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Self-complementary AAV2.5-BMP2-coated femoral allografts mediated superior bone healing versus live autografts in mice with equivalent biomechanics to unfractured femur.

ABSTRACT: Structural allografts used for critical bone defects have limited osteogenic properties for biointegration. Although ex vivo tissue-engineered constructs expressing bone morphogenetic protein-2 (BMP2) have demonstrated efficacy in critical defect models, similar success has not been achieved with off-the-shelf acellular approaches, including allografts coated with freeze-dried single-stranded adeno-associated virus (ssAAV-BMP2). To see whether the self-complementary AAV serotype 2.5 vector (scAAV2.5-BMP2) could overcome this, we performed side-by-side comparisons in vitro and in the murine femoral allograft model. Although ssAAV-BMP2 was unable to induce BMP2 expression and differentiation of C3H10T1/2 cells in culture, scAAV2.5-BMP2 transduction led to dose-dependent BMP2 expression and alkaline phosphatase activity, and displayed a 25-fold increased transduction efficiency in vivo. After 6 weeks, the ssAAV-BMP2 coating failed to demonstrate any significant effects. However, all allografts coated with 10(10) scAAV2.5-BMP2 formed a new cortical shell that was indistinguishable to that formed by live autografts. Additionally, coated allografts experienced reduced resorption resulting in a threefold increase in graft bone volume versus autograft. This led to biomechanical superiority versus both allografts and autografts, and equivalent torsional rigidity to unfractured femur. Collectively, these results demonstrate that scAAV2.5-BMP2 coating overcomes the major limitations of structural allografts, which can be used to heal critical defects of any size.

SUBMITTER: Yazici C

PROVIDER: S-EPMC3149158 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Self-complementary AAV2.5-BMP2-coated femoral allografts mediated superior bone healing versus live autografts in mice with equivalent biomechanics to unfractured femur.

Yazici Cemal C Takahata Masahiko M Reynolds David G DG Xie Chao C Samulski R Jude RJ Samulski Jade J Beecham E Jeffrey EJ Gertzman Arthur A AA Spilker Mark M Zhang Xinping X O'Keefe Regis J RJ Awad Hani A HA Schwarz Edward M EM

Molecular therapy : the journal of the American Society of Gene Therapy 20110104 8

Structural allografts used for critical bone defects have limited osteogenic properties for biointegration. Although ex vivo tissue-engineered constructs expressing bone morphogenetic protein-2 (BMP2) have demonstrated efficacy in critical defect models, similar success has not been achieved with off-the-shelf acellular approaches, including allografts coated with freeze-dried single-stranded adeno-associated virus (ssAAV-BMP2). To see whether the self-complementary AAV serotype 2.5 vector (scAA ...[more]

PMID: 21206485

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Project description:BackgroundWith the improved survival for patients with malignant bone tumors, there is a trend to reconstruct defects using biologic techniques. While the use of an intercalary allograft is an option, the procedures are technically demanding and it is unclear whether the complication rates and survival are similar to other approaches.Questions/purposesWe evaluated survivorship, complications, and functional scores of patients after receiving intercalary femur segmental allografts.Patients and methodsWe retrospectively reviewed 83 patients who underwent an intercalary femur segmental allograft reconstruction. We determined allograft survival using the Kaplan-Meier method. We evaluated patient function with the Musculoskeletal Tumor Society scoring system. Minimum followup was 24 months (median, 61 months; range, 24-182 months).ResultsSurvivorship was 85% (95% confidence interval: 93%-77%) at 5 years and 76% (95% confidence interval: 89%-63%) at 10 years. Allografts were removed in 15 of the 83 patients: one with infection, one with local recurrence, and 13 with fractures. Of the 166 host-donor junctions, 22 (13%) did not initially heal. Nonunion rate was 19% for diaphyseal junctions and 3% for metaphyseal junctions. We observed an increase in the diaphysis nonunion rate in patients fixed with nails (28%) compared to those fixed with plates (15%). Fracture rate was 17% and related to areas of the allograft not adequately protected with internal fixation. All patients without complications had mainly good or excellent Musculoskeletal Tumor Society functional results.ConclusionsDiaphyseal junctions have higher nonunion rates than metaphyseal junctions. The internal fixation should span the entire allograft to avoid the risk of fracture. Our observations suggest segmental allograft of the femur provides an acceptable alternative in reconstructing tumor resections.Level of evidenceLevel IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Project description:PurposeTo evaluate the evidence of the effectiveness and safety of allografts compared to autografts in posterior cruciate ligament reconstruction.MethodsFour electronic databases were systematically searched for eligible randomized controlled studies. Crucial effectiveness outcomes included patient-reported function, activity level and symptoms, clinical knee stability, health-related quality of life, and patient satisfaction. Safety was evaluated through graft failures, revisions, reruptures and complications. The internal validity of the studies was assessed by the Cochrane risk of bias tool, and the strength of the evidence was judged according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE).ResultsTwo randomized controlled studies were included: 50 patients were analyzed in the allograft group and 58 in the autograft group. No statistically significant postoperative differences were reported between the groups for patient-reported function, activity levels or symptoms. One study reported a statistically significant difference in instrumented postoperative anteroposterior knee laxity favoring stability in autografts. This difference is, however, not relevant in the clinical setting. Insufficient evidence was found to judge safety outcomes and because complications were poorly measured, and none of the studies reported on graft failure, revision or rerupture rates. The studies were judged with unclear to high risk of bias. The strength of the evidence for effectiveness and safety was judged to be low to very low, according to GRADE.ConclusionsAllografts may be comparable to autografts for crucial effectiveness outcomes, but insufficient evidence was found to judge crucial safety outcomes due to poor reporting of safety measures and outcomes. Results should be interpreted with caution because there is lack of good-quality evidence to support the superiority of allografts over autografts due to the high risk of bias in the primary studies and overall very low strength of the body of evidence according to GRADE.Level of evidenceSystematic review of Level II studies.

Project description:A major parameter determining the success of a bone-grafting procedure is vascularization of the area surrounding the graft. We hypothesized that implantation of a bone autograft would induce greater bone regeneration by abundant blood vessel formation. To investigate the effect of the graft on neovascularization at the defect site, we developed a micro-computed tomography (µCT) approach to characterize newly forming blood vessels, which involves systemic perfusion of the animal with a polymerizing contrast agent. This method enables detailed vascular analysis of an organ in its entirety. Additionally, blood perfusion was assessed using fluorescence imaging (FLI) of a blood-borne fluorescent agent. Bone formation was quantified by FLI using a hydroxyapatite-targeted probe and µCT analysis. Stem cell recruitment was monitored by bioluminescence imaging (BLI) of transgenic mice that express luciferase under the control of the osteocalcin promoter. Here we describe and demonstrate preparation of the allograft, calvarial defect surgery, µCT scanning protocols for the neovascularization study and bone formation analysis (including the in vivo perfusion of contrast agent), and the protocol for data analysis. The 3D high-resolution analysis of vasculature demonstrated significantly greater angiogenesis in animals with implanted autografts, especially with respect to arteriole formation. Accordingly, blood perfusion was significantly higher in the autograft group by the 7(th) day after surgery. We observed superior bone mineralization and measured greater bone formation in animals that received autografts. Autograft implantation induced resident stem cell recruitment to the graft-host bone suture, where the cells differentiated into bone-forming cells between the 7(th) and 10(th) postoperative day. This finding means that enhanced bone formation may be attributed to the augmented vascular feeding that characterizes autograft implantation. The methods depicted may serve as an optimal tool to study bone regeneration in terms of tightly bounded bone formation and neovascularization.

Dataset Information

Self-complementary AAV2.5-BMP2-coated femoral allografts mediated superior bone healing versus live autografts in mice with equivalent biomechanics to unfractured femur.

Publications

Self-complementary AAV2.5-BMP2-coated femoral allografts mediated superior bone healing versus live autografts in mice with equivalent biomechanics to unfractured femur.

Similar Datasets

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