Monitoring individual morphological changes over time in ovariectomized rats by in vivo micro-computed tomography

Predicting Bone Adaptation in Astronauts during and after Spaceflight

A method was previously developed to identify participant-specific parameters in a model of trabecular bone adaptation from longitudinal computed tomography (CT) imaging. In this study, we use these numerical methods to estimate changes in astronaut bone health during the distinct phases of spaceflight and recovery on Earth. Astronauts (N = 16) received high-resolution peripheral quantitative CT (HR-pQCT) scans of their distal tibia prior to launch (L), upon their return from an approximately six-month stay on the international space station (R+0), and after six (R+6) and 12 (R+12) months of recovery. To model trabecular bone adaptation, we determined participant-specific parameters at each time interval and estimated their bone structure at R+0, R+6, and R+12. To assess the fit of our model to this population, we compared static and dynamic bone morphometry as well as the Dice coefficient and symmetric distance at each measurement. In general, modeled and observed static morphometry were highly correlated (R2> 0.94) and statistically different (p < 0.0001) but with errors close to HR-pQCT precision limits. Dynamic morphometry, which captures rates of bone adaptation, was poorly estimated by our model (p < 0.0001). The Dice coefficient and symmetric distance indicated a reasonable local fit between observed and predicted bone volumes. This work applies a general and versatile computational framework to test bone adaptation models. Future work can explore and test increasingly sophisticated models (e.g., those including load or physiological factors) on a participant-specific basis.

Computed Tomography Bone Imaging: Pushing the Boundaries in Clinical Practice

Bone microarchitecture has several clinical implications over and above estimating bone strength. Computed tomography (CT) analysis mainly uses high-resolution peripheral quantitative CT and micro-CT, research imaging techniques, most often limited to peripheral skeleton assessment. Ultra-high-resolution (UHR) CT and photon-counting detector CT, two commercially available techniques, provide images that can approach the spatial resolution of the trabeculae, bringing bone microarchitecture analysis into clinical practice and improving depiction of bone vascularization, tumor matrix, and cortical and periosteal bone. This review presents bone microarchitecture anatomy, principles of analysis, reference measurements, and an update on the performance and potential clinical applications of these new CT techniques. We also share our clinical experience and technical considerations using an UHR-CT device.

CircRNA hsa_circ_0006859 inhibits the osteogenic differentiation of BMSCs and aggravates osteoporosis by targeting miR-642b-5p/miR-483-3p and upregulating EFNA2/DOCK3

Hsa_circ_0006859 has been found as a possible biomarker for postmenopausal osteoporosis (PMOP) with an effect on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), but the underlying mechanism is unclear. Bioinformatics analysis was used to identify dysregulated RNAs involved in osteoporosis based on public datasets. Function assays were used to determine the functions of hsa_circ_0006859 on cell proliferation and osteogenic differentiation in vitro. It was found that hsa_circ_0006859 was upregulated in OVX mice-derived BMSCs, but lowly expressed during osteogenic differentiation. Overexpressing hsa_circ_0006859 inhibited the cell proliferation and osteogenesis of BMSCs and hFOB 1.19 cells, vice versa. Bilateral ovariectomy (OVX) was used to induce PMOP in mice. The interactions among circ_0006859, miR-642b-5p/miR-483-3p, and EFNA2/DOCK3 were determined using the RIP assay. Silencing circ_0006859 relieved PMOP in mice. Mechanistically, circ_0006859 bound to miR-642b-5p/miR-483-3p directly, while miR-642b-5p and miR-483-3p respectively targeted EFNA2 and DOCK3. Hsa_circ_0006859 downregulated the expression of miR-642b-5p/miR-483-3p to upregulate EFNA2/DOCK3. Additionally, miR-642b-5p/miR-483-3p targeted EFNA2/DOCK3 to inhibit BMSCs osteogenic differentiation and facilitate osteoporosis progression by inactivating the Wnt signaling. In conclusion, hsa_circ_0006859 is involved in PMOP by targeting miR-642b-5p/EFNA2 and miR-483-3p/DOCK3 axes to maintain the Wnt-signaling pathway, which may be a novel possible therapeutic targets and biomarkers for PMOP.

A ROS/GAS5/SIRT1 reinforcing feedback promotes oxidative stress-induced adipogenesis in bone marrow-derived mesenchymal stem cells during osteoporosis

BACKGROUND

LincGAS5 have been reported to regulate the progression of osteoporosis (OP). However, the relationship between LincGAS5 and reactive oxygen species (ROS) in osteoporosis were still unclear.

METHODS

Bilateral ovariectomy (OVX) rat were established as OP model and verified by the Micro-computed tomography. The ROS level of BMSCs derived from OVX and control rat were detected by Immunofluorescence (IF) and flow cytometry. The role of GAS5, miR-23b-3p and SIRT1 on the osteogenic differentiation were dectected by ARS saining and ALP staining, while the The Oil Red O staining and flow cytometry (FCM) were hired to determine adipogenic differentiation of BMSCs under different treatment. The expression of GAS5,miR-23b-3p and SIRT1 in BMSCs was detected by RT-qPCR and the correlation among them was analyzed. In addition, Luciferase activity was used to detect whether miR-23b-3p combined with GAS5 and SIRT1 in OP mice BMSCs.

RESULTS

We established the OVX rat model and found higher ROS level in BMSCs isolated from OVX rats. Meanwhile, GAS5 was down-regulated by ROS and remarkably lowly expressed in OVX rat comparing with the negative control. We confirmed GAS5 inhibited adipogenesis and promoted osteoporosis progression. Mechanically, GAS5 bound with miR-23b-3p and suppressed its biological function. We also identified that miR-23b-3p bound with Sirtuin 1 (SIRT1) and decreased its stability. Furthermore, SIRT1 suppressed ROS production in BMSCs, which in turn un-regulated GAS5 expression through ROS-GAS5 axis.

CONCLUSION

We identified a negative feedback loop, ROS-GAS5-SIRT1, in osteoporosis progression. Our findings provided potential targets and biomarkers for osteoporosis prevention and treatment.

COVID-19 and income profile: How communities in the United States responded to mobility restrictions in the pandemic's early stages

Mobility interventions in communities play a critical role in containing a pandemic at an early stage. The real-world practice of social distancing can enlighten policymakers and help them implement more efficient and effective control measures. A lack of such research using real-world observations initiates this article. We analyzed the social distancing performance of 66,149 census tracts from 3,142 counties in the United States with a specific focus on income profile. Six daily mobility metrics, including a social distancing index, stay-at-home percentage, miles traveled per person, trip rate, work trip rate, and non-work trip rate, were produced for each census tract using the location data from over 100 million anonymous devices on a monthly basis. Each mobility metric was further tabulated by three perspectives of social distancing performance: "best performance," "effort," and "consistency." We found that for all 18 indicators, high-income communities demonstrated better social distancing performance. Such disparities between communities of different income levels are presented in detail in this article. The comparisons across scenarios also raise other concerns for low-income communities, such as employment status, working conditions, and accessibility to basic needs. This article lays out a series of facts extracted from real-world data and offers compelling perspectives for future discussions.

Comparison of the efficacy between sequential therapy with teriparatide and denosumab and denosumab monotherapy in suppressing fragility fracture risk

In this retrospective study, the effectiveness of short-term teriparatide with denosumab in reducing fragility fracture risk was determined in comparison with denosumab monotherapy. Administration of sequential teriparatide with denosumab showed excellent outcomes in suppressing the risk for fragility fractures compared with denosumab monotherapy.

INTRODUCTION

To determine the effectiveness of short-term teriparatide with denosumab in reducing the risk of fragility fractures in comparison to denosumab monotherapy.

METHODS

The data of postmenopausal patients treated with denosumab for > 2 years between August 2015 and October 2020 were retrospectively analyzed. One hundred sixty four postmenopausal women of a total 615 were excluded, since they did not undergo > 2 bone mineral density (BMD) tests, were lost to follow-up, or received long-term teriparatide therapy. Total 320 patients received denosumab monotherapy and 131 patients received teriparatide for ≥ 3 months followed by denosumab. The number of osteoporotic fractures, presence of back pain before and after treatment, and annual BMD during treatment were comparatively assessed using t-test, Chi-square test, and linear mixed model analysis.

RESULTS

Before treatment, the denosumab monotherapy group had fewer osteoporotic fractures (mean ± standard deviation; 0.459 ± 0.689) than the sequential therapy group had (1.037 ± 0.871; p < 0.001). After treatment, the sequential therapy group had fewer osteoporotic fractures than the denosumab monotherapy group had (0.119 ± 0.348 versus 0.144 ± 0.385; p < 0.001). At 1 and 2 years after treatment, the increase in lumbar spine BMD was greater in the sequential therapy group than in the denosumab monotherapy group (p = 0.08, group × time). The difference between post and pre-treatment back pain visual analog scale score was significantly lower in the sequential therapy group than in the monotherapy group (3.246 ± 3.426 versus 1.734 ± 3.049; p < 0.001).

CONCLUSION

Short-term teriparatide use before denosumab showed excellent outcomes in suppressing the risk of fragility fractures compared with denosumab monotherapy.

Biomineralization of bone tissue: calcium phosphate-based inorganics in collagen fibrillar organic matrices

Background

Bone regeneration research is currently ongoing in the scientific community. Materials approved for clinical use, and applied to patients, have been developed and produced. However, rather than directly affecting bone regeneration, these materials support bone induction, which regenerates bone. Therefore, the research community is still researching bone tissue regeneration. In the papers published so far, it is hard to find an improvement in the theory of bone regeneration. This review discusses the relationship between the existing theories on hard tissue growth and regeneration and the biomaterials developed so far for this purpose and future research directions.

Mainbody

Highly complex nucleation and crystallization in hard tissue involves the coordinated action of ions and/or molecules that can produce different organic and inorganic composite biomaterials. In addition, the healing of bone defects is also affected by the dynamic conditions of ions and nutrients in the bone regeneration process. Inorganics in the human body, especially calcium- and/or phosphorus-based materials, play an important role in hard tissues. Inorganic crystal growth is important for treating or remodeling the bone matrix. Biomaterials used in bone tissue regeneration require expertise in various fields of the scientific community. Chemical knowledge is indispensable for interpreting the relationship between biological factors and their formation. In addition, sources of energy for the nucleation and crystallization processes of such chemical bonds and minerals that make up the bone tissue must be considered. However, the exact mechanism for this process has not yet been elucidated. Therefore, a convergence of broader scientific fields such as chemistry, materials, and biology is urgently needed to induce a distinct bone tissue regeneration mechanism.

Conclusion

This review provides an overview of calcium- and/or phosphorus-based inorganic properties and processes combined with organics that can be regarded as matrices of these minerals, namely collagen molecules and collagen fibrils. Furthermore, we discuss how this strategy can be applied to future bone tissue regenerative medicine in combination with other academic perspectives.

Temporal changes in cortical microporosity during estrogen deficiency associated with perilacunar resorption and osteocyte apoptosis: A pilot study

Osteocytes can actively regulate bone microporosity, through either perilacunar resorption or micropetrosis following apoptosis. Osteocyte apoptosis is more prevalent in estrogen deficiency and changes in the lacunar-canalicular network of osteocytes have been reported. Temporal changes in bone mineralisation and osteocytes cellular strains occur, which might be associated with osteocyte-driven microporosity changes, although time dependant changes in bone microporosity are not yet fully understood. In this pilot study we conducted micro-CT analysis, backscatter electron imaging and histological analysis of femoral cortical bone form an ovariectomized rat model of osteoporosis to investigate whether estrogen deficiency causes temporal changes in lacunar and vascular porosity. We also assessed MMP14 expression, lacunar occupancy and mineral infilling, as indicators of perilacunar resorption and micropetrosis. We report temporal changes in cortical microporosity in estrogen deficiency. Specifically, canalicular and vascular porosity initially increased (4 weeks post-OVX), coinciding with the period of rapid bone loss, whereas in the longer term (14 weeks post-OVX) lacunar and canalicular diameter decreased. Interestingly, these changes coincided with an increased prevalence of empty lacunae and osteocyte lacunae were observed to be more circular with a mineralised border around the lacunar space. In addition we report an increase in MMP14+ osteocytes, which also suggests active matrix degradation by these cells. Together these results provide an insight into the temporal changes in cortical microporosity during estrogen deficiency and suggest the likelihood of occurrence of both perilacunar resorption and osteocyte apoptosis leading to micropetrosis. We propose that microporosity changes arise due to processes driven by distinct populations of osteocytes, which are either actively resorbing their matrix or have undergone apoptosis and are infilling lacunae by micropetrosis.

Bone fragility in diabetes: novel concepts and clinical implications

Increased fracture risk represents an emerging and severe complication of diabetes. The resulting prolonged immobility and hospitalisations can lead to substantial morbidity and mortality. In type 1 diabetes, bone mass and bone strength are reduced, resulting in up to a five-times greater risk of fractures throughout life. In type 2 diabetes, fracture risk is increased despite a normal bone mass. Conventional dual-energy x-ray absorptiometry might underestimate fracture risk, but can be improved by applying specific adjustments. Bone fragility in diabetes can result from cellular abnormalities, matrix interactions, immune and vascular changes, and musculoskeletal maladaptation to chronic hyperglycaemia. This Review summarises how the bone microenvironment responds to type 1 and type 2 diabetes, and the mechanisms underlying fragility fractures. We describe the value of novel imaging technologies and the clinical utility of biomarkers, and discuss current and future therapeutic approaches that protect bone health in people with diabetes.

Modulation of gut microbiota by chondroitin sulfate calcium complex during alleviation of osteoporosis in ovariectomized rats

Although chondroitin sulfate calcium complex (CSCa) was claimed to have the bioactivity for bone care in vitro, its anti-osteoporosis bioactivity was little reported in vivo. Here, the effects of CSCa on osteoporosis rats were investigated. Results showed that, compared with the osteoporosis rats, CSCa could improve the bone mineral density and microstructure of femur, and change the bone turnover markers level in serum. 16S rRNA sequencing and metabolomics analysis indicated CSCa intervention altered the composition of gut microbiota along with metabolite profiles in ovariectomized rat faeces. The correlation analysis showed some gut microbiota taxa were significantly correlated with osteoporosis phenotypes and the enriched metabolites. Taken together, dietary CSCa intervention has the potential to alleviate the osteoporosis and related symptoms probably involving gut microbiota or the metabolite profiles as demonstrated in rats. This study provides some scientific evidence for the potential effects of CSCa as the food supplement on the osteoporosis.

Menaquinone 4 Reduces Bone Loss in Ovariectomized Mice through Dual Regulation of Bone Remodeling

Epidemiologic studies showed that higher vitamin K (VK) consumption correlates with a reduced risk of osteoporosis, yet the dispute remains about whether VK is effective in improving bone mineral density (BMD). We sought to discover the anti-osteoporotic effect of menaquinone-4 (MK-4) and evaluate the expression of critical genes related to bone formation and bone resorption pathways in the body. Fifty female C57BL/6 mice (aged 13 weeks) were randomly arranged to a sham-operated group (SHAM, treated with corn oil) and four ovariectomized groups that were administered corn oil (OVX group), estradiol valerate (EV, 2 mg/kg body weight as the positive control), low or high doses of VK (LVK and HVK; 20 and 40 mg MK-4/kg body weight, respectively) by gavage every other day for 12 weeks. Body and uterine weight, serum biochemical indicators, bone microarchitecture, hematoxylin-eosin (HE) staining, and the mRNA expression of critical genes related to bone formation and bone resorption pathways were assessed. Either dose of MK-4 supplementation increased the alkaline phosphatase (ALP), decreased the undercarboxylated osteocalcin (ucOC) and tartrate-resistant acid phosphatase (TRACP, p < 0.05) levels, and presented higher BMD, percent bone volume (BV/TV), trabecular thickness (Tb.Th), and lower trabecular separation (Tb.Sp) and structure model index (SMI, p < 0.05) compared with the OVX group. Additionally, both doses of MK4 increased the mRNA expression of Runx2 and Bmp2 (p < 0.05), whereas the doses down-regulated Pu.1 and Nfatc1 (p < 0.05) mRNA expression, the high dose decreased Osx and Tgfb (p < 0.05) mRNA expression, and the low dose decreased Mitd and Akt1 (p < 0.05) mRNA expression. These data show the dual regulatory effects of MK-4 on bone remodeling in ovariectomized mice: the promotion of bone anabolic activity and inhibition of osteoclast differentiation, which provides a novel idea for treating osteoporosis.

Is the Jaw Bone Micro-Structure Altered in Response to Osteoporosis and Bisphosphonate Treatment? A Micro-CT Analysis

The aim of the study was to quantify the micro-architectural changes of the jaw bone in response to ovariectomy, exposed or not to bisphosphonate treatment. A total of 47 Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and exposed to osteoporosis preventive treatment for eight weeks either with bisphosphonates (alendronate, ALN; group OVX-ALN) three days/week at a dose of 2 mg/kg or with saline solution (untreated control condition; group OVX). The bone morphometric parameters of the trabecular jaw bone were assessed using ex vivo micro-computed tomography. The regions of interest investigated in the maxilla were the inter-radicular septum of the second molar and the tuber. The regions quantified in the mandible included the three molar regions and the condyle. A one-way analysis of variance followed by pairwise comparison using Tukey’s HSD and the Games–Howell test was conducted to explore significant differences between the groups. In the maxilla, OVX decreased the bone volume in the inter-radicular septum of the second molar. Bisphosphonate treatment was able to prevent this deterioration of the jaw bone. The other investigated maxillary regions were not affected by (un)treated ovariectomy. In the mandible, OVX had a significant negative impact on the jaw bone in the buccal region of the first molar and the inter-radicular region of the third molar. Treatment with ALN was able to prevent this jaw bone loss. At the condyle site, OVX significantly deteriorated the trabecular connectivity and shape, whereas preventive bisphosphonate treatment showed a positive effect on this trabecular bone region. No significant results between the groups were observed for the remaining regions of interest. In summary, our results showed that the effects of ovariectomy-induced osteoporosis are manifested at selected jaw bone regions and that bisphosphonate treatment is capable to prevent these oral bone changes.

Estrogen withdrawal alters cytoskeletal and primary ciliary dynamics resulting in increased Hedgehog and osteoclastogenic paracrine signalling in osteocytes

Estrogen deficiency during post-menopausal osteoporosis leads to osteoclastogenesis and bone loss. Increased pro-osteoclastogenic signalling (RANKL/OPG) by osteocytes occurs following estrogen withdrawal (EW) and is associated with impaired focal adhesions (FAs) and a disrupted actin cytoskeleton. RANKL production is mediated by Hedgehog signalling in osteocytes, a signalling pathway associated with the primary cilium, and the ciliary structure is tightly coupled to the cytoskeleton. Therefore, the objective of this study was to investigate the role of the cilium and associated signalling in EW-mediated osteoclastogenic signalling in osteocytes. We report that EW leads to an elongation of the cilium and increase in Hedgehog and osteoclastogenic signalling. Significant trends were identified linking cilia elongation with reductions in cell area and % FA area/cell area, indicating that cilia elongation is associated with disruption of FAs and actin contractility. To verify this, we inhibited FA assembly via α_vβ₃ antagonism and inhibited actin contractility and demonstrated an elongated cilia and increased expression of Hh markers and Rankl expression. Therefore, our results suggest that the EW conditions associated with osteoporosis lead to a disorganisation of α_vβ₃ integrins and reduced actin contractility, which were associated with an elongation of the cilium, activation of the Hh pathway and osteoclastogenic paracrine signalling.

Peak trabecular bone microstructure predicts rate of estrogen-deficiency-induced bone loss in rats

Postmenopausal osteoporosis affects a large number of women worldwide. Reduced estrogen levels during menopause lead to accelerated bone remodeling, resulting in low bone mass and increased fracture risk. Both peak bone mass and the rate of bone loss are important predictors of postmenopausal osteoporosis risk. However, whether peak bone mass and/or bone microstructure directly influence the rate of bone loss following menopause remains unclear. Our study aimed to establish the relationship between peak bone mass/microstructure and the rate of bone loss in response to estrogen deficiency following ovariectomy (OVX) surgery in rats of homogeneous background by tracking the skeletal changes using in vivo micro-computed tomography (μCT) and three-dimensional (3D) image registrations. Linear regression analyses demonstrated that the peak bone microstructure, but not peak bone mass, was highly predictive of the rate of OVX-induced bone loss. In particular, the baseline trabecular thickness was found to have the highest correlation with the degree of OVX-induced bone loss and trabecular stiffness reduction. Given the same bone mass, the rats with thicker baseline trabeculae had a lower rate of trabecular microstructure and stiffness deterioration after OVX. Moreover, further evaluation to track the changes within each individual trabecula via our novel individual trabecular dynamics (ITD) analysis suggested that a trabecular network with thicker trabeculae is less likely to disconnect or perforate in response to estrogen deficiency, resulting a lower degree of bone loss. Taken together, these findings indicate that the rate of estrogen-deficiency-induced bone loss could be predicted by peak bone microstructure, most notably the trabecular thickness. Given the same bone mass, a trabecular bone phenotype with thin trabeculae may be a risk factor toward accelerated postmenopausal bone loss.

Oral administration of bovine lactoferrin accelerates the healing of fracture in ovariectomized rats

INTRODUCTION

Lactoferrin has recently been reported for its potent bone growth effects. However, the effects of lactoferrin on the healing process of fragility fracture have not yet been studied, so the purpose of this study is to investigate whether oral administration of lactoferrin can promote the fracture healing in an OVX animal model.

MATERIALS AND METHODS

Three months after bilateral ovariectomy, all rats underwent unilateral tibial osteotomy and were then randomly divided into control group and bovine lactoferrin (bLF) group. At 4 and 8 weeks post-fracture, animals were sacrificed, and the fractured tibiae and serum samples were collected for evaluation.

RESULTS

Our results showed that bLF treatment not only accelerated the bone growth at an early stage of OPF healing but also shortened the remolding process of OPF healing. When compared to control group, bLF treatment induced a significant rise in callus BMD (by 35.0% at 4 weeks and by 39.7% at 8 weeks; both p < 0.05) consistent with enhanced biomechanical strength of the callus, with ultimate force increased by 3.39-fold at 4 weeks (p < 0.05) and 1.95-fold at 8 weeks (p < 0.05). Besides, bLF administration resulted in a substantial increase in serum levels of BALP and a significant decrease in serum levels of TRAP 5b and TNF-α. Moreover, both the RANKL/OPG mRNA ratio and the expression of TNF-α in the callus of bLF-treated group were markedly lower than those in the control group.

CONCLUSIONS

At a dose of 85mg/kg/day orally administrated bLF potently promoted the bone healing following tibial fracture in OVX rats.

MiR-1-3p regulates the differentiation of mesenchymal stem cells to prevent osteoporosis by targeting secreted frizzled-related protein 1

Osteoporosis (OP) is a systemic skeletal disorder with the characteristics of bone mass reduction and microarchitecture deterioration, resulting in bone fragility and increased fracture risk. A reduction in the osteoblast-differentiation of bone marrow mesenchymal stem cells (BMSCs) is considered as a basic pathogenesis of osteoporosis. miRNAs play a substantial role in the development and differentiation of BMSCs. In the present study, we found that miR-1-3p was significantly downregulated in the bones of Chinese osteoporotic patients (n = 29). Secreted frizzled-related protein 1 (SFRP1) was predicted as a target gene of miR-1-3p via the TargetScan and PicTar softwares and validated by dual-luciferase reporter assays. The findings revealed that the expression of SFRP1 was inversely correlated with miR-1-3p in osteoporotic patients. We induced mouse MSCs (mMSCs) to osteogenesis or adipogenesis and found that miR-1-3p was upregulated during osteogenesis but downregulated during adipogenesis. The overexpression of miR-1-3p stimulated osteogenesis and inhibited adipogenesis of mMSCs. In addition, ovariectomized (OVX) mice were tested and the function of miR-1-3p in vivo was explored. Immunohistochemistry and histomorphometric assays showed that in vivo inhibition of miR-1-3p increased the expression level of SFRP1 and reduced bone formation and bone mass. Furthermore, tartrate-resistant acid phosphatase (TRAP) staining indicated that the in vivo suppression of miR-1-3p promoted osteoclast activity, suggesting that miR-1-3p may influence bone mass by regulating bone resorption. It can be concluded that miR-1-3p plays a pivotal role in the pathogenesis of osteoporosis via targeting SFRP1 and may be a potential therapeutic target for osteoporosis.

Identification of circRNA-associated ceRNA network in BMSCs of OVX models for postmenopausal osteoporosis

Circular RNAs (circRNAs) serve as competing endogenous RNAs (ceRNAs) and indirectly regulate gene expression through shared microRNAs (miRNAs). However, the potential circRNAs functioning as ceRNAs in osteoporosis remain unclear. The bone marrow mesenchymal stem cells (BMSCs) were isolated from ovariectomy (OVX) mice and controls. We systematically analyzed RNA‐seq and miRNA‐microarray data, miRNA‐target interactions, and prominently coexpressed gene pairs to identify aberrantly expressed circRNAs, miRNAs, and messenger RNAs (mRNAs) between the OVX mice and controls. A total of 45 circRNAs, 22 miRNAs, and 548 mRNAs were significantly dysregulated (fold change > 1.5; p < 0.05). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted for differentially expressed mRNAs, and subsequently a circRNA‐associated ceRNA network involved in osteoporosis was constructed. We identified two ceRNA regulatory pathways in this osteoporosis mouse model—novel circRNA 0020/miR-206-3p/Nnmt and circRNA 3832/miR-3473e/Runx3, which were validated by real-time PCR. This is the first study to elucidate the circRNA-associated ceRNA network in OVX and control mice using deep RNA-seq and RNA-microarray analysis. The data further expanded the understanding of circRNA-associated ceRNA networks, and the regulatory functions of circRNAs, miRNAs and mRNAs in the pathogenesis and pathology of osteoporosis.

Mechanical regulation of bone formation and resorption around implants in a mouse model of osteopenic bone

Although mechanical stimulation is considered a promising approach to accelerate implant integration, our understanding of load-driven bone formation and resorption around implants is still limited. This lack of knowledge may delay the development of effective loading protocols to prevent implant loosening, especially in osteoporosis. In healthy bone, formation and resorption are mechanoregulated processes. In the intricate context of peri-implant bone regeneration, it is not clear whether bone (re)modelling can still be load-driven. Here, we investigated the mechanical control of peri-implant bone (re)modelling with a well-controlled mechanobiological experiment. We applied cyclic mechanical loading after implant insertion in tail vertebrae of oestrogen depleted mice and we monitored peri-implant bone response by in vivo micro-CT. Experimental data were combined with micro-finite element simulations to estimate local tissue strains in (re)modelling locations. We demonstrated that a substantial increase in bone mass around the implant could be obtained by loading the entire bone. This augmentation could be attributed to a large reduction in bone resorption rather than to an increase in bone formation. We also showed that following implantation, mechanical regulation of bone (re)modelling was transiently lost. Our findings should help to clarify the role of mechanical stimulation on the maintenance of peri-implant bone mass.

Isolated Cyclic Loading During Adolescence Improves Tibial Bone Microstructure and Strength at Adulthood

Bone is a unique living tissue, which responds to the mechanical stimuli regularly imposed on it. Adolescence facilitates a favorable condition for the skeleton that enables the exercise to positively influence bone architecture and overall strength. However, it is still dubious for how long the skeletal benefits gained in adolescence is preserved at adulthood. The current study aims to use a rat model to investigate the effects of in vivo low- (LI), medium- (MI), and high- (HI) intensity cyclic loadings applied during puberty on longitudinal bone development, morphometry, and biomechanics during adolescence as well as at adulthood. Forty-two young (4-week-old) male rats were randomized into control, sham, LI, MI, and HI groups. After a 5 day/week for 8 weeks cyclic loading regime applied on the right tibia, loaded rats underwent a subsequent 41-week, normal cage activity period. Right tibias were removed at 52 weeks of age, and a comprehensive assessment was performed using μCT, mechanical testing, and finite element analysis. HI and MI groups exhibited reduced body weight and food intake at the end of the loading period compared with shams, but these effects disappeared afterward. HI cyclic loading increased BMD, bone volume fraction, trabecular thickness, trabecular number, and decreased trabecular spacing after loading. All loading-induced benefits, except BMD, persisted until the end of the normal cage activity period. Moreover, HI loading induced enhanced bone area, periosteal perimeter, and moment of inertia, which remained up to the 52nd week. After the normal cage activity at adulthood, the HI group showed increased ultimate force and stress, stiffness, postyield displacement and energy, and toughness compared with the sham group. Overall, our findings suggest that even though both trabecular and cortical bone drifted through age-related changes during aging, HI cyclic loading performed during adolescence can render lifelong benefits in bone microstructure and biomechanics. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Supraspinatus Tendons Have Different Mechanical Properties Across Sex

Sex differences in the mechanical properties of different musculoskeletal tissues and their impact on tendon function and disease are becoming increasingly recognized. Tendon mechanical properties are influenced by the presence or absence of sex hormones and these effects appear to be tendon- or ligament-specific. The objective of this study was to determine how sex and hormone differences in rats affect supraspinatus tendon and muscle properties. We hypothesized that male supraspinatus tendons would have increased cross-sectional area but no differences in tendon material properties or muscle composition when compared to supraspinatus tendons from female or ovariectomized (OVX) female rats. Uninjured supraspinatus tendons and muscles from male, female, and OVX female rats were collected and mechanical and histological properties were determined. Our analysis demonstrated decreased dynamic modulus and increased hysteresis and cross-sectional area in male tendons. We found that male tendons exhibited decreased dynamic modulus (during low strain frequency sweep and high strain fatigue loading), increased hysteresis, and increased cross-sectional area compared to female and OVX female tendons. Despite robust mechanical differences, tendon cell density and shape, and muscle composition remained unchanged between groups. Interestingly, these differences were unique compared to previously reported sex differences in rat Achilles tendons, which further supports the concept that the effect of sex on tendon varies anatomically. These differences may partially provide a mechanistic explanation for the increased rate of acute supraspinatus tendon ruptures seen in young males.

Secondary alterations in bone mineralisation and trabecular thickening occur after long-term estrogen deficiency in ovariectomised rat tibiae, which do not coincide with initial rapid bone loss

This study delineates the time sequence of changes in bone tissue mineralisation in ovariectomised rats. We report that changes in bone mineral distribution arise secondary to the initial rapid bone loss but coincide with trabecular thickening. We propose that these changes compensate for elevated stresses in remaining trabeculae after bone resorption.

INTRODUCTION

Recent studies have shown that osteoporosis is not simply a disease of bone loss and microarchitectural degradation but that important changes in tissue composition also occur. Such changes may be a secondary response to early bone loss, but the time sequence of changes in bone mineral distribution is not fully understood. The objective of this study was to quantify the temporal effects of estrogen deficiency on trabecular mineral distribution in the tibia of ovariectomised (OVX) rats.

METHODS

Weekly in vivo micro-CT scans and morphometric and bone mineral density distribution analyses of the proximal tibia were conducted for the first 4 weeks of estrogen deficiency and then at 8, 14 and 34 weeks.

RESULTS

Here we report that although trabecular bone volume and architecture are significantly deteriorated within the first 4 weeks of estrogen deficiency, there is no change in the distribution of bone mineral within trabeculae during this initial period. The rate of bone loss in OVX animals dramatically reduced between week 4 and week 14, which coincided with the initiation of increases in trabecular thickness and mineralisation in the OVX group.

CONCLUSIONS

Together this study reveals for the first time that alterations in bone mineralisation and trabecular thickening arise secondary to the initial rapid bone loss. We propose that these secondary mineralisation changes act to reinforce the trabecular network in an attempt to compensate for the increased loading that ensues after severe bone loss. This study provides an insight into temporal changes in bone mineral distribution in estrogen deficiency.

Sex-specific responses in trabecular and cortical microstructure of tibia due to repeated irradiation from micro-computed tomography in adult CD-1 mice

While repeated in vivo micro-computed tomography (μCT) allows for longitudinal measurement of bone outcomes in rodent models, it is important to determine that the resulting irradiation – dependent on the frequency and number of scans - does not exceed the effects of the intervention. The objective of this study was to determine whether repeated irradiation exposure from μCT scans at 1-month intervals for a total of four scans would alter trabecular or cortical bone structure outcomes and/or bone mineral density in tibias from both male and female CD-1 mice. The right tibia of male (n = 12) and female (n = 11) CD-1 mice were scanned using μCT at 2, 3, 4, and 5 months of age, while the contralateral left tibia served as a control and was scanned only at 5 months of age. All scans were performed at a resolution of 9 μm using a radiation dose of 460 mGy per scan. Some outcomes of trabecular bone structure were affected by repeated irradiation in both males and females. The bone volume fraction was lower in the irradiated right tibia compared to the non-irradiated left tibia in both males (p < 0.05) and females (p < 0.01) as a result of decreased trabecular number (males p < 0.05; females p < 0.05) and increased trabecular separation (males p < 0.05; females p < 0.01). Some cortical measures were also affected in females but not in males, including lower cortical bone periosteal perimeter (p < 0.05), lower total area (p < 0.01) and lower marrow area (p < 0.05) with repeated irradiation. Exposure to repeated radiation at intervals of 1 month, for a total of four scans, altered trabecular bone in both male and female CD-1 mice while outcomes of cortical bone structure were altered only in females.

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Repeated irradiation from in vivoμCT - 4 scans at 1-month intervals - alters trabecular bone in both sexes

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Cortical bone is also altered, but to a lesser degree than trabecular bone and only in females

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Different types of bone are affected in a sex-specific response

A bioceramic scaffold composed of strontium-doped three-dimensional hydroxyapatite whiskers for enhanced bone regeneration in osteoporotic defects

Reconstruction of osteoporotic bone defects is a clinical problem that continues to inspire the design of new materials. Methods: In this work, bioceramics composed of strontium (Sr)-doped hydroxyapatite (HA) whiskers or pure HA whiskers were successfully fabricated by hydrothermal treatment and respectively named SrWCP and WCP. Both bioceramics had similar three-dimensional (3D) porous structures and mechanical strengths, but the SrWCP bioceramic was capable of releasing Sr under physiological conditions. In an osteoporotic rat metaphyseal femoral bone defect model, both bioceramic scaffolds were implanted, and another group that received WCP plus strontium ranelate drug administration (Sr-Ran+WCP) was studied for comparison. Results: At week 1 post-implantation, osteogenesis coupled blood vessels were found to be more common in the SrWCP and Sr-Ran+WCP groups, with substantial vascular-like structures. After 12 weeks of implantation, comparable to the Sr-Ran+WCP group, the SrWCP group showed induction of more new bone formation within the defect as well as at the implant-bone gap region than that of the WCP group. Both the SrWCP and Sr-Ran+WCP groups yielded a beneficial effect on the surrounding trabecular bone microstructure to resist osteoporosis-induced progressive bone loss. While an abnormally high blood Sr ion concentration was found in the Sr-Ran+WCP group, SrWCP showed little adverse effect. Conclusion: Our results collectively suggest that the SrWCP bioceramic can be a safe bone substitute for the treatment of osteoporotic bone defects, as it promotes local bone regeneration and implant osseointegration to a level that strontium ranelate can achieve.

Evaluation of longitudinal time-lapsed in vivo micro-CT for monitoring fracture healing in mouse femur defect models

Longitudinal in vivo micro-computed tomography (micro-CT) is of interest to non-invasively capture the healing process of individual animals in preclinical fracture healing studies. However, it is not known whether longitudinal imaging itself has an impact on callus formation and remodeling. In this study, a scan group received weekly micro-CT measurements (week 0-6), whereas controls were only scanned post-operatively and at week 5 and 6. Registration of consecutive scans using a branching scheme (bridged vs. unbridged defect) combined with a two-threshold approach enabled assessment of localized bone turnover and mineralization kinetics relevant for monitoring callus remodeling. Weekly micro-CT application did not significantly change any of the assessed callus parameters in the defect and periosteal volumes. This was supported by histomorphometry showing only small amounts of cartilage residuals in both groups, indicating progression towards the end of the healing period. Also, immunohistochemical staining of Sclerostin, previously associated with mediating adverse radiation effects on bone, did not reveal differences between groups. The established longitudinal in vivo micro-CT-based approach allows monitoring of healing phases in mouse femur defect models without significant effects of anesthesia, handling and radiation on callus properties. Therefore, this study supports application of longitudinal in vivo micro-CT for healing-phase-specific monitoring of fracture repair in mice.

Bone microarchitectural parameters can detect oxytocin induced changes prior to bone density on mitigating bone deterioration in rabbit osteoporosis model using micro-CT

Background

This study is aimed to determine the efficacy of X-Ray Microtomography (micro-CT) in predicting oxytocin (OT) treatment response in rabbit osteoporosis(OP) model.

Methods

Sixty-five rabbits were randomly divided into three groups: control group, ovariectomy (OVX) -vehicle and OVX-oxytocin group. The controls underwent sham surgery. OVX-vehicle and OVX-oxytocin groups were subjected to bilateral OVX. The rabbits in OVX-oxytocin group were injected with oxytocin. In the 0th, 4th, 8th, 10th and 12th weeks post OVX operation, bone mineral density (BMD) and bone micro-architectural parameters were measured in three groups.

Results

Bone mineral density (BMD), bone volume fraction (BV/TV), Trabecular Number (Tb.N), and Trabecular Thickness (Tb.Th) decreased, while Trabecular Spacing (Tb.Sp) and Structure Model Index (SMI) increased overtime in all the three groups. In OVX-oxytocin group, the bone deterioration tendency is slowing down compared with that of the OVX-vehicle group. The BMD of the OVX-oxytocin group was significantly lower than those in the OVX-vehicle group at 12th week (P = 0.017). BV/TV and Tb.Sp in OVX-oxytocin group changed significantly from 8th week (P = 0.043) and 12th week (P = 0.014), which is earlier than that of BMD and other bone micro-architectural parameters.

Conclusion

BV/TV and Tb.Sp changed prior to BMD and other bone micro-architectural parameters with oxytocin intervention, which indicate that they are more sensitive markers for predicting early osteoporosis and treatment monitoring when using micro-CT to evaluate osteoporosis rabbit model.

Human Disc Nucleotomy Alters Annulus Fibrosus Mechanics at Both Reference and Compressed Loads

Nucleotomy is a common surgical procedure and is also performed in ex vivo mechanical testing to model decreased nucleus pulposus (NP) pressurization that occurs with degeneration. Here, we implement novel and noninvasive methods using magnetic resonance imaging (MRI) to study internal 3D annulus fibrosus (AF) deformations after partial nucleotomy and during axial compression by evaluating changes in internal AF deformation at reference loads (50 N) and physiological compressive loads (∼10% strain). One particular advantage of this methodology is that the full 3D disc deformation state, inclusive of both in-plane and out-of-plane deformations, can be quantified through the use of a high-resolution volumetric MR scan sequence and advanced image registration. Intact grade II L3-L4 cadaveric human discs before and after nucleotomy were subjected to identical mechanical testing and imaging protocols. Internal disc deformation fields were calculated by registering MR images captured in each loading state (reference and compressed) and each condition (intact and nucleotomy). Comparisons were drawn between the resulting three deformation states (intact at compressed load, nucleotomy at reference load, nucleotomy at compressed load) with regard to the magnitude of internal strain and direction of internal displacements. Under compressed load, internal AF axial strains averaged -18.5% when intact and -22.5% after nucleotomy. Deformation orientations were significantly altered by nucleotomy and load magnitude. For example, deformations of intact discs oriented in-plane, whereas deformations after nucleotomy oriented axially. For intact discs, in-plane components of displacements under compressive loads oriented radially outward and circumferentially. After nucleotomy, in-plane displacements were oriented radially inward under reference load and were not significantly different from the intact state at compressed loads. Re-establishment of outward displacements after nucleotomy indicates increased axial loading restores the characteristics of internal pressurization. Results may have implications for the recurrence of pain, design of novel therapeutics, or progression of disc degeneration.

Gushukang inhibits osteocyte apoptosis and enhances BMP-2/Smads signaling pathway in ovariectomized rats

BACKGROUND

Traditional herbal formula Gushukang (GSK) has been clinically applied to treat primary osteoporosis, which can stimulate osteoblastogenesis and improve calcium homeostasis. However, it remains unknown the mechanism that GSK against ovariectomized (OVX) induced damage.

PURPOSE

The aim of this study was to investigate the effect of GSK on BMP-2/Smsds signaling pathway and osteocyte apoptosis which has been reported to play a central role in bone remodeling.

STUDY DESIGN

OVX in rat was established and GSK was administered.

RESULTS

BMP-2/Smsds signaling pathway was inhibited and the number of apoptotic osteocytes was increased in OVX rats. Treatment with GSK significantly enhanced BMP-2/Smsds signaling pathway by up-regulating the expression of BMP-2, p-Smad1 and p-Smad5, Osterix and Runx2, and inhibited osteocyte apoptosis by up-regulating Bcl-xl and down-regulating Bak, which were consistent with histological changes revealed by ALP, Trap and TUNEL staining. GSK treatment improved bone mass and micro-structure of trabecular bone at distal femur in OVX rats shown by BMD, micro-CT measurement and HE staining.

CONCLUSION

These data suggest that GSK exhibited protective effects on promoting bone formation and precluding osteocyte apoptosis. The underlying mechanism may be attributed to its regulation on BMP-2/Smads signaling pathway and Bcl2 family.

Ketogenic diet compromises vertebral microstructure and biomechanical characteristics in mice

Ketogenic diet (KD) compromised the microstructure of cancellous bone and the mechanical property in the appendicular bone of mice, while the effects of KD on the axial bone have not been reported. This study aimed to compare the changes in the microstructure and mechanical properties of the forth lumbar (L4) vertebra in KD and ovariectomized (OVX) mice. Forty eight-week-old female C57BL/6J mice were assigned into four groups: SD (standard diet) + Sham, SD + OVX, KD + Sham, and KD + OVX groups. L4 vertebra was scanned by micro-CT to examine the microstructure of cancellous bone, after which simulative compression tests were performed using finite element (FE) analysis. Vertebral compressive test and histological staining of the L4 and L5 vertebrae were performed to observe the biomechanical and histomorphologic changes. The KD + Sham and SD + OVX exhibited a remarkable declination in the parameters of cancellous bone compared with the SD + Sham group, while KD + OVX demonstrated the most serious bone loss in the four groups. The stiffness was significantly higher in the SD + Sham group than the other three groups, but no difference was found between the remaining groups. The trabecular parameters were significantly correlated with the stiffness. Meanwhile, the OVX + Sham and KD + OVX groups showed a significant decrease in the failure load of compressive test, while there was no difference between the KD + Sham and SD + Sham groups. These findings suggest that KD may compromise the vertebral microstructure and compressive stiffness to a similar level as OVX did, indicating adverse effects of KD on the axial bone of the mice.

The longitudinal effects of ovariectomy on the morphometric, densitometric and mechanical properties in the murine tibia: A comparison between two mouse strains

Oestrogen deficiency-related bone loss in the ovariectomized (OVX) mouse is a common model for osteoporosis. However, a comprehensive in vivo assessment of intervention-related changes in multiple bone properties, and in multiple mouse strains, is required in order to identify an appropriate model for future evaluation of novel anti-osteoporotic therapies. The aim of this study was to evaluate the effect of OVX on the morphometric and densitometric properties measured in the microCT images and the mechanical properties estimated with finite element models of the tibia in two mouse strains, C57BL/6 and BALB/c. 14-weeks-old female C57BL/6 and BALB/c mice were divided into two groups per strain: (1) ovariectomized, (2) non-operated control. The right tibia was scanned at baseline (14 weeks) and then every two weeks thereafter, until 24-weeks-old, using in vivo microCT. Changes in trabecular and cortical bone morphometry, spatiotemporal changes in densitometric properties and in mechanical properties (from micro-finite element (μFE) analysis) were computed. Differences between OVX and non-operated controls were evaluated by ANCOVA, adjusted for 14-weeks baseline. In morphometry, trabecular bone mass was significantly reduced in both C57BL/6 and BALB/c from four weeks following surgery. Though the OVX-effect was transient in BALB/c as bone mass reached skeletal homeostasis. OVX inhibited the age-related thickening of cortical bone only in C57BL/6. In both strains, increments in bone mineral content were significantly lower with OVX only in the proximal tibia, with intervention-related differences increasing with time. OVX had no effect on μFE estimates of stiffness nor failure load in either strain. The results of this study show strain-, time- and region-(trabecular or cortical) dependent changes in morphometric and densitometric properties. These findings highlight the importance of choosing an appropriate mouse model and time points for research of treatments against accelerated bone resorption.

Comparative anti-osteoporotic properties of the leaves and roots of Marantodes pumilum var. alata in postmenopausal rat model

Background

Marantodes pumilum var. alata (MPva), popularly known as Kacip Fatimah, is widely used to maintain female reproductive health, facilitate post-partum recovery and manage symptoms of menopause and osteoporosis in South-East Asia. This study aims to further evaluate the osteoprotective potential of MPva in view of reports of its bone-protective properties in postmenopausal condition.

Methods

Thirty female Sprague-Dawley rats were sorted into 5 groups (n = 6) namely: MPv (leaf treatment); MPr (root treatment); ERT (estrogen treatment); OVXC (untreated ovariectomized control) and Sham (untreated sham-operated control). All rats (except the Sham) were ovariectomized to induce a state of estrogen deficiency that simulates menopause. Two weeks after ovariectomy, the rats were treated for 8 weeks with oral gavages of estrogen and plant extracts. The ERT group received 64.5 μg/kg/day dose of estrogen while MPv and MPr groups received 20 mg/kg/day dose of leaf and root extracts, respectively. At the end of treatment, left femora were excised from euthanized rats and investigated for changes in bone micro-architecture, mineral density, and biomechanical properties.

Results

Bone volume fraction, degree of anisotropy and structure-model-index of bone were significantly improved (p < 0.05) in the MPv group compared to OVXC. Breaking force and maximum stress of bone were also significantly higher (p < 0.05) in the MPv group compared to the OVXC.

Conclusion

Treatment with MPva leaf protected bone microarchitecture and density against osteoporosis-related changes in postmenopausal rats. Similar to estrogen, the protective effects of MPva leaf translated into better-enhanced bone mechanical properties compared to the root treatment.

Time course of rapid bone loss and cortical porosity formation observed by longitudinal μCT in a rat model of CKD

BACKGROUND

Rodent studies of bone in chronic kidney disease have primarily relied on end-point examinations of bone microarchitecture. This study used longitudinal in vivo microcomputed tomography (in vivo μCT) to characterize the onset and progression of bone loss, specifically cortical porosity, in the Cy/+ rat of model of CKD.

METHODS

Male CKD rats and normal littermates were studied. In vivo μCT scans of the right distal tibia repeated at 25, 30, and 35 weeks were analyzed for longitudinal changes in cortical and trabecular bone morphometry. In vitro μCT scans of the tibia and femur identified spatial patterns of bone loss across distal, midshaft and proximal sites.

RESULTS

CKD animals had reduced BV/TV and cortical BV at all time points but developed cortical porosity and thinning between 30 and 35 weeks. Cortical pore formation was localized near the endosteal surface. The severity of bone loss was variable across bone sites, but the distal tibia was representative of both cortical and trabecular changes.

CONCLUSIONS

The distal tibia was found to be a sensitive suitable site for longitudinal imaging of both cortical and trabecular bone changes in the CKD rat. CKD trabecular bone loss progressed through ~30 weeks followed by a sudden acceleration in cortical bone catabolism. These changes varied in timing and severity across individuals, and cortical bone loss and porosity progressed rapidly once initiated. The inclusion of longitudinal μCT in future studies will be important for both reducing the number of required animals and to track individual responses to treatment.

Effect of parathyroid hormone on the structural, densitometric and failure behaviors of mouse tibia in the spatiotemporal space

Parathyroid hormone (PTH) is an anabolic bone drug approved by the US Food and Drug Administration (FDA) to treat osteoporosis. However, previous studies using cross-sectional designs have reported variable and sometimes contradictory results. The aim of the present study was to quantify the localized effect of PTH on the structural and densitometric behaviors of mouse tibia and their links with the global mechanical behavior of bone using a novel spatiotemporal image analysis approach and a finite element analysis technique. Twelve female C57BL/6J mice were divided into two groups: the control and PTH treated groups. The entire right tibiae were imaged using an in vivo micro-computed tomography (μCT) system eight consecutive times. Next, the in vivo longitudinal tibial μCT images were rigidly registered and divided into 10 compartments across the entire tibial space. The bone volume (BV), bone mineral content (BMC), bone tissue mineral density (TMD), and tibial endosteal and periosteal areas (TEA and TPA) were quantified in each compartment. Additionally, finite element models of all the tibiae were generated to analyze the failure behavior of the tibia. It was found that both the BMC and BV started to increase in the proximal tibial region, and then the increases extended to the entire tibial region after two weeks of treatment (p < 0.05). PTH intervention significantly reduced the TEA in most tibial compartments after two weeks of treatment, and the TPA increased in most tibial regions after four weeks of treatment (p < 0.05). Tibial failure loads significantly increased after three weeks of PTH treatment (p < 0.01). The present study provided the first evidence of the localized effect of PTH on bone structural and densitometric properties, as well as their links with the global mechanical behaviors of bone, which are important pieces of information for unveiling the mechanism of PTH intervention.

Combined Extracts of Herba Epimedii and Fructus Ligustri Lucidi Rebalance Bone Remodeling in Ovariectomized Rats

This study aimed to investigate the osteoprotective effect and the possible molecular mechanisms of the combined extracts of Herba Epimedii and Fructus Ligustri Lucidi on postmenopausal osteoporosis (PMOP). Forty-eight female SD rats were sham-operated (Sham, n = 8) or ovariectomized (OVX, n = 40). Then after a week, OVX rats were divided randomly into five groups (n = 8 in each group): OVX, extracts of Herba Epimedii (HE, 0.35 g/kg), extracts of Fructus Ligustri Lucidi (FLL, 0.35 g/kg), combined extracts of HE and FLL (HE & FLL, 0.20 g/kg HE plus 0.15 g/kg FLL), and Raloxifene hydrochloride (RH, 6.25 mg/kg) groups. All groups were administered once daily for 12 weeks. Indicators related to bone remodeling were detected, including estradiol (E₂), bone mineral density (BMD), maximal load, ultimate deflection, micro-CT properties, tartrate-resistant acid phosphatase (TRACP) and alkaline phosphatase (ALP) levels in serum and bone, and the protein and mRNA expression of bone turnover markers (RANKL, M-CSF, Wnt5a, Atp6v0d2, OPG, IGF-1, TGF-β1, and Bmp-2). Results showed that the combined extracts could increase serum E₂ levels and BMD, enhance bone strength, reserve bone microstructure degeneration, promote bone formation, and inhibit bone resorption through upregulating the mRNA and protein expression of OPG, IGF-1, TGF-β1, and Bmp-2, while downregulating RANKL, M-CSF, Wnt5a, and Atp6v0d2. These findings demonstrated that the combined extracts of Herba Epimedii and Fructus Ligustri Lucidi with bone protective effects on OVX rats might be an alternative medicine for the treatment of PMOP.

Can repeated in vivo micro-CT irradiation during adolescence alter bone microstructure, histomorphometry and longitudinal growth in a rodent model?

In vivo micro-computed tomography (micro-CT) can monitor longitudinal changes in bone mass and microstructure in small rodents but imposing high doses of radiation can damage the bone tissue. However, the effect of weekly micro-CT scanning during the adolescence on bone growth and architecture is still unknown. The right proximal tibia of male Sprague-Dawley rats randomized into three dose groups of 0.83, 1.65 and 2.47 Gy (n = 11/group) were CT scanned at weekly intervals from 4th to 12th week of age. The left tibia was used as a control and scanned only at the last time point. Bone marrow cells were investigated, bone growth rates and histomorphometric analyses were performed, and bone structural parameters were determined for both left and right tibiae. Radiation doses of 1.65 and 2.47 Gy affected bone marrow cells, heights of the proliferative and hypertrophic zones, and bone growth rates in the irradiated tibiae. For the 1.65 Gy group, irradiated tibiae resulted in lower BMD, Tb.Th, Tb.N and a higher Tb.Sp compared with the control tibiae. A decrease in BMD, BV/TV, Tb.Th, Tb.N and an increase in Tb.Sp were observed between the irradiated and control tibiae for the 2.47 Gy group. For cortical bone parameters, no effects were noticed for 1.65 and 0.83 Gy groups, but a lower Ct.Th was observed for 2.47 Gy group. Tibial bone development was adversely impacted and trabecular bone, together with bone marrow cells, were negatively affected by the 1.65 and 2.47 Gy radiation doses. Cortical bone microstructure was affected for 2.47 Gy group. However, bone development and morphometry were not affected for 0.83 Gy group. These findings can be used as a proof of concept for using the reasonable high-quality image acquisition under 0.83 Gy radiation doses during the adolescent period of rats without interfering with the bone development process.

Calcium Sulphate/Hydroxyapatite Carrier for Bone Formation in the Femoral Neck of Osteoporotic Rats

This study investigated bone regeneration in the femoral neck canal of osteoporotic rats using a novel animal model. A calcium sulphate (CS)/hydroxyapatite (HA) carrier was used to deliver a bisphosphonate, zoledronic acid (ZA), locally, with or without added recombinant human bone morphogenic protein-2 (rhBMP-2). Twenty-eight-week-old ovariectomized Sprague–Dawley rats were used. A 1 mm diameter and 8 mm long defect was created in the femoral neck by drilling from the lateral cortex in the axis of the femoral neck, leaving the surrounding cortex intact. Three treatment groups and one control group were used: (1) CS/HA alone, (2) CS/HA + ZA (10 μg) (3) CS/HA + ZA (10 μg) + rhBMP-2 (4 μg), and (4) empty defect (control). The bone formation was assessed at 4 weeks post surgery using in vivo micro computed tomography (micro-CT). At 8 weeks post surgery, the animals were sacrificed, and both defect and contralateral femurs were subjected to micro-CT, mechanical testing, and histology. Micro-CT results showed that the combination of CS/HA with ZA or ZA + rhBMP-2 increased the bone formation in the defect when compared to the other groups and to the contralateral hips. Evidence of new dense bone formation in CS/HA + ZA and CS/HA + ZA + rhBMP-2 groups was seen histologically. Mechanical testing results showed no differences in the load to fracture between the treatments in either of the treated or contralateral legs. The CS/HA biomaterial can be used as a carrier for ZA and rhBMP-2 to regenerate bone in the femoral neck canal of osteoporotic rats.

Bone Toolbox: Biomarkers, Imaging Tools, Biomechanics, and Histomorphometry

Bone is a unique tissue with turnover, metabolic, and cellular activities that vary through development to aging and with a mineralized matrix in which the current state and the history of a bone coexist. Qualitative histopathology often lacks sensitivity to detect changes in bone formation, mineralization and resorption, which often requires chronic dosing to result in structural changes such as variation in bone mass and geometry. A large panel of modalities can be used to fully analyze the health of the skeleton, including biomarker evaluation in serum or urine, imaging techniques ranging from radiology to computed tomography, biomechanical testing, and undecalcified tissue processing with bone histomorphometry. The use of clinically relevant biomarkers provides an important noninvasive, sensitive, rapid, and real-time tool to monitor bone activity at the whole skeleton level when conducting safety assessments in a preclinical setting. Imaging modalities also allow in vivo longitudinal assessments with a powerful, noninvasive and clinically translatable tools to monitor drug effects. Different imaging modalities are used in the preclinical studies to evaluate the bone tissues: standard radiography, dual-energy X-ray absorptiometry, peripheral quantitative computed tomography (pQCT), micro-computed tomography, and high-resolution pQCT. Bone histomorphometry is an important tool that provides sensitive evaluation to detect effects of test articles on bone resorption, formation, mineralization, remodeling rates and growth to address a potential target- or class-related theoretical bone liability. Ultimately, the measurement of bone mechanical properties in pharmaceutical testing is critical to understand the potential effects of that pharmaceutical on bone health and fracture risk. Important considerations are required for including these different techniques in toxicology rodents and nonrodent studies, to actually integrate these into safety assessment.

Osteogenic actions of metoprolol in an ovariectomized rat model of menopause

OBJECTIVE

Osteoporosis and hypertension are age-related chronic diseases with increased morbidity rates among postmenopausal women. Clinical epidemiological investigations have demonstrated that hypertensive patients treated with β1-selective β-blockers have a higher bone mineral density (BMD) and lower fracture risk. Nevertheless, no fundamental studies have examined the relationships between β1-selective β-blockers and these effects. The present study explored the effects and mechanisms of metoprolol in the in vitro treatment of osteoblasts and the in vivo treatment of ovariectomy-induced osteoporosis in rats.

METHODS

Primary osteoblasts were obtained by digestion of the cranial bones of 24-hour-old Sprague-Dawley rats. After metoprolol treatment, cell proliferation and differentiation capacities were assessed at the corresponding time points. In addition, 3-month-old female Sprague-Dawley rats (200-220 g) were divided into a sham-operated group (n = 8) and three ovariectomized (OVX) (bilateral removal of ovaries) groups as follows: vehicle (OVX; n = 8), low-dose metoprolol (L-M, oral, 120 mg/kg/d; n = 8), and high-dose metoprolol (H-M, oral, 240 mg/kg/d; n = 8). After 12 weeks of metoprolol treatment, BMD, microarchitecture, and biomechanical properties were evaluated.

RESULTS

The results indicated that the treatments with 0.01 to 0.1 μM metoprolol increased osteoblast proliferation, alkaline phosphatase activity, and calcium mineralization, and promoted the expression of osteogenic genes. The in vivo study indicated that administration of metoprolol to OVX rats resulted in maintenance of the BMDs of the L4 vertebrae. Moreover, amelioration of trabecular microarchitecture deterioration and preservation of bone biomechanical properties were detected in the trabecular bones of the OVX rats.

CONCLUSIONS

Our findings indicate that metoprolol prevents estrogen deficiency-induced bone loss by increasing the number and enhancing the biological functions of osteoblasts, implying its potential use as an alternative treatment for postmenopausal osteoporosis in hypertensive patients.

Intestinal microbiota: a potential target for the treatment of postmenopausal osteoporosis

Postmenopausal osteoporosis (PMO) is a prevalent metabolic bone disease characterized by bone loss and structural destruction, which increases the risk of fracture in postmenopausal women. Owing to the high morbidity and serious complications of PMO, many efforts have been devoted to its prophylaxis and treatment. The intestinal microbiota is the complex community of microorganisms colonizing the gastrointestinal tract. Probiotics, which are dietary or medical supplements consisting of beneficial intestinal bacteria, work in concert with endogenous intestinal microorganisms to maintain host health. Recent studies have revealed that bone loss in PMO is closely related to host immunity, which is influenced by the intestinal microbiota. The curative effects of probiotics on metabolic bone diseases have also been demonstrated. The effects of the intestinal microbiota on bone metabolism suggest a promising target for PMO management. This review seeks to summarize the critical effects of the intestinal microbiota and probiotics on PMO, with a focus on the molecular mechanisms underlying the pathogenic relationship between bacteria and host, and to define the possible treatment options.

In vivo Visualisation and Quantification of Bone Resorption and Bone Formation from Time-Lapse Imaging

PURPOSE OF REVIEW

Mechanoregulation of bone cells was proposed over a century ago, but only now can we visualise and quantify bone resorption and bone formation and its mechanoregulation. In this review, we show how the newest advances in imaging and computational methods paved the way for this breakthrough.

RECENT FINDINGS

Non-invasive in vivo assessment of bone resorption and bone formation was demonstrated by time-lapse micro-computed tomography in animals, and by high-resolution peripheral quantitative computed tomography in humans. Coupled with micro-finite element analysis, the relationships between sites of bone resorption and bone formation and low and high tissue loading, respectively, were shown. Time-lapse in vivo imaging and computational methods enabled visualising and quantifying bone resorption and bone formation as well as its mechanoregulation. Future research includes visualising and quantifying mechanoregulation of bone resorption and bone formation from molecular to organ scales, and translating the findings into medicine using personalised bone health prognosis.

Comparison of ex vivo and in vivo micro-computed tomography of rat tibia at different scanning settings

The parameters of a micro-computed tomography (μCT) scan, including whether a bone is imaged in vivo or ex vivo, determine the quality of the resulting image. In turn, this impacts the accuracy of the trabecular and cortical outcomes. The absolute impact of μCT scanning at different voxel sizes and whether the sample is imaged in vivo or ex vivo on the morphological outcomes of the proximal tibia in the rat is unknown. The right proximal tibia of 6-month-old Sham-control and ovariectomized (OVX) rats (n = 8/group) was scanned using μCT (SkyScan 1176, Bruker, Kontich, Belgium) using three sets of parameters (9 μm ex vivo, 18 μm ex vivo, 18 μm in vivo) to compare the trabecular and cortical outcomes. Regardless of scan protocols, differences between Sham and OVX groups were observed as expected. At a voxel size of 18 μm, scanning in vivo or ex vivo had no effect on any of the outcomes measured. However, compared to a 9 μm voxel size scan, imaging at 18 μm resulted in significant underestimation of the connectivity density (p < 0.05) of the trabecular bone and a significant overestimation (p < 0.05) of the trabecular indices (trabecular thickness, degree of anisotropy) and of the cortical indices (cortical bone area, cortical area fraction, cortical thickness) in both Sham and OVX rats. These results suggest the benefit to scanning the proximal tibia of rats at a voxel size as low as 9 μm, although considerations must be made for the increased acquisition time, anesthesia, animal welfare, and radiation exposure associated with lower voxel size in vivo scanning. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1690-1698, 2017.

Micro-computed tomography characterization of tissue engineering scaffolds: effects of pixel size and rotation step

Quantitative assessment of micro-structure of materials is of key importance in many fields including tissue engineering, biology, and dentistry. Micro-computed tomography (µ-CT) is an intensively used non-destructive technique. However, the acquisition parameters such as pixel size and rotation step may have significant effects on the obtained results. In this study, a set of tissue engineering scaffolds including examples of natural and synthetic polymers, and ceramics were analyzed. We comprehensively compared the quantitative results of µ-CT characterization using 15 acquisition scenarios that differ in the combination of the pixel size and rotation step. The results showed that the acquisition parameters could statistically significantly affect the quantified mean porosity, mean pore size, and mean wall thickness of the scaffolds. The effects are also practically important since the differences can be as high as 24% regarding the mean porosity in average, and 19.5 h and 166 GB regarding the characterization time and data storage per sample with a relatively small volume. This study showed in a quantitative manner the effects of such a wide range of acquisition scenarios on the final data, as well as the characterization time and data storage per sample. Herein, a clear picture of the effects of the pixel size and rotation step on the results is provided which can notably be useful to refine the practice of µ-CT characterization of scaffolds and economize the related resources.

miR-1827 inhibits osteogenic differentiation by targeting IGF1 in MSMSCs

We recently reported that maxillary sinus membrane stem cells (MSMSCs) have osteogenic potential. However, the biological mechanisms of bone formation remain unclear. In this study, we investigated the role and mechanisms of microRNAs (miRNAs) in the osteogenic differentiation of MSMSCs. The expression of miRNAs was determined in differentiated MSMSCs by comprehensive miRNA microarray analysis and quantitative RT-PCR (qRT-PCR). We selected miR-1827 for functional follow-up studies to explore its significance in MSMSCs. Here, miR-1827 was found to be up-regulated during osteogenic differentiation of MSMSCs. Over expression of miR-1827 inhibited osteogenic differentiation of MSMSCs in vitro, whereas the repression of miR-1827 greatly promoted cell differentiation. Further experiments confirmed that insulin-like growth factor 1 (IGF1) is a direct target of miR-1827. miR-1827 inhibited osteogenic differentiation partially via IGF1, which in turn is a positive regulator of osteogenic differentiation. Moreover, miR-1827 suppressed ectopic bone formation and silencing of miR-1827 led to increased bone formation in vivo. In summary, this study is the first to demonstrate that miR-1827 can regulate osteogenic differentiation. The increase in miR-1827 expression observed during osteogenesis is likely a negative feedback mechanism, thus offering a potential therapeutic target to address inadequate bone volume for dental implantation through inhibiting miR-1827.

Can the alendronate dosage be altered when combined with high-frequency loading in osteoporosis treatment?

Alendronate therapy has been associated with serious side effects. Altering the alendronate concentration and combining with high-frequency loading as mechanical intervention was explored in this animal study as a treatment for osteoporosis. The bone anabolic potency of high-frequency loading was overruled by the different alendronate dosages applied in the present study. Further exploration of reduced hormonal therapy associated with mechanical interventions in osteoporosis treatment should be sought.

INTRODUCTION

The aim of the present study was to investigate the effect of alendronate (ALN) administration at two different dosages, associated or not with high-frequency (HF) loading, on the bone microstructural response.

METHODS

Sixty-four female Wistar rats were used, of which 48 were ovariectomized (OVX) and 16 were sham-operated (shOVX). The OVX animals were divided into three groups: two groups were treated with alendronate, at a dosage of 2 mg/kg (ALN(₂)) or at a reduced dosage of 1 mg/kg (ALN(₁)) three times per week. A third OVX group did not receive pharmaceutical treatment. All four groups were mechanically stimulated via whole body vibration (WBV) at HF (up to 150 Hz) or left untreated (shWBV). ALN and HF were administered for 6 weeks, starting at 10-week post-(sh)OVX. Tibia bone structural parameters were analyzed using ex vivo microcomputed tomography.

RESULTS

Trabecular bone loss and structural deterioration resulting from ovariectomy were partially restored by ALN administration, demonstrated by the improvement of trabecular patter factor (Tb.Pf), trabecular separation (Tb.Sp), and structure model index (SMI) of the ALN groups compared to that of the OVX group, regardless of the applied dosage [ALN(₂) or ALN(₁)] or mechanical loading regime (shWBV or WBV). However, a significant positive effect of the ALN(₁) administration on trabecular (decrease of Tb.Sp and SMI) and cortical bone (increase of cortical thickness) microarchitecture compared to that of the OVX status group was observed for both loading regimes was not seen for ALN(₂). Furthermore, HF loading resulted in cortical bone changes, with an increased trabeculary area and endocortical perimeter. Finally, the benefits of a combined therapy of ALN with HF loading could not be discerned in the present experimental conditions.

CONCLUSIONS

The bone anabolic potency of HF loading was overruled by the ALN dosages applied in the present study. Further altering the ALN dosage combined with robust mechanical stimuli needs to be considered in osteoporosis research and eventually therapy.

Radiological features of experimental staphylococcal septic arthritis by micro computed tomography scan

BACKGROUND

Permanent joint dysfunction due to bone destruction occurs in up to 50% of patients with septic arthritis. Recently, imaging technologies such as micro computed tomography (μCT) scan have been widely used for preclinical models of autoimmune joint disorders. However, the radiological features of septic arthritis in mice are still largely unknown.

METHODS

NMRI mice were intravenously or intra-articularly inoculated with S. aureus Newman or LS-1 strain. The radiological and clinical signs of septic arthritis were followed for 10 days using μCT. We assessed the correlations between joint radiological changes and clinical signs, histological changes, and serum levels of cytokines.

RESULTS

On days 5-7 after intravenous infection, bone destruction verified by μCT became evident in most of the infected joints. Radiological signs of bone destruction were dependent on the bacterial dose. The site most commonly affected by septic arthritis was the distal femur in knees. The bone destruction detected by μCT was positively correlated with histological changes in both local and hematogenous septic arthritis. The serum levels of IL-6 were significantly correlated with the severity of joint destruction.

CONCLUSION

μCT is a sensitive method for monitoring disease progression and determining the severity of bone destruction in a mouse model of septic arthritis. IL-6 may be used as a biomarker for bone destruction in septic arthritis.