Simultaneous bone and nerve regeneration is important in facilitating osseointegration. However, regeneration of neural elements is often overlooked when designing orthopedic implants. Since nerves are electroactive tissues that regulate bone formation via neuropeptide release, developing photoelectric coating material on implants is optimal for neural-stimulated osteoblast activation. In this study, three kinds of vertically oriented TiO2 nanotube (TNT) coatings with tube diameter of 60, 110 and 180 nm were fabricated on Ti implants denoting as TNT-60, TNT-110 and TNT-180, respectively. TNT-60 coating with higher oxygen-vacancy concentration and lower crystallinity displayed higher visible-light absorption capacity and transient photocurrent density. Enhanced photoelectric activity of TNT-60 was ascribed to narrowed bandgap of TiO2 and enhanced separation efficiency of photogenerated carriers. TNTs coatings under visible-light irradiation significantly improved proliferation of PC12 cells and cell differentiation in terms of neurite outgrowth and calcitonin gene-related peptide release. Among them, TNT-60 coating exerted the greatest enhancement via Ca2 + influx mechanism. Osteoblast differentiation and mineralization of MC3T3-E1 cells were significantly enhanced when cells were cultured with conditioned medium from PC12 cells cultured on the TNTs coatings with visible-light illumination. This indicated neural-stimulated osteoblast activation. Above all, photoelectric TNT coating provides a promising approach for targeting nerve activation to stimulate osteogenesis.

The utility of the inferior alveolar neurovascular bundle for bone remodeling after mandible reconstruction is still unclear. The aim of this study is to assess the impact of inferior alveolar neurovascular bundle preservation on mandibular reconstruction and maintenance.

Patients who underwent pathological mandible resection of benign mandibular lesions and reconstruction with an autogenous bone graft between 2011 and 2021 were included. They were divided into two groups based on whether the inferior alveolar neurovascular bundle was preserved. Patient-related data were obtained from the electronic health records, and radiological images was collected immediately, 6, 12-24 months after surgery, and more than 24 months thereafter. The primary outcomes included changes in bone mass and quality. The secondary outcomes included the assessment of mouth opening, mandibular function and sensory function. SPSS software was used to analyze significant differences.

A total of 18 patients (aged 15-61 years) were included, with 9 retaining inferior alveolar neurovascular bundles and 9 not. During the follow-up period, the bone mass and bone quality in the preserved group decreased less, especially within 6 months after surgery. Linear regression models showed that among the various influencing factors, in addition to the preservation of neurovascular bundles, bone mass and quality were also related to patient age, sex and the use of non or pedicled bone grafts.

These results demonstrate that preservation of the inferior alveolar neurovascular bundle can significantly improve the stability of the grafts' mass and quality.

The results of this study indicate that preserving the inferior alveolar neurovascular bundle during mandibular reconstruction can reduce early graft resorption and enhance long-term graft stability, offering improved functional outcomes.

Despite its potential in hydrogen (H2) therapy, ammonia borane (AB) has limited biomedical applications due to its uncontrolled hydrolysis rate and potential to cause cytotoxicity. Existing material-based delivery strategies focus on accelerating AB hydrolysis for H2 production, hence exacerbating these issues. A new nanoconfinement strategy is reported, which loads AB onto oxygen-deficient, hybrid-phased titanate nanocrystals on implant surfaces through a unique one-end-anchored docking (OEAD) mechanism. This nanoconfinement strategy effectively restricts the release of AB molecules, allowing only water molecules to infiltrate the interlayer space for slow hydrolysis and sustained H2 release. This significantly prolongs the duration of H2 release and effectively circumvents the cytotoxicity associated with AB interacting with hydrogen peroxide (H2O2) in the inflammatory microenvironment. In vitro and in vivo have shown that sustained H2 release from the implant surface effectively alleviates diabetes-related oxidative stress, and combined with the release of magnesium ions (Mg2+) synergistically promotes innervated-vascularized bone regeneration.

Bone tissues are densely innervated by nerve fibers throughout the periosteum and mineralized bone. The impairment of innervated bone regeneration is a critical factor contributing to the challenges in osteoporotic bone remodeling and repair. Herein, an "ultrasound-driven innervated bone regeneration" strategy is proposed in additively manufactured degradable Zn-Cu scaffolds. The in vitro investigations with RSC96 cells elucidated the synergistic promotion of low-intensity pulsed ultrasound (LIPUS) and metal cations on Schwann cell proliferation and exosome secretion. Notably, these Schwann cell-derived exosomes, once internalized by neighboring bone marrow stromal cells (BMSCs), significantly enhanced their migration, osteogenic differentiation, and extracellular matrix deposition, indicating a potent mechanism for innervated bone regeneration. Furthermore, the in vivo evaluation validated that LIPUS stimulation significantly activated S100β-positive Schwann cells and facilitated the regeneration of peripheral nerve fibers within cranial defects, leading to accelerated bone healing of osteoporotic rats with Zn-Cu implantation over 2- and 6-week recovery periods. This work provides an innervated bone regeneration strategy by focusing on the activation of Schwann cells and enhancement of paracrine effect, especially exosome secretion, which further recruited surrounding BMSCs and promoted their osteogenic differentiation. This study holds considerable promise for clinical applications and translation in the treatment of osteoporotic bone defects.

The skeleton is in complex interplay with the other systems of the body and is highly responsive to input from the external environment. Bone mechanical loading results in interstitial fluid flow via the lacunar-canalicular system, generating fluid flow sheer stress (FFSS). FFSS variably stresses osteocytes, subsequently causing the release of metabolites and protein factors that function locally to increase bone formation and may play a role in cross talk between various organ systems, for instance between bone and skeletal muscle. Therefore, we hypothesized that this cross talk includes altering cardiac function. To test this hypothesis, media conditioned by MLO-Y4 osteocyte-like cell culture line under FFSS was used to model the endocrine effects of bone during mechanical loading on contraction of ex vivo Langendorf-perfused isolated hearts. When hearts were externally paced at a fixed rate, FFSS osteocyte conditioned media (CM) induced significant premature contractions compared with vehicle (control). FFSS osteocyte CM administration to self-paced hearts increased total contraction force by 31%. To determine whether the mechanism involved intracellular Ca2+, vehicle and FFSS bone CM were perfused over cultured H9C2 cardiomyocytes while undergoing Ca2+ imaging using Fluo-8. We observed an increase in intracellular Ca2+ with FFSS CM perfusion of cardiomyocytes compared with vehicle. These increases were only present with exogenous electrical pacing. Our findings demonstrate that FFSS bone CM enhances cardiac contractility by increasing intracellular cardiomyocyte Ca2+. The results obtained in this study suggest that the skeleton, responding to mechanical strain, has the potential to augment cardiac output and provide evidence for bone-heart cross talk.NEW & NOTEWORTHY The skeletal system operates as an endocrine organ, releasing factors that impact multi-tissue physiology. The results obtained in this study demonstrate that conditioned media collected from MLO-Y4 osteocytes exposed to fluid flow shear stress increases cardiomyocyte intracellular calcium and enhances cardiac contractility in vitro. These results support the concept of bone-heart cross talk that may have implications in exercise training, reduced-function settings such as bedrest, and the interplay between bone and heart health.

Osteogenesis-angiogenesis coupling, a dynamic and coordinated interaction between skeletal and vascular cells, is essential for fracture healing. However, the effects of these cell ratios and their interactions under microfluidic perfusion and paracrine signaling on osteogenesis-angiogenesis coupling have rarely been reported. In this study, dynamic and static models of osteogenesis-angiogenesis coupling were developed and the osteogenic and angiogenic effects of the two models were compared. Static co-cultures of MC3T3-E1 and bEnd.3 cells in Transwell inserts showed a cell ratio-dependent reciprocal relation: a ratio of 1:1 (MC3T3-E1:bEnd.3) favored osteogenesis, whereas a ratio of 2:1 (MC3T3-E1:bEnd.3) promoted angiogenesis. On that basis, we developed an osteogenesis-angiogenesis coupling chip based on microfluidic technology. The microfluidic perfusion within the chip further enhanced the mineralizing effect of osteoblasts and the angiogenic effect of endothelial cells, respectively, and increased the secretion of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) compared to the static Transwell insert model. The results suggest that the microfluidic chip enhanced the potential of osteogenesis-angiogenesis coupling mediated by paracrine signaling. Overall, the chip is not only a powerful model for understanding bone-vascular interaction but also a scalable platform for high-throughput drug screening and personalized therapy development for fractures.

Nemo-like kinase (NLK), an evolutionarily conserved MAP kinase-related kinase, is highly expressed in neural tissues and critically regulates cell proliferation, migration, and apoptosis by regulating numerous transcriptional molecules. Despite the widespread application of mesenchymal stem cells (MSCs) in regenerative medicine, the functional role and molecular mechanisms of NLK in MSC-mediated tissue repair remained poorly understood. Here, the dual regulatory effects of NLK on both neurogenic and osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) were investigated. The results showed that NLK acted as a potent inhibitor of hBMSC neurogenesis in vitro and suppressed osteogenesis both in vitro and in vivo. Mechanistically, NLK downregulated the transcriptional coactivators LEF1 and TCF4, thereby impairing their pro-differentiation functions during neural and bone formation. These findings suggested that NLK-mediated suppression of LEF1/TCF4 signaling might hinder endogenous bone repair by dual inhibition of hBMSC neurogenic and osteogenic capacities. Targeting this pathway could offer novel therapeutic strategies for enhancing bone defect regeneration and inform the design of advanced biomaterials for bone tissue engineering.

Tissue engineering aims to repair damaged tissues with physiological functions recovery. Although several therapeutic strategies are there for tissue regeneration, the functional recovery of regenerated tissues still poses significant challenges due to the lack of concerns of tissue innervation. Design rationale of multifunctional biomaterials with both tissue-induction and neural induction activities shows great potential for functional tissue regeneration. Recently, the research and application of inorganic biomaterials attracts increasing attention in innervated multi-tissue regeneration, such as central nerves, bone, and skin, because of its superior tunable chemical composition, topographical structures, and physiochemical properties. More importantly, inorganic biomaterials are easily combined with other organic materials, biological factors, and external stimuli to enhance their therapeutic effects. This review presents a comprehensive overview of recent advancements of inorganic biomaterials for innervated multi-tissue regeneration. It begins with introducing classification and properties of typical inorganic biomaterials and design rationale of inorganic-based material composites. Then, recent progresses of inorganic biomaterials in regenerating various nerves and nerve-innervated tissues with functional recovery are systematically reviewed. Finally, the existing challenges and future perspectives are proposed. This review may pave the way for the direction of inorganic biomaterials and offers a new strategy for tissue regeneration in combination of innervation.

Orthopedic implants with high elastic modulus often suffer from poor osseointegration due to stress shielding, a phenomenon that suppresses the expression of intracellular mechanotransduction molecules (IMM) such as focal adhesion kinase (FAK). We find that reduced FAK expression under stress shielding is also mediated by decreased calcitonin gene-related peptide (CGRP) released from Piezo2+ mechanosensitive nerves surrounding the implant. To activate these nerves minimally invasively, we develop a fully implantable, wirelessly rechargeable optogenetic device. In mice engineered to express light-sensitive channels in Piezo2+ neurons, targeted stimulation of the L2-3 dorsal root ganglia (DRG) enhances localized CGRP release near the implant. This CGRP elevation activates the Protein Kinase A (PKA)/FAK signaling pathway in bone marrow mesenchymal stem cells (BMSCs), thereby enhancing osteogenesis and improving osseointegration. Here we show that bioelectronic modulation of mechanosensitive nerves offers a strategy to address implant failure, bridging neuroregulation and bone bioengineering.

Sensory innervation triggers the regenerative response after injury. However, dysfunction and impairment of sensory nerves, accompanied by excessive inflammation impede tissue regeneration. Consequently, specific induction of sensory innervation to mediate immunoregulation becomes a promising therapeutic approach. Herein, we developed a cell/drug-free strategy to selectively boost endogenous sensory innervation to harness immune responses for promoting tissue rehabilitation. Specifically, a dual-functional phage was constructed with a sensory nerve-homing peptide and a β-subunit of nerve growth factor (β-NGF)-binding peptide. These double-displayed phages captured endogenic β-NGF and localized to sensory nerves to promote sensory innervation. Furthermore, regarding bone regeneration, phage-loaded hydrogels achieved rapid sensory nerve ingrowth in bone defect areas. Mechanistically, sensory neurotization facilitated M2 polarization of macrophages through the Sema3A/XIAP/PAX6 pathway, thus decreasing the M1/M2 ratio to induce the dissipation of local inflammation. Collectively, these findings highlight the essential role of sensory innervation in manipulating inflammation and provide a conceptual framework based on neuroimmune interactions for promoting tissue regeneration.

The skeleton is innervated by different types of nerves and receives signaling from the nervous system to maintain homeostasis and facilitate regeneration or repair. Although the role of peripheral nerves and signals in regulating bone homeostasis has been extensively investigated, the intimate relationship between the central nervous system and bone remains less understood, yet it has emerged as a hot topic in the bone field. In this review, we discussed clinical observations and animal studies that elucidate the connection between the nervous system and bone metabolism, either intact or after injury. First, we explored mechanistic studies linking specific brain nuclei with bone homeostasis, including the ventromedial hypothalamus, arcuate nucleus, paraventricular hypothalamic nucleus, amygdala, and locus coeruleus. We then focused on the characteristics of bone innervation and nerve subtypes, such as sensory, sympathetic, and parasympathetic nerves. Moreover, we summarized the molecular features and regulatory functions of these nerves. Finally, we included available translational approaches that utilize nerve function to improve bone homeostasis and promote bone regeneration. Therefore, considering the nervous system within the context of neuromusculoskeletal interactions can deepen our understanding of skeletal homeostasis and repair process, ultimately benefiting future clinical translation.

Severe periodontitis frequently leads to irreversible degradation of alveolar bone. Periodontal regeneration techniques hold immense potential in reconstructing alveolar bone post periodontal diseases. Schwann cells (SCs) play a critical role in supporting, maintaining, and regenerating periodontal tissues, with SC-derived exosomes (SC-EXO) exhibiting cell homing and tissue repair capabilities. Nevertheless, the specific role of SC-EXO in periodontal bone regeneration remains unknown. To address the issue, we treated human periodontal ligament cells (hPDLCs) with SC-EXO and observed a notable increase in cell proliferation, and osteogenic and neurogenic differentiation. Moreover, SC-EXO stimulated the expression of angiogenic factors in vascular endothelial cells. In a rat model of periodontal bone defects, SC-EXO facilitated the recruitment of endogenous cells, regulated neural and vascular neogenesis, and accelerated periodontal bone regeneration. This study successfully prepared SC-EXO, which effectively promotes periodontal bone regeneration by regulating the bone healing microenvironment, potentially offering a valuable strategy for periodontal tissue engineering.

Recent literature has increasingly demonstrated the significant function of autonomic nerves in regulating physiological and pathological changes associated with the skeletal system. Extensive studies have been conducted to understand the contribution of the autonomic nervous system (ANS) to skeletal metabolic homeostasis and resistance to aseptic inflammation, specifically from the viewpoint of skeletal neurobiology. There have been plenty of studies on how the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS), the two main branches of the ANS, regulate bone remodeling, which is the process of bone formation and resorption. The following studies have revealed critical neurological pathways that induce significant alterations in bone cell biology and uncover the intricate linkages between the ANS and the skeletal system. Furthermore, inspired by the connection between the ANS and bone remodeling, neuromodulation has been utilized as a therapeutic method for patients with orthopedic diseases: by directly influencing the ANS, it is possible to alter the excitability of nerve fibers and the release of neurotransmitters, which can lead to anti-inflammatory and analgesic effects, thereby directly or indirectly impacting bone formation and bone resorption. Our work aims to review the most recent findings on the impact of the ANS on bone remodeling, enhance the current understanding of the interaction between nerves and bones, and explore potential neuromodulation methods that could be used to treat orthopedic conditions, thereby drawing attention to the significant role of the ANS in the skeletal system.

Bone tissue relies on the intricate interplay between blood vessels and nerve fibers, both are essential for many physiological and pathological processes of the skeletal system. Blood vessels provide the necessary oxygen and nutrients to nerve and bone tissues, and remove metabolic waste. Concomitantly, nerve fibers precede blood vessels during growth, promote vascularization, and influence bone cells by secreting neurotransmitters to stimulate osteogenesis. Despite the critical roles of both components, current biomaterials generally focus on enhancing intraosseous blood vessel repair, while often neglecting the contribution of nerves. Understanding the distribution and main functions of blood vessels and nerve fibers in bone is crucial for developing effective biomaterials for bone tissue engineering. This review first explores the anatomy of intraosseous blood vessels and nerve fibers, highlighting their vital roles in bone embryonic development, metabolism, and repair. It covers innovative bone regeneration strategies directed at accelerating the intrabony neurovascular system over the past 10 years. The issues covered included material properties (stiffness, surface topography, pore structures, conductivity, and piezoelectricity) and acellular biological factors [neurotrophins, peptides, ribonucleic acids (RNAs), inorganic ions, and exosomes]. Major challenges encountered by neurovascularized materials during their clinical translation have also been highlighted. Furthermore, the review discusses future research directions and potential developments aimed at producing bone repair materials that more accurately mimic the natural healing processes of bone tissue. This review will serve as a valuable reference for researchers and clinicians in developing novel neurovascularized biomaterials and accelerating their translation into clinical practice. By bridging the gap between experimental research and practical application, these advancements have the potential to transform the treatment of bone defects and significantly improve the quality of life for patients with bone-related conditions.

This study aimed to investigate whether platelet-rich plasma (PRP) obtained from the blood of rats preconditioned with hyperbaric oxygen (HBOP) would enhance the biological activity of PRP and accelerate the healing process of femur fractures in a rat model.

PRP was derived from blood samples of healthy rats subjected to either hyperbaric oxygen (hPRP) or normobaric air (nPRP). A closed femur fracture model was established in male Wistar rats, with treatments of hPRP or nPRP administered around the fracture site immediately post-fracture and on days 7, 14, 21, and 28. Growth factor concentrations in hPRP and nPRP were biochemically quantified. Bone healing was assessed weekly by X-ray, while histological and immunofluorescence analyses evaluated inflammatory status, osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL) expression, and the presence of osteoblasts, osteoclasts, and osteocytes during healing. The effects of hPRP and nPRP on MC3T3-E1 preosteoblast migration and proliferation were also tested in vitro.

hPRP showed significantly higher concentrations of growth factors such as activin-A, brain-derived neurotrophic factor, nerve growth factor, Flt-3 Ligand, granulocyte-macrophage colony-stimulating factor, hepatocyte growth factor, and platelet-derived growth factor, compared to nPRP. In vitro, hPRP demonstrated more significant effects on preosteoblast migration and proliferation. In vivo, hPRP treatment resulted in enhanced bone healing, higher OPG levels in osteoblasts and osteoclasts, and an elevated OPG/RANKL ratio compared to nPRP.

HBOP enhances the biological activity of PRP and accelerates bone healing in a closed femur fracture model in rats. This study highlights the regenerative potential of PRP when preconditioned with hyperbaric oxygen for use in bone fracture therapy.

PRP is widely used in treating bone defects and fractures, but its enhancement through HBOP remains underexplored. Our findings demonstrate that HBOP potentiates the biological activity of PRP, offering promising therapeutic potential for bone fracture healing.

Enriching growth factors in PRP through HBOP could significantly improve tissue regeneration, especially in bone healing. The potential of hPRP in clinical applications is highly promising, particularly in orthopaedic surgery, trauma care, sports medicine, and managing bone healing in compromised patients.

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

The skeleton is highly innervated by numerous nerve fibers. These nerve fibers, in addition to transmitting information within the bone and mediating bone sensations, play a crucial role in regulating bone tissue formation and regeneration. Traditional bone tissue engineering (BTE) often fails to achieve satisfactory outcomes when dealing with large-scale bone defects, which is frequently related to the lack of effective reconstruction of the neurovascular network. In recent years, increasing research has revealed the critical role of nerves in bone metabolism. Nerve fibers regulate bone cells through neurotransmitters, neuropeptides, and peripheral glial cells. Furthermore, nerves also coordinate with the vascular and immune systems to jointly construct a microenvironment favorable for bone regeneration. As a signaling driver of bone formation, neuroregulation spans the entire process of bone physiological activities from the embryonic formation to postmaturity remodeling and repair. However, there is currently a lack of comprehensive summaries of these regulatory mechanisms. Therefore, this review sketches out the function of nerves during bone formation and regeneration. Then, we elaborate on the mechanisms of neurovascular coupling and neuromodulation of bone immunity. Finally, we discuss several novel strategies for neuro-bone tissue engineering (NBTE) based on neuroregulation of bone, focusing on the coordinated regeneration of nerve and bone tissue.

Adult mammals are unable to regenerate bulky bone tissues, making large bone defects clinically challenging. Deer antler represents an exception to this rule, exhibiting the fastest bony growth in mammals, offering a unique opportunity to explore novel strategies for rapid bone regeneration. Here, a bone graft exploiting the biochemical, biophysical, and structural characteristics of antlers is constructed. It is decellularized antler cancellous bone (antler-DCB) to obtain a bone scaffold. Then, an antler-based bone graft is constructed by integrating antler-DCB with antler-derived biological signals, delivered by extracellular vesicles (EVs) from antler blastema progenitor cells (ABPCs), a novel stem cells responsible for antlerogenesis is discovered. The antler-based bone graft transformed bone marrow stromal cells into cells with an ABPC-like phenotype and transcriptomic signature. In vivo, the antler-based graft triggered rapid bone formation in a rat model, with doubled volume of newly formed bones than commercial DCBs. In addition, the antler-based graft orchestrated a coordinated process of vascularization, neurogenesis, and immunomodulation during osteogenesis, partially imitating early antlerogenesis. These findings provide practical insights to develop a therapeutic intervention for treating severe bone defects.

The development of scaffolds for repairing critical-sized bone defects heavily relies on establishing a neuro-vascularized network for proper penetration of nerves and blood vessels. Despite significant advancements in using artificial bone-like scaffolds infused with various agents, challenges remain. Natural bone tissue consists of a porous bone matrix surrounded by a neuro-vascularized periosteum, with unique piezoelectric properties essential for bone growth. Drawing inspiration from this assembly, we developed a periosteum-bone-mimicking bilayer scaffold with piezoelectric properties for regeneration of critical-sized bone defects. The periosteum-like layer of this scaffold features a double network hydrogel composed of chelated alginate, gelatin methacrylate, and sintered whitlockite nanoparticles, emulating the viscoelastic and piezoelectric properties of the natural periosteum. The bone-like layer is composed of a porous structure of chitosan and bioactive hydroxyapatite created through a biomineralization process. Unlike conventional bone-like scaffolds, this bioinspired bilayer scaffold significantly enhances osteogenesis, angiogenesis, and neurogenesis combined with low-intensity pulsed ultrasound-assisted piezoelectric stimulation. Such a scheme enhances neuro-vascularized bone regeneration in vivo. The results suggest that the bilayer scaffold could serve as an effective self-powered electrical stimulator to expedite bone regeneration under dynamic physical stimulation.

Osteoporosis is a metabolic skeletal disease characterized by low bone mass and strength, and increased risk for fragility fractures. It is a major health issue in aging populations, due to fracture-associated increased disability and mortality. Antiresorptive treatments are first line choices in most of the cases.

Bone homeostasis is complicated, and multiple factors can compromise skeletal health. Bone turnover is a continuous process regulated by the coupled activities of bone cells that preserves skeletal strength and integrity. Imbalance between bone resorption and formation leads to bone loss and increased susceptibility to fractures. Antiresorptives prevent bone loss and reduce fracture risk, by targeting osteoclastogenesis and osteoclast function and survival. Their major drawback is the coupling of osteoclast and osteoblast activity, due to which any reduction in bone resorption is followed by suppression of bone formation.

During the last couple of decades significant progress has been made in understanding of the genetic and molecular basis of osteoporosis. Critical pathways and key molecules that mediate regulation of bone resorption have been identified. These factors may underpin novel therapeutic avenues for osteoporosis, but their potential for translation into clinical applications is yet to be tested.

Clinically, a multitude of factors can contribute to the development of bone defects. In the process of bone healing, the nervous system plays a vital role in bone regeneration. Small molecules from the nervous system, such as neurotrophic factors and neuropeptides, have been found to stimulate osteoblast proliferation and differentiation by activating signaling pathways associated with bone calcification and angiogenesis. These small molecules play a crucial regulatory role at various stages of bone healing. The systematic release mechanism of small molecules within the nervous system through diverse bone tissue engineering materials holds significant clinical implications for the controlled regulation of the bone healing process. This review provides an overview of the involvement of various nervous system small molecules at different stages of bone healing and discusses their regulatory mechanisms, aiming to establish a theoretical foundation for programmed regulation in bone regeneration and design of replacement materials in bone tissue engineering.

The involvement of neurons in the peripheral nervous system is crucial for bone regeneration. Mimicking extracellular matrix cues provides a more direct and effective strategy to regulate neuronal activity and enhance bone regeneration. However, the simultaneous coupling of the intrinsic mechanical-electrical microenvironment of implants to regulate innervated bone regeneration has been largely neglected. Inspired by the mechanical and bioelectric properties of the bone microenvironment, this study constructed a mechanical-electrical coupling microenvironment (M-E) model based on barium titanate piezoelectric nanoarrays, which could effectively promote innervated bone regeneration. The study found that the mechanical microenvironment provided by the nanostructure, coupled with the electrical microenvironment provided by the piezoelectric properties, created a controllable M-E. In vitro cell experiments demonstrated that this coupled microenvironment activated Piezo2 and VGCC ion channels, promoted calcium influx in DRG neurons, and activated downstream PI3K-AKT and RAS pathways. This cascade of events led to the synthesis and release of CGRP in sensory nerves, ultimately enhancing the osteogenic differentiation of BMSCs. This work not only broadens the current understanding of biomaterials that mimic the bone extracellular matrix but also provides new insights into innervated bone regeneration.

Studies have shown that the prognosis of dental implant treatment in patients with diabetes is not as good as that in the non-diabetes population. The nerve plays a crucial role in bone metabolism, but the role and the mechanism of peripheral nerves in regulating peri-implant osteogenesis under Type 2 diabetes mellitus (T2DM) situation remains unclear. In this study, it was shown that high glucose-stimulated Schwann cells (SCs) inhibited peri-implant osteogenesis via their exosomes. SCs-derived exosomes were analyzed for their miRNA cargo, identifying miR-15b-5p as significantly downregulated in high glucose conditions. T2DM rats and patients exhibited decreased miR-15b-5p expression, correlating with impaired bone microarchitecture. Luciferase assays and Western blotting confirmed TXNIP as a direct miR-15b-5p target, implicating its involvement in ROS signaling and inflammation-related osteogenesis suppression. Furthermore, normal SCs exosomes improved bone parameters around dental implants in T2DM rats. These findings underscore the therapeutic potential of miR-15b-5p and normal SCs exosomes in mitigating poor peri-implant bone regeneration of T2DM patients, offering insights into the molecular mechanisms of peripheral nerves governing bone regeneration in diabetic conditions.

Stem cells derived from adipose tissue are gaining popularity in the field of regenerative medicine due to their adaptability and clinical potential. Their rapid growth, ability to differentiate, and easy extraction with minimal complications make adipose-derived stem cells (ADSCs) a promising option for many treatments, particularly those targeting bone-related diseases. This study analyzed gene expression in canine ADSCs subjected to long-term culture and osteogenic differentiation.

ADSCs were isolated from discarded surgical waste and cultured for 14 days with and without differentiation media to assess osteogenic changes. RNA sequencing (RNA-seq) and bioinformatical analysis were performed to obtain comprehensive transcriptomic data. A total of 17793 genes were detected and GO enrichment analysis was performed on the differentially expressed genes to identify significantly up- and downregulated Biological Process (BP) GO terms across each comparison.

The upregulation of apoptosis-regulating genes and genes related to circulatory system development suggest an induction of these processes, while the downregulation of neurogenesis and gliogenesis genes points to reciprocal regulation during osteogenic differentiation of canine ADSCs.

These findings underscore the potential of ADSCs in bone regeneration and offer valuable insights for advancing tissue engineering, however further studies, including proteomic analyses, are needed to confirm these patterns and their biological significance.

Accumulating research has shed light on the significance of skeletal interoception, in maintaining physiological and metabolic homeostasis related to bone health. This review provides a comprehensive analysis of how skeletal interoception influences bone homeostasis, delving into the complex interplay between the nervous system and skeletal system. One key focus of the review is the role of various factors such as prostaglandin E2 (PGE2) in skeletal health via skeletal interoception. It explores how nerves innervating the bone tissue communicate with the central nervous system to regulate bone remodeling, a process critical for maintaining bone strength and integrity. Additionally, the review highlights the advancements in biomaterials designed to utilize skeletal interoception for enhancing bone regeneration and treatment of bone disorders. These biomaterials, tailored to interact with the body's interoceptive pathways, are positioned at the forefront of innovative treatments for conditions like osteoporosis and fractures. They represent a convergence of bioengineering, neuroscience, and orthopedics, aiming to create more efficient and targeted therapies for bone-related disorders. In conclusion, the review underscores the importance of skeletal interoception in physiological regulation and its potential in developing more effective therapies for bone regeneration. It emphasizes the need for further research to fully understand the mechanisms of skeletal interoception and to harness its therapeutic potential fully.

Peripheral nerve injury exacerbates progression of muscle heterotopic ossification (HO) and induces changes in expression of local cytokines in muscle tissue. The objective of the present study was to assess the impact of peripheral nerve injury on muscle HO development and the mechanism of cytokine modulation. A mouse model of gastrocnemius muscle HO was established and the sciatic nerve cut to simulate peripheral nerve injury. To evaluate the underlying factors contributing to the exacerbation of muscle HO resulting from denervation, fresh muscle tissue was collected and micro‑computed tomography, histochemical staining, RNA‑sequencing, reverse transcription‑quantitative PCR, Western blot, muscle tissue chip array were performed to analyze the molecular mechanisms. Sciatic nerve injury exacerbated HO in the gastrocnemius muscle of mice. Moreover the osteogenic differentiation of nerve‑injured muscle tissue‑derived fibro‑adipogenic progenitors (FAPs) increased in vitro. The expression of neuregulin 3 (NRG3) was demonstrated to be increased after nerve injury by muscle tissue chip array. Subsequent transcriptome sequencing analysis of muscle tissue revealed an enrichment of the PI3K/Akt pathway following nerve injury and an inhibitor of the PI3K/Akt pathway reduced the osteogenic differentiation of FAPs. Mechanistically, in vitro, peripheral nerve injury increased secretion of NRG3, which, following binding to ErbB4 on the cell surface of FAPs, promoted expression of osteogenesis‑associated genes via the PI3K/Akt signaling pathway, thus contributing to osteogenic differentiation of FAPs. In vivo, inhibition of the PI3K/Akt pathway effectively protected against muscle HO induced by peripheral nerve injury in mice. The present study demonstrated that the regulatory roles of NRG3 and the PI3K/Akt pathway in peripheral nerve injury exacerbated muscle HO and highlights a potential therapeutic intervention for treatment of peripheral nerve injury‑induced muscle HO.

Proteinoids-thermal proteins-are produced by heating amino acids to their melting point and initiation of polymerisation to produce polymeric chains. Proteinoids swell in aqueous solution into hollow microspheres. The proteinoid microspheres produce endogenous burst of electrical potential spikes and change patterns of their electrical activity in response to illumination. These microspheres were proposed as proto-neurons in 1950s. To evaluate pathways of potential evolution of these proto-neurons and their applicability of chimera neuromorphic circuits we decided to hybridise them with hondroitin sulphate (CS) clusters, which form a part of the brain extracellular matrix. We found a novel synergistic interaction between CS clusters and proteinoids that dramatically affects patterns of electrical activity of proteinoid microspheres. Our study might shed light on evolution of synaptic plasticity's molecular mechanisms and the role of extracellular matrix-protein interactions in learning, and open up possibilities for novel methods in unconventional computing and the development of adaptable, brain-inspired computational systems.

Cancer neuroscience, as an emerging converging discipline, provides us with new perspectives on the interactions between the nervous system and cancer progression. As the sympathetic nervous system, in particular adrenergic signaling, plays an important role in the regulation of tumor activity at every hierarchical level of life, from the tumor cell to the tumor microenvironment, and to the tumor macroenvironment, it is highly desirable to dissect its effects. Considering the far-reaching implications of drug repurposing for antitumor drug development, such a large number of adrenergic receptor antagonists on the market has great potential as one of the means of antitumor therapy, either as primary or adjuvant therapy. Therefore, this review aims to summarize the impact of adrenergic signaling on cancer development and to assess the status and prospects of intervening in adrenergic signaling as a therapeutic tool against tumors.

Knee osteoarthritis (KOA) is a chronic degenerative joint disease-causing chronic pain and disability. Neuromodulation of subchondral bone affects KOA-related pain and involves dorsal root ganglion (DRG). Our previous studies have demonstrated efficacy of icariin (ICA) in treating KOA, but neuromodulation mechanisms in peripheral nerves associated with the treatment of chronic pain in KOA remain unclear. This study aimed to investigate peripheral neuromodulation mechanisms of ICA in KOA-related chronic pain: (1) assessing therapeutic effect of ICA in a rat model of KOA-induced chronic pain; (2) investigating changes in pain-related nerve fibres and transient receptor potential vanilloid Subfamily 1 (TRPV1) pathway in subchondral bone following ICA treatment; and (3) exploring expression of pain-related Nogo-A/TRPV1 pathway in DRG, thereby elucidating neurotransmission of pain. Experimental results confirmed the curative effect of ICA on KOA by relieving chronic pain and pathological changes. ICA also effectively reduced bone remodelling, the area of pain-related positive nerve fibres and expression of TRPV1 in subchondral bone. Furthermore, ICA downregulated pain-related Nogo-A/TRPV1 pathway in the DRG. These findings provide new mechanistic insights into the therapeutic potential of ICA in relieving peripheral nervous system-related chronic pain in KOA.

This study explored the effects of prenatal exposure to fumonisins B (FB) on bone innervation in newborn Wistar rats.

Pregnant dams (n = 6 per group) were assigned to either the control or one of two FB-exposed groups (60 mg or 90 mg/kg body weight) from the 7th day of gestation until parturition. On the day of parturition, one male pup from each litter (n = 6 per group) was randomly selected and euthanised, and their femurs were dissected for analysis. Bone innervation was quantified by examining the morphology patterns of sympathetic, parasympathetic, sensory and cocaine- and amphetamine-regulated transcript (CART)-positive fibres. Prepared bone sections were analysed using immunohistochemistry staining for protein gene product 9.5, tyrosine hydroxylase, choline acetyltransferase, vasoactive intestinal peptide (VIP), substance P and CART-positive neurons.

The group that received a higher dose of FB demonstrated an increase in both the size and complexity of the complete bone neuronal network together with heightened sympathetic and sensory innervation, and displayed a decrease in neuron density and sympathetic innervation. Fumonisin B exposure led to a decrease in galanin-positive and VIP-positive bone neuronal networks in both groups exposed to FB, while in the lower-dose group, there was also a decrease in CART-positive innervation.

Prenatal FB exposure significantly influences the neuronal bone network of rats, which is essential for maintaining bone homeostasis. These findings emphasise the necessity for further research to understand the lasting effects and underlying mechanisms of alterations induced by FB.

Interactions between bone cells and neurocytes are crucial for endosseous nerve and ensuing bone regeneration. However, absence of neural stem cells in bone makes the innervation of implant osseointegration a major challenge. Herein, a nanorod-like array of sodium hydrogen titanate (ST) co-doped with Co2+ and Co3+, namely STCh that behaves as a reactive oxygen species (ROS)-scavenging enzyme, was hydrothermally formed on Ti substrate. We show that the doped Co2+ and Co3+ locate at TiO6 octahedral interlayers and within octahedra of STCh lattice, appearing releasable and un-releasable, respectively, leading to an increase in Co3+/Co2+ ratio and enzyme activity of the array with immersion. The nanoenzyme-released Co2+ triggers macrophages (MΦs) towards M1 phenotype, then the nanoenzyme scavenges extracellular ROS inducing M1-to-M2 transition. The neurogenic factors secreted by STCh-regulated MΦs, in combination with the released Co2+, promote mesenchymal stem cells to differentiate into neurons and Schwann cells compared to sole Co2+and ST. STCh array greatly enhances nerve reconstruction, type-H capillary formation and ensuing osseointegration in normal rat bone, and antibacteria via engulfing S. aureus by MΦs and osteogenesis in infective case. This nanoenzyme provides an alternative strategy to orchestrate endosseous nerve regeneration for osseointegration without loading exogenous neurotrophins in implants.

Parkinson's disease (PD), as a widespread neurodegenerative disorder, significantly impacts patients' quality of life. Its primary symptoms include motor disturbances, tremor, muscle stiffness, and balance disorders. In recent years, with the advancement of research, the concept of the bone-brain axis has gradually become a focal point in the field of PD research. The bone-brain axis refers to the interactions and connections between the skeletal system and the central nervous system (CNS), playing a crucial role in the pathogenesis and pathological processes of PD. The purpose of this review is to comprehensively and deeply explore the bone-brain axis in PD, covering various aspects such as the complex relationship between bone metabolism and PD, the key roles of neurotransmitters and hormones in the bone-brain axis, the role of inflammation and immunity, microRNA (miRNA) functional regulation, and potential therapeutic strategies. Through a comprehensive analysis and in-depth discussion of numerous research findings, this review aims to provide a solid theoretical foundation for a deeper understanding of the pathogenesis of PD and to offer strong support for the development of new treatment methods.

Diabetes has currently acquired the status of epidemic worldwide, and among its various pathological consequences like retinopathy and nephropathy, bone fragility fractures from diabetic osteopathy occurs in later stages and is equally destructive. Chronic hyperglycemia culminates into deteriorating microvasculature and quality of bone, making it prone to fractures. Among these, hip fractures are most common, especially in older diabetic patients apart from underlying neuropathy. Our study is an attempt to ameliorate hip fragility fracture and nerve trauma with electrical stimulation as an interface in a chronic diabetic rat model. We have fabricated reduced graphene oxide-substituted hydroxyapatite as an electroactive bone substitute and incorporated it into chitosan gelatin cryogels. The in situ reduction of graphene oxide during sintering of hydroxyapatite imparts higher potential to the fabricated composite in dealing with problem at question. The cryogels depicted optimum in vitro biocompatibility and enhanced mineralization after ectopic subcutaneous implantation in rats. The therapeutic potency of composite cryogels was evaluated in a hip fracture model with compression to the sciatic nerve in diabetic rats, mimicking the severe clinical trauma. The presence of cryogels in the femoral neck canal coupled with electrical stimulation and biochemical factors significantly improved bone regeneration in diabetic rats as depicted with microcomputed tomography analysis and histology images. The application of electrical stimulation also ameliorated the nerve trauma observed with 70% improvement in electrophysiological parameters such as the compound muscle action potential with combinatorial therapy. We therefore report the successful implication of a multitarget therapy in a chronic diabetic rat model unraveling the bone-nerve crosstalk with electroactive smart cryogels.

In bone tissue, nerves are primarily located in the periosteum and play an indispensable role in bone defect repair. However, most bone tissue engineering approaches ignored the reconstruction of the nerve network. Herein, we aimed to develop a bilayer hydrogel simulating periosteum-bone structure to induce innervated bone regeneration. The bottom "bone" layer consisted of gelatin methacryloyl (GelMA), poly(ethylene glycol) diacrylate (PEGDA), and nano-hydroxyapatite (nHA), whereas the upper "periosteum" layer consisted of GelMA, sodium alginate (SA) and MgCl2. The mechanical properties of the upper and bottom hydrogels were designed to be suitable for neurogenesis and osteogenesis, respectively. Besides, Mg2+ from the "periosteum" layer released at the early stage (within 7 d), which aligned with the optimal time window for nerve regeneration and osteogenic related neuropeptide release. Simultaneously, the prevention of long-term Mg2+ release (after 7 d) could avoid osteogenic inhibition caused by prolonged Mg2+ exposure. Additionally, the incorporation of nHA in the bottom "bone" layer supported the long-term osteogenesis due to its osteoconductivity and slow degradation. In vitro biological experiments revealed that the bilayer hydrogel (GS@Mg/GP@nHA) promoted neurite growth and calcitonin gene-related peptide (CGRP) expression in rat dorsal root ganglion (DRG) neurons, as well as the osteogenesis of rat bone-derived mesenchymal stem cells (BMSCs). Moreover, the in vivo experiments demonstrated that the GS@Mg/GP@nHA hydrogel efficiently promoted nerve network reconstruction and bone regeneration of rat calvarial bone defects. Altogether, the bilayer hydrogel GS@Mg/GP@nHA could promote innervated bone regeneration, providing new insights for biomaterial design for bone tissue engineering.