNA. In vivo studies showed increased bone formation in calvarial defects treated with the BMP-9-cmRNA and BMP-2-cmRNA collagen scaffolds when compared to empty defects. The connectivity density of the regenerated bone was higher (2-fold-higher) in the group that received BMP-9-cmRNA compared to BMP-2-cmRNA. Together, these findings suggest that cmRNA-activated matrix encoding osteogenic molecules can provide a powerful strategy for bone regeneration with significant clinical translational potential.

Growth Differentiation Factor 5-Mediated Enhancement of Chondrocyte Phenotype Is Inhibited by Heparin: Implications for the Use of Heparin in the Clinic and in Tissue Engineering Applications

The highly sulfated glycosaminoglycan (GAG) heparin is widely used in the clinic as an anticoagulant, and researchers are now using it to enhance stem cell expansion/differentiation protocols, as well as to improve the delivery of growth factors for tissue engineering (TE) strategies. Growth differentiation factor 5 (GDF5) belongs to the bone morphogenetic protein family of proteins and is vital for skeletal formation; however, its interaction with heparin and heparan sulfate (HS) has not been studied. We identify GDF5 as a novel heparin/HS binding protein and show that HS proteoglycans are vital in localizing GDF5 to the cell surface. Clinically relevant doses of heparin (≥10 nM), but not equivalent concentrations of HS, were found to inhibit GDF5's biological activity in both human mesenchymal stem/stromal cell-derived chondrocyte pellet cultures and the skeletal cell line ATDC5. We also found that heparin inhibited both GDF5 binding to cell surface HS and GDF5-induced induction of Smad 1/5/8 signaling. Furthermore, GDF5 significantly increased aggrecan gene expression in chondrocyte pellet cultures, without affecting collagen type X expression, making it a promising target for the TE of articular cartilage. Importantly, this study may explain the variable (and disappointing) results seen with heparin-loaded biomaterials for skeletal TE and the adverse skeletal effects reported in the clinic following long-term heparin treatment. Our results caution the use of heparin in the clinic and in TE applications, and prompt the transition to using more specific GAGs (e.g., HS derivatives), with better-defined structures and fewer off-target effects.

Comparison of a calcium phosphate bone substitute with recombinant human bone morphogenetic protein-2: a prospective study of fusion rates, clinical outcomes and complications with 24-month follow-up

PURPOSE

Recombinant human bone morphogenetic protein-2 (rhBMP-2) generally provides high rates of clinical improvement and fusion. However, rhBMP-2 has been associated with adverse effects. Recently, a beta tricalcium phosphate (β-TCP) bone substitute has been developed. The aim of this study was to determine the fusion rates and clinical outcomes of patients treated with β-TCP compared to rhBMP-2.

METHODS

One hundred and thirty-five consecutive patients who underwent lateral lumbar interbody fusion with β-TCP (n = 25) or rhBMP-2 (n = 110) in the interbody cage were included in the study. The 25 β-TCP patients were a group of consecutive patients from numbers 46 to 70. Clinical outcomes included back and leg pain, Oswestry Disability Index (ODI), and SF-36 physical and mental component scores (PCS and MCS). CT scans were performed at 6, 12, 18, and 24 months until confirmation of solid interbody fusion, with no further scans performed once fusion was achieved. Targeted CT at the operative level(s) was performed to reduce radiation exposure.

RESULTS

At 24 months there was no significant difference between clinical outcomes of the β-TCP or rhBMP-2 patients, with improvements in back pain (46% and 49%; P = 0.98), leg pain (31 and 52%; P = 0.14), ODI (38 and 41%; P = 0.81), SF-36 PCS (37 and 38%; P = 0.87), and SF-36 MCS (8 and 8%; P = 0.93). The fusion rate was significantly higher for rhBMP-2 with 96% compared to 80% for β-TCP (P = 0.01). Separating patients into those with a standalone cage and those with supplemental posterior instrumentation, there was no significant difference between instrumented fusion rates of the β-TCP and rhBMP-2 patients at 6 (P = 0.44), 12 (P = 0.49), 18 (P = 0.31) or 24 (P = 0.14) months. For standalone patients there was a significant difference at 6 (P = 0.01), 12 (P = 0.008) and 18 months (P = 0.004) with higher fusion rates in the rhBMP-2 group; however, by 24 months this was not significant (P = 0.18).

CONCLUSIONS

Comparable clinical outcomes and complication rates suggest that β-TCP is a viable alternative to rhBMP-2. The difference in fusion rates for the standalone patients suggests that β-TCP may require supplemental posterior instrumentation to enhance fusion.

Evaluation of complications associated with off-label use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in pediatric orthopaedics

The off-label use of recombinant human bone morphogenetic protein-2 to promote bone healing in adults has significantly increased in recent years, while reports of recombinant human bone morphogenetic protein-2 application in children and adolescents are very rare. The aim of this study was to evaluate the safety of single and repetitive recombinant human bone morphogenetic protein-2 use in pediatric orthoapedics. Therefore we reviewed the medical records of 39 patients who had been treated with recombinant human bone morphogenetic protein-2 at our institution. Their mean age was 10.9 years. Recombinant human bone morphogenetic protein-2 was used in 17 patients for spine fusion, in 11 patients for the treatment of congenital pseudarthrosis of the tibia or tibial nonunion, in 5 patients for the management of femoral nonunion, in 5 patients for nonunions at other locations, and in 1 case for tibial shortening. Special attention was paid to identify all adverse events that may be attributed to recombinant human bone morphogenetic protein-2 use, including local inflammatory reactions, allergic reactions, systemic toxicity, excessive wound swelling, hematoma, compartment syndrome, infection, heterotopic ossification, excessive bone growth, carcinogenicity, and the consequences of repeated applications of recombinant human bone morphogenetic protein-2. Follow-up was a mean of 39 months. Forty-six operations with application of rhBMP-2 were performed. Complications that may be due to application of recombinant human bone morphogenetic protein-2 were seen after 18 operations including swelling, increase in temperature, wound secretion, redness and hyperthermia. We consider the three cases of necessary revisions, one due to hematoma, one due to development of a compartment syndrome, and one due to deep infection, to be the only complications related to the use of recombinant human bone morphogenetic protein-2. In conclusion, we found few complications attributable to application of recombinant human bone morphogenetic protein-2 in pediatric patients.

Targeting Strategies for Renal Cell Carcinoma: From Renal Cancer Cells to Renal Cancer Stem Cells

Renal cell carcinoma (RCC) is a common form of urologic tumor that originates from the highly heterogeneous epithelium of renal tubules. Over the last decade, targeting therapies to renal cancer cells have transformed clinical care for RCC. Recently, it was proposed that renal cancer stem cells (CSCs) isolated from renal carcinomas were responsible for driving tumor growth and resistance to conventional chemotherapy and radiotherapy, according to the theory of CSCs; this has provided the rationale for therapies targeting this aggressive cell population. Precise identification of renal CSC populations and the complete cell hierarchy will accurately inform characterization of disease subtypes. This will ultimately contribute to more personalized and targeted therapies. Here, we summarize potential targeting strategies for renal cancer cells and renal CSCs, including tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors (mTOR), interleukins, CSC marker inhibitors, bone morphogenetic protein-2, antibody drug conjugates, and nanomedicine. In conclusion, targeting therapies for RCC represent new directions for exploration and clinical investigation and they plant a seed of hope for advanced clinical care.

Change in Off-Label Use of Bone Morphogenetic Protein in Spine Surgery and Associations with Adverse Outcome

Study Design Retrospective cohort study. Objective The U.S. Food and Drug Administration issued a warning in 2008 against off-label bone morphogenetic protein (BMP-2) use. We aimed to determine (off-label) BMP-2 use in two periods and associations with complications. Methods We included 340,393 patients undergoing spinal fusions from the Premier Perspective database (2006 to 2012). BMP-2 use was determined from billing in 2006 to 2008 versus 2009 to 2012. Outcomes included revisions, length of hospital stay (LOHS), and cost of hospital stay (COH). Multilevel regressions measured associations between BMP-2 and outcomes; odds ratios (ORs) and 95% confidence intervals (CIs) are reported. Results BMP-2 use decreased from 18.7% in 2006 to 11.5% in 2012. Off-label use remains but is decreasing, particularly for cervical anterior (5.1 versus 2.0%) and cervical posterior procedures (15.3 versus 8.5%; both p < 0.01 comparing 2006 to 2008 with 2009 to 2012). BMP-2 remains associated with increased LOHS (median 2 versus 3 days; both periods) and COH (median $15,455 versus $27,881 in 2006 to 2008; $17,007 versus $30,331 in 2009 to 2012). Adjusted ORs for the association between BMP-2 and adverse outcomes were generally lower in 2009 to 2012 compared with 2006 to 2008. Most notably, we demonstrate lower ORs for revision after cervical fusions in 2009 to 2012 (OR 1.67, CI 1.01 to 2.78) compared with 2006 to 2008 (OR 2.43, CI 1.66 to 3.54). Conclusions Using a previously untapped data source, we show decreased (off-label) BMP-2 use in spinal fusions, particularly in cervical fusions. Although there was a tendency of decreased odds in 2009 to 2012, higher resource utilization and odds for complications remain in patients using BMP-2. A national registry or prospective observational studies will benefit the ongoing discussion.

Porous Alpha-Tricalcium Phosphate with Immobilized Basic Fibroblast Growth Factor Enhances Bone Regeneration in a Canine Mandibular Bone Defect Model

The effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on bone regeneration was evaluated in a canine mandibular bone defect model. Identical bone defects were made in the canine mandible; six defects in each animal were filled with porous α-TCP with bFGF bound via heparin (bFGF group), whereas the other was filled with unmodified porous α-TCP (control group). Micro-computed tomography and histological evaluation were performed two, four and eight weeks after implantation. The bone mineral density of the bFGF group was higher than that of the control group at each time point (p < 0.05), and the bone mineral content of the bFGF group was higher than that of the control group at four and eight weeks (p < 0.05). Histological evaluation two weeks after implantation revealed that the porous α-TCP had degraded and bone had formed on the surface of α-TCP particles in the bFGF group. At eight weeks, continuous cortical bone with a Haversian structure covered the top of bone defects in the bFGF group. These findings demonstrate that porous α-TCP with immobilized bFGF can promote bone regeneration.

Bone morphogenetic protein in pediatric spine fusion surgery

BACKGROUND

There is a paucity of literature describing the use of bone graft substitutes to achieve fusion in the pediatric spine. Outcomes and complications involving the off-label use of bone morphogenetic protein 2 (BMP-2) in the pediatric spine are not clearly defined. The purpose of this study is to review the existing literature with respect to reported outcomes and complications involving the use of low-dose BMP-2 in pediatric patients.

METHODS

A Medline and PubMed literature search was conducted using the words bone morphogenetic protein, BMP, rh-BMP-2, bone graft substitutes, and pediatric spine.

RESULTS

To date, there are few published reports on this topic. Complications and appropriate BMP-2 dosage application in the pediatric spine remain unknown.

CONCLUSIONS

This report describes the potential for BMP-2 to achieve successful arthrodesis of the spine in pediatric patients. Usage should be judicious as complications and long-term outcomes of pediatric BMP-2 usage remain undefined in the existing literature.

Heparin-Based Polyelectrolyte Complex Enhances the Therapeutic Efficacy of Bone Morphogenetic Protein-2 for Posterolateral Fusion in a Large Animal Model

STUDY DESIGN

The study was based on porcine posterolateral fusion model.

OBJECTIVE

The study aims to prove that polyelectrolyte complex (PEC) carrier could enhance the efficacy and safety profile of bone morphogenetic protein-2 (BMP-2).

SUMMARY OF BACKGROUND DATA

BMP-2 was introduced to enhance posterolateral fusion; however, extremely high doses of this molecule were often used which contributed to various complications. This was attributed to the poor modulation capacity of the traditional carrier absorbable collagen sponge (ACS). To reduce the efficacious dose of BMP-2 and its associated complications, heparin-based PEC was introduced.

METHODS

L3/L4 and L5/L6 two-level posterolateral spinal fusion was performed on six pigs using two doses of BMP-2 with PEC or ACS: (1) PEC with 800 μg BMP-2 (n = 2); (2) PEC with 400 μg BMP-2 (n = 2); (3) ACS with 800 μg BMP-2 (n = 1); (4) ACS with 400 μg of BMP-2 (n = 1). The construct was loaded into a rigid bioabsorbable cage for implantation. Fusion rate and quality were assessed 2 months after operation.

RESULTS

Manual palpation revealed successful fusion in all groups. Radiological fusion score of PEC groups was, however, higher than that of ACS groups. The newly formed bone in PEC groups appeared to be well integrated into the native bone with no overgrowth into the adjacent structure. On comparison, in ACS groups, large gaps were observed between the newly formed bone and the fusion bed with heterotopic ossification into the psoas muscle. The microarchitecture on the newly formed bone in PEC groups was superior to that in ACS groups, which was demonstrated by higher three-dimensional parameters.

CONCLUSION

The present study demonstrated that BMP-2 delivered by PEC induced successful posterolateral fusion in porcine model. The efficacy of BMP-2 was improved and bony overgrowth was reduced. The microarchitecture of BMP-2-induced bone tissue was also enhanced by PEC.

LEVEL OF EVIDENCE

N/A.

Bone Morphogenetic Protein Use and Cancer Risk Among Patients Undergoing Lumbar Arthrodesis: A Case-Cohort Study Using the SEER-Medicare Database

BACKGROUND

Recombinant bone morphogenetic proteins (BMPs) are growth factors utilized in lumbar arthrodeses. Limited data from randomized trials suggest that BMP may increase cancer risk. We sought to evaluate cancer risk and mortality following the use of BMP in lumbar arthrodesis.

METHODS

Within the linked Surveillance, Epidemiology, and End Results (SEER) Program-Medicare cohort, we conducted a case-cohort study of 7,278 individuals who were ≥65 years of age and had undergone a lumbar arthrodesis from 2004 to 2011. Of these patients, 3,627 were individuals in a 5% random subcohort of Medicare enrollees in SEER areas including 191 who developed cancer, and there were 3,651 individuals outside the subcohort who developed cancer. Weighted Cox proportional-hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for cancer on the basis of exposure to BMP.

RESULTS

In the SEER-Medicare subcohort, 30.7% of individuals who underwent a lumbar arthrodesis received BMP. BMP was not associated with overall cancer risk in univariate analyses (HR, 0.92 [95% CI, 0.82 to 1.02]) or after adjustment for demographic characteristics, comorbidities, hospital size, history of cancer, and calendar year (adjusted HR, 0.94 [95% CI, 0.84 to 1.05]). Individual cancer types were also not significantly elevated (p > 0.05 for all) in BMP users compared with nonusers. In addition, BMP use was not associated with a new cancer in people who had cancer prior to undergoing lumbar arthrodesis (adjusted HR, 1.04 [95% CI, 0.71 to 1.52]) or with mortality after a cancer diagnosis (adjusted HR, 1.05 [95% CI, 0.93 to 1.19]).

CONCLUSIONS

In a large population of elderly U.S. adults undergoing lumbar arthrodesis, BMP use was not associated with cancer risk or mortality.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Antagonism of the Met5-enkephalin-opioid growth factor receptor-signaling axis promotes MSC to differentiate into osteoblasts

Chronic opioid therapy is associated with bone loss. This led us to hypothesize that the opioid antagonists, that include naloxone, would stimulate bone formation by regulating MSC differentiation. The opioid growth factor receptor (OGFR) is a non-canonical opioid receptor that binds naloxone with high affinity whereas the native opioid growth factor, met5-enkephalin (met5), binds both the OGFR and the canonical delta opioid receptor (OPRD). Naloxone and an shRNA OGFR lentivirus were employed to disrupt the OGFR-signaling axis in cultured MSC. In parallel, naloxone was administered to bone marrow using a mouse unicortical defect model. OPRD, OGFR, and the met5-ligand were highly expressed in MSC and osteoblasts. A pulse-dose of naloxone increased mineral formation in MSC cultures in contrast to MSC treated with continuous naloxone or OGFR deficient MSC. Importantly, SMAD1 and SMAD8/9 expression increased after a pulse dose of naloxone whereas SMAD1, SMAD7, and ID1 were increased in the OGFR deficient MSC. Inhibited OGFR signaling decreased proliferation and increased p21 expression. The addition of naloxone to the unicortical defect resulted in increased bone formation within the defect. Our data suggest that novel mechanism through which signaling through the OGFR regulates osteogenesis via negative regulation of SMAD1 and p21. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1195-1205, 2016.

Bone regeneration strategies with bone marrow stromal cells in orthopaedic surgery

Bone is the most transplanted tissue human with 1 million procedures every year in Europe. Surgical interventions for bone repair are required for varied reasons such as trauma resulting non-union fractures, or diseases including osteoporosis or osteonecrosis. Autologous bone grafting is the gold standard in bone regeneration but it requires a second surgery with associated pain and complications, and is also limited by harvested bone quantity. Synthetic bone substitutes lack the osteoinductive properties to heal large bone defects. Cell therapies based on bone marrow or ex vivo expanded mesenchymal stromal stem cells (MSCs) in association with synthetic calcium phosphate (CaP) bone substitutes may be alternatives to autologous bone grafting. This manuscript reviews the different conventional biological and synthetic bone grafting procedures as well as the more recently introduced cell therapy approaches used in orthopaedic surgery for bone regeneration. Some clinical studies have demonstrated safety and efficacy of these approaches but regeneration of large bone defects remain challenging due to the absence of rapid and adequate vascularisation. Future directions in the field of bone regeneration are presented, such as testing alternative cell sources or in situ fabrication of vascularized bone grafts in patients.

A Biphasic Calcium Sulphate/Hydroxyapatite Carrier Containing Bone Morphogenic Protein-2 and Zoledronic Acid Generates Bone

In orthopedic surgery, large amount of diseased or injured bone routinely needs to be replaced. Autografts are mainly used but their availability is limited. Commercially available bone substitutes allow bone ingrowth but lack the capacity to induce bone formation. Thus, off-the-shelf osteoinductive bone substitutes that can replace bone grafts are required. We tested the carrier properties of a biphasic, calcium sulphate and hydroxyapatite ceramic material, containing a combination of recombinant human bone morphogenic protein-2 (rhBMP-2) to induce bone, and zoledronic acid (ZA) to delay early resorption. In-vitro, the biphasic material released 90% of rhBMP-2 and 10% of ZA in the first week. No major changes were found in the surface structure using scanning electron microscopy (SEM) or in the mechanical properties after adding rhBMP-2 or ZA. In-vivo bone formation was studied in an abdominal muscle pouch model in rats (n = 6/group). The mineralized volume was significantly higher when the biphasic material was combined with both rhBMP-2 and ZA (21.4 ± 5.5 mm³) as compared to rhBMP-2 alone (10.9 ± 2.1 mm³) when analyzed using micro computed tomography (μ-CT) (p < 0.01). In the clinical setting, the biphasic material combined with both rhBMP-2 and ZA can potentially regenerate large volumes of bone.

BMP2/BMPR1A is linked to tumour progression in dedifferentiated liposarcomas

Bone Morphogenic Protein 2 (BMP2) is a multipurpose cytokine, important in the development of bone and cartilage, and with a role in tumour initiation and progression. BMP2 signal transduction is dependent on two distinct classes of serine/threonine kinase known as the type I and type II receptors. Although the type I receptors (BMPR1A and BMPR1B) are largely thought to have overlapping functions, we find tissue and cellular compartment specific patterns of expression, suggesting potential for distinct BMP2 signalling outcomes dependent on tissue type. Herein, we utilise large publicly available datasets from The Cancer Genome Atlas (TCGA) and Protein Atlas to define a novel role for BMP2 in the progression of dedifferentiated liposarcomas. Using disease free survival as our primary endpoint, we find that BMP2 confers poor prognosis only within the context of high BMPR1A expression. Through further annotation of the TCGA sarcoma dataset, we localise this effect to dedifferentiated liposarcomas but find overall BMP2/BMP receptor expression is equal across subsets. Finally, through gene set enrichment analysis we link the BMP2/BMPR1A axis to increased transcriptional activity of the matrisome and general extracellular matrix remodelling. Our study highlights the importance of continued research into the tumorigenic properties of BMP2 and the potential disadvantages of recombinant human BMP2 (rhBMP2) use in orthopaedic surgery. For the first time, we identify high BMP2 expression within the context of high BMPR1A expression as a biomarker of disease relapse in dedifferentiated liposarcomas.

A Review of the Clinical Side Effects of Bone Morphogenetic Protein-2

Bone morphogenetic protein-2 (BMP-2) is currently the only Food and Drug Administration (FDA)-approved osteoinductive growth factor used as a bone graft substitute. However, with increasing clinical use of BMP-2, a growing and well-documented side effect profile has emerged. This includes postoperative inflammation and associated adverse effects, ectopic bone formation, osteoclast-mediated bone resorption, and inappropriate adipogenesis. Several large-scale studies have confirmed the relative frequency of adverse events associated with the clinical use of BMP-2, including life-threatening cervical spine swelling. In fact, the FDA has issued a warning of the potential life-threatening complications of BMP-2. This review summarizes the known adverse effects of BMP-2, including controversial areas such as tumorigenesis. Next, select animal models that replicate BMP-2's adverse clinical effects are discussed. Finally, potential molecules to mitigate the adverse effects of BMP-2 are reviewed. In summary, BMP-2 is a potent osteoinductive cytokine that has indeed revolutionized the bone graft substitute market; however, it simultaneously has accrued a worrisome side effect profile. Better understanding of these adverse effects among both translational scientists and clinicians will help determine the most appropriate and safe use of BMP-2 in the clinical setting.

Bone healing in rabbit calvarial critical-sized defects filled with stem cells and growth factors combined with granular or solid scaffolds

PURPOSE

In pediatric neurosurgery, decompressive craniectomy and correction of congenital cranial anomalies can result in major cranial defects. Corrective cranioplasty for the repair of these critical-sized defects is not only a cosmetic issue. The limited availability of suitable autogenous bone and the morbidity of donor site harvesting have driven the search for new approaches with biodegradable and bioactive materials. This study aimed to assess the healing of rabbit calvarial critical-sized defects filled with osteogenic material, either with bioactive glass scaffolds or tricalcium phosphate granules in various combinations with adipose stem cells or bone marrow stem cells, BMP-2, BMP-7, or VEGF to enhance osteogenesis.

METHODS

Eighty-two bicortical full thickness critical-sized calvarial defects were operated. Five defects were left empty as negative control defects. The remaining 77 defects were filled with solid bioactive glass scaffolds or tricalcium phosphate granules seeded with adipose or bone marrow derived stem cells in combination with BMP-2, BMP-7, or VEGF. The defects were allowed to heal for 6 weeks before histologic and micro-CT analyses.

RESULTS

Micro-CT examination at the 6-week post-operative time point revealed that defects filled with stem cell-seeded tricalcium phosphate granules resulted in new bone formation of 6.0 %, whereas defects with bioactive glass scaffolds with stem cells showed new bone formation of 0.5 to 1.7 %, depending on the growth factor used.

CONCLUSIONS

This study suggests that tricalcium phosphate granules combined with stem cells have osteogenic potential superior to solid bioactive glass scaffolds with stem cells and growth factors.

Delivery of RANKL-Binding Peptide OP3-4 Promotes BMP-2-Induced Maxillary Bone Regeneration

Although bone morphogenetic protein 2 (BMP-2) is known to stimulate osteogenesis, there is evidence that high doses of BMP-2 can lead to side effects, including inflammation and carcinogenesis. The supplementation of other bone-augmenting agents is considered helpful in preventing such side effects by reducing the amount of BMP-2 required to obtain a sufficient amount of bone. We recently showed that a receptor activator of nuclear factor κB ligand (RANKL)-binding peptide promotes osteoblast differentiation. In the present study, we aimed to investigate whether OP3-4, a RANKL-binding peptide, promotes BMP-2-induced bone formation in the murine maxilla using an injectable gelatin hydrogel (GH) carrier. A GH carrier containing OP3-4 with BMP-2 was subperiosteally injected into the murine maxillary right diastema between the incisor and the first molar. The mice were sacrificed 28 d after the injections. The local bone formation in the OP3-4-BMP-2-injected group was analyzed in comparison to the carrier-injected, BMP-2-injected, and control-peptide-BMP-2-injected groups. The GH carrier containing OP3-4 with BMP-2 enlarged the radio-opaque area and increased the bone mineral content and density in the radiological analyses in comparison to the other experimental groups. Interestingly, fluorescence-based histological analyses revealed that the mineralization had started from the outside, then proceeded inward, suggesting that the size of the newly formed bone had already been set before calcification started and that the effects of OP3-4 might be involved in accelerating the early steps of osteogenesis. Actually, OP3-4 enhanced the BMP-2-induced 5-bromo-2'-deoxyuridine (BrdU)-positive cell numbers at the injected site on day 7 and the expression of Runx2 and Col1a1, which are early osteogenic cell markers, on day 10 after the subperiosteal injections. In summary, we demonstrated, for the first time, that the application of OP3-4 by subperiosteal injection promoted BMP-2-induced bone formation, which could lead to the development of an easy and noninvasive means of promoting alveolar ridge formation.

Bone morphogenetic protein use in spine surgery-complications and outcomes: a systematic review

PURPOSE

Because of significant complications related to the use of autologous bone grafts in spinal fusion surgery, bone substitutes and growth factors such as bone morphogenetic protein (BMP) have been developed. One of them, recombinant human (rh) BMP-2, has been approved by the Food and Drug Administration (FDA) for use under precise conditions. However, rhBMP-2-related side effects have been reported, used in FDA-approved procedures, but also in off-label use.A systematic review of clinical data was conducted to analyse the rhBMP-2-related adverse events (AEs), in order to assess their prevalence and the associated surgery practices.

METHODS

Medline search with keywords "bone morphogenetic protein 2", "lumbar spine", "anterolateral interbody fusion" (ALIF) and the filter "clinical trial". FDA published reports were also included. Study assessment was made by authors (experienced spine surgeons), based on quality of study designs and level of evidence.

RESULTS

Extensive review of randomised controlled trials (RCTs) and controlled series published up to the present point, reveal no evidence of a significant increase of AEs related to rhBMP-2 use during ALIF surgeries, provided that it is used following FDA guidelines. Two additional RCTs performed with rhBMP-2 in combination with allogenic bone dowels reported increased bone remodelling in BMP-treated patients. This AE was transient and had no consequence on the clinical outcome of the patients. No other BMP-related AEs were reported in these studies.

CONCLUSIONS

This literature review confirms that the use of rhBMP-2 following FDA-approved recommendations (i.e. one-level ALIF surgery with an LT-cage) is safe. The rate of complications is low and the AEs had been identified by the FDA during the pre-marketing clinical trials. The clinical efficiency of rhBMP-2 is equal or superior to that of allogenic or autologous bone graft in respect to fusion rate, low back pain disability, patient satisfaction and rate of re-operations. For all other off-label use, the safety and effectiveness of rhBMP-2 have not been established, and further RCTs with high level of evidence are required.

Chimeric Aptamer-Gelatin Hydrogels as an Extracellular Matrix Mimic for Loading Cells and Growth Factors

It is important to synthesize materials to recapitulate critical functions of biological systems for a variety of applications such as tissue engineering and regenerative medicine. The purpose of this study was to synthesize a chimeric hydrogel as a promising extracellular matrix (ECM) mimic using gelatin, a nucleic acid aptamer, and polyethylene glycol. This hydrogel had a macroporous structure that was highly permeable for fast molecular transport. Despite its high permeability, it could strongly sequester and sustainably release growth factors with high bioactivity. Notably, growth factors retained in the hydrogel could maintain ∼ 50% bioactivity during a 14-day release test. It also provided cells with effective binding sites, which led to high efficiency of cell loading into the macroporous hydrogel matrix. When cells and growth factors were coloaded into the chimeric hydrogel, living cells could still be observed by day 14 in a static serum-reduced culture condition. Thus, this chimeric aptamer-gelatin hydrogel constitutes a promising biomolecular ECM mimic for loading cells and growth factors.

The Use of Bone Morphogenetic Protein in Pediatric Cervical Spine Fusion Surgery: Case Reports and Review of the Literature

Study Design Case report. Objective There is a paucity of literature describing the use of bone graft substitutes to achieve fusion in the pediatric cervical spine. The outcomes and complications involving the off-label use of bone morphogenetic protein (BMP)-2 in the pediatric cervical spine are not clearly defined. The purpose of this article is to report successful fusion without complications in two pediatric patients who had instrumented occipitocervical fusion using low-dose BMP-2. Methods A retrospective review of the medical records was performed, and the patients were followed for 5 years. Two patients under 10 years of age with upper cervical instability were treated with occipitocervical instrumented fusion using rigid occipitocervical fixation techniques along with conventionally available low-dose BMP-2. A Medline and PubMed literature search was conducted using the terms "bone morphogenetic protein," "BMP," "rh-BMP2," "bone graft substitutes," and "pediatric cervical spine." Results Solid occipitocervical fusion was achieved in both pediatric patients. There were no reported perioperative or follow-up complications. At 5-year follow-up, radiographs in both patients showed successful occipital cervical fusion without evidence of instrumentation failure or changes in the occipitocervical alignment. To date, there are few published reports on this topic. Complications and the appropriate dosage application in the pediatric posterior cervical spine remain unknown. Conclusions We describe two pediatric patients with upper cervical instability who achieved successful occipital cervical fusion without complication using off-label BMP-2. This report underscores the potential for BMP-2 to achieve successful arthrodesis of the posterior occipitocervical junction in pediatric patients. Use should be judicious as complications and long-term outcomes of pediatric BMP-2 use remain undefined in the existing literature.