Molecular-genetic and immunophenotypic analysis of antigen profile and osteogenic and adipogenic potentials of mesenchymal stromal cells from fetal liver and adult bone marrow in rats

Comparative characteristics of mesenchymal stromal cells (MSCs) from adult bone marrow and fetal liver are of great interest due to the similar functions performed by these organs on the organization of a hemopoietic microenvironment at various developmental periods. It is known that MSCs play a pivotal role in the formation of niches for hemopoietic stem cells. The histogenetic relation of MSCs from these two hemopoietic organs cannot be ruled out. An analysis of antigen profile using immunocytochemistry and RT-PCR has confirmed that the studied cell populations fit the MSC criteria and have no contaminations of hemopoietic, lymphoid, and endothelial cells beginning at the second passage. Comparative analysis of osteogenic and adipogenic marker expression revealed MSC from fetal liver to have a weaker potential for adipogenesis and the extremely low capability for terminal osteogenic differentiation, in contrast to pronounced osteo- and adipogenic potentials of adult bone marrow MSC. The similar cell phenotype but different differentiation potentials under identical conditions of cultivation in vitro seem to be due to different developmental programs of the pre- and postnatal histogenesis of these MSC.     

Soy pinitol acts partly as an insulin sensitizer or insulin mediator in 3T3-L1 preadipocytes

The blood glucose-lowering property of pinitol is mediated via the insulin signaling pathway. This study was carried out to evaluate the effects of soy pinitol on adipogenesis in a 3T3-L1 cell line; 3T3-L1 preadipocytes were treated with pinitol (0-1 mM) together with insulin for 9 days. The regulation of lipid metabolism was assessed by oil-red-O staining of intracellular lipids and real-time PCR of adipogenesis-related factors. The inhibition of cell proliferation was estimated by MTT assay. Pinitol treatment did not inhibit lipid accumulation, nor did it affect expression of adipogenesis-related factors, including ADD1, aP2 and FAS, in a dose-dependent manner. Expression of adiponectin, GLUT4, IRS, C/EBPalpha and PPARgamma mRNAs, however, increased in cells treated with 0.5 mM and/or 1 mM pinitol. Pinitol treatment did not affect the inhibition of cell growth and proliferation in a dose-dependent manner. Accordingly, we suggest that pinitol is nontoxic to this cell line, and that it enhances adipogenesis by acting as an insulin sensitizer or insulin mediator via the upregulation of adiponectin, GLUT4, IRS, C/EBPalpha and PPARgamma in 3T3-L1 preadipocytes.     

dlk modulates mitogen-activated protein kinase signaling to allow or prevent differentiation

The EGF-like membrane protein dlk plays a crucial role in the control of cell differentiation. Overexpression of the protein prevents, whereas inhibition of its expression increases, adipocyte differentiation of 3T3-L1 cells in response to Insulin-like Growth Factor I (IGF-1) or insulin. We have investigated whether dlk modulates the signaling pathways known to control this process. We found that the levels of dlk expression modulated signaling through the IGF-1 receptor, causing changes in the activation levels and kinetics of Extracellular-Regulated Kinase/Mitogen-Activated Protein Kinase (ERK/MAPK) that correlated with differentiation outcome. These changes occurred in response to IGF-1 or insulin but not in response to Epidermal Growth Factor. However, the levels of expression of IGF-1 receptor, or the activation of Insulin Receptor Substrate-1 in response to IGF-1, were not affected by the levels of dlk expression. Therefore, dlk appears to modulate ERK/MAPK signaling in response to specific differentiation signals.     

The novel gene EGFL9/Dlk2, highly homologous to Dlk1, functions as a modulator of adipogenesis

The Dlk1 gene appears to function as a regulator of adipogenesis. Adult Dlk1-deficient mice are obese, but adipose tissue still develops in transgenic mice overexpressing an Fc-dlk1 fusion protein, and neither type of genetically modified mice displays serious abnormalities. It was therefore possible that one yet unidentified gene might either compensate or antagonize for the absence or for overexpression, respectively, of Dlk1 in those animals. In database searches, we found a novel gene, EGFL9, encoding for a protein whose structural features are virtually identical to those of dlk1, suggesting it may function in a similar way. As dlk1 does, the protein encoded by EGFL9/Dlk2 affects adipogenesis of 3T3-L1 preadipocytes and mesenchymal C3H10T1/2 cells; however, it does so in an opposite way to that of dlk1. In addition, expression levels of both genes appear to be inversely correlated in both cell lines. Moreover, enforced changes in the expression of one gene affect the expression levels of the other. Our data suggest that adipogenesis may be modulated by the coordinated expression of Dlk1 and EGFL9/Dlk2.     

Monocyte chemoattractant protein-1 and nitric oxide promote adipogenesis in a model that mimics obesity

Objective: An increasing body of evidence is emerging linking adipogenesis and inflammation. Obesity, alone or as a part of the metabolic syndrome, is characterized by a state of chronic low‐level inflammation as revealed by raised plasma levels of inflammatory cytokines and acute‐phase proteins. If inflammation can, in turn, increase adipose tissue growth, this may be the basis for a positive feedback loop in obesity. We have developed a tissue engineering model for growing adipose tissue in the mouse that allows quantification of increases in adipogenesis. In this study, we evaluated the adipogenic potential of the inflammogens monocyte chemoattractant protein (MCP)‐1 and zymosan‐A (Zy) in a murine tissue engineering model. Research Methods and Procedures: MCP‐1 and Zy were added to chambers filled with Matrigel and fibroblast growth factor 2. To analyze the role of inducible nitric oxide synthase (iNOS), the iNOS inhibitor aminoguanidine was added to the chamber. Results: Our results show that MCP‐1 generated proportionally large quantities of new adipose tissue. This neoadipogenesis was accompanied by an ingrowth of macrophages and could be mimicked by Zy. Aminoguanidine significantly inhibited the formation of adipose tissue. Discussion: Our findings demonstrate that low‐grade inflammation and iNOS expression are important factors in adipogenesis. Because fat neoformation in obesity and the metabolic syndrome is believed to be mediated by macrophage‐derived proinflammatory cytokines, this adipose tissue engineering system provides a model that could potentially be used to further unravel the pathogenesis of these two metabolic disorders.     

Propyl Gallate Inhibits Adipogenesis by Stimulating Extracellular Signal-Related Kinases in Human Adipose Tissue-Derived Mesenchymal Stem Cells

Propyl gallate (PG) used as an additive in various foods has antioxidant and anti-inflammatory effects. Although the functional roles of PG in various cell types are well characterized, it is unknown whether PG has effect on stem cell differentiation. In this study, we demonstrated that PG could inhibit adipogenic differentiation in human adipose tissue-derived mesenchymal stem cells (hAMSCs) by decreasing the accumulation of intracellular lipid droplets. In addition, PG significantly reduced the expression of adipocyte-specific markers including peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT enhancer binding protein-α (C/EBP-α), lipoprotein lipase (LPL), and adipocyte fatty acid-binding protein 2 (aP2). PG inhibited adipogenesis in hAMSCs through extracellular regulated kinase (ERK) pathway. Decreased adipogenesis following PG treatment was recovered in response to ERK blocking. Taken together, these results suggest a novel effect of PG on adipocyte differentiation in hAMSCs, supporting a negative role of ERK1/2 pathway in adipogenic differentiation.