-
International Journal of Molecular... Jun 2021Osteoblasts, the cells that build up our skeleton, are remarkably versatile and important cells that need tight regulation in all the phases of their differentiation to... (Review)
Review
Osteoblasts, the cells that build up our skeleton, are remarkably versatile and important cells that need tight regulation in all the phases of their differentiation to guarantee proper skeletal development and homeostasis. Although we know many of the key pathways involved in osteoblast differentiation and signaling, it is becoming clearer and clearer that this is just the tip of the iceberg, and we are constantly discovering novel concepts in osteoblast physiology. In this review, we discuss well-established pathways of osteoblastic differentiation, i.e., the classical ones committing mesenchymal stromal cells to osteoblast, and then osteocytes as well as recently emerged players. In particular, we discuss micro (mi)RNAs, long non-coding (lnc)RNAs, circular (circ)RNAs, and extracellular vesicles, focusing on the mechanisms through which osteoblasts are regulated by these factors, and conversely, how they use extracellular vesicles to communicate with the surrounding microenvironment.
Topics: Animals; Cell Differentiation; Extracellular Vesicles; Humans; MicroRNAs; Osteoblasts; RNA, Long Noncoding; Signal Transduction
PubMed: 34206294
DOI: 10.3390/ijms22136651 -
International Journal of Molecular... Apr 2019Runx2 is essential for osteoblast differentiation and chondrocyte maturation. During osteoblast differentiation, Runx2 is weakly expressed in uncommitted mesenchymal... (Review)
Review
Runx2 is essential for osteoblast differentiation and chondrocyte maturation. During osteoblast differentiation, Runx2 is weakly expressed in uncommitted mesenchymal cells, and its expression is upregulated in preosteoblasts, reaches the maximal level in immature osteoblasts, and is down-regulated in mature osteoblasts. Runx2 enhances the proliferation of osteoblast progenitors by directly regulating and . Runx2 enhances the proliferation of suture mesenchymal cells and induces their commitment into osteoblast lineage cells through the direct regulation of hedgehog (, , and ), Fgf ( and ), Wnt (, , and ), and Pthlh () signaling pathway genes, and . heterozygous mutation causes open fontanelle and sutures because more than half of the gene dosage is required for the induction of these genes in suture mesenchymal cells. Runx2 regulates the proliferation of osteoblast progenitors and their differentiation into osteoblasts via reciprocal regulation with hedgehog, Fgf, Wnt, and Pthlh signaling molecules, and transcription factors, including Dlx5 and Sp7. Runx2 induces the expression of major bone matrix protein genes, including , , , , and , in vitro. However, the functions of Runx2 in differentiated osteoblasts in the expression of these genes in vivo require further investigation.
Topics: Animals; Cell Differentiation; Cell Proliferation; Core Binding Factor Alpha 1 Subunit; Humans; Osteoblasts
PubMed: 30987410
DOI: 10.3390/ijms20071694 -
Connective Tissue Research Mar 2018Bone homeostasis depends on the resorption of bones by osteoclasts and formation of bones by the osteoblasts. Imbalance of this tightly coupled process can cause... (Review)
Review
Bone homeostasis depends on the resorption of bones by osteoclasts and formation of bones by the osteoblasts. Imbalance of this tightly coupled process can cause diseases such as osteoporosis. Thus, the mechanisms that regulate communication between osteoclasts and osteoblasts are critical to bone cell biology. It has been shown that osteoblasts and osteoclasts can communicate with each other through direct cell-cell contact, cytokines, and extracellular matrix interaction. Osteoblasts can affect osteoclast formation, differentiation, or apoptosis through several pathways, such as OPG/RANKL/RANK, RANKL/LGR4/RANK, Ephrin2/ephB4, and Fas/FasL pathways. Conversely, osteoclasts also influence formation of bones by osteoblasts via the d2 isoform of the vacuolar (H+) ATPase (v-ATPase) V0 domain (Atp6v0d2), complement component 3a, semaphorin 4D or microRNAs. In addition, cytokines released from the resorbed bone matrix, such as TGF-β and IGF-1, also affect the activity of osteoblasts. Drugs could be developed by enhancing or restricting some of these interactions. Several reviews have been performed on the osteoblast-osteoclast communication. However, few reviews have shown the research advances in the recent years. In this review, we summarized the current knowledge on osteoblast-osteoclast communication.
Topics: Animals; Apoptosis; Cell Communication; Cell Differentiation; Humans; Osteoblasts; Osteoclasts; Osteogenesis; Signal Transduction
PubMed: 28324674
DOI: 10.1080/03008207.2017.1290085 -
The Journal of Clinical Investigation Feb 2016Osteoblast-derived VEGF is important for bone development and postnatal bone homeostasis. Previous studies have demonstrated that VEGF affects bone repair and...
Osteoblast-derived VEGF is important for bone development and postnatal bone homeostasis. Previous studies have demonstrated that VEGF affects bone repair and regeneration; however, the cellular mechanisms by which it works are not fully understood. In this study, we investigated the functions of osteoblast-derived VEGF in healing of a bone defect. The results indicate that osteoblast-derived VEGF plays critical roles at several stages in the repair process. Using transgenic mice with osteoblast-specific deletion of Vegfa, we demonstrated that VEGF promoted macrophage recruitment and angiogenic responses in the inflammation phase, and optimal levels of VEGF were required for coupling of angiogenesis and osteogenesis in areas where repair occurs by intramembranous ossification. VEGF likely functions as a paracrine factor in this process because deletion of Vegfr2 in osteoblastic lineage cells enhanced osteoblastic maturation and mineralization. Furthermore, osteoblast- and hypertrophic chondrocyte-derived VEGF stimulated recruitment of blood vessels and osteoclasts and promoted cartilage resorption at the repair site during the periosteal endochondral ossification stage. Finally, osteoblast-derived VEGF stimulated osteoclast formation in the final remodeling phase of the repair process. These findings provide a basis for clinical strategies to improve bone regeneration and treat defects in bone healing.
Topics: Animals; Bone Regeneration; Calcification, Physiologic; Cell Differentiation; Mice; Mice, Knockout; Osteoblasts; Osteogenesis; Vascular Endothelial Growth Factor A
PubMed: 26731472
DOI: 10.1172/JCI82585 -
Endocrine Reviews Jun 2017Osteoblasts, the bone-forming cells of the remodeling unit, are essential for growth and maintenance of the skeleton. Clinical disorders of substrate availability (e.g.,... (Review)
Review
Osteoblasts, the bone-forming cells of the remodeling unit, are essential for growth and maintenance of the skeleton. Clinical disorders of substrate availability (e.g., diabetes mellitus, anorexia nervosa, and aging) cause osteoblast dysfunction, ultimately leading to skeletal fragility and osteoporotic fractures. Conversely, anabolic treatments for osteoporosis enhance the work of the osteoblast by altering osteoblast metabolism. Emerging evidence supports glycolysis as the major metabolic pathway to meet ATP demand during osteoblast differentiation. Glut1 and Glut3 are the principal transporters of glucose in osteoblasts, although Glut4 has also been implicated. Wnt signaling induces osteoblast differentiation and activates glycolysis through mammalian target of rapamycin, whereas parathyroid hormone stimulates glycolysis through induction of insulin-like growth factor-I. Glutamine is an alternate fuel source for osteogenesis via the tricarboxylic acid cycle, and fatty acids can be metabolized to generate ATP via oxidative phosphorylation although temporal specificity has not been established. More studies with new model systems are needed to fully understand how the osteoblast utilizes fuel substrates in health and disease and how that impacts metabolic bone diseases.
Topics: Animals; Cell Differentiation; Energy Metabolism; Glucose Transport Proteins, Facilitative; Humans; Osteoblasts; Osteogenesis; Osteoporosis; Signal Transduction; Wnt Signaling Pathway
PubMed: 28472361
DOI: 10.1210/er.2017-00064 -
International Journal of Molecular... Mar 2021Osteoblasts, which are bone-forming cells, play pivotal roles in bone modeling and remodeling. Osteoblast differentiation, also known as osteoblastogenesis, is... (Review)
Review
Osteoblasts, which are bone-forming cells, play pivotal roles in bone modeling and remodeling. Osteoblast differentiation, also known as osteoblastogenesis, is orchestrated by transcription factors, such as runt-related transcription factor 1/2, osterix, activating transcription factor 4, special AT-rich sequence-binding protein 2 and activator protein-1. Osteoblastogenesis is regulated by a network of cytokines under physiological and pathophysiological conditions. Osteoblastogenic cytokines, such as interleukin-10 (IL-10), IL-11, IL-18, interferon-γ (IFN-γ), cardiotrophin-1 and oncostatin M, promote osteoblastogenesis, whereas anti-osteoblastogenic cytokines, such as tumor necrosis factor-α (TNF-α), TNF-β, IL-1α, IL-4, IL-7, IL-12, IL-13, IL-23, IFN-α, IFN-β, leukemia inhibitory factor, cardiotrophin-like cytokine, and ciliary neurotrophic factor, downregulate osteoblastogenesis. Although there are gaps in the body of knowledge regarding the interplay of cytokine networks in osteoblastogenesis, cytokines appear to be potential therapeutic targets in bone-related diseases. Thus, in this study, we review and discuss our osteoblast, osteoblast differentiation, osteoblastogenesis, cytokines, signaling pathway of cytokine networks in osteoblastogenesis.
Topics: Animals; Cell Differentiation; Cytokines; Humans; Mesenchymal Stem Cells; Models, Biological; Osteoblasts; Osteogenesis; Signal Transduction; Transcription Factors
PubMed: 33799644
DOI: 10.3390/ijms22062851 -
Cell Jun 2019Stroma is a poorly defined non-parenchymal component of virtually every organ with key roles in organ development, homeostasis, and repair. Studies of the bone marrow...
Stroma is a poorly defined non-parenchymal component of virtually every organ with key roles in organ development, homeostasis, and repair. Studies of the bone marrow stroma have defined individual populations in the stem cell niche regulating hematopoietic regeneration and capable of initiating leukemia. Here, we use single-cell RNA sequencing (scRNA-seq) to define a cellular taxonomy of the mouse bone marrow stroma and its perturbation by malignancy. We identified seventeen stromal subsets expressing distinct hematopoietic regulatory genes spanning new fibroblastic and osteoblastic subpopulations including distinct osteoblast differentiation trajectories. Emerging acute myeloid leukemia impaired mesenchymal osteogenic differentiation and reduced regulatory molecules necessary for normal hematopoiesis. These data suggest that tissue stroma responds to malignant cells by disadvantaging normal parenchymal cells. Our taxonomy of the stromal compartment provides a comprehensive bone marrow cell census and experimental support for cancer cell crosstalk with specific stromal elements to impair normal tissue function and thereby enable emergent cancer.
Topics: Animals; Bone Marrow Cells; Cell Differentiation; Homeostasis; Humans; Leukemia, Myeloid, Acute; Mice; Osteoblasts; Osteogenesis; Stromal Cells; Tumor Microenvironment
PubMed: 31130381
DOI: 10.1016/j.cell.2019.04.040 -
Molecular Medicine Reports May 2019Vitamin K2 likely exerts its protective effects during osteoporosis by promoting osteoblast differentiation and mineralization. However, the precise mechanism remains to...
Vitamin K2 likely exerts its protective effects during osteoporosis by promoting osteoblast differentiation and mineralization. However, the precise mechanism remains to be fully elucidated. Autophagy maintains cell homeostasis by breaking down and eliminating damaged proteins and organelles. Increasing evidence in recent years has implicated autophagy in the development of osteoporosis. The aim of the present study was to verify whether vitamin K2 (VK2) can induce autophagy during the differentiation and mineralization of osteoblasts. In the present study, MC3T3‑E1 osteoblasts were treated with various doses of VK2 (10‑8‑10‑3 M) for 1‑5 days. The results revealed no cytotoxicity at concentrations below 10‑5 M, but cell viability was reduced in a dose‑dependent manner at concentrations above 10‑5 M. Furthermore, MC3T3‑E1 osteoblasts were seeded in 6‑well plates in complete medium supplemented with dexamethasone, β‑glycerophosphate and vitamin C (VC) for osteogenic differentiation. MC3T3‑E1 osteoblasts treated with different concentrations (10‑5, 10‑6 and 10‑7 M) of VK2 for 24 h on days 1, 3, 5 and 7 of the differentiation protocol. It was confirmed that VK2 promoted osteoblast differentiation and mineralization by using alkaline phosphatase (ALP) and alizarin red staining. Using western blotting, immunofluorescence, monodansylcadaverine staining and reverse transcription‑quantitative polymerase chain reaction, it was observed that VK2 induced autophagy in osteoblasts. The results revealed that VK2 (1 µM) significantly increased ALP activity and the conversion of microtubule associated protein 1 light chain 3‑α (LC3)II to LC3I in MC3T3‑E1 osteoblasts (P<0.05) at every time point. The number of fluorescent bodies and the intensity increased with VK2, and decreased following treatment with 3‑MA+VK2. There was an increase in the mRNA expression levels of ALP, osteocalcin (OCN) and Runt‑related transcription factor 2 in VK2‑treated cells (P<0.01). The present study further confirmed the association between autophagy and osteoblast differentiation and mineralization through treatment with an autophagy inhibitor [3‑methyladenine (3‑MA)]. Osteoblasts treated with 3‑MA exhibited significant inhibition of ALP activity and osteogenic differentiation (both P<0.05). In addition, ALP activity and osteogenesis in the VK2+3‑MA group was lower compared with VK2‑treated cells (P<0.05 for both). The present study confirmed that VK2 stimulated autophagy in MC3T3 cells to promote differentiation and mineralization, which may be a potential therapeutic target for osteoporosis.
Topics: Animals; Autophagy; Calcification, Physiologic; Cell Differentiation; Cell Line; Cell Survival; Mice; Osteoblasts; Osteogenesis; Vitamin K 2
PubMed: 30896842
DOI: 10.3892/mmr.2019.10040 -
Medical Science Monitor : International... Apr 2018BACKGROUND LPS-inhibited osteoblastic differentiation plays an important role in the pathogenesis of osteomyelitis. Thus, searching for drugs that affect LPS-mediated...
BACKGROUND LPS-inhibited osteoblastic differentiation plays an important role in the pathogenesis of osteomyelitis. Thus, searching for drugs that affect LPS-mediated osteoblastic differentiation may be crucial in developing therapies for osteomyelitis. The purpose of this study was to investigate the role and mechanisms of resveratrol, a natural polyphenol present in red wine, on LPS-inhibited osteoblastic differentiation. MATERIAL AND METHODS Cell viability was measured by MMT assay. Mitochondrial ATP levels, membrane potential, and superoxide production were measured to evaluate the effects of LPS and resveratrol on mitochondrial functions in osteoblast-like MC3T3-E1 cells. Osteoblast-related genes, including ALP, OCN, OPN, and RUNX2, were measured by ELISA analysis and RT-PCR in differentiated osteoblast cells treated with LPS and resveratrol. Cellular Sirt1 and PCG-1α levels were measured by Western blot to probe the impact of resveratrol treatment in LPS-stimulated MC3T3-E1 osteoblasts. RESULTS The results showed that LPS caused significant mitochondrial dysfunctions of MC3T3-E1 cells in a dose-dependent manner, which were attenuated by resveratrol. Furthermore, LPS markedly decreased the expression of ALP, OCN, OPN, and RUNX2 in MC3T3-E1 cells cultivated in osteoblast differentiation medium, suggesting that LPS inhibited the osteoblastic differentiation of MC3T3-E1 cells. However, resveratrol obviously alleviated the suppressive impact of LPS on osteoblast differentiation. In addition, resveratrol increased expression of Sirt1 and PGC-1α in MC3T3-E1 cells treated with LPS. CONCLUSIONS Taken together, these results show that resveratrol alleviated the suppression of LPS on osteoblast differentiation by improving, at least in part, mitochondrial function.
Topics: 3T3 Cells; Animals; Apoptosis; Cell Differentiation; Cell Line; Cell Survival; Lipopolysaccharides; Mice; Mitochondria; Osteoblasts; Osteogenesis; Resveratrol; Stilbenes
PubMed: 29624568
DOI: 10.12659/msm.905703 -
Cellular & Molecular Biology Letters 2019MicroRNAs (miRNAs or miRs) serve crucial roles in the progression of osteoporosis. This study investigated the role and specific molecular mechanism of miR-135-5p in...
BACKGROUND
MicroRNAs (miRNAs or miRs) serve crucial roles in the progression of osteoporosis. This study investigated the role and specific molecular mechanism of miR-135-5p in regulating osteoblast differentiation and calcification.
METHODS
Bone morphogenetic protein 2 (BMP2) was employed to interfere with the differentiation of MC3T3-E1. Then, miR-135-5p mimic or miR-135-5p inhibitor was transfected into MC3T3-E1, and quantitative RT-PCR was used to measure the expression of miR-135-5p. The expressions of runt-related transcription factor 2 (Runx2), osterix (OSX), osteopontin (OPN), and osteocalcin (OCN) were determined using western blot. Alkaline phosphatase (ALP) activity was measured using an appropriate kit assay. Calcium nodule staining was evaluated with alizarin red staining. A luciferase reporter assay was used to verify the target of miR-135-5p. Hypoxia-inducible factor 1 α inhibitor (HIF1AN) overexpression was applied to investigate its own role in the mechanism and a miR-135-5p rescue experiment was also performed.
RESULTS
Overexpression of miR-135-5p promoted osteogenic differentiation and calcification, as shown by the increase in ALP activity, calcification and osteogenic marker levels, including Runx2, OSX, OPN and OCN. Knockdown of miR-135-5p yielded the opposite results. HIF1AN was confirmed as a direct target of miR-135-5p. HIF1AN overexpression inhibited osteogenic differentiation and calcification while miR-135-5p reversed these effects.
CONCLUSIONS
These results indicate that miR-135-5p might have a therapeutic application related to its promotion of bone formation through the targeting of HIF1AN.
Topics: Animals; Cell Differentiation; Cell Line; Gene Expression Regulation, Developmental; Mice; MicroRNAs; Mixed Function Oxygenases; Osteoblasts; Osteogenesis; Up-Regulation
PubMed: 31410089
DOI: 10.1186/s11658-019-0177-6