Critical analysis and efficacy of BMPs in long bones non-union

Scaffold-guided bone regeneration in large volume tibial segmental defects

Large volume losses in weight bearing long bones are a major challenge in clinical practice. Despite multiple innovations over the last decades, significant limitations subsist in current clinical treatment options which is driving a strong clinical demand for clinically translatable treatment alternatives, including bone tissue engineering applications. Despite these shortcomings, preclinical large animal models of large volume segmental bone defects to investigate the regenerative capacity of bone tissue engineering strategies under clinically relevant conditions are rarely described in literature. We herein present a newly established preclinical ovine animal model for the treatment of XL volume (19 cm³) segmental tibial defects. In eight aged male Merino sheep (age > 6 years) a mid-diaphyseal tibial segmental defect was created and stabilized with a 5.6 mm Dynamic Compression Plate (DCP). We present short-term (3 months) and long-term (12-15 months) results of a pilot study using medical grade Polycaprolactone-Tricalciumphosphate (mPCL-TCP) scaffolds combined with a dose of 2 mg rhBMP-7 delivered in Platelet-Rich- Plasma (PRP). Furthermore, detailed analyses of the mechanical properties of the scaffolds as well as interfragmentary movement (IFM) and DCP-surface strain in vitro and a comprehensive description of the surgical and post-surgery protocol and post-mortem analysis is given.

Bone-Targeting Liposome-Encapsulated Salvianic Acid A Improves Nonunion Healing Through the Regulation of HDAC3-Mediated Endochondral Ossification

AIM

Nonunion is a major complication in fracture repair and remains a challenge in orthopaedics and trauma surgery. In this study, we aimed to evaluate the effectiveness of treatment of nonunion with a large radial defect using a bone-targeting liposome-encapsulated salvianic acid A (SAA-BTL)-incorporated collagen sponge and further elucidate whether the effects were closely related to histone deacetylase 3 (HDAC 3)-mediated endochondral ossification in nonunion healing process.

METHODS

Fifteen New Zealand female rabbits were randomly divided into three groups. Segmental radius critical size defects (15 mm) were created via surgery on both the forelimbs of the rabbits. The SAA-BTL/SAA/saline-incorporated collagen sponges were implanted into the defects in the three groups, respectively, for four weeks of treatment. X-ray imaging, micro-computed tomography (CT) analysis, histology, and immunofluorescence analysis (HDAC3, collagen II, VEGFA, and osteocalcin) were performed to determine the effects of the treatments. In addition, a short interfering RNA was applied to induce HDAC3 knockdown in the chondrogenic cell line ATDC5 to investigate the roles of HDAC3 and SAA intervention in endochondral ossification in nonunion healing.

RESULTS

X-ray imaging and micro-CT results revealed that SAA-BTL-incorporated collagen sponges significantly stimulated bone formation in the nonunion defect rabbit model. Furthermore, immunofluorescence double staining and histology analysis confirmed that SAA-BTL significantly increased the expression of P-HDAC3, collagen II, RUNX2, VEGFA, and osteocalcin in vivo; accelerated endochondral ossification turnover from cartilage to bone; and promoted long bone healing of nonunion defects. ATDC5 cells knocked down for HDAC3 showed significantly decreased expression of HDAC3, which resulted in reduced expression of chondrogenesis, osteogenesis, and angiogenesis biomarker genes (Sox9, Col10a1, VEGFA, RUNX2, and Col1a1), and increased expression of extracellular matrix degradation marker (MMP13). SAA treatment reversed these effects in the HDAC3 knockdown cell model.

CONCLUSION

SAA-BTL can improve nonunion healing through the regulation of HDAC3-mediated endochondral ossification.

Healing the Index Humeral Shaft Nonunion: Risk Factors for Development of a Recalcitrant Nonunion in 125 Patients

BACKGROUND

Humeral shaft nonunions are challenging to treat, and those that require >1 surgical procedure in order for a nonunion to heal are termed recalcitrant. Most studies on nonunion have evaluated the union rate independent of the number of procedures required to achieve union. The aims of the present study were (1) to compare the healing rates after the index operation for the treatment of a nonunion with conventional versus locked plating with or without graft augmentation, (2) to report the prevalence of recalcitrant nonunion, and (3) to identify risk factors that predict a recalcitrant nonunion.

METHODS

We performed a retrospective analysis of a prospectively collected database of 125 humeral shaft nonunions treated with open reduction and plate fixation by a single surgeon over 25 years. Univariate and multivariate regression analyses were performed to compare healing rates by type of plate fixation and biological augmentation and to identify demographic, injury, and treatment-related risk factors for the development of a recalcitrant nonunion.

RESULTS

One hundred and five patients (84%) had healing after the index procedure for the treatment of nonunion. Twenty patients (16.0%) required secondary procedures and were defined as having a recalcitrant nonunion. Eight of these patients (6.4% of the overall group) healed after the secondary interventions, and 12 (9.6% of the overall group) had a failure to unite. There were no significant differences in healing rates between conventional and locked plates or between the types of bone graft (autogenous or recombinant human bone morphogenetic protein). Risk factors for the development of a recalcitrant nonunion were plate fixation of the acute humeral fracture, a history of deep infection, and ≥2 prior procedures.

CONCLUSIONS

Plate fixation with bone graft augmentation remains a successful method for the treatment of humeral shaft nonunions. Neither plate type nor graft type reduced the risk of a recalcitrant nonunion. Factors that predicted a recalcitrant nonunion were operative fixation of the acute fracture with a plate, a history of deep infection, and ≥2 surgical procedures.

LEVEL OF EVIDENCE

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

Do osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration? Investigating the efficacy of BMP-7 and zoledronate treatment of diaphyseal fractures in an open fracture osteoporotic rat model

Osteoporotic fractures may pose a challenge for skeletal regeneration. This study investigates if pharmaceutical interventions such as bone morphogenetic protein 7 (BMP-7) alone or in combination with Zoledronate have equivalent efficacy in osteoporotic bone? Our findings suggest they do and that an osteoporotic bone environment may increase sensitivity to BMP-7.

INTRODUCTION

Osteoporosis is thought to contribute to delayed or impaired bone healing. Bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA) has proven effective in augmenting the regenerative response in healthy young male rats. Yet their comparative efficacy in an osteoporotic bone environment is unknown. Our study aimed to answer the following questions using the ovariectomized (OVX) rat model of osteoporosis: Do osteoporotic fractures pose a greater challenge for skeletal regeneration? Are interventions with BMP-7-alone or combined with ZA of equivalent efficacy in osteoporotic bone?

METHODS

Sham operations (n = 33) or ovariectomies (n = 34) were performed in 12-week-old female Sprague-Dawley rats. Mid-diaphyseal open femoral osteotomies were created at 24 weeks of age and the rats allocated to either (i) untreated, (ii) BMP-7-only or (iii) BMP-7 + ZA treatment groups. At 6 weeks post-osteotomy, fracture healing was evaluated by radiography, μCT and 3-point bending mechanical tests.

RESULTS

Cumulatively, radiological, micro-structural and mechanical measures were equivalent in both healthy and osteoporotic environments. A reduced response to BMP-7-alone was observed in healthy rats that may be age/gender- or protocol/fracture-model dependent. Conversely, the BMP-7-only treated OVX group attained 100 % union in addition to significantly increased measures of mineralized bone volume, total callus volume, peak force and absorbed energy relative to untreated OVX fractures.

CONCLUSIONS

Our findings refute the hypothesis that osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration. Furthermore, our results suggest that an oestrogen-deficient environment may in fact cause an increased sensitivity to BMP-7.

The treatment of atrophic, recalcitrant long-bone nonunion in the upper extremity with human recombinant bone morphogenetic protein-7 (rhBMP-7) and plate fixation: A retrospective review

INTRODUCTION

Recombinant Human Bone Morphogenetic Protein-7 (rhBMP-7) has been shown to promote fracture healing in both clinical studies and basic science models, however, there is little information from large-scale studies of its use for human nonunion. The purpose of this study was to determine the safety and efficacy of rhBMP-7 in the treatment of atrophic human long-bone nonunions in the upper extremity.

PATIENTS AND METHODS

This was a single center, retrospective, longitudinal cohort study of patients treated with compression plating and the application of rhBMP-7 in isolation to a long-bone nonunion. Patients over sixteen years of age with an atrophic, aseptic nonunion of a humerus, radius, ulna or clavicle were eligible for inclusion.

RESULTS

We identified seventy eligible patients who were treated with rhBMP-7 for a long-bone nonunion between July 1997 and April 2012. The mean age of the patients at the time of treatment with rhBMP-7 was 50.7 years (range, 20-92 years). Five patients were lost to follow-up prior to definitive clinical or radiographic union. During the one-year post-operative period fifty-six patients had achieved union and two patients developed a stable fibrous union after the index procedure. Two patients had early implant failure and five patients had persistent nonunion. Thus, the union rate following initial surgery was 89% (58/65) and four of the five nonunion patients went on to heal following revision open reduction and internal fixation.

CONCLUSION

We found that the application of rhBMP-7 for upper extremity nonunion was an effective method (89% union rate) of treating this challenging pathology. Additionally, if not initially successful, further reconstruction was not compromised by rhBMP-7 use.

Dual-controlled release system of drugs for bone regeneration

Controlled release systems have been noted to allow drugs to enhance their ability for bone regeneration. To this end, various biomaterials have been used as the release carriers of drugs, such as low-molecular-weight drugs, growth factors, and others. The drugs are released from the release carriers in a controlled fashion to maintain their actions for a long time period. Most research has been focused on the controlled release of single drugs to demonstrate the therapeutic feasibility. Controlled release of two combined drugs, so-called dual release systems, are promising and important for tissue regeneration. This is because the tissue regeneration process of bone formation is generally achieved by multiple bioactive molecules, which are produced from cells by other molecules. If two types of bioactive molecules, (i.e., drugs), are supplied in an appropriate fashion, the regeneration process of living bodies will be efficiently promoted. This review focuses on the bone regeneration induced by dual-controlled release of drugs. In this paper, various dual-controlled release systems of drugs aiming at bone regeneration are overviewed explaining the type of drugs and their release materials.

Bone morphogenetic protein and orthopaedic surgery: can we legitimate its off-label use?

PURPOSE

Bone morphogenetic proteins (BMP) are recombinant osteoinductive proteins with their primary role being to promote bone formation. The off-label use of BMP in orthopaedic surgery has dramatically increased. However, reports of complications with BMP have emerged, and the safety of these proteins in orthopaedics is questioned. The purpose of this review was to evaluate safe situations in which BMP should be used and situations in which their use should be restricted.

METHOD

We recorded all studies from PubMed database from 2002 (date of first authorisation for both BMPs) until January 2014 using "BMP" or "bone morphogenetic protein". Then we screened and extracted all studies dealing with orthopaedic surgery. All situations in which BMP were used, even cases reports, were considered, and complications reported were then listed.

RESULTS

Situations in which it seems safe and efficient to use BMP are long-bone nonunions, or arthrodesis as an alternative or combined to autograft in small-bone loss. Surgeons and patients should be aware of transient aseptic wound swelling when BMP is located superficially. The use of BMP in spine surgery for intersomatic fusion is efficient but should be restricted to approaches that respect the vertebral canal to avoid neurological complications.

CONCLUSION

This review is an off-label map of BMP use in orthopaedics during the past 10 years. Our results could provide a useful tool to help decisions around when to use a BMP in a specific complex, and sometimes off-label, situation.

Induction of bone formation in abdominal implants constituted by collagen sponges embedded with plant-based human transforming growth factor family proteins in ectopic dog model

Background

Trauma, osteomyelitis, bone tumour resections and congenital deformities are the main causes of bone deficiency in which autologous graft is the preferred treatment, but usually the bone supplies are limited.

Methods

An experimental model of heterotopic bone formation in the subcutaneous abdominal area of dogs was developed. This model consists in omentum wrapped implants constituted by collagen type 1 sponges embedded with demineralized bone powder, calcium cloride, thrombin and platelet rich plasma; the implant is totally converted in trabecular bone after four months of implantation. This model was improved by accelerating bone production, after the isolation of the most conspicuous histological constituents (inflammatory, bone and adipose tissues) by laser microdisection and purified from them RNA that was used to determine by RT-PCR the gene expression kinetics of the most important growth bone factors. Then, the most abundant and rapidly synthesized factors were produced by genetic engineering in tobacco plants.

Results

Bone morphogenetic proteins 2 and 7 and transforming growth factor-β1were the most rapidly and highly synthesized factors, and they were efficiently produced in a genetic engineering plant based system in tobacco leaves. Their incorporation as recombinant proteins in the scaffold collagen sponge induced in just one month mature heterotopic bone.

Conclusion

This study demonstrates for the first time that this plant system is able to produce recombinant bone growth factors in high amount and at low cost, and they were highly efficient to rapidly induce bone formation in abdominal implants potentially useful for autotransplantation.

Storage and qualification of viable intact human amniotic graft and technology transfer to a tissue bank

Human amniotic membrane (hAM) is known to have good potential to help the regeneration of tissue. It has been used for over 100 years in many medical disciplines because of its properties, namely a scaffold containing stem cells and growth factors, with low immunogenicity and anti-microbial, anti-inflammatory, anti-fibrotic and analgesic properties. In order to use this "boosted membrane" as an advanced therapeutic medicinal product for bone repair, we aimed to observe the influence of tissue culture and/or cryopreservation on cell viability and tissue structure, and secondly, to adapt to a tissue bank, identify easy processes to store hAM containing viable cells and to verify the quality of the graft before its release for use. To this end, we tested different published culture or cryopreservation storage conditions and cell viability assays. Tissue structure was evaluated by Giemsa staining and was compared to histological analysis. Preliminary results show no dramatic decrease in cell viability in cultured hAM as compared to cryopreserved hAM, but tissue structure alterations were observed with both storage conditions. Histological and immunohistochemical data highlight that tissue damage was associated with significantly modified protein expression, which could lead to a possible loss of differentiation potential. Finally, we report that trypan blue and Giemsa staining could constitute controls that are "materially and easily transferable" to a tissue bank.

A tissue engineering solution for segmental defect regeneration in load-bearing long bones

The reconstruction of large defects (>10 mm) in humans usually relies on bone graft transplantation. Limiting factors include availability of graft material, comorbidity, and insufficient integration into the damaged bone. We compare the gold standard autograft with biodegradable composite scaffolds consisting of medical-grade polycaprolactone and tricalcium phosphate combined with autologous bone marrow-derived mesenchymal stem cells (MSCs) or recombinant human bone morphogenetic protein 7 (rhBMP-7). Critical-sized defects in sheep--a model closely resembling human bone formation and structure--were treated with autograft, rhBMP-7, or MSCs. Bridging was observed within 3 months for both the autograft and the rhBMP-7 treatment. After 12 months, biomechanical analysis and microcomputed tomography imaging showed significantly greater bone formation and superior strength for the biomaterial scaffolds loaded with rhBMP-7 compared to the autograft. Axial bone distribution was greater at the interfaces. With rhBMP-7, at 3 months, the radial bone distribution within the scaffolds was homogeneous. At 12 months, however, significantly more bone was found in the scaffold architecture, indicating bone remodeling. Scaffolds alone or with MSC inclusion did not induce levels of bone formation comparable to those of the autograft and rhBMP-7 groups. Applied clinically, this approach using rhBMP-7 could overcome autograft-associated limitations.

Masquelet's procedure and bone morphogenetic protein in congenital pseudarthrosis of the tibia in children: a case series and meta-analysis

PURPOSE

A type 2 recombinant human bone morphogenetic protein (rhBMP2) and Masquelet's procedure were used in three children presenting with congenital pseudarthrosis of the tibia (CPT). Recent studies on CPT suggested the presence in situ of pathologic tissues promoting pseudarthrosis. The authors hypothesized that large segmental resection of pseudarthrosis could improve prognosis of the CPT. Masquelet's procedure and rhBMP2 have been advocated for the treatment of long bone defect.

METHOD

The authors report three cases of CPT in children treated with Masquelet's procedure and application of rhBMP2. They analyzed all published cases of CPT similarly treated.

RESULTS

In the present study, Masquelet's procedure did not improve the results in the treatment of CPT, but segmental bone reconstruction was possible. Bone healing was obtained in three out of the five applications of rhBMP2. In one case, the patient's parents asked for leg amputation. Analysis of the 33 published cases with the application of BMP in CPT points to a 62 % healing rate in this pathology.

CONCLUSION

The authors confirmed that segmental bone reconstruction is possible in CPT using Masquelet's procedure. In the literature, the success rate of the application of rhBMP in CPT appears to be lower than the healing rate usually reported without BMP. Nevertheless, the strict selection of patients, limited number of cases, and their heterogeneity make interpreting the results difficult. However, the theoretical risk which the children are exposed to during the use of BMP makes rigorous selection of the indications necessary. Finally, the interest of rhBMP2 application in Masquelet's procedure remained to be proven.

Stimulation of osteogenic differentiation in human osteoprogenitor cells by pulsed electromagnetic fields: an in vitro study

BACKGROUND

Although pulsed electromagnetic field (PEMF) stimulation may be clinically beneficial during fracture healing and for a wide range of bone disorders, there is still debate on its working mechanism. Mesenchymal stem cells are likely mediators facilitating the observed clinical effects of PEMF. Here, we performed in vitro experiments to investigate the effect of PEMF stimulation on human bone marrow-derived stromal cell (BMSC) metabolism and, specifically, whether PEMF can stimulate their osteogenic differentiation.

METHODS

BMSCs derived from four different donors were cultured in osteogenic medium, with the PEMF treated group being continuously exposed to a 15 Hz, 1 Gauss EM field, consisting of 5-millisecond bursts with 5-microsecond pulses. On culture day 1, 5, 9, and 14, cells were collected for biochemical analysis (DNA amount, alkaline phosphatase activity, calcium deposition), expression of various osteoblast-relevant genes and activation of extracellular signal-regulated kinase (ERK) signaling. Differences between treated and control groups were analyzed using the Wilcoxon signed rank test, and considered significant when p < 0.05.

RESULTS

Biochemical analysis revealed significant, differentiation stage-dependent, PEMF-induced differences: PEMF increased mineralization at day 9 and 14, without altering alkaline phosphatase activity. Cell proliferation, as measured by DNA amounts, was not affected by PEMF until day 14. Here, DNA content stagnated in PEMF treated group, resulting in less DNA compared to control.Quantitative RT-PCR revealed that during early culture, up to day 9, PEMF treatment increased mRNA levels of bone morphogenetic protein 2, transforming growth factor-beta 1, osteoprotegerin, matrix metalloproteinase-1 and -3, osteocalcin, and bone sialoprotein. In contrast, receptor activator of NF-κB ligand expression was primarily stimulated on day 14. ERK1/2 phosphorylation was not affected by PEMF stimulation.

CONCLUSIONS

PEMF exposure of differentiating human BMSCs enhanced mineralization and seemed to induce differentiation at the expense of proliferation. The osteogenic stimulus of PEMF was confirmed by the up-regulation of several osteogenic marker genes in the PEMF treated group, which preceded the deposition of mineral itself. These findings indicate that PEMF can directly stimulate osteoprogenitor cells towards osteogenic differentiation. This supports the theory that PEMF treatment may recruit these cells to facilitate an osteogenic response in vivo.

Enhancement of difficult nonunion in children with osteogenic protein-1 (OP-1): early experience

Numerous studies have described the use of osteogenic protein-1 (OP-1) in adults, but there are few reports in children. The objectives of this short-term followup cohort study were (1) to examine clinical and radiographic healing of persistent nonunions after OP-1 application in children; and (2) to determine the safety of OP-1 use in this sample. Clinical healing was defined by absence of pain and tenderness at the nonunion site and the ability to fully weight bear on the affected limb. Radiographic healing was determined by bony bridging of the nonunion site in at least one view. Safety was defined as the absence of major adverse events, including allergic reactions, infections, local inflammatory reactions, and heterotopic ossification. OP-1 was used in 19 patients who had an operative procedure for the bridging of persistent nonunions between 1999 and 2007. The mean age was 11.6 years (range, 4.8-20.3 years). Thirteen patients had persistent nonunion after one or more previous surgeries, prior to the initial OP-1 application. A single dose of 3.5 mg of OP-1 mixed with 1 g of Type I bovine collagen was applied to 23 sites of 19 patients. Three patients received additional OP-1 applications. Healing occurred clinically and radiographically in 17 of the 23 sites. Complications included four superficial pin site infections, one deep infection, and two fractures. No major local adverse event related to OP-1 application was noted in our sample. Our findings suggest OP-1 stimulates healing of persistent nonunions without major adverse events in our patient population.

LEVEL OF EVIDENCE

Level IV, case series. See the guidelines online for a complete description of levels of evidence.

Intramedullary application of bone morphogenetic protein in the management of a major bone defect after an Ilizarov procedure

We describe a patient with insufficient bone regeneration of the tibia after bone transport over an intramedullary nail, in whom union was ultimately achieved after exchange nailing and intramedullary application of rh-bone morphogenetic protein-7 at the site of distraction.

Bone morphogenetic proteins in clinical applications

The role of bone morphogenetic proteins (BMPs) in bone healing has been shown in numerous animal models. To date, at least 20 BMPs have been identified, some of which have been shown in vitro to stimulate the process of stem cell differentiation into osteoblasts in human and animal models. Having realized the osteoinductive properties of BMPs and having identified their genetic sequences, recombinant gene technology has been used to produce BMPs for clinical application - most commonly, as alternatives or adjuncts in the treatment of cases in which fracture healing is compromised. BMP-2 and BMP-7 are approved for clinical use in open fractures of long bones, non-unions and spinal fusion. However, despite significant evidence of their potential benefit to bone repair and regeneration in animal and preclinical studies, there is, to date, a dearth of convincing clinical trials. The purpose of this paper is to give a brief overview of BMPs and to critically review the clinical data currently available on the use of BMP-2 and BMP-7 in fracture healing.