The influence of Bone Morphogenic Protein-2 on the consolidation phase in a distraction osteogenesis model

Regenerative medicine in lower limb reconstruction

Bone is a highly specialized connective tissue and has a rare quality as one of the few tissues that can repair without a scar to regain pre-injury structure and function. Despite the excellent healing capacity of bone, tumor, infection, trauma and surgery can lead to significant bone loss requiring skeletal augmentation. Bone loss in the lower limb poses a complex clinical problem, requiring reconstructive techniques to restore form and function. In the past, amputation may have been the only option; however, there is now an array of reconstructive possibilities and cellular therapies available to salvage a limb. In this review, we will evaluate current applications of bone tissue engineering techniques in limb reconstruction and identify potential strategies for future work.

Sclerostin antibody enhances bone formation in a rat model of distraction osteogenesis

Neutralizing monoclonal sclerostin antibodies are effective in promoting bone formation at a systemic level and in orthopedic scenarios including closed fracture repair. In this study we examined the effects of sclerostin antibody (Scl-Ab) treatment on regenerate volume, density, and strength in a rat model of distraction osteogenesis. Surgical osteotomy was performed on 179 Sprague Dawley rats. After 1 week, rats underwent distraction for 2 weeks, followed by 6 weeks for consolidation. Two treatment groups received biweekly subcutaneous Scl-AbIII (a rodent form of Scl-Ab; 25 mg/kg), either from the start of distraction onward or restricted to the consolidation phase. These groups were compared to controls receiving saline. Measurement modalities included longitudinal DXA, ex vivo QCT, and microCT, tissue histology, and biomechanical four-point bending tests. Bone volume was increased in both Scl-Ab treatments regimens by the end of consolidation (+26-38%, p < 0.05), as assessed by microCT. This was associated with increased mineral apposition. Importantly, Scl-Ab led to increased strength in united bones, and this reached statistical significance in animals receiving Scl-Ab during consolidation only (+177%, p < 0.01, maximum load to failure). These data demonstrate that Scl-Ab treatment increases bone formation, leading to regenerates with higher bone volume and improved strength. Our data also suggest that the optimal effects of Scl-Ab treatment are achieved in the latter stages of distraction osteogenesis. These findings support further investigation into the potential clinical application of sclerostin antibody to augment bone distraction, such as limb lengthening, particularly in the prevention of refracture. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1106-1113, 2018.

A New Way to Accelerate the Distraction of the Transpalatal Suture in Growing Dogs Using Recombinant Human Bone Morphogenetic Protein-2

OBJECTIVE

The purpose of this study was to evaluate the administration of recombinant human bone morphogenetic protein-2 (rhBMP-2) on trans-sutural distraction osteogenesis (TSDO) of the transverse palatal suture in growing dogs.

STUDY DESIGN

A total of 36 growing dogs were used in this study. The experimental animals were treated with different elastic force and rhBMP-2. The bone regeneration was determined with X-ray, histology, and clinical evaluation. The computed values underwent statistical analyses using analysis of variance.

RESULTS

The maxillary complex was most noticeably advanced with an applied elastic force of 600 g (22.4 ± 5.0 mm) and 800 g + rhBMP-2 (24 ± 5.1 mm). Immunohistochemical staining showed that the expression of bone morphogenetic protein-2 and bone morphogenetic protein-4 varied with different elastic force. These changes were statistically significant when 600 g and 800 g + rhBMP-2 were applied within 2 weeks of distraction when compared with controls (P < .05).

CONCLUSIONS

The results of this study suggest that TSDO in the growing dog should be safe and well tolerated when inducing bony lengthening of the maxilla. rhBMP-2 plays an important role in bone regeneration using TSDO.

Transport distraction osteogenesis with recombinant human bone morphogenic protein-2 for large calvarial defect reconstruction

BACKGROUND

Transport distraction osteogenesis (TDO) has been used in attempts to treat large calvarial defects but has, until now, lacked consistency and reliability. To achieve sufficient bone formation, the effect of TDO was compared to the effect of TDO combined with recombinant human bone morphogenic protein-2 (rhBMP-2).

METHODS

Fourteen dogs were divided into 2 groups; 6 animals in the control group received TDO only, and 8 received TDO combined with rhBMP-2. A calvarial defect 33 × 35 mm in size was generated, and the drug-delivering internal distractor was applied. After a 5-day latency period, distraction with rhBMP-2 at 10 μg/day was initiated at a rate of 2 mm/day. This was followed by a consolidation period of 3 months, after which areas of osteogenesis and strength were measured and histologic examinations were conducted.

RESULTS

The average area of osteogenesis was higher in the experimental group (P < 0.01). Regenerated bone of the experimental group showed increased strength (P < 0.05). Histological examination showed typical mature bone in the experimental group. Prominent osteoblastic rimming was observed in the bone marrow of the experimental group.

CONCLUSIONS

TDO with an internal distraction device delivering rhBMP-2 can enhance bone regeneration of large calvarial defects in a dog model. These results suggest the potential for human clinical testing of TDO combined with rhBMP-2.

Osteogenesis and mineralization in a rabbit mandibular distraction osteogenesis model is promoted by the human LMP-1 gene

To observe the effects of LIM mineralization protein-1 (LMP-1) on bone regeneration in the distraction zone based on gene transduction, 36 New Zealand white rabbits underwent mandibular lengthening with a distraction rate of 2 mm/day. The animals were then randomly divided into group A and group B (n = 18, each). At the end of the distraction, Ad5-EGFP viruses and Ad5-LMP-1/EGFP viruses were injected into the distraction gaps in groups A and B, respectively. Seven days later, five randomly selected animals from each group were sacrificed to evaluate the survival of the virus. Four and 8 weeks after distraction osteogenesis (DO), six samples randomly selected from each group underwent CT scanning and dual energy X-ray absorptiometry detection. Eight weeks after DO, the rabbits were sacrificed, and the distracted mandibles were harvested. Six animals from each group processed for radiography, micro-CT, histology, and the rest samples were taken three-point bend testing. Using this model, better bone formation and mineralization in the distracted callus were observed in group B when compared with those in group A. The results suggest local transduction with LMP-1 gene promotes osteogenesis and mineralization in DO.

Effects of caffeic acid phenethyl ester and melatonin on distraction osteogenesis: an experimental study

Aim

The aim of this experimental animal model study is to investigate the effects of caffeic acid phenethyl ester (CAPE) and melatonin on the maturation of newly-formed regenerated bone in distraction osteogenesis.

Methods

Unilateral femoral lengthening(extension) was applied to 39 adult male Wistar albino rats, which were randomly allocated to 3 groups of 13; control, melatonin and CAPE groups. Through a 7-day latent waiting period and 15 days of distraction, melatonin of 25 mg/kg and CAPE of 10 μmol/kg were administered to the respective groups. The animals were sacrificed on Day 82. Radiographic, histological and biomechanical evaluations were made and measurements were taken.

Results

At the end of 82 days, the distraction osteogenesis area was seen to be completely filled with new bone formation in all 3 groups both radiologically and histologically. Biomechanically, the maximum torsional fracture strength (Maximum Torque (N-m)) of the melatonin group was higher compared to that of the control group, although it was not statistically significant (p > 0.05). The maximum torsional momentum of the CAPE group was statistically significantly high (p < 0.05). The degree of rigidity (N-m/deg) of both the melatonin and CAPE groups was higher than that of the control group and the CAPE group was found to be statistically significantly higher than the melatonin group (p < 0.05).

Conclusion

Melatonin and CAPE increase the maturation of new bone in distraction osteogenesis. These effects are probably due to the reducing effect on bone resorption by inhibiting NF-κB and free oxygen radicals.