Irisin promotes fracture healing by improving osteogenesis and angiogenesis

Lamb1-mediated Wnt/β-catenin signaling pathway drives endothelial angiogenesis for fracture healing

OBJECTIVES

Fractures, usually caused by trauma or osteoporosis, are the most common traumatic injuries to large organs in humans. Osteogenesis and angiogenesis are two crucial parts of fracture healing that work together to promote the repair and regeneration of damaged bone. Endothelial cell migration is critical for angiogenesis. Therefore, it is well worth exploring whether endothelial cells (ECs) can enhance fracture healing.

METHODS

The public datasets were analyzed by scRNA-seq, and the ECs were subjected to subset analysis and pseudotime analysis. Next, ECs_Lamb1+ cells underwent GO and KEGG pathway enrichment analyses, and were subjected to GSVA. Finally, the mechanism was verified and evaluated via qRT-PCR, cellular immunofluorescence staining, and transwell assay.

RESULTS

After cell annotations, 9 cell types were obtained, and it was found that the proportions of ECs were significantly reduced. EC subset analysis showed that the ratio of ECs_Lamb1+ cells was significantly up-regulated in the Fracture group; pseudotime analysis showed that ECs_Lamb1- cells were gradually reduced over time, whereas ECs_Lamb1+ cells were gradually expanding along the trajectories to reach a maximum at the end of the trajectory; pathway enrichment analyses revealed that ECs_Lamb1+ cells were mainly associated with several signaling pathways regulating cell proliferation, differentiation, repair, angiogenesis, and inflammatory responses, such as PI3K-Akt signaling pathway, Wnt/β-catenin, and MAPK. The results of basic assays demonstrated that successful knockdown of Lamb1 expression via siRNA-LAMB1 was detrimental to HUVEC proliferation, migration, and tube formation, and could suppress the expression of wnt3a, GSK-3β, β-catenin, and VEGFA; whereas, HY-141873 in combination with siRNA-LAMB1 partially reversed the down-regulated wnt3a, GSK-3β, β-catenin, and VEGFA expression, and HUVEC proliferation, migration, and tube formation were partially improved.

CONCLUSION

Lamb1 promotes fracture repair and healing by up-regulating VEGFA expression via the activation of Wnt signaling pathway to catalyze EC growth and migration and induce endothelial angiopoiesis.

Irisin alleviates steroid-induced vascular dysfunction by regulating the αVβ5-c-Abl-Caveolin-1 signaling pathway

Steroid-induced avascular necrosis of the femoral head (SANFH) is a progressive degenerative disease of the hip, primarily due to glucocorticoid (GC)-induced endothelial cell (EC) injury and compromised blood supply. Irisin is an EC-protective mytokine whose receptor is the integrin αVβ5. Caveolin-1 (CAV-1)， a major component of caveolae, causes endothelial dysfunction when phosphorylated. However, the role of irisin and CAV-1 in SANFH remains unclear. In our study, irisin levels decreased but CAV-1 phosphorylation increased in human and mouse SANFH samples. Intraperitoneal irisin injection (250 μg/kg daily) notably reduced GC-induced osteonecrosis, vascular abnormalities, and CAV-1 phosphorylation in SANFH mice. In cultured ECs, GC induced CAV-1 phosphorylation by activating c-Abl via the glucocorticoid receptor, and irisin inhibited GC-induced phosphorylation of c-Abl and CAV-1 via the integrin αVβ5. Inhibition of integrin αVβ5 also abolished the protective effects of irisin on ERK and eNOS signalling, viability, angiogenesis, and migration in ECs. Therefore, our findings indicate that irisin has a protective role against vascular dysfunction in SANFH, possibly mediated by the inhibition of GC-triggered c-Abl-CAV-1 phosphorylation through integrin αVβ5. These findings provide insights into the potential therapeutic applications of irisin in SANFH.

Irisin in the modulation of bone and cartilage homeostasis: a review on osteoarthritis relief potential

Osteoarthritis, a progressive and degenerative joint disease, disrupts the integrity of the entire joint structure, underscoring the urgency of identifying more effective therapeutic strategies and innovative targets. Among these, exercise therapy is considered a key component in the early management of osteoarthritis, functioning by stimulating the secretion of myokines from the skeletal muscle system. Irisin, a myokine predominantly secreted by skeletal muscle during exercise and encoded by the FNDC5 gene, has garnered attention for its regulatory effects on bone health. Emerging evidence suggests that irisin may play a protective role in osteoarthritis by promoting tissue homeostasis, enhancing subchondral bone density and microstructure, and inhibiting chondrocyte apoptosis. By improving chondrocyte viability, preserving extracellular matrix integrity, and maintaining homeostasis in osteoblasts, osteoclasts, and osteocytes, irisin emerges as a promising therapeutic target for osteoarthritis. This review delves into the role of irisin in osteoarthritis pathogenesis, highlighting its influence on cartilage and bone metabolism as well as its dynamic relationship with exercise. Additionally, this review suggests that further exploration on its specific molecular mechanisms, optimization of drug delivery systems, and strategic utilization of exercise-induced benefits will be pivotal in unlocking the full potential of irisin as a novel intervention for osteoarthritis.

Irisin mitigates osteoporotic-associated bone loss and gut dysbiosis in ovariectomized mice by modulating microbiota, metabolites, and intestinal barrier integrity

BACKGROUND

Osteoporotic bone defects significantly affect patient health and quality of life. The gut-bone axis plays a crucial role in osteoporosis, and disruptions in gut microbiota are linked to systemic inflammation and compromised bone metabolism. Irisin, a myokine, has shown potential in protecting against osteoporosis, but its mechanisms of action on the gut-bone axis remain unclear. This study aimed to investigate the role of irisin in mitigating osteoporotic bone defects by examining its effects on gut microbiota, related metabolites, and intestinal barrier integrity.

METHODS

An osteoporosis model was created using ovariectomized (OVX) mice. The mice were divided into Sham, OVX, and r-irisin groups. Mice in the r-irisin group received intraperitoneal injections of 100 μg/kg irisin twice weekly for five weeks. Bone parameters were analyzed by micro-CT and histological staining. Gut microbiota composition was examined via 16S rDNA sequencing. Intestinal cytokines and barrier proteins were measured using immunohistochemistry and ELISA. Fecal metabolomic profiling was conducted using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and correlations between gut microbiota, metabolites, and bone metabolism markers were evaluated.

RESULTS

Irisin treatment improved bone mineral density (BMD), bone volume/tissue volume (BV/TV), trabecular bone thickness (Tb.Th), and trabecular number (Tb.N), and reduced trabecular separation (Tb.Sp) in OVX mice. It enhanced new bone formation and collagen deposition. Irisin restored intestinal barrier integrity by increasing tight junction protein expression and reducing inflammatory cytokines in intestinal tissues. It also modulated gut microbiota diversity, reducing Firmicutes and increasing Verrucomicrobiota abundance. Key fecal metabolites, including atractylon (r = - 0.60, P < 0.01) and enterodiol (r = + 0.83, P < 0.01), showed strong correlations with BMD.

CONCLUSION

Irisin mitigates osteoporotic bone defects by enhancing bone formation, restoring intestinal barrier integrity, modulating gut microbiota composition, and influencing fecal metabolites. These preclinical findings highlight irisin's potential to mitigate osteoporosis via the gut-bone axis.

P24 Loaded Gelatin-Hydroxyapatite-Tricalcium Phosphate Scaffold Induces Bone Regeneration by Activating the ERK/ELK1/PLA2G3 Pathway

The study examined the induction and mechanism of bone regeneration facilitated by the P24-loaded Gelatin-Hydroxyapatite-Tricalcium Phosphate (Gelatin-HA-TCP (P24)) scaffold. The prepared Gelatin-HA-TCP (P24) scaffold was employed to treat human bone marrow mesenchymal stem cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs). Various assays were conducted to assess the impact of the Gelatin-HA-TCP (P24) scaffold on the osteogenic differentiation of hBMSCs and angiogenesis in HUVECs. For mechanistic investigations, hBMSCs were exposed to both the Gelatin-HA-TCP (P24) scaffold and the ERK inhibitor SCH772984. A rat cranial bone defect model was treated through the implantation of the Gelatin-HA-TCP (P24) scaffold. Micro-computed tomography, histological staining, and immunofluorescence techniques were utilized to evaluate the effect of the Gelatin-HA-TCP (P24) scaffold on cranial bone regeneration. Osteogenic differentiation of hBMSCs was facilitated by the Gelatin-HA-TCP (P24) scaffold, as evidenced by increased ALP activity, enhanced Alizarin Red S staining, and upregulated RUNX2, OSX, OCN, and BMP2. Angiogenesis in HUVECs was induced, as demonstrated by improved migration, tube formation, and upregulated CD31. However, the ability of the Gelatin-HA-TCP (P24) scaffold to promote osteogenic differentiation in hBMSCs was counteracted by SCH772984. In the rat cranial bone defect model, implantation of the Gelatin-HA-TCP (P24) scaffold reduced the bone defect area, increased the bone volume/tissue volume ratio, enhanced bone regeneration, decreased bone fibrosis, and upregulated CD31, RUNX2, and BMP2 in bone tissues. Therefore, the Gelatin-HA-TCP (P24) scaffold enhances the osteogenic differentiation of hBMSCs and promotes bone regeneration in cranial bone defects by activating the ERK/ELK1/PLA2G3 pathway. It has potential for bone regeneration therapies.

Recent advances in the multifaceted mechanisms of catalpol in treating osteoporosis

Catalpol (CAT) is a landmark active ingredient in traditional Chinese medicine Rehmannia (TCT), also known as dehydroxybenzoate catalpone, which is a kind of iridoid terpene glycoside with strong antioxidant, anti-inflammatory, antitumor and other biological activities. It can exert its anti-disease effect in a variety of ways. For some patients with chronic diseases, the application of azalea alcohol in rehmannia may bring more comprehensive and long-lasting efficacy. Studies have shown that the anti-disease effect of catalpol in osteoporosis (OP) is mainly achieved through various pathways such as Wnt/β-catenin signaling pathways to promote osteogenic differentiation, and RANKL/RANK and other signaling pathways to inhibit osteoclastic differentiation. At present, there is a slight lack of analysis of the mechanism of action of catalpa alcohol in the treatment of osteoporosis, so this study comprehensively searched the literature on the mechanism of action of catalpa alcohol in the treatment of osteoporosis in various databases, and reviewed the research progress of its role and mechanism, to provide reference and theoretical basis for the further development and application of catalpol.

Enzyme-crosslinked hyaluronic acid hydrogel scaffolds for BMSCs microenvironment and wound healing

Tissue engineering utilizing hydrogel scaffolds in combination with exogenous stem cells holds significant potential for promoting wound regeneration. However, the microenvironment provided by existing skin tissue engineering scaffold materials is often inadequate. Herein, we demonstrate an enzyme-crosslinked hyaluronic acid hydrogel to provide a growth microenvironment for exogenous bone marrow mesenchymal stem cells and promote acute wound healing. This material is developed by grafting dopamine onto hyaluronic acid, followed by enzyme crosslinking using horseradish peroxidase and hydrogen peroxide, which creates a loose, porous structure. The hydrogel possesses adhesive and self-healing properties, offering a microenvironment with excellent cell compatibility for exogenous BMSCs. In vivo studies showed that this hydrogel significantly accelerated the healing of acute full-thickness skin wounds, resulting in the formation of appendages such as hair follicles and minimal scarring. This study not only presents a novel skin tissue engineering scaffold but also offers a promising clinical strategy for achieving scar-minimized wound healing.

Ginsenoside Rd-Loaded Antioxidant Polymersomes to Regulate Mitochondrial Homeostasis for Bone Defect Healing in Periodontitis

Periodontitis is the leading cause of tooth loss in adults. Initially triggered by bacterial infection, it is characterized by subsequent dysregulation of mitochondrial homeostasis, leading to ongoing loss of periodontal tissue. Mitophagic flux, a critical physiological mechanism for maintaining mitochondrial homeostasis, is compromised in periodontitis. Additionally, increased release of reactive oxygen species (ROS) exacerbates mitochondrial damage. In this study, a ginsenoside Rd (Rd)-loaded antioxidative polymersome (RdAP) is designed, which is self-assembled from a mitochondrial-protective and ROS-scavenging block copolymer, poly(ethylene oxide)-block-poly(phenylboronic acid pinacol ester-conjugated polylysine) (PEO113-b-P(Lys-PAPE)60). The phenylboronic acid pinacol ester (PAPE) segment exhibits excellent ROS-responsive properties, enabling effective ROS scavenging through antioxidant production. Rd significantly enhances mitophagic flux by 2.5-fold in periodontal ligament stem cells (PDLSCs) under oxidative stress. Together with the antioxidative polymersome, RdAPs restore mitochondrial homeostasis and enhance the osteogenic capacity of PDLSCs, bringing it closer to that of healthy controls. In a mouse model of periodontitis, the bone mass in the RdAP-treated group is 1.37 times greater than that in the untreated periodontitis group. Overall, the findings propose a novel strategy for addressing refractory periodontitis, which may also be applicable to other diseases characterized by mitochondrial homeostasis imbalance.

Osteoporotic thoracolumbar spine fractures in the elderly: alterations in GNRI and BMP-2 in delayed union and associated factors

OBJECTIVE

To investigate the alterations in the Geriatric Nutritional Risk Index (GNRI) and bone morphogenetic protein 2 (BMP-2) levels and identify associated factors in older adults with delayed union of osteoporotic thoracolumbar spine fractures.

METHODS

From June 2021 to June 2023, 139 elderly patients with osteoporotic thoracolumbar spine fractures were selected and divided into a delayed group and a normal group according to the fracture healing status at 6 months postoperatively. GNRI and BMP-2 levels were assessed in both cohorts. Receiver operating characteristic (ROC) curves were used to determine the predictive value of GNRI and BMP-2 for delayed union. Multivariate Logistic regression was utilized to identify risk factors associated with delayed union after surgery for osteoporotic thoracolumbar spine fractures. Pearson correlation analysis was conducted to explore the relationships among independent risk factors. Finally, the Generic Quality of Life Inventory-74 (GQOL-74) was employed to assess the quality of life in both groups.

RESULTS

At 6 months post-surgery, 41 of the 139 patients had delayed union and were classified into the delayed group, while 98 cases achieved fracture healing and served as the normal group. The delayed group exhibited obviously reduced GNRI and BMP-2 levels than the normal group. ROC curve analysis indicated that the areas under the curve (AUCs) of GNRI, BMP-2, and their combination for predicting delayed union were 0.826, 0.803, and 0.883, respectively. A higher recovery rate of the injured vertebra height (OR = 1.456, 95% CI: 1.232-1.722, P < 0.001), a lower GNRI (OR = 0.590, 95% CI: 0.444-0.782, P < 0.001), and a lower BMP-2 level (OR = 0.909, 95% CI: 0.850-0.971, P = 0.005) were independent risk factors for delayed union in elderly patients undergoing surgery for osteoporotic thoracolumbar spine fractures. Pearson correlation analysis showed a negative correlation between the recovery rate of the injured vertebra height and GNRI (r = -0.640) as well as BMP-2 (r = -0.614), and a positive correlation between GNRI and BMP-2 (r = 0.751). Although the postoperative quality of life in the delayed group significantly enhanced, it remained significantly lower than that in the normal group.

CONCLUSIONS

Delayed union after surgery in elderly patients with osteoporotic thoracolumbar spine fractures is strongly associated with preoperative levels of GNRI and BMP-2. The recovery rate of the injured vertebra height, GNRI, and BMP-2 are independent risk factors for delayed fracture healing. Delayed healing of osteoporotic thoracolumbar spine fractures in the elderly negatively affects the improvement of patients' quality of life.

Extracellular matrix-mimicking cryogels composed of methacrylated fucoidan enhance vascularized skeletal muscle regeneration following volumetric muscle loss

Volumetric muscle loss (VML) significantly impairs the inherent regenerative ability of skeletal muscle and results in chronic functional impairment. Polysaccharides in the muscle extracellular matrix are crucial for regulating cell proliferation and differentiation. Recent studies indicate that fucoidan has beneficial effects on musculoskeletal conditions. However, the impact of fucoidan on skeletal muscle regeneration remains poorly understood. In this study, methacrylated fucoidan (FuMA) was synthesized through chemical grafting of the methacryloyl group onto fucoidan. In vitro experiments demonstrated that treatment with FuMA significantly up-regulated the expression of myogenic markers and promoted the formation of myotubes in C2C12 myoblast cells. Importantly, FuMA treatment led to a significant enhancement in mitochondrial energy metabolism of myoblasts via activation of the NRF2 antioxidant signaling pathway. To further investigate the regenerative properties in repairing skeletal muscle defects, we fabricated a dual crosslinked cryogel consisting of FuMA and methacrylated gelatin (GelMA) with a porous and interconnected structure. In a rat tibialis anterior muscle VML model, implantation of the FuMA/GelMA cryogel effectively promoted the regeneration of muscle fibers, reduced collagen deposition, and facilitated the formation of new blood vessels. Hence, polysaccharide-based cryogels represent a promising implantable biomimetic scaffold for facilitating skeletal muscle regeneration following severe injuries.

Poor bone health in Duchenne muscular dystrophy: a multifactorial problem beyond corticosteroids and loss of ambulation

Duchenne muscular dystrophy (DMD) is a progressive, fatal muscle wasting disease caused by X-linked mutations in the dystrophin gene. Alongside the characteristic muscle weakness, patients face a myriad of skeletal complications, including osteoporosis/osteopenia, high susceptibility to vertebral and long bone fractures, fat embolism post-fracture, scoliosis, and growth retardation. Those skeletal abnormalities significantly compromise quality of life and are sometimes life-threatening. These issues were traditionally attributed to loss of ambulation and chronic corticosteroid use, but recent investigations have unveiled a more intricate etiology. Factors such as vitamin D deficiency, hormonal imbalances, systemic inflammation, myokine release from dystrophic muscle, and vascular dysfunction are emerging as significant contributors as well. This expanded understanding illuminates the multifaceted pathogenesis underlying skeletal issues in DMD. Present therapeutic options are limited and lack specificity. Advancements in understanding the pathophysiology of bone complications in DMD will offer promising avenues for novel treatment modalities. In this review, we summarize the current understanding of factors contributing to bone problems in DMD and delineate contemporary and prospective multidisciplinary therapeutic approaches.

Hyperbaric oxygen promotes bone regeneration by activating the mechanosensitive Piezo1 pathway in osteogenic progenitors

Background

Hyperbaric oxygen (HBO) therapy is widely used to treat bone defects, but the correlation of high oxygen concentration and pressure to osteogenesis is unclear.

Methods

Bilateral monocortical tibial defect surgeries were performed on 12-week-old Prrx1-Cre; Rosa26-tdTomato and Prrx1-Cre; Piezo1fl/+ mice. Daily HBO treatment was applied on post-surgery day (PSD) 1-9; and daily mechanical loading on tibia was from PSD 5 to 8. The mice were euthanized on PSD 10, and bone defect repair in their tibias was evaluated using μCT, biomechanical testing, and immunofluorescence deep-tissue imaging. The degree of angiogenesis-osteogenesis coupling was determined through spatial correlation analysis. Bone marrow stromal cells from knockout mice were cultured in vitro, and their osteogenic capacities of the cells were assessed. The activation of genes in the Piezo1-YAP pathway was evaluated using RNA sequencing and quantitative real-time polymerase chain reaction.

Results

Lineage tracing showed HBO therapy considerably altered the number of Prrx1+ cells and their progeny in a healing bone defect. Using conditional knockdown mice, we found that HBO stimulation activates the Piezo1-YAP axis in Prrx1+ cells and promotes osteogenesis-angiogenesis coupling during bone repair. The beneficial effect of HBO was similar to that of anabolic mechanical stimulation, which also acts through the Piezo1-YAP axis. Subsequent transcriptome sequencing results revealed that similar mechanosensitive pathways are activated by HBO therapy in a bone defect.

Conclusion

HBO therapy promotes bone tissue regeneration through the mechanosensitive Piezo1-YAP pathway in a population of Prrx1+ osteogenic progenitors. Our results contribute to the understanding of the mechanism by which HBO therapy treats bone defects.

The Translational Potential of this Article

Hyperbaric oxygen therapy is widely used in clinical settings. Our results show that osteogenesis was induced by the activation of the Piezo1-YAP pathway in osteoprogenitors after HBO stimulation, and the underlying mechanism was elucidated. These results may help improve current HBO methods and lead to the formulation of alternative treatments that achieve the same functional outcomes.

Efficacy of tibial cortex transverse transport in treating diabetic foot ulcer and its effect on serum omentin-1 and irisin levels

OBJECTIVE

Diabetic foot ulcer (DFU) is a common and debilitating complication of diabetes that is associated with an increased risk of lower-limb amputation and a reduced life expectancy. Tibial cortex transverse transport (TTT) has become a newly alternative surgical method to facilitate ulcer healing and prevent lower limb amputation. Herein, we investigated the efficacy of TTT in treating DFU and changes of serum omentin-1 and irisin levels.

METHODS

This study prospectively recruited 52 consecutive patients with DFU who were treated with TTT. The follow-up was performed weekly during the first 12 weeks postoperatively and every 3 months until 1 year after TTT. The serum levels of vascular endothelial growth factor (VEGF), omentin-1, and irisin in DFU patients undergoing TTT were determined by ELISA methods on the preoperative 1st day, postoperative 2nd week and 4th week.

RESULTS

The wound healing rate was 92.3% (48/52) at the 1-year follow-up. The visual analog scale (VAS) pain scores of patients showed a significant reduction at the 4th week after TTT (p < 0.001). The dorsal foot skin temperature, ankle brachial index, and dorsal foot blood flow of patients were significantly increased at the 4th week after TTT (p < 0.001). Results of ELISA methods showed the serum levels of VEGF, omentin-1, and irisin on the 2nd week and 4th week after TTT were notably elevated compared to the levels determined on the preoperative 1st day (p < 0.001). The serum levels of VEGF, omentin-1, and irisin on the 4th week after TTT were also significantly higher than the levels determined on the 2nd week after TTT (p < 0.001).

CONCLUSION

TTT could promote the wound healing and reduce the risk of lower limb amputation, demonstrating promising clinical benefits in the treatment of DFU. Increased expressions of serum proangiogenic factors including VEGF, omentin-1, and irisin were noted in the early stage after TTT, which may provide a new mechanism of TTT promoting wound heal.

Irisin prevents trabecular bone damage and tumor invasion in a mouse model of multiple myeloma

Bone disease associated with multiple myeloma (MM) is characterized by osteolytic lesions and pathological fractures, which remain a therapeutic priority despite new drugs improving MM patient survival. Antiresorptive molecules represent the main option for the treatment of MM-associated bone disease (MMBD), whereas osteoanabolic molecules are under investigation. Among these latter, we here focused on the myokine irisin, which is able to enhance bone mass in healthy mice, prevent bone loss in osteoporotic mouse models, and accelerate fracture healing in mice. Therefore, we investigated irisin effect on MMBD in a mouse model of MM induced by intratibial injection of myeloma cells followed by weekly administration of 100 μg/kg of recombinant irisin for 5 wk. By micro-Ct analysis, we demonstrated that irisin improves MM-induced trabecular bone damage by partially preventing the reduction of femur Trabecular Bone Volume/Total Volume (P = .0028), Trabecular Number (P = .0076), Trabecular Fractal Dimension (P = .0044), and increasing Trabecular Separation (P = .0003) in MM mice. In cortical bone, irisin downregulates the expression of Sclerostin, a bone formation inhibitor, and RankL, a pro-osteoclastogenic molecule, while in BM it upregulates Opg, an anti-osteoclastogenic cytokine. We found that in the BM tibia of irisin-treated MM mice, the percentage of MM cells displays a reduction trend, while in the femur it decreases significantly. This is in line with the in vitro reduction of myeloma cell viability after 48 h of irisin stimulation at both 200 and 500 ng/mL and, after 72 h already at 100 ng/mL rec-irisin. These results could be due to irisin ability to downregulate the expression of Notch 3, which is important for cell-to-cell communication in the tumor niche, and Cyclin D1, supporting an inhibitory effect of irisin on MM cell proliferation. Overall, our findings suggest that irisin could be a new promising strategy to counteract MMBD and tumor burden in one shot.

Methods to accelerate fracture healing - a narrative review from a clinical perspective

Bone regeneration is a complex pathophysiological process determined by molecular, cellular, and biomechanical factors, including immune cells and growth factors. Fracture healing usually takes several weeks to months, during which patients are frequently immobilized and unable to work. As immobilization is associated with negative health and socioeconomic effects, it would be desirable if fracture healing could be accelerated and the healing time shortened. However, interventions for this purpose are not yet part of current clinical treatment guidelines, and there has never been a comprehensive review specifically on this topic. Therefore, this narrative review provides an overview of the available clinical evidence on methods that accelerate fracture healing, with a focus on clinical applicability in healthy patients without bone disease. The most promising methods identified are the application of axial micromovement, electromagnetic stimulation with electromagnetic fields and direct electric currents, as well as the administration of growth factors and parathyroid hormone. Some interventions have been shown to reduce the healing time by up to 20 to 30%, potentially equivalent to several weeks. As a combination of methods could decrease the healing time even further than one method alone, especially if their mechanisms of action differ, clinical studies in human patients are needed to assess the individual and combined effects on healing progress. Studies are also necessary to determine the ideal settings for the interventions, i.e., optimal frequencies, intensities, and exposure times throughout the separate healing phases. More clinical research is also desirable to create an evidence base for clinical guidelines. To make it easier to conduct these investigations, the development of new methods that allow better quantification of fracture-healing progress and speed in human patients is needed.

Global, regional, national trends of femur fracture and machine learning prediction: Comprehensive findings and questions from global burden of disease 1990-2019

Background

Femur fracture is a type of fracture with high disability and mortality. There is no comprehensive analysis and prediction of the global distribution of femur fractures, so we conducted this study.

Methods

Age-standardized incidence rate (ASIR), age-standardized prevalence rate (ASPR), and years living with disability (YLDs) of femur fractures (excluding femoral neck) were downloaded from the Global burden of disease database. Trend analysis was performed, and 6 time-series machine learning algorithms were applied to predict the global ASIR, ASPR, and YLDs.

Results

ASPR for femur fracture had been increasing in most countries worldwide from 1990 to 2019, with the highest in East Asia (AAPC = 1.25 95%Confidence Interval (1.2, 1.3)) and lowest in Central Latin America (AAPC = -0.74 95%CI (-0.81, -0.67)). However, ASIR showed a significant downward trend worldwide, with East Saharan Africa decreasing the most (AAPC = -4.04 95%CI (-5.56, -2.47)), and East Asia elevating the most (AAPC = 1.11 95%CI (0.87, 1.42)). YLDs were increasing over the world, with East Asia still elevating the most AAPC= (3.9 95%CI (3.85, 3.95)), with the only region of decrease being Eastern Europe (AAPC = -0.28 95%CI (-0.3, -0.26)). Both ASPR and ASIR were higher in women than in men in the >75 year group, whereas YLDs was lower in women than in men in the >60 year group. Globally, the ARIMA model was optimal in the prediction of ASPR, the PROPHET model effected in the prediction of ASIR, and the PROPHET WITH XGBOOST model was the best in the prediction of YLDs. The projections showed increase in both ASPR and YLDs, except for ASIR decreasing by 2030.

Conclusions

Our study found a rise in femur fracture ASPR and ASIR from 1990 to 2019 in war conflict areas and East Asia, meanwhile, the YLDs of femur fracture increased in populous countries. In both 1990 and 2019, both ASPR and ASIR were higher in women over 75 years than that in men, but YLDs was higher in men over 60 years than that in women. In 2020-2030, while global femur fracture ASIR might decline, both ASPR and YLDs might rise.

The Translational Potential of this article

Femur fracture is a high-energy injury due to direct violence, and in war, conflicting and underdeveloped regions such as East Asia. Accidental injuries may occur due to the rapid development of industry and the frequent traffic accidents. This study suggests that we should focus on elderly women (≥75 years) in the above regions in the future. For older men (>60 years old), more attention should be paid to post-fracture functional rehabilitation and early reintegration into society to reduce the disability rate and lower the socio-economic burden.

The emerging roles of irisin in vascular calcification

Vascular calcification is a common accompanying pathological change in many chronic diseases, which is caused by calcium deposition in the blood vessel wall and leads to abnormal blood vessel function. With the progress of medical technology, the diagnosis rate of vascular calcification has explosively increased. However, due to its mechanism's complexity, no effective drug can relieve or even reverse vascular calcification. Irisin is a myogenic cytokine regulating adipose tissue browning, energy metabolism, glucose metabolism, and other physiological processes. Previous studies have shown that irisin could serve as a predictor for vascular calcification, and protect against hypertension, diabetes, chronic kidney disease, and other risk factors for vascular calcification. In terms of mechanism, it improves vascular endothelial dysfunction and phenotypic transformation of vascular smooth muscle cells. All the above evidence suggests that irisin plays a predictive and protective role in vascular calcification. In this review, we summarize the association of irisin to the related risk factors for vascular calcification and mainly explore the role of irisin in vascular calcification.

Regulation of Immune Inflammation and Promotion of Periodontal Bone Regeneration by Irisin-Loaded Bioactive Glass Nanoparticles

Clinical solutions of bone defects caused by periodontitis involve surgical treatment and subsequent anti-infection treatment using antibiotics. Such a strategy faces a key challenge in that the excessive host immune response results in the damage of periodontal tissues. Consequently, it is of great importance to develop novel periodontitis treatment that allows the regulation of the host immune response and promotes the generation of periodontal tissues. Irisin has a good bone regeneration ability and could reduce the inflammatory reaction by regulating the differentiation of macrophages. In this study, we loaded irisin onto bioactive glass nanoparticles (BGNs) to prepare a composite, irisin-BGNs (IR-BGNs) with anti-inflammatory, bacteriostatic, and tissue regeneration functions, providing a novel idea for the design of ideal materials for repairing oral tissue defects caused by periodontitis. We also verified that the IR-BGNs had better anti-inflammatory properties on RAW264.7 cells compared to irisin and BGNs alone. Strikingly, when hPDLCs were stimulated with IR-BGNs, they exhibited increased expression of markers linked to osteogenesis, ALP activity, and mineralization ability in comparison to the negative control. Furthermore, on the basis of RNA sequencing results, we validated that the p38 pathway can contribute to the osteogenic differentiation of the IR-BGNs. This work may offer new thoughts on the design of ideal materials for repairing oral tissue defects.

Mechanism and physical activities in bone-skeletal muscle crosstalk

Bone and skeletal muscle work in coordination to maintain the function of the musculoskeletal system, in which skeletal muscle contraction drives the movement of the bone lever system while bone provides insert sites for skeletal muscle through the bone-muscle junction. Existing evidence suggests that factors secreted by skeletal muscle and bone mediate the interaction between the two tissues. Herein, we focused on the relationship between skeletal muscle and bone and the underlying mechanism of the interaction. Exercise can promote bone strength and secrete osteocalcin and insulin-like growth factor I into the blood, thus improving muscle quality. In addition, exercise can also promote myostatin, interleukin-6, Irisin, and apelin in muscles to enter the blood so that they can act on bones to maintain the balance between bone absorption and bone formation. There is a special regulatory axis interleukin-6/osteocalcin between myokines and osteokines, which is mainly influenced by exercise. Therefore, we pay attention to the important factors in the bone-muscle intersection that are affected by exercise, which were found or their functions were expanded, which strengthened the connection between organs of the whole body, highlighting the importance of exercise and contributing to the diagnosis, prevention, and treatment of osteoporosis and sarcopenia in the clinic.

Irisin: A Potentially Fresh Insight into the Molecular Mechanisms Underlying Vascular Aging

Aging is a natural process that affects all living organisms, including humans. Aging is a complex process that involves the gradual deterioration of various biological processes and systems, including the cardiovascular system. Vascular aging refers to age-related changes in blood vessels. These changes can increase the risk of developing cardiovascular diseases, such as hypertension, atherosclerosis, and stroke. Recently, an exercise-induced muscle factor, irisin, was found to directly improve metabolism and regulate the balance of glucolipid metabolism, thereby counteracting obesity and insulin resistance. Based on a growing body of evidence, irisin modulates vascular aging. Adenosine monophosphate-activated protein kinase (AMPK) serves as a pivotal cellular energy sensor and metabolic modulator, acting as a central signaling cascade to coordinate various cellular processes necessary for maintaining vascular homeostasis. The vascular regulatory effects of irisin are closely intertwined with its interaction with the AMPK pathway. In conclusion, understanding the molecular processes used by irisin to regulate changes in vascular diseases caused by aging may inspire the development of techniques that promote healthy vascular aging. This review sought to describe the impact of irisin on the molecular mechanisms of vascular aging, including inflammation, oxidative stress, and epigenetics, from the perspective of endothelial cell function and vascular macroregulation, and summarize the multiple signaling pathways used by irisin to regulate vascular aging.

Irisin-loaded electrospun core-shell nanofibers as calvarial periosteum accelerate vascularized bone regeneration by activating the mitochondrial SIRT3 pathway

The scarcity of native periosteum poses a significant clinical barrier in the repair of critical-sized bone defects. The challenge of enhancing regenerative potential in bone healing is further compounded by oxidative stress at the fracture site. However, the introduction of artificial periosteum has demonstrated its ability to promote bone regeneration through the provision of appropriate mechanical support and controlled release of pro-osteogenic factors. In this study, a poly (l-lactic acid) (PLLA)/hyaluronic acid (HA)-based nanofibrous membrane was fabricated using the coaxial electrospinning technique. The incorporation of irisin into the core-shell structure of PLLA/HA nanofibers (PLLA/HA@Irisin) achieved its sustained release. In vitro experiments demonstrated that the PLLA/HA@Irisin membranes exhibited favorable biocompatibility. The osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs) was improved by PLLA/HA@Irisin, as evidenced by a significant increase in alkaline phosphatase activity and matrix mineralization. Mechanistically, PLLA/HA@Irisin significantly enhanced the mitochondrial function of BMMSCs via the activation of the sirtuin 3 antioxidant pathway. To assess the therapeutic effectiveness, PLLA/HA@Irisin membranes were implanted in situ into critical-sized calvarial defects in rats. The results at 4 and 8 weeks post-surgery indicated that the implantation of PLLA/HA@Irisin exhibited superior efficacy in promoting vascularized bone formation, as demonstrated by the enhancement of bone matrix synthesis and the development of new blood vessels. The results of our study indicate that the electrospun PLLA/HA@Irisin nanofibers possess characteristics of a biomimetic periosteum, showing potential for effectively treating critical-sized bone defects by improving the mitochondrial function and maintaining redox homeostasis of BMMSCs.