Titanium with nanotopography attenuates the osteoclast-induced disruption of osteoblast differentiation by regulating histone methylation

The effect of osteoclasts on epigenetic regulation by long non-coding RNAs in osteoblasts grown on titanium with nanotopography

Titanium (Ti) implant osseointegration is regulated by the crosstalk among bone cells that are affected by epigenetic machinery, including the regulation of long non-coding RNAs (lncRNAs). Nanotopography Ti (Ti Nano) induces the differentiation of osteoblasts that are inhibited by osteoclasts through epigenetic mechanisms. Thus, we hypothesize that osteoclasts affect lncRNA expression in Ti Nano-cultivated osteoblasts. Osteoblasts were grown on Ti Nano and Ti Control that were then co-cultured with osteoclasts for 48 h. Using RNAseq, we identified 252 modulated lncRNAs in osteoblasts regulated by both surfaces of Ti, but mainly in Ti Nano-cultivated osteoblasts. A negative correlation was observed between Kcnq1ot1 and the mRNAs of Alpl, Bglap, Bmp8a, Col1a1, and Vim in Ti Nano-cultivated osteoblasts with osteoclasts. The pull-down indicated that Bglap mRNA is a direct target of Kcnq1ot1, with enhanced physical interaction in Ti Nano-cultivated osteoblasts, and greater osteoclast inhibition than the Ti Control. The bone marker expression at the levels of mRNA and protein were downregulated by the Kcnq1ot1 silencing, indicating its pivotal role in osteoblast differentiation. These results showed that nanostructured Ti surface modulates the osteoblast-osteoclast crosstalk, at least in part, through the regulation of lncRNA expression in osteoblasts. We demonstrate that the lncRNA Kcnq1ot1 directly interacts with Bglap mRNA, and this interaction is enhanced by nanotopography and reduced by osteoclasts with greater intensity in Ti Nano-cultivated osteoblasts. These findings confirm the molecular mechanisms associated with the high osteogenic potential of nanotopography and can potentially support osteointegration of dental and skeletal prostheses.

Biomaterial Cues for Regulation of Osteoclast Differentiation and Function in Bone Regeneration

Tissue regeneration involves dynamic dialogue between and among different cells and their surrounding matrices. Bone regeneration is specifically governed by reciprocity between osteoblasts and osteoclasts within the bone microenvironment. Osteoclast-directed resorption and osteoblast-directed formation of bone are essential to bone remodeling, and the crosstalk between these cells is vital to curating a sequence of events that culminate in the creation of bone tissue. Among bone biomaterial strategies, many have investigated the use of different material cues to direct the development and activity of osteoblasts. However, less attention has been given to exploring features that similarly target osteoclast formation and activity, with even fewer strategies demonstrating or integrating biomaterial-directed modulation of osteoblast-osteoclast coupling. This review aims to describe various biomaterial cues demonstrated to influence osteoclastogenesis and osteoclast function, emphasizing those that enhance a material construct's ability to achieve bone healing and regeneration. Additionally discussed are approaches that influence the communication between osteoclasts and osteoblasts, particularly in a manner that takes advantage of their coupling. Deepening our understanding of how biomaterial cues may dictate osteoclast differentiation, function, and influence on the microenvironment may enable the realization of bone-replacement interventions with enhanced integrative and regenerative capacities.

Depletion of MicroRNA-100-5p Promotes Osteogenesis Via Lysine(K)-Specific Demethylase 6B

Senescence and osteogenic differentiation potential loss limited bone nonunion treatment effects of bone marrow-derived mesenchymal stem cells (BMSCs). MiR-100-5p/Lysine(K)-specific demethylase 6B (KDM6B) can inhibit osteogenesis, but their effects on bone union remain unclear. This study aims to investigate the effects of miR-100-5p/KDM6B on osteogenic differentiation and bone defects. Wild-type or microRNA 100 (miR-100) knockdown mice underwent critical-size defect (CSD) cranial surgery and collagen I/poly-γ-glutamic acid scaffold treatment. The crania was observed using microcomputed tomography, hematoxylin and eosin staining, Masson staining, alkaline phosphatase (ALP) staining, immunohistochemistry, and immunofluorescence. Primary-cultured BMSCs transfected with miR-100-5p mimic/inhibitor and KDM6B cDNA were evaluated for osteogenic differentiation using Alizarin Red staining, ALP activity detection, and Western blot analysis. Genetic transcription levels were detected using quantitative reverse transcription polymerase chain reaction. This study found that miR-100 depletion promotes defect healing in mouse calvaria, increases the proportion of new bone and osteoblasts in calvaria, and activates the expression of KDM6B and osteocalcin (OCN) proteins, promoting the transcription of bone morphogenetic protein-2, Runt-related transcription factor 2 (Runx2), OCN, and KDM6B, while methylation of lysine 27 on histone H3 (H3K27me3) decreased. Furthermore, miR-100-5p mimics suppressed osteogenic differentiation by inhibiting KDM6B with increased H3K27me3, ALP, Runx2, OCN, and osteopontin protein expression, while miR-100-5p inhibitors have opposite effects. Moreover, KDM6B can reverse miR-100-5p mimic effects. Notably, scaffolds carrying miR-100-5p mimics/inhibitors transfected BMSCs were placed in CSD mice and found that miR-100-5p inhibitors have a better effect on CSD healing and increase new bone without inflammatory cell infiltration. This study proved that miR-100-5p depletion promotes bone union and osteogenic differentiation of BMSCs via KDM6B/H3K27me3.

Implant surface modifications and their impact on osseointegration and peri-implant diseases through epigenetic changes: A scoping review

Dental implant surfaces and their unique properties can interact with the surrounding oral tissues through epigenetic cues. The present scoping review provides current perspectives on surface modifications of dental implants, their impact on the osseointegration process, and the interaction between implant surface properties and epigenetics, also in peri-implant diseases. Findings of this review demonstrate the impact of innovative surface treatments on the epigenetic mechanisms of cells, showing promising results in the early stages of osseointegration. Dental implant surfaces with properties of hydrophilicity, nanotexturization, multifunctional coatings, and incorporated drug-release systems have demonstrated favorable outcomes for early bone adhesion, increased antibacterial features, and improved osseointegration. The interaction between modified surface morphologies, different chemical surface energies, and/or release of molecules within the oral tissues has been shown to influence epigenetic mechanisms of the surrounding tissues caused by a physical-chemical interaction. Epigenetic changes around dental implants in the state of health and disease are different. In conclusion, emerging approaches in surface modifications for dental implants functionalized with epigenetics have great potential with a significant impact on modulating bone healing during osseointegration.

Antimicrobial peptide GL13K-Modified titanium in the epigenetic regulation of osteoclast differentiation via H3K27me3

Implant surface designs have advanced to address challenges in oral rehabilitation for healthy and compromised bone. Several studies have analyzed the effects of altering material surfaces on osteogenic differentiation. However, the crucial role of osteoclasts in osseointegration has often been overlooked. Overactive osteoclasts can compromise implant stability. In this study, we employed a silanization method to alter pure titanium to produce a surface loaded with the antimicrobial peptide GL13K that enhanced biocompatibility. Pure titanium (Ti), silanization-modified titanium, and GL13K-modified titanium (GL13K-Ti) were co-cultured with macrophages. Our findings indicated that GL13K-Ti partially inhibited osteoclastogenesis and expression of osteoclast-related genes and proteins by limiting the formation of the actin ring, an important structure for osteoclast bone resorption. Our subsequent experiments confirmed the epigenetic role in regulating this process. GL13K-Ti was found to impact the degree of methylation modifications of H3K27 in the NFATc1 promoter region following RANKL-induced osteoclastic differentiation. In conclusion, our study unveils the potential mechanism of methylation modifications, a type of epigenetic regulatory modality, on osteoclastogenesis and activity on the surface of a material. This presents novel concepts and ideas for further broadening the clinical indications of oral implants and targeting the design of implant surfaces.

Biomimetic concentric microgrooved titanium surfaces influence bone marrow-derived mesenchymal stem cell osteogenic differentiation via H3K4 trimethylation epigenetic regulation

Material surface micromorphology can modulate cellular behavior and promote osteogenic differentiation through cytoskeletal rearrangement. Bone reconstruction requires precise regulation of gene expression in cells, a process governed by epigenetic mechanisms such as histone modifications, DNA methylation, and chromatin remodeling. We constructed osteon-mimetic concentric microgrooved titanium surfaces with different groove sizes and cultured bone marrow-derived mesenchymal stem cells (BMSCs) on the material surfaces to study how they regulate cell biological behavior and osteogenic differentiation through epigenetics. We found that the cells arranged in concentric circles along the concentric structure in the experimental group, and the concentric microgrooved surface did not inhibit cell proliferation. The results of a series of osteogenic differentiation experiments showed that the concentric microgrooves facilitated calcium deposition and promoted osteogenic differentiation of the BMSCs. Concentric microgrooved titanium surfaces that were 30 μm wide and 10 μm deep promoted osteogenic differentiation of BMSC by increasing WDR5 expression via H3K4 trimethylation upregulation.

Osteointegration of Ti Bone Implants: A Study on How Surface Parameters Control the Foreign Body Response

The integration of titanium (Ti)-based implants with bone is limited, resulting in implant failure. This lack of osteointegration is due to the foreign body response (FBR) that occurs after the implantation of biodevices. The process begins with protein adsorption, which is governed by implant surface properties, e.g., chemistry, charge, wettability, and/or topography. The distribution and composition of the protein layer in turn influence the recruitment, differentiation, and modulation of immune and bone cells. The subsequent events that occur at the bone-material interface will ultimately determine whether the implant is encapsulated or will integrate with bone. Despite the numerous studies evaluating the influence of surface properties in the various stages of the FBR, the factors that affect tissue-material interactions are often studied in isolation or in small correlations due to the technical challenges involved in assessing them in vitro or in vivo. Consequently, the influence of protein conformation on the Ti bone implant surface design remains an unresolved research question. The objective of this review is to comprehensively evaluate the existing literature on the effect of surface parameters of Ti and its alloys in the stages of FBR, with a particular focus on protein adsorption and osteoimmunomodulation. This evaluation aims to systematically describe these effects on bone formation.

Copper-based carbon dots modified hydrogel with osteoimmunomodulatory and osteogenesis for bone regeneration

Biomaterials with dual functions of osteoimmunomodulation and bone repair are very promising in the field of orthopedic materials. For this purpose, we prepared copper-based carbon dots (CuCDs) and doped them into oxychondroitin sulfate/poly-acrylamide hydrogel (OPAM) to obtain a hybrid hydrogel (CuCDs/OPAM). We evaluated its osteoimmunomodulatory and bone repair properties in vitro and in vivo. The obtained CuCDs/OPAM exhibited good rBMSCs-cytocompatibility and anti-inflammatory properties in vitro. It also could effectively promote rBMSCs differentiation and the expression of osteogenic differentiation factors from rBMSCs under an inflammatory environment. Moreover, CuCDs/OPAM could induce macrophage phenotype switching (from M1-type macrophages to M2-type macrophages) in vivo, which is beneficial for anti-inflammatory action and presents good osteoimmunomodulation capability to induce a bone immune microenvironment to promote the differentiation of rBMSCs. In conclusion, CuCDs/OPAM hydrogel has dual functions of osteoimmunomodulatory and bone repair and is a promising bone filling and repair material.

TiO2nanotubes promote osteogenic differentiation of human bone marrow stem cells via epigenetic regulation ofRMRP/DLEU2/EZH2 pathway

TiO2nanotubes (TNTs) significantly promote osteogenic differentiation and bone regeneration of cells. Nevertheless, the biological processes by which they promote osteogenesis are currently poorly understood. Long non-coding RNAs (lncRNAs) are essential for controlling osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Epigenetic chromatin modification is one of the pathways in which lncRNAs regulate osteogenic differentiation. Here, we reported that TNTs could upregulate lncRNARMRP, and inhibition of lncRNARMRPin human BMSCs (hBMSCs) grown on TNTs could decrease runt-related transcription factor 2 (RUNX2), alkaline phosphatase, osteopontin, and osteocalcin (OCN) expression. Furthermore, we discovered that inhibiting lncRNARMRPelevated the expression of lncRNADLEU2, and lncRNADLEU2knockdown promoted osteogenic differentiation in hBMSCs. RNA immunoprecipitation experiments showed that lncRNADLEU2could interact with EZH2 to induce H3K27 methylation in the promoter regions of RUNX2 and OCN, suppressing gene expression epigenetically. According to these results, lncRNARMRPis upregulated by TNTs to promote osteogenic differentiation throughDLEU2/EZH2-mediated epigenetic modifications.

CypD-mediated mitochondrial dysfunction contributes to titanium ion-induced MC3T3-E1 cell injury

Titanium (Ti) ion can stimulate osteoblast apoptosis and therefore have a high potential to play a negative role in the aseptic loosening of implants. Mitochondrial abnormalities are closely related to osteoblast dysfunction. However, the mitochondrial molecular mechanism of Ti ion induced osteoblastic cell apoptosis is still unclear. This study investigated in vitro mitochondrial oxidative stress (mtROS) mediated mitochondrial dysfunction involved in Ti ion-induced apoptosis of murine MC3T3-E1 osteoblastic cells. In addition to reducing mitochondrial membrane potential (MMP) and decreasing adenosine triglyceride production, exposure to Ti ions increased mitochondrial oxidative stress. Moreover, mitochondrial abnormalities significantly contributed to Ti ion induction of osteoblastic cellular apoptosis. A mitochondria-specific antioxidant, mitoquinone (MitoQ), alleviated Ti ion-induced mitochondrial dysfunction and apoptosis in osteoblastic cells, indicating that Ti ion mainly induces mitochondrial oxidative stress to produce a cytotoxic effect on osteoblasts. Here we show that the primary regulator of mitochondrial permeability transition pore (mPTP), cyclophilin D (CypD), is involved in mitochondrial dysfunction and osteoblast cell apoptosis induced by Ti ion. Overexpression of CypD exacerbates osteoblast apoptosis and impairs osteogenic function. Moreover, detrimental effects of CypD were rescued by cyclosporin A (CsA), an inhibitor of CypD, which shows its protective effect on mitochondrial and osteogenic osteoblast functions. Based on new insights into the mitochondrial mechanisms underlying Ti ion-induced apoptosis of osteoblastic cells, the findings of this study lay the foundation for the clinical use of CypD inhibitors to prevent or treat implant failure.

Effects of Modulation of the Hedgehog and Notch Signaling Pathways on Osteoblast Differentiation Induced by Titanium with Nanotopography

BACKGROUND

The events of bone formation and osteoblast/titanium (Ti) interactions may be affected by Hedgehog and Notch signalling pathways. Herein, we investigated the effects of modulation of these signalling pathways on osteoblast differentiation caused by the nanostructured Ti (Ti-Nano) generated by H₂SO₄/H₂O₂.

METHODS

Osteoblasts from newborn rat calvariae were cultured on Ti-Control and Ti-Nano in the presence of the Hedgehog agonist purmorphamine or antagonist cyclopamine and of the Notch antagonist N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) or agonist bexarotene. Osteoblast differentiation was evaluated by alkaline phosphatase activity and mineralization, and the expression of Hedgehog and Notch receptors was also evaluated.

RESULTS

In general, purmorphamine and DAPT increased while cyclopamine and bexarotene decreased osteoblast differentiation and regulated the receptor expression on both Ti surfaces, with more prominent effects on Ti-Nano. The purmorphamine and DAPT combination exhibited synergistic effects on osteoblast differentiation that was more intense on Ti-Nano.

CONCLUSION

Our results indicated that the Hedgehog and Notch signalling pathways drive osteoblast/Ti interactions more intensely on nanotopography. We also demonstrated that combining Hedgehog activation with Notch inhibition exhibits synergistic effects on osteoblast differentiation, especially on Ti-Nano. The uncovering of these cellular mechanisms contributes to create strategies to control the process of osseointegration based on the development of nanostructured surfaces.

Applications of carbon dots and its modified carbon dots in bone defect repair

Bone defect repair is a continual and complicated process driven by a variety of variables. Because of its bright multicolor luminescence, superior biocompatibility, water dispersibility, and simplicity of synthesis from diverse carbon sources, carbon dots (CDs) have received a lot of interest. It has a broad variety of potential biological uses, including bone defect repair, spinal cord injury, and wound healing. Materials including CDs as the matrix or major component have shown considerable benefits in enabling bone defect healing in recent years. By altering the carbon dots or mixing them with other wound healing-promoting agents or materials, the repair effect may be boosted even further. The report also shows and discusses the use of CDs to heal bone abnormalities. The study first presents the fundamental features of CDs in bone defect healing, then provides CDs manufacturing techniques that should be employed in bone defect repair, and lastly examines their development in the area of bioengineering, particularly in bone defect repair. In this work, we look at how carbon dots and their alteration products may help with bone defect healing by being antibacterial, anti-infective, osteogenic differentiation-promoting, and gene-regulating.

EZH2 regulates the balance between osteoclast and osteoblast differentiation to inhibit arthritis-induced bone destruction

Enhancer of zeste homolog 2 (EZH2) has been noted to contribute to the pathogenesis of autoimmune diseases. This study sought to investigate the mechanism of EZH2 in osteoclast (OCL) and osteoblast (OBL) differentiation (OCLD/OBLD) and bone destruction in RA. The animal model of collagen-induced arthritis (CIA) was established, followed by arthritis index (AI) scoring and histological staining, and measurements of inflammatory cytokines levels. The number of OCLs was detected via Tartrate-resistant acid phosphatase (TRAP) staining, and levels of OBL markers were determined by Western blot analysis. Trimethylated histone H3 at lysine 27 (H3K27me3) expression and its enrichment in the Ndrg2 promoter were detected. Collaborative experiments were performed with GSK-J1 or sh-Ndrg2 in CIA mice with EZH2 knockdown. EZH2 was upregulated while Ndrg2 was downregulated in knee joint tissues of CIA mice. Silencing EZH2 reduced AI scores, pathological injury of the knee joint, levels of inflammatory cytokines, and TRAP-positive cells, and increased protein levels of RUNX2 and BMP2. EZH2 promoted H3K27me3 level in the Ndrg2 promoter to inhibit Ndrg2 transcription. H3K27me3 upregulation or Ndrg2 downregulation reversed the role of silencing EZH2 in bone destruction. Overall, EZH2 repressed OBLD and promoted OCLD to aggravate bone destruction in CIA mice through H3K27me3/Ndrg2.