Browsing by Subject "osteoblast"

Now showing 1 - 9 of 9
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    Bisphosphonates suppress periosteal osteoblast activity independently of resorption in rat femur and tibia
    (2006-05) Iwata, Ken; Li, Jiliang; Follet, Helene; Phipps, Roger J; Burr, David B.
    Recent studies demonstrate that bisphosphonates suppress bone resorption by leading to apoptosis of the osteoclast and inhibiting the differentiation to mature osteoclasts. The influence of bisphosphonates on bone formation is unknown, although it has been hypothesized that bisphosphonates inhibit osteoblast apoptosis and stimulate osteoblast proliferation and differentiation in vitro, leading to increased bone formation. The purpose of this study was to investigate the effect of bisphosphonates on bone formation. We administered risedronate at 0.05, 0.5 or 5.0 μg/kg/day or alendronate at 0.1, 1.0 or 10 μg/kg/day subcutaneously for 17 days to 6-month-old female Sprague–Dawley rats. Control rats were given a daily subcutaneous injection of saline. Following sacrifice, the femoral and tibial mid-diaphyses were harvested and mineralizing surface (MS/BS), mineral apposition rate (MAR) and bone formation rate (BFR/BS) were measured on periosteal and endocortical surfaces. In the femur, periosteal MAR was significantly lower in all treatment groups (22–29% for risedronate, 26–36% for alendronate) than in control. In the tibia, periosteal MAR and BFR of all treatment groups were significantly lower (41–50% for risedronate, 43–52% for alendronate) than in the control group. Because the periosteal surfaces of these bones are only undergoing bone formation in modeling mode, our results show that bisphosphonates suppress bone formation independently of bone resorption. Because this effect is seen on periosteal MAR rather than on periosteal MS/BS, we hypothesize that bisphosphonates affect the activity of individual osteoblasts at the cell level. This may help to explain the reason that the anabolic effects of teriparatide are blunted when administered concurrently with or following a course of bisphosphonates in humans.
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    Chapter Six - Molecular signaling in bone cells: Regulation of cell differentiation and survival
    (Elsevier, 2019-02-04) Plotkin, Lilian I.; Bruzzaniti, Angela; Biomedical Sciences and Comprehensive Care, School of Dentistry
    The achievement of proper bone mass and architecture, and their maintenance throughout life requires the concerted actions of osteoblasts, the bone forming cells, and osteoclasts, the bone resorbing cells. The differentiation and activity of osteoblasts and osteoclasts are regulated by molecules produced by matrix-embedded osteocytes, as well as by cross-talk between osteoblasts and osteoclasts through secreted factors. In addition, it is likely that direct contact between osteoblast and osteoclast precursors, and the contact of these cells with osteocytes and cells in the bone marrow, also modulate bone cell differentiation and function. With the advancement of molecular and genetic tools, our comprehension of the intracellular signals activated in bone cells has evolved significantly, from early suggestions that osteoblasts and osteoclasts have common precursors and that osteocytes are inert cells in the bone matrix, to the very sophisticated understanding of a network of receptors, ligands, intracellular kinases/phosphatases, transcription factors, and cell-specific genes that are known today. These advances have allowed the design and FDA-approval of new therapies to preserve and increase bone mass and strength in a wide variety of pathological conditions, improving bone health from early childhood to the elderly. We have summarized here the current knowledge on selected intracellular signal pathways activated in osteoblasts, osteocytes, and osteoclasts.
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    Dose analysis of photobiomodulation therapy on osteoblast, osteoclast, and osteocyte
    (SPIE, 2018-07) Na, Sungsoo; TruongVo, ThucNhi; Jiang, Feifei; Joll, Jeffery E.; Guo, Yunxia; Utreja, Achint; Chen, Jie; Biomedical Engineering, School of Engineering and Technology
    The objective of this study was to evaluate the effects of varying light doses on the viability and cellular activity of osteoblasts, osteocytes, and osteoclasts. A light application device was developed to apply 940-nm wavelength light from light-emitting diodes on three cultured cells, MC3T3-E1, MLO-A5, and RANKL-treated RAW264.7 cells. The doses (energy density) on cells were 0, 1, 5, and 7.5  J  /  cm2. The corresponding light power densities at the cell site were 0, 1.67, 8.33, and 12.5  mW  /  cm2, respectively, and the duration was 10 min. The results showed that the three cell types respond differently to light and their responses were dose dependent. Low-dose treatment (1  J  /  cm2) enhanced osteoblast proliferation, osteoclast differentiation, and osteoclastic bone resorption activity. Osteocyte proliferation was not affected by both low- and high-dose (5  J  /  cm2) treatments. While 1  J  /  cm2 did not affect viability of all three cell types, 5  J  /  cm2 significantly decreased viability of osteocytes and osteoclasts. Osteoblast viability was negatively impacted by the higher dose (7.5  J  /  cm2). The findings suggest that optimal doses exist for osteoblast and osteoclast, which can stimulate cell activities, and there is a safe dose range for each type of cell tested.
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    The effects of electromagnetic wave stimulation (EMS) on osteoblast differentiation and activity
    (2020-06) Pauly, Katherine L.; Spolnik, Kenneth; Bruzzaniti, Angela; Ehrlich, Ygal; Bringas, Josef S.
    Introduction: The goal of nonsurgical root canal therapy is to reduce the bacterial load within an infected root canal system, and the subsequent objective is to prevent or treat apical periodontitis. Clinical studies have shown more expedient healing of apical periodontitis treated with electromagnetic wave stimulation (EMS) as compared to apical periodontitis not treated with EMS. Stimulation of osteoblasts and growth factors has been shown when EMS was applied to rat calvaria, resulting in increased bone healing. Objective: The purpose of this vitro study was to evaluate the effects of EMS on the proliferation and differentiation of osteoblasts. Using primary neonatal calvaria osteoblast-lineage cells, the effects of different EMS regimens on proliferation, alkaline phosphatase (ALP) activity, and mineral deposition were determined. Materials and Methods: EMS regimen included currents of 0mA, 0.1mA, 1mA, and 10mA delivered for five consecutive 1s pulses per day for one, two, and three days. Cell proliferation was assayed after 1 or 2 days using an MTS assay. Alkaline phosphatase activity and mineral deposition were assayed after culturing the cells in osteogenic media containing ascorbic acid and -glycerol phosphate for 7 days. Comparisons were performed using analysis of variance, with a 5% significance level. Results: There was no statistically significant differences noted in MTS proliferation and mineral deposition between the experiment EMS treatment groups of 0.1, 1.0, and 10.0 mA compared to the control group of 0 mA current on calvaria-derived osteoblast. While there were no statistically significant differences noted in ALP activity in the 0.1, and 1.0 mA EMS groups, compared to 0 mA control, alkaline phosphatase activity was significantly increased in the 10 mA EMS group. Conclusion: There was no significant differences in MTS proliferation and mineral deposition of the EMS group compared to the control group. However, 10 mA EMS favored increased ALP activity suggesting EMS can promote matrix maturation by osteoblasts. Additional in vitro experimental studies, including different stem cell populations, culture duration and EMS treatment regimens are needed to understand the mechanism of action of EMS for future applications in regenerative endodontics.
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    Estrogen receptor-β regulates mechanical signaling in primary osteoblasts
    (American Physiological Society (APS), 2014-04-15) Castillo, Alesha B.; Triplett, Jason W.; Pavalko, Fredrick M.; Turner, Charles H.; Department of Cellular & Integrative Physiology, IU School of Medicine
    Mechanical loading is an important regulator in skeletal growth, maintenance, and aging. Estrogen receptors have a regulatory role in mechanically induced bone adaptation. Estrogen receptor-α (ERα) is known to enhance load-induced bone formation, whereas ERβ negatively regulates this process. We hypothesized that ERβ regulates mechanical signaling in osteoblasts. We tested this hypothesis by subjecting primary calvarial cells isolated from wild-type and ERβ-knockout mice (BERKO) to oscillatory fluid flow in the absence or presence of estradiol (E2). We found that the known responses to fluid shear stress, i.e., phosphorylation of the mitogen-activated protein kinase ERK and upregulation of COX-2 expression, were inhibited in BERKO cells in the absence of E2. Flow-induced increase in prostaglandin E2 (PGE2) release was not altered in BERKO cells in the absence of E2, but was increased when E2 was present. Additionally, immunofluorescence analysis and estrogen response element luciferase assays revealed increased ERα expression and flow- and ligand-induced nuclear translocation as well as transcriptional activity in BERKO cells in both the presence and absence of E2. Taken together, these data suggest that ERβ plays both ligand-dependent and ligand-independent roles in mechanical signaling in osteoblasts. Furthermore, our data suggest that one mechanism by which ERβ regulates mechanotransduction in osteoblasts may result from its inhibitory effect on ERα expression and function. Targeting estrogen receptors (e.g., inhibiting ERβ) may represent an effective approach for prevention and treatment of age-related bone loss.
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    Optineurin regulates osteoblastogenesis through STAT1
    (Elsevier, 2020-05) Mizuno, Noriyoshi; Iwata, Tomoyuki; Ohsawa, Ryosuke; Ouhara, Kazuhisa; Matsuda, Shinji; Kajiya, Mikihito; Matsuda, Yukiko; Kume, Kodai; Tada, Yui; Morino, Hiroyuki; Yoshimoto, Tetsuya; Ueki, Yasuyoshi; Mihara, Keichiro; Sotomaru, Yusuke; Takeda, Katsuhiro; Munenaga, Syuichi; Fujita, Tsuyoshi; Kawaguchi, Hiroyuki; Shiba, Hideki; Kawakami, Hideshi; Kurihara, Hidemi; Biomedical Sciences and Comprehensive Care, School of Dentistry
    A sophisticated and delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts regulates bone metabolism. Optineurin (OPTN) is a gene involved in primary open-angle glaucoma and amyotrophic lateral sclerosis. Although its function has been widely studied in ophthalmology and neurology, recent reports have shown its possible involvement in bone metabolism through negative regulation of osteoclast differentiation. However, little is known about the role of OPTN in osteoblast function. Here, we demonstrated that OPTN controls not only osteoclast but also osteoblast differentiation. Different parameters involved in osteoblastogenesis and osteoclastogenesis were assessed in Optn−/- mice. The results showed that osteoblasts from Optn−/- mice had impaired alkaline phosphatase activity, defective mineralized nodules, and inability to support osteoclast differentiation. Moreover, OPTN could bind to signal transducer and activator of transcription 1 (STAT1) and regulate runt-related transcription factor 2 (RUNX2) nuclear localization by modulating STAT1 levels in osteoblasts. These data suggest that OPTN is involved in bone metabolism not only by regulating osteoclast function but also by regulating osteoblast function by mediating RUNX2 nuclear translocation via STAT1.
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    The proto‐oncogene function of Mdm2 in bone
    (Wiley, 2018-11) Olivos, David J., III; Perrien, Daniel S.; Hooker, Adam; Cheng, Ying-Hua; Fuchs, Robyn K.; Hong, Jung Min; Bruzzaniti, Angela; Chun, Kristin; Eischen, Christine M.; Kacena, Melissa A.; Mayo, Lindsey D.; Pediatrics, School of Medicine
    Mouse double minute 2 (Mdm2) is a multifaceted oncoprotein that is highly regulated with distinct domains capable of cellular transformation. Loss of Mdm2 is embryonically lethal, making it difficult to study in a mouse model without additional genetic alterations. Global overexpression through increased Mdm2 gene copy number (Mdm2Tg) results in the development of hematopoietic neoplasms and sarcomas in adult animals. In these mice, we found an increase in osteoblastogenesis, differentiation, and a high bone mass phenotype. Since it was difficult to discern the cell lineage that generated this phenotype, we generated osteoblast‐specific Mdm2 overexpressing (Mdm2TgOb) mice in 2 different strains, C57BL/6 and DBA. These mice did not develop malignancies; however, these animals and the MG63 human osteosarcoma cell line with high levels of Mdm2 showed an increase in bone mineralization. Importantly, overexpression of Mdm2 corrected age‐related bone loss in mice, providing a role for the proto‐oncogenic activity of Mdm2 in bone health of adult animals.
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    A Pyk2 Inhibitor Incorporated into a PEGDA-Gelatin Hydrogel Promotes Osteoblast Activity and Mineral Deposition
    (IOP, 2019-03) Posritong, Sumana; Chavez, Regina Flores; Chu, Tien-Min Gabriel; Bruzzaniti, Angela; Biomedical Sciences and Comprehensive Care, School of Dentistry
    Pyk2 is a non-receptor tyrosine kinase that belongs to the family of focal adhesion kinases. Studies from our laboratory and others demonstrated that mice lacking the Pyk2 gene (Ptk2B) have high bone mass, which was due to increased osteoblast activity, as well as decreased osteoclast activity. It was previously reported that a chemical inhibitor that targets both Pyk2 and its homolog FAK, led to increased bone formation in ovariectomized rats. In the current study, we developed a hydrogel containing poly(ethylene glycol) diacrylate (PEGDA) and gelatin which was curable by visible-light and was suitable for the delivery of small molecules, including a Pyk2-targeted chemical inhibitor. We characterized several critical properties of the hydrogel, including viscosity, gelation time, swelling, degradation, and drug release behavior. We found that a hydrogel composed of PEGDA1000 plus 10% gelatin (P1000:G10) exhibited Bingham fluid behavior that can resist free flowing before in situ polymerization, making it suitable for use as an injectable carrier in open wound applications. The P1000:G10 hydrogel was cytocompatible and displayed a more delayed drug release behavior than other hydrogels we tested. Importantly, the Pyk2-inhibitor-hydrogel retained its inhibitory activity against the Pyk2 tyrosine kinase, and promoted osteoblast activity and mineral deposition in vitro. Overall, our findings suggest that a Pyk2-inhibitor based hydrogel may be suitable for the treatment of craniofacial and appendicular skeletal defects and targeted bone regeneration.
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    Resolution of Inflammation Induces Osteoblast Function and Regulates the Wnt Signaling Pathway
    (2012-05) Matzelle, Melissa M; Gallant, Maxime A; Condon, Keith W; Walsh, Nicole C; Manning, Catherine A; Stein, Gary S; Lian, Jane B; Burr, David B.; Gravallese, Ellen M
    Objective Inflammation in the bone microenvironment stimulates osteoclast differentiation, resulting in uncoupling of resorption and formation. Mechanisms contributing to the inhibition of osteoblast function in inflammatory diseases, however, have not been elucidated. Rheumatoid arthritis (RA) is a prototype of an inflammatory arthritis that results in focal loss of articular bone. The paucity of bone repair in inflammatory diseases such as RA raises compelling questions regarding the impact of inflammation on bone formation. The aim of this study was to establish the mechanisms by which inflammation regulates osteoblast activity. Methods We characterized an innovative variant of a murine model of arthritis in which inflammation is induced in C57BL/6J mice by transfer of arthritogenic K/BxN serum and allowed to resolve. Results In the setting of resolving inflammation, bone resorption ceased and appositional osteoblast-mediated bone formation was induced, resulting in repair of eroded bone. Resolution of inflammation was accompanied by striking changes in the expression of regulators of the Wnt/β-catenin pathway, which is critical for osteoblast differentiation and function. Down-regulation of the Wnt antagonists secreted frizzled-related protein 1 (sFRP1) and sFRP2 during the resolution phase paralleled induction of the anabolic and pro–matrix mineralization factors Wnt10b and DKK2, demonstrating the role of inflammation in regulating Wnt signaling. Conclusion Repair of articular bone erosion occurs in the setting of resolving inflammation, accompanied by alterations in the Wnt signaling pathway. These data imply that in inflammatory diseases that result in persistent articular bone loss, strict control of inflammation may not be achieved and may be essential for the generation of an anabolic microenvironment that supports bone formation and repair.