Fracture Repair Process Research Articles

A GCaMP reporter mouse with chondrocyte specific expression of a green fluorescent calcium indicator

One of the major processes occurring during the healing of a fractured long bone is chondrogenesis, leading to the formation of the soft callus, which subsequently undergoes endochondral ossification and ultimately bridges the fracture site. Thus, understanding the molecular mechanisms of chondrogenesis can enhance our knowledge of the fracture repair process. One such molecular process is calciun (Ca++) signaling, which is known to play a critical role in the development and regeneration of multiple tissues, including bone, in response to external stimuli. Despite the existence of various mouse models for studying Ca++ signaling, none of them were designed to specifically examine the skeletal system or the various musculoskeletal cell types. As such, we generated a genetically engineered mouse model that is specific to cartilage (crossed with Col2a1 Cre mice) to study chondrocytes. Herein, we report on the characterization of this transgenic mouse line using conditional expression of GCaMP6f, a Ca++-indicator protein. Specifically, this mouse line exhibits increased GCaMP6f fluorescence following Ca++ binding in chondrocytes. Using this model, we show real-time Ca++ signaling in embryos, newborn and adult mice, as well as in fracture calluses. Further, robust expression of GCaMP6f in chondrocytes can be easily detected in embryos, neonates, adults, and fracture callus tissue sections. Finally, we also report on Ca++ signaling pathway gene expression, as well as real-time Ca++ transient measurements in fracture callus chondrocytes. Taken together, these mice provide a new experimental tool to study chondrocyte-specific Ca++ signaling during skeletal development and regeneration, as well as various in vitro perturbations.

5-Lipoxygenase: The Therapeutically Unexplored Target for Bone Health

Bone fracture is a common orthopedic condition that represents a significant health concern. Bone fracture repair process is a complex process that involves the harmonic and synchronized activity of bone cells. 5-lipoxygenase (5-LOX) is an enzyme responsible for the conversion of arachidonic acid to form leukotrienes. While leukotrienes have an empirical inflammatory role, various evidence suggests that these 5-LOX mediators, by switching the inflammatory environment and altering the activity of bone cells, have a detrimental effect on the bone fracture healing process. Additionally, various evidence suggests that 5-LOX inhibition shows improvement in the overall bone healing process and improves overall bone health. Despite this evidence, the clinical use of 5-LOX inhibitors in bone fracture healing is largely unexplored. The current review aimed to summarize the available evidences and pave the way for future large scale pre-clinical and clinical studies to evaluate the effectiveness of selective 5-LOX inhibitors in bone fracture healing. A comprehensive literature search was conducted in PubMed, Google Scholar, and ScienceDirect to identify relevant articles related to the effect of 5-LOX in bone health. The summary of available scientific evidence highlights that the selective 5-LOX inhibition can modulate the functioning of osteoclasts and osteoblasts, favoring faster bone fracture healing. The observations of this study support the selective 5-LOX inhibition as a potential treatment option that can improve bone fracture healing rate and therefore future clinical studies can be designed to confirm the observations of the current review study.

Dnmt3b ablation affects fracture repair process by regulating apoptosis

PurposePrevious studies have shown that DNA methyltransferase 3b (Dnmt3b) is the only Dnmt responsive to fracture repair and Dnmt3b ablation in Prx1-positive stem cells and chondrocyte cells both delayed fracture repair. Our study aims to explore the influence of Dnmt3b ablation in Gli1-positive stem cells in fracture healing mice and the underlying mechanism.MethodsWe generated Gli1-CreERT2; Dnmt3bflox/flox (Dnmt3bGli1ER) mice to operated tibia fracture. Fracture callus tissues of Dnmt3bGli1ER mice and control mice were collected and analyzed by X-ray, micro-CT, biomechanical testing, histopathology and TUNEL assay.ResultsThe cartilaginous callus significantly decrease in ablation of Dnmt3b in Gli1-positive stem cells during fracture repair. The chondrogenic and osteogenic indicators (Sox9 and Runx2) in the fracture healing tissues in Dnmt3bGli1ER mice much less than control mice. Dnmt3bGli1ER mice led to delayed bone callus remodeling and decreased biomechanical properties of the newly formed bone during fracture repair. Both the expressions of Caspase-3 and Caspase-8 were upregulated in Dnmt3bGli1ER mice as well as the expressions of BCL-2.ConclusionsOur study provides an evidence that Dnmt3b ablation Gli1-positive stem cells can affect fracture healing and lead to poor fracture healing by regulating apoptosis to decrease chondrocyte hypertrophic maturation.

Techniques, mechanisms, and application of 3D-printed biodegradable metals for bone regeneration

Repairing severe bone defects and restoring complete bone tissue morphology are major challenges in clinical practice. Biodegradable metals (BMs) are bioactive materials with active degradation properties. The gradual improvement of three-dimensional (3D) printing technology holds tremendous potential for development and has spurred on the growing utilization of 3D-printed BM materials in the clinical applications of bone regeneration. In this paper, we review the application of three BM (magnesium, iron, and zinc) materials for use in 3D-printed bone regeneration; define the principle of 3D-printed bone regeneration, including the method and selection of materials; and summarize the characteristics and uses of various printing technologies and the properties, advantages, and disadvantages of BMs. Compared to traditional nondegradable implants, 3D-printed degradable metal implants have the advantages of not leaving residue, avoiding stress shielding, promoting osteogenesis and vascularization, and exhibiting antimicrobial ability. In addition, we summarize the clinical applications of 3D-printed BMs. 3D-printed BMs can be used not only for fracture fixation and bone defect repair but also for osteoporotic fracture repair, cartilage repair, maxillofacial surgery, and other processes. In this article, we discuss the advantages and limitations of the current 3D printing degradable metallic materials and describe future development prospects.

Albumin-Coated Polycaprolactone (PCL)-Decellularized Extracellular Matrix (dECM) Scaffold for Bone Regeneration.

With the emphasis on collagen and hydroxyapatite, the main structural components of bone tissue, synthetic grafts fall short of matching the clinical efficacy of autologous bone grafts. Excluded non-collagenous protein (NCPs) and carbohydrates also participate in critical cell signaling cascades and guide mineral deposition during intermediate stages of bone healing. By mimicking the native fracture repair process, polymeric scaffolds that incorporate calcium-binding moieties present in fibrocartilage can potentially enhance their bioactivity, mineralization, and bone growth. Likewise, coating polymeric fibers with serum albumin is an additional strategy that can impart collagen-like biofunctionality and further increase mineral deposition on the fibrous surface. Here, a combination of electrospun polycaprolactone (PCL) fibers with chondrocyte-derived decellularized extracellular matrix (dECM) and albumin coating were investigated as a fibrocartilage-mimetic scaffold that can serve as a woven bone precursor for bone regeneration. PCL fibrous constructs coated with dECM and albumin are shown to synergistically increase calcium concentration and calcium phosphate (CaP) deposition in a simulated body fluid biomineralization assay. Albumin/dECM coating increased osteoblast proliferation and mineral deposition in culture. In contrast, CaP coating transformed osteoblast bone lining morphology into cuboidal phenotype and arrested their proliferation. Cell sheets of osteoblasts cultured on dECM/albumin/CaP-coated constructs exhibited an increase in calcium deposition and secretion of collagen, osteopontin, osteocalcin, and bone morphogenetic protein. These results highlight the potential of biomolecular coatings to enhance bone-mimetic properties of synthetic nanofibrous scaffolds, stimulate critical protein and mineral deposition, and augment the bone's capacity to heal. Thus, mimicking the intermediate stages of bone regeneration by incorporating calcium-binding moieties may prove to be a useful strategy for improving the clinical outcomes of synthetic bone grafts.

Therapeutic Ultrasound Halts Progression of Chronic Kidney Disease In Vivo via the Regulation of Markers Associated with Renal Epithelial-Mesenchymal Transition and Senescence.

Low-intensity pulsed ultrasound (LIPUS), a therapeutic type of ultrasound, is known to enhance bone fracture repair processes and help some tissues to heal. Here, we investigated the therapeutic potential of LIPUS for the treatment of chronic kidney disease (CKD) in two CKD mouse models. CKD mice were induced using both unilateral renal ischemia/reperfusion injury (IRI) with nephrectomy and adenine administration. The left kidneys of the CKD mice were treated using LIPUS with the parameters of 3 MHz, 100 mW/cm2, and 20 min/day, based on the preliminary experiments. The mice were euthanized 14 days after IRI or 28 days after the end of adenine administration. LIPUS treatment effectively alleviated the decreases in the body weight and albumin/globulin ratio and the increases in the serum renal functional markers, fibroblast growth factor-23, renal pathological changes, and renal fibrosis in the CKD mice. The parameters for epithelial-mesenchymal transition (EMT), senescence-related signal induction, and the inhibition of α-Klotho and endogenous antioxidant enzyme protein expression in the kidneys of the CKD mice were also significantly alleviated by LIPUS. These results suggest that LIPUS treatment reduces CKD progression through the inhibition of EMT and senescence-related signals. The application of LIPUS may be an alternative non-invasive therapeutic intervention for CKD therapy.

Enhancing fracture repair: cell-based approaches.

Fracture repair is based both on the macrolevel modulation of fracture fragments and the subsequent cellular activity. Surgeons have also long recognized other influences on cellular behavior: the effect of the fracture or subsequent surgery on the available pool of cells present locally in the periosteum, the interrelated effects of fragment displacement, and construct stiffness on healing potential, patient pathophysiology and systemic disease conditions (such as diabetes), and external regulators of the skeletal repair (such as smoking or effect of medications). A wide variety of approaches have been applied to enhancing fracture repair by manipulation of cellular biology. Many of these approaches reflect our growing understanding of the cellular physiology that underlies skeletal regeneration. This review focuses on approaches to manipulating cell lineages, influencing paracrine and autocrine cell signaling, or applying other strategies to influence cell surface receptors and subsequent behavior. Scientists continue to evolve new approaches to pharmacologically enhancing the fracture repair process.

Systemic Administration of Recombinant Irisin Accelerates Fracture Healing in Mice.

To date, pharmacological strategies designed to accelerate bone fracture healing are lacking. We subjected 8-week-old C57BL/6 male mice to closed, transverse, mid-diaphyseal tibial fractures and treated them with intraperitoneal injection of a vehicle or r-irisin (100 µg/kg/weekly) immediately following fracture for 10 days or 28 days. Histological analysis of the cartilaginous callus at 10 days showed a threefold increase in Collagen Type X (p = 0.0012) and a reduced content of proteoglycans (40%; p = 0.0018). Osteoclast count within the callus showed a 2.4-fold increase compared with untreated mice (p = 0.026), indicating a more advanced stage of endochondral ossification of the callus during the early stage of fracture repair. Further evidence that irisin induced the transition of cartilage callus into bony callus was provided by a twofold reduction in the expression of SOX9 (p = 0.0058) and a 2.2-fold increase in RUNX2 (p = 0.0137). Twenty-eight days post-fracture, microCT analyses showed that total callus volume and bone volume were increased by 68% (p = 0.0003) and 67% (p = 0.0093), respectively, and bone mineral content was 74% higher (p = 0.0012) in irisin-treated mice than in controls. Our findings suggest that irisin promotes bone formation in the bony callus and accelerates the fracture repair process, suggesting a possible use as a novel pharmacologic modulator of fracture healing.

Low-intensity pulsed ultrasound (LIPUS) for stimulation of bone healing - A narrative review.

The use of low intensity pulsed ultrasound (LIPUS) to accelerate the fracture repair process in humans was first reported by Xavier & Duarte in 1983 [1]. This success led to clinical trials and the 1994 approval of LIPUS in the United States for the accelerated healing of certain fresh fractures. LIPUS was approved in the US for the treatment of established non-unions in 2000, and is also approved around the world. In this article, we present relevant literature on the effect of LIPUS on bone healing in patients with acute fractures and non-unions and provide a molecular explanation for the effects of LIPUS on bone healing. Data on LIPUS accelerated fracture repair is controversial with many controlled studies showing a positive effect. However, the largest trial in acute tibial fractures stabilized with an intramedullary nail failed to show significant differences in accelerated healing and in functional outcomes. Uncontrolled data from prospective case series suggest a positive effect of LIPUS in non united fractures with healing rates of around 85%. Evaluation of results from studies, both positive and negative, has enabled an understanding that the patient population with potentially the greatest benefit from receiving LIPUS are those at-risk for fracture healing, e.g. diabetic & elderly patients. The elucidation of a pathway to activate the Rac-1 pathway by LIPUS might explain this beneficial effect. Overall, there is a strong need for further clinical trials, particularly for acute fractures at risk of progressing to non-union and in established non-unions including a comparison to the current standard of care.

Effect of ovariectomy induced osteoporosis on metaphysis and diaphysis repair process.

The fracture repair process is known to be delayed in postmenopausal women, under estrogen-deficient status. Osteoporotic fracture mainly occurs in the metaphyseal region of the long bone; however, most studies on fracture healing have focused on the diaphyseal region. In this study, we compared the repair process between metaphysis and diaphysis of ovariectomized (OVX) and Sham mice, and analyzed the effects of short-term estrogen administration in OVX mice. Mice were divided into four experimental groups, including Sham, OVX, OVX+vehicle, and OVX+17β-estradiol (E2). Bone apertures were formed in the tibial metaphysis and diaphysis. The samples were collected and examined by micro-computed tomography, and using histological, histochemical, and immunohistochemical analysis at different time points after the surgery. The cartilaginous callus was formed at the diaphysis site of both the groups, which was sequentially replaced by bone on the periosteum side. Medullary callus was formed in all the groups; however, the volume of the callus in OVX mice was significantly lesser (˜30%) than that in Sham mice. Furthermore, in the metaphysis, no differences were observed in the medullary callus and bone mineral density between the two groups from day 21 to 28. The diaphysis of OVX group was not completely repaired even by day 28. In both the sites of OVX mice, ALP activity and disappearance of Gr-1 positive cells were delayed compared to that of Sham. Estrogen administration improved medullary callus formation in the diaphysis, however not in the metaphysis. The effect of ovariectomy on the repair process in diaphysis was greater than that in metaphysis. Our findings clarify the differences between the metaphysis and diaphysis repair process using OVX mouse model and suggest that the estrogen sensitivities differ between the sites during the bone repair process.

Low-intensity pulsed ultrasound is frequently used to treat fractures after osteosynthesis in elderly patients: A study using open data from the national database of health insurance claims of Japan

BackgroundThe national database of health insurance claims of Japan (NDB) includes almost all health insurance claims in Japan. Currently, we have many cases of geriatric fracture in Japan, probably due to an increase of the elderly population. The increase of geriatric fractures may influence the use of low-intensity pulsed ultrasound (LIPUS), which is used to accelerate the fracture repair process. The present state of LIPUS treatments was analyzed using the large dataset of the NDB. MethodsThe open data from the NDB that were used included receipts from April 2015 to March 2016. The total numbers of fracture treatments were counted as the sum of the claim items that were involved in fracture treatments. Two types of the insurance claim items for LIPUS treatments were counted separately: those used for delayed or non-union fractures; and those used for fractures within two weeks after osteosynthesis. Additionally, the ratio of the LIPUS treatments per the fracture treatments was calculated. ResultsIn female patients, the number of LIPUS treatments for fractures early after osteosynthesis showed a large peak in the senile generation. Additionally, the ratio of LIPUS treatments early after osteosynthesis to all osteosynthesis treatments tended to increase with age in both males and females, while the ratio of the LIPUS treatments for delayed or non-union fractures to all fracture treatments decreased with age. ConclusionsLIPUS treatments were frequently used to treat fractures early after osteosynthesis in elderly patients, probably due to the large number of fractures in the elderly population. Additionally, the ratio of LIPUS treatments early after osteosynthesis was high in both elderly female and elderly male patients, suggesting that there is a demand for early fracture repair.

The role of mechanical stimulation in the enhancement of bone healing.

The biomechanical environment plays a dominant role in the process of fracture repair. Mechanical signals control biological activities at the fracture site, regulate the formation and proliferation of different cell types, and are responsible for the formation of connective tissues and the consolidation of the fractured bone. The mechanobiology at the fracture site can be easily manipulated by the design and configuration of the fracture fixation construct and by the loading of the extremity (weight-bearing prescription). Depending on the choice of fracture fixation, the healing response can be directed towards direct healing or towards indirect healing through callus formation. This manuscript summarizes the evidence from experimental studies and clinical observations on the effect of mechanical manipulation on the healing response. Parameters like fracture gap size, interfragmentary movement, interfragmentary strain, and axial and shear deformation will be explored with respect to their respective effects on fracture repair. Also, the role of externally applied movement on the potential enhancement on the fracture repair process will be explored. Factors like fracture gap size, type and amplitude of the mechanical deformation as well as the loading history and its timing will be discussed.

CDllb+ targeted depletion of macrophages negatively affects bone fracture healing

Inflammation is an important part of the fracture repair process which requires osteogenic cells to interact with innate immune cells such as macrophages. All murine macrophages express the F4/80 cell surface marker but they may be further subdivided into two main phenotypes: M1 (proinflammatory) or M2 (anti-inflammatory) based on surface marker expression and function. Macrophages polarize between these two main classes in response to inflammation while differentially regulating the healing process. Studies have shown that F4/80+ cell ablation impairs fracture healing, however, the distinct phenotypes that participate in the early healing process is unclear. We hypothesized that the M1 subtype is essential for the early steps of fracture healing and their depletion would impair fracture repair. To test this hypothesis, M1 (F4/80+/MHCII+/CD86+/CDllb+) macrophages were depleted using a saporin conjugated Mac-1 antibody (Mac1SAP) in vitro using primary macrophages and in vivo using a mouse femur fracture model. Primary macrophages isolated from mice femoral bone marrow were either left undifferentiated (+PBS), differentiated into M1 macrophages (+LPS), or differentiated to M2 macrophages (+IL-4), and then treated with either vehicle or 10 pM Mac1SAP. Samples were collected at day 2 and 5 post Mac1SAP treatment. Macrophage subtypes were identified by flow cytometry and cytokine secretion profiles were quantified using xMAP. For the in vivo model, mice were treated with Mac1SAP 24h prior to fracture. Femur bone marrow samples were collected and analyzed by flow cytometry, xMAP, immunohistochemistry, MicroCT, and histology. The results demonstrated that Mac1SAP significantly depleted M1 macrophages both in vivo and in vitro. Mac1SAP treatment altered expression of 75% of cytokines in vitro and 30% of cytokines in vivo including IL-6, TNF-a, and IP-10. In both the in vitro and in vivo models, the M1 subtype correlated highly with cytokines G-CSF, IL-1α, IL-6, IL-10, LIX, KC, MCP-1, IP-10, MIP1α, MIP1β, RANTES, IL-9, IL-2 and TNFα. M1 depletion was also found to reduced callus properties at day 14 via microCT analysis. Overall, the data suggests that depletion of M1 macrophages by Mac1SAP treatment alters the cytokine expression profiles during early bone repair which ultimately impairs bone healing.

Identification of antemortem, perimortem and postmortem fractures by FTIR spectroscopy based on a rabbit tibial fracture model.

The identification of antemortem, perimortem and postmortem fractures is very important for forensic pathologists and anthropologists. However, traditional methods are subjective, time-consuming, and have low accuracy, which do not fundamentally solve the problem. In this study, we utilized Fourier transform infrared (FTIR) spectroscopy and chemometrics to identify antemortem, perimortem and postmortem fractures in a rabbit tibial fracture model. Based on the results of the principal component analysis (PCA), changes in the ante-perimortem fracture repair process are mainly associated with protein variations, while postmortem fractures are more likely to result in lipid changes during degradation. Then, a partial least squares discriminant analysis (PLS-DA) was performed to assess the classification ability of the training and predictive datasets, with classification accuracies of 88.9% and 86.7%, respectively. According to the latent variable 1 (LV1) loading plot, amide I and amide II (proteins) are mostly classified as ante-perimortem and postmortem fractures. In conclusion, FTIR spectroscopy is a reliable tool to identify antemortem, perimortem and postmortem fractures. FTIR has the advantages of rapid, objective and strong discrimination. and shows great potential for analyzing forensic cases under actual natural conditions.

Conditional knockout of ephrinB1 in osteogenic progenitors delays the process of endochondral ossification during fracture repair.

The Eph receptor tyrosine kinase ligand, ephrinB1 (EfnB1) is important for correct skeletal and cartilage development, however, the role of EfnB1 in fracture repair is unknown. This study investigated the role of EfnB1 during fracture repair where EfnB1 expression increased significantly at 1 and 2weeks post fracture in C57Bl/6 wildtype mice, coinciding with the haematoma, soft callus formation/remodelling stages, respectively. To investigate the specific role of EfnB1 within the osteogenic lineage during fracture repair, male mice with a conditional deletion of EfnB1 in the osteogenic lineage (EfnB1OBfl/O), driven by the Osterix (Osx) promoter, and their male Osx:Cre counterparts were subject to a femoral fracture with internal fixation. Two weeks post fracture micro computed tomography (μCT) analysis revealed that EfnB1OBfl/O mice displayed a significant decrease in bone volume relative to tissue volume within the fracture callus. This was attributed to an alteration in the distribution of osteoclasts within the fracture site, a significant elevation in cartilaginous tissue and reduction in the osteoprogenitor population and calcein labelled bone within the fracture site of EfnB1OBfl/O mice. Supportive in vitro studies demonstrated that under osteogenic conditions, cultured EfnB1OBfl/O stromal cells derived from the 2week fracture site exhibited a reduced capacity to produce mineral and decreased expression of the osteogenic gene, Osterix, when compared to Osx:Cre controls. These findings suggest that the loss of EfnB1 delays the fracture repair process. The present study confirmed that EFNB1 activation in human BMSC, following stimulation with soluble-EphB2 resulted in de-phosphorylation of TAZ, demonstrating similarities in EfnB1 signalling between human and mouse stromal populations. Overall, the present study provides evidence that loss of EfnB1 in the osteo/chondrogenic lineages delays the soft callus formation/remodelling stages of the fracture repair process.

Effects of the duration of transcutaneous CO2 application on the facilitatory effect in rat fracture repair

BackgroundCarbon dioxide therapy has been reported to be effective in treating certain cardiac diseases and skin problems. Although a previous study suggested that transcutaneous carbon dioxide application accelerated fracture repair in association with promotion of angiogenesis, blood flow, and endochondral ossification, the influence of the duration of carbon dioxide application on fracture repair is unknown. The aim of this study was to investigate the effect of the duration of transcutaneous carbon dioxide application on rat fracture repair. MethodsA closed femoral shaft fracture was created in each rat. Animals were randomly divided into four groups: the control group; 1w-CO2 group, postoperative carbon dioxide treatment for 1 week; 2w-CO2 group, postoperative carbon dioxide treatment for 2 weeks; 3w-CO2 group, postoperative carbon dioxide treatment for 3 weeks. Transcutaneous carbon dioxide application was performed five times a week in the carbon dioxide groups. Sham treatment, where the carbon dioxide was replaced with air, was performed for the control group. Radiographic, histological, and biomechanical assessments were performed at 3 weeks after fracture. ResultsThe fracture union rate was significantly higher in the 3w-CO2 group than in the control group (p < 0.05). Histological assessment revealed promotion of endochondral ossification in the 3w-CO2 group than in the control group. In the biomechanical assessment, all evaluation items related to bone strength were significantly higher in the 3w-CO2 group than in the control group (p < 0.05). ConclusionsThe present study, conducted using an animal model, demonstrated that continuous carbon dioxide application throughout the process of fracture repair was effective in enhancing fracture healing.

Clinical pathologies of bone fracture modelled in zebrafish.

ABSTRACTReduced bone quality or mineral density predict susceptibility to fracture and also attenuate subsequent repair. Bone regrowth is also compromised by bacterial infection, which exacerbates fracture site inflammation. Because of the cellular complexity of fracture repair, as well as genetic and environmental influences, there is a need for models that permit visualisation of the fracture repair process under clinically relevant conditions. To characterise the process of fracture repair in zebrafish, we employed a crush fracture of fin rays, coupled with histological and transgenic labelling of cellular responses; the results demonstrate a strong similarity to the phased response in humans. We applied our analysis to a zebrafish model of osteogenesis imperfecta (OI), which shows reduced bone quality, spontaneous fractures and propensity for non-unions. We found deficiencies in the formation of a bone callus during fracture repair in our OI model and showed that clinically employed antiresorptive bisphosphonates can reduce spontaneous fractures in OI fish and also measurably reduce fracture callus remodelling in wild-type fish. The csf1ra mutant, which has reduced osteoclast numbers, also showed reduced callus remodelling. Exposure to excessive bisphosphonate, however, disrupted callus repair. Intriguingly, neutrophils initially colonised the fracture site, but were later completely excluded. However, when fractures were infected with Staphylococcus aureus, neutrophils were retained and compromised repair. This work elevates the zebrafish bone fracture model and indicates its utility in assessing conditions of relevance to an orthopaedic setting with medium throughput.This article has an associated First Person interview with the first author of the paper.

The Therapeutic Potential of MicroRNAs as Orthobiologics for Skeletal Fractures.

The repair of a fractured bone is critical to the well-being of humans. Failure of the repair process to proceed normally can lead to complicated fractures, exemplified by either a delay in union or a complete nonunion. Both of these conditions lead to pain, the possibility of additional surgery, and impairment of life quality. Additionally, work productivity decreases, income is reduced, and treatment costs increase, resulting in financial hardship. Thus, developing effective treatments for these difficult fractures or even accelerating the normal physiological repair process is warranted. Accumulating evidence shows that microRNAs (miRNAs), small noncoding RNAs, can serve as key regulatory molecules of fracture repair. In this review, a brief description of the fracture repair process and miRNA biogenesis is presented, as well as a summary of our current knowledge of the involvement of miRNAs in physiological fracture repair, osteoporotic fractures, and bone defect healing. Further, miRNA polymorphisms associated with fractures, miRNA presence in exosomes, and miRNAs as potential therapeutic orthobiologics are also discussed. This is a timely review as several miRNA-based therapeutics have recently entered clinical trials for nonskeletal applications and thus it is incumbent upon bone researchers to explore whether miRNAs can become the next class of orthobiologics for the treatment of skeletal fractures.

Therapeutic effectiveness of Hydroxyapatite Nanoparticles and Pulsed Electromagnetic Field in Osteoporosis and Cancer

The emergence of nanotechnology has had a profound effect on many areas of healthcare and scientific research. Several studies reported the importance Hydroxyapetite Nanoparticles in the biomedical field in general, and in emerging areas such as implants, drug delivery, cancer, composites, coatings, and ceramic materials in particular. On the other hand, low level Pulsed electromagnetic field (PEMF) therapy presents several potential advantages including non-invasiveness, safety, highly influential in the fracture repair process, lack of toxicity for non-cancerous cells, and the possibility of being combined with other available therapies. It has also been observed that the combined effect of these two can accelerate the osteognic and anticancer activity in the osteoporotic and carcinoma cell lines respectively. The objective of this review is to provide a broad recount of the applications of PEMFs and Hydroxyapatite nanoparticles in osteoporosis and cancer and to then demonstrate what is further required for enhanced therapeutic outcomes.

Bioengineering application using co-cultured mesenchymal stem cells and preosteoclasts may effectively accelerate fracture healing

Fracture non-union is the most challenging complication following fracture injuries. Despite ongoing improvements in the surgical technique and implant design, the treatment efficacy of fracture non-union is still far from satisfactory and currently there is no optimal solution. Of all of the methods used for the treatment of non-union, bone tissue bioengineering using scaffolds and mesenchymal stem cells (MSCs) is the most widely studied and has emerged as a promising approach to address these challenges. However, there are several critical limitations, such as the low survival rate of MSCs under an inflammatory, ischemic environment. Accumulating studies have demonstrated that preosteoclasts not only play a role in the remodeling of the callus, but also participate in the entire process of fracture repair. The close crosstalk between preosteoclasts and MSCs stimulates the recruitment, proliferation, and differentiation of osteoblasts and improves the osteogenic differentiation of MSCs. With no in vivo study reported thus far, we hypothesize that the administration of preosteoclasts together with MSCs at a certain ratio may effectively accelerate fracture healing and provide a new and promising therapeutic strategy for the clinical management of fracture non-union.