Publications by authors named "S I Tomarev"

140 Publications

The role of miRNA in retinal ganglion cell health and disease.

Neural Regen Res 2022 Mar;17(3):516-522

Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.

miRNA are short non-coding RNA responsible for the knockdown of proteins through their targeting and silencing of complimentary mRNA sequences. The miRNA landscape of a cell thus affects the levels of its proteins and has significant consequences to its health. Deviations in this miRNA landscape have been implicated in a variety of neurodegenerative diseases and have also garnered interest as targets for treatment. Retinal ganglion cells are the sole projection neuron of the retina with their axons making up the optic nerve. They are a focus of study not only for their importance in vision and the myriad of blinding diseases characterized by their dysfunction and loss, but also as a model of other central nervous system diseases such as spinal cord injury and traumatic brain injury. This review summarizes current knowledge on the role of miRNA in retinal ganglion cell function, highlighting how perturbations can result in disease, and how modulating their abundance may provide a novel avenue of therapeutic research.
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http://dx.doi.org/10.4103/1673-5374.320974DOI Listing
March 2022

miRNA Changes in Retinal Ganglion Cells after Optic Nerve Crush and Glaucomatous Damage.

Cells 2021 Jun 22;10(7). Epub 2021 Jun 22.

Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.

The purpose of this study was to characterize the miRNA profile of purified retinal ganglion cells (RGC) from healthy and diseased rat retina. Diseased retina includes those after a traumatic optic nerve crush (ONC), and after ocular hypertension/glaucoma. Rats were separated into four groups: healthy/intact, 7 days after laser-induced ocular hypertension, 2 days after traumatic ONC, and 7 days after ONC. RGC were purified from rat retina using microbeads conjugated to CD90.1/Thy1. RNA were sequenced using Next Generation Sequencing. Over 100 miRNA were identified that were significantly different in diseased retina compared to healthy retina. Considerable differences were seen in the miRNA expression of RGC 7 days after ONC, whereas after 2 days, few changes were seen. The miRNA profiles of RGC 7 days after ONC and 7 days after ocular hypertension were similar, but discrete miRNA differences were still seen. Candidate mRNA showing different levels of expression after retinal injury were manipulated in RGC cultures using mimics/AntagomiRs. Of the five candidate miRNA identified and subsequently tested for therapeutic efficacy, miR-194 inhibitor and miR-664-2 inhibitor elicited significant RGC neuroprotection, whereas miR-181a mimic and miR-181d-5p mimic elicited significant RGC neuritogenesis.
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http://dx.doi.org/10.3390/cells10071564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8305746PMC
June 2021

Viral delivery of multiple miRNAs promotes retinal ganglion cell survival and functional preservation after optic nerve crush injury.

Exp Eye Res 2020 08 20;197:108071. Epub 2020 Jun 20.

Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892, USA. Electronic address:

Bone marrow mesenchymal stem cell (BMSC)-derived small extracellular vesicles (sEV) but not fibroblast sEV provide retinal ganglion cell (RGC) neuroprotection both in vitro and in vivo, with miRNAs playing an essential role. More than 40 miRNAs were more abundant in BMSC-sEV than in fibroblast-sEV. The purpose of this study was to test the in vitro and in vivo neuroprotective and axogenic properties of six candidate miRNAs (miR-26a, miR-17, miR-30c-2, miR-92a, miR-292, and miR-182) that were more abundant in BMSC-sEV than in fibroblast-sEV. Adeno-associated virus 2 (AAV2) expressing a combination of three of the above candidate miRNAs were added to heterogenous adult rat retinal cultures or intravitreally injected into rat eyes one week before optic nerve crush (ONC) injury. Survival and neuritogenesis of βIII-tubulin RGCs was assessed in vitro, as well as the survival of RBPMS RGCs and regeneration of their axons in vivo. Retinal nerve fiber layer thickness (RNFL) was measured to assess axonal density whereas positive scotopic threshold response electroretinography amplitudes provided a readout of RGC function. Qualitative retinal expression of PTEN, a target of several of the above miRNAs, was used to confirm successful miRNA activity. AAV2 reliably transduced RGCs in vitro and in vivo. Viral delivery of miRNAs in vitro showed a trend towards neuroprotection but remained insignificant. Delivery of selected combinations of miRNAs (miR-17-5p, miR-30c-2 and miR-92a; miR-92a, miR-292 and miR-182) before ONC provided significant therapeutic benefits according to the above measurable endpoints. However, no single miRNA appeared to be responsible for the effects observed, whilst positive effects observed appeared to coincide with successful qualitative reduction in PTEN immunofluorescence in the retina. Viral delivery of miRNAs provides a possible neuroprotective strategy for injured RGCs that is conducive to therapeutic manipulation.
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http://dx.doi.org/10.1016/j.exer.2020.108071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484142PMC
August 2020

Extracellular vesicle therapy for retinal diseases.

Prog Retin Eye Res 2020 11 10;79:100849. Epub 2020 Mar 10.

Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institute of Health, Bethesda, MD, 20892, USA.

Extracellular vesicles (EV), which include exosomes and microvesicles, are secreted from virtually every cell. EV contain mRNA, miRNA, lipids and proteins and can deliver this expansive cargo into nearby cells as well as over long distances via the blood stream. Great interest has been given to them for their role in cell to cell communication, disease progression, or as biomarkers, and more recent studies have interrogated their potential as a therapeutic that may replace paracrine-acting cell therapies. The retina is a conveniently accessible component of the central nervous system and the proposed paradigm for the testing of many cell therapies. Recently, several studies have been published demonstrating that the delivery of EV/exosomes into the eye can elicit significant therapeutic effects in several models of retinal disease. We summarize results from currently available studies, demonstrating their efficacy in multiple eye disease models as well as highlighting where future research efforts should be directed.
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http://dx.doi.org/10.1016/j.preteyeres.2020.100849DOI Listing
November 2020

Activating Transcription Factor 3 (ATF3) Protects Retinal Ganglion Cells and Promotes Functional Preservation After Optic Nerve Crush.

Invest Ophthalmol Vis Sci 2020 02;61(2):31

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Purpose: To investigate the possible role of activating transcription factor 3 (ATF3) in retinal ganglion cell (RGC) neuroprotection and optic nerve regeneration after optic nerve crush (ONC).

Methods: Overexpression of proteins of interest (ATF3, phosphatase and tensin homolog [PTEN], placental alkaline phosphatase, green fluorescent protein) in the retina was achieved by intravitreal injections of recombinant adenovirus-associated viruses (rAAVs) expressing corresponding proteins. The number of RGCs and αRGCs was evaluated by immunostaining retinal sections and whole-mount retinas with antibodies against RNA binding protein with multiple splicing (RBPMS) and osteopontin, respectively. Axonal regeneration was assessed via fluorophore-coupled cholera toxin subunit B labeling. RGC function was evaluated by recording positive scotopic threshold response.

Results: The level of ATF3 is preferentially elevated in osteopontin+/RBPMS+ αRGCs following ONC. Overexpression of ATF3 by intravitreal injection of rAAV 2 weeks before ONC promoted RBPMS+ RGC survival and preserved RGC function as assessed by positive scotopic threshold response recordings 2 weeks after ONC. However, overexpression of ATF3 and simultaneous downregulation of PTEN, a negative regulator of the mTOR pathway, combined with ONC, only moderately promoted short distance RGC axon regeneration (200 μm from the lesion site) but did not provide additional RGC neuroprotection compared with PTEN downregulation alone.

Conclusions: These results reveal a neuroprotective effect of ATF3 in the retina following injury and identify ATF3 as a promising agent for potential treatments of optic neuropathies.
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http://dx.doi.org/10.1167/iovs.61.2.31DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7326601PMC
February 2020
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