Proteasome inhibition-enhanced fracture repair is associated with increased mesenchymal progenitor cells in mice

The ubiquitin/proteasome system controls the stability of Runx2 and JunB, proteins essential for differentiation of mesenchymal progenitor/stem cells (MPCs) to osteoblasts. Local administration of proteasome inhibitor enhances bone fracture healing by accelerating endochondral ossification. However, if a short-term administration of proteasome inhibitor enhances fracture repair and potential mechanisms involved have yet to be exploited. We hypothesize that injury activates the ubiquitin/proteasome system in callus, leading to elevated protein ubiquitination and degradation, decreased MPCs, and impaired fracture healing, which can be prevented by a short-term of proteasome inhibition. We used a tibial fracture model in Nestin-GFP reporter mice, in which a subgroup of MPCs are labeled by Nestin-GFP, to test our hypothesis. We found increased expression of ubiquitin E3 ligases and ubiquitinated proteins in callus tissues at the early phase of fracture repair. Proteasome inhibitor Bortezomib, given soon after fracture, enhanced fracture repair, which is accompanied by increased callus Nestin-GFP+ cells and their proliferation, and the expression of osteoblast-associated genes and Runx2 and JunB proteins. Thus, early treatment of fractures with Bortezomib could enhance the fracture repair by increasing the number and proliferation of MPCs.

Functional Macromolecular Adhesives for Bone Fracture Healing

Compared with traditional internal fixation devices, bone adhesives are expected to exhibit remarkable advantages, such as improved fixation of comminuted fractures and maintained spatial location of fractured scattered bone pieces in treating bone injuries. In this review, different bone adhesives are summarized from the aspects of bone tissue engineering, and the applications of bone adhesives are emphasized. The concepts of "liquid scaffold" and "liquid plate" are proposed to summarize two different research directions of bone adhesives. Furthermore, significant advances of bone adhesives in recent years in mechanical strength, osseointegration, osteoconductivity, and osteoinductivity are discussed. We conclude this topic by providing perspectives on the state-of-the-art research progress and future development trends of bone adhesives. We hope this review will provide a comprehensive summary of bone adhesives and inspire more extensive and in-depth research on this subject.

Dual-Targeted Nanoplatform Regulating the Bone Immune Microenvironment Enhances Fracture Healing

The immune system and skeletal system are closely linked. Macrophages are one of the most important immune cells for bone remodeling, playing a prohealing role mainly through M2 phenotype polarization. Baicalein (5,6,7-trihydroxyflavone, BCL) has been well documented to have a noticeable promotion effect on M2 macrophage polarization. However, due to the limitations in targeted delivery to macrophages and the toxic effect on other organs, BCL has rarely been used in the treatment of bone fractures. In this study, we developed mesoporous silica and Fe₃O₄ composite-targeted nanoparticles loaded with BCL (BCL@MMSNPs-SS-CD-NW), which could be magnetically delivered to the fracture site. This induced macrophage recruitment in a targeted manner, polarizing them toward the M2 phenotype, which was demonstrated to induce mesenchymal stem cells (MSCs) toward osteoblastic differentiation. The mesoporous silicon nanoparticles (MSNs) were prepared with surface sulfhydrylation and amination modification, and the mesoporous channels were blocked with β-cyclodextrin. The outer layer of the mesoporous silicon was added with an amantane-modified NW-targeting peptide to obtain the targeted nanosystem. After entering macrophages, BCL could be released from nanoparticles since the disulfide linker could be cleaved by intracellular glutathione (GSH), resulting in the removal of cyclodextrin (CD) gatekeeper, which is a key element in the pro-bone-remodeling functions such as anti-inflammation and induction of M2 macrophage polarization to facilitate osteogenic differentiation. This nanosystem passively accumulated in the fracture site, promoting osteogenic differentiation activities, highlighting a potent therapeutic benefit with high biosafety.

Effects of icariin on the fracture healing in young and old rats and its mechanism

CONTEXT

Icariin has attracted increasing attention because of its wide variety of pharmacological effects.

OBJECTIVE

This study investigates whether icariin could promote fracture healing in young and old rats and its mechanisms.

MATERIALS AND METHODS

A Wistar rat model for the tibia fracture in relatively young and old rats, respectively, was established. The rats were divided into four groups: model group, L-icariin (50 mg/kg icariin), M-icariin (100 mg/kg icariin) and H-icariin (200 mg/kg icariin), and intragastric administration of icariin was performed for 10 days or 20 days. In addition, isolated and cultured rat bone mesenchymal stem cells (rBMSCs) from young and old rats were cultured with 5% and 20% of icariin-containing serum, respectively, then cell viability and alkaline phosphatase (ALP) activity were measured.

RESULTS

Icariin administration induced the expression of Runx2, Osterix, BMP-2, p-Smad5 and osteocalcin secretion (young rats: model: 2.50 ± 0.71; L-icariin: 10.10 ± 1.55; M-icariin: 24.95 ± 2.19; H-icariin: 36.80 ± 2.26; old rats: model: 1.55 ± 0.49; L-icariin:6.55 ± 0.50; M-icariin: 15.00 ± 0.85; H-icariin:20.50 ± 2.27) at the fracture site, and increased the levels of bone formation markers (OC, BAP, NTX-1 and CTX-1) in a dose-dependent manner. In vitro, icariin treatment promoted rBMSC viability, increased ALP activity and the expression of BMP-2/Smad5/Runx2 pathway proteins.

DISCUSSION AND CONCLUSIONS

Icariin may accelerate fracture healing by activating the BMP-2/Smad5/Runx2 pathway in relatively young and old rats. The research on the mechanism of icariin to promote fracture healing can provide a theoretical basis for the clinical application and promotion of icariin.

Peptide 11R‑VIVIT promotes fracture healing in osteoporotic rats

Osteoporotic fracture healing is a complex clinical issue. The present study was conducted to investigate the repair properties of 11R‑VIVIT on osteoporotic fractures and to examine the potential effects of 11R‑VIVIT on osteoporotic bone marrow‑derived mesenchymal stem cells (BMSCs), A rat model of osteoporotic femoral fracture was established, and the effects of the daily local injection of 11R‑VIVIT or saline on fracture repairing were evaluated by micro‑CT scans and H&E staining. Moreover, BMSCs from osteoporotic rats were treated with 11R‑VIVIT, and the osteogenic and adipogenic differentiation of BMSCs was evaluated. The results revealed that 11R‑VIVIT promoted bone formation and increased fracture healing. In addition, 11R‑VIVIT promoted the differentiation of osteoporotic BMSCs into osteoblasts rather than adipocytes. Furthermore, mechanistic analysis revealed that 11R‑VIVIT promoted autophagy by blocking the protein kinase B (AKT)/nuclear factor of activated T‑cells (NFATc1) signaling pathway. Consistently, the activation and inhibition of autophagy using rapamycin and LY294002 confirmed the regulatory effects of 11R‑VIVIT on autophagy. On the whole, the findings of the present study demonstrate that 11R‑VIVIT promotes fracture healing in osteoporotic rats and enhances the osteogenic differentiation of osteoporotic BMSCs by dysregulating the AKT/NFATc1 signaling pathway.

The mechanism of pyrroloquinoline quinone influencing the fracture healing process of estrogen-deficient mice by inhibiting oxidative stress

It is reported that oxidative stress plays a detrimental role in the process of bone fracture healing. And pyrroloquinoline quinone (PQQ) is used as antioxidant. However, there is no report about whether PQQ supplementation can promote fracture healing by eliminating oxidative stress. To investigate the protective effect of PQQ on fracture healing, open mid-diaphyseal femur fractures model were created in sham, ovariectomized (OVX) mice and PQQ-treated OVX mice. Our results confirmed that PQQ played a preventive and protective role in OVX-induced delay of bone fracture healing by inhibiting oxidative stress, subsequently promoting osteoblastic bone formation and inhibiting osteoclastic bone resorption. The findings of this study not only revealed the mechanism of PQQ supplementation in promoting fracture healing, but also provide experimental and theoretical basis for the clinical application of PQQ in the treatment of bone fracture.

Skeletal System Biology and Smoke Damage: From Basic Science to Medical Clinic

Cigarette smoking has a negative impact on the skeletal system, as it reduces bone mass and increases fracture risk through its direct or indirect effects on bone remodeling. Recent evidence demonstrates that smoking causes an imbalance in bone turnover, making bone vulnerable to osteoporosis and fragility fractures. Moreover, cigarette smoking is known to have deleterious effects on fracture healing, as a positive correlation between the daily number of cigarettes smoked and years of exposure has been shown, even though the underlying mechanisms are not fully understood. It is also well known that smoking causes several medical/surgical complications responsible for longer hospital stays and a consequent increase in the consumption of resources. Smoking cessation is, therefore, highly advisable to prevent the onset of bone metabolic disease. However, even with cessation, some of the consequences appear to continue for decades afterwards. Based on this evidence, the aim of our review was to evaluate the impact of smoking on the skeletal system, especially on bone fractures, and to identify the pathophysiological mechanisms responsible for the impairment of fracture healing. Since smoking is a major public health concern, understanding the association between cigarette smoking and the occurrence of bone disease is necessary in order to identify potential new targets for intervention.

Hsa_circ_0045714 induced by eupatilin has a potential to promote fracture healing

It is thought that maintaining preosteoblast viability is constructive to fracture healing. Here, we explored the effects of eupatilin on preosteoblast and addressed the mechanism associated with hsa_circ_0045714. Blood specimens were collected from 32 patients with hand fracture or calcaneus fracture. MC3T3-E1 cells were treated with eupatilin. Small interfering-RNA was transfected into MC3T3-E1 cells. The ability of MC3T3-E1 cells to survive, proliferate, migrate, and express fracture-associated proteins was examined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT), 5-bromodeoxyuridine (BrdU), 24-Transwell, Quantitative reverse transcription polymerase chain reaction (qRT-PCR), and Western blot. Hsa_circ_0045714 was detected by qRT-PCR. NF-κB and PI3K/AKT were evaluated by Western blot. Eupatilin enhanced the survival, proliferation, and migration of MC3T3-E1 cells. Cyclin D1, cyclin E, collagen II, aggrecan, and sulfated glycosaminoglycan (sGAG) were upregulated, while MMP-13 was downregulated in eupatilin-treated cells. Hsa_circ_0045714 was increased in patients with hand and calcaneus fractures with the time-lapse of surgical operation. In eupatilin-treated cells, Hsa_circ_0045714 was also elevated. However, the beneficial effects of eupatilin were weakened in hsa_circ_0045714-deficient cells. Molecularly, eupatilin-induced blockage of NF-κB and activation of PI3K/AKT were abrogated in hsa_circ_0045714-silenced cells. Our results confirmed the beneficial effects of eupatilin in preosteoblast, indicating eupatilin was a promising candidate for fracture healing.

Masquelet's induced membrane technique: Review of current concepts and future directions

Masquelet's induced membrane technique (MIMT) is a relatively new, two-stage surgical procedure to reconstruct segmental bone defects. First performed by Dr. Masquelet in the mid-1980s, MIMT has shown great promise to revolutionize critical-sized bone defect repair and has several advantages over its alternative, distraction osteogenesis (DO). Also, its success in extremely challenging cases (defects > 15 cm) suggests that its study could lead to discovery of novel biological mechanisms that might be at play during segmental defect healing and fracture non-union. MIMT's advantages over DO have led to a world-wide increase in MIMT procedures over the past decades. However, MIMT often needs to be repeated and so the average initial success rate in adults lags significantly behind that of DO (86% vs 95%, respectively). The autologous foreign-body membrane created during the first stage by the immune system's response to a polymethyl methacrylate bone cement spacer is critical to supporting the morselized bone graft implanted in the second stage. However, the biological and/or physical mechanisms by which the membrane supports graft to bone union are unclear. This lack of knowledge makes refining MIMT and improving the success rates through technique improvements and patient selection a significant challenge and hinders wider adoption. In this review, current knowledge from basic, translational, and clinical studies is summarized. The dynamics of both stages under normal conditions as well as with drug or material perturbations is discussed along with perspectives on high-priority future research directions.

Apigenin promotes osteogenic differentiation of mesenchymal stem cells and accelerates bone fracture healing via activating Wnt/β-catenin signaling

Apigenin (API), a natural plant flavone, is abundantly found in common fruits and vegetables. As a bioactive flavonoid, API exhibits several activities including antiproliferation and anti-inflammation. A recent study showed that API could retard osteoporosis progress, indicating its role in the skeletal system. However, the detailed function and mechanism remain obscure. In the present study, API was found to promote osteogenic differentiation of mesenchymal stem cells (MSCs). And further investigation showed that API could enhance the expression of the critical transcription factor β-catenin and several downstream target genes of Wnt signaling, thus activated Wnt/β-catenin signaling. Using a rat femoral fracture model, API was found to improve new bone formation and accelerate fracture healing in vivo. In conclusion, our data demonstrated that API could promote osteogenesis in vitro and facilitate the fracture healing in vivo via activating Wnt/β-catenin signaling, indicating that API may be a promising therapeutic candidate for bone fracture repair.NEW & NOTEWORTHY1) API promoted osteogenic differentiation of human MSCs in vitro; 2) API facilitated bone formation and accelerated fracture healing in vivo; 3) API stimulated Wnt/β-catenin signaling during osteogenesis of human MSCs.

Locally delivered adjuvant biofilm-penetrating antibiotics rescue impaired endochondral fracture healing caused by MRSA infection

Infection is a devastating complication following an open fracture. We investigated whether local rifampin-loaded hydrogel can combat infection and improve healing in a murine model of methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. A transverse fracture was made at the tibia midshaft of C57BL/6J mice aged 10-12 weeks and stabilized with an intramedullary pin. A total of 1 × 106 colony-forming units (CFU) of MRSA was inoculated. A collagen-based hydrogel containing low-dose (60 μg) and high-dose (300 μg) rifampin was applied before closure. Postoperative treatment response was assessed through bacterial CFU counts from tissue and hardware, tibial radiographs and microcomputed tomography (μCT), immunohistochemistry, and histological analyses. All untreated MRSA-infected fractures progressed to nonunion by 28 days with profuse MRSA colonization. Infected fractures demonstrated decreased soft callus formation on safranin O stain compared to controls. Areas of dense interleukin-1β stain were associated with poor callus formation. High-dose rifampin hydrogels reduced the average MRSA load in tissue (p < 0.0001) and implants (p = 0.041). Low-dose rifampin hydrogels reduced tissue bacterial load by 50% (p = 0.021). Among sterile models, 88% achieved union compared to 0% of those infected. Mean radiographic union scale in tibia scores improved from 6 to 8.7 with high-dose rifampin hydrogel (p = 0.024) and to 10 with combination local/systemic rifampin therapy (p < 0.0001). μCT demonstrated reactive bone formation in MRSA infection. Histology demonstrated restored fracture healing with bacterial elimination. Rifampin-loaded hydrogels suppressed osteomyelitis, prevented implant colonization, and improved healing. Systemic rifampin was more effective at eliminating infection and improving fracture healing. Further investigation into rifampin-loaded hydrogels is required to correlate these findings with clinical efficacy.

The Effect of Bisphosphonates on Fracture Healing Time and Changes in Bone Mass Density: A Meta-Analysis

BACKGROUND

Osteoporosis is a common complication of acute fracture, which can lead to fracture delayed union or other complications and resulting in poor fracture healing. Bisphosphate is a common anti-osteoporosis drug, but its application in fracture patients is still controversial because of its inhibitory effect on bone resorption.

METHOD

Studies were acquired from literature databases in accordance with established inclusion criteria. Standard mean difference (SMD) and 95% confidence intervals (Cls) were calculated to evaluate the effectiveness of the bisphosphonates treatment in fracture patients. Data analysis was conducted with the Review Manager 5.4.1 software.

RESULTS

A total of 16 studies involving 5022 patients obtained from selected databases were examined. As expected, bisphosphate had no significant effect on fracture healing time, but it could significantly increase BMD and prevent osteoporosis. Meanwhile, bisphosphate can inhibit both bone resorption and bone formation markers, resulting in low bone turnover state.

CONCLUSION

This meta-analysis showed that bisphosphonate have no significant effect on fracture healing time but they do increase the changes in BMD and reduce bone synthesis and resorption markers. Early application of bisphosphonates after injury in the appropriate patient population should be considered.

A Mouse Femoral Ostectomy Model to Assess Bone Graft Substitutes

The shortcomings of autografts and allografts in bone defect healing have prompted researchers to develop suitable alternatives. Numerous biomaterials have been developed as bone graft substitutes each with their own advantages and disadvantages. However, in order to test if these biomaterials provide an adequate replacement of the clinical standard, a clinically representative animal model is needed to test their efficacy. In this chapter, we describe a mouse model that establishes a critical sized defect in the mid-diaphysis of the femur to evaluate the performance of bone graft substitutes. This is achieved by performing a femoral ostectomy and stabilization utilizing a femoral plate and titanium screws. The resulting defect enables the bone regenerative potential of bone graft substitutes to be investigated. Lastly, we provide instruction on assessing the torsional strength of the healed femurs to quantitatively evaluate the degree of healing as a primary outcome measure.

Intramedullary implants coated with cubic boron nitride enhance bone fracture healing in a rat model

BACKGROUND

Boron nitride is a biocompatible and an osteo-inductive material for orthopedic applications. The aim of this study was to evaluate the effects of two different allotrope boron nitride coated implants, cubic boron nitride and hexagonal boron nitride, on fracture healing.

METHODS

In this experimental study, a total of 24 rats were divided into three groups. Group A was the control group with Kirschner wire without coating, while the wires were coated dominantly by cubic boron nitride in Group B and hexagonal boron nitride in Group C. Then a mid-third femoral fracture was created. The fracture healing was examined in terms of new bone formation with micro-CT analysis and histopathological examination, quantitative measurement of bone turnover metabolites and scintigraphic examination of osteoblastic activity on 28th day post fracture.

RESULTS

Micro-CT measurement results revealed a statistically significant increase in bone volume/tissue volume ratio and bone surface values in group B compared to group A. Cortex diameter and osteoblast counts were statistically higher in group B compared to group A. Inflammatory response was increased in group C compared to groups A and B. Biochemical test results showed significantly increased alkaline phosphatase levels and decreased osteocalcin levels in group B compared to group A. The increase in serum phosphorus and decrease in serum calcium levels was statistically significant in group C compared to Group A.

CONCLUSION

Both types of boron nitride coating had superior fracture healing features compared to control group. Therefore, c-BN coating can accelerate the fracture healing and could lead to shorten of union time.

Akkermansia muciniphila promotes type H vessel formation and bone fracture healing by reducing gut permeability and inflammation

Improving revascularization is one of the major measures in fracture treatment. Moderate local inflammation triggers angiogenesis, whereas systemic inflammation hampers angiogenesis. Previous studies showed that Akkermansia muciniphila, a gut probiotic, ameliorates systemic inflammation by tightening the intestinal barrier. In this study, fractured mice intragastrically administrated with A. muciniphila were found to display better fracture healing than mice treated with vehicle. Notably, more preosteclasts positive for platelet-derived growth factor-BB (PDGF-BB) were induced by A. muciniphila at 2 weeks post fracture, coinciding with increased formation of type H vessels, a specific vessel subtype that couples angiogenesis and osteogenesis, and can be stimulated by PDGF-BB. Moreover, A. muciniphila treatment significantly reduced gut permeability and inflammation at the early stage. Dextran sulfate sodium (DSS) was used to disrupt the gut barrier to determine its role in fracture healing and whether A. muciniphila still can stimulate bone fracture healing. As expected, A. muciniphila evidently improved gut barrier, reduced inflammation and restored the impaired bone healing and angiogenesis in DSS-treated mice. Our results suggest that A. muciniphila reduces intestinal permeability and alleviates inflammation, which probably induces more PDGF-BB+ preosteoclasts and type H vessel formation in callus, thereby promoting fracture healing. This study provides the evidence for the involvement of type H vessels in fracture healing and suggests the potential of A. muciniphila as a promising strategy for bone healing.This article has an associated First Person interview with the first author of the paper.

Effect of triamcinolone acetonide on stiffness after surgical treatment of proximal humerus fractures: a randomized controlled study

INTRODUCTION

The primary aim of this study was to determine the effectiveness and safety of an intraarticular triamcinolone injection for the treatment of stiffness after the operative treatment of proximal humerus fractures.

MATERIALS AND METHODS

88 patients who underwent plate fixation for proximal humerus fractures were enrolled. The patients were randomly divided into two groups, with Group I receiving a glenohumeral injection of triamcinolone 8 weeks postoperatively and Group II receiving no injection postoperatively. Outcomes were measured and compared based on the range of motion (ROM) and functional scores. Follow-up outcomes were assessed at initial, 3, 6 and 12 months postoperatively and at the last follow-up. Shoulder trauma series were taken at every visit to evaluate the fracture healing. The mean follow-up period was 25.37 (± 3.85) months Group I and 24.24 (± 6.23) months for group II.

RESULTS

In both groups, the final outcome of the ROM and functional outcome was significantly better at last F/U than at postoperative 8 weeks. Group I had significantly better results than Group II at postoperative 3 and 6 month in terms of forward flexion, external rotation, and VAS for pain. Also, Group I showed better performance in terms of ASES and Constant score at postoperative 3 months. The fracture union rate did not differ between Groups I and II.

CONCLUSIONS

Postoperative glenohumeral injection of triamcinolone is a safe and effective treatment modality for shoulder stiffness after internal fixation of proximal humerus fractures during the early period of rehabilitation.

Synergistic use of biomaterials and licensed therapeutics to manipulate bone remodelling and promote non-union fracture repair

Disrupted bone metabolism can lead to delayed fracture healing or non-union, often requiring intervention to correct. Although the current clinical gold standard bone graft implants and commercial bone graft substitutes are effective, they possess inherent drawbacks and are limited in their therapeutic capacity for delayed union and non-union repair. Research into advanced biomaterials and therapeutic biomolecules has shown great potential for driving bone regeneration, although few have achieved commercial success or clinical translation. There are a number of therapeutics, which influence bone remodelling, currently licensed for clinical use. Providing an alternative local delivery context for these therapies, can enhance their efficacy and is an emerging trend in bone regenerative therapeutic strategies. This review aims to provide an overview of how biomaterial design has advanced from currently available commercial bone graft substitutes to accommodate previously licensed therapeutics that target local bone restoration and healing in a synergistic manner, and the challenges faced in progressing this research towards clinical reality.

A collagen-based hydrogel containing tacrolimus for bone tissue engineering

Bone tissue engineering aims to develop bone graft structure that can heal bone defects without using autografts or allografts. The current study was conducted to promote bone regeneration using a collagen type I hydrogel containing tacrolimus. For this purpose, different amounts of tacrolimus (10 μg/ml, 100 μg/ml, and 1000 μg/ml) were loaded into the hydrogel. The resulting drug-loaded hydrogels were characterized for their porosity, swelling capacity, weight loss, drug release, blood compatibility, and cell proliferation (MTT). For functional analysis, the developed hydrogel surrounded by a film made of gelatin and polycaprolactone (PCL) was administrated in the calvarias defect of Wistar rats. The results indicated that the hydrogel has a porosity of 89.2 ± 12.5% and an appropriate swelling, drug release, and blood compatibility behavior. The in vitro results indicated that the collagen hydrogel containing 1000 μg tacrolimus was adequate in terms of cell proliferation. Finally, in vivo studies provided some evidence of the potential of the developed hydrogel for bone healing.

Melatonin suppresses both osteoblast and osteoclast differentiation through repression of epidermal Erk signaling in the zebrafish scale

Melatonin has been implicated in the regulation of bone metabolism; however, the molecular mechanisms underlying its involvement in fracture healing are still obscure. We previously developed an in vivo fracture healing model using the scale of a double-transgenic zebrafish, trap:GFP; osterix:mCherry, which labels osteoclasts and osteoblasts with GFP and mCherry, respectively. Here we show using this model that melatonin inhibits both osteoblast and osteoclast differentiation under fracture stress through the repression of Erk signaling in epidermal cells of the scale. Melatonin treatment resulted in reduced numbers of both osteoblasts and osteoclasts in the fractured scale. Immunochemistry analysis revealed that Erk signals in epidermal cells, which express melatonin receptors, were greatly enhanced in response to fracture stress, but this enhancement was blocked by melatonin treatment. Moreover, inhibition of Erk signaling phenocopied the effects of melatonin treatment in the fractured scale. Collectively, these data suggest that the activation of epidermal Erk signaling is required for both osteoblast and osteoclast differentiation in the early stage of fracture healing, and melatonin suppresses epidermal Erk signaling, leading to impaired fracture healing.

The Cannabinoids Effect on Bone Formation and Bone Healing

PURPOSE OF REVIEW

Here, we overview the latest findings from studies investigating the skeletal endocannabinoid (EC) system and its involvement in bone formation and resorption.

RECENT FINDINGS

The endocannabinoid system consists of endogenous ligands, receptors, and enzymes. The main cannabinoids found in the cannabis plant are Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). Cannabinoid receptors CB1 and CB2 are expressed in bone and regulate bone homeostasis in rodents and humans. CBD treatment was shown to enhance fracture healing in rats. Recent studies in mice indicate that strain, age, and sex differences dictate the skeletal outcome of the EC activation. CBD treatment was shown to enhance bone healing, but needs validation in clinical trials. While research shows that EC activity protects against bone loss, studies on CB1 and CB2 agonists in bone regeneration models are lacking. Whether modulating the EC system would affect bone repair remains therefore an open question worth investigating.

Oral administration of bovine lactoferrin accelerates the healing of fracture in ovariectomized rats

INTRODUCTION

Lactoferrin has recently been reported for its potent bone growth effects. However, the effects of lactoferrin on the healing process of fragility fracture have not yet been studied, so the purpose of this study is to investigate whether oral administration of lactoferrin can promote the fracture healing in an OVX animal model.

MATERIALS AND METHODS

Three months after bilateral ovariectomy, all rats underwent unilateral tibial osteotomy and were then randomly divided into control group and bovine lactoferrin (bLF) group. At 4 and 8 weeks post-fracture, animals were sacrificed, and the fractured tibiae and serum samples were collected for evaluation.

RESULTS

Our results showed that bLF treatment not only accelerated the bone growth at an early stage of OPF healing but also shortened the remolding process of OPF healing. When compared to control group, bLF treatment induced a significant rise in callus BMD (by 35.0% at 4 weeks and by 39.7% at 8 weeks; both p < 0.05) consistent with enhanced biomechanical strength of the callus, with ultimate force increased by 3.39-fold at 4 weeks (p < 0.05) and 1.95-fold at 8 weeks (p < 0.05). Besides, bLF administration resulted in a substantial increase in serum levels of BALP and a significant decrease in serum levels of TRAP 5b and TNF-α. Moreover, both the RANKL/OPG mRNA ratio and the expression of TNF-α in the callus of bLF-treated group were markedly lower than those in the control group.

CONCLUSIONS

At a dose of 85mg/kg/day orally administrated bLF potently promoted the bone healing following tibial fracture in OVX rats.

Bone-Targeting Liposome-Encapsulated Salvianic Acid A Improves Nonunion Healing Through the Regulation of HDAC3-Mediated Endochondral Ossification

AIM

Nonunion is a major complication in fracture repair and remains a challenge in orthopaedics and trauma surgery. In this study, we aimed to evaluate the effectiveness of treatment of nonunion with a large radial defect using a bone-targeting liposome-encapsulated salvianic acid A (SAA-BTL)-incorporated collagen sponge and further elucidate whether the effects were closely related to histone deacetylase 3 (HDAC 3)-mediated endochondral ossification in nonunion healing process.

METHODS

Fifteen New Zealand female rabbits were randomly divided into three groups. Segmental radius critical size defects (15 mm) were created via surgery on both the forelimbs of the rabbits. The SAA-BTL/SAA/saline-incorporated collagen sponges were implanted into the defects in the three groups, respectively, for four weeks of treatment. X-ray imaging, micro-computed tomography (CT) analysis, histology, and immunofluorescence analysis (HDAC3, collagen II, VEGFA, and osteocalcin) were performed to determine the effects of the treatments. In addition, a short interfering RNA was applied to induce HDAC3 knockdown in the chondrogenic cell line ATDC5 to investigate the roles of HDAC3 and SAA intervention in endochondral ossification in nonunion healing.

RESULTS

X-ray imaging and micro-CT results revealed that SAA-BTL-incorporated collagen sponges significantly stimulated bone formation in the nonunion defect rabbit model. Furthermore, immunofluorescence double staining and histology analysis confirmed that SAA-BTL significantly increased the expression of P-HDAC3, collagen II, RUNX2, VEGFA, and osteocalcin in vivo; accelerated endochondral ossification turnover from cartilage to bone; and promoted long bone healing of nonunion defects. ATDC5 cells knocked down for HDAC3 showed significantly decreased expression of HDAC3, which resulted in reduced expression of chondrogenesis, osteogenesis, and angiogenesis biomarker genes (Sox9, Col10a1, VEGFA, RUNX2, and Col1a1), and increased expression of extracellular matrix degradation marker (MMP13). SAA treatment reversed these effects in the HDAC3 knockdown cell model.

CONCLUSION

SAA-BTL can improve nonunion healing through the regulation of HDAC3-mediated endochondral ossification.

Risk of Nonunion with Nonselective NSAIDs, COX-2 Inhibitors, and Opioids

BACKGROUND

Cyclooxygenase-2 (COX-2) has been found to be important for fracture-healing in animal models, raising concerns about use of nonsteroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors after fractures. We evaluated associations of NSAIDs, COX-2 inhibitors, and opioids with nonunion after long-bone fracture.

METHODS

Using private health insurance claims data from Optum's de-identified Clinformatics Data Mart database from January 1, 2000, to September 30, 2015, we identified adults with a single long-bone fracture or commonly paired long-bone fractures who had 1 year of available follow-up data. Using multivariable logistic regression models, we examined associations between NSAID, COX-2-inhibitor, or opioid prescription fills after the fracture and the risk of nonunion within 1 year, defined as a nonunion diagnosis with a procedure to treat the nonunion.

RESULTS

A nonunion diagnosis with a procedure to treat the nonunion was identified after 2,996 (0.9%) of the 339,864 fracture episodes, with rates varying by fracture site. The risk of that outcome was greater in patients who had filled COX-2-inhibitor prescriptions (adjusted odds ratio = 1.84 [95% confidence interval = 1.38 to 2.46]) or opioid prescriptions (1.69 [1.53 to 1.86]), but not in patients who had filled nonselective-NSAID prescriptions (1.07 [0.93 to 1.23]) after the fracture. Results were similar when the outcome definition was changed to just a nonunion diagnosis.

CONCLUSIONS

COX-2 inhibitors, but not nonselective NSAIDs, were associated with a greater risk of nonunion after fracture. Opioids were also associated with nonunion risk, although patients filling prescriptions for opioids may have had more severe fractures.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Effect of Postoperative Nonsteroidal Anti-inflammatory Drugs on Nonunion Rates in Long Bone Fractures

The association of nonsteroidal anti-inflammatory drugs (NSAIDs) with non-union in long bone fractures has been controversial. The purpose of this study was to evaluate whether NSAID exposure results in increased risk of non-union in operatively treated long bone fractures. The authors used International Classification of Diseases and Current Procedural Terminology codes to identify patients under a single-payer private insurance with operatively treated humeral shaft, tibial shaft, and subtrochanteric femur fractures from a large database. Patients were divided into cohorts based on NSAID use in the immediate postoperative period, and nonunion rates were compared. A cost analysis and a multivariate analysis were performed. Between 2007 and 2016, a total of 5310 tibial shaft, 3947 humeral shaft, and 8432 subtrochanteric femur fractures underwent operative fixation. Patients used NSAIDs in the first 90 days postoperatively in 900 tibial shaft, 694 humeral shaft, and 967 subtrochanteric femur fractures. In these patients, nonunion rates were 18.8%, 17.4%, and 10.4%, respectively. When no NSAIDs were used, the rates were 11.4%, 10.1%, and 4.6% for each fracture type, respectively (P<.05). Among patients taking NSAIDs, subtrochanteric femur fractures had a 2.4 times higher risk of nonunion and humeral shaft and tibial shaft fractures both had a 1.7 times higher risk of nonunion (P<.05). Multivariate analysis showed NSAID use to be an independent risk factor in all 3 types. Cost analysis showed a great increase in economic burden (P<.05). This study indicated that NSAID exposure was associated with fracture nonunion. [Orthopedics. 2020;43(4):221-227.].

Effects of a novel biodegredable implant system on a rat tibia fracture model

OBJECTIVE

This study aimed to determine the effects of a novel biodegradable implant releasing platelet-derived growth factor (PDGF) at the fracture site on fracture healing in a rat tibia fracture model.

METHODS

In this study, 35 male Sprague-Dawley rats weighing between 300 and 350 g were used. The rats were divided into four groups: Group A (control group without any treatment, n=10), Group B (spacer without PDGF Group, n=10), Group C (spacer with PDGF group, n=10), and Group D (healthy rat Group, n=5). Standardized fractures were created in the right tibias of rats, and then biodegradable implants made of poly-β-hydroxybutyrate-co-3-hydroxy valerate were implanted at the fracture sites in Groups B and C. In Group C, implants were loaded with 600 ng of PDGF. Animals were sacrificed 30 days after the operation, and fracture healing in each group was assessed radiologically based on the Goldberg score. Furthermore, the anteroposterior (AP) and mediolateral (ML) callus diameters were measured macroscopically, and fracture sites were mechanically tested.

RESULTS

In the radiological assessment, Group C showed higher fracture healing rate than Groups A and B (p=0.001), whereas no significant difference was found between group C and Group D (p>0.05). In the macroscopic assessment, while Group C exhibited the thickest AP callus diameter (p=0.02), no significant differences in ML callus diameters existed among the groups (p>0.05). Mechanical testing revealed that Group C had higher torsional strength (p=0.001) and stiffness than Groups A and B (p=0.001) while there was no significant difference between Groups C and D (p>0.05).

CONCLUSION

Biodegradable implant releasing PDGF may have positive effects on fracture healing.

NSM00158 Specifically Disrupts the CtBP2-p300 Interaction to Reverse CtBP2-Mediated Transrepression and Prevent the Occurrence of Nonunion

Carboxyl-terminal binding proteins (CtBPs) are transcription regulators that control gene expression in multiple cellular processes. Our recent findings indicated that overexpression of CtBP2 caused the repression of multiple bone development and differentiation genes, resulting in atrophic nonunion. Therefore, disrupting the CtBP2-associated transcriptional complex with small molecules may be an effective strategy to prevent nonunion. In the present study, we developed an in vitro screening system in yeast cells to identify small molecules capable of disrupting the CtBP2-p300 interaction. Herein, we focus our studies on revealing the in vitro and in vivo effects of a small molecule NSM00158, which showed the strongest inhibition of the CtBP2-p300 interaction in vitro. Our results indicated that NSM00158 could specifically disrupt CtBP2 function and cause the disassociation of the CtBP2-p300-Runx2 complex. The impairment of this complex led to failed binding of Runx2 to its downstream targets, causing their upregulation. Using a mouse fracture model, we evaluated the in vivo effect of NSM00158 on preventing nonunion. Consistent with the in vitro results, the NSM00158 treatment resulted in the upregulation of Runx2 downstream targets. Importantly, we found that the administration of NSM00158 could prevent the occurrence of nonunion. Our results suggest that NSM00158 represents a new potential compound to prevent the occurrence of nonunion by disrupting CtBP2 function and impairing the assembly of the CtBP2-p300-Runx2 transcriptional complex.

The Effect of Opiates on Bone Formation and Bone Healing

PURPOSE OF REVIEW

Opioids have been shown to be associated with an increased risk of fracture. The purpose of this paper is to review recent research into the effects of opioids on bone formation and bone healing in animal models and in human studies.

RECENT FINDINGS

Most opioids, such as morphine and fentanyl, negatively affected bone remodeling and bone healing in animal models. Conversely, remifentanil has been recently shown to promote in vitro osteoblast differentiation and to inhibit differentiation and maturation of osteoclasts, therefore reducing bone resorption. According to the possible negative role of opioids in bone healing, opioid antagonists have been shown to enhance bone mineralization, suggesting a possible therapeutic role in the future for osteoporosis. Other neuropeptides, such as the vasoactive intestinal peptide (VIP) and the neuropeptide Y (NPY), have been proved to promote osteogenesis. The increased risk of fractures among opioid users may be related to their central nervous system side effects or to the reduced bone density, partly due to their endocrine effects, and partly to their direct activity on bone cells. Clinical data strongly suggested a potential negative effect of opioids in bone healing. The risk of nonunion fracture is significantly increased in opioid users, and bone mass density was reduced in patients under long-term opioid treatment. The direct effects of opioids on bone remodeling appears evident from these reports. Not all opioids have the same potential for negatively impacting bone healing. Opioid antagonists may increase bone density and could represent a possible future treatment for low bone mass density pathologies. However, further trials are warranted to clarify the clinical relevance of these emerging findings from animal studies.

Effect of kirenol on the interaction between the WNT/β-Catenin and RUNX2/TCF/LEF1 pathways in fracture healing in vivo

OBJECTIVE

This study aimed to determine the effects of a natural diterpenoid, kirenol, on fracture healing in vivo in an experimental rat model of femur fracture and investigate its potential mechanism of action via the Wnt/β-catenin pathway.

METHODS

In this study, 64 male Wistar albino rats aged 5-7 weeks and weighing 261-348 g were randomly divided into 8 groups from A to L, with eight rats in each group. Standardized fractures were created in the right femurs of the rats and then fixed with an intramedullary Kirschner wire. Four experimental groups were administered 2 mg/kg/day kirenol (Groups C and G) and 4 mg/kg/day (Groups D and H) kirenol by oral gavage.Thereafter, the animals were sacrificed at two time points as follows: on the 10th day (Groups B, C and D) and on the 21st day (Groups F, G and H) after the surgery; fracture healing in each group was assessed radiologically and histopathologically. The Radiographic Union scale of tibia fracture scoring system was used in the radiological examination; callus volume and density were measured using computed tomography. In the histopathologic examination, the scoring system described by Huo et al. was used. Additionally, the mechanism of action was evaluated based on the analyses of protein expression of Wnt3a, LRP5, TCF-LEF1, β-catenin, and Runx-2 proteins using western blot analysis.

RESULTS

Among the animals sacrificed on the 10th day after the surgery, the highest histopathological and radiological scores were observed in Group D (p<0.05). Furthermore, the callus density (p<0.05) was highest in Group D. Among the animals sacrificed on the 21st day, the highest histopathological and radiological scores were found in Group H, although the differences among the groups were not significant (p>0.05). The callus volume and density were the highest in Groups G and H, respectively, although the differences among groups were not significant.

CONCLUSION

Kirenol may improve fracture healing in a dose-dependent manner with the early activation of the Wnt/β-catenin pathway and the activation of the Runx-2 pathway.

Evaluation of callus formation in distal femur fractures after carbon fiber composite versus stainless steel plate fixation

INTRODUCTION

Carbon-fiber-reinforced polyetheretherketone (CFR) composite plates have a more favorable stress modulus than stainless steel (SS) plates that may confer an advantage to bridge plating. The purpose of this study was to compare callus formation after CFR and SS plating of distal femur fractures.

METHODS

A retrospective review identified distal femoral fractures treated with CFR (n = 10) and SS (n = 21) plate fixation. Callus formation was measured using the modified Radiographic Union Score for Tibia (mRUST) at 3- and 6-month follow-up by three orthopedic trauma surgeons. Loss of alignment, implant failure, and revision surgeries were reviewed.

RESULTS

At 3 months, the mRUST in the CFR and SS groups was 9.0 (range, 6.3-12.3) and 6.9 (range, 4.3-11.7), respectively (p = 0.01). At 6 months, the mRUST in the CFR and SS groups was 11.4 (range, 7.7-16.0) and 10.5 (range, 6.0-15.7), respectively (p = 0.3). CFR and SS groups had a loss of fracture alignment in 1 (10%) and 1 (5%) patient, respectively (p = 0.5), and an unplanned revision surgery in 0 (0%) and 3 (15%) patients, respectively (p = 0.2). All three revisions surgeries in the SS group were for nonunion repair.

CONCLUSIONS

Treatment of distal femur fractures with CFR versus SS plating resulted in greater callus formation at 3 months. At 6 months, there was no difference in callus formation between groups. A larger series of patients is necessary to determine if the observed early increased callus formation confers a benefit to clinical outcomes.

LEVEL OF EVIDENCE

Therapeutic level III.

Icariin Promotes Fracture Healing in Ovariectomized Rats

BACKGROUND Osteoporotic fractures are common in postmenopausal women and associated with complications. Numerous studies have demonstrated that icariin can be used to treat fractures and osteoporosis. Herein, we evaluated the efficacy of gavage-administered icariin to promote fracture healing in postmenopausal osteoporotic fracture (POF) rats. MATERIAL AND METHODS In this study, ovariectomy-induced POF rats were treated with 600 mg/kg icariin. Micro-computed tomography (micro-CT) was used to assess fracture healing; besides, serum APK, TRACP-5b, and E₂ expression levels were detected by commercial kits, and the uterine index was calculated. In addition, the expression of osteogenesis-related proteins (Runx 2 and COL1A2) in the callus was measured by western blot, whereas the expression of OPG/RANKL pathway proteins was measured by western blot and immunohistochemical analysis. RESULTS Our data revealed that icariin promoted the expression level of Runx 2 and COL1A2 and suppressed the expression level of serum bone turn over biomarkers via the OPG/RANKL pathway. Besides, a more mature callus was observed in the POF rats receiving icariin than in the untreated POF rats, while serum E₂ and uterine index were unaffected by icariin treatment. CONCLUSIONS These results revealed that icariin could promote fracture healing in ovariectomized rats via OPG/RANKL signaling, and that serum E₂ and uterine index were not affected by icariin treatment.

Green Tea Catechin (-)-Epigallocatechin-3-Gallate (EGCG) Facilitates Fracture Healing

Green tea drinking can ameliorate postmenopausal osteoporosis by increasing the bone mineral density. (-)-Epigallocatechin-3-gallate (EGCG), the abundant and active compound of tea catechin, was proven to be able to reduce bone loss and ameliorate microarchitecture in female ovariectomized rats. EGCG can also enhance the osteogenic differentiation of murine bone marrow mesenchymal stem cells and inhibit the osteoclastogenesis in RAW264.7 cells by modulation of the receptor activator of nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegrin (OPG) (RANK/RANKL/OPG) pathway. Our previous study also found that EGCG can promote bone defect healing in the distal femur partially via bone morphogenetic protein-2 (BMP-2). Considering the osteoinduction property of BMP-2, we hypothesized that EGCG could accelerate the bone healing process with an increased expression of BMP-2. In this manuscript, we studied whether the local use of EGCG can facilitate tibial fracture healing. Fifty-six 4-month-old rats were randomly assigned to two groups after being weight-matched: a control group with vehicle treatment (Ctrl) and a study group with 10 µmol/L, 40 µL, EGCG treatment (EGCG). Two days after the operation, the rats were treated daily with EGCG or vehicle by percutaneous local injection for 2 weeks. The application of EGCG enhanced callus formation by increasing the bone volume and subsequently improved the mechanical properties of the tibial bone, including the maximal load, break load, stiffness, and Young’s modulus. The results of the histology and BMP-2 immunohistochemistry staining showed that EGCG treatment accelerated the bone matrix formation and produced a stronger expression of BMP-2. Taken together, this study for the first time demonstrated that local treatment of EGCG can accelerate the fracture healing process at least partly via BMP-2.

Expression and Role of IL-1β Signaling in Chondrocytes Associated with Retinoid Signaling during Fracture Healing

The process of fracture healing consists of an inflammatory reaction and cartilage and bone tissue reconstruction. The inflammatory cytokine interleukin-1β (IL-1β) signal is an important major factor in fracture healing, whereas its relevance to retinoid receptor (an RAR inverse agonist, which promotes endochondral bone formation) remains unclear. Herein, we investigated the expressions of IL-1β and retinoic acid receptor gamma (RARγ) in a rat fracture model and the effects of IL-1β in the presence of one of several RAR inverse agonists on chondrocytes. An immunohistochemical analysis revealed that IL-1β and RARγ were expressed in chondrocytes at the fracture site in the rat ribs on day 7 post-fracture. In chondrogenic ATDC5 cells, IL-1β decreases the levels of aggrecan and type II collagen but significantly increased the metalloproteinase-13 (Mmp13) mRNA by real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. An RAR inverse agonist (AGN194310) inhibited IL-1β-stimulated Mmp13 and Ccn2 mRNA in a dose-dependent manner. Phosphorylated extracellular signal regulated-kinases (pERK1/2) and p-p38 mitogen-activated protein kinase (MAPK) were increased time-dependently by IL-1β treatment, and the IL-1β-induced p-p38 MAPK was inhibited by AGN194310. Experimental p38 inhibition led to a drop in the IL-1β-stimulated expressions of Mmp13 and Ccn2 mRNA. MMP13, CCN2, and p-p38 MAPK were expressed in hypertrophic chondrocytes near the invaded vascular endothelial cells. As a whole, these results point to role of the IL-1β via p38 MAPK as important signaling in the regulation of the endochondral bone formation in fracture healing, and to the actions of RAR inverse agonists as potentially relevant modulators of this process.

The effect of topical and systemic tranexamic acid on fracture healing in rats

OBJECTIVE

The aim of the present study was to determine the effect of topical and systemic tranexamic acid (TXA) on fracture healing in a rat surgical model.

METHODS

We created standard, right-sided, open, diaphyseal femoral fractures with intramedullary Kirschner wire fixation in 48 male rats and divided them into three groups: a topical TXA (10 mg/kg) group, a systemic TXA (10 mg/kg) group, and a control group. Fracture healing was evaluated radiographically and histologically after early (week 2) and late (week 4) postoperative sacrifice.

RESULTS

The radiological scores differed significantly among the all groups (p=0.001), as did the week 2 and 4 scores (p=0.003 and p=0.010, respectively). Radiologically, the topical TXA group exhibited better bone healing at both 2 (p=0.001) and 4 (p=0.007) weeks than the control group, and the systemic group showed better healing at both 2 (p=0.027) and 4 (p=0.023) weeks than the control TXA group. Moreover, bone healing was better in the group treated with topical rather than systemic TXA on radiological examinations performed at 2 (p=0.001) and 4 (p=0.007) weeks postoperatively (p=0.001 and p=0.007, respectively). Histologically, the groups differed significantly (p=0.001). The histological scores differed significantly among the all groups (p=0.001). At 2 weeks, the topical TXA group exhibited significantly better bone healing than the control group (p=0.001).

CONCLUSION

Our results suggested that topical application of TXA in fracture patients may accelerate healing, whereas systemic administration may adversely affect healing.

The Selective Androgen Receptor Modulator Ostarine Improves Bone Healing in Ovariectomized Rats

Non-steroidal selective androgen receptor modulators, including ostarine, have been developed as an alternative to steroidal hormones. Ostarine has shown a beneficial effect on bone in experimental studies, but no data regarding the effect of ostarine on bone healing have yet been reported. We investigated effects of ostarine on bone healing in ovariectomized rats. Sprague-Dawley rats (3 months old) were ovariectomized (Ovx, n = 46) or left intact (Non-Ovx, n = 10). After 8 weeks, an osteotomy of the tibia metaphysis was created in all rats, and the Ovx rats were divided into four groups: untreated Ovx (n = 10) and three Ovx groups (each of 12 rats) treated with ostarine at doses of 0.04, 0.4, or 4 mg/kg BW (OS-0.04, OS-0.4, and OS-4 groups). Five weeks later, bone healing was analyzed. The OS-4 dose enhanced callus formation, increased callus density, accelerated bridging time of the osteotomy, and elevated alkaline phosphatase gene expression in callus and its protein expression in serum. In the Ovx group, most of the callus parameters were diminished. All OS treatments increased the weight of the gastrocnemius muscle, but only partly enhanced uterus weight in OS-0.4 and OS-4. Serum cholesterol level was reduced, and serum phosphorus was elevated in OS-0.04 and OS-4. Ostarine appeared to have a positive effect on early bone healing in ovariectomized rats. Considering its favorable effect on non-osteotomized bone and muscle, this treatment could be further explored as a therapy for osteoporosis. However, possible metabolic side effects should first be evaluated.

Pretreatment with Pamidronate Decreases Bone Formation but Increases Callus Bone Volume in a Rat Closed Fracture Model

Clinical concerns have been raised over prior exposure to bisphosphonates impairing fracture healing. To model this, groups of male Wistar rats were assigned to saline control or treatment groups receiving 0.15 mg/kg (low dose), 0.5 mg/kg (medium dose), and 5 mg/kg (high dose) Pamidronate (PAM) twice weekly for 4 weeks. At this point, closed fractures were made using an Einhorn apparatus, and bisphosphonate dosing was continued until the experimental endpoint. Specimens were analyzed at 2 and 6 weeks (N = 8 per group per time point). Twice weekly PAM dosing was found to have no effect on early soft callus remodeling at 2 weeks post fracture. At this time point, the highest dose PAM group gave significant increases in bone volume (+ 10%, p < 0.05), bone mineral content (+ 30%, p < 0.01), and bone mineral density (+ 10%, p < 0.01). This PAM dosing regimen showed more substantive effects on hard callus at 6 weeks post fracture, with PAM treatment groups showing + 46-79% increased bone volume. Dynamic bone labeling showed reduced calcein signal in the PAM-treated calluses (38-63%, p < 0.01) and reduced MAR (32-49%, p < 0.01), suggesting a compensatory reduction in bone anabolism. These data support the concept that bisphosphonates lead to profound decreases in bone turnover in fracture repair, however, this does not affect soft callus remodeling.

Lithium for Fracture Treatment (LiFT): a double-blind randomised control trial protocol

INTRODUCTION

Fracture healing can fail in up to 10% of cases despite appropriate treatment. While lithium has been the standard treatment for bipolar disorder, it may also have a significant impact to increase bone healing in patients with long bone fractures. To translate this knowledge into clinical practice, a randomised clinical trial (RCT) is proposed.

METHODS AND ANALYSIS

A multicentre double blind, placebo-controlled RCT is proposed to evaluate the efficacy of lithium to increase the rate and predictability of long bone fracture healing in healthy adults compared to lactose placebo treatment. 160 healthy individuals from 18 to 55 years of age presenting with shaft fractures of the femur, tibia/fibula, humerus or clavicle will be eligible. Fractures will be randomised to placebo (lactose) or treatment (300 mg lithium carbonate) group within 2 weeks of the injury. The primary outcome measure will be radiographic union defined as visible callus bridging on three of the four cortices at the fracture site using a validated radiographic union score. Secondary outcome measures will include functional assessment and pain scoring.

ETHICS AND DISSEMINATION

Participant confidentiality will be maintained with publication of results. Research Ethics Board Approval: Sunnybrook Research Institute (REB # 356-2016). Health Canada Approval (HC6-24-C201560). Results of the main trial and secondary endpoints will be submitted for publication in a peer-reviewed journal and presented at conferences.

TRIAL REGISTRATION NUMBER

NCT02999022.

AdipoRon promotes diabetic fracture repair through endochondral ossification-based bone repair by enhancing survival and differentiation of chondrocytes

Diabetic bone defects may exhibit impaired endochondral ossification (ECO) leading to delayed bone repair. AdipoRon, a receptor agonist of adiponectin polymers, can ameliorate diabetes and related complications, as well as overcome the disadvantages of the unstable structure of artificial adiponectin polymers. Here, the effects of AdipoRon on the survival and differentiation of chondrocytes in a diabetic environment were explored focusing on related mechanisms in gene and protein levels. In vivo, AdipoRon was applied to diet-induced-obesity (DIO) mice, a model of obesity and type 2 diabetes, with femoral fracture. Sequential histological evaluations and micro-CT were examined for further verification. We found that AdipoRon could ameliorate cell viability, apoptosis, and reactive oxygen species (ROS) production and promote mRNA expression of chondrogenic markers and cartilaginous matrix production of ATDC5 cells in high glucose medium via activating ERK1/2 pathway. Additionally, DIO mice with intragastric AdipoRon administration had more neocartilage and accelerated new bone formation. These data suggest that AdipoRon could stimulate bone regeneration via ECO in diabetes.

PTH1-34 improves bone healing by promoting angiogenesis and facilitating MSCs migration and differentiation in a stabilized fracture mouse model

Objective

PTH_1-34 (parathyroid hormone 1–34) is the only clinical drug to promote osteogenesis. MSCs (mesenchymal stem cells) have multidirectional differentiation potential and are closely related to fracture healing. This study was to explore the effects of PTH_1-34 on proliferation and differentiation of endothelial cells and MSCs in vitro, and on angiogenesis, and MSCs migration during fracture healing in vivo.

Methods

Mice with stabilized fracture were assigned to 4 groups: CON, PTH (PTH_1-34 40 μg/kg/day), MSC (transplanted with 10⁵ MSCs), PTH+MSCs. Mice were sacrificed 14 days after fracture, and callus tissues were harvested for microCT scan and immunohistochemistry analysis. The effects of PTH_1-34 on angiogenesis, and MSCs differentiation and migration were assessed by wound healing, tube formation and immunofluorescence staining.

Results

Treatment with either PTH_1-34, or MSCs promoted bone healing and vascular formation in fracture callus. The callus bone mass, bone volume, and bone mineral density were all greater in PTH and/or MSC groups than they were in CON (p<0.05). PTH_1-34 increased small vessels formation (diameter ≤50μm), whereas MSCs increased the large ones (diameter >50μm). Expression of CD31 within calluses and trabecular bones were significantly higher in PTH_1-34 treated group than that of not (p<0.05). Expression of CD31, VEGFR, VEGFR2, and vWF was upregulated, and wound healing and tube formation were increased in MSCs treated with PTH_1-34 compared to that of control.

Conclusions

PTH_1-34 improved the proliferation and differentiation of endothelial cells and MSCs, enhancing migration of MSCs to bone callus to promote angiogenesis and osteogenesis, and facilitating fracture healing.

Chinese topical herbal medicine gives additive effect on pharmaceutical agent on fracture healing

OBJECTIVE

To investigate the efficacy on the combination of oral strontium ranelate (SrR) with a topical Chinese herbal paste on facilitation of fracture healing.

METHODS

An open fracture was created at the mid-shaft of the right tibia of rat. A herbal paste called CDR containing Honghua (Flos Carthami), Chuanxuduan (Radix Dipsaci Asperoidis) and Dahuang (Radix Et Rhizoma Rhei Palmati) was prepared. The rats were treated with either CDR topically on the fracture site, or SrR orally, or their combinations. Bone turnover biochemical markers in serum were measured. Microarchitecture of the fracture was analyzed using micro-CT after 14 and 28 d, followed by histomorphometrical analysis.

RESULTS

Micro-computed tomography analysis revealed that the combined treatment of CDR with 600 mg/g SrR significantly increased the total callus density, mineralized callus volume fraction, mineralized callus mineral content and mineralized callus density of the callus after 28 d of treatment. This result was consistent with the histomorphometrical analysis on the osteoid volume. Analysis of biochemical markers showed that the combined treatments reduced the bone resorption that occurs temporarily after fracture.

CONCLUSION

This study demonstrated that the combined treatment of oral SrR and topical CDR is effective to promote fracture healing by their additive effect on promoting bone formation and retarding bone resorption.

Effect of curcumin on bone healing: An experimental study in a rat model of femur fracture

OBJECTIVE

To determine the radiologic, histologic and biomechanical effects of curcumin on bone healing using a total rat femur fracture injury model.

MATERIALS AND METHODS

Sixty four male Wistar-Albino rats weighing 170-210 g were used in this study. The animals were randomly divided into eight groups and 5 or 6 animals were placed in each cage. A transverse femur shaft fracture model used. The animals in study groups received oral curcumin at a dose of 200 mg/kg for 14 days or 28 days. Remaining animals received only saline solution by oral gavage for a period of 14 days and 28 days as control groups. After sacrification the left femurs used for radiological, histological and biomechanical evaluation.

RESULTS

The groups treated with curcumin showed no significant difference in terms of radiological, histological and biomechanical evaluations in 14 days groups. Also there was no significant difference between curcumin and control groups for 28 days according to radiological, histological and biomechanical tests.

CONCLUSIONS

According to our results, curcumin has no positive effect on fracture healing not only histologically but also radiologically and biomechanically. Curcumin's antioxidant effect may be more noticeable with long term follow up investigation as it may have a positive effect in remodelling phase. Long term follow up designed studies may be planned to investigate its effect on remodelling phase of fracture healing.

A retrospective bicenter comparative study of surgical outcomes of atypical femoral fracture: Potential effect of teriparatide on fracture healing and callus formation

BACKGROUND

The main purpose of the present study was to assess the radiologic effect of teriparatide on fracture healing, including union rate, union time, and callus formation, by quantitative measurements using serial follow-up X-ray imaging examinations in patients with complete atypical femoral fractures (AFFs) treated using closed intramedullary nailing.

METHODS

From January 2010 to October 2017, 58 consecutive patients with complete AFF who were treated with intramedullary nailing at two institutions were enrolled. Patients were classified into two groups: those who received teriparatide therapy (group A) and those who did not (group B). Teriparatide (Forsteo®; Eli Lily Co., Indianapolis, IN, USA) at a once-daily 20 μg dose was prescribed as continuous treatment of osteoporosis or with the expectation of better bone healing. Surgical outcomes, including union rate, union time, modified radiologic union score (mRUS), and callus formation at 3, 6, and 12 months postoperatively, were assessed to evaluate the effect of teriparatide on fracture healing. Quantitative measurement of callus formation was performed using the region of interest (ROI) tool in the picture archiving communication system (PACS).

RESULTS

Non-union was not observed in group A, whereas two patients had non-union in group B. Union time was 18.3 ± 4.8 (range, 12-28) weeks in group A and 23.6 ± 9.5 (range, 12-64) weeks in group B and was significantly shorter in group A than group B (p = 0.010). The average mRUSs during periods A (3-4 months postoperatively), B (6-8 months postoperatively), and C (12-14 months postoperatively) were 10.0, 13.9, and 15.9 in group A, and 8.7, 12.0, and 14.9 in group B, respectively. The average mRUSs during periods A and B were significantly different (p = 0.027 and 0.011, respectively). The medial, posterior, and total callus areas during periods A and B were also significantly greater in group A than in group B. No difference was observed in the union rate between the two groups (p = 0.492).

CONCLUSION

Teriparatide may improve callus formation and shorten union time in patients with complete diaphyseal AFF who underwent closed intramedullary nailing.

LEVEL OF EVIDENCE

Level III retrospective comparative study.

Different surgical outcomes in a patient with bilateral atypical femoral fracture related to bisphosphonate use with or without teriparatide treatment

Bisphosphonates (BPs) are first-line drugs for the treatment of osteoporotic fractures, but long-term use of BP reduces bone turnover and is associated with atypical femur fractures (AFFs). Additionally, BP treatment may cause delayed fracture healing or nonunion, which makes AFF treatment difficult. The incidence of AFF is generally low. In fact, there are only a few clinical reports of AFF and there is no controlled study on AFF treatment. Herein, we report a case of multiple osteoporotic fractures. After 5 years of BP treatment, left and right AFFs occurred within 2 years. The fracture types and surgical operations were the same, but the level of bone metabolism and drug treatment were different. The right AFF healed well following teriparatide initiation compared with non-healed left AFF with BP continuation; thus, our case can be considered a self-controlled study. Furthermore, we have reviewed the diagnosis and treatment of this case in detail and analyzed and investigated the potential causes of the different outcomes of AFFs between the two sides to inform the clinical treatment of atypical fractures. Mini Abstract We report a case of bilateral AFFs. The surgical treatments were the same, but the final treatment outcomes were different with or without teriparatide treatment. We investigated the potential causes of the different outcomes of AFFs between the two sides to inform the clinical treatment of AFFs.

Effects of anti-osteoporosis medications on radiological and clinical results after acute osteoporotic spinal fractures: a retrospective analysis of prospectively designed study

Effects of anti-osteoporosis medications such as anti-resorptive and anabolic agents on healing of osteoporotic spinal fracture were retrospectively investigated. The use of anabolic agent significantly enhanced fracture healing, reduced progressive collapse, and presented good pain relief. These findings suggest that proper selection of medication could improve initial management of acute osteoporotic spinal fractures (OSFs).

INTRODUCTION

Although anti-osteoporosis medications have beneficial effects on prevention of osteoporotic spinal fractures (OSFs), few studies have compared effects of medications on fracture healing following OSFs. Therefore, the purpose of this study was to elucidate the effects of different anti-osteoporosis medications on radiological and clinical outcomes after acute OSFs.

METHODS

A total of 132 patients diagnosed with acute OSFs were enrolled and allocated into three groups [group I (n = 39, no anti-osteoporosis medication), group II (n = 66, bisphosphonate), and group III (n = 27, parathyroid hormone (PTH)]. Radiological parameters including magnetic resonance (MR) classification, occurrence of intravertebral cleft (IVC), and clinical outcomes such as numerical rating scale (NRS) and Oswestry disability index were assessed. Risk analyses for IVC and progressive collapse were done along the related factors and medication type.

RESULTS

IVC sign was observed in 30 patients. The rate of IVC sign was lower in group III (7.4%) than that in group I (20.5%) or group II (30.3%), although the difference was not statistically significant. Moreover, the degree of NRS improvement was better in group III than that in group I or group II (5.7 vs. 3.1 vs. 3.5, p < 0.001). On multiple regression analysis, mid-portion type fracture in MR classification was a significant risk factor for progressive OSFs. The use of PTH showed significant lower incidences of occurrence of IVC (odds ratio (OR) = 0.160) and increase in height loss (OR = 0.325).

CONCLUSIONS

Different anti-osteoporosis medications presented different clinical and radiological results after acute OSFs. The use of anabolic agent significantly enhanced fracture healing, reduced progressive collapse, and presented better clinical outcomes. Proper selection of medication might improve initial management of acute OSFs.

Tanshinone IIA exerts beneficial effects on fracture healing in vitro and in vivo

BACKGROUND

Fracture healing is a very important process after fracture. Tanshinone IIA (Tan IIA) has been reported to possess beneficial impact on osteoblasts growth. Our study investigated the effects of Tan IIA on fracture healing.

METHODS

In vitro, mouse pre-osteoblast MC3T3-E1 cells were treated with Tan IIA. Then, the protein levels of Runx2, Osx, Collagen I, JNK and c-Jun, alkaline phosphatase (ALP) activity and calcium deposition were detected, respectively. Furthermore, the roles of microRNA-424 (miR-424) and Bone morphogenetic protein 2 (BMP-2) in Tan IIA-caused MC3T3-E1 cell differentiation were probed. In vivo, mice open osteotomy at femur diaphysis model was established. The callus area, callus intensity, low-density bone volume/callus total volume (BV1/TV), tissue mineral density (TMD) and bone mineral density (BMD) were tested.

RESULTS

In vitro, Tan IIA promoted MC3T3-E1 cell differentiation via increasing the Runx2, Osx and collagen I expression, along with enhancing ALP activity and calcium deposition. In addition, Tan IIA activated JNK pathway in MC3T3-E1 cells, while inhibition of JNK pathway mitigated the Tan IIA-caused MC3T3-E1 cell differentiation. Moreover, Tan IIA declined the miR-424 expression in MC3T3-E1 cells. Overexpression of miR-424 also weakened the Tan IIA-caused MC3T3-E1 cell differentiation. BMP-2 was a target gene of miR-424. BMP-2 silence reversed the Tan IIA-caused activation of JNK pathway. In vivo, Tan IIA increased the callus area, callus intensity, BV1/TV, TMD and BMD.

CONCLUSION

Tan IIA could promote fracture healing. In vitro, Tan IIA promoted MC3T3-E1 cell differentiation might be via down-regulating miR-424, up-regulating BMP-2 and then activating JNK pathway.

Effect of bone sialoprotein coating on progression of bone formation in a femoral defect model in rats

PURPOSE

In orthopedic and trauma surgery, calcium phosphate cement (CPC) scaffolds are widely used as substitute for autologous bone grafts. The purpose of this study was to evaluate bone formation in a femoral condyle defect model in rats after scaffold-coating with bioactive bone sialoprotein (BSP). Our hypothesis was that BSP-coating results in additional bone formation.

METHODS

In 20 Wistar rats, defects of 3.0 mm diameter were drilled into the lateral femoral condyles of both legs. BSP-coated scaffolds or uncoated control scaffolds were implanted into the defects. After 4 and 8 weeks, five rats of each group were euthanized, respectively. µCT scans and histological analyses were performed. The ratio of bone volume-total volume (BV/TV) was analyzed and histological sections were evaluated.

RESULTS

At week four, bone fraction reached 5.2 ± 1.7% in BSP-coated scaffolds and 4.5 ± 3.2% in the control (p = 0.06). While bone fraction of the BSP-group did not change much between week four and eight [week eight: 5.4 ± 3.8% (p = 0.53)], there was a tendency towards an increase in the control [week eight: 7.0 ± 2.2% (p = 0.08)]. No significant difference in bone fraction were observable between BSP-coated and uncoated scaffolds at week eight (p = 0.08).

CONCLUSIONS

A significant superiority of BSP-coated scaffolds over uncoated scaffolds could not be proven. However, BSP-coating showed a tendency towards improving bone ingrowth in the scaffolds 4 weeks after implantation. This effect was only short-lived: bone growth in the control scaffolds tended to outpace that of the BSP-group at week eight.

Extract and fraction of Cassia occidentalis L. (a synonym of Senna occidentalis) have osteogenic effect and prevent glucocorticoid-induced osteopenia

ETHNOPHARMACOLOGICAL RELEVANCE

Cassia occidentalis L., a synonym of Senna occidentalis (belongs to Caesalpiniaceae family) is an annual plant. Pursuing a lead from a folk practice prevalent since the late nineteenth century in Andhra Pradesh, a Southern state of India, of use of Cassia occidentalis leaf and stem for treating patients with fracture and bone diseases, we have not only confirmed its fracture healing activity but also demonstrated efficacy in preventing glucocorticoid-induced osteoporosis (GIO), the commonest form of medication-induced bone loss caused chiefly due to impairment of bone formation.

AIM OF THE STUDY

In the present work, the effects of extract and fraction of leaf and stem of Cassia occidentalis was investigated in fracture healing and GIO models of rat. The study also aimed to identify osteogenic compounds from this plant.

MATERIALS AND METHODS

Ethanolic extracts from leaf and stem of Cassia occidentalis were prepared and their efficacy tested in rat femur osteotomy (fracture healing) model. Subsequently, a butanolic fraction was prepared and osteogenic efficacy compared with the ethanolic extract, and upon finding the former to be more potent, its osteogenic effect was studied in details in GIO model. Chemical finger-printing and isolation of ten pure compounds were done to assess their osteogenic effect in rat primary osteoblast cultures.

RESULTS

Ethanolic extract of stem was more effective than the leaf extract in enhancing bone regeneration at the site of osteotomy. Further, butanolic fraction of the ethanolic extract of stem was more effective than the later in bone regeneration at the femur osteotomy site and in preventing bone loss in GIO model. The mechanism of skeletal preservation involved stimulation of new bone formation and inhibition of bone resorption. As many as six osteogenic compounds were isolated out of which apigenin-6C-glucopyranoside was most effective in vitro.

CONCLUSION

Our study found that a standardized extract of an ethanolic extract and its butanolic fraction from the stem of Cassia occidentalis has osteogenic as well as anti-resorptive effects, resulting in the protection against glucocorticoid-induced bone loss. Our results contribute towards validation of the traditional use of Cassia occidentalis in fracture healing and also suggest its beneficial use in GIO for which clinical trials are warranted.

GIT1 is critical for formation of the CD31hiEmcnhi vessel subtype in coupling osteogenesis with angiogenesis via modulating preosteoclasts secretion of PDGF-BB

G protein-coupled receptor kinase 2 interacting protein-1 (GIT1) is a scaffold protein that plays a vital role in bone modeling and remodeling during osteogenesis coupled with angiogenesis. Recent studies have shown that a specialized subset of vascular endothelium strongly positive for CD31 and Endomucin (CD31^hiEmcn^hi) is coupled with anabolic bone formation. Based on our previous finding that GIT1 knockout (GIT1 KO) mice have impaired angiogenesis and bone formation, we hypothesized that GIT1 affects formation of the CD31^hiEmcn^hi vessel subtype. In the current study, GIT1 knockout (GIT1 KO) mice displayed a significant decrease in trabecular bone mass and CD31^hiEmcn^hi vessel number, compared to their wild-type counterparts. In the fracture healing mouse model, GIT1 KO mice contained a lower number of CD31^hiEmcn^hi vessels in fracture callus at days 7 and 14. However, no significant differences in the number of preosteoclasts in bone marrow, trabecular bone and callus in GIT1 KO mice were observed, compared with wild-type mice. Notably, concentrations of serum platelet-derived growth factor-BB(PDGF-BB) secreted by preosteoclasts associated with CD31^hiEmcn^hi vessel formation were lower in GIT1 KO mice. In addition, PDGF-BB-associated expression of phosphorylated extracellular signal-regulated kinase- 1/2 (ERK1/2) and specificity protein 1 (SP1) was significantly decreased in preosteoclasts of GIT1 KO mice. These results collectively suggest that GIT1 is a critical participant in formation of the CD31^hiEmcn^hi vessel subtype, highlighting a novel biologic function of this scaffold protein in preosteoclasts.

Hypoxia and mesenchymal stromal cells as key drivers of initial fracture healing in an equine in vitro fracture hematoma model

Fractures in horses–whether simple fractures with just one clean break, or incomplete greenstick with stress fractures, or complications such as shattered bones can all be either minimal or even catastrophic. Thus, improvement in fracture healing is a hallmark in equine orthopedics. The fracture healing process implements a complex sequence of events including the initial inflammatory phase removing damaged tissue, re-establishment of vessels and mesenchymal stromal cells, a soft and hard callus phase closing the fracture gap as well as the remodeling phase shaping the bone to a scar-free tissue. Detailed knowledge on processes in equine fracture healing in general and on the initial phase in particular is apparently very limited. Therefore, we generated equine in vitro fracture hematoma models (FH models) to study time-dependent changes in cell composition and RNA-expression for the most prominent cells in the FH model (immune cells, mesenchymal stromal cells) under conditions most closely adapted to the in vivo situation (hypoxia) by using flow cytometry and qPCR. In order to analyze the impact of mesenchymal stromal cells in greater detail, we also incubated blood clots without the addition of mesenchymal stromal cells under the same conditions as a control. We observed a superior survival capacity of mesenchymal stromal cells over immune cells within our FH model maintained under hypoxia. Furthermore, we demonstrate an upregulation of relevant angiogenic, osteogenic and hypoxia-induced markers within 48 h, a time well-known to be crucial for proper fracture healing.

Assessment of fracture healing properties of lovastatin loaded nanoparticles: preclinical study in rat model

Bone fracture, being mainly caused by mechanical stress, requires special and quick attention for a rapid healing. The study presented here aims at formulating nanoparticulate system to overcome the solubility issues of lovastatin. The lovastatin nanoparticles were successfully prepared by ionotropic gelation method using chitosan and tri-polyphosphate as polymers. Thus prepared nanoparticles were found to be smooth and spherical with average particle size of 87 nm and encapsulation efficiency of 86.5%. The in-vitro drug release was found to be almost 89.6% in the first 360 minutes. Artificial fracture was produced in female Wistar rats at right leg using fracture apparatus. After administration of lovastatin nanoparticles or saline solution, the respective groups were observed for various parameters. The X-ray imaging showed that lovastatin accelerated bone healing, compared to control. The growth of animals was not hampered by lovastatin by any means. The radiographic examination confirmed a role of lovastatin in increasing bone density. The histological study showed the broken, proliferated and discontinued trabecullae in the control, while at the same time point, the normal, thick, continuous and connected trabecullae were observed in animals administered with lovastatin nanoparticles. The biomechanical studies showed high breaking resilience and minimum bone brittleness in animals injected with lovastatin nanoparticles. Considering these observations we state that lovastatin helps in rapid bone healing after fracture via increasing the bone density.