Fracture Healing Process Research Articles

Transcutaneous CO2 application combined with low-intensity pulsed ultrasound accelerates bone fracture healing in rats

BackgroundLow-intensity pulsed ultrasound (LIPUS) is a non-invasive therapy that accelerates fracture healing. As a new treatment method for fracture, we recently reported that the transcutaneous application of CO2 accelerated fracture healing in association with promoting angiogenesis, blood flow, and endochondral ossification. We hypothesized that transcutaneous CO2 application, combined with LIPUS, would promote bone fracture healing more than the single treatment with either of them.MethodsFemoral shaft fractures were produced in 12-week-old rats. Animals were randomly divided into four groups: the combination of CO2 and LIPUS, CO2, LIPUS, and control groups. As the transcutaneous CO2 application, the limb was sealed in a CO2-filled bag after applying hydrogel that promotes CO2 absorption. Transcutaneous CO2 application and LIPUS irradiation were performed for 20 min/day, 5 days/week. At weeks 1, 2, 3, and 4 after the fractures, we assessed the fracture healing process using radiography, histology, immunohistochemistry, real-time PCR, and biomechanical assessment.ResultsThe fracture healing score using radiographs in the combination group was significantly higher than that in the control group at all time points and those in both the LIPUS and CO2 groups at weeks 1, 2, and 4. The degree of bone fracture healing in the histological assessment was significantly higher in the combination group than that in the control group at weeks 2, 3, and 4. In the immunohistochemical assessment, the vascular densities of CD31- and endomucin-positive microvessels in the combination group were significantly higher than those in the control and LIPUS groups at week 2. In the gene expression assessment, significant upregulation of runt-related transcription factor 2 (Runx2) and vascular endothelial growth factor (VEGF) was detected in the combination group compared to the LIPUS and CO2 monotherapy groups. In the biomechanical assessment, the ultimate stress was significantly higher in the combination group than in the LIPUS and CO2 groups.ConclusionThe combination therapy of transcutaneous CO2 application and LIPUS had a superior effect in promoting fracture healing through the promotion of angiogenesis and osteoblast differentiation compared to monotherapy.

Longitudinal weight and plantar pressure distribution while standing after tibial or malleolar fractures in patients with or without fracture union

Fracture healing is usually monitored by clinical impressions and radiographs. Objective and easy methods for assessing fracture healing without radiation would be beneficial. The aim of this study was to analyse whether weight and plantar pressure while standing can be used to monitor healing of tibial or malleolar fractures and whether these parameters can discriminate between patients with and without union. Thirteen patients were longitudinally assessed during each postoperative clinical visit, of whom two developed a nonunion. Eleven matched healthy controls were assessed once. Additionally, five patients already experiencing nonunion were assessed once at the time of their nonunion diagnosis. All participants performed a standing task for ten seconds with pressure-sensing insoles. Greatest improvements were detected throughout the first three months in patients with union. However, six months after surgery, more than half of the parameters were still significantly different from those of the controls. The weight and pressure distributions did not differ between patients with or without union six months after surgery. A standing task can be used to monitor improvements in weight and pressure distribution throughout the healing process of tibial or malleolar fractures, but lacks potential to discriminate between patients with or without fracture union.

Magnesium-Titanium Alloys: A Promising Solution for Biodegradable Biomedical Implants

Magnesium (Mg) has attracted considerable attention as a biodegradable material for medical implants owing to its excellent biocompatibility, mitigating long-term toxicity and stress shielding. Nevertheless, challenges arise from its rapid degradation and low corrosion resistance under physiological conditions. To overcome these challenges, titanium (biocompatibility and corrosion resistance) has been integrated into Mg. The incorporation of titanium significantly improves mechanical and corrosion resistance properties, thereby enhancing performance in biological settings. Mg–Ti alloys are produced through mechanical alloying and spark plasma sintering (SPS). The SPS technique transforms powder mixtures into bulk materials while preserving structural integrity, resulting in enhanced corrosion resistance, particularly Mg80-Ti20 alloy in simulated body fluids. Moreover, Mg–Ti alloy revealed no more toxicity when assessed on pre-osteoblastic cells. Furthermore, the ability of Mg–Ti-based alloy to create composites with polymers such as PLGA (polylactic-co-glycolic acid) widen their biomedical applications by regulating degradation and ensuring pH stability. These alloys promote temporary orthopaedic implants, offering initial load-bearing capacity during the healing process of fractures without requiring a second surgery for removal. To address scalability constraints, further research is necessary to investigate additional consolidation methods beyond SPS. It is essential to evaluate the relationship between corrosion and mechanical loading to confirm their adequacy in physiological environments. This review article highlights the importance of mechanical characterization and corrosion evaluation of Mg–Ti alloys, reinforcing their applicability in fracture fixation and various biomedical implants.

Insufficient Mechanical Loading Downregulates Piezo1 in Chondrocytes and Impairs Fracture Healing Through ApoE-Induced Senescence.

Insufficient mechanical loading impairs fracture healing; however, the underlying mechanisms remain unclear. Increasing evidence indicates that Piezo1 plays an important role in fracture healing, although the effect of Piezo1 on the endochondral ossification of chondrocytes has been overlooked. This study reports that mechanical unloading down-regulates the expression of Piezo1 in chondrocytes and leads to fracture nonunion. Single-cell sequencing of calluses revealed that specific deletion of Piezo1 in chondrocytes upregulated the expression of apolipoprotein E (ApoE) in hypertrophic chondrocytes, resulting in delayed cartilage-to-bone transition due to enhanced chondrocyte senescence. Based on these results, an injectable and thermosensitive hydrogel is developed, which released an ApoE antagonist in situ at the fracture site. This hydrogel effectively attenuated chondrocyte senescence and, thus, promoted cartilage-to-bone transition as well as the fracture healing process. Overall, this data provide a new perspective on the activity of chondrocytes in fracture healing and a new direction for the treatment of fracture nonunion caused by insufficient mechanical loading.

Comparison of the effects of recombinant human epidermal growth factor (rhEGF) and alendronate sodium on tibial fracture healing in rats: an experimental study

Purpose: The objective of this study is to compare the effects of recombinant human epidermal growth factor (rhEGF) on bone healing with those of alendronate, a bisphosphonate widely used in practice. Materials and Methods: An iatrogenic fracture was created in the tibial shaft of 24 Sprague-Dawley rats with osteotome and fixed with an intramedullary Kirschner wire (K-wire). After surgery, Group 1 was given 0.2 mg/kg/day of oral alendronate sodium on postoperative Day 1 to 28, Group 2 received a single dose of 0.5 mg/kg of intraosseous rhEGF on postoperative Days 1 and 14, and Group 3 was followed for a total of four weeks with oral saline. At the end of Week 4, the animals were euthanized and the lower extremities were removed by stripping the soft tissues without damaging the callus. Tissue samples of groups were prepared and and stained with hematoxylin-eosin. After staining, histological scoring was performed to evaluate the degree of union. Results: Alendronate sodium group demonstrated a mean histological score of 6.95± 1.28. The rhEGF group had a lower mean score of 4.85±1.66. The placebo group exhibited the least progress in bone healing with a mean score of 4.10±1.68. The histological score was significantly higher in the alendronate sodium group compared to both the rhEGF and placebo groups. There was also a statistically significant difference between the rhEGF and placebo groups in terms of scores. Conclusion: Alendronate sodium enhanced fracture healing processes in rats. The role of rhEGF in bone healing requires further exploration. As the understanding of bisphosphonates and growth factors in bone healing evolves, the strategies for optimizing patient care in orthopedic settings are expected to be developed.

Utility of ultrasound imaging in monitoring fracture healing in rat femur: Comparison with other imaging modalities

ObjectiveFractures are common injuries and various imaging modalities are employed to diagnose and monitor bone union. However, the follow-up of fracture healing using ultrasound imaging (US) remains a topic of debate. In this study, we analyzed of fracture healing process and compared US and radiological analyses with histological analyses to clarify the characteristics and limitations of each modality. MethodsAn osteotomy model was created using the femur of Wistar rats, and US, radiological (radiography and micro-computed tomography (micro-CT)), and histological analyses were performed. Radiological assessments were conducted for the evaluation of calcified tissue. The gap between the bony callus and cartilaginous callus was measured. ResultsUS effectively captured changes on the fracture surface, potentially reflecting the early healing processes. Both US and radiographic findings showed strong correlation in terms of the decrease in the bony callus gap. US was unable to distinguish cartilaginous callus from the surrounding soft tissue. During the remodeling stage, micro-CT offered a detailed assessment of the internal fracture surface, whereas US was limited to evaluating the outer bone surface and lacked accuracy in visualizing the entire fracture site. Radiography provided a general overview of the fractures. The decrease in the bony callus gap measured using US correlated with the reduction in cartilaginous callus observed histologically. ConclusionThis study demonstrated that US could be a valuable tool for evaluating fracture healing. Combining fracture management with US and radiological examinations may provide a more accurate assessment of healing progress.

How Does the Stress in the Fixation Device Change during Different Stages of Bone Healing in the Treatment of Fractures? A Finite Element Study of External Fixation for Tibial Fractures.

Although the specific relationship between the stress changes in the external fixator during tibial fracture treatment and the bone healing process remains unclear, it is believed that stress variations in the external fixator scaffold can, to a certain extent, reflect the progress of tibial healing. This study aims to propose a non-invasive method for assessing the degree of fracture healing by monitoring the changes in stress transmission, the locations of stress-sensitive points, and displacement in the external fixator-tibia system during the healing process of tibial fractures. In this study, finite element models of tibial fractures at various healing stages were developed. Physiological conditions, including axial, torsional, and bending loads on the tibia, were simulated to evaluate stress and strain within the external scaffold-tibia system under normal physiological loading conditions. The results indicate variations in the stress distribution between the external fixator and the tibia during different stages of healing. In the early phase of fracture healing, the external fixator plays a crucial role as the primary load-bearing unit under all three loading conditions. As the fracture healing progresses, the stress on the tibia gradually increases, concentrating on the medial part of the tibia under axial and torsional loading, and at the upper and lower ends, as well as the central part of the anterior and posterior tibia during bending loading. The stress at the callus gradually increases, while micro-movements decrease. The stress within the external bracket gradually decreases, with a tendency for the connecting rod to transfer stress towards the screws. Throughout the fracture healing process, the location of maximum stress in the external fixator remains unchanged. Under axial and torsional loading, the maximum stress is located at the intersection of the lowest screw and the bone cortex, while under bending loading, it is at the intersection of the second screw and the connecting rod. During the bone healing process, stress is transferred between the external fixation frame and the bone. As bone healing advances, the stress on the connecting rods and screws of the external fixation frame decreases, and the amplitude of stress changes diminishes. When complete and robust fusion is achieved, stress variations stabilize, and the location of maximum stress on the external fixation frame remains unchanged. The intersections of the lowest screw and the bone cortex, as well as the second screw and the connecting rod, can serve as sensitive points for monitoring the degree of bone healing.

Anti-Shortening Screw for the Prevention of Postoperative Shortening in Displaced Femoral Neck Fractures: A Retrospective Cohort Study.

Early femoral neck shortening after femoral neck system (FNS) fixation for displaced femoral neck fractures can occur in 22.3%-39.1% of cases, leading to decreased hip joint function. This study aimed to investigate the effectiveness of using an anti-shortening screw (ASS) in FNS fixation to prevent postoperative femoral neck shortening in displaced femoral neck fractures. We retrospectively analyzed 106 cases of displaced femoral neck fractures treated with FNS at the Hospital from April 2020 to April 2023. Patients were divided into two groups based on the use of an ASS: the traditional group and the ASS group, each consisting of 53 cases. The ASS group was age-matched with the traditional group treated during the same period without an ASS. The study variables included age, sex, body mass index (BMI), smoking and drinking history, injury mechanism, side of injury, fracture type, surgical time, intraoperative blood loss, Harris Hip Score (HHS) at the final follow-up, radiographic assessment (femoral neck shortening), and complications (infection, femoral head necrosis, nonunion, and secondary surgery). Statistical analysis was performed using SPSS software, with continuous and categorical variables analyzed using appropriate parametric (t-test) and nonparametric (Mann-Whitney U test) tests, and chi-square or Fisher's exact tests, respectively. A p-value <0.05 was considered significant. There were no significant differences in background characteristics between the traditional and ASS groups. The shortening distance at postoperative day 1 did not differ significantly between the two groups (0 vs. 0 mm, p = 0.120). However, at 1, 3 months, and 1 year postoperatively, the femoral neck shortening in the ASS group was significantly less than that in the traditional group (1 month: 2.3 vs. 3.1 mm, p = 0.007; 3 months: 2.6 vs. 3.5 mm, p = 0.005; 1 year: 2.6 vs. 3.5 mm, p = 0.002). The ASS group also had a significantly lower shortening distance during the fracture healing process (0.9 vs. 2.7 mm, p = 0.005). The incidence of moderate to severe shortening (≥5 mm) at 1 year postoperatively was lower in the ASS group compared with the traditional group (15.1% vs. 37.7%, p = 0.001). The ASS group had a longer surgical time (63.0 ± 13.4 vs. 73.0 ± 23.2 min, p = 0.008) and a higher HHS (90.7 vs. 94.8, p = 0.008). There was no significant difference in fracture healing time or postoperative complications between the two groups. The traditional group had 3.8% cutouts, 7.5% nonunions, 5.7% avascular necrosis, and 7.5% secondary hip replacements. The ASS group saw 0% cutouts, 1.9% nonunions, 3.8% avascular necrosis, and 3.8% hip replacements. No significant differences in complication rates (p > 0.05). The use of an ASS in FNS fixation for displaced femoral neck fractures can reduce the degree of postoperative shortening and improve hip joint function.

Comparative biochemical analysis of platelet-rich plasma-chitosan and platelet-rich fibrin-chitosan for treating tibial bone defects in rabbits.

Fracture healing can cause serious complications, both preoperatively and postoperatively, including malunion or non-union. Biomaterials can enhance the fracture healing process. This study aimed to compare platelet-rich plasma (PRP)-chitosan and platelet-rich fibrin (PRF)-chitosan on the basis of biochemical parameters for fracture treatment in rabbits. This study involved 12 clinically healthy rabbits. After preparing PRP and PRF, a 3-mm bone defect was created in the tibia of each rabbit. The animals were divided randomly into two groups (A and B). Group A received PRP-Chitosan, and Group B received PRF-Chitosan. Bone healing was assessed using biochemical parameters (calcium [Ca], phosphorus [P], serum alkaline phosphatase [ALP], and osteocalcin [Ocn]) at 2-, 4-, 6-, and 8-week postoperatively. The data were compared using repeated-measures analysis of variance (p < 0.05) with Statistical Package for the Social Sciences statistical software. Group-wise comparison showed no significant differences (p > 0.05) between the groups, except for ALP levels, which were significantly higher in Group B than in Group A (p < 0.05). In the week-wise comparison, there was a significant difference between both groups, as Ca and ALP levels showed significant differences at all weeks postoperatively, whereas Ocn showed a significant difference at 2- and 4-week postoperatively (p < 0.05). However, there was no difference in P levels between the groups at any post-operative week (p > 0.05). Both combinations enhanced bone regeneration. However, PRF-Chitosan is a better combination for bone repair than PRP-Chitosan. There were some limitations of this study, such as a small sample size, only male rabbits were used, and a lack of mechanical testing; these limitations should be addressed in future studies. The insights gained from the present study may open a new approach to the use of a combination of biomaterials for bone healing, which should be further investigated clinically and in other animal models as a future scope.

Enhancing Bone Healing Through Localized Cold Therapy in a Murine Femoral Fracture Model.

Fracture healing, a critical and complex biological process, often presents challenges in clinical practice with the current standards failing to fully address the medical needs for rapid and effective recovery. In this work, a localized cold therapy is investigated as an alternative approach to expedite bone healing. We hypothesized that optimized cold application can enhance bone healing within a fracture model by inducing hypoxia, leading to accelerated angiogenesis along with improved osteogenesis. A short, localized cold exposure is directly applied to the fracture site over a 4-week period in a mouse fracture model, aiming to assess its impact on bone formation through mechanisms of angiogenesis and osteogenesis. Our results revealed a significantly greater volume of new bone tissue and enhanced vascularity at the fracture site in the cold-treated group compared with controls. Calcified tissue histology analysis showed that the accelerated callus maturation and development of the vascular network following cold exposure were associated with an activity increase of alkaline phosphatase and transient receptor potential vanilloid 1. These biological changes were accompanied by a hypoxic environment induced during cold therapy. The study provides compelling evidence supporting the efficacy of intermittent cold therapy in accelerating fracture healing. These promising results highlight the need for further research in larger-scale studies and diverse fracture models, underlining the potential of cold therapy as a novel, noninvasive treatment strategy in orthopedic care.

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.

Finite element solution of coupled multiphysics reaction-diffusion equations for fracture healing in hard biological tissues

This study proposes a computational framework to investigate the multi-stage process of fracture healing in hard tissues, e.g., long bone, based on the mathematical Bailon-Plaza and Van der Meulen formulation. The goal is to explore the influence of critical biological factors by employing the finite element method for more realistic configurations. The model integrates a set of variables, including cell densities, growth factors, and extracellular matrix contents, managed by a coupled system of partial differential equations. A weak finite element formulation is introduced to enhance the numerical robustness for coarser mesh grids, complex geometries, and more accurate boundary conditions. This formulation is less sensitive to mesh quality and converges smoothly with mesh refinement, exhibiting superior numerical stability compared to previously available strong-form solutions. The model accurately reproduces various stages of healing, including soft cartilage callus formation, endochondral and intramembranous ossification, and hard bony callus development for various sizes of fracture gap. Model predictions align with the existing research and are logically coherent with the available experimental data. The developed multiphysics simulation clarifies the coordination of cellular dynamics, extracellular matrix alterations, and signaling growth factors during fracture healing.

Therapeutic Potential of Platelet-Rich Plasma in Fracture Healing: A Comprehensive Review.

Fracture healing is a dynamic process essential for the restoration of bone integrity and function. However, factors such as patient age, comorbidities, and the severity of the fracture can impede this process, leading to delayed healing or nonunion. Platelet-rich plasma (PRP) has emerged as a promising therapeutic option for enhancing fracture healing. PRP is an autologous blood product containing a concentrated mixture of platelets, growth factors, and cytokines known to promote tissue regeneration and repair. This comprehensive review provides an overview of the fracture healing process, emphasizing the importance of timely and efficient bone repair. We discuss the mechanisms underlying the purported efficacy of PRP in fracture healing, drawing upon both preclinical and clinical evidence. Preclinical studies in animal models have demonstrated the ability of PRP to accelerate fracture healing, stimulate osteogenesis, and enhance bone regeneration. Clinical studies have yielded mixed results, with some reporting positive outcomes in terms of accelerated healing and improved functional outcomes, while others have shown no significant benefits over standard treatments. Factors influencing the efficacy of PRP, such as timing of administration, PRP concentration, and patient-specific variables, are also examined. Furthermore, safety considerations and potential adverse effects associated with PRP therapy are discussed. Despite the promising preclinical findings, challenges remain in standardizing PRP formulations, optimizing administration protocols, and addressing unanswered questions regarding its long-term efficacy and safety. This review aims to provide insights into the therapeutic potential of PRP in fracture healing, informing future research directions and guiding clinical practice.

Hydrogel loaded with bone marrow stromal cell-derived exosomes promotes bone regeneration by inhibiting inflammatory responses and angiogenesis.

Bone healing is a complex process involving early inflammatory immune regulation, angiogenesis, osteogenic differentiation, and biomineralization. Fracture repair poses challenges for orthopedic surgeons, necessitating the search for efficient healing methods. To investigate the underlying mechanism by which hydrogel-loaded exosomes derived from bone marrow mesenchymal stem cells (BMSCs) facilitate the process of fracture healing. Hydrogels and loaded BMSC-derived exosome (BMSC-exo) gels were characterized to validate their properties. In vitro evaluations were conducted to assess the impact of hydrogels on various stages of the healing process. Hydrogels could recruit macrophages and inhibit inflammatory responses, enhance of human umbilical vein endothelial cell angiogenesis, and promote the osteogenic differentiation of primary cranial osteoblasts. Furthermore, the effect of hydrogel on fracture healing was confirmed using a mouse fracture model. The hydrogel effectively attenuated the inflammatory response during the initial repair stage and subsequently facilitated vascular migration, promoted the formation of large vessels, and enabled functional vascularization during bone repair. These effects were further validated in fracture models. We successfully fabricated a hydrogel loaded with BMSC-exo that modulates macrophage polarization and angiogenesis to influence bone regeneration.

Osteoimmunology: An Overview of the Interplay of the Immune System and the Bone Tissue in Fracture Healing

Bone healing occurs through three consecutive and interdependent phases. While the acute inflammatory response is vital to fracture healing, chronic and systemic inflammation negatively affect the healing process. The bone tissue relies heavily on the immune system for its normal physiology and turnover. The interactions are more pronounced in injury states, such as fractures and autoimmune disorders. Recently, the field of osteoimmunology, the study of the molecular interplay of the immune and skeletal systems, has gained much-needed attention to develop new therapeutic strategies to accelerate fracture healing and prevent the complications of fracture healing. This review provides an overview of the process of fracture healing and discusses the role of immune cells, their interplay with the released cytokines, and the current state of the art in the field of osteoimmunology.

Promoting bone callus formation by taking advantage of the time-dependent fracture gap strain modulation.

Delayed union and non-union of fractures continue to be a major problem in trauma and orthopedic surgery. These cases are challenging for the surgeon. In addition, these patients suffer from multiple surgeries, pain and disability. Furthermore, these cases are a major burden on healthcare systems. The scientific community widely agrees that the stability of fixation plays a crucial role in determining the outcome of osteosynthesis. The extent of stabilization affects factors like fracture gap strain and fluid flow, which, in turn, influence the regenerative processes positively or negatively. Nonetheless, a growing body of literature suggests that during the fracture healing process, there exists a critical time frame where intervention can stimulate the bone's return to its original form and function. This article provides a summary of existing evidence in the literature regarding the impact of different levels of fixation stability on the strain experienced by newly forming tissues. We will also discuss the timing and nature of this "window of opportunity" and explore how current knowledge is driving the development of new technologies with design enhancements rooted in mechanobiological principles.

Platelets: A Potential Factor that Offers Strategies for Promoting Bone Regeneration.

Bone defects represent a prevalent category of clinical injuries, causing significant pain and escalating health care burdens. Effectively addressing bone defects is thus of paramount importance. Platelets, formed from megakaryocyte lysis, have emerged as pivotal players in bone tissue repair, inflammatory responses, and angiogenesis. Their intracellular storage of various growth factors, cytokines, and membrane protein receptors contributes to these crucial functions. This article provides a comprehensive overview of platelets' roles in hematoma structure, inflammatory responses, and angiogenesis throughout the process of fracture healing. Beyond their application in conjunction with artificial bone substitute materials for treating bone defects, we propose the potential future use of anticoagulants such as heparin in combination with these materials to regulate platelet number and function, thereby promoting bone healing. Ultimately, we contemplate whether manipulating platelet function to modulate bone healing could offer innovative ideas and directions for the clinical treatment of bone defects.

Regulatory T cell-derived exosome mediated macrophages polarization for osteogenic differentiation in fracture repair

Refractory fracture presents an intractable challenge in trauma treatment. Selective polarization of macrophages as well as the recruitment of osteogenic precursor cells play key roles in osteogenic differentiation during fracture healing. Here we constructed regulatory T cell (Treg)-derived exosomes (Treg-Exo) for the treatment of fracture. The obtained exosomes displayed a spheroid shape with a hydrated particle size of approximately 130 nm. With further purification using CD39 and CD73 antibody-modified microfluidic chips, CD39 and CD73 specifically expressing exosomes were obtained. This kind of Treg-Exo utilized the ectonucleotidases of CD39 and CD73 to catalyze the high level of ATP in the fracture area into adenosine. The generated adenosine further promoted the selective polarization of macrophages. When interacting with mesenchymal stem cells (MSCs, osteogenic precursor cells), both Treg-Exo and Treg-Exo primed macrophages facilitated the proliferation and differentiation of MSCs. After administration in vivo, Treg-Exo effectively promoted fracture healing compared with conventional T cell-derived exosome. To further improve the delivery efficacy of exosomes and integrate multiple biological processes of fracture healing, an injectable hydrogel was fabricated to co-deliver Treg-Exo and stromal cell-derived factor 1 alpha (SDF-1α). With the dual effect of Treg-Exo for macrophage polarization and SDF-1α for MSC recruitment, the multifunctional hydrogel exerted a synergistic effect on fracture repair acceleration. This study provided a promising therapeutic candidate and synergistic strategy for the clinical treatment of fracture.

Investigation of the effectiveness of intermittent electromagnetic field stimulation for early internal cartilaginous ossification in prechondrocytic ATDC5 cells.

Pulsed electromagnetic field (PEMF) stimulation has been widely applied clinically to promote bone healing; however, its detailed mechanism of action, particularly in endochondral ossification, remains elusive, and long-term stimulation is required for its satisfactory effect. The aim of this study was to investigate the involvement of the mammalian target of rapamycin (mTOR) pathway in chondrocyte differentiation and proliferation using a mouse prechondroblast cell line (ATDC5), and establish an efficient PEMF stimulation strategy for endochondral ossification. The changes in cell differentiation (gene expression levels of aggrecan, type II collagen, and type X collagen) and proliferation (cellular uptake of bromodeoxyuridine [BrdU]) in ATDC5 cells in the presence or absence of rapamycin, an mTOR inhibitor, was measured. The effects of continuous and intermittent PEMF stimulation on changes in cell differentiation and proliferation were compared. Rapamycin significantly suppressed the induction of cell differentiation markers and the cell proliferation activity. Furthermore, only intermittent PEMF stimulation continuously activated the mTOR pathway in ATDC5 cells, significantly promoting cell proliferation. These results demonstrate the involvement of the mTOR pathway in chondrocyte differentiation and proliferation and suggest that intermittent PEMF stimulation could be effective as a stimulus for endochondral ossification during fracture healing process, thereby reducing stimulationtime.

Histological Evaluation of Fracture Healing after Thyroidectomy

This study aimed to examine the impact of thyroidectomy on the process of fracture healing. A total of sixteen adult male rabbits of the local breed were utilized. The animals were segregated into two equivalent groups, namely the control group and the treatment group. The animals were administered atropine sulfate (1mg /Kg B.W) intramuscularly as a premedication. Ten minutes later, a combination of xylazine hydrochloride (20mg /Kg B.W) and Ketamine hydrochloride (40 mg /Kg B.W) was administered intramuscularly. The control group had the induction of a mid-shaft femoral fracture, followed by fixation with intramedullary pinning. In the treated group, the identical treatment mentioned above, which involved thyroidectomy, was performed. The clinical examination showed that the inflammatory symptoms, such as swelling, discomfort, and increased temperature in the surgical site, were more severe in the control group compared to the treated group. The indications vanished during a span of four to five days in the treatment group and five to six days in the control group. The histological analysis showed that the control group had a greater presence of granulation tissues, trabecular bone, and compact bone compared to the treated group. Ultimately, it was seen that the fracture healing process was more advanced in the control group compared to the treated group.