The expressions of NGF and VEGF in the fracture tissues are closely associated with accelerated clavicle fracture healing in patients with traumatic brain injury

Panax Notoginseng Saponins Regulate Angiogenic Cytokines Through the PI3K/AKT/mTOR Signaling Pathway to Promote Fracture Healing in Ovariectomized Rats

Osteoporotic fractures seriously affect the quality of life of the elderly. Panax notoginseng saponins (PNS) have the potential function of preventing osteoporosis. The Phosphatidylinositol 3-kinase (PI3K)/protein kinase (AKT)/mammalian target of rapamycin (mTOR) pathway is involved in the regulation of osteoporosis and has been proven to be related to VEGF secretion and angiogenesis. Therefore, this study aimed to explore the effects of PNS on ovariectomized rats with osteoporotic fracture through the PI3K/AKT/mTOR pathway and angiogenesis-related factors. Female Sprague-Dawley rats were randomly divided into normal control, fracture model, ovariectomized fracture model, low-dose PNS (100 mg/kg/d), and high-dose PNS (200 mg/kg/d). The ovariectomized rat fracture model was established. In low and high dose groups, PNS was administered intraperitoneally. The vascularization of fracture ends was detected in vitro by micro-CT on the 7th, 14th, and 21st day after modeling, and the area and number of blood vessels in the unit field of vision of the callus healing plane were seen by hematoxylin-eosin staining. The expression levels of PI3K, AKT1, mTOR, hypoxia inducible factor-1; VEGF: vascular endothelial growth factor (HIF-1), VEGF, Ang-1, VEGFR2, and angiopoietin like 2 Gene (ANGPTL2) were determined using Western blotting. In the PNS treatment group, the area of cortical bone increased, the area of callus decreased, and the number and area of blood vessels increased significantly when compared with the ovariectomized fracture model group. PNS regulates the PI3K/AKT/mTOR signaling pathway and promotes the expression of vascular-related cytokines (VEGF, Ang-1, VEGFR2, and ANGPTL2) in osteoporotic fractures. PNS may regulate the expression of vascular-related factors through the PI3K/AKT/mTOR pathway and promote the healing of osteoporotic fractures in ovariectomized rats.

[Research progress on mechanism of traumatic brain injury promoting fracture healing]

Objective

To summarize the research progress on the mechanism related to traumatic brain injury (TBI) to promote fracture healing, and to provide theoretical basis for clinical treatment of fracture non-union.

Methods

The research literature on TBI to promote fracture healing at home and abroad was reviewed, the role of TBI in fracture healing was summarized from three aspects of nerves, body fluids, and immunity, to explore new ideas for the treatment of fracture non-union.

Results

Numerous studies have shown that fracture healing is faster in patients with fracture combined with TBI than in patients with simple fracture. It is found that the expression of various cytokines and hormones in the body fluids of patients with fracture and TBI is significantly higher than that of patients with simple fracture, and the neurofactors released by the nervous system reaches the fracture site through the damaged blood-brain barrier, and the chemotaxis and aggregation of inflammatory cells and inflammatory factors at the fracture end of patients with combined TBI also differs significantly from those of patients with simple fracture. A complex network of humoral, neural, and immunomodulatory networks together promote regeneration of blood vessels at the fracture site, osteoblasts differentiation, and inhibition of osteoclasts activity.

Conclusion

TBI promotes fracture healing through a complex network of neural, humoral, and immunomodulatory, and can treat fracture non-union by intervening in the perifracture microenvironment.

Interoceptive regulation of skeletal tissue homeostasis and repair

Recent studies have determined that the nervous system can sense and respond to signals from skeletal tissue, a process known as skeletal interoception, which is crucial for maintaining bone homeostasis. The hypothalamus, located in the central nervous system (CNS), plays a key role in processing interoceptive signals and regulating bone homeostasis through the autonomic nervous system, neuropeptide release, and neuroendocrine mechanisms. These mechanisms control the differentiation of mesenchymal stem cells into osteoblasts (OBs), the activation of osteoclasts (OCs), and the functional activities of bone cells. Sensory nerves extensively innervate skeletal tissues, facilitating the transmission of interoceptive signals to the CNS. This review provides a comprehensive overview of current research on the generation and coordination of skeletal interoceptive signals by the CNS to maintain bone homeostasis and their potential role in pathological conditions. The findings expand our understanding of intersystem communication in bone biology and may have implications for developing novel therapeutic strategies for bone diseases.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Hallmarks of peripheral nerve function in bone regeneration

Skeletal tissue is highly innervated. Although different types of nerves have been recently identified in the bone, the crosstalk between bone and nerves remains unclear. In this review, we outline the role of the peripheral nervous system (PNS) in bone regeneration following injury. We first introduce the conserved role of nerves in tissue regeneration in species ranging from amphibians to mammals. We then present the distribution of the PNS in the skeletal system under physiological conditions, fractures, or regeneration. Furthermore, we summarize the ways in which the PNS communicates with bone-lineage cells, the vasculature, and immune cells in the bone microenvironment. Based on this comprehensive and timely review, we conclude that the PNS regulates bone regeneration through neuropeptides or neurotransmitters and cells in the peripheral nerves. An in-depth understanding of the roles of peripheral nerves in bone regeneration will inform the development of new strategies based on bone-nerve crosstalk in promoting bone repair and regeneration.

Hyperbaric oxygen therapy promotes consciousness, cognitive function, and prognosis recovery in patients following traumatic brain injury through various pathways

Objective

The aim of this study was to investigate the clinical curative effect of hyperbaric oxygen (HBO) treatment and its mechanism in improving dysfunction following traumatic brain injury (TBI).

Methods

Patients were enrolled into control and HBO groups. Glasgow coma scale (GCS) and coma recovery scale-revised (CRS-R) scores were used to measure consciousness; the Rancho Los Amigos scale-revised (RLAS-R) score was used to assess cognitive impairment; the Stockholm computed tomography (CT) score, quantitative electroencephalography (QEEG), and biomarkers, including neuron-specific enolase (NSE), S100 calcium-binding protein beta (S100β), glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and vascular endothelial growth factor (VEGF), were used to assess TBI severity. The patients were followed up 6 months after discharge and assessed with the Glasgow outcome scale-extended (GOSE), functional independence measure (FIM), and the disability rating scale (DRS).

Results

The CRS-R scores were higher in the HBO group than the control group at 10 days after treatment. The RLAS-R scores were higher in the HBO group than the control group at 10 and 20 days after treatment. The Stockholm CT scores were significantly lower in the HBO group than the control group at 10 days after treatment. HBO depressed the (δ + θ)/(α + β) ratio (DTABR) of EEG, with lower δ band relative power and higher α band relative power than those in the control group. At 20 days after treatment, the expression of NSE, S100β, and GFAP in the HBO group was lower than that in controls, whereas the expression of BDNF, NGF, and VEGF in the HBO group was higher than that in controls. Six months after discharge, the HBO group had lower DRS scores and higher FIM and GOSE scores than the control group significantly.

Conclusions

HBO may be an effective treatment for patients with TBI to improve consciousness, cognitive function and prognosis through decreasing TBI-induced hematoma volumes, promoting the recovery of EEG rhythm, and modulating the expression of serum NSE, S100β, GFAP, BDNF, NGF, and VEGF.

Hu’po Anshen Decoction Accelerated Fracture-Healing in a Rat Model of Traumatic Brain Injury Through Activation of PI3K/AKT Pathway

Hu’po Anshen decoction (HPASD) is a traditional Chinese medicine formula comprising five herbal medicines for the treatment of concussion and fracture healing, but its pharmacological mechanism is still unclear. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC/Q-TOF MS) was used to analyze the main active components of HPASD. Rats were randomly assigned to fracture group, fracture combined with traumatic brain injury (TBI) group (FBI) and FBI combined with HPASD treatment group (FBIH). Rats in the FBIH group were given oral doses of HPASD (2.4 g/kg, 4.8 g/kg and 9.6 g/kg) for 14 or 21 consecutive days. The fracture callus formation and fracture sites were determined by radiographic analysis and micron-scale computed tomography (micro-CT) analysis. Hematoxylin and eosin (H&E) staining and a three-point bending test were applied to assess histological lesions and biomechanical properties, respectively. The levels of cytokines-/protein-related to bone formation and differentiation as well as PI3K/AKT pathway-related proteins were determined by Enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription-polymerase chain reaction (qRT-PCR), or western blot assays, respectively. UPLC-Q/TOF-MS-based serum metabolomic analysis was also performed to investigate the therapeutic effects of HPASD in the treatment of FBI. UPLC/Q-TOF MS analysis showed the chemical components in HPASD, including flavonoids, amino acids, saponins, and phenylpropanoid constituents, etc. HPASD dose-dependently promoted callus formation, increased bone density, improved mechanical parameters and morphological scores, and facilitated the expressions of VEGF, PDGF, bFGF, VEGFA, CoL1A1, RUNX2, BMP2, and Aggrecan, inhibited the expression of MMP13, and activated PI3K/AKT pathway. Metabolomics analysis revealed abnormalities of malate-aspartate shuttle and glucose-alanine. HPASD accelerates fracture healing by promoting bone formation and regulating the malate-aspartate shuttle and glucose-alanine cycle, which might be associated with the activation of the PI3K/AKT pathway.

Mechanisms of bone pain: Progress in research from bench to bedside

The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening from bone biology to neuroscience, neuroendocrinology, and immunology. In particular, the roles of primary sensory neurons and non-neuronal cells in the peripheral tissues as important targets for bone pain treatment are under extensive investigation in both pre-clinical and clinical settings. An understanding of the peripheral mechanisms underlying pain conditions associated with various bone diseases will aid in the appropriate application and development of optimal strategies for not only managing bone pain symptoms but also improving bone repairing and remodeling, which potentially cures the underlying etiology for long-term functional recovery. In this review, we focus on advances in important preclinical studies of significant bone pain conditions in the past 5 years that indicated new peripheral neuronal and non-neuronal mechanisms, novel targets for potential clinical interventions, and future directions of research.

Function of peripheral nerves in the development and healing of tendon and bone

Although the functions of the peripheral nervous system in whole body homeostasis and sensation have been understood for many years, recent investigation has uncovered new roles for innervation in the musculoskeletal system. This review centers on advances regarding the function of nerves in the development and repair of two connected tissues: tendon and bone. Innervation in healthy tendons is generally confined to the tendon sheaths, and tendon-bone attachment units are typically aneural. In contrast to tendon, bone is an innervated and vascularized structure. Historically, the function of abundant peripheral nerves in bone has been limited to pain and some non-painful sensory perception in disease and injury. Indeed, much of our understanding of peripheral nerves in tendons, bones, and entheses is limited to the source and type of innervation in healthy and injured tissues. However, more recent studies have made important observations regarding the appearance, type, and innervation patterns of nerves during embryonic and postnatal development and in response to injury, which suggest a more expansive role for peripheral nerves in the formation of musculoskeletal tissues. Indeed, tendons and bones develop in a close spatiotemporal relationship in the embryonic mesoderm. Models of limb denervation have shed light on the importance of sensory innervation in bone and to a lesser extent, tendon development, and more recent work has unraveled key nerve signaling pathways. Furthermore, loss of sensory innervation also impairs healing of bone fractures and may contribute to chronic tendinopathy. However, more study is required to translate our knowledge of peripheral nerves to therapeutic strategies to combat bone and tendon diseases.

The effect of traumatic brain injury on bone healing from a novel exosome centered perspective in a mice model

Background

In patients with traumatic brain injury (TBI) combined with long bone fracture, the fracture healing is always faster than that of patients with single fracture, which is characterized by more callus growth at the fracture site and even ectopic ossification. Exosomes are nanoscale membrane vesicles secreted by cells, which contain cell-specific proteins, miRNAs, and mRNAs.

Methods

In this study, we used exosomes as the entry point to explore the mechanism of brain trauma promoting fracture healing. We established a model of tibia fracture with TBI in mice to observe the callus growth and expression of osteogenic factors at the fracture site. Blood samples of model mice were further collected, exosomes in plasma were extracted by ultra-centrifugation method, and then identified and acted on osteoblasts cultured in vitro. The effects of exosomes on osteoblast differentiation at the cell, protein and gene levels were investigated by Western Blot and q-PCR, respectively. Furthermore, miRNA sequencing of exosomes was performed to identify a pattern of miRNAs that were present at increased or decreased levels.

Results

The results suggested that plasma exosomes after TBI had the ability to promote the proliferation and differentiation of osteoblasts, which might be due to the increased expression of osteoblast-related miRNA in exosomes. They were transmitted to the osteoblasts at the fracture site, so as to achieve the role of promoting osteogenic differentiation.

Conclusion

The TBI-derived exosomes may have potential applications for promoting fracture healing in future.

The Translational Potential of this Article

Plasma exosomes early after TBI have the ability to promote osteoblast proliferation and differentiation. The mechanism may be achieved by miRNA in exosomes. Plasma exosomes may be used as breakthrough clinical treatment for delayed or non-union fractures.

Expression of nerve growth factor in the callus during fracture healing in a fracture model in aged mice

BACKGROUND

Impaired fracture healing results in extensive and prolonged disability and long-term pain. Previous studies reported that nerve growth factor (NGF) was expressed during fracture healing and that anti-NGF antibody improves physical activity associate with facture pain. However, NGF expression levels in delayed or non-union are not fully understood.

OBJECTIVE

We compared chronological changes in NGF in the callus of young mice after femur fracture with those in aged mice after femur fracture as a model of bone fracture in the elderly.

METHODS

We used young (age 8 weeks) and aged (age 10 months) male C57BL/6J mice. A fracture was generated in the femur. At 5, 7, 10, 14, 17, and 21 days after creation of a fracture, mRNA expression levels of Col2a1, Col10a1, NGF were evaluated using quantitative PCR. We examined NGF protein expression levels and localization in the callus at day 14 using ELISA and immunohistochemistry, respectively.

RESULTS

Expression of NGF in the callus after femur fracture in aged mice was significantly greater than that in young mice at days 5, 7, 10, 17, and 21 days. NGF protein levels in the callus of aged mice were also significantly higher than that in young mice. Immunohistochemical staining showed that NGF was heavily expressed in hypertrophic chondrocytes in the callus in aged mice.

CONCLUSIONS

It is suggested that delayed Col2a1 and Col10a1 expression reflects delayed chondrocyte formation and delayed chondrocyte maturation in aged mice and that higher NGF expression in aged mice at day 14 may be associated with the presence of remaining hypertrophic chondrocytes in callus with delaying endochondral ossification.

Crosstalk between Bone and Nerves within Bone

For the past two decades, the function of intrabony nerves on bone has been a subject of intense research, while the function of bone on intrabony nerves is still hidden in the corner. In the present review, the possible crosstalk between bone and intrabony peripheral nerves will be comprehensively analyzed. Peripheral nerves participate in bone development and repair via a host of signals generated through the secretion of neurotransmitters, neuropeptides, axon guidance factors and neurotrophins, with additional contribution from nerve-resident cells. In return, bone contributes to this microenvironmental rendezvous by housing the nerves within its internal milieu to provide mechanical support and a protective shelf. A large ensemble of chemical, mechanical, and electrical cues works in harmony with bone marrow stromal cells in the regulation of intrabony nerves. The crosstalk between bone and nerves is not limited to the physiological state, but also involved in various bone diseases including osteoporosis, osteoarthritis, heterotopic ossification, psychological stress-related bone abnormalities, and bone related tumors. This crosstalk may be harnessed in the design of tissue engineering scaffolds for repair of bone defects or be targeted for treatment of diseases related to bone and peripheral nerves.

The Life of a Fracture: Biologic Progression, Healing Gone Awry, and Evaluation of Union

New knowledge about the molecular biology of fracture-healing provides opportunities for intervention and reduction of risk for specific phases that are affected by disease and medications. Modifiable and nonmodifiable risk factors can prolong healing, and the informed clinician should optimize each patient to provide the best chance for union. Techniques to monitor progression of fracture-healing have not changed substantially over time; new objective modalities are needed.

Astragalus saponin IV promotes osteogenic differentiation of bone marrow mesenchymal stem cells via miR-21/NGF/BMP2/Runx2 pathway

BACKGROUND

Astragalus saponin IV(AS- IV) extracted from tranditional Chinese medicine Radix Astragali Mongolici, which had been reported to have medicinal properties in treating several types of diseases. This study aimed at investigating the biological functions of AS-IV on bone marrow mesenchymal cells(BMSCs) differentiation, therefore, seeking for a better application of AS-IV on fracture or other orthopedic disorders.

METHODS

AS-IV was co-incubated with BMSCs in vitro to testify whether it can influence the proliferation and differentiation of BMSCs. Cell proliferation activity was detected by Cell Counting Kit-8 (CCK-8), while its differentiation promoting capibility was obtained by alkaline phosphatase (ALP) activity assay and Alizarin red S staining. Besides, differentiation protein markers of preosteoblast was detected by western blots. Neuron growth factor antagonists (NGFA) and microRNA-21 (miR-21) inhibitors were co incubated with AS-IV to search the regulatory pathways it activated in BMSCs.

RESULTS

AS-IV incubation boosted the proliferation of BMSCs, and accelerated the differentiating direction into preosteoblasts. Runx2, OPN, BMP2, OCN proteins were up regulated after AS- IV treatment. MiR-21/NGF/BMP2/Runx2 pathway can participate the biological effects of AS- IV on BMSCs.

CONCLUSION

AS- IV might be used as a therapeutic agent for bone fracture or other orthopedic disorders.

No pain, no gain? The effects of pain-promoting neuropeptides and neurotrophins on fracture healing

Neuropeptides and neurotrophins are key regulators of peripheral nociceptive nerves and contribute to the induction, sensitization, and maintenance of pain. It is now known that these peptides also regulate non-neuronal tissues, including bone. Here, we review the effects of numerous neuropeptides and neurotrophins on fracture healing. The neuropeptides calcitonin-gene related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating peptide (PACAP) have varying effects on osteoclastic and osteoblastic activity. Ultimately, CGRP and SP both accelerate fracture healing, while VIP and PACAP seem to negatively impact healing. Unlike the aforementioned neuropeptides, the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have more uniform effects. Both factors upregulate osteoblastic activity, osteoclastic activity, and, in vivo, stimulate osteogenesis to promote fracture healing. Future research will need to clarify the exact mechanism by which the neuropeptides and neurotrophins influence fracture healing. Specifically, understanding the optimal expression patterns for these proteins in the fracture healing process may lead to therapies that can maximize their bone-healing capabilities and minimize their pain-promoting effects. Finally, further examination of protein-sequestering antibodies and/or small molecule agonists and antagonists may lead to new therapies that can decrease the rate of delayed union/nonunion outcomes and fracture-associated pain.

Downregulation of microRNA-16-5p accelerates fracture healing by promoting proliferation and inhibiting apoptosis of osteoblasts in patients with traumatic brain injury

Patients who suffered a traumatic brain injury (TBI) show a faster fracture healing than patients with isolated fractures. Prior studies have suggested that this process may be accelerated through the inhibition of key microRNAs. In this study, we aimed to explore the mechanisms underlying this phenomenon, with a special focus on miR-16-5p, which is markedly decreased in patients with TBI. In vitro, miR-16-5p over-expression significantly inhibited cell proliferation in MC3T3-E1 cells transfected with agomiR-16-5p. Flow cytometry analysis further demonstrated that the overexpression of miR-16-5p induced cell cycle G1/S phase arrest and apoptosis. Moreover, target prediction and luciferase reporter assay demonstrated that miR-16-5p could negatively regulate Bcl-2 and Cyclin-D1 expression. Meanwhile, Bcl-2 and Cyclin-D1 were up-regulated after osteogenic differentiation while the down-regulation of endogenous Bcl-2 and Cyclin-D suppressed the osteogenic differentiation of MC3T3-E1 cells. In vivo, PBS, agomiR-16-5p and antagomiR-16-5p were injected into fracture sites to assess any improvements in fracture healing, which further confirmed the negative effect of miR-16-5p on fracture healing. Together, these results demonstrate miR-16-5p downregulation may accelerate fracture healing by enhancing the proliferation and inhibiting the apoptosis of osteoblasts in patients with both fractures and TBI. These phenomena may be exploited in the treatment of fractures.

miRNA-26a-5p Accelerates Healing via Downregulation of PTEN in Fracture Patients with Traumatic Brain Injury

Patients who sustain a traumatic brain injury (TBI) are known to have a significantly quicker fracture healing time than patients with isolated fractures, but the underlying mechanism has yet to be identified. In this study, we found that the upregulation of miRNA-26a-5p induced by TBI correlated with a decrease in phosphatase and tensin homolog (PTEN) in callus formation. In vitro, overexpressing miRNA-26a-5p inhibited PTEN expression and accelerated osteoblast differentiation, whereas silencing of miRNA-26a-5p inhibited osteoblast activity. Reduction of PTEN facilitated osteoblast differentiation via the PI3K/AKT signaling pathway. Through luciferase assays, we found evidence that PTEN is a miRNA-26a-5p target gene that negatively regulates the differentiation of osteoblasts. Moreover, the present study confirmed that preinjection of agomiR-26a-5p leads to increased bone formation. Collectively, these results indicate that miRNA-26a-5p overexpression may be a key factor governing the improved fracture healing observed in TBI patients after the downregulation of PTEN and PI3K/AKT signaling. Upregulation of miRNA-26a-5p may therefore be a promising therapeutic strategy for promoting fracture healing.