Progenitor cells of the testosterone-producing Leydig cells revealed

The cells responsible for production of the male sex hormone testosterone, the Leydig cells of the testis, are post-mitotic cells with neuroendocrine characteristics. Their origin during ontogeny and regeneration processes is still a matter of debate. Here, we show that cells of testicular blood vessels, namely vascular smooth muscle cells and pericytes, are the progenitors of Leydig cells. Resembling stem cells of the nervous system, the Leydig cell progenitors are characterized by the expression of nestin. Using an in vivo model to induce and monitor the synchronized generation of a completely new Leydig cell population in adult rats, we demonstrate specific proliferation of vascular progenitors and their subsequent transdifferentiation into steroidogenic Leydig cells which, in addition, rapidly acquire neuronal and glial properties. These findings, shown to be representative also for ontogenetic Leydig cell formation and for the human testis, provide further evidence that cellular components of blood vessels can act as progenitor cells for organogenesis and repair.     

B cells as antigen presenting cells

Several characteristics confer on B cells the ability to present antigen efficiently: (1) they can find T cells in secondary lymphoid organs shortly after antigen entrance, (2) BCR-mediated endocytosis allows them to concentrate small amounts of specific antigen, and (3) BCR signaling and HLA-DO expression direct their antigen processing machinery to favor presentation of antigens internalized through the BCR. When presenting antigen in a resting state, B cells can induce T cell tolerance. On the other hand, activation by antigen and T cell help converts them into APC capable of promoting immune responses. Presentation of self antigens by B cells is important in the development of autoimmune diseases, while presentation of tumor antigens is being used in vaccine strategies to generate immunity. Thus, detailed understanding of the antigen presenting function of B cells can lead to their use for the generation or inhibition of immune responses.     

Stem cells: The root of all cells

The plant basic body plan is laid down during embryogenesis. All post-embryonic development has its origin in the stem cells located in niches in the heart of the shoot and root meristems. Creating the root niche requires auxin dependent patterning cues that provide positional information in combination with parallel inputs to specify and maintain the root stem cell niche from embryogenesis onwards. Once established, the architecture of the root niche differs from that in the shoot but recent findings reveal a conserved module for stem cell control. Important for stem cell maintenance is the balance between cell division and differentiation. Dealing with the environment is the biggest challenge for plants and that includes complete regeneration of stem cell systems upon damage. Here we will address these issues as we follow the formation, function and maintenance of the root stem cell niche during development.     

Differentiation of primate ES cells into retinal cells induced by ES cell-derived pigmented cells

Purpose: Photoreceptors cannot regenerate and recover their functions once disordered. Transplantation of retinal pigment epithelium (RPE) has recently become a possible therapeutic approach for retinal degeneration. In the present study, we investigated the induction of photoreceptors by coculturing primate embryonic stem cells (ESCs) with ESC-derived RPE cells. Methods: RPE cells were derived by coculturing ESCs and Sertoli cells. Photoreceptors were then induced by using ESC-derived RPE cells and retinoic acid (RA) Results: RPE cell generation was confirmed by morphological analysis, which revealed highly pigmented polygonal cells with a compact cell-cell arrangement. After coculturing ESCs and RPE cells, some ESC derivatives became immunopositive for rhodopsin. RT-PCR analysis demonstrated the expression of retina-related gene markers such as Pax6, CRX, IRBP, rhodopsin, rhodopsin kinase, and Muschx10A. When RA was added, a distinct increase in the expression of photoreceptor-specific proteins and genes was found. In addition, the differentiation of bipolar horizontal cells was demonstrated by protein and gene expression. The ESCs that were cocultured with RPE cells and treated with RA were transplanted into the renal capsule or intra-vitreal space of nude mice. Grafted ESC derivatives demonstrated extensive rhodopsin expression, and they survived and organized into recipient tissues, although they formed teratomas. Conclusion: These results indicate that coculturing ESCs with ESC-derived RPE cells is a useful and efficient method for inducing photoreceptors and providing an insight into the use of ESCs for retina regeneration.     

Regulatory T cells interfere with glutathione metabolism in dendritic cells and T cells

Naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) suppress proliferation of CD4(+)CD25(-) effector T cells (Teffs) by mechanisms that are not well understood. We have previously demonstrated a novel mechanism of Treg suppression, i.e. interference with extracellular redox remodeling that occurs during activation of T cells by dendritic cells. In this study, we demonstrate that Treg-mediated redox perturbation is antigen-dependent but not antigen-specific, is CTLA-4-dependent, and requires cell-cell contact. Furthermore, we show that Tregs use multiple strategies for extracellular redox remodeling, including diminished GSH synthesis in dendritic cells via decreased expression of γ-glutamylcysteine synthetase, the limiting enzyme for GSH synthesis. Tregs also consume extracellular cysteine and partition it more proficiently to the oxidation product (sulfate), whereas Teffs divert more of the cysteine pool toward protein and GSH synthesis. Tregs appear to block GSH redistribution from the nucleus to the cytoplasm in Teffs, which is abrogated by the addition of exogenous cysteine. Together, these data provide novel insights into modulation of sulfur-based redox metabolism by Tregs, leading to suppression of T cell activation and proliferation.     

Maintenance of adult hamster pancreas cells on fibroblastic cells

Summary The maintenance of primary cultures of adult hamster pancreatic cells on layers of irradiated C3H/10T1/2 cells was studied. Various types of pancreatic cells, acinar, islet and ductular cells could be identified in the cultures by light and electron microscopy. Morphologically the various pancreatic cells retained many differentiated characteristics of their respective in vivo cell types. Insulin production was maintained at near Day 1 levels for the 16 d in culture for which it was measured. Colonies of epithelial cells continued to grow during a 20 d culture period. It is believed that this procedure for maintaining functional and growing pancreas cells in culture may be a useful in vitro model for studying the initiation of pancreatic carcinogenesis. Supported by Grant R01 CA 20022 and Contract N01 CP33278 from the National Cancer Institute, National Institutes of Health, Bethesda, Maryland.     

Relationships between stem cells and cancer stem cells

Stem cells have been shown to exist in a variety of tissues. Recent studies have characterized stem cell gene expression patterns, phenotypes, and potential therapeutic uses. One of the most important properties of stem cells is that of self renewal. This raises the possibility that some of the clinical properties of human tumors may be due to transformed stem cells. Similar signaling pathways may regulate self renewal in normal and transformed stem cells. These rare transformed stem cells may drive the process of tumorigenesis due to their potential for self renewal. There are important ramifications for clinical cancer treatment if the growth of solid tumors is at least partially dependent on a cancer stem cell population. In the cancer stem cell model, tumor recurrence may be due to the non-targeted stem cell compartment repopulating the tumor. If cancer stem cells can be prospectively identified and isolated, it should be possible to identify therapies that will selectively target these cells.     

Bacterial morphogenesis: learning how cells make cells

Bacteria furnish tractable models for complex biological processes, and morphogenesis is now taking its turn. We can already explain in general terms how such elementary forms as rods and cocci are produced, and the shapes of several individual organisms are coming into focus. In most bacteria shape is maintained by the cell wall, specifically the peptidoglycan layer, which has the attributes of a strong stiff fabric. Compliance of that fabric with turgor pressure is an important aspect of morphogenesis. The shape of the wall sacculus is determined by the way it is deposited, which is controlled by a cytoskeleton made up of two molecular families. One, related to the eukaryotic tubulins, is responsible for the construction of the septum and the poles. The other, related to eukaryotic actins, localizes peptidoglycan synthesis in the lateral walls of rod-shaped cells. Just how the cytoskeleton itself is organized remains to be discovered, but it seems likely that, as in eukaryotes, the cytoskeleton is produced by self-organized assembly, guided by the fabric of the cell.     

Induction of oocyte-like cells from mouse embryonic stem cells by co-culture with ovarian granulosa cells

Abstract In vitro derivation of oocytes from embryonic stem (ES) cells has the potential to be an important tool for studying oogenesis as well as advancing the field of therapeutic cloning by providing an alternative source of oocytes. Here, we demonstrate a novel, two-step method for inducing mouse ES cells to differentiate into oocyte-like cells using mouse ovarian granulosa cells. First, primordial germ cells (PGCs) were differentiated within the embryonic body (EB) cells around day 4 as defined by the expression of PGC-specific markers and were distinguished from undifferentiated ES cells. Second, day 4 EB cells were co-cultured with ovarian granulosa cells. After 10 days, these cells formed germ cell colonies as indicated by the expression of the two germ cell markers Mvh and SCP3. These cells also expressed the oocyte-specific genes Fig α, GDF-9 , and ZP1-3 but not any testis-specific genes by RT-PCR analysis. EB cultured alone or cultured in granulosa cell-conditioned medium did not express any of these oocyte-specific markers. In addition, EB co-cultured with Chinese hamster ovary (CHO) cells or cultured in CHO cell-conditioned medium did not express all of these oocyte-specific markers. Immunocytochemistry analysis using Mvh and GDF-9 antibodies confirmed that some Mvh and GDF-9 double-positive oocyte-like cells were generated within the germ cell colonies. Our results demonstrate that granulosa cells were effective in inducing the differentiation of ES cell-derived PGCs into oocyte-like cells through direct cell-to-cell contacts. Our method offers a novel in vitro system for studying oogenesis; in particular, for studying the interactions between PGCs and granulosa cells.     

Lagged cells

The timing of the retinal input to the lateral geniculate nucleus is highly modified in lagged cells. Evidence is reviewed for how the responses of these cells are generated, how their structure and function differs from their nonlagged neighbors, and what their projections to cortex might do.     

Germ cells

Recently, cell signaling has been shown to be required for the formation of germ cells in the mouse embryo, direct observation of germ cell migration in living mouse embryos has been achieved, novel genes that control germ-cell migration have been identified in Drosophila, and the roles of many components of germ plasm in several species have become clearer.     

Helper T cells, dendritic cells and CTL Immunity

In this review, we examine the emerging view that all CTL responses depend on CD4 T-cell help for the generation of efficient memory. We further review the evidence that CD4 and CD8 T cells must recognize antigen on the same dendritic cell, and examine why this corecognition is required. Earlier studies have suggested that CD4 T cells must activate the dendritic cell via CD40 to license it for the capacity to prime CTL immunity. More recently, however, CD40 signalling of the CTL has been reported. Here, we argue that the main reason for corecognition of antigen on the dendritic cell may be related to the time taken to activate and release CD4 and CD8 T cells from their priming dendritic cell. CD4 T cells may only be capable of activating one dendritic cell during the period that CD8 T cells are primed. In this case, corecognition of this same dendritic cell would be essential.     

人羊膜上皮细胞和胚胎干细胞

人胚胎干细胞有着巨大的医学应用前景,但人胚胎干细胞要求的生长条件很高,体外很难模拟其生长的体内环境,因此控制人胚胎干细胞的生长常不理想,而使用鼠胚胎成纤维细胞(MEF)作为滋养层则存在动物源性污染的问题。该文阐述人羊膜上皮细胞(HAEC)的特点及其作为滋养层培养胚胎干细胞的现状,并探讨基因组DNA甲基化修饰在胚胎干细胞分化过程中的作用,为建立更优化的培养系统提供依据。     

Recognition of virus infected cells by NK cells

NK cells show cytotoxicity against virus-infected cells and tumor cells and play an important role in host defense. Although mecheanism of target cell recognition by NK cells have been unclear for a long time, it has recently been elucidated that certain NK cell receptors specifically recognize virus products. Furthermore, expression pattern of NK cell receptors, which consist of activating and inhibitory receptors, determines susceptibility to virus-infection. Here, we review recent progress of mechanism of recognition of virus-infected by NK cells.     

pH regulation in spread cells and round cells

The aim of this work was to characterize the changes in pH regulation that lead to increased intracellular pH (pHi) in well-spread cells on tissue culture plastic relative to cells on a nonadhesive surface. Bicarbonate was not required for maintenance of a control steady state pHi or of the difference in pHi between round and spread cells. In the absence of bicarbonate, lowering the sodium content of the medium led to decreased pHi and elimination of the difference between round and spread cells. In the presence or absence of bicarbonate, adding ethylisopropyl amiloride lowered pHi and eliminated the difference between round and spread cells. Measurements of recovery from acute acidification in the absence of bicarbonate confirmed that Na+/H+ exchange was enhanced in spread cells. However, recovery from both acidification and alkalinization in the presence of bicarbonate showed that bicarbonate-dependent recovery in both directions, most likely due to sodium-dependent and -independent HCO3-/Cl- exchangers, was also stimulated in spread cells. We conclude that Na+/H+ exchange has a primary role in determining steady state pHi in 3T3 cells in serum and is responsible for the lower pHi in round cells. Bicarbonate-dependent pH regulatory mechanisms are also inhibited in round cells.     

Gastrointestinal stem cells. I. Pancreatic stem cells

The transplantation of islets isolated from donor pancreas has renewed the interest in cell therapy for the treatment of diabetes. In addition, the capacity that stem cells have to differentiate into a wide variety of cell types makes their use ideal to generate beta-cells for transplantation therapies. Several studies have reported the generation of insulin-secreting cells from embryonic and adult stem cells that normalized blood glucose values when transplanted into diabetic animal models. Finally, although much work remains to be done, there is sufficient evidence to warrant continued efforts on stem cell research to cure diabetes.     

Liver sinusoidal endothelial cells that endocytose allogeneic cells suppress T cells with indirect allospecificity

A portal venous injection of allogeneic donor cells is known to prolong the survival of subsequently transplanted allografts. In this study, we investigated the role of liver sinusoidal endothelial cells (LSECs) in immunosuppressive effects induced by a portal injection of allogeneic cells on T cells with indirect allospecificity. To eliminate the direct CD4+ T cell response, C57BL/6 (B6) MHC class II-deficient C2tatm1Ccum (C2D) mice were used as donors. After portal injection of irradiated B6 C2D splenocytes into BALB/c mice, the host LSECs that endocytosed the irradiated allogeneic splenocytes showed enhanced expression of MHC class II molecules, CD80, and Fas ligand (FasL). Due to transmigration across the LSECs from BALB/c mice treated with a portal injection of B6 C2D splenocytes, the naive BALB/c CD4+ T cells lost their responsiveness to stimulus of BALB/c splenic APCs that endocytose donor-type B6 C2D alloantigens, while maintaining a normal response to stimulus of BALB/c splenic APCs that endocytose third-party C3H alloantigens. Similar results were not observed for naive BALB/c CD4+ T cells that transmigrated across the LSECs from BALB/c FasL-deficient mice treated with a portal injection of B6 C2D splenocytes. Adaptive transfer of BALB/c LSECs that had endocytosed B6 C2D splenocytes into BALB/c mice via the portal vein prolonged the survival of subsequently transplanted B6 C2D hearts; however, a similar effect was not observed for BALB/c FasL-deficient LSECs. These findings indicate that LSECs that had endocytosed allogeneic splenocytes have immunosuppressive effects on T cells with indirect allospecificity, at least partially via the Fas/FasL pathway.     

Transdifferentiation of mouse BM cells into hepatocyte-like cells

BACKGROUND: During the past few years multiple studies have revealed that adult stem cells, including BM origin stem cells, can be transdifferentiated into various cell types, including hepatocyte-like cells, under proper treatments or in a suitable microenvironment. However, little is known about the mechanism of the transdifferentiation, and the treatments employed seem to be very complicated and require simplification. It is important to determine the suitable conditions in which BM cells would be efficiently differentiated into hepatocytes. METHODS: Mouse BM cells were isolated from femurs and tibias and cultured in IMDM supplemented with 10% FBS. Hepatic differentiation was induced in a differentiation medium containing 20 ng/mL HGF, 10 ng/mL FGF-4, 10 ng/mL Oncostatin M (OSM) and different concentrations of liver-injured mouse sera. The differentiated hepatic cells were characterized by the expression of liver-associated mRNA and proteins and morphologic and functional features. RESULTS: BM cell-derived polygonal cell colonies appeared after several days of culture, and these hepatocyte-like cells expressed AFP, HNF-3beta, CK19, CK18, ALB, TAT and G-6-Pase at mRNA and protein levels, and the cells also had some hepatic cellular functions, such as glycogen storage and urea production. Interestingly, suitable concentrations of sera from liver-injured mice added to this system showed strong stimulation on the in vitro transdifferentiation of mouse BM cells into hepatocytes. DISCUSSION: In the present study we have established an effective hepatic differentiation system by a combination of HGF, FGF-4, OSM and liver-injured mouse sera in vitro. Accordingly, it will be a useful resource not only for understanding the mechanisms of transdifferentiation but also for efficient amplification of hepatocyte progenitor cells of BM origin.