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

Biology of Bone Morphogenetic Proteins in Skeleton Disease: Osteonecrosis in Sickle Cell Disease Patients

Abstract:

Sickle cell disease (SCD) is an autosomal recessive trait of genetic hemoglobin disorder whose prevalence is varied from 5 to 25 % of the world population. It is characterized by the presence of hemoglobin (HbS) instead of normal hemoglobin (HbA). An individual suffering from sickle cell disease is likely to be at risk of osteonecrosis which is a form of ischemic bone infarction which causes intolerable degenerative joint problems and can affect 30-50% of people with sickle cell disease. The femoral head is the most frequent epiphyseal location in osteonecrosis with sickle cell disease. In this review, the Bone morphogenetic protein (BMP)-a subfamily of transforming growth factor-β (TGF-β) characteristics, outlined the osteoblastogenesis potentiality via using combinatorial or advanced treatment approaches. In this review, we aim to describe the Bone morphogenetic proteins' role in Skeleton diseases and discuss the potent osteogenic BMPs (majorly BMP-2, BMP-6, and BMP-7) with therapeutic benefits.

rhBMP-2 and Intramedullary Fixation in Congenital Pseudarthrosis of the Tibia

BACKGROUND

In congenital pseudarthrosis of the tibia, use of intramedullary (IM) fixation and autogenous bone graft has long been the standard of care. This study was undertaken to determine whether the addition of rhBMP-2 to this treatment method further enhances healing potential.

METHODS

Twenty-one patients with congenital pseudarthrosis of the tibia were evaluated. Fifteen of these patients had neurofibromatosis type 1 (NF1). All had IM fixation and autogenous bone graft, followed by a BMP-soaked collagen sponge wrapped around both the fracture site and bone graft. A minimum 2 years' follow-up was required.

RESULTS

Follow-up averaged 7.2 years (range, 2.1 to 12.8 y). Sixteen of 21 tibias achieved bone union following the index surgery, at an average 6.6 months postoperatively. The 5 persistent nonunions occurred in NF1 patients. Further surgery was undertaken in these 5 NF1 patients, including the use of BMP. One of the 5 healed, 1 had persistent nonunion, and 3 eventually had amputation. Of the 16 patients who healed initially following the index surgery, 5 refractured (3 had NF1). Of these 5 patients, the IM fixation at the index surgery did not cross the ankle joint, and refracture occurred at the rod tip in 4. Three of these 5 patients healed following further surgery, 1 had persistent nonunion, and 1 had amputation. All of those with eventual amputation had NF1. No deleterious effects related to the use of BMP-2 were recognized in any patient.

CONCLUSIONS

The addition of rhBMP-2 appears to be helpful in shortening the time required to achieve fracture union in those who healed, but its use does not insure that healing will occur.

LEVEL OF EVIDENCE

Level IV-therapeutic, case series.

Strategies of enhancing bone regenerate formation in distraction osteogenesis

Distraction osteogenesis (DO) is a commonly used technique in multiple orthopedic sub-specialties, including trauma, oncology and pediatrics. This technique aims to produce new bone formation in the distraction gap in a controlled manner. The issue with this technique has been the high risk of complications, one of which is poor regenerate formation during the distraction process. Although several factors (including patient and operative factors) and techniques (including surgical, mechanical and pharmacological) have been described to ensure successful regenerate formation during the process of DO, these factors are sometimes difficult to control clinically. Our aim from this review is to highlight the different factors that affect DO, modalities to assess the regenerate and review treatment options for poor regenerate in the distraction gap. In addition, we propose a management protocol derived from the available literature that can be used to facilitate the management of inadequate regenerate formation.

Bone mesenchymal stem cells co-expressing VEGF and BMP-6 genes to combat avascular necrosis of the femoral head

The aim of the present study was to investigate the potential of bone mesenchymal stem cells (BMSCs) treated with a combination of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-6 (BMP-6) genes for the treatment of avascular necrosis of the femoral head (ANFH). Rat BMSCs were isolated and purified using a density gradient centrifugation method. The purity and characteristics of the BMSCs were detected by cell surface antigens identification using flow cytometry. The experimental groups were administered with one of the following adeno-associated virus (AAV) vector constructs: AAV-green fluorescent protein (AAV-GFP), AAV-BMP-6, AAV-VEGF or AAV-VEGF-BMP-6. The expression of VEGF and BMP-6 was detected by reverse transcription-quantitative polymerase chain reaction, western blotting and ELISA assays. The effects of VEGF and BMP-6 on BMSCs were evaluated by angiogenic and osteogenic assays. The transfected BMSCs were combined with a biomimetic synthetic scaffold poly lactide-co-glycolide (PLAGA) and they were then subcutaneously implanted into nude mice. After four weeks, the implants were analyzed with histology and subsequent immunostaining to evaluate the effects of BMSCs on blood vessel and bone formation in vivo. In the AAV-VEGF-BMP-6 group, the expression levels of VEGF and BMP-6 were significantly increased and human umbilical vein endothelial cells tube formation was significantly enhanced compared with other groups. Capillaries and bone formation in the AAV-VEGF-BMP-6 group was significantly higher compared with the other groups. The results of the present study suggest that BMSCs expressing both VEGF and BMP-6 induce an increase in blood vessels and bone formation, which provides theoretical support for ANFH gene therapy.

Bone morphogenetic protein-2 for the treatment of congenital pseudarthrosis of the tibia or persistent tibial nonunion in children and adolescents: A retrospective study with a minimum 2-year follow-up

There is a lack of studies reporting on rhBMP-2 application in pediatric orthopaedics, although few reports demonstrated promising results of the use of rhBMP-2 in children, especially for spine fusion and for the treatment of congenital pseudarthrosis of the tibia. The objectives of this study were (1) to examine clinical and radiographic healing after rhBMP-2 application for the treatment of congenital pseudarthrosis of the tibia (CPT) or persistent tibial nonunion in children and adolescents, and (2) to investigate the safety of rhBMP-2 use in these cases. Therefore we reviewed the medical records of ten patients with a mean age of 8.6 years (2.3-21) with CPT (n = 7) or persistent tibial nonunion for at least six months (n = 3) who had been treated with rhBMP-2. Nine of ten patients had union at final follow-up, after a mean of 72.9 months (25-127). In the CPT group, primary healing of the pseudarthrosis occurred in six of seven patients at a mean of 5.2 months (3-12). Repeat rhBMP-2 application was performed in three patients; two patients had one additional application each, and one patient had three additional applications. Complications that may be attributed to the use of rhBMP-2 were seen in two of fifteen applications, including a compartmemt syndrome and a hematoma. In this retrospective case series rhBMP-2 has been used successfully to treat CPT or persistent tibial nonunion in pediatric patients. However, prospective randomized controlled trials are warranted to investigate the long-term efficacy and safety of rhBMP-2 use in these cases.

Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) for the Treatment of Nonunion of the Femur in Children and Adolescents: A Retrospective Analysis

Background. The aim of this study was to examine clinical and radiographic healing after rhBMP-2 application in children and adolescents presenting with nonunion of the femur and to investigate the safety of rhBMP-2 use in these cases. Materials and Methods. We reviewed the medical records of five patients with a mean age of 11 years (5.4 to 16.2) with nonunion of the femur who were treated with rhBMP-2 and internal fixation using a locking plate at a single institution. Particular attention was paid to identify all adverse events that may be due to rhBMP-2 use. Results. Union occurred in four of five patients at a mean of 12.1 months (7.9 to 18.9). The locking plates were removed after a mean of 16 months (11 to 23). One patient had nonunion due to deep infection. After a mean follow-up of 62.5 months (17 to 100), union was still evident in all four patients and they were fully weight-bearing without pain. Discussion. In this retrospective study, rhBMP-2 combined with a locking plate has been used successfully to treat children and adolescents with nonunion of the femur in four of five cases. One major complication was thought to be possibly related to its use.

The use of recombinant morphogenic protein-2(rhBMP-2) in children undergoing revision surgery for persistent non-union

The purpose of the study was to evaluate the safety and efficacy with the use of BMP-2 for treating persistent non-unions in children with underlying complex conditions. Between October 2006 and November 2010 in our unit, 15 patients were treated with rhBMP-2 to enhance bone union. There were nine females and six males with a mean age of 9.5 years (range 4–15) at time of surgery. Seventy-five per cent of the patients required revision of internal fixation with insertion of rhBMP-2 to the non-union site, and the reminder had freshening of the non-union site with rhBMP-2 application. Patients had undergone a mean of 2 (1–5) operations prior to implantation of rhBMP-2. All the patients in the study group were available for review with mean follow-up of 44 months (range 21–70). The mean time to union was 16 weeks (range 10–28 weeks). No adverse events related to BMP-2 application were noted in our study group. Healing occurred clinically and radiographically in 16 of the 17 sites. Our study demonstrates that BMP-2 enhances healing of the persistent non-unions without any adverse events

Comprehensive Review of Adipose Stem Cells and Their Implication in Distraction Osteogenesis and Bone Regeneration

Bone is one of the most dynamic tissues in the human body that can heal following injury without leaving a scar. However, in instances of extensive bone loss, this intrinsic capacity of bone to heal may not be sufficient and external intervention becomes necessary. Several techniques are available to address this problem, including autogenous bone grafts and allografts. However, all these techniques have their own limitations. An alternative method is the technique of distraction osteogenesis, where gradual and controlled distraction of two bony segments after osteotomy leads to induction of new bone formation. Although distraction osteogenesis usually gives satisfactory results, its major limitation is the prolonged duration of time required before the external fixator is removed, which may lead to numerous complications. Numerous methods to accelerate bone formation in the context of distraction osteogenesis have been reported. A viable alternative to autogenous bone grafts for a source of osteogenic cells is mesenchymal stem cells from bone marrow. However, there are certain problems with bone marrow aspirate. Hence, scientists have investigated other sources for mesenchymal stem cells, specifically adipose tissue, which has been shown to be an excellent source of mesenchymal stem cells. In this paper, the potential use of adipose stem cells to stimulate bone formation is discussed.

Ilizarov bone transport as a treatment of congenital pseudarthrosis of the tibia: a long-term follow-up study

PURPOSE

Most studies on congenital pseudarthrosis of the tibia (CPT) report on the short-term union rate and refracture rate but do not take into account the long-term outcome. This review includes patients treated with an Ilizarov bone transport, who all reached skeletal maturity. It describes long-term results and highlights any prognostic factors that could predict the final outcome.

METHODS

The records of patients with CPT treated with an Ilizarov bone transport in our institution were retrospectively evaluated.

RESULTS

A total of 12 consecutive patients were studied. The mean follow-up was 24.5 years (range 6-39 years). Primary consolidation was seen in ten patients (83 %). Half of these patients had a refracture. At final follow-up, eight patients experienced union and four remained un-united, of whom one had an amputation.

CONCLUSIONS

The present data confirm a good primary healing rate. However, tibial union at final follow-up was only seen in 67 %, indicating that refracture is the main issue. United bone is often of inferior biological and mechanical quality, so lifetime protection with intramedullary devices, braces or a combination of both is recommended.

Bone Regeneration Using Bone Morphogenetic Proteins and Various Biomaterial Carriers

Trauma and disease frequently result in fractures or critical sized bone defects and their management at times necessitates bone grafting. The process of bone healing or regeneration involves intricate network of molecules including bone morphogenetic proteins (BMPs). BMPs belong to a larger superfamily of proteins and are very promising and intensively studied for in the enhancement of bone healing. More than 20 types of BMPs have been identified but only a subset of BMPs can induce de novo bone formation. Many research groups have shown that BMPs can induce differentiation of mesenchymal stem cells and stem cells into osteogenic cells which are capable of producing bone. This review introduces BMPs and discusses current advances in preclinical and clinical application of utilizing various biomaterial carriers for local delivery of BMPs to enhance bone regeneration.

Effectiveness of recombinant human bone morphogenetic protein-7 in the management of congenital pseudoarthrosis of the tibia: a randomised controlled trial

PURPOSE

Despite the popularity and an increased use of bone morphogenetic protein to improve bone healing in patients with congenital pseudoarthrosis of the tibia (CPT), no previous study has compared its efficacy against any other procedure.

METHODS

We randomised 20 consecutive patients (mean age 4.1 years) with CPT (Crawford type IV) associated with neurofibromatosis type 1(NF1) and no previous history of surgery into two groups. Group 1 received recombinant human bone morphogenetic protein-7 (rhBMP-7) along with intramedullary Kirschner (K)-wire fixation and autologous bone grafting; group 2 received only K wire and grafting. Outcome measures were time to achieve union, Johnston grade, tibial length and the American Orthopaedic Foot and Ankle Society (AOFAS) score, which were evaluated preoperatively and at five year follow-up.

RESULTS

Study results showed that patients in group 1 achieved primary bone union at a mean of 14.5 months [standard error (SE) 5.2], whereas group 2 took a mean of 17.11 months (SE 5.0). However, the log-rank test showed no difference in healing times between groups at all time points (P = 0.636). There was a statistically significant pre- to post operative improvement (P < 0.05) within groups for the other outcome measures.

CONCLUSION

In a five year follow-up, these results suggest that rh-BMP-7 and autologous bone grafting is no better than autologous grafting alone.

Controversies in the management of congenital pseudarthrosis of the tibia and fibula

Congenital pseudarthrosis of the tibia (CPT) is a rare but well recognised condition. Obtaining union of the pseudarthrosis in these children is often difficult and may require several surgical procedures. The treatment has changed significantly since the review by Hardinge in 1972, but controversies continue as to the best form of surgical treatment. This paper reviews these controversies.

Cite this article: Bone Joint J 2013;95-B:1027–34.

BMP Signaling in Regenerative Medicine

More than 40 years after the discovery of Bone Morphogenetic Proteins (BMPs) as bone inducers, a whole protein family of growth factors connected to a wide variety of functions in embryonic development, homeostasis, and regeneration has been characterized. Today, BMP2 and BMP7 are already used in the clinic to promote vertebral fusions and restoration of non-union fractures. Besides describing present clinical applications, the authors review ongoing trials highlighting the future possibilities of BMPs in medicine. Apparently, the physiological roles of BMPs have expanded their range from bone growth induction and connective tissue regeneration to cancer diagnosis/treatment and cardiovascular disease prevention.

Clinical applications of growth factors in bone injuries: experience with BMPs

The management of open fractures and delayed or non unions continue to be complicated by high rates of treatment failure and significant patient disability and dissatisfaction. The use of bone morphogenetic proteins (BMPs) in the treatment of these injuries has been assessed by several authors. BMPs induce the process of bone healing by recruiting bone-forming cells to the area of lesion. The use of BMP currently has two FDA-approved indications: treatment of open tibial fractures treated with intramedullary fixation and treatment of tibia long bone non-union. Despite this limited target, off-label BMP use continues to push the spectrum for new applications. This review describes the current evidence for the use of BMPs in open fractures and non-unions.

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.

Technique to prepare the bed for autologous bone grafting in nonunion surgery

This article describes a technique for preparing the bed for autologous bone grafting in nonunion surgery. The procedure is divided into 2 steps. First, both ends of the fracture fragments are chipped into small pieces using an osteotome and hammer without peeling off the periosteum, creating pathways into the bone marrow. Second, cancellous bone harvested from the iliac crest is grafted into the aperture created by the previous bone chipping treatment. The technique is easy to perform and is a promising approach for enhancing bone healing in nonunion and delayed union.

Congenital pseudarthrosis of the tibia

Congenital pseudarthrosis of the tibia (CPT) is an uncommon disease with various clinical presentations ranging from simple anterolateral tibial angulation to complete non-union with extensive bone defects. Classifications of radiographic findings include atrophic or hypertrophic pseudarthosis as well as cystic or dystrophic lesions. Although the relationship between CPT and type 1 neurofibromatosis is well known, the exact pathogenesis still remains unclear. The fibrous soft tissue found in the pseudarthosis and the abnormal periosteum are certainly a key to the pathology, possibly due to decreased osteogenic capacities and impaired local vascularization. Treatment of CPT is still challenging in pediatric orthopedics because of bone union difficulties, persistant angulation, joint stiffness and sometimes severe limb length discrepancy sequellae. Numerous treatments based on biological and/or mechanical concepts, surgical or not, have been reported with variable success rates. Vascularized fibular grafts and the Ilizarov technique have greatly transformed the prognosis of CPT. Despite these steps forward, repeated surgical procedures are often necessary to obtain bone union and the risk of amputation is never entirely eliminated. The effectiveness of new treatments (bone morphogenetic protein, bone marrow stromal cell grafts, pulsed electromagnetic fields, induced membrane technique…) still requires to be confirmed. Combining these new techniques with existing treatments may improve the final prognosis of CPT, which nevertheless remains poor.

Mesenchymal Stem Cells in Combination with Scaffolds for Bone Tissue Engineering

This article reviews past and current strategies of the use of bone graft substitutes along with the future biologic alternatives that can enhance the functional capabilities of those grafts. Many of these bone graft substitute alternatives include ceramic-based, allograft-based, factor-based and polymer-based whereas others are cell-based. The ways of achieving the goal of tissue engineering using stem cells and their lineage to regenerate tissue have been detailed with regard to both the generation of sufficient vascular invasion of the tissue to improve oxygen and nutrient supply, and the development of innovative physical/chemical stimuli to induce bone formation with the proper biomaterial to carry the cells. It is imperative to integrate basic polymer science with molecular biology and stem cell biology, in the design of new materials that perform very sophisticated signaling needed for integration and function.

Bone morphogenetic proteins in orthopaedic trauma surgery

Fracture healing describes the normal post-traumatic physiologic process of bone regeneration. Commonly, this complicated process occurs without interruption, however, certain clinical situations exist that may benefit from the usage of bone healing enhancement agents. Bone morphogenetic proteins (BMPs) assist in the process of bone healing by recruiting bone-forming cells to the area of trauma. The usage of BMP currently has two FDA-approved indications: (1) treatment of acute tibial fractures treated with intramedullary fixation and (2) treatment of long bone non-union. Despite this limited scope, off-label BMP usage continues to push the envelope for new applications. Although proven to be clinically successful, BMP use must be balanced with the large costs associated with their application. Regardless, more prospective randomised clinical trials must be conducted to validate and expand the role of BMP in the setting of trauma.

Enhancement of recombinant human BMP-7 bone formation with bmp binding peptide in a rodent femoral defect model

Bone morphogenetic binding peptide (BBP) is an 18.5 kDa fragment of a bone matrix protein peptide. A rat femoral defect model was used to test the effect of BBP combined with recombinant human bone morphogenetic protein-7 (rhBMP-7) to induced bone healing. Two doses of BBP (500 and 1000 µg) were tested with two doses of rhBMP-7 (2 and 5 µg), and the results were compared with a positive control (10 µg rhBMP-7). Bone healing was evaluated by radiology, manual palpation, microcomputed tomography, and histology. The high dose of 10 µg of rhBMP-7 resulted in a consistent 100% bone union rate and a mature histological appearance on histology, and was used as a positive control. When 1000 µg of BBP was combined with lower doses of BMP-7 (2 µg rhBMP-7 or 5 µg rhBMP-7) significant differences were seen in radiographic scores, manual palpation, and bone volume, when compared to 2 µg rhBMP-7 or 5 µg rhBMP-7 alone. The combination of 1000 µg of BBP and 5 µg rhBMP-7 also achieved 100% fusion rate, induced a larger amount of bone formation, and yielded similar maturity of bone marrow when compared with the high dosage 10 µg rhBMP-7 group. This study demonstrated that when combined together, BBP can enhance the bone healing of rhBMP-7. Improved healing imparted by the addition of BBP may result in lesser amounts of rhBMP-7 needed to achieve union in the clinical setting.

VEGF and BMP-6 enhance bone formation mediated by cloned mouse osteoprogenitor cells

New strategies such as combined utilization of growth factors may provide a better treatment for difficult fractures. We have demonstrated enhanced angiogenesis and osteogenesis through the actions of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-6 (BMP-6) on the osteogenic differentiation of a cloned mouse osteoprogenitor cell in vitro and ectopic bone formation in vivo. Human VEGF and BMP-6 genes expressed together produced a significant increase in alkaline phosphatase activity, expression of the RunX2 and osteocalcin genes and mineralization. Microcomputed tomographic analysis of subcutaneous implants consisting of cells transfected with VEGF and BMP-6 cDNA and delivered on a 3D poly (lactic-co-glycolic acid) scaffold confirmed the additive effects between VEGF and BMP-6. Ectopic bone formation in the VEGF plus BMP-6 group was greatest compared to that in either VEGF or BMP-6 alone. This is the first study that demonstrates osteogenesis in vitro and in vivo through the additive effects of VEGF and BMP-6.