Cell communication

Rice blast disease is caused by the hemibiotrophic fungus Magnaporthe oryzae, which invades living plant cells using intracellular invasive hyphae (IH) that grow from one cell to the next. The cellular and molecular processes by which this occurs are not understood. We applied live-cell imaging to characterize the spatial and temporal development of IH and plant responses inside successively invaded rice (Oryza sativa) cells. Loading experiments with the endocytotic tracker FM4-64 showed dynamic plant membranes around IH. IH were sealed in a plant membrane, termed the extra-invasive hyphal membrane (EIHM), which showed multiple connections to peripheral rice cell membranes. The IH switched between pseudohyphal and filamentous growth. Successive cell invasions were biotrophic, although each invaded cell appeared to have lost viability when the fungus moved into adjacent cells. EIHM formed distinct membrane caps at the tips of IH that initially grew in neighboring cells. Time-lapse im...

Bone marrow cells (BMC) migrate to the injured liver after transplantation, contributing to regeneration through multiple pathways, but mechanisms involved are unclear. This work aimed to study BMC migration, characterize cytokine profile, cell populations and proliferation in mice with liver fibrosis transplanted with GFP+ BMC. Confocal microscopy analysis showed GFP+ BMC near regions expressing HGF and SDF-1 in the fibrotic liver. Impaired liver cell proliferation in fibrotic groups was restored after BMC transplantation. Regarding total cell populations, there was a significant reduction in CD68+ cells and increased Ly6G+ cells in transplanted fibrotic group. BMC contributed to the total populations of CD144, CD11b and Ly6G cells in the fibrotic liver, related to an increment of anti-fibrotic cytokines (IL-10, IL-13, IFN-γ and HGF) and reduction of pro-inflammatory cytokines (IL-17A and IL-6). Therefore, HGF and SDF-1 may represent important chemoattractants for transplanted BMC ...

Gastric mucosal inflammation is frequently associated with hypergastrinemia, and a correlation exists between the level of gastrin and degree of gastritis. We have previously observed that gastrin promotes leukocyte-endothelial interactions and contributes to Helicobacter -induced inflammation in the rat mesentery. In the present study, we aimed to evaluate a possible proinflammatory activity of gastrin in humans. The interaction between human leukocytes [U-937 cells, peripheral blood polymorphonuclear (PMN), and peripheral blood mononuclear (PBMC) cells] and human umbilical vein endothelial cells (HUVEC) was analyzed in static and dynamic conditions. The endothelial expression of adhesion molecules [P-selectin, E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule (VCAM)-1] was analyzed by flow cytometry and fluorescent microscopy screening. Gastrin increased the static adhesion of U-937 cells to HUVEC (1 h; 10−9M: 122 ± 9%; 10−8M: 143 ± 17%; 10−7M: 162 ± 1...

Julie et Estelle, dès le premier jour où vous êtes arrivées j'ai ressenti immédiatement que vous étiez deux filles géniales, et je ne m'étais pas trompée ! Quel bonheur de travailler à vos côtés au quotidien, merci pour ces bons moments et soirées passées ensemble, nos discussions de filles autour d'une petite tisane ! Julie, je te souhaite le meilleur pour cette thèse débutante et que tu rencontres enfin l'homme parfait qui saura t'apprécier à ta juste valeur pas comme l'autre bougre de zigoto. Estelle, prend soin de toi et de Samy, notre miraculé… le meilleur reste à venir ! Cynthia, pour nos longues discussions, tu es une preuve de courage et d'obstination, te rencontrer fut pour moi une véritable leçon de morale, je te souhaite un plein épanouissement professionnel, que tu sois reconnu enfin comme un chercheur à part entière, mais aussi plein de bonheur avec Martial et tes deux fripons que j'ai adorés « baby-sitter ». Zeinab, pour ta gentillesse, ta disponibilité, pour nous avoir fait découvrir ta culture, ce fut un véritable bonheur de partager ce bureau ensemble, j'allais oublier….merci pour avoir sauvé ma dignité capillaire, je te souhaite le meilleur pour la suite, que ces fichues manips marchent enfin, mais surtout plein de bonheur avec ton fiancé. Ségolène, pour ton sourire radieux, ta gentillesse et les bilans lipidiques que tu m'as permis de réaliser au laboratoire de biochimie clinique. Bénédicte, pour ton rire représentatif de ta bonne humeur inébranlable et ton aide technique en RT-qPCR. Marie-Annick, pour ta sympathie, l'organisation de nos formations et tes conseils en immunohisto. Lucy, pour ta prévenance, ta gentillesse au quotidien et ta bienveillance telle une maman, merci pour ces bons moments partagés à tes côtés… Laurent, notre sagittaire international préféré, pour avoir partagé ma passion pour le vélo, pour ton aide au luminex et nos entrainements aux flatmounts. Rodolphe, pour nos discussions dans ton bureau lors de mes analyses stats, ta gentillesse, ton humour (je n'aborderai pas l'épisode des chips ou les batailles d'eau grrr) Elodie, pour m'avoir supportée en tant que colloc aux iles San Juan, pour ta bonne humeur quotidienne, je te souhaite tout plein de bonheur avec Jérome et tes deux petits loups. Olivier, mon fidèle compatriote de pistoche, pour nos discussions aquatiques, pour m'avoir initiée au Saint Véran, pour notre voyage magnifique au pays des baleines avec ta chère et tendre, ce fut un réel bonheur de partager ces moments de dépaysement et de bonheur à vos côtés. NicO, pour ta pseudO fausse bonne humeur au labO, pour m'avoir permis de survivre grâce aux dosettes nespressO et pour être toujours partant pour un petit apérO. Franck, pour nos trocs, nos longues discussions sur le perron à commérer et à refaire le monde, une belle rencontre ! Marie-Chantal, pour ta bienveillance, ton soutien et les heures passées à discuter ensemble, pour m'avoir appris à disséquer les glandes salivaires, je te souhaite une belle fin de carrière qui corresponde véritablement à tes attentes. Raymond, Laurence, Sandra et Elise pour votre sympathie pendant les nombreuses heures passées à l'animalerie. Anthony, « mon tout premier stagiaire ! », merci pour ton assiduité, la qualité de ton travail, nos fous rires (« Nif Nif et Naf Naf oublient de nettoyer la paillasse de l'animalerie… »). Pour nos échanges perpétuels, en espérant de tout coeur travailler de nouveau un jour avec toi. Kévin, mon stagiaire 2 ème du nom, merci pour ton investissement et ta gentillesse, tu disposes de grandes qualités scientifiques tu iras loin, accroche toi et aie confiance en toi ! Maëlle, mon autre petite stagiaire, bravo pour ton travail en analyse lipidique sur mes foies de rats, de rapidité et d'efficacité tu as su faire preuve, bon courage à toi pour la suite. Le Professeur Alain Bron, notre papa à tous, pour son suivi assidu, son point de vue clinique, ses nombreux conseils avisés, ses corrections sur mes articles, sa bonne humeur et son entrain que ce soit en congrès ou à l'INRA, pour m'avoir « déroulé le tapis rouge » au CHU afin d'y réaliser mes OCT et pour m'avoir finalement présenté l'homme qui partage aujourd'hui ma vie.

Abstract

This literature review explores the fundamental physiological role of synaptic transmission in neuronal communication. Synaptic transmission, the critical process by which neurons transmit signals, underpins all complex behaviors and neural functions. This review outlines the principal mechanisms, starting with the arrival of an action potential at the presynaptic terminal, leading to calcium influx, neurotransmitter release, and subsequent binding to postsynaptic receptors. The subsequent excitation or inhibition of the postsynaptic neuron is discussed, highlighting synaptic transmission's essential role in information exchange and neural network coordination. The review also briefly introduces the two primary types of synapses: electrical and chemical.

In this work, aggregation states of bacteria on engineered surfaces are investigated both from the experimental point of view and from the theoretical one. The starting point of this work is a series of experiments carried out on abiotic surfaces in which bacteria adhere forming self-organized patterns. To reproduce the main characteristics of the phenomenon a model based on self-organization of a group of agents has been used. The agents represent bacteria and are free to move on a given surface. On the basis of local rules they may adhere and then eventually form self-organized aggregates. Our numerical results demonstrate that few simple rules are able to explain the emergence of self-organized patterns. Depending on the parameters used, the model is able to reproduce the aggregation patterns observed under different experimental conditions and to predict the behavior of a culture of two bacterial species.

Dental implant placement stimulates a response in the supporting tissue; the response involves bone remodeling and release of wound-healing factors, including cytokines. Important factors such as transforming growth factor-␤ (TGF-␤), which promotes matrix synthesis, and prostaglandin E 2 (PGE 2 ), a mediator of inflammation, have the potential to alter the communication between bone cells and interfere with implant site healing. Cells responsible for the formation of bone are interconnected to form a multicellular network. Cell-to-cell communication in this network occurs in part via gap junctions. In bone cells, the predominant gap junction protein is connexin-43. TGF-␤ is a growth modulator produced by osteoblasts and released from the matrix in response to resorption and may influence the progression of periodontal disease. TGF-␤ also promotes the synthesis of extracellular matrix proteins such as collagen, fibronectin, and adhesion molecules. PGE 2 is a mediator of inflammation produced in response to periodontal pathogens. PGE 2 levels in the gingival sulcular fluid have been correlated with attachment loss and bone resorption. The relationship between these factors and connexin-43 is unclear. Oral-derived (alveolar) bone was used because the phenotype of bone can differ between species and between different sites in the body. For our studies, explants of human osteoblasts were cultured on eight well plates and characterized by their expression of osteocalcin, osteonectin, alkaline phosphatase, type 1 collagen, and connexin-43. Cells were grown to near confluence on 12 well plates in 20% fetal bovine serum (FBS) Dulbecco modified Eagle medium (DMEM) and then cultured for 24 hours in 0.5% FBS DMEM before exposure to either 1, 5, or 10 ng/mL of TGF-␤ in serum-free DMEM for 12 or 24 hours or to 20, 80, or 300 ng/mL of PGE 2 in serum-free DMEM for 12 or 24 hours. After incubation, cells were removed from plates by scraping and assayed for connexin-43 protein, first by Western blot to confirm the specificity of the anti-connexin-43 antibody and then by slot blot analysis for quantitative comparison of connexin-43 expression. Our studies showed no significant changes in connexin-43 expression in response to either factor. These studies suggest that exogenous TGF-␤ and PGE 2 do not alter connexin-43 expression.

Recent studies suggest that glial cells regulate certain aspects of synapse development. Neurons can form synapses without glia, but may require glia-derived cholesterol to form numerous and efficient synapses. During synapse maturation, soluble and contact-dependent factors from glia may influence the composition of the postsynaptic density. Finally, synaptic connections appear to require glia to support their structural stability. Given the new evidence, it may be time now to acknowledge glia as a source for synaptogenesis-promoting signals. Scrutinizing the molecular mechanisms underlying this new function of glia and testing its relevance in vivo may help to understand how synapses develop and why they degenerate under pathological conditions.

Recent studies suggest that glial cells regulate certain aspects of synapse development. Neurons can form synapses without glia, but may require glia-derived cholesterol to form numerous and efficient synapses. During synapse maturation, soluble and contact-dependent factors from glia may influence the composition of the postsynaptic density. Finally, synaptic connections appear to require glia to support their structural stability. Given the new evidence, it may be time now to acknowledge glia as a source for synaptogenesis-promoting signals. Scrutinizing the molecular mechanisms underlying this new function of glia and testing its relevance in vivo may help to understand how synapses develop and why they degenerate under pathological conditions.

Neuroinflammation, a pathological hallmark in Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), is characterized by activated microglia and infiltrating T cells at sites of neuronal injury. In PD and ALS, neurons do not die alone; neuronal injury is non-cell-autonomous and depends on a well-orchestrated dialogue in which neuronally secreted misfolded proteins activate microglia and initiate a self-propagating cycle of neurotoxicity. Diverse populations and phenotypes of CD4 + T cells crosstalk with microglia, and depending on their activation status, may influence this dialogue and promote either neuroprotection or neurotoxicity. A greater understanding of the T cell population mediating these effects as well as the molecular signals involved should provide targets for neuroprotective immunomodulation to treat these devastating neurodegenerative diseases.

Neuroinflammation, a pathological hallmark in Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), is characterized by activated microglia and infiltrating T cells at sites of neuronal injury. In PD and ALS, neurons do not die alone; neuronal injury is non-cell-autonomous and depends on a well-orchestrated dialogue in which neuronally secreted misfolded proteins activate microglia and initiate a self-propagating cycle of neurotoxicity. Diverse populations and phenotypes of CD4 + T cells crosstalk with microglia, and depending on their activation status, may influence this dialogue and promote either neuroprotection or neurotoxicity. A greater understanding of the T cell population mediating these effects as well as the molecular signals involved should provide targets for neuroprotective immunomodulation to treat these devastating neurodegenerative diseases.

Activated microglia and infiltrating lymphocytes are neuropathological hallmarks of amyotrophic lateral sclerosis (ALS), a fatal motoneuron disease. Although both cell types play pivotal roles in the ALS pathogenic process, the interactions between microglia and lymphocytes, specifically regulatory CD4 + CD25 High T lymphocytes (Tregs) and cytotoxic CD4 + CD25 -T lymphocytes (Teffs), have not been addressed. When co-cultured with mSOD1 adult microglia, mSOD1 Tregs suppressed the cytotoxic microglial factors NOX2 and iNOS through an IL-4-mediated mechanism, whereas Teffs were only minimally effective; IL-4 inhibitory antibodies blocked the suppressive function of mSOD1 Tregs, and conditioned media from mSOD1 Tregs or the addition of IL-4 reduced microglial NOX2 expression. During the stable disease phase, the total number of Tregs, specifically the numbers of CD4 + CD25 High IL-4 + , CD4 + CD25 High IL-10 + and CD4 + CD25 High TGF-β + Tregs, were increased in ALS mice compared with WT mice; Tregs isolated during this phase reduced Teffs proliferation. In contrast, during the rapidly progressing phase, the number of mSOD1 Tregs decreased while the proliferation of mSOD1 Teffs increased. The combination of IL-4, IL-10, and TGF-β was required to inhibit the proliferation of mSOD1 Teffs by mSOD1 Tregs that were isolated during the slow phase, while inhibition of mSOD1 Teffs by mSOD1 Tregs during the rapid phase, as well as WT Teffs, was not dependent on these factors. Thus, mSOD1 Tregs at the slow phase suppressed microglial toxicity and SOD1 Teffs proliferation through different mechanisms; microglial activation was suppressed through IL-4 whereas mSOD1 Teffs were suppressed by IL-4, IL-10 and TGF-β. These data suggest that mSOD1 Tregs contribute to the slowly progressing phase in ALS mice and may offer a novel therapeutic option for ALS patients.

Background: Cell surface glycosylation patterns are markers of cell type and status. However, the mechanisms regulating surface glycosylation patterns remain unknown. Methodology/Principal Findings: Using a panel of carbohydrate surface markers, we have shown that cell surface sialylation and fucosylation were downregulated in L1 2/y neurons versus L1 +/y neurons. Consistently, mRNA levels of sialyltransferase ST6Gal1, and fucosyltransferase FUT9 were significantly reduced in L1 2/y neurons. Moreover, treatment of L1 +/y neurons with L1 antibodies, triggering signal transduction downstream of L1, led to an increase in cell surface sialylation and fucosylation compared to rat IgG-treated cells. ShRNAs for both ST6Gal1 and FUT9 blocked L1 antibody-mediated enhancement of neurite outgrowth, cell survival and migration. A phospholipase Cc (PLCc) inhibitor and shRNA, as well as an Erk inhibitor, reduced ST6Gal1 and FUT9 mRNA levels and inhibited effects of L1 on neurite outgrowth and cell survival.

Spermatogenesis in rats is a well-coordinated and complex process that occurs within the seminiferous tubules of the testicular tissue. One complete seminiferous epithelium cycle would last 13 days; the whole process of spermatogenesis is last 56 days in rats and consists of a series of stages, each corresponding to a distinct phase in germ cell development. This process includes the proliferation and differentiation of spermatogonial stem cells, meiosis, and spermiogenesis. Spermatogenesis is regulated by a sophisticated interplay of hormones, primarily controlled by the hypothalamicpituitary-gonadal axis. Luteinizing hormone stimulates Leydig cells in the testes to produce testosterone, a hormone essential for the maturation of spermatocytes and spermatids within the seminiferous tubules. Follicle-stimulating hormone targets Sertoli cells, which help maintain the structure of the seminiferous epithelium and facilitate the progression of spermatogenesis by supplying nourishment and secreting of inhibin, activin, follistatin, androgen-binding protein, and other regulatory factors that participate in the feedback mechanisms that control gonadotropin secretion. Disruptions in the hormonal balance can lead to impaired spermatogenesis and male infertility. Therefore, a thorough understanding of the 14-stage spermatogenic cycle and its hormonal regulation is crucial for elucidating the mechanisms underlying male fertility. Such knowledge provides valuable insights into male reproductive physiology and can guide the development of therapeutic interventions for fertility disorders.

This study was designed to analyze the impact of multi-targeted tyrosine kinase inhibitors on the cancer stem cell subpopulation in renal cell cancer. The second objective was to evaluate the effect of tumor growth inhibition related to a tumor niche factor -oxygen deprivation -as hypoxia develops along with the anti-angiogenic activity of tyrosine kinase inhibitors in renal tumors. Cells were treated with tyrosine kinase inhibitors, sunitinib, sorafenib and axitinib, in 2D and 3D culture conditions. Cell proliferation along with drug toxicity were evaluated. It was shown that the proliferation rate of cancer stem cells was decreased by the tyrosine kinase inhibitors. The efficacy of the growth inhibition was limited by hypoxic conditions and 3D intratumoral cell-cell interactions. We conclude that understanding the complex molecular interaction feedback loops between differentiated cancer cells, cancer stem cells and the tumor microenvironment in 3D culture should aid the identification of novel treatment targets and to evalute the efficacy of renal cancer therapies. Cell-cell interaction may represent a critical microenvironmental factor regulating cancer stem cell self-renewal potential, enhancing the stem cell phenotype and limiting drug toxicity. At the same time the role of hypoxia in renal cancer stem cell biology is also significant.

Mesenchymal stem cells (MSCs) have sparked considerable interest in cancer research due to their ability to influence various stages of tumor development, from initiation to metastasis. A particularly intriguing aspect of MSC behavior is their communication with cancer cells via exosomemediated signaling. These small, extracellular vesicles released by MSCs carry a rich cargo of proteins, lipids, and nucleic acids that can drastically alter the behavior of nearby and even distant cancer cells. This review explores the multifaceted role of MSC-derived exosomes in cancer biology. It examines their formation, molecular components, and modes of communication with cancer cells. We discuss their regulatory impact on tumor behavior, ranging from angiogenesis and migration to invasion, apoptosis, and cell proliferation, emphasizing the molecular pathways that mediate these interactions. In addition, we consider their therapeutic promise, especially their potential to serve as immunomodulatory agents and targeted drug delivery platforms in oncology.

Directed intercellular interactions between distinct cell types underlie the basis for organogenesis during embryonic development. This paper focuses on the establishment of the final somatic muscle pattern in Drosophila, and on the possible cross-talk between the myotubes and the epidermal muscle attachment cells, occurring while both cell types undergo distinct developmental programs. Our findings suggest that the stripe gene is necessary and sufficient to initiate the developmental program of epidermal muscle attachment cells. In stripe mutant embryos, these cells do not differentiate correctly. Ectopic expression of Stripe in various epidermal cells transforms these cells into muscle-attachment cells expressing an array of epidermal muscle attachment cell-specific markers. Moreover, these ectopic epidermal muscle attachment cells are capable of attracting somatic myotubes from a limited distance, providing that the myotube has not yet been attached to or been influenced by a clo...

Many cell types remodel the extracellular matrix of the tissues they inhabit in response to a wide range of environmental stimuli, including mechanical cues. Such is the case in dermal wound healing, where fibroblast migrate into and remodel the provisional fibrin matrix in a complex manner that depends in part on the local mechanical environment and the evolving multi-scale mechanical interactions of the system. In this study, we report on the development of an image-based multi-scale mechanical model that predicts the short-term (24 hours), structural reorganization of a fibrin gel by fibroblasts. These predictive models are based on an in vitro experimental system where clusters of fibroblasts (i.e., explants) were spatially arranged into a triangular geometry onto the surface of fibrin gels that were subjected to either Fixed or Free in-plane mechanical constraints. Experimentally, regional differences in short-term structural remodeling and cell migration were observed for the ...

During development, cells undergo dramatic changes in their morphology. By affecting contact geometry, these morphological changes could influence cellular communication. However, it has remained unclear whether and how signaling depends on contact geometry. This question is particularly relevant for Notch signaling, which coordinates neighboring cell fates through direct cell-cell signaling. Using micropatterning with a receptor trans-endocytosis assay, we show that signaling between pairs of cells correlates with their contact area. This relationship extends across contact diameters ranging from micrometers to tens of micrometers. Mathematical modeling predicts that dependence of signaling on contact area can bias cellular differentiation in Notch-mediated lateral inhibition processes, such that smaller cells are more likely to differentiate into signal-producing cells. Consistent with this prediction, analysis of developing chick inner ear revealed that ligand-producing hair cell...

Enterocyte differentiation is a dynamic process during which reinforcement of cell-cell adhesion favours migration along the crypt-to-villus axis. Functional polarization of Caco-2 cells, the most commonly used model to study intestinal differentiation, is assessed by dome formation and tightness of the monolayer and is under the control of the extracellular matrix (ECM). Furthermore, our biochemical and confocal microscopy data demonstrate that the ECM dramatically reinforces E-cadherin targeting to the upper lateral membrane, formation of the apical actin cytoskeleton and its colocalization with E-cadherin in functional complexes. In our model, these effects were produced by native laminin-5-enriched ECM as well as by type IV collagen or laminin 2, which suggests a common pathway of induction through integrin receptors. Indeed, these effects were antagonized by blocking anti-β1-and anti-α6-integrin antibodies and directly induced by a stimulating anti-β1-integrin antibody. These results demonstrate that integrin-dependent cell to ECM adhesion reinforces E-cadherin-dependent cell-cell adhesion in Caco-2 cells and further support the notion that enterocyte differentiation is supported by a molecular crosstalk between the two adhesion systems of the cell.

Enterocyte differentiation is a dynamic process during which reinforcement of cell-cell adhesion favours migration along the crypt-to-villus axis. Functional polarization of Caco-2 cells, the most commonly used model to study intestinal differentiation, is assessed by dome formation and tightness of the monolayer and is under the control of the extracellular matrix (ECM). Furthermore, our biochemical and confocal microscopy data demonstrate that the ECM dramatically reinforces E-cadherin targeting to the upper lateral membrane, formation of the apical actin cytoskeleton and its colocalization with E-cadherin in functional complexes. In our model, these effects were produced by native laminin-5-enriched ECM as well as by type IV collagen or laminin 2, which suggests a common pathway of induction through integrin receptors. Indeed, these effects were antagonized by blocking anti-β1-and anti-α6-integrin antibodies and directly induced by a stimulating anti-β1-integrin antibody. These r...

Background: Focal adhesion sites are cell-matrix contacts that are regulated by phosphatidylinositol-4,5-bisphosphate (PIP 2 )-dependent pathways. Vinculin is a major structural component of these sites and is thought to be engaged in multiple ligand interactions at the cytoplasmic face of these contacts. Cytoplasmic vinculin is considered to be inactive due to its closed conformation involving intramolecular head-tail interactions. Recently, the vasodilatorstimulated phosphoprotein (VASP), a substrate of cyclic AMP-dependent or cyclic GMP-dependent kinases and a component of focal adhesion sites, was shown to bind to vinculin. Results: VASP-vinculin complexes could be immunoprecipitated from cell lysates and, using immunofluorescence, both proteins were found to colocalize in nascent focal adhesions. Consistent with the view that vinculin must be activated at these sites, we found that PIP 2 , levels of which are elevated during the early stages of adhesion, bound to two discrete regions in the vinculin tail, disrupting the intramolecular head-tail interaction and inducing vinculin oligomerization. Vinculin-VASP complex formation was greatly enhanced by PIP 2 and both the EVH1 and EVH2 domains of VASP participated in vinculin binding. Focal contact assembly involves interaction between VASP and vinculin, which is enhanced by PIP 2 -induced vinculin activation and oligomerization. Given that vinculin and VASP both bind to F-actin, vinculin-VASP complexes might bundle the distal ends of actin filaments in focal contacts. We propose that PIP 2 -dependent signalling modulates microfilament organization at cellular adhesion sites by regulating vinculin-VASP complexes.

Background: Focal adhesion sites are cell-matrix contacts that are regulated by phosphatidylinositol-4,5-bisphosphate (PIP 2 )-dependent pathways. Vinculin is a major structural component of these sites and is thought to be engaged in multiple ligand interactions at the cytoplasmic face of these contacts. Cytoplasmic vinculin is considered to be inactive due to its closed conformation involving intramolecular head-tail interactions. Recently, the vasodilatorstimulated phosphoprotein (VASP), a substrate of cyclic AMP-dependent or cyclic GMP-dependent kinases and a component of focal adhesion sites, was shown to bind to vinculin. Results: VASP-vinculin complexes could be immunoprecipitated from cell lysates and, using immunofluorescence, both proteins were found to colocalize in nascent focal adhesions. Consistent with the view that vinculin must be activated at these sites, we found that PIP 2 , levels of which are elevated during the early stages of adhesion, bound to two discrete regions in the vinculin tail, disrupting the intramolecular head-tail interaction and inducing vinculin oligomerization. Vinculin-VASP complex formation was greatly enhanced by PIP 2 and both the EVH1 and EVH2 domains of VASP participated in vinculin binding. Focal contact assembly involves interaction between VASP and vinculin, which is enhanced by PIP 2 -induced vinculin activation and oligomerization. Given that vinculin and VASP both bind to F-actin, vinculin-VASP complexes might bundle the distal ends of actin filaments in focal contacts. We propose that PIP 2 -dependent signalling modulates microfilament organization at cellular adhesion sites by regulating vinculin-VASP complexes.

We describe herein the enzyme behavior of MmNEU3, the plasma membrane-associated sialidase from mouse (Mus musculus). MmNEU3 is localized at the plasma membrane as demonstrated directly by confocal microscopy analysis. In addition, administration of the radiolabeled ganglioside GD1a to MmNEU3-transfected cells, under conditions that prevent lysosomal activity, led to its hydrolysis into ganglioside GM1, further indicating the plasma membrane topology of MmNEU3. Metabolic labeling with [1-3 H]sphingosine allowed the characterization of the ganglioside patterns of COS-7 cells. MmNEU3 expression in COS-7 cells led to an extensive modification of the cell ganglioside pattern, i.e. GM3 and GD1a content was decreased to about one-third compared with mock-transfected cells. At the same time, a 35% increase in ganglioside GM1 content was observed. Mixed culture of MmNEU3-transfected cells with [1-3 H]sphingosine-labeled cells demonstrates that the enzyme present at the cell surface is able to recognize gangliosides exposed on the membrane of nearby cells. Under these experimental conditions, the extent of ganglioside pattern changes was a function of MmNEU3 transient expression. Overall, the variations in GM3, GD1a, and GM1 content were very similar to those observed in the case of [1-3 H]sphingosine-labeled MmNEU3-transfected cells, indicating that the enzyme mainly exerted its activity toward ganglioside substrates present at the surface of neighboring cells. These results indicate that the plasma membrane-associated sialidase MmNEU3 is able to hydrolyze ganglioside substrates in intact living cells at a neutral pH, mainly through cell-to-cell interactions.

The T-BAM/CD40-L molecule on CD4+ T cells interacts with B cell CD40 molecules to deliver contact-dependent signals that drive B cell activation and Ig secretion. Cell surface T-BAM/CD40-L expression is transient and may be closely regulated in order to limit the activation and clonal selection of noncognate B cells. We demonstrate that B cells, but not non-B cells, rapidly and specifically down-modulate surface T-BAM/CD40-L expression in a contact-dependent and temperature-sensitive manner that renders T cells unable to activate resting bystander B cells. Because the ability to down-modulate T-BAM/CD40-L correlated with CD40 expression, the role of CD40 molecules in down-modulating its ligand was directly assessed. Anti-CD40 mAb, but not control mAb, block B cell-induced T-BAM/CD40-L down-modulation. Furthermore, CD40+ nonlymphoid transfectants specifically down-modulate surface T-BAM/CD40-L expression. B cells induce T-BAM/CD40-L internalization into cytoplasmic compartments in a ...

Tumor associated macrophages (TAMs) are an important element of tumor stroma. They originate from blood monocytes attracted by chemokines and cytokines produced by tumor cells and, being instructed by tumor microenvironment, develop into potent tumor-supporting cell population. TAMs were demonstrated to directly stimulate tumor cell proliferation and to promote angiogenesis. Further TAMs provide for efficient immune escape by producing immunosuppressive cytokines and facilitate tumor dissemination by producing extracellular matrix remodeling enzymes. In renal cell carcinoma (RCC), numerous studies were performed for elucidation of the role of TAM in tumor progression. Using pan-macrophages marker CD68 and type 2 macrophage (M2) markers CD163 and CD206, it was demonstrated that increased density of TAMs is associated with poor survival of patients. Although most of the studies are focused on M2 population in RCC, several markers rather typical for type 1 macrophages (M1) were also ch...

Too often, unique loading environments fail to alter bone mass and morphology, calling to question the validity of Wolff's Law; the skeleton's plasticity to mechanical signals(1). We propose that bone can accommodate new loading environments without the need to form or resorb tissue, and that a critical aspect of bone tissue's ability to adapt to mechanical stimuli is first achieved via the plasticity of the osteocyte. We suggest that the osteocyte is capable of "normalizing" its local mechanical environment by modulating its cytoskeletal architecture, attachment to the matrix, configuration of the periosteocytic space, and communication channels to surrounding cells. We believe that through this local adaptive mechanism the osteocyte can accommodate the majority of changes in the mechanical milieu without altering the tissue architecture. It is only when bone tissue is subject to more severe (albeit rare) increases or decreases in the functional environment, t...

Therapy of the interstitial fluid before the destruction of intercellular connections has two interrelated directions, firstly, a decrease in the interstitial fluid (interstitial fluid) and normalization of the tumor microclimate before the intercellular connections are destroyed, and secondly, the destruction of intercellular connections as part of therapy (to increase drug penetration. The interstitial fluid and the surrounding ECM environment come to the fore, and the intercellular connections themselves play a modifying role. The interstitial fluid (interstitial fluid) fills the space around the cells in the tumor. Often, its pressure is higher than normal (IFP), which limits the penetration of drugs and immune cells, contributes to hypoxia and the formation of an oxidative environment. Reducing IFP and loosening ECM improve the delivery of immunotherapy and weaken the intercellular connections of the tumor. Immune therapy focused on the interstitial fluid and ECM is aimed at destroying the connections of tumor cells, improving the penetration of immune cells into the tumor by reducing IFP and loosening ECM. Modification of intercellular connections and ECM occurs at first stages of treatment and reduces aggressive tumor growth. Modern therapies are focused on controlled modification of bonds with cytotoxic or immunotherapeutic agents. The regression effect depends on the tumor type, its microenvironment, stage, and combination of drugs used.

Variation in fin shape is one of the most prominent features of morphological diversity among fish. Regulation of fin growth has mainly been studied in zebrafish, and it is not clear whether the molecular mechanisms underlying shape variation are equally diverse or rather conserved across species. In the present study, expression levels of 37 candidate genes were tested for association with fin shape in the cichlid fish Lamprologus tigripictilis. The tested genes included members of a fin shape-associated gene regulatory network identified in a previous study and novel candidates selected within this study. Using both intact and regenerating fin tissue, we tested for expression differences between the elongated and the short regions of the spade-shaped caudal fin and identified 20 genes and transcription factors (including angptl5, cd63, csrp1a, cx43, esco2, gbf1, and rbpj), whose expression patterns were consistent with a role in fin growth. Collated with available gene expression data of two other cichlid species, our study not only highlights several genes that were correlated with fin growth in all three species (e.g., angptl5, cd63, cx43, and mmp9), but also reveals species-specific gene expression and correlation patterns, which indicate considerable divergence in the regulatory mechanisms of fin growth across cichlids.

In Pseudomonas aeruginosa, quorum sensing constitutes a highly complex cell-to-cell communication system that, along with the cognate acylhomoserine lactone signals and regulators LasR and RhlR, modulates the production of virulence factors and a wide range of metabolic functions. In a previous paper, the authors reported that mismatch repair disruption in P. aeruginosa results in the spontaneous and reproducible emergence of defined morphological colony variants after a relatively short period of cultivation in an aerated rich medium, in contrast to the non-mutator parental strain, which does not display any kind of diversification under identical incubation conditions. One of the morphotypical variants, mS2, emerges at a high frequency and displays differences in virulence traits that could be regulated by major quorum-sensing regulators. The present study shows that mutS mS2 variants had defective LasR function due to simple but different point mutations along the lasR gene sequence, indicating that LasR inactivation is the main cause of mS2 phenotypic diversification. Moreover, it was determined that a non-functional LasR would confer a selective advantage in the late stationary phase, since viability was notably higher for mS2. Interestingly, in all mS2 variants analysed, no sequence alterations were found in the gacA and rhlR genes, suggesting that the selective pressures for GacA/RhlR and LasR were not the same and differed from those in other Pseudomonas species, which, when incubated in nutrient-rich liquid stationary-phase cultures, show specific high instability in the gacA-gacS genes.

Dendritic cells (DCs) are specialized antigen-presenting cells. However, DCs exposed to human immunodeficiency virus type 1 (HIV-1) are also able to transmit a vigorous cytopathic infection to CD4 + T cells, a process that has been frequently related to the ability of DC-SIGN to bind HIV-1 envelope glycoproteins. The maturation of DCs can increase the efficiency of HIV-1 transmission through trans infection. We aimed to comparatively study the effect of maturation in monocyte-derived DCs (MDDCs) and blood-derived myeloid DCs during the HIV-1 capture process. In vitro capture and transmission of envelope-pseudotyped HIV-1 and its homologous replication-competent virus to susceptible target cells were assessed by p24 gag detection, luciferase activity, and both confocal and electron microscopy. Maturation of MDDCs or myeloid DCs enhanced the active capture of HIV-1 in a DC-SIGN- and viral envelope glycoprotein-independent manner, increasing the life span of trapped virus. Moreover, hi...

We describe a class-specific linear pseudosystolic array, with K processing elements, suitable for partitioned execution of matrix algorithms. This array achieves high efficiency, exploits pipelining within cells in a simple manner, has off-cells communication rate lower than computation rate, a small storage inside each cell (whose size is independent of the size of problems), and external storage. This array has been derived from the application of the mnltimesh graph (MMG) method to a large class of matrix algorithms. Processing elements (cells) use the decoupled access/execute model of computation, which requires two programs in each cell: one controlling the execution of operations and the other the data transfers. All storage modules in the array are accessed as FIFO queues, without the need for addressing mechanisms. We describe the proposed instruction set, which includes single-instruction loops with no overhead, and block-loops with just one extra instruction. Moreover, cells can nest up to three loops with no added overhead. These features are needed for mapping algorithms with the MMG method. Mapping onto this array is illustrated using the LU-decomposition algorithm, and results obtained with other algorithms are also given. Estimates of performance indicate that it is possible to achieve over 85 % efficiency, with low requirements in communication bandwidth and storage.

We describe a class-specific linear pseudosystolic array, with K processing elements, suitable for partitioned execution of matrix algorithms. This array achieves high efficiency, exploits pipelining within cells in a simple manner, has off-cells communication rate lower than computation rate, a small storage inside each cell (whose size is independent of the size of problems), and external storage. This array has been derived from the application of the mnltimesh graph (MMG) method to a large class of matrix algorithms. Processing elements (cells) use the decoupled access/execute model of computation, which requires two programs in each cell: one controlling the execution of operations and the other the data transfers. All storage modules in the array are accessed as FIFO queues, without the need for addressing mechanisms. We describe the proposed instruction set, which includes single-instruction loops with no overhead, and block-loops with just one extra instruction. Moreover, cells can nest up to three loops with no added overhead. These features are needed for mapping algorithms with the MMG method. Mapping onto this array is illustrated using the LU-decomposition algorithm, and results obtained with other algorithms are also given. Estimates of performance indicate that it is possible to achieve over 85 % efficiency, with low requirements in communication bandwidth and storage.

The importance of context in regulation of gene expression is now an accepted principle; yet the mechanism by which the microenvironment communicates with the nucleus and chromatin in healthy tissues is poorly understood. A functional role for nuclear and cytoskeletal architecture is suggested by the phenotypic differences observed between epithelial and mesenchymal cells. Capitalizing on recent advances in cryogenic techniques, volume electron microscopy, and super-resolution light microscopy, we studied human mammary epithelial cells in 3D cultures forming growth-arrested acini. Intriguingly, we found deep nuclear invaginations and tunnels traversing the nucleus, encasing cytoskeletal actin and/or intermediate filaments, which connect to the outer nuclear envelope. The cytoskeleton is connected also to both other cells via desmosome adhesion complexes and to the cell's ECM via hemidesmosomes. This finding supports a physical/mechanical link from the desmosomes and hemidesmosom...

Normal mammary morphogenesis involves transitions between simple and multilayered epithelial organizations. We used electron microscopy and molecular markers to determine whether intercellular junctions and apico-basal polarity were maintained in the multilayered epithelium. We found that multilayered elongating ducts had polarized apical and basal tissue surfaces both in threedimensional culture and in vivo. However, individual cells were only polarized on surfaces in contact with the lumen or extracellular matrix. The basolateral marker scribble and the apical marker atypical protein kinase C zeta localized to all interior cell membranes, whereas PAR3 displayed a cytoplasmic localization, suggesting that the apico-basal polarity was incomplete. Despite membrane localization of E-cadherin and b-catenin, we did not observe a defined zonula adherens connecting interior cells. Instead, interior cells were connected through desmosomes and exhibited complex interdigitating membrane protrusions. Single-cell labeling revealed that individual cells were both protrusive and migratory within the epithelial multilayer. Inhibition of Rho kinase (ROCK) further reduced intercellular adhesion on apical and lateral surfaces but did not disrupt basal tissue organization. Following morphogenesis, segregated membrane domains were re-established and junctional complexes re-formed. We observed similar epithelial organization during mammary morphogenesis in organotypic culture and in vivo. We conclude that mammary epithelial morphogenesis involves a reversible, spatially limited, reduction in polarity and intercellular junctions and active individualistic cell migration. Our data suggest that reductions in polarity and adhesion during breast cancer progression might reflect partial recapitulation of a normal developmental program.

Intracellular pH (pH i ) can change during physiological and pathological conditions causing significant changes of electrical and metabolic cell–cell communication through gap junction (GJ) channels. In HeLa cells expressing wild-type connexin45 (Cx45) as well as Cx45 and Cx43 tagged with EGFP, we examined how pH i affects junctional conductance (g j ) and g j dependence on transjunctional voltage (V j ). To characterize V j gating, we fit the g j –V j relation using a stochastic four-state model containing one V j -sensitive gate in each apposed hemichannel (aHC); aHC open probability was a Boltzmann function of the fraction of V j across it. Using the model, we estimated gating parameters characterizing sensitivity to V j and number of functional channels. In homotypic Cx45 and heterotypic Cx45/Cx43-EGFP GJs, pH i changes from 7.2 to ~8.0 shifted g j –V j dependence of Cx45 aHCs along the V j axis resulting in increased probability of GJ channels being in the fully open state wit...

Cancer cell communication networks represent critical therapeutic targets, with gap junctions serving as primary intercellular communication channels through connexin proteins. Recent breakthroughs in frequency-based cancer therapeutics demonstrate unprecedented convergence with gap junction biology, creating opportunities for precision targeting of cancer communication networks. This comprehensive analysis integrates validated research from molecular jackhammers achieving 99% cancer cell eradication (Nature Chemistry 2024), FDA-approved histotripsy sound wave therapy, terahertz DNA targeting demonstrating 20× acceleration of unwinding, and tumor-specific electromagnetic frequency identification across 163 cancer patients revealing 1524 frequencies with 57-92% cancer type specificity. We establish connections between connexin-43 gap junction networks operating at calculated 37.5 THz frequencies and validated frequency ranges demonstrating selective cancer targeting. The framework incorporates comprehensive analysis of 21 different connexin types, their tissue-specific functions, pathological roles in cancer progression, invasion, and metastasis, alongside clinical translation pathways including FDA-approved electromagnetic devices and ongoing clinical trials across multiple cancer types. This work represents the first comprehensive framework linking gap junction communication disruption with validated frequency medicine, establishing clear protocols for targeting cancer communication networks through multiple validated modalities including molecular resonance, acoustic cavitation, electromagnetic field therapy, and connexin-specific interventions.

Methamphetamine (meth) is a central nervous system (CNS) stimulant that results in psychological and physical dependency. The long term effects of meth within the CNS include neuronal plasticity changes, blood brain barrier compromise, inflammation, electrical dysfunction, neuronal/glial toxicity, and an increased risk to infectious diseases including HIV. Most of the reported meth effects in the CNS are related to dysregulation of chemical synapses by altering the release and uptake of neurotransmitters, especially dopamine, norepinephrine and epinephrine. However, little is known about the effects of meth on connexin (Cx) containing channels, such as gap junctions (GJ) and hemichannels (HC). We examined the effects of meth on Cx expression, function and its role in NeuroAIDS. We found that meth altered Cx expression and localization, decreased GJ communication between neurons and astrocytes, and induced the opening of Cx43/Cx36 HC. Furthermore, we found that these changes in GJ an...

Two-photon excitation makes it possible to excite molecules in volumes of much less than 1 fl. In two-photon flash photolysis (TPFP) this property is used to release effector molecules from caged precursors with high three-dimensional resolution. We describe and examine the benefits of using TPFP in model solutions and in a number of cell systems to study their spatial and temporal properties. Using TPFP of caged fluorescein, we determined the free diffusion coefficient of fluorescein (Dϭ4ϫ0 Ϫ6 cm 2 /s at 20°C, which is in close agreement with published values). TPFP of caged fluorescein in lens tissue in situ revealed spatial nonuniformities in intercellular fiber cell coupling by gap junctions. At the lens periphery, intercellular transport was predominantly directed along rows of cells, but was nearly isotropic further from the periphery. To test an algorithm aiming to reconstruct the Ca 2ϩ release flux underlying physiological Ca 2ϩ signals in heart muscle cells, TPFP of DM-Nitrophen was utilized to generate artificial microscopic Ca 2ϩ signals with known underlying Ca 2ϩ release flux. In an experiment with mouse oocytes, the recently developed Ca 2ϩ cage dimethoxynitrophenyl-ethyleneglycol-bis-(␤aminoethylether)-N,N,NЈ,NЈ tetraacetic acid-4 (DMNPE-4) was released in the oocyte cytosol and inside a nucleolus. Analysis of the resulting fluorescence changes suggested that the effective diffusion coefficient within the nucleolus was half of that in the cytosol. These experiments demonstrate the utility of TPFP as a novel tool for the optical study of biomedical systems. © 2003 Society of Photo-Optical Instrumen- tation Engineers.

Two-photon excitation makes it possible to excite molecules in volumes of much less than 1 fl. In two-photon flash photolysis (TPFP) this property is used to release effector molecules from caged precursors with high three-dimensional resolution. We describe and examine the benefits of using TPFP in model solutions and in a number of cell systems to study their spatial and temporal properties. Using TPFP of caged fluorescein, we determined the free diffusion coefficient of fluorescein (Dϭ4ϫ0 Ϫ6 cm 2 /s at 20°C, which is in close agreement with published values). TPFP of caged fluorescein in lens tissue in situ revealed spatial nonuniformities in intercellular fiber cell coupling by gap junctions. At the lens periphery, intercellular transport was predominantly directed along rows of cells, but was nearly isotropic further from the periphery. To test an algorithm aiming to reconstruct the Ca 2ϩ release flux underlying physiological Ca 2ϩ signals in heart muscle cells, TPFP of DM-Nitrophen was utilized to generate artificial microscopic Ca 2ϩ signals with known underlying Ca 2ϩ release flux. In an experiment with mouse oocytes, the recently developed Ca 2ϩ cage dimethoxynitrophenyl-ethyleneglycol-bis-(␤aminoethylether)-N,N,NЈ,NЈ tetraacetic acid-4 (DMNPE-4) was released in the oocyte cytosol and inside a nucleolus. Analysis of the resulting fluorescence changes suggested that the effective diffusion coefficient within the nucleolus was half of that in the cytosol. These experiments demonstrate the utility of TPFP as a novel tool for the optical study of biomedical systems. © 2003 Society of Photo-Optical Instrumen- tation Engineers.

The ocular lens is an ideal model system for studying gap junction structure-function relationships. Here we apply novel methods to quantitatively compare connexin expression over macroscopic distances while simultaneously resolving the intracellular distribution of gap junctions in sub-micron detail. Our approach has identified three distinct zones of connexin density and allowed changes in gap junction plaque size, number and dispersion to be quantified. Our analysis is the first to precisely correlate changes in gap junction plaque structure with the reported changes in gap junction function that occur as a consequence of fiber cell differentiation.

In the post-genomic era the complex problem of evolutionary biology can be tackled from the topdown, the bottom-up, or from the middle-out. Given the emergent and contingent nature of this process, we have chosen to take the latter approach, both as a mechanistic link to developmental biology and as a rational means of identifying signaling mechanisms based on their functional genomic significance. Using this approach, we have been able to configure a working model for lung evolution by reverse-engineering lung surfactant from the mammalian lung to the swim bladder of fish. Based on this archetypal cell-molecular model, we have reduced evolutionary biology to cell communication, starting with unicellular organisms communicating with the environment, followed by cell-cell communication to generate metazoa, culminating in the communication of genetic information between generations, i.e. reproduction. This model predicts the evolution of physiologic systems-including development, homeostasis, disease, regeneration/ repair, and aging-as a logical consequence of biology reducing entropy. This approach provides a novel and robust way of formulating refutable, testable hypotheses to determine the ultimate origins and first principles of physiology, providing candidate genes for phenotypes hypothesized to have mediated evolutionary changes in structure and/or function. Ultimately, it will form the basis for predictive medicine and molecular bioethics, rather than merely showing associations between genes and pathology, which is an unequivocal Just So Story. In this new age of genomics, our reach must exceed our grasp.

Although alveolar wall thinning has been attributed to apoptosis of interstitial lung lipofibroblasts (LFs), the underlying molecular mechanism(s) remains unknown. Although the physiological vitamin D steroid hormone 1α,25(OH)2D3 (1,25D) has been suggested as a local paracrine/autocrine effector of fetal lung maturation and is known to affect fibroblast apoptosis, its effects on LF apoptosis are unknown. We determined the role of 1,25D and its metabolite, C-3-epimer (3-epi-1,25D), on LF and alveolar type II (ATII) cell differentiation, proliferation, and apoptosis. Embryonic day 19 Sprague-Dawley fetal rat lung LFs and ATII cells were treated with 1,25D or 3-epi-1,25D (1 × 10−10 to 1 × 10−8 M) for 24 h, and cell proliferation, apoptosis, and differentiation were assessed. Both 1,25D and 3-epi-1,25D exhibited dose-dependent increases in expression of the key homeostatic epithelial-mesenchymal differentiation markers, increased LF and ATII cell proliferation, and decreased apoptosis. ...

Pathologies of retinal blood vessels are among the major causes of blindness worldwide. A key cell type that regulates retinal vascular development is the astrocyte. Generated extrinsically to the retina, astrocytes migrate into the retina through the optic nerve head. Even though there is a strong correlation between astrocyte distribution and retinal vascular development, the factors that guide astrocytes into the retina remain unclear. In this study, we show that astrocytes migrate within a laminin-containing basement membrane - the inner limiting membrane. Genetic deletion of the laminin β2 and γ3 chains affects astrocyte migration and spatial distribution. We show that laminins act as haptotactic factors in vitro in an isoform-specific manner, inducing astrocyte migration and promoting astrocyte differentiation. The addition of exogenous laminins to laminin-null retinal explants rescues astrocyte migration and spatial patterning. Furthermore, we show that the loss of laminins r...

Dans le contexte de l’analyse de la dynamique membra- naire, nous proposons un nouveau modele pour represen- ter le comportement de proteines au cours de la fusion de vesicules dans la membrane plasmique a la fin du proces- sus d’exocytose. Le modele introduit incorpore la phase de liberation continue des proteines de la vesicule, caracte- risee par le taux de liberation. Les proteines diffusent en- suite dans la membrane, ce qui ajoute un second parametre biophysique, le coefficient de diffusion. Une methode origi- nale est elaboree pour estimer ces deux parametres a par- tir d’une sequence d’images. Une evaluation quantitative en demontre l’efficacite, et les resultats sur des sequences reelles de microscopie TIRF permettent de mettre en evi- dence des differences de comportement des proteines Lan- gerin et TfR.

Mesenchymal stem cells (MSCs) possess unique immunomodulatory abilities. Many studies have elucidated the clinical efficacy and underlying mechanisms of MSCs in immune disorders. Although immunoregulatory factors, such as Prostaglandin E2 (PGE2), and their mechanisms of action on immune cells have been revealed, their effects on MSCs and regulation of their production by the culture environment are less clear. Therefore, we investigated the autocrine effect of PGE2 on human adult stem cells from cord blood or adipose tissue, and the regulation of its production by cell-to-cell contact, followed by the determination of its immunomodulatory properties. MSCs were treated with specific inhibitors to suppress PGE2 secretion, and proliferation was assessed. PGE2 exerted an autocrine regulatory function in MSCs by triggering E-Prostanoid (EP) 2 receptor. Inhibiting PGE2 production led to growth arrest, whereas addition of MSC-derived PGE2 restored proliferation. The level of PGE2 productio...