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Frontiers in Endocrinology 2020A direct action of thyrotropin (TSH, thyroid-stimulating hormone) on bone precursors in humans is controversial. Studies in rodent models have provided conflicting... (Review)
Review
A direct action of thyrotropin (TSH, thyroid-stimulating hormone) on bone precursors in humans is controversial. Studies in rodent models have provided conflicting findings. We used cells derived from a moderately differentiated osteosarcoma stably overexpressing human TSH receptors (TSHRs) as a model of osteoblast precursors (U2OS-TSHR cells) to investigate TSHR-mediated effects in bone differentiation in human cells. We review our findings that (1) TSHR couples to several different G proteins to induce upregulation of genes associated with osteoblast activity-interleukin 11 (IL-11), osteopontin (OPN), and alkaline phosphatase (ALPL) and that the kinetics of the induction and the G protein-mediated signaling pathways involved were different for these genes; (2) TSH can stimulate β-arrestin-mediated signal transduction and that β-arrestin 1 in part mediates TSH-induced pre-osteoblast differentiation; and (3) TSHR/insulin-like growth factor 1 (IGF1) receptor (IGF1R) synergistically increased OPN secretion by TSH and IGF1 and that this crosstalk was mediated by physical association of these receptors in a signaling complex that uses β-arrestin 1 as a scaffold. These findings were complemented using a novel β-arrestin 1-biased agonist of TSHR. We conclude that TSHR can signal via several transduction pathways leading to differentiation of this model system of human pre-osteoblast cells and, therefore, that TSH can directly regulate these bone cells.
Topics: Animals; Bone and Bones; Cell Differentiation; Humans; Osteoblasts; Osteosarcoma; Receptors, Thyrotropin; Signal Transduction; beta-Arrestin 1
PubMed: 32508750
DOI: 10.3389/fendo.2020.00312 -
Molecular Medicine Reports Sep 2020Circular RNAs (circRNAs) are a class of non‑coding RNAs that exhibit important regulatory roles in various biological processes. However, the role of circRNAs and...
Circular RNAs (circRNAs) are a class of non‑coding RNAs that exhibit important regulatory roles in various biological processes. However, the role of circRNAs and their potential role in osteoblast differentiation and mineralization is unclear. The aim of the present study was to investigate the expression of mmu_circ_003795 and its effect on collagen type XV α 1 chain (COL15A1). First, it was identified that the expression levels of mmu_circ_003795 and osteopontin (OPN) were upregulated in the induced cells. Silencing of mmu_circ_003795 reduced the gene and protein levels of COL15A1 and OPN, whereas the expression level of mmu‑microRNA (miR)‑1249‑5p was upregulated. In addition, after 7 or 14 days of induction, alkaline phosphatase and Alizarin Red‑S staining were decreased in the mmu_circRNA_003795 inhibitory group compared with the negative control group. In conclusion, mmu_circ_003795 may regulate osteoblast differentiation and mineralization in MC3T3‑E1 and MDPC23 cells via mmu‑miR‑1249‑5p by targeting COL15A1.
Topics: 3T3 Cells; Animals; Cell Differentiation; Cell Line; Collagen; Gene Expression Regulation; Mice; MicroRNAs; Osteoblasts; Osteogenesis; Osteopontin; RNA, Circular; Up-Regulation
PubMed: 32582985
DOI: 10.3892/mmr.2020.11264 -
BMB Reports Jul 2019Kruppel-like factor 2 (KLF2) has been implicated in the regulation of cell proliferation, differentiation, and survival in a variety of cells. Recently, it has been...
Kruppel-like factor 2 (KLF2) has been implicated in the regulation of cell proliferation, differentiation, and survival in a variety of cells. Recently, it has been reported that KLF2 regulates the p65-mediated transactivation of NF-κB. Although the NF-κB pathway plays an important role in the differentiation of osteoclasts and osteoblasts, the role of KLF2 in these bone cells has not yet been fully elucidated. In this study, we demonstrated that KLF2 regulates osteoclast and osteoblast differentiation. The overexpression of KLF2 in osteoclast precursor cells inhibited osteoclast differentiation by downregulating c-Fos, NFATc1, and TRAP expression, while KLF2 overexpression in osteoblasts enhanced osteoblast differentiation and function by upregulating Runx2, ALP, and BSP expression. Conversely, the downregulation of KLF2 with KLF2-specific siRNA increased osteoclast differentiation and inhibited osteoblast differentiation. Moreover, the overexpression of interferon regulatory protein 2-binding protein 2 (IRF2BP2), a regulator of KLF2, suppressed osteoclast differentiation and enhanced osteoblast differentiation and function. These effects were reversed by downregulating KLF2. Collectively, our data provide new insights and evidence to suggest that the IRF2BP2/KLF2 axis mediates osteoclast and osteoblast differentiation, thereby affecting bone homeostasis. [BMB Reports 2019; 52(7): 469-474].
Topics: Cell Differentiation; DNA-Binding Proteins; Homeostasis; Humans; Kruppel-Like Transcription Factors; Osteoblasts; Osteoclasts; Transcription Factors
PubMed: 31186082
DOI: 10.5483/BMBRep.2019.52.7.104 -
Cell Reports Sep 2020Osteoprotegerin (OPG) is a circulating decoy receptor for RANKL, a multifunctional cytokine essential for the differentiation of tissue-specific cells in bone and immune...
Osteoprotegerin (OPG) is a circulating decoy receptor for RANKL, a multifunctional cytokine essential for the differentiation of tissue-specific cells in bone and immune systems such as osteoclasts, medullary thymic epithelial cells (mTECs), and intestinal microfold cells (M cells). However, it is unknown whether OPG functions only at the production site or circulates to other tissues acting in an endocrine fashion. Here we explore the cellular source of OPG by generating OPG-floxed mice and show that locally produced OPG, rather than circulating OPG, is crucial for bone and immune homeostasis. Deletion of OPG in osteoblastic cells leads to severe osteopenia without affecting serum OPG. Deletion of locally produced OPG increases mTEC and M cell numbers while retaining the normal serum OPG level. This study shows that OPG limits its functions within the tissue where it was produced, illuminating the importance of local regulation of the RANKL system.
Topics: Animals; Mice; Osteoblasts; Osteoclasts; Osteoprotegerin
PubMed: 32905763
DOI: 10.1016/j.celrep.2020.108124 -
Cell Death & Disease Mar 2020The regulation of bone formation and detailed mechanisms are still largely elusive, and the roles of microRNAs in this process have attracted much attention. Recently, a...
The regulation of bone formation and detailed mechanisms are still largely elusive, and the roles of microRNAs in this process have attracted much attention. Recently, a specific subtype of CD31endomucin (CD31EMCN) endothelium has been identified to promote bone formation, together with osteoblast development. However, the role of microRNA143 in the generation of CD31 EMCN endothelium and bone formation remains unknown. In this study, we found that miR-143 was expressed both in osteoblast cells and CD31EMCN endothelial cells. Serum miR-143 level was negatively correlated with age in humans. Overexpression of miR-143 promoted osteoblast formation and angiogenic effects. Furthermore, CD31Emcn vessels and osteoblast formation were significantly inhibited in miR-143 knockout mice. Mechanistically, inhibitor HDAC7 was directly targeted by miR-143 and knockdown of HDAC7 was found to rescue the function of miR-143 deficiency. Thus, miR-143 promotes angiogenesis coupling with osteoblast differentiation by targeting HDAC7, which may serve as a potential target in angiogenic and osteogenic diseases.
Topics: Animals; Cell Differentiation; Histone Deacetylases; Humans; Male; Mice; MicroRNAs; Neovascularization, Pathologic; Osteoblasts; Osteoporosis; Transfection
PubMed: 32152265
DOI: 10.1038/s41419-020-2377-4 -
International Journal of Molecular... Jan 2020As the population of western societies on average ages, the number of people affected by bone remodeling-associated diseases such as osteoporosis continues to increase.... (Review)
Review
As the population of western societies on average ages, the number of people affected by bone remodeling-associated diseases such as osteoporosis continues to increase. The development of new therapeutics is hampered by the high failure rates of drug candidates during clinical testing, which is in part due to the poor predictive character of animal models during preclinical drug testing. Co-culture models of osteoblasts and osteoclasts offer an alternative to animal testing and are considered to have the potential to improve drug development processes in the future. However, a robust, scalable, and reproducible 3D model combining osteoblasts and osteoclasts for preclinical drug testing purposes has not been developed to date. Here we review various types of osteoblast-osteoclast co-culture models and outline the remaining obstacles that must be overcome for their successful translation.
Topics: Animals; Bone Density Conservation Agents; Bone Remodeling; Coculture Techniques; Drug Evaluation, Preclinical; Humans; Osteoblasts; Osteoclasts; Osteoporosis
PubMed: 32019244
DOI: 10.3390/ijms21030912 -
Molecules (Basel, Switzerland) Jan 2022Toll-like receptor 4 (TLR4) is a pattern-recognizing receptor that can bind exogenous and endogenous ligands. It is expressed by acute myeloid leukemia (AML) cells,... (Review)
Review
Toll-like receptor 4 (TLR4) is a pattern-recognizing receptor that can bind exogenous and endogenous ligands. It is expressed by acute myeloid leukemia (AML) cells, several bone marrow stromal cells, and nonleukemic cells involved in inflammation. TLR4 can bind a wide range of endogenous ligands that are present in the bone marrow microenvironment. Furthermore, the TLR4-expressing nonleukemic bone marrow cells include various mesenchymal cells, endothelial cells, differentiated myeloid cells, and inflammatory/immunocompetent cells. Osteoblasts are important stem cell supporting cells localized to the stem cell niches, and they support the proliferation and survival of primary AML cells. These supporting effects are mediated by the bidirectional crosstalk between AML cells and supportive osteoblasts through the local cytokine network. Finally, TLR4 is also important for the defense against complicating infections in neutropenic patients, and it seems to be involved in the regulation of inflammatory and immunological reactions in patients treated with allogeneic stem cell transplantation. Thus, TLR4 has direct effects on primary AML cells, and it has indirect effects on the leukemic cells through modulation of their supporting neighboring bone marrow stromal cells (i.e., modulation of stem cell niches, regulation of angiogenesis). Furthermore, in allotransplant recipients TLR4 can modulate inflammatory and potentially antileukemic immune reactivity. The use of TLR4 targeting as an antileukemic treatment will therefore depend both on the biology of the AML cells, the biological context of the AML cells, aging effects reflected both in the AML and the stromal cells and the additional antileukemic treatment combined with HSP90 inhibition.
Topics: Animals; Carcinogenesis; Humans; Leukemia, Myeloid, Acute; Osteoblasts; Stem Cell Niche; Toll-Like Receptor 4; Tumor Microenvironment
PubMed: 35163998
DOI: 10.3390/molecules27030735 -
International Journal of Biological... 2020The roles of long non-coding RNAs (lncRNAs) and micro RNAs (miRNAs) as regulators of mRNA expression in various diseases have recently been reported. Osteoblast...
The roles of long non-coding RNAs (lncRNAs) and micro RNAs (miRNAs) as regulators of mRNA expression in various diseases have recently been reported. Osteoblast differentiation is the vital process which mediates bone formation and fracture healing. In present study, we found microRNA-6979-5p (miR-6979-5p) to be the most differentially expressed miRNA between normal bone and calluses of mice, and overexpression of miR-6979-5p was negatively associated with osteoblast differentiation. Through luciferase assays, we found evidence that bone morphogenetic protein 2 (BMP2) is a miR-6979-5p target gene that positively regulates osteoblast differentiation. We further identified the lncRNA Rhno1 as a competing endogenous RNA (ceRNA) of miR-6979-5p, and we verified that it was able to influence osteoblast differentiation both and . In summary, our data indicates that the lncRNA Rhno1/miR-6979-5p/BMP2 axis is a significant regulatory mechanism controlling osteoblast differentiation, and it may thus offer a novel therapeutic strategy for fracture healing.
Topics: Animals; Bone Morphogenetic Protein 2; Cell Differentiation; Fracture Healing; Gene Expression Regulation; Male; Mice, Inbred C57BL; Osteoblasts; RNA, Long Noncoding
PubMed: 32226305
DOI: 10.7150/ijbs.38930 -
Purinergic Signalling Jun 2023Bone cells are known to express multiple P2 receptor subtypes, and the functional effects of receptor activation have been described for many of these. One exception is...
Bone cells are known to express multiple P2 receptor subtypes, and the functional effects of receptor activation have been described for many of these. One exception is the P2X4 receptor, which despite strong expression in osteoblasts and osteoclasts, has no defined functional activity. This study used the selective P2X4 receptor antagonists, 5-BDBD and PSB-12062, to investigate the role of this receptor in bone. Both antagonists (≥ 0.1 μM) dose-dependently decreased bone formation by 60-100%. This was accompanied by a ≤ 70% decrease in alkaline phosphatase activity, a ≤ 40% reduction in cell number, and a ≤ 80% increase in the number of adipocytes present in the culture. The analysis of gene expression showed that levels of osteoblast marker genes (e.g. Alpl, Bglap) were decreased in 5-BDBD treated cells. Conversely, expression of the adipogenic transcription factor PPARG was increased 10-fold. In osteoclasts, high doses of both antagonists were associated with a reduction in osteoclast formation and resorptive activity by ≤ 95% and ≤ 90%, respectively. Taken together, these data suggest that the P2X4 receptor plays a role in modulating bone cell function. In particular, it appears to influence osteoblast differentiation favouring the osteogenic lineage over the adipogenic lineage.
Topics: Osteogenesis; Receptors, Purinergic P2X4; Cell Differentiation; Osteoclasts; Osteoblasts
PubMed: 35976527
DOI: 10.1007/s11302-022-09887-x -
Molecular Medicine Reports Apr 2022Advanced glycation end products (AGEs) have been widely reported to play an important role in osteoporosis (OP), particularly in diabetes‑related OP. The aim of the...
Advanced glycation end products (AGEs) have been widely reported to play an important role in osteoporosis (OP), particularly in diabetes‑related OP. The aim of the present study was to investigate the effect of AGEs on osteoblast function and the underlying mechanisms. The level of bone mineral density (BMD), serum AGEs and fasting blood glucose (FBG) was measured in patients with OP and healthy individuals, and the correlation between AGE levels and BMD or FBG was then analyzed. For the experiments, the hFOB1.19 osteoblast cell line was cultured in medium containing AGEs and serum from healthy individuals or patients with OP, and with or without type‑2 diabetes mellitus (T2DM). Cell proliferation, differentiation, mineralization, apoptosis and ferroptosis were evaluated using Cell Counting Kit‑8 and alkaline phosphatase (ALP) assays, Alizarin red and TUNEL staining, iron indicator, lipid peroxidation tests and western blot analysis, respectively. In a separate set of experiments, the ferroptosis inhibitor, deferoxamine (DFO), was also added to the culture medium of cells treated with AGEs and serum from patients with OP and T2DM. The results demonstrated that patients with OP had a higher level of serum AGEs and FBG compared with that in healthy individuals. The level of serum AGEs in patients with OP was negatively correlated with BMD, but was positively correlated with FBG. In addition, AGEs and serum from patients with OP markedly inhibited hFOB1.19 cell proliferation, ALP production and mineralized nodule formation. Apoptosis and ferroptosis were significantly promoted by AGEs and serum from patients with OP. Moreover, serum from OP patients with T2DM caused stronger effect than that from OP patients with normal FBG. However, DFO reversed the effects induced by AGEs and serum from patients with OP and T2DM on hFOB1.19 cells. Collectively, AGEs could disrupt the functions of osteoblasts by inducing cell ferroptosis, thus contributing to OP.
Topics: Cell Differentiation; Ferroptosis; Glycation End Products, Advanced; Humans; Osteoblasts; Osteoporosis
PubMed: 35211757
DOI: 10.3892/mmr.2022.12656