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At least 19 recordsLinked to original sources
PubMed1978

Immuno-histochemical localization of cyclic nucleotides in mineralized tissues: mechanically-stressed osteoblasts in vivo.

Previous experiments indicate that bone cells respond to external stimuli with fluctuations of cyclic nucleotide levels. The objective of this experiment was to study the response of alveolar bone to the application of tensile forces through an examination of the osteoblastic staining pattern for cAMP and cGMP. Cat canines were tipped by 80-g force for 0 to 48 hours. Fresh frozen, unfixed, undecalcified jaws were sectioned sagittally and stained immuno-histochemically for cAMP and cGMP. In tension sites, osteoblastic staining intensity for cAMP decreased gradually from one to three hours, and then increased by 24 hours. Intense staining for cGMP, visible in osteoblasts of all treated cats, peaked after three hours of treatment and then again at 24 hours. Generally, groups of cGMP-stained osteoblasts were found adjacent to unstained osteoblasts. The observed fluctuations in the osteoblasts staining pattern for cAMP and cGMP indicates involvement of these substances in the early response of osteoblasts to mechanical stimuli in vivo.

Animals↗
PubMed1975

Mitochondrial granules in human osteoblasts with a reference to one case of osteogenesis imperfecta.

Electron-dense granules in mitochondria from prenatal human osteoblasts, postnatal human osteoblasts, and from osteoblasts derived from a child with osteogenesis imperfecta congenita are described. The mitochondrial granules were of about 600 A in diameter and were attached to the mitochondrial cristae. Sections of mitochondria from prenatal osteoblasts showed an average number of 10 granuales per mitochondrial section, whereas sections of mitochondria of postnatal osteoblasts showed only occasionally 1-2 granules per mitochondrial section. Mitochondria from osteoblasts derived from the child with an untreated osteogenesis imperfecta congenita showed an average number of 10 granules per mitochondrial section.

Adolescent↗
PubMed2004

Dlx3 transcriptional regulation of osteoblast differentiation: temporal recruitment of Msx2, Dlx3, and Dlx5 homeodomain proteins to chromatin of the osteocalcin gene.

Genetic studies show that Msx2 and Dlx5 homeodomain (HD) proteins support skeletal development, but null mutation of the closely related Dlx3 gene results in early embryonic lethality. Here we find that expression of Dlx3 in the mouse embryo is associated with new bone formation and regulation of osteoblast differentiation. Dlx3 is expressed in osteoblasts, and overexpression of Dlx3 in osteoprogenitor cells promotes, while specific knock-down of Dlx3 by RNA interference inhibits, induction of osteogenic markers. We characterized gene regulation by Dlx3 in relation to that of Msx2 and Dlx5 during osteoblast differentiation. Chromatin immunoprecipitation assays revealed a molecular switch in HD protein association with the bone-specific osteocalcin (OC) gene. The transcriptionally repressed OC gene was occupied by Msx2 in proliferating osteoblasts, while Dlx3, Dlx5, and Runx2 were recruited postproliferatively to initiate transcription. Dlx5 occupancy increased over Dlx3 in mature osteoblasts at the mineralization stage of differentiation, coincident with increased RNA polymerase II occupancy. Dlx3 protein-DNA interactions stimulated OC promoter activity, while Dlx3-Runx2 protein-protein interaction reduced Runx2-mediated transcription. Deletion analysis showed that the Dlx3 interacting domain of Runx2 is from amino acids 376 to 432, which also include the transcriptionally active subnuclear targeting sequence (376 to 432). Thus, we provide cellular and molecular evidence for Dlx3 in regulating osteoprogenitor cell differentiation and for both positive and negative regulation of gene transcription. We propose that multiple HD proteins in osteoblasts constitute a regulatory network that mediates development of the bone phenotype through the sequential association of distinct HD proteins with promoter regulatory elements.

Amino Acid Sequence↗
PubMed1978

Effects of colchicine on osteoblast in rat: an ultrastructural study.

The present study was an attempt to investigate the effects of colchicine on the ultrastructure of rat osteoblasts with special reference to the microtubular function in vivo. Rats were killed at intervals of 2, 4, 8, 12 and 24 hours after the colchicine injection (0.1 mg per 100 g of body weight, subcutaneously). At 2 and 4 hours after the injection, the secretory granules and small vesicles accumulated in the Golgi area of the osteoblasts. The dilated spherical cisterna of the rough endoplasmic reticulum and the large vacuoles appeared, being located in the periphery of the cell. Microtubules were rarely found in the cytoplasm. Small masses of microfilaments of 80 to 110 A in diameter were found also in the cytoplasm. According to the special staining for collagen, it was indicated that the contents of the secretory granules might be collagen-like materials. At 8 hours after the injection, the shape of the osteoblasts transformed to a round profile and the autophagic vacuoles increased in the cytoplasm. At 12 and 24 hours after the injection, the osteoblasts seemed to be destroyed by the breakdown of the plasma membrane and by the increase of the autophagic vacuoles. It is suggested that colchicine affects the secretory process of the bone matrix and the cytoskeletal system of the osteoblasts by interfering with the structure and the function of the microtubules and colchicine also interferes with the function of the plasma membrane followed by the destruction of the osteoblasts.

Animals↗
PubMed1978

Transmembrane potentials of osteoblasts.

Transmembrane potentials were recorded in situ from osteoblasts on the parietal bones of albino rat pups, 3 to 24 days of age. Osteoblasts exhibit a uniquely low polarization of their cell membranes (3.93 mV, inside negative). Osteoblasts respond rapidly, but transiently, to parathyroid hormone by depolarization, and to thyrocalcitonin by hyperpolarization.

Animals↗
PubMed1975

Differential cytotoxic acitivity of anticollagen serum on rat osteoblasts and fibroblasts in tissue culture.

Rat skin fibroblasts grown in tissue culture were lysed by anti-rat-tail collagen serum and antibodies to the ordered collagen-like synthetic polymer (Pro-Gly-Pro)-n. This cytotoxic effect is complement-dependent and occurs only if the fibroblasts were pretreated with trypsin. These anti-sera have very little cytotoxicity on cultured rat osteoblasts. This differential cytotoxicity is not due to differential binding of anticollagen serum to the cells. Both osteoblasts and skin fibroblasts bind the anticollagen serum as was demonstrated by fluorescent immunoglobulin.

Animals↗
PubMed2026

Generation of spCAS9 expressing human mesenchymal stem cell line to study gene function during osteoblast differentiation.

Human bone marrow-derived stromal cells (hMSCs) are a great resource for studying how genes influence cell fate and differentiation into various cell types like osteoblasts, adipocytes, and chondrocytes, among other cell types. However, genetic manipulation of primary hMSCs has been challenging due to their short lifespan and cellular senescence after limited passaging. Their low and unstable transfection efficiency also complicates gene delivery or inactivation, hindering long-term functional studies. The limited lifespan has been effectively solved by immortalizing hMSCs with telomerase reverse transcriptase (hMSCs-TERT). The use of these cells is ideal for functional studies of osteoblast and adipocyte differentiation through genetic manipulation, providing a stable and reliable model. Here, we have engineered a stable CAS9 expressing hMSC-TERT cell line (hMSC-TERTCAS9) via lentiviral transduction. The constitutive expression of spCas9 enables efficient and reproducible gene editing. We demonstrate the potential of these hMSC-TERTCAS9 cells for generating gene disruptions using plasmid delivery of guide RNAs as a fast and efficient strategy for targeted genome editing. The edited cells can be sorted and expanded as single cells to obtain homogenous clonal cell lines with mono- as well as bi-allelic gene deletions, a crucial step for producing reliable experimental results. We further validate this cell line as a powerful tool for studying gene function during hMSC proliferation and differentiation, providing 3 distinct examples of its utility. Through the generation of indels, single-cell sorting, and clonal selection, we have efficiently inactivated the vitamin D receptor and created both larger (256 nucleotides) gene disruptions in Forkhead box protein O1 and precise removals of a small genomic sequence (73 nucleotides) coding for microRNA MIR675. This novel hMSC-TERTCAS9 cell line represents a significant advancement, offering a stable, efficient, and versatile platform for advanced genetic studies, high-throughput screening, and the creation of reliable cellular disease models.

CRISPR-Cas9↗
PubMed1977

1,25-dihydroxycholecalciferol and parathormone: effects on isolated osteoclast-like and osteoblast-like cells.

The actions of 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] and parathormone, both effective bone-resorptive agents in vivo and in vitro, were tested on CT (osteoclast-like) and PT (osteoblast-like) bone cells maintained in culture. Both agents stimulated acid phosphatase activity and hyaluronate synthesis in the CT cells and decreased alkaline phosphatase, citrate decarboxylation, and collagen synthesis in the PT cells. Calcitonin inhibited the changes induced in the CT but not in the PT cells. The activity of 1,25-(OH)2D3 differed from that of parathormone in one key respect: it did not increase cellular cyclic adenosine monophosphate, whereas parathormone did. Prior incubation of the bone cells with 1,25-(OH)2D3 for 6 to 24 hours made the cells refractory to the effect of parathormone on cyclic adenosine monophosphate formation. These data suggest that 1,25-(OH)2D3 and parathormone induce bone resorption by affecting the same cell types (osteoblasts and osteoclasts) although at different cellular sites.

Acid Phosphatase↗
PubMed1979

Cell-to-cell communication of osteoblasts.

Osteoblasts were investigated by two methods, electrical conductance and dye injection. Current injection into one cell caused a change in the recorded transmembrane potential of a second cell, indicating high conductance pathways between the two cells. Dyes injected into a single osteoblast were transmitted to numerous surrounding cells.

Animals↗
PubMed1975

[Enzymatic activity in the osteoblasts of rabbits following combined trauma].

Experiments were conducted on young rabbits by the histochemical methods; the activity of NAD-, NADP-diaphorases, cytochromoxidase and alkaline phosphatase was studied in the osteoblasts 3, 6, 12, 24, 48 and 72 hours after combined radiation trauma. It appeared that a bone fracture led to an increase in the level of metabolic and energic processes in the osteoblasts as soon as in 12 hours. Irradiation of the animals depressed the activation (caused by the fracture) of all the enzymes investigated.

Acute Disease↗
PubMed1979

Induction of metabolic changes and down regulation of bovine parathyroid hormone-responsive adenylate cyclase are dissociable in isolated osteoclastic and osteoblastic bone cells.

Bovine parathyroid hormone (PTH), dibutyryl cAMP, and calcium each induce similar metabolic changes in isolated bone cells. PTH and calcium, but not dibutyryl cAMP, result in desensitization of osteoclastic and osteoblastic bone cells to PTH. In osteoblastic cells, calcium effects are specific for PTH receptor.adenylate cyclase complexes and responsiveness to other hormones is not reduced while in osteoclastic cells, small effects of high calcium on prostaglandin E1- and epinephrine-inducible cAMP accompany the large decreases seen in cAMP response to PTH. The membrane effects of calcium and of PTH appear to be independently regulated as PTH-induced desensitization can be initiated in the absence of calcium. In addition, calcium effects on PTH-sensitive adenylate cyclase follow a different calcium dose-response than PTH-like metabolic changes. These results suggest that the effect of calcium on the membrane is not directly related to its induction of PTH-like metabolic changes. A possible role of calcium as an in vivo regulator of bone cell sensitivity to PTH is discussed.

Adenylyl Cyclases↗
PubMed1975

Accumulation of collagen-containing vacuoles in osteoblasts after administration of colchicine.

Embryonic mouse radii were cultured in the presence of colchicine or vinblastine and subsequently examined in the electron microscope. As a result of the administration of these drugs large numbers of vacuoles accumulated in the cytoplasm of the osteoblasts. The electron-dense contents of at least many of the vacuoles most probably consisted of collagen. This conclusion was based on the results of special staining methods and on the similarity of the vacuoles to collagen vacuoles described in the literature. The observations made in this study provide morphological evidence that colchicine and vinblastine disturb the secretion of collagen.

Animals↗
PubMed2026

A Novel Long Noncoding RNA-LNC000133 Associated With Steroid-Induced Osteonecrosis of the Femoral Head Promotes Osteoblast Differentiation Through Bone Marrow Mesenchymal Stem Cells-Derived Exosomes Pathway: A Bioinformatics Validation and Detailed Mechanistic Study.

Steroid-induced osteonecrosis of the femoral head (SONFH) is a debilitating disease caused by glucocorticoid abuse, characterized by complex pathogenesis and unclear molecular mechanisms. Dysfunction of bone marrow mesenchymal stem cells (BMSCs) and their exosome-mediated signalling is a key contributor to SONFH, although the precise mechanisms remain to be elucidated. In this study, the differential expression profiles of long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and messenger RNAs (mRNAs) in exosomes derived from human BMSCs (hBMSCs) obtained from patients with SONFH compared to controls with femoral neck fractures were identified. Through next-generation sequencing, a novel lncRNA, LNC000133, associated with SONFH was discovered. Using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and competing endogenous RNA (ceRNA) network construction, the LNC000133/miR-362-5p/TGF-β3/SMAD3/BMP2 signalling axis was established. The definitive expression, localization and full-length sequence of LNC000133 in BMSCs were subsequently validated by Northern blot, quantitative real-time polymerase chain reaction (qRT-PCR), fluorescence in situ hybridization (FISH) and rapid amplification of cDNA ends (RACE). Most notably, mechanistic studies demonstrated that LNC000133-modified BMSCs-derived exosomes were efficiently taken up by osteoblasts, which promoted proliferation and osteogenic differentiation by targeting the miR-362-5p/TGF-β3/SMAD3/BMP2 signalling pathway.

Humans↗
PubMed1979

Osteoblastic response to successful treatment of metastatic cancer of the prostate.

Increasing sclerosis of bone in patients with prostatic cancer most commonly is associated with disease progression. In a study of serial radiographs in a group of 18 patients who experienced objective clinical remission after treatment of metastatic cancer of the prostate, eight (44%) showed an osteoblastic response as part of their healing reaction to successful therapy. The importance of a blastic response as a possible sign of clinical improvement is emphasized. Clinical, biochemical, and bone scan correlations are discussed as they apply to patients who respond favorably to treatment of metastatic cancer of the prostate.

Adenocarcinoma↗
PubMed1976

An autoradiographic assessment of the incorporation of H3-uridine into DNA and RNA of osteoblasts of aging mice.

Intracellular labeling of DNA and RNA after H3-uridine administration was investigated autoradiographically during aging. Five to 78 weeks old mice were injected with 5 muCi of H3-uridine/gm of body weight and were killed from 15 minutes to 30 days later. Five mum decalcified sagittal sections of femora were treated with RNAase, DNAase or appropriate buffers. Autoradiographs were prepared and grain counts were made over diaphyseal periosteal osteoblasts. Both DNA and RNA incorporated H3-uridine. RNA label was 88 to 95% of the total cell label. DNA labeling ranged from 2 to 5%. DNA labeling appeared slightly increased after longer exposure to H3-uridine, whereas, RNA labeling remained relatively unaltered. With increasing age, incorporation into DNA decreased, whereas, RNA label showed a slight increase. A variable amount of non-specific label was undigested by either enzyme and may reflect insoluble conversion and/or degradation products. Apparently, some conversion of uridine into a DNA precursor occurs without loss of tritium label, thus rendering uridine less than totally specific for RNA. Nevertheless, the uptake of H3-uridine is largely indicative of RNA biosynthesis especially in skeletal cells that are not normally highly proliferative.

Aging↗
PubMed1979

Lymph node metastases from osteoblastic osteogenic sarcoma visible on plain films.

The radiologic features of lymph node metastases from osteogenic sarcoma visible on plain films in two patients are described. In one patient the lymph node ossification was visible on presentation and in the other patient it was demonstrated six months after the initial diagnosis. The radiologic pattern in both cases was similar. Deposition of metastatic osteoid tissue in lymph nodes, to such a degree that it can be recognized on plain films, appears to be a distinctly uncommon complication of this malignant neoplasm. It is considered probable that this complication occurs with the osteoblastic type of osteogenic sarcoma. It is suggested that lymphography might be of value in the detection of such metastases at an earlier stage, thus influencing the plan of treatment.

Adolescent↗
PubMed1976

Biochemical characterization with parathormone and calcitonin of isolated bone cells: provisional identification of osteoclasts and osteoblasts.

Two metabolically distinct types of bone cell populations were isolated from mouse calvaria by a repetitive digestive procedure with a mixture of collagenase and trypsin. Cells released early in the digestion showed approximately two-fold increases in cAMP when treated with either parathormone or calcitonin. These populations were denoted CT type. Later eluting cells showed larger parathormone-induced increases in cAMP but did not respond to calcitonin. These populations were denoted PT type. Six metabolic and enzymatic activites were measured in the two types of populations: acid and alkaline phosphatases, hyaluronate synthesis, citrate decarboxylation, prolyl hydroxylase, and general protein synthesis. Although each of these activites was present in both cell types, the basal levels of acid phosphatase and hyaluronate synthesis were higher in the CT cells, whereas alkaline phosphatase, citrate decarboxylation, and prolyl hydroxylase were higher in te PT cells. Parathormone stimulated acid phosphatase and hyaluronate synthesis by 100-200% only in the CT cells; in inhibited alkaline phosphatase, citrate decarboxylation, and prolyl hydroxylase by 75-90% only in the PT cells. Calcitonin alone had no effect on any of these activities other than cAMP production, but in inhibited the action of parathormone in the CT cells. The sensitivities, time courses of development,and magnitudes of these hormonal effects were similar to those observed previously in intact calvaria, indicating that the isolated cell system is a reliable model for the study of bone metabolism. Based on the metabolic responses of the cells, we postulate that the CT type of populations is enriched in osteoclasts and, possibly, osteocytes, and the PT type of population is enriched in osteoblasts.

Acid Phosphatase↗