Role of gap junctions in embryonic and somatic stem cells.
ABSTRACT Stem cells provide an invaluable tool to develop cell replacement therapies for a range of serious disorders caused by cell damage or degeneration. Much research in the field is focused on the identification of signals that either maintain stem cell pluripotency or direct their differentiation. Understanding how stem cells communicate within their microenvironment is essential to achieve their therapeutic potentials. Gap junctional intercellular communication (GJIC) has been described in embryonic stem cells (ES cells) and various somatic stem cells. GJIC has been implicated in regulating different biological events in many stem cells, including cell proliferation, differentiation and apoptosis. This review summarizes the current understanding of gap junctions in both embryonic and somatic stem cells, as well as their potential role in growth control and cellular differentiation.
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ABSTRACT: Neural stem cells in the adult brain exist primarily in a quiescent state but are reactivated in response to changing physiological conditions. How do stem cells sense and respond to metabolic changes? In the Drosophila CNS, quiescent neural stem cells are reactivated synchronously in response to a nutritional stimulus. Feeding triggers insulin production by blood-brain barrier glial cells, activating the insulin/insulin-like growth factor pathway in underlying neural stem cells and stimulating their growth and proliferation. Here we show that gap junctions in the blood-brain barrier glia mediate the influence of metabolic changes on stem cell behavior, enabling glia to respond to nutritional signals and reactivate quiescent stem cells. We propose that gap junctions in the blood-brain barrier are required to translate metabolic signals into synchronized calcium pulses and insulin secretion.Developmental cell. 07/2014;
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ABSTRACT: Cigarette smoking is a major risk factor for numerous diseases including cardiovascular diseases. Exposure to cigarette smoke (CS) leads to increased cardiovascular risk, myocardial injury, and mortality. Stem cell therapy is one of the promising therapeutic options available to treat myocardial injuries. Understanding the impact of cigarette smoke extract (CSE) on stem cell function would be valuable in determining the risk passed on during transplant. In this study, the impact of CSE on cardiac stem cell (CSC) functions was investigated using c-kit+ rat cardiac stem cells as the experimental model. Here, we hypothesized that CSE attenuates CSC membrane integrity, causes cytotoxicity, and affects many CSC functions via multiple mechanisms including modulation of extracellular stress-regulated kinase (ERK) (44/42) signaling and oxidative stress. The effects of CSE on CSCs were examined in vitro. Based on a published method, CSE was prepared. CSE-induced ERK signaling was detected by western blotting. CSE-induced modulation of catalase activity was also measured. Functional modulations due to CSE were examined via several methods including Apostain, BrdU, and LDH assays. In agreement with the CSE-induced activation of ERK, CSE-induced reduction in viability, migration, and increase in both cytotoxicity and para-cellular permeability were observed in CSCs. These results suggest that CSE impaired CSC responses that contribute to decreased ability of CSC to respond to stress or injury leading to exacerbation of the damage. Our findings will contribute to the understanding of the discipline and might contribute to the development of stem cell therapy approaches in the future.Cell Biology and Toxicology 03/2014; 30(2). · 1.97 Impact Factor
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ABSTRACT: In addition to the immediate microenvironment, long-range signaling may be an important component of cancer. Molecular-genetic analyses have implicated gap junctions—key mediators of cell-cell communication—in carcinogenesis. We recently showed that the resting voltage potential of distant cell groups is a key determinant of metastatic transformation and tumor induction. Here, we show in the Xenopus laevis model that gap junctional communication (GJC) is a modulator of the long-range bioelectric signaling that regulates tumor formation. Genetic disruption of GJC taking place within tumors, within remote host tissues, or between the host and tumors significantly lowers the incidence of tumors induced by KRAS mutations. The most pronounced suppression of tumor incidence was observed upon GJC disruption taking place farther away from oncogene-expressing cells, revealing a role for GJC in distant cells in the control of tumor growth. In contrast, enhanced GJC communication through the overexpression of wild-type connexin Cx26 increased tumor incidence. Our data confirm a role for GJC in tumorigenesis, and reveal that this effect is non-local. Based on these results and on published data on movement of ions through GJs, we present a quantitative model linking the GJC coupling and bioelectrical state of cells to the ability of oncogenes to initiate tumorigenesis. When integrated with data on endogenous bioelectric signaling during left-right patterning, the model predicts differential tumor incidence outcomes depending on the spatial configurations of gap junction paths relative to tumor location and major anatomical body axes. Testing these predictions, we found that the strongest influence of GJ modulation on tumor suppression by hyperpolarization occurred along the embryonic left-right axis. Together, these data reveal new, long-range aspects of cancer control by the host's physiological parameters.Frontiers in Physiology 02/2015; 5:519.