CD301b+ macrophages mediate angiogenesis of calcium phosphate bioceramics by CaN/NFATc1/VEGF axis

Bredigite-Based Bioactive Nerve Guidance Conduit for Pro-Healing Macrophage Polarization and Peripheral Nerve Regeneration

Structural and functional healing of peripheral nerves damaged by trauma or chronic disease remain major clinical challenges, requiring the development of an effective nerve guidance conduit (NGC). The present study investigates a NGC fabrication strategy based on bredigite (BRT, Ca7MgSi4O16) bioceramic for the treatment of peripheral nerve injury. Here, BRT bioceramic shows good biocompatibility and sustainable release of Ca2+, Mg2+, and Si4+ ions. Both BRT extracts and BRT-incorporating electrospun membranes promote the proliferation and myelination potential of RSC96 cells, as well as accelerate vascular formation by human umbilical vein endothelial cells. Notably, BRT facilitates RAW 264.7 cell polarization to the pro-healing phenotype under LPS-induced inflammatory stimulation. More importantly, the macrophages activated by BRT in turn promote RSC96 cell migration and remyelination. In a rat sciatic nerve defect model, improved electrophysiological performance and alleviated gastrocnemius muscle atrophy are observed at 12 weeks post-implantation. Further experiments verify that BRT-loaded NGC facilitates axonal regrowth and revascularization with high M2-like macrophage infiltration. These findings support the beneficial effects of BRT for creating a pro-healing immune microenvironment and orchestrating multicellular processes associated with functional nerve regeneration, indicating the potential of rationally engineered bioceramics as safe, effective, and economical materials for peripheral nerve repair.

Tim4 deficiency reduces CD301b+ macrophage and aggravates periodontitis bone loss

Periodontitis is a common chronic inflammatory disease that causes the periodontal bone destruction and may ultimately result in tooth loss. With the progression of periodontitis, the osteoimmunology microenvironment in periodontitis is damaged and leads to the formation of pathological alveolar bone resorption. CD301b+ macrophages are specific to the osteoimmunology microenvironment, and are emerging as vital booster for conducting bone regeneration. However, the key upstream targets of CD301b+ macrophages and their potential mechanism in periodontitis remain elusive. In this study, we concentrated on the role of Tim4, a latent upstream regulator of CD301b+ macrophages. We first demonstrated that the transcription level of Timd4 (gene name of Tim4) in CD301b+ macrophages was significantly upregulated compared to CD301b- macrophages via high-throughput RNA sequencing. Moreover, several Tim4-related functions such as apoptotic cell clearance, phagocytosis and engulfment were positively regulated by CD301b+ macrophages. The single-cell RNA sequencing analysis subsequently discovered that Cd301b and Timd4 were specifically co-expressed in macrophages. The following flow cytometric analysis indicated that Tim4 positive expression rates in total macrophages shared highly synchronized dynamic changes with the proportions of CD301b+ macrophages as periodontitis progressed. Furthermore, the deficiency of Tim4 in mice decreased CD301b+ macrophages and eventually magnified alveolar bone resorption in periodontitis. Additionally, Tim4 controlled the p38 MAPK signaling pathway to ultimately mediate CD301b+ macrophages phenotype. In a word, Tim4 might regulate CD301b+ macrophages through p38 MAPK signaling pathway in periodontitis, which provided new insights into periodontitis immunoregulation as well as help to develop innovative therapeutic targets and treatment strategies for periodontitis.

Fn-HMGB1 Adsorption Behavior Initiates Early Immune Recognition and Subsequent Osteoinduction of Biomaterials

Implantable biomaterials are widely used in bone tissue engineering, but little is still known about how they initiate early immune recognition and the initial dynamics. Herein, the early immune recognition and subsequent osteoinduction of biphasic calcium phosphate (BCP) after implantation to the protein adsorption behavior is attributed. By liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, the biomaterial-related molecular patterns (BAMPs) formed after BCP implantation are mapped, dominated by the highly expressed extracellular matrix protein fibronectin (Fn) and the high mobility group box 1 (HMGB1). Molecular dynamics simulations show that Fn has the ability to bind more readily to the BCP surface than HMGB1. The preferential binding of Fn provides a higher adsorption energy for HMGB1. Furthermore, multiple hydrogen bonding sites between HMGB1 and Fn are demonstrated using a molecular docking approach. Ultimately, the formation of BAMPs through HMGB1 antagonist glycyrrhizic acid (GA), resulting in impaired immune recognition of myeloid differentiation factor 88 (MYD88) mediated dendritic cells (DCs) and macrophages (Mφs), as well as failed osteoinduction processes is obstructed. This study introduces a mechanism for early immune recognition of implant materials based on protein adsorption, providing perspectives for future design and application of tissue engineering materials.

Construction of functional surfaces for dental implants to enhance osseointegration

Dental implants have been extensively used in patients with defects or loss of dentition. However, the loss or failure of dental implants is still a critical problem in clinic. Therefore, many methods have been designed to enhance the osseointegration between the implants and native bone. Herein, the challenge and healing process of dental implant operation will be briefly introduced. Then, various surface modification methods and emerging biomaterials used to tune the properties of dental implants will be summarized comprehensively.

Microenvironment-Regulating Drug Delivery Nanoparticles for Treating and Preventing Typical Biofilm-Induced Oral Diseases

The oral cavity comprises an environment full of microorganisms. Dysregulation of this microbial-cellular microenvironment will lead to a series of oral diseases, such as implant-associated infection caused by Staphylococcus aureus (S. aureus) biofilms and periodontitis initiated by Streptococcus oralis (S. oralis). In this study, a liposome-encapsulated indocyanine green (ICG) and rapamycin drug-delivery nanoparticle (ICG-rapamycin) is designed to treat and prevent two typical biofilm-induced oral diseases by regulating the microbial-cellular microenvironment. ICG-rapamycin elevates the reactive oxygen species (ROS) and temperature levels to facilitate photodynamic and photothermal mechanisms under near-infrared (NIR) laser irradiation for anti-bacteria. In addition, it prevents biofilm formation by promoting bacterial motility with increasing the ATP levels. The nanoparticles modulate the microbial-cellular interaction to reduce cellular inflammation and enhance bacterial clearance, which includes promoting the M2 polarization of macrophages, upregulating the anti-inflammatory factor TGF-β, and enhancing the bacterial phagocytosis of macrophages. Based on these findings, ICG-rapamycin is applied to implant-infected and periodontitis animal models to confirm the effects in vivo. This study demonstrates that ICG-rapamycin can treat and prevent biofilm-induced oral diseases by regulating the microbial-cellular microenvironment, thus providing a promising strategy for future clinical applications.

Role of dendritic cells in MYD88-mediated immune recognition and osteoinduction initiated by the implantation of biomaterials

Bone substitute material implantation has become an important treatment strategy for the repair of oral and maxillofacial bone defects. Recent studies have shown that appropriate inflammatory and immune cells are essential factors in the process of osteoinduction of bone substitute materials. Previous studies have mainly focused on innate immune cells such as macrophages. In our previous work, we found that T lymphocytes, as adaptive immune cells, are also essential in the osteoinduction procedure. As the most important antigen-presenting cell, whether dendritic cells (DCs) can recognize non-antigen biomaterials and participate in osteoinduction was still unclear. In this study, we found that surgical trauma associated with materials implantation induces necrocytosis, and this causes the release of high mobility group protein-1 (HMGB1), which is adsorbed on the surface of bone substitute materials. Subsequently, HMGB1-adsorbed materials were recognized by the TLR4-MYD88-NFκB signal axis of dendritic cells, and the inflammatory response was activated. Finally, activated DCs release regeneration-related chemokines, recruit mesenchymal stem cells, and initiate the osteoinduction process. This study sheds light on the immune-regeneration process after bone substitute materials implantation, points out a potential direction for the development of bone substitute materials, and provides guidance for the development of clinical surgical methods.

Engineering of a NIR-activable hydrogel-coated mesoporous bioactive glass scaffold with dual-mode parathyroid hormone derivative release property for angiogenesis and bone regeneration

Osteogenesis, osteoclastogenesis, and angiogenesis play crucial roles in bone regeneration. Parathyroid hormone (PTH), an FDA-approved drug with pro-osteogenic, pro-osteoclastogenic and proangiogenic capabilities, has been employed for clinical osteoporosis treatment through systemic intermittent administration. However, the successful application of PTH for local bone defect repair generally requires the incorporation and delivery by appropriate carriers. Though several scaffolds have been developed to deliver PTH, they suffer from the weaknesses such as uncontrollable PTH release, insufficient porous structure and low mechanical strength. Herein, a novel kind of NIR-activable scaffold (CBP/MBGS/PTHrP-2) with dual-mode PTHrP-2 (a PTH derivative) release capability is developed to synergistically promote osteogenesis and angiogenesis for high-efficacy bone regeneration, which is fabricated by integrating the PTHrP-2-loaded hierarchically mesoporous bioactive glass (MBG) into the N-hydroxymethylacrylamide-modified, photothermal agent-doped, poly(N-isopropylacrylamide)-based thermosensitive hydrogels through assembly process. Upon on/off NIR irradiation, the thermoresponsive hydrogel gating undergoes a reversible phase transition to allow the precise control of on-demand pulsatile and long-term slow release of PTHrP-2 from MBG mesopores. Such NIR-activated dual-mode delivery of PTHrP-2 by this scaffold enables a well-maintained PTHrP-2 concentration at the bone defect sites to continually stimulate vascularization and promote osteoblasts to facilitate and accelerate bone remodeling. In vivo experiments confirm the significant improvement of bone reparative effect on critical-size femoral defects of rats. This work paves an avenue for the development of novel dual-mode delivery systems for effective bone regeneration.

Macrophage polarization in bone implant repair: A review

Macrophages (MΦ) are highly adaptable and functionally polarized cells that play a crucial role in various physiological and pathological processes. Typically, MΦ differentiate into two distinct subsets: the proinflammatory (M1) and anti-inflammatory (M2) phenotypes. Due to their potent immunomodulatory and anti-inflammatory properties, MΦ have garnered significant attention in recent decades. In the context of bone implant repair, the immunomodulatory function of MΦ is of paramount importance. Depending on their polarization phenotype, MΦ can exert varying effects on osteogenesis, angiogenesis, and the inflammatory response around the implant. This paper provides an overview of the immunomodulatory and inflammatory effects of MΦ polarization in the repair of bone implants.

CD301b+ macrophage: the new booster for activating bone regeneration in periodontitis treatment

Periodontal bone regeneration is a major challenge in the treatment of periodontitis. Currently the main obstacle is the difficulty of restoring the regenerative vitality of periodontal osteoblast lineages suppressed by inflammation, via conventional treatment. CD301b⁺ macrophages were recently identified as a subpopulation that is characteristic of a regenerative environment, but their role in periodontal bone repair has not been reported. The current study indicates that CD301b⁺ macrophages may be a constituent component of periodontal bone repair, and that they are devoted to bone formation in the resolving phase of periodontitis. Transcriptome sequencing suggested that CD301b⁺ macrophages could positively regulate osteogenesis-related processes. In vitro, CD301b⁺ macrophages could be induced by interleukin 4 (IL-4) unless proinflammatory cytokines such as interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) were present. Mechanistically, CD301b⁺ macrophages promoted osteoblast differentiation via insulin-like growth factor 1 (IGF-1)/thymoma viral proto-oncogene 1 (Akt)/mammalian target of rapamycin (mTOR) signaling. An osteogenic inducible nano-capsule (OINC) consisting of a gold nanocage loaded with IL-4 as the "core" and mouse neutrophil membrane as the "shell" was designed. When injected into periodontal tissue, OINCs first absorbed proinflammatory cytokines in inflamed periodontal tissue, then released IL-4 controlled by far-red irradiation. These events collectively promoted CD301b⁺ macrophage enrichment, which further boosted periodontal bone regeneration. The current study highlights the osteoinductive role of CD301b⁺ macrophages, and suggests a CD301b⁺ macrophage-targeted induction strategy based on biomimetic nano-capsules for improved therapeutic efficacy, which may also provide a potential therapeutic target and strategy for other inflammatory bone diseases.

Mechanism of vascular endothelial cell-derived exosomes modified with vascular endothelial growth factor in steroid-induced femoral head necrosis

Steroid-induced avascular necrosis of the femoral head (SANFH) is an intractable orthopedic disease. This study investigated the regulatory effect and molecular mechanism of vascular endothelial cell (VEC)-derived exosomes (Exos) modified with vascular endothelial growth factor (VEGF) in osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in SANFH. VECs were culturedin vitroand transfected with adenovirus Adv-VEGF plasmids. Exos were extracted and identified.In vitro/vivoSANFH models were established and treated with VEGF-modified VEC-Exos (VEGF-VEC-Exos). The internalization of Exos by BMSCs, proliferation and osteogenic and adipogenic differentiation of BMSCs were determined by the uptake test, cell counting kit-8 (CCK-8) assay, alizarin red staining, and oil red O staining. Meanwhile, the mRNA level of VEGF, the appearance of the femoral head, and histological analysis were assessed by reverse transcription quantitative polymerase chain reaction and hematoxylin-eosin staining. Moreover, the protein levels of VEGF, osteogenic markers, adipogenic markers, and mitogen-activated protein kinase (MAPK)/extracellular regulated protein kinases (ERK) pathway-related indicators were examined by Western blotting, along with evaluation of the VEGF levels in femur tissues by immunohistochemistry. Glucocorticoid (GC) induced adipogenic differentiation of BMSCs and inhibited osteogenic differentiation. VEGF-VEC-Exos accelerated the osteogenic differentiation of GC-induced BMSCs and inhibited adipogenic differentiation. VEGF-VEC-Exos activated the MAPK/ERK pathway in GC-induced BMSCs. VEGF-VEC-Exos promoted osteoblast differentiation and suppressed adipogenic differentiation of BMSCs by activating the MAPK/ERK pathway. VEGF-VEC-Exos accelerated bone formation and restrained adipogenesis in SANFH rats. VEGF-VEC-Exos carried VEGF into BMSCs and motivated the MAPK/ERK pathway, thereby promoting osteoblast differentiation of BMSCs in SANFH, inhibiting adipogenic differentiation, and alleviating SANFH.

Development of Neovasculature in Axially Vascularized Calcium Phosphate Cement Scaffolds

Augmenting the vascular supply to generate new tissues, a crucial aspect in regenerative medicine, has been challenging. Recently, our group showed that calcium phosphate can induce the formation of a functional neo-angiosome without the need for microsurgical arterial anastomosis. This was a preclinical proof of concept for biomaterial-induced luminal sprouting of large-diameter vessels. In this study, we investigated if sprouting was a general response to surgical injury or placement of an inorganic construct around the vessel. Cylindrical biocement scaffolds of differing chemistries were placed around the femoral vein. A contrast agent was used to visualize vessel ingrowth into the scaffolds. Cell populations in the scaffold were mapped using immunohistochemistry. Calcium phosphate scaffolds induced 2.7-3 times greater volume of blood vessels than calcium sulphate or magnesium phosphate scaffolds. Macrophage and vSMC populations were identified that changed spatially and temporally within the scaffold during implantation. NLRP3 inflammasome activation peaked at weeks 2 and 4 and then declined; however, IL-1β expression was sustained over the course of the experiment. IL-8, a promoter of angiogenesis, was also detected, and together, these responses suggest a role of sterile inflammation. Unexpectedly, the effect was distinct from an injury response as a result of surgical placement and also was not simply a foreign body reaction as a result of placing a rigid bioceramic next to a vein, since, while the materials tested had similar microstructures, only the calcium phosphates tested elicited an angiogenic response. This finding then reveals a potential path towards a new strategy for creating better pro-regenerative biomaterials.

Periosteum-inspired in situ CaP generated nanocomposite hydrogels with strong bone adhesion and superior stretchability for accelerated distraction osteogenesis

BACKGROUND

Distraction osteogenesis (DO) is an efficacious but lengthy procedure to reconstruct segmental bone defects under the principle of tension-stress, during which the periosteum-mediated mechanical stimulation plays a pivotal role. Inspired by the dynamic process of DO and the mechanical stimulation of periosteum, a new design of bionic periosteum was developed to simulate the mechanical transduction of natural periosteum for the application in DO procedure.

METHODS

In this study, an injectable organic-inorganic hybrid hydrogel was developed based on a novel combination of the PEGylated poly (glycerol sebacate) (PEGS) polymer network and in situ formed CaP nanoparticles (ICPNs). Rat bone marrow mesenchymal stem cells (rBMSCs) and human umbilical vein endothelial cells (HUVECs) were cultured and tested in vitro to evaluate biocompatibility, cell adhesion, proliferation, and pro-osteogenic and pro-angiogenic activity. In vivo experiments were conducted in the rat tibial model of distraction osteogenesis.

RESULTS

The developed nanocomposite hydrogels exhibited excellent injectability, robust bone adhesion, superior stretchability, and enhanced osteogenic activity. The results of in vitro and in vivo studies showed that PEGS/ICPN hydrogels could promote new bone formation and mineralization during the dynamic distraction process through the synergistic effects of angiogenesis and osteogenesis.

CONCLUSIONS

This periosteum-inspired nanocomposite hydrogel represents a mechanobiology approach for effectively restoring large bone defects through the dynamic DO process.

CD301b+ Macrophages as Potential Target to Improve Orthodontic Treatment under Mild Inflammation

Due to improvements of quality of life and the demand for aesthetics, more and more people are choosing orthodontic treatments, resulting in a surge in adult orthodontic patients in recent years. However, a large amount of clinical evidence shows that many orthodontic patients have mild periodontitis in the periodontal tissues, which affects the efficacy of the orthodontic treatment or aggravates the periodontal condition. Therefore, it is important to identify the key factors that affect orthodontic treatments in this inflammatory environment. The aim of this study was to investigate the role of macrophages in orthodontic treatments under inflammatory environments. By analyzing the functional groups of macrophages in the orthodontic rat model of periodontitis, we found that macrophages with high expression levels of CD301b could improve the periodontal microenvironment and improve the efficiency of the orthodontic tooth movement. CD301b+ macrophages transplanted into the model can promote osteogenesis around orthodontic moving teeth, improve bone remodeling during orthodontic treatment, and accelerate orthodontic tooth movement. Considered together, these results suggest that CD301b+ macrophages may play an active role in orthodontic treatments in inflammatory environments and may serve as potential regulatory targets.

Translating Material Science into Bone Regenerative Medicine Applications: State-of-The Art Methods and Protocols

In the last 20 years, bone regenerative research has experienced exponential growth thanks to the discovery of new nanomaterials and improved manufacturing technologies that have emerged in the biomedical field. This revolution demands standardization of methods employed for biomaterials characterization in order to achieve comparable, interoperable, and reproducible results. The exploited methods for characterization span from biophysics and biochemical techniques, including microscopy and spectroscopy, functional assays for biological properties, and molecular profiling. This review aims to provide scholars with a rapid handbook collecting multidisciplinary methods for bone substitute R&D and validation, getting sources from an up-to-date and comprehensive examination of the scientific landscape.

Catalpol modulating the crosstalking between mesenchymal stromal cells and macrophages via paracrine to enhance angiogenesis and osteogenesis

Due to the inflammatory responses associated with defect occurrence and materials implantation, immunoregulation has emerged as a promising strategy to enhance bone regeneration. It has been widely reported that a material could facilitate osteogenesis if it can guide macrophages to anti-inflammatory M2 phenotype, vice versa, a substrate will influence macrophage phenotype if it is osteoinductive. However, few studies have looked into the intercellular crosstalking directly. Herein, the compound catalpol was selected for its multiple functions to study the interactions between bone marrow mesenchymal stromal cells (BMSCs) and macrophages. This iridoid glucoside exhibits excellent anti-inflammatory and osteoinductive activities. The effects of catalpol on mediating M1/M2 polarization of macrophages, inhibiting osteoclast differentiation, promoting osteogenesis and angiogenesis were systematically investigated to correlate the biological responses of BMSCs and macrophages. To extend its in vivo application, the catalpol was then loaded onto an electrospun polylactide/gelatin composite fibrous mesh and subcutaneously implanted to evaluate the local inflammation and ectopic osteogenesis. The results revealed that the functions of catalpol displayed in modulating cellular behaviors are via cell paracrine to strengthen intercellular crosstalking, hence demonstrating that catalpol itself could serve as a promising bioactive stimulator for bone tissue engineering.