In vivo molecular imaging of adenoviral versus lentiviral gene therapy in two bone formation models.

Regional gene therapy techniques are promising methods to enhance bone formation in large bone defects that would be difficult to treat with allograft or autograft bone stock. In this study, we compared in vivo temporal expression patterns of adenoviral- and lentiviral-mediated gene therapy in two bone formation models. Primary rat bone marrow cells (RBMC) were transduced with lentiviral or adenoviral vectors containing luciferase (Luc) or BMP-2 cDNA, or cotransduced with vectors containing Luc and bone morphogenetic protein 2 (BMP-2). In vitro protein production was determined with luciferase assay or ELISA (for BMP-2 production) weekly for 12 weeks. Two bone formation models were used -- a hind limb muscle pouch or radial defect -- in SCID mice. A cooled charged-coupled device (CCD) camera was used to image in vivo luciferase expression weekly for 12 weeks. In vitro, adenoviral expression of BMP-2 and luciferase was detected by ELISA or luciferase assay, respectively, for 4 weeks. Lentiviral expression of BMP-2 and luciferase was sustained in culture for 3 months. Using the CCD camera, we found that adenoviral vectors expressed luciferase expression for up to 21 days, but lentiviral vectors expressed target gene expression for 3 months in vivo in both bone formation models. There was no detectable difference in the amount of bone formed between the adenoviral and lentiviral groups. Lentiviral-mediated delivery of BMP-2 can induce long term in vitro and in vivo gene expression, which may be beneficial when developing tissue engineering strategies to heal large bone defects or defects with a compromised biologic environment.     

Lentiviral-mediated BMP-2 gene transfer enhances healing of segmental femoral defects in rats

The objective of the present study was to assess the ability of bone marrow cells expressing BMP-2 created via lentiviral gene transfer to heal a critical sized femoral defect in a rat model. Femoral defects in Lewis rats were implanted with 5x10(6) rat bone marrow stromal cells (RBMSC) transduced with a lentiviral vector containing either the BMP-2 gene (Group I), the enhanced green fluorescent protein (LV-GFP) gene (Group IV), or RBMSC alone (Group V). We also included femoral defects that were treated with BMP-2-producing RBMSC transduced with lentivirus, 8 weeks after infection (Group III), and a group with 1x10(6) RBMSC transduced with a lentiviral vector with the BMP-2 gene (Group II). All defects (10/10) treated in Group I healed at 8 weeks compared with none of the femora in the control groups (Groups IV and V). In Group II, only one out of 10 femora healed. In Group III, 5 out of 10 femora healed. Significantly higher amounts of in vitro BMP-2 protein production were detected in Groups I, II, and III when compared to that of the control groups (p<0.05). Histomorphometric analysis revealed significantly greater total bone volume in defects in Group I and III when compared to control specimens (p<0.003). Biomechanical testing revealed no significant differences in the healed defects in Groups I and III when compared to intact, nonoperated femora with respect to peak torque and torque to failure. Our results indicate that BMP-2-producing RBMSC created through lentiviral gene transfer have the capability of inducing long-term protein production in vitro and producing substantial new bone formation in vivo.     

The effects of lentiviral gene therapy with bone morphogenetic protein-2-producing bone marrow cells on spinal fusion in rats

STUDY DESIGN: Rat spinal fusion model. OBJECTIVE: This study aimed to assess the ability of rat bone marrow cells (RBMCs) transfected with bone morphogenetic protein (BMP)-2-containing lentivirus to induce a posterolateral spinal fusion in a rat model. SUMMARY OF BACKGROUND DATA: Spinal arthrodesis is a commonly performed spinal procedure and autograft remains the standard for achieving spinal fusion. However, its procurement is associated with significant morbidity, and the rate of pseudoarthrosis has been reported to be 5% to 43%. Nonunion frequently leads to an unsatisfactory resolution of clinical symptoms and usually results in high medical costs and morbidity as well as the need for additional surgeries. These problems have led surgeons to search for alternative solutions to stimulate bone formation. Recombinant BMPs have also been used successfully in clinical trials. However, large doses of BMPs were required to induce adequate bone repair. The development of a regional gene therapy may be a more efficient method to deliver proteins to a specific anatomic site. Furthermore, adeno-BMP-2-producing rat bone marrow-derived cells have been used successfully to induce posterior spinal fusion. Recently, lentiviral vectors on the basis of human immunodeficiency virus have been developed for gene therapy. Lentiviruses are capable of insertion into the host genome, ensuring a prolonged gene expression. However, safety issues are a major concern when adopting these vectors for clinical use. METHODS: In vitro study, we used RBMCs transfected with lentivirus vectors encoding BMP-2 (Lenti-BMP-2), RBMCs transfected with lentivirus vectors encoding the green fluorescent protein (GFP) (Lenti-GFP), and untransfected RBMCs; the latter 2 were used as controls. Alkaline phosphatase (ALP) staining and ALP activity were compared between the groups to assess the ability of the Lenti-BMP-2-transfected RBMCs to stimulate osteoblastic differentiation. In the rat posterolateral spine fusion model, the experimental study comprised 4 groups. Group 1 comprised 6 animals that were implanted with a collagen sponge containing 5 million RBMCs transfected with Lenti-BMP-2. Group 2 comprised 3 animals that were implanted with a collagen sponge containing 5 million RBMCs transfected with Lenti-GFP. Group 3 comprised 6 animals that were implanted with a collagen sponge containing 5 million untransfected RBMCs. Group 4 comprised 3 animals that were implanted with a collagen sponge alone. The rats were assessed by radiographs obtained at 4, 6, and 8 weeks. After death, their spines were explanted and assessed by manual palpation, high-resolution microcomputerized tomography, and histologic analysis. RESULTS: The ALP staining was significantly greater in the Lenti-BMP-2-transfected RBMCs than in the untransfected RBMCs and the Lenti-GFP-transfected RBMCs. The ALP activity was 3-fold greater in the Lenti-BMP-2-transfected RBMCs than in the untransfected RBMCs and the Lenti-GFP-transfected RBMCs. In the rat spine fusion model, radiographic evaluation, high-resolution microcomputerized tomography, and manual palpation revealed spinal fusion in all the rats in Group 1 at 8 weeks. Groups 2, 3, and 4 comprised the control group. None of the rats in the control group (0 of 12) developed fusion at L4-L5. CONCLUSIONS: The present study demonstrated that BMP-2-producing RBMCs, created through lentiviral gene transfer, induced sufficient spinal fusion. The use of lentiviral vectors that contain the cDNA for BMP-2 will be a novel and promising approach for a spinal fusion strategy.     

The effect of regional gene therapy with bone morphogenetic protein-2-producing bone-marrow cells on the repair of segmental femoral defects in rats.

BACKGROUND: Recombinant human bone morphogenetic proteins (rhBMPs) can induce bone formation, but the inability to identify an ideal delivery system limits their clinical application. We used ex vivo adenoviral gene transfer to create BMP-2-producing bone-marrow cells, which allow delivery of the BMP-2 to a specific anatomical site. The autologous BMP-2-producing bone-marrow cells then were used to heal a critical-sized femoral segmental defect in syngeneic rats. METHODS: Femoral defects in five groups of rats were filled with 5 x 10(6) BMP-2-producing bone-marrow cells, created through adenoviral gene transfer (twenty-four femora, Group I); twenty micrograms of rhBMP-2 (sixteen femora, Group II); 5 x 10(6) beta-galactosidase-producing rat-bone-marrow cells, created through adenoviral gene transfer of the lacZ gene (twelve femora, Group III); 5 x 10(6) uninfected rat-bone-marrow cells (ten femora, Group IV); or guanidine hydrochloride-extracted demineralized bone matrix only (ten femora, Group V). Guanidine hydrochloride-extracted demineralized bone matrix served as a substrate in all experimental groups. Specimens that were removed two months postoperatively underwent histological and histomorphometric analysis as well as biomechanical testing. RESULTS: Twenty-two of the twenty-four defects in Group I (BMP-2-producing bone-marrow cells) and all sixteen defects in Group II (rhBMP-2) had healed radiographically at two months postoperatively compared with only one of the thirty-two defects in the three control groups (beta-galactosidase-producing rat-bone-marrow cells, uninfected rat-bone-marrow cells, and guanidine hydrochloride-extracted demineralized bone matrix alone). Histological analysis of the specimens revealed that defects that had received BMP-2-producing bone-marrow cells (Group I) were filled with coarse trabecular bone at two months postoperatively, whereas in those that had received rhBMP-2 (Group II) the bone was thin and lace-like. Defects that had been treated with bone-marrow cells producing beta-galactosidase (Group III), uninfected bone-marrow cells (Group IV), or guanidine hydrochloride-extracted demineralized bone matrix only (Group V) demonstrated little or no bone formation. Histomorphometric analysis revealed a significantly greater total area of bone formation in the defects treated with the BMP-2-producing bone-marrow cells than in those treated with the rhBMP-2 (p = 0.036). Biomechanical testing demonstrated no significant differences, with the numbers available, between the healed femora that had received BMP-2-producing bone-marrow cells and the untreated (control) femora with respect to ultimate torque to failure or energy to failure. CONCLUSIONS: This study demonstrated that BMP-2-producing bone-marrow cells created by means of adenoviral gene transfer produce sufficient protein to heal a segmental femoral defect. We also established the feasibility of ex vivo gene transfer with the use of biologically acute autologous short-term cultures of bone-marrow cells.     

Transplantation of skin fibroblasts expressing BMP-2 promotes bone repair more effectively than those expressing Runx2

We investigated the osteogenic potential of skin fibroblasts that overexpressed BMP-2 or Runx2 by using adenoviral vectors. In in vitro experiments, skin fibroblasts infected with adenovirus vector encoding BMP-2 (AdBMP-2) released substantial levels of BMP-2 proteins into culture media, and those infected with adenovirus vector encoding Runx2 (AdRunx2) produced its protein. Transduction of BMP-2 or Runx2, respectively, increased alkaline phosphatase (ALP) activity and induced expression of mRNAs of ALP, osteocalcin, and osterix in skin fibroblasts. In in vivo experiments, we investigated the bone induction activity by transplantation of a complex composed of carrier [poly-D,L-lactic-co-glycolic acid/gelatin sponge (PGS)] and skin fibroblasts (PGS/SF complex). Transplantation of PGS/SF complexes composed of skin fibroblasts transduced with AdBMP-2-induced ectopic bone formation when transplanted into the subfascia of back muscle, unlike those infected with AdRunx2. Transplantation of PGS/SF complexes composed of skin fibroblasts transduced with AdBMP-2 into craniotomy defects induced bone formation from 2 weeks after transplantation, and almost all PGS was replaced by newly synthesized bone at 6 weeks. To investigate the fate of the transplanted cells, we transplanted skin fibroblasts isolated from green fluorescence protein transgenic mice into craniotomy defects. Transplantation of these skin fibroblasts transfected with AdBMP-2 generated green fluorescence protein-positive osteoblasts and osteocytes, indicating that the transplanted skin fibroblasts differentiated into osteoblastic lineage cells during bone repair. In contrast, transplantation of PGS/SF complexes composed of skin fibroblasts transduced with AdRunx2 induced a few ALP-positive cells at 1 week after transplantation, but their number decreased depending on time after transplantation. In addition, transplantation of these complexes was insufficient to induce bone repair. Taken together, our results suggest that skin fibroblasts expressing BMP-2 are more suitable for cell-mediated therapy of bone repair than those expressing Runx2.     

In vivo bone formation in fracture repair induced by direct retroviral-based gene therapy with bone morphogenetic protein-4

This study sought to develop an in vivo gene therapy to accelerate the repair of bone fractures. In vivo administration of an engineered viral vector to promote fracture healing represents a potential high-efficacy, low-risk procedure. We selected a murine leukemia virus (MLV)-based retroviral vector, because this vector would be expected to target transgene expression to the proliferating periosteal cells arising shortly after bone fracture. This vector transduced a hybrid gene that consisted of a bone morphogenetic protein (BMP)-4 transgene with the BMP-2 secretory signal to enhance the secretion of mature BMP-4. The MLV vector expressing this BMP-2/4 hybrid gene or β-galactosidase control gene was administered at the lateral side of the fracture periosteum at 1 day after fracture in the rat femoral fracture model. X-ray examination by radiograph and peripheral quantitative computed tomography at 7, 14, and 28 days after fracture revealed a highly significant enhancement of fracture tissue size in the MLV-BMP-2/4-treated fractures compared to the control fractures. The tissue was extensively ossified at 14 and 28 days, and the newly formed bone exhibited normal bone histology. This tissue also exhibited strong immunohistochemical staining of BMP-4. Additional control and MLV-BMP-2/4-treated animals each were monitored for 70 days to determine the fate of the markedly enhanced fracture callus. Radiographs showed that the hard callus had been remodeled and substantial healing at the fracture site had occurred, suggesting that the union of the bone at the fracture site was at least as high in the BMP-4-treated bone as in the control bone. There was no evidence of viral vector infection of extraskeletal tissues, suggesting that this in vivo gene therapy for fracture repair is safe. In summary, we have demonstrated for the first time that a MLV-based retroviral vector is a safe and effective means of introducing a transgene to a fracture site and that this procedure caused an enormous augmentation of fracture bone formation.     

骨形态发生蛋白2基因治疗与缓释载体修复骨缺损的比较研究

[目的]比较骨形态发生蛋白2（BMP-2）基因治疗与生长因子缓释方法修复节段性骨缺损效果。[方法]于兔双侧桡骨中段造成1．5cm骨缺损，采用4种方法修复：A组植入转基因骨髓间质干细胞（MSCs）与PLA／PCL（聚乳酸／聚己内酯）支架的复合物；B组植入单纯MSCs与含重组BMP-2的PLA／PCL缓释载体的复合物；C组植入单纯MSCs与PLA／PCL复合物；D组植入单纯PLA／PCL。术后4、8、12周行X线、组织学、生物力学和骨密度等检测，[结果]A组体内植入4周后，成骨细胞和间质细胞呈BMP-2强阳性表达；其成骨速度及成骨质量均明显优于B组，12周时骨缺损完全修复、C组成骨能力较弱，而D组则无新骨形成，残留骨缺损。[结论]BMP-2基因治疗是修复节段性骨缺损的好方法。     

Genetic background influences fluoride's effects on osteoclastogenesis

Excessive fluoride (F) can lead to abnormal bone biology. Numerous studies have focused on the anabolic action of F yet little is known regarding any action on osteoclastogenesis. Little is known regarding the influence of an individual's genetic background on the responses of bone cells to F. Four-week old C57BL/6J (B6) and C3H/HeJ (C3H) female mice were treated with NaF in the drinking water (0 ppm, 50 ppm and 100 ppm F ion) for 3 weeks. Bone marrow cells were harvested for osteoclastogenesis and hematopoietic colony-forming cell assays. Sera were analyzed for biochemical and bone markers. Femurs, tibiae, and lumbar vertebrae were subjected to microCT analysis. Tibiae and femurs were subjected to histology and biomechanical testing, respectively. The results demonstrated new actions of F on osteoclastogenesis and hematopoietic cell differentiation. Strain-specific responses were observed. The anabolic action of F was favored in B6 mice exhibiting dose-dependent increases in serum ALP activity (p < 0.001); in proximal tibia trabecular and vertebral BMD (tibia at 50&100 ppm, p = 0.001; vertebrae at 50 and 100 ppm, p = 0.023&0.019, respectively); and decrease in intact PTH and sRANKL (p = 0.045 and p < 0.001, respectively). F treatment in B6 mice also resulted in increased numbers of CFU-GEMM colonies (p = 0.025). Strain-specific accumulations in bone [F] were observed. For C3H mice, dose-dependent increases were observed in osteoclast potential (p < 0.001), in situ trabecular osteoclast number (p = 0.007), hematopoietic colony forming units (CFU-GEMM: p < 0.001, CFU-GM: p = 0.006, CFU-M: p < 0.001), and serum markers for osteoclastogenesis (intact PTH: p = 0.004, RANKL: p = 0.022, TRAP5b: p < 0.001). A concordant decrease in serum OPG (p = 0.005) was also observed. Fluoride treatment had no significant effects on bone morphology, BMD, and serum PYD cross-links in C3H suggesting a lack of significant bone resorption. Mechanical properties were also unaltered in C3H. In conclusion, short term F treatment at physiological levels has strain-specific effects in mice. The expected anabolic effects were observed in B6 and novel actions hallmarked by enhanced osteoclastogenesis shifts in hematopoietic cell differentiation in the C3H strain.     

Mechanical force-induced midpalatal suture remodeling in mice

Mechanical stress is an important epigenetic factor for regulating skeletal remodeling, and application of force can lead to remodeling of both bone and cartilage. Chondrocytes, osteoblasts and osteoclasts all participate and interact with each other in this remodeling process. To study cellular responses to mechanical stimuli in a system that can be genetically manipulated, we used mouse midpalatal suture expansion in vivo. Six-week-old male C57BL/6 mice were subjected to palatal suture expansion by opening loops with an initial force of 0.56 N for the periods of 1, 3, 5, 7, 14 or 28 days. Periosteal cells in expanding sutures showed increased proliferation, with Ki67-positive cells representing 1.8 ± 0.1% to 4.5 ± 0.4% of total suture cells in control groups and 12.0 ± 2.6% to 19.9 ± 1.2% in experimental/expansion groups (p < 0.05). Starting at day 1, cells expressing alkaline phosphatase and type I collagen were seen. New cartilage and bone formation was observed at the oral edges of the palatal bones at day 7; at the nasal edges only bone formation without cartilage appeared to occur. An increase in osteoclast numbers suggested increased bone remodeling, ranging from 60 to 160% throughout the experimental period. Decreased Saffranin O staining after day 3 suggested decreased proteoglycan content in the secondary cartilage. Micro-CT showed a significant increase in maxillary width at days 14 and 28 (from 2334 ± 4 μm to 2485 ± 3 μm at day 14 and from 2383 ± 5 μm to 2574 ± 7 μm at day 28, p < 0.001). The suture width was increased at days 14 and 28, except in the oral third region at day 28 (from 48 ± 5 μm to 36 ± 4 μm, p < 0.05). Bone volume/total volume was significantly reduced at days 14 and 28 (50.2 ± 0.7% vs. 68.0 ± 3.7% and 56.5 ± 1.0% vs. 60.9 ± 1.3%, respectively, p < 0.05), indicative of increased bone marrow space. These findings demonstrate that expansion forces across the midpalatal suture promote bone resorption through activation of osteoclasts and bone and cartilage formation via increased proliferation and differentiation of periosteal cells. Mouse midpalatal suture expansion would be useful in further studies of the ability of mineralized tissues to respond to mechanical stimulation.     

BMP-14 gene therapy increases tendon tensile strength in a rat model of Achilles tendon injury

BACKGROUND: Molecular and cellular-based enhancements of healing combined with conventional methods may yield better outcomes after the surgical management of tendon injury. We examined the histological and biomechanical effects of adenovirus-mediated transgene expression of bone morphogenetic protein-14 (BMP-14) on healing in a rat Achilles tendon laceration model. Specifically, we hypothesized that this delivery system for gene therapy would hasten the restoration of the normal histological appearance and tensile strength of a surgically repaired tendon. METHODS: The right Achilles tendon of ninety male Sprague-Dawley rats was transected, repaired, and immediately infected with adenovirus expressing either the gene for green fluorescent protein (AdGFP) or the gene for human BMP-14 and green fluorescent protein (AdBMP-14). A sham control group received no viral-mediated infection after repair. Animals from each of the three groups were killed at one, two, and three weeks after surgery. The retrieved tendons were inspected, examined under light and fluorescent microscopy, and tested to determine their tensile strength. RESULTS: Tendons transduced with BMP-14 exhibited less visible gapping, a greater number of neotenocytes at the site of healing, and 70% greater tensile strength than did either those transduced with GFP or the sham controls at two weeks after repair. Histological examination revealed no inflammatory response to the adenovirus in tendons transduced with BMP-14 or GFP. No ectopic bone or cartilage formed in the tendons transduced with BMP-14. CONCLUSIONS: Adenovirus-mediated gene therapy with BMP-14 expedites tendon-healing in this animal model. No adverse immunological response to the adenoviral vector was detected in the host tissue, and the local production of BMP-14 did not induce unwelcome bone or cartilage formation within the healing tendon. CLINICAL RELEVANCE: The results of this animal study suggest that gene therapy with BMPs may improve the capacity of injured musculoskeletal tissue to heal.     

Effect of dietary B vitamins on BMD and risk of fracture in elderly men and women: the Rotterdam study

A mildly elevated homocysteine (Hcy) level is a novel and potentially modifiable risk factor for age-related osteoporotic fractures. Elevated Hcy levels can have a nutritional cause, such as inadequate intake of folate, riboflavin, pyridoxine or cobalamin, which serve as cofactors or substrates for the enzymes involved in the Hcy metabolism. We examined the association between intake of Hcy-related B vitamin (riboflavin, pyridoxine, folate and cobalamin) and femoral neck bone mineral density BMD (FN-BMD) and the risk of fracture in a large population-based cohort of elderly Caucasians.

We studied 5304 individuals aged 55 years and over from the Rotterdam Study. Dietary intake of nutrients was obtained from food frequency questionnaires. Incident non-vertebral fractures were recorded during a mean follow-up period of 7.4 years, and vertebral fractures were assessed by X-rays during a mean follow-up period of 6.4 years. We observed a small but significant positive association between dietary pyridoxine (β = 0.09, p = 1 × 10^− 8) and riboflavin intake (β = 0.06, p = 0.002) and baseline FN-BMD. In addition, after controlling for gender, age and BMI, pyridoxine intake was inversely correlated to fracture risk. As compared to the three lowest quartiles, individuals in the highest quartile of age- and energy-adjusted dietary pyridoxine intake had a decreased risk of non-vertebral fractures (HR = 0.77, 95% CI = 0.65–0.92, p = 0.005) and of fragility fractures (HR = 0.55, 95% CI = 0.40–0.77, p = 0.0004). Further adjustments for other dietary B vitamins (riboflavin, folate and cobalamin), dietary intake of calcium, vitamin D, vitamin A and vitamin K, protein and energy intake, smoking and BMD did not essentially modify these results.

We conclude that increased dietary riboflavin and pyridoxine intake was associated with higher FN-BMD. Furthermore, we found a reduction in risk of fracture in relation to dietary pyridoxine intake independent of BMD. These findings highlight the importance of considering nutritional factors in epidemiological studies of osteoporosis and fractures.     

骨形态发生蛋白2基因治疗在修复骨缺损中对血管化影响的实验研究

目的观察骨形态发生蛋白-2（BMP-2）基因治疗在修复骨缺损中对血管化的影响。方法分离培养兔骨髓基质干细胞（MSCs），经BMP-2腺病毒载体转染后复合异种骨支架移植修复1．5cm桡骨缺损。分为5组：①BMP-2基因转染细胞＋去抗原牛松质骨支架（BCB）；②未转染细胞＋重组BMP-2＋BCB；③对照基因转染细胞＋BCB；④未转染细胞＋BCB；⑤BCB。术后4、8、12周行微血管墨汁灌注、血管内皮生长因子（VEGF）免疫组化染色、组织学等检测。结果术后4周，基因治疗组骨间血管的密度在周边区域较高，通常每一个骨小梁孔隙中都有一支新形成的小血管；透射电镜见成骨细胞总是毗邻血管内皮细胞而存在，并随着微血管的增生而逐渐向骨细胞发展；间质细胞VEGF表达明显增强。结论BMP-2基因治疗可通过上调VEGF表达，间接诱导移植骨血管化，对骨不连、骨缺损的治疗具有重要意义。     

干细胞移植和BMP2基因治疗修复骨损伤和坏死的实验研究

目的:根据老年骨缺损和股骨头坏死实验模型的研究结果来评价干细胞移植和BMP2基因治疗的方法是否可用于一些特殊损伤和疾病的治疗.方法:从不同年龄段大鼠、羊骨髓中分离培养骨髓间充质干细胞,利用含BMP-2基因或βal基因的腺病毒载体感染干细胞,通过酶联免疫测定方法检测基因转染细胞培养上清中BMP-2蛋白的含量.利用基因转染细胞和多孔三磷酸钙复合,回植后修复24月龄老年大鼠股骨干6毫米节段性缺损和实验性羊股骨头坏死.通过组织学观察和生物力学测定来评价比较BMP-2治疗组和βgal对照组的新骨形成情况和修复组织的强度.结果:基因转染细胞培养上清中BMP-2蛋白的含量随时间延长而逐渐上升,不同年龄大鼠干细胞BMP-2转染后蛋白质的分泌水平没有明显差异.组织学观察表明BMP-2基因转染细胞和多孔三磷酸钙复合物已成功修复24月龄老年大鼠股骨干6毫米节段性缺损和实验性羊股骨头坏死,BMP-2治疗组的新骨形成明显多于βgal对照组(P＜0.05).治疗后第16周,BMP-2治疗组股骨头修复组织的最大压缩强度和弹性模量也明显高于Bgal对照组(P＜0.05).结论:BMP-2基因转染的自体骨髓间充质干细胞和多孔三磷酸钙复合后回植可有效修复老年大鼠骨缺损并重建羊坏死股骨头的功能.     

In Vitro andIn Vivo induction of bone formation using a recombinant adenoviral vector carrying the human BMP-2 gene

It has been well established that bone morphogenetic protein-2 (BMP-2) can induce bone formation bothin vivo andin vitro, although high concentrations (up to milligrams) of BMP-2 have been required to achieve this effectin vivo. Further, clinical applications are usually limited to a single dose at the time of implantation. In an attempt to prolong the transforming effect of BMP-2 we used a recombinant adenoviral vector carrying the human BMP-2 gene (Adv-BMP2) to transduce marrow-derived mesenchymal stem cells (MSC) of skeletally mature male New Zealand white rabbits. The pluripotential MSC were incubated with Adv-BMP2 overnight followed by culture in growth medium for 1 week. Assays on tissue cultures demonstrated that these Adv-BMP2 transduced MSC produced BMP-2 protein, differentiated into an osteoprogenitor line, and induced bone formationin vitro. These MSC had increased alkaline phosphatase activity, increased expression of type I collagen, osteopontin, and osteocalcin mRNA, and induced matrix mineralization compared with both nontransduced cells and cells transduced with a control adenoviral construct. To analyze the osteogenic potentialin vivo, Adv-BMP2-transduced MSC were autologously implanted into the intertransverse process space between L5 and L6 of the donor rabbits. The production of new bone was demonstrated by radiographic examination 4 weeks later in areas implanted with cells transduced with Adv-BMP2, whereas no bone was evident at sites implanted with cells transduced with the control adenoviral construct. Histological examination further confirmed the presence of new bone formation. These accumulated data indicate that it is possible to successfully transduce mesenchymal stem cells with a recombinant adenoviral vector carrying the gene for BMP-2 such that these cells will produce BMP-2, differentiate into an osteoprogenitor line, and induce bone formation bothin vitro andin vivo. Moreover, incubation of the Adv-BMP2-transduced cells for an additional 7 days in culture before transplantation enhances the success rate in bone formation (three out of three) as compared with our previous report (one out of five, Calcif Tissue Int 63:357–360, 1998). SLC, JL, and NMW have contributed equally to this work and therefore should be considered first authors.     

骨形成蛋白2基因修复兔桡骨缺损的实验研究

目的观察携带人骨形成蛋白2（bone morphogenetic protein 2，BMP-2）基因的腺病毒载体（adenovirus carrying BMP-2 gene，Ad—BMP2），通过纤维蛋白凝胶与牛松质骨支架（bovine cancellous bone，BCB）复合，修复骨缺损的效果。方法将60只新西兰大耳白兔随机分为4组，每组15只。制成双侧桡骨中段1．5cm骨缺损模型，采用4种材料植入修复。A组：Ad-BMP-2＋BCB；B组：重组BMP-2＋BCB；C组：携带D-半乳糖酐酶基因的腺病毒对照载体（adenovirus carrying β—galgene，Ad—Lacz）＋BCB；D组：单纯BCB支架。修复术后各组于4、8和12周各处死动物5只取材，行X线片、组织学、生物力学和免疫组织化学染色检查。结果A、B两组骨缺损均得到了修复，但术后各时间点，A组在成骨活跃程度、新生骨量、力学强度及BMP-2表达等方面均明显优于B组；C、D两组均无新骨形成。结论BMP-2直接基冈治疗，操作简便、骨诱导能力强，是修复节段性骨缺损的有效方法。     

Adenovirus-mediated direct gene therapy with bone morphogenetic protein-2 produces bone

The need to improve bone healing permeates the discipline of orthopedic surgery. Bone morphogenetic proteins (BMPs) are capable of inducing ectopic and orthotopic bone formation. However, the ideal approach with which to deliver BMPs remains unknown. Gene therapy to deliver BMPs offers several theoretical advantages over implantation of a recombinant BMP protein, including persistent BMP delivery and eliminating the need for a foreign body carrier. A replication defective adenoviral vector was constructed to carry the rhBMP-2 gene (AdBMP-2). The direct in vivo gene therapy approach was applied in both immunodeficient and immunocompetent animals to produce intramuscular bone as early as 2 weeks following injection. Radiographic and histologic analysis revealed radiodense bone containing mature bone marrow elements. Adenovirus-mediated delivery of a marker gene (β-galactosidase) into control animals produced no bone but indicated the cells transduced with the AdBMP-2 vector. Furthermore, comparisons between immunodeficient and immunocompetent animals illustrated the magnitude and significance of the immune response. Gene therapy to deliver BMP-2 has innumerable potential clinical applications from bone defect healing to joint replacement prosthesis stabilization. This study is the first to establish the feasibility of in vivo gene therapy to deliver active BMP-2 and produce bone.     

腺病毒骨形态发生蛋白2绿色荧光蛋白基因转染兔骨髓基质干细胞成骨及示踪作用

目的 观察腺病毒介导的人骨形态发生蛋白绿色荧光蛋白基因(Ad-GFP-hBMP-2)转染对骨髓间质干细胞(bMSCs)成骨能力的影响.方法 取日本大耳白兔4只自双侧股骨远端抽取骨髓培养bMSCs.以Ad-GFP-hBMP-2基因(实验组)及Ad-GFP(对照组)基因转染bMSCs后,用ALP检测试剂盒检测两组细胞的ALP活性;原位杂交检测两组细胞I型胶原的表达;Western blot 检测细胞中BMP-2的表达.将转染后24 h的bMSCs接种到裸鼠体内,术后第4、8、12周观察成骨情况.结果 转Ad-GFP-hBMP-2基因组和Ad-GFP组各时间段ALP分泌量差异分别有统计学意义(P<0.01);实验组I型胶原原位杂交实验组为阳性.实验组成骨阳性率为90%,对照组为40%.结论 bMSCs经Ad-GFP-hBMP-2基因转染后能高效表达BMP-2并诱导成骨.腺病毒介导人BMP-2转基因可以提高bMSCs的成骨能力.     

慢病毒介导SOX9基因转染骨髓间充质细胞中的基因表达

目的:构建携带小鼠SOX9基因的慢病毒载体,体外转染小鼠骨髓间充质细胞,观察小鼠SOX9基因在小鼠间充质细胞中的表达。方法:从含有小鼠SOX9基因的质粒提取总RNA,利用RT-PCR方法扩增目的基因。连接目的基因与经Age-Ⅰ酶切线性化的慢病毒载体,转化感受态的大肠杆菌对质粒进行扩增,筛出阳性转化子,经293T细胞包装,收集病毒后,通过基因测序和限制性核酸内切酶酶切的方法对质粒进行鉴定。Lenti-SOX9-EGFP体外转染小鼠骨髓间充质细胞,利用倒置荧光显微镜观察转染是否成功,并通过流式细胞仪测定转染效率。同时利用RT-PCR和Western Blot检测小鼠SOX9基因的表达。结果:成功构建了携带SOX9基因慢病毒载体,Lenti-SOX9-EGFP能高效转染小鼠骨髓间充质细胞。RT-PCR和Western Blot检测显示经SOX9基因转染的小鼠骨髓间充质细胞表达目的基因产物。结论:利用慢病毒介导SOX9基因成功地转染小鼠骨髓间充质细胞,而且SOX9基因在小鼠骨髓间充质细胞中得到表达,这为SOX9修复软骨损伤的进一步研究奠定了基础。     

Direct percutaneous gene delivery to enhance healing of segmental bone defects

BACKGROUND: Healing of segmental bone defects can be induced experimentally with genetically modified osteoprogenitor cells, an ex vivo strategy that requires two operative interventions and substantial cost. Direct transfer of osteogenic genes offers an alternative, clinically expeditious, cost-effective approach. We evaluated its potential in a well-established, critical-size, rat femoral defect model. METHODS: A critical-size defect was created in the right femur of forty-eight skeletally mature Sprague-Dawley rats. After twenty-four hours, each defect received a single, intralesional, percutaneous injection of adenovirus carrying bone morphogenetic protein-2 (Ad.BMP-2) or luciferase cDNA (Ad.luc) or it remained untreated. Healing was monitored with weekly radiographs. At eight weeks, the rats were killed and the femora were evaluated with dual-energy x-ray absorptiometry, micro-computed tomography, histological analysis, histomorphometry, and torsional mechanical testing. RESULTS: Radiographically, 75% of the Ad.BMP-2-treated femora showed osseous union. Bone mineral content was similar between the Ad.BMP-2-treated femora (0.045 +/- 0.020 g) and the contralateral, intact femora (0.047 +/- 0.003 g). Histologically, 50% of the Ad.BMP-2-treated defects were bridged by lamellar, trabecular bone; the other 50% contained islands of cartilage. The control (Ad.luc-treated) defects were filled with fibrous tissue. Histomorphometry demonstrated a large difference in osteogenesis between the Ad.BMP-2 group (mean bone area, 3.25 +/- 0.67 mm(2)) and the controls (mean bone area, 0.65 +/- 0.67 mm(2)). By eight weeks, the Ad.BMP-2-treated femora had approximately one-fourth of the strength (mean, 0.07 +/- 0.04 Nm) and stiffness (mean, 0.5 +/- 0.4 Nm/rad) of the contralateral femora (0.3 +/- 0.08 Nm and 2.0 +/- 0.5 Nm/rad, respectively). CONCLUSIONS: A single, percutaneous, intralesional injection of Ad.BMP-2 induces healing of critical-size femoral bone defects in rats within eight weeks. At this time, the repair tissue is predominantly trabecular bone, has normal bone mineral content, and has gained mechanical strength.