Prediction of bone adaptation in response to mechanical loading is useful in the clinical management of osteoporosis. However, few studies have investigated the effect of repeated mechanical loading in the mouse tibia. Therefore, this study uses a combined experimental and computational approach to evaluate the effect of mechanical loading on bone adaptation in a mouse model of osteoporosis. Six female C57BL/6 mice were ovariectomised (OVX) at week 14 and scanned using in vivo micro computed tomography (10.4µm/voxel) at week 14, 16, 18, 20 and 22. The right tibiae were mechanically loaded in vivo at week 19 and 21 with a 12N peak load, 40 cycles/day, 3 days/week. Linear isotropic homogeneous finite element (microFE) models were created from the tissue mineral density calibrated microCT images. Changes in bone adaptation, densitometric and spatial analyses were measured by comparing the longitudinal images after image registration.Abstract
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Sclerostin (SOST) is an endogenous inhibitor of Wnt/β-catenin signalling pathway to impair osteogenic differentiation and bone anabolism. SOST immunotherapy like monoclonal antibody has been observed to control bone remodeling and regeneration. This study is aimed to develop a SOST vaccine and test its protective effects on estrogen deficiency-induced bone loss in mice. Gene sequences coded SOST peptide putative targeting Wnt co-receptor LRP5 were cloned and constructed into vectors expressing Fc fragment to produced SOST-Fc fusion protein. Mice were subcutaneously injected SOST-Fc to boost anti-SOST antibody. Bone mineral density, microstructure, and mechanical property were quantified using μCT scanning and material testing system. Serum bone formation and resorption markers and anti-SOST levels were measured using ELISA. SOST-Fc injections significantly increased serum anti-SOST antibody levels but reduced serum SOST concentrations. SOST-Fc vaccination significantly reduced estrogen deficiency-induced serum bone resorption markers CTX-1 increased serum bone formation marker osteocalcin. Of note, it significantly alleviated the severity of estrogen-induced loss of bone mineral density, trabecular morphometric properties, and biomechanical forces of bone tissue. Mechanistically, SOSF-Fc vaccination attenuated trabecular loss histopathology and restored immunostaining of Wnt pathway like Wnt3a, β-catenin, and TCF4 in bone tissue along with increased serum osteoclast inhibitor OPG levels but decreased serum osteoclast enhancer RANKL concentrations. Taken together, SOST-Fc vaccination boosts anti-SOST antibody to neutralize SOST and mitigates the estrogen deficiency-induced bone mass and microstructure deterioration through preserving Wnt signalling. This study highlights an innovative remedial potential of SOST vaccine for preventing osteoporosis.
The expression of the mechanosensor, integrin αvβ3, is reduced in osteoporotic bone cells compared to controls. MLO-Y4 osteocytes experience altered mechanotransduction under estrogen deficiency and it is unknown whether this is associated with defective αvβ3 expression or signalling. The objectives of this study are to (1) investigate αvβ3 expression and spatial organisation in osteocytes during estrogen deficiency, and (2) establish whether altered responses of osteocytes under estrogen deficiency correlate to defective αvβ3 expression and functionality. MLO-Y4 cells were cultured as follows: Ctrl (no added estradiol), E+ (10nM 17β-estradiol for 5 days), and Ew (10nM 17β-estradiol for 3 days and withdrawal for 2 days). Cells were cultured with/without 0.5µM IntegriSense750 (αvβ3 antagonist). Laminar oscillatory fluid flow of 1Pa at 0.5Hz was applied for 1hr. αvβ3 content was quantified using an ELISA. The location and quantity of αvβ3 and focal-adhesions was determined by immunocytochemistry. Estrogen withdrawal under static conditions led to lower cell and focal-adhesion area (p<0.05), compared to E+ cells. Fluid flow led to higher αvβ3 content (p<0.05) in all groups, compared to static counterparts, with αvβ3 blocking altering this response. Fluid flow on Ew cells had the highest αvβ3 levels (p<0.05), but αvβ3 did not localise at focal-adhesions sites. Cell morphologies were similar after treatment with the αvβ3 antagonist to the Ew group. These results suggest there are fewer functional focal-adhesion sites at which αvβ3 integrins localise to facilitate mechanotransduction. To further understand these results, we are analysing osteocyte mechanotransduction by quantifying PGE2 and gene expression (COX-2, RANKL, OPG, SOST).
MicroRNAs are non-coding small RNAs that reportedly regulate mRNA targets or protein translation of various tissues in physiological and pathological contexts. This study was undertaken to characterise the contributions of microRNA-29a (miR-29a) to the progression of estrogen deficiency-mediated excessive osteoclast resorption and bone loss. Osteoblast-specific transgenic mice overexpressing miR-29a driven by osteocalcin promoter (C57BL/6JNarl-TgOCN-mir29a) or wild-type mice were subjected to bilateral ovariectomy. Bone mineral density, trabecular microarchitecture and osteoclast distribution was quantified by μCT and histomorphometry. Primary CD11b+CSF-1R+ preosteoclasts were isolated for detecting ex vivo osteoclast differentiation. Gene expression and transcription factor-promoter interaction were quantified by RT-PCR and chromatin immunoprecipitation.Background
Methods
3D cell culture studies more accurately represent the complex
Osteoporosis has long been associated with weak bones but recent studies have shown that bone tissue mineral becomes more heterogeneous and the expression of mechanosensors are altered during estrogen deficiency in an animal model of osteoporosis. However, whether these changes occur as a primary response to estrogen deficiency is unknown. In this study we investigate whether matrix production and mineralisation by mechanically-stimulated osteoblasts are impaired as a direct consequence of estrogen depletion. Osteoblast-like MC3T3-E1 cells were cultured for 14 days with 10−8M of 17β-estradiol and subsequently cultured with osteogenic media only, or supplemented with estrogen or an estrogen antagonist (Fulvestrant, 10−7M). Physiological shear stress (1Pa) was applied using an orbital shaker (290rpm, 40min/day), which allows long-term culture and induces oscillatory flow on cells. Osteoblasts phenotype, extracellular matrix (ECM), mineralisation and mechanosensors were tracked by qRT-PCR (Runx2, Col1a1, Col1a2, Cox2, Bglap2, FN1), by biochemical assays (ALP activity, DNA and calcium content), by immunostaining (integrin αv, BSP2, fibronectin) and by labelling with calcein the calcium. The results of this study demonstrate that after 7 days, estrogen depleted cells had less integrin αv mechanosensors compared to those that received continuous estrogen treatment. By 14 days the ECM formation (calcium, fibronectin) by osteoblasts was altered under estrogen depletion, when compared to cells that were cultured continuously with estrogen. This study provides evidence of changes in osteoblast behaviour under estrogen depletion, which might explain the alteration in tissue mineral content and the decrease of integrins observed previously in ovariectomized rats
Objectives. Ligaments which heal spontaneously have a healing process that
is similar to skin wound healing. Menopause impairs skin wound healing
and may likewise impair ligament healing. Our purpose in this study
was to investigate the effect of surgical menopause on ligament
healing in a rabbit medial collateral ligament model. Methods. Surgical menopause was induced with ovariohysterectomy surgery
in adult female rabbits. Ligament injury was created by making a
surgical gap in the midsubstance of the medial collateral ligament.
Ligaments were allowed to heal for six or 14 weeks in the presence
or absence of
Cellular movement and relocalisation are important for many physiologic properties. Local mesenchymal stem cells (MSCs) from injured tissues and circulating MSCs aid in fracture healing. Cytokines and chemokines such as Stromal cell-derived factor 1(SDF-1) and its receptor chemokine receptor type 4 (CXCR4) play important roles in maintaining mobilisation, trafficking and homing of stem cells from bone marrow to the site of injury. We investigated the differences in migration of MSCs from the femurs of young, adult and ovariectomised (OVX) rats and the effect of CXCR4 over-expression on their migration. MSCs from young, adult and OVX rats were put in a Boyden chamber to establish their migration towards SDF-1. This was compared with MSCs transfected with CXCR4, as well as MSCs differentiated to osteoblasts.Objectives
Methods
Osteoporosis has become an increasing concern for older people as it may potentially lead to osteoporotic fractures. This study is designed to assess the efficacy and safety of ten therapies for post-menopausal women using network meta-analysis. We conducted a systematic search in several databases, including PubMed and Embase. A random-effects model was employed and results were assessed by the odds ratio (OR) and corresponding 95% confidence intervals (CI). Furthermore, with respect to each outcome, each intervention was ranked according to the surface under the cumulative ranking curve (SUCRA) value.Objectives
Methods
In order to screen the altered gene expression profile in peripheral blood mononuclear cells of patients with osteoporosis, we performed an integrated analysis of the online microarray studies of osteoporosis. We searched the Gene Expression Omnibus (GEO) database for microarray studies of peripheral blood mononuclear cells in patients with osteoporosis. Subsequently, we integrated gene expression data sets from multiple microarray studies to obtain differentially expressed genes (DEGs) between patients with osteoporosis and normal controls. Gene function analysis was performed to uncover the functions of identified DEGs.Objectives
Methods
Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass and deterioration of bone microarchitecture, which results in increased bone fragility and fracture risk. Casein kinase 2-interacting protein-1 (CKIP-1) is a protein that plays an important role in regulation of bone formation. The effect of CKIP-1 on bone formation is mainly mediated through negative regulation of the bone morphogenetic protein pathway. In addition, CKIP-1 has an important role in the progression of osteoporosis. This review provides a summary of the recent studies on the role of CKIP-1 in osteoporosis development and treatment.
The treatment of osteoporotic fractures is a major challenge, and the enhancement of healing is critical as a major goal in modern fracture management. Most osteoporotic fractures occur at the metaphyseal bone region but few models exist and the healing is still poorly understood. A systematic review was conducted to identify and analyse the appropriateness of current osteoporotic metaphyseal fracture animal models. A literature search was performed on the Pubmed, Embase, and Web of Science databases, and relevant articles were selected. A total of 19 studies were included. Information on the animal, induction of osteoporosis, fracture technique, site and fixation, healing results, and utility of the model were extracted.Objectives
Materials and Methods
This study aims to evaluate if micro-CT can work as a method for the 3D assessment and analysis of cancellous bone by comparing micro-CT with undecalcified histological sections in OVX rats. The mandible and tibia of sham, ovariectomised (OVX) and zoledronate-injected ovariectomised (OVX-ZOL) rats were assessed morphometrically. Specimens were scanned by micro-CT. Undecalcified histological sections were manufactured from the specimen scanned by micro-CT and stained with haematoxylin and eosin. Bivariate linear regressions and one-way analysis of variance were undertaken for statistics using SPSS 16.0.1 software.Objectives
Methods
Sex hormones play important roles in the regulation of the proliferation, maturation and death of chondrocytes in the epiphyseal growth plate. We have investigated the effects of male castration on the cell kinetics of chondrocytes as defined by the numbers of proliferating and dying cells. The growth plates of normal rabbits and animals castrated at eight weeks of age were obtained at 10, 15, 20 and 25 weeks of age. Our study suggested that castration led to an increase in apoptosis and a decrease in the proliferation of chondrocytes in the growth plate. In addition, the number of chondrocytes in the castrated rabbits was less than that of normal animals of the same age.