Role of vascular factors in osteoporosis

Disturbance in the potential cardiovascular-bone-skeletal muscle axis and morbidity and mortality in patients undergoing haemodialysis: the Q-Cohort Study

Background

Disturbances in the cardiovascular system, bone and skeletal muscle are independent risk factors for death among patients receiving haemodialysis (HD). However, the combined impact of disorders of these three organs on morbidity and mortality is unclear in the HD population.

Methods

A total of 3031 Japanese patients on maintenance HD were prospectively followed. The outcomes were all-cause mortality, major adverse cardiovascular events (MACE) and bone fracture. Patients were divided into four groups (G1-G4) according to the baseline number of diseased organs represented as histories of cardiovascular disease and bone fractures and the presence of low skeletal muscle mass as follows: G1, no organ; G2, one organ; G3, two organs; G4, three organs. Multivariable-adjusted survival models were used to analyse associations between the number of diseased organs and outcomes.

Results

During a 4-year follow-up, 499 deaths, 540 MACE and 140 bone fractures occurred. In the Cox proportional hazards model, the risk for all-cause mortality was significantly higher in G2, G3 and G4 than in G1 as the reference {hazard ratio: G2, 2.16 [95% confidence interval (CI) 1.65-2.84], G3, 3.10 [95% CI 2.27-4.23] and G4, 3.11 [95% CI 1.89-5.14]}. Similarly, the risks for developing MACE and bone fractures were significantly elevated as the number of organ disorders increased.

Conclusions

Multiple disorders of the cardiovascular-bone-skeletal muscle axis are strong predictors of morbidity and mortality in patients undergoing HD.

Changes in Blood Pressure is Associated with Bone Loss in US Adults: A Cross-Sectional Study from NHANES 2005-2018

Hypertension and osteoporosis are common geriatric diseases, sharing similar risk factors. This study aims to investigate this association and explore relatively mixed variables. Our study included 12,787 eligible participants from the National Health and Nutrition Examination Survey (NHANES) 2005-2018. Included participants had valid data on hypertension and osteoporosis, without tumors, liver diseases, gout or thyroid diseases. We explored the association between hypertension and osteoporosis by logistic regression and examined blood pressure and BMD/BMC by linear and non-linear regression. Moreover, we used machine learning models to predict the importance of various factors in the occurrence of osteoporosis and evaluated causality by mendelian randomization. Our study found that osteoporosis is significantly associated with hypertension [OR 2.072 (95% CI 2.067-2.077), p < 0.001]. After adjusting for co-variances, the association remained significant [OR 1.223 (95% CI 1.220-1.227), p < 0.001]. Our study showed that osteoporosis is positively associated with hypertension in the US population. A variety of factors influence this relationship. Specific regulatory mechanisms and confounding factors need to be further investigated.

Mechanisms of action and synergetic formulas of plant-based natural compounds from traditional Chinese medicine for managing osteoporosis: a literature review

Osteoporosis (OP) is a systemic skeletal disease prevalent in older adults, characterized by substantial bone loss and deterioration of microstructure, resulting in heightened bone fragility and risk of fracture. Traditional Chinese Medicine (TCM) herbs have been widely employed in OP treatment owing to their advantages, such as good tolerance, low toxicity, high efficiency, and minimal adverse reactions. Increasing evidence also reveals that many plant-based compounds (or secondary metabolites) from these TCM formulas, such as resveratrol, naringin, and ginsenoside, have demonstrated beneficial effects in reducing the risk of OP. Nonetheless, the comprehensive roles of these natural products in OP have not been thoroughly clarified, impeding the development of synergistic formulas for optimal OP treatment. In this review, we sum up the pathological mechanisms of OP based on evidence from basic and clinical research; emphasis is placed on the in vitro and preclinical in vivo evidence-based anti-OP mechanisms of TCM formulas and their chemically active plant constituents, especially their effects on imbalanced bone homeostasis regulated by osteoblasts (responsible for bone formation), osteoclasts (responsible for bone resorption), bone marrow mesenchymal stem cells as well as bone microstructure, angiogenesis, and immune system. Furthermore, we prospectively discuss the combinatory ingredients from natural products from these TCM formulas. Our goal is to improve comprehension of the pharmacological mechanisms of TCM formulas and their chemically active constituents, which could inform the development of new strategies for managing OP.

Pathophysiological Aspects of Muscle Atrophy and Osteopenia Induced by Chronic Constriction Injury (CCI) of the Sciatic Nerve in Rats

Skeletal muscle atrophy is a condition characterized by a loss of muscle mass and muscle strength caused by an imbalance between protein synthesis and protein degradation. Muscle atrophy is often associated with a loss of bone mass manifesting as osteoporosis. The aim of this study was to evaluate if chronic constriction injury (CCI) of the sciatic nerve in rats can be a valid model to study muscle atrophy and consequent osteoporosis. Body weight and body composition were assessed weekly. Magnetic resonance imaging (MRI) was performed on day zero before ligation and day 28 before sacrifice. Catabolic markers were assessed via Western blot and Quantitative Real-time PCR. After the sacrifice, a morphological analysis of the gastrocnemius muscle and Micro-Computed Tomography (Micro-CT) on the tibia bone were performed. Rats that underwent CCI had a lower body weight increase on day 28 compared to the naive group of rats (p < 0.001). Increases in lean body mass and fat mass were also significantly lower in the CCI group (p < 0.001). The weight of skeletal muscles was found to be significantly lower in the ipsilateral hindlimb compared to that of contralateral muscles; furthermore, the cross-sectional area of muscle fibers decreased significantly in the ipsilateral gastrocnemius. The CCI of the sciatic nerve induced a statistically significant increase in autophagic and UPS (Ubiquitin Proteasome System) markers and a statistically significant increase in Pax-7 (Paired Box-7) expression. Micro-CT showed a statistically significant decrease in the bone parameters of the ipsilateral tibial bone. Chronic nerve constriction appeared to be a valid model for inducing the condition of muscle atrophy, also causing changes in bone microstructure and leading to osteoporosis. Therefore, sciatic nerve constriction could be a valid approach to study muscle-bone crosstalk and to identify new strategies to prevent osteosarcopenia.

Research Progress of Macrophages in Bone Regeneration

Bone tissue regeneration plays an increasingly important role in contemporary clinical treatment. The reconstruction of bone defects remains a huge challenge for clinicians. Bone regeneration is regulated by the immune system, in which inflammation is an important regulating factor in bone formation and remodeling. As the main cells involved in inflammation, macrophages play a key role in osteogenesis by polarizing into different phenotypes during different stages of bone regeneration. Considering this, this review mainly summarizes the function of macrophage in bone regeneration based on mesenchymal stem cells (MSCs), osteoblasts, osteoclasts, and vascular cells. In conclusion, anti-inflammatory macrophages (M2) have a greater potentiality to promote bone regeneration than M0 and classically activated proinflammatory macrophages (M1). In the fracture and bone defect models, tissue engineering materials can induce the transition from M1 to M2, alter the bone microenvironment, and promote bone regeneration through interactions with bone-related cells and blood vessels. The review provides a further understanding of macrophage polarization behavior in the evolving field of bone immunology.

Degraded Bone Microarchitecture in Women with PHPT-Significant Predictor of Fracture Probability

Introduction

Patients with primary hyperparathyroidism (PHPT) experience bone mineral density (BMD) loss and trabecular bone score (TBS) alteration, which current guidelines recommend assessing. Considering TBS alongside BMD for a 10-year fracture risk assessment (FRAX) may improve PHPT management.

Design

Retrospective, cross-sectional study composed of 49 Caucasian females (62 ± 10.6 years, 27.7 ± 0.87 kg/m²) with PHPT and 132 matched control subjects (61.3 ± 10.5 years, 27.5 ± 0.49 kg/m²) evaluated in 3 years. We assessed lumbar spine (LS) and femoral neck (FN) BMD, T and Z scores (GE Healthcare Lunar Osteodensitometer) and TBS (iNsight 1.8), major osteoporotic fracture (MOF), and hip FRAX.

Results

Patients with PHPT had statistically lower mean values for lumbar spine bone mineral density (LS BMD) (0.95 ± 0.25 vs 1.01 ± 0.14 g/cm², P = .01), LS T-scores (-2 ± 0.2 vs -1.4 ± 0.1 SD, P = .009), LS Z scores (-0.9 ± 0.19 vs -0.1 ± 0.11 SD, P = .009), femoral neck bone mineral density (FN BMD) (0.79 ± 0.02 vs 0.83 ± 0.01 g/cm², P = .02), FN T-scores (-1.8 ± 0.13 vs -1.5 ± 0.07 SD, P = .017), FN Z scores (-0.51 ± 0.87 vs -0.1 ± 0.82 SD, P = .006), and TBS (0.95 ± 0.25 vs 1.01 ± 0.14 g/cm², P = .01) compared with control subjects. 22.4% of patients with PHPT had degraded microarchitecture (TBS < 1.2) vs. 7.6% in control group (χ² = 0.008). PHPT proved to be a covariate with unique contribution (P = .031) alongside LS BMD (P = .040) in a linear regression model [R ² = 0.532, F(4,16) = 4.543] for TBS < 1.2. TBS adjustment elevated MOF FRAX both for PHPT (4.35  ± 0.6% vs 5.25% ± 0.73%, P < .001) and control groups (4.5  ± 0.24% vs 4.7% ± 0.26%, P < .001) compared with BMD-bases FRAX, but also increased differently between the 2 study groups (1.1-folds for PHPT patients and 1.04 for control subjects, P = .034).

Conclusion

Compared with control, TBS-adjusted FRAX provides significantly higher MOF risk than BMD-based FRAX in PHPT women.

Significance of mechanical loading in bone fracture healing, bone regeneration, and vascularization

In 1892, J.L. Wolff proposed that bone could respond to mechanical and biophysical stimuli as a dynamic organ. This theory presents a unique opportunity for investigations on bone and its potential to aid in tissue repair. Routine activities such as exercise or machinery application can exert mechanical loads on bone. Previous research has demonstrated that mechanical loading can affect the differentiation and development of mesenchymal tissue. However, the extent to which mechanical stimulation can help repair or generate bone tissue and the related mechanisms remain unclear. Four key cell types in bone tissue, including osteoblasts, osteoclasts, bone lining cells, and osteocytes, play critical roles in responding to mechanical stimuli, while other cell lineages such as myocytes, platelets, fibroblasts, endothelial cells, and chondrocytes also exhibit mechanosensitivity. Mechanical loading can regulate the biological functions of bone tissue through the mechanosensor of bone cells intraosseously, making it a potential target for fracture healing and bone regeneration. This review aims to clarify these issues and explain bone remodeling, structure dynamics, and mechano-transduction processes in response to mechanical loading. Loading of different magnitudes, frequencies, and types, such as dynamic versus static loads, are analyzed to determine the effects of mechanical stimulation on bone tissue structure and cellular function. Finally, the importance of vascularization in nutrient supply for bone healing and regeneration was further discussed.

Substance P-Mediated Vascular Protection Ameliorates Bone Loss

Estrogen deficiency causes bone loss via diverse pathological cellular events. The involvement of the vasculature in bone formation has been widely studied, and type H vasculature has been found to be closely related to bone healing. Ovariectomy- (OVX-) induced estrogen deficiency reduces type H vessel density and promotes reduction of bone density. Analysis of early events after OVX showed that estrogen deficiency preferentially induces oxidative stress, which might provoke endothelial dysfunction and reduce angiogenic factors systemically and locally. The instability of the vascular potential is expected to promote bone loss under estrogen deficiency. Substance P (SP) is an endogenous neuropeptide that controls inflammation and prevents cell death under pathological conditions. SP can elevate nitric oxide production in endothelial cells and inhibit endothelial dysfunction. This study is aimed at investigating the preventive effects of systemically injected SP on OVX-induced vascular loss and osteoporosis onset. SP was systemically administered to OVX rats twice a week for 4 weeks, immediately after OVX induction. OVX conditions could decrease antioxidant enzyme activity, type H vessels, and angiogenic growth factors in the bone marrow, followed by inflammation and bone loss. However, pretreatment with SP could block type H vessel loss, accompanied by the enrichment of nitric oxide and sustained angiogenic factors. SP-mediated early vascular protection inhibits bone density reduction. Altogether, this study suggests that early administration of SP can block osteoporosis development by modulating oxidative stress and protecting the bone vasculature and angiogenic paracrine potential at the initial stage of estrogen deficiency.

Exosomes derived from magnesium ion-stimulated macrophages inhibit angiogenesis

Angiogenesis, an essential prerequisite to osteogenesis in bone repair and regeneration, can be mediated by immunoregulation of macrophages. Magnesium and its alloys are promising biodegradable bone implant materials and can affect immunoregulation of macrophages by the degradation products (magnesium ions. Nevertheless, the mechanism of macrophage-derived exosomes stimulated by Mg ions in immunoregulation is still not well understood. Herein, 10-50 mM magnesium ions are shown to inhibit the macrophage viability and proliferation in a dose-dependent manner, but a high concentration results in macrophage apoptosis. The exosomes secreted by macrophages from magnesium ion stimulation inhibit angiogenesis of endothelial cells, as manifested by the suppressed cell viability, proliferation, migration, and tube formation, which arise at least partially from exosome-mediated downregulation of endothelial nitric oxide and the vascular endothelial growth factor. The findings reported in this paper suggest that the bio-functionality of biodegradable magnesium alloys must be considered from the perspective of immunoregulation of macrophage-derived exosomes. Our results also suggest potential cancer therapy by inhibiting tumor-associated angiogenesis.

[18F] Sodium Fluoride PET Kinetic Parameters in Bone Imaging

This report describes the significance of the kinetic parameters (k-values) obtained from the analysis of dynamic positron emission tomography (PET) scans using the Hawkins model describing the pharmacokinetics of sodium fluoride ([¹⁸F]NaF) to understand bone physiology. Dynamic [¹⁸F]NaF PET scans may be useful as an imaging biomarker in early phase clinical trials of novel drugs in development by permitting early detection of treatment-response signals that may help avoid late-stage attrition.

Association between Osteoporosis and Previous Statin Use: A Nested Case-Control Study

The relationship between statin use and osteoporosis is controversial; therefore, this study aimed to investigate this association. The ≥40-year-old population of the Korean National Health Insurance Service Health Screening Cohort was enrolled. The 68,592 osteoporosis patients were matched 1:1 with control participants for age, sex, income, and region of residence using propensity score matching. The histories of statin use for two years before the diagnosis of osteoporosis (index date) in the osteoporosis and control groups were compared using conditional/unconditional logistic regression. An increased number of days of statin use was not associated with osteoporosis (adjusted OR (aOR) = 0.97, 95% confidence interval (95% CI) = 0.94–1.00, p = 0.052). In the subgroup analyses, a large number of days of statin use was related to a reduced rate of osteoporosis in the <60-year-old female group, while the opposite was true in the ≥60-year-old female group. Both lipophilic and hydrophilic statins were related to a decreased rate of osteoporosis in the <60-year-old female group. Lipophilic statins, but not hydrophilic statins, were associated with an increased rate of osteoporosis in the ≥60-year-old female group. Statin use showed different associations in middle-aged and elderly women.

Revealing Intraosseous Blood Flow in the Human Tibia With Ultrasound

Intraosseous blood circulation is thought to have a critical role in bone growth and remodeling, fracture healing, and bone disorders. However, it is rarely considered in clinical practice because of the absence of a suitable noninvasive in vivo measurement technique. In this work, we assessed blood perfusion in tibial cortical bone simultaneously with blood flow in the superficial femoral artery with ultrasound imaging in five healthy volunteers. After suppression of stationary signal with singular‐value‐decomposition, pulsatile blood flow in cortical bone tissue is revealed, following the heart rate measured in the femoral artery. Using a method combining transverse oscillations and phase‐based motion estimation, 2D vector flow was obtained in the cortex of the tibia. After spatial averaging over the cortex, the peak blood velocity along the long axis of the tibia was measured at four times larger than the peak blood velocity across the bone cortex. This suggests that blood flow in central (Haversian) canals is larger than in perforating (Volkmann's) canals, as expected from the intracortical vascular organization in humans. The peak blood velocity indicates a flow from the endosteum to the periosteum and from the heart to the foot for all subjects. Because aging and the development of bone disorders are thought to modify the direction and velocity of intracortical blood flow, their quantification is crucial. This work reports for the first time an in vivo quantification of the direction and velocity of blood flow in human cortical bone. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Palmul-Tang, a Korean Medicine, Promotes Bone Formation via BMP-2 Pathway in Osteoporosis

Osteoporosis is a common skeletal disease in post-menopausal women. Palmul-tang, an herbal medicine, has been treated for gynecological disease such as anemia, anorexia, anti-fatigue, unspecified menstruation and female infertility in East Asia. In this study, ameliorative effects of Palmul-tang soft extracts (PMT), a Korean Medicine, on osteoporosis were investigated. Ovariectomized (OVX) osteoporotic ICR mice were intragastrically administrated PMT for 4 weeks. The level of bone mineral density (BMD) was analyzed in bone tissues by dual X-ray absorptiometry. The bone medullary cavity and deposition of collagen were investigated by histological analysis. In addition, the BMP-2 signaling-related molecules, osteoblastic differentiation and formation markers, were determined in femoral tissues. The levels of BMD and bone mineral content were significantly increased in tibia, femurs and LV by treatment of PMT. PMT replenished bone marrow cavity and increased collagen deposition in bone marrow cells of femur. In addition, administration of PMT recovered serum ALP, bALP, osteocalcin and calcium levels in osteoporotic mice. Moreover, PMT treatment up-regulated the expressions of BMP-2, RUNX2 and OSX with its downstream factors, ALP, OPN and BSP-1, in the femoral tissues. Taken together, PMT restored the bone minerals and improvement of bone integrity by bone-forming BMP-2 signaling pathway. These results demonstrate that PMT could be an ameliorative agent for osteoporosis.

Blood Vessels and Vascular Niches in Bone Development and Physiological Remodeling

Recent advances in our understanding of blood vessels and vascular niches in bone convey their critical importance in regulating bone development and physiology. The contribution of blood vessels in bone functions and remodeling has recently gained enormous interest because of their therapeutic potential. The mammalian skeletal system performs multiple functions in the body to regulate growth, homeostasis and metabolism. Blood vessels provide support to various cell types in bone and maintain functional niches in the bone marrow microenvironment. Heterogeneity within blood vessels and niches indicate the importance of specialized vascular niches in regulating skeletal functions. In this review, we discuss physiology of bone vasculature and their specialized niches for hematopoietic stem cells and mesenchymal progenitor cells. We provide clinical and experimental information available on blood vessels during physiological bone remodeling.

Bone Microvasculature: Stimulus for Tissue Function and Regeneration

Bone is a highly vascularized organ, providing structural support to the body, and its development, regeneration, and remodeling depend on the microvascular homeostasis. Loss or impairment of vascular function can develop diseases, such as large bone defects, avascular necrosis, osteoporosis, osteoarthritis, and osteopetrosis. In this review, we summarize how vasculature controls bone development and homeostasis in normal and disease cases. A better understanding of this process will facilitate the development of novel disease treatments that promote bone regeneration and remodeling. Specifically, approaches based on tissue engineering components, such as stem cells and growth factors, have demonstrated the capacity to induce bone microvasculature regeneration and mineralization. This knowledge will have relevant clinical implications for the treatment of bone disorders by developing novel pharmaceutical approaches and bone grafts. Finally, the tissue engineering approaches incorporating vascular components may widely be applied to treat other organ diseases by enhancing their regeneration capacity. Impact statement Bone vasculature is imperative in the process of bone development, regeneration, and remodeling. Alterations or disruption of the bone vasculature leads to loss of bone homeostasis and the development of bone diseases. In this study, we review the role of vasculature on bone diseases and how vascular tissue engineering strategies, with a detailed emphasis on the role of stem cells and growth factors, will contribute to bone therapeutics.

Prospect of Stem Cell Therapy and Regenerative Medicine in Osteoporosis

The field of cell therapy and regenerative medicine can hold the promise of restoring normal tissues structure and function. Additionally, the main targets of stem cell-based therapies are chronic diseases and lifelong disabilities without definite cures such as osteoporosis. Osteoporosis as one of the important causes of morbidity in older men and post-menopausal women is characterized by reduced bone quantity or skeletal tissue atrophy that leads to an increased risk of osteoporotic fractures. The common therapeutic methods for osteoporosis only can prevent the loss of bone mass and recover the bone partially. Nevertheless, stem cell-based therapy is considered as a new approach to regenerate the bone tissue. Herein, mesenchymal stem cells as pivotal candidates for regenerative medicine purposes especially bone regeneration are the most common type of cells with anti-inflammatory, immune-privileged potential, and less ethical concerns than other types of stem cells which are investigated in osteoporosis. Based on several findings, the mesenchymal stem cells effectiveness near to a great extent depends on their secretory function. Indeed, they can be involved in the establishment of normal bone remodeling via initiation of specific molecular signaling pathways. Accordingly, the aim herein was to review the effects of stem cell-based therapies in osteoporosis.

LDL uptake-dependent phosphatidylethanolamine translocation to the cell surface promotes fusion of osteoclast-like cells

Osteoporosis is associated with vessel diseases attributed to hyperlipidemia, and bone resorption by multinucleated osteoclasts is related to lipid metabolism. In this study, we generated low-density lipoprotein receptor (LDLR)/lectin-like oxidized LDL receptor-1 (LOX-1, also known as Olr1) double knockout (dKO) mice. We found that, like LDLR single KO (sKO), LDLR/LOX-1 dKO impaired cell-cell fusion of osteoclast-like cells (OCLs). LDLR/LOX-1 dKO and LDLR sKO preosteoclasts exhibited decreased uptake of LDL. The cell surface cholesterol levels of both LDLR/LOX-1 dKO and LDLR sKO osteoclasts were lower than the levels of wild-type OCLs. Additionally, the amount of phosphatidylethanolamine (PE) on the cell surface was attenuated in LDLR/LOX-1 dKO and LDLR sKO preosteoclasts, whereas the PE distribution in wild-type OCLs was concentrated on the filopodia in contact with neighboring cells. Abrogation of the ATP binding cassette G1 (ABCG1) transporter, which transfers PE to the cell surface, caused decreased PE translocation to the cell surface and subsequent cell-cell fusion. The findings of this study indicate the involvement of a novel cascade (LDLR∼ABCG1∼PE translocation to cell surface∼cell-cell fusion) in multinucleation of OCLs.

The Effect of Exercise on the Prevention of Osteoporosis and Bone Angiogenesis

Physical activity or appropriate exercise prevents the development of osteoporosis. However, the exact mechanism remains unclear although it is well accepted that exercise or mechanical loading regulates the hormones, cytokines, signaling pathways, and noncoding RNAs in bone. Accumulating evidence has shown that bone is a highly vascularized tissue, and dysregulation of vasculature is associated with many bone diseases such as osteoporosis or osteoarthritis. In addition, exercise or mechanical loading regulates bone vascularization in bone microenvironment via the modulation of angiogenic mediators, which play a crucial role in maintaining skeletal health. This review discusses the effects of exercise and its underlying mechanisms for osteoporosis prevention, as well as an angiogenic and osteogenic coupling in response to exercise.

Should clinicians pay more attention to the potential underdiagnosis of osteoporosis in patients with ankylosing spondylitis? A national population-based study in Taiwan

OBJECTIVES

There are limited studies describing the association between ankylosing spondylitis (AS) and osteoporosis. We conducted a nationwide retrospective cohort study to investigate this epidemiologic evidence.

METHODS

Data were obtained from the Taiwan National Health Insurance Research Database (NHIRD). Of 10,290 participants, 2,058 patients with AS and 8,232 patients without AS were enrolled from the NHIRD between 2000 to 2013. Cumulative incidences of osteoporosis were compared between 2 groups. Cox regression model was used to estimate the hazard ratio (HR) of developing osteoporosis after controlling for demographic and other co-morbidities, and subgroup analyses were conducted to examine the risk factors for osteoporosis in AS patients.

RESULTS

The incidence rate ratio (IRR) of osteoporosis in AS patients was 2.17 times higher than that non-AS group (95% confidence interval [CI], 1.83-2.57). The adjusted HRs of osteoporosis for AS patients after controlling for demographic characteristics and comorbid medical disorders was 1.99 (95% CI 1.68-2.36). Among AS group, after adjustment for major comorbidities, old age (≥65 years, HR 4.32, 95% CI 3.01-6.18), female sex (HR 2.48, 95% CI 1.87-3.28), dyslipidemia (HR 1.44, 95% CI 1.01-2.06) were risk factors associated with osteoporosis.

CONCLUSIONS

This cohort study demonstrated that patients with AS had a higher risk of developing osteoporosis, especially in those aged over 65, female sex and with dyslipidemia in this patient group.

Study of Endothelio- and Osteoprotective Effects of Combination of Rosuvastatin with L-Norvaline in Experiment

The experiment was carried out on 120 female white Wistar rats, to study the endothelio- and osteoprotective action of the combination of rosuvastatin with L-norvaline in the model of experimental osteoporosis. It was found that, after ovariectomy in rats, endothelial dysfunction of the vessels of the microcirculatory bed of bone tissue develops, leading to the appearance of osteoporosis, but the combination of the studied drugs prevents the decrease in the level of microcirculation in the bone tissue, thereby preventing the thinning of bone trabeculae and preventing the occurrence of microfractures in them.

Engineering in-vitro stem cell-based vascularized bone models for drug screening and predictive toxicology

The production of veritable in-vitro models of bone tissue is essential to understand the biology of bone and its surrounding environment, to analyze the pathogenesis of bone diseases (e.g., osteoporosis, osteoarthritis, osteomyelitis, etc.), to develop effective therapeutic drug screening, and to test potential therapeutic strategies. Dysregulated interactions between vasculature and bone cells are often related to the aforementioned pathologies, underscoring the need for a bone model that contains engineered vasculature. Due to ethical restraints and limited prediction power of animal models, human stem cell-based tissue engineering has gained increasing relevance as a candidate approach to overcome the limitations of animals and to serve as preclinical models for drug testing. Since bone is a highly vascularized tissue, the concomitant development of vasculature and mineralized matrix requires a synergistic interaction between osteogenic and endothelial precursors. A number of experimental approaches have been used to achieve this goal, such as the combination of angiogenic factors and three-dimensional scaffolds, prevascularization strategies, and coculture systems. In this review, we present an overview of the current models and approaches to generate in-vitro stem cell-based vascularized bone, with emphasis on the main challenges of vasculature engineering. These challenges are related to the choice of biomaterials, scaffold fabrication techniques, and cells, as well as the type of culturing conditions required, and specifically the application of dynamic culture systems using bioreactors.

Is subchondral bone cyst formation in non-load-bearing region of osteoarthritic knee a vascular problem?

Subchondral bone cyst is common in the progressive knee osteoarthritis yet its underlying mechanism remains unclear. In addition to the existing theories such as synovial fluid influx and mechanical contusion, we identified the potential link between vascular pathology and osteoarthritic bone pathologies including cystic lesion formation, particularly in the non-load-bearing region. This new hypothesis for SBC formation in non-load-bearing region for knee, which cannot be explained by the existing theories, will provide us a new angle to understand the pathomechanism and pathophysiology of subchondral bone disturbance in osteoarthritis in addition to the classical biomechanical overloading theories. It might guide us to develop a novel diagnostic and therapeutic approach to treat progressive osteoarthritis via targeting vascular pathology.

Naringin inhibits vascular endothelial cell apoptosis via endoplasmic reticulum stress‑ and mitochondrial‑mediated pathways and promotes intraosseous angiogenesis in ovariectomized rats

In this study, to investigate the effects of naringin on vascular endothelial cell (VEC) function, proliferation, apoptosis, and angiogenesis, rat VECs were cultured in vitro and randomly divided into four groups: control, serum‑starved, low‑concentration naringin treatment, and high‑concentration naringin treatment. MTT assay was used to detect cell proliferation while Hoechst 33258 staining and flow cytometry were used to detect apoptosis. Changes in the expression of apoptosis‑associated proteins [GRP78, CHOP, caspase‑12, and cytochrome c (Cyt.c)] were detected using western blotting. JC‑1 staining was employed to detect changes in mitochondrial membrane potential. Intracellular caspase‑3, ‑8, and ‑9 activity was determined by spectrophotometry. ELISA was used to detect endothelin (ET), and a Griess assay was used to detect changes in the expression of nitric oxide (NO) in culture medium. The study further divided an ovariectomized (OVX) rat model of osteoporosis randomly into four groups: OVX, sham‑operated, low‑concentration naringin treatment (100 mg/kg), and high‑concentration naringin treatment (200 mg/kg). After 3 months of treatment, changes in serum ET and NO expression, bone mineral density (BMD), and microvessel density of the distal femur (using CD34 labeling of VECs) were determined. At each concentration, naringin promoted VEC proliferation in a time‑ and dose‑dependent manner. Naringin also significantly reduced serum starvation‑induced apoptosis in endothelial cells, inhibited the expression of GRP78, CHOP, caspase‑12, and Cyt.c proteins, and reduced mitochondrial membrane potential as well as reduced the activities of caspase‑3 and ‑9. Furthermore, naringin suppressed ET in vitro and in vivo while enhancing NO synthesis. Distal femoral microvascular density assessment showed that the naringin treatment groups had a significantly higher number of microvessels than the OVX group, and that microvascular density was positively correlated with BMD. In summary, naringin inhibits apoptosis in VECs by blocking the endoplasmic reticulum (ER) stress‑ and mitochondrial‑mediated pathways. Naringin also regulates endothelial cell function and promotes angiogenesis to exert its anti‑osteoporotic effect.

Adipokines: A Possible Contribution to Vascular and Bone Remodeling in Idiopathic Pulmonary Arterial Hypertension

Osteoporosis is a major comorbidity of cardio-respiratory diseases, but the mechanistic links between pulmonary arterial hypertension and bone remain elusive. The purpose of the stud was to evaluate serum adipokines and endothelin-1 (ET-1) levels in the patients with idiopathic pulmonary arterial hypertension (IPAH) NYHA class III-IV and to determine its associations with bone mineral density (BMD). Pulmonary and hemodynamic parameters, BMD Z-scores at the lumbar spine (LS) and femoral neck (FN), serum leptin, adiponectin, visfatin and endothelin-1 (ET-1), were evaluated in 32 patients with IPAH NYHA class III-IV and 30 healthy volunteers. Leptin, adiponectin and ET-1 were higher in the patients with IPAH than in healthy subjects. Visfatin level showed a tendency to increase compared to that of healthy subjects (p = 0.076). The univariate analysis revealed a positive correlation between BMD Z-scores at both sites and 6-min walk test, and inverse relation with pulmonary vascular resistance (PVR) and mean pulmonary arterial pressure (mPAP). Adiponectin and visfatin showed positive correlations with PVR (p = 0.009 and p = 0.006). Serum adiponectin, visfatin and leptin were inversely associated with Z-scores. After adjusting for BMI and FMI, such associations persisted between visfatin and adiponectin levels and Z-scores at both sites. ET-1 related to mPAP, cardiac index and PVR. Negative correlation was observed between ET-1 and FN BMD (p = 0.01). Positive correlations have revealed between ET-1 and adiponectin (p = 0.02), visfatin (p = 0.004) in IPAH patients. These results provide further evidence that adipokine and endothelial dysregulation may cause not only a decrease in BMD, but also an increase in hemodynamic disorders of IPAH.

Role of vascular remodeling markers in the development of osteoporosis in idiopathic pulmonary arterial hypertension

Aim. To define the role of circulating biomarkers for the metabolism of collagen and intercellular substance and vascular remodeling in the development of osteoporosis (OP) in idiopathic pulmonary arterial hypertension (IPAH). Materials and methods. Functional hemodynamic parameters, bone mineral density (BMD) in the lumbar spine and femoral neck and the serum levels of matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), MMP-9/TIMP-1 complex, C-terminal telopeptide of collagen type 1 (CITP), and endothelin-1 (ET-1) were determined in 27 high-risk IPAH patients and 30 healthy volunteers. Results. OP in IPAH was detected in 50% of the examinees. The serum levels of CITP, MMP-9, TIMP-1, and ET-1 proved to be higher in the high-risk IPAH patients than in the healthy volunteers. There was a direct correlation between BMD and six-minute walk test and an inverse correlation with total pulmonary vascular resistance (TPVR). Serum TMIP-1 levels correlated with cardiac index and TPVR; ET-1 concentrations were directly related to pulmonary artery systolic pressure, cardiac index, and TPVR. Inverse relationships were found between BMD and circulating CITP, MMP-9, TMIP-1, MMP-9/TMIP-1, and ET-1. At the same time, there was only a tendency towards a positive correlation between serum CITP and ET-1 concentrations. Conclusion. The results of the investigation confirm that endothelin system dysregulation plays a leading role in the development of persistent hemodynamic disorders in high-risk IPAH and suggest that it is involved in the development of osteopenic syndrome. Enhanced ET-1 secretion initiates bone loss possibly via activation of connective tissue matrix destruction.

Histological analysis of femoral bones in rabbits administered by amygdalin

Cyanogenic glycosides are present in several economically important plant foods. Amygdalin, one of the most common cyanoglucoside, can be found abundantly in the seeds of apples, bitter almonds, apricots, peaches, various beans, cereals, cassava and sorghum. Amygdalin has been used for the treatment of cancer, it shows killing effects on cancer cells by release of cyanide. However, its effect on bone structure has not been investigated to date. Therefore, the objective of this study was to determine a possible effect of amygdalin application on femoral bone microstructure in adult rabbits. Four month old rabbits were randomly divided into two groups of three animals each. Rabbits from E group received amygdalin intramuscularly at a dose 0.6 mg.kg-1 body weight (bw) (group E, n = 3) one time per day during 28 days. The second group of rabbits without amygdalin supplementation served as a control (group C, n = 3). After 28 days, histological structure of femoral bones in both groups of rabbits was analysed and compared. Rabbits from E group displayed different microstructure in middle part of the compact bone and near endosteal bone surface. For endosteal border, an absence of the primary vascular longitudinal bone tissue was typical. This part of the bone was formed by irregular Haversian and/or by dense Haversian bone tissues. In the middle part of substantia compacta, primary vascular longitudinal bone tissue was observed. Cortical bone thickness did not change between rabbits from E and C groups. However, rabbits from E group had a significantly lower values of primary osteons' vascular canals and secondary osteons as compared to the C group. On the other hand, all measured parameters of Haversian canals did not differ between rabbits from both groups. Our results demonstrate that intramuscular application of amygdalin at the dose used in our study affects femoral bone microstructure in rabbits.

Lectin-like oxidized low-density lipoprotein receptor-1 abrogation causes resistance to inflammatory bone destruction in mice, despite promoting osteoclastogenesis in the steady state

Inflammatory bone diseases have been attributed to increased bone resorption by augmented and activated bone-resorbing osteoclasts in response to inflammation. Although the production of diverse proinflammatory cytokines is induced at the inflamed sites, the inflammation also generates reactive oxygen species that modify many biological compounds, including lipids. Among the oxidized low-density lipoprotein (LDL) receptors, lectin-like oxidized LDL receptor-1 (LOX-1), which is a key molecule in the pathogenesis of multifactorial inflammatory atherosclerosis, was downregulated with osteoclast differentiation. Here, we demonstrate that LOX-1 negatively regulates osteoclast differentiation by basically suppressing the cell-cell fusion of preosteoclasts. The LOX-1-deleted (LOX-1(-/-)) mice consistently decreased the trabecular bone mass because of elevated bone resorption during the growing phase. In contrast, when the calvaria was inflamed by a local lipopolysaccharide-injection, the inflammation-induced bone destruction accompanied by the elevated expression of osteoclastogenesis-related genes was reduced by LOX-1 deficiency. Moreover, the expression of receptor activator of NF-κB ligand (RANKL), a trigger molecule for osteoclast differentiation, evoked by the inflammation was also abrogated in the LOX-1(-/-) mice. Osteoblasts, the major producers of RANKL, also expressed LOX-1 in response to proinflammatory agents, interleukin-1β and prostaglandin E2. In the co-culture of LOX-1(-/-) osteoblasts and wild-type osteoclast precursors, the osteoclastogenesis induced by interleukin-1β and prostaglandin E2 decreased; this process occurred in parallel with the downregulation of osteoblastic RANKL expression. Collectively, LOX-1 abrogation results in resistance to inflammatory bone destruction, despite promoting osteoclastogenesis in the steady state. Our findings indicate the novel involvement of LOX-1 in physiological bone homeostasis and inflammatory bone diseases.

Enhanced osteoclastogenesis by mitochondrial retrograde signaling through transcriptional activation of the cathepsin K gene

Mitochondrial dysfunction has emerged as an important factor in wide ranging human pathologies. We have previously defined a retrograde signaling pathway that originates from dysfunctional mitochondria (Mt-RS) and causes a global nuclear transcriptional reprograming as its end point. Mitochondrial dysfunction causing disruption of mitochondrial membrane potential and consequent increase in cytosolic calcium [Ca(2) ](c) activates calcineurin and the transcription factors NF-κB, NFAT, CREB, and C/EBPδ. In macrophages, this signaling complements receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastic differentiation. Here, we show that the Mt-RS activated transcriptional coactivator heterogeneous ribonucleoprotein A2 (hnRNP A2) is induced by hypoxia in murine macrophages. We demonstrate that the cathepsin K gene (Ctsk), one of the key genes upregulated during osteoclast differentiation, is transcriptionally activated by Mt-RS factors. HnRNP A2 acts as a coactivator with nuclear transcription factors, cRel, and C/EBPδ for Ctsk promoter activation under hypoxic conditions. Notably, our study shows that hypoxia-induced activation of the stress target factors mediates effects similar to that of RANKL with regard to Ctsk activation. We therefore suggest that mitochondrial dysfunction and activation of Mt-RS, induced by various pathophysiologic conditions, is a potential risk factor for osteoclastogenesis and bone loss.

Small vessel disease/white matter disease of the brain and its association with osteoporosis

BACKGROUND

Evidence now suggests the role of neural effect on bone mass control. The effect of small vessel disease of the brain on osteoporosis has not been studied. The aim of this study was to investigate the association of white matter disease (WMD) of the brain with osteoporosis in the elderly.

METHODS

In this retrospective cross-sectional study, 780 consecutive patient charts between 2010 and 2011 were reviewed in the Senior's Outpatient Clinic at the University of Alberta Hospital. Subjects with brain computerized tomography (CT) were included in the study. Subjects with incomplete information, intracranial hemorrhage, acute stroke, cerebral edema, and/or normal pressure hydrocephalus on the CT were excluded. WMD was quantified on CT using Wahlund's scoring protocol. Osteoporosis information was obtained from the chart, which has been diagnosed based on bone mineral density (BMD) information. Logistic regression analysis was done to determine the association of WMD severity with osteoporosis after controlling for confounding vascular risk factors.

RESULTS

Of the 505 subjects who were included in the study, 188 (37%) had osteoporosis and 171 (91%) of these osteoporotic subjects were females. The mean age was 79.8 ± 7.04 years. The prevalence of WMD in osteoporosis subjects was 73%. In the unadjusted logistic regression analysis, there was a significant association between WMD severity and osteoporosis (odds ratio (OR): 1.10; 95% confidence interval (CI): 1.05 - 1.14; P < 0.001) and the significance remained in the adjusted model, after correcting for age, sex and all vascular risk factors (OR: 1.11; 95% CI: 1.05 - 1.18; P < 0.001).

CONCLUSION

WMD severity of the brain was associated with osteoporosis in the elderly.

Ankle-brachial index and bone turnover in patients on dialysis

An association between atherosclerosis and osteoporosis has been reported in several studies. This association could result from local intraosseous atherosclerosis and ischemia, which is shown by limb osteoporosis in patients with peripheral artery disease (PAD), but also could result from bidirectional communication between the skeleton and blood vessels. Systemic bone disorders and PAD are frequent in ESRD. Here, we investigated the possible interaction of these disorders. For 65 prevalent nondiabetic patients on hemodialysis, we measured ankle-brachial pressure index (ABix) and evaluated mineral and bone disorders with bone histomorphometry. In prevalent patients on hemodialysis, PAD (ABix<0.9 or >1.4/incompressible) was associated with low bone turnover and pronounced osteoblast resistance to parathyroid hormone (PTH), which is indicated by decreased double-labeled surface and osteoblast surface (P<0.001). Higher osteoblast resistance to PTH in patients with PAD was characterized by weaker correlation coefficients (slopes) between serum PTH and double-labeled surface (P=0.02) or osteoblast surface (P=0.03). The correlations between osteoclast number or eroded surface and serum mineral parameters, including PTH, did not differ for subjects with normal ABix and PAD. Common vascular risk factors (dyslipidemia, smoking, and sex) were similar for normal, low, and incompressible ABix. Patients with PAD were older and had high C-reactive protein levels and longer hemodialysis vintage. These results indicate that, in prevalent nondiabetic patients with ESRD, PAD associates with low bone turnover and pronounced osteoblast resistance to PTH.

Antagonizing the αv β3 integrin inhibits angiogenesis and impairs woven but not lamellar bone formation induced by mechanical loading

Angiogenesis and osteogenesis are critically linked, although the role of angiogenesis is not well understood in osteogenic mechanical loading. In this study, either damaging or non-damaging cyclic axial compression was used to generate woven bone formation (WBF) or lamellar bone formation (LBF), respectively, at the mid-diaphysis of the adult rat forelimb. αv β3 integrin-targeted nanoparticles or vehicle was injected intravenously after mechanical loading. β3 integrin subunit expression on vasculature was maximal 7 days after damaging mechanical loading, but was still robustly expressed 14 days after loading. Accordingly, targeted nanoparticle delivery in WBF-loaded limbs was increased compared with non-loaded limbs. Vascularity was dramatically increased after WBF loading (+700% on day 14) and modestly increased after LBF loading (+50% on day 14). This increase in vascularity was inhibited by nanoparticle treatment in both WBF- and LBF-loaded limbs at days 7 and 14 after loading. Decreased vascularity led to diminished woven, but not lamellar, bone formation. Decreased woven bone formation resulted in impaired structural properties of the skeletal repair, particularly in post-yield behavior. These results demonstrate that αv β3 integrin-mediated angiogenesis is critical for recovering fracture resistance after bone injury but is not required for bone modeling after modest mechanical strain. © 2014 American Society for Bone and Mineral Research.

Skeletal Blood Flow in Bone Repair and Maintenance

Bone is a highly vascularized tissue, although this aspect of bone is often overlooked. In this article, the importance of blood flow in bone repair and regeneration will be reviewed. First, the skeletal vascular anatomy, with an emphasis on long bones, the distinct mechanisms for vascularizing bone tissue, and methods for remodeling existing vasculature are discussed. Next, techniques for quantifying bone blood flow are briefly summarized. Finally, the body of experimental work that demonstrates the role of bone blood flow in fracture healing, distraction osteogenesis, osteoporosis, disuse osteopenia, and bone grafting is examined. These results illustrate that adequate bone blood flow is an important clinical consideration, particularly during bone regeneration and in at-risk patient groups.

The Key Role of the Blood Supply to Bone

The importance of the vascular supply for bone is well-known to orthopaedists but is still rather overlooked within the wider field of skeletal research. Blood supplies oxygen, nutrients and regulatory factors to tissues, as well as removing metabolic waste products such as carbon dioxide and acid. Bone receives up to about 10% of cardiac output, and this blood supply permits a much higher degree of cellularity, remodelling and repair than is possible in cartilage, which is avascular. The blood supply to bone is delivered to the endosteal cavity by nutrient arteries, then flows through marrow sinusoids before exiting via numerous small vessels that ramify through the cortex. The marrow cavity affords a range of vascular niches that are thought to regulate the growth and differentiation of hematopoietic and stromal cells, in part via gradients of oxygen tension. The quality of vascular supply to bone tends to decline with age and may be compromised in common pathological settings, including diabetes, anaemias, chronic airway diseases and immobility, as well as by tumours. Reductions in vascular supply are associated with bone loss. This may be due in part to the direct effects of hypoxia, which blocks osteoblast function and bone formation but causes reciprocal increases in osteoclastogenesis and bone resorption. Common regulatory factors such as parathyroid hormone or nitrates, both of which are potent vasodilators, might exert their osteogenic effects on bone via the vasculature. These observations suggest that the bone vasculature will be a fruitful area for future research.

Osteogenesis and expression of the bone marrow niche in endothelial cell-depleted HipOPs

The identification and purification of murine multipotent mesenchymal stem cells (MSCs) have been difficult due to their low frequency, the presence of contaminating cell types and lack of unambiguous markers. Using a magnetic micro-beads negative selection technique to remove hematopoietic cells from mouse bone marrow stromal cells (BMSCs), our lab recently isolated a highly purified osteoprogenitor (HipOP) population that was also enriched for other mesenchymal precursors, including MSCs [Itoh and Aubin, 2009]. We now report that HipOPs are also highly enriched in vascular endothelial cells (VECs), which we hypothesized were an accessory cell type regulating osteogenesis. However, when VECs were immunodepleted from HipOPs with anti-CD31 antibodies, the resulting CD31(-) HipOP population had equal osteogenic capacity to the HipOPs in vitro and in vivo. Analysis of gene expression of Ncad, Pth1r, Ang1, Cxcl12, Jag1, Pdgfr-β, α-sma, Desmin, and Ng2 suggested that both HipOPs and CD31(-) HipOPs are hemopoietic stem cell (HSC) niche populations. However, the data support the view that osteoblast differentiation and depletion of VECs modulate the HSC niche.

Hyperbaric hyperoxia accelerates fracture healing in mice

Increased oxygen tension influences bone metabolism. This study comprised two main experiments: one aimed to determine the bone mineral apposition and bone formation rates in vivo under hyperbaric hyperoxia (HBO), and the other aimed to evaluate the effects of exposure to HBO on fracture healing. In experiment 1, male mice were exposed to HBO [90 min/day at 90% O₂ at 2 atmospheres absolute (ATA) for 5 days]. In experiment 2, an open femur fracture model was created in mice, followed by exposure to HBO 5 times/week (90 min/day at 90% O₂ at 2 ATA) for 6 weeks after surgery. In experiment 1, HBO treatment significantly increased the mineral apposition and bone formation rates in the lumbar vertebra and femur and type 1 collagen alpha 1 and alkaline phosphatase mRNA expression in the lumbar vertebra. In experiment 2, at 2 weeks after fracture, the fracture callus was significantly larger in the HBO group than in the non-HBO group. Furthermore, at 4 and 6 weeks after fracture, radiographic findings showed accelerated fracture healing in the HBO group. At 6 weeks after fracture, femur stiffness and maximum load were significantly higher in the HBO group than in the non-HBO group. Urinary 8-hydroxy-2′-deoxyguanosine and plasma calcium concentrations were not significantly different between groups. These results suggest that exposure to HBO enhances bone anabolism and accelerates fracture healing without causing oxidative DNA damage or disruption of plasma calcium homeostasis.

Quantifying diet for nutrigenomic studies

The field of nutrigenomics shows tremendous promise for improved understanding of the effects of dietary intake on health. The knowledge that metabolic pathways may be altered in individuals with genetic variants in the presence of certain dietary exposures offers great potential for personalized nutrition advice. However, although considerable resources have gone into improving technology for measurement of the genome and biological systems, dietary intake assessment remains inadequate. Each of the methods currently used has limitations that may be exaggerated in the context of gene × nutrient interaction in large multiethnic studies. Because of the specificity of most gene × nutrient interactions, valid data are needed for nutrient intakes at the individual level. Most statistical adjustment efforts are designed to improve estimates of nutrient intake distributions in populations and are unlikely to solve this problem. An improved method of direct measurement of individual usual dietary intake that is unbiased across populations is urgently needed.

Cardiovascular and noncardiovascular disease associations with hip fractures

BACKGROUND

There is growing awareness of an association between cardiovascular disease and fractures, and a temporal increase in fracture risk after myocardial infarction has been identified. To further explore the nature of this relationship, we systematically examined the association of hip fracture with all disease categories and assessed related secular trends.

METHODS

By using resources of the Rochester Epidemiology Project, a population-based incident case-control study was conducted. Disease history was compared among all Olmsted County, Minnesota, residents aged 50 years or more with a first radiographically confirmed hip fracture in 1985-2006 and community control subjects individually matched (1:1) to cases on age, sex, and index year (n = 3808; mean age, 82 years; standard deviation, 9 years; 76% were women).

RESULTS

All cardiovascular and numerous non-cardiovascular disease categories (eg, infectious diseases, nutritional and metabolic diseases, mental disorders, diseases of the nervous system and sense organs, and diseases of the respiratory system) were associated with fracture risk. However, increasing temporal trends were detected almost exclusively in cardiovascular disease categories. The largest increases in association were observed for ischemic heart disease, other forms of heart disease (including heart failure), hypertension, and diabetes, and were more pronounced among elderly women than other demographic subgroups.

CONCLUSIONS

Although the association with hip fracture was not specific to cardiovascular disease, temporal increases were mainly detected in cardiometabolic diseases, all of which have been linked previously to frailty. This mechanism and others warrant further investigation.

Comparative evaluation of enalapril and losartan in pharmacological correction of experimental osteoporosis and fractures of its background

In the experiment on the white Wistar female rats (222 animals), the osteoprotective effect of enalapril and losartan was studied on experimental models of osteoporosis and osteoporotic fractures. It was revealed that in rats after ovariectomy, the endothelial dysfunction of microcirculation vessels of osteal tissue develops, resulting in occurrence of osteoporosis and delay of consolidation of experimental fractures. Enalapril and losartan prevented the reduction of microcirculation in bone, which was reflected in slowing the thinning of bone trabeculae and in preventing the occurrence of these microfractures, as well as increasing quality of experimental fractures healing.

Bone vascularization in normal and disease conditions

Bone vasculature is essential for many processes, such as skeletal development and growth, bone modeling and remodeling, and healing processes. Endothelium is an integral part of bone tissue, expressing a physiological paracrine function via growth factors and chemokines release, and interacting with several cellular lines. Alterations of the complex biochemical interactions between vasculature and bone cells may lead to various clinical manifestations. Two different types of pathologies result: a defect or an excess of bone vasculature or endothelium metabolism. Starting from the molecular basis of the interactions between endothelial and bone cells, the Authors present an overview of the recent acquisitions in the physiopathology of the most important clinical patterns, and the modern therapeutic strategies for their treatments.

Oral microcirculation in post-menopause: a possible correlation with periodontitis

OBJECTIVES

The reduction in the level of oestrogen, typical in menopause, has some effect on the health of the oral cavity. In fact, post-menopausal women present more severe periodontal disease than pre-menopausal women. Numerous factors can be held to be responsible for this increase, among which are the effects of oestrogens on the oral epithelium, on the salivary glands, on bone tissue and on the endothelium. Our double blind study aims to evaluate the possible variations in oral microcirculation in post-menopausal women.

METHODS

Twenty-seven women in post-menopause (age: Mean ± SD: 57.3 ± 8.73) and 27 women in pre-menopause (age: Mean ± SD: 27.77 ± 3.56) were examined. Oral microcirculation was investigated using oral videocapillaroscopy.

RESULTS

The study showed significant differences between cases and controls for the following parameters: decrease in diameter of loops (mean ± SD: 0.038 ± 0.008; 0.045 ± 0.005), increase in tortuosity (mean ± SD: 3.83 ± 1.13; 1.83 ± 1.06) in labial mucosa and decrease in density in periodontal mucosa (Mean ± SD: 28.86 ± 10.92; 89.62 ± 17.83).

CONCLUSION

The decrease in periodontal density may compromise the epithelium tropism, making it prone to inflammation. The tortuosity may indicate a greater permanence of inflammatory factors, increased in post-menopausal women.

Hypoxia inhibits osteogenesis in human mesenchymal stem cells through direct regulation of RUNX2 by TWIST

Background

Bone loss induced by hypoxia is associated with various pathophysiological conditions, however, little is known about the effects of hypoxia and related signaling pathways on osteoblast differentiation and bone formation. Because bone marrow-derived mesenchymal stem cells (MSCs) survive under hypoxic conditions and readily differentiate into osteoblasts by standard induction protocols, they are a good in vitro model to study the effects of hypoxia on osteoblast differentiation.

Methodology/Principle Findings

Using human MSCs, we discovered TWIST, a downstream target of HIF-1α, was induced under hypoxia and acted as a transcription repressor of RUNX2 through binding to the E-box located on the promoter of type 1 RUNX2. Suppression of type 1 RUNX2 by TWIST under hypoxia further inhibited the expression of BMP2, type 2 RUNX2 and downstream targets of RUNX2 in MSCs.

Conclusions/Significance

Our findings point to the important role of hypoxia-mediated signalling in osteogenic differentiation in MSCs through direct regulation of RUNX2 by TWIST, and provide a method for modifying MSC osteogenesis upon application of these cells in fracture healing and bone reconstruction.

Association between myocardial infarction and fractures: an emerging phenomenon

BACKGROUND

Data on the association between myocardial infarction (MI) and fractures are scarce. Recent changes in the epidemiology of MI justify exploring this relationship. We evaluated whether MI constitutes a risk factor for osteoporotic fracture and examined secular trends in this association.

METHODS AND RESULTS

Consecutive Olmsted County, Minnesota, residents with incident MI diagnosed in 1979 to 2006 and community control subjects individually matched (1:1) to cases on age, sex, and year of onset (n=6642) were followed up through 2009. Outcome measures were time to osteoporotic fracture, overall and by anatomic site, and death. Fracture incidence rates were stable in controls but increased markedly over time among MI cases. Accordingly, although an overall excess of fracture risk after MI was observed (adjusted hazard ratio, 1.32; 95% confidence interval, 1.12 to 1.56), substantial temporal variations were noted (1979 to 1989: hazard ratio, 0.81; 95% confidence interval, 0.58 to 1.12; 1990 to 1999: hazard ratio, 1.47; 95% confidence interval, 1.10 to 1.96; 2000 to 2006: hazard ratio, 1.73; 95% confidence interval, 1.32 to 2.27; P for trend <0.001). Trends were similar regardless of age, sex or fracture site. Conversely, the overall hazard ratio for death in MI cases versus controls did not change materially despite a continuous decline in 30-day case fatality rate (12.5% in 1979 to 1989; 6.7% in 2000 to 2006). Observed changes in the baseline prevalence of cardiovascular risk factors, MI characteristics, and comorbidities did not fully account for the trends in fracture risk.

CONCLUSIONS

Over the past decades, the association between MI and osteoporotic fractures increased steadily. The trend is consistent with the displacement of post-MI outcomes toward noncardiovascular events, highlighting the need for comprehensive prevention strategies to accommodate the changing epidemiology of MI.

Osteoporotic fractures and heart failure in the community

PURPOSE

Recent findings suggest a role for heart failure in the etiology of osteoporotic fractures, yet the temporal sequence of occurrence of the 2 conditions needs clarification.

METHODS

Using the Rochester Epidemiology Project, the authors conducted a 2-phase study: a case-control study compared osteoporotic fracture history among Olmsted County, Minnesota, residents newly diagnosed with heart failure in 1979-2002 with age- and sex-matched community controls without heart failure (961 pairs; mean age 76 years; 54% women). Both groups were then followed to July 2009 to evaluate their subsequent fracture risk in a cohort study.

RESULTS

Prior fractures were more frequent in heart failure cases than controls (23.1% vs. 18.8%, P=.02). The adjusted odds ratio (OR) for heart failure associated with prior fracture was 1.39 (95% confidence interval [CI], 1.07-1.81), mainly driven by hip fractures (OR 1.82; 95% CI, 1.25-2.66) with little or no association with other fractures. Over a mean follow-up of 7.5 years, 444 individuals developed subsequent osteoporotic fractures. The adjusted fracture risk was marginally elevated in heart failure patients compared with controls (hazard ratio [HR] 1.32; 95% CI, 0.98-1.79), again largely attributable to hip fractures (HR 1.58; 95% CI, 1.03-2.41).

CONCLUSIONS

In this community, the association with fracture risk was about as strong before as after the diagnosis of heart failure and was nearly entirely attributable to hip fractures. Additional work is needed to identify common underlying mechanisms for heart failure and hip fracture, which may define prevention opportunities.

Prediction of bone loss in elderly female subjects by MR perfusion imaging and spectroscopy

OBJECTIVE

To determine whether MR perfusion indices or marrow fat content at baseline can predict areal bone mineral density (BMDa) loss.

METHODS

Repeat dual x-ray absorptiometry (DXA) of the hip was performed in female subjects at 2 years (n = 52) and 4 years (n = 45) following baseline MR perfusion imaging and spectroscopy of the hip.

RESULTS

Percentage reduction in femoral neck BMDa at 4 years post-baseline was greater in subjects with below median acetabulum enhancement slope (E(slope)) (-5.6 ± 1.2 Vs -1.1 ± 1.2 (mean ± standard error) p = 0.014) or muscle maximum enhancement (E(max)) (-5.7 ± 1.2 Vs -0.23 ± 1.2, p = 0.009) after adjusting for baseline co-variables. Baseline MR parameters correlated with reduction in BMDa at 4 years (acetabulum E(slope) r = 0.517, p = 0.0003; muscle E(max) r = 0.306, p = 0.043) as well as traditionally applied clinical risk factors. Acetabulum E(slope), femoral neck E(max) and marrow fat content at baseline had sensitivities of 89%, 81% and 72% respectively at distinguishing between fast (>1%/annum) (n = 18) and slow (<1%/annum) (n = 27) BMD losers.

CONCLUSION

Elderly female subjects with reduced perfusion indices at baseline had increased femoral neck bone loss at 4 years. Selected perfusion indices and marrow fat content have a moderate to high sensitivity in discriminating between fast and slow bone losers.

Evaluation of MR spectroscopy and diffusion-weighted MRI in detecting bone marrow changes in postmenopausal women with osteoporosis

AIM

To prospectively investigate the role of MR spectroscopy (MRS) and diffusion-weighted magnetic resonance imaging (DWI) in assessing vertebral marrow changes in postmenopausal women with osteoporosis.

MATERIALS AND METHODS

Seventy-eight postmenopausal women (mean age 63.7+/-3.5 years; range 55-81 years), who underwent dual-energy x-ray absorptiometry of the spine, were divided into three bone density groups (24 with normal, 25 with osteopaenic, and 29 with osteoporotic) based on T score. Both MRS and DWI of the L3 vertebral body were performed to calculate the marrow fat content and apparent diffusion coefficient (ADC). The results were compared between three groups and correlated with BMD.

RESULTS

Vertebral marrow fat content was significantly increased in the osteoporotic group (59.97+/-5.78%), when compared with that of the osteopaenic group (53.04+/-7.66%, p=0.001) and the normal bone density group (48.79+/-7.1%, p<0.001). ADC values in the osteoporotic, osteopaenic, and normal bone density groups were 0.39+/-0.02x10(-3)mm(2)/s, 0.41+/-0.02x10(-3)mm(2)/s, and 0.47+/-0.03x10(-3)mm(2)/s, respectively, with statistically significant difference (P<0.001). A statistically significant positive correlation between T scores and ADC existed (r=0.835, p<0.001). The vertebral marrow fat content was negatively correlated to the bone density (r=-0.639, p<0.001) and to marrow ADC (r=-0.554, p<0.001).

CONCLUSION

The postmenopausal women with osteoporosis exhibited a corresponding increase in vertebral marrow fat content as the bone density decreased. Marrow fat content and ADC were related to the bone density. MRS and DWI are helpful in evaluating the bone marrow changes in postmenopausal women.