A 3D iPSC retina model reveals non-cell-autonomous and non-neuronal mechanism of photoreceptor degeneration in a lysosomal storage disorder.

Unlabelled: Disruption of photoreceptor-retinal pigment epithelium (RPE) interface with loss of photoreceptor outer segments (POSs) in the retina is a pathological hallmark of several neurodegenerative and retinal diseases including lysosomal storage disorder's like CLN3 disease. However, the retina is a functional composite and stem cell models of retina that enable investigation of the photoreceptor-RPE interface in healthy and diseased retina are lacking. Here, we developed a 3D human pluripotent stem cell (hPSC)-derived retina model to investigate the photoreceptor-RPE interface in healthy and disease tissue.

Microglia depletion leads to increased susceptibility to ocular hypertension-dependent glaucoma.

In recent years, microglia have been highlighted for playing integral roles in neurodegenerative diseases, like glaucoma. To better understand the role of microglia during chronic ocular hypertension, we depleted microglia from aged (9-12 months old) DBA/2 J (D2) mice, which exhibit age-related increases in intraocular pressure, using a dietary CSF1R antagonist, PLX5622. Retinal ganglion cell (RGC) somas were counted, and optic nerve cross-sections stained and assessed for glaucomatous damage.

IL1A enhances TNF-induced retinal ganglion cell death.

Glaucoma is a neurodegenerative disease that leads to the death of retinal ganglion cells (RGCs). A growing body of literature suggests a role for neuroinflammation in RGC death after glaucoma-relevant insults. For instance, it was shown that deficiency of three proinflammatory cytokines, complement component 1, subcomponent q ( ), interleukin 1 alpha ( ), and tumor necrosis factor ( ), resulted in near complete protection of RGCs after two glaucoma-relevant insults, optic nerve injury and ocular hypertension.

Neuronal protein phosphatase 1β regulates glutamate release, cortical myelination, node of Ranvier formation, and action potential propagation in the optic nerve.

Precise regulation of protein phosphorylation is critical for many cellular processes, and dysfunction in this process has been linked to various neurological disorders and diseases. Protein phosphatase 1 (PP1) is a ubiquitously expressed serine/threonine phosphatase with three major isoforms, (α, β, γ) and hundreds of known substrates. Previously, we reported that PP1α and PP1γ are essential for the known role of PP1 in synaptic physiology and learning/memory, while PP1β displayed a surprising opposing function.

Microglia Depletion leads to Increased Susceptibility to Ocular Hypertension-Dependent Glaucoma.

In recent years, microglia have been highlighted for playing integral roles in neurodegenerative diseases, like glaucoma. To better understand the role of microglia during chronic ocular hypertension, we depleted microglia from aged (9-12 months old) DBA/2J (D2) mice, which exhibit age-related increases in intraocular pressure, using a dietary CSF1R antagonist, PLX5622. Retinal ganglion cell (RGC) somas were counted, and optic nerve cross-sections stained and assessed for glaucomatous damage.

Age- and glaucoma-induced changes to the ocular glymphatic system.

The ocular glymphatic system supports bidirectional fluid transport along the optic nerve, thereby removes metabolic wastes including amyloid-β. To better understand this biological process, we examined the distributions of intravitreally and intracisternally infused tracers in full-length optic nerves from different age groups of mice. Aging was linked to globally impaired ocular glymphatic fluid transport, similar to what has seen previously in the brain.

BAX activation in mouse retinal ganglion cells occurs in two temporally and mechanistically distinct steps.

Background: Pro-apoptotic BAX is a central mediator of retinal ganglion cell (RGC) death after optic nerve damage. BAX activation occurs in two stages including translocation of latent BAX to the mitochondrial outer membrane (MOM) and then permeabilization of the MOM to facilitate the release of apoptotic signaling molecules. As a critical component of RGC death, BAX is an attractive target for neuroprotective therapies and an understanding of the kinetics of BAX activation and the mechanisms controlling the two stages of this process in RGCs is potentially valuable in informing the development of a neuroprotective strategy.

BAX activation in mouse retinal ganglion cells occurs in two temporally and mechanistically distinct steps.

Background Pro-apoptotic BAX is a central mediator of retinal ganglion cell (RGC) death after optic nerve damage. BAX activation occurs in two stages including translocation of latent BAX to the mitochondrial outer membrane (MOM) and then permeabilization of the MOM to facilitate the release of apoptotic signaling molecules. As a critical component of RGC death, BAX is an attractive target for neuroprotective therapies and an understanding of the kinetics of BAX activation and the mechanisms controlling the two stages of this process in RGCs is potentially valuable in informing the development of a neuroprotective strategy.

TNF-α and NF-κB signaling play a critical role in cigarette smoke-induced epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy.

Proliferative vitreoretinopathy (PVR) is characterized by the growth and contraction of cellular membranes within the vitreous cavity and on both surfaces of the retina, resulting in recurrent retinal detachments and poor visual outcomes. Proinflammatory cytokines like tumor necrosis factor alpha (TNFα) have been associated with PVR and the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells. Cigarette smoke is the only known modifiable risk factor for PVR, but the mechanisms are unclear.

Vascular derived endothelin receptor A controls endothelin-induced retinal ganglion cell death.

Endothelin (EDN, also known as ET) signaling has been suggested to be an important mediator of retinal ganglion cell (RGC) death in glaucoma. Antagonism of EDN receptors (EDNRA and EDNRB, also known as ET-A and ET-B) prevented RGC death in mouse models of chronic ocular hypertension, and intravitreal injection of EDN ligand was sufficient to drive RGC death. However, it remains unclear which cell types EDN ligands directly affect to elicit RGC death.

Transcriptional control of retinal ganglion cell death after axonal injury.

Injury to the axons of retinal ganglion cells (RGCs) is a key pathological event in glaucomatous neurodegeneration. The transcription factors JUN (the target of the c-Jun N-terminal kinases, JNKs) and DDIT3/CHOP (a mediator of the endoplasmic reticulum stress response) have been shown to control the majority of proapoptotic signaling after mechanical axonal injury in RGCs and in other models of neurodegeneration. The downstream transcriptional networks controlled by JUN and DDIT3, which are critical for RGC death, however, are not well defined.

Salinomycin inhibits proliferative vitreoretinopathy formation in a mouse model.

Proliferative vitreoretinopathy (PVR) is a progressive disease that develops in a subset of patients who undergo surgery for retinal detachment repair, and results in significant vision loss. PVR is characterized by the migration of retinal pigment epithelial (RPE) cells into the vitreous cavity, where they undergo epithelial-to-mesenchymal transition and form contractile membranes within the vitreous and along the retina, resulting in recurrent retinal detachments. Currently, surgical intervention is the only treatment for PVR and there are no pharmacological agents that effectively inhibit or prevent PVR formation.

Endothelin 1-induced retinal ganglion cell death is largely mediated by JUN activation.

Glaucoma is a neurodegenerative disease characterized by loss of retinal ganglion cells (RGCs), the output neurons of the retina. Multiple lines of evidence show the endothelin (EDN, also known as ET) system is important in glaucomatous neurodegeneration. To date, the molecular mechanisms within RGCs driving EDN-induced RGC death have not been clarified.

A Mouse Model of Proliferative Vitreoretinopathy Induced by Intravitreal Injection of Gas and RPE Cells.

Purpose: Develop a reproducible proliferative vitreoretinopathy (PVR) mouse model that mimics human PVR pathology.

Methods: Mice received intravitreal injections of SF gas, followed by retinal pigment epithelial cells 1 week later. PVR progression was monitored using fundus photography and optical coherence tomography imaging, and histologic analysis of the retina as an endpoint.

An ocular glymphatic clearance system removes β-amyloid from the rodent eye.

Despite high metabolic activity, the retina and optic nerve head lack traditional lymphatic drainage. We here identified an ocular glymphatic clearance route for fluid and wastes via the proximal optic nerve in rodents. β-amyloid (Aβ) was cleared from the retina and vitreous via a pathway dependent on glial water channel aquaporin-4 (AQP4) and driven by the ocular-cranial pressure difference.

Gabor domain optical coherence microscopy combined with laser scanning confocal fluorescence microscopy.

We report on the development of fluorescence Gabor domain optical coherence microscopy (Fluo GD-OCM), a combination of GD-OCM with laser scanning confocal fluorescence microscopy (LSCFM) for synchronous micro-structural and fluorescence imaging. The dynamic focusing capability of GD-OCM provided the adaptive illumination environment for both modalities without any mechanical movement. Using Fluo GD-OCM, we imaged DsRed-expressing cells in the brain of a transgenic mouse, as well as Cy3-labeled ganglion cells and Cy3-labeled astrocytes from a mouse retina.

DDIT3 (CHOP) contributes to retinal ganglion cell somal loss but not axonal degeneration in DBA/2J mice.

Glaucoma is an age-related neurodegenerative disease characterized by the progressive loss of retinal ganglion cells (RGCs). Chronic ocular hypertension, an important risk factor for glaucoma, leads to RGC axonal injury at the optic nerve head. This insult triggers molecularly distinct cascades governing RGC somal apoptosis and axonal degeneration.

The polyether ionophore salinomycin targets multiple cellular pathways to block proliferative vitreoretinopathy pathology.

Proliferative vitreoretinopathy (PVR) is characterized by membranes that form in the vitreous cavity and on both surfaces of the retina, which results in the formation of tractional membranes that can cause retinal detachment and intrinsic fibrosis of the retina, leading to retina foreshortening. Currently, there are no pharmacologic therapies that are effective in inhibiting or preventing PVR formation. One of the key aspects of PVR pathogenesis is retinal pigment epithelial (RPE) cell epithelial mesenchymal transition (EMT).

Axon injury signaling and compartmentalized injury response in glaucoma.

Axonal degeneration is an active, highly controlled process that contributes to beneficial processes, such as developmental pruning, but also to neurodegeneration. In glaucoma, ocular hypertension leads to vision loss by killing the output neurons of the retina, the retinal ganglion cells (RGCs). Multiple processes have been proposed to contribute to and/or mediate axonal injury in glaucoma, including: neuroinflammation, loss of neurotrophic factors, dysregulation of the neurovascular unit, and disruption of the axonal cytoskeleton.

Author Correction: Mkk4 and Mkk7 are important for retinal development and axonal injury-induced retinal ganglion cell death.

There was an error introduced into Figures 4, 5, and 7 during the proofing stage which has since been corrected.

Mkk4 and Mkk7 are important for retinal development and axonal injury-induced retinal ganglion cell death.

The mitogen-activated protein kinase (MAPK) pathway has been shown to be involved in both neurodevelopment and neurodegeneration. c-Jun N-terminal kinase (JNK), a MAPK important in retinal development and after optic nerve crush injury, is regulated by two upstream kinases: MKK4 and MKK7. The specific requirements of MKK4 and MKK7 in retinal development and retinal ganglion cell (RGC) death after axonal injury, however, are currently undefined.

Jnk2 deficiency increases the rate of glaucomatous neurodegeneration in ocular hypertensive DBA/2J mice.

The cJun N-terminal kinases (JNKs; JNK1, JNK2, and JNK3) promote degenerative processes after neuronal injury and in disease. JNK2 and JNK3 have been shown to promote retinal ganglion cell (RGC) death after optic nerve injury. In their absence, long-term survival of RGC somas is significantly increased after mechanical optic nerve injury.

Ciliary margin-derived BMP4 does not have a major role in ocular development.

Heterozygous Bmp4 mutations in humans and mice cause severe ocular anterior segment dysgenesis (ASD). Abnormalities include pupil displacement, corneal opacity, iridocorneal adhesions, and variable intraocular pressure, as well as some retinal and vascular defects. It is presently not known what source of BMP4 is responsible for these defects, as BMP4 is expressed in several developing ocular and surrounding tissues.

Assessment of intrinsic and extrinsic signaling pathway in excitotoxic retinal ganglion cell death.

Excitotoxicity leads to the activation of a cytotoxic cascade that causes neuronal death. In the retina, retinal ganglion cells (RGCs) die after an excitotoxic insult. Multiple pathways have been proposed to contribute to RGC death after an excitotoxic insult, including TNF signaling, JNK activation, and ER stress.