BMP-7-induced ectopic bone formation and fracture healing is impaired by systemic NSAID application in C57BL/6-mice

Translational Experimental Basis of Indirect Adenosine Receptor Agonist Stimulation for Bone Regeneration: A Review

Bone regeneration remains a significant clinical challenge, often necessitating surgical approaches when healing bone defects and fracture nonunions. Within this context, the modulation of adenosine signaling pathways has emerged as a promising therapeutic option, encouraging osteoblast activation and tempering osteoclast differentiation. A literature review of the PubMed database with relevant keywords was conducted. The search criteria involved in vitro or in vivo models, with clear methodological descriptions. Only studies that included the use of indirect adenosine agonists, looking at the effects of bone regeneration, were considered relevant according to the eligibility criteria. A total of 29 articles were identified which met the inclusion and exclusion criteria, and they were reviewed to highlight the preclinical translation of adenosine agonists. While preclinical studies demonstrate the therapeutic potential of adenosine signaling in bone regeneration, its clinical application remains unrealized, underscoring the need for further clinical trials. To date, only large, preclinical animal models using indirect adenosine agonists have been successful in stimulating bone regeneration. The adenosine receptors (A1, A2A, A2B, and A3) stimulate various pathways, inducing different cellular responses. Specifically, indirect adenosine agonists act to increase the extracellular concentration of adenosine, subsequently agonizing the respective adenosine receptors. The agonism of each receptor is dependent on its expression on the cell surface, the extracellular concentration of adenosine, and its affinity for adenosine. This comprehensive review analyzed the multitude of indirect agonists currently being studied preclinically for bone regeneration, discussing the mechanisms of each agonist, their cellular responses in vitro, and their effects on bone formation in vivo.

Evaluation and Treatment of Acute Trauma Pain in Older Adults

In the context of an ageing population, the demographic sands of trauma are shifting. Increasingly, trauma units are serving older adults who have sustained injuries in low-energy falls from a standing height. Older age is commonly associated with changes in physiology, as well as an increased prevalence of frailty and multimorbidity, including cardiac, renal and liver disease. These factors can complicate the safe and effective administration of analgesia in the older trauma patient. Trauma services therefore need to adapt to meet this demographic shift and ensure that trauma clinicians are sufficiently skilled in treating pain in complex older people. This article is dedicated to the management of acute trauma pain in older adults. It aims to highlight the notable clinical challenges of managing older trauma patients compared with their younger counterparts. It offers an overview of the evidence and practical opinion on the merits and drawbacks of commonly used analgesics, as well as more novel and emerging analgesic adjuncts. A search of Medline (Ovid, from inception to 7 November 2022) was conducted by a medical librarian to identify relevant articles using keyword and subject heading terms for trauma, pain, older adults and analgesics. Results were limited to articles published in the last 10 years and English language. Relevant articles' references were hand-screened to identify other relevant articles. There is paucity of dedicated high-quality evidence to guide management of trauma-related pain in older adults. Ageing-related changes in physiology, the accumulation of multimorbidity, frailty and the risk of inducing delirium secondary to analgesic medication present a suite of challenges in the older trauma patient. An important nuance of treating pain in older trauma patients is the challenge of balancing iatrogenic adverse effects of analgesia against the harms of undertreated pain, the complications and consequences of which include immobility, pneumonia, sarcopenia, pressure ulcers, long-term functional decline, increased long-term care needs and mortality. In this article, the role of non-opioid agents including short-course non-steroidal anti-inflammatory drugs (NSAIDs) is discussed. Opioid selection and dosing are reviewed for older adults suffering from acute trauma pain in the context of kidney and liver disease. The evidence base and limitations of other adjuncts such as topical and intravenous lidocaine, ketamine and regional anaesthesia in acute geriatric trauma are discussed.

Engineering 3D Printed Bioceramic Scaffolds to Reconstruct Critical-Sized Calvaria Defects in a Skeletally Immature Pig Model

BACKGROUND

Three-dimensional printed bioceramic scaffolds composed of 100% β-tricalcium phosphate augmented with dipyridamole (3DPBC-DIPY) can regenerate bone across critically sized defects in skeletally mature and immature animal models. Before human application, safe and effective bone formation should be demonstrated in a large translational animal model. This study evaluated the ability of 3DPBC-DIPY scaffolds to restore critically sized calvarial defects in a skeletally immature, growing minipig.

METHODS

Unilateral calvarial defects (~1.4 cm) were created in 6-week-old Göttingen minipigs ( n = 12). Four defects were filled with a 1000 μm 3DPBC-DIPY scaffold with a cap (a solid barrier on the ectocortical side of the scaffold to prevent soft-tissue infiltration), four defects were filled with a 1000 μm 3DPBC-DIPY scaffold without a cap, and four defects served as negative controls (no scaffold). Animals were euthanized 12 weeks postoperatively. Calvariae were subjected to micro-computed tomography, 3D reconstruction with volumetric analysis, qualitative histologic analysis, and nanoindentation.

RESULTS

Scaffold-induced bone growth was statistically greater than in negative controls ( P ≤ 0.001), and the scaffolds with caps produced significantly more bone generation compared with the scaffolds without caps ( P ≤ 0.001). Histologic analysis revealed woven and lamellar bone with haversian canals throughout the regenerated bone. Cranial sutures were observed to be patent, and there was no evidence of ectopic bone formation or excess inflammatory response. Reduced elastic modulus and hardness of scaffold-regenerated bone were found to be statistically equivalent to native bone ( P = 0.148 for reduced elastic modulus of scaffolds with and without caps and P = 0.228 and P = 0.902 for hardness of scaffolds with and without caps, respectively).

CONCLUSION

3DPBC-DIPY scaffolds have the capacity to regenerate bone across critically sized calvarial defects in a skeletally immature translational pig model.

CLINICAL RELEVANCE STATEMENT

This study assessed the bone generative capacity of 3D-printed bioceramic scaffolds composed of 100% β-tricalcium phosphate and augmented with dipyridamole placed within critical-sized calvarial defects in a growing porcine model.

Diclofenac, a NSAID, delays fracture healing in aged mice

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, belong to the most prescribed analgesic medication after traumatic injuries. However, there is accumulating evidence that NSAIDs impair fracture healing. Because bone regeneration in aged patients is subject to significant changes in cell differentiation and proliferation as well as a markedly altered pharmacological action of drugs, we herein analyzed the effects of diclofenac on bone healing in aged mice using a stable closed femoral facture model. Thirty-three mice (male n = 14, female n = 19) received a daily intraperitoneal injection of diclofenac (5 mg/kg body weight). Vehicle-treated mice (n = 29; male n = 13, female n = 16) served as controls. Fractured mice femora were analyzed by means of X-ray, biomechanics, micro computed tomography (μCT), histology and Western blotting. Biomechanical analyses revealed a significantly reduced bending stiffness in diclofenac-treated animals at 5 weeks after fracture when compared to vehicle-treated controls. Moreover, the callus tissue in diclofenac-treated aged animals exhibited a significantly reduced amount of bone tissue and higher amounts of fibrous tissue. Further histological analyses demonstrated less lamellar bone after diclofenac treatment, indicating a delay in callus remodeling. This was associated with a decreased number of osteoclasts and an increased expression of osteoprotegerin (OPG) during the early phase of fracture healing. These findings indicate that diclofenac delays fracture healing in aged mice by affecting osteogenic growth factor expression and bone formation as well as osteoclast activity and callus remodeling.

Effect of Diclofenac and Simvastatin on Bone Defect Healing-An In Vivo Animal Study

Non-steroidal, anti-inflammatory drugs and statins are two widely prescribed drug classes that affect bone formation. The aim of this study was to elucidate the effect of diclofenac and simvastatin in artificial bone defect healing. One hundred and forty-four male Wistar rats were used, and the specimens were divided into groups, with respect to the route of drug administration and the type of defect healing (with or without collagen membrane), and subgroups, with respect to the study duration (2, 4 or 8 weeks). Diclofenac was intramuscularly administered while simvastatin was administered both systemically and locally. Animals were euthanized and specimens were histomorphometrically analyzed to evaluate the percentage of new bone formation (%). Bone healing that occurred without any intervention developed more steadily than that of all other groups. Diclofenac exerted a clear, direct inhibitory effect on bone healing and its systemic administration should be avoided. The systemic administration of simvastatin was related to severe myopathy, while the solvent for the local administration of simvastatin seemed to play significant role in bone growth, as simvastatin, when it is administered intraperitoneally in a DMSO solution, appeared to promote bone healing. Local administration may have a significant impact on bone healing and it should be further investigated with the type of solvent or carrier that is used, which both may play a significant role in bone repair induction.

Engineering of a Long-Acting Bone Morphogenetic Protein-7 by Fusion with Albumin for the Treatment of Renal Injury

The bone morphogenetic protein-7 (BMP7) is capable of inhibiting TGF-β/Smad3 signaling, which subsequently results in protecting the kidney from renal fibrosis, but its lower blood retention and osteogenic activity are bottlenecks for its clinical application. We report herein on the fusion of carbohydrate-deficient human BMP7 and human serum albumin (HSA-BMP7) using albumin fusion technology and site-directed mutagenesis. When using mouse myoblast cells, no osteogenesis was observed in the glycosylated BMP7 derived from Chinese hamster ovary cells in the case of unglycosylated BMP7 derived from Escherichia coli and HSA-BMP7. On the contrary, the specific activity for the Smad1/5/8 phosphorylation of HSA-BMP7 was about 25~50-times lower than that for the glycosylated BMP7, but the phosphorylation activity of the HSA-BMP7 was retained. A pharmacokinetic profile showed that the plasma half-life of HSA-BMP7 was similar to that for HSA and was nearly 10 times longer than that of BMP7. In unilateral ureteral obstruction mice, weekly dosing of HSA-BMP7 significantly attenuated renal fibrosis, but the individual components, i.e., HSA or BMP7, did not. HSA-BMP7 also attenuated a cisplatin-induced acute kidney dysfunction model. The findings reported herein indicate that HSA-BMP7 has the potential for use in clinical applications for the treatment of renal injuries.

Effect of non-steroidal anti-inflammatory drugs on fracture healing in children: A systematic review

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed medications in the United States. Although they are safe and effective means of analgesia for children with broken bones, there is considerable variation in their clinical use due to persistent concerns about their potentially adverse effect on fracture healing.

AIM

To assess whether NSAID exposure is a risk factor for fracture nonunion in children.

METHODS

We systematically reviewed the literature reporting the effect of NSAIDs on bone healing. We included all clinical studies that reported on adverse bone healing complications in children with respect to NSAID exposure. The outcomes of interest were delayed union or nonunion. Study quality was assessed using the Newcastle-Ottawa scale for non-randomized studies. A final table was constructed summarizing the available evidence.

RESULTS

A total of 120 articles were identified and screened, of which 6 articles were included for final review. Nonunion in children is extremely rare; among the studies included, there were 2011 nonunions among 238822 fractures (0.84%). None of the included studies documented an increased risk of nonunion or delayed bone healing in those children who are treated with NSAIDs in the immediate post-injury or peri-operative time period. Additionally, children are likely to take these medications for only a few days after injury or surgery, further decreasing their risk of adverse side-effects.

CONCLUSION

This systematic review suggests that NSAIDS can be safely prescribed to pediatric orthopaedic patients absent other contraindications without concern for increased risk of fracture non-union or delayed bone healing. Additional prospective studies are needed focusing on higher risk fractures and elective orthopaedic procedures such as osteotomies and spinal fusion.

Strategies to Modulate the Redifferentiation of Chondrocytes

Because of the low self-healing capacity of articular cartilage, cartilage injuries and degenerations triggered by various diseases are almost irreversible. Previous studies have suggested that human chondrocytes cultured in vitro tend to dedifferentiate during the cell-amplification phase and lose the physiological properties and functions of the cartilage itself, which is currently a critical limitation in the cultivation of cartilage for tissue engineering. Recently, numerous studies have focused on the modulation of chondrocyte redifferentiation. Researchers discovered the effect of various conditions (extracellular environment, cell sources, growth factors and redifferentiation inducers, and gene silencing and overexpression) on the redifferentiation of chondrocytes during the in vitro expansion of cells, and obtained cartilage tissue cultured in vitro that exhibited physiological characteristics and functions that were similar to those of human cartilage tissue. Encouragingly, several studies reported positive results regarding the modulation of the redifferentiation of chondrocytes in specific conditions. Here, the various factors and conditions that modulate the redifferentiation of chondrocytes, as well as their limitations and potential applications and challenges are reviewed. We expect to inspire research in the field of cartilage repair toward the future treatment of arthropathy.

Non-steroidal anti-inflammatory drugs and bone healing in animal models-a systematic review and meta-analysis

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAID) have excellent anti-inflammatory and analgesic properties and are extensively used to treat post-traumatic or surgical musculoskeletal pain. Although an extensive literature exists on the administration of NSAID on animal bone healing, no systematic review and meta-analysis of animal studies that investigate the effect of NSAID administration on bone fracture healing. Objective of this study is to conduct a systematic review and meta-analysis to estimate the effect of NSAIDs administration on bone healing biomechanical and histomorphometric measurements in different animal models after bone fracture surgery.

METHODS

We performed a systematic review and meta-analysis of animal studies to estimate the effect of NSAID administration after bone fracture on healing outcomes. We searched eight databases without limiting the search to starting date up to 1 February 2021 for articles on fractured bone healing in animal models in which NSAID were administered.

RESULTS

Out of 6732 articles screened, 47 were included and 3 common bone healing outcomes were analysed: biomechanical properties (maximum force to break, stiffness, and work-to-failure), micro-computed tomography (μ-CT), and histomorphometric measurements. The studies were generally of low-quality scores because crucial information, especially concerning randomization, blinding, and allocation concealment, was poorly reported. Our results show that the negative effects of NSAID after bone fracture on certain biomechanical properties of the healing bones was not statistically significant in mice compared with other animals, in females compared with males, and in younger compared with older animals.

CONCLUSION

The findings demonstrated that NSAIDs administration decreased the biomechanical properties of healing bones after fracture surgery in comparison to the control group. Moreover, different effect on certain outcomes was detected among different sites, sex of the animals, and the time of assessment.

TRIAL REGISTRATION

Protocol published and registered in SYstematic Review Center for Laboratory animal Experimentation (SYRCLE) in 2017, https://www.radboudumc.nl/getmedia/757ec408-7a9e-4635-8233-ae951effea54/Non-Steroidal-Anti-inflammatory-Drugs-and-bone-healing-in-animal-Models-Systematic-Review-and-Meta-Analysis.aspx.

Are NSAIDs Safe? Assessing the Risk-Benefit Profile of Nonsteroidal Anti-inflammatory Drug Use in Postoperative Pain Management

In this article, we review controversies in assessing the risk of serious adverse effects caused by administration of nonsteroidal anti-inflammatory drugs (NSAIDs). Our focus is upon NSAIDs used in short courses for the management of acute postoperative pain. In our review of the literature, we found that the risks of short-term NSAID use may be overemphasized. Specifically, that the likelihood of renal dysfunction, bleeding, nonunion of bone, gastric complications, and finally, cardiac dysfunction do not appear to be significantly increased when NSAIDs are used appropriately after surgery. The importance of this finding is that in light of the opioid epidemic, it is crucial to be aware of alternative analgesic options that are safe for postoperative pain control.

Tibolone, alendronate, and simvastatin enhance implant osseointegration in a preclinical in vivo model

OBJECTIVES

The objective of the study was to evaluate and compare the effect of different drugs such as simvastatin, alendronate, and tibolone for titanium implant osseointegration enhancement.

MATERIALS AND METHODS

Eighty female albino Wistar rats were equally divided into five groups: Group I (ovariectomy), Group II (sham ovariectomy), Group III (alendronate + ovariectomy), Group IV (simvastatin + ovariectomy), and Group V (tibolone + ovariectomy). Three months after ovariectomy, we performed bilateral titanium intramedullary nailing in all groups, followed by oral administration of alendronate, simvastatin, or tibolone for 12 weeks. Examinations included micro-CT, mechanical pull-out test, histology, and bone serum markers.

RESULTS

Peri-implant micro-CT analysis showed a significantly higher overall bone tissue in tibolone compared to the ovariectomy group, while no significant difference was found between the treatment groups. Sham ovariectomy, alendronate, and tibolone groups had a higher body mass density compared to ovariectomy and simvastatin groups. All treatment groups had a greater thickness of the peri-implant compact bone layer compared to ovariectomy group, but the results were not statistically significant. Tibolone presented the highest values in pull-out test, but alendronate showed more consistently positive results compared to other groups. Osteocalcin had in the tibolone group almost three times the value in the ovariectomy group, but the results were not statistically significant.

CONCLUSION

The hypothesis that alendronate, simvastatin, and tibolone enhance the osseointegration process of intramedullary titanium implants in ovariectomized rats has been accepted, while tibolone could offer the best results.

Etoricoxib decreases subchondral bone mass and attenuates biomechanical properties at the early stage of osteoarthritis in a mouse model

Etoricoxib, a selective Cyclooxygenase-2 (COX-2) inhibitor, is commonly used in osteoarthritis (OA) for pain relief, however, little is known about the effects on subchondral bone. In the current study, OA was induced via destabilization of the medial meniscus (DMM) in C57BL/6 mice. Two days after surgery, mice were treated with different concentrations of Etoricoxib. Four weeks after treatment, micro computed tomography (Micro-CT) analysis, histological analysis, atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM) were performed to evaluate OA progression. We demonstrated that Etoricoxib inhibited osteophyte formation in the subchondral bone. However, it also reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th), and more microfractures and pores were observed in the subchondral bone. Moreover, Etoricoxib reduced the elastic modulus of subchondral bone. Exposure to Etoricoxib further increased the empty/total osteocyte ratio of the subchondral bone. Etoricoxib did not show significant improvement in articular cartilage destruction and synovial inflammation in early OA. Together, our observations suggested that although Etoricoxib can relieve OA-induced pain and inhibit osteophyte formation in the subchondral bone, it can also change the microstructures and biomechanical properties of subchondral bone, promote subchondral bone loss, and reduce subchondral bone quality in early OA mice.

Bone Tissue Engineering in the Growing Calvaria Using Dipyridamole-Coated, Three-Dimensionally-Printed Bioceramic Scaffolds: Construct Optimization and Effects on Cranial Suture Patency

BACKGROUND

Three-dimensionally-printed bioceramic scaffolds composed of β-tricalcium phosphate delivering the osteogenic agent dipyridamole can heal critically sized calvarial defects in skeletally mature translational models. However, this construct has yet to be applied to growing craniofacial models. In this study, the authors implanted three-dimensionally-printed bioceramic/dipyridamole scaffolds in a growing calvaria animal model and evaluated bone growth as a function of geometric scaffold design and dipyridamole concentration. Potential adverse effects on the growing suture were also evaluated.

METHODS

Bilateral calvarial defects (10 mm) were created in 5-week-old (approximately 1.1 kg) New Zealand White rabbits (n = 16 analyzed). Three-dimensionally-printed bioceramic scaffolds were constructed in quadrant form composed of varying pore dimensions (220, 330, and 500 μm). Each scaffold was coated with collagen and soaked in varying concentrations of dipyridamole (100, 1000, and 10,000 μM). Controls consisted of empty defects. Animals were killed 8 weeks postoperatively. Calvariae were analyzed using micro-computed tomography, three-dimensional reconstruction, and nondecalcified histologic sectioning.

RESULTS

Scaffold-induced bone growth was statistically greater than bone growth in empty defects (p = 0.02). Large scaffold pores, 500 μm, coated in 1000 μM dipyridamole yielded the most bone growth and lowest degree of scaffold presence within the defect. Histology showed vascularized woven and lamellar bone along with initial formation of vascular canals within the scaffold lattice. Micro-computed tomographic and histologic analysis revealed patent calvarial sutures without evidence of ectopic bone formation across all dipyridamole concentrations.

CONCLUSION

The authors present an effective pediatric bone tissue-engineering scaffold design and dipyridamole concentration that is effective in augmentation of calvarial bone generation while preserving cranial suture patency.

Chronotherapy of Non-Steroidal Anti-Inflammatory Drugs May Enhance Postoperative Recovery

Postoperative pain relief is crucial for full recovery. With the ongoing opioid epidemic and the insufficient effect of acetaminophen on severe pain; non-steroidal anti-inflammatory drugs (NSAIDs) are heavily used to alleviate this pain. However, NSAIDs are known to inhibit postoperative healing of connective tissues by inhibiting prostaglandin signaling. Pain intensity, inflammatory mediators associated with wound healing and the pharmacological action of NSAIDs vary throughout the day due to the circadian rhythm regulated by the clock genes. According to this rhythm, most of wound healing mediators and connective tissue formation occurs during the resting phase, while pain, inflammation and tissue resorption occur during the active period of the day. Here we show, in a murine tibia fracture surgical model, that NSAIDs are most effective in managing postoperative pain, healing and recovery when drug administration is limited to the active phase of the circadian rhythm. Limiting NSAID treatment to the active phase of the circadian rhythm resulted in overexpression of circadian clock genes, such as Period 2 (Per2) at the healing callus, and increased serum levels of anti-inflammatory cytokines interleukin-13 (IL-13), interleukin-4 (IL-4) and vascular endothelial growth factor. By contrast, NSAID administration during the resting phase resulted in severe bone healing impairment.

How Does Perioperative Ketorolac Affect Opioid Consumption and Pain Management After Ankle Fracture Surgery?

BACKGROUND

The investigation of nonnarcotic drug regimens for postoperative pain management is important in addressing the opioid epidemic. NSAIDs can be a powerful adjunct in managing postoperative pain, but the possibility of delayed bone healing is a major concern for orthopaedic surgeons. Our recent retrospective study on ketorolac administration demonstrated that the NSAID is not associated with an increased risk of delayed union or nonunion after ankle fracture surgery.

QUESTIONS/PURPOSES

To determine whether postoperative ketorolac (1) reduces opioid consumption, (2) improves VAS pain control, and (3) affects fracture healing after open reduction and internal fixation of ankle fractures.

METHODS

Between August 2016 and December 2017, 128 patients undergoing open reduction and internal fixation of an acute ankle fracture were randomized before surgery via simple randomization to treatment with or without ketorolac. No patients changed treatment regimen groups or opted out of randomization. All other aspects of perioperative care were treated identically. A once-daily survey was distributed via email on postoperative Days 1 to 7. Unblinded participants were asked to report their daily opioid consumption, pain level, and sleep interference using the VAS, and pain frequency using a five-point Likert scale, and side effects with the VAS. For VAS pain, > 20 mm/100 mm on the VAS scale was required to be considered "improved." In all, 83% (106 of 128) patients completed all seven postoperative surveys with 14 in the control group and eight in the ketorolac group lost to follow-up. Fifty-six patients were administered ketorolac with opioid medication (treatment group) and 50 were administered opioids alone (control group). Participants were comprised of 42% men (44), and 58% women (62); mean age was 48 years. The treating surgeon assessed clinical healing based on the patient's ability to ambulate comfortably at 12 weeks postoperatively. Radiographic healing was assessed by two fellowship-trained orthopaedic foot and ankle surgeons blinded to the patient's name and time since surgery. The surgeons evaluated randomized standard ankle series (anteroposterior, mortise, and lateral) radiographs for resolution of each fracture line to determine fracture union, with delayed union being defined as fracture lines present on radiographs taken at 12-week postoperative visits. Intention-to-treat analysis was performed.

RESULTS

Patients in the treatment group consumed a mean of 14 opioid pills, which was less than the mean of 19.3 opioids pills consumed by patients in the control group (p = 0.037). Patients with ketorolac had lower median VAS scores for pain (p < 0.035) postoperatively on postoperative Days 1 and 2 than did control patients. By contrast, patient-reported pain scores and scores for sleep did not convincingly show a benefit to the use of ketorolac. For patients whose ankle fractures healed at 12 weeks, there was no difference between the groups in terms of clinical healing (p = 0.575) and radiographic healing (p = 0.961).

CONCLUSIONS

In this randomized study, adding ketorolac to the postoperative drug regimen decreased the use of opioid medication after open reduction and internal fixation of ankle fractures in the early postoperative period, and there were mixed, small effects on pain reduction. This NSAID is a valuable tool in helping patients manage postoperative pain with less use of narcotic analgesia. However, our study was underpowered to determine the true safety of this drug in terms of fracture healing and side effects and these questions warrant higher-powered randomized study investigation.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Repair of Critical-Sized Long Bone Defects Using Dipyridamole-Augmented 3D-Printed Bioactive Ceramic Scaffolds

There are over two million long bone defects treated in the United States annually, of which ~5% will not heal without significant surgical intervention. While autogenous grafting is the standard of care in simple defects, a customized scaffold for large defects in unlimited quantities is not available. Recently, a three-dimensionally (3D)-printed bioactive ceramic (3DPBC) scaffold has been successfully utilized in the of repair critical-sized (CSD) long bone defects in vivo. In this study, 3DPBC scaffolds were augmented with dipyridamole (DIPY), an adenosine A2A receptor (A_2A R) indirect agonist, because of its known effect to enhance bone formation. CSD full thickness segmental defects (~11 mm × full thickness) defects were created in the radial diaphysis in New Zealand white rabbits (n = 24). A customized 3DPBC scaffold composed of β-tricalcium phosphate was placed into the defect site. Groups included scaffolds that were collagen-coated (COLL), or immersed in 10, 100, or 1,000 μM DIPY solution. Animals were euthanized 8 weeks post-operatively and the radii/ulna-scaffold complex retrieved en bloc, for micro-CT, histological, and mechanical analysis. Bone growth was assessed exclusively within scaffold pores and evaluated by microCT and advanced reconstruction software. Biomechanical properties were evaluated utilizing nanoindentation to assess the newly regenerated bone for elastic modulus (E) and hardness (H). MicroCT reconstructions illustrated bone in-growth throughout the scaffold, with an increase in bone volume dependent on the DIPY dosage. The histological evaluation did not indicate any adverse immune response while revealing progressive remodeling of bone. These customized biologic 3DPBC scaffolds have the potential of repairing and regenerating bone. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2499-2507, 2019.

Regeneration of a Pediatric Alveolar Cleft Model Using Three-Dimensionally Printed Bioceramic Scaffolds and Osteogenic Agents: Comparison of Dipyridamole and rhBMP-2

BACKGROUND

Alveolar clefts are traditionally treated with secondary bone grafting, but this is associated with morbidity and graft resorption. Although recombinant human bone morphogenetic protein-2 (rhBMP-2) is under investigation for alveolar cleft repair, safety concerns remain. Dipyridamole is an adenosine receptor indirect agonist with known osteogenic potential. This study compared dipyridamole to rhBMP-2 at alveolar cleft defects delivered using bioceramic scaffolds.

METHODS

Skeletally immature New Zealand White rabbits underwent unilateral, 3.5 × 3.5-mm alveolar resection adjacent to the growing suture. Five served as negative controls. The remaining defects were reconstructed with three-dimensionally printed bioceramic scaffolds coated with 1000 μm of dipyridamole (n = 6), 10,000 μm of dipyridamole (n = 7), or 0.2 mg/ml of rhBMP-2 (n = 5). At 8 weeks, new bone was quantified. Nondecalcified histologic evaluation was performed, and new bone was evaluated mechanically. Statistical analysis was performed using a generalized linear mixed model and the Wilcoxon rank sum test.

RESULTS

Negative controls did not heal, whereas new bone formation bridged all three-dimensionally printed bioceramic treatment groups. The 1000-μm dipyridamole scaffolds regenerated 28.03 ± 7.38 percent, 10,000-μm dipyridamole scaffolds regenerated 36.18 ± 6.83 percent (1000 μm versus 10,000 μm dipyridamole; p = 0.104), and rhBMP-2-coated scaffolds regenerated 37.17 ± 16.69 percent bone (p = 0.124 versus 1000 μm dipyridamole, and p = 0.938 versus 10,000 μm dipyridamole). On histology/electron microscopy, no changes in suture biology were evident for dipyridamole, whereas rhBMP-2 demonstrated early signs of suture fusion. Healing was highly cellular and vascularized across all groups. No statistical differences in mechanical properties were observed between either dipyridamole or rhBMP-2 compared with native bone.

CONCLUSION

Dipyridamole generates new bone without osteolysis and early suture fusion associated with rhBMP-2 in skeletally immature bone defects.

TGFβ/BMP Signaling Pathway in Cartilage Homeostasis

Cartilage homeostasis is governed by articular chondrocytes via their ability to modulate extracellular matrix production and degradation. In turn, chondrocyte activity is regulated by growth factors such as those of the transforming growth factor β (TGFβ) family. Members of this family include the TGFβs, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs). Signaling by this protein family uniquely activates SMAD-dependent signaling and transcription but also activates SMAD-independent signaling via MAPKs such as ERK and TAK1. This review will address the pivotal role of the TGFβ family in cartilage biology by listing several TGFβ family members and describing their signaling and importance for cartilage maintenance. In addition, it is discussed how (pathological) processes such as aging, mechanical stress, and inflammation contribute to altered TGFβ family signaling, leading to disturbed cartilage metabolism and disease.

Local delivery of adenosine receptor agonists to promote bone regeneration and defect healing

Adenosine receptor activation has been investigated as a potential therapeutic approach to heal bone. Bone has enhanced regenerative potential when influenced by either direct or indirect adenosine receptor agonism. As investigators continue to elucidate how adenosine influences bone cell homeostasis at the cellular and molecular levels, a small but growing body of literature has reported successful in vivo applications of adenosine delivery. This review summarizes the role adenosine receptor ligation plays in osteoblast and osteoclast biology and remodeling/regeneration. It also reports on all the modalities described in the literature at this point for delivery of adenosine through in vivo models for bone healing and regeneration.

Dipyridamole Augments Three-Dimensionally Printed Bioactive Ceramic Scaffolds to Regenerate Craniofacial Bone

BACKGROUND

Autologous bone grafts remain a standard of care for the reconstruction of large bony defects, but limitations persist. The authors explored the bone regenerative capacity of customized, three-dimensionally printed bioactive ceramic scaffolds with dipyridamole, an adenosine A2A receptor indirect agonist known to enhance bone formation.

METHODS

Critical-size bony defects (10-mm height, 10-mm length, full-thickness) were created at the mandibular rami of rabbits (n = 15). Defects were replaced by a custom-to-defect, three-dimensionally printed bioactive ceramic scaffold composed of β-tricalcium phosphate. Scaffolds were uncoated (control), collagen-coated, or immersed in 100 μM dipyridamole. At 8 weeks, animals were euthanized and the rami retrieved. Bone growth was assessed exclusively within scaffold pores, and evaluated by micro-computed tomography/advanced reconstruction software. Micro-computed tomographic quantification was calculated. Nondecalcified histology was performed. A general linear mixed model was performed to compare group means and 95 percent confidence intervals.

RESULTS

Qualitative analysis did not show an inflammatory response. The control and collagen groups (12.3 ± 8.3 percent and 6.9 ± 8.3 percent bone occupancy of free space, respectively) had less bone growth, whereas the most bone growth was in the dipyridamole group (26.9 ± 10.7 percent); the difference was statistically significant (dipyridamole versus control, p < 0.03; dipyridamole versus collagen, p < 0.01 ). There was significantly more residual scaffold material for the collagen group relative to the dipyridamole group (p < 0.015), whereas the control group presented intermediate values (nonsignificant relative to both collagen and dipyridamole). Highly cellular and vascularized intramembranous-like bone healing was observed in all groups.

CONCLUSION

Dipyridamole significantly increased the three-dimensionally printed bioactive ceramic scaffold's ability to regenerate bone in a thin bone defect environment.

A novel hybrid compound LLP2A-alendronate accelerates open fracture healing in a rabbit model

Purpose

LLP2A-alendronate (LLP2A-Ale) is a novel bone-seeking compound that recruits mesenchymal stem cells to the bone surface and stimulates bone formation. The purpose of this study was to investigate the efficacy of LLP2A-Ale in the treatment of rabbit open fracture.

Methods

Thirty New Zealand White rabbits underwent radius mid-diaphyseal osteotomy and were randomly divided into control and treatment groups with fifteen rabbits in each group. The treatment group received only one injection of LLP2A-Ale (dosage 125 μg/kg), whereas the control group received one injection of PBS. X-ray images were taken to observe the course of fracture healing at 2, 4 and 6 weeks after treatment. Rabbits were sacrificed at 4 and 6 weeks post treatment. Calluses were then harvested and were subjected to histology, immunohistochemistry, molecular biology techniques and biomechanical test.

Results

X-ray images showed that the LLP2A-Ale group exhibited abundant callus formation, stronger bony callus remodeling and earlier marrow cavity recanalization compared to the control group in a time-dependent manner. Histomorphological analysis revealed an advance in woven formation at 4 weeks and lamellar bone formation at 6 weeks in the LLP2A-Ale group. Moreover, gene and protein levels suggested that LLP2A-Ale promoted osteogenesis and angiogenesis probably via upregulating the expression of osteogenesis factors (including bone morphogenetic protein 2 and Runt-related transcription factor 2) and angiogenesis factors (vascular endothelial growth factor). Besides, the radius callus biomechanical properties were significantly enhanced in the LLP2A-Ale group compared with the control group at 6 weeks.

Conclusion

LLP2A-Ale can significantly promote open fracture healing in the rabbit model, probably through enhancing osteogenesis and angiogenesis.

Collagen I-based scaffolds negatively impact fracture healing in a mouse-osteotomy-model although used routinely in research and clinical application

Although several biomaterials for bone regeneration have been developed in the last decades, clinical application of bone morphogenetic protein 2 is clinically only approved when applied on an absorbable bovine collagen I scaffold (ACS) (Helistat; ACS-H). In research, another ACS, namely Lyostypt (ACS-L) is frequently used as a scaffold in bone-linked studies. Nevertheless, until today, the influence of ACS alone on bone healing remains unknown. Unexpectedly, in vitro studies using ASC-H revealed a suppression of osteogenic differentiation and a significant reduction of cell vitality when compared to ASC-L. In mice, we observed a significant delay in bone healing when applying ACS-L in the fracture gap during femoral osteotomy. The results of our study show for the first time a negative influence of both ACS-H and ACS-L on bone formation demonstrating a substantial need for more sophisticated delivery systems for local stimulation of bone healing in both clinical application and research. STATEMENT OF SIGNIFICANCE: Our study provides evidence-based justification to promote the development and approval of more suitable and sophisticated delivery systems in bone healing research. Additionally, we stimulate researchers of the field to consider that the application of those scaffolds as a delivery system for new substances represents a delayed healing approach rather than a normal bone healing which could greatly impact the outcome of those studies and play a pivotal role in the translation to the clinics. Moreover, we provide impulses on underlying mechanism involving the roles of small-leucine rich proteoglycans (SLRP) for further detailed investigations.

Disease-modifying effects of COX-2 selective inhibitors and non-selective NSAIDs in osteoarthritis: a systematic review

Osteoarthritis (OA) is a potentially disabling disease whose progression is dependent on several risk factors. OA management usually involves the use of non-steroidal anti-inflammatory drugs (NSAIDs) that are the primary pharmacological treatments of choice. However, NSAIDs have often been associated with unwanted side effects. Cyclooxygenase (COX)-2 specific inhibitors, such as celecoxib, have been successfully used as an alternative in the past for OA treatment and have demonstrated fewer side effects. While abundant data are available for the clinical efficacy of drugs used for OA treatment, little is known about the disease-modifying effects of these agents. A previous review published by Zweers et al. (2010) assessed the available literature between 1990 and 2010 on the disease-modifying effects of celecoxib. In the present review, we aimed to update the existing evidence and identify evolving concepts relating to the disease-modifying effects of not just celecoxib, but also other NSAIDs. We conducted a review of the literature published from 2010 to 2016 dealing with the effects, especially disease-modifying effects, of NSAIDs on cartilage, synovium, and bone in OA patients. Our results show that celecoxib was the most commonly used drug in papers that presented data on disease-modifying effects of NSAIDs. Further, these effects appeared to be mediated through the regulation of prostaglandins, cytokines, and direct changes to tissues. Additional studies should be carried out to assess the disease-modifying properties of NSAIDs in greater detail.

The effect of nonsteroidal anti-inflammatory drugs on bone healing in humans: A qualitative, systematic review

STUDY OBJECTIVE

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in postoperative pain management. While an increasing number of in vitro and animal studies point toward an inhibitory effect of NSAIDs on bone healing process, the few existing retro- and prospective clinical studies present conflicting data.

DESIGN

The aim of this qualitative, systematic review was to investigate the impact of perioperative use of NSAIDs in humans on postoperative fracture/spinal fusion healing compared to other used analgesics measured as fracture nonunion with radiological control.

PATIENTS/INTERVENTIONS

We performed a systematic literature search of the last 38 years using PubMed Embase and the Cochrane Controlled Trials Register including retro- and prospective clinical, human trials assessing the effect of NSAIDs on postoperative fracture/spinal fusion healing when used for perioperative pain management with a radiological follow up to assess eventual nonunion. Due to different study designs, drugs, dosages/exposition times and different methods to assess fracture nonunion, these studies were not pooled for a meta-analysis. A descriptive summary of all studies, level of evidence, study quality and study bias assessment using different scores were used.

MAIN RESULTS

Three prospective randomized controlled studies and thirteen retrospective cohort human studies were identified for a total of 12'895 patients. The overall study quality was low according to Jadad and Oxford Levels of Evidence scores.

CONCLUSIONS

Published results of human trials did not show strong evidence that NDAIDs for pain therapy after fracture osteosynthesis or spinal fusion lead to an increased nonunion rate. Reviewed studies present such conflicting data, that no clinical recommendation can be made regarding the appropriate use of NSAIDs in this context. Considering laboratory data of animal, human tissue research and recommendation of clinical reviews, a short perioperative exposition to NSAIDs is most likely not deleterious. However, randomized, controlled studies are warranted to support or refute this hypothesis.

The role of 3D printing in treating craniomaxillofacial congenital anomalies

Craniomaxillofacial congenital anomalies comprise approximately one third of all congenital birth defects and include deformities such as alveolar clefts, craniosynostosis, and microtia. Current surgical treatments commonly require the use of autogenous graft material which are difficult to shape, limited in supply, associated with donor site morbidity and cannot grow with a maturing skeleton. Our group has demonstrated that 3D printed bio-ceramic scaffolds can generate vascularized bone within large, critical-sized defects (defects too large to heal spontaneously) of the craniomaxillofacial skeleton. Furthermore, these scaffolds are also able to function as a delivery vehicle for a new osteogenic agent with a well-established safety profile. The same 3D printers and imaging software platforms have been leveraged by our team to create sterilizable patient-specific intraoperative models for craniofacial reconstruction. For microtia repair, the current standard of care surgical guide is a two-dimensional drawing taken from the contralateral ear. Our laboratory has used 3D printers and open source software platforms to design personalized microtia surgical models. In this review, we report on the advancements in tissue engineering principles, digital imaging software platforms and 3D printing that have culminated in the application of this technology to repair large bone defects in skeletally immature transitional models and provide in-house manufactured, sterilizable patient-specific models for craniofacial reconstruction.

Dipyridamole enhances osteogenesis of three-dimensionally printed bioactive ceramic scaffolds in calvarial defects

PURPOSE

The objective of this study was to test the osteogenic capacity of dipyridamole-loaded, three-dimensionally printed, bioactive ceramic (3DPBC) scaffolds using a translational, skeletally mature, large-animal calvarial defect model.

MATERIALS AND METHODS

Custom 3DPBC scaffolds designed to present lattice-based porosity only towards the dural surface were either coated with collagen (control) or coated with collagen and immersed in a 100 μM concentration dipyridamole (DIPY) solution. Sheep (n = 5) were subjected to 2 ipsilateral trephine-induced (11-mm diameter) calvarial defects. Either a control or a DIPY scaffold was placed in each defect, and the surgery was repeated on the contralateral side 3 weeks later. Following sacrifice, defects were evaluated through microcomputed tomography and histologic analysis for bone, scaffold, and soft tissue quantification throughout the defect. Parametric and non-parametric methods were used to determine statistical significance based on data distribution.

RESULTS

No exuberant or ectopic bone formation was observed, and no histologic evidence of inflammation was noted within the defects. Osteogenesis was higher in DIPY-coated scaffolds compared to controls at 3 weeks (p = 0.013) and 6 weeks (p = 0.046) in vivo. When bone formation was evaluated as a function of defect radius, average bone formation was higher for DIPY relative to control scaffolds at both time points (significant at defect central regions at 3 weeks and at margins at 6 weeks, p = 0.046 and p = 0.031, respectively).

CONCLUSION

Dipyridamole significantly improves the calvarial bone regeneration capacity of 3DPBC scaffolds. The most significant difference in bone regeneration was observed centrally within the interface between the 3DPBC scaffold and the dura mater.

Acceleration of Fracture Healing by Overexpression of Basic Fibroblast Growth Factor in the Mesenchymal Stromal Cells

In this study, we engineered mesenchymal stem cells (MSCs) to over‐express basic fibroblast growth factor (bFGF) and evaluated its effects on fracture healing. Adipose‐derived mouse MSCs were transduced to express bFGF and green fluorescence protein (ADSC^bFGF‐GFP). Closed‐femoral fractures were performed with osterix‐mCherry reporter mice of both sexes. The mice received 3 × 10⁵ ADSCs transfected with control vector or bFGF via intramuscular injection within or around the fracture sites. Mice were euthanized at days 7, 14, and 35 to monitor MSC engraftment, osteogenic differentiation, callus formation, and bone strength. Compared to ADSC culture alone, ADSC^bFGF increased bFGF expression and higher levels of bFGF and vascular endothelial growth factor (VEGF) in the culture supernatant for up to 14 days. ADSC^bFGF treatment increased GFP‐labeled MSCs at the fracture gaps and these cells were incorporated into the newly formed callus. quantitative reverse transcription polymerase chain reaction (qRT‐PCR) from the callus revealed a 2‐ to 12‐fold increase in the expression of genes associated with nervous system regeneration, angiogenesis, and matrix formation. Compared to the control, ADSC^bFGF treatment increased VEGF expression at the periosteal region of the callus, remodeling of collagen into mineralized callus and bone strength. In summary, MSC^bFGF accelerated fracture healing by increasing the production of growth factors that stimulated angiogenesis and differentiation of MSCs to osteoblasts that formed new bone and accelerated fracture repair. This novel treatment may reduce the time required for fracture healing. Stem Cells Translational Medicine2017;6:1880–1893

Heterotopic Ossification Following Upper Extremity Injury

Heterotopic ossification (HO) presents a substantial barrier to rehabilitation for patients with severe burns or trauma. Although surgical excision is a mainstay of management for this condition, this is unable to address the chronic sequelae of HO, including chronic pain, joint contractures, nerve dysfunction, and open wounds. Current therapeutic modalities are aimed at excision and the prevention of recurrence using nonsteroidal antiinflammatory drugs (NSAIDs) or radiation therapy. Research is now focused on identifying alternative strategies to prevent the initial occurrence of HO through NSAIDs and novel inhibitors of the bone morphogenetic protein signaling pathway.

Biodegradable poly (lactic acid-co-glycolic acid) scaffolds as carriers for genetically-modified fibroblasts

Recent advances in gene delivery into cells allow improved therapeutic effects in gene therapy trials. To increase the bioavailability of applied cells, it is of great interest that transfected cells remain at the application site and systemic spread is minimized. In this study, we tested clinically used biodegradable poly(lactic acid-co-glycolic acid) (PLGA) scaffolds (Vicryl & Ethisorb) as transient carriers for genetically modified cells. To this aim, we used human fibroblasts and examined attachment and proliferation of untransfected cells on the scaffolds in vitro, as well as the mechanical properties of the scaffolds at four time points (1, 3, 6 and 9 days) of cultivation. Furthermore, the adherence of cells transfected with green fluorescent protein (GFP) and vascular endothelial growth factor (VEGF165) and also VEGF165 protein secretion were investigated. Our results show that human fibroblasts adhere on both types of PLGA scaffolds. However, proliferation and transgene expression capacity were higher on Ethisorb scaffolds most probably due to a different architecture of the scaffold. Additionally, cultivation of the cells on the scaffolds did not alter their biomechanical properties. The results of this investigation could be potentially exploited in therapeutic regiments with areal delivery of transiently transfected cells and may open the way for a variety of applications of cell-based gene therapy, tissue engineering and regenerative medicine.

Bone morphogenetic protein-2 for the treatment of congenital pseudarthrosis of the tibia or persistent tibial nonunion in children and adolescents: A retrospective study with a minimum 2-year follow-up

There is a lack of studies reporting on rhBMP-2 application in pediatric orthopaedics, although few reports demonstrated promising results of the use of rhBMP-2 in children, especially for spine fusion and for the treatment of congenital pseudarthrosis of the tibia. The objectives of this study were (1) to examine clinical and radiographic healing after rhBMP-2 application for the treatment of congenital pseudarthrosis of the tibia (CPT) or persistent tibial nonunion in children and adolescents, and (2) to investigate the safety of rhBMP-2 use in these cases. Therefore we reviewed the medical records of ten patients with a mean age of 8.6 years (2.3-21) with CPT (n = 7) or persistent tibial nonunion for at least six months (n = 3) who had been treated with rhBMP-2. Nine of ten patients had union at final follow-up, after a mean of 72.9 months (25-127). In the CPT group, primary healing of the pseudarthrosis occurred in six of seven patients at a mean of 5.2 months (3-12). Repeat rhBMP-2 application was performed in three patients; two patients had one additional application each, and one patient had three additional applications. Complications that may be attributed to the use of rhBMP-2 were seen in two of fifteen applications, including a compartmemt syndrome and a hematoma. In this retrospective case series rhBMP-2 has been used successfully to treat CPT or persistent tibial nonunion in pediatric patients. However, prospective randomized controlled trials are warranted to investigate the long-term efficacy and safety of rhBMP-2 use in these cases.

Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) for the Treatment of Nonunion of the Femur in Children and Adolescents: A Retrospective Analysis

Background. The aim of this study was to examine clinical and radiographic healing after rhBMP-2 application in children and adolescents presenting with nonunion of the femur and to investigate the safety of rhBMP-2 use in these cases. Materials and Methods. We reviewed the medical records of five patients with a mean age of 11 years (5.4 to 16.2) with nonunion of the femur who were treated with rhBMP-2 and internal fixation using a locking plate at a single institution. Particular attention was paid to identify all adverse events that may be due to rhBMP-2 use. Results. Union occurred in four of five patients at a mean of 12.1 months (7.9 to 18.9). The locking plates were removed after a mean of 16 months (11 to 23). One patient had nonunion due to deep infection. After a mean follow-up of 62.5 months (17 to 100), union was still evident in all four patients and they were fully weight-bearing without pain. Discussion. In this retrospective study, rhBMP-2 combined with a locking plate has been used successfully to treat children and adolescents with nonunion of the femur in four of five cases. One major complication was thought to be possibly related to its use.

Ticagrelor regulates osteoblast and osteoclast function and promotes bone formation in vivo via an adenosine-dependent mechanism

As many as 10% of bone fractures heal poorly, and large bone defects resulting from trauma, tumor, or infection may not heal without surgical intervention. Activation of adenosine A2A receptors (A2ARs) stimulates bone formation. Ticagrelor and dipyridamole inhibit platelet function by inhibiting P2Y12 receptors and platelet phosphodiesterase, respectively, but share the capacity to inhibit cellular uptake of adenosine and thereby increase extracellular adenosine levels. Because dipyridamole promotes bone regeneration by an A2AR-mediated mechanism we determined whether ticagrelor could regulate the cells involved in bone homeostasis and regeneration in a murine model and whether inhibition of P2Y12 or indirect A2AR activation via adenosine was involved. Ticagrelor, dipyridamole and the active metabolite of clopidogrel (CAM), an alternative P2Y12 antagonist, inhibited osteoclast differentiation and promoted osteoblast differentiation in vitro. A2AR blockade abrogated the effects of ticagrelor and dipyridamole on osteoclast and osteoblast differentiation whereas A2BR blockade abrogated the effects of CAM. Ticagrelor and CAM, when applied to a 3-dimentional printed resorbable calcium-triphosphate/hydroxyapatite scaffold implanted in a calvarial bone defect, promoted significantly more bone regeneration than the scaffold alone and as much bone regeneration as BMP-2, a growth factor currently used to promote bone regeneration. These results suggest novel approaches to targeting adenosine receptors in the promotion of bone regeneration.-Mediero, A., Wilder, T., Reddy, V. S. R., Cheng, Q., Tovar, N., Coelho, P. G., Witek, L., Whatling, C., Cronstein, B. N. Ticagrelor regulates osteoblast and osteoclast function and promotes bone formation in vivo via an adenosine-dependent mechanism.

Improved Mobilization of Exogenous Mesenchymal Stem Cells to Bone for Fracture Healing and Sex Difference

Mesenchymal stem cell (MSC) transplantation has been tested in animal and clinical fracture studies. We have developed a bone-seeking compound, LLP2A-Alendronate (LLP2A-Ale) that augments MSC homing to bone. The purpose of this study was to determine whether treatment with LLP2A-Ale or a combination of LLP2A-Ale and MSCs would accelerate bone healing in a mouse closed fracture model and if the effects are sex dependent. A right mid-femur fracture was induced in two-month-old osterix-mCherry (Osx-mCherry) male and female reporter mice. The mice were subsequently treated with placebo, LLP2A-Ale (500 μg/kg, IV), MSCs derived from wild-type female Osx-mCherry adipose tissue (ADSC, 3 x 10⁵ , IV) or ADSC + LLP2A-Ale. In phosphate buffered saline-treated mice, females had higher systemic and surface-based bone formation than males. However, male mice formed a larger callus and had higher volumetric bone mineral density and bone strength than females. LLP2A-Ale treatment increased exogenous MSC homing to the fracture gaps, enhanced incorporation of these cells into callus formation, and stimulated endochondral bone formation. Additionally, higher engraftment of exogenous MSCs in fracture gaps seemed to contribute to overall fracture healing and improved bone strength. These effects were sex-independent. There was a sex-difference in the rate of fracture healing. ADSC and LLP2A-Ale combination treatment was superior to on callus formation, which was independent of sex. Increased mobilization of exogenous MSCs to fracture sites accelerated endochondral bone formation and enhanced bone tissue regeneration. Stem Cells 2016;34:2587-2600.

Analgesia via blockade of NGF/TrkA signaling does not influence fracture healing in mice

Abatement of fracture-related pain is important in patient welfare. However, the frequently used non-steroidal anti-inflammatory drugs are considered to impair fracture healing through blockade of cyclooxygenase-2. An alternative for fracture-related pain treatment may be blockade of nerve growth factor (NGF)/neurotrophic tyrosine kinase receptor type 1 (TrkA) signaling. Because the effect of blocking this signal-pathway on bone healing has not been extensively investigated, we addressed this issue by applying neutralizing antibodies that target NGF and TrkA, respectively, in a mouse fracture model. Mice with a knock-in for human TrkA underwent femur osteotomy and were randomly allocated to phosphate-buffered-saline, anti-NGF-antibody, or anti-TrkA-antibody treatment. The analgesic effect of the antibodies was determined from the activity and the ground reaction force of the operated limb. The effect of antibody administration on fracture healing was assessed by histomorphometry, micro-computed tomography, and biomechanics. NGF/TrkA-signaling blockade had no negative effect on fracture healing as callus formation and maturation were not altered. Mice treated with anti-TrkA antibody displayed significantly greater activity on post-operative day 2 compared to PBS treatment indicating effective analgesia. Our data indicate, that blockade of NGF/TrkA signaling via specific neutralizing antibodies for pain reduction during fracture healing does not influence fracture healing.

Direct or indirect stimulation of adenosine A2A receptors enhances bone regeneration as well as bone morphogenetic protein-2

Promoting bone regeneration and repair of bone defects is a need that has not been well met to date. We have previously found that adenosine, acting via A2A receptors (A2AR) promotes wound healing and inhibits inflammatory osteolysis and hypothesized that A2AR might be a novel target to promote bone regeneration. Therefore, we determined whether direct A2AR stimulation or increasing endogenous adenosine concentrations via purine transport blockade with dipyridamole regulates bone formation. We determined whether coverage of a 3 mm trephine defect in a mouse skull with a collagen scaffold soaked in saline, bone morphogenetic protein-2 (BMP-2; 200 ng), 1 μM CGS21680 (A2AR agonist, EC50 = 160 nM), or 1 μM dipyridamole (EC50 = 32 nM) promoted bone regeneration. Microcomputed tomography examination demonstrated that CGS21680 and dipyridamole markedly enhanced bone regeneration as well as BMP-2 8 wk after surgery (60 ± 2%, 79 ± 2%, and 75 ± 1% bone regeneration, respectively, vs. 32 ± 2% in control, P < 0.001). Blockade by a selective A2AR antagonist (ZM241385, 1 μM) or deletion of A2AR abrogated the effect of CGS21680 and dipyridamole on bone regeneration. Both CGS21680 and dipyridamole treatment increased alkaline phosphatase-positive osteoblasts and diminished tartrate resistance acid phosphatase-positive osteoclasts in the defects. In vivo imaging with a fluorescent dye for new bone formation revealed a strong fluorescent signal in treated animals that was equivalent to BMP-2. In conclusion, stimulation of A2AR by specific agonists or by increasing endogenous adenosine levels stimulates new bone formation as well as BMP-2 and represents a novel approach to stimulating bone regeneration.

Single Nucleotide Polymorphisms in Osteogenic Genes in Atrophic Delayed Fracture-Healing: A Preliminary Investigation

UpdateThis article was updated on September 10, 2014, because of a previous error. On page 1242, in the byline, and on page 1247, in the author addresses, the academic degree for Henry J. Donahue had previously read "MD." The degree now reads "PhD."

BACKGROUND

We propose that fracture-healing potential is affected by the patient's genome. This genotype is then phenotypically expressed by the patient at the time of injury. We examined the hypothesis that patients who exhibit delayed or impaired fracture-healing may have one or more single nucleotide polymorphisms (SNPs) within a series of genes related to bone formation.

METHODS

We performed a population-based, case-controlled study of delayed fracture-healing. Sixty-two adults with a long-bone fracture were identified from a surgical database. Thirty-three patients had an atrophic nonunion (delayed healing), and twenty-nine displayed normal fracture-healing. These patients underwent buccal mucosal cell harvesting. SNP genotyping was performed with use of bead array technology. One hundred and forty-four SNPs (selected from HapMap) within thirty genes associated with fracture-healing were investigated. Three SNPs did not segregate in the population and were excluded from the analysis. Eight of the remaining SNPs failed the test for Hardy-Weinberg equilibrium (p value smaller than the Bonferroni-corrected level of 0.05/141 = 0.000355) and were excluded.

RESULTS

Five SNPs on four genes were found to have a p value of <0.05 in the additive genetic model. Of these five significant SNPs, three had an odds ratio (OR) of >1, indicating that the presence of the allele increased the risk of nonunion. The rs2853550 SNP, which had the largest effect (OR = 5.9, p = 0.034), was on the IL1B gene, which codes for interleukin 1 beta. The rs2297514 SNP (OR = 3.98, p = 0.015) and the rs2248814 SNP (OR = 2.27, p = 0.038) were on the NOS2 gene coding for nitric oxide synthase. The remaining two SNPs had an OR of <1, indicating that the presence of the allele may be protective against nonunion. The rs3819089 SNP (OR = 0.26, p = 0.026) was on the MMP13 gene for matrix metallopeptidase 13, and the rs270393 SNP (OR = 0.30, p = 0.015) was on the BMP6 gene for bone morphogenetic protein 6.

CONCLUSIONS

Variations in the IL1B and NOS2 genes may contribute to delayed fracture-healing and warrant further investigation.

CLINICAL RELEVANCE

Impaired fracture union may have genetic contributions.

Nonsteroidal anti-inflammatory drugs' impact on nonunion and infection rates in long-bone fractures

BACKGROUND

There is a dearth of clinical data regarding the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on long-bone fracture (LBF) healing in the acute trauma setting. The orthopedic community believes that the use of NSAIDs in the postoperative period will result in poor healing and increased infectious complications. We hypothesized that, first, NSAID use would not increase nonunion/malunion and infection rates after LBF. Second, we hypothesized that tobacco use would cause higher rates of these complications.

METHODS

A retrospective study of all patients with femur, tibia, and/or humerus fractures between October 2009 and September 2011 at a Level 1 academic trauma center was performed . In addition to nonunion/malunion and infection rates, patient records were reviewed for demographic data, mechanism of fracture, type of fracture, tobacco use, Injury Severity Score (ISS), comorbidities, and medications given.

RESULTS

During the 24-month period, 1,901 patients experienced LBF; 231 (12.1%) received NSAIDs; and 351 (18.4%) were smokers. The overall complication rate including nonunion/malunion and infection was 3.2% (60 patients). Logistic regression analysis with adjusted odds ratios were calculated on the risk of complications given NSAID use and/or smoking, and we found that a patient is significantly more likely to have a complication if he or she received an NSAID (odds ratio, 2.17; 95% confidence interval, 1.15-4.10; p < 0.016) in the inpatient postoperative setting. Likewise, smokers are significantly more likely to have complications (odds ratio, 3.19; 95% confidence interval, 1.84-5.53; p < 0.001).

CONCLUSION

LBF patients who received NSAIDs in the postoperative period were twice as likely and smokers more than three times likely to suffer complications such as nonunion/malunion or infection. We recommend avoiding NSAID in traumatic LBF.

LEVEL OF EVIDENCE

Epidemiologic & therapeutic study; level II.

NSAIDs and fracture healing

PURPOSE OF REVIEW

Published data raise concerns about the use of nonselective NSAIDs and selective cyclo-oxygenase (COX)-2 inhibitors as anti-inflammatory or analgesic drugs in patients after a recent fracture or who are undergoing (uncemented) arthroplasty or osteotomy. However, clinical reports on the effect of COX-2 inhibition on fracture healing in humans have been variable and inconclusive. This review gives an overview of the published data and an advice when to avoid NSAIDs.

RECENT FINDINGS

Prostaglandins play an important role as mediators of inflammation and COX are required for their production. Inflammation is an essential step in the fracture healing process in which prostaglandin production by COX-2 is involved. Data from animal studies suggest that NSAIDs, which inhibit COX-2, can impair fracture healing due to the inhibition of the endochondral ossification pathway. Animal data suggest that the effects of COX-2 inhibitors are dependent on the timing, duration, and dose, and that these effects are reversible.

SUMMARY

These animal data, together with the view of limited scientifically robust clinical evidence in humans, indicate that physicians consider only short-term administration of COX-2 inhibitors or other drugs in the pain management of patients who are in the phase of fracture or other bone defect healing. COX-2-inhibitors should be considered a potential risk factor for fracture healing, and therefore to be avoided in patients at risk for delayed fracture healing.

The SERM raloxifene improves diaphyseal fracture healing in mice

Although several studies reported that raloxifene treatment improves postmenopausal osteoporotic bone structure and reduces fracture risk, only a few animal and no human studies have examined its effects on the fracture healing process. Thus the aim of the present study was to determine, whether systemic application of the selective estrogen receptor modulator raloxifene promotes fracture healing compared to untreated control-, estrogen-deficient-, as well as estrogen-treated mice using a standardized femoral osteotomy model (n = 60 mice). Ten days after surgery, contact radiography and undecalcified histomorphometric analysis revealed that raloxifene administration significantly improved the early stage of fracture healing compared to all other groups. At day 20, raloxifene and estrogen treatment led to a significant increase in callus mineralization and trabecular thickness compared to control mice. μCT analyses revealed no evidence of complete bony bridging of the fracture site in any control-, nor estrogen-deficient mouse after 20 days, while all femoral fractures in the raloxifene and estrogen group already healed adequately at this time. These data indicate that raloxifene treatment significantly improves all phases of fracture healing at least in mice. Therefore, raloxifene could be a possible pharmaceutical to enhance fracture healing in women, without the known side effects of estrogen.

Ketorolac administration does not delay early fracture healing in a juvenile rat model: a pilot study

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective at controlling pain in children, especially in the treatment of fractures. Adult animal and adult clinical studies demonstrate conflicting evidence for the inhibitory relationship between NSAIDs and fracture healing. Published pediatric orthopaedic clinical studies do not demonstrate an inhibitory effect of ketorolac on bone healing. Little is known about the effects of any NSAID on bone formation in juvenile animals. This study investigates the effects of the NSAID ketorolac on fracture healing in a juvenile rat model.

METHODS

Unilateral surgically induced and stabilized tibial shaft fractures were created in 45 juvenile (3 to 4 wk old) male Sprague-Dawley rats. Either ketorolac (5 mg/kg; n=24) or saline (0.9% normal saline; n=21) was then administered to the rats 6 d/wk by intraperitoneal injections. Animals were then randomly assigned into time groups and euthanized at 7 days (n=8 ketorolac, n=7 saline), 14 days (n=8 ketorolac, n=7 saline), or 21 days (n=8 ketorolac, n=7 saline) postfracture. Biomechanical analysis was performed using a custom-designed 4-point bending loading apparatus. Statistics for tibial stiffness and strength data were performed using software package Systat 11. Specimens were also evaluated histologically using hematoxylin and eosin staining.

RESULTS

Strength and stiffness of all fractured tibiae increased over time from day 7 to day 21 regardless of treatment type. No statistical difference was found between the fractured tibiae strength or stiffness in the ketorolac or control-treated specimens at the same time point. In addition, the quality of the fracture callus was similar in both groups at each of the time points.

CONCLUSIONS

In this study of a juvenile rat model with a stabilized tibia fracture, fracture callus strength, stiffness, and histologic characteristics were not affected by the administration of ketorolac during the first 21 days of fracture healing.

CLINICAL RELEVANCE

The absence of inhibitory effects of ketorolac on early juvenile rat fracture healing supports the clinical practice of utilizing NSAIDs for analgesia in children with long bone fractures.

The effect of nonsteroidal anti-inflammatory drugs on tissue healing

PURPOSE

Non-selective (NSAIDs) and selective (COX-2) nonsteroidal anti-inflammatory drugs are commonly used for their analgesic and anti-inflammatory effects. Their role after orthopaedic surgery has been infrequently described and remains controversial because of unclear effects on soft tissue and bone healing. This study critically reviews the available literature to describe the effects of NSAIDs and COX-2 inhibitors on soft tissue and bone healing.

METHODS

A Medline search was performed using NSAIDs or COX-2 inhibitors and tissue healing. The combined search yielded 637 articles. Following exclusion, 44 articles were deemed relevant with 9 articles on soft tissue healing and 35 articles on bone healing. The available evidence is based primarily on animal data (39 studies), with considerable variation in study methods.

RESULTS

In regard to soft tissue healing, there is insufficient evidence of a detrimental effect when using either NSAIDs or COX-2 inhibitors at standard doses for ≤2 weeks. For soft tissue to bone healing, a limited number of studies demonstrate impairment in healing. However, with respect to bone healing, indomethacin appears to have a clear detrimental effect, with less substantial evidence for other NSAIDs.

CONCLUSIONS

Short-term, low-dose use of NSAIDs and COX-2 inhibitors does not appear to have a detrimental effect following soft tissue injury, but is inhibitory in cases involving bony healing. However, additional well-controlled human studies are necessary to draw more definitive conclusions regarding their role. Clinically, the prudent use of anti-inflammatory medications following sports medicine injuries and surgeries appears to be a reasonable option in clinical practice unless bone healing is required.

LEVEL OF EVIDENCE

III.

Small animal bone healing models: standards, tips, and pitfalls results of a consensus meeting

Small animal fracture models have gained increasing interest in fracture healing studies. To achieve standardized and defined study conditions, various variables must be carefully controlled when designing fracture healing experiments in mice or rats. The strain, age and sex of the animals may influence the process of fracture healing. Furthermore, the choice of the fracture fixation technique depends on the questions addressed, whereby intra- and extramedullary implants as well as open and closed surgical approaches may be considered. During the last few years, a variety of different, highly sophisticated implants for fracture fixation in small animals have been developed. Rigid fixation with locking plates or external fixators results in predominantly intramembranous healing in both mice and rats. Locking plates, external fixators, intramedullary screws, the locking nail and the pin-clip device allow different degrees of stability resulting in various amounts of endochondral and intramembranous healing. The use of common pins that do not provide rotational and axial stability during fracture stabilization should be discouraged in the future. Analyses should include at least biomechanical and histological evaluations, even if the focus of the study is directed towards the elucidation of molecular mechanisms of fracture healing using the largely available spectrum of antibodies and gene-targeted animals to study molecular mechanisms of fracture healing. This review discusses distinct requirements for the experimental setups as well as the advantages and pitfalls of the different fixation techniques in rats and mice.

Combined treatment of congenital pseudarthrosis of the tibia, including recombinant human bone morphogenetic protein-2: a case series

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) for the treatment of congenital pseudarthrosis of the tibia has been investigated in only one previous study, with promising results. The aim of this study was to determine whether rhBMP-2 might improve the outcome of this disorder. We reviewed the medical records of five patients with a mean age of 7.4 years (2.3 to 21) with congenital pseudarthrosis of the tibia who had been treated with rhBMP-2 and intramedullary rodding. Ilizarov external fixation was also used in four of these patients. Radiological union of the pseudarthrosis was evident in all of them at a mean of 3.5 months (3.2 to 4) post-operatively. The Ilizarov device was removed after a mean of 4.2 months (3.0 to 5.3). These results indicate that treatment of congenital pseudarthrosis of the tibia using rhBMP-2 in combination with intramedullary stabilisation and Ilizarov external fixation may improve the initial rate of union and reduce the time to union. Further studies with more patients and longer follow-up are necessary to determine whether this surgial procedure may significantly enhance the outcome of congenital pseudarthrosis of the tibia, considering the refracture rate (two of five patients) in this small case series.

Noncanonical BMP signaling regulates cyclooxygenase-2 transcription

Activation of p38 MAPK has been shown to be relevant for a number of bone morphogenetic protein (BMP) physiological effects. We report here the involvement of noncanonical phosphorylated mothers against decapentaplegic (Smad) signaling in the transcriptional induction of Cox2 (Ptgs2) by BMP-2 in mesenchymal cells and organotypic calvarial cultures. We demonstrate that different regulatory elements are required for regulation of Cox2 expression by BMP-2: Runt-related transcription factor-2 and cAMP response element sites are essential, whereas a GC-rich Smad binding element is important for full responsiveness. Efficient transcriptional activation requires cooperation between transcription factors because mutation of any element results in a strong decrease of BMP-2 responsiveness. BMP-2 activation of p38 leads to increased recruitment of activating transcription factor-2, Runx2, Smad, and coactivators such as p300 at the responsive sites in the Cox2 proximal promoter. We demonstrate, by either pharmacological or genetic analysis, that maximal BMP-2 effects on Cox2 and JunB expression require the function of p38 and its downstream effector mitogen/stress-activated kinase 1. Altogether our results strongly suggest that cooperative effects between canonical and noncanonical BMP signaling allow the fine-tuning of BMP transcriptional responses on specific target genes.