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ABSTRACT: Successful repair of craniofacial and periodontal tissue defects ideally involves a combined therapy that includes inflammation modulation, control of soft tissue infiltration, and bone regeneration. In this study, an anti-inflammatory polymer, salicylic acid-based poly(anhydride-ester) (SAPAE) and a three-dimensional osteoconductive ceramic scaffold were evaluated as a combined guided bone regeneration (GBR) system for concurrent control of inflammation, soft tissue ingrowth, and bone repair in a rabbit cranial defect model. At time periods of 1, 3, and 8 weeks, five groups were compared: (1) scaffolds with a solid ceramic cap (as a GBR structure); (2) scaffolds with no cap; (3) scaffolds with a poly(lactide-glycolide) (PLGA) cap; (4) scaffolds with a slow release SAPAE polymer cap; and (5) scaffolds with a fast release SAPAE polymer cap. Cellular infiltration and bone formation in these scaffolds were evaluated to assess inflammation and bone repair capacity of the test groups. The SAPAE polymers suppressed inflammation and displayed no deleterious effect on bone formation. Additional work is warranted to optimize the anti-inflammatory action of the SAPAE, GBR suppression of soft tissue infiltration, and stimulation of bone formation in the scaffolds and create a composite device for successful repair of craniofacial and periodontal tissue defects.
Journal of Biomedical Materials Research Part A 03/2013; · 2.63 Impact Factor
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David N Paglia,
Aaron Wey,
Eric A Breitbart,
Jonathan Faiwiszewski,
Siddhant K Mehta,
Loay Al-Zube,
Swaroopa Vaidya,
Jessica A Cottrell,
Dana Graves,
Joseph Benevenia, J Patrick O'Connor,
Sheldon S Lin
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ABSTRACT: Local insulin delivery has been shown to improve osseous healing in diabetic animals. The purpose of this study was to quantify the effects of local intramedullary delivery of saline or Ultralente insulin (UL) on various fracture healing parameters using an in vivo non-diabetic BB Wistar rat model. Quantitation of local insulin levels showed a rapid release of insulin from the fractured femora, demonstrating complete release at 2 days. RT-PCR analysis revealed that the expression of early osteogenic markers (Col1α2, osteopontin) was significantly enhanced with UL treatment when compared with saline controls (p < 0.05). Significant differences in VEGF + cells and vascularity were evident between the treatment and control groups at day 7 (p < 0.05). At day 21, histomorphometric analysis demonstrated a significant increase in percent mineralized tissue in the UL-treated animals compared with controls (p < 0.05), particularly within the subperiosteal region of the fracture callus. Mechanical testing at 4 weeks showed significantly greater mechanical strength for UL-treated animals (p < 0.05), but healing in control animals caught up at 6 weeks post-fracture. These results suggest that the primary osteogenic effect of UL during the early stages of fracture healing (1-3 weeks) is through an increase in osteogenic gene expression, subperiosteal angiogenesis, and mineralized tissue formation. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
Journal of Orthopaedic Research 12/2012; · 2.81 Impact Factor
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ABSTRACT: A significant number of lower extremity fractures result in mal-union necessitating effective treatments to restore ambulation. Prior research in diabetic animal fracture models demonstrated improved healing following local insulin application to the fracture site and indicated that local insulin therapy can aid bone regeneration, at least within an insulin-dependent diabetic animal model. This study tested whether local insulin therapy could accelerate femur fracture repair in normal, non-diabetic rats. High (20 units) and low (10 units) doses of insulin were delivered in a calcium sulfate carrier which provided sustained release of the exogenous insulin for 7 days after fracture. Histomorphometry, radiographic scoring, and torsional mechanical testing were used to measure fracture healing. The fracture calluses from rats treated with high-dose insulin had significantly more cartilage than untreated rats after 7 and 14 days of healing. After 4 weeks of healing, femurs from rats treated with low-dose insulin had significantly higher radiographic scores and mechanical strength (p < 0.05), compared to the no treatment control groups. The results of this study suggest that locally delivered insulin is a potential therapeutic agent for treating bone fractures. Further studies are necessary, such as large animal proof of concepts, prior to the clinical use of insulin for bone fracture treatment. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
Journal of Orthopaedic Research 12/2012; · 2.81 Impact Factor
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ABSTRACT: This study quantified the effects of local intramedullary delivery of an organic vanadium salt, which may act as an insulin-mimetic on fracture healing. Using a BB Wistar rat femoral fracture model, local vanadyl acetylacetonate (VAC) was delivered to the fracture site and histomorphometry, mechanical testing, and immunohistochemistry were performed. Callus percent cartilage was 200% higher at day 7 (p < 0.05) and 88% higher at day 10 (p < 0.05) in the animals treated with 1.5 mg/kg of VAC. Callus percent mineralized tissue was 37% higher at day 14 (p < 0.05) and 31% higher at day 21 (p < 0.05) in the animals treated with 1.5 mg/kg of VAC. Maximum torque to failure was 104% and 154% higher at 4 weeks post-fracture (p < 0.05) for the healing femurs from the VAC-treated (1.5 and 3.0 mg/kg) animals. Animals treated with other VAC doses demonstrated increased mechanical parameters at 4 weeks (p < 0.05). Immunohistochemistry detected 62% more proliferating cells at days 7 (p < 0.05) and 94% more at day 10 (p < 0.05) in the animals treated with 1.5 mg/kg VAC. Results showed 100% more vascular endothelial growth factor-C (VEGF-C) positive cells and 80% more blood vessels at day 7 (p < 0.05) within the callus subperiosteal region of VAC-treated animals (1.5 mg/kg) compared to controls. The results suggest that local VAC treatment affects chondrogenesis and angiogenesis within the first 7-10 days post-fracture, which leads to enhanced mineralized tissue formation and accelerated fracture repair as early as 3-4 weeks post-fracture. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1971-1978, 2012.
Journal of Orthopaedic Research 05/2012; 30(12):1971-8. · 2.81 Impact Factor
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Jemin Dedania,
Robert Borzio,
David Paglia,
Eric A Breitbart,
Ashley Mitchell,
Swaroopa Vaidya,
Aaron Wey,
Siddhant Mehta,
Joseph Benevenia, J Patrick O'Connor,
Sheldon S Lin
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ABSTRACT: Each year, over one million orthopedic operations are performed which a bony defect is presence, requiring the use of further augmentation in addition to bony fixation. Application of autogenous bone graft is the standard of care to promote healing of these defects, but several determents exist in using autogenous bone graft exist including limited supply and donor site morbidity. Prior work has demonstrated that local insulin application to fracture sites promote fracture healing, but no work has been performed to date in its effects upon defect healing/allograft incorporation. The goal of this study was to examine the potential role of local insulin application upon allograft incorporation. Microradiographic, histologic, and histomorphometric analysis outcome parameters showed that local insulin significantly accelerated new bone formation. Histological comparisons using predetermined scoring systems demonstrated significantly greater healing in femora treated with insulin compared to control femora (p < 0.001). Quantitatively more bone production was also observed, specifically in areas of endosteal (p = 0.010) and defect (p = 0.041) bone in femora treated with local insulin, compared to control femora, 6 weeks after implantation. This study demonstrates the potential of local insulin as an adjunct for the treatment of segmental defect and allograft incorporation.
Journal of Orthopaedic Research 01/2011; 29(1):92-9. · 2.81 Impact Factor
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ABSTRACT: Cyclooxygenase-2 (COX-2) promotes inflammation by synthesizing pro-inflammatory prostaglandins from arachidonic acid. Inflammation is an early response to bone fracture, and ablation of COX-2 activity impairs fracture healing. Arachidonic acid is also converted into leukotrienes by 5-lipoxygenase (5-LO). We hypothesized that 5-LO is a negative regulator of fracture healing and that in the absence of COX-2, excess leukotrienes synthesized by 5-LO will impair fracture healing.
Fracture healing was assessed in mice with a targeted 5-LO mutation (5-LO(KO) mice) and control mice by radiographic and histological observations, and measured by histomorphometry and torsional mechanical testing. To assess effects on arachidonic acid metabolism, prostaglandin E2, F2α, and leukotriene B4 levels were measured in the fracture calluses of control, 5-LO(KO) COX-1(KO), and COX-2(KO) mice by enzyme linked immunoassays.
Femur fractures in 5-LO(KO) mice rapidly developed a cartilaginous callus that was replaced with bone to heal fractures faster than in control mice. Femurs from 5-LO(KO) mice had substantially better mechanical properties after 1 month of healing than did control mice. Callus leukotriene levels were 4-fold higher in mice homozygous for a targeted mutation in the COX-2 gene (COX-2(KO)), which indicated that arachidonic acid was shunted into the 5-LO pathway in the absence of COX-2.
These experiments show that 5-LO negatively regulates fracture healing and that shunting of arachidonic acid into the 5-LO pathway may account, at least in part, for the impaired fracture healing response observed in COX-2(KO) mice.
Acta Orthopaedica 11/2010; 81(6):748-55. · 2.17 Impact Factor
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ABSTRACT: In the United States, over 17 million people are diagnosed with type 1 diabetes mellitus (DM) with its inherent morbidity of delayed bone healing and nonunion. Recent studies demonstrate the utility of pulsed low-intensity ultrasound (LIPUS) to facilitate fracture healing. The current study evaluated the effects of daily application of LIPUS on mid-diaphyseal femoral fracture growth factor expression, cartilage formation, and neovascularization in DM and non-DM BB Wistar rats. Polymerase chain reaction (PCR) and ELISA assays were used to measure and quantify growth factor expression. Histomorphometry assessed cartilage formation while immunohistochemical staining for PECAM evaluated neovascularization at the fracture site. In accordance with previous studies, LIPUS was shown to increase growth factor expression and cartilage formation. Our study also demonstrated an increase in fracture callus neovascularization with the addition of LIPUS. The DM group showed impaired growth factor expression, cartilage formation, and neovascularization. However, the addition of LIPUS significantly increased all parameters so that the DM group resembled that of the non-DM group. These findings suggest a potential role of LIPUS as an adjunct for DM fracture treatment.
Journal of Orthopaedic Research 09/2010; 29(2):181-8. · 2.81 Impact Factor
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ABSTRACT: Besides its anti-inflammatory effects, nonsteroidal anti-inflammatory drug therapy may affect tendon healing and the development of peritendinous adhesions. The purpose of this study was to compare the effect of nonselective (ibuprofen) and COX-2 selective (rofecoxib) nonsteroidal anti-inflammatory drugs on the adhesion formation after tendon repair.
We assigned 67 rabbits to one of 3 (placebo, ibuprofen, or rofecoxib) groups. The deep flexor tendon was transected, followed by a primary repair. Dosing of the medication began the day after surgery and continued for 27 days. The animals were immobilized in a cast for the first 14 days. Postoperatively, tendon adhesion formation was assessed histologically by calculating the total adhesion in serial axial tendon sections at 3 and 6 weeks and by range of motion measurements at 6 and 12 weeks. We measured range of motion by fixing the metacarpal, applying increasing weight to the free end of the flexor digitorum profundus, and measuring the flexion angle between the metacarpal and the proximal phalanx. Comparison was performed between the treatment groups, as well as to the unoperated forepaws.
Based on histology, we found no difference between the treatment groups when determining the percentage of adhesion between the flexor tendon and its sheath. Control unoperated forepaws had a significantly greater range of metacarpophalangeal joint flexion than the surgically repaired groups. At 12 weeks, range of motion in the ibuprofen group was significantly better than the placebo (p=.009) and rofecoxib (p=.009) groups.
Ibuprofen has a more important effect in limiting adhesion formation compared with rofecoxib after flexor tendon repair. Because ibuprofen inhibits both COX-1 and COX-2, whereas rofecoxib only inhibits COX-2, ibuprofen therapy appears to offer a greater beneficial effect on tendon repair by reducing formation of adhesions.
The Journal of hand surgery 06/2010; 35(6):941-7. · 1.33 Impact Factor
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ABSTRACT: The long-term success of arthroplastic joints is dependent on the stabilization of the implant within the skeletal site. Movement of the arthroplastic implant within the bone can stimulate osteolysis, and therefore methods which promote rigid fixation or bone growth are expected to enhance implant stability and the long-term success of joint arthroplasty. In the present study, we used a simple bilateral bone defect model to analyze the osteogenic activity of three small-molecule drug implants via microcomputerized tomography (micro-CT) and histomorphometry. In this study, we show that local delivery of alendronate, but not lovastatin or omeprazole, led to significant new bone formation at the defect site. Since alendronate impedes osteoclast-development, it is theorized that alendronate treatment results in a net increase in bone formation by preventing osteoclast mediated remodeling of the newly formed bone and upregulating osteoblasts.
Journal of Biomedicine and Biotechnology 01/2010; 2010:597641. · 2.44 Impact Factor
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ABSTRACT: Loss of cyclooxygenase-2 activity is known to impair fracture-healing in animal models and to inhibit heterotopic ossification in humans. Cyclooxygenase-2 is the rate-limiting enzyme involved in the conversion of arachidonic acid into prostaglandins. Arachidonic acid also is a substrate for 5-lipoxygenase, which catalyzes the initial steps in leukotriene synthesis. In contrast to cyclooxygenase-2, genetic ablation of 5-lipoxygenase accelerates and enhances fracture-healing in mice. The goal of this study was to determine if systemic inhibition of 5-lipoxygenase with an orally delivered drug could accelerate fracture-healing.
Closed femoral fractures were made in Sprague-Dawley rats. The rats were treated with oral doses of vehicle (ninety-five rats), celecoxib (fifty-nine rats), or AA-861 (a 5-lipoxygenase inhibitor; eighty-nine rats). Fracture-healing was measured with use of radiographs, histomorphometry, and biomechanical testing. Effects of drug treatments on callus cell proliferation and gene expression were determined by incorporation of bromodeoxyuridine and quantitative polymerase chain reactions, respectively.
AA-861 treatment decreased fracture-bridging time, significantly increased early callus cartilage (5.6-fold; p < 0.001) and bone formation (4.2-fold; p = 0.015), and significantly increased callus mechanical properties compared with the vehicle-treated rat fractures. Callus cell proliferation rate was increased by AA-861 treatment, compared with vehicle, at day 2 after fracture (3.68% compared with 2.08%; p < 0.001; 95% confidence interval, -2.81 to -0.039) but was reduced by celecoxib treatment at day 4 after fracture (4.22% compared with 1.84%; p < 0.001; 95% confidence interval, 2.27 to 4.07). At day 10 after fracture, AA-861 and celecoxib treatment increased Type-II collagen mRNA levels (16.0-fold and 6.1-fold, respectively; p < 0.001 for both), but only AA-861 treatment caused an increase in Type-X collagen mRNA (6.3-fold; p < 0.001). AA-861 treatment significantly increased cyclooxygenase-2 (4.0-fold at day 10; p < 0.001) and osteopontin mRNA levels (3.6-fold at day 7; p = 0.024), while decreasing 5-lipoxygenase mRNA levels (5.6-fold at day 4; p < 0.001).
Systemic inhibition of 5-lipoxygenase with an orally delivered drug significantly accelerated and enhanced fracture-healing in this rat model. Gene expression analysis indicates that cyclooxygenase-2 is necessary for callus chondrocytes to progress into hypertrophy so as to complete endochondral ossification. Conversely, inhibition of 5-lipoxygenase alters the inflammatory response, which enhances callus chondrocyte hypertrophy and accelerates endochondral ossification.
The Journal of Bone and Joint Surgery 11/2009; 91(11):2653-65. · 3.27 Impact Factor
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ABSTRACT: Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) activity, which is the rate-limiting enzyme in the synthesis of prostaglandins. Previous studies have indicated that NSAID therapy, and in particular NSAIDs that specifically target the inflammatory cyclooxygenase (COX-2), impair bone healing. We compared the effects of ibuprofen and rofecoxib on fibula osteotomy healing in rabbits to determine whether nominal, continuous inhibition of COX-2 with rofecoxib would differentially affect fracture healing more than cyclical inhibition of COX-2 using ibuprofen, which inhibits COX-1 and COX-2 and has a short half-life in vivo.
Bilateral fibula osteotomies were done in 67 skeletally mature male New Zealand white rabbits. The rabbits were treated with placebo, rofecoxib (12.5 mg once a day), or ibuprofen (50 mg 3 times a day) for 28 days after surgery. Plasma ibuprofen levels were measured by HPLC analysis. Bone healing was assessed by histomorphometry at 3 and 6 weeks after osteotomy, and at 6 and 12 weeks by torsional mechanical testing.
Plasma ibuprofen levels peaked and declined between successive doses. Fracture callus morphology was abnormal in the rofecoxib-treated rabbits and torsional mechanical testing showed that fracture healing was impaired. Ibuprofen treatment caused persistence of cartilage within the fracture callus and reduced peak torque at 6 weeks after osteotomy as compared to the fibulas from the placebo-treated rabbits. In the specimens allowed to progress to possible healing, non-union was seen in 5 of the 26 fibulas from the rofecoxib-treated animals as compared to 1 of 24 in the placebo group and 1 of 30 in the ibuprofen treatment group.
Continuous COX-2 inhibition as modeled by rofecoxib treatment appears to be more deleterious to fracture repair than cyclical cyclooxygenase inhibition as modeled by ibuprofen treatment. Ibuprofen treatment appeared to delay bone healing based upon the persistence of cartilage within the fracture callus and diminished shear modulus. Despite the ibuprofen-induced delay, rofecoxib treatment produced worse fracture (osteotomy) healing than ibuprofen treatment.
Acta Orthopaedica 10/2009; 80(5):597-605. · 2.17 Impact Factor
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ABSTRACT: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to enhance new bone formation in fracture and bone defect models in both normal and diabetic rats. Effects of rhBMP-2 in a segmental femoral defect model in diabetes mellitus (DM) BB Wistar rats have not been reported.
Collagen sponge soaked with either buffer or rhBMP-2 was inserted in a mid-diaphyseal 3.0-mm defect fixed with polyimide plate and stainless steel screws, in 62 DM BB Wistar rats. Progress of new bone formation in the defect was monitored with serial radiographs every 2 weeks. Histomorphometric analysis of the new bone formation was done on undecalcified sections of the extracted femurs at 3 and 6 weeks post surgery. Further analysis of the new bone was done by assessment of neoangiogenesis using immunohistochemical staining for Platelet endothelial cell adhesion molecule-1. Mechanical testing was performed at 9 weeks to assess the new bone with respect to 4 different parameters of mechanical and structural properties of bone.
Radiographs assessed over a 6-point grading system showed statistically significant improvement in scores in rhBMP-2-treated rats at 6 weeks (P < 0.001). Histomorphometric analysis showed statistically significant increase in area of new bone formation between rats treated with rhBMP-2 compared with buffer at both 3 and 6 weeks (P < 0.001). On Platelet endothelial cell adhesion molecule-1 staining at 3 weeks, the mean number of vessels in rhBMP-2-treated DM rats was 12.76 +/- 5.43/mm(2) compared with 4.49 +/- 1.89/mm(2) in buffer treated DM rats (P = 0.034). On mechanical testing, all 4 DM/buffer rats had nonunion. In DM/rhBMP-2 rats, the torque to failure and torsional rigidity values were 393.57 +/- 233.3 (P < 0.03) and 29,711 +/- 6224 (P < 0.002), respectively.
Clearly, although DM has a known impact on osseous healing, its negative effects are ameliorated with the application of the rhBMP-2-collagen carrier and demonstrates the potential clinical role of this adjunct in the clinical arena.
Journal of orthopaedic trauma 05/2009; 23(4):267-76. · 1.78 Impact Factor
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ABSTRACT: Traditional and COX-2 selective non-steroidal anti-inflammatory drug (NSAID) treatment inhibits fracture healing in animal models. This indicates that either the inflammatory phase following a bone fracture is necessary for efficient or sufficient bone regeneration to heal the fracture or COX-2 may have a specific function during bone regeneration unrelated to inflammation. These observations also indicate that NSAID use during fracture healing may be contra-indicated. Thus, identification of different analgesics for fracture pain or other orthopaedic surgical procedures would be of significant clinical benefit. Inhibitors of p38 kinase also have significant analgesic properties. However, p38 kinase is a critical regulator of inflammation. To assess the potential use of p38 kinase inhibition as a therapeutic strategy to manage fracture pain, the analgesic properties of SCIO-469, a p38alpha kinase inhibitor, were assessed in a rat fracture model and compared to other common analgesics. In addition, the effects of SCIO-469 treatment on ultimate fracture healing outcomes were measured by radiography and torsional mechanical testing. The data indicate that SCIO-469 was an effective analgesic. No adverse events related to fracture healing were observed in rats treated with SCIO-469. Immunohistochemistry showed that p38 kinase is activated primarily in the first days following a fracture. These observations suggest that p38alpha kinase inhibition may be an effective therapeutic strategy to manage orthopaedic-related pain. These observations also indicate that COX-2 has a specific function during bone regeneration other than promoting inflammation.
Pain 02/2009; 142(1-2):116-26. · 5.78 Impact Factor
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ABSTRACT: Diabetes mellitus is a common systemic disease that has been associated with poor fracture healing outcomes. The mechanism through which diabetes impairs bone regeneration is unknown. One possible mechanism may be related to either decreased or uncoordinated release of local growth factors at the fracture site. Indeed, previous studies have found reduced platelet-derived growth factor (PDGF) levels in the fracture callus of diabetic rats, suggesting that local application of PDGF may overcome the negative effects of diabetes and promote fracture healing. To test this hypothesis, low (22 microg) and high (75 ug) doses of recombinant human PDGF-BB (rhPDGF-BB) were applied directly to femur fracture sites in BB Wistar diabetic rats that were then compared to untreated or vehicle-treated animals. rhPDGF-BB treatment significantly increased early callus cell proliferation compared to that in control specimens. Low dose rhPDGF-BB treatment significantly increased callus peak torque values (p < 0.05) at 8 weeks after fracture as compared to controls. High dose rhPDGF-BB treatment increased callus bone area at 12 weeks postfracture. These data indicate that rhPDGF-BB treatment ameliorates the effects of diabetes on fracture healing by promoting early cellular proliferation that ultimately leads to more bone formation. Local application of rhPDGF-BB may be a new therapeutic approach to treat diabetes-impaired fracture healing.
Journal of Orthopaedic Research 01/2009; 27(8):1074-81. · 2.81 Impact Factor
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ABSTRACT: Treating acute and chronic musculoskeletal pain is essential for improving healing of traumatic injuries and surgical procedures, and for improving patient quality of life. Physicians are limited primarily to treating musculoskeletal pain with nonsteroidal antiinflammatory drugs (NSAIDs), cyclooxygenase type 2 (COX-2)-selective NSAIDs such as celecoxib, or narcotics. Patients often treat their pain with over-the-counter NSAIDs. Unlike narcotics that target the central nervous system to alleviate pain, NSAIDs inhibit cyclooxygenase activity within the central nervous system and at the peripheral pain site to prevent the conversion of arachidonic acid into prostaglandins. Thus, NSAID use can and does alter certain fundamental processes involved in the normal healing of injured tissues. Cyclooxygenase activity and prostaglandin signaling are critical regulators of normal skeletal metabolism and inflammation related to injury or disease. Since most people only use NSAIDs sporadically to treat pain, few data indicate that short-term or repeated occasional use of NSAIDs is deleterious to skeletal health. However, clinical data suggest that chronic use of celecoxib, may impair normal skeletal function leading to decreased bone mineral density in older male patients. Experimental studies also have documented the negative effects of NSAIDs on healing of skeletal tissues. Fracture healing and tendon-to-bone healing appear to be particularly susceptible to inhibition by celecoxib. Limited retrospective clinical data tends to support the experimental data that COX-2 function is critical for normal bone healing. In contrast, NSAID use and perhaps COX-2-selective NSAID use may be beneficial for healing of other skeletal injuries. In particular, NSAID use does not appear to have a long-term negative effect on the ultimate healing of tendons and ligaments. Indeed, NSAID therapy may inhibit adhesion formation during tendon healing, which leads to a better functional recovery. Certainly, NSAID therapy following acetabular fractures, other hip fractures, or following hip replacement surgery is beneficial for reducing heterotopic ossification that can limit joint mobility. The effects of NSAID or celecoxib therapy on healing of other skeletal tissues is less clear. For instance, clinical data indicates that celecoxib therapy does not impair spinal fusion but experimental data indicates the opposite. Similarly, some reports suggest that NSAID therapy may prevent further erosion of cartilage in certain arthritic conditions while other reports indicate that NSAID treatment will exacerbate cartilage damage. The difference in effects caused by NSAID or celecoxib therapy likely relate to the role cyclooxygenase has in the biology of the injured tissue or its healing response. Differences in pharmacology between NSAIDs, treatment regimens, experimental models and potential off-target effects also may confuse many of these issues. It is clear, however, that cyclooxygenase activity is involved in the healing of many skeletal tissues, either directly or indirectly through modulation of the inflammatory response. Consequently, pharmacological manipulation of cyclooxygenase using NSAIDs or celecoxib can profoundly affect skeletal health.
Drugs of today (Barcelona, Spain: 1998) 10/2008; 44(9):693-709. · 1.28 Impact Factor
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ABSTRACT: Crk II and Crk L have both cytosolic and nuclear functions. While Crk L is a bona fide nuclear signaling protein because of its ability to bind tyrosine-phosphorylated STAT5 and act as a transcriptional coactivator, the function of nuclear Crk II is less well understood. The present study was undertaken to investigate whether Crk II is in the nucleus, how Crk II translocates into the nucleus, whether it possesses a functional NES, and to determine if nuclear Crk II affects cell cycle checkpoints and promotes apoptosis. Toward this goal, we used several independent techniques to show that a significant percentage of the total endogenous Crk II partitions in the nucleus in mammalian cells, where it forms distinct complexes with DOCK180, Wee1, and Abl. We found no evidence that Crk II bound to Crm1 nor that the localization of GFP-Crk II was sensitive to LMB, an inhibitor of Crm1. To better define the significance of nuclear Crk II localization, we generated a GFP-Crk II protein (GFP-Crk-nuc) fused to three tandem nuclear localization signals derived from the SV40 large T-antigen. GFP-Crk-nuc exhibited exclusive nuclear localization, and in contrast to wild-type Crk, GFP-Crk-nuc expressing cells could not be propagated upon selection in G418-containing media, suggesting nuclear accumulation of Crk II caused either growth arrest or apoptosis. When transiently transfected cells were FACS sorted, GFP-expressing cells showed defective cell adhesion on tissue culture surfaces and showed an increased level of apoptosis assessed by pycnotic nuclei, annexin V staining, and PARP cleavage. Although we found that Crk II bound to the cell cycle protein Wee1, expression of GFP-Crk-nuc did not induce a G2/M cell cycle block or cause increased Cdc2 Tyr15 phosphorylation. Finally, upon UV stimulation, we found that endogenous Crk II translocated to the nucleus and potentiated the extent of UV-inducible apoptosis after 4 h. These data suggest that nuclear compartmentalization of Crk II antagonizes its cytoskeletal functions and assign a proapoptotic role to the nuclear pool of Crk II.
Biochemistry 10/2007; 46(38):10828-40. · 3.42 Impact Factor
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ABSTRACT: Mammalian models of longevity are related primarily to caloric restriction and alterations in metabolism. We examined mice in which type 5 adenylyl cyclase (AC5) is knocked out (AC5 KO) and which are resistant to cardiac stress and have increased median lifespan of approximately 30%. AC5 KO mice are protected from reduced bone density and susceptibility to fractures of aging. Old AC5 KO mice are also protected from aging-induced cardiomyopathy, e.g., hypertrophy, apoptosis, fibrosis, and reduced cardiac function. Using a proteomic-based approach, we demonstrate a significant activation of the Raf/MEK/ERK signaling pathway and upregulation of cell protective molecules, including superoxide dismutase. Fibroblasts isolated from AC5 KO mice exhibited ERK-dependent resistance to oxidative stress. These results suggest that AC is a fundamentally important mechanism regulating lifespan and stress resistance.
Cell 08/2007; 130(2):247-58. · 32.40 Impact Factor
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ABSTRACT: Fracture-healing is impaired in mice lacking a functional cyclooxygenase-2 (COX-2) gene or in rats continuously treated with COX-2 inhibitors. These observations indicate that COX-2 is a critical regulator of fracture repair. Nonsteroidal anti-inflammatory drugs are commonly used to treat pain associated with musculoskeletal trauma and disease. Nonsteroidal anti-inflammatory drugs inhibit COX-2 function and in so doing can impair fracture-healing. The goal of the present study was to determine how variations in nonsteroidal anti-inflammatory drug therapy ultimately affect fracture-healing.
Closed femoral fractures were made in female Sprague-Dawley rats. The rats were treated with different doses of celecoxib (a COX-2-selective nonsteroidal anti-inflammatory drug) or were treated for different periods before or after fracture with celecoxib. Eight weeks after the fracture, healing was assessed with radiography and destructive torsional mechanical testing. The effect of celecoxib treatment on fracture callus prostaglandin E2 and F(2alpha) levels was determined as a measure of cyclooxygenase activity.
Celecoxib doses as small as 2 mg/kg/day reduced fracture callus mechanical properties and caused a significant increase in the proportion of nonunions. Similarly, treatment with celecoxib at a dose of 4 mg/kg/day for just five days reduced fracture callus mechanical properties and significantly increased the proportion of nonunions. Conversely, celecoxib therapy prior to fracture or initiated fourteen days after fracture did not significantly increase the proportion of nonunions. Celecoxib treatment at a dose of 4 mg/kg/day reduced fracture callus prostaglandin E2 and F(2alpha) levels by >60%.
COX-2-selective nonsteroidal anti-inflammatory drug therapy during the early stages of fracture repair significantly reduced fracture callus mechanical properties at later stages of healing and increased the proportion of nonunions in this animal model.
The Journal of Bone and Joint Surgery 03/2007; 89(3):500-11. · 3.27 Impact Factor
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ABSTRACT: Several studies have documented that diabetes impairs bone healing clinically and experimentally. The percutaneous delivery of platelet rich plasma (PRP) was used in the diabetic BB Wistar femur fracture model to investigate the use of PRP as a concentrated source of critical early growth factors on bone healing. PRP delivery at the fracture site normalized the early (cellular proliferation and chondrogenesis) parameters while improving the late (mechanical strength) parameters of diabetic fracture healing. These results suggest a role for PRP in mediating diabetic fracture healing and potentially other high risk fractures.
Bone 05/2006; 38(4):540-6. · 4.02 Impact Factor
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ABSTRACT: Several studies have documented that diabetes impairs bone healing clinically and experimentally. Systemic insulin treatment has been shown to ameliorate impaired diabetic bone healing. However, these studies failed to distinguish between a direct and a systemic effect of insulin upon bone healing. A novel intramedullary insulin delivery system was used in the diabetic BB Wistar femur fracture model to investigate the potential direct effects of insulin on bone healing. Insulin delivery at the fracture site normalized the early (cellular proliferation and chondrogenesis) and late (mineralized tissue, cartilage content and mechanical strength) parameters of diabetic fracture healing without affecting the systemic parameters of blood glucose. These results suggest a critical role for insulin in directly mediating fracture healing and that decreased systemic insulin levels in the diabetic state lead to reduced localized insulin levels at fracture site with concomitant increases in diabetic fracture healing time.
Bone 11/2005; 37(4):482-90. · 4.02 Impact Factor
