Preparation of Al-doped mesoporous silica spheres (Al-MSSs) for the improvement of mechanical properties and aging resistance of dental resin composites.

OBJECTIVE: The purpose of this study was to synthesize Al-doped mesoporous silica spheres (Al-MSSs) and evaluate the effect of them as functional fillers on the mechanical properties and aging resistance of dental resin composites. METHODS: Al-MSSs were prepared by a two-step method. The effect of Al-MSSs on the performance of the composites was evaluated using neat resin matrix, commercial composites 3M Z350XT and samples containing mesoporous silica spheres (MSSs) and nonporous silica spheres (NSSs) as control. The neat resin matrix consisted of resin monomer (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 49.5/49.5, wt%) and photoinitiator (camphor quinone/Ethyl-4-dimethylaminobenzoate, 0.2/0.8, wt%). The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of them were evaluated by a universal testing machine and microhardness tester. The mechanical stabilities of the prepared composites in wet environment were evaluated by immersing them in deionized water at 37 °C. In addition, we evaluated the effect of Al-MSSs on other properties of the dental resin composites such as polymerization shrinkage, degree of conversion, curing depth, contact angle, water sorption and solubility according to ISO 4049: 2019. RESULTS: The synthesized Al-MSSs possessed good dispersibility with an average particle size of about 505 ± 16 nm. The mechanical properties of resin composites gradually increased with the increase of the loading amounts of inorganic fillers. The reinforcing effect of Al-MSSs was similar to that of MSSs and better than that of the NSSs groups at the same filler loading. After aging in deionized water at 37 °C for 30 days, the mechanical properties of all resin composites decreased. However, the decrease percentage of the composites filled with Al-MSSs was significantly lower than the other groups, indicating that the stability of the dental composites in wet environments was significantly improved by the Al-MSSs fillers. Furthermore, Al-MSSs had no obvious influence on the biocompatibility and other properties of dental resins. SIGNIFICANCE: The prepared Al-MSSs could effectively improve the mechanical properties and aging resistance without sacrificing other physic-chemical properties of dental resin composites.

Ultrasound-driven radical chain reaction and immunoregulation of piezoelectric-based hybrid coating for treating implant infection.

The poor efficiency of US-responsive coatings on implants restricts their practical application. Immunotherapy that stimulates immune cells to enhance their antibacterial activity is expected to synergize with sonodynamic therapy for treating implant infection effectively and safely. Herein, US-responsive hybrid coatings composed of the oxygen-deficient BaTiO3 nanorod arrays and l-arginine (BaTiO3-x/LA) are designed and prepared on titanium implants for sonocatalytic therapy-cooperated immunotherapy to treat Methicillin-resistant Staphylococcus aureus (MRSA) infection. BaTiO3-x/LA can generate more oxidizing reactive oxygen species (ROS, hydroxyl radical (·OH)) and reactive nitrogen species (RNS, peroxynitrite anion (ONOO-)). The construction of nanorod arrays and oxygen defects balances the piezoelectric properties and sonocatalytic capability during US treatment. The generated piezoelectric electric field provides a sufficient driving force to separate electrons and holes, and the oxygen defects attenuate the electron-hole recombination efficiency, consequently increasing the yield of ROS during the US treatment. Moreover, nitric oxide (NO) released by l-arginine reacts with the superoxide radical (·O2-) to produce ONOO-. Since, this radical chain reaction improves the oxidizing ability between bacteria and radicals, the cell membrane (argB, secA2) and DNA (dnaBGXN) are destroyed. The bacterial self-repair mechanism indirectly accelerates bacterial death based on the transcriptome analysis. In addition to participating in the radical chain reaction, NO positively affects macrophage M1 polarization to yield potent phagocytosis to MRSA. As a result, without introducing an extra sonosensitizer, BaTiO3-x/LA exhibits excellent antibacterial activity against MRSA after the US treatment for 15 min. Furthermore, BaTiO3-x/LA facilitates macrophage M2 polarization after implantation and improves osteogenic differentiation. The combined effects of sonodynamic therapy and immunoregulation lead to an effective and safe treatment method for implant-associated infections.

Piezoelectric dressings for advanced wound healing.

The treatment of chronic refractory wounds poses significant challenges and threats to both human society and the economy. Existing research studies demonstrate that electrical stimulation fosters cell proliferation and migration and promotes the production of cytokines that expedites the wound healing process. Presently, clinical settings utilize electrical stimulation devices for wound treatment, but these devices often present issues such as limited portability and the necessity for frequent recharging. A cutting-edge wound dressing employing the piezoelectric effect could transform mechanical energy into electrical energy, thereby providing continuous electrical stimulation and accelerating wound healing, effectively addressing these concerns. This review primarily reviews the selection of piezoelectric materials and their application in wound dressing design, offering a succinct overview of these materials and their underlying mechanisms. This study also provides a perspective on the current limitations of piezoelectric wound dressings and the future development of multifunctional dressings harnessing the piezoelectric effect.

Impact of surface biofunctionalization strategies on key effector cells response in polyacrylamide hydrogels for bone regeneration.

Despite the clinical prevalence of various bone defect repair materials, a full understanding of their influence on bone repair and regeneration remains elusive. This study focuses on poly(acrylamide) (PAAm) hydrogels, popular 2D model substrates, which have regulable mechanical properties within physiological. However, their bio-inert nature requires surface biofunctionalization to enhance cell-material interactions and facilitate the study of bone repair mechanisms. We utilized PAAm hydrogels of varying stiffness (18, 76 and 295 kPa), employed sulfosuccinimidyl-6-(4'-azido-2'-nitropheny-lamino) hexanoate (sulfo-SANPAH) and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride/N-hydroxysuccinimidyl acrylate (EDC/NHS) as crosslinkers, and cultured macrophages, endothelial cells, and bone mesenchymal stem cells on these hydrogels. Our findings indicated that sulfo-SANPAH's crosslinking efficiency surpassed that of EDC/NHS, irrespective of pore size and stiffness. Importantly, we observed that the stiffness and surface biofunctionalization method of hydrogels significantly impacted cell adhesion and proliferation. The collagen-modified hydrogels by EDC/NHS strategy failed to support the normal biological behavior of bone mesenchymal stem cells and hindered endothelial cell spreading. In contrast, these modified hydrogels by the sulfo-SANPAH method showed good cytocompatibility with the three types of cells. This study underscores the critical role of appropriate conjugation strategies for PAAm hydrogels, providing valuable insights for hydrogel surface modification in bone repair and regeneration research.

Osteoporosis remission via an anti-inflammaging effect by icariin activated autophagy.

The pace of bone formation slows down with aging, which leads to the development of osteoporosis. In addition to senescent bone marrow mesenchymal stem cells (S-BMSCs), senescent macrophages (S-MΦs) present in the bone marrow produce numerous inflammatory cytokines that contribute to the inflammaged microenvironment and are involved in the development of osteoporosis. Although autophagy activation has shown a significant anti-aging effect, its influence on inflammaging and its role in osteoporosis treatment remain unclear. Traditional Chinese herbal medicine contains bioactive components that exhibit remarkable advantages in bone regeneration. We have demonstrated that icariin (ICA), a bioactive component of traditional Chinese herbal medicine, activates autophagy, exerts a significant anti-inflammaging effect on S-MΦs, and rejuvenates osteogenesis of S-BMSCs, thereby alleviating bone loss in osteoporotic mice. The transcriptomic analysis further reveals that the TNF-α signaling pathway, which is significantly associated with the level of autophagy, regulates this effect. Moreover, the expression of senescence-associated secretory phenotype (SASP) is significantly reduced after ICA treatment. In summary, our findings suggest that bioactive components/materials targeting autophagy can effectively modulate the inflammaging of S-MΦs, offering an innovative treatment strategy for osteoporosis remission and various age-related comorbidities.

Matrix stiffness-induced platelet activation determines immunomodulation of macrophages.

Although various bone defect repair materials have been used clinically, the influence of the material properties on bone repair and regeneration as well as the underlying mechanisms are not fully understood. We hypothesize that the material stiffness affects initial platelet activation during hemostasis phase, which in turn mediates subsequent osteoimmunomodulation of macrophages, finally determining clinical outcomes. To verify the hypothesis, the present work used polyacrylamide hydrogels with different stiffness (10, 70, and 260 kPa) as model materials to investigate matrix stiffness induced platelet activation behavior and its mediation on osteoimmunomodulation of macrophages. The results showed that the matrix stiffness was positively related with activation degree of platelets. However, the extracts of platelets incubated on middle-stiff matrix polarized macrophages to pro-healing M2 phenotype when compared with that on soft and stiff matrixes. ELISA results showed when compared with that on soft and stiff matrixes, the platelets incubated on middle-stiff matrix released more TGF-ß and PGE2, both of which could polarize macrophages to M2 phenotype. The M2 macrophages could promote angiogenesis of endothelial cells and osteogenesis of bone marrow mesenchymal stem cells, two important and coupled processes involved in bone repair and regeneration. These findings suggest bone repair materials with 70 kPa stiffness can mediate proper platelet activation, which can polarize macrophages to pro-healing M2 phenotype, potentially contributing to bone repair and regeneration.

In situ titanium phosphate formation on a titanium implant as ultrahigh bonding with nano-hydroxyapatite coating for rapid osseointegration.

Titanium (Ti) has been widely used as a dental implant material due to its excellent mechanical property and good biocompatibility. However, its poor biological activity severely limits its ability to bond with bony tissues. To ameliorate this situation, a preparation method of ultra-high bonding nano-hydroxyapatite (n-HA) coating on the Ti surface is urgently needed. Here, Ti phosphate/n-HA (TiP-Ca) composite coatings with ultra-high bonding were prepared by a two-step hydrothermal treatment. The TiP coating was first formed in situ on the pure Ti substrate and then n-HA crystals further grew on the TiP surface. The formation mechanism of composite coating and reasons for increased bonding strength were systematically investigated. The results show that the TiP-Ca coating remains stable and exhibits an ultra-high bonding strength with the Ti implant (up to 783.30 ± 207.46 N). An effective solution was designed to address the problems of easy peel off. Cell experiments showed that TiP-Ca could promote the adhesion of MC3T3-E1 and expression of OCN, Runx2, and ALP. In vivo evaluation further confirmed that the TiP-Ca composite coating significantly enhanced osseointegration. The designed coating shows great potential in clinical application of implants.

The role of nanopores constructed on the micropitted titanium surface in the immune responses of macrophages and the potential mechanisms.

The delayed transition of macrophages (MΦs) from pro-inflammatory M1 to the pro-healing M2 state on implant surfaces is one of the most important reasons for poor osseointegration. This work reports the construction of closely packed nanopores with a small diameter on the micropitted titanium (Ti) surface by two-step acid etching to promote the M1-to-M2 transition of MΦs and pays special attention to the potential mechanisms by which the nanopores decorating the micropits exert immunomodulatory effects. The results show that the structure composed of hybrid nanopores (10-25 nm) and micropits (5-15 µm) can be produced on the Ti surface by a two-step acid etching process. Compared with the unitary micropits, the micropit/nanopore surface could facilitate the switch of MΦs from the pro-inflammatory M1 to the pro-healing M2 phenotype. RNA sequencing reveals that the MAPK, PI3K-AKT and C-type lectin signaling pathways play key roles in the micro/nano-structure-mediated transition. In addition, the micro/nano-structured surface down-regulated CYP1A2 expression, reducing the generation of mitochondrial ROS, in turn restraining the oxidative stress and further attenuating inflammation. This work provides novel insights into the underlying mechanisms of immunomodulation by the nano-structure-decorated micro-structures on the Ti surface, which is significant for designing the surface of orthopedic implants from the perspective of immunomodulation.

Multifunctional exosomes derived from bone marrow stem cells for fulfilled osseointegration.

Bone marrow mesenchymal stem cells (BMSCs) have self-renewal, multi-directional differentiation potential, and immune regulation function and are widely used for de novo bone formation. However, the wide variation in individual amplification, the potential risk of cancer cell contamination, and the need for culture time significantly limit their widespread use clinically. Alternatively, numerous studies have shown that exosomes secreted by BMSCs in the nanoscale can also affect the functionality of endothelial cells (angiogenesis), macrophages (immunomodulation), and osteoblasts/osteoclasts (osteogenesis), which is a highly promising therapy for osseointegration with pronounced advantages (e.g., safety, high efficiency, and no ethical restrictions). The review aims to summarize the multifaceted effect of BMSCs-derived exosomes on osseointegration and provide reference and basis for rapid and qualified osseointegration.

Fabrication and characterization of biodegradable Zn scaffold by vacuum heating-press sintering for bone repair.

Bone repair materials with excellent mechanical properties are highly desirable, especially in load-bearing sits. However, the currently used ceramic- and polymer-based ones mainly show poor mechanical properties. Recently, biodegradable metals have attracted extensive attention due to their reliable mechanical strength and degradability. As biodegradable metals, zinc-based materials are promising due to their suitable degradation rate and good biocompatibility. Here, we fabricated biodegradable porous Zn scaffolds with relatively high mechanical properties by vacuum heating-press sintering using NaCl particles as space holders. The microstructure, actual porosity, compressive mechanical properties, in vitro degradation behavior and the vitality of osteoblasts of porous Zn scaffolds were tested and investigated. The results show the porosities of the prepared porous Zn scaffolds are ranging from 11.3 % to 63.3 %, and the pore sizes are similar to the size range of the screened NaCl particles (200-500 µm). Compressive yield strength of 14.2-73.7 MPa and compressive elastic modulus of 1.9-6.7 GPa are shown on porous Zn scaffolds, some of which approach to that of cancellous bone (2-12 MPa and 0.1-5 GPa). Compared to bulk Zn, although the porous structures cause a partial loss of strength, the reliable mechanical properties are still retained. In addition, the porous structures not only greatly increase the degradation rate, but also promote the proliferation of osteoblasts. Based on these results, biodegradable porous Zn scaffolds (porosity in the 40 %-50 %) fabricated by vacuum heating-press sintering method show high application potential for clinical bone repair.

Type I collagen decorated nanoporous network on titanium implant surface promotes osseointegration through mediating immunomodulation, angiogenesis, and osteogenesis.

Osseointegration of implants is a complex physiological process that requires temporal and spatial regulation of immune responses, angiogenesis, and osteogenesis. To achieve efficient and long-term osseointegration, type I collagen (COL1) decorated nanoporous network was developed on titanium substrates via alkali treatment, polydopamine coating, and layer-by-layer (LBL) self-assembly. It was noted that the simple physisorbed COL1 could be easily desorbed from the nanostructured surface, however, multilayer COL1 constructed by polydopamine and LBL self-assembly obscured the nanoporous network of the alkali-treated titanium surfaces. Interestingly, the nanostructured surface covalently immobilized with COL1 (T-ADC) could timely convert macrophages (MΦs) from pro-inflammatory M1 to pro-healing M2 phenotype, generating a beneficial osteoimmune microenvironment and promoting angio/osteo-genesis. RNA sequencing revealed that the nanostructure and COL1 could synergistically activate RhoA/ROCK, PI3K-AKT, and classical MAPK signaling pathways in MΦs to sustain the cell cycle, and trigger autocrine feedback-mediated JAK-STAT and FoxO signaling pathways, which in turn motivated autophagy and oxidative stress resistance and attenuated lipopolysaccharide-induced Toll-like receptor signaling pathway and its downstream NF-κB and JNK/p38 MAPK signaling cascades, leading to the inhibition of inflammation and osteoclastic-related gene expression of MΦs. Simultaneously, T-ADC prominently facilitated angiogenesis of endothelial cells and osteogenesis of osteoblasts as well as their cross-talks, further highlighting synergistically positive effects of the nanostructure and COL1 on osseointegration. In vivo experiments revealed that T-ADC could induce abundant new bone mass and ameliorative osseointegration, corroborating the in vitro results. The study elucidated that the COL1 decorated nanoporous network on titanium surfaces could significantly regulate early inflammatory reaction and subsequent angio/osteo-genesis processes, resulting in favorable osseointegration.

Biocompatible silane adhesion layer on titanium implants improves angiogenesis and osteogenesis.

Silane adhesion layer strategy has been widely used to covalently graft biomolecules to the titanium implant surface, thereby conferring the implant bioactivity to ameliorate osseointegration. However, few researchers pay attention to the effects of silanization parameters on biocompatibility and biofunctionality of the silane adhesion layers. Accordingly, the present study successfully fabricated the silane adhesion layers with different thickness, intactness, and surface morphologies by introducing 3-aminopropyltriethoxysilane on the alkali-treated titanium surface in time-varied processing of silanization. The regulatory effects of the silane adhesion layers on angiogenesis and osteogenesis were assessed in vitro. Results showed that the prolonged silanization processing time increased the thickness and intactness of the silane adhesion layer and significantly improved its biocompatibility. Notably, the silane adhesion layer prepared after 12 h of silanization exhibited a brain-like surface morphology and benefited the adhesion and proliferation of endothelial cells (ECs) and osteoblasts (OBs). Moreover, the layer promoted angiogenesis via stimulating vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production of ECs. Simultaneously, it improved osteogenesis by enhancing alkaline phosphatase (ALP) activity, collagen secretion, and extracellular matrix mineralization of OBs. This work systematically investigated the biocompatibility and biofunctionality of the modified silane adhesion layers, thus providing valuable references for their application in covalently grafting biomolecules on the titanium implant surface.

Resveratrol promotes osteogenesis and angiogenesis through mediating immunology of senescent macrophages.

Orthopedic implants have been used clinically to restore the functions of the compromised bone tissues, but there is still a relatively high risk of failure for elderly people. A critical reason is pro-inflammatory immune microenvironment created by senescent macrophages with homeostasis imbalance impairs osteogenesis and angiogenesis, two major processes involved in implant osseointegration. The present work proposes to use resveratrol as an autophagy inducing agent to upregulate the autophagy level of senescent macrophages to restore homeostasis, consequently generating a favorable immune microenvironment. The results show 0.1-1 µM of resveratrol can induce autophagy of senescent macrophages, promote cell viability and proliferation, reduce intracellular reactive oxygen species level, and polarize the cells to pro-healing M2 phenotype. The immune microenvironment created by senescent macrophages upon resveratrol stimulation can promote osteogenesis and angiogenesis, as manifested by upregulated proliferation, alkaline phosphatase activity, type I collagen secretion, and extracellular matrix mineralization of senescent osteoblasts as well as nitric oxide production, migration, andin vitroangiogenesis of senescent endothelial cells. In addition, resveratrol-loaded silk fibroin coatings can be fabricated on titanium surface through electrophoretic co-deposition and the coatings show beneficial effects on the functions of senescent macrophages. Our results suggest resveratrol can be used as surface additive of titanium implants to promote osseointegration of elderly people though regulating immunology of senescent macrophages.

Simultaneously enhanced osteogenesis and angiogenesis via macrophage-derived exosomes upon stimulation with titania nanotubes.

Fulfilled angiogenesis and osteogenesis are prerequisites for achieving favorable osseointegration of the bone implants. Incremental evidences have pinpointed that macrophages (MΦs) manipulated osteoimmunomodulation plays a pivotal role in the regulation of angio-/osteo-genesis. However, the underlying mechanism of osteoimmunomodulation is still unclear. Exosomes derived from MΦs are recently recognized as a novel mediator of intercellular communication while the role in osteoimmunomodulation is unraveled yet. In the present study, titania nanotube arrays (TNAs) with diameters of 25 and 95 nm were fabricated via one-step anodization with the voltage of 10 (TNA-10) and 40 V (TNA-40). The results showed that although TNA-10 and TNA-40 have no significant effect on the adhesion, skeleton, morphology, and proliferation of MΦs compared with the pristine titanium (P-Ti), the alkaline phosphatase (ALP) activity and osteogenic-related genes expression of bone mesenchymal stem cells (BMSCs) can be significantly up-regulated after incubated with exosomes extracted from MΦs cultured on TNA-40 (TNA-40Exo). Meanwhile, TNA-40Exo can promote endothelial cells (ECs) migration and enhance the angiogenesis capacity in vitro and in vivo. miRNA sequencing analysis of the exosomes further demonstrated that MΦs-derived exosomal microRNA-3473e (miR-3473e) may be of pivotal importance in the promotion of osteo-/angio-genesis via upregulation of the Akt1 gene. The study indicated that surface morphology of the implant can significantly impact the composition of the derived exosomes, which provides a new insight into understanding immunomodulation mediated osseointegration.

Exosomes derived from magnesium ion-stimulated macrophages inhibit angiogenesis.

Angiogenesis, an essential prerequisite to osteogenesis in bone repair and regeneration, can be mediated by immunoregulation of macrophages. Magnesium and its alloys are promising biodegradable bone implant materials and can affect immunoregulation of macrophages by the degradation products (magnesium ions). Nevertheless, the mechanism of macrophage-derived exosomes stimulated by Mg ions in immunoregulation is still not well understood. Herein, 10-50 mM magnesium ions are shown to inhibit the macrophage viability and proliferation in a dose-dependent manner, but a high concentration results in macrophage apoptosis. The exosomes secreted by macrophages from magnesium ion stimulation inhibit angiogenesis of endothelial cells, as manifested by the suppressed cell viability, proliferation, migration, and tube formation, which arise at least partially from exosome-mediated downregulation of endothelial nitric oxide and the vascular endothelial growth factor. The findings reported in this paper suggest that the bio-functionality of biodegradable magnesium alloys must be considered from the perspective of immunoregulation of macrophage-derived exosomes. Our results also suggest potential cancer therapy by inhibiting tumor-associated angiogenesis.

Differential Nanoscale Topography Dedicates Osteocyte-Manipulated Osteogenesis via Regulation of the TGF-ß Signaling Pathway.

Osteocytes function as the master orchestrator of bone remodeling activity in the telophase of osseointegration. However, most contemporary studies focus on the manipulation of osteoblast and/or osteoclast functionality via implant surface engineering, which neglects the pivotal role of osteocytes in de novo bone formation. It is confirmative that osteocyte processes extend directly to the implant surface, but whether the surface physicochemical properties can affect the functionality of osteocytes and determine the fate of the osseointegration in the final remodeling stage remains to be determined. Titania nanotube arrays (NTAs) with distinct diameters were fabricated to investigate the relationship between the nanoscale topography and the functionality of osteocytes. In vitro results pinpointed that NTA with a diameter of 15 nm (NTA-15) significantly promote osteogenesis of osteocytes via the enhancement of spreading, proliferation, and mineralization. The osteocyte transcriptome of each group further revealed that the TGF-ß signaling pathway plays a pivotal role in osteocyte-mediated osteogenesis. The in vivo study definitely mirrored the aforementioned results, that NTA-15 significantly promotes bone formation around the implant. Consequently, nanoscaled topography-induced osteocyte functionality is important in late osseointegration. This suggests that surface designs targeting osteocytes may, therefore, be a potential approach to solving the aseptic loosening of the implant, and thus strengthen osseointegration.

A micro/nano-biomimetic coating on titanium orchestrates osteo/angio-genesis and osteoimmunomodulation for advanced osseointegration.

Osseointegration is a sophisticated bone and implant healing process comprising of initial hematoma formation, immediate osteoimmunomodulation, angiogenesis, and osteogenesis. To fulfill rapid and satisfying osseointegration, this study developed a biomimetic implant coating that could confer the intraosseous implants a systematical regulation of the participatory processes. Herein, we shaped dissimilar nano-scale (NS) to form highly biomimetic structures of natural extracellular matrix (ECM) of the host bone and bone healing hematoma with micro/nano-scale (MNS) titania fiber-like network on the surface of titanium (Ti) implants. In vitro experiments revealed that the MNS not only facilitated osteogenic and angiogenic differentiation of bone marrow stromal cells (BMSCs) and endothelial cells, respectively, but also suppressed M1 macrophages (MΦs), whereas, stimulated pro-healing M2 phenotype. Notably, BMSCs on MNS surfaces enabled a significant immunomodulatory effect on MΦs resulting in the downregulation of inflammation-related cell signaling pathways. The favorable osteoimmune microenvironment manipulated by MNS further facilitated osteo-/angio-genesis via the crosstalk of multi-signaling pathways. In vivo evaluation mirrored the aforementioned results, and depicted that MNS induced ameliorative osseointegration when compared with the NS as well as the pristine Ti implant. The study demonstrated the modulatory effect of the multifaceted biomimetic structure on spatiotemporal regulation of the participatory processes during osseointegration.

Correlation between LncRNA Profiles in the Blood Clot Formed on Nano-Scaled Implant Surfaces and Osseointegration.

Implant surfaces with a nanoscaled pattern can dominate the blood coagulation process resulting in a defined clot structure and its degradation behavior, which in turn influence cellular response and the early phase of osseointegration. Long non-coding (Lnc) RNAs are known to regulate many biological processes in the skeletal system; however, the link between the LncRNA derived from the cells within the clot and osseointegration has not been investigated to date. Hence, the sequence analysis of LncRNAs expressed within the clot formed on titania nanotube arrays (TNAs) with distinct nano-scaled diameters (TNA 15 of 15 nm, TNA 60 of 60 nm, TNA 120 of 120 nm) on titanium surfaces was profiled for the first time. LncRNA LOC103346307, LOC103352121, LOC108175175, LOC103348180, LOC108176660, and LOC108176465 were identified as the pivotal players in the early formed clot on the nano-scaled surfaces. Further bioinformatic prediction results were used to generate co-expression networks of LncRNAs and mRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that distinct nano-scaled surfaces could regulate the biological functions of target mRNAs in the clot. LOC103346307, LOC108175175, and LOC108176660 upregulated mRNAs related to cell metabolism and Wnt, TGF-beta, and VEGF signaling pathways in TNA 15 compared with P-Ti, TNA 60, and TNA 120, respectively, whereas LOC103352121, LOC103348180, and LOC108176465 downregulated mRNAs related to bone resorption and inflammation through negatively regulating osteoclast differentiation, TNF, and NF-kappa signaling pathways. The results indicated that surface nano-scaled characteristics can significantly influence the clot-derived LncRNAs expression profile, which affects osseointegration through multiple signaling pathways of the targeted mRNAs, thus paving a way for better interpreting the link between the properties of a blood clot formed on the nano-surface and de novo bone formation.

Exosomes derived from macrophages upon cobalt ion stimulation promote angiogenesis.

Angiogenesis is critical for tissue repair and regeneration, including implant osseointegration. It is well known that macrophages exert immunomodulatory functions in angiogenesis. However, whether macrophage-derived exosomes participate in the process is still unclear. Cobalt (Co) ions are frequently used as implant additives to mimic hypoxic microenvironment, which can induce angiogenesis through stabilizing hypoxia inducible factor-1α (HIF-1α) of macrophages and endothelial cells (ECs). The present work attempts to investigate whether exosomes derived from macrophages upon Co ion stimulation can mediate angiogenesis and the possible mechanism. The results show that the exosomes promote endothelial migration and angiogenesis in vitro and in vivo, particularly when Co ion concentration is 200 µM. Further studies reveal that the exosomes upregulating nitric oxide (NO), vascular endothelial growth factor (VEGF), and integrin ß1 expression may be the underlying mechanism of the observations. Our findings provide new insights for Co ion mediated macrophage-EC communication and surface design of biomaterials from the perspective of pro-angiogenesis.

Exosomes secreted by macrophages upon copper ion stimulation can promote angiogenesis.

Copper, a frequently used additive of implant materials, can alter macrophage phenotype thus directing the fate of the implants. Exosomes, secreted by mammalian cells, can target to recipient cells and mediate their functions. However, whether exosomes derived from macrophages upon copper ion stimulation can modulate angiogenesis, a key index for implant osseointegration, is still unclear. Herein, the influence of copper ions on macrophage-derived exosome secretion, ingestion behavior by endothelial cells, and angiogenic-induction ability is investigated. The results show copper ions (0-100 µM) have little influence on the secretion of macrophage-derived exosomes. Endothelial cells can uptake the exosomes from all the groups in a time-dependent manner. The exosomes have little influence on endothelial adhesion and proliferation, but can upregulate angiogenic ability of endothelial cells in vitro and in vivo, which may be related to trafficking of integrin ß1. The results provide insight into the effect of copper ions on immunomodulatory mechanism of macrophages, which is important for implant design from the perspective of material compositions.