A Chemotactic Functional Scaffold with VEGF-Releasing Peptide Amphiphiles Facilitates Bone Regeneration by BMP-2 in a Large-Scale Rodent Cranial Defect Model

Zoledronic Acid-Treated Rats Show Altered Jaw Histology and Gene Expression in Nonexposed Medication-Related Osteonecrosis of the Jaws

BACKGROUND

Diagnosis and management of medication-related osteonecrosis of the jaws (MRONJ) prior to clinical exposure induced by trauma may lead to improved patient management. Currently, few studies have examined early histologic and molecular MRONJ-related changes in the jaws.

PURPOSE

This study aimed to identify histological and gene expression changes in the maxilla and mandible of Sprague-Dawley (SD) rats after zoledronic acid (ZA) treatment.

STUDY DESIGN, SETTING, AND SAMPLE

This was an in vivo animal study. The experiments were conducted in the laboratory at the Stomatology Hospital of Tianjin Medical University. A total of 12 SD rats were included.

PREDICTOR VARIABLE

The predictor variable was ZA exposure. Twelve SD rats were divided into 2 groups: experimental (n = 6) and control (n = 6), and they were intraperitoneally injected with ZA and saline, respectively.

MAIN OUTCOME VARIABLE

The outcome variables were histological and molecular changes. The maxilla, mandible, and ilium bone tissue samples were examined using Masson's trichrome and hematoxylin-eosin staining. Gene expression changes were identified using transcriptome sequencing, the Kyoto encyclopedia of genes and genomes, and gene interactome network analysis. The key changes were validated using the quantitative real-time polymerase chain reaction and immunohistochemistry.

COVARIATES

None.

ANALYSES

The t-test, χ2 test, and Fisher's exact probability method were used for statistical analyses using the Statistical Package for the Social Sciences software (version 26.0).

RESULTS

All animals remained healthy during the experiments. Histological staining revealed that the percentage of empty bone lacunae in the maxilla and mandible was significantly higher than that in the ilium (P < .01). In total, 552 genes were screened using transcriptome sequencing. The sonic hedgehog (Shh) signaling pathway was highly enriched. The key gene for the Shh interaction was distal-less homeobox 5. The Shh, distal-less homeobox 5, and bone morphogenetic protein 2 genes and protein expression levels in the maxilla and mandible were higher in the experimental group than in the control group (P < .05).

CONCLUSION AND RELEVANCE

MRONJ-induced osteonecrosis and gene expression changes precede trauma-induced clinical changes in the SD rat model. These findings may provide additional support for timely and clinically early diagnosis and intervention.

Wound healing induced by new synthetic peptide, A7-1, in C57BL/6 mouse model

The effects of the novel synthetic peptide, A7-1, on wound healing and skin grafts were evaluated in a C57BL/6 mouse model. Two 15-mm wide circular skin excisions were made on the backs of mice and to each excision, 100 µM A7-1 or normal saline was applied daily. The treatments were applied and sutured for skin graft analysis. Digital photos were acquired on days 4, 7, 11, and 14 and fluorescein angiography was conducted. Wound sizes were verified using stereoscopic microscopy. Histological analysis was performed via hematoxylin and eosin staining and Masson's trichrome staining. Western blotting was performed using vascular endothelial growth factor. Using a stereoscopic microscope, significantly faster wound healing (17.3%) and skin graft healing (16.5%) were observed in the A7-1 treatment group in comparison to that of the control. The angiogenesis was significantly faster in fluorescein angiography examination in wound healing (11%) and skin grafts (15%). However, the average completion of epithelization (overall time for wound healing), did not show any significant differences. In comparison to the control, the new protein, A7-1, led to significantly faster wound healing in the initial angiogenesis.

Research progress of vascularization strategies of tissue-engineered bone

The bone defect caused by fracture, bone tumor, infection, and other causes is not only a problematic point in clinical treatment but also one of the hot issues in current research. The development of bone tissue engineering provides a new way to repair bone defects. Many animal experimental and rising clinical application studies have shown their excellent application prospects. The construction of rapid vascularization of tissue-engineered bone is the main bottleneck and critical factor in repairing bone defects. The rapid establishment of vascular networks early after biomaterial implantation can provide sufficient nutrients and transport metabolites. If the slow formation of the local vascular network results in a lack of blood supply, the osteogenesis process will be delayed or even unable to form new bone. The researchers modified the scaffold material by changing the physical and chemical properties of the scaffold material, loading the growth factor sustained release system, and combining it with trace elements so that it can promote early angiogenesis in the process of induced bone regeneration, which is beneficial to the whole process of bone regeneration. This article reviews the local vascular microenvironment in the process of bone defect repair and the current methods of improving scaffold materials and promoting vascularization.

Bioactive Scaffolds as a Promising Alternative for Enhancing Critical-Size Bone Defect Regeneration in the Craniomaxillofacial Region

Reconstruction of critical-size bone defects (CSDs) in the craniomaxillofacial (CMF) region remains challenging. Scaffold-based bone-engineered constructs have been proposed as an alternative to the classical treatments made with autografts and allografts. Scaffolds, a key component of engineered constructs, have been traditionally viewed as biologically passive temporary replacements of deficient bone lacking intrinsic cues to promote osteogenesis. Nowadays, scaffolds are functionalized, giving rise to bioactive scaffolds promoting bone regeneration more effectively than conventional counterparts. This review focuses on the three approaches most used to bioactivate scaffolds: (1) conferring microarchitectural designs or surface nanotopography; (2) loading bioactive molecules; and (3) seeding stem cells on scaffolds, providing relevant examples of in vivo (preclinical and clinical) studies where these methods are employed to enhance CSDs healing in the CMF region. From these, adding bioactive molecules (specifically bone morphogenetic proteins or BMPs) to scaffolds has been the most explored to bioactivate scaffolds. Nevertheless, the downsides of grafting BMP-loaded scaffolds in patients have limited its successful translation into clinics. Despite these drawbacks, scaffolds containing safer, cheaper, and more effective bioactive molecules, combined with stem cells and topographical cues, remain a promising alternative for clinical use to treat CSDs in the CMF complex replacing autografts and allografts.

TBX3 regulates the transcription of VEGFA to promote osteoblasts proliferation and microvascular regeneration

Objective

Osteochondral decellularization can promote local vascular regeneration, but the exact mechanism is unknown. The aim of this study is to study osteogenic microvascular regeneration in single cells.

Methods

The scRNA-seq dataset of human periosteal-derived cells (hPDCs) were analyzed by pySCENIC. To examine the role of TBX3 in osteogenesis and vascularization, cell transfection, qRT-PCR, western blot, and CCK-8 cell proliferation assays were performed.

Results

TCF7L2, TBX3, FLI1, NFKB2, and EZH2 were found to be transcription factors (TFs) most closely associated with corresponding cells. The regulatory network of these TFs was then visualized. Our study knocked down the expression of TBX3 in human osteoblast cell lines. In the TBX3 knockdown group, we observed decreased expression of VEGFA, VEGFB, and VEGFC. Moreover, Western blot analysis showed that downregulating TBX3 resulted in a reduction of VEGFA expression. And TBX3 stimulated osteoblast proliferation in CCK-8 assays.

Conclusion

TBX3 regulates VEGFA expression and promotes osteoblast proliferation in skeletal microvasculature formation. The findings provide a theoretical basis for investigating the role of TBX3 in promoting local vascular regeneration.

Designing bioresponsive nanomaterials for intracellular self-assembly

Supramolecular assemblies are essential components of living organisms. Cellular scaffolds, such as the cytoskeleton or the cell membrane, are formed via secondary interactions between proteins or lipids and direct biological processes such as metabolism, proliferation and transport. Inspired by nature’s evolution of function through structure formation, a range of synthetic nanomaterials has been developed in the past decade, with the goal of creating non-natural supramolecular assemblies inside living mammalian cells. Given the intricacy of biological pathways and the compartmentalization of the cell, different strategies can be employed to control the assembly formation within the highly crowded, dynamic cellular environment. In this Review, we highlight emerging molecular design concepts aimed at creating precursors that respond to endogenous stimuli to build nanostructures within the cell. We describe the underlying reaction mechanisms that can provide spatial and temporal control over the subcellular formation of synthetic nanostructures. Showcasing recent advances in the development of bioresponsive nanomaterials for intracellular self-assembly, we also discuss their impact on cellular function and the challenges associated with establishing structure–bioactivity relationships, as well as their relevance for the discovery of novel drugs and imaging agents, to address the shortfall of current solutions to pressing health issues.

Creating artificial nanostructures inside living cells requires the careful design of molecules that can transform into active monomers within a complex cellular environment. This Review explores the recent development of bioresponsive precursors for the controlled formation of intracellular supramolecular assemblies.

Supramolecular Peptide Nanofiber Hydrogels for Bone Tissue Engineering: From Multihierarchical Fabrications to Comprehensive Applications

Bone tissue engineering is becoming an ideal strategy to replace autologous bone grafts for surgical bone repair, but the multihierarchical complexity of natural bone is still difficult to emulate due to the lack of suitable biomaterials. Supramolecular peptide nanofiber hydrogels (SPNHs) are emerging biomaterials because of their inherent biocompatibility, satisfied biodegradability, high purity, facile functionalization, and tunable mechanical properties. This review initially focuses on the multihierarchical fabrications by SPNHs to emulate natural bony extracellular matrix. Structurally, supramolecular peptides based on distinctive building blocks can assemble into nanofiber hydrogels, which can be used as nanomorphology-mimetic scaffolds for tissue engineering. Biochemically, bioactive motifs and bioactive factors can be covalently tethered or physically absorbed to SPNHs to endow various functions depending on physiological and pharmacological requirements. Mechanically, four strategies are summarized to optimize the biophysical microenvironment of SPNHs for bone regeneration. Furthermore, comprehensive applications about SPNHs for bone tissue engineering are reviewed. The biomaterials can be directly used in the form of injectable hydrogels or composite nanoscaffolds, or they can be used to construct engineered bone grafts by bioprinting or bioreactors. Finally, continuing challenges and outlook are discussed.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

Mesenchymal Stem Cell-Immune Cell Interaction and Related Modulations for Bone Tissue Engineering

Critical bone defects and related delayed union and nonunion are still worldwide problems to be solved. Bone tissue engineering is mainly aimed at achieving satisfactory bone reconstruction. Mesenchymal stem cells (MSCs) are a kind of pluripotent stem cells that can differentiate into bone cells and can be used as one of the key pillars of bone tissue engineering. In recent decades, immune responses play an important role in bone regeneration. Innate immune responses provide a suitable inflammatory microenvironment for bone regeneration and initiate bone regeneration in the early stage of fracture repair. Adaptive immune responses maintain bone regeneration and bone remodeling. MSCs and immune cells regulate each other. All kinds of immune cells and secreted cytokines can regulate the migration, proliferation, and osteogenic differentiation of MSCs, which have a strong immunomodulatory ability to these immune cells. This review mainly introduces the interaction between MSCs and immune cells on bone regeneration and its potential mechanism, and discusses the practical application in bone tissue engineering by modulating this kind of cell-to-cell crosstalk. Thus, an in-depth understanding of these principles of bone immunology can provide a new way for bone tissue engineering.

Vascularization Strategies in Bone Tissue Engineering

Bone is a highly vascularized tissue, and its development, maturation, remodeling, and regeneration are dependent on a tight regulation of blood vessel supply. This condition also has to be taken into consideration in the context of the development of artificial tissue substitutes. In classic tissue engineering, bone-forming cells such as primary osteoblasts or mesenchymal stem cells are introduced into suitable scaffolds and implanted in order to treat critical-size bone defects. However, such tissue substitutes are initially avascular. Because of the occurrence of hypoxic conditions, especially in larger tissue substitutes, this leads to the death of the implanted cells. Therefore, it is necessary to devise vascularization strategies aiming at fast and efficient vascularization of implanted artificial tissues. In this review article, we present and discuss the current vascularization strategies in bone tissue engineering. These are based on the use of angiogenic growth factors, the co-implantation of blood vessel forming cells, the ex vivo microfabrication of blood vessels by means of bioprinting, and surgical methods for creating surgically transferable composite tissues.