scholarly journals The Role of the Wnt Signaling Pathway in the Osteogenic Differentiation of Human Adipose-derived Stem Cells under Mechanical Stimulation

2015 ◽  
Vol 24 (2) ◽  
pp. 169-180
Author(s):  
Hong-ming Du ◽  
Li-ya Wang ◽  
Xiao-hui Zheng ◽  
Wei Tang ◽  
Lei Liu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Wnt Signaling ◽  
Osteogenic Differentiation ◽  
Signaling Pathway ◽  
Mechanical Stimulation ◽  
Wnt Signaling Pathway ◽  
Adipose Derived Stem Cells

Polycomb Repressive Complex 1 Enhances HSC Self-Renewal through Repressing the Canonical Wnt Signaling Pathway

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2378-2378
Author(s):  
Sisi Chen ◽  
Xicheng Liu ◽  
Rui Gao ◽  
Michihiro Kobayashi ◽  
Hao Yu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Wnt Signaling Pathway ◽  
Canonical Wnt Signaling ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Canonical Wnt

Abstract Polycomb group (PcG) proteins are epigenetic gene silencers that have been implicated in stem cell maintenance and cancer development. Genetic and biochemical studies indicate that Polycomb group proteins exist in at least two protein complexes, Polycomb repressive complex 2 (PRC2) and Polycomb repressive complex 1 (PRC1), that act in concert to initiate and maintain stable gene repression. While studies on individual PRC1 component suggest that PRC1 plays an important role in hematopoiesis, how PRC1 regulates transcriptional repression in hematopoietic stem cells (HSCs) is largely unknown. Bmi1 and Mel18 are two major homologs of the PCGF subunit within the PRC1 complex. Bmi1 is a positive regulator of HSC self-renewal; however, the role of Mel18 in hematopoiesis has been controversial. To determine whether Bmi1 and Mel18 play redundant or distinct role in HSC self-renewal, we have generated Bmi1 and Mel18 conditional knockout mice. While acute deletion of Mel18 affects neither HSC frequency nor lineage commitment, we found that Mel18-deficent hematopoietic progenitor cells showed enhanced replating potential compared to wild type cells. To determine the role of Mel18 in HSC self-renewal, we performed serial HSC transplantation assays and found that the repopulating ability of Mel18-/- HSCs was significantly higher than WT HSCs in both primary and secondary transplantation assays, demonstrating that the loss of Mel18 enhances HSC self-renewal in vivo. We hypothesize that loss of Bmi1 and Mel18 in hematopoietic stem cells will disrupt PRC1 complex and impairs HSC self-renewal. To determine the role of PRC1 complex in HSCs, we analyzed the HSC behavior in Bmi1 and Mel18 double-deficient mice. While we found that Bmi1-deficient HSCs showed decreased repopulating potential compared to WT HSCs 16 weeks following transplantation, loss of both Bmi1 and Mel18 in HSCs resulted in even more severe self-renewal defects. In addition, loss of both Bmi1 and Mel18 resulted in decreased myeloid differentiation and increased B cell differentiation compared to WT, Mel18 KO, and Bmi1 KO mice. These data demonstrate that Bmi1 and Mel18 have non-overlapping role in HSC maintenance and lineage commitment. Given that Bmi1 plays a dominant role in the PRC1 complex, we decided to identify Bmi1 target genes in hematopoietic stem cells to understand how PRC1 complex regulates HSC self-renewal. We performed transcript profiling assays to compare gene expression in HSCs isolated from wild type and Bmi1-/- mice. The Ingenuity Pathways indicates that the canonical Wnt signaling is significantly elevated in Bmi1 null HSCs compared to WT HSCs. We confirmed the upregulation of several genes of the Wnt pathway in Bmi1 null HSCs by quantitative real-time PCR analysis. To determine whether Bmi1 can repress the activation of Wnt signaling in cells, we utilized the Top-Flash Wnt reporter system. Stimulation of 293T cells with Wnt3a activates the Wnt reporter and this activation can be efficiently repressed by Bmi1. Furthermore, we detected the association of Bmi1 with the Lef1, Tcf4, and Axin2 promoters in Baf3 cells by ChIP experiment. Thus, Bmi1 directly represses the expression of several Wnt genes in hematopoietic cells. To determine the functional significance of activation of Wnt signaling in Bmi1 null HSCs, we have generated R26StopFL Bmi1-Apcf/f-Mx1-Cre+ and Bmi1f/f-Ctnnb1f/f-Mx1-Cre+ mice. Loss of Apc in hematopoietic cells activates the Wnt signaling pathway and impairs HSC self-renewal. We found that expressing three-copies of Bmi1 from the Rosa26 locus enhanced the self-renewal capabilities of Apc deficient HSCs in transplantation assays. Ctnnb1 encodes b-catenin and loss of Ctnnb1 in HSCs diminishes Wnt signaling. Acute deletion of Bmi1 in hematopoietic compartments resulted in decreased bone marrow cellularity and enhanced apoptosis of hematopoietic stem and progenitor cells. Deletion of Ctnnb1 in Bmi1 null hematopoietic cells rescued these defects. Thus, impaired HSC self-renewal seen in Bmi1 null mice is, at least in part, due to activation of the canonical Wnt signaling pathway. Taken together, we demonstrate that PRC1 complex enhances HSC self-renewal through inhibiting the canonical Wnt signaling. Disclosures No relevant conflicts of interest to declare.

scholarly journals Role of Fzd6 in Regulating the Osteogenic Differentiation of Adipose-derived Stem Cells in Osteoporosis

2021 ◽  
Author(s):  
Tianli Wu ◽  
Zhihao Yao ◽  
Gang Tao ◽  
Fangzhi Lou ◽  
Hui Tang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Osteogenic Differentiation ◽  
Wnt Signaling Pathway ◽  
Osteogenic Potential ◽  
Adipose Derived Stem Cells ◽  
Alizarin Red ◽  
Differentiation Potential

Abstract Objective: Although it has been demonstrated that adipose-derived stem cells (ASCs) from osteoporosis mice (OP-ASCs) exhibit impaired osteogenic differentiation potential, the molecular mechanism has not yet been elucidated. We found that Fzd6 was decreased in OP-ASCs compared with ASCs. This study investigates the effects and underlying mechanisms of Fzd6 in the osteogenic potential of OP-ASCs. Methods: Fzd6 expression in ASCs and OP-ASCs was measured by PCR gene chip. Fzd6 overexpression and silencing lentiviruses were used to evaluate the role of Fzd6 in the osteogenic differentiation of OP-ASCs. Real-time PCR (qPCR) and western blotting (WB) was performed to detect the expression of Fzd6 and bone-related molecules, including runt-related transcription factor 2 (Runx2) and osteopontin (Opn). Alizarin red staining and Alkaline phosphatase (ALP) staining was performed following osteogenic induction. Microscopic CT (Micro-CT), hematoxylin and eosin staining (H&E) staining, and Masson staining were used to assess the role of Fzd6 in osteogenic differentiation of osteoporosis (OP) mice in vivo.Results: Expression of Fzd6 was decreased significantly in OP-ASCs. Fzd6 silencing down-regulated the osteogenic ability of OP-ASCs in vitro. Overexpression of Fzd6 rescued the impaired osteogenic capacity in OP-ASCs in vitro. We obtained similar results in vivo.Conclusions: Fzd6 plays an important role in regulating the osteogenic ability of OP-ASCs both in vivo and in vitro. Overexpression of Fzd6 associated with the Wnt signaling pathway promotes the osteogenic ability of OP-ASCs, which provides new insights for the prevention and treatment of OP.

scholarly journals JKAMP Inhibits the Osteogenic Capacity of Adipose-derived Stem Cells in Diabetic Osteoporosis by Modulating the Wnt Signaling Pathway Through Intragenic DNA Methylation

2020 ◽  
Author(s):  
Shuanglin Peng ◽  
Sirong Shi ◽  
Gang Tao ◽  
Yanjing Li ◽  
Dexuan Xiao ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Stem Cells ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Wnt Signaling Pathway ◽  
Underlying Mechanism ◽  
Osteogenic Potential ◽  
Adipose Derived Stem Cells ◽  
Alizarin Red ◽  
Diabetic Osteoporosis

Abstract Background: Diabetic osteoporosis (DOP) is a systemic metabolic bone disease caused by diabetes mellitus (DM). Adipose-derived stem cells (ASCs) play an important role in bone regeneration. Our previous study confirmed that ASCs from DOP mice (DOP-ASCs) have a lower osteogenesis potential compared with control ASCs (CON-ASCs). However, the cause of this poor osteogenesis has not been elucidated. Therefore, this study investigated the underlying mechanism of the decline in the osteogenic potential of DOP-ASCs from the perspective of epigenetics and explored methods to enhance their osteogenic capacity. Methods: The expression level of JNK1-associated membrane protein (JKAMP) and degree of DNA methylation in CON-ASCs and DOP-ASCs were measured by mRNA expression profiling and MeDIP sequencing, respectively. JKAMP small interfering RNA (siRNA) and a Jkamp overexpression plasmid were used to assess the role of JKAMP in osteogenic differentiation of CON-ASCs and DOP-ASCs. Immunofluorescence, qPCR, and western blotting were used to measure changes in expression of Wnt signaling pathway-related genes and osteogenesis-related molecules after osteogenesis induction. Alizarin red and ALP staining was used to confirm the osteogenic potential of stem cells. Bisulfite-specific PCR (BSP) was used to detect JKAMP methylation degree. Results: Expression of JKAMP and osteogenesis-related molecules (RUNX2 and OPN) in DOP-ASCs was decreased significantly in comparison with CON-ASCs. JKAMP silencing inhibited the Wnt signaling pathway and reduced the osteogenic ability of CON-ASCs. Overexpression of JKAMP in DOP-ASCs rescued the impaired osteogenic capacity caused by DOP. Moreover, JKAMP in DOP-ASCs contained intragenic DNA hypermethylated regions related to the downregulation of JKAMP expression. Conclusions: Intragenic DNA methylation inhibits the Wnt signaling pathway by suppressing expression of JKAMP and the osteogenic ability of DOP-ASCs. This study shows an epigenetic explanation for the reduced osteogenic ability of DOP-ASCs, and provides a potential therapeutic target to prevent and treat osteoporosis.

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