scholarly journals At the Crossroads of the Adipocyte and Osteoclast Differentiation Programs: Future Therapeutic Perspectives

2020 ◽  
Vol 21 (7) ◽  
pp. 2277 ◽  
Author(s):  
Shanmugam Muruganandan ◽  
Andreia M. Ionescu ◽  
Christopher J. Sinal

The coordinated development and function of bone-forming (osteoblasts) and bone-resorbing (osteoclasts) cells is critical for the maintenance of skeletal integrity and calcium homeostasis. An enhanced adipogenic versus osteogenic potential of bone marrow mesenchymal stem cells (MSCs) has been linked to bone loss associated with diseases such as diabetes mellitus, as well as aging and postmenopause. In addition to an inherent decrease in bone formation due to reduced osteoblast numbers, recent experimental evidence indicates that an increase in bone marrow adipocytes contributes to a disproportionate increase in osteoclast formation. Therefore, a potential strategy for therapeutic intervention in chronic bone loss disorders such as osteoporosis is to interfere with the pro-osteoclastogenic influence of marrow adipocytes. However, application of this approach is limited by the extremely complex regulatory processes in the osteoclastogenic program. For example, key regulators of osteoclastogenesis such as the receptor activator of nuclear factor-kappaB ligand (RANKL) and the soluble decoy receptor osteoprotegerin (OPG) are not only secreted by both osteoblasts and adipocytes, but are also regulated through several cytokines produced by these cell types. In this context, biologically active signaling molecules secreted from bone marrow adipocytes, such as chemerin, adiponectin, leptin, visfatin and resistin, can have a profound influence on the osteoclast differentiation program of hematopoietic stem cells (HSCs), and thus, hold therapeutic potential under disease conditions. In addition to these paracrine signals, adipogenic transcription factors including CCAAT/enhancer binding protein alpha (C/EBPα), C/EBP beta (C/EBPβ) and peroxisome proliferator-associated receptor gamma (PPARγ) are also expressed by osteoclastogenic cells. However, in contrast to MSCs, activation of these adipogenic transcription factors in HSCs promotes the differentiation of osteoclast precursors into mature osteoclasts. Herein, we discuss the molecular mechanisms that link adipogenic signaling molecules and transcription factors to the osteoclast differentiation program and highlight therapeutic strategies targeting these mechanisms for promoting bone homeostasis.

Cancers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 1059
Author(s):  
Jinyeong Yu ◽  
Sanghyuk Choi ◽  
Aran Park ◽  
Jungbeom Do ◽  
Donghyun Nam ◽  
...  

Cancer cachexia is a multifactorial systemic inflammation disease caused by complex interactions between the tumor and host tissues via soluble factors. However, whether cancer cachexia affects the bone marrow, in particular the hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs), remains unclear. Here, we investigated the bone marrow and bone in a cancer cachexia animal model generated by transplanting Lewis lung carcinoma cells. The number of bone marrow mononuclear cells (BM-MNCs) started to significantly decrease in the cancer cachectic animal model prior to the discernable loss of muscle and fat. This decrease in BM-MNCs was associated with myeloid skewing in the circulation and the expansion of hematopoietic progenitors in the bone marrow. Bone loss occurred in the cancer cachexia animal model and accompanied the decrease in the bone marrow MSCs that play important roles in both supporting HSCs and maintaining bone homeostasis. Glucocorticoid signaling mediated the decrease in bone marrow MSCs in the cancer cachectic environment. The cancer cachexia environment also skewed the differentiation of the bone marrow MSCs toward adipogenic fate via JAK/STAT as well as glucocorticoid signaling. Our results suggest that the bone loss induced in cancer cachexia is associated with the depletion and the impaired differentiation capacity of the bone marrow MSCs.


Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 557
Author(s):  
Elena Sánchez-Luis ◽  
Andrea Joaquín-García ◽  
Francisco J. Campos-Laborie ◽  
Fermín Sánchez-Guijo ◽  
Javier De las Rivas

Mesenchymal Stromal Cells (MSC) are multipotent cells characterized by self-renewal, multilineage differentiation, and immunomodulatory properties. To obtain a gene regulatory profile of human MSCs, we generated a compendium of more than two hundred cell samples with genome-wide expression data, including a homogeneous set of 93 samples of five related primary cell types: bone marrow mesenchymal stem cells (BM-MSC), hematopoietic stem cells (HSC), lymphocytes (LYM), fibroblasts (FIB), and osteoblasts (OSTB). All these samples were integrated to generate a regulatory gene network using the algorithm ARACNe (Algorithm for the Reconstruction of Accurate Cellular Networks; based on mutual information), that finds regulons (groups of target genes regulated by transcription factors) and regulators (i.e., transcription factors, TFs). Furtherly, the algorithm VIPER (Algorithm for Virtual Inference of Protein-activity by Enriched Regulon analysis) was used to inference protein activity and to identify the most significant TF regulators, which control the expression profile of the studied cells. Applying these algorithms, a footprint of candidate master regulators of BM-MSCs was defined, including the genes EPAS1, NFE2L1, SNAI2, STAB2, TEAD1, and TULP3, that presented consistent upregulation and hypomethylation in BM-MSCs. These TFs regulate the activation of the genes in the bone marrow MSC lineage and are involved in development, morphogenesis, cell differentiation, regulation of cell adhesion, and cell structure.


Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3051-3059 ◽  
Author(s):  
TC Burn ◽  
AB Satterthwaite ◽  
DG Tenen

Abstract The human CD34 hematopoietic stem cell antigen is a highly glycosylated type 1 membrane protein of unknown function. CD34 is expressed on 1% to 4% of bone marrow cells, including pluripotent stem cells and committed progenitors of each hematopoietic lineage. CD34 has also been shown to be expressed on the small vessel endothelium of a variety of tissues and on a subset of bone marrow stromal cells. We have chosen to use the human CD34 gene as model to examine the transcription factors and cis-elements required for stem cell/progenitor cell-specific gene regulation. We show here that the CD34 gene is transcriptionally regulated in tissue culture cells. Using a luciferase reporter gene, we have isolated and characterized an active CD34 promoter. A CD34- luciferase construct, containing 4.5 kb of 5′ flanking DNA from a CD34 genomic clone, was 30-fold more active in CD34+ tissue culture cells than in HeLa cells. Sequences from the 3′ end of the CD34 gene were shown to have enhancing activity in CD34+ T-lymphoblastic RPMI-8402 cells and not in CD34- U937 cells or in nonhematopoietic HeLa cells. We also show that a cytidine-guanosine island in the 5′ end of the CD34 gene is heavily methylated in two CD34- hematopoietic cell lines and demethylated in two CD34+ cell lines. Analysis of the CD34 promoter should result in the identification of stem cell/progenitor cell- specific transcription factors and should provide a means to direct the expression of heterologous genes in hematopoietic stem cells and progenitors.


Author(s):  
Fengjie Li ◽  
Rong Zhang ◽  
Changpeng Hu ◽  
Qian Ran ◽  
Yang Xiang ◽  
...  

PurposeRepairing the irradiation-induced osteogenic differentiation injury of bone marrow mesenchymal stem cells (BM-MSCs) is beneficial to recovering haematopoiesis injury in radiotherapy; however, its mechanism is elusive. Our study aimed to help meet the needs of understanding the effects of radiotherapy on BM-MSC osteogenic potential.Methods and MaterialsBalb/c mice and the BM-MSCs were used to evaluate the irradiation-induced osteogenic differentiation injury in vivo. The cellular and molecular characterization were applied to determine the mechanism for recovery of irradiation-derived haematopoiesis injuries.ResultsWe report a functional role of IL-12 in acute irradiation hematopoietic injury recovery and intend to dissect the possible mechanisms through BM-MSC, other than the direct effect of IL-12 on hematopoietic stem and progenitor cells (HSPCs). Specifically, we show that early use of IL-12 enhanced the osteogenic differentiation of BM-MSCs through IL-12Rβ1/TYK2/STAT3 signaling; furthermore, IL-12 induced osteogenesis facilitated bone formation and irradiation hematopoiesis recovery when transplanted BM-MSCs in the femur of Balb/c mice. For the mechanism of action, we found that IL-12 receptor beta 1 (IL-12Rβ1) expression of irradiated BM-MSCs was upregulated rapidly, coincidentally consistent with early use of IL-12 induced osteogenic differentiation enhancement. IL-12Rβ1 and tyrosine kinase 2 gene (Tyk2) silencing experiments and phosphotyrosine of signal transducer and activator of transcription 3 (p-STAT3) suppression experiments indicated the IL-12Rβ1/TYK2/STAT3 signaling was essential in IL-12-induced osteogenic differentiation enhancement of BM-MSCs.ConclusionThese findings suggested that IL-12 may exert BM-MSCs-based hematopoietic recovery by repairing osteogenic differentiation abilities damages through IL-12Rβ1/TYK2/STAT3 signaling pathway post-irradiation.


Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2533-2533
Author(s):  
Benjamin Povinelli ◽  
Michael Baranello ◽  
Kathleen Kokolus ◽  
Michael Nemeth

Abstract Abstract 2533 Poster Board II-510 Multiple members of the Wnt family of ligands have been implicated in the regulation of self-renewal and proliferation of hematopoietic stem cells (HSCs). Previously, we have observed that ex vivo expansion of HSCs in the presence of recombinant murine Wnt5a (rmWnt5a) resulted in increased hematopoietic repopulation. Based on these data, we hypothesized that Wnt5a is necessary for normal function of HSCs and hematopoietic progenitors (HPCs). Since Wnt5a deficiency (Wnt5a−/−) is perinatal lethal in vivo, we tested this hypothesis using in vitro Dexter stroma cultures established using whole bone marrow. To determine the ability of Wnt5a to support hematopoiesis in the context of the adult hematopoietic microenvironment, we cultured lineage-negative (lin−) HPCs on irradiated bone marrow stroma in the presence of 5 μg/ml Wnt5a-neutralizing antibody (Wnt5a-Ab). After two weeks, we observed that hematopoietic cells cultured on untreated stroma contained 4.8-fold more myeloid CFU (33.1 ± 12.3 CFU/104 cells) than cells cultured on Wnt5a-Ab stroma (6.9 ± 0.7 CFU; n = 3, p < .01). A similar difference was observed after 4 weeks (control: 16.0 ± 7.2 CFU/104 cells; Wnt5a-Ab: 1.3 ± 2.3 CFU; n = 3; p = .03). In the converse experiment, lin− HPCs were cultured on stroma in the presence of Wnt5a conditioned medium (Wnt5a-CM). We observed after two weeks that hematopoietic cells cultured on stroma with control-CM contained 4.4-fold more myeloid CFU (29.8 ± 13.5 CFU/104 cells) than cells cultured on Wnt5a-CM stroma (6.8 ± 2.2 CFU; n = 4, p = .02). Together, these data indicate that Wnt5a-mediated signaling must be balanced in order for normal hematopoiesis to occur. To determine if the effects of Wnt5a required the presence of developmental stage-specific factors, we established stroma cultures from fetal spleens harvested from E17.5 Wnt5a−/− mice and littermate controls and seeded them with lin− HPCs. We observed that hematopoietic cells cultured on control fetal spleen stroma contained 12.5-fold more myeloid CFU (72.6 ± 21.6 CFU/104 cells) than cells cultured on Wnt5a−/− fetal spleen stroma (5.8 ± 5.8; n = 6, p < .001) after two weeks. These data indicate that the effect of Wnt5a on hematopoietic cells is independent of the developmental stage of the surrounding microenvironment. To determine if the effects of Wnt5a were due to regulation of proliferation or differentiation of hematopoietic cells, we cultured bone marrow cells in cytokine-supplemented methylcellulose in the presence of 300 ng/ml rmWnt5a. We observed a 5.5-fold decrease in the number of myeloid CFU formed in cultures with rmWnt5a (14.1 ± 3.8/104 cells) compared to control (77.6 ± 5.1 CFU; n = 3; p < .001), suggesting that Wnt5a could be regulating both processes. In the converse experiment, we cultured bone marrow cells for 4 days in cytokine-supplemented serum-free media with the same dose of rmWnt5a after which equal numbers of cells were plated in rmWnt5a-free methylcellulose. We did not observe any difference in CFU frequency between control (19.3 ± 4.2 CFU/104 cells) and rmWnt5a (24.0 ± 2.6 CFU; n = 3) cultures, indicating that treatment with rmWnt5a inhibited hematopoietic proliferation but not differentiation. To identify the mechanism by which Wnt5a regulates HSC and HPC proliferation, we analyzed potential Wnt5a-mediated signaling pathways. We observed that Wnt5a induced intracellular Ca2+ (iCa2+) flux in HSCs (defined as lin−, Sca-1HI, c-kitHI; LSK). Previous studies have shown that Wnt5a-mediated induction of iCa2+ can result in activation of the NFAT family of transcription factors. Since NFATc1 promotes quiescence of hair follicle stem cells and is expressed in HSCs, we hypothesized that the effects of Wnt5a required activation of NFAT family members. We cultured bone marrow cells with Wnt5a-CM in the presence of cyclosporine A (CsA), which inhibits activation of NFAT factors. In agreement with our earlier findings, we observed that culturing bone marrow cells in Wnt5a-CM increased the percentage of quiescent (defined as Ki-67-) LSKCD34− HSCs (79.7 ± 3.3%) compared to control-CM (55.0 ± 1.6%; n = 3; p < .001). This increase was inhibited by CsA (69.4 ± 2.6%; n = 3; p = .01 compared to Wnt5a-CM alone). In conclusion, our data point to a role for Wnt5a in regulating HSC and HPC proliferation and that this function may require the activation of NFAT transcription factors. Disclosures: No relevant conflicts of interest to declare.


2019 ◽  
Vol 8 (5) ◽  
pp. 707 ◽  
Author(s):  
Vincent Cuminetti ◽  
Lorena Arranz

Bone marrow adipocytes (BMA) exert pleiotropic roles beyond mere lipid storage and filling of bone marrow (BM) empty spaces, and we are only now beginning to understand their regulatory traits and versatility. BMA arise from the differentiation of BM mesenchymal stromal cells, but they seem to be a heterogeneous population with distinct metabolisms, lipid compositions, secretory properties and functional responses, depending on their location in the BM. BMA also show remarkable differences among species and between genders, they progressively replace the hematopoietic BM throughout aging, and play roles in a range of pathological conditions such as obesity, diabetes and anorexia. They are a crucial component of the BM microenvironment that regulates hematopoiesis, through mechanisms largely unknown. Previously considered as negative regulators of hematopoietic stem cell function, recent data demonstrate their positive support for hematopoietic stem cells depending on the experimental approach. Here, we further discuss current knowledge on the role of BMA in hematological malignancies. Early hints suggest that BMA may provide a suitable metabolic niche for the malignant growth of leukemic stem cells, and protect them from chemotherapy. Future in vivo functional work and improved isolation methods will enable determining the true essence of this elusive BM hematopoietic stem cell niche component, and confirm their roles in a range of diseases. This promising field may open new pathways for efficient therapeutic strategies to restore hematopoiesis, targeting BMA.


2020 ◽  
Author(s):  
Fei Xiao ◽  
Bin Zuo ◽  
Chuandong Wang ◽  
Yang Li ◽  
Jianping Peng ◽  
...  

Abstract Background: Skeletal unloading usually induces severe disuse osteoporosis (DOP), which often occurs in patients subjected to prolonged immobility or in spaceflight astronauts. Increasing evidence suggests that exosomes are important mediators in maintaining the balance between bone formation and bone resorption. We hypothesized that exosomes play a pivotal role in the maintenance of bone homeostasis through intercellular communication between bone marrow mesenchymal stem cells (BMSCs) and osteoclasts under mechanical loading.Methods: Cells were divided into cyclic mechanical stretch (CMS)-treated BMSCs and normal static-cultured BMSCs, and exosomes were extracted by ultracentrifugation. After incubation with CMS-treated BMSC-derived exosomes (CMS_Exos) or static-cultured BMSC-derived exosomes (static_Exos), the apoptosis rates of bone marrow macrophages (BMMs) were determined by flow cytometry, and cell viability was detected with a CCK-8 assay. Osteoclast differentiation was determined with an in vitro osteoclastogenesis assay. Signaling pathway activation was evaluated by Western blotting and immunofluorescence staining. Hindlimb unloading (HU)-induced DOP mouse models were prepared to evaluate the function of exosomes in DOP.Results: Both CMS_Exos and static_Exos could be internalized by BMMs, and CMS_Exos did not affect BMM viability or increase apoptosis. CMS_Exos effectively suppressed receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation and F-actin ring formation. Further molecular investigation demonstrated that CMS_Exos impaired osteoclast differentiation via inhibition of the RANKL-induced NF-κB signaling pathway. Both CMS_Exos and static_Exos partly rescued the osteoporosis caused by mechanical unloading; however, the CMS_Exo group showed more obvious rescue. CMS_Exo treatment significantly decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts.Conclusions: Exosomes derived from CMS-treated BMSCs strongly inhibited osteoclast differentiation by attenuating the NF-κB signaling pathway in vitro and rescued osteoporosis caused by mechanical unloading in an HU mouse model in vivo.


Blood ◽  
1992 ◽  
Vol 80 (12) ◽  
pp. 3051-3059 ◽  
Author(s):  
TC Burn ◽  
AB Satterthwaite ◽  
DG Tenen

The human CD34 hematopoietic stem cell antigen is a highly glycosylated type 1 membrane protein of unknown function. CD34 is expressed on 1% to 4% of bone marrow cells, including pluripotent stem cells and committed progenitors of each hematopoietic lineage. CD34 has also been shown to be expressed on the small vessel endothelium of a variety of tissues and on a subset of bone marrow stromal cells. We have chosen to use the human CD34 gene as model to examine the transcription factors and cis-elements required for stem cell/progenitor cell-specific gene regulation. We show here that the CD34 gene is transcriptionally regulated in tissue culture cells. Using a luciferase reporter gene, we have isolated and characterized an active CD34 promoter. A CD34- luciferase construct, containing 4.5 kb of 5′ flanking DNA from a CD34 genomic clone, was 30-fold more active in CD34+ tissue culture cells than in HeLa cells. Sequences from the 3′ end of the CD34 gene were shown to have enhancing activity in CD34+ T-lymphoblastic RPMI-8402 cells and not in CD34- U937 cells or in nonhematopoietic HeLa cells. We also show that a cytidine-guanosine island in the 5′ end of the CD34 gene is heavily methylated in two CD34- hematopoietic cell lines and demethylated in two CD34+ cell lines. Analysis of the CD34 promoter should result in the identification of stem cell/progenitor cell- specific transcription factors and should provide a means to direct the expression of heterologous genes in hematopoietic stem cells and progenitors.


Author(s):  
Semun Seong ◽  
Jung Ha Kim ◽  
Kabsun Kim ◽  
Inyoung Kim ◽  
Jeong-Tae Koh ◽  
...  

AbstractSTAT5 is a transcription factor that is activated by various cytokines, hormones, and growth factors. Activated STAT5 is then translocated to the nucleus and regulates the transcription of target genes, affecting several biological processes. Several studies have investigated the role of STAT5 in adipogenesis, but unfortunately, its role in adipogenesis remains controversial. In the present study, we generated adipocyte-specific Stat5 conditional knockout (cKO) (Stat5fl/fl;Apn-cre) mice to investigate the role of STAT5 in the adipogenesis of bone marrow mesenchymal stem cells (BMSCs). BMSC adipogenesis was significantly inhibited upon overexpression of constitutively active STAT5A, while it was enhanced in the absence of Stat5 in vitro. In vivo adipose staining and histological analyses revealed increased adipose volume in the bone marrow of Stat5 cKO mice. ATF3 is the target of STAT5 during STAT5-mediated inhibition of adipogenesis, and its transcription is regulated by the binding of STAT5 to the Atf3 promoter. ATF3 overexpression was sufficient to suppress the enhanced adipogenesis of Stat5-deficient adipocytes, and Atf3 silencing abolished the STAT5-mediated inhibition of adipogenesis. Stat5 cKO mice exhibited reduced bone volume due to an increase in the osteoclast number, and coculture of bone marrow-derived macrophages with Stat5 cKO adipocytes resulted in enhanced osteoclastogenesis, suggesting that an increase in the adipocyte number may contribute to bone loss. In summary, this study shows that STAT5 is a negative regulator of BMSC adipogenesis and contributes to bone homeostasis via direct and indirect regulation of osteoclast differentiation; therefore, it may be a leading target for the treatment of both obesity and bone loss-related diseases.


2013 ◽  
Author(s):  
Melo Ocarino Natalia de ◽  
Silvia Silva Santos ◽  
Lorena Rocha ◽  
Juneo Freitas ◽  
Reis Amanda Maria Sena ◽  
...  

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