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Mesenchymal stem cells (MSCs) are adult multipotent cells able to differentiate toward mature mesodermal lineages. In spite of more than a decade of investigation, little is known about the molecular mechanisms regulating the undifferentiated state and the identity of distinct functional subpopulations in these cells. Transcription factors that regulate the maintenance of the pluripotent state in embryonic stem cells, including NANOG, SOX2, and OCT4, have been proposed to play a similar role also in adult stem cells, although with conflicting results. We performed a critical evaluation of expression of these 3 transcription factors and found that NANOG, but not OCT-4 and SOX-2, is expressed in cultured human adult MSCs. Actually, NANOG was not expressed in freshly isolated MSCs, but was detected only after in vitro culture. NANOG was detected only in proliferating cells, but not in MSCs induced to differentiate. The percentage of cells expressing NANOG was maintained throughout early passages of MSCs, but then started to decrease in late passages in MSCs from adipose tissue and heart but not from bone marrow. However, the number of NANOG-expressing cells did not associate with the proliferative and differentiative capabilities of MSC populations, neither its expression appeared to identify cells having stem or progenitor cell properties. Accordingly, we propose that activation of NANOG expression in MSCs is associated with, although cannot directly regulate, the transition from in vivo quiescence to adaptation to in vitro growth conditions.

Cellular models and culture conditions for in vitro expansion of insulin-producing cells represent a key element to develop cell therapy for diabetes. Initial evidence that human b-cells could be expanded after undergoing a reversible epithelialmesenchymal transition has been recently negated by genetic lineage tracing studies in mice. Here, we report that culturing human pancreatic islets in the presence of serum resulted in the emergence of a population of nestin-positive cells. These proliferating cells were mainly C-peptide negative, although in the first week in culture, proliferating cells, insulin promoter factor-1 (Ipf-1) positive, were observed. Later passages of islet-derived cells were Ipf-1 negative and displayed a mesenchymal phenotype. These human pancreatic islet-derived mesenchymal (hPIDM) cells were expanded up to 10 14 cells and were able to differentiate toward adipocytes, osteocytes and chondrocytes, similarly to mesenchymal stem/precursor cells. Interestingly, however, under serum-free conditions, hPIDM cells lost the mesenchymal phenotype, formed islet-like clusters (ILCs) and were able to produce and secrete insulin. These data suggest that, although these cells are likely to result from preexisting mesenchymal cells rather than b-cells, hPIDM cells represent a valuable model for further developments toward future replacement therapy in diabetes. Cell Death and Differentiation (2007) 14, 1860-1871; doi:10.1038/sj.cdd.4402199; published online 6 July 2007Type 1 diabetes mellitus is a chronic disease resulting from the selective autoimmune destruction of pancreatic insulinproducing b-cells. Transplantation therapy represents a potential cure for type 1 diabetes mellitus, 1 but is limited by availability of human pancreatic tissue. For this reason, a great effort has been made to develop new methods for generating b-like cells in vitro, 2,3 despite of evidence that cultured b-cells have limited proliferative capacity and reduced insulin production. 4 Several attempts have been made to identify stem/progenitors cells within pancreatic tissue as a potential source for transplantable insulinproducing tissue. Unfortunately, the origin of new b-cells in adult pancreas is not known. Some in vivo studies suggested the presence of pancreatic progenitor cells within islets, 5 whereas others reported that new adult b-cells might rather originate from pre-existing b-cells. 6 Additional studies suggested that progenitor cells may reside within the pancreatic ductal epithelium 2-7 or in the acinar tissue. 8,9 Nevertheless, the exact nature and localization of adult pancreatic stem/ progenitor cells remains controversial [9][10][11][12][13][14][15][16] and their existence in vivo, at least in mice, has recently been questioned. 6 Recent evidence has shown that human embryonic stem cells are able to differentiate into insulin-producing cells in vitro, thus potentially leading to an unlimited source of cells for transplantation. 17 These two authors contributed equally to this work. 5 These two authors share...

The antimetastatic ruthenium complex imidazolium transimidazoledimethylsulfoxide-tetrachlorouthenate (NAMI-A) is tested in the B16 melanoma model in vitro and in vivo. Treatment of B6D2F1 mice carrying intra-footpad B16 melanoma with 35 mg/kg/day NAMI-A for 6 days reduces metastasis weight independently of whether NAMI-A is given before or after surgical removal of the primary tumor. Metastasis reduction is unrelated to NAMI-A concentration, which is 10-fold lower than on primary site (1 versus 0.1 mM), and is correlated to the reduction of plasma gelatinolitic activity and to the decrease of cells expressing CD44, CD54, and integrin-␤ 3 adhesion molecules. Metastatic cells also show the reduction of the S-phase cells with accumulation in the G 0 /G 1 phase. In vitro, on the highly metastatic B16F10 cell line, NAMI-A reduces cell Matrigel invasion and its ability to cross a layer of endothelial cells after short exposure (1 h) to 1 to 100 M concentrations. In these conditions, NAMI-A reduces the gelatinase activity of tumor cells, and it also increases cell adhesion to poly-L-lysine and, in particular, to fibronectin, and this effect is associated to the increase of F-actin condensation. This work shows the selective effectiveness of NAMI-A on the metastatic melanoma and suggests that metastasis inhibition is due to the negative modulation of tumor cell invasion processes, a mechanism in which the reduction of the gelatinolitic activity of tumor cells plays a crucial role.

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