Guangxi cobra venom-derived NGF promotes the osteogenic and therapeutic effects of porous BCP ceramic

Bone-nerve crosstalk: a new state for neuralizing bone tissue engineering-A mini review

Neuro bone tissue engineering is a multidisciplinary field that combines both principles of neurobiology and bone tissue engineering to develop innovative strategies for repairing and regenerating injured bone tissues. Despite the fact that regeneration and development are considered two distinct biological processes, yet regeneration can be considered the reactivation of development in later life stages to restore missing tissues. It is noteworthy that the regeneration capabilities are distinct and vary from one organism to another (teleost fishes, hydra, humans), or even in the same organism can vary dependent on the injured tissue itself (Human central nervous system vs. peripheral nervous system). The skeletal tissue is highly innervated, peripheral nervous system plays a role in conveying the signals and connecting the central nervous system with the peripheral organs, moreover it has been shown that they play an important role in tissue regeneration. Their regeneration role is conveyed by the different cells' resident in it and in its endoneurium (fibroblasts, microphages, vasculature associated cells, and Schwann cells) these cells secrete various growth factors (NGF, BDNF, GDNF, NT-3, and bFGF) that contribute to the regenerative phenotype. The peripheral nervous system and central nervous system synchronize together in regulating bone homeostasis and regeneration through neurogenic factors and neural circuits. Receptors of important central nervous system peptides such as Serotonin, Leptin, Semaphorins, and BDNF are expressed in bone tissue playing a role in bone homeostasis, metabolism and regeneration. This review will highlight the crosstalk between peripheral nerves and bone in the developmental stages as well as in regeneration and different neuro-bone tissue engineering strategies for repairing severe bone injuries.

Nerve growth factor promote osteogenic differentiation of dental pulp stem cells through MEK/ERK signalling pathways

Nerve growth factor (NGF) and its receptor, tropomyosin receptor kinase A (TrkA), are known to play important roles in the immune and nervous system. However, the effects of NGF on the osteogenic differentiation of dental pulp stem cells (DPSCs) remain unclear. This study aimed to investigate the role of NGF on the osteogenic differentiation of DPSCs in vitro and the underlying mechanisms. DPSCs were cultured in osteogenic differentiation medium containing NGF (50 ng/mL) for 7 days. Then osteogenic-related genes and protein markers were analysed using qRT-PCR and Western blot, respectively. Furthermore, addition of NGF inhibitor and small interfering RNA (siRNA) transfection experiments were used to elucidate the molecular signalling pathway responsible for the process. NGF increased osteogenic differentiation of DPSCs significantly compared with DPSCs cultured in an osteogenic-inducing medium. The NGF inhibitor Ro 08-2750 (10 μM) and siRNA-mediated gene silencing of NGF receptor, TrkA and ERK signalling pathways inhibitor U0126 (10 μM) suppressed osteogenic-related genes and protein markers on DPSCs. Furthermore, our data revealed that NGF-upregulated osteogenic differentiation of DPSCs may be associated with the activation of MEK/ERK signalling pathways via TrkA. Collectively, NGF was capable of promoting osteogenic differentiation of DPSCs through MEK/ERK signalling pathways, which may enhance the DPSCs-mediated bone tissue regeneration.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

FBXO22 Mediates the NGF/TRKA Signaling Pathway in Bone Metastases in Prostate Cancer

Prostate cancer (PC) is a malignancy with high morbidity and mortality. Bone metastasis is the main driver of short survival time and difficulties in the treatment and prevention of PC. The goal of this study was to explore the biological function of E3 ubiquitin ligase F-box only protein 22 (FBXO22) in PC metastasis and its specific regulation mechanism. According to transcriptome sequencing, FBXO22 was overexpressed in PC tissues (versus adjacent tissues) and bone tissues (versus biopsied bone tissues without bone metastases). Fbxo22 down-regulation reduced bone metastases and macrophage M2 polarization in mice. FBXO22 was down-regulated in macrophages, and polarization was observed by flow cytometry. Macrophages were co-cultured with PC cells and osteoblasts to assess PC cell and osteoblast activity. FBXO22 knockdown restored osteoblast capacity. FBXO22 ubiquitinated and degraded Krüppel-like factor 4 (KLF4), which regulated the nerve growth factor (NGF)/tropomyosin receptor kinase A pathway by repressing NGF transcription. Silencing of KLF4 mitigated the metastasis-suppressing properties of FBXO22 knockdown, whereas NGF reversed the metastasis-suppressing properties of KLF4 in vitro and in vivo. Cumulatively, these data indicate that FBXO22 promotes PC cell activity and osteogenic lesions by stimulating macrophage M2 polarization. It also degrades KLF4 in macrophages and promotes NGF transcription, thereby activating the NGF/tropomyosin receptor kinase A pathway.

Nerves within bone and their application in tissue engineering of bone regeneration

Nerves within bone play an irreplaceable role in promoting bone regeneration. Crosstalk between the nerve system and bone has arisen to the attention of researchers in the field of basic medicine, clinical medicine, and biomaterials science. Successful bone regeneration relies on the appropriate participation of neural system components including nerve fibers, signaling molecules, and neural-related cells. Furthermore, more about the mechanisms through which nerves took part in bone regeneration and how these mechanisms could be integrated into tissue engineering scaffolds were under exploration. In the present review, we aimed to systematically elaborate on the structural and functional interrelationship between the nerve system and bone. In particular, peripheral nerves interact with the bone through innervated axons, multiple neurotrophins, and bone resident cells. Also, we aimed to summarize research that took advantage of the neuro-osteogenic network to design tissue engineering scaffolds for bone repair.

Nervous System-Driven Osseointegration

Implants are essential therapeutic tools for treating bone fractures and joint replacements. Despite the in-depth study of osseointegration for more than fifty years, poor osseointegration caused by aseptic loosening remains one of the leading causes of late implant failures. Osseointegration is a highly sophisticated and spatiotemporal process in vivo involving the immune response, angiogenesis, and osteogenesis. It has been unraveled that the nervous system plays a pivotal role in skeletal health via manipulating neurotrophins, neuropeptides, and nerve cells. Herein, the research related to nervous system-driven osseointegration was systematically analyzed and reviewed, aiming to demonstrate the prominent role of neuromodulation in osseointegration. Additionally, it is indicated that the implant design considering the role of neuromodulation might be a promising way to prevent aseptic loosening.

Tissue Engineered Neurovascularization Strategies for Craniofacial Tissue Regeneration

Craniofacial tissue injuries, diseases, and defects, including those within bone, dental, and periodontal tissues and salivary glands, impact an estimated 1 billion patients globally. Craniofacial tissue dysfunction significantly reduces quality of life, and successful repair of damaged tissues remains a significant challenge. Blood vessels and nerves are colocalized within craniofacial tissues and act synergistically during tissue regeneration. Therefore, the success of craniofacial regenerative approaches is predicated on successful recruitment, regeneration, or integration of both vascularization and innervation. Tissue engineering strategies have been widely used to encourage vascularization and, more recently, to improve innervation through host tissue recruitment or prevascularization/innervation of engineered tissues. However, current scaffold designs and cell or growth factor delivery approaches often fail to synergistically coordinate both vascularization and innervation to orchestrate successful tissue regeneration. Additionally, tissue engineering approaches are typically investigated separately for vascularization and innervation. Since both tissues act in concert to improve craniofacial tissue regeneration outcomes, a revised approach for development of engineered materials is required. This review aims to provide an overview of neurovascularization in craniofacial tissues and strategies to target either process thus far. Finally, key design principles are described for engineering approaches that will support both vascularization and innervation for successful craniofacial tissue regeneration.

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.

Effects of exogenous nerve growth factor on the expression of BMP-9 and VEGF in the healing of rabbit mandible fracture with local nerve injury

BACKGROUND

Mandibular fracture healing is a complex process involving nerves and growth factors. Nerve growth factor (NGF) not only facilitates the maintenance of sympathetic neurite growth but also stimulates other growth factors that can promote the essential osteogenesis and angiogenesis for fracture healing. Therefore, it is necessary to analyze the combined effects of NGF, bone morphogenic protein-9 (BMP-9), and vascular endothelial growth factor (VEGF) to accelerate the healing of mandible fractures.

METHODS

The models of mandible fracture with local nerve injury established in 48 rabbits were randomly divided into nerve growth factor group (NGF group), gelatin sponge group (GS group), blank group, and intact group. The recovery of nerve reflex was assessed by observing the number of rabbits with lower lip responses to acupuncture. The fracture healing was observed with visual and CBCT, and then callus tissues from the mandibular fracture area were collected for hematoxylin and eosin (HE) staining observation, and the expression of BMP-9 and VEGF in callus at different stages was detected by quantitative real-time PCR (qRT-PCR).

RESULTS

Needling reaction in the lower lip showed the number of animals with nerve reflex recovery was significantly higher in the NGF group than that in the GS and blank groups at the 2nd and 4th weeks after the operation. The combined results of macroscopic observation, CBCT examination, and histological analysis showed that a large number of osteoblasts and some vascular endothelial cells were found around the trabecular bone in the NGF group and the amount of callus formation and reconstruction was better than that in the GS group at the 2nd week after the operation. The qRT-PCR results indicated that the expression levels of BMP-9 and VEGF in the four groups reached the highest values at the 2nd week, while the expression levels of both in the NGF group were significantly higher than that in the GS group.

CONCLUSION

The exogenous NGF could accelerate the healing of mandible fractures. This work will provide a new foundation and theoretical basis for clarifying the mechanism of fracture healing, thereby promoting fracture healing and reducing the disability rate of patients.

Astragaloside‑IV modulates NGF‑induced osteoblast differentiation via the GSK3β/β‑catenin signalling pathway

Astragaloside (AST) is derived from the Chinese herb Astragalus membranaceus, and studies have demonstrated that it promotes differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). To the best of our knowledge, however, the functions of the component AST-IV in osteogenesis have not previously been elucidated. The present study aimed to verify the effects of AST-IV in osteogenesis. First, the proliferation and differentiation status of human BMSCs incubated with AST-IV were analysed and compared with a control (no AST-IV treatment). In order to determine the involvement of the glycogen synthase kinase (GSK)3β signalling pathway in AST-IV, overexpression and inhibition of GSK3β was induced during incubation of BMSCs with AST-IV. In order to investigate how neuronal growth factor (NGF) contributes to BMSCs differentiation, BMSCs were co-incubated with an anti-NGF antibody and AST IV, and then levels of osteogenesis markers were assessed. The results demonstrated for the first time that AST-IV contributed to BMSCs differentiation. Furthermore, the GSK3β/β-catenin signalling pathway was revealed to be involved in AST-IV-induced osteogenesis; moreover, AST-IV accelerated differentiation by enhancing the expression levels of NGF. In summary, the present study demonstrated that AST-IV promotes BMSCs differentiation, thus providing a potential target for the treatment of osteoporosis.

NGF-CS/HA-coating composite titanium facilitates the differentiation of bone marrow mesenchymal stem cells into osteoblast and neural cells

Dental implant is the most effective way to repair the defect or absence of dentition. Currently, the modification in titanium surface properties has become a hot topic in the study of oral implantology. However, more suitable titanium surface coating still needs to be further explored. We prepared the nerve growth factor-chondroitin sulfate/hydroxyapatite (NGF-CS/HA)-coating composite titanium by modified biomimetic method. We also observed the surface morphology, thickness, surface adhesion and component analysis of NGF-CS/HA-coating composite titanium by scanning electron microscope, and the release of NGF was also identified via ELISA assay. Besides, the identification of bone marrow mesenchymal stem cells (BMSCs) was conducted through alizarin red staining, oil red O staining and fluorescence detection. and the osteogenesis differentiation and neuronal differentiation-related genes were determined by RT-qPCR assay. The surface of NGF-CS/HA coating with the 65.4 ± 6.4 μm thickness presented a porous network, and the main components of NGF-CS/HA coating were Ti and HA, and maintained the activity and release of NGF. Besides, we successfully obtained and identified BMSCs, and proved that NGF-CS/HA-coating composite titanium could notably upregulated the expression levels of the osteogenesis differentiation and neuronal differentiation-related genes and proteins in BMSCs. In conclusion, NGF-CS/HA-coating composite titanium has significant promoting effects on the differentiation of BMSCs into osteoblast and neural cells.

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.

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

Background

Angiogenesis and bone formation are vital for fracture healing. Nerve growth factor (NGF) not only promotes neuronal survival but also enhances the proliferation and differentiation of osteoblasts. Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis. However, the potential correlation of NGF and VEGF levels with fracture healing in patients with traumatic brain injury (TBI) remains unclear.

Methods

This study enrolled 22 patients with clavicle fracture and concomitant TBI (CFT group) and 25 patients with clavicle fracture alone (CF group). Serum NGF levels were measured with ELISA. The expressions of NGF, VEGF, and CD31 in callus tissues were measured with immunohistochemistry.

Results

The fracture healing time in CFT group (82.22±13.61 days) was significantly shorter than that in CF group (127±25.05 days; P<0.001). The expression of CD31, marker of blood vessels, in callus tissues of CFT group was higher compared with that of CF group. Serum NGF levels and the expression of NGF in callus tissues of CFT group were higher than those in CF group (P<0.01). The expressions of CD31, NGF, and VEGF are correlated with shorter fracture healing time.

Conclusion

The formation of blood vessels was increased in CFT group compared with CF group. NGF and VEGF levels were higher in CFT group than in CF group and correlated with shorter fracture healing time. Accelerated fracture healing in patients with TBI may be due to NGF- and VEGF-mediated angiogenesis at the fracture site.