Maturation-induced changes in L-aspartate receptors from muller cells

Abstract Background Contrasting with zebrafish, retinal regeneration from Müller cells (MCs) is largely limited in mammals, where they undergo reactive gliosis that consist of a hypertrophic response and ultimately results in vision loss. Transforming growth factor β (TGFβ) is essential for wound healing, including both scar formation and regeneration. However, targeting TGFβ may affect other physiological mechanisms, owing its pleiotropic nature. The regulation of various cellular activities by TGFβ relies on its interaction with other pathways including Notch. Here, we explore the interplay of TGFβ with Notch and how this regulates MC response to injury in zebrafish and mice. Furthermore, we aimed to characterize potential similarities between murine and human MCs during chronic reactive gliosis. Methods Focal damage to photoreceptors was induced with a 532 nm diode laser in TgBAC (gfap:gfap-GFP) zebrafish (ZF) and B6-Tg (Rlbp1-GFP) mice. Transcriptomics, immunofluorescence, and flow cytometry were employed for a comparative analysis of MC response to laser-induced injury between ZF and mouse. The laser-induced injury was paired with pharmacological treatments to inhibit either Notch (DAPT) or TGFβ (Pirfenidone) or TGFβ/Notch interplay (SIS3). To determine if the murine laser-induced injury model translates to the human system, we compared the ensuing MC response to human donors with early retinal degeneration. Results Investigations into injury-induced changes in murine MCs revealed TGFβ/Notch interplay during reactive gliosis. We found that TGFβ1/2 and Notch1/2 interact via Smad3 to reprogram murine MCs towards an epithelial lineage and ultimately to form a glial scar. Similar to what we observed in mice, we confirmed the epithelial phenotype of human Müller cells during gliotic response. Conclusion The study indicates a pivotal role for TGFβ/Notch interplay in tuning MC stemness during injury response and provides novel insights into the remodeling mechanism during retinal degenerative diseases. Graphical abstract

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Extracellular H+ fluxes from tiger salamander Müller (glial) cells measured using self-referencing H+-selective microelectrodes

Journal of Neurophysiology ◽

10.1152/jn.00409.2017 ◽

2017 ◽

Vol 118 (6) ◽

pp. 3132-3143 ◽

Cited By ~ 2

Author(s):

Matthew A. Kreitzer ◽

David Swygart ◽

Meredith Osborn ◽

Blair Skinner ◽

Chad Heer ◽

...

Keyword(s):

Glial Cells ◽

Müller Cells ◽

Bicarbonate Transport ◽

Extracellular Potassium ◽

Tiger Salamander ◽

Muller Cells ◽

Extracellular Acidification ◽

Müller Glial Cells ◽

Bicarbonate Transporter ◽

Induced Changes

Self-referencing H+-selective electrodes were used to measure extracellular H+ fluxes from Müller (glial) cells isolated from the tiger salamander retina. A novel chamber enabled stable recordings using H+-selective microelectrodes in a self-referencing format using bicarbonate-based buffer solutions. A small basal H+ flux was observed from the end foot region of quiescent cells bathed in 24 mM bicarbonate-based solutions, and increasing extracellular potassium induced a dose-dependent increase in H+ flux. Barium at 6 mM also increased H+ flux. Potassium-induced extracellular acidifications were abolished when bicarbonate was replaced by 1 mM HEPES. The carbonic anhydrase antagonist benzolamide potentiated the potassium-induced extracellular acidification, while 300 μM DIDS, 300 μM SITS, and 30 μM S0859 significantly reduced the response. Potassium-induced extracellular acidifications persisted in solutions lacking extracellular calcium, although potassium-induced changes in intracellular calcium monitored with Oregon Green were abolished. Exchange of external sodium with choline also eliminated the potassium-induced extracellular acidification. Removal of extracellular sodium by itself induced a transient alkalinization, and replacement of sodium induced a transient acidification, both of which were blocked by 300 μM DIDS. Recordings at the apical portion of the cell showed smaller potassium-induced extracellular H+ fluxes, and removal of the end foot region further decreased the H+ flux, suggesting that the end foot was the major source of acidifications. These studies demonstrate that self-referencing H+-selective electrodes can be used to monitor H+ fluxes from retinal Müller cells in bicarbonate-based solutions and confirm the presence of a sodium-coupled bicarbonate transporter, the activity of which is largely restricted to the end foot of the cell. NEW & NOTEWORTHY The present study uses self-referencing H+-selective electrodes for the first time to measure H+ fluxes from Müller (glial) cells isolated from tiger salamander retina. These studies demonstrate bicarbonate transport as a potent regulator of extracellular levels of acidity around Müller cells and point toward a need for further studies aimed at addressing how such glial cell pH regulatory mechanisms may shape neuronal signaling.

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The TGFβ/Notch axis facilitates Müller cell-to-epithelial transition to ultimately form a chronic glial scar

10.21203/rs.3.rs-66116/v1 ◽

2020 ◽

Author(s):

Federica Maria Conedera ◽

Ana Maria Quintela Pousa ◽

Nadia Mercader ◽

Markus Tschopp ◽

Volker Enzmann

Keyword(s):

Vision Loss ◽

Transforming Growth Factor ◽

Müller Cells ◽

Transforming Growth Factor Β ◽

Glial Scar ◽

Reactive Gliosis ◽

Muller Cells ◽

Hypertrophic Response ◽

Epithelial Phenotype ◽

Induced Changes

Abstract Background Contrasting with zebrafish, retinal regeneration from Müller cells (MCs) is largely limited in mammals. There, MCs undergo reactive gliosis that consist of a hypertrophic response and ultimately results in vision loss. Transforming growth factor β (TGFβ) is essential for wound healing, including both scar formation and regeneration. However, targeting TGFβ may affect other physiological mechanisms, owing its pleiotropic nature. The regulation of various cellular activities by TGFβ relies on its interaction with other pathways including Notch. Here, we explore the interplay of TGFβ with Notch and how this regulates MC response to injury in zebrafish and mice. Furthermore, we aimed to characterize potential similarities between murine and human MCs during chronic reactive gliosis. Methods Focal damage to photoreceptors was induced with a 532 nm diode laser in TgBAC (gfap:gfap-GFP) zebrafish (ZF) and B6-Tg (Rlbp1-GFP) mice. Transcriptomics, immunofluorescence, and flow cytometry were employed for a comparative analysis of MC response to laser-induced injury between ZF and mouse. The laser-induced injury was paired with pharmacological treatments to inhibit either Notch (DAPT) or TGFβ (Pirfenidone) or TGFβ/Notch interplay (SIS3). To determine if the murine laser-induced injury model translates to the human system, we compared the related MC response to human donors with early retinal degeneration. Results Investigations into injury-induced changes in murine MCs revealed TGFβ/Notch interplay during reactive gliosis. We found that TGFβ1/2 and Notch1/2 interact via Smad3 to reprogram murine MCs towards an epithelial lineage and ultimately to form a glial scar. Similar to what we observed in mice, we confirmed the epithelial phenotype of human Müller cells during gliotic response. Conclusion This study indicates a pivotal role for TGFβ/Notch interplay in tuning MC stemness during injury response and provides novel insights into the remodeling mechanism during retinal degenerative diseases.

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Faculty Opinions recommendation of Muller cells are living optical fibers in the vertebrate retina.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1083850.535980 ◽

2007 ◽

Author(s):

Roger Hardie

Keyword(s):

Optical Fibers ◽

Müller Cells ◽

Muller Cells ◽

Vertebrate Retina

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K+ Channels of Müller Glial Cells in Retinal Disorders

CNS & Neurological Disorders - Drug Targets ◽

10.2174/1871527317666180202114233 ◽

2018 ◽

Vol 17 (4) ◽

pp. 255-260 ◽

Cited By ~ 2

Author(s):

Feng Gao ◽

Lin-Jie Xu ◽

Yuan Zhao ◽

Xing-Huai Sun ◽

Zhongfeng Wang

Keyword(s):

Müller Cells ◽

Major Type ◽

Delayed Rectifier ◽

Muller Cells ◽

Bkca Channels ◽

K Channels ◽

Functional Changes ◽

Physiological Properties ◽

Retinal Disorders ◽

Inwardly Rectifying

Background & Objective: Müller cell is the major type of glial cell in the vertebrate retina. Müller cells express various types of K+ channels, such as inwardly rectifying K+ (Kir) channels, big conductance Ca2+-activated K+ (BKCa) channels, delayed rectifier K+ channels (KDR), and transient A-type K+ channels. These K+ channels play important roles in maintaining physiological functions of Müller cells. Under some retinal pathological conditions, the changed expression and functions of K+ channels may contribute to retinal pathogenesis. Conclusion: In this article, we reviewed the physiological properties of K+ channels in retinal Müller cells and the functional changes of these channels in retinal disorders.

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