Ultrasound-triggered biomimetic ultrashort peptide nanofiber hydrogels promote bone regeneration by modulating macrophage and the osteogenic immune microenvironment

HAMA-SBMA hydrogel with anti-inflammatory properties delivers cartilage organoids, boosting cartilage regeneration

Cartilage tissue lacks blood supply, which limits its ability to self-repair. Cartilage organoid (CO) technology, which replicates the structure and function of cartilage, holds significant promise. However, it is essential to maintain cellular function and ensure secure fixation at the site of injury. Therefore, we loaded allogeneic bone marrow mesenchymal stem cells (BMSCs) onto decellularized extracellular matrix microparticles of porcine articular cartilage (CEP) to construct CO-CCO, which demonstrated characteristics of articular cartilage. Additionally, betaine sulfonate methacrylate (SBMA) was incorporated into hyaluronic acid methacrylate (HAMA) to synthesize a novel hydrogel, HAMA-SBMA (HS), characterized by its adhesive properties, promotion of chondrogenesis, and inhibition of inflammation. In Vivo studies revealed that the combination of HS and CCO (HS + CCO) exhibited excellent repair efficacy in both rat and sheep models of cartilage defects. Mechanistically, we found that HS + CCO promoted cartilage repair by activating the Frizzled-related protein (Frzb), which inhibited inflammatory factors and enhanced the expression of the adhesion factor integrin ɑ5β1. This strategy, which combines hydrogels and organoids, enhances cartilage repair, offering substantial potential for clinical applications in cartilage regeneration.

Targeting TYROBP to influence the immune microenvironment and osteogenic differentiation of mesenchymal stem cells

Background

Lactate, as an end product of glycolysis, plays an important role in cellular metabolism and signal transduction, and recent studies have shown that it is closely related to cellular differentiation, but its potential role in osteogenic differentiation has not yet been fully investigated.

Methods

We obtained two datasets containing human mesenchymal stem cells and human osteoblasts, GSE12266 and GSE18043 , from the GEO database, which contained a total of 14 samples with sequencing data, and searched for lactate metabolism-related genes from the Genecards database. Ten differentially expressed core genes related to lactate metabolism were identified by differential expression analysis, protein interaction network analysis, and correlation expression analysis, and determined to play a key role in osteogenic differentiation. The effects of hub genes on the immune microenvironment of osteogenic differentiation were explored by enrichment analysis and immune infiltration analysis, and the significant effects of the key gene TYRO Protein Tyrosine Kinase-Binding Protein(TYROBP) on the characterization of bone marrow mesenchymal stem cells (BMSCs) were experimentally verified, and it was determined by drug sensitivity analysis that TYROBP may be a regulatory target of certain drugs affecting osteogenic differentiation.

Result

We successfully screened 10 differentially expressed hub genes related to lactate metabolism, and their area under the curve AUC values for predicting osteogenic differentiation were all highly favorable. Enrichment analysis showed that lactate metabolism may affect osteoblast differentiation through immune infiltration, and the immune infiltration results confirmed the strong association between hub genes and osteoblast immune infiltration status. It was verified that decreasing TYROBP expression promoted cell viability, proliferation and migration ability of BMSCs. Drug sensitivity analysis showed that TYROBP may be a major regulator of drug-induced MSC differentiation.

Conclusion

Our study reveals the critical role of lactate metabolism in osteoblast differentiation, identifies the role of the key gene TYROBP in the regulation of BMSCs, and provides new insights for studies related to the regulation of osteoblast differentiation.

Optimally Aligned Nerve Scaffolds with Sustained Astaxanthin Release Improve the Inflammatory Microenvironment through Mitophagy Activation

Effective repair of peripheral nerve injury (PNI) depends on the scaffold orientation and immunomodulatory capabilities of functionalized scaffolds, both of which substantially influence nerve regeneration. In this study, composite nerve scaffolds incorporating astaxanthin (AXT) and polycaprolactone (PCL) are developed to investigate the influence of scaffold orientation and blend concentration on cellular behavior, including adhesion, migration, and proliferation. In vitro analysis identifies 0.2% AXT/PCL fabricated at a rotational speed of 400 rpm as the optimal configuration for facilitating directed cell growth and guiding nerve repair. Moreover, the controlled release of AXT improves the microenvironment by preserving mitochondrial homeostasis, promoting mitophagy, and reducing oxidative stress and inflammation. In vivo assessments reveal that the AXT/PCL group (0.2% AXT/PCL-400) achieves better morphological, histological, electrophysiological, and functional recovery than the PCL, AXT/PCL+M0, and AXT/PCL+M4 groups, approaching the outcomes observed in the autograft (Auto) group. Moreover, the AXT/PCL+M4 group demonstrates better regenerative outcomes than the PCL and AXT/PCL+M0 groups, underscoring the critical role of mitophagy in regulating the regenerative microenvironment.

Hydrogel promotes bone regeneration through various mechanisms: a review

Large defects in bone tissue due to trauma, tumors, or developmental abnormalities usually require surgical treatment for repair. Numerous studies have shown that current bone repair and regeneration treatments have certain complications and limitations. With the in-depth understanding of bone regeneration mechanisms and biological tissue materials, a variety of materials with desirable physicochemical properties and biological functions have emerged in the field of bone regeneration in recent years. Among them, hydrogels have been widely used in bone regeneration research due to their biocompatibility, unique swelling properties, and ease of fabrication. In this paper, the development and classification of hydrogels were introduced, and the mechanism of hydrogels in promoting bone regeneration was described in detail, including the promotion of bone marrow mesenchymal stem cell differentiation, the promotion of angiogenesis, the enhancement of the activity of bone morphogenetic proteins, and the regulation of the microenvironment of bone regeneration tissues. In addition, the future research direction of hydrogel in bone tissue engineering was discussed.

Electron Pump and Photon Trap Effect-Derived Selective Antitumor of Fe-Ppy@CaO2-Modified Polyetheretherketone for Bone Tumor Therapy

Bone tumors with high mortality and disability have become a major clinical challenge. Herewith, it is necessary to design materials for bone tumor therapy and bone repair. In this work, Fe-doped polypyrrole (Fe-Ppy) and CaO2 are constructed on sulfonated polyetheretherketone (SP) to form a multistage-responsive coating. The coating achieves long-lasting antitumor through chemodynamic therapy (CDT), photothermal therapy (PTT), and combined immunotherapy. Fe-Ppy acts as an electron pump to replenish Fe2+ through oxidizing -NH- to -N+-, which lasts the Fenton reaction and persistently produces reactive oxygen species (ROS) in the tumor microenvironment (TME). CaO2 selectively provides exogenous H2O2 in response to TME to boost the electron cycle. Stronger near-infrared light absorption due to Fe doping and more photon traps caused by porous structure-induced scattering and refraction diminishment improve the photothermal conversion of modified SP. Furthermore, long-lasting ROS and effective photothermal conversion enhance M1 activation to secrete TNF-α and IFN to kill tumor cells. After tumor therapy, Fe-Ppy@CaO2-modified SP could adaptively switch the macrophage to M2 and promote osteogenesis with the abolishment of TME and NIR stimulation. In summary, Fe-Ppy@CaO2-modified SP with long-lasting ROS, enhanced photothermal conversion, and immunomodulation is a potential candidate for bone tumor therapy and tissue repair.

Immobilization of KR-12 on a Titanium Alloy Surface Using Linking Arms Improves Antimicrobial Activity and Supports Osteoblast Cytocompatibility

Implant-associated infections pose significant challenges due to bacterial resistance to antibiotics. Recent research highlights the potential of immobilizing antimicrobial peptides (AMPs) onto implants as an alternative to conventional antibiotics for the prevention of bacterial infection. While various AMP immobilization methodologies have been investigated, they lack responsiveness to biological cues. This study proposes an enzyme-responsive antimicrobial coating for orthopedic devices using KR-12, an AMP derived from Cathelicidin LL-37, coupled with the Human Elastin-Like Polypeptide (HELP) as a biomimetic and stimuli-responsive linker, while mimicking the extracellular matrix (ECM). During implantation, these customized interfaces encounter the innate immune response triggering elastase release, which degrades HELP biopolymers, enabling the controlled release of KR-12. After coupling KR-12 with HELP to titanium surfaces, the antimicrobial activity against four pathogenic bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa) was assessed, revealing an inhibition ratio of bacterial adhesion and colonization exceeding 92% for all tested strains, compared with surfaces functionalized with KR-12 only. It is thought that the enhanced antimicrobial activity was due to the improved mobility of KR-12 when coupled with HELP. Furthermore, the prepared coatings boosted the adhesion and proliferation of human osteoblasts, confirming the cytocompatibility. These findings suggest the potential for smart coatings that combine the antimicrobial functions of AMPs with HELP's biological properties for use in a variety of settings, including medical devices.

NIR-programmable 3D-printed shape-memory scaffold with dual-thermal responsiveness for precision bone regeneration and bone tumor management

Clinically, intraoperative treatment of bone tumors presents several challenges, including the effective inactivation of tumors and filling of irregular bone defects after tumor removal. In this study, intelligent thermosensitive composite materials with shape-memory properties were constructed using polylactic acid (PLA) and polycaprolactone (PCL), which have excellent biocompatibility and degradability. Additionally, beta-tricalcium phosphate (β-TCP), with its osteogenic properties, and magnesium (Mg) powder, with its photothermal and bone-promoting abilities, were incorporated to improve the osteogenic potential of the composite and enable the material to respond intelligently to near-infrared (NIR) light. Utilizing 3D printing technology, the composite material was prepared into an NIR-responsive shape-memory bone-filling implant that deforms when the scaffold temperature increases to 48 ℃ under NIR laser irradiation. Moreover, at a lower temperature of 42 ℃, mild photothermal therapy promotes macrophage polarization toward the M2 phenotype. This process regulates the secretion of interleukin (IL)-4, IL-10, tumor necrosis factor-α, IL-6, and bone morphogenetic protein (BMP)-2, reducing local inflammation, enhancing the release of pro-healing factors, and improving osteogenesis. Overall, this innovative scaffold is a promising and efficient treatment for filling irregular bone defects after bone tumor surgery.

Probiotic Membrane-Modified Nanocomposite Alleviates Inflammation and Microbiota Dysbiosis in Colitis by Scavenging Oxidative Stress and Restoring Immune Homeostasis

Inflammatory bowel disease (IBD) is a complex chronic intestinal disorder in which excessive oxidative stress, dysregulated immune response, and microbiota dysbiosis contribute to recurrent episodes of inflammation in the colonic mucosa. Current clinical treatments focusing solely on inflammation resolution often exhibit limited efficacy due to the inability to fundamentally improve the pathological microenvironment. Herein, a probiotic membrane-modified drug delivery nanocomposite, namely, MPDA@Cur@EM, is developed for the comprehensive treatment of IBD. It contains two components: the curcumin-loaded mesoporous polydopamine nanoparticle (MPDA@Cur) as the core and the Escherichia coli Nissle 1917 outer membrane (EM) as the surface. For MPDA@Cur, the pathological microenvironment triggers the responsive release of curcumin. Importantly, MPDA@Cur can effectively alleviate the inflammatory response of LPS-activated macrophages through MPDA-mediated ROS scavenging and curcumin-induced M2 polarization. In the dextran sulfate sodium (DSS)-induced colitis model, the EM coating not only allows for the targeting enrichment of orally administered MPDA@Cur@EM to the inflamed colonic mucosa, but also participates in the regulation of intestinal flora. Consequently, MPDA@Cur@EM efficiently attenuates the inflammatory reaction and restores the intestinal barrier functions, demonstrated by the multipronged manner of restoring redox balance, remodeling immune homeostasis, and reshaping the gut microecology. Collectively, this work provides a safe and promising codelivery strategy of probiotic product, antioxidative nanoenzyme, and therapeutic drug for comprehensive management of IBD.

Recent Advances in Peptide-Functionalized Hydrogels for Bone Tissue Engineering

Efficient therapeutic approaches for bone regeneration are urgently required to address the significant challenges associated with the repair of large-scale or long-segment bone defects. Peptide-functionalized hydrogels (PFHs) have emerged as important bioactive materials in bone tissue engineering because they produce biomimetic microenvironments enriched with multiple biochemical signals. This review summarizes the key fabrication techniques for PFHs and discusses their diverse applications in different fields. Furthermore, we systematically highlighted the biochemical functionalization of PFHs, which includes basic functions such as cell adhesion, cell recruitment, and osteoinduction; improved functions such as angiogenesis, biomineralization, immune regulation, and hormone regulation; and other functions, including antimicrobial and antitumor effects. Finally, critical biosafety considerations associated with PFHs and perspectives on developing intelligent PFHs are addressed. This review aims to inspire further research on PFHs and accelerate their applications in bone tissue engineering.

Accelerating repair of infected bone defects through post-reinforced injectable hydrogel mediated antibacterial/immunoregulatory microenvironment at bone-hydrogel interface

Functional injectable hydrogel (IH) is promising for infected bone defects (IBDs) repair, but how to endow it with desired antibacterial/immunoregulatory functions as well as avoid mechanical failures during its manipulation has posed as main challenges. Herein, rosmarinic acid (RosA), a natural product with antibacterial/immunoregulatory activities, was utilized to develop a FCR IH through forming phenylboronic acid ester bonds with 4-formylphenyl phenylboronic acid (4-FPBA) grafted chitosan (CS) (FC). After being applied to the IBD site, the FCR IH was then injected with tobramycin (Tob) solution, another alkaline antibacterial drug, to induce in situ crystallization of the FC, endowing the resultant FCRT hydrogel with adaptively enhanced mechanical strength and structural stability. Owing to the specific structural composition, the FCRT hydrogel could sustainedly release Tob and RosA molecules at the IBD interface, effectively eliminating in situ bacterial infection. In addition, the released RosA molecules also induced the M2 polarization of in situ macrophages (Mφ), which was identified to be related to the NF-κB and PI3K-AKT pathways, therefore promoting the osteogenic differentiation of in situ bone marrow stromal cells (BMSCs). Due to the simultaneous antibacterial/osteo-immunoregulatory microenvironment at the IBD interface, the repair of IBDs was proved to be greatly accelerated by the FCRT hydrogel.

Yeast-Inspired Orally-Administered Nanocomposite Scavenges Oxidative Stress and Restores Gut Immune Homeostasis for Inflammatory Bowel Disease Treatment

Excessive oxidative stress, dysregulated immune homeostasis, and disruption of the intestinal epithelial barrier are crucial features of inflammatory bowel disease (IBD). Traditional treatments focusing solely on inflammation resolution remain unsatisfactory. Herein, a yeast-inspired orally administered nanocomposite was developed. First, the MD@MPDA core was fabricated by integrating manganese dioxide (MnO2) nanozymes onto diallyl trisulfide (H2S prodrug)-loaded mesoporous polydopamine nanoparticles (MPDA). Then, yeast cell wall (YCW) was chosen to encapsulate MD@MPDA, namely, YMD@MPDA. The β-glucan embedded in the YCW shell not only protected the nanocomposite from the harsh gastrointestinal environment but also allowed the targeting enrichment in the inflamed colon. Furthermore, M1 macrophages triggered the intracellular GSH-responsive H2S release in the pathological microenvironment. MD@MPDA effectively alleviated inflammatory responses by MnO2-mediated ROS-scavenging and H2S-participated immunomodulation. The synergistic action contributed to macrophage mitochondrial function restoration and M2 polarization by suppressing NOX4 signaling and p38 MAPK pro-inflammatory signaling. In the mice model of dextran sulfate sodium (DSS)-induced IBD, the multipronged manner of scavenging oxidative stress, remodeling innate and adaptive immune homeostasis, and reshaping gut microbiota caused by YMD@MPDA effectively ameliorated inflammation and restored intestinal barrier functions. Overall, the YMD@MPDA nanocomposite provides a promising codelivery strategy of antioxidative nanozymes and gas prodrugs for the comprehensive management of IBD.

An injectable shape-adaptive hydrogel system for subconjunctival injuries: In situ and permanently releases rapamycin to prevent fibrosis via promoting autophagy

Subconjunctival fibrosis (SCF) is a common and refractory eye disease that is a serious threat to vision. The severe side effects of existing drugs and low drug bioavailability due to the ocular barrier are major challenges in SCF treatment. Hence, there is an urgent need to explore safer and more effective strategies for administering anti-SCF drugs. Herein, an injectable and adaptable hydrogel system containing the antifibrotic drug rapamycin was fabricated to address this complex need. This system possesses moderate mechanical properties, self-healing and shape-adaptive capabilities, injectability, and biosafety. It is designed to promote autophagy by modulating the PI3K/AKT/mTOR/WIPI2 pathway, thereby inhibiting SCF. In vivo experiments utilizing a rat subconjunctival injury model indicated that in situ administration of this hydrogel system effectively inhibited SCF. This system constitutes a promising method for promoting autophagy to protect against SCF, which will foster its widespread application for other fibrotic diseases.

Recent Development of Fibrous Hydrogels: Properties, Applications and Perspectives

Fibrous hydrogels (FGs), characterized by a 3D network structure made from prefabricated fibers, fibrils and polymeric materials, have emerged as significant materials in numerous fields. However, the challenge of balancing mechanical properties and functions hinders their further development. This article reviews the main advantages of FGs, including enhanced mechanical properties, high conductivity, high antimicrobial and anti-inflammatory properties, stimulus responsiveness, and an extracellular matrix (ECM)-like structure. It also discusses the influence of assembly methods, such as fiber cross-linking, interfacial treatments of fibers with hydrogel matrices, and supramolecular assembly, on the diverse functionalities of FGs. Furthermore, the mechanisms for improving the performance of the above five aspects are discussed, such as creating ion carrier channels for conductivity, in situ gelation of drugs to enhance antibacterial and anti-inflammatory properties, and entanglement and hydrophobic interactions between fibers, resulting in ECM-like structured FGs. In addition, this review addresses the application of FGs in sensors, dressings, and tissue scaffolds based on the synergistic effects of optimizing the performance. Finally, challenges and future applications of FGs are discussed, providing a theoretical foundation and new insights for the design and application of cutting-edge FGs.

Ultrasound-Triggered Mg2+ Blasting Release Hydrogel Microspheres for Promoting Bone Reconstruction

Mg2+ (Magnesium ion) can affect bone tissue metabolism by regulating related signaling pathways in bone metabolism. However, how to realize precise controlled release of Mg2+ in bone regeneration treatment still presents a challenge. Herein, for the first time, the GelMA-BP (Gelatin Methacryloyl-Bisphosphonate) and the composite nano-bubble system are fused to construct the Mg2+ blasting controlled-release hydrogel microspheres, the stability of the nano-bubbles in the microspheres is enhanced through metal coordination complexation, and the burst of the nano-bubbles is controlled by using ultrasonic cavitation to achieve the precise controlled release of Mg2+, ultimately effectively promoting bone reconstruction. First, GelMA-BP composite is prepared by Schiff base reaction. Second, the nanobubble BP (Bisphosphonate) system is constructed, and Mg2+ is combined with the ligand coordination to prepare the composite nanobubble system. Thirdly, through Mg2+ co-coordination, the ultrasound-triggered Mg2+ blasting controlled release microspheres were prepared to achieve bone repair. Overall, this innovative strategy effectively solves the problem of accurate controlled release of Mg2+, and finally effectively activates in situ bone tissue regeneration.

Hydrogel Fibers-Based Biointerfacing

The unique 1D structure of fibers offers intriguing attributes, including a high length-to-diameter ratio, miniatured size, light-weight, and flexibility, making them suitable for various biomedical applications, such as health monitoring, disease treatment, and minimally invasive surgeries. However, traditional fiber devices, typically composed of rigid, dry, and non-living materials, are intrinsically different from the soft, wet, and living essence of biological tissues, thereby posing grand challenges for long-term, reliable, and seamless interfacing with biological systems. Hydrogel fibers have recently emerged as a promising candidate, in light of their similarity to biological tissues in mechanical, chemical and biological aspects, as well as distinct fiber geometry. In this review, a comprehensive overview of recent progress in hydrogel fibers-based biointerfacing technology is provided. It thoroughly summarizes the manufacturing strategy and functional design, especially for hydrogel fibers with distinct optical and electron conductive performance, as well as responsiveness to triggers including thermal, magnetic field and ultrasonic wave, etc. Such unique attributes enable various biomedical applications, which are also examined in detail. Future challenges and potential directions, including biosafety, long-term reliability, sterilization, multi-modalities integration and intelligent therapeutic systems, are raised. This review will serve as a valuable resource for further advancement and implementation as next-generation biointerfacing technology.

Bioactive peptides and proteins for tissue repair: microenvironment modulation, rational delivery, and clinical potential

Bioactive peptides and proteins (BAPPs) are promising therapeutic agents for tissue repair with considerable advantages, including multifunctionality, specificity, biocompatibility, and biodegradability. However, the high complexity of tissue microenvironments and their inherent deficiencies such as short half-live and susceptibility to enzymatic degradation, adversely affect their therapeutic efficacy and clinical applications. Investigating the fundamental mechanisms by which BAPPs modulate the microenvironment and developing rational delivery strategies are essential for optimizing their administration in distinct tissue repairs and facilitating clinical translation. This review initially focuses on the mechanisms through which BAPPs influence the microenvironment for tissue repair via reactive oxygen species, blood and lymphatic vessels, immune cells, and repair cells. Then, a variety of delivery platforms, including scaffolds and hydrogels, electrospun fibers, surface coatings, assisted particles, nanotubes, two-dimensional nanomaterials, and nanoparticles engineered cells, are summarized to incorporate BAPPs for effective tissue repair, modification strategies aimed at enhancing loading efficiencies and release kinetics are also reviewed. Additionally, the delivery of BAPPs can be precisely regulated by endogenous stimuli (glucose, reactive oxygen species, enzymes, pH) or exogenous stimuli (ultrasound, heat, light, magnetic field, and electric field) to achieve on-demand release tailored for specific tissue repair needs. Furthermore, this review focuses on the clinical potential of BAPPs in facilitating tissue repair across various types, including bone, cartilage, intervertebral discs, muscle, tendons, periodontal tissues, skin, myocardium, nervous system (encompassing brain, spinal cord, and peripheral nerve), endometrium, as well as ear and ocular tissue. Finally, current challenges and prospects are discussed.

Sequential delivery of IL-10 and icariin using nanoparticle/hydrogel hybrid system for prompting bone defect repair

The treatment of large bone defects remains challenging due to the lack of spatiotemporal management of the immune microenvironment, inflammation response and bone remodeling. To address these issues, we designed and developed a nanoparticle/hydrogel hybrid system that can achieve the combined and sequential delivery of an anti-inflammatory factor (IL-10) and osteogenic drug (icariin, ICA). A photopolymerizable composite hydrogel was prepared by combining gelatin methacryloyl (GelMA) and heparin-based acrylated hyaluronic acid (HA) hydrogels containing IL-10, and poly(dl-lactide-co-glycolide) (PLGA)-HA nanoparticles loaded with ICA were incorporated into the composite hydrogels. The nanoparticle/hydrogel hybrid system demonstrates an array of features including mechanical strength, injectability and photo-crosslinking. The rapid release of IL-10 from the hydrogel effectively exerts immunomodulatory activity, whereas the long-term sustained release of icariin from the PLGA-HA nanoparticles significantly triggers the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Notably, the combined delivery of IL-10 and ICA from the hybrid system exhibit a synergistic effect for bone remodeling in a critical cranial defect rat model. Our findings indicate the importance of the immunomodulatory microenvironment and osteogenic differentiation for high-quality skull remodeling, and thus the dual-factor releasing nanoparticle/hydrogel hybrid system could be a promising candidate for repairing bone defects.

Recent Strategies and Advances in Hydrogel-Based Delivery Platforms for Bone Regeneration

Bioactive molecules have shown great promise for effectively regulating various bone formation processes, rendering them attractive therapeutics for bone regeneration. However, the widespread application of bioactive molecules is limited by their low accumulation and short half-lives in vivo. Hydrogels have emerged as ideal carriers to address these challenges, offering the potential to prolong retention times at lesion sites, extend half-lives in vivo and mitigate side effects, avoid burst release, and promote adsorption under physiological conditions. This review systematically summarizes the recent advances in the development of bioactive molecule-loaded hydrogels for bone regeneration, encompassing applications in cranial defect repair, femoral defect repair, periodontal bone regeneration, and bone regeneration with underlying diseases. Additionally, this review discusses the current strategies aimed at improving the release profiles of bioactive molecules through stimuli-responsive delivery, carrier-assisted delivery, and sequential delivery. Finally, this review elucidates the existing challenges and future directions of hydrogel encapsulated bioactive molecules in the field of bone regeneration.

Uniaxial static strain enhances osteogenic and angiogenic potential under hypoxic conditions in distraction osteogenesis

OBJECTIVE

Bone incision leads to interrupted and sluggish blood flow in the process of distraction osteogenesis (DO), creating a hypoxia (0-2% oxygen tension) at the center of the bone callus. This hypoxia is critical in the coupling of osteogenesis and angiogenesis during DO. This study aimed to investigate the effect of Uniaxial Static Strain (USS) on osteogenesis in osteoblasts under hypoxic conditions, with a focus on the expression of osteogenic markers and angiogenic factors.

METHODS

The USS was made by a multi-unit tension compression device.Osteoblasts were subjected to 10% USS made under hypoxic conditions to mimic the process of DO in vitro. The cell proliferation, alkaline phosphatase (ALP) activity, mineralized nodule formation, and expression of osteogenic and angiogenic markers were evaluated by using a CCK-8 assay, alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qRT-PCR, Western blotting and ELISA.

RESULTS

Hypoxia inhibited osteoblast cell proliferation, ALP activity, mineralized nodule formation, and the expression of runt-related transcription factor 2 (Runx- 2), osteopontin(OPN), osteocalcin (OCN), collagen type I (Col1a1). Conversely, hypoxia upregulated the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF), which are associated with angiogenesis. However, the application of USS enhanced osteoblasts' osteogenic capacity and upregulated angiogenic factors under hypoxic conditions.

CONCLUSION

USS can enhance osteogenesis in osteoblasts under hypoxic conditions. Moreover, it may stimulate angiogenesis by promoting the expression of VEGF, which further contributes to bone formation. This finding provides important implications for understanding the mechanisms involved in bone regeneration and may have clinical applications in optimizing the effectiveness of DO techniques.

A multifunctional self-reinforced injectable hydrogel for enhancing repair of infected bone defects by simultaneously targeting macrophages, bacteria, and bone marrow stromal cells

Injectable hydrogels (IHs) have demonstrated huge potential in promoting repair of infected bone defects (IBDs), but how to endow them with desired anti-bacterial, immunoregulatory, and osteo-inductive properties as well as avoid mechanical failure during their manipulation are challenging. In this regard, we developed a multifunctional AOHA-RA/Lap nanocomposite IH for IBDs repair, which was constructed mainly through two kinds of reversible cross-links: (i) the laponite (Lap) crystals mediated electrostatic interactions; (ii) the phenylboronic acid easter bonds between the 4-aminobenzeneboronic acid grafted oxidized hyaluronic acid (AOHA) and rosmarinic acid (RA). Due to the specific structural composition, the AOHA-RA/Lap IH demonstrated superior injectability, self-recoverability, spatial adaptation, and self-reinforced mechanical properties after being injected to the bone defect site. In addition, the RA molecules could be locally released from the hydrogel following a Weibull model for over 10 days. Systematic in vitro/vivo assays proved the strong anti-bacterial activity of the hydrogel against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Moreover, its capability of inducing M2 polarization of macrophages (Mφ) and osteogenic differentiation of bone marrow stromal cells (BMSCs) was verified either, and the mechanism of the former was identified to be related to the JAK1-STAT1 and PI3K-AKT signaling pathways and that of the latter was identified to be related to the calcium signaling pathway, extracellular matrix (ECM) receptor interaction and TGF-β signaling pathway. After being implanted to a S. aureus infected rat skull defect model, the AOHA-RA/Lap IH significantly accelerated repair of IBDs without causing significant systemic toxicity. STATEMENT OF SIGNIFICANCE: Rosmarinic acid and laponite were utilized to develop an injectable hydrogel, promising for accelerating repair of infected bone defects in clinic. The gelation of the hydrogel was completely driven by two kinds of reversible cross-links, which endow the hydrogel superior spatial adaption, self-recoverability, and structural stability. The as-prepared hydrogel demonstrated superior anti-bacterial/anti-biofilm activity and could induce M2 polarization of macrophages and osteogenic differentiation of BMSCs. The mechanism behind macrophages polarization was identified to be related to the JAK1-STAT1 and PI3K-AKT signaling pathways. The mechanism behind osteogenic differentiation of BMSCs was identified to be related to the ECM receptor interaction and calcium signaling/TGF-β signaling pathways.

Self-Assembled Peptide with Morphological Structure for Bioapplication

Peptide materials, such as self-assembled peptide materials, are very important biomaterials. Driven by multiple interaction forces, peptide molecules can self-assemble into a variety of different macroscopic forms with different properties and functions. In recent years, the research on self-assembled peptides has made great progress from laboratory design to clinical application. This review focuses on the different morphologies, including nanoparticles, nanovesicles, nanotubes, nanofibers, and others, formed by self-assembled peptide. The mechanisms and applications of the morphology transformation are also discussed in this paper, and the future direction of self-assembled nanomaterials is envisioned.

Ultrasound Tissue Engineering Technology for Regulating Immune Microenvironment

The immune microenvironment is critical for the occurrence, progression, and treatment of diseases. Ultrasound tissue engineering technology utilizes ultrasound and the principles of tissue engineering to repair, regenerate, and functionally reconstruct biological tissues. Ultrasound therapy is a non‐invasive treatment modality that regulates the immune microenvironment and maintains homeostasis through various characteristic effects. Ultrasound‐responsive biomaterials utilize biological properties or drug/gene delivery to regulate the immune microenvironment under ultrasound stimulation for targeted and purposeful treatment. This article comprehensively and systematically reviews advancements in ultrasound tissue engineering technology for regulating the immune microenvironment. First, the changes in the immune microenvironment at different stages of the disease is briefly illustrated. It is then reviewed the regulation of the immune microenvironment by ultrasound and ultrasound‐responsive biomaterials in five types of diseases: tumor, cardiovascular system diseases, nervous system diseases, musculoskeletal diseases, and wound. Finally, the prospects of the ultrasound tissue engineering technology for regulating the immune microenvironment is summarized.

Unlocking the potential of stimuli-responsive biomaterials for bone regeneration

Bone defects caused by tumors, osteoarthritis, and osteoporosis attract great attention. Because of outstanding biocompatibility, osteogenesis promotion, and less secondary infection incidence ratio, stimuli-responsive biomaterials are increasingly used to manage this issue. These biomaterials respond to certain stimuli, changing their mechanical properties, shape, or drug release rate accordingly. Thereafter, the activated materials exert instructive or triggering effects on cells and tissues, match the properties of the original bone tissues, establish tight connection with ambient hard tissue, and provide suitable mechanical strength. In this review, basic definitions of different categories of stimuli-responsive biomaterials are presented. Moreover, possible mechanisms, advanced studies, and pros and cons of each classification are discussed and analyzed. This review aims to provide an outlook on the future developments in stimuli-responsive biomaterials.

Decellularized Amnion Membrane Triggers Macrophage Polarization for Desired Host Immune Response

Appropriate regulation of immunomodulatory responses, particularly acute inflammation involving macrophages, is crucial for the desired functionality of implants. Decellularized amnion membrane (DAM) is produced by removing cellular components and antigenicity, expected to reduce immunogenicity and the risk of inflammation. Despite the potential of DAM as biomaterial implants, few studies have investigated its specific effects on immunomodulation. Here, it is demonstrated that DAM can regulate macrophage-driven inflammatory response and potential mechanisms are investigated. In vitro results show that DAM significantly inhibits M1 polarization in LPS-induced macrophages by inhibiting Toll-like receptors (TLR) signaling pathway and TNF signaling pathway and promotes macrophage M2 polarization. Physical signals from the 3D micro-structure and the active protein, DCN, binding to key targets may play roles in the process. In the subcutaneous implant model in rats, DAM inhibits the persistence of inflammation and fibrous capsule formation, while promoting M2 macrophage polarization, thereby facilitating tissue regeneration. This study provides insights into DAM's effect and potential mechanisms on the balance of M1/M2 macrophage polarization in vitro and vivo, emphasizing the immunomodulation of ECM-based materials as promising implants.

Mg-Cross-Linked Alginate Hydrogel Induces BMSC/Macrophage Crosstalk to Enhance Bone Tissue Regeneration via Dual Promotion of the Ligand-Receptor Pairing of the OSM/miR-370-3p-gp130 Signaling Pathway

Macrophages play a pivotal role in the crosstalk between the immune and skeletal systems, while Mg-based biomaterials demonstrate immunomodulatory capabilities in this procedure. However, the mechanism of how Mg2+ promotes osteogenesis through the interplay of bone marrow-derived mesenchymal stem cells (BMSCs) and macrophages remains undescribed. Here, we demonstrated that a Mg-cross-linked alginate hydrogel exerted a dual enhancement of BMSCs osteogenic differentiation through the ligand-receptor pairing of the OSM/miR-370-3p-gp130 axis. On the one hand, Mg2+, released from the Mg-cross-linked hydrogel, stimulates bone marrow-derived macrophages to produce and secrete more OSM. On the other hand, Mg2+ lowers the miR-370-3p level in BMSCs and in turn, reverses its suppression on gp130. Then, the OSM binds to the gp130 heterodimer receptor and activates intracellular osteogenic programs in BMSCs. Taken together, this study reveals a novel cross-talk pattern between the skeletal and immune systems under Mg2+ stimulation. This study not only brings new insights into the immunomodulatory properties of Mg-based biomaterials for orthopedic applications but also enriches the miRNA regulatory network and provides a promising target to facilitate bone regeneration in large bone defects.

An ultrasound-triggered injectable sodium alginate scaffold loaded with electrospun microspheres for on-demand drug delivery to accelerate bone defect regeneration

Biological processes, such as bone defects healing are precisely controlled in both time and space. This spatiotemporal characteristic inspires novel therapeutic strategies. The sustained-release systems including hydrogels are commonly utilized in the treatment of bone defect; however, traditional hydrogels often release drugs at a consistent rate, lacking temporal precision. In this study, a hybrid hydrogel has been developed by using sodium alginate, sucrose acetate isobutyrate, and electrospray microspheres as the base materials, and designed with ultrasound response, and on-demand release properties. Sucrose acetate isobutyrate was added to the hybrid hydrogel to prevent burst release. The network structure of the hybrid hydrogel is formed by the interconnection of Ca2+ with the carboxyl groups of sodium alginate. Notably, when the hybrid hydrogel is exposed to ultrasound, the ionic bond can be broken to promote drug release; when ultrasound is turned off, the release returned to a low-release state. This hybrid hydrogel reveals not only injectability, degradability, and good mechanical properties but also shows multiple responses to ultrasound. And it has good biocompatibility and promotes osteogenesis efficiency in vivo. Thus, this hybrid hydrogel provides a promising therapeutic strategy for the treatment of bone defects.

Cell-homing and immunomodulatory composite hydrogels for effective wound healing with neovascularization

Wound healing in cases of excessive inflammation poses a significant challenge due to compromised neovascularization. Here, we propose a multi-functional composite hydrogel engineered to overcome such conditions through recruitment and activation of macrophages with adapted degradation of the hydrogel. The composite hydrogel (G-TSrP) is created by combining gelatin methacryloyl (GelMA) and nanoparticles (TSrP) composed of tannic acid (TA) and Sr2+. These nanoparticles are prepared using a one-step mineralization process assisted by metal-phenolic network formation. G-TSrP exhibits the ability to eliminate reactive oxygen species and direct polarization of macrophages toward M2 phenotype. It has been observed that the liberation of TA and Sr2+ from G-TSrP actively facilitate the recruitment and up-regulation of the expression of extracellular matrix remodeling genes of macrophages, and thereby, coordinate in vivo adapted degradation of the G-TSrP. Most significantly, G-TSrP accelerates angiogenesis despite the TA's inhibitory properties, which are counteracted by the released Sr2+. Moreover, G-TSrP enhances wound closure under inflammation and promotes normal tissue formation with strong vessel growth. Genetic analysis confirms macrophage-mediated wound healing by the composite hydrogel. Collectively, these findings pave the way for the development of biomaterials that promote wound healing by creating regenerative environment.

The Impact of NLRP3 Inflammasome on Osteoblasts and Osteogenic Differentiation: A Literature Review

Osteoblasts (OBs), which are a crucial type of bone cells, derive from bone marrow mesenchymal stem cells (MSCs). Accumulating evidence suggests inflammatory cytokines can inhibit the differentiation and proliferation of OBs, as well as interfere with their ability to synthesize bone matrix, under inflammatory conditions. NLRP3 inflammasome is closely associated with cellular pyroptosis, which can lead to excessive release of pro-inflammatory cytokines, causing tissue damage and inflammatory responses, however, the comprehensive roles of NLRP3 inflammasome in OBs and their differentiation have not been fully elucidated, making targeting NLRP3 inflammasome approaches to treat diseases related to OBs uncertain. In this review, we provide a summary of NLRP3 inflammasome activation and its impact on OBs. We highlight the significant roles of NLRP3 inflammasome in regulating OBs differentiation and function. Furthermore, current available strategies to affect OBs function and osteogenic differentiation targeting NLRP3 inflammasome are listed and analyzed. Finally, through the prospective discussion, we seek to provide novel insights into the crucial role of NLRP3 inflammasome in diseases related to OBs and offer valuable information for devising treatment strategies.

Macrophage exosomes modified by miR-365-2-5p promoted osteoblast osteogenic differentiation by targeting OLFML1

In the bone immune microenvironment, immune cells can regulate osteoblasts through a complex communication network. Macrophages play a central role in mediating immune osteogenesis, exosomes derived from them have osteogenic regulation and can be used as carriers in bone tissue engineering. However, there are problems with exosomal therapy alone, such as poor targeting, and the content of loaded molecules cannot reach the therapeutic concentration. In this study, macrophage-derived exosomes modified with miR-365-2-5p were developed to accelerate bone healing. MC3T3-E1 cells were incubated with the culture supernatants of M0, M1 and M2 macrophages, and it was found that the culture medium of M2 macrophages had the most significant effects in contributing to osteogenesis. High-throughput sequencing identified that miR-365-2-5p was significantly expressed in exosomes derived from M2 macrophages. We incubated MC3T3-E1 with exosomes overexpressing or knocking down miR-365-2-5p to examine the biological function of exosome miR-365-2-5p on MC3T3-E1 differentiation. These findings suggested that miR-365-2-5p secreted by exosomes increased the osteogenesis of MC3T3-E1. Moreover, miR-365-2-5p had a direct influence over osteogenesis for MC3T3-E1. Sequencing analysis combined with dual luciferase detection indicated that miR-365-2-5p binded to the 3'-UTR of OLFML1. In summary, exosomes secreted by M2 macrophages targeted OLFML1 through miR-365-2-5p to facilitate osteogenesis.

Thermodynamically stable ionic liquid microemulsions pioneer pathways for topical delivery and peptide application

Copper peptides (GHK-Cu) are a powerful hair growth promoter with minimal side effects when compared with minoxidil and finasteride; however, challenges in delivering GHK-Cu topically limits their non-invasive applications. Using theoretical calculations and pseudo-ternary phase diagrams, we designed and constructed a thermodynamically stable ionic liquid (IL)-based microemulsion (IL-M), which integrates the high drug solubility of ILs and high skin permeability of microemulsions, thus improving the local delivery of copper peptides by approximately three-fold while retaining their biological function. Experiments in mice validated the effectiveness of our proposed IL-M system. Furthermore, the exact effects of the IL-M system on the expression of growth factors, such as vascular endothelial growth factor, were revealed, and it was found that microemulsion increased the activation of the Wnt/β-catenin signaling pathway, which includes factors involved in hair growth regulation. Overall, the safe and non-invasive IL microemulsion system developed in this study has great potential for the clinical treatment of hair loss.

Mechanisms and influencing factors of peptide hydrogel formation and biomedicine applications of hydrogels

Self-assembled peptide-based hydrogels have shown great potential in bio-related applications due to their porous structure, strong mechanical stability, high biocompatibility, and easy functionalization. Herein, the structure and characteristics of hydrogels and the mechanism of action of several regular secondary structures during gelation are investigated. The factors influencing the formation of peptide hydrogels, especially the pH responsiveness and salt ion induction are analyzed and summarized. Finally, the biomedical applications of peptide hydrogels, such as bone tissue engineering, cell culture, antigen presentation, antibacterial materials, and drug delivery are reviewed.