Zinc supplementation inhibits the increase in osteoclastogenesis and decrease in osteoblastogenesis in streptozotocin-induced diabetic rats

Multifunctional Bionic Periosteum with Ion Sustained-Release for Bone Regeneration

In this study, a novel bionic periosteum (BP)-bioactive glass fiber membrane (BGFM) is designed. The introduction of magnesium ion (Mg2+) and zinc ion (Zn2+) change the phase separation during the electrospinning (ES) jet stretching process. The fiber's pore structure transitions from connected to closed pores, resulting in a decrease in the rapid release of metal ions while also improving degradation via reducing filling quality. Additionally, the introduction of magnesium (Mg) and zinc (Zn) lead to the formation of negative charged tetrahedral units (MgO4 2- and ZnO4 2-) in the glass network. These units effectively trap positive charged metal ions, further inhibiting ion release. In vitro experiments reveal that the deigned bionic periosteum regulates the polarization of macrophages toward M2 type, thereby establishing a conducive immune environment for osteogenic differentiation. Bioinformatics analysis indicate that BP enhanced bone repair via the JAK-STAT signaling pathway. The slow release of metal ions from the bionic periosteum can directly enhance osteogenic differentiation and vascularization, thereby accelerating bone regeneration. Finally, the bionic periosteum exhibits remarkable capabilities in angiogenesis and osteogenesis, demonstrating its potential for bone repair in a rat calvarial defect model.

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.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Protective effect of zinc supplementation on tricalcium phosphate particles-induced inflammatory osteolysis in mice

Zinc (Zn), an essential trace element, can stimulate bone formation and inhibit osteoclastic bone resorption, which controls the growth and maintenance of bone. However, the effect of Zn supplementation on tricalcium phosphate (TCP) wear particles-induced osteolysis remains unknown. Here, we doped Zn into TCP particles (ZnTCP), and explore the protective effects of Zn on TCP particles-induced osteolysis in vivo. TCP particles and ZnTCP particles were embedded under the periosteum around the middle suture of the mouse calvaria. After 2 weeks, blood, the periosteal tissue, and the calvaria were collected to determine serum levels of Zn and osteocalcin, pro-inflammatory cytokines, bone biochemical markers, osteoclastogenesis and bone resorption area, and to explain its mechanism. Data revealed that Zn significantly prevented TCP particles-induced osteoclastogenesis and bone loss, and increased bone turnover. The Zn supplement remarkably suppressed the release of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Immunoblotting demonstrated that Zn alleviated expression levels of ER stress-related proteins such as glucose-regulated protein 78 (GRP78), PKR-like ER kinase (PERK), phospho-PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α), phospho-eIF2α (p-eIF2α), activating transcription factor 4 (ATF4), inositol-requiring enzyme 1α (IRE1-α) and transcription factor X-box binding protein spliced (XBP1s), leading to decreasing the ratios of p-PERK/PERK and p-eIF2α/eIF2α. Taken together, Zn supplementation strongly prevents TCP particles-induced periprosthetic osteolysis via inhibition of the ER stress pathway, and it may be a novel therapeutic approach for the treatment of aseptic prosthesis loosening.

Melatonin inhibits osteoclastogenesis via RANKL/OPG suppression mediated by Rev-Erbα in osteoblasts

Diabetic osteoporosis is secondary osteoporosis and a serious complication of diabetes with a high incidence rate and poor prognosis. The specific mechanism of diabetic osteoporosis is unclear, and prevention and treatment options are limited. Recently, melatonin has been found to prevent and treat diabetic osteoporosis. Herein, we investigated the mechanism whereby melatonin inhibits osteoclastogenesis and identified a new target for osteoporosis treatment. We established an in vitro osteoblast–osteoclast co‐culture system as a diabetic osteoporosis model. Osteoclastogenesis was determined using tartrate‐resistant acid phosphatase staining and cathepsin K expression. Real‐time PCR was used to ascertain expression of microRNA mir‐882, targeting Rev‐Erbα. Western blotting was performed to detect the expression of Rev‐Erbα, receptor activator of NF‐kB ligand (RANKL), and osteoprotegerin (OPG), and ELISA was utilized to analyse the secreted form of RANKL. High glucose promoted osteoclastogenesis and elevated the RANKL/OPG ratio in osteoblasts, while melatonin reversed these effects. High glucose inhibited Rev‐Erbα expression, while melatonin promoted its expression. Conversely, high glucose promoted mir‐882 expression, while melatonin inhibited it. We infer that melatonin inhibits RANKL expression in osteoblasts via the mir‐882/Rev‐Erbα axis, thus inhibiting osteoclastogenesis. Our findings provide insights into diabetic osteoporosis and identify a new therapeutic target for osteoporosis.

Formononetin attenuates osteoclast differentiation and calcium loss by mediating transcription factor AP-1 in type I diabetic mice

Formononetin (FMN) has been reported as a prospective antiosteoporotic medication. However, the antiosteoporotic properties of FMN are still unclear in a mouse model with diabetes-induced osteoporosis. An osteoporotic or osteopenic mouse model with type I diabetes mellitus (T1DM) was established using streptozotocin (40 mg/kg) injection for 5 consecutive days. After 12 weeks with FMN intragastric administration (0.5, 5, 20 mg/kg), the antiosteoporotic activity of FMN was evaluated in T1DM mice. FMN supplementation effectively improves Ca excretion and trabecular bone degeneration and impedes osteoclast differentiation and function to attenuate hyperglycemia-induced bone deterioration. In addition, FMN inhibited activating protein 1 (AP-1) and osteoclast-specific gene expression, Nfatc1, Ctsk, and TRAP. The administration of FMN has a beneficial effect to attenuate hyperglycemia-induced bone deteriorations, including osteoclastogenesis, trabecular bone, and Ca loss. Our study provided a prospective medication for the treatment of T1DM-related osteopenia or osteoporosis with FMN.

Role of nitric oxide in type 1 diabetes-induced osteoporosis

Type 1 diabetes (T1D)-induced osteoporosis is characterized by decreased bone mineral density, bone quality, rate of bone healing, bone formation, and increased bone resorption. Patients with T1D have a 2-7-fold higher risk of osteoporotic fracture. The mechanisms leading to increased risk of osteoporotic fracture in T1D include insulin deficiency, hyperglycemia, insulin resistance, lower insulin-like growth factor-1, hyperglycemia-induced oxidative stress, and inflammation. In addition, a higher probability of falling, kidney dysfunction, weakened vision, and neuropathy indirectly increase the risk of osteoporotic fracture in T1D patients. Decreased nitric oxide (NO) bioavailability contributes to the pathophysiology of T1D-induced osteoporotic fracture. This review discusses the role of NO in osteoblast-mediated bone formation and osteoclast-mediated bone resorption in T1D. In addition, the mechanisms involved in reduced NO bioavailability and activity in type 1 diabetic bones as well as NO-based therapy for T1D-induced osteoporosis are summarized. Available data indicates that lower NO bioavailability in diabetic bones is due to disruption of phosphatidylinositol 3‑kinase/protein kinase B/endothelial NO synthases and NO/cyclic guanosine monophosphate/protein kinase G signaling pathways. Thus, NO bioavailability may be boosted directly or indirectly by NO donors. As NO donors with NO-like effects in the bone, inorganic nitrate and nitrite can potentially be used as novel therapeutic agents for T1D-induced osteoporosis. Inorganic nitrites and nitrates can decrease the risk for osteoporotic fracture probably directly by decreasing osteoclast activity, decreasing fat accumulation in the marrow cavity, increasing osteoblast activity, and increasing bone perfusion or indirectly, by improving hyperglycemia, insulin resistance, and reducing body weight.

A Correlation Between Intracellular Zinc Content and Osteosarcoma

Zinc is a trace element in human body involved in many biological processes. It is critical for cell growth and acts as a cofactor for the structure and function of a wide range of cellular proteins such as enzymes. Mounting evidence has shown the involvement of intracellular zinc in the bone-related biological processes such as bone growth, homeostasis, and regeneration; however, the molecular mechanism(s) whereby zinc impels tumorigenesis in bone remains largely unexplored. In this article, selective outline related to the content of intracellular zinc in osteosarcoma cells was provided, and its correlation with signaling molecules that are activated and consequently guide the cells toward tumorigenesis or osteogenesis was discussed. Based on preclinical and clinical evidence, dysregulation of zinc homeostasis, both at intracellular and tissue level, has the main role in the pathogenesis of osteosarcoma. Based on the intracellular zinc content, this element could have a direct role in the dynamics of bone cell transformation and tumor development and play an indirect role in the modulation of the inflammatory and pro/antitumorigenic responses in immune cells. In this context, zinc transporters and the proteins containing zinc domain are regulated by the availability of zinc, playing a crucial role in bone cell transformation and differentiation. According to recent studies, it seems that intracellular zinc levels could be considered as an early prognosis marker. Besides, identification and targeting of zinc-dependent signaling molecules could tilt the balance of life and death toward the latter in chemoresistant malignant cells and may pave a way for designing of the novel osteosarcoma treatment strategies.

Type 1 diabetic Akita mice have low bone mass and impaired fracture healing

Type 1 diabetes (T1DM) impairs bone formation and fracture healing in humans. Akita mice carry a mutation in one allele of the insulin-2 (Ins2) gene, which leads to pancreatic beta cell dysfunction and hyperglycemia by 5-6 weeks age. We hypothesized that T1DM in Akita mice is associated with decreased bone mass, weaker bones, and impaired fracture healing. Ins2 ± (Akita) and wildtype (WT) males were subjected to femur fracture at 18-weeks age and healing assessed 3-21 days post-fracture. Non-fractured left femurs were assessed for morphology (microCT) and strength (bending or torsion) at 19-21 weeks age. Fractured right femurs were assessed for callus mechanics (torsion), morphology and composition (microCT and histology) and gene expression (qPCR). Both Akita and WT mice gained weight from 3 to 18 weeks age, but Akita mice weighed less starting at 5 weeks (-5.2%, p < 0.05). At 18-20 weeks age Akita mice had reduced serum osteocalcin (-30%), cortical bone area (-16%), and thickness (-17%) compared to WT, as well as reduced cancellous BV/TV (-39%), trabecular thickness (-23%) and vBMD (-31%). Mechanical testing of non-fractured femurs showed decreased structural (stiffness, ultimate load) and material (ultimate stress) properties of Akita bones. At 14 and 21 days post fracture Akita mice had a significantly smaller callus than WT mice (~30%), with less cartilage and bone area. Assessment of torsional strength showed a weaker callus in Akita mice with lower stiffness (-42%), maximum torque (-44%) and work to fracture (-44%). In summary, cortical and cancellous bone mass were reduced in Akita mice, with lower bone mechanical properties. Fracture healing in Akita mice was impaired by T1DM, with a smaller, weaker fracture callus due to decreased cartilage and bone formation. In conclusion, the Akita mouse mimics some of the skeletal features of T1DM in humans, including osteopenia and impaired fracture healing, and may be useful to test interventions.

Is Zinc an Important Trace Element on Bone-Related Diseases and Complications? A Meta-analysis and Systematic Review from Serum Level, Dietary Intake, and Supplementation Aspects

Bone-related diseases are very common problems, especially in the elderly population. Zinc takes part in the growth and maintenance of healthy bones. This meta-analysis aims to evaluate the effects of zinc supplementation or dietary zinc intake on serum zinc levels and bone turnover markers. A systematical research was performed with 2899 articles in PubMed, WoS, and Scopus for relevant articles in English which have mean/standard deviation values of serum zinc levels, dietary zinc intake/zinc supplementation (mg/day), and bone turnover markers up to February 2020. In the overall analysis, serum zinc level was significantly lower in patients with osteoporosis compared with controls (p 0.0002). Dietary zinc intake decreased in the fracture group compared with controls according to subgroup analysis patients with fracture (p 0.02). Zinc supplementation was effective on the femoral neck (p < 0.0001) and lumbar spine (p 0.05) bone mineral density (BMD). In the correlation analysis of the data obtained from all of the included studies, serum osteocalcin (p 0.0106, r - 0.9148) correlated with serum zinc level. In conclusion, serum zinc level and dietary zinc intake could have an essential role in preventing osteoporosis. Zinc supplementation might improve bone turnover markers for bone formation such as serum osteocalcin and serum alkaline phosphatase and also, BMD at the site of the femoral neck.

IGF-1R/β-catenin signaling axis is implicated in streptozotocin exacerbating bone impairment in ovariectomized rats

OBJECTIVE

The aim of this study was to investigate the role of the insulin-like growth factor-1 receptor (IGF-1R)/β-catenin signaling axis in bone impairment induced by hyperglycemia in ovariectomized rats.

METHODS

Rats were divided into four groups. The sham group received sham operation and a single intraperitoneal administration of vehicle. The ovariectomy (OVX) group was subjected to bilateral OVX and vehicle injection. The streptozotocin (STZ) group received sham operation and a single STZ injection to induce hyperglycemia. The OVX + STZ group received bilateral OVX and a single STZ injection. Dual-energy X-ray absorptiometry measurement, bone biomechanics test, micro-computed tomography scan, and hematoxylin-eosin staining were performed to evaluate bone alteration in this model. The expression of relevant signals including IGF-1R, glycogen synthase kinase-3β (GSK-3β), and β-catenin were examined by quantitative real-time polymerase chain reaction and western blot.

RESULTS

The OVX, STZ, and OVX + STZ groups induced bone loss, attenuated bone strength, and impaired microarchitecture compared with the sham group, respectively. Compared with OVX, more serious bone damage was found in the OVX + STZ group, which showed enhanced phosphorylation of IGF-1R, GSK-3β, and β-catenin.

CONCLUSION

OVX plus STZ induced more serious bone impairment than OVX alone, which involves the IGF-1R/β-catenin signaling axis in the pathogenesis. This may provide a potential target for treatment of postmenopausal diabetic osteoporosis.

MiR-1908/EXO1 and MiR-203a/FOS, regulated by scd1, are associated with fracture risk and bone health in postmenopausal diabetic women

BACKGROUND

Stearoyl-coenzyme A desaturase-1 (SCD1) can inhibit the development of diabetic bone disease by promoting osteogenesis. In this study, we examined whether this regulation by SCD1 is achieved by regulating the expression of related miRNAs.

METHODS

SCD1 expression levels were observed in human bone-marrow mesenchymal stem cells (BM-MSCs) of patients with type 2 diabetes mellitus (T2DM), and the effect of SCD1 on osteogenesis was observed in human adipose-derived MSCs transfected with the SCD1 lentiviral system. We designed a bioinformatics prediction model to select important differentially expressed miRNAs, and established protein-protein interaction and miRNA-mRNA networks. miRNAs and mRNAs were extracted and their differential expression was detected. The SCD1-miRNA-mRNA network was validated.

FINDINGS

SCD1 expression in bone marrow was downregulated in patients with T2DM and low-energy fracture, and SCD1 expression promotes BM-MSC osteogenic differentiation. The predictors in the nomogram were seven microRNAs, including hsa-miR-1908 and hsa-miR-203a. SCD1 inhibited the expression of CDKN1A and FOS, but promoted the expression of EXO1 and PLS1. miR-1908 was a regulator of EXO1 expression, and miR-203a was a regulator of FOS expression.

INTERPRETATION

The regulation of BM-MSCs by SCD1 is a necessary condition for osteogenesis through the miR-203a/FOS and miR-1908/EXO1 regulatory pathways.

SERS activity and spectroscopic properties of Zn and ZnO nanostructures obtained by electrochemical and green chemistry methods for applications in biology and medicine

This work evaluates the ability of homogeneous, stable, and pure zinc oxide nanoparticles (ZnONPs-GS) synthesized by “green chemistry” for the selective detection of four neurotransmitters present in body fluids and promotion of the SERS effect.

Zinc supplements and bone health: The role of the RANKL-RANK axis as a therapeutic target

BACKGROUND

To this day, empirical data suggests that zinc has important roles in matrix synthesis, bone turnover, and mineralization and its beneficial effects on bone could be mediated through different mechanisms. The influence of zinc on bone turnover could be facilitated via regulating RANKL/RANK/OPG pathway in bone tissue. Therefore, the aim of the study was to conduct a review to investigate the possible effect of the zinc mediated bone remodeling via RANKL/RANK/OPG pathway.

METHODS

A comprehensive systematic search was performed in MEDLINE/PubMed, Cochrane Library, SCOPUS, and Google Scholar to explore the studies investigating the effect of zinc as a bone remodeling factor via RANKL/RANK/OPG pathway regulation. Subsequently, the details of the pathway and the impact of zinc supplements on RANKL/RANK/OPG pathway regulation were discussed.

RESULTS

The pathway could play an important role in bone remodeling and any imbalance between RANKL/RANK/OPG components could lead to extreme bone resorption. Although the outcomes of some studies are equivocal, it is evident that zinc possesses protective properties against bone loss by regulating the RANKL/RANK/OPG pathway. There are several experiments where zinc supplementation resulted in upregulation of OPG expression or decreases RANKL level. However, the results of some studies oppose this.

CONCLUSION

It is likely that sufficient zinc intake will elicit positive effects on bone health by RANKL/RANK/OPG regulation. Although the outcomes of a few studies are equivocal, it seems that zinc can exert the protective properties against bone loss by suppressing osteoclastogenesis via downregulation of RANKL/RANK. Additionally, there are several experiments where zinc supplementation resulted in upregulation of OPG expression. However, the results of limited studies oppose this. Therefore, aside from the positive role zinc possesses in preserving bone mass, further effects of zinc in RANKL/RANK/OPG system requires further animal/human studies.

Regulation of insulin resistance by targeting the insulin-like growth factor 1 receptor with microRNA-122-5p in hepatic cells

Insulin resistance (IR) is a common etiology of type 2 diabetes (T2D) defined by a state of decreased reactivity to insulin in multiple organs, such as the liver. This study aims to investigate how microRNA-122-5p (miR-122) regulates the hepatic IR in vitro. We first found that the miR-122 level was upregulated in the liver of rats fed with a high-fat diet and injected with streptozotocin (T2D rats), while the expression level of insulin-like growth factor 1 receptor (IGF-1R), a potential target of miR-122, was downregulated in the diabetic liver. In vitro, glucosamine-induced IR was introduced in HepG2 hepatic cells, and the levels of miR-122 and IGF-1R were further assessed. An increase of miR-122 level and a decrease of IGF-IR level were observed in IR hepatic cells, which was the same as that in the diabetic liver. Results of the luciferase reporter assay validated IGF-1R as a direct target of miR-122. Moreover, in IR HepG2 cells, antagonizing miR-122 with its specific inhibitor enhanced glucose uptake and suppressed the expression of glucose 6-phosphatase and phosphoenolpyruvate carboxykinase, two key enzymes in regulating gluconeogenesis. Such alterations induced by the miR-122 inhibitor in IR hepatic cells were impaired when IGF-1R was simultaneously knocked down. In addition, the PI3K/Akt pathway was deactivated in IR cells, and then reactivated with miR-122 inhibitor transfection. In conclusion, our study demonstrates that miR-122 is able to regulate IR in hepatic cells by targeting IGF-1R.

Hyperglycemia Induces Osteoclastogenesis and Bone Destruction Through the Activation of Ca2+/Calmodulin-Dependent Protein Kinase II

Hyperglycemia induces osteoclastogenesis and bone resorption through complicated, undefined mechanisms. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) promotes osteoclastogenesis, and could be activated by hyperglycemia. Here, we investigated whether CaMKII is involved in hyperglycemia-induced osteoclastogenesis and subsequent bone resorption. Osteoclast formation, bone resorption, CaMKII expression and phosphorylation were measured under high glucose in vitro and in streptozotocin-induced hyperglycemia rats with or without CaMKII inhibitor KN93. The results showed that 25 mmol/L high glucose in vitro promoted cathepsin K and tartrate-resistant acid phosphatase expression (p < 0.05) and osteoclast formation (p < 0.01) associated with enhancing β isoform expression (p < 0.05) and CaMKII phosphorylation (p < 0.001). Hyperglycemia promoted the formation of osteoclasts and resorption of trabecular and alveolar bone, and inhibited sizes of femur and mandible associated with enhanced CaMKII phosphorylation (p < 0.001) in rats. All these changes could be alleviated by KN93. These findings imply that CaMKII participates not only in hyperglycemia-induced osteoclastogenesis and subsequent bone resorption, but also in the hyperglycemia-induced developmental inhibition of bone.

Enhanced cellular osteogenic differentiation on Zn-containing bioglass incorporated TiO2 nanorod films

Surface nanotopography and bioactive ions have been considered to play critical roles on the interactions of biomaterials with cells. In this study, a TiO₂ nanorod film incorporated with Zn-containing bioactive glass (TiO₂/Zn-BG) was prepared on tantalum substrate, trying to evaluate the synergistic effects of nanotopograpgy and bioactive ions to promote cellular osteogenic differentiation activity. The expression of osteogenic-related genes, ALP as well as the ECM mineralization on TiO₂/Zn-BG film were significantly upregulated compared to that of the film without TiO₂ nanorod nanostructure (Zn-BG) or without Zn (TiO₂/BG). Moreover, a much low Zn²⁺ release level on TiO₂/Zn-BG film was beneficial to promote the osteogenesis, which could be ascribed to that a semi-closed space established by TiO₂ nanorods with adhered cells provided an appropriate micro-environment that facilitated Zn²⁺ adsorption.

The beneficial effects of Zn on Akt-mediated insulin and cell survival signaling pathways in diabetes

Zinc is one of the essential trace elements and participates in numerous physiological processes. Abnormalities in zinc homeostasis often result in the pathogenesis of various chronic metabolic disorders, such as diabetes and its complications. Zinc has insulin-mimetic and anti-diabetic effects and deficiency has been shown to aggravate diabetes-induced oxidative stress and tissue injury in diabetic rodent models and human subjects with diabetes. Akt signaling pathway plays a central role in insulin-stimulated glucose metabolism and cell survival. Anti-diabetic effects of zinc are largely dependent on the activation of Akt signaling. Zn is also an inducer of metallothionein that plays important role in anti-oxidative stress and damage. However, the exact molecular mechanisms underlying zinc-induced activation of Akt signaling pathway remains to be elucidated. This review summarizes the recent advances in deciphering the possible mechanisms of zinc on Akt-mediated insulin and cell survival signaling pathways in diabetes conditions. Insights into the effects of zinc on epigenetic regulation and autophagy in diabetic nephropathy are also discussed in the latter part of this review.

Zinc Inhibits Collagenolysis by Cathepsin K and Matrix Metalloproteinases in Demineralized Dentin Matrix

The enzymatic degradation of dentin organic matrix occurs via both the action of matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs). Zinc can prevent collagen hydrolysis by MMPs. However, its effect on the activity of dentin-bound CCs is not known. The aim of this study was to investigate the effect of zinc on matrix-bound cathepsin K and MMP activity in dentin. Completely demineralized dentin beams were divided into test groups (n = 9) and incubated at 37°C in an incubation media (1 mL) containing ZnCl2 of 0.02 (physiological level, control), 0.2, 0.5, 1, 5, 10, 20, 30, or 40 mM. The dry mass changes of the beams were determined, and incubation media were analyzed for cathepsin K- and MMP-specific collagen degradation end products - CTX (C-terminal cross-linked telopeptide of type I collagen) and ICTP (cross-linked carboxy-terminal telopeptide of type I collagen) - at 1, 3, and 7 days of incubation. The mass loss of the beams decreased when the zinc level in the incubation media was ≥5 mM (p < 0.05). The release of liberated collagen degradation telopeptides decreased in accordance with the decrease in the mass loss rates of the beams. Cathepsin K-induced dentin collagen degradation can be strongly inhibited by zinc. Zinc levels of ≥5 mM can be considered as a reliable threshold for the stabilization of dentin matrices.

Zinc-Containing Hydroxyapatite Enhances Cold-Light-Activated Tooth Bleaching Treatment In Vitro

Cold-light bleaching treatment has grown to be a popular tooth whitening procedure in recent years, but its side effect of dental enamel demineralization is a widespread problem. The aim of this study was to synthesize zinc-substituted hydroxyapatite as an effective biomaterial to inhibit demineralization or increase remineralization. We synthesized zinc-substituted hydroxyapatite containing different zinc concentrations and analysed the product using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and energy dispersive spectrometer (EDS). The biological assessment of Zn-HA was conducted by CCK-8 assay and bacterial inhibition tests. pH cycling was performed to estimate the effect of Zn-HA on the enamel surface after cold-light bleaching treatment. The XRD, FTIR, and EDS results illustrated that zinc ions and hydroxyapatite combined in two forms: (1) Zn²⁺ absorbed on the surface of HA crystal and (2) Zn²⁺ incorporated into the lattice of HA. The results indicated that 2% Zn-HA, 4% Zn-HA, and 8% Zn-HA effectively inhibited the growth of bacteria yet showed poor biocompatibility, whereas 1% Zn-HA positively affected osteoblast proliferation. The XRD and scanning electron microscopy (SEM) results showed that the use of Zn-HA in pH cycling is obviously beneficial for enamel remineralization. Zinc-substituted hydroxyapatite could be a promising biomaterial for use in cold-light bleaching to prevent enamel demineralization.

Effect of Resveratrol on Critical-Sized Calvarial Defects of Diabetic Rats: Histometric and Gene Expression Analysis

PURPOSE

This study investigated the influence of resveratrol (RESV) on the repair of bone critical defects in calvaria of animals with induced diabetes mellitus (DM).

MATERIAL AND METHODS

One hundred rats were divided into 5 groups: induced DM + RESV administration (DM + RESV; n = 20); induced DM plus placebo solution administration (DM + PLAC; n = 20); induced DM plus insulin therapy (DM + INS; n = 20); induced DM plus administration of RES and INS (DM + RESV + INS; n = 20); and nondiabetic controls (NDM; n = 20). DM was induced by intraperitoneal injection of streptozotocin 50 mg/kg 3 days before the surgical procedures. Two critical calvarial defects were created in each animal at the start of the study (day 0). Treatments were administered from day 0 to day 30 of the experiment, when animals were euthanized. One defect was processed for histometric analysis to measure closure of the bone defect. The tissue of the other defect was analyzed for quantification of bone morphogenetic protein-2 (BMP-2), osteopontin, osteoprotegerin, receptor activator of nuclear factor-κB ligand, runt-related transcription factor-2, osterix (Osx), β-catenin, lipoprotein receptor-related protein-5, and dikkop-1 mRNA by quantitative polymerase chain reaction.

RESULTS

Histometric results showed that the DM + RESV, DM + RESV + INS, and NDM groups exhibited greater closure of the bone defects compared with the PLAC- or INS-treated groups (P < .05). Diabetic animals treated with RESV plus INS showed higher levels of BMP-2 and Osx; Osx also was positively increased in animals treated with INS alone (P < .05).

CONCLUSIONS

The use of RESV, regardless of the presence of INS, positively influenced bone repair in animals with induced DM. Further, the combination of INS plus RESV was necessary for the modulation of BMP-2 gene expression.

Zinc supplementation reduces RANKL/OPG ratio and prevents bone architecture alterations in ovariectomized and type 1 diabetic rats

Type 1 diabetes mellitus (T1DM) and estrogen deficiency are associated with several alterations in bone turnover. Zinc (Zn) is required for growth, development, and overall health. Zinc has been used in complementary therapy against bone loss in several diseases. We hypothesized that Zn supplementation represents a potential therapy against severe bone loss induced by the combined effect of estrogen deficiency and T1DM. We evaluated the protective effect of Zn against bone alterations in a chronic model of these disorders. Female Wistar rats were ramdomized into 3 groups (5 rats each): control, OVX/T1DM (ovariectomized rats with streptozotocin-induced T1DM), and OVX/T1DM+Zn (OVX/T1DM plus daily Zn supplementation). Serum biochemical, bone histomorphometric, and molecular analyses were performed. Histomorphometric parameters were similar between the control and OVX/T1DM+Zn groups, suggesting that Zn prevents bone architecture alterations. In contrast, the OVX/T1DM group showed significantly lower trabecular width and bone area as well as greater trabecular separation than the control. The OVX/T1DM and OVX/T1DM+Zn groups had significantly higher serum alkaline phosphatase activity than the control. The supplemented group had higher levels of serum-ionized calcium and phosphorus than the nonsupplemented group. The RANKL/OPG ratio was similar between the control and OVX/T1DM+Zn groups, whereas it was higher in the OVX/T1DM group. In conclusion, Zn supplementation prevents bone alteration in chronic OVX/T1DM rats, as demonstrated by the reduced RANKL/OPG ratio and preservation of bone architecture. The findings may represent a novel therapeutic approach to preventing OVX/T1DM-induced bone alterations.

Zinc Up-Regulates Insulin Secretion from β Cell-Like Cells Derived from Stem Cells from Human Exfoliated Deciduous Tooth (SHED)

Stem cells from human exfoliated deciduous tooth (SHED) offer several advantages over other stem cell sources. Using SHED, we examined the roles of zinc and the zinc uptake transporter ZIP8 (Zrt- and irt-like protein 8) while inducing SHED into insulin secreting β cell-like stem cells (i.e., SHED-β cells). We observed that ZIP8 expression increased as SHED differentiated into SHED-β cells, and that zinc supplementation at day 10 increased the levels of most pancreatic β cell markers-particularly Insulin and glucose transporter 2 (GLUT2). We confirmed that SHED-β cells produce insulin successfully. In addition, we note that zinc supplementation significantly increases insulin secretion with a significant elevation of ZIP8 transporters in SHED-β cells. We conclude that SHED can be converted into insulin-secreting β cell-like cells as zinc concentration in the cytosol is elevated. Insulin production by SHED-β cells can be regulated via modulation of zinc concentration in the media as ZIP8 expression in the SHED-β cells increases.

Effects of Type 1 Diabetes on Osteoblasts, Osteocytes, and Osteoclasts

PURPOSE OF REVIEW

To describe the effects of type 1 diabetes on bone cells.

RECENT FINDINGS

Type 1 diabetes (T1D) is associated with low bone mineral density, increased risk of fractures, and poor fracture healing. Its effects on the skeleton were primarily attributed to impaired bone formation, but recent data suggests that bone remodeling and resorption are also compromised. The hyperglycemic and inflammatory environment associated with T1D impacts osteoblasts, osteocytes, and osteoclasts. The mechanisms involved are complex; insulinopenia, pro-inflammatory cytokine production, and alterations in gene expression are a few of the contributing factors leading to poor osteoblast activity and survival and, therefore, poor bone formation. In addition, the observed sclerostin level increase accompanied by decreased osteocyte number and enhanced osteoclast activity in T1D results in uncoupling of bone remodeling. T1D negatively impacts osteoblasts and osteocytes, whereas its effects on osteoclasts are not well characterized, although the limited studies available indicate increased osteoclast activity, favoring bone resorption.

Long term bone alterations in aged rats suffering type 1 diabetes

Increasing duration of type 1 diabetes mellitus alters bone metabolism. Clinical studies and experimental studies in long bones of rats with experimentally induced diabetes have reported a decrease in bone density. Few studies have explored this diabetes related alteration in the maxillae. Given that this finding could indicate the possible development of osteopenia in the maxilla in the long term, the present study sought to analyze alterations in alveolar bone in aged rats, 12, 18, and 24weeks after inducing diabetes, and compare alveolar bone response to that of tibial subchondral bone at the same experimental times. Thirty-six male Wistar rats, 130g body weight, were divided into 2 groups: an experimental group (E) receiving a single i.p. 60mg/kg dose of streptozotocin, and a control group (C). Both the control and experimental groups were divided into 3 sub-sets, according to the time of euthanasia: 12, 18 and 24weeks. The alveolar bone and tibiae were examined histologically and histomorphometrically. The results were analyzed using Student's t-test; a value of p<0.05 was considered statistically significant.

RESULTS

Subchondral bone volume and bone activity/remodeling, mainly bone rest, were significantly lower in diabetic animals compared to controls, at both 12 and 18weeks. No differences in alveolar bone parameters were observed between diabetic and control animals at either of the experimental times. Animals surviving at 24weeks showed few trabeculae at rest and severe destruction of dental and periodontal tissues. The results of the present study show that diabetic osteopenia is evident in the tibia at 12 and at 18weeks, whereas its effects on the maxilla can be seen at 24weeks, with substantial destruction of alveolar bone and of the remaining periodontal and dental tissues. All the above observations highlight the need for preventive oral care in diabetic patients, before irreversible damage to dental and periodontal tissues occurs.

JiangTang XiaoKe granule attenuates cathepsin K expression and improves IGF-1 expression in the bone of high fat diet induced KK-Ay diabetic mice

AIM

To assess the beneficial effects of JiangTang XiaoKe (JTXK) granule on the bone metabolism in high fat diet (HFD) fed KK-Ay diabetic mice.

MATERIALS AND METHODS

The KK-Ay mice were used as a diabetic model, while C57BL/6 mice were utilized as the non-diabetic control. The left tibia was used for determining bone mineral density (BMD) and bone ash coefficient. The HE and alizarin red S staining of femur were employed to evaluate bone pathology and calcium deposition. The expressions of alkaline phosphatase (ALP), insulin growth factor 1 (IGF-1) and cathepsin K were assessed by western blotting and immunohistochemical staining.

KEY FINDINGS

JTXK granule significantly improved the bone ash coefficient, the distribution of trabecular bone and the calcification nodules deposition in KK-Ay mice with diabetes. IGF-1 and ALP expressions were significantly decreased, and cathepsin K expression was dramatically increased in the HFD fed KK-Ay diabetic model mice, which can be reversed by JTXK granule treatment. JTXK granule at medium or high dosage was more efficient in improving diabetic bone quality when compared with that in mice with a low dosage. However, the BMD values in each group of KK-Ay diabetic mice were not significantly different.

SIGNIFICANCE

We demonstrate that cathepsin K expression is increased in KK-Ay diabetic mouse model. JTXK granule treatment inhibits osteoclastic bone resorption and promotes the new bone formation by decreasing cathepsin K activity and increasing IGF-1 and ALP levels. These changes may contribute to the increase of bone strength and thus reducing the risk of bone fractures.

Sclerostin antibody treatment improves fracture outcomes in a Type I diabetic mouse model

Type 1 diabetes mellitus (T1DM) patients have osteopenia and impaired fracture healing due to decreased osteoblast activity. Further, no adequate treatments are currently available that can restore impaired healing in T1DM; hence a significant need exists to investigate new therapeutics for treatment of orthopedic complications. Sclerostin (SOST), a WNT antagonist, negatively regulates bone formation, and SostAb is a potent bone anabolic agent. To determine whether SOST antibody (SostAb) treatment improves fracture healing in streptozotocin (STZ) induced T1DM mice, we administered SostAb twice weekly for up to 21days post-fracture, and examined bone quality and callus outcomes at 21days and 42days post-fracture (11 and 14weeks of age, respectively). Here we show that SostAb treatment improves bone parameters; these improvements persist after cessation of antibody treatment. Markers of osteoblast differentiation such as Runx2, collagen I, osteocalcin, and DMP1 were reduced, while an abundant number of SP7/osterix-positive early osteoblasts were observed on the bone surface of STZ calluses. These results suggest that STZ calluses have poor osteogenesis resulting from failure of osteoblasts to fully differentiate and produce mineralized matrix, which produces a less mineralized callus. SostAb treatment enhanced fracture healing in both normal and STZ groups, and in STZ+SostAb mice, also reversed the lower mineralization seen in STZ calluses. Micro-CT analysis of calluses revealed improved bone parameters with SostAb treatment, and the mineralized bone was comparable to Controls. Additionally, we found sclerostin levels to be elevated in STZ mice and β-catenin activity to be reduced. Consistent with its function as a WNT antagonist, SostAb treatment enhanced β-catenin activity, but also increased the levels of SOST in the callus and in circulation. Our results indicate that SostAb treatment rescues the impaired osteogenesis seen in the STZ induced T1DM fracture model by facilitating osteoblast differentiation and mineralization of bone.

Diabetes and bone: biological and environmental factors

PURPOSE OF REVIEW

Type 1 and type 2 diabetes mellitus are known to increase fracture risk. It is known that type 1 diabetes mellitus is associated with lower bone mineral density, but for type 2 diabetes mellitus, the real risk of increasing osteoporotic fractures is not explained by bone mineral density, which was found to be normal or paradoxically higher than controls in several studies, thus claiming for further investigations. This review summarizes some of the newest findings about factors that contribute to bone alterations in diabetic patients.

RECENT FINDINGS

Most recent evidences showed that bone of diabetic patients presents a cortical porosity which is not captured by the bidimensional densitometric measurements as performed by dual energy X-ray absorptiometry. Other studies investigated bone matrix searching for molecular mechanisms underlying the reduced bone strength in diabetic patients. The loss of bone biomechanical properties in diabetes has been associated to the glycated collagen matrix induced by hyperglycemia. Other studies analyzed the effect on bone microarchitecture of the most common antidiabetic drugs.

SUMMARY

Disease management of fracture risk in diabetic patients needs new methodologies of assessment that also take into account bone quality and evaluation of clinical risk factors, including balance, visual, and neurological impairments.

The Antidiabetic and Antihypercholesterolemic Effects of an Aqueous Extract from Pecan Shells in Wistar Rats

Pecan shell decoction has been used to treat diabetes and obesity-related diseases. In this study, the effects of a pecan shell aqueous extract (PSAE) were evaluated in diabetic and hypercholesterolemic Wistar rats, analyzing clinical signs and biochemical as well as genotoxic and mutagenic parameters, to assess its safe use and efficacy. Diabetes mellitus and hypercholesterolemia were induced with streptozotocin (STZ) and tyloxapol, respectively. Animals were orally administered PSAE (100 mg/kg body weight, b.w.) for 28 days. Biochemical analyses and genotoxicity were evaluated in blood samples and mutagenicity was evaluated in bone marrow. PSAE treatment decreased the blood glucose level and stabilized clinical signs of diabetes in diabetic rats. PSAE diminished the increase in total cholesterol and triglyceride levels in hypercholesterolemic rats. The urea levels were higher in diabetic rats than in treated ones; however, creatinine values were the same in all groups. Elevated transaminase levels were suggestive of liver injuries in diabetic rats, and were not altered by PSAE treatment. PSAE did not show genotoxic or mutagenic activities in diabetic and hypercholesterolemic rats, indicating its safe use at 100 mg/kg b.w. not only in healthy rats but also in rats with induced metabolic alterations. The findings on PSAE's efficacy may indicate that its successful and popular use is in accordance with our results. Thus, PSAE might be a potential candidate for medical purposes as a complementary treatment of diabetes and hypercholesterolemia.

Dietary zinc supplementation increased TNFα and IL1β-induced RANKL expression, resulting in a decrease in bone mineral density in rats

We investigated the effect of dietary zinc supplementation on bone metabolism in rats. Four-week-old male Wistar rats were fed a 30.0 mg zinc/kg diet (C), a 300.0 mg zinc/kg diet (HZ) or a 3,000.0 mg zinc/kg diet (EZ) for 4 weeks. The zinc content of the femur gradually increased in accordance with the gradual increase in the dietary zinc level. Although the mRNA expression of zinc transporters in bone did not differ between the groups, the mRNA expression of metallothioneins was increased in the HZ and EZ groups compared to the C group. Moreover, the bone mineral density was significantly decreased in the HZ and EZ groups compared to the C group. Furthermore, the mRNA expression of tumor necrosis factor α, Interleukin-1β and osteoclastogenesis-related genes such as receptor for activator of nuclear factor-κB (NF-κB) ligand, tumor necrosis factor receptor-associated factor 6, and nuclear factor of activated T cells cytoplasmic 1 was significantly increased in the HZ and EZ groups compared to the C group. These findings suggested that dietary zinc supplementation reduced bone mineral density through the promotion of bone resorption via an increase in the expression of receptor for activator of NF-κB ligand induced by tumor necrosis factor α and Interleukin-1β.

Polysaccharides of Trametes versicolor Improve Bone Properties in Diabetic Rats

This study investigates the effects of Trametes versicolor (L.:Fr.) Pilát (TVP, also known as Yunzhi) on bone properties in diabetic rats. Forty-five male Wistar rats (8 weeks old) were fed either a chow diet (control) or a high-fat diet throughout the study period of 28 days. Animals in the high-fat-diet group were injected with nicotinamide and streptozotocin to induce diabetes mellitus (DM). The DM rats were divided into a group receiving distilled water (vehicle) and another group receiving TVP at 0.1 g/kg weight by gavage. Relative to the vehicle group, TVP gavage lowered postprandial blood sugar (225 ± 18 mg/dL for TVP vs 292 ± 15 mg/dL for vehicle, p < 0.001) on day 26. Compared to the vehicle group, TVP mitigated DM-induced bone deterioration as determined by increasing bone volume of proximal tibia (22.8 ± 1.4% for TVP vs 16.8 ± 1.3% for vehicle, p = 0.003), trabecular number (p = 0.011), and femoral bone strength (11% in maximal load, 22% in stiffness, 14% in modulus, p < 0.001), and by reducing loss of femoral cortical porosity by 25% (p < 0.001). Our study demonstrates the protective effect of TVP on bone properties was mediated through, in part, the improvement of hyperglycemic control in DM animals.

Inhibition of osteolysis after local administration of osthole in a TCP particles-induced osteolysis model

PURPOSE

Wear debris-induced osteolysis and aseptic loosening are the most frequent late complications of total joint arthroplasty leading to revision of the prosthesis. However, no effective measures for the prevention and treatment of particles-induced osteolysis currently exist. Here, we investigated the efficacy of local administration of osthole on tricalcium phosphate (TCP) particles-induced osteolysis in a murine calvarial model.

METHODS

TCP particles were implanted over the calvaria of ICR mice, and established TCP particles-induced osteolysis model. On days one, four, seven, ten and thirteen post-surgery, osthole (10 mg/kg) or phosphate buffer saline (PBS) were subcutaneously injected into the calvaria of TCP particles-implanted or sham-operated mice. Two weeks later, blood, the periosteum and the calvaria were collected and processed for bone turnover markers, pro-inflammatory cytokine, histomorphometric and molecular analysis.

RESULTS

Osthole (10 mg/kg) markedly prevented TCP particles-induced osteoclastogenesis and bone resorption in a mouse calvarial model. Osthole also inhibited the decrease of serum osteocalcin level and calvarial alkaline phosphatase (ALP) activity, and prevented the increase in the activity of tartrate resistant acid phosphatase (TRAP) and cathepsin K in the mouse calvaria. Furthermore, osthole obviously reduced the release of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) into the periosteum. Western blotting demonstrated TCP particles caused a remarkable endoplasmic reticulum (ER) stress response in the mouse calvaria, which was obviously blocked by osthole treatment.

CONCLUSION

These results suggest that local administration of osthole inhibits TCP particles-induced osteolysis in the mouse calvarial in vivo, which may be mediated by inhibition of the ER stress signaling pathway, and it will be developed as a new drug in the prevention and treatment of destructive diseases caused by prosthetic wear particles.

Pulsed electromagnetic fields inhibit bone loss in streptozotocin-induced diabetic rats

Evidences have shown that pulsed electromagnetic fields (PEMFs) can partially prevent bone loss in streptozotocin (STZ)-induced diabetic rats. However, the precise mechanisms accounting for these favorable effects are unclear. This study aimed to investigate the effects of PEMFs on bone mass and receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) and Wnt/β-catenin signaling pathway in STZ rats. Thirty 3-month-old Sprague Dawley rats were randomly divided into the following three groups (n = 10): control group (injection of saline vehicle), DM group (injection of STZ), and PEMFs group (injection of STZ + PEMFs exposure). One week following injection of STZ, rats in the PEMFs group were subject to PEMFs stimulus for 40 min/day, 5 days/week, and lasted for 12 weeks. After 12 week intervention, the results showed that PEMFs increased serum bone-specific alkaline phosphatase level and bone mineral density, and inhibited deterioration of bone microarchitecture and strength in STZ rats. Furthermore, PEMFs up-regulated the mRNA expressions of low-density lipoprotein receptor-related protein 5, β-catenin and runt-related gene 2 (Runx2), and down-regulated dickkopf1 in STZ rats. However, mRNA expressions of RANKL and OPG were not affected by PEMFs. PEMFs can prevent the diabetes-induced bone loss and reverse the deterioration of bone microarchitecture and strength by restoring Runx2 expression through regulation of Wnt/β-catenin signaling, regardless of its no glucose lowering effect.

Protection against T1DM-Induced Bone Loss by Zinc Supplementation: Biomechanical, Histomorphometric, and Molecular Analyses in STZ-Induced Diabetic Rats

Several studies have established an association between diabetes and alterations in bone metabolism; however, the underlying mechanism is not well established. Although zinc is recognized as a potential preventive agent against diabetes-induced bone loss, there is no evidence demonstrating its effect in chronic diabetic conditions. This study evaluated the effects of zinc supplementation in a chronic (90 days) type 1 diabetes-induced bone-loss model. Male Wistar rats were distributed in three groups: control, type 1 diabetes mellitus (T1DM), and T1DM plus zinc supplementation (T1DMS). Serum biochemical analysis; tibia histomorphometric, biomechanical, and collagen-content analyses; and femur mRNA expression were evaluated. Relative to T1DM, the zinc-supplemented group showed increased histomorphometric parameters such as TbWi and BAr and decreased TbSp, increased biomechanical parameters (maximum load, stiffness, ultimate strain, and Young's modulus), and increased type I collagen content. Interestingly, similar values for these parameters were observed between the T1DMS and control groups. These results demonstrate the protective effect of zinc on the maintenance of bone strength and flexibility. In addition, downregulation of OPG, COL1A, and MMP-9 genes was observed in T1DMS, and the anabolic effects of zinc were evidenced by increased OC expression and serum ALP activity, both related to osteoblastogenesis, demonstrating a positive effect on bone formation. In contrast, T1DM showed excessive bone loss, observed through reduced histomorphometric and biomechanical parameters, characterizing diabetes-associated bone loss. The bone loss was also observed through upregulation of OPG, COL1A, and MMP-9 genes. In conclusion, zinc showed a positive effect on the maintenance of bone architecture and biomechanical parameters. Indeed, OC upregulation and control of expression of OPG, COL1A, and MMP-9 mRNAs, even in chronic hyperglycemia, support an anabolic and protective effect of zinc under chronic diabetic conditions. Furthermore, these results indicate that zinc supplementation could act as a complementary therapy in chronic T1DM.

The bifunctional regulation of interconnected Zn-incorporated ZrO2 nanoarrays in antibiosis and osteogenesis

Bifunctional regulation in antibiosis and osteogenesis is obtained using well-organized Zn-incorporated ZrO₂ nanoarrays with interconnected internal space.

Regulation of the biological functions of osteoblasts and bone formation by Zn-incorporated coating on microrough titanium

To improve the biological performance of titanium implant, a series of Zn-incorporated coatings were fabricated on the microrough titanium (Micro-Ti) via sol-gel method by spin-coating technique. The successful fabrication of the coating was verified by combined techniques of scanning electron microscopy, surface profiler, X-ray diffraction, X-ray photoelectron spectroscopy, and water contact angle measurements. The incorporated zinc existed as ZnO, which released Zn ions in a sustained manner. The Zn-incorporated samples (Ti-Zn0.08, Ti-Zn0.16, and Ti-Zn0.24) efficiently inhibited the adhesion of both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. The in vitro evaluations including cell activity, alkaline phosphatase (ALP), mineralization, osteogenic genes expressions (Runx2, ALP, OPG, Col I, OPN, and OC), and tartrate-resistant acid phosphatase, confirmed that Ti-Zn0.16 sample was the optimal one to regulate the proliferation or differentiation for both osteoblasts and osteoclasts. More importantly, in vivo evaluations including Micro-CT analysis, push-out test, and histological observations verified that Ti-Zn0.16 implants could efficiently promote new bone formation after implantation for 4 and 12 weeks, respectively. The resulting material thus has potential application in orthopedic field.