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Penelope D Ottewell
The primary role of osteoblasts is to lay down new bone during skeletal development and remodelling. Throughout this process osteoblasts directly interact with other cell types within bone, including osteocytes and haematopoietic stem cells. Osteoblastic cells also signal indirectly to bone-resorbing osteoclasts via the secretion of RANKL. Through these mechanisms, cells of the osteoblast lineage help retain the homeostatic balance between bone formation and bone resorption. When tumour cells disseminate in the bone microenvironment, they hijack these mechanisms, homing to osteoblasts and disrupting bone homeostasis...
September 2016: Journal of Bone Oncology
Marc N Wein, Yanke Liang, Olga Goransson, Thomas B Sundberg, Jinhua Wang, Elizabeth A Williams, Maureen J O'Meara, Nicolas Govea, Belinda Beqo, Shigeki Nishimori, Kenichi Nagano, Daniel J Brooks, Janaina S Martins, Braden Corbin, Anthony Anselmo, Ruslan Sadreyev, Joy Y Wu, Kei Sakamoto, Marc Foretz, Ramnik J Xavier, Roland Baron, Mary L Bouxsein, Thomas J Gardella, Paola Divieti-Pajevic, Nathanael S Gray, Henry M Kronenberg
Parathyroid hormone (PTH) activates receptors on osteocytes to orchestrate bone formation and resorption. Here we show that PTH inhibition of SOST (sclerostin), a WNT antagonist, requires HDAC4 and HDAC5, whereas PTH stimulation of RANKL, a stimulator of bone resorption, requires CRTC2. Salt inducible kinases (SIKs) control subcellular localization of HDAC4/5 and CRTC2. PTH regulates both HDAC4/5 and CRTC2 localization via phosphorylation and inhibition of SIK2. Like PTH, new small molecule SIK inhibitors cause decreased phosphorylation and increased nuclear translocation of HDAC4/5 and CRTC2...
October 19, 2016: Nature Communications
Jun Qiu, Fang-Fang Li
Mechanical properties of a single cell and its mechanical response under stimulation play an important role in regulating interactions between cell and extracellular matrix and affecting mechanotransduction. Osteocytes exhibit solid-like viscoelastic behavior in response to the interstitial fluid shear resulting from tissue matrix deformation. This study intends to quantitatively describe the mechanical behavior of osteocytes combining in vitro experiment and fluid-structure interaction (FSI) finite element (FE) model...
October 17, 2016: Biomechanics and Modeling in Mechanobiology
Monica Montesi, Katharina Jähn, Lynda Bonewald, Susanna Stea, Barbara Bordini, Alina Beraudi
Skeletal unloading leads to hypoxia in the bone microenvironment, resulting in imbalanced bone remodeling that favors bone resorption. Osteocytes, the mechanosensors of bone, have been demonstrated to orchestrate bone homeostasis. Hypoxic osteocytes either undergo apoptosis or actively stimulate osteoclasts to remove bone matrix during hypoxia. Oxygen‑regulated protein 150 (ORP150) is an endoplasmic reticulum‑associated chaperone that has been observed to serve an important role in the cellular adaptation to hypoxia and in preventing cellular apoptosis in various tissue types...
September 26, 2016: Molecular Medicine Reports
Bipradas Roy, Mary E Curtis, Letimicia S Fears, Samuel N Nahashon, Hugh M Fentress
Obesity and osteoporosis are two alarming health disorders prominent among middle and old age populations, and the numbers of those affected by these two disorders are increasing. It is estimated that more than 600 million adults are obese and over 200 million people have osteoporosis worldwide. Interestingly, both of these abnormalities share some common features including a genetic predisposition, and a common origin: bone marrow mesenchymal stromal cells. Obesity is characterized by the expression of leptin, adiponectin, interleukin 6 (IL-6), interleukin 10 (IL-10), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), macrophage colony stimulating factor (M-CSF), growth hormone (GH), parathyroid hormone (PTH), angiotensin II (Ang II), 5-hydroxy-tryptamine (5-HT), Advance glycation end products (AGE), and myostatin, which exert their effects by modulating the signaling pathways within bone and muscle...
2016: Frontiers in Physiology
Ibrahim El Deeb Zakhary, Karl Wenger, Mohammed Elsalanty, James Cray, Mohamed Sharawy, Regina Messer
OBJECTIVE: The mandible is continuously undergoing remodeling as a result of mechanobiologic factors, such as chewing forces, tooth loss, orthodontic forces, and periodontitis. The effects of mechanical stress and biologic signals in bone homeostasis have been the focus of many investigations. However, much of this research utilized osteocytes derived from long bones, but little is known about the mandible-derived osteocytes. This study tests a protocol to isolate and grow osteocytes from rat mandible...
September 9, 2016: Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology
Aline G Costa, Serge Cremers, John P Bilezikian
Sclerostin a potent regulator of bone formation, is an antagonist of the Wnt-signaling pathway. The advent of assays to measure circulating sclerostin has enabled research to be performed with the aim to understand the potential role of circulating sclerostin as a pathophysiological marker in a variety of clinical settings. At this time, however, assays to measure circulating sclerostin are still relatively new and have not demonstrated consistent internal agreement in addition to which there are differences between serum and plasma levels...
October 11, 2016: Bone
Gabriel L Galea, Lance E Lanyon, Joanna S Price
Mechanical loading is the primary functional determinant of bone mass and architecture, and osteocytes play a key role in translating mechanical signals into (re)modelling responses. Although the precise mechanisms remain unclear, Wnt signalling pathway components, and the anti-osteogenic canonical Wnt inhibitor Sost/sclerostin in particular, play an important role in regulating bone's adaptive response to loading. Increases in loading-engendered strains down-regulate osteocyte sclerostin expression, whereas reduced strains, as in disuse, are associated with increased sclerostin production and bone loss...
October 12, 2016: Bone
Jesus Delgado-Calle, Amy Y Sato, Teresita Bellido
After discovering that lack of Sost/sclerostin expression is the cause of the high bone mass human syndromes Van Buchem disease and sclerosteosis, extensive animal experimentation and clinical studies demonstrated that sclerostin plays a critical role in bone homeostasis and that its deficiency or pharmacological neutralization increases bone formation. Dysregulation of sclerostin expression also underlies the pathophysiology of skeletal disorders characterized by loss of bone mass as well as the damaging effects of some cancers in bone...
October 11, 2016: Bone
Jolanda R Vetsch, Ralph Müller, Sandra Hofmann
Bone remodelling is the continuous turnover of bone by resorption and formation. It is controlled by interstitial fluid flow sensed by osteocytes. The refilling of bone resorption sites has been shown to be curvature driven. In vitro, curvature influences tissue growth and cytoskeletal arrangements under static and perfused conditions. Nevertheless, this has only been demonstrated for non-mineralized tissue in limited three-dimensional volumes. This study aims at investigating the influence of three different channel curvatures (S, -2...
October 2016: Journal of the Royal Society, Interface
Yuko Fujiwara, Marilina Piemontese, Yu Liu, Jeff D Thostenson, Jinhu Xiong, Charles A O'Brien
The cytokine receptor activator of NFkB ligand (RANKL) produced by osteocytes is essential for osteoclast formation in cancellous bone under physiological conditions and RANKL production by B lymphocytes is required for the bone loss caused by estrogen deficiency. Here, we examined whether RANKL produced by osteocytes is also required for the bone loss caused by estrogen deficiency. Mice lacking RANKL in osteocytes were protected from the increase in osteoclast number and the bone loss caused by ovariectomy...
October 12, 2016: Journal of Biological Chemistry
Patience Meo Burt, Liping Xiao, Caroline Dealy, Melanie C Fisher, Marja M Hurley
Humans with X-linked hypophosphatemia (XLH) and Hyp mice, the murine homologue of the disease, develop severe osteoarthropathy and the precise factors that contribute to this joint degeneration remain largely unknown. Fibroblast growth factor 2 (FGF2) is a key regulatory growth factor in osteoarthritis. Although there are multiple FGF2 isoforms the potential involvement of specific FGF2 isoforms in joint degradation has not been investigated. Mice that overexpress the high molecular weight FGF2 isoforms in bone (HMWTg mice) phenocopy Hyp mice and XLH subjects and Hyp mice overexpress the HMWFGF2 isoforms in osteoblasts and osteocytes...
October 12, 2016: Endocrinology
Lixia Fan, Shaopeng Pei, X Lucas Lu, Liyun Wang
The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system (LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching (FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis (FEA) approach...
2016: Bone Research
Laura Frese, Petra E Dijkman, Simon P Hoerstrup
In regenerative medicine, adult stem cells are the most promising cell types for cell-based therapies. As a new source for multipotent stem cells, human adipose tissue has been introduced. These so called adipose tissue-derived stem cells (ADSCs) are considered to be ideal for application in regenerative therapies. Their main advantage over mesenchymal stem cells derived from other sources, e.g. from bone marrow, is that they can be easily and repeatable harvested using minimally invasive techniques with low morbidity...
July 2016: Transfusion Medicine and Hemotherapy
Xingbin Hu, Mayra Garcia, Lihong Weng, Xiaoman Jung, Jodi L Murakami, Bijender Kumar, Charles D Warden, Ivan Todorov, Ching-Cheng Chen
Microenvironment cues received by haematopoietic stem cells (HSC) are important in regulating the choice between self-renewal and differentiation. On the basis of the differential expression of cell-surface markers, here we identify a mesenchymal stromal progenitor hierarchy, where CD45(-)Ter119(-)CD31(-)CD166(-)CD146(-)Sca1(+)(Sca1(+)) progenitors give rise to CD45(-)Ter119(-)CD31(-)CD166(-)CD146(+)(CD146(+)) intermediate and CD45(-)Ter119(-)CD31(-)CD166(+)CD146(-)(CD166(+)) mature osteo-progenitors. All three progenitors preserve HSC long-term multi-lineage reconstitution capability in vitro; however, their in vivo fates are different...
October 10, 2016: Nature Communications
Bilu Xiang, Yang Liu, Lu Xie, Qian Zhao, Ling Zhang, Xueqi Gan, Haiyang Yu
Osteoclasts demineralize and resorb bone once they attach to its surface. However, it's still unclear how the osteoclasts choose the specific sites for their attachments. It is postulated in this article that the decreased extracellular free ionized calcium concentration (Ca(2+)[e]) can provide a microenvironment for osteoclasts to recognize and then initiate the attachment process. The osteoclasts initially attach to the bone surface via integrating its integrin αvβ3 and RGD containing ligands in bone matrix...
October 7, 2016: Cell Biochemistry and Biophysics
Christian Schem, Robert J Tower, Philipp Kneissl, Anna-Christina Rambow, Graeme M Campbell, Christine Desel, Timo Damm, Thorsten Heilmann, Sabine Fuchs, Maaz Zuharya, Anna Trauzold, Claus C Glüer, Sarah Schott, Sanjay Tiwari
Bisphosphonates have effects which are anti-resorptive, anti-tumor and anti-apoptotic to osteoblasts and osteocytes, but an effective means of eliciting these multiple activities in the treatment of bone metastases has not been identified. Antimetabolite-bisphosphonate conjugates have potential for improved performance as a class of bone specific anti-neoplastic drugs. The primary objective of the study was to determine whether an antimetabolite-bisphosphonate conjugate will preserve bone formation concomitant with anti-resorptive and anti-tumor activity...
October 7, 2016: Journal of Bone and Mineral Research: the Official Journal of the American Society for Bone and Mineral Research
J Delgado-Calle, X Tu, R Pacheco-Costa, K McAndrews, R Edwards, G Pellegrini, K Kuhlenschmidt, N Olivos, A Robling, M Peacock, L I Plotkin, T Bellido
Osteocytes integrate the responses of bone to mechanical and hormonal stimuli by mechanisms poorly understood. We report here that mice with conditional deletion of the parathyroid hormone (PTH) receptor 1 (Pth1r) in DMP1-8kb-expressing cells (cKO) exhibit a modest decrease in bone resorption leading to a mild increase in cancellous bone without changes in cortical bone. However, bone resorption in response to endogenous chronic elevation of PTH in growing or adult cKO mice induced by a low calcium diet remained intact, as the increased bone remodeling and bone loss was indistinguishable from that exhibited by control littermates...
October 5, 2016: Journal of Bone and Mineral Research: the Official Journal of the American Society for Bone and Mineral Research
Evangelia Kalaitzoglou, Iuliana Popescu, R Clay Bunn, John L Fowlkes, Kathryn M Thrailkill
PURPOSE OF REVIEW: To describe the effects of type 1 diabetes on bone cells. RECENT FINDINGS: Type 1 diabetes (T1D) is associated with low bone mineral density, increased risk of fractures, and poor fracture healing. Its effects on the skeleton were primarily attributed to impaired bone formation, but recent data suggests that bone remodeling and resorption are also compromised. The hyperglycemic and inflammatory environment associated with T1D impacts osteoblasts, osteocytes, and osteoclasts...
October 4, 2016: Current Osteoporosis Reports
Hongwang Cui, Yongjun Zhu, Qiming Yang, Weikang Zhao, Shiyang Zhang, Ao Zhou, Dianming Jiang
Estrogen (E2) deficiency has been associated with accelerated osteocyte apoptosis. Our previous study showed necroptosis accelerated the loss of osteocytes in E2 deficiency-induced osteoporosis in rats in addition to apoptosis, but the mechanism involved remains. Necroptosis is a caspase-independent form of programmed cell death. In the necroptosis pathway, receptor interaction proteins 1 and 3 (RIP1/3) play vital roles. Necrostatin-1 (Nec-1) has been confirmed to be a specific inhibitor of necroptosis. However, the effect of Nec-1 on postmenopausal osteoporosis remains ambiguous...
October 5, 2016: Scientific Reports
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