Magnetic Aggregation-Induced Bone-Targeting Nanocarrier with Effects of Piezo1 Activation and Osteogenic-Angiogenic Coupling for Osteoporotic Bone Repair

Elevated sclerostin levels contribute to reduced bone mineral density in non-ambulatory stroke patients

Osteoporosis following stroke is a significant impediment to patient recovery. Decreased mechanical loading and locomotion following the onset of paralysis in stroke patients, especially those who are non-ambulatory, contributes greatly to bone loss. Sclerostin, a protein encoded by the SOST gene, accumulates as a result of reduced mechanical loading and inhibits bone formation. This study explores the relationship between mechanical unloading, sclerostin levels, and bone mineral density (BMD) in stroke patients, utilizing three cohorts. Analysis of Cohort 1, consisting of patients with available sclerostin level measurements, found significantly elevated sclerostin levels in non-ambulatory patients compared to ambulatory patients, indicating the influence of ambulatory status on sclerostin regulation. Cohort 2, consisting of patients with BMD measurements, demonstrated that prolonged mechanical unloading in non-ambulatory patients resulted in a greater decline in BMD over time. Analysis in Cohort 3 patients, who had bilateral BMD measurements available, revealed that hemiplegic sides subjected to reduced mechanical loading exhibited lower BMD compared to non-hemiplegic sides. These findings collectively confirm the hypothesis that reduced mechanical loading elevates sclerostin levels and accelerates bone loss. By integrating data across the three cohorts, this study underscores the critical impact of mechanical unloading on bone health, particularly in chronic stroke patients with limited mobility. Our study provides clinical insights for treatments integrating ambulatory status, sclerostin levels, and BMD in chronic stroke patients and highlights an increased need for therapeutics targeting mechanical loading pathways and sclerostin accumulation which can be administered to treat chronic osteoporosis following stroke.

Yoda1-Loaded Microfibrous Scaffolds Accelerate Osteogenesis through Piezo1-F-Actin Pathway-Mediated YAP Nuclear Localization and Functionalization

Yoda1 has been recognized as an effective pharmacological intervention for the treatment of critical bone defects. However, the local delivery strategy of Yoda1 is uncommon, and the underlying mechanism through which Yoda1 enhances osteogenesis has been poorly investigated. Here, we propose utilizing electrohydrodynamic (EHD)-printed microfibrous scaffolds as a drug carrier for loading Yoda1 through a polydopamine (PDA) coating, and the synthetic mechanisms for enhancing bone regeneration are explored. Yoda1 was successfully loaded on the surface of the EHD-printed microfibrous scaffolds with the assistance of PDA. The results of in vitro experiments demonstrated that the Yoda1-loaded microfibrous scaffold group exhibited a more than 2-fold increase in COL-I protein levels compared to the control group. Additionally, the expression levels of osteogenic indicators such as ALP, Runx2, and OCN genes were significantly increased by 2-4-fold compared to those in the control group. We revealed that Yoda1 can effectively activate the Piezo1-F-actin pathway, thereby facilitating YAP nucleation and promoting lysine histone acetylation. Consequently, this mechanism enhanced the functionality of YAP nucleation and upregulated the expression of COL-I. Moreover, when implanted in vivo, the Yoda1-loaded microfibrous scaffold group could promote macrophage M2 polarization, thereby enhancing bone regeneration at defect sites. It is believed that the localized release of Yoda1 via EHD-printed PCL scaffolds might represent a promising strategy for the clinically precise treatment of bone defects.

Self-assembled water soluble and bone-targeting phosphorylated quercetin ameliorates postmenopausal osteoporosis in ovariectomy mice

Natural compounds have shown promising application prospects in preventing or treating various diseases, including osteoporosis on account of their abundant sources, low price, multi-targeting and multiple biological effects. As a bioactive natural product, quercetin (Que) has previously demonstrated to ameliorate osteoporosis (OP), however, its poor bioavailability resulting from low water solubility, poor stability and lack of bone-targeting largely restricted its efficacy and clinical applications. Inspired by the bone-targeting capability of phosphate compounds, we reported a one-step procedure for synthesis of phosphorylated Que (p-Que) by direct phosphorylating phenol groups of Que for the first time. The phosphate groups on p-Que could not only improve the water dispersibility of Que, but also endow p-Que desirable bioavailability and bone-targeting feature. The results from biological assays suggested that p-Que could inhibit osteoclastogenesis and bone resorption and alleviate trabeculae loss in osteoporotic mice. In conclusion, this work demonstrated that phosphorylation strategy can effectively solve low water solubility, lack of bone-targeting capability and poor bioavailability of natural compounds, providing a novel and efficient approach for development of OP nanomedicines.

Nanomaterials-Based Drug Delivery Systems for Therapeutic Applications in Osteoporosis

The etiology of osteoporosis is rooted in the disruption of the intricate equilibrium between bone formation and bone resorption processes. Nevertheless, the conventional anti-osteoporotic medications and hormonal therapeutic regimens currently employed in clinical practice are associated with a multitude of adverse effects, thereby constraining their overall therapeutic efficacy and potential. Recently, nanomaterials have emerged as a promising alternative due to their minimal side effects, efficient drug delivery, and ability to enhance bone formation, aiding in restoring bone balance. This review delves into the fundamental principles of bone remodeling and the bone microenvironment, as well as current clinical treatment approaches for osteoporosis. It subsequently explores the research status of nanomaterial-based drug delivery systems for osteoporosis treatment, encompassing inorganic nanomaterials, organic nanomaterials, cell-mimicking carriers and exosomes mimics and emerging therapies targeting the osteoporosis microenvironment. Finally, the review discusses the potential of nanomedicine in treating osteoporosis and outlines the future trajectory of this burgeoning field. The aim is to provide a comprehensive reference for the application of nanomaterial-based drug delivery strategies in osteoporosis therapy, thereby fostering further advancements and innovations in this critical area of medical research.

Cell communication and relevant signaling pathways in osteogenesis-angiogenesis coupling

Osteogenesis is the process of bone formation mediated by the osteoblasts, participating in various bone-related physiological processes including bone development, bone homeostasis and fracture healing. It exhibits temporal and spatial interconnectivity with angiogenesis, constructed by multiple forms of cell communication occurring between bone and vascular endothelial cells. Molecular regulation among different cell types is crucial for coordinating osteogenesis and angiogenesis to facilitate bone remodeling, fracture healing, and other bone-related processes. The transmission of signaling molecules and the activation of their corresponding signal pathways are indispensable for various forms of cell communication. This communication acts as a "bridge" in coupling osteogenesis to angiogenesis. This article reviews the modes and processes of cell communication in osteogenesis-angiogenesis coupling over the past decade, mainly focusing on interactions among bone-related cells and vascular endothelial cells to provide insights into the mechanism of cell communication of osteogenesis-angiogenesis coupling in different bone-related contexts. Moreover, clinical relevance and applications are also introduced in this review.

Aging Impairs Implant Osseointegration Through a Novel Reactive Oxygen Species-Hypoxia-Inducible Factor 1α/p53 Axis

Enhancing bone-vessel coupling to form high-quality vascular-rich peri-implant bone is crucial for improving implant prognosis in elder patients. Notably, hypoxia-inducible factor 1α (HIF1α) is known to promote osteogenesis-angiogenesis coupling; however, this effect remains to be investigated in aged bone owing to the dual effect of HIF1α in different aged organs. In this study, HIF1α inhibitor or activator was applied to aged mice and their bone mesenchymal stem cells (BMSCs) to investigate the effects and inner mechanism of HIF1α on the peri-implant osteogenesis and angiogenesis in senescent status. Cell senescence, along with osteogenic and angiogenic abilities of aged BMSCs, was detected, respectively. Meanwhile, a femur implant implantation model was constructed on aged mice, and the bone-vessel coupling of peri-implant bone was observed. Mandibular bone morphology was also detected to further provide evidence for clinical oral implantation. Furthermore, p53 expression was examined in vivo and in vitro following HIF1α intervention. A reactive oxygen species (ROS) scavenger was also adopted to further investigate the roles of ROS in the HIF1α-p53 axis. Results showed that the suppression of HIF1α alleviated senescence and osteogenesis-angiogenesis coupling of aged BMSCs, while its activation aggravated these effects. The mandible phenotype and bone-vessel coupling in aged peri-implant bone also changed accordingly upon regulation of HIF1α. Mechanistically, p53 changed in the same direction as HIF1α in vivo and in vitro. Moreover, the ROS scavenger reversed the HIF1α-p53 relationship and weakened the effect of HIF1α inhibitor on peri-implant bone improvement. In conclusion, in aged mice, highly expressed HIF1α impaired peri-implant bone-vessel coupling and implant osseointegration through p53, and accumulated ROS was a prerequisite for HIF1α to positively regulate p53. These findings provide new insights into the role of HIF1α and the ROS-HIF1α/p53 signaling axis, offering potential therapeutic targets to improve implant outcomes in elderly patients.

Dual functional hydrogel of osteoclastic-inhibition and osteogenic-stimulation for osteoporotic bone defect regeneration

Osteoporotic bone regeneration poses significant challenges due to the complexity of the condition. Osteoporosis, a degenerative disorder, results from an imbalance in bone homeostasis driven by dysregulation of osteoblast and osteoclast activity. This complicates the treatment of osteoporosis and its related bone injuries in clinical practice. Despite the development of various polymer scaffolds for bone defect repair, achieving effective regeneration in osteoporotic bones-especially when combined with osteoporosis medications-remains difficult. In this study, we designed a drug delivery system composed of mesoporous bioactive glass (MBG) and photo-crosslinked hyaluronic acid methacrylate (HAMA). This system, loaded with the osteogenesis-promoting peptide DWIVA (D5) and the osteoclastogenesis-inhibiting drug alendronate (ALN), is gelled using a light initiator and 405 nm wavelength light. The MBG@D5-Gel complex enables the controlled spatiotemporal release of these agents, markedly enhancing bone regeneration in osteoporotic conditions within ovariectomized rats by inhibiting osteoclastogenesis and bone resorption while promoting osteogenic differentiation and mineralization. This dual-action system synergistically regulates osteoblast and osteoclast activity, optimizing the pathological microenvironment of osteoporosis and facilitating the repair of osteoporotic bone defects. MBG@D5-Gel holds great potential as an effective organic-inorganic hybrid biomimetic implant material for the treatment of osteoporotic bone defects.

Intelligent Nanomaterials Design for Osteoarthritis Managements

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, characterized by progressive joint degradation, pain, and diminished mobility, all of which collectively impair patients' quality of life and escalate healthcare expenditures. Current treatment options are often inadequate due to limited efficacy, adverse side effects, and temporary symptom relief, underscoring the urgent need for more effective therapeutic strategies. Recent advancements in nanomaterials and nanomedicines offer promising solutions by improving drug bioavailability, reducing side effects and providing targeted therapeutic benefits. This review critically examines the pathogenesis of OA, highlights the limitations of existing treatments, and explores the latest innovations in intelligent nanomaterials design for OA therapy, with an emphasis on their engineered properties, therapeutic mechanisms, and translational potential in clinical application. By compiling recent findings, this work aims to inspire further exploration and innovation in nanomedicine, ultimately advancing the development of more effective and personalized OA therapies.

Albiflorin improves osteoporotic bone regeneration by promoting osteogenesis-angiogenesis coupling of bone marrow mesenchymal stem cells

Albiflorin (ALB) has been shown to promote osteogenesis, however, its effect on angiogenesis still remains unclear. This research aimed to explore the effect of ALB on angiogenesis and bone regeneration under osteoporotic conditions. The pro-osteogenesis capacity of ALB was assessed by osteogenic differentiation assays. Subsequent research examined the effect of ALB on angiogenesis. After revealing the pro-angiogenesis capacity of ALB, we explored the relationship between the pro-osteogenesis capacity and the pro-angiogenesis capacity of ALB by angiogenesis-related assays. Whereafter, the osteoporotic bone defect rat model was constructed to explore the effect of ALB on osteoporotic bone regeneration. Our research found that ALB promoted osteogenesis of bone marrow mesenchymal stem cells (BMSCs) and enhanced the expression of angiogenesis-specific markers, but it couldn't promote angiogenesis of human umbilical vein endothelial cells (HUVECs) directly. Further research revealed that ALB enhanced HUVECs migration and tube formation when the cells cultured in BMSCs-conditioned medium. Subsequently, it is observed that ALB facilitated bone regeneration under osteoporotic conditions by promoting osteogenesis and the formation of CD31hiEMCNhi type H-positive vessels. To sum up, this research indicated that ALB could improve osteoporotic bone regeneration by promoting osteogenesis-angiogenesis coupling of BMSCs, which provided a novel perspective for improving osteoporotic bone regeneration.

Regulation of Bone Remodeling by Metal-Phenolic Networks for the Treatment of Systemic Osteoporosis

Osteoporosis is a systemic metabolic disease that impairs bone remodeling by favoring osteoclastic resorption over osteoblastic formation. Nanotechnology-based therapeutic strategies focus on the delivery of drug molecules to either decrease bone resorption or increase bone formation rather than regulating the entire bone remodeling process, and osteoporosis interventions suffer from this limitation. Here, we present a multifunctional nanoparticle based on metal-phenolic networks (MPNs) for the treatment of systemic osteoporosis by regulating both osteoclasts and osteoblasts. In the osteoporotic microenvironment, the MPN nanoparticles degrade and trigger the release of bioactive metals (strontium ions, SrII) to promote osteogenesis and functionalized phenols (epigallocatechin gallate, EGCG) to suppress osteoclastogenesis. Injecting these nanoparticles into the tail vein of an ovariectomized mouse model, trabecular bone loss has been significantly prevented in the femoral head and vertebrae, along with increased trabecular bone volume and decreased trabecular bone separation. Overall, this work represents a versatile approach to explore MPN nanomaterials for the treatment of systemic osteoporosis and related orthopedic diseases.

Polydatin accelerates osteoporotic bone repair by inducing the osteogenesis-angiogenesis coupling of bone marrow mesenchymal stem cells via the PI3K/AKT/GSK-3β/β-catenin pathway

BACKGROUND

Polydatin (POL), a natural stilbenoid, has multiple pharmacological activities. However, its effect on osteoporotic bone defects has not yet been examined. This study was designed to explore the unknown role of POL on osteoporotic bone repair.

METHODS

The effect of POL on osteogenesis and angiogenesis were investigated firstly. Then a series of angiogenesis-related assays were carried out to explore the relationship between osteogenesis and angiogenesis of POL, and the underlying mechanism was further explored. Whereafter, ovariectomy-induced osteoporosis rats with bone defect were treated with POL or placebo, the imageological and histological examinations were conducted to assess the effect of POL on osteoporotic bone repair.

RESULTS

The moderate concentrations (1 μM and 10 μM) of POL enhanced the osteogenesis of bone marrow mesenchymal stem cells (BMSCs) and elevated the expression of angiogenic-specific markers. Further research found that POL-induced human umbilical vein endothelial cells migration and tube formation through the osteogenesis-angiogenesis coupling of BMSCs, and the POL-induced osteogenesis-angiogenesis coupling was reversed after co-cultured with LY294002. Mechanistically, this was conducted via activating PI3K/AKT/GSK-3β/β-catenin pathway. After that, using the osteoporotic bone defect rat model, the authors, observed that POL facilitated osteoporotic bone repair through enhancing osteogenesis and CD31 hi EMCN hi type H-positive vessels formation via the PI3K/AKT/GSK-3β/β-catenin pathway.

CONCLUSION

The data above indicated that POL could accelerate osteoporotic bone repair by inducing the osteogenesis-angiogenesis coupling of BMSCs via the PI3K/AKT/GSK-3β/β-catenin pathway, which provided new insight and strategy for osteoporotic bone repair.

Nanoparticle-Mediated Gene Delivery for Bone Tissue Engineering

Critical-sized bone defects represent an urgent clinical problem, necessitating innovative treatment approaches. Gene-activated grafts for bone tissue engineering have emerged as a promising solution. However, traditional gene delivery methods are constrained by limited osteogenic efficacy and safety concerns. Recently, organic and inorganic nanoparticle (NP) vectors have attracted significant attention in bone tissue engineering for their safe, stable, and controllable gene delivery. Targeted gene delivery guided by insights into bone healing mechanisms, coupled with the multifunctional design of NPs, is crucial for enhancing therapeutic outcomes. Here, the theoretical foundations underlying NP-mediated gene therapy for enhancing bone healing across different histological stages are elucidated. Furthermore, the distinct attributes of functionalized NP vectors are discussed, and cutting-edge strategies aimed at optimizing gene delivery efficiency throughout the therapeutic process are highlighted. Additionally, the review addresses the unresolved challenges and prospects of this technology. This review may contribute to the continued development and clinical application of NP-mediated gene delivery for treating critical-sized bone defects.

Pharmacology of PIEZO1 channels

PIEZO1 is a eukaryotic membrane protein that assembles as trimers to form calcium-permeable, non-selective cation channels with exquisite capabilities for mechanical force sensing and transduction of force into effect in diverse cell types that include blood cells, endothelial cells, epithelial cells, fibroblasts and stem cells and diverse systems that include bone, lymphatics and muscle. The channel has wide-ranging roles and is considered as a target for novel therapeutics in ailments spanning cancers and cardiovascular, dental, gastrointestinal, hepatobiliary, infectious, musculoskeletal, nervous system, ocular, pregnancy, renal, respiratory and urological disorders. The identification of PIEZO1 modulators is in its infancy but useful experimental tools emerged for activating, and to a lesser extent inhibiting, the channels. Elementary structure-activity relationships are known for the Yoda series of small molecule agonists, which show the potential for diverse physicochemical and pharmacological properties. Intriguing effects of Yoda1 include the stimulated removal of excess cerebrospinal fluid. Despite PIEZO1's broad expression, opportunities are suggested for selective positive or negative modulation without intolerable adverse effects. Here we provide a focused, non-systematic, narrative review of progress with this pharmacology and discuss potential future directions for research in the area.

Smart Implantable Hydrogel for Large Segmental Bone Regeneration

Large segmental bone defects often lead to nonunion and dysfunction, posing a significant challenge for clinicians. Inspired by the intrinsic bone defect repair logic of "vascularization and then osteogenesis", this study originally reports a smart implantable hydrogel (PDS-DC) with high mechanical properties, controllable scaffold degradation, and timing drug release that can proactively match different bone healing cycles to efficiently promote bone regeneration. The main scaffold of PDS-DC consists of polyacrylamide, polydopamine, and silk fibroin, which endows it with superior interfacial adhesion, structural toughness, and mechanical stiffness. In particular, the adjustment of scaffold cross-linking agent mixing ratio can effectively regulate the in vivo degradation rate of PDS-DC and intelligently satisfy the requirements of different bone defect healing cycles. Ultimately, PDS hydrogel loaded with free desferrioxamine (DFO) and CaCO3 mineralized ZIF-90 loaded bone morphogenetic protein-2 (BMP-2) to stimulate efficient angiogenesis and osteogenesis. Notably, DFO is released rapidly by free diffusion, whereas BMP-2 is released slowly by pH-dependent layer-by-layer disintegration, resulting in a significant difference in release time, thus matching the intrinsic logic of bone defect repair. In vivo and in vitro results confirm that PDS-DC can effectively realize high-quality bone generation and intelligently regulate to adapt to different demands of bone defects.

Extracellular Vesicle-Inspired Therapeutic Strategies for the COVID-19

Emerging infectious diseases like coronavirus pneumonia (COVID-19) present significant challenges to global health, extensively affecting both human society and the economy. Extracellular vesicles (EVs) have demonstrated remarkable potential as crucial biomedical tools for COVID-19 diagnosis and treatment. However, due to limitations in the performance and titer of natural vesicles, their clinical use remains limited. Nonetheless, EV-inspired strategies are gaining increasing attention. Notably, biomimetic vesicles, inspired by EVs, possess specific receptors that can act as "Trojan horses," preventing the virus from infecting host cells. Genetic engineering can enhance these vesicles by enabling them to carry more receptors, significantly increasing their specificity for absorbing the novel coronavirus. Additionally, biomimetic vesicles inherit numerous cytokine receptors from parent cells, allowing them to effectively mitigate the "cytokine storm" by adsorbing pro-inflammatory cytokines. Overall, this EV-inspired strategy offers new avenues for the treatment of emerging infectious diseases. Herein, this review systematically summarizes the current applications of EV-inspired strategies in the diagnosis and treatment of COVID-19. The current status and challenges associated with the clinical implementation of EV-inspired strategies are also discussed. The goal of this review is to provide new insights into the design of EV-inspired strategies and expand their application in combating emerging infectious diseases.

Estrogen and estrogen receptors mediate the mechanobiology of bone disease and repair

It is well understood that the balance of bone formation and resorption is dependent on both mechanical and biochemical factors. In addition to cell-secreted cytokines and growth factors, sex hormones like estrogen are critical to maintaining bone health. Although the direct osteoprotective function of estrogen and estrogen receptors (ERs) has been reported extensively, evidence that estrogen signaling also has a role in mediating the effects of mechanical loading on maintenance of bone mass and healing of bone injuries has more recently emerged. Recent studies have underscored the role of estrogen and ERs in many pathways of bone mechanosensation and mechanotransduction. Estrogen and ERs have been shown to augment integrin-based mechanotransduction as well as canonical Wnt/b-catenin, RhoA/ROCK, and YAP/TAZ pathways. Estrogen and ERs also influence the mechanosensitivity of not only osteocytes but also osteoblasts, osteoclasts, and marrow stromal cells. The current review will highlight these roles of estrogen and ERs in cellular mechanisms underlying bone mechanobiology and discuss their implications for management of osteoporosis and bone fractures. A greater understanding of the mechanisms behind interactions between estrogen and mechanical loading may be crucial to addressing the shortcomings of current hormonal and pharmaceutical therapies. A combined therapy approach including high-impact exercise therapy may mitigate adverse side effects and allow an effective long-term solution for the prevention, treatment, and management of bone fragility in at-risk populations. Furthermore, future implications to novel local delivery mechanisms of hormonal therapy for osteoporosis treatment, as well as the effects on bone health of applications of sex hormone therapy outside of bone disease, will be discussed.

Application of advanced surface modification techniques in titanium-based implants: latest strategies for enhanced antibacterial properties and osseointegration

Titanium-based implants, renowned for their excellent mechanical properties, corrosion resistance, and biocompatibility, have found widespread application as premier implant materials in the medical field. However, as bioinert materials, they often face challenges such as implant failure caused by bacterial infections and inadequate osseointegration post-implantation. Thus, to address these issues, researchers have developed various surface modification techniques to enhance the surface properties and bioactivity of titanium-based implants. This review aims to outline several key surface modification methods for titanium-based implants, including acid etching, sol-gel method, chemical vapor deposition, electrochemical techniques, layer-by-layer self-assembly, and chemical grafting. It briefly summarizes the advantages, limitations, and potential applications of these technologies, presenting readers with a comprehensive perspective on the latest advances and trends in the surface modification of titanium-based implants.

Intelligent Supramolecular Modification for Implants: Endogenous Regulation of Bone Defect Repair in Osteoporosis

Addressing osteoporosis-related bone defects, a supramolecular strategy is innovated for modifying carbon fiber reinforced polyether ether ketone (CF/PEEK) composites. By covalently attaching intelligent macromolecules via in situ RAFT polymerization, leveraging the unique pathological microenvironment in patients with iron-overloaded osteoporosis, intelligent supramolecular modified implant surface possesses multiple endogenous modulation capabilities. After implantation, surface brush-like macromolecules initially resist macrophage adhesion, thereby reducing the level of immune inflammation. Over time, the molecular chains undergo conformational changes due to Fe (III) mediated supramolecular self-assembly, transforming into mechanistic signals. These signals are then specifically transmitted to pre-osteoblast cell through the binding capacity of the KRSR short peptide at the molecular terminus, induced their osteogenic differentiation via the YAP/β-catenin signaling axis. Furthermore, osteoblasts secrete alkaline phosphatase (ALP), which significantly hydrolyzes phosphate ester bonds in surface macromolecular side groups, resulting in the release of alendronate (ALN). This process further improves the local osteoporotic microenvironment. This intelligent surface modification tailors bone repair to individual conditions, automatically realize multiple endogenous regulation once implanted, and truly realize spontaneous activation of a series of responses conducive to bone repair in vivo. It is evidenced by improved bone regeneration in iron-overloaded osteoporotic rabbits and supported by in vitro validations.

Ultrasound-triggered piezoelectric polyetheretherketone with boosted osteogenesis via regulating Akt/GSK3β/β-catenin pathway

Maxillofacial bone defects can severely impact quality of life by impairing physiological functions such as chewing, breathing, swallowing, and pronunciation. Polyether ether ketone (PEEK) is commonly used for the repair of maxillofacial defects due to its mechanical adaptability, while its osteogenic properties still need refinement. Herein, we have utilized the piezoelectric effect exhibited by barium titanate (BTO) under low-intensity pulsed ultrasound (LIPUS) to develop an ultrasound responsive PEEK (PDA@BTO-SPEEK, PBSP) through the mediating effect of polydopamine (PDA), for repairing maxillofacial bone defects. After modification by PDA@BTO, PBSP possesses better hydrophilicity, which is conducive to cell growth and adhesion. Simultaneously, by virtue of the piezoelectric characteristics of BTO, PBSP obtains a piezoelectric coefficient that matches the bone cortex. Notably, when PBSP is stimulated by LIPUS, it can generate stable electricity and effectively accelerate the osteogenic differentiation of osteoblasts through the regulation of the Piezo1-induced calcium (Ca2+) influx and Akt/GSK3β/β-catenin pathway. In addition, PBSP presents satisfactory therapeutic effects in rat skull defect models, and its osteogenic efficiency can be further improved under LIPUS stimulation with high tissue penetration. Collectively, PBSP + LIPUS exhibits great potential as a promising alternative strategy for the repair of maxillofacial bone defects.

A Novel Piezo1 Agonist Promoting Mesenchymal Stem Cell Proliferation and Osteogenesis to Attenuate Disuse Osteoporosis

Disuse osteoporosis (OP) is a state of bone loss due to lack of mechanical stimuli, probably induced by prolonged bed rest, neurological diseases, as well as microgravity. Currently the precise treatment strategies of disuse OP remain largely unexplored. Piezo1, a mechanosensitive calcium (Ca2+) ion channel, is a key force sensor mediating mechanotransduction and it is demonstrated to regulate bone homeostasis and osteogenesis in response to mechanical forces. Using structure-based drug design, a novel small-molecule Piezo1 agonist, MCB-22-174, which can effectively activate Piezo1 and initiate Ca2+ influx, is developed and is more potent than the canonical Piezo1 agonist, Yoda1. Moreover, MCB-22-174 is found as a safe Piezo1 agonist without any signs of serious toxicity. Mechanistically, Piezo1 activation promotes the proliferation of bone marrow mesenchymal stem cells by activating the Ca2+-related extracellular signal-related kinases and calcium-calmodulin (CaM)-dependent protein kinase II (CaMKII) pathway. Importantly, MCB-22-174 could effectively promote osteogenesis and attenuate disuse OP in vivo. Overall, the findings provide a promising therapeutic strategy for disuse OP by chemical activation of Piezo1.

Structure-optimized and microenvironment-inspired nanocomposite biomaterials in bone tissue engineering

Critical-sized bone defects represent a significant clinical challenge due to their inability to undergo spontaneous regeneration, necessitating graft interventions for effective treatment. The development of tissue-engineered scaffolds and regenerative medicine has made bone tissue engineering a highly viable treatment for bone defects. The physical and biological properties of nanocomposite biomaterials, which have optimized structures and the ability to simulate the regenerative microenvironment of bone, are promising for application in the field of tissue engineering. These biomaterials offer distinct advantages over traditional materials by facilitating cellular adhesion and proliferation, maintaining excellent osteoconductivity and biocompatibility, enabling precise control of degradation rates, and enhancing mechanical properties. Importantly, they can simulate the natural structure of bone tissue, including the specific microenvironment, which is crucial for promoting the repair and regeneration of bone defects. This manuscript provides a comprehensive review of the recent research developments and applications of structure-optimized and microenvironment-inspired nanocomposite biomaterials in bone tissue engineering. This review focuses on the properties and advantages these materials offer for bone repair and tissue regeneration, summarizing the latest progress in the application of nanocomposite biomaterials for bone tissue engineering and highlighting the challenges and future perspectives in the field. Through this analysis, the paper aims to underscore the promising potential of nanocomposite biomaterials in bone tissue engineering, contributing to the informed design and strategic planning of next-generation biomaterials for regenerative medicine.

The role of mechanically sensitive ion channel Piezo1 in bone remodeling

Piezo1 (2010) was identified as a mechanically activated cation channel capable of sensing various physical forces, such as tension, osmotic pressure, and shear force. Piezo1 mediates mechanosensory transduction in different organs and tissues, including its role in maintaining bone homeostasis. This review aimed to summarize the function and possible mechanism of Piezo1 in the mechanical receptor cells in bone tissue. We found that it is a potential therapeutic target for the treatment of bone diseases.