Early osteoimmunomodulation by mucin hydrogels augments the healing and revascularization of rat critical-size calvarial bone defects

Macrophage is crucial for tongue development by regulating myogenesis and vascularization

BACKGROUND

Abnormal tongue development is a craniofacial deformity that affects dental-maxillofacial esthetics and function. Recent evidence has identified macrophages as multi-functional immune cells crucial for heart and brain development. However, it is still unknown whether macrophages affect tongue development. Therefore, this study aims to assess the distribution, phenotype, and roles of macrophages in the developing tongue.

METHODS

In this study, immunohistochemical (IHC) and multiplex immunofluorescence (mIF) staining were conducted on C57BL/6 mice at embryonic day (E) 13.5, E14.5, E16.5, and E18.5 to analyze the distribution and phenotype of macrophages. Hematoxylin-Eosin (HE), IHC, IF, and mIF staining were also performed on embryonic CX3 CR1-CreERT2; Rosa-DTA conditional macrophage-depleted mice to investigate the effects on fetal tongue development and elucidate mechanisms from myogenesis, vascularization, and cell apoptosis. Statistical significance between the two groups was determined using unpaired two-tailed Student's t-tests. For comparisons involving three or more groups, one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison tests was utilized. A significance level of P < 0.05 was set for statistical significance.

RESULTS

Macrophages were present in the developing tongue from E13.5 to E18.5, with a majority being of the M2 phenotype. Depletion of macrophages resulted in abnormal tongue morphology, decreased tongue height, width, and size, as well as reduced and disorganized muscle fibers. Depletion of macrophages also increased apoptosis. Vascular morphogenesis was impacted, with reductions in the luminal and vascular wall cross-sectional areas of the lingual artery. Vascular endothelial cells were reduced and disorganized with decreased expression of VEGFA and TGF-β1. Moreover, macrophages were located near vascular endothelial cells and secreted pro-angiogenic factors, suggesting their involvement in promoting vascularization.

CONCLUSIONS

Our findings indicate that macrophages play crucial roles in fetal tongue development by affecting myogenesis, cell apoptosis, and vascular growth.

Regulation of T Cell Glycosylation by MXene/β-TCP Nanocomposite for Enhanced Mandibular Bone Regeneration

Immune-mediated bone regeneration driven by bone biomaterials offers a therapeutic strategy for repairing bone defects. Among 2D nanomaterials, Ti3C2Tx MXenes have garnered substantial attention for their potential in tissue regeneration. This investigation concentrates on the role of MXene nanocomposites in modulating the immune microenvironment within bone defects to facilitate bone tissue restoration. Ti3C2Tx MXenes are synthetized, incorporated into beta-tricalcium phosphate ceramics (β-TCP) nanocomposites (T-MXene), and their osteoinductive and immunomodulatory effects are evaluated. The effects of T-MXene-treated T-cells on bone marrow stromal cells (BMSCs) are explored. In addition, its therapeutic potential for bone regeneration is assessed in vivo using a critical-sized mandibular bone defect model. The underlying mechanisms by which T-MXene regulates T-cell differentiation and bone regeneration are explored via whole-transcriptome RNA sequencing. The scaffolds activate N-glycosylation in T cells, which possess anti-inflammatory and antioxidant effects, thereby inducing a pro-regenerative response. T-MXene increased the proportion of IL-4+ T cells among primary T cells and mandibular lymph nodes, ultimately promoting osteogenesis in BMSCs and injured mandibles. The distinctive function of MXene-based nanocomposites in osteoimmunomodulation provides a solid foundation for further exploration and application of MXenes as immune response modulators, potentially advancing their use in regenerative medicine.

Functionalized 3D-printed GelMA/Laponite hydrogel scaffold promotes BMSCs recruitment through osteoimmunomodulatory enhance osteogenic via AMPK/mTOR signaling pathway

The migration and differentiation of bone marrow mesenchymal stem cells (BMSCs) play crucial roles in bone repair processes. However, conventional scaffolds often lack of effectively inducing and recruiting BMSCs. In our study, we present a novel approach by introducing a 3D-bioprinted scaffold composed of hydrogels, with the addition of laponite to the GelMA solution, aimed at enhancing scaffold performance. Both in vivo and in vitro experiments have confirmed the outstanding biocompatibility of the scaffold. Furthermore, for the first time, Apt19s has been chemically modified onto the surface of the hydrogel scaffold, resulting in a remarkable enhancement in the migration and adhesion of BMSCs. Moreover, the scaffold has demonstrated robust osteogenic differentiation capability in both in vivo and in vitro environments. Additionally, the hydrogel scaffold has shown the ability to induce the polarization of macrophages from M1 to M2, thereby facilitating the osteogenic differentiation of BMSCs via the bone immune pathway. Through RNA-seq analysis, it has been revealed that macrophages regulate the osteogenic differentiation of BMSCs through the AMPK/mTOR signaling pathway. In summary, the functionalized GelMA/Laponite scaffold offers a cost-effective approach for tailored in situ bone regeneration.

Preserving the Immune-Privileged Niche of the Nucleus Pulposus: Safeguarding Intervertebral Discs from Degeneration after Discectomy with Synthetic Mucin Hydrogel Injection

Intervertebral disc (IVD) herniation is a prevalent spinal disorder, often necessitating surgical intervention such as microdiscectomy for symptomatic relief and nerve decompression. IVDs comprise a gel-like nucleus pulposus (NP) encased by an annulus fibrosus (AF), and their avascular nature renders them immune-privileged. Microdiscectomy exposes the residual NP to the immune system, precipitating an immune cell infiltration and attack that exacerbates IVD degeneration. While many efforts in the tissue engineering field are directed toward IVD regeneration, the inherently limited regenerative capacity due to the avascular and low-cellularity nature of the disc and the challenging mechanical environment of the spine often impedes success. This study, aiming to prevent IVD degeneration post-microdiscectomy, utilizes mucin-derived gels (Muc-gels) that form a gel at the surgical site, inspired by the natural mucin coating on living organisms to evade immune reorganization. It is shown that type I macrophages are present in severely degenerated human discs. Encapsulating IVDs within Muc-gels prevents fibrous encapsulation and macrophage infiltration in a mouse subcutaneous model. The injection of Muc-gels prevents IVD degeneration in a rat tail IVD degeneration model up to 24 weeks post-operation. Mechanistic investigations indicate that Muc-gels attenuate immune cell infiltration into NPs, offering durable protection against immune attack post-microdiscectomy.

Multifunctionally disordered TiO2 nanoneedles prevent periprosthetic infection and enhance osteointegration by killing bacteria and modulating the osteoimmune microenvironment

Rationale: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are effective interventions for end-stage osteoarthritis; however, periprosthetic infection is a devastating complication of arthroplasty. To safely prevent periprosthetic infection and enhance osteointegration, the surface modification strategy was utilized to kill bacteria, modulate the osteoimmune microenvironment, and improve new bone formation. Methods: We used the hydrothermal method to fabricate a bionic insect wing with the disordered titanium dioxide nanoneedle (TNN) coating. The mussel-inspired poly-dopamine (PDA) and antibacterial silver nanoparticles (AgNPs) were coated on TNN, named AgNPs-PDA@TNN, to improve the biocompatibility and long-lasting bactericidal capacity. The physicochemical properties of the engineered specimen were evaluated with SEM, AFM, XPS spectrum, and water contact assay. The biocompatibility, bactericidal ability, and the effects on macrophages and osteogenic differentiation were assessed with RT-qPCR, Western blotting, live/dead staining, immunofluorescent staining, etc. Results: The AgNPs-PDA@TNN were biocompatible with macrophages and exhibited immunomodulatory ability to promote M2 macrophage polarization. In addition, AgNPs-PDA@TNN ameliorated the cytotoxicity caused by AgNPs, promoted cell spreading, and increased osteogenesis and matrix deposition of BMSCs. Furthermore, AgNPs-PDA@TNN exhibited bactericidal ability against E. coli and S. aureus by the bionic nanostructure and coated AgNPs. Various imaging analyses indicated the enhanced bactericidal ability and improved new bone formation by AgNPs-PDA@TNN in vivo. H&E, Gram, and Masson staining, verified the improved bone formation, less inflammation, infection, and fibrosis encapsulation. The immunofluorescence staining confirmed the immunomodulatory ability of AgNPs-PDA@TNN in vivo. Conclusion: The bionic insect wing AgNPs-PDA@TNN coating exhibited bactericidal property, immunomodulatory ability, and enhanced osteointegration. Thus, this multidimensional bionic implant surface holds promise as a novel strategy to prevent periprosthetic infection.

A tutorial on optical photothermal infrared (O-PTIR) microscopy

This tutorial reviews the rapidly growing field of optical photothermal infrared (O-PTIR) spectroscopy and chemical imaging. O-PTIR is an infrared super-resolution measurement technique where a shorter wavelength visible probe is used to measure and map infrared (IR) absorption with spatial resolution up to 30× better than conventional techniques such as Fourier transform infrared and direct IR laser imaging systems. This article reviews key limitations of conventional IR instruments, the O-PTIR technology breakthroughs, and their origins that have overcome the prior limitations. This article also discusses recent developments in expanding multi-modal O-PTIR approaches that enable complementary Raman spectroscopy and fluorescence microscopy imaging, including wide-field O-PTIR imaging with fluorescence-based detection of IR absorption. Various practical subjects are covered, including sample preparation techniques, optimal measurement configurations, use of IR tags/labels and techniques for data analysis, and visualization. Key O-PTIR applications are reviewed in many areas, including biological and biomedical sciences, environmental and microplastics research, (bio)pharmaceuticals, materials science, cultural heritage, forensics, photonics, and failure analysis.

Mucus-Mimicking Mucin-Based Hydrogels by Tandem Chemical and Physical Crosslinking

Mucosal tissues represent a major interface between the body and the external environment and are covered by a highly hydrated mucins gel called mucus. Mucus lubricates, protects and modulates the moisture levels of the tissue and is capitalized in transmucosal drug delivery. Pharmaceutical researchers often use freshly excised animal mucosal membranes to assess mucoadhesion and muco-penetration of pharmaceutical formulations which may struggle with limited accessibility, reproducibility, and ethical questions. Aiming to develop a platform for the rationale study of the interaction of drugs and delivery systems with mucosal tissues, in this work mucus-mimicking mucin-based hydrogels are synthesized by the tandem chemical and physical crosslinking of mucin aqueous solutions. Chemical crosslinking is achieved with glutaraldehyde (0.3% and 0.75% w/v), while physical crosslinking by one or two freeze-thawing cycles. Hydrogels after one freeze-thawing cycle show water content of 97.6-98.1%, density of 0.0529-0.0648 g cm⁻3, and storage and loss moduli of ≈40-60 and ≈3-5 Pa, respectively, that resemble the properties of native gastrointestinal mucus. The mechanical stability of the hydrogels increases over the number of freeze-thawing cycles. Overall results highlight the potential of this simple, reproducible, and scalable method to produce artificial mucus-mimicking hydrogels for different applications in pharmaceutical research.

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.

Glycoprotein Injectable Hydrogels Promote Accelerated Bone Regeneration through Angiogenesis and Innervation

Glycoproteins are gaining prominence as multifunctional biomaterials. The study reports development of glycoprotein mucin as biomaterial promoting bone regeneration. Mucin 1 deletion has resulted in stiffer femoral bones with scarce presence of osteoblasts in trabecular linings and its role has been established in determining bone mass and mineralization. Limited information about its structure limits its processability, exploration as biomaterial, which is discussed in this study. The role of mucin in ECM (extracellular cellular matrix) formation validated by RNA sequencing analysis of human bone marrow derived mesenchymal stem cells is reported. The structure and stability of mucins is dependent on the presence of glycans in its structure. A thermosensitive hydrogel acquired from thermosensitive Poly (N-isopropyl acrylamide)-(PNIPAM) modified mucin and collagen is developed. The hydrogel demonstrates porous structure and mechanical strength. Newly formed bone tissue is observed at 8 weeks post-implantation in the hydrogel treated groups. The formation of blood vessels, nerves, and bone is observed with upregulation of angiopoietin (ANG), neurofilament heavy chain (NF-H), and osteoadherin (OSAD) or osteocalcin (OCN) respectively in rat calvarial defects. The outcome demonstrates that the thermosensitive injectable hydrogel accelerates repair and healing in calvarial bone defects making it a promising biodegradable biomaterial capable of regenerating bone by promoting angiogenesis and innervation.

Synthetic mucus biomaterials for antimicrobial peptide delivery

Despite the promise of antimicrobial peptides (AMPs) as treatments for antibiotic-resistant infections, their therapeutic efficacy is limited due to the rapid degradation and low bioavailability of AMPs. To address this, we have developed and characterized a synthetic mucus (SM) biomaterial capable of delivering LL37 AMPs and enhancing their therapeutic effect. LL37 is an AMP that exhibits a wide range of antimicrobial activity against bacteria, including Pseudomonas aeruginosa. LL37 loaded SM hydrogels demonstrated controlled release with 70%-95% of loaded LL37 over 8 h due to charge-mediated interactions between mucins and LL37 AMPs. Compared to treatment with LL37 alone where antimicrobial activity was reduced after 3 h, LL37-SM hydrogels inhibited P. aeruginosa (PAO1) growth over 12 h. LL37-SM hydrogel treatment reduced PAO1 viability over 6 h whereas a rebound in bacterial growth was observed when treated with LL37 only. These data demonstrate LL37-SM hydrogels enhance antimicrobial activity by preserving LL37 AMP activity and bioavailability. Overall, this work establishes SM biomaterials as a platform for enhanced AMP delivery for antimicrobial applications.

3D-Printed lattice-inspired composites for bone reconstruction

Mechanical performance is crucial for biomedical applications of scaffolds. In this study, the stress distribution of six lattice-inspired structures was investigated using finite element simulations, and scaffolds with pre-designed structures were prepared using selective laser sintering (SLS) technology. The results showed that scaffolds with face-centered cubic (FCC) structures exhibited the highest compressive strength. Moreover, scaffolds composed of polylactic acid/anhydrous calcium hydrogen phosphate (PLA/DCPA) showed good mechanical properties and bioactivity. An in vitro study showed that these scaffolds promoted cell proliferation significantly and showed excellent osteogenic performance. Composite scaffolds with FCC structures are promising for bone tissue engineering.

Synthetic Mucus Biomaterials for Antimicrobial Peptide Delivery

Despite the promise of antimicrobial peptides (AMPs) as treatments for antibiotic-resistant infections, their therapeutic efficacy is limited due to the rapid degradation and low bioavailability of AMPs. To address this, we have developed and characterized a synthetic mucus (SM) biomaterial capable of delivering AMPs and enhancing their therapeutic effect. LL37 loaded SM hydrogels demonstrated controlled release of LL37 over 8 hours as a result of charge-mediated interactions between mucins and LL37 AMPs. Compared to treatment with LL37 alone where antimicrobial activity was reduced after 3 hours, LL37-SM hydrogels inhibited Pseudomonas aeruginosa PAO1 growth over 12 hours. LL37-SM hydrogel treatment reduced PAO1 viability over 6 hours whereas a rebound in bacterial growth was observed when treated with LL37 only. These data demonstrate LL37-SM hydrogels enhance antimicrobial activity by preserving LL37 AMP activity and bioavailability. Overall, this work establishes SM biomaterials as a platform for enhanced AMP delivery for antimicrobial applications.