Biomedical subjects

Andreas Bringmann

Publications and source records attributed to Andreas Bringmann.

At least 37 records · Page 2Linked to original sources

PubMed2005

The glucocorticoid triamcinolone acetonide inhibits osmotic swelling of retinal glial cells via stimulation of endogenous adenosine signaling.

The glucocorticoid triamcinolone acetonide is clinically used for the treatment of macular edema. However, the edema-resolving mechanisms of triamcinolone are incompletely understood. Since cell swelling is a central cause of cytotoxic edema in the brain and retina, we determined the effects of triamcinolone acetonide on the swelling of retinal ganglion and Müller glial cells in acutely isolated retinas from rats and guinea pigs in situ. Triamcinolone acetonide (100 microM) had no effect on the swelling of ganglion cells that was evoked in isolated whole mounts of the guinea pig retina by acute application of glutamate (1 mM) or high K+ (50 mM). However, triamcinolone reversed the osmotic swelling of Müller glial cells in retinas of the rat that was observed under various experimental conditions: in retinas isolated at 3 days after transient retinal ischemia, in retinas of eyes with lipopolysaccharide-induced ocular inflammation, and in control retinas in the presence of Ba2+ (1 mM), H2O2 (200 microM), arachidonic acid (10 microM), or prostaglandin E2 (30 nM). The inhibiting effect of triamcinolone on osmotic glial cell swelling was mediated by stimulation of transporter-mediated release of endogenous adenosine and subsequent A1 receptor activation, resulting in an elevation of the intracellular cAMP level and activation of the protein kinase A, and, finally, in an opening of extrusion pathways for K+ and Cl- ions. The inhibitory effect on the cytotoxic swelling of glial cells may contribute to the fast edema-resolving effect of vitreal triamcinolone observed in human patients.

Adenosine↗

PubMed2005

Changes in retinal gene expression in proliferative vitreoretinopathy: glial cell expression of HB-EGF.

PURPOSE: To compare the gene expression pattern of control postmortem retinas with retinas from patients with proliferative vitreoretinopathy (PVR), to determine the expression of the heparin binding epidermal growth factor-like growth factor (HB-EGF) by glial cells in fibroproliferative membranes, and to examine whether cells of the human Müller cell line, MIO-M1, respond to HB-EGF with proliferation, migration, and secretion of the vascular endothelial growth factor (VEGF). METHODS: To identify genes that were differently expressed in PVR and control retinas, the RNA from the neural retinas of seven postmortem donors and of two patients with PVR were analyzed for differential gene expression, by hybridization of labeled cRNA probes to an Affymetrix human genome microarray set. The results were validated by real time PCR experiments investigating RNA from 6 postmortem retinas and 4 PVR retinas. Epiretinal PVR membranes were immunohistochemically stained for colocalization of HB-EGF and the glial cell marker, glial fibrillary acidic protein (GFAP). The HB-EGF evoked proliferation of cultured Müller cells was investigated by a bromodeoxyuridine immunoassay, chemotaxis was assessed with a migration assay, and the release of VEGF was evaluated by ELISA. RESULTS: Out of the 12,600 genes and expressed sequence tags investigated, the levels of 80 showed an increased expression, and 21 were expressed at decreased levels, in the retinas of PVR patients compared to the control retinas. The upregulated signals include genes for nuclear and cell cycle related proteins, extracellular secretory proteins, cytosolic signaling proteins, and proteins of the membrane and the extracellular matrix. The genes of the hepatocyte growth factor and of HB-EGF were found to be expressed in PVR retinas but not in control retinas. In epiretinal membranes of patients with PVR, HB-EGF immunoreactivity partially colocalized with GFAP. In cultured Müller cells, HB-EGF stimulated both proliferation and chemotaxis, and the secretion of VEGF, via activation of the extracellular signal regulated kinases 1 and 2 and of the phosphatidylinositol-3 kinase. CONCLUSIONS: The development of PVR is accompanied by complex changes of the gene expression in the neural retina, with an upregulation of genes that support cell proliferation, cell signaling, cell motility, and extracellular matrix remodeling. HB-EGF is one of the factors that are significantly upregulated in PVR retinas. HB-EGF expression in fibroproliferative tissue and its stimulatory effect on glial cell proliferation, chemotaxis, and VEGF secretion suggest that HB-EGF may be a factor mediating glial cell responses during PVR.

Adolescent↗

PubMed2005

Effect of alpha2-macroglobulin on retinal glial cell proliferation.

BACKGROUND: Activation of the receptor for alpha2-macroglobulin (alpha2 M), the low-density lipoprotein-related protein (LRP1; CD91), has been suggested to represent a possible strategy for the inhibition of uncontrolled retinal cell proliferation via stimulation of the clearance of alpha2 M-bound growth factors and proteinases from the extracellular space. In order to prove this assumption, we investigated the effect of alpha2 M on the proliferation of Müller glial cells in vitro. METHODS: Proliferation assays using bromodeoxyuridine were carried out on cultured Müller glial cells of the guinea pig in the absence and presence of alpha2 M. RESULTS: Activated alpha2 M evoked a slight increase of the cell proliferation at control conditions. Addition of alpha2 M to the culture medium inhibited the proliferation evoked by agonists of G-protein-coupled receptors [adenosine 5'-triphosphate (ATP), neuropeptide Y]. However, alpha2 M did not diminish the proliferation evoked by agonists of receptor tyrosine kinases (epidermal and platelet-derived growth factors) and by serum, respectively. Inhibition of LRP1 by a neutralizing antibody did not alter the ATP-evoked proliferation while it increased the proliferation in the presence of alpha2 M. CONCLUSION: It is concluded that alpha2 M inhibits the proliferation evoked by agonists of G-protein-coupled receptors, possibly via enhanced growth factor clearance by LRP.

Adenosine Triphosphate↗

PubMed2005

Glial cell-mediated spread of retinal degeneration during detachment: a hypothesis based upon studies in rabbits.

In human subjects with peripheral retinal detachments, visual deficits are not restricted to the detached retina but are also present in the non-detached tissue. Based upon studies on a rabbit model of rhegmatogenous retinal detachment, we propose a glial cell-mediated mechanism of spread of retinal degeneration into non-detached retinal areas which may also have importance for the understanding of alterations in the human retina. Both detached and attached portions of the rabbit retina display photoreceptor cell degeneration and cystic degeneration of the innermost layers. An inverse mode of photoreceptor cell degeneration in the attached tissue suggests a disturbed support of the photoreceptor cells by Müller cells which show various indications of gliosis (increased expression of intermediate filaments, cell hypertrophy, decreased plasma membrane K(+) conductance, increased Ca(2+) responsiveness to purinergic stimulation) in both detached and attached tissues. We propose that gliotic alterations of Müller cells contribute to the degeneration of the attached retina, via disturbance of glial homeostasis mechanisms. A down-regulation of the K(+) conductance of Müller cells may prevent effective retinal K(+) and water clearance, and may favor photoreceptor cell degeneration and edema development.

Adenosine Triphosphate↗

PubMed2005

Altered membrane physiology in Müller glial cells after transient ischemia of the rat retina.

Inwardly rectifying K+ (Kir) channels have been implicated in the mediation of retinal K+ homeostasis by Muller glial cells. To assess possible involvement of altered glial K+ channel expression in ischemia-reperfusion injury, transient retinal ischemia was induced in rat eyes. Acutely isolated Muller cells from postischemic retinae displayed a fast downregulation of their Kir currents, which began within 1 day and reached a maximum at 3 days of reperfusion, with a peak decrease to 20% as compared with control. This strong decrease of Kir currents was accompanied by an increase of the incidence of cells which displayed depolarization-evoked fast transient (A-type) K+ currents. While no cell from untreated control rats expressed A-type K+ currents, all cells investigated from 3- and 7-day postischemic retinae displayed such currents. An increased incidence of cells displaying fast transient Na+ currents was observed at 7 days after ischemia. These results suggest a role of altered glial Kir channel expression in postischemic neuronal degeneration via disturbance of retinal K+ siphoning.

Animals↗

PubMed2005

Diversity of aquaporin mRNA expressed by rat and human retinas.

Muller glial cells of the sensory retina mediate K+ and water fluxes that are facilitated by aquaporin-4 (AQP4) water channels and by Kir4.1-K+ channels. However, it is not known which subtypes of aquaporins are expressed in the mammalian retina. Using RT-PCR, we found that both human and rat retinas express mRNA for a diversity of water channel proteins. The human retina expresses mRNAs for AQP0 to AQP12 proteins. Using real-time PCR, we found that the mRNAs for AQP4 and Kir4.1 are downregulated in retinas that were obtained from patients with proliferative retinopathy compared with post-mortem controls. The data suggest that the development of proliferative gliosis is accompanied by disturbed transglial water and ion movements.

Animals↗

PubMed2005

Ocular inflammation alters swelling and membrane characteristics of rat Müller glial cells.

Ocular inflammation is a common cause of retinal edema that may involve swelling of Müller glial cells. In order to investigate whether endotoxin-induced ocular inflammation in rats alters the swelling and membrane characteristics of Müller cells, lipopolysaccharide (LPS; 0.5%) was intravitreally injected. At 3 and 7 days after treatment, hypotonic challenge induced swelling of Müller cell somata that was not observed in non-treated control eyes. Müller cells of LPS-treated eyes displayed a downregulation of inward K(+) currents and upregulation of A-type K(+) currents that was associated with a decreased expression of Kir4.1 protein in retinal slices. The data suggest that ocular inflammation induces alterations of both the swelling characteristics and the K(+) channel expression of Müller cells.

Analysis of Variance↗

PubMed2005

Physiological properties of retinal Muller glial cells from the cynomolgus monkey, Macaca fascicularis--a comparison to human Muller cells.

Retinae from rabbits and laboratory rodents are often used as 'models' of the human retina, although there are anatomical differences. To test whether monkey eyes provide a better model, a physiological study of Muller glial cells was performed comparing isolated cells and retinal wholemounts from the cynomolgus monkey, Macaca fascicularis and from man. The membrane conductance of Muller cells from both species was dominated by inward and outward K(+) currents. Cells displayed glutamate uptake currents and responded to nucleotides by intracellular Ca(2+) increases. However, there were also species differences, such as a lack of GABA(A) receptors and of Ca(2+)-dependent K(+) currents in monkey cells. Thus, the use of Muller cells from cynomolgus monkeys may be advantageous for investigating a few specific properties; in general, monkey cells are no more similar to human cells than those from standard laboratory animals.

Adult↗

PubMed2005

Triamcinolone does not alter glial cell activation in the experimentally detached rabbit retina.

AIMS: Retinal detachment induces neural and photoreceptor cell degeneration and fast activation of micro- (immune) and macroglial cells. Hypoxia caused by increased distance between the choriocapillaris and the neural retina, and retinal oedema during detachment, are factors causing gliotic responses and cell degeneration. Triamcinolone may inhibit some cellular responses that accompany hypoxia. Therefore, we investigated whether triamcinolone acetonide may be effective to reduce the gliotic alterations in the detached retina. METHODS: Local retinal detachment in rabbit eyes was created by subretinal injection of sodium hyaluronate, and triamcinolone acetonide (8 mg) was applied intravitreally. Wholecell patch-clamp records from Muller cells and Ca2+ imaging from retinal wholemounts were carried out. Microglial/immune cells in the nerve-fiber layer of retinal wholemounts were labeled with Griffonia simplicifolia agglutinin (GSA) isolectin. Additionally, two morphological parameters which characterize microglial activation/immune cell infiltration were estimated: the cross-sectional area of the somata of the cells in the nerve-fiber layer and the number of cell processes which evolve from the soma. RESULTS: Three days after detachment, gliotic alterations were apparent in Muller cells isolated from both detached and nondetached retinal areas, as indicated by the cellular hypertrophy, by the downregulation of the plasma membrane K+ conductance, and by the upregulation of intracellular Ca2+ responsiveness to stimulation of purinergic P2Y receptors. Intravitreal triamcinolone did not alter these gliotic alterations of Muller cells. Furthermore, triamcinolone could not inhibit the immune cell activation present in detached and attached retinal areas. However, intravitreal triamcinolone led to a strong decrease in the process number of GSA lectin-positive cells from detached retinas. CONCLUSIONS: The results suggest that triamcinolone is ineffective to inhibit gliotic responses in the detached retina. However, the immune cell activation after detachment was partially influenced by triamcinolone.

Animals↗

PubMed2005

Neuronal versus glial cell swelling in the ischaemic retina.

Under normal conditions, the pigment epithelium dehydrates the outer retina while Müller glial cells mediate the rapid water transport within the inner retina. Gliotic alterations of Müller cells may be implicated in the development of oedema in the post-ischaemic retina. Here, we suggest a mechanism of Müller cell-supported neuronal cell swelling and apoptosis in the ischaemic retina. During ischaemia, over-excitation of ionotropic glutamate receptors leads to neuronal cell depolarization that causes excess Ca(2+) influx into the cells, and to activation of the apoptosis machinery. The ion fluxes into the retinal neurons are associated with water movements that are mediated by aquaporin-4 water channels expressed by Müller cells and result in neuronal cell swelling. After reperfusion, the glial cells may swell due to the down-regulation of their K(+) conductance, which results in intracellular K(+) overload and water movements from the blood and vitreous into the cells. An inhibition of the glial cell-mediated water movements during ischaemic episodes should reduce the ion shifts at the neuronal synapses, resulting in decreased neuronal cell swelling and apoptosis. An inhibition of the water movements in the post-ischaemic phase may prevent cytotoxic Müller cell swelling but may impair the fluid clearance from retinal tissue in the presence of vasogenic oedema. Thus, pharmacological modification of the ion and fluid clearance functions of Müller cells may become a novel way to resolve both cytotoxic and vasogenic oedema in the retina.

Animals↗

PubMed2005

Resensitization of P2Y receptors by growth factor-mediated activation of the phosphatidylinositol-3 kinase in retinal glial cells.

PURPOSE: To determine whether activation of receptor tyrosine kinases enhances the responsiveness of purinergic P2Y receptors in Muller glial cells, known to induce Muller cell proliferation. METHODS: The P2Y receptors of primary cultured Muller cells of the guinea pig were desensitized by short (30 seconds to 10 minutes)- and long (24 or 48 hours)-term application of adenosine 5'-triphosphate (ATP). Recordings of ATP-evoked intracellular calcium responses showed whether short-term application of different growth factors evoke a resensitization of the receptors. Coapplication of pharmacologic inhibitors showed whether activation of protein kinases is involved in receptor resensitization. RESULTS: Both short- and long-term incubation with ATP induced a significant P2Y receptor desensitization, which was indicated by a strongly reduced intracellular calcium mobilization and which lasted for at least 48 hours. However, the receptors were significantly resensitized after short-term application of platelet-derived, epidermal, or nerve growth factors. The growth factor-mediated resensitization was dependent on an intact cytoskeleton and on the activation of protein phosphatases and of the phosphatidylinositol-3 kinase (PI3K), but was independent of the activation of protein kinase C, src kinases, or extracellular signal-regulated kinases. CONCLUSIONS: The results show that activation of receptor tyrosine kinases causes, via activation of PI3K and protein phosphatases, a resensitization of P2Y receptors formerly desensitized by agonist application. The growth factor-mediated resensitization may underlie the previously observed enhanced responsiveness of P2Y receptors in retinal glial cells in experimental retinal detachment and proliferative vitreoretinopathy and may contribute to the induction of reactive gliosis and Muller cell proliferation.

Adenosine Triphosphate↗

PubMed2005

Ischemia-reperfusion causes exudative detachment of the rabbit retina.

PURPOSE: To characterize the activation of macroglial (Müller) and microglial cells, as well as neuronal cell degeneration, during ischemia-reperfusion in rabbit retina and to test the possible effect of triamcinolone acetonide on gliosis. METHODS: Transient retinal ischemia was produced by increasing intraocular pressure for 60 minutes. Triamcinolone (8 mg) was intravitreally applied immediately after the cessation of ischemia. At 3 and 8 days after reperfusion, the K+ currents of acutely isolated Müller cells were recorded, and the Ca2+ responses of Müller cells on stimulation of P2Y receptors were recorded fluorometrically in retinal wholemounts. Microglial/immune cells in the nerve fiber layer of retinal wholemounts were labeled with isolectin. To evaluate neuronal and Müller cell loss, the numbers of cells were counted in retinal slices. RESULTS: Transient ischemia caused exudative detachment of the central retina that was characterized by disruption of the pigment epithelial monolayer, the presence of scattered pigment epithelial and immune cells in the expanded subretinal space, and retinal folds. A significant loss of photoreceptor cells was observed at 8 days after reperfusion. At 3 and 8 days after reperfusion, Müller cell gliosis was apparent, as indicated by cellular hypertrophy, downregulation of K+ channel expression, and an increased number of cells that displayed P2Y receptor-mediated Ca2+ responses. The number of microglial/immune cells increased strongly after reperfusion. Intravitreal triamcinolone did not affect the parameters of Müller cell gliosis but decreased the number of microglial/immune cells. CONCLUSIONS: Ischemia-reperfusion of the rabbit retina causes exudative retinal detachment that is characterized by a loss of photoreceptor cells, whereas the inner retina remains largely preserved. Micro- and macroglial cells are activated early during reperfusion, even before dropout of the photoreceptor cells. Intravitreal triamcinolone may decrease the degree of microglial/immune cell activation.

Animals↗

PubMed2005

Identification of P2Y receptor subtypes in human muller glial cells by physiology, single cell RT-PCR, and immunohistochemistry.

PURPOSE: Retinal Müller glial cells are known to express metabotropic P2Y receptors. The present study was conducted to identify certain subtypes of P2Y receptors in human Müller cells. METHODS: The patch-clamp technique was used to measure increases of Ca(2+)-dependent K+ currents mediated by the activation of P2Y receptors in freshly isolated human Müller cells. Several P2 agonists were used. Subsequently, the cells were harvested into the patch pipette and a single cell RT-PCR was performed. Moreover, retinal tissue from organ donors was used for immunohistochemistry. RESULTS: The electrophysiological data were consistent with the expression of P2Y1, P2Y2, P2Y4, and P2Y6 receptor subtypes. RT-PCR revealed that mRNA for all these subtypes was present in Müller cells. However, the incidence of P2Y2 receptor mRNA was significantly lower than that of the other subtypes. Immunoreactivity for all four subtypes was found in retinal tissue, partly colocalized with immunoreactivity for vimentin. CONCLUSIONS: The presented data obtained by different techniques revealed that human Müller cells express P2Y1, P2Y2, P2Y4, and P2Y6 receptors. The specific roles of these receptor subtypes in retinal physiology and/or pathophysiology remain to be investigated in future studies.

Fluorescent Antibody Technique, Indirect↗

PubMed2004

Glutamate-evoked alterations of glial and neuronal cell morphology in the guinea pig retina.

Neuronal activity is accompanied by transmembranous ion fluxes that cause cell volume changes. In whole mounts of the guinea pig retina, application of glutamate resulted in fast swelling of neuronal cell bodies in the ganglion cell layer (GCL) and the inner nuclear layer (INL) (by approximately 40%) and a concomitant decrease of the thickness of glial cell processes in the inner plexiform layer (IPL) (by approximately 40%) that was accompanied by an elongation of the glial cells, by a thickening of the whole retinal tissue, and by a shrinkage of the extracellular space (by approximately 18%). The half-maximal effect of glutamate was observed at approximately 250 mum, after approximately 4 min. The swelling was caused predominantly by AMPA-kainate receptor-mediated influx of Na+ into retinal neurons. Similar but transient morphological alterations were induced by high K+ and dopamine, which caused release of endogenous glutamate and subsequent activation of AMPA-kainate receptors. Apparently, retinal glutamatergic transmission is accompanied by neuronal cell swelling that causes compensatory morphological alterations of glial cells. The effect of dopamine was elicitable only during light adaptation but not in the dark, and glutamate and high K+ induced strong ereffects in the dark than in the light. This suggests that not only the endogenous release of dopamine but also the responsiveness of glutamatergic neurons to dopamine is regulated by light-dark adaptation. Similar morphological alterations (neuronal swelling and decreased glial process thickness) were observed in whole mounts isolated immediately after experimental retinal ischemia, suggesting an involvement of AMPA-kainate receptor activation in putative neurotoxic cell swelling in the postischemic retina.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2004

Neuropeptide Y-evoked proliferation of retinal glial (Muller) cells.

BACKGROUND: Glial cells in human retinas and in fibrocellular membranes from patients with proliferative vitreoretinopathy (PVR) have been described to upregulate their expression of Y1 receptors for neuropeptide Y (NPY) (Soler et al.: Glia 39:320, 2002). However, it is unknown whether Y1 receptor activation causes proliferation of retinal glial cells. We investigated whether NPY exerts a proliferation-stimulating effect on retinal glial cells, and compared the NPY-evoked signaling with the signaling of purinergic P2Y receptors. METHODS: Proliferation assays using bromodeoxyuridine were carried out on primarily cultured Muller glial cells of the guinea pig, in the absence and presence of blockers of Y1 receptors, of receptor tyrosine kinases (RTKs), of mitogen-activated protein kinases (MAPKs) and of phosphatidylinositol-3 kinase (PI3K). RESULTS: NPY exerted a biphasic effect on Muller cell proliferation. At low concentrations (0.1 ng/ml and 1 ng/ml) it decreased the proliferation rate of the cells, while at higher concentration (100 ng/ml) it increased Muller cell proliferation. The NPY-evoked proliferation was mediated by Y1 receptor stimulation and by activation of the p44/p42 MAPKs and partially of the p38 MAPK. Moreover, Y1 receptor-induced activation of PI3K as well as transactivations of the platelet-derived and the epidermal growth factor RTKs were necessary for full mitogenic effect of NPY. Y1 and P2Y receptors share partially common signal transduction pathways in Muller cells. CONCLUSION: It is suggested that NPY may be involved in stimulation of retinal glial cell proliferation during PVR when it is released at higher amounts into the injured retina.

Adenosine Triphosphate↗

PubMed2004

Switch of K+ buffering conditions in rabbit retinal Müller glial cells during postnatal development.

Although spatial buffering of excess extracellular K+ by K+ channels is a main function of retinal glial (Müller) cells, there are severe limitations to long distance K+-spatial buffering that have been predicted for (immature) glial cells: (i) a lack of inwardly rectifying K+ (Kir) channels [Glia 21(1997) 46]; and (ii) high internal resistance of outgrowing (cable like) processes [W. Rall, Handbook of Physiology, Section 1, vol. 1, Part 1, American Physiological Society, Bethesda, 1977, pp. 39-97]. In order to determine if changes in developing Müller cells improve or worsen their capability of carrying K+ spatial buffering currents, we compared the whole-cell currents of acutely isolated Müller cells at 5, 11 and 28 postnatal days of rabbits. Both K+-spatial buffer limitations described above were found in early postnatal stage (5 days), however, the cells overcome these limitations shortly after 11 days. During the period of 11-28 days, rabbit Müller cells simultaneously increase stalk axial conductance and express Kir channels. Both processes take place during the critical stage of retinal maturation, and should dramatically improve "cable" K+-spatial buffering.

Animals↗

PubMed2004

Characterization of the basic fibroblast growth factor-evoked proliferation of the human Müller cell line, MIO-M1.

BACKGROUND: Basic fibroblast growth factor (bFGF) has been suggested to mediate activation of Müller glial cells in the ischemic-hypoxic retina. However, the intracellular pathways activated by bFGF in human Müller cells have been little explored. We characterized the signaling transduction pathways which are involved in the control and growth factor-evoked proliferation of a recently described human Müller cell line, MIO-M1. In addition, we investigated whether bFGF evoked the release of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) from the cells. METHODS: The growth factor-evoked proliferation of cultured MIO-M1 cells was estimated by means of a bromodeoxyuridine immunoassay, in the absence and presence of blockers of mitogen-activated protein kinases (MAPKs) and of the phosphatidylinositol-3 kinase (PI3K). The activation state of the p44/p42 MAPK was determined by Western blotting, and the bFGF-evoked release of VEGF and HGF was evaluated by ELISA. RESULTS: bFGF evoked a concentration-dependent increase of the cell proliferation, with an EC50 of approximately 1 ng/ml, via activation of both the p44/p42 MAPK and the p38 MAPK. In contrast, the mitogenic effects of the platelet-derived and the heparin-binding epidermal growth factors were dependent on p44/p42 MAPK activation and independent of activation of p38 MAPK. The transforming growth factors beta1 and beta2 also evoked cell proliferation which was independent of activation of the MAPKs investigated. bFGF evoked a release of VEGF and of HGF by the cells; these effects were independent of MAPK activation and were possibly mediated by activation of the PI3K signaling pathway. CONCLUSION: bFGF evokes multiple intracellular signaling pathways in human Müller cells which underlie the gliotic cell responses upon ischemic-hypoxic insults in the retina. Beside the stimulation of cell proliferation, which is dependent on activation of p44/p42 and p38 MAPKs, bFGF induces the secretion of VEGF and HGF by Müller cells.

Blotting, Western↗

PubMed2004

Selective staining by vital dyes of Müller glial cells in retinal wholemounts.

Müller glial cells within the retina may respond to different signaling molecules with an elevation of their intracellular free calcium. To prove the localization of the recorded calcium responses in Müller cells within acutely isolated retinal wholemounts, retinal pieces from adult animals and humans were exposed to different vital dyes just after the calcium imaging records were finished. The dyes, Mitotracker Orange, Mitotracker Green, Celltracker Orange, Celltracker Green, and monochlorobimane, are all selectively taken up by Müller glial cells, while neuronal cells remain largely devoid of the dyes. By using this method, it can be demonstrated that the free calcium alterations within the wholemounts indeed occur within Müller cells. Moreover, the cross-sectional areas of (dye-filled) Müller glial cell bodies, as well as of (dye-free) neuronal cell bodies, can be measured in retinal wholemounts, and the spatial densities of both types of cells can be determined. The vital dye loading of Müller cells may facilitate investigations of stimulus-induced alterations of retinal glial cell physiology and morphology.

Animals↗