Vancomycin-bearing Synthetic Bone Graft Delivers rhBMP-2 and Promotes Healing of Critical Rat Femoral Segmental Defects

Background

Bone grafts simultaneously delivering therapeutic proteins and antibiotics may be valuable in orthopaedic trauma care. Previously, we developed a poly(2-hydroxyethyl methacrylate)-nanocrystalline hydroxyapatite (pHEMA-nHA) synthetic bone graft that, when preabsorbed with 400-ng rhBMP-2/7, facilitated the functional repair of critical-size rat femoral defects. Recently, we showed that pHEMA-nHA effectively retains/releases vancomycin and rhBMP-2 in vitro. The success of such a strategy requires that the incorporation of vancomycin does not compromise the structural integrity of the graft nor its ability to promote bone healing.

Questions/purposes

(1) To evaluate the ability of pHEMA-nHA-vancomycin composites in combination with 3-µg rhBMP-2 to repair 5 mm rat femoral segmental defects, and (2) To determine if the encapsulated vancomycin impairs the graft/rhBMP-2-assisted bone repair.

Methods

pHEMA-nHA-vancomycin, pHEMA-nHA, or collagen sponge control with/without 3-µg rhBMP-2 were press-fit in 5 mm femoral defects in SASCO-SD male rats (289–300 g). Histology, microcomputed tomography, and torsion testing were performed on 8- and 12-week explants to evaluate the extent and quality of repair. The effect of vancomycin on the temporal absorption of endogenous BMP-2 and stromal cell-derived factor-1 was evaluated by immunohistochemistry. These factors are important for bone healing initiation and stem cell recruitment, respectively.

Results

Partial bridging of the defect with bony callus by 12 weeks was observed with pHEMA-nHA-vancomycin without rhBMP-2 while full bridging with substantially mineralized callus and partial restoration of torsional strength was achieved with 3-µg rhBMP-2. The presence of vancomycin changed the absorption patterns of endogenous proteins on the grafts, but did not appear to substantially compromise graft healing.

Conclusions

The composite pHEMA-nHA-vancomycin preabsorbed with 3-µg rhBMP-2 promoted repair of 5 mm rat femoral segmental defects. With the sample sizes applied, vancomycin encapsulation did not appear to have a negative effect on bone healing.

Clinical Relevance

pHEMA-nHA-vancomycin preabsorbed with rhBMP-2 may be useful in the repair of critical-size long bone defects prone to infections.     

Effect of Dosing Interval Duration of Intermittent Ibandronate Treatment on the Healing Process of Femoral Osteotomy in a Rat Fracture Model

The effects of bisphosphonate treatment schedule on fracture healing have not previously been tested. We evaluated the effect of ibandronate dosing interval duration on healing following surgical “fracture” (osteotomy) using a rat femoral fracture model. Six-week-old rats (n = 160) underwent osteotomy and were then allocated into vehicle control (CNT) or an ibandronate treatment group: 5 μg/kg daily (DAY, 5 days/week), 75 μg/kg once every 3 weeks (I-3), 150 μg/kg once every 6 weeks (I-6), resulting in the same total ibandronate dose over the study. Rats were killed after 6 or 18 weeks. At 18 weeks, all fracture lines had disappeared in the CNT and I-6 groups; approximately 10% of fracture lines remained in the DAY and I-3 groups. Ibandronate-treated groups showed large callus areas around the fractures, which shrank between 6 and 18 weeks after surgery; the extent of shrinkage decreased with shorter dosing interval. In histomorphometry, callus remodeling was suppressed by ibandronate; this became more apparent at shorter dose intervals. The structural properties of osteotomized femora were increased in the DAY group compared with CNT, but intrinsic material properties reduced inversely and became closer to those of CNT in response to increased dosing interval. Ibandronate induced formation of large calluses around osteotomies but delayed woven bone remodeling into lamellar bone and reduced intrinsic material properties in a rat fracture model. Extending the dosing interval of intermittent ibandronate treatment appeared to reduce the suppression of callus remodeling caused by ibandronate, which would have delayed healing after osteotomy.     

rhPDGF-BB Promotes Early Healing in a Rat Rotator Cuff Repair Model

Background

Tendon-bone healing after rotator cuff repair occurs by fibrovascular scar tissue formation, which is weaker than a normal tendon-bone insertion site. Growth factors play a role in tissue formation and have the potential to augment soft tissue healing in the perioperative period.

Questions/purposes

Our study aim was to determine if rhPDGF-BB delivery on a collagen scaffold can improve tendon-to-bone healing after supraspinatus tendon repair compared with no growth factor in rats as measured by (1) gross observations; (2) histologic analysis; and (3) biomechanical testing.

Methods

Ninety-five male Sprague-Dawley rats underwent acute repair of the supraspinatus tendon. Rats were randomized into one of five groups: control (ie, repair only), scaffold only, and three different platelet-derived growth factor (PDGF) doses on the collagen scaffold. Animals were euthanized 5 days after surgery to assess cellular proliferation and angiogenesis. The remaining animals were analyzed at 4 weeks to assess repair site integrity by gross visualization, fibrocartilage formation with safranin-O staining, and collagen fiber organization with picrosirius red staining, and to determine the biomechanical properties (ie, load-to-failure testing) of the supraspinatus tendon-bone construct.

Results

The repaired supraspinatus tendon was in continuity with the bone in all animals. At 5 days, rhPDGF-BB delivery on a scaffold demonstrated a dose-dependent response in cellular proliferation and angiogenesis compared with the control and scaffold groups. At 28 days, with the numbers available, rhPDGF-BB had no effect on increasing fibrocartilage formation or improving collagen fiber maturity at the tendon-bone insertion site compared with controls. The control group had higher tensile loads to failure and stiffness (35.5 ± 8.8 N and 20.3 ± 4.5 N/mm) than all the groups receiving the scaffold, including the PDGF groups (scaffold: 27 ± 6.4 N, p = 0.021 and 13 ± 5.7 N/mm, p = 0.01; 30 µg/mL PDGF: 26.5 ± 7.5 N, p = 0.014 and 13.3 ± 3.2 N/mm, p = 0.01; 100 µg/mL PDGF: 25.7 ± 6.1 N, p = 0.005 and 11.6 ± 3.3 N/mm, p = 0.01; 300 µg/mL PDGF: 27 ± 6.9 N, p = 0.014 and 12.7 ± 4.1 N/mm, p = 0.01).

Conclusions

rhPDGF-BB delivery on a collagen scaffold enhanced cellular proliferation and angiogenesis during the early phase of healing, but this did not result in either a more structurally organized or stronger attachment site at later stages of healing. The collagen scaffold had a detrimental effect on healing strength at 28 days, and its relatively larger size compared with the rat tendon may have caused mechanical impingement and extrinsic compression of the healing tendon. Future studies should be performed in larger animal models where healing occurs more slowly.

Clinical Relevance

Augmenting the healing environment to improve the structural integrity and to reduce the retear rate after rotator cuff repair may be realized with continued understanding and optimization of growth factor delivery systems.     

Temporal Variation in Fixation Stiffness Affects Healing by Differential Cartilage Formation in a Rat Osteotomy Model

Background  

Dynamization involves a reduction in fixation construct stiffness during bone healing, allowing increased interfragmentary movement of the fracture through physiologic weightbearing and muscle contraction. Within some optimal range, interfragmentary movement stimulates healing, but this range likely varies across stages of bone healing.     

维生素K2促进BM-MSCs成骨分化及其机制研究

目的探讨维生素K2对骨髓来源间充质干细胞(BM-MSCs)成骨分化能力的影响和机制。方法通过CCK-8活细胞计数法检测维生素K2不同浓度(1 nmol/L,10 nmol/L,100 nmol/L,1μmol/L,10μmol/L)在不同时间(24、48、72 h)对BMMSCs生长增殖的影响,运用Q-PCR检测不同浓度维生素K2对BM-MSCs成骨分化相关基因BMP-2表达水平的影响,进一步探讨维生素K2是否通过成骨信号通路Smad1/5/8、Runx2及Osterix调控BM-MSCs成骨分化。结果与对照组比较,低浓度(1 nmol/L)的维生素K2不影响BM-MSCs的生长活性,中浓度(10 nmol/L,100 nmol/L,1μmol/L)明显促进BM-MSCs的生长,高浓度(10μmol/L)明显抑制细胞的生长(P0.05)。中浓度范围的维生素K2呈剂量依赖性地促进BM-MSCs成骨过程中BMP-2 mRNA表达及钙结节的形成,且1μmol/L的维生素K2明显促进BM-MSCs的Smad1/5/8、Runx2及Osterix蛋白水平。结论维生素K2能够促进BM-MSCs的成骨分化,并且可能通过成骨信号轴BMP-2/Smad/Runx2/Osterix来调控BM-MSCs的成骨分化过程。     

1,25-Dihydroxyvitamin D3 Promotes Vitamin K2 Metabolism in Human Osteoblasts

It has been reported that vitamin K₂ (menaquinone-4) promoted 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃)-induced mineralization and enhanced γ-carboxyglutamic acid (Gla)-containing osteocalcin accumulation in cultured human osteoblasts. In the present study, we investigated whether menaquinone-4 (MK-4) was metabolized in human osteoblasts to act as a cofactor of γ-glutamyl carboxylase. Both conversions of MK-4 to MK-4 2,3-epoxide (epoxide) and epoxide to MK-4 were observed in cell extracts of cultured human osteoblasts. The effect of 1,25(OH)₂D₃ and warfarin on the vitamin K cycle to cultured osteoblasts were examined. With the addition of 1 nM 1,25(OH)₂D₃ or 25 μM warfarin in cultured osteoblasts, the yield of epoxide from MK-4 increased. However, the conversion of epoxide to MK-4 was strongly inhibited by the addition of warfarin (2.5–25 μM), whereas it was almost not inhibited by 1,25(OH)₂D₃ (0.1–10 nM). To clarify the mechanism for this phenomenon, a cell-free assay system was studied. Osteoblast microsomes were incubated with 10 μM epoxide in the presence or absence of warfarin and 1,25(OH)₂D₃. Epoxide reductase, one of the enzymes in the vitamin K cycle was strongly inhibited by warfarin (2.5–25 μM), whereas it was not affected by 1,25(OH)₂D₃ (0.1–1 nM). Moreover, there was no effect of pretreatment of osteoblasts with 1 nM 1,25(OH)₂D₃ on the activity of epoxide reductase. However, the activity of epoxidase, that is the γ-glutamyl carboxylase was induced by the pretreatment of osteoblasts with 1 nM 1,25(OH)₂D₃. In the present study, it was demonstrated that the vitamin K metabolic cycle functions in human osteoblasts as well as in the liver, the post-translational mechanism, by which 1,25(OH)₂D₃ caused mineralization in cooperation with vitamin K₂ was clarified. Received: 20 September 2000 / Accepted: 19 February 2001     

Treatment with Fluoride or Bisphosphonates Prevents Bone Loss Associated with Colitis in the Rat

Idiopathic inflammatory bowel disease (IBD) is associated with osteoporosis in over 30% of cases. We have previously shown that 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced colitis in rats is associated with considerable bone loss. In the current study we tested the ability of sodium fluoride (NaF) or the bisphosphonate pamidronate to prevent the bone loss associated with TNBS-induced colitis in 22-week-old male Wistar rats. As previously found, there was a 43% decrease in cancellous bone volume in rats with TNBS-induced colitis after 4 weeks. This was associated with marked suppression of the bone formation rate to less than 25% of control animals. Treatment with NaF had no effect on the severity of colitis, but the bone volume and bone formation rate were increased to levels indistinguishable from those of control animals. In animals treated with pamidronate, cancellous bone volume was also restored to that of control animals despite persistence of the colitis. In these animals there was marked suppression of bone formation, associated with suppression of bone resorption. This data shows the bone loss associated with colitis may be prevented by treatment with NaF or bisphosphonates without requiring improvement in severity of the colitis. Received: 20 May 1999 / Accepted: 19 June 2000 / Online publication: 22 September 2000     

Enhancement of the Effects of Exfoliated Carbon Nanofibers by Bone Morphogenetic Protein in a Rat Femoral Fracture Model

Exfoliated carbon nanofibers (ExCNFs) are expected to serve as excellent scaffolds for promoting and guiding bone‐tissue regeneration. We aimed to enhance the effects of ExCNFs with bone morphogenetic proteins (BMPs) and examine their feasibility and safety in clinical applications using a rat femoral fracture model. Group I (n = 16) animals were implanted with control MedGEL. Group II (n = 17) animals were implanted with MedGEL containing ExCNFs. Group III (n = 15) animals were implanted with MedGEL containing 1 μg rhBMP‐2. Group IV (n = 15) animals were implanted with MedGEL containing 1 μg rhBMP‐2 and ExCNFs. The rats were euthanized after 6 weeks, and their fractured femurs were explanted and assessed by manual palpation, radiographs, and high‐resolution microcomputerized tomography (micro‐CT); the femurs were also subjected to biomechanical and histological analysis. The fusion rates in Group IV (73.3%) were considerably higher than those in Groups I (25.0%), II (52.9%), and III (46.7%). The results demonstrated the enhancement of the bone repair effects of ExCNFs by BMP in a rat femoral fracture model. Our results suggest that the enhancement of the effects of ExCNFs by BMP makes the combination a possible attractive therapy for various orthopedic surgeries. © 2014 Orthopaedic Research Society. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:185–192, 2015.

     

Sclerostin Antibody Treatment Increases Bone Formation,Bone Mass,and Bone Strength in a Rat Model of Postmenopausal Osteoporosis

The development of bone‐rebuilding anabolic agents for potential use in the treatment of bone loss conditions, such as osteoporosis, has been a long‐standing goal. Genetic studies in humans and mice have shown that the secreted protein sclerostin is a key negative regulator of bone formation, although the magnitude and extent of sclerostin's role in the control of bone formation in the aging skeleton is still unclear. To study this unexplored area of sclerostin biology and to assess the pharmacologic effects of sclerostin inhibition, we used a cell culture model of bone formation to identify a sclerostin neutralizing monoclonal antibody (Scl‐AbII) for testing in an aged ovariectomized rat model of postmenopausal osteoporosis. Six‐month‐old female rats were ovariectomized and left untreated for 1 yr to allow for significant estrogen deficiency‐induced bone loss, at which point Scl‐AbII was administered for 5 wk. Scl‐AbII treatment in these animals had robust anabolic effects, with marked increases in bone formation on trabecular, periosteal, endocortical, and intracortical surfaces. This not only resulted in complete reversal, at several skeletal sites, of the 1 yr of estrogen deficiency‐induced bone loss, but also further increased bone mass and bone strength to levels greater than those found in non‐ovariectomized control rats. Taken together, these preclinical results establish sclerostin's role as a pivotal negative regulator of bone formation in the aging skeleton and, furthermore, suggest that antibody‐mediated inhibition of sclerostin represents a promising new therapeutic approach for the anabolic treatment of bone‐related disorders, such as postmenopausal osteoporosis.     

Anastomotic Healing in a Small Bowel Transplantation Model in the Rat

Anastomotic healing is impaired after intestinal surgery because of ischemia and reperfusion injury (IRI), which can result in intestinal leaks leading to increased mortality. The objective of this study was to determine the effects of transplant IRI and immune mechanisms on intestinal graft anastomotic healing. Orthotopic intestinal transplantations (OIT) were performed in rats. The experimental design consisted of six groups A–F (n = 5/group): A, allogeneic OIT treated with tacrolimus (1mg/kg/day); B, syngeneic OIT treated with tacrolimus; C, syngeneic OIT; D, allogeneic OIT; E, proximal and distal anastomoses performed in nontransplanted animals; F, same as in group E but treated with tacrolimus. Anastomotic bursting pressure (ABP), hydroxyproline content (HPC), and mucosal inflammatory infiltrate (MII) were determined at the anastomotic sites (proximal and distal) and compared between groups. ABP was significantly (p < 0.001) reduced in OIT groups A, B, C, and D compared to control groups E and F at both the proximal and distal anastomotic sites. HPC was 1 g/mg of tissue in groups A, B, C, and D, and 5g/mg of tissue in groups E and F. This demonstrates a significant (p < 0.001) reduction in HPC after OIT. MII was significantly (p < 0.001) increased in OIT groups when compared to nontransplanted control groups. MII was also significantly (p < 0.05) increased in allogeneic OIT groups A and D compared to syngeneic OIT groups B and C. Generally, ABP and HPC were inversely proportional to MII in both nontransplanted control and OIT groups. Reduced anastomotic strength was demonstrated in both syngeneic and allogeneic OIT anastomotic sites irrespective of immunosuppressive therapy, and is probably related to IRI.     

OP-1 Augments Glucocorticoid-inhibited Fracture Healing in a Rat Fracture Model

Glucocorticoids inhibit bone remodeling and fracture healing. We sought to determine whether osteogenic protein 1 (OP-1) can overcome this inhibition in a closed fracture model in the rat. Time-released prednisolone or placebo pellets were implanted subcutaneously; closed femoral fractures were created 2 weeks later in rats. Fractures received sham, OP-1 and collagen, or collagen-only implants. Femurs were harvested at 3, 10, 21, 28, and 42 days postfracture. Fractures were examined radiographically for amount of hard callus; mechanically for torque and stiffness (also expressed as a percentage of the contralateral intact femur); and histomorphometrically for amount of cartilaginous and noncartilaginous soft callus, hard callus, and total callus. Glucocorticoid administration inhibited fracture healing. The application of a devitalized Type I collagen matrix mitigated the inhibitory effects of prednisolone on fracture healing However, further increases in indices of fracture healing were observed when OP-1 was added to the collagen matrix compared with collagen alone. OP-1 and collagen was more effective than collagen alone.     

Combined MEK Inhibition and BMP2 Treatment Promotes Osteoblast Differentiation and Bone Healing in Nf1Osx−/− Mice

Neurofibromatosis type I (NF1) is an autosomal dominant disease with an incidence of 1/3000, caused by mutations in the NF1 gene, which encodes the RAS/GTPase‐activating protein neurofibromin. Non‐bone union after fracture (pseudarthrosis) in children with NF1 remains a challenging orthopedic condition to treat. Recent progress in understanding the biology of neurofibromin suggested that NF1 pseudarthrosis stems primarily from defects in the bone mesenchymal lineage and hypersensitivity of hematopoietic cells to TGFβ. However, clinically relevant pharmacological approaches to augment bone union in these patients remain limited. In this study, we report the generation of a novel conditional mutant mouse line used to model NF1 pseudoarthrosis, in which Nf1 can be ablated in an inducible fashion in osteoprogenitors of postnatal mice, thus circumventing the dwarfism associated with previous mouse models where Nf1 is ablated in embryonic mesenchymal cell lineages. An ex vivo–based cell culture approach based on the use of Nf1^flox/flox bone marrow stromal cells showed that loss of Nf1 impairs osteoprogenitor cell differentiation in a cell‐autonomous manner, independent of developmental growth plate–derived or paracrine/hormonal influences. In addition, in vitro gene expression and differentiation assays indicated that chronic ERK activation in Nf1‐deficient osteoprogenitors blunts the pro‐osteogenic property of BMP2, based on the observation that only combination treatment with BMP2 and MEK inhibition promoted the differentiation of Nf1‐deficient osteoprogenitors. The in vivo preclinical relevance of these findings was confirmed by the improved bone healing and callus strength observed in Nf1_osx^?/? mice receiving Trametinib (a MEK inhibitor) and BMP2 released locally at the fracture site via a novel nanoparticle and polyglycidol‐based delivery method. Collectively, these results provide novel evidence for a cell‐autonomous role of neurofibromin in osteoprogenitor cells and insights about a novel targeted approach for the treatment of NF1 pseudoarthrosis. © 2014 American Society for Bone and Mineral Research.     

Mechanical Properties of Bone in a Paraplegic Rat Model

Abstract

Pathologic fractures may occur with minimal trauma after spinal cord injury (SCI) because of osteoporosis. Rats were evaluated to determine whether they could be used as an SCI animal model. Male Sprague-Dawley rats underwent spinal cord transection at the ninth thoracic vertebrae. Control rats underwent a sham procedure. Mechanical testing of the humeral shaft, femoral shaft, tibial shaft, femoral neck, distal femur, and proximal tibia was performed separately at 0, 8, and 24 weeks after surgery. At 24 weeks, significant differences between SCI and control rats were found in maximum torque needed to produce failure in the femoral shaft (63 percent of control, p < 0.05) and tibial shaft (63 percent, p < 0.01), and in compressive load to produce failure in cross-sectional specimens of the distal femur (51 percent, p < 0.05) and proximal tibia (50 percent, p < 0.01 ). No differences were found in the maximum torque needed to produce failure of the humeral shaft (106 percent, p = 0.77) between SCI and control rats. Reductions in relative bone strength in SCI rats at 24 weeks were similar in magnitude to bone mineral density changes reported in humans with chronic paraplegia. Thus, Sprague-Dawley rats appear to be good animal models in which to evaluate changes in bone strength following SCI. U Spinal Cord Med 1998; 21:302-308)     

Bone Changes due to Glucocorticoid Application in an Ovariectomized Animal Model for Fracture Treatment in Osteoporosis

In a pilot experiment comparing four different modalities for inducing osteoporosis in the sheep, a combination of ovariectomy, calcium/vitamin D-restricted diet and steroid administration was found to generate the highest decrease in bone mineral density (BMD). The aim of the present study was to quantify the outcome of this triple treatment in an animal model of osteoporosis in terms of alteration in bone mass, bone structure and bone mechanics. A total of 32 sheep were divided into two equal groups. Group 1 (age 3–5 years) was used as a normal control. Group 2 (age 7–9 years) was ovariectomized, fed a calcium/vitamin D-restricted diet and injected with methylprednisolone (MP) over 7 months (22 weeks MP solution, 6 weeks MP suspension). The BMD at the distal radius and tibia was determined preoperatively and at repeated intervals bilaterally using quantitative computed tomography. Steroid blood levels were determined 4 and 24 h after selected injections. BMD was measured at L3 and L4 after 7 months. Biopsies were taken from iliac crests, vertebral bodies and femoral heads, and bone structure parameters investigated by three-dimensional micro-CT. Compressive mechanical properties of cancellous bone were determined from biopsies of vertebral bodies and femoral heads. After 7 months of osteoporosis induction the BMD of cancellous bone decreased 36 ± 3% in the radius and 39 ± 4% in the tibia. Steroid blood levels 24 h after injection of MP suspension were significantly higher than after injection of MP solution. Changes in structural parameters of cancellous bone from the iliac crest, lumbar spine and femoral head in group 2 indicated osteoporosis-associated changes. In group 2 there was a significant reduction in BMD of the lumbar spine and a significant reduction in stiffness and failure load in compression testing of biopsies of lumbar vertebrae. In sheep, changes in the structural parameters of bone such as trabecular number and separation during osteoporosis induction are comparable to the human situation. The sheep model presented seems to meet the criteria for an osteoporosis model for fracture treatment with respect to mechanical and morphometric bone properties. Received: 4 May 2001 / Accepted: 6 December 2001     

Effect of Denosumab Compared With Risedronate on Bone Strength in Patients Initiating or Continuing Glucocorticoid Treatment

In a randomized clinical trial in patients initiating glucocorticoid therapy (GC-I) or on long-term therapy (GC-C), denosumab every 6 months increased spine and hip bone mineral density at 12 and 24 months significantly more than daily risedronate. The aim of this study was to evaluate the effects of denosumab compared with risedronate on bone strength and microarchitecture measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) in GC-I and GC-C. A subset of 110 patients had high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and tibia at baseline and at 12 and 24 months. Cortical and trabecular microarchitecture were assessed with standard analyses and failure load (FL) with micro-finite element analysis. At the radius at 24 months, FL remained unchanged with denosumab and significantly decreased with risedronate in GC-I (−4.1%, 95% confidence interval [CI] −6.4, −1.8) and, in GC-C, it significantly increased with denosumab (4.3%, 95% CI 2.1, 6.4) and remained unchanged with risedronate. Consequently, FL was significantly higher with denosumab than with risedronate in GC-I (5.6%, 95% CI 2.4, 8.7, p < 0.001) and in GC-C (4.1%, 95% CI 1.1, 7.2, p = 0.011). We also found significant differences between denosumab and risedronate in percentage changes in cortical and trabecular microarchitectural parameters in GC-I and GC-C. Similar results were found at the tibia. To conclude, this HR-pQCT study shows that denosumab is superior to risedronate in terms of preventing FL loss at the distal radius and tibia in GC-I and in increasing FL at the radius in GC-C, based on significant differences in changes in the cortical and trabecular bone compartments between treatment groups in GC-I and GC-C. These results suggest that denosumab could be a useful therapeutic option in patients initiating GC therapy or on long-term GC therapy and may contribute to treatment decisions in this patient population. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Patterns and Localization of Gene Expression During Intramembranous Bone Regeneration in the Rat Femoral Marrow Ablation Model

Tissue formation and repair are dependent upon cascades of biological events, but the signals involved and the possible gene coexpression patterns during intramembranous bone repair are only poorly understood. We sought to place this mode of regeneration in context by profiling quantitative gene expression for a panel of 39 genes between days 1 and 14 following rat femoral marrow ablation. In situ hybridization was employed to localize a subset of genes. Additionally, principal components analysis was conducted to identify underlying factors suggestive of coexpression patterns. During inflammation (days 1–5), several genes, including cyclooxygenase-1 and -2, showed downregulation. Other proinflammatory cytokines, tumor necrosis factor-α and interleukin-1β, exhibited increasing levels around day 5. During repair (days 3–10), growth factors, receptors, and inhibitor genes for transforming growth factor- β; basic fibroblast growth factor; bone morphogenetic proteins 2, 4, and 7; vascular endothelial growth factor; and insulin-like growth factor-I were upregulated. In addition, the gene for core binding factor-α1 and markers of osteoblast function such as alkaline phosphatase, collagen type I, osteonectin, osteopontin, and osteocalcin had peak expression at day 5 or 7. The remodeling phase (days 10–14) was characterized by peaks for cytokines associated with osteoclastic activity including receptor activator of nuclear factor-κB, receptor activator of nuclear factor-κB ligand (RANKL), cathepsin K, tumor necrosis factor-α, interleukin-6, and cyclooxygenase-2. In situ hybridization showed that the most common sites of increased signal were within osteoblastic cells on trabecular and endosteal surfaces. Principal components analysis identified eight underlying factors that together explained over 80% of the variance in the data. Shinji Kuroda and Amarjit S. Virdi, contributed equally to this report.     

糖皮质激素建立老年大鼠骨质疏松症模型的实验研究

通过对老年期前雄性SD大鼠肌注地塞米松注射液，利用糖皮质激素的促骨质吸收作用，观察了实验鼠的全身骨密度、骨小梁容积及生物力学抗弯强度三项指标在高、中、低三种剂量中的变化。结果表明，中剂量地多米松连续肌注6周后，骨的抗弯强度、骨密度及骨小梁容积都显著降低（P＜0．05），低剂量虽已有降低趋势，尚无统计学意义（P＞0．05）。认为用介乎中、高剂量之间的量0．25mg／100g体重每周2次，连续6周可建立老年性大鼠骨质疏松症模型。     

Evolution and Development of Ilizarov Technique in the Treatment of Infected Long Bone Nonunion with or without Bone Defects

The treatment of infected bone nonunion and bone defects is a considerable challenge in the orthopedics field. The standard clinical therapy methods include local free bone transplantation, vascularized bone graft, and the Ilizarov technique; the first two are controversial due to the iatrogenic self‐injury. The Ilizarov bone transport technique has been widely used to treat infected bone nonunion and bone defects, and good clinical effect has been demonstrated. Yet, it brings many related complications, which exerts additional suffering to the patient. The best treatment is to combine bone defect rehabilitation with infection control, intramedullary nail fixation, appropriate time for bone grafts, beaded type scaffold slippage and new Taylor fixation, reducing the external fixation time and the incidence of complications, thereby reducing the occurrence of patients'' physical and psychological problems. This review focuses on the induction, summary and analysis of the Ilizarov bone transport technique in the treatment of infected long bone nonunion with or without bone defects, providing new ideas and methods for orthopedic disease prevention and treatment by the Ilizarov technique, which is following the development direction of digital orthopedics.