Characterization of oxidative stress status during diabetic bone healing

Application of extracellular vesicles in diabetic osteoporosis

As the population ages, the occurrence of osteoporosis is becoming more common. Diabetes mellitus is one of the factors in the development of osteoporosis. Compared with the general population, the incidence of osteoporosis is significantly higher in diabetic patients. Diabetic osteoporosis (DOP) is a metabolic bone disease characterized by abnormal bone tissue structure due to hyperglycemia and insulin resistance, reduced bone strength and increased risk of fractures. This is a complex mechanism that occurs at the cellular level due to factors such as blood vessels, inflammation, and hyperglycemia and insulin resistance. Although the application of some drugs in clinical practice can reduce the occurrence of DOP, the incidence of fractures caused by DOP is still very high. Extracellular vesicles (EVs) are a new communication mode between cells, which can transfer miRNAs and proteins from mother cells to target cells through membrane fusion, thereby regulating the function of target cells. In recent years, the role of EVs in the pathogenesis of DOP has been widely demonstrated. In this article, we first describe the changes in the bone microenvironment of osteoporosis. Second, we describe the pathogenesis of DOP. Finally, we summarize the research progress and challenges of EVs in DOP.

Role of Enzymic Antioxidants in Mediating Oxidative Stress and Contrasting Wound Healing Capabilities in Oral Mucosal/Skin Fibroblasts and Tissues

Unlike skin, oral mucosal wounds are characterized by rapid healing and minimal scarring, attributable to the "enhanced" healing properties of oral mucosal fibroblasts (OMFs). As oxidative stress is increasingly implicated in regulating wound healing outcomes, this study compared oxidative stress biomarker and enzymic antioxidant profiles between patient-matched oral mucosal/skin tissues and OMFs/skin fibroblasts (SFs) to determine whether superior oral mucosal antioxidant capabilities and reduced oxidative stress contributed to these preferential healing properties. Oral mucosa and skin exhibited similar patterns of oxidative protein damage and lipid peroxidation, localized within the lamina propria/dermis and oral/skin epithelia, respectively. SOD1, SOD2, SOD3 and catalase were primarily localized within epithelial tissues overall. However, SOD3 was also widespread within the lamina propria localized to OMFs, vasculature and the extracellular matrix. OMFs were further identified as being more resistant to reactive oxygen species (ROS) generation and oxidative DNA/protein damage than SFs. Despite histological evaluation suggesting that oral mucosa possessed higher SOD3 expression, this was not fully substantiated for all OMFs examined due to inter-patient donor variability. Such findings suggest that enzymic antioxidants have limited roles in mediating privileged wound healing responses in OMFs, implying that other non-enzymic antioxidants could be involved in protecting OMFs from oxidative stress overall.

Metformin suppresses Oxidative Stress induced by High Glucose via Activation of the Nrf2/HO-1 Signaling Pathway in Type 2 Diabetic Osteoporosis

BACKGROUND

Metformin (MET) is widely used as a first-line hypoglycemic agent for the treatment of type 2 diabetes mellitus (T2DM) and was also confirmed to have a therapeutic effect on type 2 diabetic osteoporosis (T2DOP). However, the potential mechanisms of MET in the treatment of T2DOP are unclear.

OBJECTIVE

To clarify the effect of MET in T2DOP and to explore the potential mechanism of MET in the treatment of T2DOP.

METHODS

In vitro, we used MC3T3-E1 cells to study the effects of MET on osteogenic differentiation and anti-oxidative stress injury in a high glucose (Glucose 25 mM) environment. In vivo, we directly used db/db mice as a T2DOP model and assessed the osteoprotective effects of MET by Micro CT and histological analysis.

RESULTS

In vitro, we found that MET increased ALP activity in MC3T3-E1 cells in a high-glucose environment, promoted the formation of bone mineralized nodules, and upregulated the expression of the osteogenesis-related transcription factors RUNX2, Osterix, and COL1A1-related genes. In addition, MET was able to reduce high glucose-induced reactive oxygen species (ROS) production. In studies on the underlying mechanisms, we found that MET activated the Nrf2/HO-1 signaling pathway and alleviated high-glucose-induced oxidative stress injury. In vivo results showed that MET reduced bone loss and bone microarchitecture destruction in db/db mice.

CONCLUSION

Our results suggest that MET can activate the Nrf2/HO-1 signaling pathway to regulate the inhibition of osteogenic differentiation induced by high glucose thereby protecting T2DOP.

Survival rate and peri-implant evaluation of immediately loaded dental implants in individuals with type 2 diabetes mellitus: a systematic review and meta-analysis

Objectives

To evaluate the survival rate, success rate, and peri-implant biological changes of immediately loaded dental implants (ILs) placed in type 2 diabetic patients (DM2).

Materials and methods

The present study was registered on PROSPERO and followed the PRISMA checklist. The search was performed by the first reviewer in January 2021. The electronic databases used were MEDLINE via PubMed, Cochrane, BVS, Web of Science, Scopus, LIVIVO, and gray literature. The risk of bias analysis was performed using an instrument from the Joanna Briggs Institute.

Results

A total of 3566 titles and abstracts were obtained. The qualitative synthesis included 7 studies, while the quantitative synthesis included 5 studies. The meta-analysis of IL in individuals with DM2 compared to nondiabetic individuals showed no significant difference among the groups regarding the survival rate of dental implants (RR = 1.00, 95% CI 0.96–1.04; p = 0.91; I² = 0%), even if the patient had poor glycemic control (RR = 1.08, 95% CI 0.87–1.33; p = 0.48; I² = 70%). Meta-analysis of marginal bone loss in IL compared to conventional loading in DM2 patients also showed no significant difference (mean difference =  − 0.08, 95% CI − 0.25–0.08; p = 0.33; I² = 83%).

Conclusions

Type 2 diabetes mellitus does not seem to be a risk factor for immediately loaded implants if the glycemic level is controlled, the oral hygiene is satisfactory, and the technical steps are strictly followed.

Clinical relevance

Rehabilitation in diabetic individuals is more common due to the highest prevalence of edentulism in this population. It is essential to establish appropriate protocols for loading dental implants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04154-6.

Differential SOD2 and GSTZ1 profiles contribute to contrasting dental pulp stem cell susceptibilities to oxidative damage and premature senescence

Background

Dental pulp stem cells (DPSCs) are increasingly being advocated as viable cell sources for regenerative medicine-based therapies. However, significant heterogeneity in DPSC expansion and multi-potency capabilities are well-established, attributed to contrasting telomere profiles and susceptibilities to replicative senescence. As DPSCs possess negligible human telomerase (hTERT) expression, we examined whether intrinsic differences in the susceptibilities of DPSC sub-populations to oxidative stress-induced biomolecular damage and premature senescence further contributed to this heterogeneity, via differential enzymic antioxidant capabilities between DPSCs.

Methods

DPSCs were isolated from human third molars by differential fibronectin adhesion, and positive mesenchymal (CD73/CD90/CD105) and negative hematopoietic (CD45) stem cell marker expression confirmed. Isolated sub-populations were expanded in H₂O₂ (0–200 μM) and established as high or low proliferative DPSCs, based on population doublings (PDs) and senescence (telomere lengths, SA-β-galactosidase, p53/p16^INK4a/p21^waf1/hTERT) marker detection. The impact of DPSC expansion on mesenchymal, embryonic, and neural crest marker expression was assessed, as were the susceptibilities of high and low proliferative DPSCs to oxidative DNA and protein damage by immunocytochemistry. Expression profiles for superoxide dismutases (SODs), catalase, and glutathione-related antioxidants were further compared between DPSC sub-populations by qRT-PCR, Western blotting and activity assays.

Results

High proliferative DPSCs underwent > 80PDs in culture and resisted H₂O₂₋induced senescence (50–76PDs). In contrast, low proliferative sub-populations exhibited accelerated senescence (4–32PDs), even in untreated controls (11-34PDs). While telomere lengths were largely unaffected, certain stem cell marker expression declined with H₂O₂ treatment and expansion. Elevated senescence susceptibilities in low proliferative DPSC (2–10PDs) were accompanied by increased oxidative damage, absent in high proliferative DPSCs until 45–60PDs. Increased SOD2/glutathione S-transferase ζ1 (GSTZ1) expression and SOD activities were identified in high proliferative DPSCs (10–25PDs), which declined during expansion. Low proliferative DPSCs (2–10PDs) exhibited inferior SOD, catalase and glutathione-related antioxidant expression/activities.

Conclusions

Significant variations exist in the susceptibilities of DPSC sub-populations to oxidative damage and premature senescence, contributed to by differential SOD2 and GSTZ1 profiles which maintain senescence-resistance/stemness properties in high proliferative DPSCs. Identification of superior antioxidant properties in high proliferative DPSCs enhances our understanding of DPSC biology and senescence, which may be exploited for selective sub-population screening/isolation from dental pulp tissues for regenerative medicine-based applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02209-9.

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.

Effect of gomisin A on osteoblast differentiation in high glucose-mediated oxidative stress

BACKGROUND

Gomisin A is a lignan isolated from the hexane of Schisandra chinensis fruit extract with antioxidant properties. Oxidative stress mediated by high glucose is one of the major complications of diabetes mellitus.

PURPOSE

This study investigates the role of gomisin A in osteoblast differentiation under high glucose-induced oxidative stress in MC3T3 E1 cells and determines its relationship with heme oxygenase-1 (HO-1) and mitochondrial biogenesis.

METHODS

MC3T3 E1 cells were treated by gomisin A following induced by high glucose levels and glucose oxidase to investigate the inhibitory effect of gomisin A against high glucose oxidative stress. Western blot analysis, alizarin red staining, alkaline phosphatase (ALP) activity, analysis of reactive oxygen species (ROS) and confocal microscopy were used to determine mitochondrial biogenesis, oxidative stress, osteoblast differentiation and mineralization. To analyze the role of HO-1, the MC3T3 E1 cells were treated with the HO-1 inhibitor zinc protoporphyrin IX (ZnPP).

RESULTS

Gomisin A enhanced the expression of HO-1, increased mitochondrial biogenesis factors (peroxisome proliferator-activated receptor gamma coactivator 1-alpha, nuclear respiratory factor-1, and mitochondrial transcription factor A), antioxidant enzymes (copper-zinc superoxide dismutases and manganese superoxide dismutase), osteoblast differentiation molecules (bone morphogenic protein-2/7, osteoprotegerin and Runt-related transcription factor-2) and mineralization by upregulation of ALP and alizarin red staining, which were decreased by ZnPP and high glucose oxidative stress. Similarly, gomisin A inhibited ROS which was increased by ZnPP and the high glucose-mediated oxidative stress.

CONCLUSIONS

The findings demonstrated the antioxidative effects of gomisin A, and its role in mitochondrial biogenesis and osteoblast differentiation. It potentially regulated osteoblast differentiation under high glucose-induced oxidative stress via upregulation of HO-1 and maintenance of mitochondrial homeostasis. Thus, gomisin A may represent a potential therapeutic agent for prevention of bone fragility fractures and implant failure triggered by diabetes.

Role of Nrf2 in Fracture Healing: Clinical Aspects of Oxidative Stress

Fracture healing is a natural process that recapitulates embryonic skeletal development. In the early phase after fracture, reactive oxygen species (ROS) are produced under inflammatory and ischemic conditions due to vessel injury and soft tissue damage, leading to cell death. Usually, such damage during the course of fracture healing can be largely prevented by protective mechanisms and functions of antioxidant enzymes. However, intrinsic oxidative stress can cause excessive toxic radicals, resulting in irreversible damage to cells associated with bone repair during the fracture healing process. Clinically, patients with type-2 diabetes mellitus, osteoporosis, habitual drinkers, or heavy smokers are at risk of impaired fracture healing due to elevated oxidative stress. Although increased levels of oxidative stress markers upon fracture and effects of antioxidants on fracture healing have been reported, a detailed understanding of what causes impaired fracture healing under intrinsic conditions of oxidative stress is lacking. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been identified as a key transcriptional regulator of the expression of antioxidants and detoxifying enzymes. It further not only plays a crucial role in preventing degenerative diseases in multiple organs, but also during fracture healing. This narrative review evaluates the influence of intrinsic oxidative stress on fracture healing and sheds new light on the intriguing role of Nrf2 during bone regeneration in pathological fractures.

The Impact of Type 2 Diabetes on Bone Fracture Healing

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease known by the presence of elevated blood glucose levels. Nowadays, it is perceived as a worldwide epidemic, with a very high socioeconomic impact on public health. Many are the complications caused by this chronic disorder, including a negative impact on the cardiovascular system, kidneys, eyes, muscle, blood vessels, and nervous system. Recently, there has been increasing evidence suggesting that T2DM also adversely affects the skeletal system, causing detrimental bone effects such as bone quality deterioration, loss of bone strength, increased fracture risk, and impaired bone healing. Nevertheless, the precise mechanisms by which T2DM causes detrimental effects on bone tissue are still elusive and remain poorly studied. The aim of this review was to synthesize current knowledge on the different factors influencing the impairment of bone fracture healing under T2DM conditions. Here, we discuss new approaches used in recent studies to unveil the mechanisms and fill the existing gaps in the scientific understanding of the relationship between T2DM, bone tissue, and bone fracture healing.

Involvement of FAK-mediated BMP-2/Smad pathway in mediating osteoblast adhesion and differentiation on nano-HA/chitosan composite coated titanium implant under diabetic conditions

Nanophase HA/CS composite coated porous titanium implant exhibited superior biological performance under diabetic conditions compared to pure Ti.

Cerebral Oxidative Stress and Microvasculature Defects in TNF-α Expressing Transgenic and Porphyromonas gingivalis-Infected ApoE-/- Mice

The polymicrobial dysbiotic subgingival biofilm microbes associated with periodontal disease appear to contribute to developing pathologies in distal body sites, including the brain. This study examined oxidative stress, in the form of increased protein carbonylation and oxidative protein damage, in the tumor necrosis factor-α (TNF-α) transgenic mouse that models inflammatory TNF-α excess during bacterial infection; and in the apolipoprotein knockout (ApoE-/-) mouse brains, following Porphyromonas gingivalis gingival monoinfection. Following 2,4-dinitrophenylhydrazine derivatization, carbonyl groups were detected in frontal lobe brain tissue lysates by immunoblotting and immunohistochemical analysis of fixed tissue sections from the frontotemporal lobe and the hippocampus. Immunoblot analysis confirmed the presence of variable carbonyl content and oxidative protein damage in all lysates, with TNF-α transgenic blots exhibiting increased protein carbonyl content, with consistently prominent bands at 25 kDa (p = 0.0001), 43 kDa, and 68 kDa, over wild-type mice. Compared to sham-infected ApoE-/- mouse blots, P. gingivalis-infected brain tissue blots demonstrated the greatest detectable protein carbonyl content overall, with numerous prominent bands at 25 kDa (p = 0.001) and 43 kDa (p = 0.0001) and an exclusive band to this group between 30-43 kDa* (p = 0.0001). In addition, marked immunostaining was detected exclusively in the microvasculature in P. gingivalis-infected hippocampal tissue sections, compared to sham-infected, wild-type, and TNF-α transgenic mice. This study revealed that the hippocampal microvascular structure of P. gingivalis-infected ApoE-/- mice possesses elevated oxidative stress levels, resulting in the associated tight junction proteins being susceptible to increased oxidative/proteolytic degradation, leading to a loss of functional integrity.

Brown rice (Oryza sativa L. cv. Hiami) extract promotes cellular growth by upregulation of GH and IGF-1 expression and secretion

The effects of the ethanolic extract of brown rice (BRE, Oryza sativa L. cv. Hiami) on cellular growth were investigated. Gene expression analysis by qPCR showed that the expression of the mRNA expressions of growth hormone (GH) and insulin-like growth factor (IGF)-1 genes was significantly induced in cells stimulated with BRE compared with controls, and the effects were dose dependent. In addition, the hormone secretion of GH and IGF-1 was significantly induced in GH3 and HepG2 cells stimulated with BRE in line with the qPCR results. Collectively, these results suggest that BRE induces the expression and secretion of GH and IGF-1 in vitro; therefore, application may promote cellular growth.

Insulin improves osteogenesis of titanium implants under diabetic conditions by inhibiting reactive oxygen species overproduction via the PI3K-Akt pathway

Clinical evidence indicates that insulin therapy improves implant survival rates in diabetic patients; however, the mechanisms responsible for this effect are unknown. Here, we test if insulin exerts anti-oxidative effects, thereby improving diabetes-associated impaired osteoblast behavior on titanium implants. To test this hypothesis, we cultured primary rabbit osteoblasts in the presence of titanium implants and studied the impact of treatment with normal serum (NS), diabetic serum (DS), DS + insulin, DS + tempol (a superoxide dismutase mimetic), DS + insulin + tempol, and DS + insulin + wortmannin. We analyzed cell function, apoptosis, and reactive oxygen species (ROS) production in osteoblasts following the various treatments. Treatment with DS induced osteoblast dysfunction, evidenced by impaired cell attachment and morphology, decreased cell proliferation and ALP activity, and decreased expression of osteogenesis-related genes. We also observed a significant increase in apoptosis. Importantly, treatment with DS resulted in increased production of ROS in osteoblasts. In contrast, treatment with insulin inhibited ROS production, alleviated cell dysfunction, and decreased apoptosis of osteoblasts on the implants. Scavenging ROS with tempol also attenuated cell dysfunction. Compared to insulin treatment alone, the combination of insulin and tempol failed to further improve osteoblast functional recovery. Moreover, the anti-oxidative and pro-osteogenic effects afforded by insulin were almost completely abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. These results demonstrate, for the first time, that insulin treatment alleviates the impaired osteogenesis of titanium implants under diabetic conditions by inhibiting ROS overproduction via a PI3K/Akt-dependent mechanism. Both the anti-oxidative and metabolic properties of insulin should make it a viable therapeutic option to combat diabetic implant failure.

10-Shogaol, an antioxidant from Zingiber officinale for skin cell proliferation and migration enhancer

In this work, one of Zingiber officinale components, 10-shogaol, was tested with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, metal chelating ability, and reducing power to show antioxidant activity. 10-Shogaol promoted human normal epidermal keratinocytes and dermal fibroblasts cell growths. 10-Shogaol enhanced growth factor production in transforming growth factor-β (TGF-β), platelet derived growth factor-αβ (PDGF-αβ) and vascular endothelial growth factors (VEGF) of both cells. In the in vitro wound healing assay for 12 or 24 h, with 10-shogaol, the fibroblasts and keratinocytes migrated more rapidly than the vehicle control group. Thus, this study substantiates the target compound, 10-shogaol, as an antioxidant for human skin cell growth and a migration enhancer with potential to be a novel wound repair agent.

Cellular dysfunction in diabetes as maladaptive response to mitochondrial oxidative stress

Oxidative stress has been implicated in diabetes long-term complications. In this paper, we summarize the growing evidence suggesting that hyperglycemia-induced overproduction of superoxide by mitochondrial electron transport chain triggers a maladaptive response by affecting several metabolic and signaling pathways involved in the pathophysiology of cellular dysfunction and diabetic complications. In particular, it is our goal to describe physiological mechanisms underlying the mitochondrial free radical production and regulation to explain the oxidative stress derived from a high intracellular glucose concentration and the resulting maladaptive response that leads to a cellular dysfunction and pathological state. Finally, we outline potential therapies for diabetes focused to the prevention of mitochondrial oxidative damage.