Impairment of bone microstructure and upregulation of osteoclastogenic markers in spontaneously hypertensive rats

Efficacy of mesenchymal stem cell-based therapy on the bone repair of hypertensive rats

OBJECTIVE

Hypertension disrupts the bone integrity and its repair ability. This study explores the efficiency of a therapy based on the application of mesenchymal stem cells (MSCs) to repair bone defects of spontaneously hypertensive rats (SHR).

METHODS

First, we evaluated SHR in terms of bone morphometry and differentiation of MSCs into osteoblasts. Then, the effects of the interactions between MSCs from normotensive rats (NTR-MSCs) cocultured with SHR (SHR-MSCs) on the osteoblast differentiation of both cell populations were evaluated. Also, bone formation into calvarial defects of SHR treated with NTR-MSCs was analyzed.

RESULTS

Hypertension induced bone loss evidenced by reduced bone morphometric parameters of femurs of SHR compared with NTR as well as decreased osteoblast differentiation of SHR-MSCs compared with NTR-MSCs. NTR-MSCs partially restored the capacity of SHR-MSCs to differentiate into osteoblasts, while SHR-MSCs exhibited a slight negative effect on NTR-MSCs. An enhanced bone repair was observed in defects treated with NTR-MSCs compared with control, stressing this cell therapy efficacy even in bones damaged by hypertension.

CONCLUSION

The use of MSCs derived from a heathy environment can be in the near future a smart approach to treat bone loss in the context of regenerative dentistry for oral rehabilitation of hypertensive patients.

Simultaneous visualization of micro-damage in cortical bone, trabecular bone, and intracortical vasculature for diagnosing osteoporosis: An animal model synchrotron imaging

Osteoporosis (OP) is difficult to diagnose through the three-dimensional visualization of micro-damage. In this study, aimed to make an objective diagnosis by visualizing micro-damage caused by OP using synchrotron radiation-based μCT (SR-μCT). Female mice (n = 12) were randomly divided into an ovariectomized group (OVX, n = 6) in which both ovaries were excised and OP occurred, and a sham-operated group (SHAM, n = 6). After six weeks, all femurs (left and right) were excised from both groups (n = 12 per group). Thereafter, femurs were randomly divided into SR-μCT (OVX group, n = 6; SHAM group, n = 6) and μCT (OVX group, n = 6; SHAM group, n = 6) groups. In the SR-μCT group, micro-damage was visualized by manually segmenting the cortical bone, trabecular bone, and intracortical vasculature using a water-shedding algorithm. In addition, trabecular bone was obtained by automatic segmentation using μCT. Cortical bone volume/total volume was greater (p = .015), and cortical thickness was greater in the SHAM group than in the OVX group (p = .007). Among the trabecular bone parameters, the bone volume/total volume (TV) in OVX was significantly lower than that in the SHAM group (p = .012). The canal volume was greater (p = .021) and lacuna volume was greater (p < .001) in the SHAM group than in the OVX group. We expect that it will be possible to analyze damage and recovery mechanisms in the field of rehabilitation. SR-μCT has been proposed as an objective method for OP diagnosis as it allows the visualization of microstructures. RESEARCH HIGHLIGHTS: Damage mechanism for diagnosis and evaluation in an osteoporosis model. Synchrotron radiation can objectively diagnose osteoporosis. Visualization is possible by segmenting microdamage caused by osteoporosis.

The Role of Osteogenic Effect and Vascular Function in Bone Health in Hypertensive Rats: A Study of Anti-hypertensive and Hemorheologic Drugs

Vascular dysfunction contributes to the development of osteopenia in hypertensive patients, as decreased blood supply to bones results in tissue damage and dysfunction. The effect of anti-hypertensive medicines on bone mass in hypertensive individuals is inconclusive because of the varied mechanism of their action, and suggests that reducing blood pressure (BP) alone is insufficient to enhance bone mass in hypertension. Pentoxifylline (PTX), a hemorheological drug, improves blood flow by reducing blood viscosity and angiogenesis, also has an osteogenic effect. We hypothesized that improving vascular function is critical to increasing bone mass in hypertension. To test this, we screened various anti-hypertensive drugs for their in vitro osteogenic effect, from which timolol and hydralazine were selected. In adult female spontaneously hypertensive rats (SHRs), timolol and hydralazine did not improve vascular function and bone mass, but PTX improved both. In female SHR animals, PTX restored bone mass, strength and mineralization, up to the level of normotensive control rats. In addition, we observed lower blood vasculature in the femur of adult SHR animals, and PTX restored them. PTX also restored the bone vascular and angiogenesis parameters that had been impaired in OVX SHR compared to sham SHR. This study demonstrates the importance of vascular function in addition to increased bone mass for improving bone health as achieved by PTX without affecting BP, and suggests a promising treatment option for osteoporosis in hypertensive patients, particularly at-risk postmenopausal women.

Tissue-specific expression of senescence biomarkers in spontaneously hypertensive rats: evidence of premature aging in hypertension

Background

Cellular senescence is an age-related physiological process that contributes to tissue dysfunction and accelerated onset of chronic metabolic diseases including hypertension. Indeed, elevation of blood pressure in hypertension coincides with premature vascular aging and dysfunction. In addition, onsets of metabolic disturbance and osteopenia in patients with hypertension have also been reported. It is possible that hypertension enhances premature aging and causes progressive loss of function in multiple organs. However, the landscape of cellular senescence in critical tissues affected by hypertension remains elusive.

Materials and Methods

Heart, liver, bone, hypothalamus, and kidney were collected from spontaneously hypertensive rats (SHR) and age- and sex-matched normotensive Wistar rats (WT) at 6, 12, 24 and 36 weeks of age (n = 10 animals/group). Changes in mRNA levels of senescence biomarkers namely cyclin-dependent kinase (CDK) inhibitors (CDKIs), i.e., Cdkn2a (encoding p16Ink4a) and Cdkn1a (encoding p21cip1) as well as senescence-associated secretory phenotypes (SASPs), i.e., Timp1, Mmp12, Il6 and Cxcl1, were determined. Additionally, bone collagen alignment and hydroxy apatite crystal dimensions were determined by synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS) techniques.

Results

Real-time PCR revealed that transcript levels of genes encoding CDKIs and SASPs in the heart and liver were upregulated in SHR from 6 to 36 weeks of age. Expression of Timp1 and Cxcl1 was increased in bone tissues isolated from 36-week-old SHR. In contrast, we found that expression levels of Timp1 and Il6 mRNA were decreased in hypothalamus and kidney of SHR in all age groups. Simultaneous SAXS/WAXS analysis also revealed misalignment of bone collagen fibers in SHR as compared to WT.

Conclusion

Premature aging was identified in an organ directly affected by high blood pressure (i.e., heart) and those with known functional defects in SHR (i.e., liver and bone). Cellular senescence was not evident in organs with autoregulation of blood pressure (i.e., brain and kidney). Our study suggested that cellular senescence is induced by persistently elevated blood pressure and in part, leading to organ dysfunction. Therefore, interventions that can both lower blood pressure and prevent cellular senescence should provide therapeutic benefits for treatment of cardiovascular and metabolic consequences.

Azilsartan inhibits inflammation-triggered bone resorption and osteoclastogenesis in vivo via suppression of TNF-α expression in macrophages

Introduction

Hypertension is a major risk factor for cardiovascular disease (CVD) and is associated with increased bone loss due to excessive activity of the local renin-angiotensin system (RAS). Angiotensinogen/Angiotensin (ANG) II/Angiotensin II type 1 receptor (AT1R) axis is considered as the core axis regulating RAS activity. Azilsartan is an FDA-approved selective AT1R antagonist that is used to treat hypertension. This study aimed to determine whether azilsartan affects formation of osteoclast, resorption of bone, and the expression of cytokines linked with osteoclastogenesis during lipopolysaccharide (LPS)-triggered inflammation in vivo.

Methods

In vivo, following a 5-day supracalvarial injection of LPS or tumor necrosis factor-alpha (TNF-α) with or without azilsartan, the proportion of bone resorption and the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells, which are identified as osteoclasts on mice calvariae were counted. The mRNA expression levels of TRAP, cathepsin K, receptor activator of NF-κB ligand (RANKL), and TNF-α were also evaluated. In vitro, the effect of azilsartan (0, 0.01, 0.1, 1, and 10 μM) on RANKL and TNF-α-triggered osteoclastogenesis were investigated. Also, whether azilsartan restrains LPS-triggered TNF-α mRNA and protein expression in macrophages and RANKL expression in osteoblasts were assessed. Furthermore, western blotting for analysis of mitogen-activated protein kinases (MAPKs) signaling was conducted.

Results

Azilsartan-treated calvariae exhibited significantly lower bone resorption and osteoclastogenesis than those treated with LPS alone. In vivo, LPS with azilsartan administration resulted in lower levels of receptor activator of RANKL and TNF-α mRNA expression than LPS administration alone. Nevertheless, azilsartan did not show inhibitory effect on RANKL- and TNF-α-triggered osteoclastogenesis in vitro. Compared to macrophages treated with LPS, TNF-α mRNA and protein levels were lower in macrophages treated by LPS with azilsartan. In contrast, RANKL mRNA and protein expression levels in osteoblasts were the same in cells co-treated with azilsartan and LPS and those exposed to LPS only. Furthermore, azilsartan suppressed LPS-triggered MAPKs signaling pathway in macrophages. After 5-day supracalvarial injection, there is no difference between TNF-α injection group and TNF-α with azilsartan injection group.

Conclusion

These findings imply that azilsartan prevents LPS-triggered TNF-α production in macrophages, which in turn prevents LPS-Triggered osteoclast formation and bone resorption in vivo.

Research Progress on the Pathogenesis of Knee Osteoarthritis

Knee osteoarthritis (KOA) is a chronic joint bone disease characterized by inflammatory destruction and hyperplasia of bone. Its main clinical symptoms are joint mobility difficulties and pain, severe cases can lead to limb paralysis, which poses major pressure to the quality of life and mental health of patients, but also brings serious economic burden to society. The occurrence and development of KOA is influenced by many factors, including systemic factors and local factors. The joint biomechanical changes caused by aging, trauma and obesity, abnormal bone metabolism caused by metabolic syndrome, the effects of cytokines and related enzymes, genetic and biochemical abnormalities caused by plasma adiponectin, etc. all directly or indirectly lead to the occurrence of KOA. However, there is little literature that systematically and comprehensively integrates macro- and microscopic KOA pathogenesis. Therefore, it is necessary to comprehensively and systematically summarize the pathogenesis of KOA in order to provide a better theoretical basis for clinical treatment.

Mechanical Performance, Microstructure, and Porosity Evolution of Fly Ash Geopolymer after Ten Years of Curing Age

This paper elucidates the mechanical performance, microstructure, and porosity evolution of fly ash geopolymer after 10 years of curing age. Given their wide range of applications, understanding the microstructure of geopolymers is critical for their long-term use. The outcome of fly ash geopolymer on mechanical performance and microstructural characteristics was compared between 28 days of curing (FA28D) and after 10 years of curing age (FA10Y) at similar mixing designs. The results of this work reveal that the FA10Y has a beneficial effect on strength development and denser microstructure compared to FA28D. The total porosity of FA10Y was also lower than FA28D due to the anorthite formation resulting in the compacted matrix. After 10 years of curing age, the 3D pore distribution showed a considerable decrease in the range of 5-30 µm with the formation of isolated and intergranular holes.

Influence of prazosin on systemic iron levels and the associated iron metabolic alterations in spontaneously hypertensive rats

The relationship between cardiovascular diseases and iron disorders has gained increasing attention; however, the effects of hypotensive drugs on iron metabolic alterations in hypertension are not well understood. The purpose of this study was to investigate iron metabolic changes after prazosin treatment of spontaneously hypertensive rats (SHRs) and Wistar–Kyoto (WKY) rats. Our second objective was to examine the effects of hypertension and anti‐hypertensive drugs on bone formation and resorption. SHRs and WKY rats were randomized into either prazosin‐treated groups (WKY + PZ and SHR + PZ) or untreated groups (WKY and SHR). After 7 days of intragastric prazosin administration, the rats were sacrificed for analysis; blood samples and organs (the duodenum, liver, kidneys, spleen, and femur) were collected. Both WKY + PZ and SHR groups exhibited iron deficiency in the serum and liver. Prazosin increased the iron levels in the bone tissue of SHRs. Prazosin stimulated the expression of hepcidin mRNA in the liver of SHRs and inhibited the expression of this iron‐regulatory hormone in WKY rats. FPN1 expression in the duodenum was increased significantly in SHRs, however markedly decreased after prazosin treatment. The expression of TLR4 and Ctsk was enhanced in the bone tissue of SHRs, whereas CLC‐7 expression was inhibited. Both hypotension and hypertension can lead to iron deficiency. Treatment with prazosin restored iron homeostasis in SHRs. The inverse impacts of prazosin on hepatic hepcidin expression in SHRs versus WKY rats indicates differing iron regulatory mechanisms between hypertensive and normal animals. The osteoclast activity was found to be enhanced in SHRs. Further study is needed to address whether the changes in osteoblast and osteoclast activity in SHRs correlates with the effects on iron metabolism.

Impact of Whole Body Vibration and Zoledronic Acid on Femoral Structure after Ovariectomy: Morphological Evaluation

Our study aimed to evaluate the effect of whole body vibration (WBV) treatment as an non-pharmacological method of treatment for early osteopenia in ovariectomized female rats. In total, 48 female Wistar rats were assigned to two groups: sham-operated control (SHAM, n = 12) and ovariectomized (n = 36). Four weeks after ovariectomy, the animals were divided into three experimental groups (n = 12 each): ovariectomized (OVX), ovariectomized subjected to whole body vibration with acceleration level of 0.3 g (OVX + WBV), or ovariectomized subjected to i.m. injection of Zoledronic acid at a dose of 0.025 mg/kg (OVX + ZOL). After the 8th and 16th week of treatment n = 6 rats from each group were euthanized and isolated femora were subjected to histological examination of trabecular bone and analysis of the expression of collagen 1 (Col1), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-Β ligand (RANKL) involved in bone turnover. The obtained results indicated that widespread vibration therapy can provide negative outcomes such as deterioration of trabecular bone histomorphometry.

Mild-intensity physical activity prevents cardiac and osseous iron deposition without affecting bone mechanical property or porosity in thalassemic mice

Thalassemia causes anemia, ineffective erythropoiesis, bone loss and iron accumulation in several tissues, e.g., liver, bone and heart, the last of which leads to lethal cardiomyopathy and arrhythmia. Although exercise reportedly improves bone density in thalassemic mice, exercise performance is compromised and might pose risk of cardiovascular accident in thalassemic patients. Therefore, we sought to explore whether mild-intensity physical activity (MPA) with 30–50% of maximal oxygen consumption was sufficient to benefit the heart and bone. Herein, male hemizygous β-globin knockout (BKO) mice and wild-type littermates were subjected to voluntary wheel running 1 h/day, 5 days/week for 3 months (MPA group) or kept sedentary (SDN; control). As determined by atomic absorption spectroscopy, BKO-MPA mice had less iron accumulation in heart and bone tissues compared with BKO-SDN mice. Meanwhile, the circulating level of fibroblast growth factor-23—a factor known to reduce serum iron and intestinal calcium absorption—was increased early in young BKO-MPA mice. Nevertheless, MPA did not affect duodenal calcium transport or body calcium retention. Although MPA restored the aberrant bone calcium-phosphorus ratio to normal range, it did not change vertebral calcium content or femoral mechanical properties. Microstructural porosity in tibia of BKO-MPA mice remained unaltered as determined by synchrotron radiation X-ray tomographic microscopy. In conclusion, MPA prevents cardiac and bone iron accumulation, which is beneficial to thalassemic patients with limited physical fitness or deteriorated cardiac performance. However, in contrast to moderate-intensity exercise, MPA does not improve bone mechanical properties or reduce bone porosity.

Salt-Sensitive Hypertension Induces Osteoclastogenesis and Bone Resorption via Upregulation of Angiotensin II Type 1 Receptor Expression in Osteoblasts

Hypertension is a chronic-low grade inflammatory disease, which is known to be associated with increased bone loss. Excessive activity of the local renin–angiotensin system (RAS) in bone leads to increased bone resorption. As inflammatory cytokines may activate RAS components, we hypothesized that the elevated proinflammatory cytokine levels in hypertension activate bone RAS and thus lead to increased bone resorption. To investigate whether salt-sensitive hypertension (SSHTN) induces osteoclastogenesis and bone resorption, we generated a model of SSHTN in C57BL/6J mice by post-N^ω-nitro-l-arginine methyl ester hydrochloride (l-NAME) high-salt challenge. SSHTN led to the reduction of distal femur trabecular number and bone volume fraction, while trabecular separation of femoral bone showed a significant increase, with no change in cortical thickness. Histomorphometric examination showed a significant reduction in trabecular bone volume fraction with an increased number of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive cells and increased osteoclast surface fraction in the trabecular distal femur of hypertensive mice. Furthermore, analysis of gene expression in bone tissue revealed that TRAP and RANKL/OPG mRNA were highly expressed in hypertensive mice. TNF-α and angiotensin II type 1 receptor (AGTR1) mRNA and protein expression were also upregulated in SSHTN mice. These observations suggested that TNF-α may have an effect on AGTR1 expression leading to osteoclast activation. However, TNF-α stimulation did not promote AGTR1 mRNA expression in osteoclast precursors in culture, while TNF-α increased AGTR1 mRNA expression in osteoblast culture by activation of downstream p38. Angiotensin II was also shown to increase TNF-α-induced RANKL/OPG mRNA expression in primary osteoblast culture and osteoclastogenesis in a TNF-α-primed osteoblast and osteoclast precursor co-culture system. In addition, local injection of lipopolysaccharide into the supracalvariae of SSHTN mice markedly promoted osteoclast and bone resorption. In conclusion, mice with SSHTN show increased osteoclastogenesis and bone resorption due mainly to increased TNF-α and partly to the upregulation of AGTR1 in osteoblasts.

Telmisartan impairs the in vitro osteogenic differentiation of mesenchymal stromal cells from spontaneously hypertensive male rats

Telmisartan (TELM) is an angiotensin II (Ang II) type 1 receptor (Agtr1) antagonist, with partial agonism for Pparg, and has been shown to affect bone metabolism. Therefore, the aim of this study was to investigate the effects of TELM in the in vitro osteogenic differentiation of bone marrow-derived mesenchymal stromal cells (BMSC) from spontaneously hypertensive rats (SHRs). BMSC were obtained from male SHR, and the osteogenic medium (OM) was added to the cells concomitantly with TELM (0.005, 0.05, and 0.5 μM). Undifferentiated BMSC, in control medium (CM), showed an increased viability, while the addition of OM reduced this parameter, and TELM did not show cytotoxicity in the concentrations used. BMSC in OM had an alkaline phosphatase (ALP) activity peak at d10, which decreased at d14 and d21, and TELM reduced ALP at d10 in a dose-dependent manner. Mineralization was observed in the OM at d14, which intensified at d21, but was inhibited by TELM. Agtr1b was increased in the OM, and TELM inhibited its expression. TELM reduced Opn, Ocn, and Bsp and increased Pparg expression, and at the higher concentration TELM also increased the expression of adipogenic markers, Fabp4 and Adipoq. In addition, TELM 0.5 μM increased Irs1 and Glut4, insulin and glucose metabolism markers, known to be regulated by Pparg and to be related to adipogenic phenotype. Our data shows that TELM inhibited the osteogenic differentiation and mineralization of SHR BMSC, by favoring an adipogenic prone phenotype due to Pparg upregulation.

β1-adrenergic receptor but not β2 mediates osteogenic differentiation of bone marrow mesenchymal stem cells in normotensive and hypertensive rats

The sympathetic nervous system regulates bone remodeling via adrenergic receptors on the surface of bone cells. Herein, we evaluated the role of beta-adrenergic receptors (ADRBs) in osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs) derived from normotensive (Wistar) and spontaneously hypertensive rats (SHRs). BMSCs were cultured in a proliferation medium or osteogenic medium (OM). Cells cultured in OM were treated with carvedilol (Cv) or nebivolol (Nb).In OM, cell proliferation was decreased in both strains. In Wistar rats, Cv increased BMSC proliferation and increased alkaline phosphatase (ALP) activity in OM. Both Cv and Nb decreased ALP activity. In addition, Cv and Nb reduced mineral deposition in Wistar rats. Moreover, NB decreased mineralization in SHRs, exhibiting superior efficacy. In OM, cells from Wistar rats and SHRs showed Adrb1 and Adrb2 expression. On day 7, Nb, but not Cv, reduced Adrb1 levels in BMSCs from Wistar rats. Nb inhibited Adrb2 in both strains, and Cv demonstrated superior efficacy. In BMSCs from Wistar rats, both antagonists inhibited Runx2, osterix, and β-catenin; in SHRs, Cv and Nb inhibited only osterix. Cv decreased osteopontin (Opn), osteocalcin (Ocn), and bone morphogenetic protein (Bmp2) in BMSCs from Wistar rats, inhibiting only Opn in SHRs. Nb effectively inhibited Ocn, bone sialoprotein, and Bmp2, but not Ocn, in BMSCs from Wistar rats, while suppressing Opn in BMSCs from SHRs. In addition, Nb inhibited p-p38 in BMSCs from Wistar rats; Cv inhibited p-p38 in BMSCs from SHRs. In Wistar rats, both antagonists inhibited p-ERK and reduced p-JNK; Cv reduced these expressions only in SHRs. In conclusion, ADRB1, but not ADRB2, could be involved in the osteogenic differentiation of BMSCs from Wistar rats and SHRs. The high ADRB1 expression might suppress the effect of ADRB2 on BMSCs.

Guanabenz inhibits alveolar bone resorption in a rat model of periodontitis

Increase of sympathetic activity has been known to exacerbate osteoporosis through promotion of bone resorption. However, it is largely unknown about involvement of sympathetic activity in exacerbation of periodontitis. In this study, we investigated whether α2-adrenergic receptor (α2-AR) agonist guanabenz which decreases sympathetic activity, attenuates alveolar bone resorption in rats having high sympathetic activity with periodontitis. Volumes of residual alveolar bone and attachment levels in periodontium were examined using micro-computed tomography and hematoxylin-eosin staining, respectively. Furthermore, osteoclast numbers per bone surface and osteoclast surface per bone surface were measured using tartrate-resistant acid phosphatase staining. To examine the suppressive effects of guanabenz on pro-inflammatory cytokines, expression levels of tyrosine hydroxylase (TH), TNF-α, IL1-β, and IL-6 in periodontium were measured using immunohistostaining. Administration of guanabenz attenuated loss of alveolar bone and attachment levels in rats having high sympathetic activity. Furthermore, its administration suppressed osteoclast numbers in rats having high sympathetic activity. TH, TNF-α, IL-1β, and IL-6 positive cells in periodontium in rats treated with guanabenz for 12 weeks, were lower than those in control rats having high sympathetic activity. This study demonstrated administration of α2-AR agonist guanabenz attenuates alveolar bone resorption through decrease of sympathetic activity in rats.

Hypertension meets osteoarthritis - revisiting the vascular aetiology hypothesis

Osteoarthritis (OA) is a whole-joint disease characterized by subchondral bone perfusion abnormalities and neovascular invasion into the synovium and articular cartilage. In addition to local vascular disturbance, mounting evidence suggests a pivotal role for systemic vascular pathology in the aetiology of OA. This Review outlines the current understanding of the close relationship between high blood pressure (hypertension) and OA at the crossroads of epidemiology and molecular biology. As one of the most common comorbidities in patients with OA, hypertension can disrupt joint homeostasis both biophysically and biochemically. High blood pressure can increase intraosseous pressure and cause hypoxia, which in turn triggers subchondral bone and osteochondral junction remodelling. Furthermore, systemic activation of the renin-angiotensin and endothelin systems can affect the Wnt-β-catenin signalling pathway locally to govern joint disease. The intimate relationship between hypertension and OA indicates that endothelium-targeted strategies, including re-purposed FDA-approved antihypertensive drugs, could be useful in the treatment of OA.

Ultrasound-assisted preparation of calcium malate and its absorption

In this experiment, response surface methodology was used to study the preparation of malic acid calcium salt from bovine bones assisted by ultrasonication. The results showed that the optimum conditions for ultrasound-assisted preparation of calcium malate from bovine bone were as follows: solid-liquid ratio 1:15, solid-acid ratio 1:1.5, ultrasonic power 200 W, ultrasonic temperature 35°C, and ultrasonication time 17 min. The efficiency of calcium recovery was 66.16%, and the purity was 92.54%. After three ultrasonic treatments of 17 min each, the calcium malate conversion rate of bovine bone reached 95.73%. Animal experiments showed that feeding bovine bone-derived calcium malate significantly increased alkaline phosphatase (ALP) activity and bone calcium content, reduced tartrate-resistant acid phosphatase (TRAP) activity, and maintained the balance of serum calcium and phosphorus. These results indicated that the ultrasonic method effectively ionized calcium in bovine bone, which provides a reference point for the industrial production of calcium products with bovine bone as the raw material.

Effect of zoledronic acid on bone nanocomposites organization and prevention of bone mineral density loss in ovariectomized rats

OBJECTIVES

Osteoporosis often occurs in individuals of different age groups, frequently during menopause and after ovariectomy. It increases the risk of pathological fractures almost twice. The aim of our research was to assess bone metabolism, nanocomposite structure of the tibia under conditions of ovariectomy and zoledronic acid treatment.

METHODS

X-ray diffraction has been performed for nanostructure analysis of mineral crystallites and crystal lattice of hydroxyapatite in the tibia samples of ovariectomized rats with additional application of bisphosphonate zoledronic acid (0.025 mg/kg). Markers of remodeling - osteocalcin, alkaline phosphatase, tartrate resistant acid phosphatase 5b - were determined. Quantitative amount of calcium in the bones was detected by atomic absorption method.

RESULTS

Zoledronic acid prevented loss of mineral mass after ovariectomy. Rats after ovariectomy, treated with zoledronic acid, showed statistically higher (р<0.05) values of crystalline phase and calcium content compared with the SHAM-surgery and ovariectomy groups (р<0.05). Zoledronic acid inhibited bone remodeling, which is proved by tartrate resistant acid phosphatase 5b reduction and inhibition of osteoclasts during the experiment.

CONCLUSIONS

These results enable to suggest that zoledronic acid can improve mineral mass of the bone during menopause in individuals of different age groups.

Mast cells contribute to alveolar bone loss in Spontaneously Hypertensive Rats with periodontal disease regulating cytokines production

Mast cells (MCs) play a pivotal role in inflammatory responses and had been studied in inflammatory bone disorders, however, their role in alveolar bone loss induced by periodontal disease (PD) is not yet fully understood. We, therefore, aimed to evaluate the effects of MCs depletion in the PD-induced alveolar bone loss in Wistar (W) and Spontaneously Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk thread one day after the MCs depletion, by the pre-treatment with compound 48/80 for 4 days. After 15 days of PD induction, the hemi-mandibles were surgically collected for qRT-PCR, histological analyses, immunostaining, and ELISA. Systolic blood pressure (SBP) was verified by tail plethysmography to confirm the hypertensive status, and SHR presented SBP >150 mmHg, and previous MC depletion alone or associated with PD did not alter this parameter. SHRs showed a more severe alveolar bone loss compared to W, and MC depletion significantly inhibited this response in both strains, with a more significant response in SHRs. MCs were less abundant in 48/80+PD groups, thus validating the previous MCs depletion in our model. PD increased the number of MC in the gingival tissue of SHR. Cytokine production (TNF-α, IL-6, IL-1β, and CXCL3) was constitutively higher in SHR and increased further after PD, which was also significantly reduced in the MCs-depleted animals. PD led to an increased expression of Opn, Rankl, Rank, Vtn, Itga5, Itgb5, Trap, and Ctsk in the mandible of W and SHRs, which was reversed in MCs-depleted animals. These results suggest that MCs significantly contributes to the PD-induced alveolar bone resorption, especially in the SHR, which is associated with a more severe PD progression compared to Wistar, partly explained by these cells contribution to the inflammatory status and mediator production, stimulating osteoclast-related response markers, which were reduced after MC depletion in our experimental model.

Excessive salt consumption causes systemic calcium mishandling and worsens microarchitecture and strength of long bones in rats

Excessive salt intake has been associated with the development of non-communicable diseases, including hypertension with several cardiovascular consequences. Although the detrimental effects of high salt on the skeleton have been reported, longitudinal assessment of calcium balance together with changes in bone microarchitecture and strength under salt loading has not been fully demonstrated. To address these unanswered issues, male Sprague-Dawley rats were fed normal salt diet (NSD; 0.8% NaCl) or high salt diet (HSD; 8% NaCl) for 5 months. Elevation of blood pressure, cardiac hypertrophy and glomerular deterioration were observed in HSD, thus validating the model. The balance studies were performed to monitor calcium input and output upon HSD challenge. The HSD-induced increase in calcium losses in urine and feces together with reduced fractional calcium absorption led to a decrease in calcium retention. With these calcium imbalances, we therefore examined microstructural changes of long bones of the hind limbs. Using the synchrotron radiation x-ray tomographic microscopy, we showed that trabecular structure of tibia and femur of HSD displayed a marked increase in porosity. Consistently, the volumetric micro-computed tomography also demonstrated a significant decrease in trabecular bone mineral density with expansion of endosteal perimeter in the tibia. Interestingly, bone histomorphometric analyses indicated that salt loading caused an increase in osteoclast number together with decreases in osteoblast number and osteoid volume. This uncoupling process of bone remodeling in HSD might underlie an accelerated bone loss and bone structural changes. In conclusion, long-term excessive salt consumption leads to impairment of skeletal mass and integrity possibly through negative calcium balance.

Telmisartan Prevents Alveolar Bone Loss by Decreasing the Expression of Osteoclasts Markers in Hypertensive Rats With Periodontal Disease

Periodontal disease (PD) is a prevalent inflammatory disease with the most severe consequence being the loss of the alveolar bone and teeth. We therefore aimed to evaluate the effects of telmisartan (TELM), an angiotensin II type 1 receptor (Agtr1) antagonist, on the PD-induced alveolar bone loss, in Wistar (W) and Spontaneous Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk, and 10 mg/kg TELM was concomitantly administered for 15 days. The hemimandibles were subjected to microtomography, ELISA was used for detecting tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), CXCL3, and CCL2, while qRT-PCR was used for analyzing expression of components of renin-angiotensin system (RAS) (Agt, Ace, Agt1r, Agt2r, Ace2, and Masr), and bone markers (Runx2, Osx, Catnb, Alp, Col1a1, Opn, Ocn, Bsp, Bmp2, Trap, Rank, Rankl, CtsK, Mmp-2, Mmp-9, and osteoclast-associated receptor (Oscar)). The SHR + PD group showed greater alveolar bone loss than the W + PD group, what was significantly inhibited by treatment with TELM, especially in the SHR group. Additionally, TELM reduced the production of TNF-α, IL-1β, and CXCL3 in the SHR group. The expression of Agt increased in the groups with PD, while Agtr2 reduced, and TELM reduced the expression of Agtr1 and increased the expression of Agtr2, in W and SHRs. PD did not induce major changes in the expression of bone formation markers, except for the expression of Alp, which decreased in the PD groups. The bone resorption markers expression, Mmp9, Ctsk, and Vtn, was higher in the SHR + PD group, compared to the respective control and W + PD group. However, TELM attenuated these changes and increased the expression of Runx2 and Alp. Our study suggested that TELM has a protective effect on the progression of PD, especially in hypertensive animals, as evaluated by the resorption of the lower alveolar bone. This can be partly explained by the modulation in the expression of Angiotensin II receptors (AT1R and AT2R), reduced production of inflammatory mediators, the reduced expression of resorption markers, and the increased expression of the bone formation markers.

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.