IntroductionThe ability to self-renew, be easily expanded in vitro and differentiate into different mesenchymal tissues, render mesenchymal stem cells (MSCs) an attractive therapeutic method for degenerative diseases. The subsequent discovery of their immunosuppressive ability encouraged clinical trials in graft-versus-host disease and auto-immune diseases. Despite sharing several immunophenotypic characteristics and functional capabilities, the differences between MSCs arising from different tissues are still unclear and the published data are conflicting.MethodsHere, we evaluate the influence of human MSCs derived from umbilical cord matrix (UCM), bone marrow (BM) and adipose tissue (AT), co-cultured with phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (MNC), on T, B and natural killer (NK) cell activation; T and B cells’ ability to acquire lymphoblast characteristics; mRNA expression of interleukin-2 (IL-2), forkhead box P3 (FoxP3), T-bet and GATA binding protein 3 (GATA3), on purified T cells, and tumor necrosis factor-alpha (TNF-α), perforin and granzyme B on purified NK cells.ResultsMSCs derived from all three tissues were able to prevent CD4+ and CD8+ T cell activation and acquisition of lymphoblast characteristics and CD56dim NK cell activation, wherein AT-MSCs showed a stronger inhibitory effect. Moreover, AT-MSCs blocked the T cell activation process in an earlier phase than BM- or UCM-MSCs, yielding a greater proportion of T cells in the non-activated state. Concerning B cells and CD56bright NK cells, UCM-MSCs did not influence either their activation kinetics or PHA-induced lymphoblast characteristics, conversely to BM- and AT-MSCs which displayed an inhibitory effect. Besides, when co-cultured with PHA-stimulated MNC, MSCs seem to promote Treg and Th1 polarization, estimated by the increased expression of FoxP3 and T-bet mRNA within purified activated T cells, and to reduce TNF-α and perforin production by activated NK cells.ConclusionsOverall, UCM-, BM- and AT-derived MSCs hamper T cell, B cell and NK cell-mediated immune response by preventing their acquisition of lymphoblast characteristics, activation and changing the expression profile of proteins with an important role in immune function, except UCM-MSCs showed no inhibitory effect on B cells under these experimental conditions. Despite the similarities between the three types of MSCs evaluated, we detect important differences that should be taken into account when choosing the MSC source for research or therapeutic purposes.

BackgroundEnhanced lysosomal trafficking is associated with metastatic cancer. In an attempt to discover cancer relevant lysosomal motor proteins, we compared the lysosomal proteomes from parental MCF-7 breast cancer cells with those from highly invasive MCF-7 cells that express an active form of the ErbB2 (ΔN-ErbB2).Methodology/Principal FindingsMass spectrometry analysis identified kinesin heavy chain protein KIF5B as the only microtubule motor associated with the lysosomes in MCF-7 cells, and ectopic ΔN-ErbB2 enhanced its lysosomal association. KIF5B associated with lysosomes also in HeLa cervix carcinoma cells as analyzed by subcellular fractionation. The depletion of KIF5B triggered peripheral aggregations of lysosomes followed by lysosomal destabilization, and cell death in HeLa cells. Lysosomal exocytosis in response to plasma membrane damage as well as fluid phase endocytosis functioned, however, normally in these cells. Both HeLa and MCF-7 cells appeared to express similar levels of the KIF5B isoform but the death phenotype was weaker in KIF5B-depleted MCF-7 cells. Surprisingly, KIF5B depletion inhibited the rapamycin-induced accumulation of autophagosomes in MCF-7 cells. In KIF5B-depleted cells the autophagosomes formed and accumulated in the close proximity to the Golgi apparatus, whereas in the control cells they appeared uniformly distributed in the cytoplasm.Conclusions/SignificanceOur data identify KIF5B as a cancer relevant lysosomal motor protein with additional functions in autophagosome formation.

Tamoxifen (TAM), the widely prescribed drug in the prevention and therapy of breast cancer, is a well-known modulator of estrogen receptor (ER) that also inhibits the proliferation of different cell types that lack the ER. However, the ER-independent action mechanisms of TAM and its side effects have not been yet clarified. Mitochondria are essential in supporting the energy-dependent regulation of cell functions. Changes in mitochondria result in bioenergetic deficits leading to the loss of vital functions to cell survival. Therefore, this study describes the effects of TAM on mitochondrial bioenergetics, contributing to a better understanding of the biochemical mechanisms underlying the multiple antiproliferative and toxic effects of this drug. TAM at concentrations above 20 nmol/mg protein, preincubated with isolated rat liver mitochondria at 25°C for 3 min, significantly depresses, in a dose-dependent manner, the phosphorylation efficiency of mitochondria as inferred from the decrease in the respiratory control and ADP/O ratios, the perturbations in mitochondrial transmembrane potential (⌬⌿), the fluctuations associated with mitochondrial energization, and the phosphorylative cycle induced by ADP. Furthermore, TAM at up to 40 nmol/mg protein stimulates the rate of state 4 respiration and at higher concentrations it strongly inhibits state 3 and uncouples the mitochondrial respiration. The stimulation of state 4 respiration parallels the decrease of ⌬⌿ as a consequence of proton permeability. The TAM-stimulatory action of ATPase is also observed in intact mitochondria, suggesting that TAM promotes extensive permeability to protons due to destructive effects in the structural integrity of the mitochondrial inner membrane. These multiple effects of TAM on mitochondrial bioenergetic functions, causing changes in the respiration, phosphorylation efficiency, and membrane structure, may explain the cell death induced by this drug in different cell types, its anticancer activity in ER-negative cells, and its side effects. © 2001 Academic Press Key Words: tamoxifen; anticancer drug; mitochondria; respiration rate; mitochondrial transmembrane potential; mitochondrial proton leak; membrane disruption.Tamoxifen (TAM) is the most used nonsteroidal antiestrogen drug for chemotherapy and chemoprevention of breast cancer (Neven and Vernaeve, 2000;Radmacher and Simon, 2000). The antiproliferative effects of TAM in estrogen-dependent breast cancer cells are mediated by high-affinity binding to the estrogen receptor (ER) (Coezy et al., 1982). However, TAM inhibits also the growth of ER-negative breast cancer cells and other cell types that lack ER (Couldwell et al., 1993;Croxtall et al., 1994;Charlier et al., 1995). Actually, TAM has been reported to have several physiological effects that are ER independent, including sensitization of resistant tumor cells to many chemotherapeutic agents (Altan et al., 1999) and several pleiotropic effects both in vivo and in vitro and references therein). Moreover, it has been reported that...

Mesenchymal stem cells (MSC) could potentially be applied in therapeutic settings due to their multilineage differentiation ability, immunomodulatory properties, as well as their trophic activity. The umbilical cord matrix (UCM) represents a promising source of MSC for biomedical applications. The number of cells isloated per umbilical cord (UC) unit is limited and ex vivo expansion is imperative in order to reach clinically meaningful cell numbers. The limitations of poorly defined reagents (e.g. fetal bovine serum, which is commonly used as a supplement for human MSC expansion) make the use of serum-/xeno-free conditions mandatory. We demonstrated the feasibility of isolating UCM-MSC by plastic adherence using serum-/xeno-free culture medium following enzymatic digestion of UCs, with a 100% success rate. 2.6 ± 0.21 × 10(5) cells were isolated per UC unit, of which 1.9 ± 0.21 × 10(5) were MSC-like cells expressing CD73, CD90, and CD105. When compared to adult sources (bone marrow-derived MSC and adipose-derived stem/stromal cells), UCM-MSC displayed a similar immunophenotype and similar multilineage differentiation ability, while demonstrating a higher expansion potential (average fold increase of 7.4 for serum-containing culture medium and 11.0 for xeno-free culture medium (P3-P6)). The isolation and expansion of UCM-MSC under defined serum-/xeno-free conditions contributes to safer and more effective MSC cellular products, boosting the usefulness of MSC in cellular therapy and tissue engineering.

Phagosome maturation follows a defined biochemical program and, in the vast majority of cases, the microbe inside the phagosome is killed and digested. Although, an important number of pathogens, including Mycobacterium tuberculosis, which kills around two million people every year, have acquired the ability to survive, and even replicate by arresting phagosomal maturation. To identify more of the machinery involved in phagocytosis and phagosomal maturation, we investigated the function of Rab10 in engulfment and maturation of inert particles and Mycobacterium bovis bacille Calmette-Guérin (BCG). We showed that Rab10 association with phagosomes is transient and confocal microscopy revealed detectible levels of Rab10 on phagosomal membranes at very early time-points, occurring even before Rab5 acquisition. Rab10 recruitment had strong functional consequence, as the knockdown of endogenous Rab10 by RNA interference or overexpression of Rab10 dominantnegative mutant delayed maturation of phagosomes of IgG-opsonized latex beads or heat killed-mycobacteria. These results can be explained, at least in part, by the involvement of Rab10 in recycling of some phagosomal components. More importantly, overexpression of the constitutively active mutant of Rab10 partially rescued live-Mycobacterium-containing phagosomes maturation. Indeed, we found that the membrane harbouring Mycobacterium acquired early endosome antigen 1 (EEA-1), a marker excluded from phagosomes in control cells. Altogether these results indicate that Rab10, acting upstream of Rab5, plays a prominent role in phagolysosome formation and can modulate Mycobacterium-containing phagosomes maturation.