Effect of reactive oxygen species overproduction on osteogenesis of porous titanium implant in the present of diabetes mellitus

Effect of DNA methylation on the osteogenic differentiation of mesenchymal stem cells: concise review

Mesenchymal stem cells (MSCs) have promising potential for bone tissue engineering in bone healing and regeneration. They are regarded as such due to their capacity for self-renewal, multiple differentiation, and their ability to modulate the immune response. However, changes in the molecular pathways and transcription factors of MSCs in osteogenesis can lead to bone defects and metabolic bone diseases. DNA methylation is an epigenetic process that plays an important role in the osteogenic differentiation of MSCs by regulating gene expression. An increasing number of studies have demonstrated the significance of DNA methyltransferases (DNMTs), Ten-eleven translocation family proteins (TETs), and MSCs signaling pathways about osteogenic differentiation in MSCs. This review focuses on the progress of research in these areas.

Activation of BK channels prevents diabetes-induced osteopenia by regulating mitochondrial Ca2+ and SLC25A5/ANT2-PINK1-PRKN-mediated mitophagy

Osteopenia and osteoporosis are among the most common metabolic bone diseases and represent major public health problems, with sufferers having an increased fracture risk. Diabetes is one of the most common diseases contributing to osteopenia and osteoporosis. However, the mechanisms underlying diabetes-induced osteopenia and osteoporosis remain unclear. Bone reconstruction, including bone formation and absorption, is a dynamic process. Large-conductance Ca2+-activated K+ channels (BK channels) regulate the function of bone marrow-derived mesenchymal stem cells, osteoblasts, and osteoclasts. Our previous studies revealed the relationship between BK channels and the function of osteoblasts via various pathways under physiological conditions. In this study, we reported a decrease in the expression of BK channels in mice with diabetes-induced osteopenia. BK deficiency enhanced mitochondrial Ca2+ and activated classical PINK1 (PTEN induced putative kinase 1)-PRKN/Parkin (parkin RBR E3 ubiquitin protein ligase)-dependent mitophagy, whereas the upregulation of BK channels inhibited mitophagy in osteoblasts. Moreover, SLC25A5/ANT2 (solute carrier family 25 (mitochondrial carrier, adenine nucleotide translocator), member 5), a critical inner mitochondrial membrane protein participating in PINK1-PRKN-dependent mitophagy, was also regulated by BK channels. Overall, these data identified a novel role of BK channels in regulating mitophagy in osteoblasts, which might be a potential target for diabetes-induced bone diseases.Abbreviations: AGE, advanced glycation end products; Baf A1, bafilomycin A1; BK channels, big-conductance Ca2+-activated K+ channels; BMSCs, bone marrow-derived mesenchymal stem cells; BSA, bovine serum albumin; FBG, fasting blood glucose; IMM, inner mitochondrial membrane; ITPR1, inositol 1,4,5-trisphosphate receptor 1; MAM, mitochondria-associated ER membrane; OMM, outer mitochondrial membrane; PINK1, PTEN induced putative kinase 1; PPID/CyP-D, peptidylprolyl isomerase D (cyclophilin D); PRKN/PARK2, parkin RBR E3 ubiquitin protein ligase; ROS, reactive oxygen species; SLC25A5/ANT2, solute carrier family 25 (mitochondrial carrier, adenine nucleotide translocator), member 5; STZ, streptozotocin.

Interleukin-17 prevents oxidative stress from damaging osteoblast formation by inhibiting autophagic degradation of metallothionein-2

Interleukin 17A (IL-17A) is a key cytokine promoting osteoblast formation, which contributes to osteogenesis. IL-17A functions in autophagy inhibition within osteoblasts. Metallothionein-2 (MT-2), as an important reactive oxygen species (ROS)-scavenging molecule, prevents oxidative stress from damaging osteoblast formation. The relationship between IL-17A-regulated autophagy and MT-2 production under oxidative stress deserves further exploration. In this study, we first investigated the roles of IL-17A in osteoblastic differentiation and ROS production in osteoblast precursors in the presence of hydrogen peroxide (H2O2). Next, we explored the effects of IL-17A on autophagic activity and MT-2 protein expression in osteoblast precursors in the presence of H2O2. Ultimately, by using autophagic pharmacological agonist (rapamycin) and lentiviral transduction technology, the relationship between autophagy, IL-17A-regulated MT-2 protein expression and IL-17A-regulated ROS production was further elucidated. Our results showed that in the presence of H2O2, IL-17A promoted osteoblastic differentiation and inhibited ROS production. Moreover, in the presence of H2O2, IL-17A inhibited autophagic activity and promoted MT-2 protein expression in osteoblast precursors. Importantly, IL-17A-promoted MT-2 protein levels and -inhibited ROS production were reversed by autophagy activation with rapamycin. Furthermore, IL-17A-inhibited ROS production were blocked by MT-2 silencing. In conclusion, IL-17A promotes ROS clearance by inhibiting autophagic degradation of MT-2, thereby protecting osteoblast formation from oxidative stress.

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Mitochondrial reactive oxygen species promote mitochondrial damage in high glucose-induced dysfunction and apoptosis of human dental pulp cells

Background/purpose

High glucose (HG)-induced aberrant proliferation, apoptosis and odontoblastic differentiation of dental pulp cells (DPCs) have been implicated in the pathogenesis of impaired diabetic pulp healing; however, the underlying mechanism remains unclear. This study aimed to investigate the role of mitochondrial reactive oxygen species (mtROS) and mitochondria in HG-induced dysfunction and apoptosis of DPCs.

Materials and methods

Human DPCs (hDPCs) were cultured in a low-glucose, high-glucose, mannitol, and MitoTEMPO medium in vitro. Methylthiazol tetrazolium assay, Annexin V-FITC/PI staining and scratch-wound assay were used to analyze cell proliferation, apoptosis and migration, respectively. Alkaline phosphatase staining and alizarin red S staining were used to evaluate cell differentiation. DCF-DA staining, MitoSOX staining, MitoTracker Red staining, JC-1 staining, and adenosine triphosphate (ATP) kit assay were performed to investigate total ROS and mtROS generation, mitochondrial density, mitochondrial membrane potential (MMP), and ATP synthesis, respectively. Quantitative PCR assay was performed to detect the mRNA expression of mitochondrial biogenesis- and dynamics-related markers. Transmission electron microscopy was used to observe the mitochondrial ultrastructure.

Results

HG augmented the production of total ROS and mtROS, and triggered mitochondrial damage in hDPCs, as reflected by decreased mitochondrial density, depolarized MMP, reduced ATP synthesis, altered mRNA expression of mitochondrial biogenesis- and dynamics-related markers, and abnormal mitochondrial ultrastructure. Supplementation of MitoTEMPO alleviated the mitochondrial damage and reversed the aberrant proliferation, apoptosis, migration and odontoblastic differentiation of HG-stimulated hDPCs.

Conclusion

HG triggers mitochondrial damage via augmenting mtROS generation, resulting in the inhibited proliferation, migration, and odontoblastic differentiation of hDPCs and enhanced their apoptosis.

The Preparation and Effects of Organic-Inorganic Antioxidative Biomaterials for Bone Repair

Reactive oxygen species (ROS) has great influence in many physiological or pathological processes in organisms. In the site of bone defects, the overproduced ROS significantly affects the dynamic balance process of bone regeneration. Many antioxidative organic and inorganic antioxidants showed good osteogenic ability, which has been widely used for bone repair. It is of great significance to summarize the antioxidative bone repair materials (ABRMs) to provide guidance for the future design and preparation of osteogenic materials with antioxidative function. Here, this review introduced the major research direction of ABRM at present in nanoscale, 2-dimensional coating, and 3-dimensional scaffolds. Moreover, the referring main active substances and antioxidative properties were classified, and the positive roles of antioxidative materials for bone repair have also been clearly summarized in signaling pathways, antioxidant enzymes, cellular responses and animal levels.

Diabetes-related Screw Loosening: The Distinction of Surgical Sites and the Relationship among Diabetes, Implant Stabilization and Clinical Outcomes

OBJECTIVES

Diabetes mellitus (DM) is correlated with poor clinical outcomes in spinal surgery. However, the effect of it on screw stabilization has not been investigated. The aim of this study was to evaluate the screw loosening rate and postoperative outcomes in diabetic patients and to identify potential risk factors associated with loosening.

METHODS

This was a retrospective study. Two hundred and forty-three patients who received cervical or lumbar internal fixation between 2015 and 2019 were enrolled. Screw loosening was assessed on radiography, and clinical outcomes were evaluated by the improvement of visual analogue scale (VAS), Oswestry disability index (ODI) or Japanese Orthopaedic Association (JOA) scores. The relationship of DM, screw loosening and clinical outcomes were analyzed with chi-square tests and regression analyses.

RESULTS

One hundred and twenty-two patients (50.2%) with diabetes were included in this study. Diabetes led to the increase of the rate of screw loosening in the lumbar spine, while the loosening rate did not vary significantly in the cervical spine. The occurrence of screw loosening in the lumbar spine was more likely to be associated with clinical outcomes for motor performance including walking and sitting. However, no significant effect on JOA and VAS scores in the cervical spine of screw loosening was found. Moreover, the history of DM affected the outcomes of the patients who underwent spinal surgery.

CONCLUSION

DM had an adverse effect on screw stabilization. The impaired improvement of clinical outcomes in diabetics after spinal surgery was related to screw loosening. In addition to the direct effects on operative wounds and neural function, the impact on the screws due to DM was also worth noting.

Influence of Reactive Oxygen Species on Wound Healing and Tissue Regeneration in Periodontal and Peri-Implant Tissues in Diabetic Patients

Diabetes mellitus (DM) is associated with periodontal disease. Clinically, periodontal treatment is less effective for patients with DM. Oxidative stress is one of the mechanisms that link DM to periodontitis. The production of reactive oxygen species (ROS) is increased in the periodontal tissues of patients with DM and is involved in the development of insulin resistance in periodontal tissues. Insulin resistance decreases Akt activation and inhibits cell proliferation and angiogenesis. This results in the deterioration of wound healing and tissue repair in periodontal tissues. Antioxidants and insulin resistance ameliorants may inhibit ROS production and improve wound healing, which is worsened by DM. This manuscript provides a comprehensive review of the most recent basic and clinical evidence regarding the generation of ROS in periodontal tissues resulting from microbial challenge and DM. This study also delves into the impact of oxidative stress on wound healing in the context of periodontal and dental implant therapies. Furthermore, it discusses the potential benefits of administering antioxidants and anti-insulin resistance medications, which have been shown to counteract ROS production and inflammation. This approach may potentially enhance wound healing, especially in cases exacerbated by hyperglycemic conditions.

Oxidative Stimuli-Responsive "Pollen-Like" Exosomes from Silver Nanoflowers Remodeling Diabetic Wound Microenvironment for Accelerating Wound Healing

The hostile oxidative wound microenvironment, defective angiogenesis, and uncontrolled release of therapeutic factors are major challenges in improving the diabetic wound healing. Herein, adipose-derived-stem-cell-derived exosomes (Exos) are first loaded into Ag@bovine serum albumin (BSA) nanoflowers (Exos-Ag@BSA NFs) to form a protective "pollen-flower" delivery structure, which are further encapsulated into the injectable collagen (Col) hydrogel (Exos-Ag@BSA NFs/Col) for concurrent remodeling of the oxidative wound microenvironment and precise release of Exos. The Exos-Ag@BSA NFs can selectively dissociate in an oxidative wound microenvironment, which triggers sustained release of Ag ions (Ag+ ) and cascades controllable release of "pollen-like" Exos at the target site, thus protecting Exos from oxidative denaturation. Such a wound-microenvironment-activated release property of Ag+ and Exos effectively eliminates bacteria and promotes the apoptosis of impaired oxidative cells, resulting in improved regenerative microenvironment. Additionally, Exos-Ag@BSA NFs/Col markedly accelerates wound healing and regeneration in vivo in a diabetic murine silicone-splinted excisional wound model by promoting blood perfusion, tissue granulation, collagen deposition, neovascularization, angiogenesis, and re-epithelization. It is anticipated that this work will inspire the development of more delicate and disease-specific therapeutic systems for clinical wound management.

Bioinspired drug-delivery system emulating the natural bone healing cascade for diabetic periodontal bone regeneration

Diabetes mellitus (DM) aggravates periodontitis, resulting in accelerated periodontal bone resorption. Disordered glucose metabolism in DM causes reactive oxygen species (ROS) overproduction resulting in compromised bone healing, which makes diabetic periodontal bone regeneration a major challenge. Inspired by the natural bone healing cascade, a mesoporous silica nanoparticle (MSN)-incorporated PDLLA (poly(dl-lactide))-PEG-PDLLA (PPP) thermosensitive hydrogel with stepwise cargo release is designed to emulate the mesenchymal stem cell "recruitment-osteogenesis" cascade for diabetic periodontal bone regeneration. During therapy, SDF-1 quickly escapes from the hydrogel due to diffusion for early rat bone marrow stem cell (rBMSC) recruitment. Simultaneously, slow degradation of the hydrogel starts to gradually expose the MSNs for sustained release of metformin, which can scavenge the overproduced ROS under high glucose conditions to reverse the inhibited osteogenesis of rBMSCs by reactivating the AMPK/β-catenin pathway, resulting in regulation of the diabetic microenvironment and facilitation of osteogenesis. In vitro experiments indicate that the hydrogel markedly restores the inhibited migration and osteogenic capacities of rBMSCs under high glucose conditions. In vivo results suggest that it can effectively recruit rBMSCs to the periodontal defect and significantly promote periodontal bone regeneration under type 2 DM. In conclusion, our work provides a novel therapeutic strategy of a bioinspired drug-delivery system emulating the natural bone healing cascade for diabetic periodontal bone regeneration.

Mussel inspired multifunctional bovine serum albumin (BSA) coatings loaded with Baicalein (BAI) to enhance osteogenesis and resist oxidative stress for potential application on implant

Oxidative stress is associated with most traumatic or pathological bone defects, and seriously affects the effect of implantation. The construction of antioxidative and osteogenic coatings is of great significance to accelerate the bone regeneration of implants. In this study, baicalein (BAI), a nature flavonoid drug, was loaded in bovine serum albumin (BSA) by desolvent method to prepare BAI-BSA composite protein, and tannic acid (TA)/BAI-BSA coatings were further built via layer by layer self-assembly technology. BAI-BSA possesses good biocompatibility that showed no cytotoxicity to osteoblasts and erythrocytes, and helps to enhance the activity of alkaline phosphatase (ALP) and promote the formation of osteogenic mineralized calcium nodules. After assembled with TA, BAI-BSA coating significantly promoted cell adhesion and in vitro osteogenic mineralization of MC3T3-E1. Moreover, BAI drug loading improved the antioxidative function of BSA coatings effectively. The scavenging rates of (TA/BAI-BSA-10)₄ for ABTS^+• and DPPH^• free radicals were 69.6 ± 16.1 % and 53.4 ± 2.4 %, respectively. At cellular level, the TA/BAI-BSA coating effectively inhibited the impact of oxidative stress on the oxidative damage of osteoblasts. The drug-loaded protein coatings possess both great antioxidative and osteogenic functions, which have important potential in the field of bone repair.

Resveratrol Modulates Bone Mineral Density and Bone Mineral Content in A Rat Model of Male Hypogonadism

OBJECTIVE

To determine whether resveratrol (Res) can correct osteoporosis induced in a rat model of male hypogonadism.

METHODS

Thirty-two rats were randomly divided into 4 groups, 8 in each group; 1) a control sham group: underwent a similar surgical procedure for induction of orchiectomy (ORCD) without ligation of any arteries or veins or removal of the testis and epididymis; 2) a control + Res-treated group (Con+Res): underwent sham surgery similar to the control, but was then treated with Res, as described below; 3) an ORCD-induced group: bilateral ORCD surgery as described above, and 4) a ORCD+Res-treated group: bilateral ORCD surgery followed by Res treatment. Res treatment began 4 weeks after ORCD and continued for 12 weeks. After 12 weeks, bone mineral density (BMD) and bone mineral content (BMC) were measured in the tibia and femur of each rat's right hind leg. Blood levels of bone turnover indicators such as deoxypyridinoline (Dpd), N-telopeptide of type I collagen (NTX I), alkaline phosphatase (ALP), and osteocalcin (OC), as well as receptor activator of nuclear factor kappa B (RANK) and osteoprotegerin (OPG) were assessed.

RESULTS

ORCD significantly decreased BMD (P<0.01) and significantly increased bone resorption, manifested by increased RANK. In addition, it inhibited serum levels of OPG and OC. Res treatment after ORCD effectively increased serum levels of bone formation markers such as OPG and OC, compared with testisectomized rats (P<0.05).

CONCLUSION

Res could ameliorate bone loss induced by male hypogonadism, possible via restoration of the normal balance between RANK and OPG.

A review: strategies to reduce infection in tantalum and its derivative applied to implants

Implant-associated infection is the main reasons for implant failure. Titanium and titanium alloy are currently the most widely used implant materials. However, they have limited antibacterial performance. Therefore, enhancing the antibacterial ability of implants by surface modification technology has become a trend of research. Tantalum is a potential implant coating material with good biological properties. With the development of surface modification technology, tantalum coating becomes more functional through improvement. In addition to improving osseointegration, its antibacterial performance has also become the focus of attention. In this review, we provide an overview of the latest strategies to improve tantalum antibacterial properties. We demonstrate the potential of the clinical application of tantalum in reducing implant infections by stressing its advantageous properties.

The progress in titanium alloys used as biomedical implants: From the view of reactive oxygen species

Titanium and Titanium alloys are widely used as biomedical implants in oral and maxillofacial surgery, due to superior mechanical properties and biocompatibility. In specific clinical populations such as the elderly, diabetics and patients with metabolic diseases, the failure rate of medical metal implants is increased significantly, putting them at increased risk of revision surgery. Many studies show that the content of reactive oxygen species (ROS) in the microenvironment of bone tissue surrounding implant materials is increased in patients undergoing revision surgery. In addition, the size and shape of materials, the morphology, wettability, mechanical properties, and other properties play significant roles in the production of ROS. The accumulated ROS break the original balance of oxidation and anti-oxidation, resulting in host oxidative stress. It may accelerate implant degradation mainly by activating inflammatory cells. Peri-implantitis usually leads to a loss of bone mass around the implant, which tends to affect the long-term stability and longevity of implant. Therefore, a great deal of research is urgently needed to focus on developing antibacterial technologies. The addition of active elements to biomedical titanium and titanium alloys greatly reduce the risk of postoperative infection in patients. Besides, innovative technologies are developing new biomaterials surfaces conferring anti-infective properties that rely on the production of ROS. It can be considered that ROS may act as a messenger substance for the communication between the host and the implanted material, which run through the entire wound repair process and play a role that cannot be ignored. It is necessary to understand the interaction between oxidative stress and materials, the effects of oxidative stress products on osseointegration and implant life as well as ROS-induced bactericidal activity. This helps to facilitate the development of a new generation of well-biocompatible implant materials with ROS responsiveness, and ultimately prolong the lifespan of implants.

Retrograde tibiotalocalcaneal nailing for the treatment of acute ankle fractures in the elderly: a systematic review and meta-analysis

Introduction

Methods

Results

Conclusion

Metformin enhances the osteogenic activity of rat bone marrow mesenchymal stem cells by inhibiting oxidative stress induced by diabetes mellitus: an in vitro and in vivo study

PURPOSE

The purpose of this study was to determine whether metformin (MF) could alleviate the expresssion of reactive oxygen species (ROS) and improve the osteogenic ability of bone marrow mesenchymal stem cells derived from diabetic rats (drBMSCs) in vitro, and to evaluate the effect of MF on the ectopic osteogenesis of drBMSCs in a nude mouse model in vivo.

METHODS

BMSCs were extracted from normal and diabetic rats. In vitro, a cell viability assay (Cell Counting Kit-8), tests of alkaline phosphatase (ALP) activity, and western blot analysis were first used to determine the cell proliferation and osteogenic differentiation of drBMSCs that were subjected to treatment with different concentrations of MF (0, 50, 100, 200, 500 μM). The cells were then divided into 5 groups: (1) normal rat BMSCs (the BMSCs derived from normal rats group), (2) the drBMSCs group, (3) the drBMSCs + Mito-TEMPO (10 μM, ROS scavenger) group, (4) the drBMSCs + MF (200 μM) group, and (5) the drBMSCs + MF (200 μM) + H₂O₂ (50 μM, ROS activator) group. Intracellular ROS detection, a senescence-associated β-galactosidase assay, ALP staining, alizarin red staining, western blotting, and immunofluorescence assays were performed to determine the effects of MF on oxidative stress and osteogenic differentiation in drBMSCs. In vivo, the effect of MF on the ectopic osteogenesis of drBMSCs was evaluated in a nude mouse model.

RESULTS

MF effectively reduced ROS levels in drBMSCs. The cell proliferation, ALP activity, mineral deposition, and osteogenic-related protein expression of drBMSCs were demonstrably higher in the MF-treated group than in the non-MF-treated group. H₂O₂ inhibited the effects of MF. In addition, ectopic osteogenesis was significantly increased in drBMSCs treated with MF.

CONCLUSIONS

MF promoted the proliferation and osteogenic differentiation of drBMSCs by inhibiting the oxidative stress induced by diabetes and enhenced the ectopic bone formation of drBMSCs in nude mice.

Mesenchymal stem cell-seeded porous tantalum-based biomaterial: A promising choice for promoting bone regeneration

Porous tantalum-based biomaterial is a novel tissue engineering material widely used in repairing bone defects due to its corrosion resistance, low elastic modulus, high friction coefficient, and excellent biocompatibility. Bone marrow-derived mesenchymal stem cells (BMSCs), a type of pluripotent stem cell, can travel from their original ecological niche to bone injury sites, where they differentiate into osteoblasts and osteocytes. Multiple factors regulate the proliferation, migration, and differentiation of BMSCs. In recent years, the regulatory effects of porous tantalum on BMSCs have been widely studied. Hence, in this study, we reviewed the characteristics of porous tantalum-based biomaterials and the mechanism of action of their regulatory effects on BMSCs. Further, we discuss the feasibility of seeding BMSCs in porous tantalum-based biomaterials for use in tissue repair.

Silk Fibroin/Hydroxyapatite Coating Improved Osseointegration of Porous Titanium Implants under Diabetic Conditions via Activation of the PI3K/Akt Signaling Pathway

The application of three-dimensional printed porous titanium implants (TIs) is compromised in patients suffering from diabetes mellitus (DM), which disturbs the normal process of implant osseointegration, resulting in fixation failure. It was possibly because of reactive oxygen species (ROS) overproduction at the bone-implant interface. A silk fibroin-based hydroxyapatite (SF/HA) hybrid material emerged as a novel biological material for accelerating new bone formation. We proposed that the SF/HA hybrid coated titanium implant (SHT) could mitigate DM-mediated impaired osseointegration, which had never been reported previously. To test this assumption and further elucidate the mechanisms, primary rabbit osteoblasts were seeded on TIs or SHTs and cultured with normal serum, diabetic serum (DS), DS + N-acetyl-L-cysteine (NAC) (a potent ROS inhibitor), and DS + LY294002 (a specific PI3K/Akt inhibitor) for osteoblast behavior examinations. An animal study was performed on diabetic rabbits implanted with the two kinds of implants for osseointegration tests. DM-mediated ROS overproduction caused osteoblastic biological dysfunctions and apoptotic injury, associated with suppression of PI3K/Akt signaling in osteoblasts cultured on a TI substrate. Of note, the SHT substrate significantly suppressed ROS overproduction under diabetic conditions, improved osteoblast functional recovery including ameliorative osteoblast adhesion and morphology, improved cellular proliferation and differentiation, and abrogated apoptosis, which exhibited the same effect as NAC administration on the TI. The in vitro results were further corroborated in vivo by enhanced osteogenesis and osseointegration of SHTs in diabetic rabbits. Moreover, the aforesaid promotive effects afforded by the SF/HA coating were totally abolished with administration of LY294002 for blocking PI3K/Akt signaling. The above results collectively demonstrated that the SF/HA hybrid coating significantly ameliorated DM-mediated impaired osseointegration of the TI via reactivation of the ROS-mediated PI3K/Akt signaling pathway. The hybrid coating elicited a novel surface biofunctionalization strategy to attain favorable clinical performance of TI in diabetics.

The dual-effects of PLGA@MT electrospun nanofiber coatings on promoting osteogenesis at the titanium-bone interface under diabetic conditions

The high failure risk of endosseous titanium implants under diabetes conditions appeals to strengthen the osteointegration on the titanium-bone (Ti-B) interface. Melatonin (MT) is a neurohormone involved in bone homeostasis, which can promote osteogenesis and inhibit ROS overproduction through multiple pathways, but its effects on the Ti-B interface in diabetes remain elusive. The biodegradable poly(lactic-co-glycolic acid) (PLGA) has excellent controlled and sustained release properties, low cytotoxicity, and biocompatibility. Our study fabricated a nanofiber in which MT was encapsulated in PLGA to generate a nanofiber coating on a polydopamine (PDA)-modified titanium surface using electrospinning technology. The surface characteristic showed that MT was fully encapsulated in the PLGA carrier, and PLGA@MT was strongly coupled to the titanium matrix. Furthermore, the PLGA@MT-Ti nanofiber could release MT for at least 30 days. In vitro cellular tests demonstrated that PLGA@MT-Ti directly stimulates osteogenesis on the Ti-B interface by activating the BMP-4/WNT pathway in a dose-dependent manner. The effect of suppressing diabetes-induced ROS overproduction and promoting cell proliferation was not proportional to the content of MT. In vivo experiments revealed that PLGA@MT-Ti screws promoted the bone formation and osteointegration in type 1 diabetes mellitus (T1DM) mice with tibial bone defects. Our findings demonstrate that PLGA@MT-Ti exerted dual effects through activating the BMP-4/WNT pathway and attenuating ROS overproduction to promote osteogenesis and osteointegration at the Ti-B interface, providing a novel strategy to fabricate biomaterial modification and biofunctionalization under diabetic conditions.

Insulin growth factor binding protein-3 enhances dental implant osseointegration against methylglyoxal-induced bone deterioration in a rat model

PURPOSE

The aim of this study was to determine the effect of insulin growth factor binding protein-3 (IGFBP-3) on the inhibition of glucose oxidative stress and promotion of bone formation near the implant site in a rat model of methylglyoxal (MGO)-induced bone loss.

METHODS

An in vitro study was performed in MC3T3 E1 cells treated with chitosan gold nanoparticles (Ch-GNPs) conjugated with IGFBP-3 cDNA followed by MGO. An in vivo study was conducted in a rat model induced by MGO administration after the insertion of a dental implant coated with IGFBP-3.

RESULTS

MGO treatment downregulated molecules involved in osteogenic differentiation and bone formation in MC3T3 E1 cells and influenced the bone mineral density and bone volume of the femur and alveolar bone. In contrast, IGFBP-3 inhibited oxidative stress and inflammation and enhanced osteogenesis in MGO-treated MC3T3 E1 cells. In addition, IGFBP-3 promoted bone formation by reducing inflammatory proteins in MGO-administered rats. The application of Ch-GNPs conjugated with IGFBP-3 as a coating of titanium implants enhanced osteogenesis and the osseointegration of dental implants.

CONCLUSIONS

This study demonstrated that IGFBP-3 could be applied as a therapeutic component in dental implants to promote the osseointegration of dental implants in patients with diabetes, which affects MGO levels.

Oxygen-Carrying and Antibacterial Fluorinated Nano-Hydroxyapatite Incorporated Hydrogels for Enhanced Bone Regeneration

Insufficient oxygen availability in tissue engineering is one of the major factors for the failure of clinical transplantation. One potential strategy to conquer this limitation is the fabrication of spontaneous and continuous oxygen supplying scaffolds for in situ tissue regeneration. In this work, a versatile fluorine-incorporating hydrogel is designed which can not only timely and continuously supply oxygen for mesenchymal stem cells (MSCs) to overcome deficient oxygen before vascularization in scaffolds, but can present a higher antibacterial capability to avoid bacterial infections. The HAp@PDA-F nanoparticles are first prepared and then incorporated with the quaternized and methacrylated chitosan forming CS/HAp@PDA-F by photo-crosslinking. In vitro results indicate that CS/HAp@PDA-F hydrogel has outstanding mechanical performance, moreover, it also has the oxygen-carrying ability to prolong survival ability, enhance proliferation activity, and preserve osteogenic differentiation potency and promote osteogenic-related genes expression of rat bone mesenchymal stem cells (rBMSCs) under hypoxic environment. Furthermore, the CS/HAp@PDA-F hydrogel can inhibit the growth of Staphylococcus aureus and Escherichia coli, providing a good antibacterial activity. Additionally, in vivo experiments demonstrate higher bone volume and bone mineral density, and more new bone tissue generation in CS/HAp@PDA-F group than in CS/HAp@PDA group. These results indicate that the rational design of fluorinated hydrogel possesses a good clinical application prospect for bone regeneration.

Impaired dental implant osseointegration in rat with streptozotocin-induced diabetes

OBJECTIVE

Few studies have reported on the impact of oxidative stress on the dental implant failure. The aim of this study was to investigate the impact of hyperglycemia-induced oxidative stress on dental implant osseointegration in diabetes mellitus (DM).

METHODS

Acid-treated titanium implants were bilaterally placed in the maxillary alveolar ridge of streptozotocin-induced diabetic (DM group) and control rats after extraction of first molars. Histological analysis and micro-push-out test were performed 4 weeks after surgery. Oxidative stress and osteogenic markers in the surrounding bone were quantified by real-time polymerase chain reaction. In the in vitro study, rat bone marrow-derived mesenchymal stem cells (BMMSCs) were cultured on acid-treated titanium discs in a high-glucose (HG) or normal environment. Intracellular reactive oxygen species (ROS), cell proliferation, alkaline phosphatase (ALP) activity, and extracellular calcification were evaluated following antioxidant treatment with N-acetyl-L-cysteine (NAC).

RESULTS

The implant survival rate was 92.9% and 75.0% in control and DM group, respectively. Bone-implant contact and push-out loads were significantly lower in the DM group. Expression of superoxide dismutase 1 at the mRNA level and on immunohistochemistry was significantly lower in the DM group. In vitro experiments revealed that the HG condition significantly increased ROS expression and suppressed the proliferation and extracellular calcification of BMMSCs, while NAC treatment significantly restored ROS expression, cell proliferation, and calcification. The ALP activity of both groups was not significantly different.

CONCLUSION

In diabetes, high-glucose-induced oxidative stress downregulates proliferation and calcification of BMMSCs, impairing osseointegration and leading to implant failure.

Enabling technologies towards personalization of scaffolds for large bone defect regeneration

Additive manufacturing (AM) can deliver personalized scaffolds to support large volume defect tissue regeneration - a major clinical challenge in many medical disciplines. The freedom in scaffold design and composition (biomaterials and biologics) offered by AM yields a plethora of possibilities but is confronted with a heterogenous biological regeneration potential across individuals. A key challenge is to make the right choice for individualized scaffolds that match biology, anatomy, and mechanics of patients. This review provides an overview of state-of-the-art technologies, that is, in silico modelling for scaffold design, omics and bioinformatics to capture patient biology and information technology for data management, that, when combined in a synergistic way with AM, have great potential to make personalized tissue regeneration strategies available to all patients, empowering precision medicine.

Dexamethasone-loaded, injectable pullulan-poly(ethylene glycol) hydrogels for bone tissue regeneration in chronic inflammatory conditions

Chronic inflammation, infection, and fixation stability disrupts bone tissue regeneration by implants. The elevated levels of inflammatory markers and reactive oxygen species (ROS) damage tissues, inhibit osteoblastic differentiation, and promote bone resorption. Activation of local and chronic inflammatory responses due to the implantable biomaterial poses a high risk of implant failure and compromised bone repair in several pathological conditions. Not much progress has been made in the development of biomaterials that can counter inflammation and ROS along with inducing osteogenic activities for managing bone defects/injuries. We have developed, for the first time, injectable polymeric hydrogels by crosslinking oxidized pullulan (OP, 1% w/v) and 8-arm PEG hydrazine (PEG-HY, 10% w/v) using pH-sensitive and dynamic hydrazone linkages at 37 °C in buffer. The hydrogels were loaded with dexamethasone (Dex), an anti-inflammatory corticosteroid and osteogenic inducer, by covalently linking it to PEG-HY by hydrazone linkages, and their morphological, injectability, viscoelastic, self-healing, swelling, and drug-release properties were investigated. The hydrogels provided a pH-sensitive sustained release of PEG-Dex conjugate (3.62 wt%, 9.22 × 10^-5 mol of Dex/gram) for 28 days, with 74.54 and 55.15% PEG-Dex conjugate being released at pH 6.5 and 7.4. ABTS assay showed that hydrogels inhibited 68% radicals within 1 h, and treatment with hydrogel releasates inhibited the pro-inflammatory markers, IL-6 and IL-1β, and elevated the anti-inflammatory marker, TGF-β, in murine osteoblast precursor cells (MC3T3-E1). The hydrogels were found suitable for cell encapsulation and they exhibited 110% viability on treatment with releasates. Finally, the osteogenic activities of hydrogels were ascertained by alkaline phosphatase (ALP) activities, alizarin red S staining, and osteogenic gene expressions- RUNX2, Col-I, OPN, and IBSP. Overall, PEG-Dex conjugate released from hydrogels improved the cell viability and proliferation, and induced the osteoblastic differentiation. The hydrogels with their promising antioxidant and anti-inflammatory properties along with the osteogenic activities show a strong potential as an injectable, extracellular matrix (ECM)-mimicking implantable drug-depot for bone repair applications in chronic inflammatory conditions.

Nutrient Element Decorated Polyetheretherketone Implants Steer Mitochondrial Dynamics for Boosted Diabetic Osseointegration

As a chronic metabolic disease, diabetes mellitus (DM) creates a hyperglycemic micromilieu around implants, resulting inthe high complication and failure rate of implantation because of mitochondrial dysfunction in hyperglycemia. To address the daunting issue, the authors innovatively devised and developed mitochondria-targeted orthopedic implants consisted of nutrient element coatings and polyetheretherketone (PEEK). Dual nutrient elements, in the modality of ZnO and Sr(OH)2 , are assembled onto the sulfonated PEEK surface (Zn&Sr-SPEEK). The results indicate the synergistic liberation of Zn2+ and Sr2+ from coating massacres pathogenic bacteria and dramatically facilitates cyto-activity of osteoblasts upon the hyperglycemic niche. Intriguingly, Zn&Sr-SPEEK implants are demonstrated to have a robust ability to recuperate hyperglycemia-induced mitochondrial dynamic disequilibrium and dysfunction by means of Dynamin-related protein 1 (Drp1) gene down-regulation, mitochondrial membrane potential (MMP) resurgence, and reactive oxygen species (ROS) elimination, ultimately enhancing osteogenicity of osteoblasts. In vivo evaluations utilizing diabetic rat femoral/tibia defect model at 4 and 8 weeks further confirm that nutrient element coatings substantially augment bone remodeling and osseointegration. Altogether, this study not only reveals the importance of Zn2+ and Sr2+ modulation on mitochondrial dynamics that contributes to bone formation and osseointegration, but also provides a novel orthopedic implant for diabetic patients with mitochondrial modulation capability.

PGC-1α attenuates the oxidative stress-induced impaired osteogenesis and angiogenesis regulation effects of mesenchymal stem cells in the presence of diabetic serum

Oxidative stress is believed to induce dysfunction of the bone remodeling process and be associated with progressive loss of bone mass. The peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) is a master controller during mitochondrial biogenesis and the antioxidant response. We postulated that PGC-1α could function as a cyto-protective effector in mesenchymal stem cells (MSCs) under oxidative stress conditions. In this study, diabetic serum was firstly used to treat MSCs to induce oxidative damage. The anti-oxidative protective effects of PGC-1α overexpression on MSCs, as well as MSCs' osteogenesis and angiogenic regulation effects were investigated in vitro. Results showed that diabetic conditions induced significantly increase of intracellular oxidative damage and mitochondrial permeability transition pore (mPTP) opening activity, decrease of cellular viability, and osteogenic differentiation and pro-angiogenic regulation effects of MSCs. However, the diabetic conditions induced oxidative impair on MSCs were significantly alleviated via PGC-1α overexpression under diabetic conditions. Taken together, this study indicates the anti-oxidative treatment potential of PGC-1α regulation as a promising strategy to promote coupling pro-osteogenesis and pro-angiogenesis effects of MSCs.

Oxidative Stress-Induced Hypermethylation of KLF5 Promoter Mediated by DNMT3B Impairs Osteogenesis by Diminishing the Interaction with β-Catenin

Aims: Emerging evidence suggests that the pathogenesis of osteoporosis, characterized by impaired osteogenesis, is shifting from estrogen centric to oxidative stress. Our previous studies have shown that the zinc-finger transcription factor krüppel-like factor 5 (KLF5) plays a key role in the degeneration of nucleus pulposus and cartilage. However, its role in osteoporosis remains unknown. We aimed to investigate the effect and mechanism of KLF5 on osteogenesis under oxidative stress. Results: First, KLF5 was required for osteogenesis and stimulated osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). KLF5 was hypermethylated and downregulated in ovariectomy-induced osteoporosis mice and in BMSCs treated with H2O2. Interestingly, DNA methyltransferases 3B (DNMT3B) upregulation mediated the hypermethylation of KLF5 induced by oxidative stress, thereby impairing osteogenic differentiation. The inhibition of KLF5 hypermethylation using DNMT3B siRNA or 5-AZA-2-deoxycytidine (5-AZA) protected osteogenic differentiation of BMSCs from oxidative stress. Regarding the downstream mechanism, KLF5 induced β-catenin expression. More importantly, KLF5 promoted the nuclear translocation of β-catenin, which was mediated by the armadillo repeat region of β-catenin. Consistently, oxidative stress-induced KLF5 hypermethylation inhibited osteogenic differentiation by reducing the expression and nuclear translocation of β-catenin. Innovation: We describe the novel effect and mechanism of KLF5 on osteogenesis under oxidative stress, which is linked to osteoporosis for the first time. Conclusion: Our results suggested that oxidative stress-induced hypermethylation of KLF5 mediated by DNMT3B impairs osteogenesis by diminishing the interaction with β-catenin, which is likely to contribute to osteoporosis. Targeting the hypermethylation of KLF5 might be a new strategy for the treatment of osteoporosis. Antioxid. Redox Signal. 35, 1-20.

Osseointegration Aspects of Implants at the Bone Reconstruction Site by a Novel Porous Titanium Scaffold

OBJECTIVES

Porous titanium is used for the reconstruction of large bone defects due to its excellent mechanical strength. The quality of osseointegration of implants placed in bone reconstructed with porous titanium is unknown. The purpose of this in vivo study was to evaluate the osseointegration of implants at sites reconstructed using porous titanium.

MATERIAL AND METHODS

Hollow porous titanium (Ti) (outer-diameter 6 mm, inner-diameter 2 mm, length 4 mm, 85% porosity) and similar-sized porous hydroxyapatite (porous HA: 75% porosity) samples were prepared and implanted in 6 New Zealand white rabbit femurs. Four weeks later, an implant bed was created to receive a Ti implant (diameter 2 mm, length 4 mm). An implant placed at a pristine bone site served as the control. Four weeks later, histological and histomorphometric evaluations of the test and control sites were conducted.

RESULTS

Osseointegration was observed in all groups. There was no significant difference in the bone formation ratio and bone-implant contact (BIC) ratio across all groups for the whole area. At the cancellous bone area of the bone defect, superior bone formation ratio and BIC ratio were observed with porous Ti and porous HA compared to the control (bone formation ratio: control 1.8 [SD 3]%, HA 23 [SD 3]%, Ti 23.6 [SD 5]%; BIC ratio: control 5.4 [SD 5.3]%, HA 28.9 [SD 10.7]%, Ti 41.6 [SD 14]%). Porous Ti demonstrated good osteoconduction and osseointegration abilities, similar to porous HA.

CONCLUSIONS

To our knowledge, this is the first report of implant treatment after preliminary bone reconstruction using a titanium biomaterial. Porous titanium is a suitable material for bone reconstruction before implant treatment in load-bearing areas that allow subsequent prosthetic treatment.

Additive manufacturing of Ti6Al4V alloy via electron beam melting for the development of implants for the biomedical industry

Additive Manufacturing (AM) or rapid prototyping technologies are presented as one of the best options to produce customized prostheses and implants with high-level requirements in terms of complex geometries, mechanical properties, and short production times. The AM method that has been more investigated to obtain metallic implants for medical and biomedical use is Electron Beam Melting (EBM), which is based on the powder bed fusion technique. One of the most common metals employed to manufacture medical implants is titanium. Although discovered in 1790, titanium and its alloys only started to be used as engineering materials for biomedical prostheses after the 1950s. In the biomedical field, these materials have been mainly employed to facilitate bone adhesion and fixation, as well as for joint replacement surgeries, thanks to their good chemical, mechanical, and biocompatibility properties. Therefore, this study aims to collect relevant and up-to-date information from an exhaustive literature review on EBM and its applications in the medical and biomedical fields. This AM method has become increasingly popular in the manufacturing sector due to its great versatility and geometry control.

The synergistic promotion of osseointegration by nanostructure design and silicon substitution of hydroxyapatite coatings in a diabetic model

Accumulating evidence indicates much higher failure rates for biomedical titanium implants in diabetic patients. This phenomenon is attributed to impaired osteoblastic function, suppressed angiogenesis capacity, and abnormal osteoclast activation in diabetic patients. Our previous study demonstrated that titanium implants coated with highly crystalline nanostructured hydroxyapatite (nHA) promoted the osteogenic differentiation of bone marrow stromal cells (BMSCs) and bone-implant osseointegration under healthy conditions. Furthermore, recent studies showed that silicon-substituted biomaterials exhibited excellent osteogenesis and angiogenesis performance while repressing osteoclastogenesis. Hence, we proposed that a combination of nanostructural modification and Si substitution might produce synergetic effects to mitigate the impaired osseointegration of bone implants under diabetes mellitus (DM) conditions. To confirm this hypothesis, titanium implants coated with highly crystalline Si-substituted nHA (Si-nHA) were successfully fabricated via atmospheric plasma spraying combined with hydrothermal treatment. An in vitro study demonstrated that compared to the original HA coating, the nHA coating improved osteogenic and angiogenic differentiation and altered the OPG/RANKL ratio of DM-BMSCs. In addition, the Si-nHA coating further enhanced cell proliferation, improved osteogenic and angiogenic differentiation, and repressed osteoclastogenesis in DM-BMSCs. An in vivo study confirmed that the titanium implants coated with nHA or Si-nHA effectively promoted bone formation and bone-implant osseointegration in a diabetic rabbit model, with the Si-nHA coating exhibiting the best stimulatory effect. Collectively, the results suggest that the nanostructured topography and Si substitution act synergistically to ameliorate the poor bone regeneration and osseointegration associated with DM. Thus, the results provide a promising coating method for dental and orthopedic applications under diabetic conditions.

3D‑printed Ti6Al4V scaffolds combined with pulse electromagnetic fields enhance osseointegration in osteoporosis

The loosening and displacement of prostheses after dental implantation and arthroplasty is a substantial medical burden due to the complex correction surgery. Three-dimensional (3D)-printed porous titanium (pTi) alloy scaffolds are characterized by low stiffness, are beneficial to bone ingrowth, and may be used in orthopedic applications. However, for the bio-inert nature between host bone and implants, titanium alloy remains poorly compatible with osseointegration, especially in disease conditions, such as osteoporosis. In the present study, 3D-printed pTi scaffolds with ideal pore size and porosity matching the bone tissue, were combined with pulse electromagnetic fields (PEMF), an exogenous osteogenic induction stimulation, to evaluate osseointegration in osteoporosis. In vitro, external PEMF significantly improved osteoporosis-derived bone marrow mesenchymal stem cell proliferation and osteogenic differentiation on the surface of pTi scaffolds by enhancing the expression of alkaline phosphatase, runt-related transcription factor-2, osteocalcin, and bone morphogenetic protein-2. In vivo, Microcomputed tomography analysis and histological evaluation indicated the external PEMF markedly enhanced bone regeneration and osseointegration. This novel therapeutic strategy has potential to promote osseointegration of dental implants or artificial prostheses for patients with osteoporosis.

Improved osteogenesis and angiogenesis of theranostic ions doped calcium phosphates (CaPs) by a simple surface treatment process: A state-of-the-art study

Surface treatment of biomaterials could enable reliable and quick cellular responses and accelerate the healing of the host tissue. Here, a series of calcium phosphates (CaPs) were surface treated by hydrogen peroxide (H₂O₂) and the treatment effects were physicochemically and biologically evaluated. For this aim, as-synthesized CaPs doped with strontium (Sr²⁺), iron (Fe²⁺), silicon (Si⁴⁺), and titanium (Ti⁴⁺) ions were sonicated in H₂O₂ media. The results showed that the specific surface area and zeta potential values of the surface-treated CaPs were increased by ~50% and 25%, respectively. Moreover, the particle size and the band-gap (Eg) values of the surface-treated CaPs were decreased by ~25% and ~2-10%, respectively. The concentration of oxygen vacancies was increased in the surface-treated samples, which was confirmed by the result of ultraviolet (UV), photoluminescence (PL), Commission Internationale de l'éclairage (CIE 1931), and X-ray photoelectron spectroscopy (XPS) analyses. In vitro cellular assessments of surface-treated CaPs exhibited an improvement in cytocompatibility, reactive oxygen species generation (ROS) capacity, bone nodule formation, and the migration of cells up to ~8%, 20%, 35%, and 13%, respectively. Based on the obtained data, it can be stated that improved physicochemical properties of H₂O₂-treated CaPs could increase the ROS generation and subsequently enhance the biological activities. In summary, the results demonstrate the notable effect of the H₂O₂ surface treatment method on improving surface properties and biological performance of CaPs.

Diabetes as a Risk Factor for Orthopedic Implant Surface Performance: A Retrieval and In Vitro Study

Orthopedic devices are often associated with increased risk for diabetic patients due to impaired wound healing capabilities. Adverse biological responses for immunocompromised patients at the implant-tissue interface can lead to significant bone resorption that may increase failure rates. The goal of this study was to characterize the surface of implants removed from diabetic patients to determine underlying mechanisms of diabetes-induced impaired osseointegration. Thirty-nine retrieved titanium and stainless-steel orthopedic devices were obtained from diabetic and non-diabetic patients, and compared to non-implanted controls. Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and X-ray Photoelectron Spectroscopy revealed changes in morphology, chemical composition, oxidation state, and oxide thickness of the retrieval specimens, respectively. Additionally, titanium disks were immersed for 28 days in simulated in vitro diabetic conditions followed by Inductively Coupled Plasma-Optical Emission Spectroscopy to quantify metal dissolution. Electrochemical testing was performed on specimens from retrievals and in vitro study. Aside from biological deposits, retrievals demonstrated surface discoloration, pit-like formations and oxide thinning when compared to non-implanted controls, suggesting exposure to unfavorable acidic conditions. Cyclic load bearing areas on fracture-fixation screws and plates depicted cracking and delamination. The corrosion behavior was not significantly different between diabetic and non-diabetic conditions of immersed disks or implant type. However, simulated diabetic conditions elevated aluminum release. This elucidates orthopedic implant failures that potentially arise from diabetic environments at the implant-tissue interface. Design of new implant surfaces should consider specific strategies to induce constructive healing responses in immunocompromised patients while also mitigating corrosion in acidic diabetic environments.

In Situ Regulation of Macrophage Polarization to Enhance Osseointegration Under Diabetic Conditions Using Injectable Silk/Sitagliptin Gel Scaffolds

As a chronic inflammatory disease, diabetes mellitus creates a proinflammatory microenvironment around implants, resulting in a high rate of implant loosening or failure in osteological therapies. In this study, macroporous silk gel scaffolds are injected at the bone-implant interface for in situ release of sitagliptin that can regulate macrophage response to create a prohealing microenvironment in diabetes mellitus disease. Notably, it is discovered that sitagliptin induces macrophage polarization to the M2 phenotype and alleviates the impaired behaviors of osteoblasts on titanium (Ti) implants under diabetic conditions in a dose-dependent manner. The silk gel scaffolds loaded with sitagliptin elicite a stronger recruitment of M2 macrophages to the sites of Ti implants and a significant promotion of osteointegration, as compared to oral sitagliptin administration. The results suggest that injectable silk/sitagliptin gel scaffolds can be utilized to modulate the immune responses at the bone-implant interface, thus enhancing bone regeneration required for successful implantation of orthopedic and dental devices in diabetic patients.

Infliximab-based self-healing hydrogel composite scaffold enhances stem cell survival, engraftment, and function in rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a severe inflammatory autoimmune disease, but its treatment has been very difficult. Recently, stem cell-based therapies have opened up possibilities for the treatment of RA. However, the hostile RA pathological conditions impede the survival and differentiation of transplanted cells, and it remains challenging to fabricate a suitable biomaterial for the improvement of stem cells survival, engraftment, and function. Here we construct an optimal scaffold for RA management through the integration of 3D printed porous metal scaffolds (3DPMS) and infliximab-based hydrogels. The presence of rigid 3DPMS is appropriate for repairing large-scale bone defects caused by RA, while the designed infliximab-based hydrogels are introduced because of their self-healable, anti-inflammatory, biocompatible, and biodegradable properties. We demonstrate that the bioengineered composite scaffolds support adipose-derived mesenchymal stem cells (ADSCs) proliferation, differentiation, and extracellular matrix production in vitro. The composite scaffolds, along with ADSCs, are then implanted into the critical-sized bone defect in the RA rabbit model. In vivo results prove that the bioengineered composite scaffolds are able to down-regulate inflammatory cytokines, rebuild damaged cartilage, as well as improve subchondral bone repair. To the best of the authors' knowledge, this is the first time that using the antirheumatic drug to construct hydrogels for stem cell-based therapies, and this inorganic-organic hybrid system has the potential to alter the landscape of RA study.

Genipin and insulin combined treatment improves implant osseointegration in type 2 diabetic rats

BACKGROUND

Type 2 diabetes mellitus (T2DM) has a harmful effect on the stability and osseointegration of dental implants. T2DM induces mitochondrial damage by inhibiting AMPK signaling, resulting in oxidative stress and poor osteogenesis in the peri-implant bone area. Genipin is a major component of gardenia fruits with strong antioxidant, anti-inflammation, and antidiabetic actions, and it also can activate mitochondrial quality control via the AMPK pathway. The purpose of this study was to investigate the effects of genipin and insulin treatment on implant osseointegration in T2DM rats and explore the underlying mechanisms.

METHODS

Streptozotocin-induced diabetic rats received implant surgery in their femurs and were then assigned to five groups that were subjected to different treatments for three months: control group, T2DM group, insulin-treated T2DM group (10 IU/kg), genipin-treated T2DM group (50 mg/kg), and the genipin and insulin combination-treated T2DM group. Then, we regularly assessed the weight and glucose levels of the animals. Rats were euthanized at 3 months after the implantation procedure, and the femora were harvested for microscopic computerized tomography analysis, biomechanical tests, and different histomorphometric assessment.

RESULTS

The results indicated that the highest blood glucose and oxidative stress levels were measured for the T2DM group, resulting in the poorest osseointegration. The combination-treated T2DM group mitigated hyperglycemia and normalized, reactivated AMPK signaling, and alleviated oxidative stress as well as reversed the negative effect of osseointegration. There were beneficial changes observed in the T2DM-genipin and T2DM-insulin groups, but these were less in comparison to the combination treatment group.

CONCLUSION

Our study suggests that treatment with genipin in combination with insulin could be an effective method for promoting implant osseointegration in T2DM rats, which may be related to AMPK signaling.

Ag and peptide co-decorate polyetheretherketone to enhance antibacterial property and osteogenic differentiation

Polyetheretherketone (PEEK) has been well concerned as a promising material for hard tissue repair because of its outstanding mechanical behavior and superior biocompatibility. However, its clinical application is limited by its biological inertness and the susceptibility to bacterial infection during implantation. To improve the original shortcomings, self-polymerized dopamine (PDA) was used to enrich silver ions on the PEEK surface. Moreover, a layer of carboxymethyl chitosan (CMC) film was formed on the PEEK surface by the spin-coating method, aiming to control the release of silver ions on the surface. At the same time, bone forming peptide (BFP) was modified onto the PEEK surface by 1-(3-dimethylaminopropyl)-3-ethylcarbonimide hydrochloride (EDC) / N-hydroxy succinimide (NHS). The characterization results showed that PEEK-Ag-CMC-BFP could be obtained successfully. The inhibition zone and bacterial kinetic curve showed a favorable inhibitory effect of the sliver-modified PEEK on gram-negative and gram-positive bacteria. In vitro experiments exhibited that PEEK-Ag-CMC-BFP had a better biological activity than that of PEEK, which could promote cell proliferation and osteogenic differentiation. It is expected that this dual-function material with antibacterial and bone-promoting properties has a vast potential applied in the field of hard tissue repair.

Impact of diabetes mellitus simulations on bone cell behavior through in vitro models

Diabetes mellitus (DM) is related to impaired bone healing and an increased risk of bone fractures. While it is recognized that osteogenic differentiation and the function of osteoblasts are suppressed in DM, the influence of DM on osteoclasts is still unclear. Hyperglycemia and inflammatory environment are the hallmark of DM that causes dysregulation of various pro-inflammatory cytokines and alternated gene expression in periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. A methodological review on conceptual and practical implications of in vitro study models is used for DM simulation on bone cells. Several major databases were screened to find literature related to the study objective. Published literature within last 20 years that used in vitro DM-simulated models to study how DM affects the cellular behavior of bone cells were selected for this review. Studies utilizing high glucose and serum acquired from diabetic animals are the mainly used methods to simulate the diabetic condition. The combination with various simulating factors such as lipopolysaccharide (LPS), hydrogen peroxide (H₂O₂), and advanced glycation end products (AGEs) have been reported in diabetic situations in vitro, as well. Through screening procedure, it was evident DM-simulated conditions exerted negative impact on bone-related cells. However, inconsistent results were found among different reported studies, which could be due to variation in culture conditions, concentrations of the stimulating factors and cell lineage, etc. This manuscript has concisely reviewed currently existing DM-simulated in vitro models and provides valuable insights of detailed components in simulating DM conditions in vitro. Studies using DM-simulated microenvironment revealed that in vitro simulation negatively impacted periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. Contrarily, studies also indicated beneficial influence on bone-related cells when such conditions are reversed.

Promotion of osteointegration by silk fibroin coating under diabetic conditions on 3D printed porous titanium implants via ROS-mediated NF-κB pathway

The clinical evidence indicates the compromised application of titanium implants (TI) in diabetics, associated with reactive oxygen species (ROS) overproduction at the bone-implant interface. Silk fibroin has exerted impressive biocompatibility in application of biomedical material and optimal anti-diabetic effect as oriental medicine. We proposed that SF coated titanium implant (STI) could alleviate diabetes-induced compromised osteointegration, which had been rarely reported before. To confirm the hypothesis and explore the underlying mechanisms, rat osteoblasts cultured on 3-dimensional (3D) printed TI and STI were subjected to normal serum (NS), diabetic serum (DS), DS with NAC (a ROS inhibitor) or SN50 (a NF-κB inhibitor). In vivo study was performed on diabetic sheep implanted with TI or STI into the bone defect on crista iliaca. Results demonstrated that ROS overproduction induced by diabetes lead to osteoblast dysfunctions and cellular apoptosis on TI substrate, associated with activation of NF-κB signaling pathway in osteoblasts. Importantly, STI substrate significantly attenuated ROS production and NF-κBp65 phosphorylation, through which the osteoblast biological dysfunctions were ameliorated. These results were further confirmed in vivo by the improved osteointegration of STI evidenced by Micro-CT and histological examinations compared with TI. These results demonstrated that ROS-mediated NF-κB signaling pathway played a crucial role in diabetes-induced implant destabilization. Importantly, SF coating as a promising material for biomaterial-engineering markedly improved clinical treatment effect of TI under diabetic conditions, possibly associated with the suppression of NF-κB pathway.

TiO2 Nanotubes Alleviate Diabetes-Induced Osteogenetic Inhibition

Background

Patients with diabetes mellitus (DM) have a higher failure rate of dental implant treatments. However, whether titanium (Ti) implants with TiO₂ nanotubes (TNT) surface can retain their biocompatibility and osteogenetic ability under DM conditions has not been investigated; in addition, their behavior in DM conditions is not well characterized.

Materials and Methods

Pure Ti discs were surface treated into the polishing (mechanically polished, MP), sandblasted and acid-etched (SLA), and TNT groups. Scanning electron microscopy was used to examine the surface morphology. The cell adhesion and proliferation ability on different modified Ti surfaces at various glucose concentrations (5.5, 11, 16.5, and 22 mM) was detected by the CCK-8 assay. The osteogenetic ability on different modified Ti surfaces under high-glucose conditions was evaluated by alkaline phosphatase (ALP), osteopontin (OPN) immunofluorescence, Western blot, and Alizarin Red staining in vitro. Detection of cell apoptosis and intracellular reactive oxygen species (ROS) was undertaken both before and after N-acetylcysteine (NAC) treatment to assess the oxidative stress associated with different modified Ti surfaces under high-glucose conditions. An in vivo study was conducted in DM rats with different modified Ti femoral implants. The osteogenetic ability of different modified Ti implants in DM rats was assessed using a micro-CT scan.

Results

High-glucose conditions inhibited cell adhesion, proliferation, and osteogenetic ability of different modified Ti surfaces. High-glucose conditions induced higher apoptosis rate and intracellular ROS level on different modified Ti surfaces; these effects were alleviated by NAC. Compared with the SLA surface, the TNT surface alleviated the osteogenetic inhibition induced by high-glucose states by reversing the overproduction of ROS in vitro. In the in vivo experiment, micro-CT scan analysis further confirmed the best osteogenetic ability of TNT surface in rats with DM.

Conclusion

TNT surface modification alleviates osteogenetic inhibition induced by DM. It may provide a more favorable Ti implant surface for patients with DM.

Excessive production of mitochondrion‑derived reactive oxygen species induced by titanium ions leads to autophagic cell death of osteoblasts via the SIRT3/SOD2 pathway

The incidence of peri-implant bone loss is high, and is a difficult condition to treat. Previous studies have shown that titanium (Ti) ions released from implants can lead to osteoblast cell damage, but the specific mechanisms have not been elucidated. The present study established a Ti ion damage osteoblast cell model. The levels of mitochondrion-derived reactive oxygen species (mROS) and autophagy, cell viability and the sirtuin 3 (SIRT3)/superoxide dismutase 2 (SOD2) pathway were examined in this model. It was found that Ti ions decreased osteoblast viability. Moreover, with increased Ti ion concentration, the expression levels of microtubule associated protein 1 light chain 3α (LC3) progressively increased, P62 decreased, autophagic flow increased and mROS levels increased. After the addition of an autophagy inhibitor Bafilomycin A1 and Mito-TEMPO, a mitochondrial antioxidant, the production of mROS was inhibited, the level of autophagy was decreased and cell activity was improved. In addition, with increased Ti ion concentration, the activity of SOD2 decreased, the acetylation level of SOD2 increased, the SIRT3 mRNA and protein expression levels decreased, and the activity of SIRT3 was significantly decreased. Furthermore, it was demonstrated that SIRT3 overexpression reduced the acetylation of SOD2 and increased the activity of SOD2, as well as reducing the production of mROS and the expression level of LC3, thus increasing cell viability. Therefore, the present results suggested that excessive production of mROS induced by Ti ions led to autophagic cell death of osteoblasts, which is dependent on the SIRT3/SOD2 pathway.

Enhanced osseointegration of three-dimensional supramolecular bioactive interface through osteoporotic microenvironment regulation

Purpose: Osteoporosis is more likely to cause serious complications after joint replacement, mainly due to physiological defects of endogenous osteogenic cells and the pathological osteoclast activity. It is a feasible solution to design a prosthetic surface interface that specifically addresses this troublesome situation. Methods: A novel "three-dimensional (3D) inorganic-organic supramolecular bioactive interface" was constructed consisting of stiff 3D printing porous metal scaffold and soft multifunctional, self-healable, injectable, and biodegradable supramolecular polysaccharide hydrogel. Apart from mimicking the bone extracellular matrix, the bioactive interface could also encapsulate bioactive substances, namely bone marrow mesenchymal stem cells (BMSCs) and bone morphogenetic protein-2 (BMP-2). A series of in vitro characterizations, such as topography and mechanical characterization, in vitro release of BMP-2, biocompatibility analysis, and osteogenic induction of BMSCs were carried out. After that, the in vivo osseointegration effect of the bioactive interface was investigated in detail using an osteoporotic model. Results: The administration of injectable supramolecular hydrogel into the inner pores of 3D printing porous metal scaffold could obviously change the morphology of BMSCs and facilitate its cell proliferation. Meanwhile, BMP-2 was capable of being sustained released from supramolecular hydrogel, and subsequently induced osteogenic differentiation of BMSCs and promoted the integration of the metal microspores-bone interface in vitro and in vivo. Moreover, the osteoporosis condition of bone around the bioactive interface was significantly ameliorated. Conclusion: This study demonstrates that the 3D inorganic-organic supramolecular bioactive interface can serve as a novel artificial prosthesis interface for various osteogenesis-deficient patients, such as osteoporosis and rheumatoid arthritis.

Multi-Layered Polyamide/Collagen Scaffolds with Topical Sustained Release of N-Acetylcysteine for Promoting Wound Healing

Background

Impaired wound healing might be associated with many issues, especially overactive of reactive oxygen species (ROS), deficiency of blood vessels and immature of epidermis. N-acetylcysteine (NAC), as an antioxidant, could solve these problems by inhibiting overreactive of ROS, promoting revascularization and accelerating re-epithelialization. How to deliver NAC in situ with a controllable releasing speed still remain a challenge.

Materials and Methods

In this study, we combined collagen (Col) with N-acetylcysteine to perform the characteristics of sustained release and chemically crosslinked Col/NAC composite with polyamide (PA) nanofibers to enhance the mechanical property of collagen and fabricated this multi-layered scaffold (PA-Col/NAC scaffold). The physical properties of the scaffolds such as surface characteristics, water absorption and tensile modulus were tested. Meanwhile, the ability to promote wound healing in vitro and in vivo were investigated.

Results

These scaffolds were porous and performed great water absorption. The PA-Col/NAC scaffold could sustainably release NAC for at least 14 days. After cell implantation, PA-Col/NAC scaffold showed better cell proliferation and cell migration than the other groups. In vivo, PA-Col/NAC scaffolds could promote wound healing best among all the groups.

Conclusion

The multi-layered scaffolds could obviously accelerate the process of wound healing and exert better and prolonged effects.

The development of novel bioactive porous titanium as a bone reconstruction material

Porous titanium fabricated by the resin-impregnated titanium substitute technique has good mechanical strength and osteoconduction. The alkali treatment of the titanium surface creates a bioactive surface. Alkali-treated porous titanium is expected to accelerate bone formation. The purpose of this study was to evaluate the bone reconstruction ability of alkali-treated porous titanium. Porous titanium (85% porosity) was treated with an alkali solution (5 N NaOH, 24 h). To assess material properties, we analyzed the surface structure by scanning electron microscopy (SEM) and mechanical strength testing. To assess bioactivity, each sample was soaked in a simulated body fluid (Hank's solution) for 7 days. Surface observations, weight change ratio measurement (after/before being soaked in Hank's solution) and surface elemental analysis were performed. We also designed an in vivo study with rabbit femurs. After 2 and 3 weeks of implantation, histological observations and histomorphometric bone formation ratio analysis were performed. All data were statistically analyzed using a Student's t-test (P < 0.05) (this study was approved by the Hiroshima University animal experiment ethics committee: A11-5-5). Non-treated porous titanium (control) appeared to have a smooth surface and the alkali-treated porous titanium (ATPT) had a nano-sized needle-like rough surface. ATPT had similar mechanical strength to that of the control. After soaking into the Hank's solution, we observed apatite-like crystals in the SEM image, weight gain, and high Ca and P contents in ATPT. There was significant bone formation at an early stage in ATPT compared with that in control. It was suggested that the alkali-treated porous titanium had a bioactive surface and induced bone reconstruction effectively. This novel bioactive porous titanium can be expected to be a good bone reconstruction material.

Porous titanium fabricated by the resin-impregnated titanium substitute technique has good mechanical strength and osteoconduction.

Dnmt3a-Mediated DNA Methylation Changes Regulate Osteogenic Differentiation of hMSCs Cultivated in the 3D Scaffolds under Oxidative Stress

Oxidative stress (OS) caused by multiple factors occurs after the implantation of bone repair materials. DNA methylation plays an important role in the regulation of osteogenic differentiation. Moreover, recent studies suggest that DNA methyltransferases (Dnmts) are involved in bone formation and resorption. However, the effect and mechanism of DNA methylation changes induced by OS on bone formation after implantation still remain unknown. Three-dimensional (3D) cell culture systems are much closer to the real situation than traditional monolayer cell culture systems in mimicking the in vivo microenvironment. We have developed porous 3D scaffolds composed of mineralized collagen type I, which mimics the composition of the extracellular matrix of human bone. Here, we first established a 3D culture model of human mesenchymal stem cells (hMSCs) seeded in the biomimetic scaffolds using 160 μM H₂O₂ to simulate the microenvironment of osteogenesis after implantation. Our results showed that decreased methylation levels of ALP and RUNX2 were induced by H₂O₂ treatment in hMSCs cultivated in the 3D scaffolds. Furthermore, we found that Dnmt3a was significantly downregulated in a porcine anterior lumbar interbody fusion model and was confirmed to be reduced by H₂O₂ treatment using the 3D in vitro model. The hypomethylation of ALP and RUNX2 induced by H₂O₂ treatment was abolished by Dnmt3a overexpression. Moreover, our findings demonstrated that the Dnmt inhibitor 5-AZA can enhance osteogenic differentiation of hMSCs under OS, evidenced by the increased expression of ALP and RUNX2 accompanied by the decreased DNA methylation of ALP and RUNX2. Taken together, these results suggest that Dnmt3a-mediated DNA methylation changes regulate osteogenic differentiation and 5-AZA can enhance osteogenic differentiation via the hypomethylation of ALP and RUNX2 under OS. The biomimetic 3D scaffolds combined with 5-AZA and antioxidants may serve as a promising novel strategy to improve osteogenesis after implantation.

Adhesion Behaviour of Primary Human Osteoblasts and Fibroblasts on Polyether Ether Ketone Compared with Titanium under In Vitro Lipopolysaccharide Incubation

The aim of this in vitro pilot study was to analyse the adhesion behaviour of human osteoblasts and fibroblasts on polyether ether ketone (PEEK) when compared with titanium surfaces in an inflammatory environment under lipopolysaccharide (LPS) incubation. Scanning electron microscopy (SEM) images of primary human osteoblasts/fibroblasts on titanium/PEEK samples were created. The gene expression of the LPS-binding protein (LBP) and the LPS receptor (toll-like receptor 4; TLR4) was measured by real-time polymerase chain reaction (PCR). Immunocytochemistry was used to obtain evidence for the distribution of LBP/TLR4 at the protein level of the extra-cellular-matrix-binding protein vinculin and the actin cytoskeleton. SEM images revealed that the osteoblasts and fibroblasts on the PEEK surfaces had adhesion characteristics comparable to those of titanium. The osteoblasts contracted under LPS incubation and a significantly increased LBP gene expression were detected. This was discernible at the protein level on all the materials. Whereas no increase of TLR4 was detected with regard to mRNA concentrations, a considerable increase in the antibody reaction was detected on all the materials. As is the case with titanium, the colonisation of human osteoblasts and fibroblasts on PEEK samples is possible under pro-inflammatory environmental conditions and the cellular inflammation behaviour towards PEEK is lower than that of titanium.

N-acetyl cysteine-loaded graphene oxide-collagen hybrid membrane for scarless wound healing

Wound dressings composed of natural polymers, such as type I collagen, possess good biocompatibility, water holding capacity, air permeability, and degradability, and can be used in wound repair. However, due to the persistent oxidative stress in the wound area, the migration and proliferation of fibroblasts might be suppressed, leading to poor healing. Thus, collagen-containing scaffolds are not suitable for accelerated wound healing. Antioxidant N-acetyl cysteine (NAC) is known to reduce the reactive oxygen species (ROS) and has been widely used in the clinic. Theoretically, the carboxyl group of NAC allows loading of graphene oxide (GO) for sustained release and may also enhance the mechanical properties of the collagen scaffold, making it a better wound-dressing material. Herein, we demonstrated an innovative approach for a potential skin-regenerating hybrid membrane using GO incorporated with collagen I and NAC (N-Col-GO) capable of continuously releasing antioxidant NAC. Methods: The mechanical stability, water holding capacity, and biocompatibility of the N-Col-GO hybrid membrane were measured in vitro. A 20 mm rat full-skin defect model was created to evaluate the repair efficiency of the N-Col-GO hybrid membrane. The vascularization and scar-related genes in the wound area were also examined. Results: Compared to the Col only scaffold, N-Col-GO hybrid membrane exhibited a better mechanical property, stronger water retention capacity, and slower NAC release ability, which likely promote fibroblast migration and proliferation. Treatment with the N-Col-GO hybrid membrane in the rat wound model showed complete healing 14 days after application which was 22% faster than the control group. HE and Masson staining confirmed faster collagen deposition and better epithelization, while CD31 staining revealed a noticeable increase of vascularization. Furthermore, Rt-PCR demonstrated decreased mRNA expression of profibrotic and overexpression of anti-fibrotic factors indicative of the anti-scar effect. Conclusion: These findings suggest that N-Col-GO drug release hybrid membrane serves as a better platform for scarless skin regeneration.

Development of an Accurate and Proactive Immunomodulatory Strategy to Improve Bone Substitute Material-Mediated Osteogenesis and Angiogenesis

Background: Treatment of large bone defects represents a major clinical problem worldwide. Suitable bone substitute materials are commonly required to achieve successful bone regeneration, and much effort has been spent to optimize their chemical compositions, 3D architecture and mechanical properties. However, material-immune system interactions are increasingly being recognized as a crucial factor influencing regeneration. Here, we envisioned an accurate and proactive immunomodulation strategy via delivery of IL-4 (key regulator of macrophage polarization) to promote bone substitute material-mediated regeneration.

Methods: Four different IL-4 doses (0 ng, 10 ng, 50 ng and 100 ng) were delivered into rat large cranial bone defects at day 3 post-operation of decellularized bone matrix (DBM) material implantation, and the osteogenesis, angiogenesis and macrophage polarization were meticulously evaluated.

Results: Micro-CT analysis showed that immunomodulation with 10 ng IL-4 significantly outperformed the other groups in terms of new bone formation (1.23-5.05 fold) and vascularization (1.29-6.08 fold), achieving successful defect bridging and good vascularization at 12 weeks. Histological analysis at 7 and 14 days showed that the 10 ng group generated the most preferable M1/M2 macrophage polarization profile, resulting in a pro-healing microenvironment with more IL-10 and less TNF-α secretion, a reduced apoptosis level in tissues around the materials, and enhanced mesenchymal stem cell migration and osteogenic differentiation. Moreover, in vitro studies revealed that M1 macrophages facilitated mesenchymal stem cell migration, while M2 macrophages significantly increased cell survival, proliferation and osteogenic differentiation, explaining the in vivo findings.

Conclusions: Accurate immunomodulation via IL4 delivery significantly enhanced DBM-mediated osteogenesis and angiogenesis via the coordinated involvement of M1 and M2 macrophages, revealing the promise of this accurate and proactive immunomodulatory strategy for developing new bone substitute materials.