Understanding the mechanisms of senile osteoporosis: new facts for a major geriatric syndrome

Unraveling the molecular and immunological landscape: Exploring signaling pathways in osteoporosis

Osteoporosis, characterized by compromised bone density and microarchitecture, represents a significant global health challenge, particularly in aging populations. This comprehensive review delves into the intricate signaling pathways implicated in the pathogenesis of osteoporosis, providing valuable insights into the pivotal role of signal transduction in maintaining bone homeostasis. The exploration encompasses cellular signaling pathways such as Wnt, Notch, JAK/STAT, NF-κB, and TGF-β, all of which play crucial roles in bone remodeling. The dysregulation of these pathways is a contributing factor to osteoporosis, necessitating a profound understanding of their complexities to unveil the molecular mechanisms underlying bone loss. The review highlights the pathological significance of disrupted signaling in osteoporosis, emphasizing how these deviations impact the functionality of osteoblasts and osteoclasts, ultimately resulting in heightened bone resorption and compromised bone formation. A nuanced analysis of the intricate crosstalk between these pathways is provided to underscore their relevance in the pathophysiology of osteoporosis. Furthermore, the study addresses some of the most crucial long non-coding RNAs (lncRNAs) associated with osteoporosis, adding an additional layer of academic depth to the exploration of immune system involvement in various types of osteoporosis. Finally, we propose that SKP1 can serve as a potential biomarker in osteoporosis.

Bone turnover and mineralisation kinetics control trabecular BMDD and apparent bone density: insights from a discrete statistical bone remodelling model

The mechanical quality of trabecular bone is influenced by its mineral content and spatial distribution, which is controlled by bone remodelling and mineralisation. Mineralisation kinetics occur in two phases: a fast primary mineralisation and a secondary mineralisation that can last from several months to years. Variations in bone turnover and mineralisation kinetics can be observed in the bone mineral density distribution (BMDD). Here, we propose a statistical spatio-temporal bone remodelling model to study the effects of bone turnover (associated with the activation frequency Ac . f ) and mineralisation kinetics (associated with secondary mineralisation T sec ) on BMDD. In this model, individual basic multicellular units (BMUs) are activated discretely on trabecular surfaces that undergo typical bone remodelling periods. Our results highlight that trabecular BMDD is strongly regulated by Ac . f and T sec in a coupled way. Ca wt% increases with lower Ac . f and short T sec . For example, aAc . f = 4 BMU/year/mm3 and T sec = 8 years result in a mean Ca wt% of 25, which is in accordance with Ca wt% values reported in quantitative backscattered electron imaging (qBEI) experiments. However, for lower Ac . f and shorter T sec (from 0.5 to 4 years) one obtains a high Ca wt% and a very narrow skew BMDD to the right. This close link between Ac . f and T sec highlights the importance of considering both characteristics to draw meaningful conclusion about bone quality. Overall, this model represents a new approach to modelling healthy and diseased bone and can aid in developing deeper insights into disease states like osteoporosis.

M2 macrophages secrete glutamate-containing extracellular vesicles to alleviate osteoporosis by reshaping osteoclast precursor fate

Osteoclast precursors (OCPs) are thought to commit to osteoclast differentiation, which is accelerated by aging-related chronic inflammation, thereby leading to osteoporosis. However, whether the fate of OCPs can be reshaped to transition into other cell lineages is unknown. Here, we showed that M2 macrophage-derived extracellular vesicles (M2-EVs) could reprogram OCPs to downregulate osteoclast-specific gene expression and convert OCPs to M2 macrophage-like lineage cells, which reshaped the fate of OCPs by delivering the molecular metabolite glutamate. Upon delivery of glutamate, glutamine metabolism in OCPs was markedly enhanced, resulting in the increased production of α-ketoglutarate (αKG), which participates in Jmjd3-dependent epigenetic reprogramming, causing M2-like macrophage differentiation. Thus, we revealed a novel transformation of OCPs into M2-like macrophages via M2-EVs-initiated metabolic reprogramming and epigenetic modification. Our findings suggest that M2-EVs can reestablish the balance between osteoclasts and M2 macrophages, alleviate the symptoms of bone loss, and constitute a new approach for bone-targeted therapy to treat osteoporosis.

Understanding the characteristics of idiopathic osteoporosis by a systematic review and meta-analysis

PURPOSE

To understand the pathophysiology of idiopathic osteoporosis (IOP) better, we conducted a systematic review and meta-analysis of bone mineral density (BMD), hormones, and bone turnover markers (BTMs) between IOP patients and healthy controls.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, an appropriate search query was created, and three databases, including PubMed, ScienceDirect, and Google Scholar, were searched for screening relevant original articles. Feasible information, both qualitative and quantitative, was extracted and used to conduct meta-analyses. Publication bias and heterogeneity among studies were evaluated using appropriate statistical tools.

RESULTS

A total of 21 studies were included in the meta-analysis. There was reduced BMD at the lumbar spine (LS) (pooled: SDM: -2.38, p-value: 0.0001), femoral neck (FN) (pooled: SDM: -1.75 p-value: 0.0001), total hip (TH) (pooled: SDM: -1.825, p-value: 0.0001) and distal radius (DR) (pooled: SDM of -0.476, p-value: 0.0001), of which LS was the most affected site. There was no significant change in BTMs compared with healthy controls. Total estradiol (SDM: -1.357, p-value: 0.003) was reduced, and parathyroid hormone (PTH) (SDM: 1.51, p-value: 0.03) and sex hormone-binding globulin (SHBG) (SDM: 1.454, p-value: 0.0001) were elevated in IOP patients compared with healthy controls.

CONCLUSION

Our meta-analysis, the first of its kind on IOP, defines it as showing BMD decline maximally at LS compared with healthy controls without any alterations in the BTMs. Further studies are required to understand gender differences and the significance of altered hormonal profiles in this condition.

Type H vessels in osteogenesis, homeostasis, and related disorders

The vascular system plays a crucial role in bone tissue. Angiogenic and osteogenic processes are coupled through a spatial-temporal connection. Recent studies have identified three types of capillaries in the skeletal system. Compared with type L and E vessels, type H vessels express high levels of CD31 and endomucin, and function to couple angiogenesis and osteogenesis. Endothelial cells in type H vessels interact with osteolineage cells (e.g., osteoblasts, osteoclasts, and osteocytes) through cytokines or signaling pathways to maintain bone growth and homeostasis. In imbalanced bone homeostases, such as osteoporosis and osteoarthritis, it may be a new therapeutic strategy to regulate the endothelial cell activity in type H vessels to repair the imbalance. Here, we reviewed the latest progress in relevant factors or signaling pathways in coupling angiogenesis and osteogenesis. This review would contribute to further understanding the role and mechanisms of type H vessels in coupling angiogenic and osteogenic processes. Furthermore, it will facilitate the development of therapeutic approaches for bone disorders by targeting type H vessels.

Long-term human spaceflight and inflammaging: Does it promote aging?

Spaceflight and its associated stressors, such as microgravity, radiation exposure, confinement, circadian derailment and disruptive workloads represent an unprecedented type of exposome that is entirely novel from an evolutionary stand point. Within this perspective, we aimed to review the effects of prolonged spaceflight on immune-neuroendocrine systems, brain and brain-gut axis, cardiovascular system and musculoskeletal apparatus, highlighting in particular the similarities with an accelerated aging process. In particular, spaceflight-induced muscle atrophy/sarcopenia and bone loss, vascular and metabolic changes, hyper and hypo reaction of innate and adaptive immune system appear to be modifications shared with the aging process. Most of these modifications are mediated by molecular events that include oxidative and mitochondrial stress, autophagy, DNA damage repair and telomere length alteration, among others, which directly or indirectly converge on the activation of an inflammatory response. According to the inflammaging theory of aging, such an inflammatory response could be a driver of an acceleration of the normal, physiological rate of aging and it is likely that all the systemic modifications in turn lead to an increase of inflammaging in a sort of vicious cycle. The most updated countermeasures to fight these modifications will be also discussed in the light of their possible application not only for astronauts' benefit, but also for older adults on the ground.

Augmentation in fragility fractures, bone of contention: a systematic review

BACKGROUND

Osteoporosis is a complex multifactorial disease characterized by reduced bone mass and microarchitectural deterioration of bone tissue linked to an increase of fracture risk. Fragility fractures occur in osteoporotic subjects due to low-energy trauma. Osteoporotic patients are a challenge regarding the correct surgical planning, as it can include fixation augmentation techniques to reach a more stable anchorage of the implant, possibly lowering re-intervention rate and in-hospital stay.

METHODS

The PubMed database and the Google Scholar search engine were used to identify articles on all augmentation techniques and their association with fragility fractures until January 2022. In total, we selected 40 articles that included studies focusing on humerus, hip, spine, and tibia.

RESULTS

Literature review showed a quantity of materials that can be used for reconstruction of bone defects in fragility fractures in different anatomic locations, with good results over the stability and strength of the implant anchorage, when compared to non-augmented fractures.

CONCLUSION

Nowadays there are no recommendations and no consensus about the use of augmentation techniques in osteoporotic fractures. Our literature review points at implementing the use of bone augmentation techniques with a specific indication for elderly patients with comminuted fractures and poor bone quality.

Glucosamine delays the progression of osteoporosis in senile mice by promoting osteoblast autophagy

Background

Senile osteoporosis (SOP) is one of the most prevalent diseases that afflict the elderly population, which characterized by decreased osteogenic ability. Glucosamine (GlcN) is an over-the-counter dietary supplement. Our previous study reported that GlcN promotes osteoblast proliferation by activating autophagy in vitro. The purpose of this study is to determine the effects and mechanisms of GlcN on senile osteoporosis and osteogenic differentiation in vivo.

Methods

Aging was induced by subcutaneous injection of d-Galactose (d-Gal), and treated with GlcN or vehicle. The anti-senile-osteoporosis effect of GlcN was explored by examining changes in micro-CT, serum indicators, body weight, protein and gene expression of aging and apoptosis. Additionally, the effects of GlcN on protein and gene expression of osteogenesis and autophagy were observed by inhibiting autophagy with 3-methyladenine (3-MA).

Results

GlcN significantly improved bone mineral density (BMD) and bone micro-architecture, decreased skeletal senescence and apoptosis and increased osteogenesis in d-Gal induced osteoporotic mice. While all effect was reversed with 3-MA.

Conclusion

GlcN effectively delayed the progression of osteoporosis in senile osteoporotic mice by promoting osteoblast autophagy. This study suggested that GlcN may be a prospective candidate drug for the treatment of SOP.

STAT3-mediated osteogenesis and osteoclastogenesis in osteoporosis

Osteoporosis is a common skeletal disease with marked bone loss, deterioration of the bone microstructure and bone fragility. An abnormal bone remodelling cycle with relatively increased bone resorption is the crucial pathophysiological mechanism. Bone remodelling is predominantly controlled by osteoblasts and osteoclasts, which are specialized cell types that are regulated by a variety of osteogenic and osteoclastic factors, including cytokines expressed within the bone microenvironment under local or systemic inflammatory conditions. Signal transducer and activator of transcription 3 (STAT3) plays a prominent role in the communication between cytokines and kinases by binding downstream gene promotors and is involved in a wide range of biological or pathological processes. Emerging evidence suggests that STAT3 and its network participate in bone remodelling and the development of osteoporosis, and this factor may be a potent target for osteoporosis treatment. This review focuses on the role and molecular mechanism of the STAT3 signalling pathway in osteogenesis, osteoclastogenesis and osteoporosis, particularly the bone-related cytokines that regulate the osteoblastic differentiation of bone marrow stromal cells and the osteoclastic differentiation of bone marrow macrophages by initiating STAT3 signalling. This review also examines the cellular interactions among immune cells, haematopoietic cells and osteoblastic/osteoclastic cells.

Immunoporosis: Role of immune system in the pathophysiology of different types of osteoporosis

Osteoporosis is a skeletal system disease characterized by low bone mass and altered bone microarchitecture, with an increased risk of fractures. Classical theories hold that osteoporosis is essentially a bone remodeling disorder caused by estrogen deficiency/aging (primary osteoporosis) or secondary to diseases/drugs (secondary osteoporosis). However, with the in-depth understanding of the intricate nexus between both bone and the immune system in recent decades, the novel field of "Immunoporosis" was proposed by Srivastava et al. (2018, 2022), which delineated and characterized the growing importance of immune cells in osteoporosis. This review aimed to summarize the response of the immune system (immune cells and inflammatory factors) in different types of osteoporosis. In postmenopausal osteoporosis, estrogen deficiency-mediated alteration of immune cells stimulates the activation of osteoclasts in varying degrees. In senile osteoporosis, aging contributes to continuous activation of the immune system at a low level which breaks immune balance, ultimately resulting in bone loss. Further in diabetic osteoporosis, insulin deficiency or resistance-induced hyperglycemia could lead to abnormal regulation of the immune cells, with excessive production of proinflammatory factors, resulting in osteoporosis. Thus, we reviewed the pathophysiology of osteoporosis from a novel insight-immunoporosis, which is expected to provide a specific therapeutic target for different types of osteoporosis.

Aging as a Risk Factor on the Immunoexpression of Pro-Inflammatory IL-1β, IL-6 and TNF-α Cytokines in Chronic Apical Periodontitis Lesions

Persistent inflammatory responses in the elderly may act as modifiers on the progression and repair of chronic apical periodontitis lesions (CAPLs). While the involvement of IL-1β, IL-6 and TNF-α in inflammatory responses and, particularly, in CAPL has been documented, their expression in elderly patients needs to be further characterized. Therefore, the purpose of this study was to evaluate and compare the expressions of pro-inflammatory cytokines in CAPL from elderly individuals with young/middle-aged individuals. Thirty CAPL (15 cysts and 15 granulomas) from elderly patients (>60 years) and 30 CAPL (15 cysts and 15 granuloma) from young/middle-aged individuals (20–56 years) were selected. Immunohistochemical reactions were performed against IL-1β, IL-6 and TNF-α. The slides were subdivided into five high-magnification fields and analyzed. The number of positive stains was evaluated for each antibody. There was no significant difference between the cytokines when the cysts and granuloma were compared in the two groups. In the young/middle-aged, only IL-1β showed a difference and was significantly higher in granulomas (p = 0.019). CAPL pro-inflammatory cytokine levels in the elderly were significantly higher than in young/middle-aged individuals (p < 0.05). The pro-inflammatory cytokines IL-1β, IL-6 and TNF-α were significantly higher in CAPL in the elderly compared with the young/middle-aged group. Further elaborate research studies/analyses to elucidate the reasons for and consequences of inflammation in the elderly are recommended.

Lifetime risks of hip fracture in patients with type 2 diabetic: Taiwan Diabetes Study

This study is to estimate the lifetime risks of hip fracture in Chinese patients with type 2 diabetes.

INTRODUCTION

The lifetime risks of hip fracture have not been reported across the age spectrum in male adults and female adults with type 2 diabetes.

METHODS

A retrospective cohort study was conducted on 25275 men and 27953 women with type 2 diabetes aged 30-100 years old and participated in the National Diabetes Case Management Program in 2002-2004 in Taiwan. Sociodemographic factors, biomarkers, and comorbidity at the baseline and hip fracture events were analyzed with Cox proportional hazards regression models with age as the time scale.

RESULTS

Significant differences in the lifetime risks of hip fracture were observed between men and women with type 2 diabetes. The cumulative lifetime incidences (%) of hip fracture at 50, 60, 65, 70, 75, 80, and 85 years old for men were 0.11, 0.40, 0.84, 1.84, 3.82, 8.53, and 16.72, respectively. The corresponding lifetime incidences (%) for women at 50, 60, 65, 70, 75, 80, and 85 years old were 0.05, 0.50, 1.36, 3.89, 9.56, 21.19, and 35.45, respectively. With competing risks, the significant multivariate-adjusted hazard ratio of developing hip fracture included smoking, alcohol drinking, duration of diabetes, type of oral hypoglycemic drugs use (no medication, sulfonylurea only, thiazolidinediones (TZD) only or TZD plus others, other single or multiple oral agents, insulin use, insulin plus oral hypoglycemic drug use), loop diuretics use, use of corticosteroids, normal weight or underweight, hyperlipidemia, and chronic obstructive pulmonary disease.

CONCLUSIONS

The gender differences in lifetime hip fracture risk were significant. Thiazolidinediones and insulin use are factors with the greater magnitude of strength of association among those significantly associated with hip fracture.

Metabolomics in Bone Research

Identifying the changes in endogenous metabolites in response to intrinsic and extrinsic factors has excellent potential to obtain an understanding of cells, biofluids, tissues, or organisms' functions and interactions with the environment. The advantages provided by the metabolomics strategy have promoted studies in bone research fields, including an understanding of bone cell behaviors, diagnosis and prognosis of diseases, and the development of treatment methods such as implanted biomaterials. This review article summarizes the metabolism changes during osteogenesis, osteoclastogenesis, and immunoregulation in hard tissue. The second section of this review is dedicated to describing and discussing metabolite changes in the most relevant bone diseases: osteoporosis, bone injuries, rheumatoid arthritis, and osteosarcoma. We consolidated the most recent finding of the metabolites and metabolite pathways affected by various bone disorders. This collection can serve as a basis for future metabolomics-driven bone research studies to select the most relevant metabolites and metabolic pathways. Additionally, we summarize recent metabolic studies on metabolomics for the development of bone disease treatment including biomaterials for bone engineering. With this article, we aim to provide a comprehensive summary of metabolomics in bone research, which can be helpful for interdisciplinary researchers, including material engineers, biologists, and clinicians.

The miR-4739/DLX3 Axis Modulates Bone Marrow-Derived Mesenchymal Stem Cell (BMSC) Osteogenesis Affecting Osteoporosis Progression

Osteoporosis is a complex multifactorial disorder linked to various risk factors and medical conditions. Bone marrow-derived mesenchymal stem cell (BMSC) dysfunction potentially plays a critical role in osteoporosis pathogenesis. Herein, the study identified that miR-4739 was upregulated in BMSC cultures harvested from osteoporotic subjects. BMSCs were isolated from normal and osteoporotic bone marrow tissues and identified for their osteogenic differentiation potential. In osteoporotic BMSCs, miR-4739 overexpression significantly inhibited cell viability, osteoblast differentiation, mineralized nodule formation, and heterotopic bone formation, whereas miR-4739 inhibition exerted opposite effects. Through direct binding, miR-4739 inhibited distal-less homeobox 3 (DLX3) expression. In osteoporotic BMSCs, DLX3 knockdown also inhibited BMSC viability and osteogenic differentiation. Moreover, DLX3 knockdown partially attenuated the effects of miR-4739 inhibition upon BMSCs. Altogether, the miR-4739/DLX3 axis modulates the capacity of BMSCs to differentiate into osteoblasts, which potentially plays a role in osteoporosis pathogenesis. The in vivo and clinical functions of the miR-4739/DLX3 axis require further investigation.

Effects of a dynamic combined training on impulse response for middle-aged and elderly patients with osteoporosis and knee osteoarthritis: a randomized control trial

Dynamic combined training is a crucial component in treating musculoskeletal conditions to increase muscle strength and improve functional ability. This randomized control trial aimed to examine the effect of dynamic combined training on muscle strength and contractile rate of force development (RFD) in patients with osteoporosis (OP) and knee osteoarthritis (KOA). 58 participants with OP or KOA were randomly assigned to a control group (CG) (CGOP, n = 12; CGKOA, n = 15) or training group (TG) (TGOP, n = 14; TGKOA, n = 17). The training group participated in a 12-week, three-days-per-week supervised program consisting of stretching and warm-up exercises (10 min), hydraulic resistance training (40 min), and cool-down and relaxation exercises (10 min). All participants were evaluated at baseline and post-training. The maximal voluntary contraction (MVC) and contractile RFD at 0-200 ms increased significantly in middle-aged and older patients with OP. As for KOA, the dynamic combined training program was effective in improving the muscle strength. The maximal voluntary contraction (MVC) and contractile RFD at 0-200 ms increased significantly (by 29.22%, P = .000 and 27.25%, P = .019, respectively) in middle-aged and older patients with OP. In the KOA group, MVC and contractile RFD improved but did not reach statistical significance. The dynamic combined training program is effective for health promotion in older adults with OP or KOA.

Age-dependent modulation of bone metabolism in zebrafish scales as new model of male osteoporosis in lower vertebrates

After middle age, in human bone, the resorption usually exceeds formation resulting in bone loss and increased risk of fractures in the aged population. Only few in vivo models in higher vertebrates are available for pathogenic and therapeutic studies about bone aging. Among these, male Danio rerio (zebrafish) can be successfully used as low vertebrate model to study degenerative alterations that affect the skeleton during aging, reducing the role of sex hormones.

In this paper, we investigated the early bone aging mechanisms in male zebrafish (3, 6, 9 months old) scales evaluating the physiological changes and the effects of prednisolone, a pro-osteoporotic drug.

The results evidentiated an age-dependent reduction of the mineralization rate in the fish scales, as highlighted by growing circle measurements. Indeed, the osteoblastic ALP activity at the matrix deposition site was found progressively downregulated.

The higher TRAP activity was found in 63% of 9-month-old fish scales associated with resorption lacunae along the scale border. Gene expression analysis evidentiated that an increase of the tnfrsf1b (homolog of human rank) in aging scales may be responsible for resorption stimulation.

Interestingly, prednisolone inhibited the physiological growth of the scale and induced in aged scales a more significant bone resorption compared with untreated fish (3.8% vs 1.02%). Bone markers analysis shown a significant reduction of ALP/TRAP ratio due to a prednisolone-dependent stimulation of tnfsf11 (homolog of human rankl) in scales of older fish.

The results evidentiated for the first time the presence of a senile male osteoporosis in lower vertebrate. This new model could be helpful to identify the early mechanisms of bone aging and new therapeutic strategies to prevent age-related bone alterations in humans.

Potential Role of Lycopene in the Prevention of Postmenopausal Bone Loss: Evidence from Molecular to Clinical Studies

Osteoporosis is a metabolic bone disease characterized by reduced bone mineral density, which affects the quality of life of the aging population. Furthermore, disruption of bone microarchitecture and the alteration of non-collagenous protein in bones lead to higher fracture risk. This is most common in postmenopausal women. Certain medications are being used for the treatment of osteoporosis; however, these may be accompanied by undesirable side effects. Phytochemicals from fruits and vegetables are a source of micronutrients for the maintenance of bone health. Among them, lycopene has recently been shown to have a potential protective effect against bone loss. Lycopene is a lipid-soluble carotenoid that exists in both all-trans and cis-configurations in nature. Tomato and tomato products are rich sources of lycopene. Several human epidemiological studies, supplemented by in vivo and in vitro studies, have shown decreased bone loss following the consumption of lycopene/tomato. However, there are still limited studies that have evaluated the effect of lycopene on the prevention of bone loss in postmenopausal women. Therefore, the aim of this review is to summarize the relevant literature on the potential impact of lycopene on postmenopausal bone loss with molecular and clinical evidence, including an overview of bone biology and the pathophysiology of osteoporosis.

Oxytocin Controls Chondrogenesis and Correlates with Osteoarthritis

This study investigated the relationship of oxytocin (OT) to chondrogenesis and osteoarthritis (OA). Human bone marrow and multipotent adipose-derived stem cells were cultured in vitro in the absence or presence of OT and assayed for mRNA transcript expression along with histological and immunohistochemical analyses. To study the effects of OT in OA in vivo, a rat model and a human cohort of 63 men and 19 women with hand OA and healthy controls, respectively, were used. The baseline circulating OT, interleukin-6, leptin, and oestradiol levels were measured, and hand X-ray examinations were performed for each subject. OT induced increased aggrecan, collagen (Col) X, and cartilage oligomeric matrix protein mRNA transcript levels in vitro, and the immunolabelling experiments revealed a normalization of Sox9 and Col II protein expression levels. No histological differences in lesion severity were observed between rat OA groups. In the clinical study, a multivariate analysis adjusted for age, body mass index, and leptin levels revealed a significant association between OA and lower levels of OT (odds ratio = 0.77; p = 0.012). Serum OT levels are reduced in patients with hand OA, and OT showed a stimulatory effect on chondrogenesis. Thus, OT may contribute to the pathophysiology of OA.

Ovariectomized rat model of osteoporosis: a practical guide

Osteoporosis affects about 200 million people worldwide and is a silent disease until a fracture occurs. Management of osteoporosis is still a challenge that warrants further studies for establishing new prevention strategies and more effective treatment modalities. For this purpose, animal models of osteoporosis are appropriate tools, of which the ovariectomized rat model is the most commonly used. The aim of this study is to provide a 4-step guideline for inducing a rat model of osteoporosis by ovariectomy (OVX): (1) selection of the rat strain, (2) choosing the appropriate age of rats at the time of OVX, (3) selection of an appropriate surgical method and verification of OVX, and (4) evaluation of OVX-induced osteoporosis. This review of literature shows that (i) Sprague-Dawley and Wistar rats are the most common strains used, both responding similarly to OVX; (ii) six months of age appears to be the best time for inducing OVX; (iii) dorsolateral skin incision is an appropriate choice for initiating OVX; and (iv) the success of OVX can be verified 1-3 weeks after surgery, following cessation of the regular estrus cycles, decreased estradiol, progesterone, and uterine weight as well as increased LH and FSH levels. Current data shows that the responses of trabecular bones of proximal tibia, lumbar vertebrae and femur to OVX are similar to those in humans; however, for short-term studies, proximal tibia is recommended. Osteoporosis in rats is verified by lower bone mineral density and lower trabecular number and thickness as well as higher trabecular separation, changes that are observed at 14, 30, and 60 days post-OVX in proximal tibia, lumbar vertebrae and femur, respectively.

IDO activation, inflammation and musculoskeletal disease

The IDO/kynurenine pathway is now established as a major regulator of immune system function. The initial enzyme, indoleamine 2,3-dioxygenase (IDO1) is induced by IFNγ, while tryptophan-2,3-dioxygenase (TDO) is induced by corticosteroids. The pathway is therefore positioned to mediate the effects of systemic inflammation or stress-induced steroids on tissue function and its expression increases with age. Disorders of the musculoskeletal system are a common feature of ageing and many of these conditions are characterized by an inflammatory state. In inflammatory arthritis and related disorders, kynurenine protects against the development of disease, while inhibition or deletion of IDO1 increases its severity. The long-term regulation of autoimmune disorders may be influenced by the epigenetic modulation of kynurenine pathway genes, with recent data suggesting that methylation of IDO may be involved. Osteoporosis is also associated with abnormalities of the kynurenine pathway, reflected in an inversion of the ratio between blood levels of the metabolites anthranilic acid and 3-hydroxy-anthranilic acid. This review discusses evidence to date on the role of the IDO/kynurenine pathway and the highly prevalent age-related disorders of osteoporosis and rheumatoid arthritis and identifies key areas that require further research.

Biomarkers of Osteoporosis: An Update

Background:

Osteoporosis, characterized by compromised bone quality and strength is associated with bone fragility and fracture risk. Biomarkers are crucial for the diagnosis or prognosis of a disease as well as elucidating the mechanism of drug action and improve decision making.

Objective:

An exhaustive description of traditional markers including bone mineral density, vitamin D, alkaline phosphatase, along with potential markers such as microarchitectural determination, trabecular bone score, osteocalcin, etc. is provided in the current piece of work. This review provides insight into novel pathways such as the Wnt signaling pathway, neuro-osseous control, adipogenic hormonal imbalance, gut-bone axis, genetic markers and the role of inflammation that has been recently implicated in osteoporosis.

Methods:

We extensively reviewed articles from the following databases: PubMed, Medline and Science direct. The primary search was conducted using a combination of the following keywords: osteoporosis, bone, biomarkers, bone turnover markers, diagnosis, density, architecture, genetics, inflammation.

Conclusion:

Early diagnosis and intervention delay the development of disease and improve treatment outcome. Therefore, probing for novel biomarkers that are able to recognize people at high risk for developing osteoporosis is an effective way to improve the quality of life of patients and to understand the pathomechanism of the disease in a better way.

Bench-to-bedside strategies for osteoporotic fracture: From osteoimmunology to mechanosensation

Osteoporosis is characterized by a decrease in bone mass and strength, rendering people prone to osteoporotic fractures caused by low-energy forces. The primary treatment strategy for osteoporotic fractures is surgery; however, the compromised and comminuted bones in osteoporotic fracture sites are not conducive to optimum reduction and rigid fixation. In addition, these patients always exhibit accompanying aging-related disorders, including high inflammatory status, decreased mechanical loading and abnormal skeletal metabolism, which are disadvantages for fracture healing around sites that have undergone orthopedic procedures. Since the incidence of osteoporosis is expected to increase worldwide, orthopedic surgeons should pay more attention to comprehensive strategies for improving the poor prognosis of osteoporotic fractures. Herein, we highlight the molecular basis of osteoimmunology and bone mechanosensation in different healing phases of elderly osteoporotic fractures, guiding perioperative management to alleviate the unfavorable effects of insufficient mechanical loading, high inflammatory levels and pathogen infection. The well-informed pharmacologic and surgical intervention, including treatment with anti-inflammatory drugs and sufficient application of antibiotics, as well as bench-to-bedside strategies for bone augmentation and hardware selection, should be made according to a comprehensive understanding of bone biomechanical properties in addition to the remodeling status of osteoporotic bones, which is necessary for creating proper biological and mechanical environments for bone union and remodeling. Multidisciplinary collaboration will facilitate the improvement of overall osteoporotic care and reduction of secondary fracture incidence.

Bone and plasma citrate is reduced in osteoporosis

High concentration of citrate exists in bone of humans and all osteo-vertebrates, and citrate incorporation imparts important biomechanical and other functional properties to bone. However, which cells are responsible for citrate production in bone remains unclear and whether the citrate component changes with bone loss during osteoporosis is also not known. Here, we show that the citrate content is markedly reduced in the bone of mice or rats with age-related, ovariectomy-induced or retinoic acid-induced bone loss. Plasmic citrate is also downregulated in osteoporotic animals. Importantly, the plasmic citrate level of aged osteoporotic males is significantly lower than that of young healthy males and positively correlates with human lumbar spine bone mineral density (BMD) and total hip BMD. Furthermore, citrate production increases with in vitro osteoblastic differentiation, accompanied by upregulation of proteins involved in citrate secretion, suggesting that osteoblasts are highly specialized cells that produce citrate in bone. Our findings establish a novel relationship between citrate content and bone loss-related diseases such as osteoporosis, suggesting a critical role of bone citrate in the maintenance of the citrate balance in the circulation. Serum citrate level may thus represent a novel marker for osteoporosis.

Bone marrow stromal cells from low-turnover osteoporotic mouse model are less sensitive to the osteogenic effects of fluvastatin

This study aimed to investigate the effects of fluvastatin on the differentiation of bone marrow stromal cells (BMSCs) into osteoblasts in senescence-accelerated mouse prone 6 (SAMP6) compared with that in the normal senescence-accelerated-resistant mouse (SAMR1) model. SAMP strains arose spontaneously from the AKR/J background and display shortened life span and an array of signs of accelerated aging, compared with control SAMR strains. The dose effects of fluvastatin were also evaluated. BMSCs were cultured with/without fluvastatin (0 μM, 0.1 μM, 0.5 μM, and 1.0 μM). WST-1-based colorimetry was performed to evaluate cell proliferation. To evaluate cell differentiation, gene expression levels of bmp2 and runx2 were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), and protein expression levels were determined using enzyme-linked immunosorbent assay (BMP2) and immunofluorescence staining (BMP2 and Runx2). Alkaline phosphatase (ALP) activity assay and histochemical detection were determined; the effect of noggin, a BMP-specific antagonist, was examined using ALP histochemical detection. To assess for mature osteogenic marker, gene expression levels of bglap2 were determined by qRT-PCR and mineralization was determined by alizarin red staining. RhoA activity was also examined by Western blotting. In SAMP6, BMP2, Runx2 and Bglap2 mRNA and protein expressions were significantly increased by fluvastatin, and ALP activity was increased by BMP2 action. RhoA activity was also inhibited by fluvastatin. The concentration of fluvastatin sufficient to increase BMP2 and Runx2 expression and ALP activity was 0.5 μM in SAMP6 and 0.1 μM in SAMR1. In conclusion, the present study revealed that fluvastatin promoted BMSC differentiation into osteoblasts by RhoA-BMP2 pathway in SAMP6. BMSCs of SAMP6 are less sensitive to the osteogenic effects of fluvastatin than SAMR1.

Whole-body vibration training and bone health in postmenopausal women: A systematic review and meta-analysis

BACKGROUND

The aims of the present systematic review and meta-analysis were to evaluate published, randomized controlled trials that investigate the effects on whole-body vibration (WBV) training on total, femoral neck, and lumbar spine bone mineral density (BMD) in postmenopausal women, and identify the potential moderating factors explaining the adaptations to such training.

METHODS

From a search of electronic databases (PubMed, Web of Science, and Cochrane) up until September 2017, a total 10 studies with 14 WBV groups met the inclusion criteria. Three different authors tabulated, independently, the selected indices in identical predetermined forms. The methodological quality of all studies was evaluated according to the modified PEDro scale. For each trial, differences within arms were calculated as mean differences (MDs) and their 95% confidence intervals between pre- and postintervention values. The effects on bone mass between exercise and control groups were also expressed as MDs. Both analyses were performed in the total sample and in a specific class of postmenopausal women younger than 65 years of age (excluding older women).

RESULTS

The BMD of 462 postmenopausal women who performed WBV or control protocol was evaluated. Significant pre-post improvements in BMD of the lumbar spine were identified following WBV protocols (P = .03). Significant differences in femoral neck BMD (P = .03) were also found between intervention and control groups when analyzing studies that included postmenopausal women younger than 65 years.

CONCLUSIONS

WBV is an effective method to improve lumbar spine BMD in postmenopausal and older women and to enhance femoral neck BMD in postmenopausal women younger than 65 years.

A Review of Osteoporosis in the Older Adult: An Update

Osteoporosis in the elderly population is common. It results in more than 1.5 million fractures per year in the United States. The goal of managing osteoporosis is to prevent fractures. In men, osteoporosis is underrecognized and undertreated. More men than women die every year as a consequence of hip fractures. Bisphosphonates are the first-line treatment of men and women. In the past several years, advances in bone biology have resulted in major therapeutic advances. A review of diagnosis and treatment of osteoporosis is described.

Bioinspired bone therapies using naringin: applications and advances

The use of natural compounds for treating chronic bone diseases holds remarkable potential. Among these therapeutics, naringin, a flavanone glycoside, represents one of the most promising candidates owing to its multifaceted effect on bone tissues. This review provides an up-to-date overview on naringin applications in the treatment of bone disorders, such as osteoporosis and osteoarthritis, and further highlights its potential for stem cell pro-osteogenic differentiation therapies. A critical perspective on naringin clinical translation is also provided. The topic is discussed in light of recently developed biomaterial-based approaches that potentiate its bioavailability and bioactivity. Overall, the reported pro-osteogenic, antiresorptive and antiadipogenic properties establish this flavanone as an exciting candidate for application in bone tissue engineering and regenerative medicine.

A Review of Osteoporosis in the Older Adult

Osteoporosis in the elderly population is common. It results in more than 1.5 million fractures per year in the United States. The goal of managing osteoporosis is to prevent fractures. In men, osteoporosis is underrecognized and undertreated. More men than women die every year as a consequence of hip fractures. A review of diagnosis and treatment of osteoporosis is described in this article. Bisphosphonates are the first-line treatment for men and women. In the past several years, advances in bone biology have resulted in major therapeutic advances.

Screening for Geriatric Syndromes: Falls, Urinary/Fecal Incontinence, and Osteoporosis

The geriatric syndromes of falls, incontinence, and osteoporosis are concerns in older adults because of their potential impact on quality of life. Asking about history of falls or a fear of falling should prompt a multifactorial assessment of fall risk and targeted interventions to reduce falls. Urinary and fecal incontinence should be screened because they are common conditions that are underreported due to embarrassment and general perception that incontinence is a normal part of aging. Women over age 65, men over age 70, and younger patients with high-risk characteristics should be screened with bone mineral density testing with dual-energy x-ray absorptiometry.

Dietary phlorizin enhances osteoblastogenic bone formation through enhancing β-catenin activity via GSK-3β inhibition in a model of senile osteoporosis

Osteoporosis is one of the most prevalent forms of age-related bone diseases. Increased bone loss with advancing age has become a grave public health concern. This study examined whether phlorizin and phloretin, dihydrochalcones in apple peels, inhibited senile osteoporosis through enhancing osteoblastogenic bone formation in cell-based and aged mouse models. Submicromolar phloretin and phlorizin markedly stimulated osteoblast differentiation of MC3T3-E1 cells with increased transcription of Runx2 and osteocalcin. Senescence-accelerated resistant mouse strain prone-6 (SAMP6) mice were orally supplemented with 10 mg/kg phlorizin and phloretin daily for 12 weeks. Male senescence-accelerated resistant mouse strain R1 mice were employed as a nonosteoporotic age-matched control. Oral administration of ploretin and phorizin boosted bone mineralization in all the bones of femur, tibia and vertebra of SAMP6. In particular, phlorizin reduced serum RANKL/OPG ratio and diminished TRAP-positive osteoclasts in trabecular bones of SAMP6. Additionally, treating phlorizin to SAMP6 inhibited the osteoporotic resorption in distal femoral bones through up-regulating expression of BMP-2 and collagen-1 and decreasing production of matrix-degrading cathepsin K and MMP-9. Finally, phlorizin and phloretin antagonized GSK-3β induction and β-catenin phosphorylation in osteoblasts and aged mouse bones. Therefore, phlorizin and phloretin were potential therapeutic agents encumbering senile osteoporosis through promoting bone-forming osteoblastogenesis via modulation of GSK-3β/β-catenin-dependent signaling.

The Role of AOPP in Age-Related Bone Loss and the Potential Benefits of Berry Anthocyanins

Age-related bone loss is a major factor in osteoporosis and osteoporotic fractures among the elderly. Because bone homeostasis involves a balance between bone formation and resorption, multiple mechanisms may induce age-dependent changes in bone. Oxidative stress is one such factor that contributes to the pathology of aging-associated osteoporosis (AAO). Advanced oxidation protein products (AOPP) are a biomarker of oxidant-mediated protein damage, and can also act to increase the production of reactive oxygen species (ROS), thereby perpetuating oxidative damage. AOPP is a relatively novel marker of oxidative stress, and its role in bone aging has not been fully elucidated. Furthermore, it has been theorized that dietary antioxidants may decrease AOPP levels, thereby reducing AAO risk, but a limited number of studies have been specifically targeted at addressing this hypothesis. Therefore, the objective of this review is to examine the findings of existing research on the role of AOPP in age-related bone loss, and the potential use of dietary antioxidants to mitigate the effects of AAOP on age-related bone loss. Cross-sectional studies have delivered mixed results, showing that AOPP levels are inconsistently associated with bone loss and aging. However, in vitro studies have documented multiple mechanisms by which AOPP may lead to bone loss, including upregulation of the JNK/p38 MAPK signaling pathways as well as increasing expression of sclerostin and of receptor activator of NFκB ligand (RANKL). Studies also indicate that antioxidants—especially berry anthocyanins—may be an effective dietary agent to prevent aging-associated bone deterioration by inhibiting the formation of AOPP and ROS. However, the understanding of these pathways in AAO has largely been based on in vitro studies, and should be examined in further animal and human studies in order to inform recommendations regarding dietary anthocyanin use for the prevention of AAO.

The effect of magnesium on early osseointegration in osteoporotic bone: a histological and gene expression investigation

Magnesium has a key role in osteoporosis and could enhance implant osseointegration in osteoporotic patients. Titanium implants impregnated with Mg ions were installed in the tibia of ovariectomized rats. The release of Mg induced a significant increase of bone formation and the expression of anabolic markers in the peri-implant bone.

INTRODUCTION

The success of endosseous implants is highly predictable in patients possessing normal bone status, but it may be impaired in patients with osteoporosis. Thus, the application of strategies that adjuvate implant healing in compromized sites is of great interest. Magnesium has a key role in osteoporosis prevention and it is an interesting candidate for this purpose. In this study, the cellular and molecular effects of magnesium release from implants were investigated at the early healing stages of implant integration.

METHODS

Osteoporosis was induced in 24 female rats by means of ovariectomy and low-calcium diet. Titanium mini-screws were coated with mesoporous titania films and were loaded with magnesium (test group) or left as native (control group). The implants were inserted in the tibia and femur of the rats. One, 2 and 7 days after implantation, the implants were retrieved and histologically examined. In addition, expression of genes was evaluated in the peri-implant bone tissue at day 7 by means of quantitative polymerase chain reactions with pathway-oriented arrays.

RESULTS

The histological evaluation revealed that new bone formation started already during the first week of healing for both groups. However, around the test implants, new bone was significantly more abundant and spread along a larger surface of the implants. In addition, the release of magnesium induced a significantly higher expression of BMP6.

CONCLUSIONS

These results provide evidence that the release of magnesium promoted rapid bone formation and the activation of osteogenic signals in the vicinity of implants placed in osteoporotic bone.

Implications of exercise-induced adipo-myokines in bone metabolism

Physical inactivity has been recognized, by the World Health Organization as the fourth cause of death (5.5 % worldwide). On the contrary, physical activity (PA) has been associated with improved quality of life and decreased risk of several diseases (i.e., stroke, hypertension, myocardial infarction, obesity, malignancies). Bone turnover is profoundly affected from PA both directly (load degree is the key determinant for BMD) and indirectly through the activation of several endocrine axes. Several molecules, secreted by muscle (myokines) and adipose tissues (adipokines) in response to exercise, are involved in the fine regulation of bone metabolism in response to the energy availability. Furthermore, bone regulates energy metabolism by communicating its energetic needs thanks to osteocalcin which acts on pancreatic β-cells and adipocytes. The beneficial effects of exercise on bone metabolism depends on the intermittent exposure to myokines (i.e., irisin, IL-6, LIF, IGF-I) which, instead, act as inflammatory/pro-resorptive mediators when chronically elevated; on the other hand, the reduction in the circulating levels of adipokines (i.e., leptin, visfatin, adiponectin, resistin) sustains these effects as well as improves the whole-body metabolic status. The aim of this review is to highlight the newest findings about the exercise-dependent regulation of these molecules and their role in the fine regulation of bone metabolism.

Loss of Rictor with aging in osteoblasts promotes age-related bone loss

Osteoblast dysfunction is a major cause of age-related bone loss, but the mechanisms underlying changes in osteoblast function with aging are poorly understood. This study demonstrates that osteoblasts in aged mice exhibit markedly impaired adhesion to the bone formation surface and reduced mineralization in vivo and in vitro. Rictor, a specific component of the mechanistic target of rapamycin complex 2 (mTORC2) that controls cytoskeletal organization and cell survival, is downregulated with aging in osteoblasts. Mechanistically, we found that an increased level of reactive oxygen species with aging stimulates the expression of miR-218, which directly targets Rictor and reduces osteoblast bone surface adhesion and survival, resulting in a decreased number of functional osteoblasts and accelerated bone loss in aged mice. Our findings reveal a novel functional pathway important for age-related bone loss and support for miR-218 and Rictor as potential targets for therapeutic intervention for age-related osteoporosis treatment.

Dietary Restriction-Induced Alterations in Bone Phenotype: Effects of Lifelong Versus Short-Term Caloric Restriction on Femoral and Vertebral Bone in C57BL/6 Mice

Caloric restriction (CR) is a well-described dietary intervention that delays the onset of aging-associated biochemical and physiological changes, thereby extending the life span of rodents. The influence of CR on metabolism, strength, and morphology of bone has been controversially discussed in literature. Thus, the present study evaluated whether lifelong CR versus short-term late-onset dietary intervention differentially affects the development of senile osteoporosis in C57BL/6 mice. Two different dietary regimens with 40% food restriction were performed: lifelong CR starting in 4-week-old mice was maintained for 4, 20, or 74 weeks. In contrast, short-term late-onset CR lasting a period of 12 weeks was commenced at 48 or 68 weeks of age. Control mice were fed ad libitum (AL). Bone specimens were assessed using microcomputed tomography (μCT, femur and lumbar vertebral body) and biomechanical testing (femur). Adverse effects of CR, including reduced cortical bone mineral density (Ct.BMD) and thickness (Ct.Th), were detected to some extent in senile mice (68+12w) but in particular in cortical bone of young growing mice (4+4w), associated with reduced femoral failure force (F). However, we observed a profound capacity of bone to compensate these deleterious changes of minor nutrition with increasing age presumably via reorganization of trabecular bone. Especially in lumbar vertebrae, lifelong CR lasting 20 or 74 weeks had beneficial effects on trabecular bone mineral density (Tb.BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N). In parallel, lifelong CR groups showed reduced structure model index values compared to age-matched controls indicating a transformation of vertebral trabecular bone microarchitecture toward a platelike geometry. This effect was not visible in senile mice after short-term 12-week CR. In summary, CR has differential effects on cortical and trabecular bone dependent on bone localization and starting age. Our study underlines that bone compartments possess a lifelong capability to cope with changing nutritional influences.

Evaluating resveratrol as a therapeutic bone agent: preclinical evidence from rat models of osteoporosis

Resveratrol (RSV) is a naturally occurring plant polyphenol that has potential to attenuate osteoporosis with distinct pathologies. This review evaluates preclinical evidence regarding the efficacy and safety of RSV as a therapeutic bone agent using different rat models. Limitations of these animal models are discussed, and suggestions for strengthening the experimental design of future studies are provided. The ovariectomized rat model of postmenopausal osteoporosis reported that RSV supplementation attenuated estrogen deficiency-induced bone loss and trabecular structural deterioration. RSV safety was indicated by the absence of stimulation of estrogen-sensitive tissue. Providing RSV to rats aged >6 months attenuated age-related bone mass loss and structural deterioration but produced inconsistent effects on bones in rats aged <6 months. The hindlimb-suspension rat model of disuse osteoporosis reported that RSV attenuated bone loss in old rats, but higher doses and longer duration supplementation before mechanical loading were required for younger rats. Limitations common to studies using rat models of osteoporosis include requirements to include animals that are skeletally mature, longer study durations, and to adjust for potential confounding effects due to altered body weight and endocrine function. Strengthening experimental design can contribute to translation of animal results to clinically relevant recommendations for humans.

Resveratrol supplementation affects bone acquisition and osteoporosis: Pre-clinical evidence toward translational diet therapy

Osteoporosis is a major public health issue that is expected to rise as the global population ages. Resveratrol (RES) is a plant polyphenol with various anti-aging properties. RES treatment of bone cells results in protective effects, but dose translation from in vitro studies to clinically relevant doses is limited since bioavailability is not taken into account. The aims of this review is to evaluate in vivo evidence for a role of RES supplementation in promoting bone health to reduced osteoporosis risk and potential mechanisms of action. Due to multiple actions on both osteoblasts and osteoclasts, RES has potential to attenuate bone loss resulting from different etiologies and pathologies. Several animal models have investigated the bone protective effects of RES supplementation. Ovariectomized rodent models of rapid bone loss due to estrogen-deficiency reported that RES supplementation improved bone mass and trabecular bone without stimulating other estrogen-sensitive tissues. RES supplementation prior to age-related bone loss was beneficial. The hindlimb unloaded rat model used to investigate bone loss due to mechanical unloading showed RES supplementation attenuated bone loss in old rats, but had inconsistent bone effects in mature rats. In growing rodents, RES increased longitudinal bone growth, but had no other effects on bone. In the absence of human clinical trials, evidence for a role of RES on bone heath relies on evidence generated by animal studies. A better understanding of efficacy, safety, and molecular mechanisms of RES on bone will contribute to the determination of dietary recommendations and therapies to reduce osteoporosis. This article is part of a Special Issue entitled: Resveratol: Challenges in translating pre-clinical findings to improved patient outcomes.

Bone three-dimensional microstructural features of the common osteoporotic fracture sites

Osteoporosis is a common metabolic skeletal disorder characterized by decreased bone mass and deteriorated bone structure, leading to increased susceptibility to fractures. With aging population, osteoporotic fractures are of global health and socioeconomic importance. The three-dimensional microstructural information of the common osteoporosis-related fracture sites, including vertebra, femoral neck and distal radius, is a key for fully understanding osteoporosis pathogenesis and predicting the fracture risk. Low vertebral bone mineral density (BMD) is correlated with increased fracture of the spine. Vertebral BMD decreases from cervical to lumbar spine, with the lowest BMD at the third lumbar vertebra. Trabecular bone mass of the vertebrae is much lower than that of the peripheral bone. Cancellous bone of the vertebral body has a complex heterogeneous three-dimensional microstructure, with lower bone volume in the central and anterior superior regions. Trabecular bone quality is a key element to maintain the vertebral strength. The increased fragility of osteoporotic femoral neck is attributed to low cancellous bone volume and high compact porosity. Compared with age-matched controls, increased cortical porosity is observed at the femoral neck in osteoporotic fracture patients. Distal radius demonstrates spatial inhomogeneous characteristic in cortical microstructure. The medial region of the distal radius displays the highest cortical porosity compared with the lateral, anterior and posterior regions. Bone strength of the distal radius is mainly determined by cortical porosity, which deteriorates with advancing age.

Fat and bone interactions

Fat and bone have a complicated relationship. Although obesity has been associated with low fracture risk, there is increasing evidence that some of the factors that are released by peripheral fat into the circulation may also have a deleterious effect on bone mass, thus, predisposing to fractures. More importantly, the local interaction between fat and bone within the bone marrow seems to play a significant role in the pathogenesis of age-related bone loss and osteoporosis. This "local interaction" occurs inside the bone marrow and is associated with the autocrine and paracrine release of fatty acids and adipokines, which affect the cells in their vicinity including the osteoblasts, reducing their function and survival. In this review, we explore the particularities of the fat and bone cell interactions within the bone marrow, their significance in the pathogenesis of osteoporosis, and the potential therapeutic applications that regulating marrow fat may have in the near future as a novel pharmacologic treatment for osteoporosis.

Resveratrol supplementation preserves long bone mass, microstructure, and strength in hindlimb-suspended old male rats

Resveratrol has gained popularity as an "anti-aging" compound due to its antioxidant and anti-inflammatory properties. Few studies have investigated the role of resveratrol supplementation in the prevention of age-related bone loss and skeletal disuse despite increased inactivity and age-related bone loss in the elderly. The objective of the study was to investigate the effect of resveratrol supplementation on disuse and age-related bone loss. Old (age 33 months) Fischer 344 × Brown Norway male rats were provided either trans-resveratrol (12.5 mg/kg bw/day) or deionized distilled water by oral gavage for 21 days. Rats were hindlimb-suspended (HLS) or kept ambulatory (AMB) for 14 days. Both femora and tibiae were collected. Bone mass was measured by dual-energy X-ray absorptiometry and bone microstructure was determined by micro-computed tomography. HLS of old male rats accelerated loss of bone mineral content, decreased trabecular bone volume per unit of total volume, and increased trabecular separation. Resveratrol supplementation ameliorated bone demineralization and loss of bone microarchitecture in HLS old male rats. The peak force measured by the three-point bending test was reduced (P = 0.007) in HLS/control compared to AMB/control rats. Resveratrol supplementation ameliorated HLS-induced loss of femur strength. Plasma osteocalcin and alkaline phosphatase was higher (P < 0.04) and C-reactive protein was lower (P = 0.04) in old male rats given resveratrol. The bone protective effects of resveratrol appeared to be mediated through increased osteoblast bone formation, possibly due to reduced inflammation. Based on the results, resveratrol supplementation appeared to provide a feasible dietary therapy for preserving the skeletal system during disuse and age-related bone loss.

Recent advances: osteoporosis in the "oldest old"

Osteoporosis and related fractures disproportionately impact patients with advanced age, those with the frailty phenotype, and those with multiple comorbidities. Recent studies report a changing incidence in fracture type among the oldest old throughout the world, a finding not satisfactorily explained by advances in treatment of lifestyle factors. A growing recognition of the importance of muscle and bone interaction is leading to improved understanding of the underlying biochemical pathways linking them and new therapeutic targets. New models of care for frail older populations, particularly after hip fracture, are being developed but have been challenged to identify appropriate outcomes to target. An appreciation for the relationship between age-related comorbidities, fracture risk, and competing mortality risk is essential for practitioners caring for the oldest-old population.

Micro-morphological properties of osteons reveal changes in cortical bone stability during aging, osteoporosis, and bisphosphonate treatment in women

SUMMARY

We analyzed morphological characteristics of osteons along with the geometrical indices of individual osteonal mechanical stability in young, healthy aged, untreated osteoporotic, and bisphosphonate-treated osteoporotic women. Our study revealed significant intergroup differences in osteonal morphology and osteocyte lacunae indicating different remodeling patterns with implications for fracture susceptibility.

INTRODUCTION

Bone remodeling is the key process in bone structural reorganization, and its alterations lead to changes in bone mechanical strength. Since osteons reflect different bone remodeling patterns, we hypothesize that the femoral cortices of females under miscellaneous age, disease and treatment conditions will display distinct osteonal morphology and osteocyte lacunar numbers along with different mechanical properties.

METHODS

The specimens used in this study were collected at autopsy from 35 female donors (young group, n = 6, age 32 ± 8 years; aged group, n = 10, age 79 ± 9 years; osteoporosis group, n = 10, age 81 ± 9 years; and bisphosphonate group, n = 9, age 81 ± 7 years). Von Kossa-modified stained femoral proximal diaphyseal sections were evaluated for osteonal morphometric parameters and osteocyte lacunar data. Geometrical indices of osteonal cross-sections were calculated to assess the mechanical stability of individual osteons, in terms of their resistance to compression, bending, and buckling.

RESULTS

The morphological assessment of osteons and quantification of their osteocyte lacunae revealed significant differences between the young, aged, osteoporosis and bisphosphonate-treated groups. Calculated osteonal geometric indices provided estimates of the individual osteons' resistance to compression, bending and buckling based on their size. In particular, the osteons in the bisphosphonate-treated group presented improved osteonal geometry along with increased numbers of osteocyte lacunae that had been formerly impaired due to aging and osteoporosis.

CONCLUSIONS

The data derived from osteons (as the basic structural units of the cortical bone) in different skeletal conditions can be employed to highlight structural factors contributing to the fracture susceptibility of various groups of individuals.

Evidence for the treatment of osteoporosis with vitamin D in residential care and in the community dwelling elderly

Introduction. Vitamin D is common treatment for osteoporosis. Both age >70 years and living in residential care are associated with increased fracture risk. Community dwelling elderly are a heterogeneous group who may have more similatiry with residential care groups than younger community dwelling counterparts. Aims. To review the evidence for cholecalciferol or ergocalciferol tretment of osteoporosis in either community dwelling patients aged ≥70 years of age, or redidential care patients. Secondly endpoints were changes in bone mineral denisty, and in bone turnover markers. Methods. We performed a literature search using search terms for osteoporosis and vitamin D. Treatment for at least one year was required. Results. Only one residential care study using cholecalciferol, showed non-vertebral and hip fracture reduction in vitamin D deficient subjects. In the community setting one quasi randomised study using ergocalciferol showed reduction in total but not hip or non-vertebral fracture, and a second randomised study showed increased hip fracture risk. Three studies reported increases in hip bone mineral denisty. Discussion. A minority of studies demonstrated a fracture benefit form vitamin D and one suggested possible harm in a community setting. Current practice should be to only offer this treatment to subjects identified as deficient.

Causes, consequences, and treatment of osteoporosis in men

Men undergo gradual bone loss with aging, resulting in fragile bones. It is estimated that one in five men will suffer an osteoporotic fracture during their lifetime. The prognosis for men after a hip fracture is very grim. A major cause is reduction of free testosterone. Many other factors result in secondary osteoporosis, including treatment for other diseases such as cancer and diabetes. Patients should be screened not only for bone density but also assessed for their nutritional status, physical activity, and drug intake. Therapy should be chosen based on the type of osteoporosis. Available therapies include testosterone replacement, bisphosphonates, and nutritional supplementation with calcium, vitamin D, fatty acids, and isoflavones, as well as certain specific antibodies, like denosumab and odanacatib, and inhibitors of certain proteins.

Functional impairment of bone formation in the pathogenesis of osteoporosis: the bone marrow regenerative competence

The skeleton is a high-renewal organ that undergoes ongoing cycles of remodeling. The regenerative bone formation arm ultimately declines in the aging, postmenopausal skeleton, but current therapies do not adequately address this deficit. Bone marrow is the primary source of the skeletal anabolic response and the mesenchymal stem cells (MSCs), which give rise to bone matrix-producing osteoblasts. The identity of these stem cells is emerging, but it now appears that the term 'MSC' has often been misapplied to the bone marrow stromal cell (BMSC), a progeny of the MSC. Nevertheless, the changes in BMSC phenotype associated with age and estrogen depletion likely contribute to the attenuated regenerative competence of the marrow and may reflect alterations in MSC phenotype. Here we summarize current concepts in bone marrow MSC identity, and within this context, review recent observations on changes in bone marrow population dynamics associated with aging and menopause.