Visualization of CD44 and CD133 in Normal Pancreas and Pancreatic Ductal Adenocarcinomas: Non-overlapping Membrane Expression in Cell Populations Positive for Both Markers

Tumor-initiating cells of pancreatic ductal adenocarcinoma (PDAC) have been isolated based on expression of either CD133 or CD44. The authors aimed to visualize pancreatic cells simultaneously expressing both these cell surface markers by employing the same antibodies commonly used in cell-sorting studies. Normal and diseased pancreatic tissue, including 51 PDAC cases, were analyzed. CD44 and CD133 expression was determined by immunohistochemical double staining on formalin-fixed material and subcellular protein distribution evaluated by immunofluorescence/confocal microscopy. In the normal pancreas, CD44 and CD133 were coexpressed in the centroacinar regions but in non-overlapping subcellular compartments. As expected, CD44 was found mainly basolaterally, whereas CD133 was present on the apical/endoluminal membrane. This was also the case in chronically inflamed/atrophic pancreatic tissue and in PDAC. In some malignant ducts, CD44 was found at the apical cell membrane adjacent to but never overlapping with CD133 expression. CD44 level was significantly associated with the patient’s lymph node status. In conclusion, a CD44+/CD133+ cell population does exist in the normal and neoplastic pancreas. The preferentially centroacinar localization of the doubly positive cells in the normal parenchyma suggests that this population could be of particular interest in attempts to identify tumor-initiating cells in PDAC. This article contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.     

The Development of Diet-Induced Obesity and Glucose Intolerance in C57Bl/6 Mice on a High-Fat Diet Consists of Distinct Phases

High–fat (HF) diet-induced obesity and insulin insensitivity are associated with inflammation, particularly in white adipose tissue (WAT). However, insulin insensitivity is apparent within days of HF feeding when gains in adiposity and changes in markers of inflammation are relatively minor. To investigate further the effects of HF diet, C57Bl/6J mice were fed either a low (LF) or HF diet for 3 days to 16 weeks, or fed the HF-diet matched to the caloric intake of the LF diet (PF) for 3 days or 1 week, with the time course of glucose tolerance and inflammatory gene expression measured in liver, muscle and WAT. HF fed mice gained adiposity and liver lipid steadily over 16 weeks, but developed glucose intolerance, assessed by intraperitoneal glucose tolerance tests (IPGTT), in two phases. The first phase, after 3 days, resulted in a 50% increase in area under the curve (AUC) for HF and PF mice, which improved to 30% after 1 week and remained stable until 12 weeks. Between 12 and 16 weeks the difference in AUC increased to 60%, when gene markers of inflammation appeared in WAT and muscle but not in liver. Plasma proteomics were used to reveal an acute phase response at day 3. Data from PF mice reveals that glucose intolerance and the acute phase response are the result of the HF composition of the diet and increased caloric intake respectively. Thus, the initial increase in glucose intolerance due to a HF diet occurs concurrently with an acute phase response but these effects are caused by different properties of the diet. The second increase in glucose intolerance occurs between 12 - 16 weeks of HF diet and is correlated with WAT and muscle inflammation. Between these times glucose tolerance remains stable and markers of inflammation are undetectable.     

Myeloid Derived Suppressor Cells Are Present at High Frequency in Neonates and Suppress In Vitro T Cell Responses

Over 4 million infants die each year from infections, many of which are vaccine-preventable. Young infants respond relatively poorly to many infections and vaccines, but the basis of reduced immunity in infants is ill defined. We sought to investigate whether myeloid-derived suppressor cells (MDSC) represent one potential impediment to protective immunity in early life, which may help inform strategies for effective vaccination prior to pathogen exposure. We enrolled healthy neonates and children in the first 2 years of life along with healthy adult controls to examine the frequency and function of MDSC, a cell population able to potently suppress T cell responses. We found that MDSC, which are rarely seen in healthy adults, are present in high numbers in neonates and their frequency rapidly decreases during the first months of life. We determined that these neonatal MDSC are of granulocytic origin (G-MDSC), and suppress both CD4+ and CD8+ T cell proliferative responses in a contact-dependent manner and gamma interferon production. Understanding the role G-MDSC play in infant immunity could improve vaccine responsiveness in newborns and reduce mortality due to early-life infections.     

One-pot, mix-and-read peptide-MHC tetramers

Background

Cytotoxic T Lymphocytes (CTL) recognize complexes of peptide ligands and Major Histocompatibility Complex (MHC) class I molecules presented at the surface of Antigen Presenting Cells (APC). Detection and isolation of CTL''s are of importance for research on CTL immunity, and development of vaccines and adoptive immune therapy. Peptide-MHC tetramers have become important reagents for detection and enumeration of specific CTL''s. Conventional peptide-MHC-tetramer production involves recombinant MHC production, in vitro refolding, biotinylation and tetramerization; each step followed by various biochemical steps such as chromatographic purification, concentration etc. Such cumbersome production protocols have limited dissemination and restricted availability of peptide-MHC tetramers effectively precluding large-scale screening strategies involving many different peptide-MHC tetramers.

Methodology/Principal Findings

We have developed an approach whereby any given tetramer specificity can be produced within 2 days with very limited effort and hands-on time. The strategy is based on the isolation of correctly oxidized, in vivo biotinylated recombinant MHC I heavy chain (HC). Such biotinylated MHC I HC molecules can be refolded in vitro, tetramerized with streptavidin, and used for specific T cell staining-all in a one-pot reaction without any intervening purification steps.

Conclusions/Significance

We have developed an efficient “one-pot, mix-and-read” strategy for peptide-MHC tetramer generation, and demonstrated specific T cell straining comparable to a commercially available MHC-tetramer. Here, seven peptide-MHC tetramers representing four different human MHC (HLA) class I proteins have been generated. The technique should be readily extendable to any binding peptide and pre-biotinylated MHC (at this time we have over 40 different pre-biotinylated HLA proteins). It is simple, robust, and versatile technique with a very broad application potential as it can be adapted both to small- and large-scale production of one or many different peptide-MHC tetramers for T cell isolation, or epitope screening.     

Regulation of integrin gene expression by substrate adherence.

Under substrate adherent conditions, integrin gene expression can be regulated by transforming growth factor-beta, interleukin-1 beta, and prostaglandins. This report demonstrates a new mechanism that can differentially control the expression of several integrins. When MG-63 osteosarcoma cells are maintained in suspension, up-regulation of several integrin alpha-subunits takes place. Within as little as 4 h, the mRNA levels for both the alpha 2- and alpha 4-subunits are increased 4- and 6-fold, respectively. It was found that mRNA levels for the alpha 2-, alpha 4-, and alpha v-subunits were markedly increased in several differentiated cell lines under nonadherent conditions; however, cells that did not express a given integrin under substrate adherent conditions also did not express this integrin when maintained in suspension. The alpha 5-subunit did not upregulate during suspension growth. By immunocytochemistry, changes in integrin mRNA levels were confirmed at the protein level. Both cytochalasin B and a phorbol ester were found to induce the expression of the alpha 2-subunit, but not the alpha 4- and alpha 5-subunits, in a dose-dependent fashion. Many investigators have documented changes in gene expression that result from changes in "cell shape." These phenomena may result from up-regulation of integrin gene expression induced by the lack of substrate adherence.     

Aquaporins in complex tissues. II. Subcellular distribution in respiratory and glandular tissues of rat

The molecular pathways for fluid transport in pulmonary, oral,and nasal tissues are still unresolved. Here we use immunocytochemistry and immunoelectron microscopy to define the sites of expression of fouraquaporins in the respiratory tract and glandular epithelia, where theyreside in distinct, nonoverlapping sites. Aquaporin-1 (AQP1) is presentin apical and basolateral membranes of bronchial, tracheal, andnasopharyngeal vascular endothelium and fibroblasts. AQP5 is localizedto the apical plasma membrane of type I pneumocytes and the apicalplasma membranes of secretory epithelium in upper airway and salivaryglands. In contrast, AQP3 is present in basal cells of tracheal andnasopharyngeal epithelium and is abundant in basolateral membranes ofsurface epithelial cells of nasal conchus. AQP4 resides in basolateralmembranes of columnar cells of bronchial, tracheal, and nasopharyngealepithelium; in nasal conchus AQP4 is restricted to basolateralmembranes of a subset of intra- and subepithelial glands. These sitesof expression suggest that transalveolar water movement, modulation ofairway surface liquid, air humidification, and generation ofnasopharyngeal secretions involve a coordinated network of aquaporinwater channels.

     

PSAMM: A Portable System for the Analysis of Metabolic Models

The genome-scale models of metabolic networks have been broadly applied in phenotype prediction, evolutionary reconstruction, community functional analysis, and metabolic engineering. Despite the development of tools that support individual steps along the modeling procedure, it is still difficult to associate mathematical simulation results with the annotation and biological interpretation of metabolic models. In order to solve this problem, here we developed a Portable System for the Analysis of Metabolic Models (PSAMM), a new open-source software package that supports the integration of heterogeneous metadata in model annotations and provides a user-friendly interface for the analysis of metabolic models. PSAMM is independent of paid software environments like MATLAB, and all its dependencies are freely available for academic users. Compared to existing tools, PSAMM significantly reduced the running time of constraint-based analysis and enabled flexible settings of simulation parameters using simple one-line commands. The integration of heterogeneous, model-specific annotation information in PSAMM is achieved with a novel format of YAML-based model representation, which has several advantages, such as providing a modular organization of model components and simulation settings, enabling model version tracking, and permitting the integration of multiple simulation problems. PSAMM also includes a number of quality checking procedures to examine stoichiometric balance and to identify blocked reactions. Applying PSAMM to 57 models collected from current literature, we demonstrated how the software can be used for managing and simulating metabolic models. We identified a number of common inconsistencies in existing models and constructed an updated model repository to document the resolution of these inconsistencies.