Iron overload-induced ferroptosis of osteoblasts inhibits osteogenesis and promotes osteoporosis: An in vitro and in vivo study

Iron dysregulation, ferroptosis, and oxidative stress in diabetic osteoporosis: Mechanisms, bone metabolism disruption, and therapeutic strategies

Diabetic osteoporosis (DOP) is a common complication in diabetes, driven by hyperglycemia-induced metabolic disturbances, chronic inflammation, and oxidative stress. This review describes the critical role of iron metabolism dysregulation in DOP pathogenesis, focusing on ferroptosis, a novel iron-dependent cell death pathway characterized by lipid peroxidation and reactive oxygen species (ROS) overproduction. Diabetic conditions exacerbate iron overload, impairing osteoblast function and enhancing osteoclast activity, while triggering ferroptosis in bone cells. Ferroptosis not only accelerates osteoblast apoptosis but also amplifies osteoclast-mediated bone resorption, synergistically promoting bone loss. Furthermore, chronic inflammation and oxidative stress disrupt the balance between bone formation and resorption, with elevated pro-inflammatory cytokines (e.g., tumor necrosis factor-α, interleukin-6) and ROS exacerbating cellular dysfunction. Therapeutic strategies targeting iron metabolism (e.g., deferoxamine) and ferroptosis inhibition (e.g., nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway activation, antioxidants like melatonin) demonstrate potential to mitigate DOP progression. Future research should prioritize personalized interventions, clinical trials of iron chelators and antioxidants, and mechanistic studies to refine therapeutic approaches. This review provides a comprehensive framework for understanding DOP pathogenesis and highlights innovative strategies to improve bone health in diabetic patients.

Pathophysiology of the Effects of Oxidative Stress on the Skeletal System

Reactive oxygen species (ROS) are molecules that are generated primarily during energy production in cells. ROS are involved in critical biological functions such as signal transduction; when the production of ROS is imbalanced, excessive ROS causes oxidative stress, and subsequent cellular damage. Oxidative stress is linked to numerous pathological disorders in major organs including the skeletal system. In an aging society, understanding the role of ROS in skeletal health is critical to developing preventative and therapeutic interventions. Oxidative stress causes defects in cellular differentiation, apoptosis, mitochondrial dysfunction, and inflammation. The effects of oxidative stress on the skeletal system have been implicated in the development of osteoporosis, knee osteoarthritis, and osteonecrosis by inhibiting bone remodeling, increasing osteoclast activity, and decreasing osteoblast function. ROS are also involved in many signaling pathways that regulate immune defense, cell proliferation, and inflammation. This underscores the importance of maintaining a balance between ROS and antioxidants to prevent oxidative stress and related diseases. Targeting ROS and oxidative stress mechanisms may offer new treatments for diseases affecting the skeletal system and other organs, potentially improving health outcomes, and extending healthy lifespans. This review highlights the significant impact of oxidative stress on skeletal health and explores potential preventative and therapeutic strategies to mitigate the adverse effects of ROS.

Focusing on ferroptosis in alveolar bone loss during periodontitis: From mechanisms to therapies

Periodontitis is an oral immunoinflammatory disease induced by bacterial infection. During periodontitis, the aggravating destruction of the alveolar bone can result in tooth movement and even tooth loss. Current conventional treatments for periodontitis primarily focus on infection control, but their effectiveness in halting and restoring alveolar bone destruction is limited. To identify additional therapeutic targets, researchers have been dedicated to investigating other pathological mechanisms underlying alveolar bone loss during periodontitis. Recently, findings indicate that ferroptosis plays a role in the development of periodontitis. Ferroptosis is a nonapoptotic type of cell death marked by iron accumulation and lipid peroxidation. Recent investigations have revealed the complex interplay of ferroptosis and inflammation. The positive feedback loop between ferroptosis and inflammation may significantly contribute to the exacerbation of alveolar bone loss. In light of the advancements in research within this field in recent years, this review intends to thoroughly summarize the processes by which ferroptosis aggravates alveolar bone loss during periodontitis, along with relevant ferroptosis-targeted therapeutic agents. By highlighting the latest advancements in this area, we hope this review will inspire researchers to develop novel therapeutic strategies for more effective inflammation control and regeneration of alveolar bone.

Ferroptosis-mediated immune responses in osteoporosis

Osteoporosis is a common systemic metabolic disease, characterized by decreased bone mass and susceptibility to fragility fractures, often associated with aging, menopause, genetics, and immunity. Ferroptosis plays an underestimated yet crucial role in the further impact of immune function changes on osteoporosis. Cell ferroptosis can induce alterations in immune function, subsequently influencing bone metabolism. In this context, this review summarizes several mechanisms of ferroptosis and introduces the latest insights on how ferroptosis regulates immune responses, exploring the interactions between ferroptosis and other mechanisms such as oxidative stress, inflammation, etc. This review elucidates potential treatment strategies for osteoporosis, emphasizing the promising potential of ferroptosis as an emerging target in the treatment of osteoporosis. In conclusion, preparations related to ferroptosis exhibit substantial clinical promise for enhancing bone mass restoration. The translational potential of this article: This review elucidates a nuanced conversation between the immune system and osteoporosis, with ferroptosis serving as the connecting link. These findings underscore the potential of ferroptosis inhibition as a therapeutic strategy for osteoporosis.

Lipocalin-2 Regulates Osteocyte Ferroptosis and Osteocyte-Osteoblast Crosstalk via Wnt Signaling to Control Bone Formation

Osteoporosis is a multifactorial disease, and emerging evidence suggests that iron overload contributes to its progression. Here, we identify Lipocalin-2 (LCN2), a cytokine secreted by bone cells with endocrine effects on other tissues, as a local regulator of osteocyte iron metabolism and a mediator of skeletal deterioration. Our findings reveal that LCN2 promotes iron accumulation, mitochondrial dysfunction, and ferroptosis in osteocytes in a process dependent on LCN2 receptor SLC22A17. Genetic ablation of Lcn2 (Dmp1-Cre; Lcn2 fl/fl ) in osteocytes mitigates their ferroptotic vulnerability by preserving mitochondrial integrity and limiting iron overload. Remarkably, LCN2 deletion enhances osteocyte dendricity and lacunocanalicular network, supporting their function in bone remodeling. Mechanistically, we demonstrate that Lcn2 ablation in osteocytes decreases DKK1 and SOST expression in bone, leading to increased Wnt/β-catenin signaling and osteoblast-driven bone formation. Using in vitro and in vivo approaches, we establish the LCN2-SLC22A17 axis as a key pathway linking iron homeostasis, osteocyte dysfunction, and skeletal remodeling. These findings provide insight into a previously unrecognized mechanism underlying iron-driven bone loss and suggest that targeting LCN2 could offer therapeutic potential for osteoporosis.

Evaluation of proanthocyanidins in treating Type 2 diabetic osteoporosis via SIRT6/Nrf2/GPX4 pathways

This study investigates the therapeutic potential of proanthocyanidins (PAC) in addressing Type 2 diabetic osteoporosis (T2DOP) by activating the SIRT6/Nrf2/GPX4 signaling pathways. T2DOP is characterized by compromised bone structure and heightened oxidative stress, where ferroptosis plays a pivotal role. Utilizing a T2DOP mouse model and MC3T3-E1 cells under high glucose conditions, we evaluated the impact of PAC on bone health and iron homeostasis. Our results, obtained through micro-CT, histological staining, Western blot, and immunofluorescence analyses, revealed reductions in bone density and decreased GPX4 expression in T2DOP conditions, indicating ferroptosis and oxidative stress. However, PAC treatment improved trabecular bone structure, reduced bone marrow adipocytes, decreased oxidative stress, and enhanced expression of key osteogenic proteins. These findings highlight PAC's potential in mitigating T2DOP through the SIRT6/Nrf2/GPX4 pathways, offering promising therapeutic insights for managing diabetic osteoporosis.

Circular RNA circSTX12 regulates osteo-adipogenic balance and proliferation of BMSCs in senile osteoporosis

Increased adipogenic differentiation and decreased osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) along with slow self-renewal are pivotal causes for decreased bone formation in senile osteoporosis. Circular RNAs (circRNAs) play important roles in cell proliferation and differentiation, and are closely related to osteoporosis. Whether circRNAs orchestrate the adipo-osteogenic balance and the proliferation of BMSCs in osteoporosis remains unclear. We found in this study that circSTX12 was abnormally upregulated in bone sections from osteoporosis patients and in BMSCs from aged mice, as well as in later-generation human BMSCs in culture. Knockdown of circSTX12 in BMSCs resulted in enhanced osteogenesis, decreased adipogenesis, and increased proliferation capacity; circSTX12 overexpression had the opposite effect. RNA pull-down and mass spectrometry revealed the interactions between circSTX12 with CBL and LMO7. At the molecular level, circSTX12 regulated cell fate in BMSCs by competitively binding to CBL, reducing the ubiquitination-mediated degradation of MST1 and thereby activating the Hippo pathway, a key regulator of adipo-osteogenic balance. Knockdown of circSTX12 promoted the nuclear localization of YAP. In addition, our findings suggest that LMO7 mediates circSTX12-induced BMSCs proliferation by regulating the transcription of CCNA2, CCNH, and CCND1. In vivo, injection of antisense oligonucleotides (ASOs) to knockdown circSTX12 promoted bone formation in aged mice. Our results provide evidence for circSTX12 as a regulator of adipo-osteogenic differentiation and proliferation of BMSCs through binding to CBL and LMO7, respectively. Targeting circSTX12 may be a novel approach for osteoporosis treatment.

The Role of Ferroptosis in Osteoporosis and Advances in Chinese Herbal Interventions

OP, a systemic bone disorder marked by reduced bone mass and heightened fracture risk, poses a significant global health burden, particularly among aging populations. Current treatments, including bisphosphonates and calcium supplementation, are limited by adverse effects and incomplete efficacy. Emerging research highlights ferroptosis-an iron-dependent cell death driven by lipid peroxidation-as a critical contributor to OP pathogenesis, characterized by dysregulated iron metabolism, oxidative stress, and lipid peroxide accumulation, which disrupt bone remodeling by impairing osteoblast function and enhancing osteoclast activity. This review elucidates the mechanistic interplay between ferroptosis and OP subtypes (diabetic osteoporosis (DOP), glucocorticoid-induced (GIOP), and postmenopausal osteoporosis (PMOP)) and evaluates the efficacy of Chinese herbal interventions in mitigating ferroptosis-driven bone loss. Key findings reveal that excess iron exacerbates lipid peroxidation via the Fenton reaction, while glutathione peroxidase 4 (GPX4) inactivation and system Xc- inhibition amplify oxidative damage. In DIOP, hyperglycemia-induced ROS and advanced glycation end products suppress osteogenesis, countered by melatonin and naringenin via nuclear factor -related factor 2 (Nrf2)/GPX4 activation. GIOP involves dexamethasone-mediated GPX4 downregulation, mitigated by exosomes and melatonin through phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling. PMOP driven by estrogen deficiency-induced iron overload is alleviated by aconitine and icariin (ICA) via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signal transducer and activator of transcription 3 (STAT3) pathways. Chinese herbs, including active compounds (quercetin, gastrodin, ICA, etc.) and formulations (Bugu Shengsui Capsule, Erxian Decoction (EXD), etc.), regulate iron metabolism, enhance antioxidant defenses (Nrf2/heme oxygenase 1(HO-1)), and inhibit lipid peroxidation, effectively restoring bone homeostasis. These findings underscore ferroptosis as a pivotal mechanism in OP progression and highlight the therapeutic promise of Chinese herbs in bridging traditional medicine with modern mechanistic insights. Future research should prioritize elucidating precise molecular targets, optimizing formulations, and validating clinical efficacy to address current therapeutic gaps.

Key role of the CSE/transsulfuration pathway in macrophage phenotypic change under iron overload

BACKGROUND

Iron homeostasis has a significant impact on the phenotypic transformation of macrophages and is implicated in various diseases. In this study, we evaluated the effect of cystathionine-gamma-lyase (CSE)/transsulfuration pathway in iron-overload induced macrophage phenotype change.

METHODS

The biochemical parameters, such as qRT-PCR, western blot, fluorescence staining, were assessed both in vitro and in vivo.

RESULTS

Iron overload disrupts iron metabolism and alters the expression of genes involved in iron transport, resulting in the polarization of macrophages towards the M1 phenotype and an alternating activation state of M2. Meanwhile, excessive iron led to an increase in lipid peroxidation levels and disrupted cysteine metabolism. By utilizing erastin to inhibit SLC7A11 activity and block exogenous cysteine uptake, we were able to observe the exacerbation of the proinflammatory state in macrophages under conditions of cysteine deprivation. The CSE/transsulfuration pathway, serves as the primary route for endogenous cysteine synthesis. In the presence of iron overload, the expression of CSE was upregulated and further enhanced by cysteine deprivation. Deletion of CSE in CSE-knockout mice exacerbated the inflammatory transition of iron-overloaded macrophages by impacting cysteine metabolism and ferritinophagy.

CONCLUSION

The CSE/transsulfuration pathway regulated macrophage phenotype change under iron-overload, which may offer novel insights into potential therapeutic strategies for iron overload-related disorders.

Crocin facilitates osteogenesis and angiogenesis by moderating oxidative stress and ferroptosis via Nrf2/GPX4 pathway

Bone formation is a complex multi-factor process of bone defect healing. Oxidative stress (OS) is predisposed to induce regulatory cell death (RCD), such as ferroptosis. At present, the antioxidant effects of Crocin on erastin induced oxidative damage were studied. The activity of bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) was detected by CCK-8 and EdU staining. The production of reactive oxygen species (ROS), MDA, SOD and GSH were evaluated. Western blotting assay was used to detect ferroptosis-related proteins. The osteogenic function of BMSCs was determined by alkaline phosphatase (ALP) activity, ALP staining and alizarin red S (ARS) staining. Western blotting and RT-PCR assays were used to detect the expression of osteogenic proteins and genes. Angiogenesis of HUVECs was evaluated by tube formation, RT-PCR, scratch test and Transwell assay. The results showed that Crocin can promote the osteogenic function of BMSCs and angiogenesis of HUVECs. In addition, Crocin protects cells from erastin-induced oxidative injury and inhibits ferroptosis via the Nrf2/GPX4 pathway. These findings suggest that Crocin can promote bone defect healing by regulating OS and inhibiting ferroptosis through the Nrf2/GPX4 pathway.

Human umbilical cord mesenchymal stem cell-derived exosomes promote osteogenesis in glucocorticoid-induced osteoporosis through PI3K/AKT signaling pathway-mediated ferroptosis inhibition

Glucocorticoid-induced osteoporosis (GIOP), the most common cause of secondary osteoporosis, is characterized by significant bone loss, decreased bone quality, and increased fracture risk. The current treatments for GIOP have several drawbacks. Exosomes are vital for cellular processes. However, very few studies have focused on using human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-EXOs) for GIOP treatment. In vitro and in vivo dexamethasone was used to evaluate the therapeutic effects of hUCMSC-EXOs on GIOP. CCK-8 and EdU assays were used to evaluate cell viability and proliferation, respectively. We conducted an alkaline phosphatase activity assay, alizarin red staining, Western blotting, and real-time PCR to detect the effect on osteogenesis. TMT-labeled quantitative proteomic and bioinformatic analyses were performed. Furthermore, we performed Western blotting, immunofluorescence, reactive oxygen species assays, and lipid peroxidation assays to investigate the regulatory mechanism by which hUCMSC-EXOs affect cell proliferation and osteogenic differentiation. The in vivo effects of hUCMSC-EXOs were evaluated using micro-CT, hematoxylin, and eosin staining, and immunohistochemical staining. We found that hUCMSC-EXOs reversed the inhibitory effects of glucocorticoids on human bone marrow stromal cell (hBMSC) proliferation and osteogenic differentiation and demonstrated that hUCMSC-EXOs reversed GIOP via the PI3K/AKT signaling pathway, inhibiting lipid peroxidation in vitro and in vivo. HUCMSC-EXOs promote hBMSC osteogenesis through the PI3K/AKT signaling pathway, inhibit ferroptosis, and have therapeutic potential for GIOP in mice.

Hepcidin knockout exacerbates hindlimb unloading-induced bone loss in mice through inhibiting osteoblastic differentiation

BACKGROUND

An oligopeptide hepcidin is encoded by the human HAMP gene (Hamp in mice). Its deficiency can result in iron overload, while excess may lead to iron deficiency. Hepcidin knockout mice exhibited iron accumulation in multiple tissues, accompanied by degeneration of bone microarchitecture and reduced biomechanical properties. Astronauts who are exposed to weightlessness during prolonged spaceflight experience bone loss. After space missions, an interrelation exists between iron stores and bone mineral density (BMD). Bone loss in mice due to unloading is linked to iron excess and involves hepcidin. The potential role of hepcidin in unloading-induced bone loss remains unclear.

METHODS

Our study conducted relevant experiments using hepcidin knockout mice and their primary osteoblasts as the research subjects. We used the hindlimb unloading (HLU) model and the random positioning machine (RPM) system to simulate weightlessness in vivo and in vitro.

RESULTS

HLU mice exhibited reduced hepcidin levels in the serum and liver. Hepcidin knockout further diminished BMD and bone mineral content (BMC) in the femurs of HLU mice. Similarly, the bone volume fraction (BV/TV) and connectivity density (Conn.Dn) followed this downward trend, whereas trabecular separation (Tb.Sp) showed an inverse pattern. Moreover, hepcidin knockout decreased the ultimate load and elastic modulus in the tibias of HLU mice. Hepcidin knockout decreased PINP levels in the serum, a commonly used marker for bone formation, alongside elevated iron levels in the serum, liver, and bone of HLU mice. We also found higher serum MDA and SOD levels in these mice. In vitro, experimental data indicated that hepcidin knockout suppresses the osteoblastic differentiation capacity under RPM conditions. Additionally, this condition upregulates SOST protein levels and downregulates LRP6 and β-catenin protein levels in osteoblasts.

CONCLUSION

Hepcidin knockout exacerbates bone loss in HLU mice, most likely due to reduced osteoblastic activity.

BMP9 alleviates iron accumulation-induced osteoporosis via the USP10/FOXO1/GPX4 axis

INTRODUCTION

Ferroptosis induced by iron accumulation can disrupt the physiological functions of bone marrow mesenchymal stem cells (BMSCs). BMP9 is an effective osteogenic factor. However, the role of BMP9 and its molecular mechanisms in osteoporosis induced by iron accumulation remain unclear.

OBJECTIVES

This study aims to explore the role and mechanism of BMP9 in alleviating iron accumulation induced osteoporosis.

METHODS

Clinical samples were collected to analyze the relationship between iron accumulation and osteoporosis. The effect of BMP9 on lipid peroxidation levels in BMSCs under iron accumulation conditions was assessed using C11-BODIPY staining, MitoSOX staining, MDA and SOD activity measurement. The osteogenic capacity of BMP9 in BMSCs under iron accumulation conditions was evaluated by measuring ALP activity and calcium nodule formation. The mechanisms of BMP9 in regulating BMSCs under iron accumulation conditions were explored through experiments including cycloheximide treatment, RT-PCR, Western blot, GST pull-down, ChIP, and CO-IP.

RESULTS

It was observed in human samples that serum ferritin levels were negatively correlated with the bone mineral density of the lumbar spine and femoral neck. Meanwhile, ferroptosis is considered a key factor affecting bone health. Further research indicated that BMP9 could inhibit ferroptosis in cells and animal models with iron accumulation, while also improving oxidative stress and osteogenic capacity. In-depth investigation of its mechanism reveals that BMP9 promotes the expression of USP10, which removes the K48-linked ubiquitin chains on FOXO1, inhibiting its excessive ubiquitination in the cytoplasm. This stabilization allows FOXO1 to accumulate in the cytoplasm and eventually re-enter the nucleus. This process activated the expression of the key inhibitor of cell death, GPX4, enhancing the cell's antioxidant response, reducing ferroptosis-induced damage to BMSCs, and promoting their osteogenic differentiation.

CONCLUSION

This study reveals that BMP9 inhibits ferroptosis through the USP10/FOXO1/GPX4 axis, providing a new therapeutic strategy for osteoporosis caused by iron accumulation.

Mechanisms of Ferroptosis in bone disease: A new target for osteoporosis treatment

Osteoporosis (OP) is a common disease in the elderly, characterized by decreased bone strength, reduced bone density, and increased fracture risk. There are two clinical types of osteoporosis: primary osteoporosis and secondary osteoporosis. The most common form is postmenopausal osteoporosis, which is caused by decreased estrogen production after menopause. Secondary osteoporosis, on the other hand, occurs when certain medications, diabetes, or nutritional deficiencies lead to a decrease in bone density. Ferroptosis, a new iron-dependent programmed cell death process, is critical in regulating the development of osteoporosis, but the underlying molecular mechanisms are complex. In the pathologic process of osteoporosis, several studies have found that ferroptosis may occur in osteocytes, osteoblasts, and osteoclasts, cell types closely related to bone metabolism. The imbalance of iron homeostasis in osteoblasts and excessive iron accumulation can promote lipid peroxidation through the Fenton reaction, which induces ferroptosis in osteoblasts and affects their role in regulating bone metabolism. Ferroptosis in osteoblasts inhibits bone formation and reduces the amount of new bone production. Osteoclast-associated ferroptosis abnormalities, on the other hand, may alter the homeostasis of bone resorption. In this paper, we start from the molecular mechanism of ferroptosis, and introduce the ways in which ferroptosis affects the physiological and pathological processes of the body. After that, the effects of ferroptosis on osteoblasts and osteoclasts will be discussed separately to elucidate the molecular mechanism between ferroptosis and osteoporosis, which will provide a new breakthrough for the prevention and treatment of osteoporosis and a more effective and better idea for the treatment strategy of osteoporosis.

Iron-lead mixed exposure causes bone damage in mice: A multi-omics analysis

Excessive intake of essential and toxic metals affects the pathological process of osteoporosis. At present, the effects of single forms of iron (Fe), lead (Pb) and other metals on bone injury have been widely studied. However, these metal elements usually do not exist in the environment in a separate form. They are ingested in various ways and are often found together in the human body. However, the mechanism of bone damage caused by Fe and Pb mixed exposure is still unclear at this stage. At present, the combined analysis of multi-omics is the conventional method to explore the molecular mechanism behind the disease. Therefore, we attempted to combine proteomics and metabolomics to explain the mechanism of bone damage caused by mixed Fe and Pb exposure. Differential proteins and metabolites were found to be predominantly enriched in the JAK-STAT signalling pathway, inflammatory bowel disease (IBD), and osteoclast differentiation. Combined analysis showed that Fpr2, Lifr, Lisofylline, 7-Ketocholesterol, LacCer (d18: 1/14:0) and other substances may be involved in the process of bone injury mediated by mixed metal exposure. In summary, we hypothesise that mixed exposure to Fe and Pb leads to osteoclast activation via the JAK-STAT signalling pathway in situ and indirectly via the gut-bone axis, resulting in bone damage. In general, our study potentially suggests that bone injury induced by mixed exposure of Fe and Pb may be related to osteoclast proliferation mediated by changes in inflammatory levels in vivo.

Reducing PDK4 level constitutes a pivotal mechanism for glucocorticoids to impede osteoblastic differentiation through the enhancement of ferroptosis in mesenchymal stem cells

BACKGROUND

This study mainly explores the possible role and mechanism of pyruvate dehydrogenase kinase 4 (PDK4) in the onset and development of Glucocorticoid-induced osteoporosis (GIOP), and seeks potential targets for the treatment of GIOP.

METHODS

Mesenchymal stem cells (MSCs) were treated with osteogenic induction medium. An in vitro osteogenic damage model was established by exposing MSCs to a high concentration (10- 6 M) of dexamethasone (DEX). Osteogenic markers were measured with real-time quantitative polymerase chain reaction, western blot, alkaline phosphatase staining, and Alizarin Red S staining. Ferroptosis markers were assessed through reactive oxygen species (ROS) fluorescent probe, transmission electron microscopy, and measurement of malondialdehyde (MDA). The potential mechanism was investigated using RT-qPCR, western blot, lysosomal probes, molecular docking, and other analytical approaches. The role of PDK4 was validated by using a GIOP rat model, micro-computed tomography and Masson's trichrome staining.

RESULTS

High concentrations (10- 6 M) of DEX inhibited osteogenic differentiation in C3H10T1/2 cells, and PDK4 exhibited the opposite effect. PDK4 partially reversed the osteogenic inhibitory effect of DEX both in vivo and in vitro. DEX caused mitochondrial shrinkage and disappearance of cristae in C3H10T1/2 cells, as well as an increase in total iron, ROS, MDA contents, and the level of ferroptosis key factors. These changes were partially weakened by PDK4. The ferroptosis inhibitor ferrostatin-1 partially blocked the inhibitory effect of DEX, while ferroptosis inducer RSL3 inhibited osteogenic differentiation and weakened the reversal effect of PDK4. DEX reduced the protein level of PDK4, which was partially weakened by Bafilomycin A1. The molecular docking results showed that DEX can directly bind with PDK4.

CONCLUSION

PDK4 can enhance the osteogenic differentiation ability of MSCs and bone mass of GIOP rats. DEX may promote the degradation of PDK4 via lysosome pathway, through which to weaken the osteogenic ability of MSCs by increasing ferroptosis. PDK4 may become a potential target for improving GIOP.

Three signalling pathways for iron overload in osteoporosis: a narrative review

Osteoporosis is a metabolic bone disease characterized by a decrease in the amount of bone tissue per unit volume and changes in bone microstructure, often resulting in bone fragility and increased susceptibility to fracture. Iron plays an important role in the normal physiological activities of human body, and its abnormal metabolism is one of the risk factors of osteoporosis. Iron overload, as an abnormality of iron metabolism, has been reported to be associated with osteoporosis in recent years. However, the mechanism of iron overload involved in the process of osteoporosis is not fully understood. In this review, we summarize what we have learned about iron overload-associated bone loss from clinical studies and animal models. Starting from the three signaling pathways of Wnt/β-catenin, BMP/SMADs, PI3K/AKT/mTOR, the mechanism of iron overload affecting the process of osteoporosis was explored, we got the conclusion that iron overload accelerates the process of osteoporosis by inhibiting normal wnt signaling, suppressing the BMP-2/SMADs pathway, down-regulating the PI3K/AKT/mTOR pathway to inhibit bone formation, and destroying the bone strength and load-bearing capacity, which providing a new direction for clinical treatment.

Analysis of the association between mixed exposure to multiple metals and comorbidity of osteopenia or osteoporosis: baseline data from the Chinese Multi-Ethnic Cohort study (CMEC)

Both osteoporosis and metal exposure are well-recognized public health concerns globally, particularly in the aging population. However, studies investigating the relationship between metal exposure and bone health conditions such as osteopenia and osteoporosis have either produced inconsistent results or are scarce, especially among the ethnic minorities in China. Herein, we correlated single-metal and metal mixture exposure with osteopenia and osteoporosis using a log-binomial regression model and quantile g-computation. In total, 9,206 ethnic Chinese individuals (Dong and Miao) aged 30-79 years were investigated in this study utilizing the baseline data from the Chinese multi-ethnic cohort study. In the single-metal exposure model, urinary concentrations of arsenic (As), cadmium (Cd), chromium (Cr), iron(Fe), mercury(Hg), and manganese (Mn) were positively associated with of osteopenia, whereas those of cobalt(Co) and zinc(Zn) concentrations were negatively associated. Additionally, urinary As, Cd, Cr, and Mn concentrations were positively associated with osteoporosis, whereas that of vanadium(V) was negatively associated. Furthermore, Quantile g-computation results indicated that metal mixture exposure was positively associated with both osteopenia and osteoporosis. Altogether, these findings suggest that simultaneous exposure to multiple metals can affect bone health, providing a theoretical basis for further studies on underlying complex mechanisms.

Osteosarcoma Cells and Undifferentiated Human Mesenchymal Stromal Cells Are More Susceptible to Ferroptosis than Differentiated Human Mesenchymal Stromal Cells

Current research suggests that promoting ferroptosis, a non-apoptotic form of cell death, may be an effective therapy for osteosarcoma, while its inhibition could facilitate bone regeneration and prevent osteoporosis. Our objective was to investigate whether the susceptibility to and regulation of ferroptosis differ between undifferentiated (UBC) and differentiated (DBC) human bone marrow stromal cells, as well as human osteosarcoma cells (MG63). Ferroptosis was induced by either inhibiting glutathione peroxidase 4 (GPX4) using RSL3 or blocking all glutathione-dependent enzymes through inhibition of the glutamate/cysteine antiporter with Erastin. Lipid peroxidation was assessed using the fluorescent probe BODIPY™581/591C11, while Ferrostatin-1 was used to inhibit ferroptosis. We demonstrate that neither Erastin nor RSL3 induces ferroptosis in DBC. However, both RSL3 and Erastin induce ferroptosis in UBC, while Erastin predominantly induces ferroptosis in MG63 cells. Our data suggest that ferroptosis induction in undifferentiated hBMSCs is primarily regulated by GPX4, whereas glutathione S-Transferase P1 (GSTP1) plays a key role in controlling ferroptosis in osteosarcoma cells. In conclusion, targeting the key pathways involved in ferroptosis across different bone cell types may improve the efficacy of cancer treatments while minimizing collateral damage and supporting regenerative processes, with minimal impact on cancer therapy.

Association of dietary niacin intake with osteoporosis in the postmenopausal women in the US: NHANES 2007-2018

Background

Elderly individuals with inadequate vitamin B level are at increased risk of degenerative conditions, notably cardiovascular disorders, cognitive impairments, and osteoporosis. The relationship between niacin (vitamin B3) consumption and osteoporosis risk remains a subject of debate. This study aimed to clarify the relationship between dietary niacin intake and the incidence of osteoporosis in postmenopausal women aged ≥50 years.

Methods

In this study, we gathered details on participants' bone mineral density, osteoporosis status, dietary niacin intake, and several other critical variables. Multivariate logistic regression models were constructed to determine the association between dietary niacin intake and the incidence of osteoporosis. Restricted cubic splines were employed to further assess the linearity and explore the shape of the dose-response associations. Additionally, we performed stratified and interaction analyses to illustrate the stability of the observed relationships across different subgroups.

Results

After adjusting for all covariates, there was a significant inverse association with osteoporosis (OR = 0.87; 95% CI: 0.77-0.97; p = 0.016). A negative relationship was observed between dietary niacin intake and the risk of osteoporosis (nonlinear: p = 0.672). While stratified analyses revealed some differences in the association between dietary niacin intake and osteoporosis risk, these differences were not statistically significant.

Conclusion

Dietary niacin intake exhibited an inverse correlation with the incidence of osteoporosis. The risk of osteoporosis was significantly reduced by 13% with every 10 mg/day increase in daily dietary niacin consumption among postmenopausal women.

Lipid peroxidation inhibition by icaritin and its glycosides as a strategy to combat iron overload-induced osteoporosis in zebrafish

This study provides a comprehensive evaluation of the anti-osteoporotic effects of flavonoids derived from Epimedium, including icaritin and its six glycosides-icariside I, icariside II, icariin, epimedin A, epimedin B, and epimedin C-using a zebrafish model of iron overload-induced osteoporosis. Our results demonstrate a significant increase in lipid peroxidation in zebrafish subjected to ferric ammonium citrate (FAC)-induced osteoporosis, along with impaired expression and activity of glutathione peroxidase 4 (GPX4). Treatment with ferrostatin-1, a lipid peroxide scavenger, partially alleviated the osteoporotic effects induced by FAC, implying that lipid peroxidation may play a key role in iron overload-related osteoporosis. We observed varying degrees of anti-osteoporotic activity and enhancement of osteogenic differentiation markers, such as bmp2b, runx2b, col1a1a, and alp, among icaritin and its glycosides. Notably, icaritin exhibited the most potent inhibitory effects on osteoporosis, while epimedin A and epimedin B showed enhanced efficacy compared to other glycosides, correlating closely with their ability to suppress lipid peroxidation. Additionally, through CETSA, molecular docking, and dynamic simulation studies, we identified an interaction between icaritin and GPX4, which may help stabilizing GPX4 against FAC-induced lipid peroxidation. These findings suggest that the anti-osteoporotic effects of icaritin and its glycosides are linked to their ability to suppress lipid peroxidation, offering potential therapeutic insights for managing iron overload-induced osteoporosis.

Indoxyl sulfate exacerbates alveolar bone loss in chronic kidney disease through ferroptosis

OBJECTIVES

The purpose of this study was to determine whether indoxyl sulfate (IS) is involved in alveolar bone deterioration and to elucidate the mechanism underlying alveolar bone loss in chronic kidney disease (CKD) patients.

MATERIALS AND METHODS

Mice were divided into the control group, CP group (ligature-induced periodontitis), CKD group (5/6 nephrectomy), and CKD + CP group. The concentration of IS in the gingival crevicular fluid (GCF) was determined by HPLC. The bone microarchitecture was evaluated by micro-CT. MC3T3-E1 cells were stimulated with IS, and changes in mitochondrial morphology and ferroptosis-related factors were detected. RT-PCR, western blotting, alkaline phosphatase activity assays, and alizarin red S staining were utilized to assess how IS affects osteogenic differentiation.

RESULTS

Compared with that in the other groups, alveolar bone destruction in the CKD + CP group was more severe. IS accumulated in the GCF of mice with CKD. IS activated the aryl hydrocarbon receptor (AhR) in vitro, inhibited MC3T3-E1 cell osteogenic differentiation, caused changes in mitochondrial morphology, and activated the SLC7A11/GPX4 signaling pathway. An AhR inhibitor attenuated the aforementioned changes induced by IS.

CONCLUSIONS

IS activated the AhR/SLC7A11/GPX4 signaling pathway, inhibited osteogenesis in MC3T3-E1 cells, and participated in alveolar bone resorption in CKD model mice through ferroptosis.

Depletion of macrophages and osteoclast precursors mitigates iron overload-mediated bone loss

Iron is an essential element for physiological cellular processes, but is toxic in excess. Iron overload diseases are commonly associated with low bone mass. Increased bone resorption by osteoclasts as well as decreased bone formation by osteoblasts have been implicated in bone loss under iron overload conditions. However, the exact contribution of individual cell types has not yet been formally tested. In this study, we aimed to investigate the role of osteoclast precursors in iron overload-induced bone loss. To that end, we used clodronate liposomes to deplete phagocytic cells (including macrophages and osteoclast precursors) in male C57BL/6J mice that were exposed to ferric derisomaltose. Bone microarchitecture and bone turnover were assessed after 4 weeks. The application of clodronate resulted in the efficient depletion of circulating myeloid-lineage cells by about 70%. Depletion of osteoclast precursors mitigated iron overload-induced trabecular bone loss at the lumbar vertebrae and distal femur. While clodronate treatment led to a profound inhibition of bone turnover in control mice, it significantly reduced osteoclast numbers in iron-treated mice without further impacting the bone formation rate or serum PINP levels. Our observations suggest that even though bone formation is markedly suppressed by iron overload, osteoclasts also play a key role in iron overload-induced bone loss and highlight them as potential therapeutic targets.

Aucubin Promotes BMSCs Proliferation and Differentiation of Postmenopausal Osteoporosis Patients by Regulating Ferroptosis and BMP2 Signalling

Postmenopausal osteoporosis (PMOP) is a chronic systemic bone metabolism disorder. Promotion in the patterns of human bone marrow mesenchymal stem cells (hBMSCs) differentiation towards osteoblasts contributes to alleviating osteoporosis. Aucubin, a natural compound isolated from the well-known herbal medicine Eucommia, was previously shown to possess various pharmacological effects. However, its effects on hBMSCs of PMOP patients are unknown. The aim of this present research was to investigate the impact and underlying process of aucubin on cell proliferation and osteogenic differentiation in hBMSCs isolated from PMOP patients. The ability of aucubin to inhibit the ferroptosis induced by erastin in hBMSCs was detected; ROS production, ferrous ion levels, SOD, MDA, and GPX activities were tested by using commercial kits. Next, ALP staining, ARS staining, RT-qPCR, RNA-sequencing, and Western blot were applied for determining the mRNA and protein expression levels associated with the osteogenesis of hBMSCs. The study also explored the involvement of BMP2/Smads signalling in aucubin promoting the osteogenesis of hBMSCs and evaluated the effects of aucubin intervention on osteoporosis using an ovariectomised rat model. The results indicated that aucubin significantly inhibited ROS generation and oxidative stress induced by erastin and protected against ferroptosis in hBMSCs. Additionally, aucubin facilitated osteogenic differentiation of hBMSCs by activating the BMP2/SMADs pathway and attenuated the progression of osteoporosis in OVX rats, suggesting a potential therapeutic benefit for postmenopausal osteoporosis (PMOP).

Natural Products in the Prevention of Degenerative Bone and Joint Diseases: Mechanisms Based on the Regulation of Ferroptosis

Degenerative bone and joint diseases (DBJDs), characterized by osteoporosis, osteoarthritis, and chronic inflammation of surrounding soft tissues, are systemic conditions primarily affecting the skeletal system. Ferroptosis, a programmed cell death pathway distinct from apoptosis, autophagy, and necroptosis. Accumulating evidence suggests that ferroptosis is intricately linked to the pathogenesis of DBJDs, and targeting its regulation could be beneficial in managing these conditions. Natural products, known for their anti-inflammatory and antioxidant properties, have shown unique advantages in preventing DBJDs, potentially through modulating ferroptosis. This article provides an overview of the latest research on ferroptosis, with a focus on its role in the pathogenesis of DBJDs and the therapeutic potential of natural products targeting this cell death pathway, offering novel insights for the prevention and treatment of DBJDs.

Targeting EZH2 attenuates the ferroptosis-mediated osteoblast-osteoclast imbalance in rheumatoid arthritis

OBJECTIVE

The enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) can regulate osteogenesis and osteoclastogenesis. This study aimed to further explore the effects of EZH2 modification on ferroptosis and the osteoblast-osteoclast balance in rheumatoid arthritis (RA) in vitro and in vivo.

METHODS

Bone marrow mesenchymal stromal cells were transfected with EZH2 overexpression (oeEZH2) and EZH2 shRNA (shEZH2) plasmids with or without ferrostatin-1 (Fer-1) treatment and subjected to an osteoblast differentiation assay. The cells were then cocultured with bone marrow-derived macrophages and subjected to an osteoclast differentiation assay. Collagen-induced arthritis (CIA) mice were generated and injected with shEZH2 adeno-associated virus (AAV).

RESULTS

OeEZH2 repressed osteoblast differentiation, as reflected by decreased ALP and Alizarin Red S staining and increased OPN, RUNX2, OPG and RANKL; however, shEZH2 had the opposite effects. Besides, oeEZH2 promoted osteoblast ferroptosis, as suggested by increased MDA, Fe2+, ROS, and PTGS2 but decreased GPX4 and SLC7A11; these effects could be attenuated by Fer-1 treatment. In contrast, shEZH2 ameliorated osteoblast ferroptosis. OeEZH2 subsequently increased osteoclast differentiation, as indicated by increased TRAP+ multinucleated cells, NFATC1, CTSK, and c-FOS; however, shEZH2 had the opposite effect, except that it did not regulate CTSK. In CIA mice, shEZH2 AAV decreased the clinical symptom score, histological score of cartilage, and systemic inflammation (TNF-α and IL-6) and repressed bone ferroptosis and restored the osteoblast-osteoclast balance to some extent, as reflected by immunohistochemical staining of related markers.

CONCLUSION

Targeting EZH2 attenuates the ferroptosis-mediated osteoblast-osteoclast imbalance in RA, revealing its potential as a treatment target.

Integrative bioinformatics and experimental analysis of curcumin's role in regulating ferroptosis to combat osteoporosis

This study utilized bioinformatics and data mining techniques to explore the molecular mechanism of curcumin in treating osteoporosis (OP) through the lens of ferroptosis, thereby identifying novel therapeutic targets. The datasets GSE35958, GSE35956, GSE7429, and GSE7158 were obtained from the Gene Expression Omnibus (GEO) database. GSE35958 and GSE35956 were employed as training sets for data integration, while GSE7429 and GSE7158 served as independent validation sets. Through retrieval from the FerrDb database, iron death-related genes (FRGs) were identified, and the differentially expressed genes (DEGs) were intersected to obtain differentially expressed FRGs (DEFRGs). Subsequently, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted, followed by the construction of a Protein-Protein Interaction (PPI) network to identify Hub genes. The DGIdb database was utilized to predict candidate drugs associated with the Hub genes, and molecular docking and in vitro experiments confirmed that curcumin targets the Hub genes EGFR and PTGS2.Through in vitro testing of curcumin on BMSC cells, researchers examined cell vitality, iron death, osteogenic differentiation, mineralization, and the impact on EGFR and PTGS2 levels. The analysis yielded 2212 DEGs, 484 FRGs, with 45 FDEGs at the intersection. GO analysis revealed involvement in regulating mitochondrial proteins, amino acid transport across plasma membranes, and protein ubiquitination. KEGG pathway analysis indicated associations with iron death, FoxO signaling, mTOR signaling, cell aging, osteoclast differentiation, and GSH metabolism. Utilizing the MCC algorithm, five Hub genes were identified: MAPK3, PTGS2, TGFB1, CYBB, and EGFR, showing diagnostic potential for iron death. Curcumin displayed affinity for EGFR and PTGS2, mitigating iron-induced effects on BMSCs such as increased reactive oxygen species, Fe3+ levels, and decreased mitochondrial membrane potential. Furthermore, curcumin reversed these effects, suggesting EGFR and PTGS2 as targets for curcumin to inhibit BMSC ferroptosis and potentially delay osteoporosis development. Maintaining iron homeostasis and targeting BMSC ferroptosis could offer therapeutic avenues for iron overload-induced osteoporosis.

Pharmacology and mechanisms of apigenin in preventing osteoporosis

Osteoporosis (OP) stands as the most prevalent systemic skeletal condition associated with aging. The current clinical management of OP predominantly depends on anti-resorptive and anabolic agents. Nevertheless, prolonged use of some of these medications has been observed to reduce efficacy and elevate adverse effects. Given the necessity for sustained or even lifelong treatment of OP, the identification of drugs that are not only effective but also safe and cost-efficient is of utmost significance. As disease treatment paradigms continue to evolve and recent advancements in OP research come to light, certain plant-derived compounds have emerged, presenting notable benefits in the management of OP. This review primarily explores the pharmacological properties of apigenin and elucidates its therapeutic mechanisms in the context of OP. The insights provided herein aspire to offer a foundation for the judicious use of apigenin in forthcoming research, particularly within the scope of OP.

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.

Salidroside alleviates ferroptosis in FAC-induced Age-related macular degeneration models by activating Nrf2/SLC7A11/GPX4 axis

INTRODUCTION

Age-related macular degeneration (AMD) is a significant contributor to irreversible impairment in visual capability, particularly in its non-neovascular (dry) form. Ferroptosis, an emerging form of programmed necrosis, involves generating lipid peroxidation (LOS) through free iron and reactive oxygen species (ROS). Salidroside, a glycoside from Rhodiola rosea, known for anti-inflammatory and antioxidant properties. The research aim was exploring whether ferroptosis exists in dry AMD pathogenesis and elucidate salidroside's protective mechanisms against ferroptosis in AMD murine models and ARPE-19 cells.

METHODS

ARPE-19 cells were treated with varying concentrations of ferrous ammonium citrate (FAC) and salidroside. In an in vivo model, C57BL/6 mice were administered intraperitoneal injections of salidroside for 7 consecutive days, followed by an intravitreal injection (IVT) of FAC. After 7 days, the eyeballs were harvested for subsequent analyses. Ferroptosis markers were assessed using western blotting, immunofluorescence staining, and flow cytometry. To further elucidate the modulatory role of Nrf2 in ferroptosis, ARPE-19 cells were transfected with si-Nrf2.

RESULTS

In vitro, FAC-treated ARPE-19 cells exhibited reduced viability, decreased mitochondrial membrane potential (MMP), and accumulation of iron and lipid peroxidation (LOS) products. In vivo, FAC administration by IVT led to outer nuclear layer thinning and compromised tight junctions in RPE cells. The GPX4, Nrf2, and SLC7A11 expressions were downregulated both in vitro and in vivo. Salidroside upregulated Nrf2 and ameliorated these outcomes, but its effects were attenuated in ARPE-19 cells transfected with si-Nrf2.

CONCLUSION

Our study establishes that FAC induces RPE cell ferroptosis within dry AMD, and salidroside exerts therapeutic effects by triggering Nrf2/SLC7A11/GPX4 signaling axis.

A two-pronged approach to inhibit ferroptosis of MSCs caused by the iron overload in postmenopausal osteoporosis and promote osseointegration of titanium implant

Postmenopausal osteoporosis (PMOP) is a prevalent condition among elderly women. After menopause, women exhibit decreased iron excretion, which is prone to osteoporosis. To design a specific titanium implant for PMOP, we first analyze miRNAs and DNA characteristics of postmenopausal patients with and without osteoporosis. The results indicate that iron overload disrupts iron homeostasis in the pathogenesis of PMOP. Further experiments confirm that iron overload can cause lipid peroxidation and ferroptosis of MSCs, thus breaking bone homeostasis. Based on the findings above, we have designed a novel Ti implant coated with nanospheres of caffeic acid (CA) and deferoxamine (DFO). CA can bind on the Ti surface through the two adjacent phenolic hydroxyls and polymerize into polycaffeic acid (PCA) dimer, as well as the PCA nanospheres with the repetitive 1,4-benzodioxan units. DFO was grafted with PCA through borate ester bonds. The experimental results showed that modified Ti can inhibit the ferroptosis of MSCs in the pathological environment of PMOP and promote osseointegration in two main ways. Firstly, DFO was released under high oxidative stress, chelating with excess iron and decreasing the labile iron pool in MSCs. Meanwhile, CA and DFO activated the KEAP1/NRF2/HMOX1 pathway in MSCs and reduced the level of intracellular lipid peroxidation. So, the ferroptosis of MSCs is inhibited by promoting the SLC7A11/GSH/GPX4 pathway. Furthermore, the remained CA coating on the Ti surface could reduce the extracellular oxidative stress and glutathione level. This study offers a novel inspiration for the specific design of Ti implants in the treatment of PMOP.

The Role and Interactive Mechanism of Endoplasmic Reticulum Stress and Ferroptosis in Musculoskeletal Disorders

Endoplasmic reticulum (ER) stress is a cellular phenomenon that arises in response to the accumulation of misfolded proteins within the ER. This process triggers the activation of a signalling pathway known as the unfolded protein response (UPR), which aims to restore ER homeostasis by reducing protein synthesis, increasing protein degradation, and promoting proper protein folding. However, excessive ER stress can perturb regular cellular function and contribute to the development of diverse pathological conditions. As is well known, ferroptosis is a kind of programmed cell death characterized by the accumulation of lipid peroxides and iron-dependent reactive oxygen species (ROS), resulting in oxidative harm to cellular structures. In recent years, there has been increasing evidence indicating that ferroptosis occurs in musculoskeletal disorders (MSDs), with emerging recognition of the complex relationship between ER stress and ferroptosis. This review presents a summary of ER stress and the ferroptosis pathway. Most importantly, it delves into the significance of ER stress in the ferroptosis process within diverse skeletal or muscle cell types. Furthermore, we highlight the potential benefits of targeting the correlation between ER stress and ferroptosis in treating degenerative MSDs.

[Research progress on the regulatory cell death of osteoblasts in periodontitis]

Periodontitis is a chronic inflammatory disease characterized by progressive destruction of alveolar bone. The most critical mechanism underlying alveolar bone destruction is the imbalance of bone homeostasis, where osteoblast-mediated bone matrix synthesis plays an important role in regulating bone homeostasis. Regulated cell death is instrumental in both the inflammatory microenvironment and the regulation of bone homeostasis. Chronic inflammation, oxidative stress, and other factors can be directly involved in mitochondrial and death receptor-mediated signaling pathways, modulating B-cell lymphoma 2 family proteins and cysteine aspartic acid specific protease (caspase) activity, thereby affecting osteoblast apoptosis and alveolar bone homeostasis. Chronic inflammation and cellular damage induce osteoblast necroptosis via the RIPK1/RIPK3/MLKL signaling pathway, exacerbating the inflammatory response and accelerating alveolar bone destruction. Stimuli such as pathogenic microorganisms and cellular injury may also activate caspase-1-dependent or independent signaling pathways and gasdermin D family proteins, promoting osteoblast pyroptosis and releasing pro-inflammatory cytokines to mediate alveolar bone damage. Iron overload and lipid peroxidation in periodontitis can trigger ferroptosis in osteoblasts, impacting their survival and function, ultimately leading to bone homeostasis imbalance. This article focuses on the mechanism of periodontal disease affecting bone homeostasis through regulatory cell death, aiming to provide research evidence for the treatment of periodontitis and alveolar bone homeostasis imbalance.

Intelligent Supramolecular Modification for Implants: Endogenous Regulation of Bone Defect Repair in Osteoporosis

Addressing osteoporosis-related bone defects, a supramolecular strategy is innovated for modifying carbon fiber reinforced polyether ether ketone (CF/PEEK) composites. By covalently attaching intelligent macromolecules via in situ RAFT polymerization, leveraging the unique pathological microenvironment in patients with iron-overloaded osteoporosis, intelligent supramolecular modified implant surface possesses multiple endogenous modulation capabilities. After implantation, surface brush-like macromolecules initially resist macrophage adhesion, thereby reducing the level of immune inflammation. Over time, the molecular chains undergo conformational changes due to Fe (III) mediated supramolecular self-assembly, transforming into mechanistic signals. These signals are then specifically transmitted to pre-osteoblast cell through the binding capacity of the KRSR short peptide at the molecular terminus, induced their osteogenic differentiation via the YAP/β-catenin signaling axis. Furthermore, osteoblasts secrete alkaline phosphatase (ALP), which significantly hydrolyzes phosphate ester bonds in surface macromolecular side groups, resulting in the release of alendronate (ALN). This process further improves the local osteoporotic microenvironment. This intelligent surface modification tailors bone repair to individual conditions, automatically realize multiple endogenous regulation once implanted, and truly realize spontaneous activation of a series of responses conducive to bone repair in vivo. It is evidenced by improved bone regeneration in iron-overloaded osteoporotic rabbits and supported by in vitro validations.

Ferroptosis: Regulatory mechanisms and potential targets for bone metabolism: A review

Bone homeostasis is a homeostasis process constructed by osteoblast bone formation and osteoclast bone resorption. Bone homeostasis imbalance and dysfunction are the basis for the development of various orthopedic diseases such as osteoporosis, osteoarthritis, and steroid-induced avascular necrosis of femoral head. Previous studies have demonstrated that ferroptosis can induce lipid peroxidation through the generation of reactive oxygen species, activate a number of signaling pathways, and participate in the regulation of osteoblast bone formation and osteoclast bone resorption, resulting in bone homeostasis imbalance, which is an important factor in the pathogenesis of many orthopedic diseases, but the mechanism of ferroptosis is still unknown. In recent years, it has been found that, in addition to iron metabolism and intracellular antioxidant system imbalance, organelle dysfunction is also a key factor affecting ferroptosis. This paper takes this as the starting point, reviews the latest literature reports at home and abroad, elaborates the pathogenesis and regulatory pathways of ferroptosis and the relationship between ferroptosis and various organelles, and summarizes the mechanism by which ferroptosis mediates bone homeostasis imbalance, with the aim of providing new directions for the research related to ferroptosis and new ideas for the prevention and treatment of bone and joint diseases.

Picein alleviates oxidative stress and promotes bone regeneration in osteoporotic bone defect by inhibiting ferroptosis via Nrf2/HO-1/GPX4 pathway

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to abnormal oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation, making the OP-related bone healing a significant clinical challenge. As the osteogenic differentiation ability of bone marrow mesenchymal stem cells (BMSCs) is closely related to bone regeneration; currently, this study assessed the effects of Picein on BMSCs in vitro and bone regeneration in osteoporotic bone defect in vivo. Cell viability was determined by CCK-8 assay. The production of (ROS), malonaldehyde, superoxide dismutase activities, and glutathione was evaluated by using commercially available kits, and a flow cytometry analysis was adopted to detect macrophage polarization. Osteogenic capacity of BMSCs was evaluated by alkaline phosphatase (ALP) activity, ALP staining, and Alizarin red S staining. The expression of osteogenic-related proteins (OPN, Runx-2, OCN) and osteogenic-related genes (ALP, BMP-4, COL-1, and Osterix) were evaluated by Western blotting and real-time PCR (RT-PCR). In addition, proliferation, migration ability, and angiogenic capacity of human umbilical vein endothelial cells (HUVECs) were evaluated by EdU staining, scratch test, transwell assay, and tube formation assay, respectively. Angiogenic-related genes (VEGF, vWF, CD31) were also evaluated by RT-PCR. Results showed that Picein alleviated erastin-induced oxidative stress, enhanced osteogenic differentiation capacity of BMSCs, angiogenesis of HUVECs, and protects cells against ferroptosis through Nrf2/HO-1/GPX4 axis. Moreover, Picein regulate immune microenvironment by promoting the polarization of M2 macrophages in vitro. In addition, Picein also reduce the inflammation levels and promotes bone regeneration in osteoporotic bone defect in OP rat models in vivo. Altogether, these results suggested that Picein can promote bone regeneration and alleviate oxidative stress via Nrf2/HO-1/GPX4 pathway, offering Picein as a novel antioxidant agent for treating osteoporotic bone defect.

Exogenous Iron Induces Mitochondrial Lipid Peroxidation, Lipofuscin Accumulation, and Ferroptosis in H9c2 Cardiomyocytes

Lipid peroxidation plays an important role in various pathologies and aging, at least partially mediated by ferroptosis. The role of mitochondrial lipid peroxidation during ferroptosis remains poorly understood. We show that supplementation of exogenous iron in the form of ferric ammonium citrate at submillimolar doses induces production of reactive oxygen species (ROS) and lipid peroxidation in mitochondria that precede ferroptosis in H9c2 cardiomyocytes. The mitochondria-targeted antioxidant SkQ1 and the redox mediator methylene blue, which inhibits the production of ROS in complex I of the mitochondrial electron transport chain, prevent both mitochondrial lipid peroxidation and ferroptosis. SkQ1 and methylene blue also prevented accumulation of lipofuscin observed after 24 h incubation of cardiomyocytes with ferric ammonium citrate. Using isolated cardiac mitochondria as an in vitro ferroptosis model, it was shown that rotenone (complex I inhibitor) in the presence of ferrous iron stimulates lipid peroxidation and lipofuscin accumulation. Our data indicate that ROS generated in complex I stimulate mitochondrial lipid peroxidation, lipofuscin accumulation, and ferroptosis induced by exogenous iron.

CRYAB suppresses ferroptosis and promotes osteogenic differentiation of human bone marrow stem cells via binding and stabilizing FTH1

BACKGROUND

Bone formation and homeostasis are greatly dependent on the osteogenic differentiation of human bone marrow stem cells (BMSCs). Therefore, revealing the mechanisms underlying osteogenic differentiation of BMSCs will provide new candidate therapeutic targets for osteoporosis.

METHODS

The osteogenic differentiation of BMSCs was measured by analyzing ALP activity and expression levels of osteogenic markers. Cellular Fe and ROS levels and cell viability were applied to evaluate the ferroptosis of BMSCs. qRT-PCR, Western blotting, and co-immunoprecipitation assays were harnessed to study the molecular mechanism.

RESULTS

The mRNA level of CRYAB was decreased in the plasma of osteoporosis patients. Overexpression of CRYAB increased the expression of osteogenic markers including OCN, OPN, RUNX2, and COLI, and also augmented the ALP activity in BMSCs, on the contrary, knockdown of CRYAB had opposite effects. IP-MS technology identified CRYAB-interacted proteins and further found that CRYAB interacted with ferritin heavy chain 1 (FTH1) and maintained the stability of FTH1 via the proteasome mechanism. Mechanically, we unraveled that CRYAB regulated FTH1 protein stability in a lactylation-dependent manner. Knockdown of FTH1 suppressed the osteogenic differentiation of BMSCs, and increased the cellular Fe and ROS levels, and eventually promoted ferroptosis. Rescue experiments revealed that CRYAB suppressed ferroptosis and promoted osteogenic differentiation of BMSCs via regulating FTH1. The mRNA level of FTH1 was decreased in the plasma of osteoporosis patients.

CONCLUSIONS

Downregulation of CRYAB boosted FTH1 degradation and increased cellular Fe and ROS levels, and finally improved the ferroptosis and lessened the osteogenic differentiation of BMSCs.

Eldecalcitol protected osteocytes against ferroptosis of D-gal-induced senescent MLO-Y4 cells and ovariectomized mice

BACKGROUND

Active vitamin D analog eldecalcitol is clinically applied in treatment of postmenopausal osteoporosis. This study aims to determine the role of eldecalcitol in the protection of osteocytes from senescence and the associated ferroptosis.

METHODS

The MLO-Y4 osteocytes were exposed to D-gal inducing senescence. The ovariectomized (OVX) mice treated with D-gal using as an aging inducer were intraperitoneally injected with eldecalcitol. The multiplexed confocal imaging, fluorescence in situ hybridization and transmission electron microscopy were applied in assessing osteocytic properties. Immunochemical staining and immunoblotting were carried out to detect abundance and expression of molecules.

RESULTS

The ablation of vitamin D receptor led to a reduction in amounts of osteocytes, a loss of dendrites, an increase in mRNA expression of SASP factors and in protein expression of senescent factors, as well as changes in mRNA expression of ferroptosis-related genes (PTGS2 & RGS4). Eldecalcitol reversed senescent phenotypes of MLO-Y4 cells shown by improving cell morphology and density, decreasing β-gal-positive cell accumulation, and down-regulating protein expression (P16, P21 & P53). Eldecalcitol reduced intracellular ROS and MDA productions, elevated JC-1 aggregates, and up-regulated expression of Nrf2 and GPX4. Eldecalcitol exhibited osteopreserve effects in D-gal-induced aging OVX mice. The confocal imaging displayed its improvement on osteocytic network organization. Eldecalcitol decreased the numbers of senescent osteocytes at tibial diaphysis by SADS assay and attenuated mRNA expression of SASP factors as well as down-regulated protein expression of senescence-related factors and restored levels of ferroptotic biomarkers in osteocytes-enriched bone fraction. It reduced 4-HNE staining area, stimulated Nrf2-positive staining, and promoted nuclear translocation of Nrf2 in osteocytes of mice as well as inhibited and promoted protein expression of 4-HNE and Nrf2, respectively, in osteocytes-enriched bone fraction.

CONCLUSIONS

The present study revealed the ameliorative effects of eldecalcitol on senescence and the associated ferroptosis of osteocytes, contributing to its preservation against osteoporosis of D-gal-induced senescent ovariectomized mice.

Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute promotes bone regeneration by moderating oxidative stress in osteoporotic bone defect

The treatment of osteoporotic bone defect remains a big clinical challenge because osteoporosis (OP) is associated with oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation. Anti-oxidative nanomaterials such as selenium nanoparticles (SeNPs) have positive effect on osteogenesis owing to their pleiotropic pharmacological activity which can exert anti-oxidative stress functions to prevent bone loss and facilitate bone regeneration in OP. In the current study a strategy of one-pot method by introducing Poly (lactic acid-carbonate) (PDT) and β-Tricalcium Phosphate (β-TCP) with SeNPs, is developed to prepare an injectable, anti-collapse, shape-adaptive and adhesive bone graft substitute material (PDT-TCP-SE). The PDT-TCP-SE bone graft substitute exhibits sufficient adhesion in biological microenvironments and osteoinductive activity, angiogenic effect and anti-inflammatory as well as anti-oxidative effect in vitro and in vivo. Moreover, the PDT-TCP-SE can protect BMSCs from erastin-induced ferroptosis through the Sirt1/Nrf2/GPX4 antioxidant pathway, which, in together, demonstrated the bone graft substitute material as an emerging biomaterial with potential clinical application for the future treatment of osteoporotic bone defect. STATEMENT OF SIGNIFICANCE: Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute was successfully synthesized. Incorporation of SeNPs with PDT into β-TCP regenerated new bone in-situ by moderating oxidative stress in osteoporotic bone defects area. The PDT-TCP-SE bone graft substitute reduced high ROS levels in osteoporotic bone defect microenvironment. The bone graft substitute could also moderate oxidative stress and inhibit ferroptosis via Sirt1/Nrf2/GPX4 pathway in vitro. Moreover, the PDT-TCP-SE bone graft substitute could alleviate the inflammatory environment and promote bone regeneration in osteoporotic bone defect in vivo. This biomaterial has the advantages of simple synthesis, biocompatibility, anti-collapse, injectable, and regulation of oxidative stress level, which has potential application value in bone tissue engineering.

Type 2 diabetic mellitus related osteoporosis: focusing on ferroptosis

With the aging global population, type 2 diabetes mellitus (T2DM) and osteoporosis(OP) are becoming increasingly prevalent. Diabetic osteoporosis (DOP) is a metabolic bone disorder characterized by abnormal bone tissue structure and reduced bone strength in patients with diabetes. Studies have revealed a close association among diabetes, increased fracture risk, and disturbances in iron metabolism. This review explores the concept of ferroptosis, a non-apoptotic cell death process dependent on intracellular iron, focusing on its role in DOP. Iron-dependent lipid peroxidation, particularly impacting pancreatic β-cells, osteoblasts (OBs) and osteoclasts (OCs), contributes to DOP. The intricate interplay between iron dysregulation, which comprises deficiency and overload, and DOP has been discussed, emphasizing how excessive iron accumulation triggers ferroptosis in DOP. This concise overview highlights the need to understand the complex relationship between T2DM and OP, particularly ferroptosis. This review aimed to elucidate the pathogenesis of ferroptosis in DOP and provide a prospective for future research targeting interventions in the field of ferroptosis.

A biodegradable PVA coating constructed on the surface of the implant for preventing bacterial colonization and biofilm formation

BACKGROUND

Bone implant infections pose a critical challenge in orthopedic surgery, often leading to implant failure. The potential of implant coatings to deter infections by hindering biofilm formation is promising. However, a shortage of cost-effective, efficient, and clinically suitable coatings persists. Polyvinyl alcohol (PVA), a prevalent biomaterial, possesses inherent hydrophilicity, offering potential antibacterial properties.

METHODS

This study investigates the PVA solution's capacity to shield implants from bacterial adhesion, suppress bacterial proliferation, and thwart biofilm development. PVA solutions at concentrations of 5%, 10%, 15%, and 20% were prepared. In vitro assessments evaluated PVA's ability to impede bacterial growth and biofilm formation. The interaction between PVA and mCherry-labeled Escherichia coli (E. coli) was scrutinized, along with PVA's therapeutic effects in a rat osteomyelitis model.

RESULTS

The PVA solution effectively restrained bacterial proliferation and biofilm formation on titanium implants. PVA solution had no substantial impact on the activity or osteogenic potential of MC3T3-E1 cells. Post-operatively, the PVA solution markedly reduced the number of Staphylococcus aureus and E. coli colonies surrounding the implant. Imaging and histological scores exhibited significant improvements 2 weeks post-operation. Additionally, no abnormalities were detected in the internal organs of PVA-treated rats.

CONCLUSIONS

PVA solution emerges as an economical, uncomplicated, and effective coating material for inhibiting bacterial replication and biofilm formation on implant surfaces, even in high-contamination surgical environments.

Ferroptosis in Osteocytes as a Target for Protection Against Postmenopausal Osteoporosis

Ferroptosis is a necrotic form of iron-dependent regulatory cell death. Estrogen withdrawal can interfere with iron metabolism, which is responsible for the pathogenesis of postmenopausal osteoporosis (PMOP). Here, it is demonstrated that estrogen withdrawal induces iron accumulation in the skeleton and the ferroptosis of osteocytes, leading to reduced bone mineral density. Furthermore, the facilitatory effect of ferroptosis of osteocytes is verified in the occurrence and development of postmenopausal osteoporosis is associated with over activated osteoclastogenesis using a direct osteocyte/osteoclast coculture system and glutathione peroxidase 4 (GPX4) knockout ovariectomized mice. In addition, the nuclear factor erythroid derived 2-related factor-2 (Nrf2) signaling pathway is confirmed to be a crucial factor in the ferroptosis of osteocytic cells. Nrf2 regulates the expression of nuclear factor kappa-B ligand (RANKL) by regulating the DNA methylation level of the RANKL promoter mediated by DNA methyltransferase 3a (Dnmt3a), which is as an important mechanism in osteocytic ferroptosis-mediated osteoclastogenesis. Taken together, this data suggests that osteocytic ferroptosis is involved in PMOP and can be targeted to tune bone homeostasis.

MicroRNA-877-5p promotes osteoblast differentiation by targeting EIF4G2 expression

Stimulating bone formation potentially suggests therapeutics for orthopedic diseases including osteoporosis and osteoarthritis. Osteoblasts are key to bone remodeling because they act as the only bone-forming cells. miR-877-5p has a chondrocyte-improving function in osteoarthritis, but its effect on osteoblast differentiation is unknown. Here, miR-877-5p-mediated osteoblast differentiation was studied. Real-time reverse transcriptase-polymerase chain reaction was performed to measure miR-877-5p expression during the osteogenic differentiation of MC3T3-E1 cells. Osteoblast markers, including alkaline phosphatase (ALP), collagen type I a1 chain, and osteopontin, were measured and detected by alizarin red staining and ALP staining. Potential targets of miR-877-5p were predicted from three different algorithms: starBase ( http://starbase.sysu.edu.cn/ ), PITA ( http://genie.weizmann.ac.il/pubs/mir07/mir07_data.html ), and miRanda ( http://www.microrna.org/microrna/home.do ). It was further verified by dual luciferase reporter gene assay. The experimental results found that miR-877-5p was upregulated during the osteogenic differentiation of MC3T3-E1 cells. Overexpression of miR-877-5p promoted osteogenic differentiation, which was characterized by increased cell mineralization, ALP activity, and osteogenesis-related gene expression. Knockdown of miR-877-5p produced the opposite result. Dual luciferase reporter gene assay showed that miR-877-5p directly targeted eukaryotic translation initiation factor 4γ2 (EIF4G2). Overexpression of EIF4G2 inhibited osteogenic differentiation and reversed the promoting effect of overexpression of miR-135-5p on osteogenic differentiation. These results indicate that miR-877-5p might have a therapeutic application related to its promotion of bone formation through targeting EIF4G2.

Fructus Ligustri Lucidi inhibits ferroptosis in ovariectomy‑induced osteoporosis in rats via the Nrf2/HO‑1 signaling pathway

Postmenopausal osteoporosis (PMOP) has increased in prevalence in recent years, thus researchers have evaluated alternative medicine therapies. Fructus Ligustri Lucidi (FLL) can inhibit bone loss, and ferroptosis serves an important role in osteoporosis. Therefore, the present study assessed the presence of ferroptosis in PMOP and whether FLL could inhibit ferroptosis to improve bone microstructure in ovariectomized rats. Ovariectomized rats were treated with FLL (1.56 g/kg/day) for 12 weeks. Micro-CT was performed to evaluate the bone microstructure and bone mineral density. Western blotting and reverse transcription-quantitative PCR were performed to assess the relative expression levels of proteins and mRNA. Subsequently, malondialdehyde (MDA) and Fe2+ assay kits were used to quantify the MDA and Fe2+ content, respectively. The results demonstrated that ovariectomy (OVX) resulted in iron overload and the accumulation of lipid peroxide. Furthermore, the expression of key factors that inhibited ferroptosis, glutathione peroxidase 4 and solute carrier family 7 member 11 was significantly downregulated in ovariectomized rats, which was significantly reversed by FLL treatment. Furthermore, bone formation was assessed using the expression of osteogenesis-related genes, runt-related transcription factor 2 and osterix, which revealed significantly higher levels in FLL-treated rats compared with ovariectomized rats. The levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) were also significantly recovered following FLL treatment. In the present study, OVX of postmenopausal osteoporotic rats was found to induce ferroptosis by enhancing lipid peroxidation and Fe2+ levels. FLL significantly suppressed ferroptosis, protected the osteogenic ability of ovariectomized rats and promoted the Nrf2/HO-1 signaling pathway.

Exploring the boost of steaming with wine on Ligustri Lucidi Fructus in treating postmenopausal osteoporosis based on superior "multi-component structure" and iron/bone metabolism coregulation

BACKGROUND

Clinical studies indicated that postmenopausal osteoporosis (PMOP) often accompanied by iron overload risk factor, which exacerbated bone metabolism disorders and accelerated PMOP. Previous research found that multicomponent in Ligustri Lucidi Fructus (FLL) or wine-steamed FLL (WFLL) acted on the common targets of iron overload and PMOP simultaneously, which indicated that FLL and WFLL probably regulated iron/bone metabolism dually. Additionally, WFLL had more superior effect according to the theory of Chinese medicine for thousands of years.

PURPOSE

To reveal the "superior multi-component structure (SMCS)" and its molecular mechanisms in parallelly down-regulating iron overload and rescuing bone metabolism by WFLL.

DESIGNS AND METHODS

HPLC fingerprinting was established to compare the chemical profiles of FLL and WFLL; Then, the chemical compositions and quality markers of FLL and WFLL were analyzed by UPLC-Orbitrap-MS/MS coupled with OPLS-DA; the dynamic contents of quality markers and the multi-component structure at different wine steaming times (WST) were simultaneously determined by HPLC-DAD. Meanwhile, the dynamic efficacy of FLL at different WST were hunt by systematic zebrafish model. Subsequently, potential mechanism of WFLL in treating PMOP accompanied with iron overload was obtained from network pharmacology (NP) and molecular docking (MD). Finally, zebrafish and ovariectomy rat model were carried out to validate this potential mechanism.

RESULTS

HPLC fingerprints similarity of 15 batches in FLL and WFLL were among 0.9-1.0. 126 compositions were identified, including 58 iridoids, 25 terpenes, 30 phenylethanoids, 7 flavonoids and 6 others. 20 quality markers associated with WFLL was revealed, and the ratio of phenylethanols: Iridoids: Triterpenes (P/I/T) was converted from 1: 15: 4.5 to 1: 0.8: 0.9 during steaming (0 - 24 h) calculated by the quantification of 11 quality markers; the bone mineralization and motor performance of zebrafish larvae indicated that the optimum efficacy of WFLL at 12 h (p < 0.05) in which the SMCS of P/I/T was converted to 1: 4: 1.8. NP discovered that BMP-Smad pathway is one of the potential mechanisms of FLL in anti PMOP and then regulated bone formation and iron overload simultaneously. MD revealed that 17 active ingredients and 10 core targets genes could spontaneously bind with appropriate affinity. Rats model verified that FLL and WFLL significantly reversed PMOP, based on the improvement in bone formation indexes (ALP, OPG, OGN), iron metabolism indicators (hepcidin, ferritin), bone microstructure (BMD, BV/TV, Tb. Th, Tb. N); Moreover, WFLL significant enhanced reversal effect in anti-PMOP compared to FLL (p < 0.05). FLL and WFLL increased genes and proteins expression (Hep, BMP-6, p-Smad1/5, Smad4) related to BMP-Smad pathway compared with model group, and WFLL was more superior than FLL (p< 0.05).

CONCLUSION

The SMCS of FLL was optimized by wine-steam, WFLL represented a dual effect in downregulating iron overload and promoting bone formation, and the BMP-Smad pathway is one of the potential molecular mechanisms.

The Therapeutic Effect of Natural Compounds on Osteoporosis through Ferroptosis

Ferroptosis is a newly discovered non-apoptotic cell death whose key is lipid peroxidation. It has been reported that ferroptosis is involved in the occurrence and development of tumors and nervous system and musculoskeletal diseases. Cellular ferroptosis contributes to the imbalance of bone homeostasis and is involved in the development of osteoporosis; however, the detailed mechanism of which is still unclear though it may provide a new direction for anti-osteoporosis. The current drugs used in the treatment of osteoporosis, such as bisphosphonates and teriparatide, have many side effects, increasing people's search for natural compounds to treat osteoporosis. This review paper briefly summarizes the current research regarding the mechanisms of ferroptosis and natural anti-osteoporosis compounds targeting its pathway.

ATP-induced cell death: a novel hypothesis for osteoporosis

ATP-induced cell death has emerged as a captivating realm of inquiry with profound ramifications in the context of osteoporosis. This study unveils a paradigm-shifting hypothesis that illuminates the prospective involvement of ATP-induced cellular demise in the etiology of osteoporosis. Initially, we explicate the morphological attributes of ATP-induced cell death and delve into the intricacies of the molecular machinery and regulatory networks governing ATP homeostasis and ATP-induced cell death. Subsequently, our focus pivots towards the multifaceted interplay between ATP-induced cellular demise and pivotal cellular protagonists, such as bone marrow-derived mesenchymal stem cells, osteoblasts, and osteoclasts, accentuating their potential contributions to secondary osteoporosis phenotypes, encompassing diabetic osteoporosis, glucocorticoid-induced osteoporosis, and postmenopausal osteoporosis. Furthermore, we probe the captivating interplay between ATP-induced cellular demise and alternative modalities of cellular demise, encompassing apoptosis, autophagy, and necroptosis. Through an all-encompassing inquiry into the intricate nexus connecting ATP-induced cellular demise and osteoporosis, our primary goal is to deepen our comprehension of the underlying mechanisms propelling this malady and establish a theoretical bedrock to underpin the development of pioneering therapeutic strategies.

Prevention and treatment of osteoporosis with natural products: Regulatory mechanism based on cell ferroptosis

CONTEXT

With the development of society, the number of patients with osteoporosis is increasing. The prevention and control of osteoporosis has become a serious and urgent issue. With the continuous progress of biomedical research, ferroptosis has attracted increased attention. However, the pathophysiology and mechanisms of ferroptosis and osteoporosis still need further study. Natural products are widely used in East Asian countries for osteoporosis prevention and treatment.

OBJECTIVE

In this paper, we will discuss the basic mechanisms of ferroptosis, the relationship between ferroptosis and osteoclasts and osteoblasts, and in vitro and in vivo studies of natural products to prevent osteoporosis by interfering with ferroptosis.

METHODS

This article takes ferroptosis, natural products, osteoporosis, osteoblasts and osteoclast as key words. Retrieve literature from 2012 to 2023 indexed in databases such as PubMed Central, PubMed, Web of Science, Scopus and ISI.

RESULTS

Ferroptosis has many regulatory mechanisms, including the system XC -/GSH/GPX4, p62/Keap1/Nrf2, FSP1/NAD (P) H/CoQ10, P53/SAT1/ALOX15 axes etc. Interestingly, we found that natural products, such as Artemisinin, Biochanin A and Quercetin, can play a role in treating osteoporosis by promoting ferroptosis of osteoclast and inhibiting ferroptosis of osteoblasts.

CONCLUSIONS

Natural products have great potential to regulate OBs and OCs by mediating ferroptosis to prevent and treat osteoporosis, and it is worthwhile to explore and discover more natural products that can prevent and treat osteoporosis.

Gallium-doped thermochemically treated titanium reduces osteoclastogenesis and improves osteodifferentiation

Excessive bone resorption is one of the main causes of bone homeostasis alterations, resulting in an imbalance in the natural remodeling cycle. This imbalance can cause diseases such as osteoporosis, or it can be exacerbated in bone cancer processes. In such cases, there is an increased risk of fractures requiring a prosthesis. In the present study, a titanium implant subjected to gallium (Ga)-doped thermochemical treatment was evaluated as a strategy to reduce bone resorption and improve osteodifferentiation. The suitability of the material to reduce bone resorption was proven by inducing macrophages (RAW 264.7) to differentiate to osteoclasts on Ga-containing surfaces. In addition, the behavior of human mesenchymal stem cells (hMSCs) was studied in terms of cell adhesion, morphology, proliferation, and differentiation. The results proved that the Ga-containing calcium titanate layer is capable of inhibiting osteoclastogenesis, hypothetically by inducing ferroptosis. Furthermore, Ga-containing surfaces promote the differentiation of hMSCs into osteoblasts. Therefore, Ga-containing calcium titanate may be a promising strategy for patients with fractures resulting from an excessive bone resorption disease.