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Vanzo-Sparks HK, Webster SE, Webster MK, Linn CL. Quantification of Proliferating and Mitotically Active Retinal Cells in Mice by Flow Cytometry. Bio Protoc 2024; 14:e5024. [PMID: 39011369 PMCID: PMC11247376 DOI: 10.21769/bioprotoc.5024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 04/08/2024] [Accepted: 06/13/2024] [Indexed: 07/17/2024] Open
Abstract
Adult mammals lack the ability to regenerate retinal neurons after injury. However, in previous studies from this lab, topical application of the selective alpha7 nicotinic acetylcholine receptor (nAChR) agonist, PNU-282987, has been associated with an increase in the number of retinal neurons in adult murine models both in the presence and absence of injury to the retina. Additionally, studies assaying mitotic markers have shown a substantial increase in the amount of mitotically active and proliferating cells with the topical application of the alpha7 nAChR agonist. However, these previous studies were performed using fluorescent immunolabeling and subsequent confocal microscopy, thus limiting the number of antibodies that can be multiplexed. As a result, we have developed a flow cytometry method that allows for the multiplexing and analysis of multiple external and internal markers in dissociated retinal cells. In this paper, a step-by-step protocol is described for the labeling of multiple retinal cell types such as retinal ganglion cells, rod photoreceptors, and Müller glia, concurrently with Müller glia-derived progenitor cells that arise after treatment with PNU-282987. Key features • Neurogenesis in the adult mammalian retina. • Flow cytometry of retinal cells. • PNU-282987-induced mitotic activity in the retina. • Dissociation of the retina for flow cytometry analysis. Graphical overview Schematic demonstrating the protocol for preparation of retinal cells for flow cytometry analysis. (A) Adult mice (3-6 months) are subjected to topical PBS eyedrop treatment containing DMSO (control groups) or PNU-282987 (experimental groups). Both eyedrop treatments contain 1 mg/mL of BrdU to label proliferating cells. After treatment, mice are euthanized, and retinae are harvested for dissociation using papain. (B) Dissociated retina cells are fixed and permeabilized before aliquots are taken for cell counts on a hemocytometer. After determining the number of cells present, conjugated antibodies and unconjugated primary antibodies are added at the appropriate dilutions. Fluorescent secondary antibodies are added for markers that are unconjugated. Cells are then subjected to flow cytometric analysis using a BD LSRFortessa.
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Affiliation(s)
- Hope K Vanzo-Sparks
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, USA
| | - Sarah E Webster
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, USA
| | - Mark K Webster
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, USA
| | - Cindy L Linn
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, USA
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Webster SE, Spitsbergen JB, Linn DM, Webster MK, Otteson D, Cooley-Themm C, Linn CL. Transcriptome Changes in Retinal Pigment Epithelium Post-PNU-282987 Treatment Associated with Adult Retinal Neurogenesis in Mice. J Mol Neurosci 2022; 72:1990-2010. [PMID: 35867327 DOI: 10.1007/s12031-022-02049-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 07/12/2022] [Indexed: 10/17/2022]
Abstract
PNU-282987, a selective alpha7 nicotinic acetylcholine receptor agonist, has previously been shown to have both neurogenic and broad regenerative effects in the adult murine retina. The objective of this study was to assay the molecular mechanism by which PNU-282987 promotes the production of Muller-derived progenitor cells through signaling via the resident retinal pigment epithelium. These Muller-derived progenitor cells generate a myriad of differentiated neurons throughout the retina that have previously been characterized by morphology. Herein, we demonstrate that topical application of PNU-282987 stimulates production of functional neurons as measured by electroretinograms. Further, we examine the mechanism of how this phenomenon occurs through activation of this atypical receptor using a transcriptomic approach isolated retinal pigment epithelium activated by PNU-282987 and in whole retina. We provide evidence that PNU-282987 causes a bi-modal signaling event in which early activation primes the retina with an inflammatory response and developmental signaling cues, followed by an inhibition of gliotic mechanisms and a decrease in the immune response, ending with upregulation of genes associated with specific retinal neuron generation. Taken together, these data provide evidence that PNU-282987 activates the retinal pigment epithelium to signal to Muller glia to produce Muller-derived progenitor cells, which can differentiate into new, functional neurons in adult mice. These data not only increase our understanding of how adult mammalian retinal regeneration can occur, but also provide therapeutic promise for treating functional vision loss.
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Affiliation(s)
- Sarah E Webster
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA
| | - Jake B Spitsbergen
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA
| | - David M Linn
- Department of Biomedical Sciences, Grand Valley State University, Grand Rapids, MI, USA
| | - Mark K Webster
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA
| | - Deborah Otteson
- University of Houston College of Optometry, Houston, TX, USA
| | - Cynthia Cooley-Themm
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA
| | - Cindy L Linn
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI, USA.
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Peña JS, Vazquez M. Harnessing the Neuroprotective Behaviors of Müller Glia for Retinal Repair. FRONT BIOSCI-LANDMRK 2022; 27:169. [PMID: 35748245 PMCID: PMC9639582 DOI: 10.31083/j.fbl2706169] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/18/2022] [Accepted: 05/05/2022] [Indexed: 11/29/2022]
Abstract
Progressive and irreversible vision loss in mature and aging adults creates a health and economic burden, worldwide. Despite the advancements of many contemporary therapies to restore vision, few approaches have considered the innate benefits of gliosis, the endogenous processes of retinal repair that precede vision loss. Retinal gliosis is fundamentally driven by Müller glia (MG) and is characterized by three primary cellular mechanisms: hypertrophy, proliferation, and migration. In early stages of gliosis, these processes have neuroprotective potential to halt the progression of disease and encourage synaptic activity among neurons. Later stages, however, can lead to glial scarring, which is a hallmark of disease progression and blindness. As a result, the neuroprotective abilities of MG have remained incompletely explored and poorly integrated into current treatment regimens. Bioengineering studies of the intrinsic behaviors of MG hold promise to exploit glial reparative ability, while repressing neuro-disruptive MG responses. In particular, recent in vitro systems have become primary models to analyze individual gliotic processes and provide a stepping stone for in vivo strategies. This review highlights recent studies of MG gliosis seeking to harness MG neuroprotective ability for regeneration using contemporary biotechnologies. We emphasize the importance of studying gliosis as a reparative mechanism, rather than disregarding it as an unfortunate clinical prognosis in diseased retina.
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Affiliation(s)
- Juan S. Peña
- Department of Biomedical Engineering, Rutgers, The State
University of New Jersey, Piscataway (08854), New Jersey, USA
| | - Maribel Vazquez
- Department of Biomedical Engineering, Rutgers, The State
University of New Jersey, Piscataway (08854), New Jersey, USA
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Webster SE, Sklar NC, Spitsbergen JB, Stanchfield ML, Webster MK, Linn DM, Otteson DC, Linn CL. Stimulation of α7 nAChR leads to regeneration of damaged neurons in adult mammalian retinal disease models. Exp Eye Res 2021; 210:108717. [PMID: 34348130 PMCID: PMC8459670 DOI: 10.1016/j.exer.2021.108717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/10/2021] [Accepted: 07/30/2021] [Indexed: 12/13/2022]
Abstract
The adult mammal lacks the ability to regenerate neurons lost to retinal damage or disease in a meaningful capacity. However, previous studies from this laboratory have demonstrated that PNU-282987, an α7 nicotinic acetylcholine receptor agonist, elicits a robust neurogenic response in the adult murine retina. With eye drop application of PNU-282987, Müller glia cells re-enter the cell cycle and produce progenitor-like cells that can differentiate into various types of retinal neurons. In this study, we analyzed the regenerative capability of PNU-282987 in two retinal disease models and identified the source of newly regenerated neurons. Wild-type mice and mice with a transgenic Müller-glia lineage tracer were manipulated to mimic loss of retinal cells associated with glaucoma or photoreceptor degeneration. Following treatment with PNU-282987, the regenerative response of retinal neurons was quantified and characterized. After onset of photoreceptor degeneration, PNU-282987 was able to successfully regenerate both rod and cone photoreceptors. Quantification of this response demonstrated significant regeneration, restoring photoreceptors to near wild-type density. In mice that had glaucoma-like conditions induced, PNU-282987 treatment led to a significant increase in retinal ganglion cells. Retrograde labeling of optic nerve axon fibers demonstrated that newly regenerated axons projected into the optic nerve. Lineage tracing analysis demonstrated that these new neurons were derived from Müller glia. These results demonstrate that PNU-282987 can induce retinal regeneration in adult mice following onset of retinal damage. The ability of PNU-282987 to regenerate retinal neurons in a robust manner offers a new direction for developing novel and potentially transformative treatments to combat neurodegenerative disease.
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Affiliation(s)
- Sarah E Webster
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, United States
| | - Nathan C Sklar
- Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI, United States
| | - Jake B Spitsbergen
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, United States
| | - Megan L Stanchfield
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, United States
| | - Mark K Webster
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, United States
| | - David M Linn
- Grand Valley State University, Department of Biomedical Sciences, Allendale, MI, United States
| | - Deborah C Otteson
- University of Houston College of Optometry, Houston, TX, United States
| | - Cindy L Linn
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI, United States.
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Paris JR, Sklar NC, Linn CL. BrdU Positive Cells Induced in a Genetic Mouse Model of Glaucoma. JOURNAL OF OPHTHALMOLOGY & VISUAL SCIENCES 2021; 6:1046. [PMID: 33829147 PMCID: PMC8023645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Previous studies have shown that eye drop application of the selective α7 nicotinic acetylcholine receptor agonist, PNU-282987, induces neurogenesis of RGCs in adult wild-type rodents. This study was designed to test the hypothesis that PNU-282987 reverses the loss of RGCs associated with glaucoma. A DBA/2J mouse model that auto-induces a glaucoma-like condition in adulthood was used for these studies. Short-term effects using PNU-282987 and BrdU eye drop treatments were examined, as well as the effects of early treatment and the effects in a chronic early treatment group in DBA/2J mice aged 3, 6 and 10 months. With and without treatment, retinas were removed, fixed, immunostained and RGC counts were assessed. IOP measurements were obtained weekly using a Tonolab tonometer. Results showed an average typical loss of BrdU positive RGCs by 29% by 10 months of age in this DBA/2J colony corresponding with a significant increase in IOP. However, the two-week short term application of PNU-282987 and BrdU induced a significant 21% increase in RGCs for DBA/2J mice at all ages. Chronic early PNU-282987 treatment produced a similarly significant increase in RGCs, while acute early treatment had no effect on RGC numbers. IOP measurements were not affected with PNU-282987 treatment. These studies demonstrated that 2-week treatment with PNU-282987, as well as chronic long-term treatment, induced a significant increase in the number of RGCs in the DBA/2J retina, counteracting the effects of the DBA/2J genetic glaucoma-like condition. These results suggest a potential future treatment of degenerative retinal diseases with PNU-282987.
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Affiliation(s)
- J R Paris
- Department of Biological Sciences, Western Michigan University, Kalamazoo MI, 49008, United States
| | - N C Sklar
- Western Michigan University Homer Stryker M.D. School of Medicine, Kalamazoo, MI, United States
| | - C L Linn
- Department of Biological Sciences, Western Michigan University, Kalamazoo MI, 49008, United States
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