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Frederick, MA, United States

Rippo M.R.,Marche Polytechnic University | Babini L.,Marche Polytechnic University | Prattichizzo F.,Marche Polytechnic University | Graciotti L.,Marche Polytechnic University | And 9 more authors.
Cell Death and Disease | Year: 2013

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that can differentiate into several cell types. Bone marrow (BM)-MSCs mainly differentiate into osteoblasts or adipocytes. MSC interactions with their microenvironment directly affect their self-renewal/differentiation program. Here, we show for the first time that Fas ligand (FasL), a well-explored proapoptotic cytokine, can promote proliferation of BM-derived MSCs in vitro and inhibits their differentiation into adipocytes. BM-MSCs treated with a low FasL dose (0.5 ng/ml) proliferated more rapidly than untreated cells without undergoing spontaneous differentiation or apoptosis, whereas higher doses (25 ng/ml) induced significant though not massive BM-MSC death, with surviving cells maintaining a stem cell phenotype. At the molecular level, 0.5 ng/ml FasL induced ERK1/2 phosphorylation and survivin upregulation, whereas 25 ng/ml FasL induced caspase activation. Importantly, 25 ng/ml FasL reversibly prevented BM-MSC differentiation into adipocytes by modulating peroxisome proliferator-activated receptor gamma (PPARc) and FABP4/aP2 expression induced by adipogenic medium. All such effects were inhibited by anti-Fas neutralizing antibody. The in vitro data regarding adipogenesis were confirmed using Fas lpr mutant mice, where higher PPARc and FABP4/aP2 mRNA and protein levels were documented in whole tibia. These data show for the first time that the FasL/Fas system can have a role in BM-MSC biology via regulation of both proliferation and adipogenesis, and may have clinical relevance because circulating Fas/FasL levels decline with age and several age-related conditions, including osteoporosis, are characterized by adipocyte accumulation in BM. © 2013 Macmillan Publishers Limited All rights reserved. Source

Fishwick K.J.,Neural Development Group | Li R.A.,Neural Development Group | Halley P.,Neural Development Group | Deng P.,Neural Development Group | Storey K.G.,Neural Development Group
Developmental Biology | Year: 2010

Regulated neuron production within the vertebrate nervous system relies on input from multiple signalling pathways. Work in the Drosophila retina has demonstrated that PI3-kinase and downstream TOR signalling regulate the timing of photoreceptor differentiation; however, the function of such signals during vertebrate neurogenesis is not well understood. Here we show that mutant mice lacking PKB activity downstream of PDK1, the master kinase of the PI3-kinase pathway, exhibit deficient neuron production. We further demonstrate expression of PI3-kinase signalling components and active PKB and TOR signalling in the chick spinal cord, an early site of neurogenesis. Neuron production was also attenuated in the chick neural tube following exposure to small molecule inhibitors of PI3-kinase (LY294002) or TOR (Rapamycin) activity. Furthermore, Rapamycin repressed expression of early neuronal differentiation genes, such as Ngn2, but did not inhibit expression of Sox1B genes characteristic of proliferating neural progenitors. In addition, some cells expressing an early neuronal marker were mis-localised at the ventricular surface in the presence of Rapamycin and remained aberrantly within the cell cycle. These findings suggest that TOR signalling is necessary to initiate neuronal differentiation and that it may facilitate coordination of cell cycle and differentiation programmes. In contrast, stimulating PI3-kinase signalling did not increase neuron production, suggesting that such activity is simply permissive for vertebrate neurogenesis. © 2009 Elsevier Inc. All rights reserved. Source

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