Thrombin receptor deficiency leads to a high bone mass phenotype by decreasing the RANKL/OPG ratio

Effect of direct oral anticoagulant dabigatran on early bone healing: An experimental study in rats

Background

Dabigatran belongs to the new generation of direct oral anticoagulants (DOACs). Its advantages are oral administration and no need for international normalized ratio (INR) monitoring. Although its use has increased, its potential side effects on bone healing and remodeling have not been fully investigated. The present study aimed to evaluate the possible effects of dabigatran on early bone healing.

Methods

Sixteen male Wistar rats were divided into two groups; in group A, 20-mg/kg dabigatran dose was administered orally daily for 15 days, while group B served as a control. Two circular bone defects (d=6 mm) were created on either side of the parietal bones. Two weeks after surgery and euthanasia of the animals, tissue samples (parietal bones that contained the defects) were harvested for histological and histomorphometric analysis. Statistical analysis was performed with a significance level of α=0.5.

Results

No statistically significant differences were found between the two groups regarding the regenerated bone (21.9% vs. 16.3%, P=0.172) or the percentage of bone bridging (63.3% vs. 53.5%, P=0.401).

Conclusion

Dabigatran did not affect bone regeneration, suggesting that it might be a safer drug compared to older anticoagulants known to lead to bone healing delay.

CRISPR/Cas13d targeting GZMA in PARs pathway regulates the function of osteoclasts in chronic apical periodontitis

Chronic apical periodontitis is a prevalent oral disease characterized by bone loss, and its underlying mechanisms remain unclear. This study aimed to investigate the role and mechanism of the serine protease GZMA in osteoclasts during chronic apical periodontitis. To address this, we employed crRNA/Cas13d to inhibit GZMA expression and examined its impact on osteoclast behavior. Our findings revealed that GZMA plays a significant role in promoting osteoclast cell proliferation while inhibiting cell apoptosis. Additionally, the inhibition of GZMA led to a notable increase in miR-25-3p expression, which, in turn, downregulated the expression of TGF-β. Consequently, the reduction in TGF-β expression led to a decrease in PAR1 expression within the PARs pathway. These results suggest that GZMA might serve as a promising therapeutic target for the treatment of chronic apical periodontitis. Furthermore, our study highlights the potential of targeting GZMA using crRNA/Cas13d as a valuable approach for future therapeutic interventions.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

Osteoporosis in hemophilia: what is its importance in clinical practice?

INTRODUCTION

The relationship between severe hemophilia and osteoporosis has been well established in the literature. However, although the importance of its prevention in order to reduce the risk of bone fractures has been reported, the importance of its treatment in clinical practice has not been well analyzed.

AREAS COVERED

In this paper a review of the available clinical and experimental information on osteoporosis in hemophilia has been performed, to better understand the relationship between hemophilia and osteoporosis. Prevention of osteoporosis in hemophilia should include primary hematological prophylaxis; a diet appropriate in calcium and vitamin D; a regular exercise program that includes aerobics, strength training and balance and flexibility activities; restriction of tobacco and alcohol use; and limitation of the duration of immobilization.

EXPERT OPINION

Prevention of osteoporosis in hemophilic patients is paramount. However, it is noteworthy that there is only one publication on the treatment of osteoporosis in patients with hemophilia. Until further research is done on this topic, the existing recommendations for non-hemophilic patients should be followed. They include the use of antiresorptives (estrogens, selective estrogen receptor modulators, bisphosphonates, denosumab) and anabolic agents (teriparatide, abaloparatide, romosozumab). Further studies on the management of osteoporosis in patients with hemophilia are required.

The Roles of RANK/RANKL/OPG in Cardiac, Skeletal, and Smooth Muscles in Health and Disease

Although their physiology and functions are very different, bones, skeletal and smooth muscles, as well as the heart have the same embryonic origin. Skeletal muscles and bones interact with each other to enable breathing, kinesis, and the maintenance of posture. Often, muscle and bone tissues degenerate synchronously under various conditions such as cancers, space travel, aging, prolonged bed rest, and neuromuscular diseases. In addition, bone tissue, skeletal and smooth muscles, and the heart share common signaling pathways. The RANK/RANKL/OPG pathway, which is essential for bone homeostasis, is also implicated in various physiological processes such as sarcopenia, atherosclerosis, and cardiovascular diseases. Several studies have reported bone-skeletal muscle crosstalk through the RANK/RANKL/OPG pathway. This review will summarize the current evidence indicating that the RANK/RANKL/OPG pathway is involved in muscle function. First, we will briefly discuss the role this pathway plays in bone homeostasis. Then, we will present results from various sources indicating that it plays a physiopathological role in skeletal, smooth muscle, and cardiac functions. Understanding how the RANK/RANKL/OPG pathway interferes in several physiological disorders may lead to new therapeutic approaches aimed at protecting bones and other tissues with a single treatment.

Low Bone Mineral Density in Hemophiliacs

Objective

To review the current knowledge on bone health in patients with hemophilia A and the underlying pathogenetic mechanisms.

Data Sources

Original research articles, meta-analyses, and scientific reviews.

Data Synthesis

Already in childhood, patients with hemophilia A are prone to low bone mineral density, leading to osteopenia and/or osteoporosis. Initially associated with the life style of hemophilia, today we are faced with accumulating evidence that coagulation factor VIII is involved directly or indirectly in bone physiology.

Conclusion

Understanding the role of factor VIII and the mechanisms of decreased bone mineral density in hemophilia A is critically important, especially as non-factor replacement therapies are available, and treatment decisions potentially impact bone health.

FVIII at the crossroad of coagulation, bone and immune biology: Emerging evidence of biological activities beyond hemostasis

Hemophilia A is an X-linked hereditary disorder that results from deficient coagulation factor VIII (FVIII) activity, leading to spontaneous bleeding episodes, particularly in joints and muscles. FVIII deficiency has been associated with altered bone remodeling, dysregulated macrophage polarization, and inflammatory processes that are associated with the neoformation of abnormal blood vessels. Treatment based on FVIII replacement can lead to the development of inhibitors that render FVIII concentrate infusion ineffective. In this context, hemophilia has entered a new therapeutic era with the development of new drugs, such as emicizumab, that seek to restore the hemostatic balance by bypassing pathologically acquired antibodies. We discuss the potential extrahemostatic functions of FVIII that may be crucial for defining future therapies in hemophilia.

Mechanisms of Bone Remodeling Disorder in Hemophilia

Hemophilia is caused by a lack of antihemophilic factor(s), for example, factor VIII (FVIII; hemophilia A) and factor IX (FIX; hemophilia B). Low bone mass is widely reported in epidemiological studies of hemophilia, and patients with hemophilia are at an increased risk of fracture. The detailed etiology of bone homeostasis imbalance in hemophilia is unclear. Clinical and experimental studies show that FVIII and FIX are involved in bone remodeling. However, it is likely that antihemophilic factors affect bone biology through thrombin pathways rather than via their own intrinsic properties. In addition, among patients with hemophilia, there are pathophysiological processes in several systems that might contribute to bone loss. This review summarizes studies on the association between hemophilia and bone remodeling, and might shed light on the challenges facing the care and prevention of osteoporosis and fracture in patients with hemophilia.

Dehydroepiandrosterone and age-related musculoskeletal diseases: Connections and therapeutic implications

Musculoskeletal disorders related to ageing are one of the most common causes of mortality and morbidity among elderly individuals worldwide. The typical constitutive components of the musculoskeletal system, including bone, muscle, and joints, gradually undergo a process of tissue loss and degeneration as a result of life-long mechanical and biological stress, ultimately leading to the onset of a series of age-related musculoskeletal diseases, including osteoporosis (OP), sarcopenia, and osteoarthritis (OA). Dehydroepiandrosterone (DHEA), a precursor of androgen secreted mainly by the adrenal gland, has attracted much attention as a marker for senescence due to its unique age-related changes. This pre-hormone has been publicly regarded as an "antidote for ageing" because of its favourable effect against a wide range of age-related diseases, such as Alzheimer disease, cardiovascular diseases, immunosenescence and skin senescence, though its effect on age-related musculoskeletal diseases has been explored to a lesser extent. In the present review, we summarized the action of DHEA against OP, sarcopenia and OA. Extensive detailed descriptions of the pathogenesis of each of these musculoskeletal disorders are beyond the scope of this review; instead, we aim to highlight the association of changes in DHEA with the processes of OP, sarcopenia and OA. A special focus will also be placed on the overlapping pathogeneses among these three diseases, and the molecular mechanisms underlying the action of DHEA against these diseases are discussed or postulated.

Inhibitory effects of dabigatran etexilate, a direct thrombin inhibitor, on osteoclasts and osteoblasts

INTRODUCTION

Anticoagulants are widely used in orthopedic surgery to decrease the risk of deep vein thrombosis. While significant bone impairment is induced by long-term heparin therapy, little is known about the effects of direct oral anticoagulants (DOACs). Herein, we investigated the effects of dabigatran etexilate (Pradaxa®), a DOAC inhibitor of thrombin, on bone cells using in vitro and ex vivo cell culture models.

MATERIALS AND METHODS

Osteoblasts and osteoclasts exposed to different concentrations of dabigatran etexilate and untreated cells were assayed for cell differentiation and activity. Favorable osteogenic conditions for osteoblasts were tested using titanium with nanotopography (Ti-Nano). In addition, mice treated with a dabigatran etexilate solution had bone marrow cells analyzed for the ability to generate osteoclasts.

RESULTS

Dabigatran etexilate at concentrations of 1 μg/mL and 2 μg/mL did not impact osteoclast or osteoblast viability. The drug inhibited osteoclast differentiation and activity as observed by the reduction of TRAP+ cells, resorption pits and gene and protein expression of cathepsin K. Consistently, osteoclasts from mice treated with dabigatran showed decreased area, resorptive activity, as well as gene and protein expression of cathepsin K. In osteoblast cultures, grown both on polystyrene and Ti-Nano, dabigatran etexilate reduced alkaline phosphatase (ALP) activity, matrix mineralization, gene expression of ALP and osteocalcin.

CONCLUSIONS

Dabigatran etexilate inhibited osteoclast differentiation in ex vivo and in vitro models in a dose-dependent manner. Moreover, the drug reduced osteoblast activity even under optimal osteogenic conditions. This study provides new evidence regarding the negative overall impact of DOACs on bone cells.

Interactions between cancer cells and bone microenvironment promote bone metastasis in prostate cancer

Bone metastasis is the leading cause of death in prostate cancer patients, for which there is currently no effective treatment. Since the bone microenvironment plays an important role in this process, attentions have been directed to the interactions between cancer cells and the bone microenvironment, including osteoclasts, osteoblasts, and bone stromal cells. Here, we explained the mechanism of interactions between prostate cancer cells and metastasis-associated cells within the bone microenvironment and further discussed the recent advances in targeted therapy of prostate cancer bone metastasis. This review also summarized the effects of bone microenvironment on prostate cancer metastasis and the related mechanisms, and provides insights for future prostate cancer metastasis studies.

Protease-Activated Receptor 1 Deletion Causes Enhanced Osteoclastogenesis in Response to Inflammatory Signals through a Notch2-Dependent Mechanism

We found that protease-activated receptor 1 (PAR1) was transiently induced in cultured osteoclast precursor cells. Therefore, we examined the bone phenotype and response to resorptive stimuli of PAR1-deficient (knockout [KO]) mice. Bones and bone marrow-derived cells from PAR1 KO and wild-type (WT) mice were assessed using microcomputed tomography, histomorphometry, in vitro cultures, and RT-PCR. Osteoclastic responses to TNF-α (TNF) challenge in calvaria were analyzed with and without a specific neutralizing Ab to the Notch2-negative regulatory region (N2-NRR Ab). In vivo under homeostatic conditions, there were minimal differences in bone mass or bone cells between PAR1 KO and WT mice. However, PAR1 KO myeloid cells demonstrated enhanced osteoclastogenesis in response to receptor activator of NF-κB ligand (RANKL) or the combination of RANKL and TNF. Strikingly, in vivo osteoclastogenic responses of PAR1 KO mice to TNF were markedly enhanced. We found that N2-NRR Ab reduced TNF-induced osteoclastogenesis in PAR1 KO mice to WT levels without affecting WT responses. Similarly, in vitro N2-NRR Ab reduced RANKL-induced osteoclastogenesis in PAR1 KO cells to WT levels without altering WT responses. We conclude that PAR1 functions to limit Notch2 signaling in responses to RANKL and TNF and moderates osteoclastogenic response to these cytokines. This effect appears, at least in part, to be cell autonomous because enhanced osteoclastogenesis was seen in highly purified PAR1 KO osteoclast precursor cells. It is likely that this pathway is involved in regulating the response of bone to diseases associated with inflammatory signals.

The effect of oral dabigatran etexilate on bone density, strength, and microstructure in healthy mice

Thrombin is a key component in the coagulation cascade where it converts factor V, VIII, XI, and fibrinogen. In addition to the abundant production of thrombin in the liver, osteoclasts synthesize and secrete thrombin as well. Osteoblasts express thrombin receptors, and it has been reported that thrombin stimulates the expression of RANKL relatively to OPG, resulting in greater osteoclast activation and bone degradation. Pradaxa (dabigatran etexilate, DE) is a new anticoagulant, which has recently been approved for clinical use. DE is a direct thrombin inhibitor with potential to modulate the RANKL/OPG ratio and thereby limit osteoclast activation and bone degradation. The purpose of the study was to investigate whether DE can increase bone density, bone strength, and bone microstructure in healthy male and female mice and to investigate whether the effect of DE is sex-dependent. Twenty-eight 14-week-old male C57BL/6 mice were stratified by weight into 4 groups: 1. Control 3 weeks; 2. DE 3 weeks; 3. Control 6 weeks; 4. DE 6 weeks. An identical study design was applied to twenty-four 14-week-old female C57BL/6 mice. Chow mixed with DE was offered ad libitum, resulting in a dose of 1.70 mg DE/g body weight and 1.52 mg DE/g body weight, to female and male mice, respectively. The animals were euthanized after 3 or 6 weeks. Bone mineral density (aBMD) and bone mineral content (BMC) were evaluated with DEXA, 3D microstructural properties were determined with μCT, bone strength was determined with mechanical testing, and bone formation and resorption was evaluated with bone histomorphometry. In female mice, DE resulted in significant higher tibial aBMD values after 6 weeks of intervention. Furthermore, DE significantly increased tibial diaphyseal cortical bone area and tissue area, which was accompanied by significantly increased strength of the tibial shaft. DE had no effect on femoral cortical bone or on femoral and vertebral trabecular 3D microstructure. Finally, bone histomorphometry showed that DE had no effect on MS/BS or Oc.S/BS. In male mice, no bone positive effects of DE were found in any of the parameters investigated. In conclusion, intervention with DE may result in a weak positive site specific effect at tibial cortical bone in female mice, and importantly, no major deleterious effects of DE on bone tissue were seen in either female or male mice despite the relatively high dose of DE used.

Increased bone resorption in hemophilia

In patients with hemophilia, osteoporosis is frequently observed for which the etiology remains unclear. The aim of this paper is to review the available experimental evidence indicating the presence of this disorder in patients with hemophilia, explore the potential mechanisms which may lead to reduced bone mineral density (BMD) and speculate on useful interventions to circumvent it. A narrative review of the English literature up to April 2018 was performed. The available evidence demonstrates an increased rate of bone resorption and an excess of osteoporosis among patients with hemophilia. FVIII and FIX may act through at least two pathways: promoting bone formation by a thrombin-mediated mitogenic effect on osteoblasts and by cytokine-mediated osteoclast activity. Another potential indirect mechanism mediated through the RANK-RANKL pathway has been suggested but remains controversial. The role of confounders such as lack of activity and immobility must be considered.

Dehydroepiandrosterone and Bone

In humans, dehydroepiandrosterone (DHEA), secreted mainly from the adrenal cortex, and its sulfate ester, DHEAS, are the most abundant circulating steroids. DHEA/DHEAS possess pleiotropic effects in human aging, bone, metabolic diseases, neurologic function/neurodegenerative diseases, cancer, immune system and disorders, cardiovascular diseases, diabetes, muscle function, sexual dysfunction, and other health conditions. The age-related reduced levels of DHEA and DHEAS are associated with bone mineral density measures of osteopenia and osteoporosis. Clinical, epidemiological, and experimental studies indicate that DHEA replacement therapy may be beneficial for bone health through its inhibition of skeletal catabolic IL-6 and stimulation of osteoanabolic IGF-I-mediated mechanisms. Studies with primary cultures of human bone marrow-derived mesenchymal stem cells (hMSCs) were used to show that DHEA stimulates osteoblastogenesis. The in vitro stimulation of both osteoblastogenesis and IGF-I gene expression by DHEA in hMSCs requires IGF-I receptor, PI3K, p38 MAPK, or p42/44 MAPK signaling pathways. The in vitro inhibition of IL-6 secretion in hMSCs by DHEA was more consistent and extensive than by estradiol or dihydrotestosterone. In summary, evidence from us and others indicates that DHEA may be useful for treating bone diseases through its inhibition of skeletal catabolic IL-6 and stimulation of anabolic IGF-I-mediated mechanisms.

A study on OPG/RANK/RANKL axis in osteoporotic bile duct-ligated rats and the involvement of nitrergic and opioidergic systems

Chronic liver disease (CLD) affects millions of people and its impact on bone loss has become a subject of interest. Nitric oxide and endogenous opioids are suggested to increase during cholestasis/cirrhosis and may impact bone resorption by different mechanisms. The receptor activator of nuclear factor-κB (RANK)/RANK-ligand (RANKL)/osteoprotegerin (OPG) signaling pathway regulates bone resorption, but its role in metabolic bone disease subsequent to CLD is unknown. We aimed to investigate the involvement of nitrergic and opioidergic systems in bone loss relative to the RANK/RANKL/OPG pathway, in bile duct-ligated (BDL) rats. Eighty BDL/sham-operated (SO) rats received injections of 3 mg/kg/day Nω-Nitro-L-arginine methyl ester ± naltrexone (10 mg/kg/day) or saline for 28 days. Plasma bone turnover markers, OPG, RANK, and RANKL along with mRNA expression levels of the latter three were assessed. Plasma bone turnover markers and OPG level increased, but RANKL decreased in the BDL group compared with their SO controls (both: P ≤ 0.05). Administration of naltrexone reduced bone turnover markers and OPG level while increased RANKL content in comparison to BDL rats (P ≤ 0.05). As compared to untreated BDL rats, nitric oxide inhibition showed no effect on bone turnover marker i.e. OPG, RANK, and RANKL levels. BDL significantly increased RANK mRNA, but had no significant effect on RANKL and OPG mRNA expression. The lack of association between plasma levels and quantitative gene expression of RANKL and OPG suggests an indirect function of these markers in BDL rats. Considering that opioid receptor blockage by naltrexone in BDL animals caused a significant decrease in OPG and an increase in RANKL plasma contents, it could be postulated that the opioidergic system may have a regulatory effect on these bone markers.

TGF-β induced PAR-1 expression promotes tumor progression and osteoclast differentiation in giant cell tumor of bone

Although protease activated receptor-1 (PAR-1) has been confirmed as an oncogene in many cancers, the role of PAR-1 in giant cell tumor (GCT) of bone has been rarely reported. The mechanism of PAR-1 in tumor-induced osteoclastogenesis still remains unclear. In the present study, we detected that PAR-1 was significantly upregulated in GCT of bone compared to normal tissues, while TGF-β was also overexpressed in GCT tissues and could promote the expression of PAR-1 in a dose and time dependent manner. Using the luciferase reporter assay, we found that two downstreams of TGF-β, Smad3 and Smad4, could activate the promoter of PAR-1, which might explain the mechanism of TGF-β induced PAR-1 expression. Meanwhile, PAR-1 was also overexpressed in microvesicles from stromal cells of GCT (GCTSCs), and might be transported from GCTSCs to monocytes through microvesicles. In addition, knockout of PAR-1 by TALENs in GCTSCs inhibited tumor growth, angiogenesis and osteoclastogenesis in GCT in vitro. Using the chick CAM models, we further showed that inhibition of PAR-1 suppressed tumor growth and giant cell formation in vivo. Using microarray assay, we detected a number of genes involved in osteoclastogenesis as the possible downstreams of PAR-1, which may partly explain the mechanism of PAR-1 in GCT. In brief, for the first time, these results reveal an upstream regulatory role of TGF-β in PAR-1 expression, and PAR-1 expression promotes tumor growth, angiogenesis and osteoclast differentiation in GCT of bone. Hence, PAR-1 represents a novel potential therapeutic target for GCT of bone.

Regulation of long-term repopulating hematopoietic stem cells by EPCR/PAR1 signaling

The common developmental origin of endothelial and hematopoietic cells is manifested by coexpression of several cell surface receptors. Adult murine bone marrow (BM) long-term repopulating hematopoietic stem cells (LT-HSCs), endowed with the highest repopulation and self-renewal potential, express endothelial protein C receptor (EPCR), which is used as a marker to isolate them. EPCR/protease-activated receptor-1 (PAR1) signaling in endothelial cells has anticoagulant and anti-inflammatory roles, while thrombin/PAR1 signaling induces coagulation and inflammation. Recent studies define two new PAR1-mediated signaling cascades that regulate EPCR(+) LT-HSC BM retention and egress. EPCR/PAR1 signaling facilitates LT-HSC BM repopulation, retention, survival, and chemotherapy resistance by restricting nitric oxide (NO) production, maintaining NO(low) LT-HSC BM retention with increased VLA4 expression, affinity, and adhesion. Conversely, acute stress and clinical mobilization upregulate thrombin generation and activate different PAR1 signaling that overcomes BM EPCR(+) LT-HSC retention, inducing their recruitment to the bloodstream. Thrombin/PAR1 signaling induces NO generation, TACE-mediated EPCR shedding, and upregulation of CXCR4 and PAR1, leading to CXCL12-mediated stem and progenitor cell mobilization. This review discusses new roles for factors traditionally viewed as coagulation related, which independently act in the BM to regulate PAR1 signaling in bone- and blood-forming progenitor cells, navigating their fate by controlling NO production.

PAR1 signaling regulates the retention and recruitment of EPCR-expressing bone marrow hematopoietic stem cells

Retention of long-term repopulating hematopoietic stem cells (LT-HSCs) in the bone marrow is essential for hematopoiesis and for protection from myelotoxic injury. We report that signaling cascades that are traditionally viewed as coagulation related also control retention of endothelial protein C receptor-positive (EPCR(+)) LT-HSCs in the bone marrow and their recruitment to the blood via two pathways mediated by protease activated receptor 1 (PAR1). Thrombin-PAR1 signaling induces nitric oxide (NO) production, leading to EPCR shedding mediated by tumor necrosis factor-α-converting enzyme (TACE), enhanced CXCL12-CXCR4-induced motility and rapid stem and progenitor cell mobilization. Conversely, bone marrow blood vessels provide a microenvironment enriched with activated protein C (aPC) that retains EPCR(+) LT-HSCs by limiting NO generation, reducing Cdc42 activity and enhancing integrin VLA4 affinity and adhesion. Inhibition of NO production by aPC-EPCR-PAR1 signaling reduces progenitor cell egress from the bone marrow, increases retention of bone marrow NO(low) EPCR(+) LT-HSCs and protects mice from chemotherapy-induced hematological failure and death. Our study reveals new roles for PAR1 and EPCR in controlling NO production to balance maintenance and recruitment of bone marrow EPCR(+) LT-HSCs, with potential clinical relevance for stem cell transplantation.

Nanosecond pulsed electric field inhibits proliferation and induces apoptosis in human osteosarcoma

OBJECTIVE

Recent studies suggest that nanosecond pulsed electric field (nsPEF) is a novel minimal invasive and non-thermal ablation method that can induce apoptosis in different solid tumors. But the efficacy of nsPEF on bone-related tumors or bone metastasis is kept unknown. The current study investigates antitumor effect of nsPEF on osteosarcoma MG-63 cells in vitro.

METHOD

MG-63 cells were treated with nsPEF with different electric field strengths (0, 10, 20, 30, 40, and 50 kV/cm) and different pulse numbers (0, 6, 12, 18, 24, and 30 pulses). The inhibitory effect of nsPEF on the growth of MG-63 cells was measured by Cell Counting Kit-8 (CCK-8) assay at different time points (0, 3, 12, 24, and 48 h post nsPEF treatment). The apoptosis was analyzed by Hoechst stain, in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL), and flow cytometric analysis. The expression of osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), and tumor necrosis factor α (TNF-α) was examined by reverse-transcription polymerase chain reaction (RT-PCR) and western blot.

RESULTS

The CCK-8 assay showed that nsPEF induced a distinct electric field strength- and pulse number-dependent reduction of cell proliferation. For treatment parameter optimizing, the condition 40 kV/cm and 30 pulses at 24 h post nsPEF achieved the most significant apoptotic induction rate. Hoechst, TUNEL, and flow cytometric analysis showed that the cell apoptosis was induced and cells were arrested in the G0/G1 phase. PCR and western blot analysis demonstrated that nsPEF up-regulated OPG expression had no effect on RANKL, increased OPG/RANKL ratio.

CONCLUSION

NsPEF inhibits osteosarcoma growth, induces apoptosis, and affects bone metabolism by up-regulating OPG, indicating nsPEF-induced apoptosis in osteosarcoma MG-63 cells. NsPEF has potential to treat osteosarcoma or bone metastasis. When nsPEF is applied on metastatic bone tumors, it might be beneficial by inducing osteoblastic differentiation without cancer proliferation. In the future, nsPEF might be one of the treatments of metastatic bone tumor.