Iron chelator deferoxamine alters iron-regulatory genes and proteins and suppresses osteoblast phenotype in fetal rat calvaria cells

Research progress on roles of iron metabolism in the occurrence and development of periodontitis

Iron metabolism refers to the process of absorption, transport, excretion and storage of iron in organisms, including the biological activities of iron ions and iron-binding proteins in cells. Clinical research and animal experiments have shown that iron metabolism is associated with the progress of periodontitis. Iron metabolism can not only enhance the proliferation and toxicity of periodontal pathogens, but also activate host immune- inflammatory response mediated by macrophages, neutrophils and lymphocytes. In addition, iron metabolism is also involved in regulating the cellular death sensitivity of gingival fibroblasts and osteoblasts and promoting the differentiation of osteoclasts to play a regulatory role in the regeneration and repair of periodontal tissue. This article reviews the research progress on the pathogenesis of periodontitis from the perspective of iron metabolism, aiming to provide new ideas for the treatment of periodontitis.

Fibroblast growth factor 23 is pumping iron: C-terminal-fibroblast growth factor 23 cleaved peptide and its function in iron metabolism

PURPOSE OF REVIEW

Iron deficiency regulates the production of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) but also its cleavage, to generate both intact (iFGF23) and C-terminal (Cter)-FGF23 peptides. Novel studies demonstrate that independently of the phosphaturic effects of iFGF23, Cter-FGF23 peptides play an important role in the regulation of systemic iron homeostasis. This review describes the complex interplay between iron metabolism and FGF23 biology.

RECENT FINDINGS

C-terminal (Cter) FGF23 peptides antagonize inflammation-induced hypoferremia to maintain a pool of bioavailable iron in the circulation. A key mechanism proposed is the down-regulation of the iron-regulating hormone hepcidin by Cter-FGF23.

SUMMARY

In this manuscript, we discuss how FGF23 is produced and cleaved in response to iron deficiency, and the principal functions of cleaved C-terminal FGF23 peptides. We also review possible implications anemia of chronic kidney disease (CKD).

Iron Deficiency and Iron Deficiency Anemia: Potential Risk Factors in Bone Loss

Iron is one of the essential mineral elements for the human body and this nutrient deficiency is a worldwide public health problem. Iron is essential in oxygen transport, participates in many enzyme systems in the body, and is an important trace element in maintaining basic cellular life activities. Iron also plays an important role in collagen synthesis and vitamin D metabolism. Therefore, decrease in intracellular iron can lead to disturbance in the activity and function of osteoblasts and osteoclasts, resulting in imbalance in bone homeostasis and ultimately bone loss. Indeed, iron deficiency, with or without anemia, leads to osteopenia or osteoporosis, which has been revealed by numerous clinical observations and animal studies. This review presents current knowledge on iron metabolism under iron deficiency states and the diagnosis and prevention of iron deficiency and iron deficiency anemia (IDA). With emphasis, studies related to iron deficiency and bone loss are discussed, and the potential mechanisms of iron deficiency leading to bone loss are analyzed. Finally, several measures to promote complete recovery and prevention of iron deficiency are listed to improve quality of life, including bone health.

HIF-1α Regulates Bone Homeostasis and Angiogenesis, Participating in the Occurrence of Bone Metabolic Diseases

In the physiological condition, the skeletal system's bone resorption and formation are in dynamic balance, called bone homeostasis. However, bone homeostasis is destroyed under pathological conditions, leading to the occurrence of bone metabolism diseases. The expression of hypoxia-inducible factor-1α (HIF-1α) is regulated by oxygen concentration. It affects energy metabolism, which plays a vital role in preventing bone metabolic diseases. This review focuses on the HIF-1α pathway and describes in detail the possible mechanism of its involvement in the regulation of bone homeostasis and angiogenesis, as well as the current experimental studies on the use of HIF-1α in the prevention of bone metabolic diseases. HIF-1α/RANKL/Notch1 pathway bidirectionally regulates the differentiation of macrophages into osteoclasts under different conditions. In addition, HIF-1α is also regulated by many factors, including hypoxia, cofactor activity, non-coding RNA, trace elements, etc. As a pivotal pathway for coupling angiogenesis and osteogenesis, HIF-1α has been widely studied in bone metabolic diseases such as bone defect, osteoporosis, osteonecrosis of the femoral head, fracture, and nonunion. The wide application of biomaterials in bone metabolism also provides a reasonable basis for the experimental study of HIF-1α in preventing bone metabolic diseases.

Oriented nanofibrous P(MMD-co-LA)/Deferoxamine nerve scaffold facilitates peripheral nerve regeneration by regulating macrophage phenotype and revascularization

Delayed injured nerve regeneration remains a clinical problem, partly ascribing to the lack of regulation of regenerative microenvironment, topographical cues, and blood nourishment. Functional electrospun conduits have been established as an efficacious strategy to facilitate nerve regeneration by providing structural guidance, regulating the regenerative immune microenvironment, and improving vascular regeneration. However, the synthetic polymers conventionally used to fabricate electrospinning scaffolds, such as poly(L-lactic acid), poly(glycolic acid), and poly(lactic-co-glycolic acid), can cause aseptic inflammation due to acidic degradation products. Therefore, a poly[3(S)-methyl-morpholine-2,5-dione-co-lactic] [P(MMD-co-LA)] containing alanine units with good mechanical properties and reduced acid degradation products, was obtained by melt ring-opening polymerization (ROP). Here, we aimed to explore the effect of oriented nanofiber/Deferoxamine (DFO, a hydrophilic angiogenic drug) scaffold in the rapid construction of a favorable regenerative microenvironment, including cell bridge, polarized vascular system, and immune microenvironment. In vitro studies have shown that the scaffold can sustainably release DFO, which accelerates the migration and tube formation of human umbilical vein endothelial cells (HUVECs), as well as the expression of genes related to angiogenesis. The physical clues provided by the arranged nanofibers can regulate the polarization of macrophages and reduce the expression of inflammatory factors. Furthermore, the in vivo results demonstrated a higher M2 polarization level of the oriented nanofibrous scaffold treatment group with reducedinflammation reaction in the injured nerve. Moreover, the in-situ release of DFO up-regulated the expression of HIF1-α and SDF-1α genes, as well as the expression of HIF1-α's target gene VEGF, further promoting revascularization and enhancing nerve regeneration at the defect site. The obtained results provide essential insights on accelerating the creation of the nerve regeneration microenvironment by combining the physiological processes of nerve regeneration with topographical cues and chemical signal induction.

Differential Iron Requirements for Osteoblast and Adipocyte Differentiation

Bone marrow mesenchymal progenitor cells are precursors for various cell types including osteoblasts, adipocytes, and chondrocytes. The external environment and signals act to direct the pathway of differentiation. Importantly, situations such as aging and chronic kidney disease display alterations in the balance of osteoblast and adipocyte differentiation, adversely affecting bone integrity. Iron deficiency, which can often occur during aging and chronic kidney disease, is associated with reduced bone density. The purpose of this study was to assess the effects of iron deficiency on the capacity of progenitor cell differentiation pathways. Mouse and human progenitor cells, differentiated under standard osteoblast and adipocyte protocols in the presence of the iron chelator deferoxamine (DFO), were used. Under osteogenic conditions, 5μM DFO significantly impaired expression of critical osteoblast genes, including osteocalcin, type 1 collagen, and dentin matrix protein 1. This led to a reduction in alkaline phosphatase activity and impaired mineralization. Despite prolonged exposure to chronic iron deficiency, cells retained viability as well as normal hypoxic responses with significant increases in transferrin receptor and protein accumulation of hypoxia inducible factor 1α. Similar concentrations of DFO were used when cells were maintained in adipogenic conditions. In contrast to osteoblast differentiation, DFO modestly suppressed adipocyte gene expression of peroxisome-proliferating activated receptor gamma, lipoprotein lipase, and adiponectin at earlier time points with normalization at later stages. Lipid accumulation was also similar in all conditions. These data suggest the critical importance of iron in osteoblast differentiation, and as long as the external stimuli are present, iron deficiency does not impede adipogenesis. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Neuroprotective Therapies for Spontaneous Intracerebral Hemorrhage

Patients who survive the initial ictus of spontaneous intracerebral hemorrhage (ICH) remain vulnerable to subsequent injury of the perilesional parenchyma by molecular and cellular responses to the hematoma. Secondary brain injury after ICH, which contributes to long-term functional impairment and mortality, has emerged as an attractive therapeutic target. This review summarizes preclinical and clinical evidence for neuroprotective therapies targeting secondary injury pathways following ICH. A focus on therapies with pleiotropic antiinflammatory effects that target thrombin-mediated chemotaxis and inflammatory cell migration has led to studies investigating statins, anticholinergics, sphingosine-1-phosphate receptor modulators, peroxisome proliferator activated receptor gamma agonists, and magnesium. Attempts to modulate ICH-induced blood-brain barrier breakdown and perihematomal edema formation has prompted studies of nonsteroidal antiinflammatory agents, matrix metalloproteinase inhibitors, and complement inhibitors. Iron chelators, such as deferoxamine and albumin, have been used to reduce the free radical injury that ensues from erythrocyte lysis. Stem cell transplantation has been assessed for its potential to enhance subacute neurogenesis and functional recovery. Despite promising preclinical results of numerous agents, their outcomes have not yet translated into positive clinical trials in patients with ICH. Further studies are necessary to improve our understanding of the molecular events that promote damage and inflammation of the perihematomal parenchyma after ICH. Elucidating the temporal and pathophysiologic features of this secondary brain injury could enhance the clinical efficacy of neuroprotective therapies for ICH.

Bone Mineral Density in Population Long-Term Exposed to Rare Earth Elements from a Mining Area of China

This study aims to investigate the effects of individuals' exposure to rare earth elements (REEs) on bone metabolism. Adopting the inductively coupled plasma mass spectrometry, we measured REEs and eight other elements (Ca, Fe, Cu, Na, K, Zn, Mg, and P) in the hair of 53 miners exposed to REEs from Baiyunebo and 57 healthy farmers as the control group. Furthermore, bone mineral density (BMD) in both groups was assessed by dual-energy X-ray absorptiometry. Analysis of variance showed that the concentrations of La, Ce, Pr, Nd, Tb, Ho, Tm, and Yb in male hair of exposed group were significantly higher compared with the control group, whereas the concentrations of Ca and Fe in exposed group were significantly lower; the results of female hair, except for Ce, Tb, Ho, Tm, and Yb, were consistent with male hair. Student's t test showed that the BMD of exposed males at lumbar vertebrae, femoral neck, greater trochanter, and intertrochanter was significantly lower than that of controls, and exposed females reported lower BMD values at lumbar vertebrae and femoral neck. Multiple linear regression analysis showed that concentrations of differential REEs were inversely related to BMD in males, and concentrations of Ca and Fe were positively related to BMD both in males and females. Our study suggests that long-term environmental and occupational exposure leads to REE accumulation, and a low level of iron and calcium due to the competitive binding of REEs, which together induce bone metabolism disorders, and further reduce BMD.

Extrusion-based 3D printed biodegradable porous iron

Extrusion-based 3D printing followed by debinding and sintering is a powerful approach that allows for the fabrication of porous scaffolds from materials (or material combinations) that are otherwise very challenging to process using other additive manufacturing techniques. Iron is one of the materials that have been recently shown to be amenable to processing using this approach. Indeed, a fully interconnected porous design has the potential of resolving the fundamental issue regarding bulk iron, namely a very low rate of biodegradation. However, no extensive evaluation of the biodegradation behavior and properties of porous iron scaffolds made by extrusion-based 3D printing has been reported. Therefore, the in vitro biodegradation behavior, electrochemical response, evolution of mechanical properties along with biodegradation, and responses of an osteoblastic cell line to the 3D printed iron scaffolds were studied. An ink formulation, as well as matching 3D printing, debinding and sintering conditions, was developed to create iron scaffolds with a porosity of 67%, a pore interconnectivity of 96%, and a strut density of 89% after sintering. X-ray diffracometry confirmed the presence of the α-iron phase in the scaffolds without any residuals from the rest of the ink. Owing to the presence of geometrically designed macropores and random micropores in the struts, the in vitro corrosion rate of the scaffolds was much improved as compared to the bulk counterpart, with 7% mass loss after 28 days. The mechanical properties of the scaffolds remained in the range of those of trabecular bone despite 28 days of in vitro biodegradation. The direct culture of MC3T3-E1 preosteoblasts on the scaffolds led to a substantial reduction in living cell count, caused by a high concentration of iron ions, as revealed by the indirect assays. On the other hand, the ability of the cells to spread and form filopodia indicated the cytocompatibility of the corrosion products. Taken together, this study shows the great potential of extrusion-based 3D printed porous iron to be further developed as a biodegradable bone substituting biomaterial.

Neuroinflammation, oxidative stress, and blood-brain barrier (BBB) disruption in acute Utah electrode array implants and the effect of deferoxamine as an iron chelator on acute foreign body response

The use of intracortical microelectrode arrays has gained significant attention in being able to help restore function in paralysis patients and study the brain in various neurological disorders. Electrode implantation in the cortex causes vasculature or blood-brain barrier (BBB) disruption and thus elicits a foreign body response (FBR) that results in chronic inflammation and may lead to poor electrode performance. In this study, a comprehensive insight into the acute molecular mechanisms occurring at the Utah electrode array-tissue interface is provided to understand the oxidative stress, neuroinflammation, and neurovascular unit (astrocytes, pericytes, and endothelial cells) disruption that occurs following microelectrode implantation. Quantitative real time polymerase chain reaction (qRT-PCR) was used to quantify the gene expression at acute time-points of 48-hr, 72-hr, and 7-days for factors mediating oxidative stress, inflammation, and BBB disruption in rats implanted with a non-functional 4 × 4 Utah array in the somatosensory cortex. During vascular disruption, free iron released into the brain parenchyma can exacerbate the FBR, leading to oxidative stress and thus further contributing to BBB degradation. To reduce the free iron released into the brain tissue, the effects of an iron chelator, deferoxamine mesylate (DFX), was also evaluated.

Influence of Iron on Bone Homeostasis

Bone homeostasis is a complex process, wherein osteoclasts resorb bone and osteoblasts produce new bone tissue. For the maintenance of skeletal integrity, this sequence has to be tightly regulated and orchestrated. Iron overload as well as iron deficiency disrupt the delicate balance between bone destruction and production, via influencing osteoclast and osteoblast differentiation as well as activity. Iron overload as well as iron deficiency are accompanied by weakened bones, suggesting that balanced bone homeostasis requires optimal-not too low, not too high-iron levels. The goal of this review is to summarize our current knowledge about how imbalanced iron influence skeletal health. Better understanding of this complex process may help the development of novel therapeutic approaches to deal with the pathologic effects of altered iron levels on bone.

Expression of iron-regulators in the bone tissue of rats with and without iron overload

Recently, more and more studies indicate that iron overload would cause osteopenia or osteoporosis. However, the molecular mechanism of it remains unclear. Moreover, very little is known about the iron metabolism in bone tissue at present. Therefore, the mRNA expression of iron-regulators, transferrin receptor1 (Tfr1), divalent metal transporter1 (Dmt1 + IRE and Dmt1 - IRE), ferritin (FtH and FtL), and ferroportin1 (Ireg1), and the localization of ferroportin1 protein were examined in the bone tissue of rats. In addition, the mRNA expression of each gene was compared between groups of rats with and without iron overload. The results showed that ferroportin1 protein was localized in the cytoplasm of osteoblast, osteocyte, chondrocyte and osteoclast of rats' femur. The six iron-regulatory genes, Tfr1, ferritin (FtH and FtL), (Dmt1 + IRE and Dmt1 - IRE) and ferroportin1 (Ireg1), were found in femurs of rats. In addition, significantly up-regulated expression of FtH and FtL mRNA, and markedly down-regulated expression of Tfr1, Dmt1 + IRE and Ireg1 mRNA, were observed in the iron overload group compared with the control group. The result indicates that ferroportin1 protein is localized in the cytoplasm of bone cells of rats. Tfr1, Dmt1, ferritin and ferroportin1 exist in bone tissue of rats, and they may be involved in the pathological process of iron overload-induced bone lesion.

Studying hepcidin and related pathways in osteoblasts using a mouse model with insulin receptor substrate 1‑loss of function

Hepcidin is one of the most important proteins in iron metabolism. In the present study, its role in iron metabolism and the associated signaling pathways involved was investigated in a mouse model with insulin receptor substrate 1‑loss of function (IRS‑/‑), and osteoblasts in the iron overload condition. Protein expression levels of hepcidin, interleukin 6 (IL‑6), bone morphogenetic protein receptor 1α and ferritin demonstrated a significant increase in the liver of the IRS‑/‑ mice compared with the IRS+/‑ and IRS+/+ mice. Hepcidin levels in the jaw bone were also increased in the IRS‑/‑ mice (although not significantly). Furthermore, mRNA expression levels of bone morphogenetic protein 6 (BMP6) and ferroportin (FPN) were significantly increased in the liver of the IRS‑/‑ mice compared with the other two models, but no significant differences were observed in the transferrin receptor mRNA expression levels. Additionally, the mRNA expression of hepcidin, FPN and IL‑6 was upregulated in osteoblasts after ferric ammonium citrate exposure, while the mRNA expression of BMP6 was inhibited. Collectively, the results of the present study indicated that hepcidin is involved in iron metabolism in IRS‑1‑/‑ mice via the signaling pathways involving BMP6 and IL‑6. Furthermore, hepcidin is also involved in iron metabolism in osteoblasts under iron overload conditions. Therefore, hepcidin and its associated signaling pathway proteins may represent potential targets for the treatment of conditions associated with iron overload.

Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors

Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function, and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of deferoxamine is mediated via Wnt signaling, we performed a Wnt profiler array of deferoxamine-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated 2-fold after 48 h at 50 μM deferoxamine. Pathway analysis using specific inhibitors revealed that deferoxamine utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cell pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the deferoxamine-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The promoting effect of deferoxamine on matrix mineralization in wild-type cells was completely abolished in Wnt5a^-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using deferoxamine.

Copper, iron, and selenium dietary deficiencies negatively impact skeletal integrity: A review

Nutrients have been known to have a significant role in maintaining the health of the skeleton, both bone and cartilage. The nutrients that have received the majority of the attention are Vitamin D and calcium. However, limited attention has been directed toward three trace elements that may have mechanistic impact upon the skeletal tissues and could compromise skeletal health resulting from inadequate intakes of copper, iron, and selenium. The role of copper and selenium has been known, but the role of iron has only received recent attention. Copper deficiency is thought to impact bone health by a decrease in lysyl oxidase, a copper-containing enzyme, which facilitates collagen fibril crosslinking. Iron deficiency impact upon bone has only recently been discovered but the exact mechanism on how the deficient states enhance bone pathology is speculative. Selenium deficiency has an impact on cartilage thereby having an indirect impact on bone. However, several studies suggest that a mycotoxin when consumed by humans is the culprit in some cartilage disorders and the presence of selenium could attenuate the pathology. This review summarizes the current knowledge base with respect to skeletal integrity when each of these three trace elements are inadequate in diets of both animals and humans.

Thalassemia bone disease: a 19-year longitudinal analysis

Thalassemia is an inherited disorder of alpha or beta globin chain synthesis leading to ineffective erythropoiesis requiring chronic transfusion therapy in its most severe form. This leads to iron overload, marrow expansion, and hormonal complications, which are implicated in bone deformity and loss of bone mineral density (BMD). In this 19-year retrospective longitudinal study, the relationships between BMD (determined by dual-energy X-ray absorptiometry) and risk factors for osteoporosis in 277 subjects with transfusion-dependent thalassemia were examined. The mean age at first review was 23.2 ± 11.9 years and 43.7% were male. Hypogonadism was present in 28.9%. Fractures were confirmed in 11.6% of subjects and were more frequent in males (16.5%) compared with females (7.7%). Lumbar spine (LS), femoral neck (FN), and total body (TB) Z-scores were derived. Patients with transfusion-dependent thalassemia had a significant longitudinal decline in BMD at the FN and TB. In the linear mixed-model analysis of BMD and risk factors for bone loss, FN Z-score was more significantly associated with risk factors compared with the LS and TB. The rate of decline at the FN was 0.02 Z-score per year and was 3.85-fold greater in males. The decline in FN Z-score over the last 5 years (years 15 to 19) was 2.5-fold that of the previous 7 years (years 8 to 14) and coincided with a change in iron chelator therapy from desferrioxamine to deferasirox. Hemoglobin (Hb) levels positively correlated with higher TB and LS Z-scores. In conclusion, the FN is the preferred site for follow-up of BMD. Male patients with β-thalassemia experienced a greater loss of BMD and had a higher prevalence of fractures compared with females. Transfusing patients (particularly males) to a higher Hb target may reduce the decline in BMD. Whether deferasirox is implicated in bone loss warrants further study.

Iron regulates the expression of ferroportin 1 in the cultured hFOB 1.19 osteoblast cell line

Iron metabolism is tightly regulated in osteoblasts, and ferroportin 1 (FPN1) is the only identified iron exporter in mammals to date. In the present study, the regulation of FNP1 in human osteoblasts was investigated following various iron treatments. The human osteoblast cell line hFOB 1.19 was treated with ferric ammonium citrate (FAC) or desferrioxamine (DFO) of various concentrations. The intracellular iron ion levels were measured using a confocal laser scanning microscope. In addition, the mRNA and protein expression levels of FPN1 were detected by quantitative polymerase chain reaction, western blot analysis and immunofluorescence. The results demonstrated that increasing iron concentrations via FAC treatment increased the expression of FPN1. By contrast, decreasing the iron concentration by DFO treatment decreased FNP1 expression levels. In addition to demonstrating that the FNP1 expression changed according to the iron concentration, the observations indicated that changes in FPN1 expression may contribute to the maintenance of the intracellular iron balance in osteoblasts.

High dose deferoxamine in intracerebral hemorrhage (HI-DEF) trial: rationale, design, and methods

BACKGROUND

Hemoglobin degradation products, in particular iron, have been implicated in secondary neuronal injury following intracerebral hemorrhage (ICH). The iron chelator Deferoxamine Mesylate (DFO) exerts diverse neuroprotective effects, reduces perihematoma edema (PHE) and neuronal damage, and improves functional recovery after experimental ICH. We hypothesize that treatment with DFO could minimize neuronal injury and improve outcome in ICH patients. As a prelude to test this hypothesis, we conducted a Phase I, open-label study to determine the tolerability, safety, and maximum tolerated dose (MTD) of DFO in patients with ICH. Intravenous infusions of DFO in doses up to 62 mg/kg/day (up to a maximum of 6000 mg/day) were well-tolerated and did not seem to increase serious adverse events (SAEs) or mortality. We have initiated a multi-center, double-blind, randomized, placebo-controlled, Phase II clinical trial (High Dose Deferoxamine [HI-DEF] in Intracerebral Hemorrhage) to determine if it is futile to move DFO forward to Phase III efficacy evaluation.

METHODS

We will randomize 324 subjects with spontaneous ICH to either DFO at 62 mg/kg/day (up to a maximum daily dose of 6000 mg/day) or saline placebo, given by intravenous infusion for 5 consecutive days. Treatment will be initiated within 24 hours after ICH symptom onset. All subjects will be followed for 3 months and will receive standard of care therapy while participating in the study. At 3 months, the proportion of DFO-treated subjects with a good clinical outcome, assessed by modified Rankin Scale, will be compared to the placebo proportion in a futility analysis.

CONCLUSIONS

The Hi-Def trial is expected to advance our understanding of the pathopgysiology of secondary neuronal injury in ICH and will provide a crucial "Go/No Go" signal as to whether a Phase III trial to investigate the efficacy of DFO is warranted.

Deferoxamine promotes osteoblastic differentiation in human periodontal ligament cells via the nuclear factor erythroid 2-related factor-mediated antioxidant signaling pathway

BACKGROUND AND OBJECTIVE

Recently it was reported that deferoxamine (DFO), an iron chelator, stimulates bone formation from MG63 and mesenchymal stem cells, but inhibits differentiation in rat calvarial cells; however, the effect of DFO on osteoblastic differentiation in human periodontal ligament cells (hPDLCs) has not been reported. The aim of this study was to investigate the effects and the possible underlying mechanism of DFO on osteoblastic differentiation of hPDLCs.

MATERIAL AND METHODS

The effect of DFO on osteoblast differentiation was determined by the staining intensity of calcium deposits with Alizarin red and by RT-PCR analysis of the expression of osteoblastic markers. Signal transduction pathways were analyzed by western blotting.

RESULTS

DFO increased osteogenic differentiation in a concentration-dependent manner by expression of the mRNA for differentiation markers and calcium nodule formation. Exposure of hPDLCs to DFO resulted in increases in the production of reactive oxygen species and in the levels of nuclear factor erythroid 2-related factor (Nrf2) protein in nuclear extractions, as well as a dose-dependent increase in the expression of Nrf2 target genes, including glutathione (GSH), glutathione S-transferase, γ-glutamylcysteine lygase, glutathione reductase and glutathione peroxidase. Pretreatment with Nrf2 small interfering RNA, GSH depletion by buthionine sulfoximine and diethyl maleate, and with antioxidants by N-acetylcysteine and vitamin E, blocked DFO-stimulated osteoblastic differentiation. Furthermore, pretreatment with GSH depletion and antioxidants blocked DFO-induced p38 MAPK, ERK, JNK and nuclear factor-kappaB pathways.

CONCLUSION

These data indicate, for the first time, that nontoxic DFO promotes osteoblastic differentiation of hPDLCs via modulation of the Nrf2-mediated antioxidant pathway.

Iron plays a key role in the cytodifferentiation of human periodontal ligament cells

BACKGROUND AND OBJECTIVE

The periodontal ligament (PDL) is vital to maintaining the homeostasis of the tooth and periodontal tissue. The influence of iron levels on the cytodifferentiation of PDL cells has not been studied, despite evidence that iron overload or deficiency can have adverse effects on alveolar bone density. The purpose of this study was to examine the effects of altered iron levels on cytodifferentiation in human PDL cells.

MATERIAL AND METHODS

Human PDL cells were incubated with culture media supplemented with 10-50 μm ammonium ferric citrate or 5 μm deferoxamine (an iron chelator) during differentiation. Intracellular iron status was assessed by measuring changes in the expression of ferritin RNA and protein. PDL cell differentiation and function were evaluated by measuring osteoblast differentiation gene markers and the capacity of cultures to form mineralized nodules.

RESULTS

Iron accumulation resulted in upregulation of light and heavy chain ferritin proteins. Concurrently, osteoblast differentiation gene markers and mineralized nodule formation were suppressed. Iron deficiency resulted in downregulation of light and heavy chain ferritin proteins, suppression of alkaline phosphatase activity and formation of mineralized nodules during PDL cell differentiation.

CONCLUSION

We conclude that iron is critical for normal cell differentiation of human PDL cells.

A comparison of the biological activities of human osteoblast hFOB1.19 between iron excess and iron deficiency

Bone metabolism has a close relationship with iron homeostasis. To examine the effects of iron excess and iron deficiency on the biological activities of osteoblast in vitro, human osteoblast cells (hFOB1.19) were incubated in a medium supplemented with 0-200 μmol/L ferric ammonium citrate and 0-20 μmol/L deferoxamine. The intracellular iron was measured by a confocal laser scanning microscope. Proliferation of osteoblasts was evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apoptotic cells were detected using annexin intervention V/PI staining with a flow cytometry. Alkaline phosphatase (ALP) activity was measured using an ALP assay kit. The number of calcified nodules and mineral area was evaluated by von Kossa staining assay. The expressions of type I collagen and osteocalcin of cultured osteoblasts were detected by reverse transcriptase polymerase chain reaction and Western blot. Intracellular reactive oxygen species (ROS) was measured using the oxidation-sensitive dye 2,7-dichlorofluorescin diacetate by flow cytometry. The results indicated that excessive iron inhibited osteoblast activity in a concentration-dependent manner. Low iron concentrations, in contrast, produced a biphasic manner on osteoblasts: mild low iron promoted osteoblast activity, but serious low iron inhibited osteoblast activity. Osteogenesis was optimal in certain iron concentrations. The mechanism underlying biological activity invoked by excessive iron may be attributed to increased intracellular ROS levels.