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

Cardamonin attenuates iron overload-induced osteoblast oxidative stress through the HIF-1α/ROS pathway

BACKGROUND

Osteoporosis(OP) is a bone disease under research. Iron overload is a significant risk factor. Iron balance is crucial for bone metabolism and biochemical processes. When there is an excess of iron in the body, it tends to produce reactive oxygen species (ROS) which can cause oxidative damage to cells. The flavonoid compound, Cardamonin (CAR), possesses potent anti-inflammatory and anti-iron overload properties that can be beneficial in mitigating the risk of OP.

PURPOSE

This study investigates the potential therapeutic interventions and underlying mechanisms of CAR for treating OP in individuals with iron overload.

METHODS

The model of iron-overloaded mice was established by intraperitoneally injecting iron dextran(ID) into the mice. OP severity was evaluated with micro-CT and Hematoxylin-Eosin (HE) staining in vivo. In vitro, the iron-overloaded osteoblast model was induced by ferric ammonium citrate. Cell counting kit 8 assay to evaluate cell viability, Annexin V-FITC/PI assay to detect cell apoptosis. A range of cellular markers were detected, including the variation in mitochondrial membrane potential (MMP), levels of malondialdehyde (MDA), ROS, and lipid hydroperoxide (LPO).

RESULTS

CAR can reverse bone loss in iron overload-induced OP mouse models in vivo. CAR attenuates the impairment of iron overload on the activity and apoptosis of MC3T3-E1 cells as well as the accumulation of ROS and LPO activation via HIF-1α/ROS pathways.

CONCLUSION

CAR downregulating HIF-1α pathways prevents inhibition of iron overload-induced osteoblasts dysfunctional by attenuating ROS accumulation, reducing oxidative stress, promotes bone formation, and alleviates OP.

Effects of unilateral nasal obstruction on mandibular condyle in mice of different ages: An exploration based on H-type angiogenesis coupling osteogenesis

Nasal obstruction leads to a hypoxia condition throughout the entire body. In this study, the unilateral nasal obstruction (UNO) mouse model was established by blocking the left nostril of mice. The aim of this study was to investigate the effects of UNO-induced hypoxia on mandibular condyle in juvenile (3-week-old), adolescent (6-week-old) and adult (12-week-old) male C57BL/6J mice from the perspective of H-type angiogenesis coupling osteogenesis. Firstly, UNO exerted a significant inhibitory effect on weight gain in mice of all ages. However, only in adolescent mice did UNO have an obvious detrimental effect on femoral bone mass accrual. Subsequently, micro-computed tomography (CT) analysis of mandibular condylar bone mass revealed that UNO significantly retarded condylar head volume gain but increased condylar head trabecular number (Tb.N) in juvenile and adolescent mice. Furthermore, UNO promoted the ratio of proliferative layer to cartilage layer in condylar cartilage and facilitated the chondrocyte-to-osteoblast transformation in juvenile and adolescent mice. Moreover, although UNO enhanced the positive expression of hypoxia-inducible factor (HIF)-1α in the condylar subchondral bone of mice in all ages, an increase in H-type vessels and Osterix+ cells was only detected in juvenile and adolescent mice. In summary, on the one hand, in terms of condylar morphology, UNO has a negative effect on condylar growth, hindering the increase in condylar head volume in juvenile and adolescent mice. However, on the other hand, in terms of condylar microstructure, UNO has a positive effect on condylar osteogenesis, promoting the increase of condylar Tb.N, chondrocyte-to-osteoblast transformation, HIF-1α expression, H-type angiogenesis and Osterix+ cells in juvenile and adolescent mice. Although the changes in condylar morphology and microstructure caused by UNO have not yet been fully elucidated, these findings improve our current understanding of the effects of UNO on condylar bone homeostasis.

USP26 Combats Age-Related Declines in Self-Renewal and Multipotent Differentiation of BMSC by Maintaining Mitochondrial Homeostasis

Age-related declines in self-renewal and multipotency of bone marrow mesenchymal stem cells (BMSCs) limit their applications in tissue engineering and clinical therapy. Thus, understanding the mechanisms behind BMSC senescence is crucial for maintaining the rejuvenation and multipotent differentiation capabilities of BMSCs. This study reveals that impaired USP26 expression in BMSCs leads to mitochondrial dysfunction, ultimately resulting in aging and age-related declines in the self-renewal and multipotency of BMSCs. Specifically, decreased USP26 expression results in decreased protein levels of Sirtuin 2 due to its ubiquitination degradation, which leads to mitochondrial dysfunction in BMSCs and ultimately resulting in aging and age-related declines in self-renewal and multilineage differentiation potentials. Additionally, decreased USP26 expression in aging BMSCs is a result of dampened hypoxia-inducible factor 1α (HIF-1α) expression. HIF-1α facilitates USP26 transcriptional expression by increasing USP26 promoter activity through binding to the -191 - -198 bp and -262 - -269 bp regions on the USP26 promoter. Therefore, the identification of USP26 as being correlated with aging and age-related declines in self-renewal and multipotency of BMSCs, along with understanding its expression and action mechanisms, suggests that USP26 represents a novel therapeutic target for combating aging and age-related declines in the self-renewal and multipotent differentiation of BMSCs.

Deferoxamine Accelerates Mandibular Condylar Neck Fracture Early Bone Healing by Promoting Type H Vessel Proliferation

BACKGROUND

Condylar fractures (CFs) are a common type of maxillofacial trauma, especially in adolescents. Conservative treatment of CF avoids the possible complications of surgical intervention, but prolongs the patient's suffering because of the requirement for extended intermaxillary fixation. Therefore, the development of a new strategy to accelerate the rate of fracture healing to shorten the period of conservative treatment is of great clinical importance.

OBJECTIVE

To investigate the potential of deferoxamine (DFO) in promoting the healing process of CF in adolescent mice.

METHODS

Thirty-two 4-week-old male C57BL/6J mice were randomly assigned to four groups: vehicle + sham group, vehicle + CF group, DFO + sham group and DFO + CF group. After constructing the mandibular CF model, mandibular tissue samples were collected respectively at 1, 2 and 4 weeks postoperatively. Radiographic and histomorphometric analyses were employed to assess bone tissue healing and vascular formation.

RESULTS

Deferoxamine was observed to promote the early bone healing of fracture, both radiologically and histomorphometrically. Furthermore, this enhancement of condylar neck fracture healing was attributed to the upregulation of the hypoxia-inducible factor-1α (HIF-1α) signalling pathway while facilitating the formation of type H vessels. In addition, DFO did not produce significant effects on the condylar neck between vehicle + sham and DFO + sham group.

CONCLUSION

The application of the HIF-1α inducer DFO can enhance type H vessels expansion thereby accelerating condylar neck fracture healing.

Hypoxia-inducible Factor 1α Contributes to Matrix Metalloproteinases 2/9 and Inflammatory Responses in Periodontitis

Periodontitis is a prevalent condition characterized by inflammation and tissue destruction within the periodontium, with hypoxia emerging as a contributing factor to its pathogenesis. Hypoxia-inducible factor 1α (HIF-1α) has a crucial role in orchestrating adaptive responses to hypoxic microenvironments and has been implicated in various inflammatory-related diseases. Understanding the interplay between HIF-1α, matrix metalloproteinases (MMPs), and inflammatory responses in periodontitis could provide insights into its molecular mechanisms. We investigated the relationship between HIF-1α, MMP2, and MMP9 in gingival crevicular fluid (GCF) and periodontal ligament stem cells (PDLSCs) from periodontitis patients. The expression levels of HIF-1α, MMP2, MMP9, and inflammatory factors (IL-6, IL-1β, TNF-α) were assessed using enzyme-linked immunosorbent assay (ELISA) and real-time PCR (RT-PCR). Additionally, osteogenic differentiation of PDLSCs was identified by alkaline phosphatase activity. Significantly elevated levels of HIF-1α, MMP2, and MMP9 were observed in GCF of periodontitis patients compared to controls. Positive correlations were found between HIF-1α and MMP2/MMP9, as well as with IL-6, IL-1β, and TNF-α. Modulation of HIF-1α expression in PDLSCs revealed its involvement in MMP2/9 secretion and inflammatory responses, with inhibition of HIF-1α mitigating these effects. Furthermore, HIF-1α inhibition alleviated the reduction in osteogenic differentiation induced by inflammatory stimuli. Our findings elucidate the regulatory role of HIF-1α in MMP expression, inflammatory responses, and osteogenic differentiation in periodontitis. In conclusion, targeting HIF-1α signaling pathways may offer therapeutic opportunities for managing periodontitis and promoting periodontal tissue regeneration.

Interaction between macrophages and ferroptosis: Metabolism, function, and diseases

ABSTRACT

Ferroptosis, an iron-dependent programmed cell death process driven by reactive oxygen species-mediated lipid peroxidation, is regulated by several metabolic processes, including iron metabolism, lipid metabolism, and redox system. Macrophages are a group of innate immune cells that are widely distributed throughout the body, and play pivotal roles in maintaining metabolic balance by its phagocytic and efferocytotic effects. There is a profound association between the biological functions of macrophage and ferroptosis. Therefore, this review aims to elucidate three key aspects of the unique relationship between macrophages and ferroptosis, including macrophage metabolism and their regulation of cellular ferroptosis; ferroptotic stress that modulates functions of macrophage and promotion of inflammation; and the effects of macrophage ferroptosis and its role in diseases. Finally, we also summarize the possible mechanisms of macrophages in regulating the ferroptosis process at the global and local levels, as well as the role of ferroptosis in the macrophage-mediated inflammatory process, to provide new therapeutic insights for a variety of diseases.

Mild Thermotherapy-Assisted GelMA/HA/MPDA@Roxadustat 3D-Printed Scaffolds with Combined Angiogenesis-Osteogenesis Functions for Bone Regeneration

Early reconstruction of the vascular network is a prerequisite to the effective treatment of substantial bone defects. Traditional 3D printed tissue engineering scaffolds designed to repair large bone defects do not effectively regenerate the vascular network, and rely only on the porous structure within the scaffold for nutrient transfer and metabolic waste removal. This leads to delayed bone restoration and hence functional recovery. Therefore, strategies for generation scaffolds with the capacity to efficiently regenerate vascularization should be developed. This study loads roxarestat (RD), which can stabilize HIF-1α expression in a normoxic environment, onto the mesopore polydopamine nanoparticles (MPDA@RD) to enhance the reconstruction of vascular network in large bone defects. Subsequently, MPDA@RD is mixed with GelMA/HA hydrogel bioink to fabricate a multifunctional hydrogel scaffold (GHM@RD) through 3D printing. In vitro results show that the GHM@RD scaffolds achieve good angiogenic-osteogenic coupling by activating the PI3K/AKT/HSP90 pathway in BMSCs and the PI3K/AKT/HIF-1α pathway in HUVECs under mild thermotherapy. In vivo experiments reveal that RD and mild hyperthermia synergistically induce early vascularization and bone regeneration of critical bone defects. In conclusion, the designed GHM@RD drug delivery scaffold with mild hyperthermia holds great therapeutic value for future treatment of large bone defects.

The impact and mechanism study of Sijunzi decoction and Rg1 on proliferation and differentiation of human umbilical cord mesenchymal stem cells: An experimental study

BACKGROUND

Previous researches have demonstrated that the traditional Chinese medicine could therapeutically treat inflammatory and hypoxic diseases by enhancing the functionality of mesenchymal stem cells. However, its mechanism was not yet clear. This research aimed to investigate the impact of the traditional Chinese medicine Sijunzi decoction and its herb monomer ginsenoside Rg1 on the proliferation and differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs) and explore the underlying mechanisms.

METHODS

Different concentrations of Sijunzi decoction and Rg1 were applied to differentiating induced hUC-MSCs. The CCK-8 test was utilized to evaluate cell proliferation activity and identify suitable drug concentrations. Alizarin Red staining was employed to detect the formation of calcium nodules, and Oil Red O staining was used to assess the formation of lipid droplets. PCR was utilized to examine gene expression related to osteogenic differentiation, adipogenic differentiation, and the HIF-1α signaling pathway in hUC-MSCs. Western blot analysis was conducted to evaluate protein expression in osteogenic differentiation and HIF-1α. ELISA was performed to measure HIF-1α signaling factors and inflammatory cytokine expression. Biochemical assays were used to assess changes in oxidative stress indicators.

RESULTS

The Sijunzi decoction and Rg1 both demonstrated a dose-dependent promotion of hUC-MSC proliferation. The Sijunzi decoction significantly increased the expression of genes and proteins relevant to osteogenesis, such as osterix, osteocalcin, RUNX2, and osteopontin, and activated the HIF-1α pathway in hUC-MSCs. (P < .05). Similar effects were observed at the gene level after treatment with Rg1. Simultaneously, Sijunzi decoction significantly reduced the secretion of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, while increasing the secretion of the anti-inflammatory cytokine IL-10 during osteogenic differentiation (P < .05). Moreover, Sijunzi decoction lowered oxidative stress levels and enhanced the antioxidant capacity of hUC-MSCs during osteogenic differentiation (P < .05). However, the impact of Sijunzi decoction on hUC-MSCs toward adipogenic differentiation was not significant (P > .05).

CONCLUSION

Sijunzi decoction promotes the proliferation and osteogenic differentiation of hUC-MSCs, potentially through the activation of the HIF-1α signaling pathway and by modulating the microenvironment via reducing inflammation and oxidative stress levels. Rg1 might be involved in this process.

Approaches to scarless burn wound healing: application of 3D printed skin substitutes with dual properties of anti-infection and balancing wound hydration levels

BACKGROUND

Severe burn wounds face two primary challenges: dysregulated cellular impairment functions following infection and an unbalanced wound hydration microenvironment leading to excessive inflammation and collagen deposition. These results in hypertrophic scar contraction, causing significant deformity and disability in survivors.

METHODS

A three-dimensional (3D) printed double-layer hydrogel (DLH) was designed and fabricated to address the problem of scar formation after burn injury. DLH was developed using methacrylated silk fibroin (SFMA) and gelatin methacryloyl (GelMA) for the upper layer, and GelMA and hyaluronic acid methacryloyl (HAMA) for the lower layer. To combat infection, copper-epigallocatechin gallate (Cu-EGCG) was incorporated into the lower layer bioink, collectively referred to as DLS. To balance wound hydration levels, HaCaT cells were additionally encapsulated in the upper layer, designed as DLS/c.

FINDINGS

DLH demonstrated suitable porosity, appropriate mechanical properties, and excellent biocompatibility. DLS exhibited potent antimicrobial properties, exerted anti-inflammatory effects by regulating macrophage polarisation, and may enhance angiogenesis through the HIF-1α/VEGF pathway. In the DLS/c group, animal studies showed significant improvements in epidermal formation, barrier function, and epidermal hydration, accompanied by reduced inflammation. In addition, Masson's trichrome and Sirius red staining revealed that the structure and ratio of dermal collagen in DLS/c resembled that of normal skin, indicating considerable potential for scarless wound healing.

INTERPRETATION

This biomimetic matrix shows promise in addressing the challenges of burn wounds and aiming for scarless repair, with benefits such as anti-infection, epidermal hydration, biological induction, and optimised topological properties.

FUNDING

Shown in Acknowledgements.

Regulation of bone homeostasis: signaling pathways and therapeutic targets

As a highly dynamic tissue, bone is continuously rebuilt throughout life. Both bone formation by osteoblasts and bone resorption by osteoclasts constitute bone reconstruction homeostasis. The equilibrium of bone homeostasis is governed by many complicated signaling pathways that weave together to form an intricate network. These pathways coordinate the meticulous processes of bone formation and resorption, ensuring the structural integrity and dynamic vitality of the skeletal system. Dysregulation of the bone homeostatic regulatory signaling network contributes to the development and progression of many skeletal diseases. Significantly, imbalanced bone homeostasis further disrupts the signaling network and triggers a cascade reaction that exacerbates disease progression and engenders a deleterious cycle. Here, we summarize the influence of signaling pathways on bone homeostasis, elucidating the interplay and crosstalk among them. Additionally, we review the mechanisms underpinning bone homeostatic imbalances across diverse disease landscapes, highlighting current and prospective therapeutic targets and clinical drugs. We hope that this review will contribute to a holistic understanding of the signaling pathways and molecular mechanisms sustaining bone homeostasis, which are promising to contribute to further research on bone homeostasis and shed light on the development of targeted drugs.

The relationship between hypoxia and Alzheimer's disease: an updated review

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and the most prevalent form of dementia. The main hallmarks for the diagnosis of AD are extracellular amyloid-beta (Aβ) plaque deposition and intracellular accumulation of highly hyperphosphorylated Tau protein as neurofibrillary tangles. The brain consumes more oxygen than any other organs, so it is more easily to be affected by hypoxia. Hypoxia has long been recognized as one of the possible causes of AD and other neurodegenerative diseases, but the exact mechanism has not been clarified. In this review, we will elucidate the connection between hypoxia-inducible factors-1α and AD, including its contribution to AD and its possible protective effects. Additionally, we will discuss the relationship between oxidative stress and AD as evidence show that oxidative stress acts on AD-related pathogenic factors such as mitochondrial dysfunction, Aβ deposition, inflammation, etc. Currently, there is no cure for AD. Given the close association between hypoxia, oxidative stress, and AD, along with current research on the protective effects of antioxidants against AD, we speculate that antioxidants could be a potential therapeutic approach for AD and worth further study.

Biomimetic Hydrogels as the Inductive Endochondral Ossification Template for Promoting Bone Regeneration

Repairing critical size bone defects (CSBD) is a major clinical challenge and requires effective intervention by biomaterial scaffolds. Inspired by the fact that the cartilaginous template-based endochondral ossification (ECO) process is crucial to bone healing and development, developing biomimetic biomaterials to promote ECO is recognized as a promising approach for repairing CSBD. With the unique highly hydrated 3D polymeric network, hydrogels can be designed to closely emulate the physiochemical properties of cartilage matrix to facilitate ECO. In this review, the various preparation methods of hydrogels possessing the specific physiochemical properties required for promoting ECO are introduced. The materiobiological impacts of the physicochemical properties of hydrogels, such as mechanical properties, topographical structures and chemical compositions on ECO, and the associated molecular mechanisms related to the BMP, Wnt, TGF-β, HIF-1α, FGF, and RhoA signaling pathways are further summarized. This review provides a detailed coverage on the materiobiological insights required for the design and preparation of hydrogel-based biomaterials to facilitate bone regeneration.

The current insights of mitochondrial hormesis in the occurrence and treatment of bone and cartilage degeneration

It is widely acknowledged that aging, mitochondrial dysfunction, and cellular phenotypic abnormalities are intricately associated with the degeneration of bone and cartilage. Consequently, gaining a comprehensive understanding of the regulatory patterns governing mitochondrial function and its underlying mechanisms holds promise for mitigating the progression of osteoarthritis, intervertebral disc degeneration, and osteoporosis. Mitochondrial hormesis, referred to as mitohormesis, represents a cellular adaptive stress response mechanism wherein mitochondria restore homeostasis and augment resistance capabilities against stimuli by generating reactive oxygen species (ROS), orchestrating unfolded protein reactions (UPRmt), inducing mitochondrial-derived peptides (MDP), instigating mitochondrial dynamic changes, and activating mitophagy, all prompted by low doses of stressors. The varying nature, intensity, and duration of stimulus sources elicit divergent degrees of mitochondrial stress responses, subsequently activating one or more signaling pathways to initiate mitohormesis. This review focuses specifically on the effector molecules and regulatory networks associated with mitohormesis, while also scrutinizing extant mechanisms of mitochondrial dysfunction contributing to bone and cartilage degeneration through oxidative stress damage. Additionally, it underscores the potential of mechanical stimulation, intermittent dietary restrictions, hypoxic preconditioning, and low-dose toxic compounds to trigger mitohormesis, thereby alleviating bone and cartilage degeneration.

SIRT1 activation promotes bone repair by enhancing the coupling of type H vessel formation and osteogenesis

Bone repair is intricately correlated with vascular regeneration, especially of type H vessels. Sirtuin 1 (SIRT1) expression is closely associated with endothelial function and vascular regeneration; however, the role of SIRT1 in enhancing the coupling of type H vessel formation with osteogenesis to promote bone repair needs to be investigated. A co-culture system combining human umbilical vein endothelial cells and osteoblasts was constructed, and a SIRT1 agonist was used to evaluate the effects of SIRT1 activity. The angiogenic and osteogenic capacities of the co-culture system were examined using short interfering RNA. Mouse models with bone defects in the femur or mandible were established to explore changes in type H vessel formation and bone repair following modulated SIRT1 activity. SIRT1 activation augmented the angiogenic and osteogenic capacities of the co-culture system by activating the PI3K/AKT/FOXO1 signalling pathway and did not significantly regulate osteoblast differentiation. Inhibition of the PI3K/AKT/FOXO1 pathway attenuated SIRT1-mediated effects. The SIRT1 activity in bone defects was positively correlated with the formation of type H vessels and bone repair in vivo, whereas SIRT1 inhibition substantially weakened vascular and bone formation. Thus, SIRT1 is crucial to the coupling of type H vessels with osteogenesis during bone repair.

Role of miRNA-regulated type H vessel formation in osteoporosis

Osteoporosis (OP) is a chronic systemic bone metabolism disease characterized by decreased bone mass, microarchitectural deterioration, and fragility fractures. With the demographic change caused by long lifespans and population aging, OP is a growing health problem. The role of miRNA in the pathogenesis of OP has also attracted widespread attention from scholars in recent years. Type H vessels are unique microvessels of the bone and have become a new focus in the pathogenesis of OP because they play an essential role in osteogenesis-angiogenesis coupling. Previous studies found some miRNAs regulate type H vessel formation through the regulatory factors, including platelet-derived growth factor-BB (PDGF-BB), hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), and so on. These findings help us gain a more in-depth understanding of the relationship among miRNAs, type H vessels, and OP to find a new perspective on treating OP. In the present mini-review, we will introduce the role of type H vessels in the pathogenesis of OP and the regulation of miRNAs on type H vessel formation by affecting regulatory factors to provide some valuable insights for future studies of OP treatment.

Eight Weeks of Intermittent Exercise in Hypoxia, with or without a Low-Carbohydrate Diet, Improves Bone Mass and Functional and Physiological Capacity in Older Adults with Type 2 Diabetes

In an increasingly aging and overweight population, osteoporosis and type 2 diabetes (T2DM) are major public health concerns. T2DM patients experience prejudicial effects on their bone health, affecting their physical capacity. Exercise in hypoxia (EH) and a low-carbohydrate diet (LCD) have been suggested for therapeutic benefits in T2DM, improving bone mineral content (BMC) and glycemic control. This study investigated the effects of EH combined with an LCD on body composition and functional and physiologic capacity in T2DM patients. Older T2DM patients (n = 42) were randomly assigned to the following groups: (1) control group: control diet + exercise in normoxia; (2) EH group: control diet + EH; (3) intervention group: LCD + EH. Cardiopulmonary tests (BRUCE protocol), body composition (DEXA), and functional capacity (6MWT, handgrip strength) were evaluated. Body mass index (kg/m2) and body fat (%) decreased in all groups (p < 0.001). BMC (kg) increased in all groups (p < 0.001) and was significantly higher in the EH and EH + LCD groups (p < 0.001). VO2peak improved in all groups (p < 0.001), but more so in the hypoxia groups (p = 0.019). Functional capacity was increased in all groups (p < 0.001), but more so in the EH group in 6MWT (p = 0.030). EH with and without an LCD is a therapeutic strategy for improving bone mass in T2DM, which is associated with cardiorespiratory and functional improvements.

The role of photobiomodulation in accelerating bone repair

Bone repair is faced with obstacles such as slow repair rates and limited bone regeneration capacity. Delayed healing even nonunion could occur in bone defects, influencing the life quality of patients severely. Photobiomodulation (PBM) utilizes different light sources to derive beneficial therapeutic effects with the advantage of being non-invasive and painless, providing a promising strategy for accelerating bone repair. In this review, we summarize the parameters, mechanisms, and effects of PBM regulating bone repair, and further conclude the current clinical application of PBM devices in bone repair. The wavelength of 635-980 nm, the output power of 40-100 mW, and the energy density of less than 100 J/cm2 are the most commonly used parameters. New technologies, including needle systems and biocompatible and implantable optical fibers, offer references to realize an efficient and safe strategy for bone repair. Further research is required to establish the reliability of outcomes from in vivo and in vitro studies and to standardize clinical trial protocols.

Research Progress on the Mechanism of the SFRP-Mediated Wnt Signalling Pathway Involved in Bone Metabolism in Osteoporosis

Osteoporosis (OP) is a metabolic bone disease linked to an elevated fracture risk, primarily stemming from disruptions in bone metabolism. Present clinical treatments for OP merely alleviate symptoms. Hence, there exists a pressing need to identify novel targets for the clinical treatment of OP. Research indicates that the Wnt signalling pathway is modulated by serum-secreted frizzled-related protein 5 (SFRP5), potentially serving as a pivotal regulator in bone metabolism disorders. Moreover, studies confirm elevated SFRP5 expression in OP, with SFRP5 overexpression leading to the downregulation of Wnt and β-catenin proteins in the Wnt signalling pathway, as well as the expression of osteogenesis-related marker molecules such as RUNX2, ALP, and OPN. Conversely, the opposite has been reported when SFRP5 is knocked out, suggesting that SFRP5 may be a key factor involved in the regulation of bone metabolism via the Wnt signalling axis. However, the molecular mechanisms underlying the action of SFRP5-induced OP have yet to be comprehensively elucidated. This review focusses on the molecular structure and function of SFRP5 and the potential molecular mechanisms of the SFRP5-mediated Wnt signalling pathway involved in bone metabolism in OP, providing reasonable evidence for the targeted therapy of SFRP5 for the prevention and treatment of OP.

The Impact of NLRP3 Inflammasome on Osteoblasts and Osteogenic Differentiation: A Literature Review

Osteoblasts (OBs), which are a crucial type of bone cells, derive from bone marrow mesenchymal stem cells (MSCs). Accumulating evidence suggests inflammatory cytokines can inhibit the differentiation and proliferation of OBs, as well as interfere with their ability to synthesize bone matrix, under inflammatory conditions. NLRP3 inflammasome is closely associated with cellular pyroptosis, which can lead to excessive release of pro-inflammatory cytokines, causing tissue damage and inflammatory responses, however, the comprehensive roles of NLRP3 inflammasome in OBs and their differentiation have not been fully elucidated, making targeting NLRP3 inflammasome approaches to treat diseases related to OBs uncertain. In this review, we provide a summary of NLRP3 inflammasome activation and its impact on OBs. We highlight the significant roles of NLRP3 inflammasome in regulating OBs differentiation and function. Furthermore, current available strategies to affect OBs function and osteogenic differentiation targeting NLRP3 inflammasome are listed and analyzed. Finally, through the prospective discussion, we seek to provide novel insights into the crucial role of NLRP3 inflammasome in diseases related to OBs and offer valuable information for devising treatment strategies.

Inhibition of SUV39H1 reduces tumor angiogenesis via Notch1 in oral squamous cell carcinoma

Targeting tumor angiogenesis is an important approach in advanced tumor therapy. Here we investigated the effect of the suppressor of variegation 3-9 homolog 1 (SUV39H1) on tumor angiogenesis in oral squamous cell carcinoma (OSCC). The GEPIA database was used to analyze the expression of SUV39H1 in various cancer tissues. The expression of SUV39H1 in OSCC was detected by immunohistochemistry, and the correlation between SUV39H1 and Notch1 and microvascular density (MVD) was analyzed. The effect of SUV39H1 inhibition on OSCC was investigated in vivo by chaetocin treatment. The migration and tube formation of vascular endothelial cells by conditioned culture-medium of different treatments of oral squamous cell cells were measured. The transcriptional level of SUV39H1 is elevated in various cancer tissues. The transcription level of SUV39H1 in head and neck squamous cell carcinoma was significantly higher than that in control. Immunohistochemistry result showed increased SUV39H1 expression in OSCC, which was significantly correlated with T staging. The expression of SUV39H1 was significantly correlated with Notch1 and CD31. In vivo experiment chaetocin treatment significantly inhibit the growth of tumor, and reduce SUV39H1, Notch1, CD31 expression. The decreased expression of SUV39H1 in OSCC cells lead to the decreased expression of Notch1 and VEGF proteins, as well as the decreased migration and tube formation ability of vascular endothelial cells. Inhibition of Notch1 further enhance this effect. Our results suggest inhibition of SUV39H1 may affect angiogenesis by regulating Notch1 expression. This study provides a foundation for SUV39H1 as a potential therapeutic target for OSCC.

Role of Trimetazidine in Ameliorating Endothelial Dysfunction: A Review

Endothelial dysfunction is a hallmark of cardiovascular diseases, contributing to impaired vasodilation, altered hemodynamics, and atherosclerosis progression. Trimetazidine, traditionally used for angina pectoris, exhibits diverse therapeutic effects on endothelial dysfunction. This review aims to elucidate the mechanisms underlying trimetazidine's actions and its potential as a therapeutic agent for endothelial dysfunction and associated cardiovascular disorders. Trimetazidine enhances vasodilation and hemodynamic function by modulating endothelial nitric oxide synthase activity, nitric oxide production, and endothelin-1. It also ameliorates metabolic parameters, including reducing blood glucose, mitigating oxidative stress, and dampening inflammation. Additionally, trimetazidine exerts antiatherosclerotic effects by inhibiting plaque formation and promoting its stability. Moreover, it regulates apoptosis and angiogenesis, fostering endothelial cell survival and neovascularization. Understanding trimetazidine's multifaceted mechanisms underscores its potential as a therapeutic agent for endothelial dysfunction and associated cardiovascular disorders, warranting further investigation for clinical translation.

Network pharmacology prediction, molecular docking and in vitro experiment explored the potential mechanism of Gaoyuan'an capsule in improving hypoxia tolerance

BACKGROUND

Tibetan medicine Gaoyuan'an capsule (GYAC) is widely used to prevent pulmonary edema at high altitude, but the specific mechanism has not been explored. In this study, we analyzed the mechanism of GYAC in hypoxia tolerance, and provided a new idea for the prevention and treatment of altitude disease.

METHODS

The effective components and corresponding targets of GYAC were screened out by the Chinese herbal medicine network database, and the key targets of hypoxia tolerance were retrieved by Genecards, OMIM and PubMed database. Cytoscape 3.7.2 was used to construct GYAC ingredient-target-hypoxia tolerance-related target network. GO function annotation and KEGG enrichment analysis were performed to predict the pathways in which target genes may be involved, and molecular docking was used to verify the binding ability of the compound to target genes. In vitro, the above results were further verified by molecular experiment.

RESULTS

We found that GYAC can improve hypoxia tolerance by regulating various target genes, including IL6, IFNG, etc. The main regulatory pathways were HIF-1 signaling pathway. Molecular docking showed that the affinity between luteolin and target genes (IL6, IFNG) were better. In vitro, we observed that hypoxia can inhibit cell viability and promote apoptosis of H9C2 cell. And hypoxia can promote the expression of LDH. After the addition of luteolin, the decrease of cell viability, the increase of cell apoptosis, LDH release and the decrease of mitochondrial membrane potential were inhibited. Besides, inflammatory related factors (IL-6, IL-10, IL-2, IFNG and VEGFA) expression were also inhibited hypoxic cell models.

CONCLUSIONS

The results of network pharmacology and molecular docking showed that luteolin, a monomeric component of GYAC, played a role in hypoxia tolerance through a variety of target genes, such as IL6, IFNG. What's more, we have discovered that luteolin can reduce the inflammatory response in cardiac myocytes, thereby alleviating mitochondrial damage, and ultimately enhancing the hypoxia tolerance of H9C2 cardiomyocytes.

HIF signaling overactivation inhibits lateral line neuromast development through Wnt in zebrafish

The lateral line is critical for prey detection, predator avoidance, schooling, and rheotaxis behavior in fish. As similar to hair cells in the mammalian inner ear, the lateral line sensory organ called neuromasts is a popular model for hair cell regeneration. However, the mechanism of lateral line development has not been fully understood. In this study, we showed for the first time that hypoxia-inducible factor (HIF) signaling is involved in lateral line development in zebrafish. hif1ab and epas1b were highly expressed in neuromasts during lateral line development. Hypoxia response induced by a prolyl hydroxylase domain-containing proteins (PHD) inhibitor treatment or vhl gene knockout significantly reduced hair cells and support cells in neuromast during lateral line development. In addition, inhibition of Hif-1α or Epas1 could partially rescue hair cells in the larvae with increased HIF activity, respectively. Moreover, the support cell proliferation and the expression of Wnt target genes decreased in vhl mutants which suggests that Wnt signaling mediated the role of HIF signaling in lateral line development. Collectively, our results demonstrate that HIF signaling overactivation inhibits lateral line development in zebrafish and suggest that inhibition of HIF signaling might be a potential therapeutic method for hair cell death.

A Multifunctional Scaffold for Bone Infection Treatment by Delivery of microRNA Therapeutics Combined With Antimicrobial Nanoparticles

Treating bone infections and ensuring bone repair is one of the greatest global challenges of modern orthopedics, made complex by antimicrobial resistance (AMR) risks due to long-term antibiotic treatment and debilitating large bone defects following infected tissue removal. An ideal multi-faceted solution would will eradicate bacterial infection without long-term antibiotic use, simultaneously stimulating osteogenesis and angiogenesis. Here, a multifunctional collagen-based scaffold that addresses these needs by leveraging the potential of antibiotic-free antimicrobial nanoparticles (copper-doped bioactive glass, CuBG) to combat infection without contributing to AMR in conjunction with microRNA-based gene therapy (utilizing an inhibitor of microRNA-138) to stimulate both osteogenesis and angiogenesis, is developed. CuBG scaffolds reduce the attachment of gram-positive bacteria by over 80%, showcasing antimicrobial functionality. The antagomiR-138 nanoparticles induce osteogenesis of human mesenchymal stem cells in vitro and heal a large load-bearing defect in a rat femur when delivered on the scaffold. Combining both promising technologies results in a multifunctional antagomiR-138-activated CuBG scaffold inducing hMSC-mediated osteogenesis and stimulating vasculogenesis in an in vivo chick chorioallantoic membrane model. Overall, this multifunctional scaffold catalyzes killing mechanisms in bacteria while inducing bone repair through osteogenic and angiogenic coupling, making this platform a promising multi-functional strategy for treating and repairing complex bone infections.

Hypoxia-Inducible Factor and Oxidative Stress in Tendon Degeneration: A Molecular Perspective

Tendinopathy is a debilitating condition marked by degenerative changes in the tendons. Its complex pathophysiology involves intrinsic, extrinsic, and physiological factors. While its intrinsic and extrinsic factors have been extensively studied, the role of physiological factors, such as hypoxia and oxidative stress, remains largely unexplored. This review article delves into the contribution of hypoxia-associated genes and oxidative-stress-related factors to tendon degeneration, offering insights into potential therapeutic strategies. The unique aspect of this study lies in its pathway-based evidence, which sheds light on how these factors can be targeted to enhance overall tendon health.

A bone-targeting near-infrared luminescence nanocarrier facilitates alpha-ketoglutarate efficacy enhancement for osteoporosis therapy

Osteoporosis (OP), which largely increases the risk of fractures, is the most common chronic degenerative orthopedic disease in the elderly due to the imbalance of bone homeostasis. Alpha-ketoglutaric acid (AKG), an endogenous metabolic intermediate involved in osteogenesis, plays critical roles in osteogenic differentiation and mineralization and the inhibition of osteoclastogenic differentiation. However, the low bioavailability and poor bone-targeting efficiency of AKG seriously limit its efficacy in OP treatment. In this work, a bone-targeting, near-infrared emissive lanthanide luminescence nanocarrier loaded with AKG (β-NaYF4:7%Yb, 60%Nd@NaLuF4@mSiO2-EDTA-AKG, abbreviated as LMEK) is developed for the enhancement of AKG efficacy in OP therapy. By utilizing the NIR-II luminescence (>1000 nm) of LMEK, whole-body bone imaging with high spatial resolution is achieved to confirm the bone enrichment of AKG noninvasively in vivo. The results reveal that LMEK exhibits a remarkable OP therapeutic effect in improving the osseointegration of the surrounding bone in the ovariectomized OP mice models, which is validated by the enhanced inhibition of osteoclast through hypoxia-inducible factor-1α suppression and promotion of osteogenic differentiation in osteoblast. Notably, the dose of AKG in LMEK can be reduced to only 0.2 % of the dose when pure AKG is used in therapy, which dramatically improves the bioavailability of AKG and mitigates the metabolism burden. This work provides a strategy to conquer the low utilization of AKG in OP therapy, which not only overcomes the challenges in AKG efficacy for OP treatment but also offers insights into the development and application of other potential drugs for skeletal diseases. STATEMENT OF SIGNIFICANCE: Alpha-ketoglutarate (AKG) is an intermediate within the Krebs cycle, participating in diverse metabolic and cellular processes, showing potential for osteoporosis (OP) therapy. However, AKG's limited bioavailability and inefficient bone-targeting hinder its effectiveness in treating OP. Herein, a near-infrared emissive nanocarrier is developed that precisely targets bones and delivers AKG, bolstering its effectiveness in OP therapy. Thanks to this efficient bone-targeting delivery, the AKG dosage is reduced to 0.2 % of the conventional treatment level. This marks the first utilization of a bone-targeting nanocarrier to amplify AKG's bioavailability and OP therapy efficacy. Furthermore, the mechanism of AKG-loaded nanocarrier regulating the biological behavior of osteoclasts and osteoblasts mediated is tentatively explored.

The autocrine action of salidroside on osteoclast during osteoclastogenesis via hypoxia-inducible factor-1α pathway

BACKGROUND AND OBJECTIVE

The objective of this study was to investigate the potential of salidroside (SAL) (a major active compound in Rhodiola rosea L.) in regulating osteoclast differentiation and function by modulating the HIF-1α pathway and its downstream target genes.

METHODS

The expression of HIF-1α and its downstream target genes was examined at both mRNA and protein levels in osteoclasts treated with SAL. Immunofluorescence analysis was performed to assess the nuclear translocation and transcriptional activity of HIF-1α in response to SAL. MTT, flow cytometry, qPCR, TRAP staining and bone resorption assays were used to evaluate the potential effect of salidroside on osteoclasts.

RESULTS

SAL enhanced the expression of HIF-1α and its downstream target genes in osteoclasts. Immunofluorescence analysis confirmed the facilitation of HIF-1α nuclear translocation and transcriptional activity by SAL. In addition, SAL enhanced osteoclast viability, differentiation and bone resorption activity in an autocrine manner through HIF-1α/VEGF, IL-6 and ANGPTL4 pathways.

CONCLUSION

SAL promotes osteoclast proliferation, differentiation and bone resorption through HIF-1α/VEGF, IL-6 and ANGPTL4 pathways.

Bone repair and key signalling pathways for cell-based bone regenerative therapy: A review

Advances in cell-based regenerative therapy create new opportunities for the treatment of bone-related disorders and injuries, by improving the reparative phase of bone healing. Apart from the classical approach of bone grafting, the application of cell-based therapies, particularly stem cells (SCs), has gained a lot of attention in recent years. SCs play an important role in regenerative therapy due to their excellent ability to differentiate into bone-forming cells. Regeneration of new bone is regulated by a wide variety of signalling molecules and intracellular networks, which are responsible for coordinating cellular processes. The activated signalling cascade is significantly involved in cell survival, proliferation, apoptosis, and interaction with the microenvironment and other types of cells within the healing site. Despite the increasing evidence from studies conducted on signalling pathways associated with bone formation, the exact mechanism involved in controlling the differentiation stage of transplanted cells is not well understood. Identifying the key activated pathways involved in bone regeneration may allow for precise manipulation of the relevant signalling molecules within the progenitor cell population to accelerate the healing process. The in-depth knowledge of molecular mechanisms would be advantageous in improving the efficiency of personalised medicine and targeted therapy in regenerative medicine. In this review, we briefly introduce the theory of bone repair mechanism and bone tissue engineering followed by an overview of relevant signalling pathways that have been identified to play an important role in cell-based bone regenerative therapy.

The Wnt/β-catenin signaling pathway inhibits osteoporosis by regulating the expression of TERT: an in vivo and in vitro study

Our study was performed to investigate whether the Wingless and int-1 (Wnt) signaling pathway promotes osteogenic differentiation and inhibits apoptosis in bone marrow mesenchymal stem cells (BMSCs) by regulating telomerase reverse transcriptase (TERT) expression. An in vivo model of osteoporosis (OP) in C57BL/6J mice by bilateral ovariectomy (OVX) and an in vitro model of H2O2-induced BMSCs were established separately. Western blotting was used to detect the expression of the pathway-related proteins TERT, β-catenin, and phosphorylated-glycogen synthase kinase-3beta (p-GSK3β)/GSK3β, the osteogenic-related markers osteopontin (OPN), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (Runx2), and the apoptosis-related indicators B-cell lymphoma-2 (Bcl-2) and BAX. Osteoblastic phenotypes were also evaluated by alkaline phosphatase (ALP) staining and serum ALP activity assays. Osteogenic differentiation phenotypes in mice were verified by H&E staining, micro-CT, and parameter analysis of the femur. Western blotting results showed that the expression of the pathway-related proteins TERT, β-catenin, p-GSK3β/GSK3β was reduced in OVX mice and H2O2-induced BMSCs, accompanied by downregulated protein expression of osteogenic-related markers and antiapoptotic indicators and upregulated protein expression of apoptotic proteins compared to those in the control group. Mechanistic studies showed that the activation of Wnt signaling pathway in BMSCs promoted β-catenin translocation to the nucleus, as verified by immunofluorescence and facilitated colocalization between β-catenin and TERT, as verified by double-labeling immunofluorescence, thereby promoting osteogenic differentiation and reducing apoptosis. In summary, our experiments confirmed that the GSK3β/β-catenin/TERT pathway could regulate the osteogenic differentiation and apoptosis of BMSCs and that TERT might be a promising target for the future treatment of osteoporosis.

Curculigoside attenuates osteoporosis through regulating DNMT1 mediated osteoblast activity

This work aims to study the function of curculigoside in osteoporosis and explore whether DNMT1 is closely involved in osteoblast activity. After OB-6 osteoblasts were treated with hydrogen peroxide (H2O2), a curculigoside treatment group was set up and a series of biological tests including MTT, flow cytometry, western blotting, ROS fluorescence intensity, mitochondrial membrane potential, and ELISA experiments were performed to verify the effect of curculigoside on the activity of osteoblasts. Then, alkaline phosphatase (ALP) activity, alizarin red staining, PCR, and western blotting assays were performed to detect the effects of curculigoside on osteoblast function. By constructing DNMT1 knockdown and overexpression OB-6 cell lines, the effect of DNMT1 on osteoblast function was verified. In addition, the expression level of Nrf2 in each group was detected to speculate the mechanism of DNMT1 in osteoporosis. The cell activity and level of bcl-2 and SOD were significantly increased; the cell apoptosis, ROS fluorescence intensity, mitochondrial membrane potential, MDA and level of caspase-3, Bax, and CAT was reduced in curculigoside treatment group compared with H2O2-induced OB-6 osteoblasts. Meanwhile, the ALP activity, number and area of bone mineralized nodules, and gene and protein expression of OSX and OPG were significantly elevated in curculigoside group. Moreover, DNMT1 knockdown had a similar promotion effect on osteoblast function as curculigoside, and DNMT1 overexpression could reverse the promotion effect of curculigoside on osteoblast function. Further mechanistic studies speculated that DNMT1 might play a role in osteoporosis by affecting Nrf2 methylation. Curculigoside enhances osteoblast activity through DNMT1 controls of Nrf2 methylation.

HIF-1α increases the osteogenic capacity of ADSCs by coupling angiogenesis and osteogenesis via the HIF-1α/VEGF/AKT/mTOR signaling pathway

BACKGROUND

Stabilization and increased activity of hypoxia-inducible factor 1-α (HIF-1α) can directly increase cancellous bone formation and play an essential role in bone modeling and remodeling. However, whether an increased HIF-1α expression in adipose-derived stem cells (ADSCs) increases osteogenic capacity and promotes bone regeneration is not known.

RESULTS

In this study, ADSCs transfected with small interfering RNA and HIF-1α overexpression plasmid were established to investigate the proliferation, migration, adhesion, and osteogenic capacity of ADSCs and the angiogenic ability of human umbilical vein endothelial cells (HUVECs). Overexpression of HIF-1α could promote the biological functions of ADSCs, and the angiogenic ability of HUVECs. Western blotting showed that the protein levels of osteogenesis-related factors were increased when HIF-1α was overexpressed. Furthermore, the influence of upregulation of HIF-1α in ADSC sheets on osseointegration was evaluated using a Sprague-Dawley (SD) rats implant model, in which the bone mass and osteoid mineralization speed were evaluated by radiological and histological analysis. The overexpression of HIF-1α in ADSCs enhanced bone remodeling and osseointegration around titanium implants. However, transfecting the small interfering RNA (siRNA) of HIF-1α in ADSCs attenuated their osteogenic and angiogenic capacity. Finally, it was confirmed in vitro that HIF-1α promotes osteogenic differentiation and the biological functions in ADSCs via the VEGF/AKT/mTOR pathway.

CONCLUSIONS

This study demonstrates that HIF-1α has a critical ability to promote osteogenic differentiation in ADSCs by coupling osteogenesis and angiogenesis via the VEGF/AKT/mTOR signaling pathway, which in turn increases osteointegration and bone formation around titanium implants.

Peonidin-3-O-glucoside and Resveratrol Increase the Viability of Cultured Human hFOB Osteoblasts and Alter the Expression of Genes Associated with Apoptosis, Osteoblast Differentiation and Osteoclastogenesis

High-throughput RNA-sequencing can determine the impact of nutrients and their combinations on gene transcription levels in osteocytes, and clarify the biological pathways associated with their impact on bone tissues. Previously, we reported that resveratrol (RES) and peonidin-3-O-glucoside (POG) increased osteoblastogenesis, as well as reduced osteoclastogenesis in transgenic teleost fish models. Here, we perform whole-genome transcriptomic profiling of osteoblasts treated with POG or RES to provide a comprehensive understanding of alterations in gene expression and the molecular mechanisms involved. Cultured human fetal osteoblastic hFOB 1.19 cells were treated with the test compounds, and then RNA was used to prepare RNA-seq libraries, that were sequenced using a NovaSeq 6000. Treatment with POG or RES increased osteoblast proliferation and reduced apoptosis. Transcriptomic profiling showed that of the 29,762 genes investigated, 3177 were differentially expressed (1481 upregulated, 1696 downregulated, FDR ≤ 0.05) in POG-treated osteoblasts. In the RES-treated osteoblasts, 2288 genes were differentially expressed (DGEs, 1068 upregulated, 1220 downregulated, FDR ≤ 0.05). Ingenuity^® Pathway Analysis (IPA) of DGEs from RES or POG-treated osteoblasts revealed significant downregulation of the apoptosis, osteoarthritis and HIF1α canonical pathways, and a significant reduction in Rankl mRNA expression. The data suggest that RES and POG have both anabolic and anticlastogenic effects.