A pilot study: Nano-hydroxyapatite-PEG/PLA containing low dose rhBMP2 stimulates proliferation and osteogenic differentiation of human bone marrow derived mesenchymal stem cells

Background

Bone morphogenetic protein 2 (BMP2) can enhance posterolateral spinal fusion (PLSF). The minimum effective dose that may stimulate mesenchymal stem cells however remains unknown. Nano-hydroxyapatite (nHAp) polyethylene glycol (PEG)/polylactic acid (PLA) was combined with recombinant human BMP2 (rhBMP2). We in vitro evaluated proliferation, differentiation, and osteogenic genes of human bone marrow mesenchymal stem cells with 0.5, 1.0, and 3.0 μg/mL rhBMP2 doses in this study.

Methods

In vitro experimental study was designed to proliferation by a real-time quantitative cell analysis system and the osteogenic differentiation by alkaline phosphatase (ALP) activity and osteogenic marker (Runx2, OPN, and OCN) gene expressions of human derived bone marrow mesenchymal stem cells (hBMMSCs). nHAp was produced by wet chemical process and characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. PEG/PLA polymer was produced at a 51:49 molar ratio. 0.5, 1.0, and 3.0 μg/mL rhBMP2 and nHAp was combined with the polymers. hBMMSCs were characterized by multipotency assays and surface markers were assessed by flow cytometer. The hBMMSC-rhBMP2 containing nHAp-PEG/PLA composite interaction was evaluated by transmission electron microscopy. Proliferative effect was evaluated by real-time proliferation analysis, and osteogenic capacity was evaluated by ALP activity assay and qPCR.

Results

hBMMSC proliferation in the 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA and the 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA groups were higher compared to control. 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA and 3.0 μg/mL rhBMP2 + nHAp-PEG/PLA containing composites induced ALP activity on days 3 and 10. 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA application stimulated Runx2 and OPN gene expressions.

Conclusion

rhBMP2 + nHAp-PEG/PLA composites stimulate hBMMSC proliferation and differentiation. The nHAp-PEG/PLA composite with low dose of rhBMP2 may enhance bone formation in future clinical PLSF applications.

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.

Bone Generation Following Repeated Administration of Recombinant Bone Morphogenetic Protein 2

BACKGROUND

The delivery of recombinant human bone morphogenetic protein 2 (rhBMP2) by using various carriers has been used to successfully induce bone formation in many animal models. However, the effect of multiple administration of rhBMP2 on bone formation and BMP2 antibody production has not been determined. Our aim was to examine the bone formation activity of rhBMP2 and serum levels of anti-BMP2 antibodies following the repeated administration of rhBMP2 in mice.

METHODS

Absorbable collagen sponges or polyphosphazene hydrogels containing rhBMP2 were subcutaneously implanted or injected into one side on the back of six-week-old C57BL/6 mice. Three or 4 weeks later, the same amount of rhBMP2 was administered again with the same carrier into the subcutaneous regions on the other side of the back or into calvarial defects. The effects of a single administration of rhBMP2 on the osteoinductive ability in the ectopic model were compared with those of repeated administrations. In vivo ectopic or orthotopic bone formation was evaluated using microradiography and histological analyses. Serum concentrations of anti-rhBMP2 antibodies were measured by ELISAs.

RESULTS

Re-administration of the same amount of rhBMP2 into the subcutaneous area showed a comparable production of ectopic bone as after the first administration. The bone forming ability of repeated rhBMP2 administrations was equal to that of single rhBMP2 administration. The administration of rhBMP2 into calvarial defects, following the first subcutaneous administration of rhBMP2 on the back, completely recovered the defect area with newly regenerated bone within 3 weeks. Repeated administration of rhBMP2 at 4-week intervals did not significantly alter the serum levels of anti-BMP2 antibodies and did not induce any inflammatory response. The serum obtained from rhBMP2-exposed mice had no effect on the ability of rhBMP2 to induce osteogenic gene expressions in MC3T3-E1.

CONCLUSION

We suggest that the osteoinductive ability of rhBMP2 is not compromised by repeated administrations. Thus, rhBMP2 can be repeatedly used for bone regeneration at various sites within a short duration.

rhBMP2 alone does not induce macrophage polarization towards an increased inflammatory response

Once thought to have revolutionized therapeutic intervention in surgery, Recombinant Human Bone Morphogenic Protein 2 (rhBMP2) is now in its second decade of sustained controversy over the side effects associated with its use. Side effects associated with clinical use of rhBMP2 (Infuse, Medtronic Inc) include a marked inflammatory response, pain, therapeutic failures, ectopic bone, tissue degradation, and death. What is missing, despite the depth of literature on the subject, is a direct interrogation of rhBMP2, specifically for inflammation. Here we set out to determine if rhBMP2 alters traditional macrophage markers associated with pro-inflammatory responses, and pro-reparative responses to injury. Based on our previous work, we hypothesized there would be no direct effect of the peptide on macrophage polarization. Here we utilized commercially available murine macrophages, RAW 264.7, and treated these cells with rhBMP2 in standard growth media or macrophage polarizing media (M1 and M2) at several doses of the peptide. Our readouts were cell viability, apoptosis, gene expression of M1 and M2 markers, and ELISA for M1 marker iNOS, and M2 marker Arg1. Our data give very little evidence to support an alteration in macrophage phenotype by rhBMP2 alone, or alteration of the phenotype when cultured in enriched M1 or M2 media. These results further suggest that other factors associated with the clinical use of Infuse, likely supraphysiological rhBMP2 doses and off label usage, are more likely the culprit for poor outcomes. This further reinforces the utility of rhBMP2 and other peptides in tissue engineering therapies when conditions are tightly controlled.

Complication Rates in Posterior Lumbar Interbody Fusion (PLIF) Surgery With Human Bone Morphogenetic Protein 2: Medicare Population

STUDY DESIGN

Retrospective cohort study among Medicare beneficiaries who underwent posterior lumbar interbody fusion (PLIF) surgery.

OBJECTIVE

To identify the complication rates associated with the use of bone morphogenetic protein 2 (BMP2) in PLIF. Human BMP2 is commonly used in the "off-label" manner for various types of spine fusion procedures, including PLIF. However, recent studies have reported potential complications associated with the recombinant human BMP2 (rhBMP2) use in the posterior approach.

METHODS

Medicare records within the PearlDiver database were queried for patients undergoing PLIF procedure with and without rhBMP2 between 2005 and 2010. We evaluated complications within 1 year postoperatively. Chi-square was used to compare the complication rates between the 2 groups.

RESULTS

A total of 8609 patients underwent PLIF procedure with or without rhBMP2. Individual complication rates in the rhBMP2 group ranged from 0.45% to 7.68% compared with 0.65% to 10.99 in the non-rhBMP2 group. Complication rates for cardiac, pulmonary, lumbosacral neuritis, infection, wound, and urinary tract (include acute kidney failure and post-operative complications) were significantly lower in the rhBMP2 group (P < .05). There was no difference in the rates of central nervous system complications or radiculitis between the 2 groups.

CONCLUSION

Our data showed that the patients who received rhBMP2 had lower complication rates compared to the non-rhBMP2 group. However, use of rhBMP2 was associated with a higher rate of pseudarthrosis. We did not observe any difference in radiculitis and central nervous system complications between the groups.

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.

Fabrication of a three-dimensional β-tricalcium-phosphate/gelatin containing chitosan-based nanoparticles for sustained release of bone morphogenetic protein-2: Implication for bone tissue engineering

Fabrication of an ideal scaffold having proper composition, physical structure and able to have sustained release of growth factors still is challenging for bone tissue engineering. Current study aimed to design an appropriate three-dimensional (3-D) scaffold with suitable physical characteristics, including proper compressive strength, degradation rate, porosity, and able to sustained release of bone morphogenetic protein-2 (BMP2), for bone tissue engineering. A highly porous 3-D β-tricalcium phosphate (β-TCP) scaffolds, inside of which two perpendicular canals were created, was fabricated using foam-casting technique. Then, scaffolds were coated with gelatin layer. Next, BMP2-loaded chitosan (CS) nanoparticles were dispersed into collagen hydrogel and filled into the scaffold canals. Physical characteristics of fabricated constructs were evaluated. Moreover, the capability of given construct for bone regeneration has been evaluated in vitro in interaction with human buccal fat pad-derived stem cells (hBFPSCs). The results showed that gelatin-coated TCP scaffold with rhBMP2 delivery system not only could act as a mechanically and biologically compatible framework, but also act as an osteoinductive graft by sustained delivering of rhBMP2 in a therapeutic window for differentiation of hBFPSCs towards the osteoblast lineage. The proposed scaffold model can be suggested for delivering of cells and other growth factors such as vascular endothelial growth factor (VEGF), alone or in combination, for future investigations.

Anterior approach with expandable cage implantation in management of unstable thoracolumbar fractures: Results of a series of 93 patients

INTRODUCTION

Anterior approach indications in unstable thoracolumbar fractures (UTLF) are debated. The aim of this study was to evaluate the results of anterior fixation and expandable prosthetic vertebral body cage (EPVBC) implantation alone or combined with a posterior approach in the management of UTLF.

MATERIALS AND METHODS

Ninety-three patients underwent anterior fixation with implantation of an EPVBC for UTLF from T7 to L5. Long-term kyphosis and vertebral height loss reduction, functional outcomes including visual analogical scale and Oswestry disability index were evaluated.

RESULTS

Anterior fixation led to a significant increase of vertebral body height with a gain of 13% after a previous posterior approach, 38% after a single anterior approach and 65% after combined posterior and anterior approaches (P=0.0001). However, anterior fixation did not significantly enhance the vertebral regional kyphosis angle (P=0.08), except in cases of single anterior approach for thoracic fractures (P=0.03). No significant difference was found between early, 3 months and 1 year postoperative vertebral regional kyphosis angle and vertebral body height (P=0.6). Complete fusion was routinely observed at 1 year postoperatively. rhBMP2 implantation in selected cases appears to be a safe and reliable strategy. No infections or surgical revisions were observed after the anterior approach.

CONCLUSION

Anterior approach and EPVBC implantation, in UTLF, is a safe and effective procedure, providing long-term vertebral body height and kyphosis correction. Adverse effects of anterior approach remain acceptable. Single anterior fixation is a reliable surgical alternative in thoracic fractures without posterior spine segment injury or spinal cord compression. These results prompted us to extend anterior approach indications in oncology and infectious diseases.

Comparison of a novel oxysterol molecule and rhBMP2 fusion rates in a rabbit posterolateral lumbar spine model

BACKGROUND CONTEXT

The nonunion rate after lumbar spinal fusion is as high as 25%. Recombinant human bone morphogenetic protein 2 (rhBMP2) has been used as a biological adjunct to promote bony fusion. However, recently there have been concerns about BMP2. Oxysterol 133 (Oxy133) has been shown to promote excellent fusion rates in rodent lumbar spine models and offers a potential alternative to rhBMP2.

PURPOSE

The purpose of this study was to compare the fusion rate of rhBMP2 and Oxy133 in a randomized controlled trial using a posterolateral lumbar rabbit spinal fusion model.

STUDY DESIGN

This was a randomized control animal study.

METHODS

Twenty-four male adult white New Zealand rabbits (3-3.5 kg) underwent bilateral posterolateral lumbar spinal fusion at L4-L5. Rabbits were divided into four groups: control (A), 30-μg rhBMP2 (B), 20-mg Oxy133 (C), and 60-mg Oxy133 (D). At 4 weeks, fusion was evaluated by fluoroscopy, and at 8 weeks, the rabbits were sacrificed and fusion was evaluated radiographically, by manual palpation, and with microcomputed tomography.

RESULTS

Fusion rates by radiographic analysis at 8 weeks were Group A, 40.0%; Group B, 91.7%; Group C, 91.7%; and Group D, 100%. Evaluation of fusion masses by manual palpation of excised spines after sacrifice showed the following fusion rates: Group A, 0%; Group B, 83.3%; Group C, 83.3%; and Group D, 90%. Microcomputed tomography scanning confirmed these findings.

CONCLUSIONS

These findings in a rabbit model demonstrate that both 20- and 60-mg Oxy133 doses promote fusion that is equivalent to fusion induced by 30-μg rhBMP2 and significantly greater than the control group. The present findings confirm that Oxy133 is a promising candidate for therapeutic development as an alternative to rhBMP2 to promote spinal fusion.

Complications and cancer rates in spine fusion with recombinant human bone morphogenetic protein-2 (rhBMP-2)

PURPOSE

To quantitatively synthesize the available best evidence for general complications, heterotopic ossification (HO), retrograde ejaculation, cervical swelling, and cancer rates with the use of rhBMP-2 in lumbar and cervical spine fusion.

METHODS

We conducted an online search for relevant controlled trials and extracted data on the abovementioned endpoints. Studies were eligible for inclusion if they reported on spinal fusion with rhBMP-2 in humans. Publication bias and heterogeneity were assessed mathematically. These data were synthesized in a meta-analysis using DerSimonian-Laird random effects modeling to calculate pooled odds ratios.

RESULTS

We identified 26 studies reporting on a total of 184,324 patients (28,815 experimental, 155,509 controls) with a mean age of 51.1 ± 1.8 years. There was a significantly higher risk of general complications with rhBMP-2 compared to iliac crest bone graft (ICBG) with an odds ratio (OR) of 1.78 (95 %CI 1.20-2.63), (p = 0.004). The odds ratio for HO was 5.57 (95 %CI 1.90-16.36), (p = 0.002), for retrograde ejaculation 3.31 (95 %CI 1.20-9.09), (p = 0.020), and for cervical swelling 4.72 (95 %CI 1.42-15.67), (p = 0.011), all significantly higher in the rhBMP-2 group. The pooled odds ratio for new onset of tumor was 1.35 (95 %CI 0.93-1.96), which represents no statistically significant difference between the groups (p = 0.111).

CONCLUSION

rhBMP-2 is associated with a higher rate of general complications as well as retrograde ejaculation, HO, and cervical tissue swelling in spine fusion. There is a slightly increased risk of new onset of tumors, however, without statistical significance.

Tissue engineering scaffold for sequential release of vancomycin and rhBMP2 to treat bone infections

The ability of silica calcium phosphate nanocomposite (SCPC75) for the controlled sequential delivery of vancomycin (Vanc) and rhBMP2 was evaluated. Fourier transform infrared spectroscopy analyses of the SCPC75 showed an increase in the bond energy of the PO4 (-3) due to the interactions with negatively charged moieties of Vanc. Furthermore, a decrease in the bond energy of the Si-O-Si functional groups was observed after rhBMP2 adsorption. In conjunction with the differences in bond site and bond energy at the ceramic/drug interface, significant differences in drug release kinetics and bioceramic dissolution rate were found. UV-vis spectrometry showed a burst release of Vanc in the first 8 h followed by a sustained release stage for up to 28 days. ELISA showed first-order release kinetics of rhBMP2 without burst release. The rhBMP2 release from SCPC75 was associated with a significantly lower rate of Ca and a higher rate of Si dissolutions when compared with Vanc release over identical time periods. Differences in the release kinetic profiles of Vanc and rhBMP2 from the SCPC75-Vanc/SCPC75-rhBMP2 scaffolds at 70/30, 50/50, or 20/80 ratios allowed for sequential drug release profiles that could be exploited to customize doses and release duration of each drug. The released rhBMP2 significantly upregulated MC3T3-E1 expression of collagen type I, osteopontin, and osteocalcin mRNA by 12.6-, 3.3-, and 2.4-fold, respectively. The released Vanc demonstrated bactericidal effects on Staphylococcus aureus in vitro. These results suggest the potential of SCPC75-Vanc-rhBMP2 scaffolds in the treatment of damaged and/or infected bone.

Use of recombinant human Bone Morphogenetic Protein (rhBMP-2) in reconstruction of maxillary alveolar clefts

BACKGROUND

Use of rhBMP2 has been demonstrated to be an ideal bone reconstructive material for alveolar clefts. There is a lack of such studies from Indian cleft patients.

AIM

To compare rhBMP2 alveolar cleft repair and iliac crest graft treated cases.

MATERIALS AND METHOD

Retrospective analysis of rhBMP2 alveolar cleft repair and iliac crest graft treated cases.

PREDICTOR VARIABLES

Gender, type of surgery and type of cleft

OUTCOME VARIABLES

Total surgery time, blood loss at surgical and harvest site, length of scar, number of days on antibiotics, serratiopeptidase and NSAIDS; sutured days, number of days to regain masticatory functions, pain VAS on 5th postoperative day and at harvest site on a scale of 10; duration of edema, number of working days lost, time until child could walk 'normally'; mean efficiency of bone deposition.

STATISTICS

Descriptive, paired 't' test, one way ANOVA RESULTS: Difference between rhBMP2 and iliac crest graft treated cases in terms of antibiotic use, serratopeptidase, NSAIDS, pain at surgical site, edema, number of working lost for attendees and number of days to walk unaided were statistically significant. The mean length of surgery for unilateral cases was 87.60 minutes whereas it was 108.75 minutes for bilateral cases (p=0.003). The mean efficiency of bone deposition as revealed loss in radiolucency for rhBMP2 treated cases was 91.74% whereas iliac crest graft cases showed a 87.96% (p=0.006).

DISCUSSION

It is evident that one has to reject null hypothesis in favor of the alternate hypothesis. The rhBMP2 is better than the conventional gold standard of iliac crest graft for restoration of maxillary alveolar clefts in terms of considered surgical, post surgical and radiographic planimetry parameters.

CONCLUSION

Sparing children from the procedure of iliac crest harvesting is by itself a compelling reason to favor rhBMP2 use. It avoids the unnecessary surgery, loss of blood and postoperative morbidity of iliac crest harvesting.