Duration and magnitude of extracellular signal-regulated protein kinase phosphorylation determine adipogenesis or osteogenesis in human bone marrow-derived stem cells

Purpose

Imbalances between osteogenic and adipogenic differentiation leads to diseases such as osteoporosis. The aim of our study was to demonstrate the differences in extracellular signal-regulated kinase (ERK) phosphorylation during both adipogenesis and osteogenesis of human bone marrow-derived stem cells (BMSCs).

Materials and Methods

Using troglitazone, GW9662 and U0126, we investigated their role in hBMSC differentiation to adipogenic and osteogenic fates.

Results

ERK1/2 inhibition by U0126 suppressed proliferator-activated receptor (PPAR)γ expression and lipid accumulation, while it decreased the mRNA expression of adipogenic genes (lipoprotein lipase, PPARγ, and adipocyte protein) and osteogenic genes (type I collagen and osteopontin). ERK phosphorylation was transient and decreased during adipogenesis, whereas it occurred steadily during osteogenesis. Troglitazone, a PPARγ agonist, induced adipogenesis by inhibiting ERK phosphorylation even in an osteogenic medium, suggesting that ERK signaling needs to be shut off in order to proceed with adipose cell commitment. Cell proliferation was greatly increased in osteogenesis but was not changed during adipogenesis, indicating that ERK might play different roles in cellular proliferation and differentiation between the two committed cell types.

Conclusion

The duration and magnitude of ERK activation might be a crucial factor for the balance between adipogenesis and osteogenesis in human bone marrow-derived stem cells.     

3种不同来源CD146阳性间充质干细胞亚群的生物学特性比较

目的比较脐带间充质干细胞(UCMSCs)、脂肪间充质干细胞(AMSCs)以及骨髓间充质干细胞(BM-MSCs)中CD146^+细胞亚群的生物学特性。方法用磁珠分选法分选不同组织来源的间充质干细胞,获得高纯度CD146^+亚群;用流式细胞计量术分析表型;透射电子显微镜观察细胞结构;成脂诱导分化后油红O染色;RT-qPCR检测成脂相关基因LPL、C/EBPα和PPARγ表达;成骨诱导分化后ALP染色,检测成骨相关基因ALP、OPN和RUNX2表达;检测细胞干性基因及血管生成相关基因表达;检测细胞体外成管能力。结果3种组织来源CD146^+MSCs具有相似的形态,表达除CD106外相似的细胞表面标志分子。与其他两种细胞比较,CD146^+AMSCs表达更高的干性基因OCT-4、SOX2和NANOG。在相同的诱导时间,CD146^+UCMSCs成脂和成骨能力较其他两种来源的CD146^+MSCs弱。3种组织来源的CD146^+MSCs均可表达血管内皮相关刺激因子BFGF、VEGF、Ang-1和EGF,但CD146^+BM-MSCs具有更强的体外成管能力。结论3种不同来源的CD146^+MSC具有不同的生物学特性,为进一步研究不同组织来源的间充质干细胞的特定应用提供了基础。     

Effects of Human Fibroblast-Derived Extracellular Matrix on Mesenchymal Stem Cells

Stem cell fate is largely determined by the microenvironment called niche. The extracellular matrix (ECM), as a key component in the niche, is responsible for maintaining structural stability and regulating cell proliferation, differentiation, migration and other cellular activities. Each tissue has a unique ECM composition for its needs. Here we investigated the effect of a bioengineered human dermal fibroblast-derived ECM (hECM) on the regulation of human mesenchymal stem cell (hMSC) proliferation and multilineage differentiation. Human MSCs were maintained on hECM for two passages followed by the analysis of mRNA expression levels of potency- and lineage-specific markers to determine the capacity of MSC stemness and differentiation, respectively. Mesenchymal stem cells pre-cultured with or without hECM were then induced and analyzed for osteogenesis, adipogenesis and chondrogenesis. Our results showed that compared to MSCs maintained on control culture plates without hECM coating, cells on hECM-coated plates proliferated more rapidly with a higher percentage of cells in S phase of the cell cycle, resulting in an increase in the CD90⁺/CD105⁺/CD73⁺/CD45^? subpopulation. In addition, hECM downregulated osteogenesis and adipogenesis of hMSCs but significantly upregulated chondrogenesis with increased production of collagen type 2. In sum, our findings suggest that hECM may be used to culture hMSCs for the application of cartilage tissue engineering.     

Modulation of intercellular adhesion molecule 1 (ICAM-1) expression on the human mast-cell line (HMC)-1 by inflammatory mediators

The effect of inflammatory mediators on the expression of several surface adhesion molecules on the human mast-cell line (HMC)-1 was studied. By flow cytometry, it could be shown that among several surface adhesion molecules (ICAM-UCDS4, VLA-4/CD49d, Mac-UCD11b, LFA-1/CD11a, LFA-2/CD2, LFA-3/CDS8, VCAM-1), only the constitutively expressed immunoglobulin family member intercellular adhesion molecule-1 (ICAM-1) is modulated by proinflammatory cytokines on HMC-1 mast cells. Stimulation with tumor necrosis factor-a (TNF-α) and interferon-γ (IFN-γ) resulted, in addition to interleukin-(lL-)4, in selective upregulation of ICAM-1 expression. Costimulation of either IL-4 or IFN-γ with TNF-α further increased the ICAM-1 expression as compared to the stimuli alone. In contrast, stem-cell factor (SCF), granulocyte/macrophage colonystimulating factor (GM-CSF), IL-10, IL-8, monocyte chemotactic and activating factor (MCAF), and the complement split product C5a failed to modulate the expression of any adhesion molecule examined. The levels of cytoplasmic free calcium in HMC-1 mast cells were not altered by cross-linking surface ICAM-1, suggesting linkage of other intracellular signaling pathways. This cytokine-induced upregulation of ICAM-1 expression might reveal a putative regulatory mechanism of mast-cell interaction with effector cells bearing the counterparts of ICAM-1 (CD54), the molecules Mac-1 (CD11b/CD18) and leukosialin (CD43), and the principal ligand LFA-1 (CD11a/CD18).     

Gene Expression Pattern of Human Chorion-Derived Mesenchymal Stem Cells during Adipogenic Differentiation

Purpose: The aim of this study was to identify the adipocyte-specific gene expression patterns in chorion-derived mesenchymal stem cells during adipogenic differentiation. Materials and Methods: Chorionic cells were isolated from the third trimester chorions from human placenta at birth and identified morphologically and by fluorescence-activated cell sorting analysis. After inducing adipogenic differentiation for 28 days, cells at days 3, 10, 21 and 28 were analyzed by Oil red O staining and RNA extraction in order to assess the expression levels of adipocyte marker genes, including CCAAT-enhancer binding protein α (C/EBPα), peroxisome proliferator- activated receptor γ (PPARγ), fatty acid binding protein 4 (FABP4) and Glycerol-3-phosphate dehydrogenase (GPD2). Cells not induced for differentiation were compared with the induced cells as a control group. Results: Chorion-derived cells showed the same pattern as fibroblasts, and expressed CD73, CD105, and CD166 antigens, but not CD45, CD34, and HLA-DR antigens. On day 3 after differentiation, cells began to stain positively upon Oil red O staining, and continuously increased in lipid granules for 4 weeks. The expression level of C/EBPα increased 4.6 fold on day 3 after induction, and continued to increase for 4 weeks. PPARγ was expressed at a maximum of 2.9 fold on day 21. FABP4 and GPD2 were significantly expressed at 4.7- and 3.0-fold, respectively, on day 21, compared to controls, and further increased thereafter. Conclusion: Human chorion-derived mesenchymal stem cells exhibited the sequential expression pattern of adipocyte marker genes during differentiation, corresponding to adipogenesis.